GB862516A - Improvements in or relating to means for hitching agricultural implements to tractors - Google Patents

Abstract

862,516. Tractor power-lift mechanisms. CLAUSING, H., [trading as RABEWERK H. CLAUSING.]. March 4, 1959 [March 4, 1958], No. 7601/59. Class 79(1). In an automatic draft control system for attachment to the three-point hitch linkage 2, 3, Fig. 1 of a tractor 1 and in which a spring 11 yields under preset draft forces of a plough 5, with resultant lifting of the plough a damping device 13 is connected to the spring 11 to prevent oscillation. The lower links 2 are attached to one arm 7 of a bell crank 8, the other arm 9 having alternative connections for a compression unit 12 containing the spring 11 and incorporating a hydraulic damper 13 and restriction valve 60. The arm 9 is also coupled to a push rod 18 having a slotted end 19 permitting lost motion and engaging a pin 20 attached to the lift arm 21 of the hydraulic lift system 22 so that the lift arm is automatically raised to lift the lower links 2 through lift rod 23 when the spring 11 yields. Initial compression of the spring 11 is preset by a hand control 16. Numerous examples are described in which a two armed lever such as 7, 9 is attached to the tractor or parts of the hitch linkage and in one example the arm 9 Fig. 5 is coupled through a push rod 33 to a second bell crank 30, 31 to which the upper hitch link 3 is attached so that the plough coupling member 4 undergoes parallel movements to maintain the plough at the same angle of operation. In other examples in which the lower links 2, Fig. 8 are held in a fixed position through the lift linkage 22, 23 the coupling member 4 is connected between the top link 3 and a bell crank 36 on the lower links and carries the spring unit 11. The plough 3 has a second coupling member 38 attached between the bell crank 36 and a link 39 on the member 4 so that the plough 5 lifts against spring 11 with increased draft force. In another example in which the linkages 2, 3 Fig. 13 are free to float and are supported by a wheel 50 through a bell crank 48, 49 which is yieldingly held by the spring unit 11 and causes the linkages 2, 3 to rise with increases of draft load. In another example a hydraulic control unit 58 Fig. 15 incorporating the spring unit 11 is attached to the support 4 and carries the plough 5 on an arm 47 which is rotated by a hydraulic ram (not shown) under the control of a valve which is actuated when the draft forces in the lower link 2 cause the spring 11 to deflect.