Patent GB-778686-A (GB)
Title: Improvements in or relating to implement control mechanisms for tractors
Inventor: SENKOWSKI ALEXANDER
IPC: A01B63/111
Filed: 1952-05-16
Abstract: 778,686. Tractor power-lift mechanisms. MASSEY-HARRIS-FERGUSON (SALES), Ltd. May 18, 1953 [May 16, 1952], No. 12397/52. Class 79(1). [Also in Group XXIX] Relates to a tractor power-lift system of the type having a hydraulic ram 8, 54, which operates on an implement suspended on draught-links, the upper link being connected to a spring-loaded plunger 33 attached to a lever system 47, 56, 65 actuating the control valve 9C for the ram 8 so that variations in draught-resistance will effect movement of the valve to cause the power-lift to rise or fall and to so restore the draught-resistance to its previous value. According to the invention, the lever system comprises two levers 47, 65 pivotally interconnected by a link 56 which is adjustable to vary the ratio of their movements without appreciably affecting their relative positions during the adjustment. The ram is fed by a pump driven continuously from the engine and the setting of the valve 9C may be controlled either in response to changes in draught-resistance (load-control) or to changes in the position of a handle 51 having a crankmember 50 bearing on the lever 47 (positioncontrol). The selection is made by a lever 74A, Fig. 2, on a shaft 74 which moves a pawl 40 along a shaft 43, to which it is keyed into and out of engagement with a roller 39, Fig. 9, on the end of the plunger 33 and simultaneously moves a follower 75 out of or into engagement with a cam 76 keyed to the shaft 6 carrying the liftarms. The lever 47 which transmits the motion to the valve 9C is a floating lever suspended intermediately by a bifurcated pivotal link 48 from the casing 1 and swingable either about the crank 50 as fulcrum (for load-control) or about the point of pivotal attachment 46, of a link 45 connected to the pawl 40 (for position-control). In either case, the motion is transmitted by the link 56 to a bell-crank lever 65 pivoted at 66 and having one arm 67 attached to the valve 9C. The link 56 carries a roller 63 engageable in an arcuate slot 64 centred about the pivot 55 at the lower end of the lever 47 and the link 56 is extended beyond the pivot 55 and its further end is connected to a hand-lever 61 by means of which the position of the roller 63 in the slot 64 is adjustable. Because the slot is arcuate about the pivot 55 the adjustment of the sensitivity by this means does not affect the setting of the system at the moment of adjustment. Load-control. When set for load-control, Fig. 12, the lever 47 fulcrums about the crank 50 which is then fixed. Outward movement of the plunger due to reduced draught-resistance will cause the roller 39 to contact the pawl 40 and rotate the shaft 43 this being transmitted to the lever-system by the link 45 and the valve 9C being moved accordingly. Inward movement of the plunger would tend to cause separation of the members 39, 40, but the spring 68 causes the lever 47 to follow up. A sudden movement in either direction would cause momentary separation of the parts 39, 40 or the parts 47A, 50 thus obviating damage. If the ram piston reaches the end of its travel an abutment 7A contacts an abutment 65A on the lever 65 to open the valve 9C. Position-control. In position-control, Fig. 13, a movement of the lever 51 causes the crank 50 to move the lever 47 about the pivot 46 and the system resets itself by the cam 76 causing the follower 75 to move the link 45 and lever 47 to shut the valve in a position of the arms 5 corresponding to the new position of the handlever 51. In the fully-raised position of the arms 5, a gap exists between the cam and follower so that oscillations of the lifted implement on uneven ground will not actuate the servo-mechanism. Overload-release valve. An overload-release valve, Fig. 6, is provided for venting the ram cylinder rapidly in the event of excessive draught-resistance. The valve is mounted on the ram cylinder 54 and is operated by a link and pushrod, Fig. 4 (not shown), on excessive moment of the plunger 33, the movement being transmitted by a rocker 89 to a composite member comprising a tubular plunger 98, having a seating 97, and an integral annular piston 92 sliding in a housing 91 having an outlet 94. A spring 101 is adequate normally to maintain the seating 97, 98 closed, but if the valve is opened by the rocker 89 the pressure of oil on the piston 92 overcomes the spring until sufficient oil has escaped through the outlet 94 to permit the valve to close. Specifications 470, 069, 470,087, 617,166 [Group I], 666,878, 743,117 [both in Group XXIX] and 778,687 are referred to.