US3867077A

US3867077A - Compacting apparatus having improved rotating table means for indexing molds to and from a compacting chamber

Info

Publication number: US3867077A
Application number: US469980A
Authority: US
Inventors: Thomas A Deprez
Original assignee: Gleason Works
Current assignee: Gleason Works
Priority date: 1974-05-15
Filing date: 1974-05-15
Publication date: 1975-02-18
Anticipated expiration: 1992-02-18
Also published as: JPS5754959Y2; CA1039016A; FR2271041B1; JPS5120074U; GB1451036A; FR2271041A1

Abstract

A powder compacting apparatus of the type which includes a rotating table means for advancing individual molds into and out of a chamber, in which an isostatic force can be applied to each mold, is provided with (1) a lifting and lowering mechanism for the table for inserting and removing molds into and out of the compacting chamber and (2) a blocking means for restraining movement of a mold out of the chamber when an isostatic force is being applied to the mold. The blocking means is arranged to operate through openings in the table so that the table and its associated lifting and lowering mechanism can be moved out of supporting contact with a mold after the mold has been inserted into the compacting chamber.

Description

[ Feb. 18, 1975 United States Patent [1 1 Deprez [5 COMPACTING APPARATUS HAVING 3 730 666 5/1973 Bowles.......................l..., 42s/405 H P O D ROTATING TABLE MEANS 3,76l,574 9/1973 Rietmnnn.. 425/405 H COMPACTING CHAMBER Primary Examiner-J. Howard Flint, Jr

[75] Inventor: Thomas A. Deprez, Rochester, NY.

Attorney, Agent, or FirmRalph E. Harper [73] Assignee: The Gleason Works, Rochester,

4 7 9 l 0 m m 9 m6 4 O N .ml 0. mo. FA UH 22 [l [52] U S Cl 425/405 A 425/86 425/443 (1) a lifting and lowering mechanism for the table for inserting and removing molds into .and out of the com- 425/450 B30b 5/02, B30b 11/00 Field of Search.......,.................

pacting chamber and (2) a blocking means for rer h s ed ua b mw moh m w d a m me n smm h et whme r m m m 6 s 6 e cl p n mr. kO ama l M f 0-0 a .l uplmm F Dad Mg n .m.m lngtam fl t Ra mbm w p aEm m m feSw WC OC ES m k hm n w mtl 6 8a no o t mfim o C 6a e cl mfl m dl 0 m ne m.B .lg UH n mw naim fi n m bi hwfi mee dsm U pmfe swToaob ml m m an "8 mnmm no w wn o WLBB [51] Int.

[56] References Cited UNITED STATES PATENTS PATENTEBFEBIBIQTS SHEET 2 OF 5 1 COMPACTING APPARATUS HAVING IMPROVED ROTATING TABLE MEANS FOR INDEXING MOLDS TO AND FROM A COMPACTING CHAMBER BACKGROUND AND BRIEF DESCRIPTION OF INVENTION The present invention relates to powder compacting apparatus of the type which includes (a) a compacting chamber for receiving a charge of powder material so that an isostatic force can be applied thereto, (b) a plurality of molds for containing the powder material while it is advanced into the compacting chamber, (c) a table means having a plurality of openings formed therethrough for receiving and supporting the plurality of molds, and (d) rotating means for indexing the table about its axis of rotation. The improvements of the present invention are directed to mechanisms and structures which allow the table means to be rotated, lifted, and lowered without subjecting the mechanisms or structures to forces resulting from an application of isostatic pressure to a mold within the compacting chamber of the apparatus.

It is generally known in the art of isostatic compacting to place a charge of powder material into a compacting chamber so that an isostatic force can be applied to the powder material to densify and compact the material into a coherent form. Typically, the powder material is measured into an elastomeric mold, and the elastomeric mold is inserted into the compacting chamber for receiving a compacting force from an isostatic system within the chamber. Prior to compacting, the chamber is sealed so that relatively high pressures, on the order of 50,000 psi or more can be applied to the powder material contained within the elastomeric mold.

It is also known to provide for means to advance a plurality of molds, one at a time, into and out of a compacting chamber so that isostatic compacting processes can be applied to high volume production requirements of a particular industry. In this regard, it is known to provide for a rotating table which can support a plurality of molds so that each mold can be indexed to various positions of filling, compacting, and unloading of a finished part therefrom. Rotating table arrangements of this type are generally disclosed and described in US. Pat. Nos. 3,677,674 and 3,698,843, and a type of indexing mechanism for machine tool applications is shown in US. Pat. No. 3,212,363. Other arrangements for rotating or lifting workholding tables are disclosed in US. Pat. Nos. 2,290,910; 3,193,900, 3,374,500; 3,548,466; 3,591,903; 3,677,674; and 3,730,666.

The present invention is directed to improvements in high volume production systems which utilize a rotating table as a means for rapidly indexing a plurality of molds into and out of a compacting chamber. In accordance with the present invention, a lifting and lowering means is operatively associated with a rotating table means so that the entire table means, and all molds carried thereon, can be lifted and lowered relative to an inverted, open-ended compacting chamber. Thus, instead of attempting to lift a single mold at a given station away from a rotating table, as has been done with prior art arrangements, the present invention contemplates a lifting of the entire table each time a mold is in a position for insertion into the compacting chamher. The main advantage in this arrangement is one of keeping the lifting and lowering mechanism out of the pressure chain which would otherwise transmit part of the isostatic force in the compacting chamber to any lifting and lowering mechanism directly associated with an individual mold positioned within the compacting chamber. The arrangement of the present invention provides for a blocking means which can be moved into position beneath the compacting chamber to receive force from the compacting chamber without such forces being transmitted to the table means or the lifting and lowering mechanism associated with the table means.

Another advantage in providing for a lfiting and lowering of the entire table means is that the table means can be locked to a rotating mechanism in its lowered position and disengaged from the rotating mechanism in its raised position, thereby permitting the use of a simple and reliable rotating means which translates reciprocating motion into rotary motion.

The arrangement of the present invention is especially useful in industrial applications requiring relatively high production rates (400-750 parts per hour, for example) of precisely formed parts with very reliable equipment. A number of operations, such as filling, leveling, vibrating, and part removal, can be carried out simultaneously with each compacting operation while the table means is in its raised position, and thus the production rate can equal the time it takes to index the table means and to raise and lower the table means for a compacting operation.

Thus, a specific embodiment of the invention provides for a lifting and lowering means for moving the table means, along its axis of rotation, toward and away from an inverted, open-ended compacting chamber so as to provide for an insertion and removal of molds, one at a time, into and out of the compacting chamber. In addition, there is provided a blocking means for restraining movement of a mold out of the compacting chamber after it is inserted into the chamber and when an isostatic force is applied thereto. The blocking means is arranged to operate through openings provided in the table means so that the table means and its associated lifting and lowering means can be moved out of supporting contact with a mold after the mold has been inserted into the compacting chamber. When an isostatic pressure is developed within the compacting chamber, the force of the isostatic pressure tends to move the mold out of the chamber, but this force is transmitted to the blocking means which functions as a very rigid lock to restrain unwanted movement of the mold out of the chamber.

These and other features and advantages of the invention will become apparent in the more detailed discussion which follows, and in that discussion reference will be made to the accompanying drawings as briefly described below.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an elevational view of the compacting apparatus of this invention, with portions of the view shown in cross-section for clarity;

FIG. 2 is a top plan view of part of the apparatus shown in FIG. 1, as seen generally on line 22 of FIG. 1;

FIG. 3 is an elevational view in enlarged scale, and partly in cross-section, of a lifting, lowering, and indexing mechanism associated with the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a view in enlarged scale, and partly in crosssection, of the relative positioning of a mold within a compacting chamber as it would be seen during a compacting operation with the table means moved out of supporting contact with the mold and its associated structures.

FIG. 5 is a top plan view of a modified form of rotating means for indexing the table means; and

FIG. 6 is a sectional view taken on line 66 of FIG. 5.

DETAILED DESCRIPTION OF INVENTION Referring to FIG. 1, the improvements of the present invention are illustrated with reference to a type of compacting apparatus which carries a bottom entry compacting chamber 10 within a cylindrical vessel structure 12 positioned between a pair of spaced

apart pressure plates

14 and 16. A table means is provided for receiving and supporting a plurality of upright molds (only one being shown in the FIG. 1 view for purposes of clarity) so that each mold can be advanced to different positions for filling, compacting, and unloading. The table means 18 is provided with a plurality of openings therethrough for receiving and supporting base structures associated with the plurality of molds. Arrangements of this type also include rotating means for rotating the table means 18, and FIG. 1 shows a type of rotating means 22 which is preferred for the illustrated embodiment of this invention.

In addition to the above structures, which are all generally known in the art, the present invention provides for a lifting and lowering mechanism 24 operatively associated with the table means 18 for moving the entire table means, along its axis of rotation 26, toward and away from the compacting chamber 10 so as to provide for an insertion and removal of the plurality of molds, one at a time, into and out of the inverted chamber 10. The lifting action also serves to raise all remaining molds on the table means to a level where filling, vibrating, leveling and unloading can take place at different positions around the table means while a compacting operation is being performed. The table means 18 is illustrated in FIG. 1 in a lowered position, and its raised position is shown with dashed lines. Once an individual mold is lifted upwardly into the chamber 10 by a lifting motion ofthe entire table means 18, a blocking means 28 is swung into a position beneath the table means and in line with a base structure 30 associated with the inserted mold means 20 so that isostatic forces applied to the mold means and its base structure 30 will be transmitted to the blocking means 28 and to the lower pressure plate 16 rather than to any part of the table means 18 or its associated rotating means 22 or lifting and lowering means 24. The blocking means 28 is designed to fit through the openings provided in the table means 18 so that the table means can be lowered slightly out of contact with the base structure 30 of the inserted mold means during a compacting operation. During the compacting operation, a relatively high isostatic pressure is developed within the chamber means 10, as is well known in the art, so as to apply a force to a powder material contained within the mold means 20. This high pressure force tends to push the mold means and its associated base structure out of the compacting chamber. but this movement is restrained by the blocking means 28 as soon as a slight movement takes place. The blocking means, in turn, is maintained in contact with the lower pressure plate 16 so as to be fully supported during a compacting operation.

Referring to FIG. 2, it can be seen that the illustrated embodiment of the invention provides for a table means 18 having five mold positions equally spaced about its periphery so that each mold can be indexed to and from various stations around the table means. Of course, a greater or lesser number of mold positions may be used. Preferably, each mold is secured to a base structure 30 which is normally fitted into an opening 32 formed through the table means 18. Thus, there are five openings 32 spaced around the table means 18 for receiving five base structures of five separate molds 20. FIG. 2 also illustrates a mechanism 34 for advancing and retracting the blocking means 28 into a position (shown by dashed lines) beneath a mold which has been inserted into the compacting chamber 10. The

compacting chamber is positioned at a midpoint be-.

tween tension rods 36 which secure the pressure plates 14 and 16 (see FIG. 1) in their respective positions above and below the compacting chamber. Also, it can be seen from the FIG. 1 view that the tension rods 36 do not pass through any part of the table means 18,

thereby providing for simpler components which can.

be easily assembled and disassembled and which do not interfere with a placement of the rotating means and lifting and lowering means on the center axis of the table means.

The mechanism 34 for advancing and retracting the blocking means 28 into and out of a restraining position for a compacting operation includes a hydraulically operated ram 37 pivotally mounted on the pressure plate 16 and having a connecting rod portion 38 pivotally connected at 40 to an arm member 42 fixed to the blocking means 28. The arm member 42 of the blocking means 28 is secured to a fixed-position pivot at 44 for limited oscillation back and forth around the pivot point at 44. Thus, when the connecting rod 38 of the ram 37 is advanced or retracted relative to the main cylinder of the ram 37, there is a corresponding pivotal movement of the arm 42 and the blocking means 28. This arrangement serves to advance and retract the blocking means 28 back and forth between the limit positions shown in FIG. 2.

FIGS. 2 and 3 illustrate details of the rotating means 22 which functions to rotate the table means 18 through increments of rotation which successively advance the molds 20 into and out of alignment with a compacting chamber. The rotating means 22 is functionally dependent upon operation of the lifting and lowering means 24 which is illustrated in FIG. 1 (and partly illustrated in FIG. 3).

Components which function to rotate the table means 18 include a support spindle 46 for supporting the load of the table means and its associated structures, a turret structure 48 mounted coaxially around the support spindle means 46, and a driving means generally indicated at 50. The driving means 50 may be in the form of a crank element 52 connected to a hydraulic ram means 54 (see FIG. 2) in such a way that reciprocating movements of a connecting arm 56 of the hydraulic ram means 54 will be translated to increments of rotation of the turret structure 48. The turret structure 48 is separated from the support spindle 46 by bearing means 58, and thus, rotational movements of the turret structure 48 are not transmitted directly to the support spindle 46. As shown in FIG. 3, rotational movements of the turret structure 48 are imparted to the table means 18 only when the table means 18 is in the illustrated lower limit position where a locking bar element 60 secured to the table means 18 is engaged into one of five slots 62 formed into an upper terminal end of the turret structure 48. Each slot corresponds to an index position for the table means 18, and each increment of rotation imparted to the turret structure 48 is equal to the rotational movement required to index the table for one position (72 in the example where five positions are provided around the table).

Since the rotating means 22 is of a type which translates reciprocating movements of a driving means 50 into increments of rotation, it is necessary to provide for a disengagement of the turret structure 48 from the table means 18 each time the driving means 50 is returned to its start position. Each time the table means 18 is lifted, its locking bar element 60 is removed from a slot 62, and this action results in a disengagement of the table means from the turret structure 48. As can be appreciated from the FIG. 3 orientation, a lifting movement of the support spindle 46 carries the table means 18 upwardly, but leaves the turret structure 48 in its illustrated position. Thus, a lifting of the table means 18 results in a disengagement of the table means 18 from the rotating means 22, and then the rotating means 22 can be brought back to its starting position while the table means is in a raised position. A sequence of operation for indexing the table means 18 would involve an increment of rotation being applied to the table means 18 while in its lowermost position (as illustrated in FIG. 3), followed by a lifting of the table means to insert a filled mold 20 into a compacting chamber, during which time the driving means 22 would be returned to its start position by moving the connecting rod 56 of the ram 54 is an opposite direction from that required for rotating the table means 18.

Referring back to FIG. 1, the lifting and lowering means 24 is illustrated as including a hydraulic ram means 66 which functions to lift and lower a connecting rod 68 coupled to a lower end of the support spindle 46 of the table means 18. As shown in FIG. 3, the connecting rod 68 is coupled to the support spindle 46 through a coupling 73 which permits rotation of the support spindle 46 relative to the connecting rod 68. In this way, the support spindle 46 is free to rotate with rotational movements of the table means 18, and there is no requirement for a corresponding rotation of the connecting rod 68 of the hydraulic ram means 66.

FIG. 4 illustrates details of relationships which exist between the blocking means 28 and an individual mold 20 when the mold is inserted in a compacting chamber 10. The mold 20 is of a type which includes an upright elastomeric bag for receiving a measure of powder material through a top opening thereof. The illustrated elastomeric mold is designed and shaped to be received by and mated with another elastomeric bag 69 and a plug 71 carried within the cylindrical vessel 12. Also the mold 20 is provided with a core rod 73 which is precisely centered in the mold 20 to define a bore through each part compacted within the mold. In order to main tain a precise relationship between the mold and the core rod, the mold 20 is secured to an intermediate assembly 70 fitted and retained within a circular recess 72 formed into a top surface of the base structure 30.

The intermediate assembly fixes the positions of the mold 20 and the core rod element 73 to maintain concentricity of the mold (and the part formed thereby) and the core rod element. The intermediate assembly 70 has different diameters than the receiving diameters of the recess 72 so that the mold means can seek a centered position as it is inserted into the compacting chamber 10 without a shifting of position of the base structure 30. During a lifting of the table means and the resulting insertion of the mold means 20 upwardly into the compacting chamber 10, the base structure 30 is in intimate contact with the opening 32 of the table means 18, and thus, it would be impossible for the base structure 30 alone to provide for a centering adjustment of the mold 20 into the compacting chamber during the insertion movement. After the mold means 20 is fully inserted into the compacting chamber 10, the bottom of the chamber is effectively sealed by the base structure 30, the intermediate structure 70 and an annular ring means 74 (carried by the cylindrical vessel which defines the compacting chamber). The annular ring means 74, in turn, is suspended for limited axial movement by another ring element and by spring loaded screws 76 (similar to those shown in US Pat. No. 3,6 I 3,157) so that the mold 20 and its associated structures can move downwardly slightly when the compacting chamber 10 is pressurized This is done to balance forces within the compacting zone, as described in greater detail in Baxendale et al application Ser. No. 321",438, filedJan. 5, 1973. However, this downward movement is limited by a contact of a bottom surface of the base structure 30 with a top surface of the blocking means 28 which has been moved into an aligned position beneath the compacting chamber. FIG. 4 shows the basic relationships which exist after the mold 20 has been inserted into a compacting chamber and the table means 18 has been lowered slightly (by about 0.230 inches) to move the table means and its associated structures out of contact with the mold and its associated structures. This assures that all forces directed downwardly from the compacting chamber will be transmitted only to the blocking means 28 and not to any of the working mechanisms of the table rotating and lifting means.

FIG. 4 also illustrates a guide rail 80 which depends downwardly from the cylindrical vessel 12 to receive and guide the table means 18 after the table means is raised from its lowermost position.

The above descriptions have been directed mainly to essential features of the invention because persons skilled in this art will appreciate and understand the manner in which various components of the invention can be manufactured and assembled in accordance with known techniques. In addition, certain features shown in the drawings or mentioned in the specification are not further discussed because they are not part of the improvements of the present invention. For example, FIG. 2 illustrates locking devices and a gripping mechanism 102 for engaging the base structures 30 of the plurality of molds shown. The locking devices 100 are mounted on the table means 18 and function to hold the base structures in loose engagement (to permit limited disengagement of the table means from the base structures during compacting) with their respective openings 32 until a part has been formed. After compacting is completed and the table means is indexed to a new position, the gripping mechanism 102 functions to lift the entire base structure and mold combination for dumping or removing the part from the mold. Details of these devices and mechanisms are further described in a copending application Ser. No.

469,979, filed May 15, 1974 by Thomas A. Deprez and Frank M. Whalley and entitled Improved Means for Securing and Removing Molds from Compacting Apparatus." Another feature which is not explained in detail in the present application is related to the isostatic system used for pressurizing the compacting chamber 10. Any known system may be used, but preferably a self-contained system of the type described in copending application Ser. No. 321,438 is used with the apparatus of this invention. A self-contained system generates relatively high pressures in the compacting chamber 10 through the use of large and small piston combinations which amplify pressure from a relatively low pressure supply, and this eliminates a need for high pressure conduits and fittings carried externally of the compacting vessel.

FIGS. 5 and 6 illustrate a modification of the table rotating means 22 described above. The modified rotating means offers better control of table velocity so as to provide for controlled acceleration and deceleration at the beginning and end of each rotation. Such an arrangement may be preferred where there is a danger of spilling or upsetting a powder fill in individual molds during a rapid indexing of a table means 18 during normal operation of the rotating means.

FIG. 5 shows a rotating means 22 having a hydraulic ram means 54 and connecting rod 56 for reciprocating a crank element 52 in an arrangement similar to that discussed for FIG. 2. However, the crank element of FIG. 5 is formed with a slot 200 for guiding a pin member 202 (see FIG. 6) carried between a pair of plate elements 204 secured to the rod 56. An extended end portion of the pin member 202 carries a roller element 206 which functions as a cam follower for guiding the advancement and retraction of the connecting rod 56 along a cam surface defined by the cam groove 208. The cam groove 208, or other equivalent cam surface, is formed in a plate element 210 fixed to a bulkhead or frame portion of the apparatus.

As the connecting rod 56 advances or retracts from the centered position shown in FIG. 5, the shape of the cam groove 208 (shown as a segment of a circle but which could be of another curvilinear shape) adds a component of radial travel to the connecting rod, and this effectively decelerates the rotational moment imparted to the table means 18 at each end of travel of the connecting rod 52. A similar effect could be obtained by providing for a mounting of the plate element 210 to pivot about a point 212 to thereby carry the pin 202 in a circular path of travel dictated by the radius distance from the point 212 to the position of the pin 202. Such an arrangement could eliminate the cam groove 208.

Of course, the arrangementjust described with reference to FIGS. 5 and 6 can be applied to any apparatus using a reciprocating driving means and requiring a control of linear or rotational velocity. For example, a machine tool slide may utilize a ram to slide one machine component relative to another, and the velocity of the sliding component could be controlled at each end of its travel with the mechanical control arrangement discussed above.

Although the invention has been described with reference to a presently preferred embodiment as illustrated herein, it can be appreciated that fully equivalent structures can be substituted for those which have been shown and described. Equivalent structures and functions are intended to be included in the definitions of the claims which follow.

What is claimed is:

1. In a powder compacting apparatus of the type which includes (a) a chamber for receiving a charge of powder material so that an isostatic force can be applied thereto, (b) a plurality of molds for containing the powder material while it is advanced into the chamber and subjected to an isostatic force, (c) a table means having a plurality of openings formed therethrough for receiving and supporting said plurality of molds. and (d) rotating means for indexing the table means about an axis of rotation, the improvements comprising:

lifting and lowering means operatively associated with said table means for moving the table means, along its axis of rotation, toward and away from said chamber so as to provide for an insertion and removal of said molds, one at a time, into and out of said chamber. and

blocking means for restraining movement of a mold out of said chamber after the mold is inserted into the chamber and when an isostatic force is applied to the mold, said blocking means being arranged to operate through said openings in the table means so that the table means and said lifting and lowering means can be moved out of supporting contact with a mold after the mold has been inserted into said chamber.

2. The apparatus of claim 1 wherein said chamber is defined by cylindrical structure having an open-ended bore defined therein for receiving one of said molds during a compacting operation, and including means for allowing limited axial movement of a mold within said chamber when an isostatic force is applied to that mold, said limited axial movement being in a direction which advances the mold against said blocking means.

3. The apparatus of claim 1 wherein said rotating means for indexing the table means includes:

a support spindle for supporting the load of said table means and its associated structures and for transmitting lifting and lowering movements to the table means,

a turret structure mounted coaxially around the support spindle for the table means, said turret structure having table engaging means for positively engaging and driving a portion of said table means when the table is in a limit axial position for being contacted by said engaging means, and

driving means for imparting an increment of rotation to said turret structure.

4. The apparatus of claim 3 wherein said driving means includes a crank means attached to said turret structure, and hydraulic ram means for reciprocating said crank means so as to translate the reciprocating motions of the hydraulic ram means to rotational motions of the turret structure.

5. The apparatus of claim 3 wherein said lifting and lowering means includes a hydraulic ram means for contacting said support spindle so as to lift and lower the support spindle, and including coupling means for connecting said hydraulic ram means and said support spindle so as to permit rotation of said support spindle relative to said hydraulic ram means.

6. The apparatus of claim 1 and including moving means for advancing said blocking means into and out of a position for restraining movement of a mold out of said chamber.

7. The apparatus of claim 1 wherein said chamber and said blocking means are arranged between two spaced pressure plates so that the blocking means can be inserted between a mold and one of said pressure plates to thereby transmit the isostatic force on said mold to said one pressure plate.

8. The apparatus of claim 4 wherein said hydraulic ram means is mechanically guided to provide for a change in rotational velocity of said table means near ing element.

Claims

1. In a powder compacting apparatus of the type which includes (a) a chamber for receiving a charge of powder material so that an isostatic force can be applied thereto, (b) a plurality of molds for containing the powder material while it is advanced into the chamber and subjected to an isostatic force, (c) a table means having a plurality of openings formed therethrough for receiving and supporting said plurality of molds, and (d) rotating means for indexing the table means about an axis of rotation, the improvements comprising: lifting and lowering means operatively associated with said table means for moving the table means, along its axis of rotation, toward and away from said chamber so as to provide for an insertion and removal of said molds, one at a time, into and out of said chamber, and blocking means for restraining movement of a mold out of said chamber after the mold is inserted into the chamber and when an isostatic force is applied to the mold, said blocking means being arranged to operate through said openings in the table means so that the table means and said lifting and lowering means can be moved out of supporting contact with a mold after the mold has been inserted into said chamber.

3. The apparatus of claim 1 wherein said rotating means for indexing the table means includes: a support spindle for supporting the load of said table means and its associated structures and for transmitting lifting and lowering movements to the table means, a turret structure mounted coaxially around the support spindle for the table means, said turret structure having table engaging means for positively engaging and driving a portion of said table means when the table is in a limit axial position for being contActed by said engaging means, and driving means for imparting an increment of rotation to said turret structure.

8. The apparatus of claim 4 wherein said hydraulic ram means is mechanically guided to provide for a change in rotational velocity of said table means near each end of reciprocating travel of the hydraulic ram means.

9. The apparatus of claim 8 wherein said hydraulic ram means is guided by a cam surface.

10. In apparatus which utilizes a reciprocating driving means for imparting motion to a member, the improvement which provides for a change in velocity of the imparted motion, comprising means for guiding a reciprocating element of said driving means so as to introduce a component of travel which changes the effective velocity imparted to a member connected to said reciprocating element.