US2333529A - Press - Google Patents

Description

Nov. 2, 1.943.

W. ERNST PRESS Filed Aug. 2, 1940 2 sheets-sheet 1 I Ig 45 m5 9 [00 Y l04 n L 7 l0! II I| lll 102 130 [07 19g 1 .I /29- 95 99 50 55 H [03 I 126 101s 135 l2 vISI z5110Il I [[22 1: l37` III f 1- i24- M H3 '(2 I I lllla? 136. 115] 121' ,5 /33 f' H6" /20 4l I U4 1;] /20 [I4- '19+' I ,38 62' 11k Il 2 74 l I l 47 93 0 5 I 50- '1" 15/ la 22 21 WALTER ERNsw;

W. ERNST Nov@ 2, 1943.

PRESS 2 Sheets-Sheet 2 Filed Aug. 2 19,40

Nm NN 1/ w im m,

r--ff' l I l Patented Nov. 2, 1943" l oer-ic I t PRESS 'waiter Emst, Mount Gilead, ohio. signor to The Hydraulic Development Corp., "1110., Wil` 'mingtom Dcl.,.a corporation of Delaware Application August 2, '1940, semi No. 34.9;976,

This invention relates to presses, and in particular to hydraulic presses having a cushioning cylinder piston assembly for supporting the work piece tobe shaped and a blankholder for-clamping the work piece against a support during the shaping operation.

'With hydraulic presses of the above type it sometimes occurs that on the retraction stroke of the press platen, when thework piece is still clamped on its support by the .blankholder, the cushioning piston suddenly jumps up and ruins the work piece.Av The reason for this phenominon consists in that as long as the work piece is held down by the blanlrholder platen, the oil beneath the die cushion ram is under high pressure, and while oil is only slightly compressible, yet there is a tendency of the oil tc expand with a jerk when the pressure on the oil is suddenly released. Y

Accordingly it is an object of the invention to provide a hydraulic press of the type referred to, which will eliminate the drawback set forth above. 1t is another object of the invention to provide a hydraulic press having a cushioning cylinder and a blanlrholder, in which the hydraulic pressure beneath the cushioning piston is released in response to the initiation of the 'retractionstroke of the press platen.

It is a further object of the invention to provide a hydraulic press having a cushioning cyl` inder and a blankholder platen in which the release of the hydraulic pressure beneath the blankholder platen is effected in response to a predetermined pressure acting upon the press platen.

Still another object of the invention consists in the provision of a hydraulic press of the character set forth in the preceding paragraph in which the rate of the release of the hydraulic pressure is variable.

These and other objects and advantages of the l c sioiaims. (ci. 11e-45) 'f General arrangement According to the present' invention, the cushioning'cylinder-piston assembly is provided with a hydraulic circuit rcomprising a relief valve which at the time when the press is operatedy for starting its retractiony stroke i's` actuated so as to release the oil pressurev acting beneath the cushioning piston. More specifically, a tonnage' control valve, which in response to a'predet'ermined pressure acting upon the press platen causes the initiation'oi the retraction stroke of-the press platen, establishes a communication between uid under pressure and a shiftable valve which due to this fluid pressure is operated so as. to effeet Communication between that portion of the cushioning cylinder which is beneath the cushioning piston and an exhaust.

Structural arrangement v .Referring to the drawings in detail, the hydrauliometal drawing press of Figure l comprises a base member lil connected to a top member il (reduced in size for clearness of showing) by means of tie rods I2, the latter being secured in position by means of the nutsiS upon the ends thereof. lProvided in the base member i0 is a. bore le guiding a supporting member i5 carrying supporting pins i6 for supporting the work piece to be drawn. The pins I6 pass through Corresponding openings in the bolster plate' I1 which is connected in any con venient manner with the base member HJ and is adapted to receive a die. The supporting member i5 is connected with a piston rod it carrying on its lower end a cushioning piston i9 reciprocab-ly mounted in the cushioning cylinder 2B. I he cushioning cylinder 2li has a port 2|. communicating witha conduit 22 which in its turn communicates with a check valve 23. The check valve 23 has a bore 24 normally closed by a ball 25. When the ball 25 is lifted the conduit 22 is adapted .to communicate with the conduit 26 leading from the Acheck valve 23 to a shutoff valve 21. The shutoi va-lve 21 comprises a valve bore 28- adapted to lbe closed by a valve member 29 `operableby means of the threadedshaft 30 and the .hand when 3| .con-

nected thereto. When the valve member 29 is in its open position the valvebore 2 8 communicates with the conduit. 32 leading to a two-way valve 33, The two-,way valve 33 comprises a cylinder bore 3 4 having reciprocably mounted therein a valve member generally designated 35 which comprises two pistons 36 and 31 interconnected by a valve member portion 38 of smaller diameter than the pistons 35 and 31. The valve member 35 is connected by means of a shaft 39 passing through a bore 48 of the valve 33 with a push rod 4|. The valve 33 is closed at its bottom and top by closure members 42 and 43 and a packing 44. The valve 33 furthermore comprises an annular recess 45 communicating with a conduit 46. Branching of! from the conduit 46 is a conduit 41 leading through a choke valve 48 to the port 49 of `a pilot operated valve gen.

the other hand with the port of a relief valve generally designated 52. The relief valve 52 comprises a casing 53 housing a spring 54 the upper end of which engages a plunger 55 which is adjustable so as to vary the thrust of the spring 54, while the other end of the spring 94 engages a plunger 55 with a piston rod 51. The piston rod 51 is reciprocably mounted in the bore 58 and adapted in response to a predetermined pressure in the conduit 59 to beliited against the thrust of the spring 5 4 so as to eil'ect communication between the conduit 59 and a recess 59 in the valve 52, which recess communicates through conduit 18 with the conduit 1| leading to the port 12 of a .tonnage control valve generally designated 13. The tonnage control v valve 13 comprises a. casing '14 with a,bore 15 in which is reciprocably mounted a plunger 15. The plunger 16 is connected with a cam 11 normally urged downwardly by a spring 18 and adapted when moving upwardly to actuate a lever 19 so as to break a circuit comprising a solenoid 88, The spring 18 is adjustable by means of the threaded shaft |34 so as to vary the thrust of the spring. The interior of the casing 14 communicates with a conduit 82 one end of which is connected with a choke valve 56 while the other end of the conduit 82 is connected with a port 83 of a check valve 84. The port 83 is normally closed by a ball 85 which in its elevated position allows communication between the conduit 82 and a conduit 85 communicating with the conduit 1|.

The pilotI operated valve 58 has a further portV 81 communicating with a conduit 88 from which branches oi a conduit 89. The conduit 89 communicates with a conduit 98 leading to the upper portion of the cushioning cylinder 28 and communicating with a conduit 9| leading to a safety valve 92 which is adapted to effect communication between the conduit 22 and the conduit 9|. Also communicating with the conduit 98 is a conduit 93 communicating with the interior of the casing 63 of the relief valve 62. Branching oiI from the conduit 59 is a conduit 94 leading to a pressure indicating gauge 95.

The conduit 46 communicating with the annular recess 45 of the two-way valve 33 leads to a conduit |85 communicatingon one hand with a four-way valve 95 and on the other hand with the' lower portion of the main cylinder 91. The

main cylinder 91 has reciprocably mounted therein a double acting piston head 98 of the drawing plunger 99. The cylinder 91 is furthermore provided with an upper port |88 .communicating with a conduit |9| leading to the four-way valve 96. The four-way valve 95 communicates ythrough a conduit |92 with a variable delivery present arrangement the valve 95 is normally urged by a spring into such a position as to establish communication between the conduit |82 and the conduit |99 so as to cause the pressure duid delivered by the pump to eiect a retraction stroke of the plunger 99. When the solenoid 99 is energized it shifts the valve against the thrust of the spring |35 to a position in which communication is effected between the conduit |92 and the conduit |9| thereby causing the pressure fluid delivered by the pump |93 to eiIect an advancing stroke of the plunger 99. Discharge line |91 also connected to the four-way valve 99 leads to the interior of the surge tank The main cylinder 91 lis supplied near the mouth of its cylinder bore |99 with a packing ring |99 beyond which is a packing ||9 adapted to be compressed by a gland so as to prevent leakage around the drawing plunger 99. Connected to the drawing plunger 99 isthe platen |I2, within which are arranged the clamping cylinders I I3 having clamping plungers `I; |4 operating therein. Each clamping plunger 4 is provided with a packing '||5 and gland ||8 for the prevention of leakage. Secured to the platen ||2 is a drawing punch ||1 adapted to pass through an aperture l I8 in the clamping member or blankholder |I9 secured to the outer ends of the clamping plungers l I4. A The extent to which the clamping member ||9 may move relative to the platen ||2 is limited by the rods |35 connected with the clamping member 9 and provided with nuts |31 on the opposite ends thereof which l' are adapted to engage the platen |2.

Each of the clamping cylinders I|3 communicates with a fluid passageway y|29 leading by way of an outwardly opening check valve |2| to a common passageway |22 which extends upwardly through the drawing plunger 99 and opens into the drawing cylinder bore |88 immediately beneath the drawing piston head 98. Consequently, iluid is free to pass from the pull-back or return side of the drawing piston head 98 into the clamping cylinders H3, but is prevented from passing in the opposite direction by the action of the check valves |2|. Also passing outwardly from each clamping cylinder ||3 is a fluid passageway |23 leading to an intermediate portion of a pipe |24 having on one end a safety valve |25 and on the other hand a pressure relief valve |25. Leadingfrom the discharge side of the safety valve |25 is a discharge line |21 connected to the discharge side of-therelief valve |25 by the line |29.

The discharge line |21 passes upwardiy into the telescoping cylinder |29, thereby forming a slip connection, enabling the telescoping cylinder |29` and the discharge line |21 to move vertically relatively to each other, an action which necessarily occurs when the platen ||2 moves downwardly in response to the action of the drawing plunger 9S. A discharge line |30 leads from the telescoping cylinder |29 into the interior of the surge tank and serves to discharge fluid expelled from the pressurerelief valve |26 or the safety valve |25. lThe safety valve |25 is provided merely as an additional safety feature in the event of a jamming or'other failure of the pressure relief valve |26, and is set at a higher pressure than the relief valve |26 so as to operate in case of the accumulation of a dangerous pressure within the corresponding clamping cylinder ||3 and a failure of the corresponding pressure relief valve |26 to act. Each clamping cylinder I3 is provided with its own pressure relief valve |26 and safety valve |25 so that a different pressure release point may be given to each clamping cylinder. The pressure relief valvesv |26 are connected to the drawing plunger passageway |22 by conduits I3| for the purpose of counter-acting the action of the relief valves |28 during the return stroke of the drawing plunger 99.

The relief valve |26 does not form a part of the present invention and may be of any convenient type. Preferably a relief valve of the type described in Patent No. 2,167,941 to Walter Ernst maybe used.

The conduit 8S communicating with the port 8l of the pilot operated valve 50 leads to the surge tank |05. The' conduit 'HI communicating with the port "l2 of the tonnage control valve I3 communicates with the conduit |0I leading to the upper portion of the cylinder bore |99 of the press.

The push rod 9| connected by shaft 39 with the valve member 35 of the two-way valve 33 has adjustably connected therewith a collar |32 which is adapted to be engaged by the platen arm |33 connected to the platen H2. When the collar |32 is engaged by the upwardly moving platen arm |33 the valve member 35 will be lifted upwardly. The push rod 4 I has furthermore adjusted thereon a collar |38 which when the platen nears the limit of its downward stroke is engaged by the platen arm |33 thereby shifting the valve member 35 downwardly so as to interrupt communication between the conduits 32 and 56.

Operation Pressure fluid is then delivered by the pump |03,

through the valve 95 and the conduit IIlI into the space above the piston head 98. This fluid forces the drawing plunger S9 and the platen |I2 downwardly, carrying with them the clamping member II9. When the latter engages the periphery of the work piece it comes to a standstill whereas theplaten I|2 continues to move downwardly. Due to the relative movement between the press platen |28 into the discharge line |21 leading to the telescoping cylinder |29 and thence by the line |30 to the surge tank |05. In this manner each clamping plunger ||4 may be caused to exert a different force upon the portion of the blank periphery which is engaged by the clamping mem-- ber II9. As soon as the drawing punch II'I engages the work piece and begins its actual drawing operation, the supporting pins supporting the work piece intermediate its ends are gradually moved downwardly by the punch'l Il as the drawing progresses. Since at this time the pilot operated valve 50 is in such position that the communication between the conduit 58 and the conduit 88 is interrupted, the' only way in which the oil beneath the cushioning piston I9 can escape from the cushioning cylinder 20 is through the die 'cushion relief valve 62 -or the safety valve 92. The check valve 23 prevents the oil discharged by the downward movement of the piston I9 from returning through the valves 2l and 33. The safety valve 92 is set at the maximum pressure for which the die cushion cylinder 20 is designed and it is intended only to function in case the valve 62 fails to operate. As the cushioning pisf ton I9 is moved downwardly, oil escapes through the conduit 22, port 60, port 6I, and from here,

' since the piston rod 61 is lifted, through the recess I I2 and the clamping member I I9 with its clamp- I ing plungers I Ill pressure builds up in the clamping cylinders II3 thereby causing the clampmg member I I9 to firmly clamp the work piece against its support. When the pressure within cach 69, conduit 10, conduit and conduit IDI into the main cylinder. Leakage past the plunger 66 of the valve 62 passes through the conduit 93 and the conduits 89 and 88 into the surge tank |05.

:As pressure builds up in the main cylinder 91 it is transmitted through the conduit '|I to the tonnage control valve 13. When this pressure yreaches a value corresponding to the setting of the tonnage control valve, the plunger 'I6 of the tonnage control valve '|3 is lifted against the thrust of the spring 18 and shifts the lever 'I9 so that the latter breaks the circuit comprising the solenoid which, as previously mentioned, when energized shifts the four-way valve 98 so as to establish a. communication between the pressure sideof the pump |03 and the conduit IOI. Consequently, the solenoid 80 is now -de-energized so that the spring |35 moves the four-way valve 95 into such a position where the communication between the' conduit |02 and I0| is broken while communication between conduit |02 and |06 is established. This results in a reversal of the movement of the drawing plunger 99.

,Due to the lifting movement of the plunger 18 pertaining to the tonnage control valve 'i3 also communication between the conduit `II, and the conduit 8| is established, thereby allowing pressure uid to pass from the conduit 7| through conduits 8| and 82 and through the choke Valve 56 and conduit 55 so as to shift the valve member 5| toward the left thereby establishing cornmunication between the conduits 58 and .88. Now the oil slightly compressed beneath the cushioning piston I9 is relieved through the conduits-22, 59, 58, the port 81 of the valve 58 and the conduit 88 to the tank. Consequently, when the blankholder ||9 during the retraction stroke of the press platen releases the work piece, the

cushioning piston I9 cannot push the work piece A kupwardly due to the expansion 'of oil trapped beneath the cushioning piston I9. The press is now on its retraction stroke. As soon as pressure builds up in the push-back line, pressure fluid passes through conduits 46 andll'I and shifts the reciprocable valve member 5| back to the right so that the communicationl between the conduit 88 and the conduit 58 is again inter-v rupted. At the same time oil in the right cavity |38 of the valve 50 is exhausted through the ,choke valve 56, check'valve 84, conduit 1|, conduit and discharge line |01 into the tank |05. The function of the check valve 84 is tomost position so that the conduit 46 does not communicate with the conduit 32 no pressure fluid can be conveyed through conduit 26 beneath the cushioning piston I9. However, when the platen I2 has almost reached the end of its retraction stroke, the platen arm |33 engages the collar |32 so as to lift the valve member 35l and establish communication between the conduits 46 and the conduit 32. Now pressure fluid is passed through conduit 46, communieating with the pressure side of the pump |03, to the conduit 26 so that the check valve ball 25 is lifted and the pressure in the conduit 26 conveyed beneath the cushioning piston I9 thereby lifting the latter to its initial position. When the platen |.|2 has reached the end of its retraction stroke, the pump |03 is moved to its neutral position by any convenient means well known to those lskilled in the art, for instance, by causing the platen ||2 or an arm connected therewith to shift the flow control member of the variable delivery pump |03 to neutral or no delivery position. In case a constant delivery pump is used instead of the variable delivery pump |03 valve means may be provided which at the end of the retraction stroke are actuated in response to the movement of the-platen so as to by-pass the delivery of the pump into the tank |05. The press is now ready for a new cycle.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having now fully described my invention what I claim as new and desire to secure by Letters Patent, is:

1. A hydraulic press comprising in combination, a press ram and main cylinder, hydraulic motor means for reciprocating said ram, hydraulically operable cushioning means, means adapted to supply pressure fluid to said motor means and said cushioning means for actuating the same, fluid operable means controlling the initiation of the retraction stroke of said ram and being responsive to a predetermined. fluid pressure within said main cylinder exerted by said motor means on the Work piece to be shaped during the pressing operation for initiating the retraction stroke of said ram, and valve means operatively connected with said iiuid operable means and adapted in response to the pressure within said main cylinder to `release fluid pressure on said cushioning means.

2. A hydraulic press comprising in combination a press ram having associated therewith fluid operable advancing and retracting means,

.tions of said work piece while it is being shaped,

' means for supplying pressure fluid to said advancing and retracting means and to said cylinder-piston-assembly for actuating the same, control vmeans responsive to a predetermined pressure on said advancing means for releasing pressure fluid-therefrom, and valve means normally preventing hydraulic communication beeration, fluid operable cushioning means for supclamping means for clamping a work piece against a support, means for actuating said clamping means, a fluid operable cushioning cylinder-piston-assemblyadapted to support porporting portions of the work piec'e while it ls being drawn, a fluid source adapted to supply pressure iiuid to said ram and said cushioning means, controlling means associated with said fluid source for directing pressure fluid from said fluid source to said ram and said cushioning means so as selectively to effect an advancing stroke and a retraction stroke thereof, and fluid pressure responsive means adaptedin response to a predetermined pressure on said ram to actuate said controlling means for initiating the retraction stroke of said ram and also adapted to cause release of pressure fluid from said cushioning means.

4. In a hydraulic press, a press platen, clamping means associated with said platen for holding a work piece during the shaping operation thereof, hydraulically operable cushioning means for supporting portions of the work piece while it is being drawn, a fluid source adapted to supply pressure fluid to said ram and said cushioning means for actuating the same, pilot valve means operable independently of the travel of said 'platen to release pressure fluid from said cushioning means While the latter engages the work piece, and means adapted at the end of the pressing operation to cause actuation of said pilot valve means for releasing pressure fluid from said cushioning means.

5. In combination in a hydraulic press, a fiuid operable press ram having an advancing side and a retraction side, clamping means associated with said ram for holding a work'piece while it is being shaped, a fluid operable cushioning cylinder piston assembly for supporting portions of the work piece during the pressing operation, a variable delivery pump` for supplying pressure fluid to said ram and said cushioning piston,

electrically operable means for controlling the said ram, fluid pressure operable means adapted in responseto a predetermined pressure exerted by said pump on said ram to control the energization of said electrically operable means so as to cause said pump to deliver fluid to the retraction side of said ram, pilot valve means responsive to the operation of said pressure responsive means for releasing pressure fluid from said cushioning cylinder piston assembly, and means responsive to a predetermined pressure on said ram for reducing fluid pressure to said cushioning means.

6. In a hydraulic press, a fluid operable press ram, clamping means associated with said ram for holding a work piece in clamped position during the pressing operation, :duid operable cushioning means adapted to support portio oi the work piece while it is being drawn, a iluid source for supplying pressure uid to said ram and said cushioning means, uld pressure responsive means operable by a predetermined fiuid pressure acting on said ram for causing initiation of the retraction stroke of said ram. pilot valve means operable independentLv of the travel of said ram and adaptedm response to the operation of said pressure responsive to release pressure uid from said cushioning means, and adjustable means for varying` the rate of operation of said pilot valve means.

21. in a hydraulic press, a press ram having associated therewith uid operable advancing and reti-estime means for actuating the same, clamp ing means for holding e. work piece in clped assenso f n position while it is being drawn,means for actasting said clamping means, a hydraulically operable cushioning cylinder-piston-assembly for supporting portions of the Work piece during the pressing operation, a pressure uid source for supplying pressure fluid to said ram advancing and retreating means and said cushioning pllmger for actuating the same, iiuid pressure responsive means responsive to a predetermined fluid pressure on said ram advancing means for initiating e reverse movement of said ram, and means operable by pressure iuid. controlled by said pressure responsive means for releasing pressure iiuid from said cushioning cyiinderpiston-assembly. i

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