GB550680A - Improvements in or relating to hydraulic press circuits - Google Patents

Abstract

550,680. Hydraulic presses; fluid-pressure servomotor control systems ; valves. MULLER, J. A. May 26, 1942, No. 7112. [Classes 69 (ii) and 135] A hydraulic press which is especially applicable for acting at a predetermined pressure but not beyond is constructed with a pressure relief valve 18 connected to the pressure supply pipe 88 which delivers the pressure-fluid to an aperture 89 in the pressure cylinder 90, the valve 18 being adapted to open against the action of an adjustable spring 42 and byepass the pressure fluid via a pipe 106 to tank 85 when the predetermined pressure is reached. At this pressure also the pump 72 is adapted to be reversed by servomotor means as described in Specification 535,625, the rod 79 which controls the servomotor valve being operated by an electromagnet 75 under control of a switch 29 which is normally closed but which is opened to break a circuit which ultimately causes de-energization of the magnet 75 and reversal of the servomotor valve rod 79. The valve plunger 18 normally is closed under the action of the spring 42 and the differential pressure of the upper part 19 of the rod and the smaller part 20. The plunger carries an adjustable cam 25 which opens the switch 29 as the plunger rises to open the valve and permit the liquid to flow from an inlet 39 to outlet 40 and thence via pipe 106.