CA1162461A - Hydraulic digital stepper actuator - Google Patents
Hydraulic digital stepper actuatorInfo
- Publication number
- CA1162461A CA1162461A CA000365585A CA365585A CA1162461A CA 1162461 A CA1162461 A CA 1162461A CA 000365585 A CA000365585 A CA 000365585A CA 365585 A CA365585 A CA 365585A CA 1162461 A CA1162461 A CA 1162461A
- Authority
- CA
- Canada
- Prior art keywords
- ports
- apertures
- housing
- aperture
- wall
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
- F15B11/12—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor providing distinct intermediate positions; with step-by-step action
- F15B11/121—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor providing distinct intermediate positions; with step-by-step action providing distinct intermediate positions
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/8593—Systems
- Y10T137/86389—Programmer or timer
- Y10T137/86445—Plural, sequential, valve actuations
- Y10T137/86461—Variable cycle
Abstract
Abstract of the Disclosure An apparatus for converting pressure into motion includes a housing having a plurality of ports formed therein. Movably disposed within the housing is a piston having a first plurality of apertures communicating with a first chamber and a second plurality of apertures communicating with a second chamber therein.
The piston is positioned within the housing so that the apertures can register with consecutive ones of the ports as the piston is moved in either of two directions within the housing. The movable member is moved by a pressurizing substance applied to a selectable one of the ports through an appropriate valve circuit. The valve circuit is operated by excitation signals from a control member.
By operating the valve circuit in an appropriate sequence, the pressurizing substance is sequentially applied to consecutive ones of the ports to move the piston longitudinally through the housing.
The piston is positioned within the housing so that the apertures can register with consecutive ones of the ports as the piston is moved in either of two directions within the housing. The movable member is moved by a pressurizing substance applied to a selectable one of the ports through an appropriate valve circuit. The valve circuit is operated by excitation signals from a control member.
By operating the valve circuit in an appropriate sequence, the pressurizing substance is sequentially applied to consecutive ones of the ports to move the piston longitudinally through the housing.
Description
1 1 ~2461 HYDE~IJLIC DIGITAL STEPPER ACTUATOR
This invention relates generally to apparatus for convertinq pressure into motion and more particularly, but not by way of limitation, to linear actuator apparatus which convert pressure into predetermined increments of linear displacement.
Precise control of linear movement is often required for meeting manufacturing specifications in machine tool aDplications and mater-ial handling applications. For example, when cutting a workpiece on a lathe, the cutting tool of-ten needs to be moved in specific increments with respect to the workpiece to make the appropriate cut at the proper place along the length of the workpiece. This requires an apparatus which can move the work-piece and the tool in specific increments with respect to each other.
l'; Such an apparatus might include a cylinder having a double-acting piston slidably positioned therein for bi-directional move-ment with respect thereto in response to an application of press-lre to one side or the other of the piston. Examples of devices havin~
double-actin~ pistons movable in response to prèssure inputs are ~0 shown in U.S. Patent No. 4,152,971 in the name of Leonard, U.S.
Patent No. 4,106,390 in the name of Kodaira et al., U.S. Patent No. 3,779,136 in the name of Elohlein and U.S. Patent No. 2,75],752 in the name of Metcalf. Although these references disclose apparatus having double-acting piston, they do not disclose apparatus which
This invention relates generally to apparatus for convertinq pressure into motion and more particularly, but not by way of limitation, to linear actuator apparatus which convert pressure into predetermined increments of linear displacement.
Precise control of linear movement is often required for meeting manufacturing specifications in machine tool aDplications and mater-ial handling applications. For example, when cutting a workpiece on a lathe, the cutting tool of-ten needs to be moved in specific increments with respect to the workpiece to make the appropriate cut at the proper place along the length of the workpiece. This requires an apparatus which can move the work-piece and the tool in specific increments with respect to each other.
l'; Such an apparatus might include a cylinder having a double-acting piston slidably positioned therein for bi-directional move-ment with respect thereto in response to an application of press-lre to one side or the other of the piston. Examples of devices havin~
double-actin~ pistons movable in response to prèssure inputs are ~0 shown in U.S. Patent No. 4,152,971 in the name of Leonard, U.S.
Patent No. 4,106,390 in the name of Kodaira et al., U.S. Patent No. 3,779,136 in the name of Elohlein and U.S. Patent No. 2,75],752 in the name of Metcalf. Although these references disclose apparatus having double-acting piston, they do not disclose apparatus which
2'; meet specific desirable needs for achieving accurate and repeatable ~L
~' ~l ~
~16~61 control of incremental movements.
These needs include providing an apparatus which can aceomplish precise r repeatable incremental movement independently of the magnitude of a pressure applied to a movable member which 5' is to be displaced the speeified increment. This obviates the need for correlating the applied pressure with the distance the movable member is to be moved, In other words, it is desirable to construct an apparatus whieh ineludes a plurality of ports through which a pressurizing substance ean be applied whereby the movemen-t to be aehieved by such apparatus is dependent on the present position o~ the movable member therein and the port through whieh the pressurizing substanee is applied to the movable member.
It is also desirable that such an apparatus for preeisely eontrolling movement not require electrical feedback to the lS primary eontrolling means so that no eleetrieal oseillatory control signals are generated. To achieve precise control without primary control feedbaek, there is the need for the apparatus to inelude a set of interrelated ports and openings in the apparatus to preeisely position the movable member through the applieation of a pressurizing substanee therethrough. To compensate any overshoot of the movable member whieh might oecur, it is necessary to inelude in the apparatus a pressure feedback ~eans to properl~
stop the movable member at the predetermined loeation.
So that the preeise movements ean be eontrolled without ~5 feedback to the main controller, there is the need for control means for generating a eyclical sequence of electrical control signals, sueh as a Gray Code sequenee of digital signals, for uniformly moving the movable member in speeifie inerements. It ~ ~ 62461 is also desirable to provide -the se~uence of electrical control sig-nals at varying rates so the speed at which the movable member is moved may also be varied.
A further need is for the movable member to be moved with variable magnitudes of forces so that various leve]s of forces can be exerted by the movable member on the object which it is positioning.
The present invention overcomes the above-noted and other shortcomings of the prior art by providing a novel and improved hydraulic digital stepper actuator. The actuator constructed in accordance with the present invention incrementally displaces a movable member a predetermined distance independently of the magnitude of the force exerted by a pressurizing substance used to move the movable member. More particularly, the present invention achieves accurate, repeatable incremental displacement of the movable member because of the interrelationship of a plurality of ports and openings included in the apparatus constructed according to the present invention:
The present invention achieves precise incremental displace-ment without any electrical feedback to the primary controlling mealls. Instead, precise positioning is dependent on the size and separation of the ports and openings included within the appara-tus.
Ho~ever, the present invention does include a pressure feedback means to compensate overshoot whereby the movable member stops at the appropriate location.
- - o ~ ~ ~,2~
The present apparatus controls the movement of the movable member by applying a pressurizing substance through particular ones of the ports and openings in re~onse ~o a cyclica~ sequence of electrical signals, such as a Gray Code sequence of digita signals. By varying the time between each signal within the sequence of signals, the speed of movement of the movab]e member is controlled.
Furthermore, although the magnitude of force exerted by the pressurizing substance applied through the ports and openings does not affect the distance the movable member is displaced, the magnitude of the force exerted thereky does permit high levels of force, as well as other levels of force, to be exerted by the movable member on whatever object the movable member is associated with.
Broadly, the pre-sent invention prQvides an apparatus for converting pressure into motion comprising a movable member responsive to pressure and means for supplying a first flow of pressurizing substance to a selected one of a plurality of selectable areas on the movable member until the movable member 2n has moved a predetermined distance. The plurality of selectable areas on the movable member includes a first opening formed therein.
The apparatus urther comprises means for releasing a second flow of pressurizing substance from a second opening formed in the movable member when the supplying means supplies the first flow of pres-2~ surizing substance to the first opening formed in the movablemember. The apparatus also includes means for controlling the supplying means and the releasing means. The controlling means ~ 3 6~
includes means for generating a coded sequence o~ control signals.
In one aspect of the present invention, there is provided an apparatus ~or converting pressure into limited motion, comprising- a movable member responsive to pressure;
and means for supplying a first flow of pressurizing substance to a selected one of a plurality of selectable areas on said movable member until said movable member is moved a predeter-mined distance.
In a further aspect of the present invention, there is provided an apparatus for converting pressure into motion, comprising: a movable member having receiving means for re-ceiving a pressurizing substance; control means for generating a sequence of control signals; and supplying means, responsive to said control means, for supplying the pressurizing substance to the receiving means of said movable member so that said mov-able member is moved a predetermined distance in a number of predetermined increments.
In a further aspect of the pres~nt invention, there is provided an apparatus for converting pressure, exerted by a pressurizing substance from a pressure source, into motion, comprising: a housing having a plurality of ports formed therein, control means for selectably connecting the pressure source to one of the ports and for selectably connecting a pressure sink to another of the ports; and a movable member, having a plurality of openings formed therein, movably disposed within said housing so that a first one of the openings regist-ers with one of the ports of said housing for communicating a first flow of the pressuring substance from the pressure source to said movable member through the first opening when said con-trol means connects the pressure source to that port register-ing with the first opening and so that a second one of the openings registers with another of the 1~2~6~
ports of said housing for communicating a second flow of thepressurizing substance from said movable member to the pressure sink through the sêcond opening when said control means con-nects the pressure sink to that port registering with the sec-ond opening, whereby said movable member is caused to move with respect to said housing.
In a further aspect of the present invention, there is provided a linear actuator, comprising: a housing having a cylindrical wall in which 2n ports are formed, where n is an interger greater than 1; a piston movably disposed within said housing, said piston includingo a first chamber extending from a first closed end of said piston to a first open end thereof, a second cham~er extending from a second closed end of said piston to a second open end of said piston: a first row of apertures formed along a first portion of said piston in com-munication with said first chamber; and a second row of aper-tures formed along a second portion of said piston in communi-cation with said second chamber, valve means for connecting a first flow of pressurizing substance from a pressure source to one of the ports and for connecting a second flow of pressur-izing substance from another of the ports to a pressure sink, and means for operating said valve means so that the first flow of pressurizing substance is directed to one of the ports in register with one of the apertures of one of said first or second rows of apertures and so that the second flow of pres-surizing substance is received from another of the ports in register with one of the apertures of the other of said first or second rows of apertures.
In a ~urther aspect of the present invention, there is provided a method of converting pressure to motion in in-cremental steps, comprising the steps of: supplying a first flow of pressurizing substance through consecutive ones of a : -5a-1 ~ 62~6~
plurality of ports to a first opening in a movable member, and releasing a second flow of pressurlzing substance through different consecutive ones of the plurality of ports from a second opening in the movable member.
In a further aspect of the present invention, there is provlded an apparatus for converting pressure, exerted by a pressurlzing substance between a pressure sourae and a pressure sink, into increments of displacement, each i.ncrement having a length S, said apparatus comprising, a housing including a wall having four grooves defined in spaced relationship to each other on an interior surface of said wall and said wall further having four holes defined therethrough so that each hole extends from a respective one of the grooves to an exterior surface of said wall, said grooves and holes thereby defining four ports of said housing, each of said grooves being 0.5S
wide and being spaced from each adjacent groove on centers spaced l.OS, and a double-acting piston disposed for movement in said housing in response to the pressurizing substance, said piston including, a side wall having an inner surface and an outer surface and further having a first plurality of apertures and a second plurality of apertures defined in said side wall so that each of said apertures extends from the inner sur-face to the outer surface, each of said apertures having a dia-meter of 1.5S with each aperture of sai.d first plurality of apertures being spaced on a center separated a distance of 4.0S
from a center of each adjacent aperture of said first plurality of apertures and with each aperture of said second plurality of apertures being spaced on a center Separated a distance of 4.0S from a center of each adjacent aperture of said second plurality of apertures, said first plurality of apertures in-cluding a first aperture and a second aperture and said second plurality of apertures including a third aperture, wherein, said -5b-1 ~2~L6~
third aperture is defined in said side wall so that said third aperture registers with a first one of said ports ~hen said first aperture registers with a second one of said ports and further so that said third aperture registers with said second one of said ports when said first aperture overshoots in a first direction said second one of said ports, and said second aperture is defined in said side wall so that said second aperture registers with said first one of said ports when said first aperture overshoots in said first direction said second one of said ports, said first, second and third apertures thereby providing feedback means for precisely positioning said piston relative to said housing; a first end wall closing a first portion of a first end of said side wall and leaving a second portion of said irst end open, a second end wall closing a first portion of a second end of said side wall and leaving a second portion of said second end open, and a central wall extending from said first end wall to said second end wall and from a first region of the inner surface of said side wall to a second region of the inner surface of said side wall so that a first chamber extending from the first end wall to the open portion of the second end of said side wall and a second chamber extending from said second end wall to the open portion of the first end of said side wall are formed, wherein said first plurality of apertures communicates with said first chamber and wherein said second plurality of apertures communicates with said second chamber.
From the foregoing it is a general object of the present invention to provide a novel and improved hydraulic digital stepper actuator. Other and further objects, features and advantages of the present invention will be readily appa-rent to those skilled in the art when the following descrip--5c-~7 ;`
2 ~ ~ 1 tion of the preferred embodiments is read in conjunction with the accompanying drawings.
FIG. 1 is a sectional view of a specific embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line 2-2 shown in FIG. 1.
FIG. 3 is a schematic illustration of a preferred embodiment of the present invention showing the movable member in a first position.
FIG. 4 is a schematic illustration of a preferred embodiment of the present invention showing the movable member in a second position.
FIG. 5 is à schematic diagram of a first preferred embodiment of the valve means of the present invention.
FIG. 6 is a schematic illustration of a second pre-ferred embodiment of the valve means of the present invention.
FIG. 7 is a schematic illustration of another embodi-ment of the present invention.
-5~--2~1 With reference to the drawings an apparatus for converting pressure into motion, and particu~arly into limited motion, con-structed in accordance with the present invention will be de-scribed. In FIG. 3 the apparatus, generally indicated by the reference numeral 2, includes aihousing 4 and a movable member 6 movably disposed within the housing 4. Connected to the housing 4 is a control means 8 for controlling the flow of a pressurizing substance (such as an incompressible hydraulic material or any other suitable substance) from a pressure source (such as a tank and pump system) to the housing 4 and the movable member 6 and from the housing 4 and movable member 6 to a pressure sink (such as the tank or a sump). Embodiments of the control means are shown in FI~S. 5-7.
The housing 4 includes a wall 10 which preferably has a cyl-`5 indrical shape and further includes a first closed end 11 and asecond closed end 12. Tlle wall 10 has an interior surface 13 and an exterior surface 14.
The housing 4 also includes pressurizIng substance channeling means 16 disposed in the wall 10 thereof. The channellng means 16 directs the pressurizing substance from -the pressure source to the movable member 6 as subsequently described. The channeling means 16 also directs the pressurizing fluid from the movable member 6 to t}~e pressure sink also as subsequently described. The channeling means 16 also directs the pressurizing fluid from the movable ~5 member 6 to the pressure sink also as subsequently described. In FIG. 3 the channeling means 16 is shown to par-ticularly include a plurality of ports 18. In the embodiment shown in the figures there are four ports identified by the letters ~, X, Y and Z. The ports are defined by a plurality of grooves 20 formed in spaced relationship to each other on the interior surface 13 of the wall 10 and by a plurality of holes 22 formed through the ~"all 10 so that each hole extends from a respective one of the grooves 20 to the exterior surface 14 of the wall 10.
This porting system provides means for supplying a flrst flow of the pressurizing substance to a selected one of a plurality of selectable areas on the movable member 6 until the movable member has moved a predetermined distance in a number of predetermined increments in relation to the housing 4 within wilich the mouable member 6 is movably disposed.
The movable member 6 is shown in FIG. 3 to include a double-acting piston 24 movably disposed within the housing 4 for sliding engagement along the interior surface 13. The piston 24 includes a side wall 26 having an inner surface 28 and an outer surface 30.
The piston 24 also includes a first end wall 32 closing a first portio~
of a first end of the side wall 26 but leaving a second portion of the first end open. The piston 24 further includes a second end wall 34 closing a first portion of a second end of -the side wall 26 but leavlng a second portion of the second end open. Additionall~, the piston 24 includes a central wall. 36 e~tending from the first end ~all 32 to the second end wall 34 and from a firs-t region of the inner surface 28 of the side wall 26 to a second region of the inner surface 28 of the side wall 26 so that a first chamber 38 extending fro ~ ~ 62~ ~
the first end wall 32 to the open portion of the second end of the side wall 26 and a second chamber 40 extending from the second end wall 34 to the open portion of the flrst end of the side wall 26 are formed. Connected to the first end wall 32 is a connecting rod 42 which extends through a bore in the first closed end ll of the housing 4 for engaging the workpiece to be incrementally positioned by the present invention.
~ he movable member 6, which is responsive to pressure, includes receiving means for receiving the pressurizing substance from the pressure source. The receiving means includes the plura]ity of selectable areas to which the supplying means directs the first flow of pressuri~ing substance for moving the movable member 6 with respect to the housing. As shown in FIG~ 3 these areas include a first opening 44 and a second opening 46. Other openings 48, 50, 52, 54, 56 and 58 are shown in FIG. 3 to be included within the movable member 6, and more particularly, the first, second and remaining openings 44-58 include a-first plurality of apertures extending from the outer surface 30 of the side wall 26 to the inner surface 28 thereof for communicating with the first chamber 38 and a second plurality of apertures extending from the outer surface 30 of the side wall 26 to the inner surface 28 thereof for communicating ~lth the second chamber 40. In FIG. 3, the apertures 44 and 48-52 constitute the first plurality, and the apertures 46 and 54-58 constitute the second plurality. Each aperture of the first plurality of apertures is equidistantly spaced from each adjacen-t one of the ... ... . . . . .. _ _ _ 1 ~ 62~6 ~
first plurallty of apertures, and each aperture of the second plurality of apertures is centered on a line perpendicularly bisecting a line extending between the centers of a respective set of two adjacent apertures of the first plurality of apertures.
In the embodiment shown in the drawings the first plurality of apertures is positioned on the side wall 26 of the movable member 6 diametrically opposite the second plurality of apertures. Also as shown in the drawings, the first plurality of aperturés is disposed in a row along a first portion of the piston 24 in communication with the first chamber 38, and the second pLurality of apertures is aligned in a row along a second portion of the piston 24 in Fommunication with the second chamber 40.
The openings 44-58 formed in the movable member 6 and the ports 18 of the housing 4 provide means for releasing a second flow~of the pressurizing substance from an opening communicating with one of the :
chambers 28 or 40 when the supplying means supplies the~first flow of pressurizing substance to another opening communicating with the other of the two chambers.
The movable member 6 and the housing 4~are positioned with re-spect to each other whereby the ports 18 of the channeling means of the housing 4 are disposed adjacent the movable member 6 for sequent-ially .registering with the openings 44-58 formed in the movable member 6, such as the first opening 44 and the second opening ~5 46 as shown in FIG. 3, as the movable member 6 is incrementally moved so that the pressurizing substance can be supplied through the channeling means to one of the registering openings to thereby move the movable memeber 6 in either of the two directions long-_g _ ~ 1 62~
itudinally through the housing 4. More particularly, the movablemember 6 is disposed within the housing 4 so that a firs-t one of the openings registers with one of the ports of the housing 4 for communicating the first flow of pressurizing substance from the pressure source to the movable member 6 through the first opening when the pressure source is connected to that port registering with the first opening and so that a second one of the openings registers with another of the ports of the housing 4 for communica-ting the second flow of the pressurizing substance from the movable member 6 to the pressure sink through the second opening when the pressure sink is connected to that port registerlng with the second opening.
By controlling the ports through which the~first and second~flows are directed, the movable member 6 is caused to~move with respect to the housing 4.~ ~
The control of the communication of -the first and second flows of pressurizing substance with the ports and openings is~achieved by means of the control means 8. Generally, the control~means 8 provi.des means for controlling the supplying means and~the releasing means whereby the first and second flows of pressurizing substance are appropriately dlrected to and from the housing 4 and movable ~0 member 6. With reference to FIGS. 5-7 preferred embodiments Oe the control means 8 will be described.
FIG. 5 schematically illustrates that the control means 8 lnclude conduit means 60 for connecting the ports 18 of the housing 4 to the pressure source and the pressure sink. 'rhe conduit means 60 includes a plurallty of ducts schematically illustrated by numbered lines 62, 64, 66 and 68. Each duct is associated with a respective one of the ports as indicated hy the labeling of the ducts with a letter cor-responding to its respective poxt shown in FIGURES 3 and 4.
Connected within the conduit means 60 is a valve means 70 for .
l l 6~61 appropriately connecting respective ones of the ducts 62-68 within the condult means 60 to either the source or the sink of pressurizing substance or to a blocking means as subsequently discussed. The valve means 70 is used to connect a first flow of pressurlzing substance from the pressure source to one of the ports 18 and to connect a second flow of pressurizing substance from another of the ports 18 to the pressure sink. As shown in the FIG. 5 embodiment the valve means 70 includes four interconnected two-position valves .
72, 74, 76 and 78 having respective solenoid-operated valve ; lO elements ~ositioned therein. The solenoids of the valves shown in FIG. 5 are controlled by ~Ycitation signals generated by~a control signal generator 80. More particularly, the valves 72-7;8 and ducts 62-68 of the FIG. 5 embodiment are interconnected so that the valves are responsive to two-diglt Gray~Code excitatlon ~signa~ls for~ ~
sequentially connecting each port within ~a respective set of two ports of the portsl~ oarespective~one~ of the p;ressure~source, the pressure sink, or the blocking means.;
The control signal generator 80 provi~des;means for generating ~
a coded sequence of control signals,~such as a sequence of~two-digit :
~ Gray Code excitation signals or a sequence of four-variable excitation signals,as subsequently described or any~;o~th~er sequence of ex~
citation signals. Through the creati~on of such~control signals -the control signal generator 80 provides means for operat1ng the~valve means 70 in a predetermined sequence so -that the pressure source, thè pressure sink, and the blocking;means are~sequentiaIly communicat~ed ~ith respective ones of the ports 18 which are registered~wi~th respective ones of the openings 44-58 of the movable~member~6 ::
;
1 162~
whereby the movable member 6 moves in incremental steps. In other ~ords, the control signal generator 80 provides means ~or operating the valve means 70 so that the first flow of pressurizing substance is directed to one of the por-ts in register with one of the apertures of one of the first or second rows of apertures and so that the second flow of pressuring substance is received from another of the ports in register with one of the apertures of the other of the first or second rows of apertures. Speciflcally, the control signal generator 80 preferrably is a mlc;rocomputer or other apparatus for providing digital output signals.
The embodiment of the control means 8 shown in FIG. 6 includes two three-position valves 82 and 84 responsive to;four-variab~le excit-ation signals which are generated by the control~signal g;enerator 80 ;
;~ associated therewith for sequentlally connectlng each port within a respective set of two~ports of~the ports~18 to a~respective~ one of~
the~pressure~source, the pressure ~sink, or the blocking means.~ ~
FIG. 7 shows that the control means~8 further lncludes emergency actuation valve means 86 having a pressurizing substance~
conducting duct connected to each end of~the housing 4 90 ~ that the ~0 piston can be rapidly moved in either;directlon to qulckly extend or retract the connecting rod 42 connected thereto.~
FIGS. 1 and 2 disclose a specific embod.lment of the present invention containing various ones of the elements previously discussed.
More particularly, the apparatus includes a first housing~section 88 ~5 having a first closed end 90 and a second housing sectlon 92~having a second closed end 94 through which a connecting rod 96;is slidably disposed. The connecting rod 96 is connec-ted to a piston 98 contained within the cylinder defined by the first and second housing sections 88 and 92. The first and second housing sections 88 and 92 are joined by a housing coupling sleeve 100 in which are formed ports 102 for conducting the pressurizing substance to and from 1~2461 respective ones of a plurality of apertures 104 formed in the piston 98. FIG. 1 further shows several O-rings 106, 108, 110, 112, 114, 116, 118, 120 and 122 positioned for effecting fluid-tight seals between the joined elements of the apparatus shown therein.
The apparatus disclosed in FIG. 1 further includes a coupling collar 124 by ~"hich a control means, including appropriate valve means, conduit means, and signal generator means, are connected to the assembled housing sections 88 and 92 and coupling sleeve 100.
FIG. 2 discloses that a first chamber 126 and a second chamber 128 ormed within the piston 98 have circular cross-sections. ~IG.
2 further discloses a groove 130 of one of the ports 102 formed in the housing coupling sleeve 100.
As will be apparent upon an examinatlon of the structure shown in FIG. 1, as the pressurizing substance lS directed into~
one of the chambers 126 or 128 through one of the apertures;104 formed in the piston 98 and~through the appropriate one of;the ports 102 formed in the housing coupling sle~eve lOO and the pressurizing substance from the other of the chambers 126 and 128 is released through the appropriately allgned aperture and port, the piston 98 will move longitudlnally through the~cylinder defined by the housing assembly to thereby incrementally move the connecting rod 96 and the workpiece connected thereto. ~This operation will be more specifically descrlbed with reference to FIGURES 3-6.
~efore the operation is more specifically described, hcwever, the preferred dimensional relationships among the various elements will be considered. For the embodiments disclosed in -13- ~
~ 3 62~6~
FIGURES 3-6, the desired length of each increment by which the piston 24 and the connecting rod 42 are to be moved is designated as a distance S. For e~ample, S might equal one-sixteenth inch. With a step size of S, each of the apertures 44-58 formed in the piston 24 has a diameter 1.5S and the apertures are spaced on centers separated a distance of 4S. With such a center spacing, this makes ; the width of the portion of the side wall 26 between each adjacent aperture have a length of 2.5S. With the apertures and separating portions having these proportions, each aperture communicating with one of the chambers is to be positioned exactly ~in the middle of a respective set of two apertures communlcating with the other chamber.
, The four ports W, X, Y and Z are centered between~the~ends 11 and 12 of the cylinder define~by the houslng 4. ~Each of the grooves 20 defining a portion of each~port~is 0.5S wide, and adjacent grooves are spaced on l.OS centers. That is, the portion of the housing 4 separating each o~ the grooves~20 is~0.5S~wide. ;~
By using the valve means disclosed in FIGS~ 5 an~d~6,;or another suitable valve means, each of the ports 18 can be connected ::
to the pressure source, the pressure sink, or the blocking means.
The bloc~ing means is provided by merely plugging, capping, or other-::
wi~e closing the approPriate end of the~respective duct to be blocked.
Whether a particular port is connected to the pressure~source, -the pressure sink or a blocking means is determined by the positioning of ths particular valve~s as controllsd by~the~control signal generator 30 and the excitation siqnals generated thereby.
:
I l ~2~61 The.operation of the apparatus can be explained b~t the following steps. Initially, it will be assumed that the piston 24 is located with the opening or aperture 44 in register with port Y as shown in FIG. 3. To move piston 24 to the right, port Y must be connected to the pressure source so that a fi.rst flow of the pressurizing sub-stance will be permitted to enter into the first chamber 38 through the first aperture ~4 whereby the substance acts through the first chamber 38 and against the second closed end 12 of the housing 4.
Simultaneously, the port W must be connected to the pressure sink so that pressurizing substance contained wlthin the~second chamber 40 can be released in a second flow through the second opening 46 and port W into the pressure sink or tank. Ports X and Z should be blocked at this time so that no pressurizing substance flo~.~s therethrough. This connection of the valves 72 78 to the port~s W, X, Y and Z~moves~the ~
piston 24 to the right until the trailing edge of the first opening 44 passes the port Y thereby shutting off the first flow of pressurizing sù~bstance therethrough. This places the piston 24 in the position relative to the ports 18 shown ln FIG. 4.
In FIG. 4 it is to be noted that should the piston 24 ~0 overshoot the port Y prior to stopping, the first flow~of pressuri.zing substance through port Y will enter the second chamber 40 through the second aperture 46 and the second flow of pressurlzing substance will come from the first chamber 38 through the~aperture~50 adjacent port W. Therefore, the piston is moved to the left:to compensate for the overshoot. This provides pressurized feedback to pre-cisely position the piston 24 and thereby move the piston 24 and associated connecting rod 42 only the desired incremen-t. This precise posltioning permits each increment to be repeatably obtained.
, -1 :~ 62~6~
Further movement of the piston 24 to the right can be achieved by next pressurizing (i.e., connecting the pressure SO~ thereto) port Z while tanking ti-e-, connecting the pressure sink thereto) port X. Ports W and Y should be blocked during this movement.
~ urther movement is effected by pressurizing port W, tanking port Y and blocking ports X and %. The fourth step is achieved by pressurizlng port X, tanking port Z and blocking the other two ports.
By cyclically performing these steps in thls order moves the piston 24 to the right, whereas performing the cycle in the reverse order moves the piston 24 to the left. That is, to move the piston 24 to the left, the pressure source must be co~munlcated with~re-spective ones of the apertures 46, 54, 56 and 58 and the second chamber 40, and the pressure sink must be commanicated with respe_tive ones of the apertures 44, 48, 50 and 52 and the first chamber 40.
It is apparent that the distance which the piston 24 moves ln each increment is the distance across a single port and a single separating portion of the housing 4. Based~on the previous dimensions, this gives the desired incremental step size of S. The sDeed at which the movement is effected depends upon the speed at which the excitation signals are generated and applied to the valve means to thereby change the different connections among the pressure source, pressure sink, blocking means and ports.
As previously discussed, the pressure feedback prevents over-; shoot. Also preventing overshoot is the relationship between the ports 18 and apertures 44-58 whereby the aperture through wllich the pressurizing substance is being inpu-t graduallY closes the pressurizing port to ~hereby cause deceleration of the piston 24 1 ~ 62~L61 as it is moved within the housing 4.
As mentioned above the actuation of the apparatus ls controlled by a cyclical sequence of excitation signals generated by the control signal generator means 80 for operating the valves in the valve means to establish different ducting connections to the various ports. Preferrably these signals are digltal signals representing either a first state or a second state. For the four-port device disclosed in the drawings, each cycle consists of four steps involving the application of the pressure source and the pressure sink to four different two-port combinations. To distinguish each of these four steps, at least two excitatlon signals are required as represented,for example, by the letters A and B in FIG. 5. By using these two signals four different combinations of control signals can be gene~rated to opera-te the valves so that four different ducting combinations between the pressure source, pressure sink and blocking means and the ports W, X, Y and Z can be effected. By arranging the sequence of the four combinations in the Reflective Binary Code (also known as the Gray Code), a truth table as follows can be established:
PORT EXCITATION SIGNAL
W X Y Z A B
M P M T O
T M P M
In the preceding table P represents that the respective port is 1 ~ 6~6~
to be connected to the pressure source, T indicates that the respective port is to be connected to the pressure sink and M designates those ports to be connected to the blocking means.
From this table the following logic expressions are derived:
W = P A'B' + T A B + M [ A ~ B]
X = P A' B + T A B'+ M I A ~ B]
Y = P A B + T A' B' + M [ A ~ B]
Z = P A B' + T A' B + M [ A ~ B]
Where "~" and "-" designate EXCLUSIVE OR and COINCIDENCE
functions r respectively.
Solving for P and T yields:
P = W A' B' + X A' B + Y A B + Z A B' T = W A B + X A B' + Y A' B'~+ Z A' B
These last two expressions are implemented by means of the four-valve circuit shown in FIG. 5 to appropriately control the~
.
present invention.~
~ Other excitation schemes can also be~derived. For example, the four-variable excitation àpproach shown ln the followlng~
truth table can be used~
PORT EXCITATION SIGNA~L
W X Y Z C D: E F
.
25 p M T ~M ~ 1 0 0 T M P M : 0 : 0 1 0 -18-:
~ J ~246~
Assuming that the actuating signals c.annot occur -together, expressions for W, X, Y and Z are developed as follows:
W - P C + T E ~ M [D + F]
X = P D + T F + M [C + E]
Y = P E + T C + M [D + F]
Z = P F + T D + M [C + E]
These expressions are shown implemented~with the two blocked-centered, double-solenoid valves 82 and 84 shown in FIG. 6.
It is to be noted that although the preferred embodiment 5hown in the drawings includes four ports, any 2n, n being an:
integer greater than l, number of ports may be ùsed. Increasing the number of ports increases the~resolution with whlch the movable member 6 can be mo~ed, but also causes the~manufacturing and mach-ining of the apparàtus to be more difficult. When 2n ports;are used and binary control signals and two-position~valves~are used,~
the operating means includes means for generating at 1east~n-dlgit , ~
: excitation signals, such as an :n-digit Gray Code~, and the valve means includes 2n interconnected two-positlon valves~which are responsive to the n-digit excitation signals. Other typ~es ?O oE operating means and valve means can be used for dlfferent types ; of control signals and valves.
Thus the present invention of a hydraulic digital stepper àctuator is well adapted to carry out the objects and attain the ends and advantages mentioned~above as well as thosè:inherent therein. While preferred embodiments of the inv~ention have been .
.
described for the purpose of this disclosure, numerous changes in the construction and arrangement of parts can be made by those skilled in the art, which changes are encompassed with-in the spirit of this invention as defined by the appended claims.
' :: : ` : :
~' ' ;: : :
:: : :
;: ; : ~ ;
~: ~
, O - :
.
' . ~
~' ~l ~
~16~61 control of incremental movements.
These needs include providing an apparatus which can aceomplish precise r repeatable incremental movement independently of the magnitude of a pressure applied to a movable member which 5' is to be displaced the speeified increment. This obviates the need for correlating the applied pressure with the distance the movable member is to be moved, In other words, it is desirable to construct an apparatus whieh ineludes a plurality of ports through which a pressurizing substance ean be applied whereby the movemen-t to be aehieved by such apparatus is dependent on the present position o~ the movable member therein and the port through whieh the pressurizing substanee is applied to the movable member.
It is also desirable that such an apparatus for preeisely eontrolling movement not require electrical feedback to the lS primary eontrolling means so that no eleetrieal oseillatory control signals are generated. To achieve precise control without primary control feedbaek, there is the need for the apparatus to inelude a set of interrelated ports and openings in the apparatus to preeisely position the movable member through the applieation of a pressurizing substanee therethrough. To compensate any overshoot of the movable member whieh might oecur, it is necessary to inelude in the apparatus a pressure feedback ~eans to properl~
stop the movable member at the predetermined loeation.
So that the preeise movements ean be eontrolled without ~5 feedback to the main controller, there is the need for control means for generating a eyclical sequence of electrical control signals, sueh as a Gray Code sequenee of digital signals, for uniformly moving the movable member in speeifie inerements. It ~ ~ 62461 is also desirable to provide -the se~uence of electrical control sig-nals at varying rates so the speed at which the movable member is moved may also be varied.
A further need is for the movable member to be moved with variable magnitudes of forces so that various leve]s of forces can be exerted by the movable member on the object which it is positioning.
The present invention overcomes the above-noted and other shortcomings of the prior art by providing a novel and improved hydraulic digital stepper actuator. The actuator constructed in accordance with the present invention incrementally displaces a movable member a predetermined distance independently of the magnitude of the force exerted by a pressurizing substance used to move the movable member. More particularly, the present invention achieves accurate, repeatable incremental displacement of the movable member because of the interrelationship of a plurality of ports and openings included in the apparatus constructed according to the present invention:
The present invention achieves precise incremental displace-ment without any electrical feedback to the primary controlling mealls. Instead, precise positioning is dependent on the size and separation of the ports and openings included within the appara-tus.
Ho~ever, the present invention does include a pressure feedback means to compensate overshoot whereby the movable member stops at the appropriate location.
- - o ~ ~ ~,2~
The present apparatus controls the movement of the movable member by applying a pressurizing substance through particular ones of the ports and openings in re~onse ~o a cyclica~ sequence of electrical signals, such as a Gray Code sequence of digita signals. By varying the time between each signal within the sequence of signals, the speed of movement of the movab]e member is controlled.
Furthermore, although the magnitude of force exerted by the pressurizing substance applied through the ports and openings does not affect the distance the movable member is displaced, the magnitude of the force exerted thereky does permit high levels of force, as well as other levels of force, to be exerted by the movable member on whatever object the movable member is associated with.
Broadly, the pre-sent invention prQvides an apparatus for converting pressure into motion comprising a movable member responsive to pressure and means for supplying a first flow of pressurizing substance to a selected one of a plurality of selectable areas on the movable member until the movable member 2n has moved a predetermined distance. The plurality of selectable areas on the movable member includes a first opening formed therein.
The apparatus urther comprises means for releasing a second flow of pressurizing substance from a second opening formed in the movable member when the supplying means supplies the first flow of pres-2~ surizing substance to the first opening formed in the movablemember. The apparatus also includes means for controlling the supplying means and the releasing means. The controlling means ~ 3 6~
includes means for generating a coded sequence o~ control signals.
In one aspect of the present invention, there is provided an apparatus ~or converting pressure into limited motion, comprising- a movable member responsive to pressure;
and means for supplying a first flow of pressurizing substance to a selected one of a plurality of selectable areas on said movable member until said movable member is moved a predeter-mined distance.
In a further aspect of the present invention, there is provided an apparatus for converting pressure into motion, comprising: a movable member having receiving means for re-ceiving a pressurizing substance; control means for generating a sequence of control signals; and supplying means, responsive to said control means, for supplying the pressurizing substance to the receiving means of said movable member so that said mov-able member is moved a predetermined distance in a number of predetermined increments.
In a further aspect of the pres~nt invention, there is provided an apparatus for converting pressure, exerted by a pressurizing substance from a pressure source, into motion, comprising: a housing having a plurality of ports formed therein, control means for selectably connecting the pressure source to one of the ports and for selectably connecting a pressure sink to another of the ports; and a movable member, having a plurality of openings formed therein, movably disposed within said housing so that a first one of the openings regist-ers with one of the ports of said housing for communicating a first flow of the pressuring substance from the pressure source to said movable member through the first opening when said con-trol means connects the pressure source to that port register-ing with the first opening and so that a second one of the openings registers with another of the 1~2~6~
ports of said housing for communicating a second flow of thepressurizing substance from said movable member to the pressure sink through the sêcond opening when said control means con-nects the pressure sink to that port registering with the sec-ond opening, whereby said movable member is caused to move with respect to said housing.
In a further aspect of the present invention, there is provided a linear actuator, comprising: a housing having a cylindrical wall in which 2n ports are formed, where n is an interger greater than 1; a piston movably disposed within said housing, said piston includingo a first chamber extending from a first closed end of said piston to a first open end thereof, a second cham~er extending from a second closed end of said piston to a second open end of said piston: a first row of apertures formed along a first portion of said piston in com-munication with said first chamber; and a second row of aper-tures formed along a second portion of said piston in communi-cation with said second chamber, valve means for connecting a first flow of pressurizing substance from a pressure source to one of the ports and for connecting a second flow of pressur-izing substance from another of the ports to a pressure sink, and means for operating said valve means so that the first flow of pressurizing substance is directed to one of the ports in register with one of the apertures of one of said first or second rows of apertures and so that the second flow of pres-surizing substance is received from another of the ports in register with one of the apertures of the other of said first or second rows of apertures.
In a ~urther aspect of the present invention, there is provided a method of converting pressure to motion in in-cremental steps, comprising the steps of: supplying a first flow of pressurizing substance through consecutive ones of a : -5a-1 ~ 62~6~
plurality of ports to a first opening in a movable member, and releasing a second flow of pressurlzing substance through different consecutive ones of the plurality of ports from a second opening in the movable member.
In a further aspect of the present invention, there is provlded an apparatus for converting pressure, exerted by a pressurlzing substance between a pressure sourae and a pressure sink, into increments of displacement, each i.ncrement having a length S, said apparatus comprising, a housing including a wall having four grooves defined in spaced relationship to each other on an interior surface of said wall and said wall further having four holes defined therethrough so that each hole extends from a respective one of the grooves to an exterior surface of said wall, said grooves and holes thereby defining four ports of said housing, each of said grooves being 0.5S
wide and being spaced from each adjacent groove on centers spaced l.OS, and a double-acting piston disposed for movement in said housing in response to the pressurizing substance, said piston including, a side wall having an inner surface and an outer surface and further having a first plurality of apertures and a second plurality of apertures defined in said side wall so that each of said apertures extends from the inner sur-face to the outer surface, each of said apertures having a dia-meter of 1.5S with each aperture of sai.d first plurality of apertures being spaced on a center separated a distance of 4.0S
from a center of each adjacent aperture of said first plurality of apertures and with each aperture of said second plurality of apertures being spaced on a center Separated a distance of 4.0S from a center of each adjacent aperture of said second plurality of apertures, said first plurality of apertures in-cluding a first aperture and a second aperture and said second plurality of apertures including a third aperture, wherein, said -5b-1 ~2~L6~
third aperture is defined in said side wall so that said third aperture registers with a first one of said ports ~hen said first aperture registers with a second one of said ports and further so that said third aperture registers with said second one of said ports when said first aperture overshoots in a first direction said second one of said ports, and said second aperture is defined in said side wall so that said second aperture registers with said first one of said ports when said first aperture overshoots in said first direction said second one of said ports, said first, second and third apertures thereby providing feedback means for precisely positioning said piston relative to said housing; a first end wall closing a first portion of a first end of said side wall and leaving a second portion of said irst end open, a second end wall closing a first portion of a second end of said side wall and leaving a second portion of said second end open, and a central wall extending from said first end wall to said second end wall and from a first region of the inner surface of said side wall to a second region of the inner surface of said side wall so that a first chamber extending from the first end wall to the open portion of the second end of said side wall and a second chamber extending from said second end wall to the open portion of the first end of said side wall are formed, wherein said first plurality of apertures communicates with said first chamber and wherein said second plurality of apertures communicates with said second chamber.
From the foregoing it is a general object of the present invention to provide a novel and improved hydraulic digital stepper actuator. Other and further objects, features and advantages of the present invention will be readily appa-rent to those skilled in the art when the following descrip--5c-~7 ;`
2 ~ ~ 1 tion of the preferred embodiments is read in conjunction with the accompanying drawings.
FIG. 1 is a sectional view of a specific embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line 2-2 shown in FIG. 1.
FIG. 3 is a schematic illustration of a preferred embodiment of the present invention showing the movable member in a first position.
FIG. 4 is a schematic illustration of a preferred embodiment of the present invention showing the movable member in a second position.
FIG. 5 is à schematic diagram of a first preferred embodiment of the valve means of the present invention.
FIG. 6 is a schematic illustration of a second pre-ferred embodiment of the valve means of the present invention.
FIG. 7 is a schematic illustration of another embodi-ment of the present invention.
-5~--2~1 With reference to the drawings an apparatus for converting pressure into motion, and particu~arly into limited motion, con-structed in accordance with the present invention will be de-scribed. In FIG. 3 the apparatus, generally indicated by the reference numeral 2, includes aihousing 4 and a movable member 6 movably disposed within the housing 4. Connected to the housing 4 is a control means 8 for controlling the flow of a pressurizing substance (such as an incompressible hydraulic material or any other suitable substance) from a pressure source (such as a tank and pump system) to the housing 4 and the movable member 6 and from the housing 4 and movable member 6 to a pressure sink (such as the tank or a sump). Embodiments of the control means are shown in FI~S. 5-7.
The housing 4 includes a wall 10 which preferably has a cyl-`5 indrical shape and further includes a first closed end 11 and asecond closed end 12. Tlle wall 10 has an interior surface 13 and an exterior surface 14.
The housing 4 also includes pressurizIng substance channeling means 16 disposed in the wall 10 thereof. The channellng means 16 directs the pressurizing substance from -the pressure source to the movable member 6 as subsequently described. The channeling means 16 also directs the pressurizing fluid from the movable member 6 to t}~e pressure sink also as subsequently described. The channeling means 16 also directs the pressurizing fluid from the movable ~5 member 6 to the pressure sink also as subsequently described. In FIG. 3 the channeling means 16 is shown to par-ticularly include a plurality of ports 18. In the embodiment shown in the figures there are four ports identified by the letters ~, X, Y and Z. The ports are defined by a plurality of grooves 20 formed in spaced relationship to each other on the interior surface 13 of the wall 10 and by a plurality of holes 22 formed through the ~"all 10 so that each hole extends from a respective one of the grooves 20 to the exterior surface 14 of the wall 10.
This porting system provides means for supplying a flrst flow of the pressurizing substance to a selected one of a plurality of selectable areas on the movable member 6 until the movable member has moved a predetermined distance in a number of predetermined increments in relation to the housing 4 within wilich the mouable member 6 is movably disposed.
The movable member 6 is shown in FIG. 3 to include a double-acting piston 24 movably disposed within the housing 4 for sliding engagement along the interior surface 13. The piston 24 includes a side wall 26 having an inner surface 28 and an outer surface 30.
The piston 24 also includes a first end wall 32 closing a first portio~
of a first end of the side wall 26 but leaving a second portion of the first end open. The piston 24 further includes a second end wall 34 closing a first portion of a second end of -the side wall 26 but leavlng a second portion of the second end open. Additionall~, the piston 24 includes a central wall. 36 e~tending from the first end ~all 32 to the second end wall 34 and from a firs-t region of the inner surface 28 of the side wall 26 to a second region of the inner surface 28 of the side wall 26 so that a first chamber 38 extending fro ~ ~ 62~ ~
the first end wall 32 to the open portion of the second end of the side wall 26 and a second chamber 40 extending from the second end wall 34 to the open portion of the flrst end of the side wall 26 are formed. Connected to the first end wall 32 is a connecting rod 42 which extends through a bore in the first closed end ll of the housing 4 for engaging the workpiece to be incrementally positioned by the present invention.
~ he movable member 6, which is responsive to pressure, includes receiving means for receiving the pressurizing substance from the pressure source. The receiving means includes the plura]ity of selectable areas to which the supplying means directs the first flow of pressuri~ing substance for moving the movable member 6 with respect to the housing. As shown in FIG~ 3 these areas include a first opening 44 and a second opening 46. Other openings 48, 50, 52, 54, 56 and 58 are shown in FIG. 3 to be included within the movable member 6, and more particularly, the first, second and remaining openings 44-58 include a-first plurality of apertures extending from the outer surface 30 of the side wall 26 to the inner surface 28 thereof for communicating with the first chamber 38 and a second plurality of apertures extending from the outer surface 30 of the side wall 26 to the inner surface 28 thereof for communicating ~lth the second chamber 40. In FIG. 3, the apertures 44 and 48-52 constitute the first plurality, and the apertures 46 and 54-58 constitute the second plurality. Each aperture of the first plurality of apertures is equidistantly spaced from each adjacen-t one of the ... ... . . . . .. _ _ _ 1 ~ 62~6 ~
first plurallty of apertures, and each aperture of the second plurality of apertures is centered on a line perpendicularly bisecting a line extending between the centers of a respective set of two adjacent apertures of the first plurality of apertures.
In the embodiment shown in the drawings the first plurality of apertures is positioned on the side wall 26 of the movable member 6 diametrically opposite the second plurality of apertures. Also as shown in the drawings, the first plurality of aperturés is disposed in a row along a first portion of the piston 24 in communication with the first chamber 38, and the second pLurality of apertures is aligned in a row along a second portion of the piston 24 in Fommunication with the second chamber 40.
The openings 44-58 formed in the movable member 6 and the ports 18 of the housing 4 provide means for releasing a second flow~of the pressurizing substance from an opening communicating with one of the :
chambers 28 or 40 when the supplying means supplies the~first flow of pressurizing substance to another opening communicating with the other of the two chambers.
The movable member 6 and the housing 4~are positioned with re-spect to each other whereby the ports 18 of the channeling means of the housing 4 are disposed adjacent the movable member 6 for sequent-ially .registering with the openings 44-58 formed in the movable member 6, such as the first opening 44 and the second opening ~5 46 as shown in FIG. 3, as the movable member 6 is incrementally moved so that the pressurizing substance can be supplied through the channeling means to one of the registering openings to thereby move the movable memeber 6 in either of the two directions long-_g _ ~ 1 62~
itudinally through the housing 4. More particularly, the movablemember 6 is disposed within the housing 4 so that a firs-t one of the openings registers with one of the ports of the housing 4 for communicating the first flow of pressurizing substance from the pressure source to the movable member 6 through the first opening when the pressure source is connected to that port registering with the first opening and so that a second one of the openings registers with another of the ports of the housing 4 for communica-ting the second flow of the pressurizing substance from the movable member 6 to the pressure sink through the second opening when the pressure sink is connected to that port registerlng with the second opening.
By controlling the ports through which the~first and second~flows are directed, the movable member 6 is caused to~move with respect to the housing 4.~ ~
The control of the communication of -the first and second flows of pressurizing substance with the ports and openings is~achieved by means of the control means 8. Generally, the control~means 8 provi.des means for controlling the supplying means and~the releasing means whereby the first and second flows of pressurizing substance are appropriately dlrected to and from the housing 4 and movable ~0 member 6. With reference to FIGS. 5-7 preferred embodiments Oe the control means 8 will be described.
FIG. 5 schematically illustrates that the control means 8 lnclude conduit means 60 for connecting the ports 18 of the housing 4 to the pressure source and the pressure sink. 'rhe conduit means 60 includes a plurallty of ducts schematically illustrated by numbered lines 62, 64, 66 and 68. Each duct is associated with a respective one of the ports as indicated hy the labeling of the ducts with a letter cor-responding to its respective poxt shown in FIGURES 3 and 4.
Connected within the conduit means 60 is a valve means 70 for .
l l 6~61 appropriately connecting respective ones of the ducts 62-68 within the condult means 60 to either the source or the sink of pressurizing substance or to a blocking means as subsequently discussed. The valve means 70 is used to connect a first flow of pressurlzing substance from the pressure source to one of the ports 18 and to connect a second flow of pressurizing substance from another of the ports 18 to the pressure sink. As shown in the FIG. 5 embodiment the valve means 70 includes four interconnected two-position valves .
72, 74, 76 and 78 having respective solenoid-operated valve ; lO elements ~ositioned therein. The solenoids of the valves shown in FIG. 5 are controlled by ~Ycitation signals generated by~a control signal generator 80. More particularly, the valves 72-7;8 and ducts 62-68 of the FIG. 5 embodiment are interconnected so that the valves are responsive to two-diglt Gray~Code excitatlon ~signa~ls for~ ~
sequentially connecting each port within ~a respective set of two ports of the portsl~ oarespective~one~ of the p;ressure~source, the pressure sink, or the blocking means.;
The control signal generator 80 provi~des;means for generating ~
a coded sequence of control signals,~such as a sequence of~two-digit :
~ Gray Code excitation signals or a sequence of four-variable excitation signals,as subsequently described or any~;o~th~er sequence of ex~
citation signals. Through the creati~on of such~control signals -the control signal generator 80 provides means for operat1ng the~valve means 70 in a predetermined sequence so -that the pressure source, thè pressure sink, and the blocking;means are~sequentiaIly communicat~ed ~ith respective ones of the ports 18 which are registered~wi~th respective ones of the openings 44-58 of the movable~member~6 ::
;
1 162~
whereby the movable member 6 moves in incremental steps. In other ~ords, the control signal generator 80 provides means ~or operating the valve means 70 so that the first flow of pressurizing substance is directed to one of the por-ts in register with one of the apertures of one of the first or second rows of apertures and so that the second flow of pressuring substance is received from another of the ports in register with one of the apertures of the other of the first or second rows of apertures. Speciflcally, the control signal generator 80 preferrably is a mlc;rocomputer or other apparatus for providing digital output signals.
The embodiment of the control means 8 shown in FIG. 6 includes two three-position valves 82 and 84 responsive to;four-variab~le excit-ation signals which are generated by the control~signal g;enerator 80 ;
;~ associated therewith for sequentlally connectlng each port within a respective set of two~ports of~the ports~18 to a~respective~ one of~
the~pressure~source, the pressure ~sink, or the blocking means.~ ~
FIG. 7 shows that the control means~8 further lncludes emergency actuation valve means 86 having a pressurizing substance~
conducting duct connected to each end of~the housing 4 90 ~ that the ~0 piston can be rapidly moved in either;directlon to qulckly extend or retract the connecting rod 42 connected thereto.~
FIGS. 1 and 2 disclose a specific embod.lment of the present invention containing various ones of the elements previously discussed.
More particularly, the apparatus includes a first housing~section 88 ~5 having a first closed end 90 and a second housing sectlon 92~having a second closed end 94 through which a connecting rod 96;is slidably disposed. The connecting rod 96 is connec-ted to a piston 98 contained within the cylinder defined by the first and second housing sections 88 and 92. The first and second housing sections 88 and 92 are joined by a housing coupling sleeve 100 in which are formed ports 102 for conducting the pressurizing substance to and from 1~2461 respective ones of a plurality of apertures 104 formed in the piston 98. FIG. 1 further shows several O-rings 106, 108, 110, 112, 114, 116, 118, 120 and 122 positioned for effecting fluid-tight seals between the joined elements of the apparatus shown therein.
The apparatus disclosed in FIG. 1 further includes a coupling collar 124 by ~"hich a control means, including appropriate valve means, conduit means, and signal generator means, are connected to the assembled housing sections 88 and 92 and coupling sleeve 100.
FIG. 2 discloses that a first chamber 126 and a second chamber 128 ormed within the piston 98 have circular cross-sections. ~IG.
2 further discloses a groove 130 of one of the ports 102 formed in the housing coupling sleeve 100.
As will be apparent upon an examinatlon of the structure shown in FIG. 1, as the pressurizing substance lS directed into~
one of the chambers 126 or 128 through one of the apertures;104 formed in the piston 98 and~through the appropriate one of;the ports 102 formed in the housing coupling sle~eve lOO and the pressurizing substance from the other of the chambers 126 and 128 is released through the appropriately allgned aperture and port, the piston 98 will move longitudlnally through the~cylinder defined by the housing assembly to thereby incrementally move the connecting rod 96 and the workpiece connected thereto. ~This operation will be more specifically descrlbed with reference to FIGURES 3-6.
~efore the operation is more specifically described, hcwever, the preferred dimensional relationships among the various elements will be considered. For the embodiments disclosed in -13- ~
~ 3 62~6~
FIGURES 3-6, the desired length of each increment by which the piston 24 and the connecting rod 42 are to be moved is designated as a distance S. For e~ample, S might equal one-sixteenth inch. With a step size of S, each of the apertures 44-58 formed in the piston 24 has a diameter 1.5S and the apertures are spaced on centers separated a distance of 4S. With such a center spacing, this makes ; the width of the portion of the side wall 26 between each adjacent aperture have a length of 2.5S. With the apertures and separating portions having these proportions, each aperture communicating with one of the chambers is to be positioned exactly ~in the middle of a respective set of two apertures communlcating with the other chamber.
, The four ports W, X, Y and Z are centered between~the~ends 11 and 12 of the cylinder define~by the houslng 4. ~Each of the grooves 20 defining a portion of each~port~is 0.5S wide, and adjacent grooves are spaced on l.OS centers. That is, the portion of the housing 4 separating each o~ the grooves~20 is~0.5S~wide. ;~
By using the valve means disclosed in FIGS~ 5 an~d~6,;or another suitable valve means, each of the ports 18 can be connected ::
to the pressure source, the pressure sink, or the blocking means.
The bloc~ing means is provided by merely plugging, capping, or other-::
wi~e closing the approPriate end of the~respective duct to be blocked.
Whether a particular port is connected to the pressure~source, -the pressure sink or a blocking means is determined by the positioning of ths particular valve~s as controllsd by~the~control signal generator 30 and the excitation siqnals generated thereby.
:
I l ~2~61 The.operation of the apparatus can be explained b~t the following steps. Initially, it will be assumed that the piston 24 is located with the opening or aperture 44 in register with port Y as shown in FIG. 3. To move piston 24 to the right, port Y must be connected to the pressure source so that a fi.rst flow of the pressurizing sub-stance will be permitted to enter into the first chamber 38 through the first aperture ~4 whereby the substance acts through the first chamber 38 and against the second closed end 12 of the housing 4.
Simultaneously, the port W must be connected to the pressure sink so that pressurizing substance contained wlthin the~second chamber 40 can be released in a second flow through the second opening 46 and port W into the pressure sink or tank. Ports X and Z should be blocked at this time so that no pressurizing substance flo~.~s therethrough. This connection of the valves 72 78 to the port~s W, X, Y and Z~moves~the ~
piston 24 to the right until the trailing edge of the first opening 44 passes the port Y thereby shutting off the first flow of pressurizing sù~bstance therethrough. This places the piston 24 in the position relative to the ports 18 shown ln FIG. 4.
In FIG. 4 it is to be noted that should the piston 24 ~0 overshoot the port Y prior to stopping, the first flow~of pressuri.zing substance through port Y will enter the second chamber 40 through the second aperture 46 and the second flow of pressurlzing substance will come from the first chamber 38 through the~aperture~50 adjacent port W. Therefore, the piston is moved to the left:to compensate for the overshoot. This provides pressurized feedback to pre-cisely position the piston 24 and thereby move the piston 24 and associated connecting rod 42 only the desired incremen-t. This precise posltioning permits each increment to be repeatably obtained.
, -1 :~ 62~6~
Further movement of the piston 24 to the right can be achieved by next pressurizing (i.e., connecting the pressure SO~ thereto) port Z while tanking ti-e-, connecting the pressure sink thereto) port X. Ports W and Y should be blocked during this movement.
~ urther movement is effected by pressurizing port W, tanking port Y and blocking ports X and %. The fourth step is achieved by pressurizlng port X, tanking port Z and blocking the other two ports.
By cyclically performing these steps in thls order moves the piston 24 to the right, whereas performing the cycle in the reverse order moves the piston 24 to the left. That is, to move the piston 24 to the left, the pressure source must be co~munlcated with~re-spective ones of the apertures 46, 54, 56 and 58 and the second chamber 40, and the pressure sink must be commanicated with respe_tive ones of the apertures 44, 48, 50 and 52 and the first chamber 40.
It is apparent that the distance which the piston 24 moves ln each increment is the distance across a single port and a single separating portion of the housing 4. Based~on the previous dimensions, this gives the desired incremental step size of S. The sDeed at which the movement is effected depends upon the speed at which the excitation signals are generated and applied to the valve means to thereby change the different connections among the pressure source, pressure sink, blocking means and ports.
As previously discussed, the pressure feedback prevents over-; shoot. Also preventing overshoot is the relationship between the ports 18 and apertures 44-58 whereby the aperture through wllich the pressurizing substance is being inpu-t graduallY closes the pressurizing port to ~hereby cause deceleration of the piston 24 1 ~ 62~L61 as it is moved within the housing 4.
As mentioned above the actuation of the apparatus ls controlled by a cyclical sequence of excitation signals generated by the control signal generator means 80 for operating the valves in the valve means to establish different ducting connections to the various ports. Preferrably these signals are digltal signals representing either a first state or a second state. For the four-port device disclosed in the drawings, each cycle consists of four steps involving the application of the pressure source and the pressure sink to four different two-port combinations. To distinguish each of these four steps, at least two excitatlon signals are required as represented,for example, by the letters A and B in FIG. 5. By using these two signals four different combinations of control signals can be gene~rated to opera-te the valves so that four different ducting combinations between the pressure source, pressure sink and blocking means and the ports W, X, Y and Z can be effected. By arranging the sequence of the four combinations in the Reflective Binary Code (also known as the Gray Code), a truth table as follows can be established:
PORT EXCITATION SIGNAL
W X Y Z A B
M P M T O
T M P M
In the preceding table P represents that the respective port is 1 ~ 6~6~
to be connected to the pressure source, T indicates that the respective port is to be connected to the pressure sink and M designates those ports to be connected to the blocking means.
From this table the following logic expressions are derived:
W = P A'B' + T A B + M [ A ~ B]
X = P A' B + T A B'+ M I A ~ B]
Y = P A B + T A' B' + M [ A ~ B]
Z = P A B' + T A' B + M [ A ~ B]
Where "~" and "-" designate EXCLUSIVE OR and COINCIDENCE
functions r respectively.
Solving for P and T yields:
P = W A' B' + X A' B + Y A B + Z A B' T = W A B + X A B' + Y A' B'~+ Z A' B
These last two expressions are implemented by means of the four-valve circuit shown in FIG. 5 to appropriately control the~
.
present invention.~
~ Other excitation schemes can also be~derived. For example, the four-variable excitation àpproach shown ln the followlng~
truth table can be used~
PORT EXCITATION SIGNA~L
W X Y Z C D: E F
.
25 p M T ~M ~ 1 0 0 T M P M : 0 : 0 1 0 -18-:
~ J ~246~
Assuming that the actuating signals c.annot occur -together, expressions for W, X, Y and Z are developed as follows:
W - P C + T E ~ M [D + F]
X = P D + T F + M [C + E]
Y = P E + T C + M [D + F]
Z = P F + T D + M [C + E]
These expressions are shown implemented~with the two blocked-centered, double-solenoid valves 82 and 84 shown in FIG. 6.
It is to be noted that although the preferred embodiment 5hown in the drawings includes four ports, any 2n, n being an:
integer greater than l, number of ports may be ùsed. Increasing the number of ports increases the~resolution with whlch the movable member 6 can be mo~ed, but also causes the~manufacturing and mach-ining of the apparàtus to be more difficult. When 2n ports;are used and binary control signals and two-position~valves~are used,~
the operating means includes means for generating at 1east~n-dlgit , ~
: excitation signals, such as an :n-digit Gray Code~, and the valve means includes 2n interconnected two-positlon valves~which are responsive to the n-digit excitation signals. Other typ~es ?O oE operating means and valve means can be used for dlfferent types ; of control signals and valves.
Thus the present invention of a hydraulic digital stepper àctuator is well adapted to carry out the objects and attain the ends and advantages mentioned~above as well as thosè:inherent therein. While preferred embodiments of the inv~ention have been .
.
described for the purpose of this disclosure, numerous changes in the construction and arrangement of parts can be made by those skilled in the art, which changes are encompassed with-in the spirit of this invention as defined by the appended claims.
' :: : ` : :
~' ' ;: : :
:: : :
;: ; : ~ ;
~: ~
, O - :
.
' . ~
Claims (11)
1. An apparatus for converting pressure, exerted by a pressurizing substance between a pressure source and a pressure sink, into increments of displacement, each increment having a length S, said apparatus comprising:
a housing including a wall having four grooves de-fined in spaced relationship to each other on an interior sur-face of said wall and said wall further having four holes defined therethrough so that each hole extends from a res-pective one of the grooves to an exterior surface of said wall, said grooves and holes thereby defining four ports of said housing, each of said grooves being 0.5S wide and being spaced from each adjacent groove on centers spaced 1.OS, and a double-acting piston disposed for movement in said housing in response to the pressurizing substance, said piston including:
a side wall having an inner surface and an outer surface and further having a first plurality of apertures and a second plurality of apertures defined in said side wall so that each of said apertures extends from the inner surface to the outer surface, each of said apertures having a diameter of 1.5S with each apertùre of said first plurality of apertures being spaced on a center separated a distance of 4.0S from a center of each adjacent aperture of said first plurality of apertures and with each aperture of said second plurality of apertures being spaced on a center separated a distance of 4.0S from a center of each adjacent aperture of said second plurality of apertures, said first plurality of apertures including a first aperture and a second aperture and said second plurality of apertures including a third aperture, wherein: said third aperture is defined in said side wall so that said third aperture registers with a first one of said ports when said first aperture registers with a second one of said ports and further so that said third aperture registers with said second one of said ports when said first aperture overshoots in a first direction said second one of said ports, and said second aperture is defined in said side wall so that said second aperture registers with said first one of said ports when said first aperture overshoots in said first direction said second one of said ports, said first, second and third apertures thereby providing feedback means for precisely positioning said piston relative to said housing;
a first end wall closing a first portion of a first end of said side wall and leaving a second portion of said of said first end open;
a second end wall closing a first portion of a second end of said side wall and leaving a second portion of said second end open; and a central wall extending from said first end wall to said second end wall and from a first region of the inner surface of said side wall to a second region of the inner surface of said side wall so that a first chamber extending from the first end wall to the open portion of the second end of said side wall and a second chamber extending from said second end wall to the open portion of the first end of said side wall are formed, wherein said first plurality of apertures communicates with said first chamber and wherein said second plurality of apertures communicates with said second chamber.
a housing including a wall having four grooves de-fined in spaced relationship to each other on an interior sur-face of said wall and said wall further having four holes defined therethrough so that each hole extends from a res-pective one of the grooves to an exterior surface of said wall, said grooves and holes thereby defining four ports of said housing, each of said grooves being 0.5S wide and being spaced from each adjacent groove on centers spaced 1.OS, and a double-acting piston disposed for movement in said housing in response to the pressurizing substance, said piston including:
a side wall having an inner surface and an outer surface and further having a first plurality of apertures and a second plurality of apertures defined in said side wall so that each of said apertures extends from the inner surface to the outer surface, each of said apertures having a diameter of 1.5S with each apertùre of said first plurality of apertures being spaced on a center separated a distance of 4.0S from a center of each adjacent aperture of said first plurality of apertures and with each aperture of said second plurality of apertures being spaced on a center separated a distance of 4.0S from a center of each adjacent aperture of said second plurality of apertures, said first plurality of apertures including a first aperture and a second aperture and said second plurality of apertures including a third aperture, wherein: said third aperture is defined in said side wall so that said third aperture registers with a first one of said ports when said first aperture registers with a second one of said ports and further so that said third aperture registers with said second one of said ports when said first aperture overshoots in a first direction said second one of said ports, and said second aperture is defined in said side wall so that said second aperture registers with said first one of said ports when said first aperture overshoots in said first direction said second one of said ports, said first, second and third apertures thereby providing feedback means for precisely positioning said piston relative to said housing;
a first end wall closing a first portion of a first end of said side wall and leaving a second portion of said of said first end open;
a second end wall closing a first portion of a second end of said side wall and leaving a second portion of said second end open; and a central wall extending from said first end wall to said second end wall and from a first region of the inner surface of said side wall to a second region of the inner surface of said side wall so that a first chamber extending from the first end wall to the open portion of the second end of said side wall and a second chamber extending from said second end wall to the open portion of the first end of said side wall are formed, wherein said first plurality of apertures communicates with said first chamber and wherein said second plurality of apertures communicates with said second chamber.
2. An apparatus as defined in claim 1, wherein:
said first plurality of apertures is disposed in a row along a first portion of said side wall;
said second plurality of apertures is disposed in a row along a second portion of said side wall; and each aperture of said second plurality of apertures has its center on a line perpendicularly bisecting a line extending between the centers of a respective set of two adjacent apertures of said first plurality of apertures so that said third aperture is disposed between said first and second apertures but spaced circumferentially therefrom.
said first plurality of apertures is disposed in a row along a first portion of said side wall;
said second plurality of apertures is disposed in a row along a second portion of said side wall; and each aperture of said second plurality of apertures has its center on a line perpendicularly bisecting a line extending between the centers of a respective set of two adjacent apertures of said first plurality of apertures so that said third aperture is disposed between said first and second apertures but spaced circumferentially therefrom.
3. An apparatus as defined in claim 2, wherein said housing includes:
a first housing section having a first closed end and a first open end;
a second housing section having a second closed end and a second open end; and a housing coupling sleeve for coupling said first and second housing sections so that said first and second open ends are directed towards each other for permitting said piston to move therebetween, said housing coupling sleeve in-cluding said wall having said ports defined therethrough.
a first housing section having a first closed end and a first open end;
a second housing section having a second closed end and a second open end; and a housing coupling sleeve for coupling said first and second housing sections so that said first and second open ends are directed towards each other for permitting said piston to move therebetween, said housing coupling sleeve in-cluding said wall having said ports defined therethrough.
4. An apparatus as defined in claim 3, further comprising a coupling collar associated with said housing coupling sleeve for connecting said ports with the pressure source and the pressure sink.
5. An apparatus as defined in claim 4, wherein:
said holes which in part define said four ports are spaced circumferentially from each other around said housing coupling sleeve; and said coupling collar includes four passageways spaced circumferentially from each other so that each of said four passageways communicates with a respective one of said holes.
said holes which in part define said four ports are spaced circumferentially from each other around said housing coupling sleeve; and said coupling collar includes four passageways spaced circumferentially from each other so that each of said four passageways communicates with a respective one of said holes.
6. An apparatus as defined in claim 1, wherein said housing includes:
a first housing section having a first closed end and a first open end;
a second housing section having a second closed end and a second open end; and a housing coupling sleeve for coupling said first and second housing sections so that said first and second open ends are directed towards each other for permitting said piston to move therebetween, said housing coupling sleeve including said wall having said ports defined there-through.
a first housing section having a first closed end and a first open end;
a second housing section having a second closed end and a second open end; and a housing coupling sleeve for coupling said first and second housing sections so that said first and second open ends are directed towards each other for permitting said piston to move therebetween, said housing coupling sleeve including said wall having said ports defined there-through.
7. An apparatus as defined in claim 6, further comprising a coupling collar associated with said housing coupling sleeve for connecting said ports with the pressure source and the pressure sink.
8. An apparatus as defined in claim 7, wherein:
said holes which in part define said four ports are spaced circumferentially from each other around said housing coupling sleeve; and said coupling collar includes four passageways spaced circumferentially from each other so that each of said four passageways communicates with a respective one of said holes.
said holes which in part define said four ports are spaced circumferentially from each other around said housing coupling sleeve; and said coupling collar includes four passageways spaced circumferentially from each other so that each of said four passageways communicates with a respective one of said holes.
9. The apparatus of claim 1 further including:
valve means for correcting a first flow of said pressurizing substance from said pressure source to one of said ports and for connecting a second flow of said pres-surizing substance from another of said ports to said pres-sure sink; and means for operating said valve means so that the first flow of pressurizing substance is directed to one of said ports in register with one of said first or second pluralities of apertures and so that the second flow of pressurizing substance is reviewed from another of said ports in register with one of the apertures of the other of said first or second pluralities of apertures.
valve means for correcting a first flow of said pressurizing substance from said pressure source to one of said ports and for connecting a second flow of said pres-surizing substance from another of said ports to said pres-sure sink; and means for operating said valve means so that the first flow of pressurizing substance is directed to one of said ports in register with one of said first or second pluralities of apertures and so that the second flow of pressurizing substance is reviewed from another of said ports in register with one of the apertures of the other of said first or second pluralities of apertures.
10. A linear actuator as defined in claim 9 , wherein:
said operating means includes means for generating a sequence of n-digit Gray Code excitation signals; and said valve means includes 2n interconnected two-position valves responsive to the n-digit Gray Code excitation signals for sequentially connecting each port of respective sets of two ports to a respective one of the pressure source and the pressure sink.
said operating means includes means for generating a sequence of n-digit Gray Code excitation signals; and said valve means includes 2n interconnected two-position valves responsive to the n-digit Gray Code excitation signals for sequentially connecting each port of respective sets of two ports to a respective one of the pressure source and the pressure sink.
11. A linear actuator as defined in claim 10, wherein:
said operating means includes means for generating a sequence of four-variable excitation signals; and said valve means includes two three-position valves responsive to the four-variable excitation signals for sequentially connecting each port of respective sets of two ports to a respective one of the pressure source and the pressure sink.
said operating means includes means for generating a sequence of four-variable excitation signals; and said valve means includes two three-position valves responsive to the four-variable excitation signals for sequentially connecting each port of respective sets of two ports to a respective one of the pressure source and the pressure sink.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US140,126 | 1980-04-14 | ||
| US06/140,126 US4434704A (en) | 1980-04-14 | 1980-04-14 | Hydraulic digital stepper actuator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1162461A true CA1162461A (en) | 1984-02-21 |
Family
ID=22489869
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000365585A Expired CA1162461A (en) | 1980-04-14 | 1980-11-27 | Hydraulic digital stepper actuator |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4434704A (en) |
| CA (1) | CA1162461A (en) |
Families Citing this family (71)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19617927A1 (en) * | 1996-05-05 | 1997-11-13 | Rudolf Kohlert | Support element for fragile workpieces on machine tools |
| US6833242B2 (en) * | 1997-09-23 | 2004-12-21 | California Institute Of Technology | Methods for detecting and sorting polynucleotides based on size |
| US7214298B2 (en) * | 1997-09-23 | 2007-05-08 | California Institute Of Technology | Microfabricated cell sorter |
| US7214540B2 (en) * | 1999-04-06 | 2007-05-08 | Uab Research Foundation | Method for screening crystallization conditions in solution crystal growth |
| DE60034033T2 (en) * | 1999-04-06 | 2007-12-06 | University of Alabama, Birmingham Research Foundation, Birmingham | DEVICE FOR SCREENING CRYSTALLIZATION CONDITIONS IN SOLUTIONS FOR CRYSTAL BREEDING |
| US20020164812A1 (en) * | 1999-04-06 | 2002-11-07 | Uab Research Foundation | Method for screening crystallization conditions in solution crystal growth |
| US7244396B2 (en) * | 1999-04-06 | 2007-07-17 | Uab Research Foundation | Method for preparation of microarrays for screening of crystal growth conditions |
| US7247490B2 (en) * | 1999-04-06 | 2007-07-24 | Uab Research Foundation | Method for screening crystallization conditions in solution crystal growth |
| US7250305B2 (en) * | 2001-07-30 | 2007-07-31 | Uab Research Foundation | Use of dye to distinguish salt and protein crystals under microcrystallization conditions |
| US8052792B2 (en) * | 2001-04-06 | 2011-11-08 | California Institute Of Technology | Microfluidic protein crystallography techniques |
| US6899137B2 (en) * | 1999-06-28 | 2005-05-31 | California Institute Of Technology | Microfabricated elastomeric valve and pump systems |
| US7217321B2 (en) * | 2001-04-06 | 2007-05-15 | California Institute Of Technology | Microfluidic protein crystallography techniques |
| US7052545B2 (en) * | 2001-04-06 | 2006-05-30 | California Institute Of Technology | High throughput screening of crystallization of materials |
| US7459022B2 (en) * | 2001-04-06 | 2008-12-02 | California Institute Of Technology | Microfluidic protein crystallography |
| US7144616B1 (en) * | 1999-06-28 | 2006-12-05 | California Institute Of Technology | Microfabricated elastomeric valve and pump systems |
| US7244402B2 (en) * | 2001-04-06 | 2007-07-17 | California Institute Of Technology | Microfluidic protein crystallography |
| MXPA01012959A (en) * | 1999-06-28 | 2002-07-30 | California Inst Of Techn | Microfabricated elastomeric valve and pump systems. |
| US7195670B2 (en) * | 2000-06-27 | 2007-03-27 | California Institute Of Technology | High throughput screening of crystallization of materials |
| US8709153B2 (en) | 1999-06-28 | 2014-04-29 | California Institute Of Technology | Microfludic protein crystallography techniques |
| US20080277007A1 (en) * | 1999-06-28 | 2008-11-13 | California Institute Of Technology | Microfabricated elastomeric valve and pump systems |
| US6929030B2 (en) * | 1999-06-28 | 2005-08-16 | California Institute Of Technology | Microfabricated elastomeric valve and pump systems |
| US7306672B2 (en) | 2001-04-06 | 2007-12-11 | California Institute Of Technology | Microfluidic free interface diffusion techniques |
| US8550119B2 (en) * | 1999-06-28 | 2013-10-08 | California Institute Of Technology | Microfabricated elastomeric valve and pump systems |
| AU2001240040A1 (en) * | 2000-03-03 | 2001-09-17 | California Institute Of Technology | Combinatorial array for nucleic acid analysis |
| US7867763B2 (en) | 2004-01-25 | 2011-01-11 | Fluidigm Corporation | Integrated chip carriers with thermocycler interfaces and methods of using the same |
| US20050118073A1 (en) * | 2003-11-26 | 2005-06-02 | Fluidigm Corporation | Devices and methods for holding microfluidic devices |
| US7351376B1 (en) * | 2000-06-05 | 2008-04-01 | California Institute Of Technology | Integrated active flux microfluidic devices and methods |
| WO2002000343A2 (en) * | 2000-06-27 | 2002-01-03 | Fluidigm Corporation | A microfluidic design automation method and system |
| EP1334347A1 (en) * | 2000-09-15 | 2003-08-13 | California Institute Of Technology | Microfabricated crossflow devices and methods |
| US7097809B2 (en) * | 2000-10-03 | 2006-08-29 | California Institute Of Technology | Combinatorial synthesis system |
| AU2002211389A1 (en) * | 2000-10-03 | 2002-04-15 | California Institute Of Technology | Microfluidic devices and methods of use |
| US7678547B2 (en) * | 2000-10-03 | 2010-03-16 | California Institute Of Technology | Velocity independent analyte characterization |
| EP1336097A4 (en) * | 2000-10-13 | 2006-02-01 | Fluidigm Corp | Microfluidic device based sample injection system for analytical devices |
| WO2002065005A1 (en) * | 2000-11-06 | 2002-08-22 | California Institute Of Technology | Electrostatic valves for microfluidic devices |
| AU2002248149A1 (en) * | 2000-11-16 | 2002-08-12 | Fluidigm Corporation | Microfluidic devices for introducing and dispensing fluids from microfluidic systems |
| WO2002040874A1 (en) | 2000-11-16 | 2002-05-23 | California Institute Of Technology | Apparatus and methods for conducting assays and high throughput screening |
| US20050196785A1 (en) * | 2001-03-05 | 2005-09-08 | California Institute Of Technology | Combinational array for nucleic acid analysis |
| US7670429B2 (en) * | 2001-04-05 | 2010-03-02 | The California Institute Of Technology | High throughput screening of crystallization of materials |
| US20020164816A1 (en) * | 2001-04-06 | 2002-11-07 | California Institute Of Technology | Microfluidic sample separation device |
| US6752922B2 (en) * | 2001-04-06 | 2004-06-22 | Fluidigm Corporation | Microfluidic chromatography |
| EP1384022A4 (en) * | 2001-04-06 | 2004-08-04 | California Inst Of Techn | Nucleic acid amplification utilizing microfluidic devices |
| EP2338670A1 (en) * | 2001-04-06 | 2011-06-29 | Fluidigm Corporation | Polymer surface modification |
| US20050149304A1 (en) * | 2001-06-27 | 2005-07-07 | Fluidigm Corporation | Object oriented microfluidic design method and system |
| US7075162B2 (en) * | 2001-08-30 | 2006-07-11 | Fluidigm Corporation | Electrostatic/electrostrictive actuation of elastomer structures using compliant electrodes |
| WO2003031066A1 (en) | 2001-10-11 | 2003-04-17 | California Institute Of Technology | Devices utilizing self-assembled gel and method of manufacture |
| US8440093B1 (en) | 2001-10-26 | 2013-05-14 | Fuidigm Corporation | Methods and devices for electronic and magnetic sensing of the contents of microfluidic flow channels |
| US7691333B2 (en) | 2001-11-30 | 2010-04-06 | Fluidigm Corporation | Microfluidic device and methods of using same |
| JP4355210B2 (en) * | 2001-11-30 | 2009-10-28 | フルイディグム コーポレイション | Microfluidic device and method of using microfluidic device |
| US7312085B2 (en) * | 2002-04-01 | 2007-12-25 | Fluidigm Corporation | Microfluidic particle-analysis systems |
| AU2003224817B2 (en) | 2002-04-01 | 2008-11-06 | Fluidigm Corporation | Microfluidic particle-analysis systems |
| US20070026528A1 (en) * | 2002-05-30 | 2007-02-01 | Delucas Lawrence J | Method for screening crystallization conditions in solution crystal growth |
| WO2004000721A2 (en) * | 2002-06-24 | 2003-12-31 | Fluidigm Corporation | Recirculating fluidic network and methods for using the same |
| AU2003256469A1 (en) * | 2002-07-10 | 2004-01-23 | Uab Research Foundation | Method for distinguishing between biomolecule and non-biomolecule crystals |
| US8220494B2 (en) * | 2002-09-25 | 2012-07-17 | California Institute Of Technology | Microfluidic large scale integration |
| EP2298448A3 (en) * | 2002-09-25 | 2012-05-30 | California Institute of Technology | Microfluidic large scale integration |
| WO2004040001A2 (en) | 2002-10-02 | 2004-05-13 | California Institute Of Technology | Microfluidic nucleic acid analysis |
| US7604965B2 (en) | 2003-04-03 | 2009-10-20 | Fluidigm Corporation | Thermal reaction device and method for using the same |
| US7476363B2 (en) * | 2003-04-03 | 2009-01-13 | Fluidigm Corporation | Microfluidic devices and methods of using same |
| US8828663B2 (en) * | 2005-03-18 | 2014-09-09 | Fluidigm Corporation | Thermal reaction device and method for using the same |
| JP5419248B2 (en) * | 2003-04-03 | 2014-02-19 | フルイディグム コーポレイション | Microfluidic device and method of use thereof |
| US20050145496A1 (en) * | 2003-04-03 | 2005-07-07 | Federico Goodsaid | Thermal reaction device and method for using the same |
| WO2004094020A2 (en) * | 2003-04-17 | 2004-11-04 | Fluidigm Corporation | Crystal growth devices and systems, and methods for using same |
| CA2526368A1 (en) | 2003-05-20 | 2004-12-02 | Fluidigm Corporation | Method and system for microfluidic device and imaging thereof |
| CA2532530A1 (en) * | 2003-07-28 | 2005-02-10 | Fluidigm Corporation | Image processing method and system for microfluidic devices |
| US7413712B2 (en) * | 2003-08-11 | 2008-08-19 | California Institute Of Technology | Microfluidic rotary flow reactor matrix |
| US7407799B2 (en) * | 2004-01-16 | 2008-08-05 | California Institute Of Technology | Microfluidic chemostat |
| AU2005208879B2 (en) * | 2004-01-25 | 2010-06-03 | Fluidigm Corporation | Crystal forming devices and systems and methods for making and using the same |
| US20060024751A1 (en) * | 2004-06-03 | 2006-02-02 | Fluidigm Corporation | Scale-up methods and systems for performing the same |
| US7815868B1 (en) | 2006-02-28 | 2010-10-19 | Fluidigm Corporation | Microfluidic reaction apparatus for high throughput screening |
| US7849924B2 (en) * | 2007-11-27 | 2010-12-14 | Halliburton Energy Services Inc. | Method and apparatus for moving a high pressure fluid aperture in a well bore servicing tool |
| WO2011037588A1 (en) * | 2009-09-28 | 2011-03-31 | Halliburton Energy Services, Inc. | Pipe conveyed extendable well logging tool |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1329572A (en) | 1916-04-06 | 1920-02-03 | Adam Folger | Locking mechanism |
| US2751752A (en) | 1953-04-17 | 1956-06-26 | Northrop Aircraft Inc | Electric-hydraulic flap control system |
| US3164065A (en) | 1961-12-29 | 1965-01-05 | Martin Marietta Corp | Incremental digital fluid actuator |
| US3114297A (en) | 1962-01-24 | 1963-12-17 | Gizeski Terrence | Pilot digital positioner |
| US3246572A (en) | 1964-11-23 | 1966-04-19 | Bertea Products | Fluid control apparatus |
| GB1260289A (en) | 1968-02-12 | 1972-01-12 | Butterworth Hydraulic Dev Ltd | Improvements in or relating to fluid pressure operated reciprocating motors |
| US3732027A (en) | 1970-06-18 | 1973-05-08 | K Lupke | Method and apparatus for converting digital input signals into distinct output positions or velocities |
| US4014248A (en) | 1972-04-04 | 1977-03-29 | D.B.A. | Servomechanism controlled step by step |
| US3779136A (en) | 1972-04-11 | 1973-12-18 | Volkswagenwerk Ag | Valve unit for controlling double acting fluid operating cylinders |
| US4094229A (en) | 1974-11-05 | 1978-06-13 | Leonard Willie B | Fluidic repeater |
| FR2309746A1 (en) | 1975-05-02 | 1976-11-26 | Dba | STEP-BY-STEP SERVOMECHANISM |
| JPS6014201B2 (en) | 1975-12-01 | 1985-04-12 | 黒田精工株式会社 | Pneumatic digital cylinder device |
| JPS52151496A (en) | 1976-06-10 | 1977-12-15 | Nisshin Sangyo Co | Hydraulic servo mechanism |
-
1980
- 1980-04-14 US US06/140,126 patent/US4434704A/en not_active Expired - Lifetime
- 1980-11-27 CA CA000365585A patent/CA1162461A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4434704A (en) | 1984-03-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1162461A (en) | Hydraulic digital stepper actuator | |
| CA1172132A (en) | Variable gain servo controlled directional valve | |
| CA1123709A (en) | Differential area electrohydraulic doser actuator | |
| DE3114437C2 (en) | Pressure control valve | |
| EP0313899A3 (en) | Flight control system employing two dual controllers operating a dual actuator | |
| WO1992008899A1 (en) | Device for stroke end cushioning and speed regulating the movement of a piston in a fluid pressure cylinder | |
| US4194719A (en) | Hydraulic control valve | |
| GB2119966A (en) | Pressure equalization of multiple valves | |
| US4457341A (en) | Variable pressure drop proportional motor controlled hydraulic directional valve | |
| GB2050875A (en) | Device for distributing paints solvents or varnishes | |
| US6651546B2 (en) | Multi-stroke cylinder | |
| US2870789A (en) | Pneumatically operated control valve for hydraulic actuators | |
| DE69814539T2 (en) | Solenoid valve with three connections in the housing of a solenoid valve with five connections | |
| US4898203A (en) | Valve apparatus | |
| GB2156105A (en) | Coded fluid control system | |
| DE3228900A1 (en) | FEEDBACK-CONTROLLED, HYDRAULIC VALVE SYSTEM | |
| US4602481A (en) | Fluid actuator for binary selection of output force | |
| US6550369B2 (en) | Linear actuator | |
| US4860638A (en) | Actuator driving system | |
| EP0950816B1 (en) | Ball-poppet pneumatic control valve | |
| US3444877A (en) | Hydraulic fluid amplifier controlled servovalve | |
| US4700747A (en) | Proportional hydraulic distributor | |
| GB2277573A (en) | Variable flow valves | |
| US4191202A (en) | Polarity control valve | |
| DE4422528C2 (en) | Fluid operated drive unit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |