GB927678A - A control apparatus for hydraulically manipulated implements of commercial vehicles - Google Patents

Abstract

927,678. Tractor power-lift linkage mechanisms. ROBERT BOSCH G.m.b.H. June 8, 1961 [June 9, 1960], No. 20656/61. Class 79(1) A tractor hydraulic control apparatus comprises a slide valve 7 automatically adjustable in the cylinder 5 under the action of an implement supported by the tractor whereby either pressure fluid flows from a pump 1 to an implement working ram 20 via conduit 3, grooves 4 and 9, chamber 13 and conduits 17, 17<SP>1</SP> which include a non-return valve 18, or the pressure fluid is guided via conduit 3, grooves 4 and 8 to chamber 12 from where it is returned to reservoir 2 via return conduit 15. An auxiliary control device 32 is connected, in the " lowering " position S of the slide valve 7, to the pressure supply via conduits 26 and 31 and grooves 27, 28 so that a spring biased piston 35 is forced into the position shown in Fig. 1 whereby the chamber 13 is connected via conduit 40, and bore 42 with the return conduit 15. In this position the pressure conduit 17<SP>1</SP> is connected to the return conduit via conduit 21 and groove 23 and bore 24. in the slide valve to release pressure in the ram. In the " raising " position H of the slide valve, the pressure supply is cut off from the piston 35 so that its spring moves it to cut off the chamber 13 from the return conduit so that pressure fluid is supplied to the ram 20. In an embodiment a pressure relief valve is incorporated between conduits 3 and 15 and a blocking valve is inserted in the conduit 21 which is then connected directly to the conduit 15. The blocking valve is opened, in the " lowering " position, by pressure from the conduit 26. A compact arrangement in which all the control elements are located in one block, the auxiliary control device being located in one end of the slide valve, is also described.