Patent GB-897002-A (GB)
Title: Improvements in or relating to hydraulic power lift systems for tractors
Inventor: HERSHMAN GORDON LEITH
IPC: A01B63/111
Filed: 1960-11-04
Abstract: 897,002. Tractor power lifts. INTERNATIONAL HARVESTER CO. Nov. 4, 1960, No. 37954/60. Class 79(1). A tractor power lift mechanism having a double acting ram controlled by a valve which may be put into positions appropriate to raising and depressing the lift arms is also provided with depth control means comprising a variable capacity chamber, means normally mantaining the chamber at minimum capacity, manually operable means for determining selectively, the maximum capacity of the chamber, means operated by downward movement of the lift arm to deliver fluid into the variable capacity chamber until it reaches its maximum capacity, at which point the fluid pressure in the chamber operates means in the control valve to restore it to a neutral or "hold" position. The variable capacity chamber comprises a cylinder 144 and piston 149 urged in one direction by a spring 163 and having its movement in the other direction limited by a shoulder on a rod 155. The tractor linkage mechanism comprises lower links 15 and 16, Fig. 2 pivoted by bolts 18 to downwardly projecting lugs 19 pivoted by bolts 20 to brackets 21 attached to the tractor frame, swinging movement of the arms 19 being limited by bumper stops 71. Pivoted by bolts 24 to the links 15 and 16 are socket members 23, their downward movement being limited by upwardly inclined portions 25 of the links, the socket members receiving against locating members 28 the drawbars 26 of the implement. The sockets and arms are recessed at 29 to receive a spring loaded latch member 30. The sockets are biased downwardly by springs 73, 75, 76. The lift cylinder 60 is pivoted at 62 to a lever 63 pivoted at 64 to a bracket 38 and bearing against a stop 66. The lift arms 40 and 41 are pivoted by the shaft 35 to the brackets 38 and 39 and the arm 40 is pivoted at 68 to the lift cylinder 61. The arm 40 is connected to the link 15 by the link 44 having a telescoping clevis device 46, the telescoping being limitable when desired by the insertion of a stop 46. The arm 41 is connected to the link 16 by the link 51 constructed in two parts having threaded engagement so that by rotating one part by the handle 55 a levelling adjustment of the implement may be effected. Limited telescoping of this arm may also be permitted. Stabilising means limiting the swing- ing of the arm may be provided. The ram 61 may be double acting, receiving liquid through the conduits 58 and 59 through a control valve 86 supplied by a pump 57. The valve 86 comprises a spool 110, Fig. 3, displaceable to left or right by a handle 111, inlet port 87 from the pump, outlet ports 97 and 99 to the hydraulic ram 61 and a conduit 104 connected by the line 92 to reservoir. A garter spring 123 in a groove 122 co-operates with a collar 117 on the spool to locate it in a position whereby both ports 97 and 99 are closed and the lift arms are held at an operational depth. To raise the lift arms, the spool is moved to the right so that port 99 is connected to the pressure supply and port 97 to reservoir. To lower the arms, the spool is moved to the left. The valve also comprises a piston 128 and this is connected by a line 80 to a cylinder 79 in which a piston 135 is pivotally connected to the lift arm 40, the cylinder being connected by a spring loaded telescoping device 143, 138, 139 to the lever 63. The line 80 is also connected to the depth setting member 83 which comprises the cylinder 144, piston 149, acted upon by spring 143, and rod 155, the position of which is determined by a handle 160 with reference to a scale 171, which may be graduated according to the depth of implement, the handle 160 being connected to the tractor frame by a friction disc 161. When lowering the implement to a given depth setting, the handle 160 is put to the depth setting as indicated by the scale 171, and the spool 110 is moved to the left by handle 111. The piston 67 of ram 61 is forced downwards by fluid pressure from line 59 and fluid from the cylinder 79 is forced into the line 80. At the point where the piston 149 in depth control member 83 abuts the shoulder of rod 155, pressure in line 80 builds up, moving the piston 128 to the right and so returning spool 110 to the position whereby both ports 97 and 99 are closed and the movement ceases. Stops 132 and 152 are provided in valves 86 and 83 to limit the movement of pistons 128 and 149 respectively. Leftward movement of the spool 110 is limited by the engagement of a shoulder 133 with the garter spring 123. The depth control device may be temporarily overridden by moving handle 111 to a "lowering" position, forcing the piston 128 to move to the left, the movement being accommodated by a slight compression of spring 143 which is further compressed by the additional contraction of the ram 60. The original depth is regained by moving the handle 111 first into the "raise" position and again into the "lower" position. Specifica-, tions 820,063 and 820,064 are referred to.