Patent ID: 7721830
Filing Date: 2010-05-25
Classification: A01B,B62D

Abstract:
1. A tractor comprising: a tractor frame; an engine mounted on the tractor frame; a cab mounted on the tractor frame; a first and a second driven wheels of the tractor mounted at a driven end of the tractor, the first driven wheel including a first hydraulic drive motor for driving the first wheel and the second driven wheel including a second hydraulic drive motor for driving the second wheel; two non-driven castor wheels of the tractor mounted at a second end of the tractor; the driven end having mounting assemblies for supporting a crop cutting header at a position in front of the driven end and in front of the cab when the driven end is forwards; a first and a second hydraulic pump each driven by the engine for generating a source of hydraulic fluid under pressure, with the first hydraulic pump arranged for driving the first hydraulic motor of the first driven wheel and the second hydraulic pump arranged for driving the second hydraulic motor of the second driven wheel; the first hydraulic pump including a first cam plate movable to vary the displacement of the pump to vary the volume of fluid generated as the pump is driven and the second hydraulic pump including a second cam plate movable to vary the displacement of the pump to vary the volume of fluid generated as the pump is driven; a manually operable steering control movable between left and right positions through a center position; the manually operable steering control including a steering wheel and a steering shaft rotatable by the steering wheel; a manually operable speed control movable between forward and reverse positions through a neutral position; the manually operable speed control being arranged to control a rate of supply of hydraulic fluid from the first hydraulic pump to the first drive motor and from the second hydraulic pump to the second drive motor to control a common speed of rotation of the driven wheels and thus a speed of movement of the tractor; the manually operable steering control being arranged to control a differential in rate of supply of hydraulic fluid from the first hydraulic pump to the first drive motor and from the second hydraulic pump to the second drive motor to control a relative speed of rotation of the driven wheels and thus a turning direction of the tractor; a linkage including a first link for controlling the first cam plate and a second link for controlling the second cam plate; the linkage including a speed control member operable by the manually operable speed control with the speed control member arranged, when actuated in an actuation direction, to move both the first and second links for moving the first and second cam plates; the linkage including a steering link member pivotally mounted relative to the speed control member so as, when actuated, to pivot to respective sides so as to move the first and second links relative to the speed control member to effect differential movement of the first and second cam plates; the steering link member being pivoted by input caused by rotation of the steering shaft; and an automatic steering system for providing a steering action in response to position information so as to steer the tractor to required positions comprising: