Patent GB-1075450-A (GB)
Title: Tractor hydraulic control system
IPC: A01B63/111
Filed: 1963-12-27
Abstract: 1,075,450. Tractor power, lift mechanisms. MASSEY-FERGUSON Inc. Dec. 27, 1963 [Dec. 26, 1962]; No. 51090/63. Heading A1P. The lift arm 18 of a tractor hitch linkage is actuated by a hydraulic actuator 25 under the control of a valve 41 The valve 41 is positioned in accordance with draft load on the implement carried by the. linkage or by a manual up and down position, selector there being an override control responsive to the fluid pressure in the actuator 25. The valve 41 is movable between at supply position in which a fluid source is connected to the inlet of a pump 40 to lift the implement a neutral position in which the implement is locked in position and a discharge position in which the line 45 leading to the actuator is connected to the source to lower the implement The valve 41 is actuated by a lever 54 through a drafty linkage 51, position linkage 52 or pressure linkage 53 each of which incorporate a lost notion connection, the valve 41 being biased to an actuator supply position by a spring 50 Draft Load Control. The load on the implement is applied to a lever 14 of the linkage to move a piston 69 against a spring 67. A rod 60 is urged into.abutment with the piston 69 whereby movements of the piston cause rotation of a lever 61 which acts through a cam 76 to adjust the valve 41 through a lever 54. Thus the implement is raised or lowered through the actuator 25 andshaft. 20 to maintain the draft load constant. The setting of the draft load is obtained by a lever 75 which acts through shaft 77 and link 78 to adjust a rod 79 which carries the cam 76. Positional Control. The manual control' for lifting and lowering the implement is provided by movement of a lever 9 through the range C-D. This lever rotates a shaft 91 to adjust a cam 89 to actuate the valve 41. A feedback is< provided upon shaft 20 rotation by a cam 87 which acts on a link 52 to rotate the rod 93 which carries the cam 89. Pressure Control. A control in response to the pressure in the actuator is provided by a valve 103 which is opened against the loading of a spring 106 to actuate a piston 101 and linkage 53 when the pressure rises above the setting of the spring. The link 53 acts on the valve 41 through lever 54 as before. The lever 90 for adjusting the piston is also used to adjust the loading of spring 106 when this lever is moved within the range F-J. The lever causes movement of a cam 110 which abuts a fixed stop 113. Within the range F-J the surface 115 of the cam is operative and'when the lever is between C and F the portion 116 maintains maximum loading of the spring 106. The lost motion in the linkages. 51, 52, 53 allows the pressure control to, override. the draft or position control. Between the fully up position D of the lever 90 and the maximum pressure position F the valve 41 is actuated directly through rod 93. and cam 89 but a stop 120 prevents movement of the shaft 20 and the feedback. 52 is ineffective. A relief valve 108 is provided in the circuit which is operable when the valve 103 is opened. In a modification the movement of lever 54 is. subjected' to the control of a dashpot. The system may also be used to control a ram in a trailer linkage whereby part of the load of the trailer is transferred to the tractor.