Abstract: A working vehicle has a grass cutting unit vertically movable relative to a vehicle body, a lift mechanism for raising and lowering the grass cutting unit, a clutch for making and breaking transmission of blade driving power to the grass cutting unit, and a device for controlling the lift mechanism. The control device controls the lift mechanism to lower the grass cutting unit when the clutch is operated to transmit power to the grass cutting unit, and to raise the grass cutting unit when the clutch is operated to break power tranmission to the grass cutting unit. According to this construction, only a device for actuating the clutch may be operated to switch between an operative condition in which the grass cutting unit is lowered and its cutting blades driven, and an inoperative condition in which the grass cutting unit is raised with the cutting blades stopped. Alternatively, the control device may control the clutch through a device for actuating the lift mechanism.

Abstract: A two-axle four-wheel tractor is equipped at its front and rear ends with working implements, individually, which are of the same type, opposite in working direction and shiftable between a working position and a nonworking position. The tractor has a steering system for steering the front and rear four wheels in the same direction through the same angle, a running transmission system for driving only the wheels positioned toward one of the working implements which is lifted to the nonworking position or, in a special case, a system for restraining the wheels positioned rearward with respect to the direction of advance of the tractor in a straight running position without permitting steering.

Abstract: A control apparatus having a boom control system for controlling the movement of a liftable boom supported by a vehicle body and a working device control system for controlling a working device pivoted to the boom. Each of the control system includes a proportional solenoid valve and comprises an instruction circuit for producing an instruction signal in accordance with the amount of manipulation of an operating lever, discriminating circuit for determining the direction of operation of the valve from the instruction signal, a reference signal generator, a comparison circuit for comparing the instruction signal with the reference signal from the generator to obtain a pulse signal of a width in proportion to the amount of manipulation, and drive circuit for converting the pulse signal into a current to drive the valve in the direction determined by the discriminating circuit. The boom, as well as the working device, is movable at a speed corresponding to the amount of manipulation of the operating lever.