Patent ID: 7788914

Claim:
An apparatus operating a hydraulic actuator for opening and closing a valve, comprising: a first pump port which is connected with an outlet part of a hand pump; a second pump port which is connected with an inlet part of the hand pump; a first supply port which is connected with the first pump port to supply operating fluid; a second supply port which is connected with the second pump port to supply the operating fluid; a first actuator port which can be connected with the hydraulic actuator; a second actuator port which can be connected with the hydraulic actuator; a first direction port which is connected with the first actuator port; a second direction port which is connected with the second actuator port; a direction converting valve which is disposed between the first and second pump ports and the first and second direction ports, and functions to connect the first pump port with one of the first and second direction ports and connect the second pump port with the rest of them so as to convert a flowing path of the operating fluid; a first supply side pilot check valve which is disposed between the first supply port and the first pump port; a second supply side pilot check valve which is disposed between the second supply port and the second pump port; a first actuator side pilot check valve which is disposed between the first direction port and the first actuator port; a second actuator side pilot check valve which is disposed between the second direction port and the second actuator port; a first actuator side pilot path which is disposed so that the pressure of the operating fluid from the second direction port is served as a pilot pressure on the first actuator side pilot check valve; a second actuator side pilot path which is disposed so that the pressure of the operating fluid from the first direction port is served as a pilot pressure on the second actuator side pilot check valve; a first relief valve which is provided between the first actuator port and the first direction port so as to be parallel with the first actuator side pilot check valve and functions to reduce the pressure of the operating fluid in the hydraulic actuator; and a second relief valve which is provided between the second actuator port and the second direction port so as to be parallel with the second actuator side pilot check valve and functions to reduce the pressure of the operating fluid in the hydraulic actuator.