Abstract: A control system for a working machine which has a boom equipped with a working implement at its forward end and pivoted to a vehicle body movably about a vertical axis, and control valve for controlling the movement of the boom. The system comprises a variable resistor for setting a target position where the boom is to be stopped to produce a setting signal, a sensor for detecting the moved position of the boom to produce a detection signal, differential device for determining the difference between the setting signal and the detection signal to produce a difference signal, a detector for detecting the direction of movement of the boom from the magnitude of the difference signal, a pulse-width modulator for subjecting the difference signal to pulse-width modulation to produce a pulse signal, and a driver for driving the control valve by the pulse signal in the detected direction in proportion to the difference signal.

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.

Abstract: An earth handling vehicle is proposed which is capable of traveling forwardly or rearwardly to accomplish digging and loading operations, said vehicle having a chassis supported for movement on the earth by a track mechanism. The vehicle is further provided with an engine, transmission, a gearshift lever and a main clutch and further includes a maneuvering apparatus comprising front and rearwardly disposed interconnected actuators associated with steering clutches and lever mechanisms for operation of the actuators. Also, included is a supplemental clutch actuator lever which includes a portion that is operably interconnected with at least one actuator lever.