Patent GB-1062443-A (GB)
Title: Improvements relating to implement height-control mechanisms for farming tractors
IPC: A01B63/112
Filed: 1964-03-03
Abstract: 1,062,443. Tractor power lift mechanisms. REGIE NATIONALE DES USINES RENAULT. March 3, 1964 [March 4, 1963; Sept. 16, 1963], No. 8978/64. Heading A1P. A tractor power lift mechanism includes draft control wherein movement in a traction link 1 operates; through/pivoted levers 12, 16 having a biasing spring 15, a push rod 18 of a slide valve 44. The lever 16 is pivoted at 17 on the lever 12 which has a; bent end arranged to engage limit stops 13, 14. A handlever 23 operates on lever 16 to set the draft control, the lever being biased into contact with the push rod 18 by a spring 19. Follow-up, is provided by a cam 26 which engages push rod 18 and is. connected to the lifting arm 8 on rockshaft. 9. A handlever 32 also operates on cam 26 for position control. Draft control. In operation the forces in link 1 disengage lever 12 from the stops 13, 14 and are countered by the spring 15. In the neutral position, Fig. 5 (not shown), hydraulic fluid passes from pump 38 to chamber 46 of the slide valve, through a throttling point 85 to unseat valve 40, the chamber 79 of which is vented to exhaust through compartment 51 of the slide valve and passage 62, the fluid then passing to exhaust conduit 42 through sleeve 76. Because of the throttling point 85 the pump pressure at valve 36 is greater than in the chamber 72 and the valve is unseated to allow fluid to pass directly to exhaust. On an increase in draft the link 1 and associated linkage operate to move valve 44 to the left thus allowing fluid to pass between the chambers 46, 47 and 48 of the slide valve but blocking off the conduit 62 to exhaust. Valves 40 and 36 are therefore both reseated by the pressure built up in the chambers 47 and 48 of the slide valve and non-return valve 34 opens to supply fluid to the operating ram 10 via conduit 43. As the ram moves the follow-up linkage operates cam 26 to return the slide valve to the neutral position. On a decrease in draft, lever 16 moves to allow the slide valve to move to the right under the action of spring 45 to open valve 35 through a ball and rod 61 whereby fluid is exhausted from the ram 10 through conduit 42. Position control. Handlever 32 is moved to operate cam 26 whereby the slide valve is moved either to the left or the right with the above described results. A telescopic connection 20, 21 between handlever 23 and lever 16 is arranged to limit the movement of lever 16. To relieve excess pressure in the system a collar 76 which normally seats against member 73 in valve 40 can move against the action of a spring 77 to open a passage to exhaust. A cock 86 can be moved to connect auxiliary apparatus to the hydraulic system. In an embodiment (Fig. 7, not shown) the cam 26 and lever 16 are replaced by two levers 171, 172 pivoted about a common point 170 of a spring telescopic push rod 18. A distance e between lever 172 and handlever 180 replaces the lost motion connection 20, 21. Rate of descent can be limited by a hand-adjustable valve 141 and pressure relief instead of being incorporated in the valve 40 is provided by a valve 150 separate from the pilot valve 40.