Patent GB-433673-A (GB)
Title: Improvements in valve mechanism and valve controls for hydraulic presses
IPC: B30B15/16
Filed: 1934-12-01
Abstract: 433,673. Hydraulic presses. SHAW & SONS (SALFORD), Ltd., J., and SHAW, J. B., Wellington Street Works, Salford, Lancashire. Dec. 1, 1934, No. 34563. [Classes 69 (ii) and 135] Mechanism for operating an hydraulic press comprises a valve which can be operated either manually or mechanically by a differential-pressure device, the latter only allowing of manual operation when it has been exhausted. The pressure device comprises two pistons 7, 8, Fig. 1, working in pneumatic cylinders 1, 2 of different diameters and connected by a pistonrod 9 formed with a rack 10 to engage a pinion 11 on a shaft 12 operatively connected to the valve, which is of the screwdown type. An arrangement of such mechanisms is described for operating automatically a hydraulic press of the kind in which an upper ram first descends to nip and hold the work against a stationary intermediate platen and the lower ram then ascends to press the work, such as sheet metal parts of motor-car bodies, to the required shape ; the lower ram being returned by gravity, and a jack being provided for raising the upper ram. Five pressuredevices are provided, the device 27, Fig. 7, operating the admission valve to the jack, the device 29 operating simultaneously and in reverse direction the exhaust valves of the upper cylinder and the jack, the devices 25, 26 operating the admission and exhaust valves respectively of the bottom cylinder, and the device 28 operating the admission valve to the upper cylinder. The cylinders 2 of the devices 25-29 are connected directly to a compressed-air supply pipe 41 by pipes 5 so that normally the valves are kept in the positions indicated in full lines in Fig. 7, and the cylinders 1 of the devices 27, 29, 26 are connected to the air supply through a solenoid operated valve A, while the cylinders 1 of the devices 28, 25 are connected through solenoid-operated valves B, C respectively. When the solenoids are energized, the valves connect the cylinders 1 to exhaust so as to actuate the piston rods 9, but normally they are connected to the pipe 41. A cock 41<a> in the pipe 41 can be operated so that in one position it puts the devices 25-29 in connection with the compressed air supply and in another position shuts off the supply and exhausts all the cylinders 1, 2 so that the valves of the press can be operated manually by levers 30<a>-35<a>. Mushroom valves 42, 43 with small through-passages therein are situated in the feed pipes to the cylinders 1 of the devices 27, 29 so that when the valve A is connected to exhaust, the action of the device 29 lags behind that of the device 27, while when the valve A is connected to the compressed air supply the reverse action takes place. The solenoids of the valves A, B, C are connected in parallel across electric supply-lines 52 and, when a starting switch 53, 58 is operated, are adapted automatically to come into operation in the order A, B, C and then to cut out in the reverse order. For this purpose switches 45, 47 and 48 in series are provided which are operated electrically by subsidiary circuits. When the starting switch is closed, the switch 45 is closed through the circuit 54 and operates the valve A so that the devices 27, 29 operate in succession as previously described and the upper ram starts to move downwardly under the action of gravity. The subsidiary circuit 541 of the switch 47 contains a switch 55 operated simultaneously with the switch 45 and a switch 46 connected to the clapper of the switch 45 by a delay-action device so that the switch 47 and therefore the valve B operate a certain time after the valve A, whereupon the admission valve to the upper cylinder is actuated and pressure is applied by the upper ram. When the pressure in the upper cylinder 57 of the press reaches a certain value it actuates a switch 56 in the subsidiary circuit 54<11> of the switch 48 whereby the valve C is operated and causes the admission valve to the lower cylinder 60 to be opened and the lower ram to rise to press the work to the required shape. When the pressure in the lower cylinder reaches a predetermined value, it causes a normally-closed switch 59 in the circuit of the switch 58 to break and start the reverse sequence of operations. Opening of the switch 59 causes the switch 55 to be deenergized thus opening the switch 47 and consequently the switch 48 which is in series with it. The valves B, C are thus opened to exhaust, and the admission valves to the press cylinders 57, 60 closed. A switch 61 in the subsidiary circuit 54 of the switch 45 is connected to the clapper of the switch 55 by a device which closes the switch 61 immediately the switch 55 is closed but delays the opening of the switch 61 when the switch 55 is opened. The breaking of the circuit 54 therefore takes place some time after the valves B, C are opened, and causes, through the de-energizing of the solenoid of the valve A, the jack-cylinder exhaust to be closed, the upper-cylinder exhaust to be opened and the jack-cylinder admission valve to be opened. The differential pressure-devices 25-29 may operate reciprocating valves through cams. Specification 338,946, [Class 69 (ii)], is referred to.