GB632214A - Improvements in or relating to hydraulic control systems especially for tractor-mounted agricultural implements - Google Patents

Abstract

632,214. Agricultural implements. FERGUSON HOLDINGS, Ltd., H., FERGUSON, H. G., SANDS, W. J., and CHAMBERS, J. March 7, 1947, No. 6455. [Class 6(i)] [Also in Group XXIX] Relates to tractors having a hydraulic system of the type wherein a continuouslydriven pump 20 feeds oil to a hydraulic ram 6 the piston 7 of which is connected to lifting arms for raising and lowering implements mounted on the tractor and wherein the oil is supplied to or ejected from the ram as the result of the movement of a valve 21, the position of which is affected by the depth of working of the tools. According to the invention, the system includes a reservoir 26 for fluid under pressure which is supplied by the pump, and the fluid inlet 23 on the suction side of the pump is controlled by a valve movable in accordance with the pressure attained in the reservoir. The system is shown applied to a tractor which is connected to the implement by upper and lower hitch links. The implement-controlled valve includes a double plunger 21, 39 slidable in a bushing 37 having ports 35, 40 through which fluid passes to and from the ram. The plunger is connected by pivoted links to a double lever, of the type described in Specification 550,142, whereby the valve may be operated manually, or automatically by the movement of the lifting links, to regulate the depth of cut of the tools. The pump includes a cam-operated piston 20 and is fed with oil from a sump through an inlet 23 controlled by a piston valve 24 working against a spring 25. On the delivery side 27, the pump feeds the implement-controlled valve 21 through a conduit 22 and the reservoir 26 through a conduit 22a. The reservoir 26 includes an airfilled chamber 54 separated from the oil chamber 53 by a diaphragm 52. A conduit 48 connects the reservoir with a passage 44 within which is located a plunger 24a connected to the piston valve 24. When the reservoir pressure exceeds a predetermined quantity the valve cuts off the intake of oil to the pump. Since the reservoir provides an immediately-available supply of oil for operating the ram, the lag in the system is much reduced. Specifications 470,069 and 470,087 also are referred to.