Patent GB-923435-A (GB)
Title: Improvements relating to tractor hydraulic power lift mechanisms
Inventor: MERRITT HENRY EDWARD
IPC: A01B63/111
Filed: 1958-08-23
Abstract: 923,435. Tractor power-lift mechanisms. MASSEY-FERGUSON (UNITED KINGDOM) Ltd. Aug. 13, 1959 [Aug. 23, 1958], No. 27124/58. Class 79(1) In a tractor power-lift mechanism wherein the hitch linkage may be raised by hydraulic means under the control of a valve, the valve may be subject to (1) manual-control and draftcontrol means, or (2) manualcontrol and position-control means, or (3) manual-control means or position-control means selectively, there being also provided a secondary valve preceding the main valve in the hydraulic circuit, each of the valves being devised to spill the liquid from the hydraulic system, and a non-return valve assembly. The hydraulic system comprises an inlet filter 20 disposed in a sump 18, a pump 17, an overload release valve 22, a valve assembly comprising the valves 50, 31 and 26 (Fig. 3), a main hydraulic ram 12 and an auxiliary ram 30 controlled by a valve 29. A ball-ended connecting rod 14 is disposed between the ram 12 and a crank arm 15 through which the power-lift arm 16A, mounted on shaft 16, may be raised. The valve 50 discharges, in the position shown, through the apertures 51 back to the sump. Depression of the member 50 closes the apertures 51 and the fluid passes to the valve 31, which, in the position shown, transmits the fluid through the sleeve 34 and into the conduit 28. Depression of the valve 31 brings a waisted portion 32 into register with apertures 33 in the sleeve 34 and the fluid discharges to the sump. Valve 31 has a damping device 25. The assembly also comprises a sleeve valve 87 and a non- return valve 26 which permit unrestricted passage of the fluid to the ram conduit 28 and provide a restriction in the return flow to provide speed control when lowering the implement. The overload release valve comprises a spring 82 urging a conical member 81 against an aperture 83. Spilling apertures 84 and a relief aperture 85 are provided. The valves 50 and 31 are actuated by a cam 48 and cranks 46, 47 respectively, the cranks being mounted on eccentrics 44 and 45 disposed at 120 degrees to one another and which with the cam are mounted on a shaft 43 and controlled by a handle 42. The crank 46 is connected through a linkage 58 to a member 57 which is attached to a draft control link of the hitch. The handle 42 may be moved from the neutral position shown to positions where the valve 50 is closed by the cam 49 and valve 31 may be operated by either of the cranks 46 and 47, the crank 47 having a follower 70 spring urged against a cam 71 attached to the shaft 16 upon which is mounted the power-lift arm 16A. When the lever 42 is moved to the range A-B, Fig. 2, and the implement is on the ground, the crank 46 will be in the position to operate valve 31 and the implement, will embed to a depth determined by the position of the handle and operation of the valve 31 through the link 58 and crank 46. By moving the handle 42 into the range C-D, Fig: 2, the depth control 46 is inoperative and the valve 31 is operated through the position control " crank 47 by means of which the implement is held at a fixed height relative to the tractor according to the setting of the handle. A transport position is provided wherein a face 73 on the arm 15 engages an abutment 72 on the tractor casing 11 in which position the hitch may be latched by a locking pin 75. When the faces 72 and 73 are forced into contact, the overload release valve becomes effective. To operate the auxiliary ram 30, which may be on an implement attached to the tractor, the faces 72 and 73 are forced into contact and the valve 29 is opened, and the arms latched in this position, the valve 31 being held closed by the crank 47, and the valve 50 operated by the handle 42 within the range E-F (Fig. 2). In a similar process, with the valve 29 closed, the main ram 12 may be manually controlled by the lever 42 within the range E-F.