GB894398A - Improvements in or relating to hydraulic systems - Google Patents

Abstract

894,398. Fluid-pressure servomotor-control systems; valves ; hydraulic apparatus. HOUGH CO., FRANK G. July 18, 1960, No. 24931/60. Classes 69 (2) and 135. A double-acting ram 12 which is actuated by supplying fluid pressure to either side and exhausting the other side under the control of a selector valve, not shown, is provided with valve means 22 comprising a closure member 15 slidable in a bore 21 to increase or decrease the speed of ram extension in dependence upon the load opposing the extension. With a heavy load fluid passes from the conduit 11 via a groove 24, a valve bore 21 and a groove 23 to the conduit 18, the fluid from the conduit 11 also traversing a passage 37 in the closure member 15 and entering a chamber 14 after opening an adjustably loaded relief-valve 13 seated on a member 15 whereby the latter is maintained in the position shown against fluid pressure in the groove 24 acting on a surface 40, of the member 15 ; fluid from the rod end of the ram passes to exhaust via a conduit 17, a groove 25, bore 21, a groove 26 and a conduit 16. If the load is light the fluid-pressure is insufficient to unseat the relief valve 13 but in acting on the surface 40 moves the closure 15 rightwardly to disconnect conduit 16, 17 and connect the exhausting fluid from conduit 17 to the conduit 18 through a passage 19 and groove 24 whereby the ram 12 extends at a greater speed. Should the load change during the ram extension the relief valve will either be opened or closed to cause a movement of the closure 15 to provide either an increase or a decrease in speed. A slidable element 29 is provided which in one position limits the movement of the closure member 15 and in another position prevents movement of the latter. A bleed passage 39 interconnects the space behind the relief valve 13 with the groove 25. The closure member 15 is also formed with another surface 40a opposite to surface 40 and open to groove 25 to maintain the member 15 in the position shown when conduit 16 is connected to the supply. In another form, the conduit 18 is connected directly to the supply, the groove 23 is dispensed with and conduit 11 is branched from conduit 18. In a further form a simple spool or other valve controls fluid flow from the piston-rod end of the ram to either the respective return line or the other end of the ram, the valve being operated by a load-responsive device.