Title:
Hydraulic press system
United States Patent 2407855


Abstract:
This invention relates to a hydraulic system, more particularly to an automatic cycling system for the control and operation of hydraulic machinery using a plurality of operating cylinders. It is a general object of the present invention to provide a novel hydraulic system including automatic...



Inventors:
Stephens, William T.
Application Number:
US58822145A
Publication Date:
09/17/1946
Filing Date:
04/13/1945
Assignee:
HYDRAULIC CONTROL ENGINEERING
Primary Class:
Other Classes:
72/63
International Classes:
B30B15/16
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Description:

This invention relates to a hydraulic system, more particularly to an automatic cycling system for the control and operation of hydraulic machinery using a plurality of operating cylinders.

It is a general object of the present invention to provide a novel hydraulic system including automatic control valves for causing the operation of a plurality of control cylinders sequentially and cyclically.

More particularly it is an object of the invention to provide a hydraulic system for operating mechanism similar to forming presses and including automatic pressure actuated valves adapted to deliver fluid first to a die closing cylinder, then to a forming plunger cylinder and to provide for maintaining pressure on the die closing cylinder by deriving this pressure from the exhaust side of the forming plunger cylinder, thus eliminating the usual accumulator.

An important feature of the invention comprises the use of an automatic cycling valve together with a flow diverting valve whereby the die closing cylinder, the forming plunger cylinder and the knock-out operating cylinder can be actuated cyclically and sequentially to first close the dies; then project the forming plunger; then open the dies, lift the knockout plunger and simultaneously retract the forming plunger.

The system comprises an assemblage of cylinders, pistons, valves and piping and obviously the design and construction of any of the individual units is independent of the novel concept of this invention involving the system and specific arrangement of the units.

Other and further objects and features of the invention will be more apparent, to those skilled in the art, upon a consideration of the accompanying drawings and following specification, wherein are disclosed a single exemplary embodiment, with the understanding that such modifications of and rearrangements of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings: Fig. 1 is a central vertical section through a hydraulic press constructed in accordance with the present invention and illustrating schematically the fluid system for controlling the same, the press being shown in position for loading; Fig. 2 is a vertical central section through the press only of Fig. 1 shown in the final forming position; Fig. 3 is a central section through a flow diverting valve used in the hydraulic system, and Fig. 4 is a fragmentary central vertical section on an enlarged scale of the plunger head showing the air relief valve.

The present invention which is concerned primarily with hydraulic operating means and systems for presses is illustrated in conjunction with what is generally termed a forming press, but it will be understood that this is merely for convenience, for the hydraulic cylinders and associated actuating system may be incorporated with numerous types of presses and other devices such as machine tools which require similar sequential operation.

Referring now to Figs. 1 and 2 it will be seen that the press is built up about a suitable base plate 10 on which is rigidly secured the lower half II of the forming die. Standards or rods 12 connect the base plate 10 to and space from it a top plate or frame member 14. A suitable slide 15 is equipped with bushings 16 for guiding the same on the rods 12 and carries the upper or movable die section 17 which can be reciprocated from the full open position illustrated in Fig. 1 to the fully closed position illustrated in Fig. 2.

To the upper surface of the slide 15 is attached a plate 18 into which is threaded the lower end of the hollow piston rod 19 arranged to reciprocate the slide and movable die.

Intermediate its length this hollow piston rod 19 has fixed thereto a piston 20 adapted to reciprocate in a die closing cylinder 21 which is rigidly attached to a cylinder head 22 secured in an aperture in the top press plate 14. This head 22 is provided with appropriate packing glands and tightening nuts as shown at 23. The upper cylinder head 24 is likewise equipped with packing glands and tightening elements since the hollow rod 19 passes out through the same and is of such a length that when the piston 20 is at the bottom of its stroke a portion of the rod extends above the upper cylinder head.

The upper end of the hollow rod is internally threaded to receive the externally threaded neck on the lower head 26 of the cylinder 27 which is bodily carried by the hollow piston rod 19. The upper end of cylinder 27 is closed by a suitable head 28 and a piston 29 is arranged for reciprocation in the cylinder 27. It is attached to a smaller diameter piston rod 30 which has a packed fit in the cylinder head 26, extends through hollow piston rod 19 and slide i15 and is attached to a forming plunger 32 adapted to reciprocate in an opening 33 in the movable die 17. The stationary die 11 is provided with a central vertical bore 34 to accommodate the plunger 35 of a knock-out device having a head 36 adapted to be received in a suitable counter-bore 37 in the bottom of the die recess. The plunger 35 is threaded to the upper end of a piston rod 38 passing through a hole in the base plate 10 and having a piston 39 operable in a cylinder 40 whose upper head 41 is suitably packed about the piston rod and attached to the under face of the base plate.

As seen in Fig. 1, with the dies spaced apart or open, with the forming plunger 32 retracted and the knock-out device 36 elevated, the press is ready for loading with a pre-formed blank cylinder 42 of sheet metal having a closed bottom and an open top. In the manipulation of the press the movable die 17 and the plunger 32 are moved downwardly simultaneously until the upper edge of the cylinder blank 42 is engaged by the shoulder 44 at the top of the recess in the movable die. Continued movement of the die 17 forces the blank to drive the knock-out device 36 into its recess 37 which is accomplished just as the top of the upper face of the stationary die and the lower face of the movable die close together at 45 as seen in Fig. 2.

With these two dies held together the forming plunger is now moved downwardly and passes into the neck of the blank, which has been filled with water to approximately the level shown at W in Fig. 1. The plunger is a close fit into the neck of the blank and any air trapped beneath it is permitted to escape during the time the plunger is approaching the surface of the -water through the check valve illustrated in Fig. 4.

This valve unit is received in a central bore 47 in the forming plunger 32 and comprises a housing 48 and a plunger 49 centrally bored as at 50 and having a sliding fit in the passage 51 in the housing. A snap ring 52 engaging the back face of the housing prevents the plunger from dropping out. The central bore 50 of the plunger intersects radial bores 53 just beneath the head 54 thereof which is of the poppet type and engages the seat 55 when closed. The relatively slow movement of the forming plunger permits air to be forced out through bores 53 and 50 into the central passage 47 from which it passes upwardly into the bore 50 at the lower end of the smaller piston rod 30 which bore is connected with radial bores 58. Air is thus delivered inside of the hollow piston rod 19 which is provided with radial bores 60, normally closed in the packing 23 when the piston 20 is at the top of its stroke, but uncovered, as clearly seen in Fig.'2, when the dies are closed.

When the plunger encounters the predetermined quantity of liquid in the blank, this material, being more dense than air, immediately closes the valve and the forming plunger is moved on down, displacing the liquid and distending the blank until it engages the walls of the die which cause it to assume the desired shape as shown in Fig. 2 as determined by the configuration of the die recesses.

The next operation consists in separating the dies II and 17 and simultaneously raising the knock-out device 36 to push the finished blank out of the lower die for later manual removal.

While the dies are reaching their maximum separation the forming plunger 32 is being withdrawn 7 and the device is ready to have the form blank removed and a fresh one inserted for the next similar operation.

It is the purpose of the present invention to provide a hydraulic system for automatically cy- 7 cling the press mechanism to carry out the sequence of events just described, requiring, on the part of the operator, but the simple pushing of a button to start each complete cycle which thereafter is carried out entirely automatically.

The hydraulic mechanism includes a tank 70 for suitable hydraulic liquid, a continually operating positive displacement pump 71, a plurality of valves and suitable piping. Fluid is taken by the pump and delivered by pipe 72 to an automatic cycling valve 73 of the type disclosed in my copending application for Full cycle hydraulic valve, Serial No. 556,191, filed September 28, 1944, which is provided with a pipe return 74 to the tank and with delivery pipes 75 and 78. This valve is also equipped with internal bypass means so that when in the neutral position with no liquid being delivered for use the pump merely circulates oil freely from the tank through the valve 13 and pipe 74 back to the tank. When it is desired to operate the forming press the attendant pushes the button 73B which automatically conditions the valve to close the bypass and deliver fluid from the pump into the pipe line 75. At the same time the cycling valve connects pipes 76 and 74 so that liquid being returned from certain cylinders of the press is conducted to the tank 70.

Liquid in pipe 75 under suitable high pressure flows to the diverting valve 80, better shown in Fig. 3, which causes the liquid to be delivered only to pipe 81, hence through check valve 82 to pipes 83 and 84. Pipe 83 delivers liquid into cylinder 21 above or to the outer face of piston 20 and causes the hollow piston rod to move downwardly for the die closing operation. Liquid endeavoring to enter pipe 84 merely serves to maintain the piston 29 at the outer end of its stroke, insuring against unwarranted relative movement between the movable die and the forming plunger. Liquid is continuously delivered until the dies are closed when the resistance causes the pressure to build up to such an extent that diverting valve 80 disconnects line 75 from line 81 and connects the former to line 85 which delivers liquid to line 86 connected to the top head of cylinder 27 and pressure is applied to the outer face of piston 29 to advance the forming plunger on its working stroke.

During the time that piston 20 is being forced downwardly the liquid beneath it is being discharged through pipe line 88 into pipe line 78 and thence by valve 73 and pipe 74 to the tank.

During the latter part of the stroke of the upper die the knock-out device 36 and its piston 39 is driven downwardly by the action of the blank and liquid is forced out of cylinder 40 through pipe 89, joining pipe 78, and finds its way back to the tank as just described.

The cycling valve 73 is so constructed that, as for instance, when the resistance to movement i of plunger 32 is such that the fluid pressure builds up within this valve to a predetermined point, it automatically reverses itself and thereafter delivers high pressure liquid from pipe 72 5 to pipe 76 and connects pipe 75 to return pipe 74. This now reverses the operation of the press, for liquid is now delivered beneath or on the inner side of piston 20 which moves upwardly carrying with it the movable die. Liquid dis0 charged from above piston 20 by this operation cannot return from pipe 83 to pipe 81 because of check valve 82 so that it moves upwardly through 84 and supplies the liquid for lifting piston 29 which retracts the forming plunger dur5 ing the upward movement of the die 17. A larger volume of liquid is delivered from the upper or outer side of piston 20 than can be received beneath piston 29 and some of it returns via pipe 91 and relief valve 92 to the tank through pipe 93.

As the die and forming plunger are lifted the load is removed from the knock-out device 36 and liquid passing from pipe 76 into pipe 89 elevates piston 39 and with it the plunger 35 and lifts the finished product from the die. When 1 all of the pistons reach their uppermost position, continued application of pressure from the pump causes the cycling valve 73 to reset itself to neutral, whereby the excess pressure from the pump is returned through the bypass to pipe 1 74 and the button 73B is positioned in readiness for the next operation. While the piston 29 is being lifted, as just described, liquid is discharged from above it through pipe 86, check valve 95, pipe 75, valve 73 and pipe 74 to the tank. 2 It has been found by experiment that the pressure needed to form the work piece is of the order of four times that necessary to hold the dies together during the forming operation.

This then requires a particular setting of the several valves mentioned in the system. It is assumed that 60 p. s. i. will be required to hold the dies together while the forming plunger is moving down, and it will be seen that this pressure is obtained from the underside of piston 29 via pipe 84 and pipe 83. Part of the pressure applied to the top of piston 29 is endeavoring to discharge liquid from beneath it and creates a pressure which operates to hold plunger 20 down. Since there can be no flow of liquid from beneath piston 29 to above piston 20 because the system is full of liquid and the piston 20 is at the bottom of its stroke, as it is before piston 29 starts to move down, the discharging liquid beneath 29 follows the pipes 84, 91 and discharges through the relief valve 92 which is set to discharge at the said 60 p. s. i. The 240 pounds necessary to operate the piston 29 is achieved by setting the relief valve which is built into the cycling valve 73 at or above this pressure. Since but little pressure is needed to initially close the dies the diverting valve 80 is set to operate at about 50 pounds, that is, it transfers the flow from 81 to 85 when the pressure above piston 20 builds up to above 50 pounds.

The flow diverting valve 80 is illustrated in greater detail in Fig. 3 where it will be seen to comprise a housing 100 to which pines 85 and R8 are attached as shown and into which leads the high pressure pine 75. The port to which pine 75 is attached connects to a through bore 101 in which is slidably mounted a plunger 102 normally urged downwardly azainst a ston. 103 by means of a helical spring 104 and the closure can If5. The lower end of the olunger is hollow at 106 and open to the fluid in pipe 75. The unner end of the hollow portion has radial bores 107 which. when the valve is in the position shown resting against the ston, coonerate with chamber 108 connected to pipe line 81. When the resistance in line 81 becomes in excess of the pressure setting of the valve, the plunger is lifted until the radial ports 107 cooperate with chamber 110 connected to pipe line 85. Whenever the pressure is above the setting of the valve, pipes 75 and 85 are connected while at other times pipes and 81 are connected.

I claim: 1. The combination with a press having a stationary die, a movable die and a forming plunger extending through the movable die, of a slide for said movable die, means supporting a hydraulic cylinder above said slide, a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, means 0 to sequentially supply hydraulic liquid under pressure to the upper faces of the pistons in said first and second mentioned cylinders, and means to automatically associate the upper side of the first piston with the lower side of the second after 5 the first piston has reached its lower limit whereby the dies are held together during the forming plunger stroke.

2. The combination with a press having a stationary die, a movable die, a forming plunger S0 extending through the movable die, a slide for said movable die, and means supporting a hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, means to sequentially supply hydraulic liquid under pressure to the upper faces of the pistons in said first and second mentioned cylinders, means to automatically associate the upper side of the first piston with the lower side of the second after the first piston has reached its lower limit whereby the dies are held together during the forming plunger stroke and means to maintain said association when fluid is delivered beneath the first piston to withdraw the movable die and plunger.

3. The combination with a press having a stationary die, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, means to simultaneously supply hydraulic liquid under pressure to the upper face of the piston in said first cylinder and to the under face of the second cylinder, and means automatically actuated by the first piston reaching its limit of movement to associate the supply means with the upper side of the second piston.

4. The combination with a press having a stationary die, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, means to simultaneously supply hydraulic liquid under pressure to the upper face of the piston in said first cylinder and to the under face of the second cylinder, means automatically actuated by the first piston reaching its limit of movement to associate the supply means with the upper side of the second piston, and means to simultaneously maintain pressure on the upper surface of the first piston derived from the discharge from below the second piston.

5. The combination with a press having a stationary die, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, means to simultaneously supply hydraulic liquid under pressure to the upper face of the piston in said first cylinder and to the under face of the second cylinder, means including a diverter valve actuated by the increased liquid pressures resulting from the first piston reaching its limit of movement to associate the supply means with the upper side of the second piston, means to simultaneously maintain pressure on the upper surface of the first piston derived solely from the discharge from below the second piston, and a relief valve associated with said last mentioned means arranged to vent the excess liquid while maintaining a hold pressure for the movable die.

6. The combination with a press having a stationary die, a knock-out member operable therein, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, a piston and cylinder for said knock-out member, a pump to continuously supply hydraulic liquid under pressure, valve and pipe means to connect said pump first to the upper face of the piston in said first cylinder and to the under face of the piston in the second cylinder, means to automatically transfer the connection to the upper side of the second piston and to connect the upper side of the first piston with the lower side of the second piston, said last mentioned connection including a relief valve whereby the dies are held together during the forming plunger stroke, and piping and valves to simultaneously vent the liquid beneath the first piston and the knockout piston when the first connection is made.

7. The combination with a press having a stationary die, a knock-out member operable therein, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow-rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of 6 said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, a piston and cylinder for said knock-out member, a pipe connecting the upper side of the first pis- 7 ton to the lower side of the second, a pump to continuously supply hydraulic liquid under pressure, manually actuated means to connect said pump discharge first to said pipe valve means responsive to excess pump pressure to automati- 7 cally transfer the connection to the upper side of the second piston a relief valve for said pipe whereby the dies are held together during the forming plunger stroke, means to simultaneously vent the liquid beneath the first piston and the knock-out piston when the first connection is made, and a cycling valve constructed and arranged to react to pressure increase due to stoppage of the forming plunger to connect the pump to the underside of the first and knock-out pistons to return the parts to initial positions.

8. The combination with a press having a stationary die, a knock-out member operable therein, a movable die, a forming plunger extending through the movable die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollod rod and secured to said forming plunger, a piston and cylinder for said knockout member, a pipe continuously connecting the upper end of the first cylinder to the lower end of the second, a pump to continuously supply hydraulic liquid under pressure, manually actuated means to connect said pump discharge to said pipe and including a diverter valve and a check valve, said diverter valve being constructed to react to excess pressure to automatically transfer the connection to the upper side of the second piston, a relief valve for said pipe whereby the dies are held together during the forming plunger stroke, said manually actuated means being arranged to simultaneously vent the liquid beneath the first piston and the knock-out piston when the first connection is made, said manually actuated means being associated with a cycling valve means constructed and arranged to react to pressure increase due to stoppage of the forming plunger to then connect the pump to the underside of the first and knock-out pistons to return the parts to initial positions, said check valve being between the said pipe and diverter valve whereby the liquid displaced above the first piston serves to lift the second piston and retract the forming plunger.

9. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of the dies, a knock-out plunger operable in the other die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending 0 through said hollow rod and secured to one of said plungers, an oppositely disposed third cylinder, piston and rod associated with the other plunger, a pump to continuously supply hydraulic 5 liquid under pressure, valve and pipe means to connect said pump. first to the upper face of the piston, in said first cylinder and to the under face of the piston in the cylinder for the forming plunger, pressure responsive means to automati0 cally transfer the connection to the upper side of the the forming: plunger piston and to connect the upper side of the first piston with the lower side of the second piston, said last mentioned connection including a relief- valve, where5 by the dies are held together during the forming blunger stroke as a result of pressure producing the forming stroke.

10. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of the dies, a knock-out plunger operable in the other die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to one of said plungers, an oppositely disposed third cylinder, piston and rod associated with the other plunger, a pump to continuously supply hydraulic liquid under pressure, valve and pipe means to connect said pump first to the upper face of the piston in said first cylinder and to the under face of the piston in the cylinder for the forming plunger, pressure responsive means to automatically transfer the connection to the upper side of the forming plunger piston and to connect the upper side of the first piston with the lower side of the second piston, said last mentioned connection including a relief valve whereby the dies are held together during the forming plunger stroke as a result of pressure producing the forming stroke, and piping and valves to simultaneously vent the liquid beneath the first piston and the piston for the knock-out plunger when the first connection is made.

11. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of the dies, a knock-out plunger operable in the other die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to one of said plungers, an oppositely disposed third cylinder, piston and rod associated with the other plunger, a pump to continuously supply hydraulic liquid under pressure, valve and pipe means to connect said pump first to the upper face of the piston in said first cylinder and to the under face of the piston in the cylinder for the forming plunger, pressure responsive means to automatically transfer the connection to the upper side of the forming plunger piston and to connect the upper side of the first piston with the lower side of the second piston, said last mentioned connection including a relief valve whereby the dies are held together during the forming plunger stroke as a result of pressure producing the forming stroke, piping and valves to simultaneously vent the liquid beneath the first piston and the piston for the knock-out plunger when the first connection is made, and a cycling valve and piping associating said pump, cylinders and previous mentioned valves and piping and so constructed as to be pressure responsive to connect the pump to the underside of the first and knock-out pistons to return the parts to their initial positions.

12. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of the dies, a knock-out plunger operable in the other die, a slide for said movable die, and means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to one of said plungers, an oppositely disposed third cylinder, piston and rod associated with the other plunger, a pump to continuously supply hydraulic liquid under pressure, valve and pipe means to connect said pump first to the upper face of the piston in said first cylinder and to the under face of the piston in the cylinder for the forming plunger, pressure responsive means to automatically transfer the connection to the upper side of the forming plunger piston and to connect the upper side of the first piston with the lower side of the second piston, said last mentioned connection including a relief valve whereby the dies are held together during the forming plunger stroke as a result of pressure producing the forming stroke, piping and valves to simultaneously vent the liquid beneath the first piston and the piston for the knock-out plunger when the first connecStion is made, and a cycling valve and piping associating said pump, cylinders and previous mentioned valves and piping and so constructed as to be pressure responsive to connect the pump to the underside of the first and knock-out pistons to return the parts to their initial positions, said 3connection provided with the relief valve remaining in condition to transfer fluid from the upper side of the first piston to the underside of the forming plunger piston to retract the latter.

S 13. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of said dies, a slide for said movable die, means supporting a hydraulic cylinder above said slide, a rod secured to said slide, extending into said cylinder, and having an operating piston therein, a second hydraulic cylinder, a piston in said second cylinder, a rod on said piston secured to said forming plunger, a pump to supply hydraulic liquid under pressure, piping connecting said pump to the outer face of the piston in the first cylinder, and to the inner face of the piston in the second cylinder, a pressure responsive valve in said piping adapted to divert all the pump supply to the outer face of the piston in the second cylinder when the first piston reaches its limit of stroke, a portion of the piping now serving to apply pressure to the outer face of the piston in the first cylinder from the inner face of the piston in the second cylinder, and a relief valve adapted to discharge the excess liquid from the inner face of the second piston.

14. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of said dies, a slide for said movable die, means supporting a hydraulic cylinder above said slide, a rod secured to said slide, extending into said cylinder, and having an operating piston therein, a second hydraulic 65 cylinder, a piston in said second cylinder, a rod on said piston secured to said forming plunger, a pump to supply hydraulic liquid under pressure, piping connecting said pump to the outer face of the piston in the first cylinder, and to the inner face of the piston in the second cylinder, a pressure responsive valve in said piping adapted to divert all the pump supply to the outer face of the piston in the second cylinder when the first piston reaches its limit of stroke, a portion of the piping now serving to apply pressure to the outer face of the piston in the first cylinder from the inner face of the piston in the second cylinder, and a relief valve adapted to discharge the excess liquid from the inner face of the second piston, said system having a check valve by- -5 passing the said diverter valve or the return of liquid from the outer face of the piston in the second cylinder during the first operation.

15. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of said dies, a slide for said movable die, means supporting a hydraulic cylinder above said slide, a rod secured to said slide, extending into said cylinder, and having an operating piston therein, a second hydraulic cylinder, a piston in said second cylinder, a rod on said piston secured to said forming plunger, a pump to supply liquid under pressure, piping connecting said pump to the outer face of the piston in the first cylinder, and to the inner face of the piston in the second cylinder, a pressure responsive valve in said piping adapted to divert all the pump supply to the outer face of the piston in the second cylinder when the first piston reaches its limit of stroke, a portion of the piping now serving to apply pressure to the outer face of the piston in the first cylinder from the inner face of the piston in the second cylinder, a relief valve adapted to discharge the excess liquid from the inner face of the second piston, and a check valve between' said portion of the piping and said diverter valve.

16. The combination with a press having a stationary die, a movable die, a forming plunger extending through one of said dies, a slide for said movable die, means supporting a hydraulic cylinder above said slide, a rod secured to said slide, extending into said cylinder, and having an operating piston therein, a second hydraulic cylinder, a piston in said second cylinder, a rod on said piston secured to said forming plunger, a pump to supply hydraulic liquid under pressure, piping connecting said pump to the outer face of the piston in the first cylinder and to the inner face of the piston in the second cylinder, a pressure responsive valve in said piping adapted to divert all the pump supply to the outer face of the piston in the second cylinder when the first piston reaches its limit of stroke, a portion of the piping now serving to apply pressure to the outer face of the piston in the first cylinder from the inner face of the piston in the second cylinder, a relief valve adapted to discharge the excess liquid from the inner face of the second piston, said system having a check valve bypassing the said diverter ,5 valve for the return of liquid from the outer face of the piston in the second cylinder during the first operation, and a check valve between said portion of the piping and said diverter valve.

17. The combination with a press having a sta- o6 tionary die, a knock-out member operable therein, a movable die, a forming plunger extending through the movable die, a slide for said movable die, means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, a piston and cylinder for said knock-out member, a pump to supply hydraulic liquid under pressure, an automatic cycling valve and piping adapted to first supply liquid from the pump to sequentially actuate the pistons in said first and second mentioned cylinders to close the dies and move the forming plunger, pipe means to automatically associate the upper side of the first piston with the lower side of the second after the first piston has reached its lower limit whereby the dies are held together during the forming plunger stroke, said cycling valve being arranged to then supply liquid from the pump to the inner face of the piston in the first cylinder and to the knock-out cylinder, said pipe means now delivering liquid from the outer face of the first piston to the inner face of the second.

18. The combination with a press having a stationary die, a knock-out member operable therein, a movable die, a forming plunger extending through the movable die, a slide for said movable die, means supporting a first hydraulic cylinder above said slide, of a hollow rod secured to said slide, extending through said cylinder, and having an operating piston therein, a second hydraulic cylinder carried by the upper end of said hollow rod, a piston in said second cylinder, a rod on said piston extending through said hollow rod and secured to said forming plunger, a piston and cylinder for said knock-out member, a pump to supply hydraulic liquid under pressure, an automatic cycling valve and piping adapted to first supply liquid from the pump to sequentially actuate the pistons in said first and second mentioned cylinders to close the dies and move the forming plunger, pipe means to automatically associate the upper side of the first piston with the lower side of the second after the first piston has reached its lower limit whereby the dies are held together during the forming plunger stroke, said cycling valve being arranged to then supply liquid from the pump to the inner face of the piston in the first cylinder and to the knock-out cylinder, said pipe means now delivering liquid from the outer face of the first piston to the inner face of the second, and an adjustable relief valve associated with said pipe means.

WILLIAM T. STEPHENS.