Improvements relating to control mechanism in tractors for hitched implements

摘要

886,677. Tractor power lift mechanisms. MASSEY-FERGUSON Inc. April 21, 1958 [May 6, 1957], No. 12499/58. Class 79(1). In a tractor hydraulic power lift system a control valve 82, Fig. 3, operated from draft and position control levers 61, 62 to effect movements of the ram 68 at different speeds according to the valve deflection has means for damping the movement of the valve to prevent actuation of the linkages at excessive speeds. The position control lever 61 actuates the valve 82 through cam 117, cranked follower 121, lost motion linkage 127, 128, lever 113 and plunger 111. Follow-up for returning the valve 82 to neutral is provided from a stud 146 on an arm 74 of the lift arm cross-shaft 76 which moves a spring-loaded link 124 to which the hinge pin 122 of the cranked follower 121 is attached. In the event of rapid movement of the lever 61 the link 124 acts as a safety device to permit delayed response in the follow-up system, the movement of the valve 82 being limited by a stop (not shown) engaged by the lower end of the link 127, and by an adjustable cam stop 176 engaging the top surface of the cranked follower 121. Adjustable damping for limiting the speed of movement of the valve 82 is provided by a plunger 184 coupled to the lever 113 through a push rod 187 to provide a one-way connection and having a needle valve 199 adjustable by a manually actuated cam 207 to control the fluid flow between opposite ends of the plunger 184. The control lever 62 for automatic draft control adjusts the valve 82 through a second cam 152 and cranked follower 156 coupled to the lever 113. Movements resulting from changes in draft loads in the draft links 19 are transmitted to the hinge pin 163 of the cranked follower 156 through a bell crank 169 engaging a stop 171 on a spring-loaded draft responsive frame 22 carrying the draft links. Various lost-motion or one-way connections provide for either the position or the draft control to over-ride the other. The draft responsive frame 22 carrying the draft links 19 is generally "A" shaped and is attached to the underside of the tractor by links 41, Fig. 2, at the rear end while the forward end is slidable longitudinally between plates 34. Longitudinal movement of the frame 22 according to the draft loads is balanced by a spring 53. Rollers 37, 49 mounted on the tractor underside and engaging guide ways 38, 50 in the frame prevent side-ways movements. Alternative attachment points 20 are provided for the top link 18 so that adjustments may be made according to the degree of pitching, soil conditions expected on different implements. Specifications 886,678, 886,679 and 886,680 are referred to.