Abstract: A feedback link which transmits a movement of a servo piston to a control sleeve of a regulator is constituted by a link lever formed of a rigid material and an expansion spring formed of a spring material. The expansion spring is formed by folding a narrow leaf spring substantially into U-shape, and provided with a pair of convexly curved plate portions extending forward from a bent portion as a base end and spread apart from each other in a forward direction. On the other hand, an indented groove which is provided on the servo piston is composed of a parallel groove portion and a tapered groove portion. The convexly curved plate portions are engaged in the parallel groove portion of the indented groove in a resilient deformed state to transmit a displacement of the servo piston from the expansion spring to the link lever.

Abstract: A feedback link which transmits a movement of a servo piston to a control sleeve of a regulator is constituted by a link lever formed of a rigid material and an expansion spring formed of a spring material. The expansion spring is formed by folding a narrow leaf spring substantially into U-shape, and provided with a pair of convexly curved plate portions extending forward from a bent portion as a base end and spread apart from each other in a forward direction. On the other hand, an indented groove which is provided on the servo piston is composed of a parallel groove portion and a tapered groove portion. The convexly curved plate portions are engaged in the parallel groove portion of the indented groove in a resilient deformed state to transmit a displacement of the servo piston from the expansion spring to the link lever.

Abstract: A hydraulic actuator is driven by hydraulic fluid discharged from a hydraulic pump, for controlling driving of the actuator. A valve has a meter-in circuit for introducing the hydraulic fluid discharged from the hydraulic pump into the actuator. The valve also has a meter-out circuit for returning fluid from the actuator, into a tank. The meter-out circuit is provided with a main valve for controlling the return fluid from the actuator, and a pilot circuit including a variable restrictor. When the main valve is closed, the pilot circuit is closed, and when the main valve is open, its degree of opening varies depending upon an amount of restriction of the variable restrictor. A controller varies the amount of restriction of the variable restrictor valve in accordance with the driving pressure of the actuator.

Abstract: A pressure control valve has a main valve element of seat type slidably accommodated in a valve case for controlling communication between inlet and outlet sections of the valve case by movement of the main valve element, a control chamber defined within the valve case and between the valve case and an end face of the main valve remote from the outlet section for biasing the main valve element in a valve closing direction, and a variable restriction variable in its opening in response to the movement of the main valve element for communication between the control chamber and the inlet section of the valve case.