Patent GB-833670-A (GB)
Title: Power lift system
IPC: A01B63/14
Filed: 1956-07-03
Abstract: 833,670. Agricultural implements. ALLIS-CHALMERS MANUFACTURING CO. July 3, 1956 [July 11, 1955], No. 20548/56. Class 6(1). [Also in Groups XXIX and XXXI] A power system for lifting a tractortowed implement such as a plough or harrow 38 comprises two fluid-pressure servomotors, the first comprising two rams 21 mounted on opposite sides of the tractor and lifting the implement bodily about a horizontal pivot pin 33 at the hitch point, the second a single ram 81, mounted on the implement for raising the implement frame 38 relatively to ground wheels 49 which support the frame and are mounted on it for vertical movement on a pivoting shaft 52, all the rams being controlled in accordance with three operating conditions as follows:- First, all rams ineffective ; second, energising the first rams 21 to raise the implement for applying additional downward load to the rear wheels of the tractor to increase traction under adverse conditions ; and third, implement frame raised relative to the wheels 49 to a non-working transport position by the combined effort of all the rams. Control is by a combination of a manual lever 169 and draught, which latter automatically energises the first rams 21 to vary the lift force with draught. The same fluid pressure supplied to the first rams 21 is always fed to the second ram 81, but it reaches a value sufficient to cause the second ram 81 to raise the implement frame only when the draught load exceeds a predetermined value. Mechanical arrangement. The two ground wheels 49 are carried on radius arms 51 on the shaft 52 which is turned on the implement frame 38 by the single ram 81 acting between the frame and an arm 84 on the shaft 52. Screwed stops 57 adjustably set the lowest position of the frame 38 relative to the wheels 49, the frame being lifted on the wheels 49 by extending the ram 81 by pressure supplied through a pipe 143. Harrow discs 48 are carried on a pair of inclined shafts fast with the frame 38, and adjustment for depth of cut is provided by turning a hand crank 71, which causes the frame 38 to pivot about a pin 68 on draught bars 63. For this purpose the crank 71 is fast on a threaded shaft 67 passing freely through a swivel on the draught bars 63 and screwing into a swivel on a frame member 74. An adjustably compressed spring on the shaft 67 yields to permit the frame to lift relative to the draught bars when necessary. The draught bars 63 pivot on a universal hitch 33 on a draught lever 29 about which the bars pivot upwards when the implement frame and bars are raised as a whole by supplying pressure fluid through a pipe 141 to extend the two first rams 21 which turn a shaft 16 having side arms 18 which lift the draught arms 63 through a single chain or cable 92 attached at its ends to the arms 18 and passing through a central loop on the draught arms. The draught lever 29 to which the draught bars 63 are hitched at 33, pivots on a fulcrum 31 fixed on the tractor, and is biased clockwise by a strong spring 32, yielding of which, in response to drag resistance of the implement, pivots the draught lever 29 anticlockwise to operate valve mehcanism in the lift control as described below. Hydraulic control. Fluid pressure is supplied by four plunger pumps P1 ... P4, driven by a camshaft 97 driven through the master clutch of the tractor, the pumps delivering to a common pressure duct 122 or to a common exhaust 117 under control of a piston valve 93, graduated leftward movement of which, against spring resistance 113, from an initial exhausting position shown, causes each pump successively to supply pressure to the duct 122. The pressure duct 122 has a relief valve 134 and communicates through a non-return valve 137 with the permanently connected pipes 141, 143 feeding the frame and wheel rams 21, 81. The proportions are such that, whilst the lower pressures suffice for operating the frame-lift rams 21 only the highest pressures are able to operate in addition the wheel-ram 81. The valve 93 is operated by a floating lever 156, the upper end of which is loaded leftwards by a spring 157 whilst its lower end is operatively connected to the drag-responsive draught lever 29 through two contacting plates 146, 153 which turn on fixed pivots 148, 152. The valve lever 156 is also linked at 163 to the manual control lever 169 on the tractor steering column. Placing the manual lever 169 about halfway along its quadrant 172 brings the lever 156 into contact with the valve 93 but without effect until drag resistance of the implement turns the draught lever 29 sufficiently anticlockwise for the consequent rightward movement of the lower end of the valve lever 156 about the manually set pivot 163 to move the valve 93 leftward developing pressure to energise the frame lift rams 21 to transfer adhesive weight to the rear wheels of the tractor as required, or also to energise the wheel ram 81 on excessive draught. Movement of the manual lever 169 to its full extent shifts the valve 29 fully left irrespective of draught condition, developing the maximum pressure of all the pumps, to operate the ram 81 for lowering the ground wheels 49 for transport. The valve 93 may be automatically shifted back to the position in which it blocks exhaust from the ram line after all the rams have been extended, as described in Specification 672,701. Specifications 833,671 [Group XXIX] and 833,672 also are referred to.