Abstract: When a hydraulic circuit for driving actuators of a construction machine or the like includes a single hydraulic pump and a plurality of direction changeover valves connected to the hydraulic pump for controlling the respective actuators, operation of one of the direction changeover valves may result in undesirable change in the output oil pressure of the other direction changeover valves. The inventive hydraulic circuit includes means for driving a regulator of the hydraulic pump in response to any oil puressure change at the inlets of the direction changeover valves corresponding to the output oil pressure change, thereby compensating for the pressure change.

Abstract: An automatic pressure control device built in a hydraulic actuator driving circuit for driving a plurality of actuators of a construction machine or the like by a single hydraulic pump through respective pilot changeover valves is provided for automatically shuttling the changeover valve of each actuator to reduce its demanded flow rate and uniformly control the operation speeds of all actuators. To this end, the device is arranged to drain an excessive flow rate of the hydraulic pump through a series connection of a flow rate control valve controlled by the highest load pressure of the actuators and a resistance passage including a shuttle and to control the pilot pressure of each pilot changeover valve in response to a pressure at the junction of the series connection.

Abstract: A pipe coupling consisting of male and female elements for connecting and disconnecting a hydraulic or pneumatic piping used for industrial machinery. Each coupling element includes a check valve therein which is actuated by connecting and disconnecting operation to automatically open the passageway of the coupling when it is connected and to automatically close it when it is disconnected.The inventive pipe coupling is designed for use with a conventional automatic connecting and disconnecting device such as automatic coupling device for large scaled industrial machinery.

Abstract: A hydraulic motor control circuit for use in a device for driving construction equipment, such as shovel loader, which comprises a hydraulic driving motor, a pump for feeding compressed oil to the hydraulic motor and a tank for receiving the compressed oil discharged from the hydraulic motor. The circuit comprises a pilot operation type main valve for controlling the oil flow between the pump and the motor and between the motor and the tank, and a remote control valve for feeding a pilot oil pressure to a pilot chamber of the main valve to turn the main valve to a first position for driving the hydraulic motor. As a feature of this invention, the control circuit further comprises an apparatus for detecting the slanting angle of a downward slope and feeding an oil pressure corresponding to the slanting angle to a second pilot chamber of the main valve.

Abstract: A double operate check valve used in a hydraulic pressure circuit for locking and unlocking a vibration absorbing hydraulic cylinder included in a wheel suspension mechanism of a vehicle, which includes an improvement in its structure for providing the suspension with improved compliance with respect to road surface undulation and corresponding comfortable drive of the vehicle. The check valve pilot pistons have fluid conducting surfaces which are connected by a valve body passageway and which communicate the main fluid paths when hydraulic pressure in the pilot chamber urges the pilot pistons to open the check valves.

Abstract: A flow passage coupling unit is provided for connection and disconnection of pipings e.g. on a tooling die exchanger of a press or a former machine, in which both the cylindrical body and the valve head of a slide valve actuated for communication and discommunication between flow paths are slidably fitted into the small and large diameter bores of a main body respectively which is designated as a housing for the slide valve, so that the sliding distance of the slide valve can be determined by summing up of the sliding lengths of their respective small and large diameter bores. Accordingly, the entire length of the main body is minimized and thus, the flow passage coupling unit will become compact in size while assuring consistent action in coupling the flow passages. Also, the flow passage coupling unit is further reduced in the overall size by improviding both the sealing arrangement in the sliding regions and the opening arrangement in the cylindrical body.

Abstract: A pipe coupling consisting of a male and female elements for connecting and disconnecting a hydraulic or pneumatic piping used for industrial machinery. Each coupling element includes a check valve therein which is actuated by connecting and disconnecting operation to automatically open the passageway of the coupling when it is connected and to automatically close it when it is disconnected. The inventive pipe coupling is designed to be used with a conventional automatic connecting and disconnecting device such as automatic coupling device for large scaled industrial machinery.