GB927355A - Improvements relating to hydraulic power lifting means for tractors - Google Patents

Abstract

927,355. Tractor power-lift mechanisms. FAIREY CO. Ltd. Sept. 18, 1959 [June 20, 1958], No. 19896/58. Class 79(1) In a hydraulic power lift mechanism with a pair of spaced parallel lifting arms 23, 24 pivoted about a common transverse horizontal axis at the rear of the vehicle, the jack 10 is of the rotating vane type with the vane 13 or vanes carried by a shaft 21 which protrudes from the jack casing 11, the lifting arms 23, 24 being secured to either the shaft or the casing. In the preferred embodiment, the arms are secured to the shaft and the casing to the vehicle, the spaces at opposite sides of the vane 13 being connected by passages 32, 33 to pairs of ports in the end face of a follow-up valve member 38 secured to the shaft 21. This valve member cooperates with an input valve member 37 having a pair of ports surrounded by accurate bearing pads and connected to an inlet P while a second pair of ports surrounded by recesses are connected to a return line R. When the valve member 37 is rotated by a hand lever 61 and a linkage 40 fluid is supplied to the jack until the valve member 38 has been restored to its original position in relation to the valve member 37. A pocket 49 causes the fluid pressure to bias the member 37 towards the member 38, a thrust race being provided for the shaft 21. In the event of an overload, for example due to an obstruction, a spring-loaded rod 72 connected to the implement displaces the fulcrum 62 of the hand lever 61 which is thus swung about a friction pad 71 normally displaceable in a quadrant 70 to operate the valve members and raise the implement. When the overload ceases, the rod 72 is returned to its normal position by its spring. The jack is constructed as described in Specification 893,361.