Abstract: A control system for a tractor with a semi-mounted plough (2) hitched to it comprises a control system (13) for setting a delay between the lifting/lowering of the tractor linkage (3) and the rear of the plough (2) to cause the individual ploughshares to enter to leave work along a given line parallel to a field boundary. To accommodate field boundaries which are not perpendicular to the ploughing direction, adjustment values representative of the angle of each field boundary to the ploughing direction may be entered into a control unit (13) to cause the delay between lifting/lowering of the front and rear of the plough to be adjusted automatically as each field boundary is reached to take account of the angle of that boundary and also whether the plough is being taken out of or put into work.

Abstract: A wet clutch assembly comprises an input shaft and a stack comprising interleaved first and second sets of clutch members. A hydraulic actuator piston is located concentrically around the input shaft, but is static. A member rotationally fast with one of the sets of clutch members is journalled to the actuator piston by means of a bearing whose inner race is integral with the piston.

Abstract: A gearshift control system comprises an electrical control unit which operates hydraulic valves controlling a hydraulic gearshift actuator. The vehicle in which the system operates has a dashboard control to preselect a gear change, which is actuated by depressing the clutch pedal operating a switch, both the switch and control being connected to the unit. The system includes means for updating the electronic stored values representative of the position of the gearshift actuator. The system also includes means for aborting a gearshift if, after given time periods, either the shift has not been completed, or the clutch pedal is released. In any event the gearshift will be aborted if the clutch is released during a change. The system will not initiate a gearshift unless the clutch pedal is held down for a given period of time.

Abstract: A hydraulic control valve assembly is described comprising a cut-off valve, a control valve and structure for connection to at least a supply line, a hydraulic apparatus line and a return line. The assembly is constructed and arranged such that the cut-off valve is bistable and controls flow of pressurised fluid from the supply line to the control valve, permitting it when primed and preventing it when closed, and the control valve controls the pressure of fluid supplied to the hydraulic apparatus line. In addition structure means are provided to initiate priming of the cut-off valve, complete the priming of the cut-off valve provided the supply line pressure is above a first predetermined pressure, and maintain the priming of the cut-off valve provided the supply line pressure remains above a second predetermined pressure.

Abstract: A combined powershift transmission and main clutch assembly for a vehicle includes a casing containing an input shaft and an output shaft. A planetary transmission is disposed within the casing and is co-axially mounted around the input shaft. The planetary powershift unit includes a sun gear and an annulus gear interconnected by one or more planet gears carded on a planet carder. A first one of the sun gear, the annulus gear, and the planet carder is connected to the input shaft, while a second one of the sun gear, the annulus gear, and the planet carder acts as an output member of the planetary powershift unit. A first clutch is disposed within the casing and co-axially surrounds the output shaft for drivingly connecting the output member of the planetary powershift unit with the output shaft.

Abstract: A vehicle transmission unit is housed in a casing and includes a plurality of drive ratio paths selectively engageable by a ratio selection system. The ratio selection system includes fluid-pressure-operated actuators under the control of solenoid-operated valves to select the operative drive ratio of the transmission. The transmission also includes one or more mechanical actuator members accessible from outside the casing which can be manipulated to select one or more drive ratios of the unit in the event of the failure of the fluid-pressure-operated actuators or valves.

Abstract: An implement control system includes desired draft force setting apparatus and draft force sensing apparatus providing a draft force signal. It also includes engine speed sensing apparatus arranged to provide an engine speed signal of the same form as the draft force signal. The draft force signal and engine speed signal are averaged and compared with the set desired draft force to produce an error signal which is used to control the movement of the implement. The system is particularly suitable for the control of engine driven implements such as stone-breakers and rotivators where it prevents the engine stalling under heavy load, it is, however, suitable for use with fully-mounted, semi-mounted and trailed implements.

Abstract: A continuously variable transmission includes an input shaft, an output shaft, and first and second epicyclic gear trains, each with an input member, an output member and a reaction member. An hydrostatic shunt loop including first and second hydraulically interconnected variable displacement hydraulic units interconnects the two epicyclic gear trains. The input members of both epicyclic gear trains are driven from the input shaft, and the output members of both epicyclic gear trains drive the output shaft. First and second drive trains are provided for alternatively coupling the first variable displacement hydraulic unit respectively to either the input shaft or the reaction member of the first epicyclic gear train. Third and fourth drive trains are provided for alternatively coupling the second variable displacement hydraulic unit respectively to either the output shaft or the reaction member of the second epicyclic gear train.

Abstract: A system for controlling the selection of the operative ratio of a vehicle powershift transmission driven from an engine via a main clutch. The system includes a clutch status sensor for sensing engaged and disengaged conditions of the main clutch. A selector is provided for selecting the operative ratio of the transmission. Also, a control circuit is provided which includes a ratio-change modulating function which, when the main clutch is engaged and a change to a non-adjacent ratio is selected, invokes a serial routine which ensures that each intermediate ratio between the current ratio and the selected ratio is engaged for a moment to ensure a smooth substantially jerk-free progression between the current ratio and the selected ratio. When the main clutch is disengaged and a change to a non-adjacent ratio is selected, the control circuit invokes a direct routine which permits changes from a current ratio to a non-adjacent selected ratio without engagement of any intermediate ratio.