Abstract: A working machine equipped with a boom, an arm and a bucket and is mounted on a construction vehicle, the working machine being capable of being folded compactly at rest. The working machine is easily brought into an operating position without any special apparatus. The boom is divided into two portions that allow it to be folded compactly. The two boom portions are pivotally attached to each other and the first of the two boom portions is pivotally attached to the chassis of the machine. The boom portions work in cooperation with at least one hydraulic cylinder to move between operative and inoperative positions. A retaining device, which can be in the form of another hydraulic cylinder or pins, is used to hold the boom portions in position with respect to each other.

Abstract: There is disclosed a hydraulic circuit system for use in a swivel type excavator. The circuit system having a plurality of variable displacement pumps for supplying pressurized fluid for manipulations of work implements and swivel means of the excavator, and control means operative to automatically adjust pump displacement to the output hosepower of a prime mover driving the pumps. The control means includes hydraulic pressure detector means, servo-control means respectively provided in the pumps, negative control valves for respectively controlling the servo-control means by the action of the pressure detector means, cut off valves respectively connected in series with the negative control valves, and summing valves respectively connected in series with some of the cut off valves so as to control pressurized fluid to be supplied into the servo-control means by the action of the fluid pressure delivered from the pumps.

Abstract: Steering system for an endless track type tractor having an engine, a power distribution device for equally distributing the power of the engine to two outputs, a pair of power trains each including a torque converter, a transmission and a steering brake for transmitting the power to each of a pair of lateral shafts adapted to selectively drive an endless track through a sprocket for turning the tractor rightwardly or leftwardly. The transmissions and the steering brakes are hydraulically actuated through hydraulic cylinders and electromagnetic valves controlled by a manually operable steering switch mechanism so as to shift either one of the transmissions to neutral while the related one of the steering brakes is actuated to braking position for the turning of the tractor at a rate determined by the fluid pressure supplied to the hydraulic cylinders.