Patent GB-1376217-A (GB)
Title: Control system for tractor implement combination
IPC: A01B63/11
Filed: 1972-05-17
Abstract: 1376217 Depth and draft control of an agricultural implement DEERE & CO 17 May 1972 [17 May 1971] 23115/72 Headings A1B and A1P An impliment 12 having two outer sections hinged to a central section is connected to a conventional three point linkage of a tractor 10 incorporating a hydraulic lift mechanism and an electro-hydraulic control system including depth and draft control mechanisms is provided whereby either both outer sections are responsive to the depth control mechanism or one of the outer sections is responsive to the depth control mechanism whilst the other section is responsive to the draft control mechanism. The control system in conjunction with the tractor's three point linkage, also allows the implement to be raised to a transport position or lowered to a working position. The two outer sections are each supported by a respective ground wheel 106 which is adjusted vertically by an associated double acting hydraulic cylinder 110 acting on a four point linkage, supporting the wheel, on response from the control system. The fluid flow to each of the cylinders, 110R and 110L, from a tractor mounted pump is controlled by a respective double solenoid, spring centred, four way direction, flow control valve 114L, 114R whose solenoids are incorporated in the electrical network of the control system. The depth control mechanism for each outer section includes a ground follower wheel 242, which is adjustable via a set screw 234 to the desired operating height and two micro-switches 156, 162. The movement of the wheel 242, as it follows the contours of the ground, causes an associated lever 250 to close one of the two micro-switches and hence complete a circuit which actuates the associated solenoid in the respective control valve 114R, 114L, to raise/ lower the associated ground wheel accordingly. The draft control mechanism includes two micro-switches 194, 202 in a mounting 260, adjacent the compression link 22 of tractor's three point lift, whose lateral movement, due to unequal forces on the two outer sections, causes a lever 268 to contact one of these two switches, and hence complete a circuit which actuates the associated solenoid in the associated control valve. The electrical network (Fig. 7, not shown) includes a first, two position, manually operated switch which when in a first position allows the outer sections of the implement to be lowered, in conjunction with the central section which is lowered by the three point linkage to the working position and when in this position to operate under the influence of the depth control mechanism. In a second position of the switch the outer sections are raised in conjunction with the central section. A second manually operated switch, operating in conjunction with the first switch in the first position, actuates the draft control mechanism. Two mercury switches 200 and 206 are also fitted to the mounting 260 and are respectively included in the circuits for micro-switches 194 and 202. The mercury switch 200 is in parallel with the switch 194 and is arranged at an attitude so that it is open when the implement is in the working position and closed in raised position. The mercury switch 206 is in series with the switch 202 and is arranged at an attitude so that it is closed in the working position and open in the raised position, The arrangement of these two mercury switches allows the implement to be raised/ lowered irrespective of whether the control system is set to depth or draft control,