Patent GB-1392234-A (GB)
Title: Control devices for agricultural tractor-mounted implements
IPC: A01B59/06
Filed: 1972-05-15
Abstract: 1392234 Tractor power lift mechanisms FIAT SpA 15 May 1972 [27 May 1971] 22624/72 Heading A1P The lower draft links 13, 14, of a tractor power lift mechanism each has an associated double acting hydraulic cylinder 10, 11 for lifting and lowering the linkage, allowing it to "float", or to transfer weight from the implement to the tractor, the cylinders being connected in series and being arranged to provide independent movement and lateral tilting of an attached implement. The upper link also includes a double-acting hydraulic cylinder 17 to adjust the angle of attack of an attached implement and to sense draft control forces. Position control. Fluid is supplied through conduit 44 and a transverse regulation distributor 23, to conduit 43 and vertical regulation distributor 24 from whence it traverses passageway 34 to the lifting distributor valve 21. For lifting, a manual lever 27 slides an outer sleeve 26 of a slide valve with slidable inner core 28 to supply fluid via passage 41 to valve 38 which cuts off the discharge passage 42 whereby the pressure fluid opens ball valve 37 to pass into conduit 19 and thus to a transverse stabilisation valve 20. The slide 50 of this valve allows the fluid to flow into the lower chamber 10a of cylinder 10 and force fluid from chamber 10b into the lower chamber 11a of cylinder 11. Fluid from the upper chamber 11 b flows to the valve 20 and through conduit 53 to valve 23 where it is directed into conduit 60 and to a discharge chamber 45. Follow-up is provided by link 32 attached to the draft link 14 and acting on the inner slide 28 of valve 21. For lowering, the sleeve 26 is moved so that pressure fluid from passage 34 no longer holds valve 38 closed whereby ball valve 37 closes and allows the fluid to flow through valve 38 to the discharge chamber 45. Fluid from the actuator chamber 10a is thus allowed to flow through conduit 19 to open valve 37a leading to a discharge chamber 46. Fluid is drawn into chamber 11b since this is still connected to the discharge chamber; the pressure in conduit 22 keeping the slide 50 biased against its spring as shown. Float. Lever 27 is moved to its limit so that it moves the lost motion sleeve 27b to operate valve 26a whereby the conduit 22 is connected via conduit 22b to the discharge chamber 45 and the pressure in the actuators 10, 11 is reduced to zero. Lateral tilting. Operation of lever 58 moves slide valve 57 so that pressure fluid is supplied through conduit 44 to conduit 22 to the upper chamber of actuator 10 and the lower chamber of actuator 11, thus moving the pistons in opposite directions. The pressure in the conduit 22 operates valve slide 50 to allow discharge of fluid from the other chambers of the rams. If the slide 57 is moved to supply fluid to conduit 53 the actuators are moved in the opposite direction. Adjusting angle of attack. The length of the upper link is adjusted by actuator 17 supplied with pressure fluid from distributor 24 by operation of manual lever 69. Pressure fluid is directed from conduit 43 to conduit 71 or 72 by movement of slide valve 68. Draft control forces arising in the actuator 17 are fed to a lever 77 via the fluid in conduits 70, 71 and act on the slide 28 to control the lifting of the implement. Weight transfer. The valve 38 which operates during the lowering operation is biased by a spring adjustable by a lever 40. Thus the lifting pressure maintained in the actuators 10, 11 can be adjusted to give a controlled transfer of weight from the implement to the tractor. A visual indication of the lateral tilt of the implement is given by member 62 associated with lever 58 and being coupled to the respective draft links by levers 63, 64, 65, 66 and 32, 32a. Implement forces exerted on the actuator 17 are controlled by a differential manometric device 74 comprising pistons 75 76 subjected to the fluid pressure in conduits 71, 72 and acting on a lever 77 to operate the lifting valve 21.