Patent GB-691347-A (GB)
Title: Improvements in or relating to hydraulic presses
Inventor: ZIMMERMAN LOUIS
IPC: B21D24/14
Filed: 1948-11-09
Abstract: 691,347. Hydraulic presses. CLEARING MACHINE CORPORATION. Oct. 20, 1949 [Nov. 9, 1948], No. 29099/48. Class 69(ii) In a hydraulic press comprising a work-performing slide 1, with an advance ram 6 and retracting rams 18, and a work-holding slide 2 suspended from the slide 1 by bolts 3 which permit further downward motion of the slide 1 after the slide 2 engages the work, rams 5 apply a predetermined work-holding pressure to the slide 2, said pressure being maintained constant by accumulators 23 which at a predetermined pressure isolate the workholding cylinders from the source of fluid pressure. The press is operated by a main pump 10 under the control of a solenoid-controlled valve 11. To start the operation, valve 11 directs pressure liquid through a pipe 9 to the cylinder 7 and through a branch 32 to pipes 31 connected by the devices 23 to pipes 22 leading to the work-holding rams 5. Valves 12, 20 open to allow free flow of liquid from the tanks 7<SP>1</SP> and 21 to the cylinders 7, 5, and the slides 1, 2 fall rapidly under gravity, the liquid forced out of the retracting rams 18 flowing through pipes 16, 17 to a pipe 15 leading to a check valve 14 which allows it to escape freely through a pipe 13<SP>1</SP>. The valve 14, Fig. 3, comprises a plunger 142 which when operated by a solenoid 14<SP>1</SP> connects the space 141a behind a shuttle valve 141 to exhaust through a passage 13b and allows the valve 141 to open, whereby the liquid from the pipe 15 escapes freely to the pipe 13<SP>1</SP>. When the slides 1, 2 are a predetermined distance from the work, the solenoid 14<SP>1</SP> is deenergized and plunger 142 blocks the passage 13b to close the. valve 141, preventing the escape of liquid from the rams 18 and arresting the movement of the slides. The pressure builds up in the cylinders 7, 5, and the pressure in the cylinders 18 finally overcomes a spring-loaded valve 14a, Fig. 3, to allow the slides to move down slowly, the liquid from the cylinders 18 escaping through the valve 14a and pipe 43 to the valve 11 which directs it through a pipe 34 and pipes 31 to the rams 5 to supplement the liquid from the pump 10. Each accumulator 23, Fig. 2, comprises a piston valve 30 attached to a spring-loaded piston 29 in a cylinder 24 filled with liquid, the bottom end of which is closed by a diaphragm 26 loaded by an adjustable predetermined air pressure. The liquid from the pipes 31 flows through ports 31b to the pipes 22 leading to the rams 5 and at a pressure determined by the air pressure in chamber 27 the valve 30 is forced down until a passage 30a therein admits pressure liquid below a valve 44 to raise it to cut off the supply to the rams 5, the pressure in which is then maintained constant by the accumulators 23 to apply the slide 2 to the work at constant pressure. The slide 1 continues to be forced down, the liquid from the rams 18 escaping through a check valve 50, Fig. 2, and pipes 49 leading to a relief valve 45. At the end of the working stroke, the valve 11 is reversed to direct the pressure liquid through a pipe 13 to the retracting rams 18 to raise the slide 1. Opening of the valve 60 connects the pipe 9 to the tank, releasing the pressure in cylinder 7 and causing check valves 50 in the accumulators 23, Fig. 2, to open, which connects the space below the valves 44 to exhaust, whereby the pressure in the rams 5 is released through the pipes 31. The valves 20 are opened by the pressure in the pipes 13a to facilitate return of the slide 2. The pressure in the pipe 13 also opens the valve 12 to connect the cylinder 7 to 'the tank 7<SP>1</SP> and permit rapid initial movement of the slide 1, and a valve 45 is opened, by-passing some of the liquid from the pipe 13, to slow down the slide 1 just before it begins to pick up the slide 2. At the end of the retracting stroke, the valve 11 is shifted to neutral to by-pass the discharge of the pump 10 to the tank, the valve 14 holding the rams 18 locked against downward movement. A valve 53 is opened by a ram 18 to release the pressure in the pipe 9 to prevent overtravel on the downstroke, and a pump 10a may be inserted in the pipes 31 to recharge the accumulators 23 if leakage occurs. In a modification the rams 18 are replaced by a skirt on the main ram 6, and in a further modification a valve in the pipe 9 directs pressure fluid to the work-holding cylinders .5 alone until the slide 2 contacts the work, the fluid from the cylinders 18 escaping to the supply tank. Specification 592,037 is referred to.