Patent GB-732775-A (GB)
Title: Improvements in or relating to control means for hydraulic forging presses
IPC: B21J9/12
Filed: 1951-05-24
Abstract: 732,775. Hydraulic presses; fluid-pressure servomotor-control systems valves. ELECTRAULIC PRESSES, Ltd., TOWLER, J. M., and TOWLER, F. H. May 9, 1952 [May 24, 1951], No. 12125/51. Classes 69 (2) and 135. Hydraulic control means for a forging press, the ram of which may make a series of rapidly repeated short planishing strokes in addition to the normal forging strokes and which may be instantly reversed or arrested in any position, comprises a piston control valve A, Fig. 1A, controlling the supply and exhaust of pressure. liquid to and from the main press cylinder 75, Fig. 1, a manually - actuated pilot valve E controlling the movements of the piston valve A and of a spring-loaded needle valve C controlling the movements of an automatically-operating reversing valve B and a press unloading and refill valve D. The piston valve A comprises a valve piston 1 having lands 15, 16, 17 co-operating with recesses 6 ... 11 in the valve casing and one end continuously subjected to liquid pressure transmitted through a line 97 from an accumulator 98. The pilot valve E comprises a sleeve 5 slidably mounted on one end 3 of the valve piston 1 and connected by a link 20 and an arm 19 to a manual operating lever 18 which is also operatively connected to the needle valve C controlling the supply of pressure liquid through a line 43 to the end chamber 71 of the reversing valve B. The reversing valve comprises a plunger 49 having lands 49a, 49b co-operating with casing recesses 50, 51, 52 connected respectively by lines 97, 54, 55 to the accumulator 98, the recess 11 of the valve A and exhaust. One end of the plunger 49 is formed with a double cone which co-operates with spring-pressed balls 56 to hold the plunger in either of two operating positions. The other end of the plunger 49 co-operates with a piston 61 slidable in a chamber 63 connected by a line 105 to a cylinder 104 slidably mounting a small ram 103 operably associated with the main ram 77 of the press. Leftward movement of the piston 61 and hence of the plunger 49 is limited by an adjustable stop 62. The unloading and prefill valve D connects the press cylinder 75 to a prefill tank 111 so that the press cylinder may be rapidly filled and emptied and comprises a main valve 74 loaded by a light spring 76 and an even number of circumferentially arranged valves 78 having stems 80 and controlling passages through the main valve 74. The lengths of the stems 80 are arranged so that the valves operate sequentially in pairs on the engagement of the stems by a hollow striker rod 81 controlled by a differential piston 82 having chambers 85, 87, connected by lines 110, 116, to the recesses 8 and 7 respectively of the piston valve A. Pumps 94, Fig. 1B, deliver pressure liquid directly to the press cylinder 75 through a line 96 and control pumps 88 deliver pressure liquid through a line 114, the valve A, and a line 113 to the press cylinder 75 and to the push-back cylinders 86. The line 114 is connected to the recess 9 of the valve A and through a check valve 115 to the recess 8. The pushback cylinders are connected to the recess 8 by lines 99, 107, and to the accumulator 98 by the line 99 and a choke 99a, reducing valve 100, and relief valve 100a. A spring-loaded valve 119 having a connection 122 with the recess 7 to additionally load the spring controls the flow of pressure liquid between the pushback cylinders 86 and the main press cylinder 75 through the lines 99, 96 and a line 118. Operation.-On movement of the lever 18 to move the sleeve 5, e.g. to the right, due to the pressure liquid acting on the end 2 of the valve piston 1, the valve piston follows up the movement of the sleeve. Should the valve piston overshoot the sleeve 5, ports 24 are opened so that pressure liquid acts on the larger righthand end of the valve piston 1 until the ports are again closed and the valve piston and sleeve are restored to their previous relative positions. The lever 18 may be moved to any of four operating positions, viz., " return," " neutral," " forge " and " auto." In the " return " position the sleeve 5 is moved so that the valve piston 1 occupies its extreme left position, the land 16 being disposed in the recess 8 so that the control pumps 88 are connected through the lines 114, 107 to the push-back cylinders and through the lines 110, 116 to the chambers 85, 87. The differential piston 82 thus moves downwardly to open in turn the pairs of valves 78 and the main valve 74 to connect the press cylinder 75 to the tank 111 whilst the push-back rams move upwardly to raise the main 77 so that the press cylinder is rapidly emptied of liquid. At this stage the valve 119 is held closed by its spring and liquid pressure transmitted through the line 122, and, after the push-back cylinders are fully charged pressure liquid from the pumps 88 is available to recharge the accumulator 98. In the " neutral " position of the lever 18, the valve piston 1 is positioned slightly to the right of its " return " position, the pumps 88 now being connected to the press cylinder through lines 114, 113, 96 and to the chambers 85, 87, through the lines 110 116. As before the valves 74, 78 are open and pressure liquid is supplied to the tank 111 through the press cylinder. In the " forge " position, the sleeve 5 is moved so that the valve piston 1 is positioned to connect the pumps 88 through the lines 114, 113 and 96 to the press cylinder, the chamber 87 through lines 116, 109 and the spring chamber of the valve 119 to exhaust. Hence the differential piston 82 moves upwardly to permit closing of the valves 74, 78, whilst the valve 119 opens, permitting pressure liquid from the push-back cylinders to flow through the lines 99, 118, 96 to the main press cylinder to augment that supplied by the pumps 88, 94. The ram 77 of the press then moves downwardly to contact the workpiece. When sufficient pressure has been built up in the press cylinder, the pumps are relieved through valves 123, 124. In the " auto " position the press is used for short rapid planishing strokes. In this position the link 20 engages the pin 30 of the needle valve C to compress its spring to load this valve, the valve piston 1 being positioned to connect the chamber 87 to exhaust through a choke 93 and lines 116, 109 and the chamber 85 to the push-back cylinders through lines 110, 107, 99. Since the pressure in the chamber 85 falls more rapidly than that in the chamber 87, the valves 74, 78 open to allow liquid to flow from the tank 111 into the press cylinder 75, the ram 77 falling under gravity moving the push-back rams to transfer liquid from the push-back cylinders to the main press cylinder 75 through the lines 99, 107, 117 and 96 and an adjustable choke 106 which controls the rate of descent of the ram 77. The pumps 88 are connected to the press cylinder and when the ram contacts the workpiece pressure is built-up in the press cylinder whence the valve 74 closes. The pressure in the press cylinder is transmitted through a line 44 to a chamber 36 of the valve C to oppose and eventually overcome the pressure applied to this valve by the operator and so open the needle valve C whence pressure liquid is supplied to the chamber 71 of the reversing valve B. The plunger 49 of this valve then moves leftwardly and connects the accumulator 98 to the right-hand end of the valve piston 1 through the lines 97, 54, the recess 11, a check valve 101 and a line 102 to a chamber 21a of the valve A. The valve piston 1 is then automatically moved to its extreme left or " return " position and, as previously described, the control pumps 88 supply the push-back cylinders and the valves 74, 78 open to exhaust pressure liquid from the press cylinder 75 to the tank 111, the ram 77 then moving upwards. At the same time the ram 103 moves upwards to increase pressure in the chamber 63 of the valve B to move the piston 61 and the plunger 49 to the right and connect the chamber 21a to exhaust through lines 54, 55. The valve piston 1 now being relieved of pressure on its right-hand end automatically moves to the right to again cause downward movement of the ram 77 and buildup of pressure in the chamber 36, opening of the needle valve C &c. This cycle of operations continuing all the time the lever 18 is held in the " auto " position. The pressure in the press cylinder is dependent upon the amount of pressure applied to the spring 41 by the operator.