GB1221654A - A valve assembly for a fluid-operated ram - Google Patents

Abstract

1,221,654. Hydraulic presses. FORSYTH PRESSES Ltd. 8 April, 1968 [24 May, 1967], No. 24152/67. Heading B5F. [Also in Divisions F2 and G3] A pair of valves 20 are mechanically linked by a lever 11 in such a way that in an intermediate control position, fluid under pressure is admitted to both sides of a press ram 1 to stop it. The lever 11 is pivotally mounted at 12 and connected by a link 10 to a control handle 9. The handle 9 is adjustably fulcrummed on an arm 8 connected to a telescopic link 5 pivoted at 6 to the press frame and at 7 to a guide 2 on the ram 1. The lever 11 is weighted to bias the valves to a position in which the fluid is supplied to the underside of the ram. Each valve 20 is connected to a piston 23 in a cylinder 24 which is at the respective outlet pressure for exerting an equal and opposite pressure on the respective valve element, thus ensuring a pressure balance on each valve. Fluid under pressure is supplied to the system by a two-stage pump 4 having a plunger stage and a meshing gear stage. Operation.-When the operator depresses the handle 9, lever 11 is raised and both valves 20 adopt the intermediate position. Fluid is therefore supplied to both sides of the ram and returned to the reservoir (not shown). As the lever 11 rises further the RH valve 20 closes on its top seat 27 and the LH valve closes on its bottom seat 27<SP>1</SP> causing the fluid to flow through a LH by-pass 22 and port 28 to the upper side of the ram 1. Expelled fluid from the underside of the ram 1 enters the RH port 28 and leaves the RH outlet 17 through a one-way valve 29 to the upper side of ram 1. As the ram descends the tilt relationship of the lever 11 to the valves 20 is maintained until the operator halts the handle 9. This allows the ram to overtake the handle 9 whereupon the intermediate position is regained and the ram halts. A more positive stoppage of the ram may be ensured by providing a sub-circuit A.