GB728256A - Improvements in or relating to a hydraulic press or shearing device - Google Patents

Abstract

728,256. Hydraulic presses. BROEKHOVEN, A. J. VAN. Jan. 23, 1953 [Jan. 25, 1952], No. 2046/53. Class 69 (2). A hydraulic press comprises a fixed member 2 and a movable member 3 having secured thereto pistons 7, 8 operating in cylinders 5, 6 connected to supply and exhaust lines 19, 20 by lines 11, 13 and '12, 14 controlled by regulating valves 35, 36 and connected to common lines 16, 17 connected to the lines 19, 20 through an operating valve 18. The regulating valves 35, 36 comprise piston valves 38 biased upwardly by springs 39 and having lands which permit the flow between the pipes 11, 12, 16 and 13, 14, 17, when the piston valves are in the upper position. In a lower position the pipes 11, 12, 13, 14 are blocked. Secured adjacent to the cylinders 5, 6 are cylinders 21, 22 having pistons 23, 24 connected by rods 25, 26 to the pistons 7, 8 respectively. The cylinders 21, 22 are crossconnected as shown and the connection from the lower end of each cylinder is connected to the space above the piston 38 of the regulating valve controlling the adjacent operating cylinder. A valve 34 interconnects the cross-connections and a reservoir 33 when the member 3 is in its upper position. Unequal movement of the pistons 7, 8 and in consequence the pistons 23, 24 creates a pressure in one or other of the cross connections which operates the appropriate piston valve 38 to block the supply and exhaust lines of the operating cylinder, the piston of which is in advance of the other. In a modification, Fig. 3, the valves 35, 36, 34 and 18 are combined in a body 45 which is immersed in the reservoir. The operating valve comprises a piston valve 49 slidable in a bore 46 and having lands forming chambers 50, 52 connected to the reservoir and a chamber 51 connected to the pressure supply. The pressureregulating valves comprise a piston valve 73 controlling the flow between port 61, line 11 and port 67, line 13 and a piston valve 74 controlling the flow between port 64, line 12 and port 70, line 14, the ports 61, 67, 64, 70 being controlled by the valve 49. The piston valves 73, 74 are biased upwardly by springs 83, 84 and are depressed by separate pistons 89, 90 in cylinders supplied from,the cross connections by lines 43, 44, these cylinders having ducts communicating with the reservoir and controlled by valves 97, 98 closed by pistons 99, 100 connected to the pressure supply. Grooves 110, 111 on further pressure in the cross connections due to certain conditions connect the lines 13 or 14 through ducts 112 or 113 to the pressure supply to raise the leading main piston. To prevent the regulating valves operating during the raising movement links 106, 107 operated by the valve stem 48 in its lower position are forced into contact with the stems of the valves 73, 74. A change-over arrangement may be fitted whereby the regulating valves are effective during the raising movement.