Patent GB-757723-A (GB)
Title: Improvements in or relating to hydraulic presses
IPC: B30B15/16
Filed: 1953-08-26
Abstract: 757,723. Hydraulic presses. ZOLLER, H. Aug. 26, 1953 [Aug. 28, 1952; March 19, 1953], No. 23620/53. Class 69 (2). The piston of a hydraulic press is moved up to the work under comparatively low pressure, whereupon a high pressure pump is automatically brought into operation to provide the working pressure. On turning a valve 4 to the position shown in Fig. 1, compressed air, entering through a conduit 1, passes into a tank 80 through a conduit 6, a one-way throttle valve 10, and a valve 69. Liquid in the tank 80 is forced through a conduit 82, past non-return valves 57, 60 into a press cylinder 64 to move the piston 65 to its working position. Liquid in the cylinder 64 above the piston flows into a tank 93 which communicates with the atmosphere through valve 4. The pressure in tank 80 builds up until the liquid, entering a valve control 14 through a conduit 21, is able to raise a piston 15 upwardly against the force of the compressed air acting on a bar 17. A main valve member 22 is thereby freed and moves upwardly under the influence of a spring 26. The compressed air in conduit 1 is thus brought into communication with a cylinder 50 having a piston 51 which is thereby urged forwardly so that a piston 55 forces liquid in a cylinder 49 past the valve 60 to increase the pressure acting on piston 65. At the end of its stroke piston 51 uncovers a port 54 and the compressed air enters a conduit 41 and moves a valve 37 to the left, thus enabling compressed air from a conduit 7 to enter a chamber 33 of the main valve cylinder 23 and to move the member 22 downwardly. Cylinder 50 is thus put into communication with the atmosphere through ports 32, and piston 51 is returned to the left by a spring 53. The return of piston 55 draws liquid from tank 80 into the cylinder 49 through the valve 57. Towards the end of its return stroke the piston 51 moves a member 43 to the left and thus enables the air in chamber 33 to escape through ports 48 so that the valve member 22 may rise and put the piston 51 again under pressure to initiate a new stroke. To release the pressure in the press cylinder the valve 4 is moved so that the conduit 6 is open, and tank 93 remains open, to the atmosphere, whereupon the compressed air in tank 80 escapes through ports 77 in the valve 69; the fall in pressure enabling the liquid in a conduit 91 to open a valve 84 so that the liquid below the press piston 65 may return to the tank 80. For a speedy return of piston 65 the valve 4 may be turned to put the tank 93 into communication with conduit 1 so that liquid is forced into the top of cylinder 64 to return the press piston to its idle position. In Fig. 4 the valve 4 is replaced by a pressure reducing valve 101 which is operatively connected to a valve 113 which controls the movement of the pressure fluid to and from the tank 93. By adjusting the position of an operating lever 110 of the valve 101 the pressure of the fluid driving the piston 51 is altered, and thus it is possible to control the maximum pressure obtainable with the pump 100. In place of a valve 113 a valve similar to valve 101 may be used, this valve being coupled to valve 101 and 180 degrees out of phase with it.