Patent GB-839689-A (GB)
Title: Improvements relating to a control mechanism for a tractor hydraulic system
IPC: A01B63/111
Filed: 1956-08-23
Abstract: 839,689. Tractor power lift mechanisms. MASSEY-HARRIS-FERGUSON Inc. Aug. 23, 1956 [Aug. 31, 1955], No. 25806/56. Class 79(1) A tractor has an implement hitch linkage raised and lowered to a transport and working positions respectively, by the delivery of fluid to, and exhaust of fluid from, a hydraulic actuator under the control of draft responsive mechanism including a main valve mechanism, and auxiliary valve mechanism between the actuator and main valve mechanism, controlling the exhaust of fluid from, and the supply of fluid to, the actuator to provide positional control of the hitch linkage between the working and transport positions. An implement C on tractor T is raised and lowered by an actuator A, Figs. 1, 2, through a lever 39, 41 connected to draft links 30 by links 42. A pump P, Fig. 2, supplies fluid through conduit 43, ports 44, 45 of an auxiliary valve AV to cylinder 35 under the control of the main valve mechanism V comprising a plunger 46 operated manually and by draft responsive means, e.g. spring 50, through a lever 51 to control ports 48, 49, closing 49 and opening 48 passes fluid to the system and opening 49 and closing 48 allows fluid to return to the sump R. The auxiliary valve AV also controls an auxiliary actuator AA operating a further implement 55 between the front and rear wheels through a linkage comprising a T lever 80, Fig. 1, connected to the actuator piston and to a link 82 which raises and lowers implement 55 through linkages 83, 84, 87, 7Q, 71. The auxiliary valve mechanism AV comprises a housing 90 and an end section 91 secured to a cover plate 36 by screws 93, the housing 90 comprising two valve bores 94, 95, Figs. 13, 14, with similar valve spools 96, 97 comprising two axially spaced portions 98, 98<SP>1</SP>, and 99, 99<SP>1</SP>. Delivery of fluid through auxiliary valve. On movement of a manual quadrant lever L, Fig. 1, to the lift position lever 51, Fig. 2, moves plunger 46 to open port 48 to deliver fluid from pump P through valve V, conduit 43, port 44, passages 103, 100, 104, Figs. 13, 14, to port 105 and valve bore 94, port 106, passages 107 to port 108, Fig. 13, to valve bore 95, port 110, passage 111 and back to sump R. To raise the rear implement section 56. Lever 154, Fig. 3, is moved to the lift position moving valve spool 96, Fig. 13, to open port 112 and close exhaust port 106 to terminate flow to sump R; the fluid passing via port 112, passages 113,116, port 45, to actuator A, Fig. 2. By returning the spool 96 to the neutral position raising is stopped and the implement held in any required position. To lower the rear section 56. Lever 154 is moved to "drop", Fig. 14, to move valve spool 96 rearwardly closing inlet port 101 and opening exhaust port 112 to allow fluid to exhaust from actuator A by port 106, passage 107, ports 108, 110, passage 111 to sump R. To operate the implement 56 by draft control, i.e. spring 50. The lever 154 is latched in lift position by latch 160, Fig. 3, thus spool 96 allows fluid to enter main actuator A via port 112 under the control of the main valve V whose plunger 46 operates in response to changes in draft load or by manipulation of lever L. To raise the front implement 55. Lever 155, Figs. 3, 14, is moved to "lift" and fluid flows through port 44, passages 103, 100, an inlet port, not shown, to bore 95 then through port 117, passage 118, port 119, Fig. 14, through slots 141<SP>1</SP> in bushing 137<SP>1</SP> forcing ball 139<SP>1</SP> from its seat, then through check valve 136, outlet port 133 and conduit 165, Fig. 2, to actuator AA. On return of spool 97 to "neutral" the fluid is locked in the auxiliary actuator by the check valve 136 to hold the implement in any required position. To lower the front implement 55. Lever 155 is moved to "drop" position, Fig. 13, and spool 97 closes the inlet port not shown and plunger 142<SP>1</SP> lifts ball 139<SP>1</SP> from its seat to permit fluid to exhaust from actuator AA. to sump R via passages 138<SP>1</SP>, port 119, passages 118, ports 117 and 110 and passage 111. The rate of lowering is governed by the extent of the displacement of plunger 142<SP>1</SP>. General. The movement of lever 155 to lift closes port 110 so that the main actuator. can only lower the rear implement when the front one is raised. The spools 96, 97 are biased to the neutral position by compression springs, e.g. spring 150<SP>1</SP>, interposed between washers 149<SP>1</SP> and 151<SP>1</SP>, Fig. 3. The lever 154 may be locked in the drop position, Fig. 3, for the operation, through the draft control, of implements following the ground contours, e.g. side delivery rakes. A second auxiliary actuator may be operated through check valve 135 and port 132 which is shown plugged with plug 166 in Figs. 13, 14.