Patent GB-1046621-A (GB)
Title: Control system for a tractor
IPC: A01B63/111
Filed: 1963-04-16
Abstract: 1,046,621. Tractor power lift mechanisms. MASSEY-FERGUSON Inc. April 16, 1963 [Aug. 1, 1962], No. 14736/63. Heading A1P. A tractor hydraulic system provides for position control, automatic draft control and weight transfer, the latter being conrolled by a lever 132 which is operatively connected with a spring 126 biasing a valve 128 for controlling the pressure in the system, the two former controls being operated by respective backward or forward movement of lever 75 which is connected to operate valve 62 which controls the supply and exchange of pressure fluid between the pump 50 and the main actuating cylinder 52. As shown in figure 1 an implement is pivoted to the draw bar 25 of a tractor whose draft links 22 have a connecting member 43 which underlies a bridge piece 44 on the implement. Main control valve 62. In the central position shown the valve plunger 63 cuts off the fluid supply to the pump 50 and also blocks the return to sump of fluid in the actuating cylinder 52 and conduit 67. When the plunger is raised the pump inlet is connected to the pump which then delivers pressure fluid to the cylinder 52. When the plunger is lowered the conduit 67 is connected to exhaust. The plunger is biased by a spring 74. Position control. A bell crank 101 is connected by a lost motion linkage to an arm 76 which is pivoted at 77 and operates the main control valve 62. The ball crank is pivoted at 102 to an assembly 103 connected to a lever 107 pivoted at 108 and engagable by a stud 109 on the actuating arm 57 of the rock shaft 58. To select position control the hand lever 75 is moved rearwardly whereby an eccentric pin 100 on a disc 94 moves the bell crank 101 about pivot 102 and thereby operates the main control valves 62 whereby pressure fluid is supplied to the actuating cylinder 52. As the actuating arm 57 is moved the pin 109 operates through the linkage 107, 103 to pivot the bell crank 101 about stud 100 and thereby return the valve plunger 63 to the neutral position. A cam 150 may be moved into contact with the bell crank 101, when the lever 75 is in the transport position in which the supply to the pump is normally cut off, and thereby keep the plunger 63 raised so that the pump is still supplied. An abutment 155 may be moved to limit the pivoting movement of lever 76 whereby the rate of drop is limited to any desired maximum speed. Movement of the lever 76 is damped by a dash-pot arrangement 165. Draft control. The draft links of the tractor are pivoted to a swinging arm pivoted to the tractor, and also pivoted to this arm for longitudinal movement relative to the tractor is a spring-biased draft control member 24 which has a stud 90 co-operating with a bell crank 89 operatively connected with a bifurcated bell crank 81. This latter bell crank has a lost motion connection with the control valve operating lever 76 and is also operated on by an eccentric pin 96 which is moved into engagement with the bell crank by forward movement of the lever 75. As the draft varies movement of the control member 24 makes the bell crank 81 pivot about the previously set pin 96 thereby operating the main control valve. Weight transfer. A constant transfer of weight from the implement to the tractor is accomplished by means of an auxiliary actuator supplied with pump pressure and incorporating a valve 119 controlling supply of pressure fluid to a cylinder 110 housing a spring- biased piston 112 mounting a rod 113 for operating the main control valve. The valve 119 is biased by a spring 126 the pressure of which can be adjusted by a linkage operated from hand lever 132. If the pressure in the system increases, the valve 119 is moved against its spring bias to allow fluid to operate piston 112 and thereby the control plunger 63 to cut off the supply of fluid to the pump. If the pressure in the system decreases the valve 119 moves to connect the cylinder 110 to drain 123 thereby releasing pressure of the main control valve. The pressure in the cylinder 110 is limited by a relief valve 141. A filter 125 is incorporated in the conduit. In an embodiment, valve member 119 may be formed to permit a small constant flow of fluid whereby response of pump to valve changes is quickened.