US1746419A

US1746419A - Control mechanism for hydraulic presses

Info

Publication number: US1746419A
Application number: US296582A
Authority: US
Inventors: Ernst Walter
Original assignee: HYDRAULIC PRESS Manufacturing CO
Current assignee: HYDRAULIC PRESS Manufacturing CO
Priority date: 1928-07-31
Filing date: 1928-07-31
Publication date: 1930-02-11
Anticipated expiration: 1947-02-11

Description

Feb. 1l, 1930. w. ERNST 1,746,419

CONTROL MECHANISM FOR HYDRAULIC PRESSES Filed July 31, 1928 2 Sheets-Sheet l E Feb. 1l, 1930. w. ERNST CONTROL MECHANISM FOR HYDRAULIC PRESSES Filed July 31, 1928 2 Sheets-Sheet 2 Patented Feb. 11, 1930 UNITED STATES Pari-:rrr oFFrcE WALTER ERNST, OF MOUNT GILEAD, OHIO, ASSIGNOR T0 THE HYDRAULIC PRESS MANUFACTURING COMPANY, OF MOUNT GILEAD, OHIO CONTROL MECHANISM FOR HYDRAULIC PRESSES Application led July 31, 1928. Serial No. 296,582.`

This invention is particularly adapted for use with a hydraulic press of the character disclosed in my co-pending application Serial No. 153,410, tiled December 8, 1926, but is adapted for use with other types of presses.

It is common to employ in hydraulic press mechanisms a pump for forcing fluid under pressure to the press, which pump is of the type known as a variable stroke, variable and reversible discharge. A pump of this character is disclosed in the Patent 1,250,170, December 18, 1917, to Hele-Shaw et al., and is well known to those familiar with this art. In such pumps the direction of movement of the liquid discharge may be'reversed and the speed may be varied simply by reciprocating a cross head from one position to another, which cross head is connected to a floating ringwhieh may be shifted off center with relation to other elements of the pump or may be held in a central position. 'When in a central position, the pump runs idly, while, when the i oatin g ring is ofl' center, the iiuid under pressure will be discharged in one direction and in the opposite direction when the ring is moved off center on the other side.

It is unnecessary to set forth thespecitic construction of the pump in any more detail, and the same is not illustrated herein, since the present invention relates to control mechanism interposed between the pump and the press whereby the operation of the pump will be controlled in the manner hereinafter described. v

In my co-pending application referred to above. there is provided a semi-automatic control mechanism for the press wherein the downward movement of the platen is initially started by a hand controlled lever, the pump being automatically reversed by the control mechanism when the platen reaches the lower end of itsstroke in order to return the platen in its initial position, and thc pump control mechanism being automatically moved to neutral position when the platen reaches the upper end of its stroke, whereby the platen will be stopped automatically vat the upper end of its stroke and consequent ly at the end of a single cycle.

The principal object of the present inven tion -is to provide a control mechanism whereby either a. single complete operation of the press may be o tained, or whereby an indeterminate number of completeoperations of the press may be obtained, as may be desired.

In the accompanying drawings are illustrated one form of my invention.

Figure l is a side elevation of the control mechanism with the pump and press more or less diagrammatically disclosed.

Figure 2 is a longitudinal section through a partof the control mechanism.

Figure 3 is a sectional View taken on the line 3-3 of Figure 2.

Figure 4 is a detailed horizontal plan view of the cross head and its connection with the 4 control mechanism, and i Figure 5 is a perspective view of the loose control linkage.

The hydraulic press is herein illustrated as comprising a frame including a bed A and a top B, which are connected by a plurality of rods C. A platen D is vertically guided by the rods C and is operated/by a main cylinder It is to be understood that this showing is merely illustrative and that va rious types of presses may be equipped with the control mechanism constituting the present invention. This control mechanism comprises certain elements which are preferably supported by the press frame and which ma) be referred to broadly as the controlling linkage, and control mechanism which may be carried by or attached to the pump and constitutes the control mechanism proper.

The pump, which is indicated as a whole by the reference letter F, is one having aV variable stroke, and a variable and reversible discharge. As is usual in pumps of this type,

the direction of movement of the liquid discharge ma be reversed andthe speed may be variedy reciprocatingsa cross head G, as is well known by those familiar with this art. In the construction herein illustrated the cross head G is supported for sliding movements by the rods 55, the inner ends of the rods extending into the pump casing for connection with the contr means therein. The outer ends of each ro? 5 respectively pass through opening 66 formed `in the cross head adjacent the ends thereof. The outer ends of the rods are each provided with a nut 7 for limiting the movement of the cross head in one direction relative to said rods. The inner` ends of the rods 5 are mounted in the bearings 8 of the pump, and each rod 5 between the cross head G and the bearings 8 is threaded to receive a sleeve or bushing 9 havin an integral flange 10 and nut 11 at the en thereof opposite the cross head. Positioned around each sleeve 9 is a coil spring 12 which bears at one end against the associated flange and at its other end a ainst the cross head G. The outer end of t e sleeve or bushing 9 is normally spaced from the cross head G and, inasmuch as the rods 5 have sliding connections with the cross head G, it follows that a relative movement between the rods 5 and the cross head G may take place.

Associated with the cross head G is my improved control mechanism H which is suppprted on the pump casing. This mechanism includes a su porting frame or casing 13 in which is slida 1v mounted a stem 14. This stem is located on the side of the cross head G opposite the rods 5. The outer end of the stem 14 is formed with a cylindrical bearing portion 15 which is mounted for sliding movements within an adjustable bearinfr sleeve 16, the latter being held in an adjusted position by means of stop collars 17-17. The inner end of the stem 14 is provided with a reduced portion 18, which is preferably iiat sided and slides in a bearing opening 19 formed in the casing 13. The inner end of the fiat portion 18 is provided with a reduced threaded end 20 for engagement with the cross head G at a point intermediate with the guide rods 5-5. The stem 14 intermediate the ends of

portions

15 and 18 is provided with a liattened center portion 21, forming a resultant shoulder 22 which merges with the inner end of the flat portion 18. A collar 23 is slid on to the end portion 18 and bears against the shoulder 22. A coil spring 24 is dis osed around the flat portion 18 and one en bears against the frame 13 andthe other end bears against the collar 23. This frame normall tends to urge the stem 14 outward- 1y, that 1s, towards the left as viewed in Figure 2.

A main control lever 25 is fulcrumed at 26 to the casing or frame 13 of the control mechanism and is pivoted at 27 to the center portion 21 of the stem 14. The free end of the lever is adapted to engage a trip 28, which is pivoted at 29 to the frame 13, the trip normally serving to retain the lever 25 a ainst outward movement by the spring 24.

e trip 28 is yieldably retained in its latched position with the lever 25 through the medium of a coil spring 30 which is arranged within a telescopic housing formed of cupshaped members 31 and 32 respectively. The

cup-shaped member 31 is provided with an arm 33 which is pivoted as at 34 to the trip 28. A shaft 35 has a smooth inner end portion 36 which is journaled in a bearing in the frame 13 and an outer end portion 37 which is threaded for engagement with the cup-shaped member 32. A hand Wheel 38 is fixed to the projecting end of the inner portion 36 of said shaft for the purpose of turning the latter, and a set screw 39 is threaded into the frame 13 for engagement with the inner portion 36 of the shaft to retain the latter against movement. Vhen it is desired to adjust the tension of the spring 30 the inner cup-shaped member 32 is held by the spring against rotation, the set screw 39 is released, and the hand wheel 38 is turned. As a result, the shaft 35 will be turned and the cupshaped member 32 will be moved endwise on the inner threaded portion 37 to either increase or decrease the tension of the spring 30.

A piston 40 is slidably mounted in the frame 13 and is connected by a rod 41 to a clevis 42 which is pivoted as at 43 to the trip 28. The piston 40 has a head 44 which is located within a chamber 45 formed in the frame or casing 13. From this chamber 45 a pipe 46 communicates with the main cylinder E of the press.

From the foregoing it will be observed that when suficient pressure is built up within the chamber 45 the piston 40 will be moved towards the right as viewed in Figure 2. This action will raise the trip 28 against the tension of the spring 30 and thereby release the control lever 25, whereupon the spring 24 will swing the control lever on its fulcrum 26 and simultaneously shift the stein 14 and the cross head G towards the left.

Journaled on the frame A of the press is a shaft 47 having a rock arm 48 fixed thereto. A link 49 is pivotally connected at one ond to the rock arm 48 and at its other end to the control lever 25. A hand lever 50 is pivoted on the press frame as at 51 and to one end of this lever is pivotally connected the upper end of a vertical link 52. The lever 50 is yieldingly held in its normal position by a spring 50a. The lower end of this link 52 is pivotally connected as at 53 to a rock arm 54, fixed to a hub 55 which is journaled on the shaft 47. Fixed to the shaft 47 is a. collar 56. The hub 55 and the collar 56 are respectively formed with interlocking projections 55 and 56a to ,provide for a certain amount of lost motion in either direction of one part relative to the other. The shaft 47 is also provided with a rock arm 58 having a forked outer end 59 which overlies a head 6() fixed to the lower end of a rod 61. The rod 61 is mounted to slide in upper and lower bracket arms 62 and 63 fixed to the press frame and intermediate the bracket arms 62 and 63 is an arm 64, which is fixed on the platen D and is y so provided at its outer end with a bearing` for receiving the rod 61. Fixed to the rod 61 between the bearing 65 and the upper bracket arm `.62 is a stop collar 66, whichis mounted for adjustment along said rod 61g.

The trip Q8 is adapted to be released by hand at any time, and to this `end I have `pivoted a link 67 which ispivotally connected at one `end to the arm 33 and at its other` end by a pivot 68 to one end of a hand lever 69, which ispivoted as at to the press arm.

j In the operation of the press asthus tar described, and assuming the press to be in the positionshown in Figure 1, the hand lever 50 will be lirst depressed to raise the link 52 and the rock arm 54, which will produce a movement of the rock arm` 48 and link 49 to move `the control lever `25 to the left, thus moving the stem 14 and cross head G to the right to cause the pump to deliver the fluid in a proper direction to initiate the downward movement of the platen D. At the termination of the downward movement of the platen the control mechanism H will operate to move the link 49 towards the right to reverse the pump; The pump will then deliver fluid under pressure in a direction to return the platen D to its upper position. In this upward movement the bearing 65 of the arm 64 will ultimately contact with the collar 66, which will lift the r-od 61 and thereby elevate the rock arm 58, rotate the shaft 47 and move the rock arm,` 48, link 49 and control lever25 tothe lett, whereby the control lever Q5 will be brought to central or neutral `position in which the pump will remain idle, `thus producing one complete operation.

In order t-o more clearly understand the complete single operation, I will describe the movements ot the various parts. Assuming, therefore, that the platen is in its upper position, the operator initiates the operation by moving the hand lever 50, which through the link 52, rock arm 54, interlocking projections 57, shaft 47, rock arm 48, and link 49, causes the lower end of the control lever 25 tobe moved towards the left. The `movement- `causes the upper end of the lever 25 to cam the trip 28 out otits path, after which said trip will .snap into engagement with the lever 25, asshown in Figure 2, and thereby hold the lever in that position. This movement of the upper end of the control lever towards the right also moves the cross head G and thereby controls the pump so that fluid under pressure will be delivered to the main cylinderE of the press. The spring 12 permits a little `over-travel of the stem 14 ln order that the free end of the controllever Q5 may be moved far enough to insure its being retained by the trip 28.

y y Since fluid is now being delivered under the desiredv pressure to the main cylinder of the press, the platen D will be moved downwardly until it meets with a certain resistance. The pressure in the system and consequently in the chamber 45 will now build up and will ultimately overcome the tension of the spring 30 and move thepiston 40 to the right, thus releasing the trip 28 from engagement with the control lever 25. As a result ot' the loose connections 55a and 56a, the hand lever 50 will not be violently returned when the trip 28 is released. `The tension of the spring BO'may be varied as above described, thus varying the pressure at which the control mechanism will be operated and consequently varying the maximum pressure to be exerted by the press.

`As soon as the trip 28 releases the operating lever 25, the spring 24 will cause the stem 14 and the cross head G to move towards the left a suilicient distance to reverse the pump and thereby cause fluid to be discharged under pressure in the opposite direction to return the platen to its normal or upper position. The extent of this movement of the stem 14 to the lett, and consequently the return speed ot the press, may be regulated by adjusting the bearing sleeve 16, as will be readily understood. j d

The platen will now return at the predetermined rate of speed until arm 64 contacts with the stop collar 66. The continued upper movement of the platen and the arm 64 will, through the collar 66, elevate the rod 61, and through the various connections swing the lower end of the control 25 to the lett,whereby the uper end of the lever will be moved to its intermediate position. In this movement ofthe lever 25 the stem 14 and the cross head employed the collar 66 is moved upwardly along the rod61 and fixed in a position on said rod whereby the arm 64 ot the platen will not engage the collar 66.

In carrying out the full automatic control mechanism, I provide themain control 1nc`chf7 `anism H with a piston 71 which is movable in a plane parallel to the stem 14. The piston 71 is provided with a head 72 having a larger surface than the head 44 of the` piston 4t).

The head 72 operates within a chamber 73 otl 'f the trame or casingl 13, and this chamber com municates through the medium ot' an inlet port 74 with the fluid under pressure. The end of the piston 71 opposite the head 72 is provided with an extension 75 which slides in

bearings

76 and 77 ot the casing 13. A stop collar 78 is held in an adjusted position on the extension 75 by a set screw 79. Disposed around the piston extension 75 between the stop collar 78 and the hearing 77 is a coil s r' 8O which is adapted to ur e the piston 7x1 tudvards the left, as viewed in Figure 2. The stop collar 78 is provided with a shoulder 81 which is adapted to be engaged by the latch 82 pivoted at 83 to the casing 13. The latch S2 is provided with a rigid arm 84 which is arranged in. angular relation thereto so that the latch 82 and the arm 84 form in effect. a bell crank lever. The latch 82 is yieldably held in en agement with the shoulder 81 ot the stop co lar 7 8 b means of thc coil spring 85, having one end xed to the arm 84 and the other end fixed to the casing 13. The piston 71 is provided with an elongated and transversel extending opening 86 through which exten s a pin 87 fixed to the control lever 25. J ournaled on the press frame A is a shaft 88 having a rock arm 89 fixed thereto. A link 90 has one end ivotally connected to the rock arm 89 and t ie other en'd is slidably mounted in a block 90l pivoted on the lever 84. The link 90 projects beyond the block 90* and is threaded for engagement by a pair of hand wheels 90h which normally bear directly against the lever 84. These hand wheels may be adj usted to a position in spaced relation to the lever 84 in order to provide for a loose movement for a purpose hereinafter escribed The shaft 88 is provided with a second rock arm 91 which is similar to the rock arm 58. A vertically disposed rod 92 is mounted in upper and lower bracket arms 93 and 94 fixed to the press frame so as to per* mit said rod 92 to slide vertically therein. A bracket arm 95 is fixed to the platen D and is provided at its outer end with a bearing 96 for receiving the rod 92. Adjustably secured on the rod 92 above the bearing 96 is a stop collar 97.

In the operation of my full automatic control, the initial movement of the parts is started by themanipulation ofthe hand lever- 50 after which the mechanism just described will'automatically cause the platen to be reciprocated an indeterminate number of times. or until the operation is stopped by manual means.

Assuming the platen D to be at the upper end of its stroke and the pump running i ly In this condition the control lever 25 will not be enga ed by the trip 28, but will be in an interme iate position, that is, between its extreme limits of movement. In this position of the control lever 25 the cross head G of the pump is in a corresponding position so that the pump control is in its neutral position. The operator then bears down on the hand lever 50 which rocks the shaft 47 and oscillates the control lever 25 so that the upper end thereof is moved towards the right and engaged by the trip 28. This movement of the control lever 25 moves the stem 14 to the right and consequently the cross head G of the pump is correspondingly moved to the right,

`and the fluid pressure is then directed to the main cylinder E of the press above the platen D. The platen thereu on moves downwardly under the pressure an as it reaches the lower end of its stroke this pressure is built up until there is a sufiicient pressure in the chamber 73 which will then move the piston 71 to the right and compress the spring 80, whereupon the latch 82 will engage the collar 78 and thereby retain the piston 71 in its extreme right hand osition, as shown in Figure 2. By reason ci) the slot 86 in the piston 71 the movement of said piston will not affect the control lever 25. Immediately thereafter the pressure in the chamber 45 will act on the piston 40 and thereby release the trip 28 from the control lever 25. The spring 24 will then swing the control lever 25 to its extreme left handv position, which is determined by the position of the bearing 16. This movement of the control lever 25 moves the stem 14 and cross head G a corresponding distance and the pump is thereby reversed. The platen D is then elevated by the pressure and as the laten approaches the upper endvof its stro e the bearing 96 engages the stop collar 97 and thereby elevates the rod 92. This upward movement of the rod 92 will rock the shaft 88, which in turn will swing the arm 84 to the left and thereby release the latch 82 from its engagement with the sto a collar 78. Immediately the sprintf 80 will cause the piston 71 to be moved to tlie left or to its initial position, the right hand end of the Wall of slot 86 of the piston engaging the pin 87 of the control lever 25 and causing the lever 25 to be rocked on its fulcrum so as to re-engage the upper end of said lever 25 with the trip 28, this movement of the control lever 25 of course moving the stem 14 to its extreme right hand position, and again reversing the action of the pump.

From the foregoing it is apparent that my automatic control mechanism includes means operated by the platen for reversing the latter when it approaches the end of its return stroke. This platen operated means is the rod 92 which is elevated when the boss 96 carried by the platen contacts with the collar 97. It is also apparent that the rod 92 and connected linkage acts to control the spring actuated piston 71, and that the latter, when the spring 80 is released, serves to quickly swing the control lever 25 to a position in which fluid is directed to impart a pressing movement of the platen.

Means must be provided to prevent the press from releasing trip 82 whenever it is desired to stop the operation of the press, otherwise the spring 80 will move the piston 71 to the left as viewed in Figure 2 and swing the control lever 25 to its latched position, thereby continuing the operation of the press. To this end the adjustable hand wheels 90b are provided. By backing these hand wheels a short distance from the block 90l on the lever V84, as shown `by the dotted line position in Figure 2, a loose movement between the linlr 90 and the lever 84 will be created.

. The collar 66 is previously adjusted upwardlyon therodl `and consequently the loose movement between the linlr90 and the lever 84 will permit the rod 61 to be moved upwardly by the arm 64 of the platen withoutreleasing the latch 82, and the upward movement of the rod 6l will rock the shaftl 47, move the link 49 to the left, swing the control lever 25 to its control position and hold the same in that position as the platen comes to a state of rest at the upperl end of its movement. y

`From the foregoing it will be observed that I have provided a control mechanism for hydraulic presses which may be adjusted for either a semi-automatic control or a full automatic control,whereby a complete single operaon or `an indeterminate number of complete operations may be employed, as desired.

Although I have illust-rated a press provided with a platenl especially adapted for performing compressing operations, it is to be understood that the invention described herein may be embodied in presses used for punching, forging, shearing, or other like purposes and that theV term platen is 1ntended to cover any tool, die, or other appliance with which a press embodying my invention might be provided. f Other modifications in` construction and arrangement of parts may be also made without` departing from the scopeof my invention.

I claim: l p

1. The combination with a hydraulic press including a stationary table and a reciprocatory platenmovable towards and from the table, of a pump, means forming with the `press and pump ahydraulic circuit, and controlling means operatively connected with the pump and circuit for reciprocating the platen and includingr means responsive to built-up pressure in the circuit .during pressing movement of the platen for automatically reversing the direction ot movement of the platen irrespective `of the position of the platen relative to the table, and means operated by the platen during the return movement thereof for automatically reversing the direction of movement of theplaten.

2. The combination with a hydraulic press including a stationary table and a reciprocatory platen movable towards and from the` table, of a pump, means forming with the press and pump a hydraulic circuit, and controlling 'means operatively connected with the pumpand circuit for reciprocating the platen and including a control lever for controlling the direction of movement of the platen, a trip for holding said lever in one extreme position for directing the Huid to impart pressing movement to the platen, means responsive to built-up pressure in the circuit during said pressing movement of the platen to release said trip, means for moving the control lever to the otherextreme position upon release ot said trip whereby the platen will be returned to its initial position. and means operatedby the platen during said return movement thereof to move the control lever to its-trip-engaging position whereby a pressing movement will be impartedv to the platen. t

3. The combination with a hydraulic press including a stationary table and a reciprocatory platen movable towards and from the table, of a pump, means forming with the press and pump a hydraulic circuit, and controlling means operatively connected with the pump and circuit for reciprocating the platen and including a control lever operatively connected with the pump for controlling the direction of movement of the platen, a trip for holding said lever in one extremeposition` for directing the fluid to impart pressing movement to the platen, apiston having a loose connection with said control and movable toone extreme position in response to built-up pressure in the circuit during the pressing movement of the platen and without moving said lever, a spring for urging the piston in the opposite direction, a latch for holding the piston in said extreme position against the tension of said means, means responsive to built-up pressure in the circuit during said pressing movement of the platen to release said trip,`means for moving the control lever to the other extreme position upon release of said trip whereby fluid will be directed to return theplaten toits initial position, and means operated by the platen during said return movement thereof to release said latch andpermit the spring to return the piston to its initial position and thereby return the control lever to its tripengaging position whereby the Huid will be ldirected to impart a pressing movement of the platen. v

4. The combination with a hydraulic press including a stationary table and a reciprocatory` platen movable towards and from the table, of a pump, means formingr with the press and pump a hydraulic circuit, and controlling means operatively connected with the pump and circuit for reciprocating the platen and including means responsive to built-up pressure in the circuit during pressing movement ofthe platen for automatically reversing the direction of movement of the platen irrespective of the position of the platen relative to the table, and means operated by the platen during the return `movement thereof for automatically reversing the direction of movement ofthe platen, said platen operated means including a manually operable part movable to place the pump control in neutral position and thereby bring the press to a state of rest. e y

5. The combination with a hydraulic press including a stationary table and a reciprocatoryplaten movable towards and from the table, of a reversible pump, means forming with the press and pump a hydraulic circuit, and controlling means operatively connected with the pum and circuit for reciprocating the platen an including means responsive to built-up. pressure in the circuit during pressing movement of the platen for automatically reversing the ump and platen irrespective of the position oi) the platen relative to the table, and means operated by the laten during the return movement thereof or automatically reversing the pump and the platen, said platen operated means including a manually operable part movable to place the pump control in neutral position and thereby bring the press to a state of rest, and manually controlled means for moving the pump control into position for directing a pressing movement to the platen.

6. The combination with a hydraulic press including a stationary table and a reciprocatory platen movable towards and from the table, of a pump, means forming with the press and pump a hydraulic circuit. and controlling means operatively connected with the pump and circuit for reciprocating the plateny and including a control lever operatively connected with the pump for controlling the direction of movement of the platen, a trip for holding said lever in one extreme position for directing the iluid to impart a pressing movement to the platen, a piston having a loose connection with said control and movable to one extreme position in response to built-up pressure in the circuit during the pressing movement of the platen and without moving said lever, a spring for urging the piston in the opposite direction, a latch for holding the piston in said extreme position against the tension of said spring` means responsive to built-up pressure in the circuit during said pressing movement of the platen to release said trip, means for moving the control lever to the other extreme position upon release ofl said trip-whereby Huid will be directed to return the platen to its initial position, and mcansxoperated bv the platen during said return movement thereof to release said latch and permit the spring to return the piston to its initial position and thereby return the control lever to its trip-engaging position whereby fiuid'will be directed to impart a pressing movement to the platen.I said platen operated means including a link having a sliding connection with the latch. and a stop mounted on the linkl for cooperating with the latch, said stops being adjustable along the link to prov-ide a loosemovement for placing the pump control in neutral vpoi sition and thereby bring the press to a state tory platen movable towards and from the table, of a pump, means forming with the press and pump a hydraulic circuit, and controlling means operatively connected with the pum and circuit for reciprocating the platen and including means responsive to built-up pressure in the circuit during pressing movement of the platen for automatically reversing the direction of movement of the platen irrespective of the position of the platen relative to the table, and means operated by the platen during the return movement thereof for automatically reversing the platen, and separate means associated with the platen operated means and adjustable independently for respective operation by the platen during its return movement for moving the control means to reverse the platen at the end of each return stroke or to bring the platen to restat the end of each return stroke.

8. The combination with a hydraulic press including a stationary table and a reciprocatory platen movable towards and from the table, of a pump, means forming with the Dressand pump, a hydraulic circuit, and controlling means operatively connected with the pump and circuit for reciprocating the platen and including means responsive to built-up pressure in the circuit during pressing movement of the platen for automatically reversing the direction of movement of the platen irrespective of the position of the platen relative to the table, and spring actuated means controlled by the platen during the return movement thereof for automatically reversing the direction of the platen.

9. The combination with a hydraulic press including a stationary table and a reciprocatory platen movable towards and from the table, of a pump, means forming with the press and pump, a hydraulic circuit, and controlling means operatively connected with the pump and circuit for reciprocating the platen and including a control lever for controlling thedirection of movement of the platen, a trip for holding said lever in one extreme position for directing the fluid to impart pressing movement to the platen, means responsive to built-up pressure ,in the circuit during said pressing movement of the platen to release said trip, means for moving the control lever to the other extreme position upon release of said trip whereby the platen will be returned to its initial position, and spring actuated means controlled by the platen during said return movement thereof to move the control lever to its trip-engaging position whereby a pressing movement will be imparted to the platen.

In testimony whereof, I have hereunto subscribed my name. `l

WALTER ERNST.