Patent GB-992867-A (GB)
Title: An improved hydraulic power lift mechanism for agricultural tractors or the like
Inventor: HULL CHARLES HARTLEY
IPC: A01B63/111
Filed: 1963-02-08
Abstract: 992,867. Fluid-pressure servomotor systems. DAVID BROWN TRACTORS Ltd. Feb. 7, 1964 [Feb. 8,1963], No. 5203/63. Heading G3P. A tractor power lift mechanism is actuated by a manual control or in response to draft force, means being provided to select the required control. The hitch mechanisms 70 Fig. 4 is operated by rotation of a shaft 73 actuated by fluid pressure acting on a piston 69. Fluid pressure is supplied and exhausted to the cylinder 22 through a conduit 21 under the control of valves 18, and 27. When the valve 18 is closed, fluid from a pump 10 opens a non-return valve 23 to supply fluid to the cylinder 22 and when the valve 18 is open, fluid from the pump flows to the sump through port 11. When valve 27 is open, fluid in the cylinder 22 flows to the sump through a flow control valve 26 and throttle valve 61. Each of the valves 18,27 are loaded to the closed position and have bleed passages which allow flow to chambers 19 and 28 respectively. The chambers 19 and 28 are connected to exhaust to open the valves 18, 27 by a control valve 37 having lands 42, 43 controlling the flow through passages 34, 35 to an exhaust passage 50, the passage 35 being connected to the passage 50 when the land 43 opens passage 35 by passages 47, 48, 49 in the valve 37. A non-return valve 68 is also provided in the exhaust passage 50 and the loading of this valve is adjustable by a member 64. The valve 37 is loaded by a spring 40 into contact with a lever 84 which is movable along a shaft 85 connected to a manual lever 88 through a bell crank 86 and rod 87. The lever is movable along the shaft 85 by a fork 123 Fig. 1 on rotation of a shaft 126. The sahft 126 is movable to three positions 131, 132 and 133. In the position 131 the end 110 of the lever 84 is located below both rods 113, 108, in the position 132 the end is below rod 113 but not below 108 and in position 113, the end 110 is not below either of the rods 113, 108 but a pin 115 on the lever lies below the member 64. Manual control. With the lever 84 in the position 132, rotation of the manual control 88 actuates the valve 37 through lever 84 to cause actuation of valves 18 or 27. A feedback is provided from the lift shaft 73 through link 112 and rod 113 to the lever 84. Draft force control. With the lever 84 in the position 131, the manual control lever 88 sets the initial height of the implement as above. Variation in the draft force acts through a Bourdon cable 82 on a lever 104 to adjust the rod 108 which actuates the valve 37 through the lever 84 to maintain a constant draft force. Controlling transfer of weight. To transport the implement, the lever 84 is set to the position 133 and the lever 84 is then actuated by the control lever 88 to lift the implement. This actuation of the lever increases the loading of ball valve 68 in drain passage 50 thus ensuring a sufficient back pressure in the line 21 which is less than that required to lift the implement, the position of the lever providing a predetermined back pressure.