GB1289983A - - Google Patents

Abstract

1289983 Tractor power lift FIAT SpA 3 Oct 1969 [4 Oct 1968] 48719/69 Heading A1P A tractor power lift comprises a lever system adapted to raise and lower the lift arms 5 and to effect a draft control with lower link sensing, the lever system comprising a principal control lever 47 to act on valves 41, 42 to control flow of hydraulic fluid to and from the power cylinder 17. The valve system forms a primary distributor with a lever 114 controlling the sensitivity of the draft control. A further distributor T.C. for load transfer and supplementary distributors 58 for other hydraulic controls are connected directly to the primary distributor through conduits in the casing 1. To vary the position of the lift arms 5 the manual lever 124 when rotated clockwise (in Fig. 2) reciprocates the wedge shaped lever 218 by means of an eccentrically mounted pin 219 in the shaft 220. In the lowering of the implement the wedge shaped lever is moved to allow the rollers 224, 217 on the rocker 221 and lever 215 respectively to approach each other. However, the lever 215 is fixed by engagement of a roller 213, mounted on a pin 212 on the crankshaft 208 of the lift arms 5, with the extention 215a of the lever 215 so that it is the roller 224 on the rocker 221 which moves, rotating the principal control lever 47 away from the valve stems 45, 46 by engagement of the screw 221b. If large movements of the control levers are made the spring 229 absorbs them and transmits them slowly to the valve stems. This causes fluid to enter the sump 50 via the chamber 99 in the outlet valve 42 from that section of its bore included between sections 46 and 46a. This flow of fluid causes the lift arms to lower as fluid is drained from the space 120 behind the piston at a constant rate. This rates is governed by the valve 39 which varies the constricting passage 76, the rate of descent being governed ultimately by the tension in the spring 79. The valves 40, 41 control the raising of the lift arms by distribution of fluid from the point 48. Draft control is effected by feed-back through the lever 14 from the implement linkage. The shaft 15 of the lever 14 is fast with a lever 235, see Fig. 8, and movement of the manual lever 125 causes rotation of the shaft 24 and the eccentrically mounted lever 237 reciprocates. This causes the lever 231 to roll on the roller 233 on the lever 235 and operate the rocker 221 causing the principal control lever 47 to operate the valves. The sensitivity control varies the stroke of the valves 41, 42 by rotation of the head 112 causing the pin 115 to cam on the inclined surface 116 of the cap 108 by means of the lever 114. Sensitivity is reduced in two stages while shortening the valve stroke initially by gradual reduction in the stroke and then a sharp reduction as the pin is forced downwards by a stop (not shown). This latter position is used when supplementary distributors 61 are used to control hydraulic cylinders external of the lift. In this position automatic control is overridden so that the operator manually controls the flow of fluid. If the supplementary distributors are not used the conduits to them may be blanked off by a plate 35. The load transfer distributor T.C. may be attached directly to the principal distributor or the respective conduits may be blanked off by a plate 31.