US3550469A - Rotary actuator for push-pull cables - Google Patents

Description

1970 J. F. MORSE ROTARY ACTUATOR FOR PUSH-PULL CABLES 5 Sheets-Sheet 1 Filed Jan. 21, 1969 mvsmoa JOHN F.. MORSE M 21 NW ATTORNEYS Dec- 29, 1970 J, F, MORSE 3,550,469

ROTARY ACTUATOR FOR PUSH-PULL CABLES Filed Jan. 21, 1969 5 Sheets-Sheet 2 INVENTOR. JOHN F MORSE ATTORNEYS Dec. 29, 1970 J MORSE 3,550,469

ROTARY ACTUATOR FOR PUSH-PULL CABLES Filed Jan. 21. 1969 5 Sheets-Sheet 5 INVENTOR. JOHN F. MORSE WWI/TM ATTORNEYS ROTARY ACTUATOR FOR PUSH-PULL CABLES Filed Jan. 21, 1969 5 Sheets-Sheet L N INVENTOR. JOHN F. RS

BY 441%,. I

PM? W ATTORNEYS 1970 J. F. MORSE 3,550,469

ROTARY ACTUATOR FOR PUSH-PULL CABLES Filed Jan. 21. 1969 5 Sheets-Sheet r INVENTOR. OHN F. MORSE ATTORNEYS United States Patent US. Cl. 74-501 13 Claims ABSTRACT OF THE DISCLOSURE A rotary actuator for reciprocating the core of a pushpull cable. The actuator has a circular drive member received within a housing for rotation about a central axis. The cable casing is secured to the housing, but the cable core is attached to the drive member and is receivable in a peripheral groove therein. A cylindrical inner surface of an annular retaining means within the housing embraces the major portion of at least the peripheral groove. An annular gear is fixed within the housing axial- 1y of the retaining means and is intermeshed with a plurality of intermediate gears rotatably carried on the drive member. Each intermediate gear is rotatable about an individual axis located eccentrically of the central axis; the axes of the several intermediate gears being concentric to the central axis. A propelling gear means is simultaneously intermeshed with all the intermediate gears and is rotatable about the central axis selectively to rotate the drive member for winding the core into the groove or unwinding it therefrom.

BACKGROUND OF THE INVENTION The present invention relates to an actuating mechanism by which the application of selective rotary motion imparts desired reciprocation to the core of a push-pull cable for transmitting mechanical motion.

Motion transfer from the wheel to the rudder in the marine environment, in particular, has for years conventionally utilized rope and pulley, or other balanced remote control systems. Balanced remote control systems are almost as old as ships themselves and, when used as steering mechanisms, have traditionally comprised a wheel and shaft with a rope drum to provide the required movement of the rope necessary to operate the rudder or other controllably driven components. The appellation balanced appears quite appropriate when it is realized that the mechanical motion transmitting ropes, or cables, form a closed system because of their inability to relay mechanical motion by other than tensile stresses.

These balanced systems are still widely used. However, they are quite bulky and cumbersome. Moreover, misalignment between the guiding pulleys, rope drum, rudder tiller or any of the other components can cause excessive binding and wear to the system.

The advent of the push-pull control cable provided, in a single cable, the necessary structure for effecting remote control by the application of either tensile or compressive forces. The push-pull cable thus provides a transfer device which overcomes the difiiculties incident to balanced systems and is particularly easy to install in the conventional boat, either during or after construction of the boat, without requiring specialized engineering or mechanical ability.

Actuation of the core of a push-pull cable, however, requires something more than the prior rope drum of the balanced system, and complex actuating heads have been developed to translate rotative motion into the linear motion of the push-pull control cable core.

Most prior art actuating heads are not satisfactorily adaptable to a wide variety of installation situations. One type of prior art rotary actuating head employs a pinion shaft of relatively small diameter directly to drive an in- 3,550,469 Patented Dec. 29, 1970 ternally toothed ring gear. One of the major disadvantages of this type rotary actuator is the required eccentric location of the drive shaft. This eccentricity tends to locate the bulk of the actuator housing to one side of the drive shaft. When space is at a premium such an eccentric locations of the housing can severely limit the installation adaptability.

Another type of prior known actuating head employs a rack and pinion, but the extreme lateral expanse required to accommodate the rack and its housing assembly is, similarly, a disadvantage inherent to this type of actu ator. Further disadvantages, to varying degrees, of both style prior art actuators is that they cannot be efiiciently employed as driven assemblies, primarily because excessively high frictional forces generally develop in the bearing supporting the pinion shaft when such heads are used as the driven units rather than the drivers.

Still further disadvantages reside with the core support afforded by most prior art actuators and the attendant wear and/or frictional resistance.

In marine steering units using a push-pull cable for motion transfer, a maximum core travel of 8 to 9 inches is usually employed. This travel length is long enough to minimize the loading on, and backlash ratio of, the cable and yet is short enough to keep the terminal fittings of the cable within practical lengths.

Small craft steering generally requires from 3 to 4 wheel turns for stop-to-stop rudder travel. This has been found to be the most useful steering ratio to combine: good leverage for heavy steering loads; good feel and stability at high speeds; and, minimum wheel turning for slow speed maneuvering around docks. As an example, in a steering unit using twelve pitch tooth size and a pinion of nine teeth, three and one-half wheel turns will move the cable core approximately eight inches.

The conventional employment, for economic reasons, of die cast and/or molded plastic parts in steering units makes the use of gear tooth sizes smaller than twelve pitch impractical due to a general lack of precision tooth mesh in such structures.

On the other hand, gears with less than sixteen to twenty teeth, show poor load life due to compromised tooth form and the increasing tendency toward single tooth contact as the number of teeth is reduced. However, the designers of steering devices of this type are constrained to use a drive pinion having considerably fewer teeth than are considered good engineering practice, as exemplified by the aforementioned nine tooth, twelve pitch pinion.

The load carrying capacity of a gear train employing such a nine tooth pinion is seriously impaired by single tooth contact, high tooth loading and poor meshing characteristics. As a result, many, if not most, of the failures with such units in service or on wearout test result from the drive pinion (usually steel) cutting the teeth out of the rack or ring gear (usually plastic or a die casting of zinc or aluminum).

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a rotary actuator for push-pull cables, the actuator affording full support to the core with minimal frictional contact.

It is another object of the present invention to provide a rotary actuator, as above, in which the housing is substantially centered about the drive shaft to permit installation in the most advantageous location.

It is still another object of the present invention to provide a rotary actuator, as above, which, even while employing a nine tooth, twelve pitch propelling gear means, effects load transfer to and from. such a gear means 3 through multiple teeth and thereby promotes exceptional service life to the steering unit.

It is a further object of the present invention to provide a rotary actuator, as above, that is readily adapted to operate multiple push-pull cables.

It is a still further object of the present invention to provide a rotary actuator, as above, which is readily adaptable for use as the driven, as well as the driving, head.

It is an even further object of the present invention to provide a rotary actuator, as above, which have a variable drag.

These and other objects, together with the advantages thereof over existing and prior art forms, which Will become apparent from the following specifiication are accomplished by means hereinafter described and claimed.

In general, a rotary actuator embodying the concept of the present invention has a housing to which the casing of a push-pull control cable is attached. A circular drive member is received within the housing and is rotatable about a central axis. The core of the push-pull cable is secured to the drive member and is receivable within a groove provided around the periphery of the drive member.

Presented within the housing is a retaining means that embraces the drive member to confine the core radially of the groove. Fixed to the housing axially of the retaining means is an annular gear means that is intermeshingly engaged with a plurality of intermediate gear mounted on the drive member, each intermediate gear being mounted for rotation about an axis located eccentrically of the central axis about which the drive member is rotatable. Compositely, the axes about which all the intermediate gears are located are concentric with respect to the central axis.

A propelling gear means, incorporated on a drive shaft, is supported within the housing by the intermediate gears with which it meshes for rotation about the central axis. Rotation of the drive shaft, and the propelling gear means, rotates the intermediate gears against the fixed annular gear. The rotation of the intermediate gears against the fixed annular gear results in rotion of the drive member selectively to wind the core into the groove or unwind it therefrom.

One preferred embodiment of the subject invention and an alternative mounting arrangement therefor are shown by way of example in the accompanying drawings and are described in detail without attempting to show all of the various forms and modifications in which the invention might be embodied; the invention being measured by the appended claims and not by the details of the specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation, partly broken away and partly in section, of a rotary actuator embodying the concept of the present invention;

FIG. 2 is a longitudinal section taken substantially on line 22 of FIG. 1;

FIG. 3 is a cross sectional view taken substantially on line 33 of FIG. 2 and depicting the relationship of the propelling, intermediate and fixed annular gear means;

FIG. 4 is a further cross sectional view taken substantially on line 44 of FIG. 2 and depicting the relationship of, and the connection between, the push-pull cable core and the drive member;

FIG. 5 is a still further cross sectional view taken substantially on line 55 of FIG. 2 to show the actuator housing in elevation, the housing being partly broken away to depict the bumper stops on the housing;

FIG. 6 is a partial end elevation taken substantially on line 6-6 of FIG. 1; and,

FIG. 7 is a view similar to FIG. 2 but depicting a tandem arrangement of rotary actuators embodying the concept of the present invention being actuated by a common propelling gear means.

4 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings, the preferred form of a rotary actuator embodying the concept of the present invention is designated generally by the numeral 10 in FIGS. 16 and is depicted operatively connected to the end of a push-pull cable 11.

The 'push-pull cable 11, as best shown in FIG. 4, may be of any conventional construction in which a core 12 slidably reciprocates within a casing, indicated generally by the numeral 13, to transmit mechanical motion by the application of tensile or compressive forces to the core 12 while at least the ends of the casing 13 are clamped in a relatively fixed position with respect to the core 12. In the exemplary construction depicted, the casing 13 is formed of a plurality of easing wires 14 laid contiguously, in the form of a long pitched helical coil, about the radially outer surface of an inner, flexible, plastic tube 15 which extends the full length of the casing 13. An outer cover 16 encases the coil of wires 14 up to within a short distance from the ends thereof. A fitting 18 is positioned over the end of the cable casing 13 and is cold swaged, or otherwise suitably connected, onto the exposed portion of the cylindrical grouping of wires 14. A plurality of ribs, not shown, may be provided within the end fitting 18 which, when crimped onto the outer cover 16, effects a seal between the end fitting 18 and the cover 16.

A retaining notch 19 extends annularly about the end fitting 18 for attaching the casing 13 to the housing 20 of the actuator 10. Specifically, the fitting 18 is inserted into a cylindrical recess 21 within the housing, and one or more securing bolts 22 are mounted in the housing 20 transversely of the fitting 18 so as to lie within a portion of the notch 19 and fixedly position the end of the casing 13 to the actuator 10.

The interior of the housing 20 has a generally cylindrical cavity 23 (FIG. 2) in which a circular drive member 25 is rotatably received. A groove 26 provided in the periphery of the drive member 25 intercepts a chordal groove 27 therein (FIG. 4). The grooves 26 and 27 are adapted fully to receive the core 12 that extends from the fitting 18, through an access passage 28 that lies along the entrance head 29 of the retaining ring 30 and into the cavity 23 substantially tangentially of the peripheral groove 26. Although the ring 30 is substantially annular, the entrance head 29 bulges radially outwardly thereof to accommodate the access passage 28. The access passage 28, like the interior of the tube 15, embraces the core 12 so as to give it full circumferential support against buckling under compressive loading and yet permit it freely to reciprocate therein. The ring 30 even contributes radial support after the core enters the groove 26. Radially outer support is achieved by a smooth transition between the access passage 28 and the inner circumference of the ring 30, and radially inner support is achieved by a spur 30' that extends radially inwardly of the ring 30 and circumferentially within the groove 26 beneath the core 12.

A sleeve 31 is cold swaged, or otherwise suitably connected, onto the end portion of the core 12. The sleeve 31 is received within an anchor niche 32 located along the medial portion of the chordal groove 27 to affix the core 12 against axial translation with respect to the chordal groove 27 and thereby anchor it to the drive member 25. Accordingly, when the drive member 25 is rotated coun terclockwise, as viewed in FIG. 4, this anchoring of the core 12 to the drive member will apply a tension loading to the core and thereby tend to extract it from the casing 13. Under this tension loading the core will lay tightly against the base 33 of the peripheral groove 26, the base 33 being preferably of semicircular cross section as best seen in FIG. 2.

In response to clockwise rotation of the drive member 25 (again as viewed in FIG. 4) the core 12, unless fully supported, will tend to follow the line of least resistance whether that be a lateral buckling or a mere radial displacement. With the core fully received within the peripheral groove 26 the substantially simultaneous engage ment of the core 12 with the opposed radial side walls 34 and 35 (FIG. 2) of that groove preclude lateral buckling. Radial displacement is precluded by the annular retaining ring 30 that lines the circumference of the cavity 23 in radial proximity to the drive member 25 and, thereby, the peripheral groove 26. Inasmuch as the radial depth of the groove 26 is preferably equal to-i.e., approximatesthe diameter of the core 12, only a lineal contact exists between the core 12 and the retaining ring 30, so that as the drive member 25 is rotated clockwise the core 12 has moving contact only along the line at which it engages the retaining ring 30. In this regard it must be noted that even though the drive member 25 presents a transitional curve 27' to join the base of groove 26 with the base of groove 27, the transition is still sufficiently sharp that the core should be kinked, or otherwise preset, so that it will naturally follow from the transitional curve 27 immediately against the base 33 of groove 26 without arching radially outwardly against the retaining ring 30*.

Movement of the core 12 with respect to the peripheral groove 26 occurs only as the core passes from the groove 26 into the access passage 28. This itself greatly reduces the frictional resistance as the application of a compressive load to the core 12 resulting from clockwise rotation of drive member 25 effects an insertion of the core 12 into the casing 13, and, if desired, the retaining ring 30 may be made of a plastic material further to reduce the frictional resistance. Although any number of plastic materials will perform quite satisfactorily, an acetyl co polymer such as Celcon, by Celanese Plastics Company, provides an excellent material for the retaining ring 30, particularly in view of the fact that it possesses almost identical static and dynamic coefficients of friction.

Rotation of the retaining ring 30 with respect to the housing 20 is precluded by the interengagement of one or more lugs 36 on ring 30 with corresponding notches 37 in the peripheral wall of cavity 23. The radially outward bulge of the entrance head 29 and the false entrance head 29A also tend to preclude rotation of retaining ring 30 by their interengagement with the conforming periphery of the cavity 23.

Certain other prior art rotary actuators have also employed friction reducing plastic material against which to slide the core, but the concept of these constructions required that the plastic member include a groove within which the core is at least partially received. Such a groove provides a surface, as distinguished for a linear, contact between the core and the plastic material and that configuration inherently includes at least two major drawbacks that are nonexistent to the present concept. First, the very fact that the plastic member partially embraces the core positions the bouudry between the drive member and the plastic member laterally of the core so that full support of the core against lateral buckling cannot be assured. Second, the provision of a substantial area of contact with the core in two members that are relatively movable-the drive member and the plastic member induces a very effective snubbing action by the mutuality of their contact with substantial areas of the core, particularly in the situation where any lateral misalignment occurs between the drive member and the plastic member. When the retaining ring has a purely cylindrical inner surface, as in the present invention, misalignment between the ring and drive member 25, whether occasioned by manufacturing tolerances or eccentric loading to the drive member, will not result in such a snubbing action. The mutuality of contact inherent to the prior art construction also increases the exposure of the plastic member to wear occasioned as the core slides along the groove. In this situation even modest, acceptable snaking (limited lateral buckling) of the core will have an eroding action on the groove of the plastic member.

Rotation of the drive member 25 in actuator embodying the full concept of the present invention is accomplished by a mechanism which requires no friction imparting bearing assembly for the propelling gear means. The present concept also employs a much more favorable tooth loading between the propelling gear means and the toothed members with which it meshes. As best seen from FIGS. 2 and 3, a plurality, preferably three, stub axles 37A, 37B and 37C extend from the drive member 25 into a gear chamber 38 adjacent the substantially cylindrical cavity 23 in which the drive member 25 is rotatably received. Each of the stub axles 37A, 37B and 37C is located eccentrically of, and parallel with, the central axis 39 about which the drive member 25 rotates, and the three are, compositely, concentric therewith. Intermediate gears 40A, 40B and 40C are rotatably mounted on the respective axles 37A, 37B and 37C intermeshingly to engage with an annular gear 41 fixed to the housing 20 and defining the circumference of gear chamber 38.

A drive shaft 42, having a rotational axis concurrent with the control axis 39, is provided with a propelling gear portion 43 that mutually intermeshes with the three intermediate gears 40A, 40B and 40C. Because the propelling gear portion 43 is cradled medially of the three, circumferentially spaced, intermediate gears 40A, 40B and 40C, the interaction therebetween does not induce lateral thrust and no bearing is required between the propelling gear portion and either the housing or the drive member. However, for some installations, and particularly when operating multiple actuators from a common propelling gear, a bearing may be desirable.

Most prior art constructions that utilize a pinion gear meshing directly against the drive member to rotate the latter require a large bearing in close association with the pinion to support it against the lateral thrust that is inherent thereto. With the diameter of the journal surface of such a bearing being generally larger than the pitch circle of the pinion teeth, the bearing tends to act, because of the lateral thrust, as a brake when the core applies back pressure into the actuator. This situation most frequently obtains when the actuator is employed as the driven member. By having the intermediate gears 40A, 40B and 40C provide equally spaced circuferential support for the propelling gear portion 43 of the shaft 42, any tendency toward lateral displacement of the propelling gear means 43 is eliminated. This tendency toward lateral displacement in prior art actuators contributes greatly to the existence of the undesirable braking action, and it is also the absence of this induced braking that permits the present actuator to be efficiently employed as a driven, as well as a driving, unit.

The use of the three intermediate gears to contact the propelling gear also drastically reduces the tooth loading as compared with that inherent to prior known devices in which the relatively small diameter pinion directly engages the drive member. In such a device the contact ratio is only about 1 and the tooth loading can become quite high. This is a major disadvantage, because, while the small pinion gear is often steel, the larger member with which it meshes is, for economical considerations, generally fabricated from a weaker material, often a die casting. As such, failure in prior known actuators most often occurs by tooth failure on the member made of the weaker material. However, it must be appreciated that the environmental requirements of a rotary actuator, particularly when employed in a steering system, do not permit the adoption of a pinion having sufficient size to afford a more favorable contact ratio. Similarly also, the diametral pitch is limited by the nature of the steering environment. In brief, it is desirable that the shaft connected to the actuator turn through three or four revolutions to effect full travel to the push-pull cable core. It is also highly desirable that the travel of the push-pull cable core be on the order of eight to nine inches. Moreover, experience has shown that when economically feasible manufacturing tolerances are employed, the diameteral pitch of the pinion-type gear member must be as low as ten to twelve in order to provide sufficiently large teeth to transfer the typical loads encountered.

Within the above parameters the pinion-type gear member will have only about nine teeth, and that is well below the number of teeth considered generally acceptable in accordance with standard engineering practice. Nevertheless, the art has persisted in the employment of such pinions with the resulting excessive loading and wear, particularly to the teeth on the member with which the pinion meshes.

An actuator embodying the concept of the present invention benefits in this regard because the number of intermediate gears reduces the tooth loadand, concomitantly, the wearproportionately to the number of intermediate gears employed.

The drive shaft 42 is joumaled within a shaft support column 45 that may be mounted to the dashboard, or the like, in a well-known manner (not shown). To facilitate mounting of the actuator and permit the housing to be most suitably aligned -with the push-pull cable 11, the housing 20 may be variably mounted with respect to the shaft support column 45.

T o accomplish this adjustability that end of the support column adjacent housing 20 is necked to provide an annular mounting flange 46. The axially outermost side of the mounting flange 46 presents radial serrations 48 to engage with mating, radial serrations 49 in the base of a coupling recess 50 in the housing 20. The cylindrical side wall of recess 50 embraces the outer perimeter of the mounting flange 46 and a pair of clamps 52 and 53 are secured to the housing 20, as by cap screws 54 and 55, respectively, so as to engage the mounting flange 46 and selectively maintain serrations 48 and 49 engaged. This arrangement permits adjustment of the radial orientation of the housing 20 with respect to the support column 45 in order to assure accommodation of the run of cable 11, as, for example, from positions 11A through 11B depicted, in phantom, in FIG. 5.

The housing 20 is also provided with a second cylindrical recess 56 (FIG. 4), opposed to recess 21, so that the push-pull cable may, with equal facility, be admitted into the opposite side of housing 20. This permts selective adoption of either a push or a pull to the cable core in response to either clockwise or counterclockwise rotation of the drive member. The only internal change required is that the substantially annular retaining ring 30 be repositioned. It should be noted that the lug, or lugs, 36 and the recesses 37, the entrance head 29 and the false entrance head 29A are all symmetrical with respect to the housing 20 in order that the ring 30 may be selectively positioned within the cavity 23 to accept a core irrespective of whether the cable is secured to recess 21 or 56.

In addition, the housing 20 may be secured to the support column 45 through a similar variable range with the housing oriented at generally 180 with respect to the orientation depicted. This permits selective rotation of the drive member to effect a push or a pull to core 12 without limiting that selection on the basis of the side to which the cable 11 is attached to the actuator housing 20.

Because of the extremely low frictional resistance possessed by a control embodying the concept of the present invention, it has been found desirable to incorporate a braking mechanism that imparts a resistance, or drag, preselected for the particular installation. However, in order to maintain the desired feel for the operator of the subject actuator, it is mandatory that no backlash be inherent to the braking mechanism employed. This result has been effectively accomplished by applying a unique frictional brake to the drive shaft 42.

As best shown in FIGS. 1, 2 and 6, the drive shaft 42 may be provided with a cylindrical drum portion 58 beyond the propelling gear portion 43. The drum portion 58 preferably extends through an opening 59 in the cover plate 60, the cover plate 60 being removably secured to the housing 20 as by cover plate bolts 61 in addition to the securing bolts 22 that also fasten the end fitting of the control cable 11 to the housing 20. A pair of stabilizing pins in the form of shoulder bolts 62 and 63 are secured to the cover plate 60 and extend outwardly thereof in spaced, parallel relation with respect to the axis of the drum portion 58-an axis concurrent with the central axis 39. A pair of shoes 64 and 65 simultaneously embrace the pins 62 and 63 as well as the drum portion 58, and adjusting means, such as the nuts and bolts 66 which extend through the. shoes 64 and 65 on opposite sides of drum portions 58, are provided to vary the embracing pressure. The pressure applied against the drum portion 58 selectively effects a drag against the rotation thereof and the corresponding pressure against the stabilizing pins 61 and 62 assures that no backlash exists in the braking mechanism.

It should be noted that the braking mechanism disclosed should be somewhat flexible and should also be positionable somewhat laterally within the plane of stabilizing bolts 62 and 63 to accommodate the drum portion 58 and not restrict the shaft against assuming its natural axis. The flexibility of the shoes may Well be accomplished by the use of a plastic material, and the variable location of the shoes may be accomplished by having the embracing ear 57 on each end of each shoe 64 and 65 extend sufliciently beyond the body portion of the shoe to effect this result.

It has been found that the acetyl copolymenCelcon, also provides an excellent material for the shoes 64 and 65, again particularly in view of its substantially identical static and dynamic coefficients of friction.

In operation, the drive shaft 42 may be rotated, as by a wheel or other mechanism (not shown), in either a clockwise or a counterclockwise direction to effect the desired movement of the core 12 within the casing 13. Should the drive shaft 42 be rotated clockwise, as viewed in FIG. 3, the propelling gear portion 43 thereof would similarly rotate in a clockwise fashion and thereby rotate all three intermediaee gears 40A, 40B and 40C in a counterclockwise fashion against thefixed annular gear 41. With the annular gear 41 fixed the intermediate gears will therefore accomplish a motion compounded of rotation about their axles 37A, 37B and 37C, respectively, and a rotation of those axles about the central axis 39. The drive member 25 will, therefore, rotate clockwise in response to clockwise rotation of the propelling gear portion 43. By the same token, the drive member 25 will rotate counterclockwise in response to counterclockwise rotation of the. propelling gear portion 43. And, rotation of the drive member 25 will effect a push or a pull to the core 12, as hereinbefore set forth.

To limit the range through which the drive member 25 can rotate, and thus assure that the actuator will not bind as a result of attemping to wind a second wrap of cable core in the same peripheral groove 26, an engaging arm 67 carried on the drive member 25 is permitted to move only between two, opposed, circumferentially spaced stops 68 and 69 (FIG. 5) secured to the housing 20. As best seen from FIG. 2, the engaging arm 67 extends from the drive member 25, through gear chamber 38 and into a cavity 70 arcuate about central axis 39. The stops 68 and 69 are located, one at each of the circumferentially spaced ends of the cavity 70. In order to provide a shook-absorbing cushion, it is de sirable that the stops be made of a resilient material, such as rubber.

' When the faces 71 and 72 of the stops 68 and 69, respectively, are oriented radially of the drive member it is convenient to utilize a trapezoidal cross section for the engaging arm 67 in order to provide a full surface contact between the arm 67 and either stop 68 or 69 while assuring a rigid, but light weight, arm 67.

Although the construction hereinbefore described is suitable primarly for the actuation of a single push-pull control cable, it should be appreciated that multiple cables as well can be actuated. Because the actuator operates primarily about a central axis 39, it is quite convenient to stack multiple housings for operation from a single drive shaft.

As shown in FIG. 7, two housings 120 and 220 are mounted back to back on the common propelling gear portion 143 of a drive shaft 142 simultaneously to actuate two control cables 111 and 211. The intermediate gears 140 in housing 120 and the intermediate gears 240 in housing 220 are both engaged by the single propelling gear portion 143.

The housing 120 is secured to the drive shaft support 145 by clamps 152 and 153 and cap screws 154 and 155 in the same manner as the housing is secured to support column 45, and the two housings 120 and 220 are secured together by the use of cover plate bolts 161 and securing bolts 122 having sufiicient length to extend through both housings 120 and 220.

The brake mechanism, however, can not readily be mounted on the cover plates 160 and 260 but can be mounted on the housing 220 remote from the support column 145. A pair of shoulder bolts 75 and 76, identical to bolts 62 and 63, are received in the bores 78 and 79 which normally accept the cap screws by which the mounting clamps are tightened, and the shoulder bolts 75 and 76 function as stabilizing pins against which the shoes 164 and 165 are tightened by adjusting means 166. The drum portion 158 of drive shaft 142 extends axially beyond the housing 220 for embracing engagement by the brake shoes 164 and 165 in the same manner as shoes 64 and 65 embrace drum portion 58.

It must be appreciated that when the housings are stacked in this manner, and thus carried from only one end on support column 145, cumulative dimensional variations, even within permissible manufacturing tolerances, could well tend to impose a misalignment of the axis of the drag shaft 142, and propeller gear portion 143, with respect to the central axis 139 of the housings. This tendency can be easily precluded by the use of a bearing between the propelling gear portion 143 and that housing located most remotely from the support column 154. As shown in FIG. 7, an internally toothed sleeve bearing 80 may be fitted over a section of the propelling gear portion 143 to turn in a raceway 81 provided in housing 220. Similar bearings, while not generally required, may, in the unusual situation, also be interposed between the propelling gear portions 43 or 143 and a raceway 82 formed as the hub of the drive member 25, 125 or 225. t

A typical unusual situation might occur when the core is being subjected to such heavy loading that even the nominal eccentricity of the drive member with respect to the intermediate gears requires additional support.

It should now be apparent that a rotary actuator constructed in accordance with the concept of the present invention fulfills all the objects thereof.

I claim:

1. A rotary actuator for at least one push-pull cable having a core that slidably reciprocates within a casing, said actuator comprising, at least a first housing, means for attaching the casing to said housing, a circular drive member received within said housing to rotate about the central axis thereof, a peripheral groove in said drive member, means for attaching the cable core to said drive member so that the core is received in said peripheral groove, retaining means within said housing radially embracing at least that portion of said peripheral groove in which the core is received, annular gear means located axially of said retaining means and fixed within said housing,

a plurality of intermediate gears carried on said drive member and each rotatable about an axis eccentrically of the axis about which said drive member rotates, said intermediate gears intermeshed with said annular gear means, a propelling gear means intermeshed with said intermediate gears, and means to rotate said propelling gear means selectively to wind said core into said groove and to unwind said core therefrom.

2. A rotary actuator, as set forth in claim 1, in which the depth of said peripheral groove approximates the diameter of the core received therein and in which said retaining means makes only lineal contact with that portion of the core received in said peripheral groove.

3. A rotary actuator, as set forth in claim 2, in which the retaining means comprises a ring, said ring having an entrance head, an access passage lying along said head and fully supporting the core from substantially said casing into said peripheral groove.

4. A rotary actuator, as set forth in claim 3, in which an engaging means is carried on said drive member and opposed circumferentially spaced stops are carried on said housing, rotation of said drive member being restricted to the range defined by the travel of said engaging means arcuately between said stops.

5. A rotary actuator, as set forth in claim 4, in which the means for attaching the cable core to said drive member comprises a chordal groove in said drive member that intercepts said peripheral groove, a niche medially of said chordal groove, an anchor sleeve secured to the core, said anchor sleeve received in said niche to attach the core to said drive member.

6. A rotary actuator, as set forth in claim 5, in which there are at least three, circumferentially spaced, intermediate gears, the circumferentially spaced location of said intermediate gears supporting said propelling gear means.

7. A rotary actuator, as set forth in claim 6, in which a brake means applies a preselected drag to resist rotation of said propelling gear means.

8. A rotary actuator, as set forth in claim 1, for operating at least two push-pull cables, said rotary actuating means comprising at least a second housing conjoined with the first housing about a common central axis, means for attaching the casing of a second push-pull cable to said second housing, a second drive member rotatably received within said second housing, a peripheral groove in said second drive member, retaining means within said second housing radially embracing the peripheral groove in said second drive member, a second annular gear means located axially of said retaining means and fixed within said second housing, a plurality of intermediate gears carried on said second drive member and each rotatable about an axis eccentrically of the common central axis, the intermediate gears carried on said second drive member intermeshed with said second annular gear means, said propelling gear means intermeshed with the intermediate gears carried on both said drive members, and common means to rotate said propelling gear means selectively to push or pull said cores.

9. A rotary actuator, as set forth in claim 8, in which there are at least three, circumferentially spaced, intermediate gears carried on each said drive member, the circumferentially spaced location of said intermediate gears supporting said propelling gear means within said housings.

10. A rotary actuator, as set forth in claim 9, in which the depths of said peripheral grooves approximates the diameter of the cores received therein and in which said retaining means make only lineal contact with that portion of the cores received in the corresponding peripheral grooves.

11. A rotary actuator, as set forth in claim 10, in which the retaining means comprises a ring in each said housing, said rings each having an entrance head, an access passage piercing each said head and fully supporting the 11 corresponding core from substantially said corresponding easing into said corresponding peripheral groove.

12. A rotary actuator, as set forth in claim 11, in Which an engaging means is carried on at least one of said drive members, and opposed, circumferentially spaced stops are carried in the corresponding housing means, rotation of said drive members being restricted to the range defined by the travel of said engaging means arcuately between said stops.

13. A rotary actuator, as set forth in claim 12, in which at least one brake means applies preselected drag to resist rotation of said propelling gear means.

References Cited UNITED STATES PATENTS 2,452,178 10/1948 Brownlee 74801 2,579,368 12 /1951 Curtis' et 61. 74 789 3,060,7 7 10/1962 Parrett 74798 2,890,595 6/1959 Loeffier 74-501 5 FOREIGN PATENTS V 853,933 12/1959 Great Britain 74 501 FRED C. MATTERN, JR., Primary Examiner 10 W. S. RATLIFF, JR., Assistant Examiner s. c1. X.R.

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