GB871251A - Improvements in or relating to the pressing of sheet metal or other material - Google Patents

Abstract

871,251. Hydraulic. presses. BOULTON PAUL AIRCRAFT Ltd. Nov. 5, 1958 [Nov. 6, 1957], No. 34573/57. Class 69 (2). [Also in Group XXII] An hydraulic system for operating a sheet metal working press includes an hydraulic ram 33 for reciprocating an upper pressure chamber 1 containing an elastic diaphragm 18, damper rams 17 for controlling the rate of descent of the chamber 1, a manually operable control valve 36 which supplies pressure fluid from an electrically driven pump assembly 57 via two check valves 43 and 44 to the ram cylinder and an hydraulic cylinder 32 for actuating locking means 29 for securing the chamber 1 to the lower platen 23 of the press which supports a die 24. The locking means are controlled by a valve 64 operated by a solenoid-actuated pilot valve 67 energized by a ram-operated limit switch 68 via a time-delay switch 70. The pressure chamber 1 is connected to a manifold 91 which communicates with a high-pressure solenoid-controlled switch-off valve 83 and thence via a conduit 71 through a medium pressure shut-off valve 75, actuated by a beam 11 on the ram 63, to tubular reservoirs 72. The reservoir assembly comprises two tubular members interconnected at their ends. At one end is arranged an air charging valve 98 and the other end houses a metal float 73 for sealing the conduit 71 from the pressure chamber 1 when the exit of fluid from the reservoir is completed. A second tubular reservoir 79 is arranged for injecting a supplementary supply of hydraulic fluid into the reservoir 72 when female tools 24 are being used. The pressure pump assembly 80 is of the spring-loaded swash plate type. An intensifier 84 is included in the system and manually operated valves 86 and 77 control the pressurization and intensification of the fluid in the chamber 1. In operation, when the chamber and lower die are brought together and the elastic diaphragm is distorted by engagement with the die the pressure inside the chamber rises and fluid is returned to the reservoirs 72. The chamber is pressurized by actuation of the control valve 77 and when a predetermined pressure is reached, e.g. 2000 p.s.i., a pressuresensitive switch operates a solenoid-controlled shut-off valve 83. If intensification of the pressure is required control valve 86 is operated to admit fluid pressure direct from the pump assembly to the intensifier 84, which supplies the required pressure fluid to the chamber to deform the workpiece.