| 摘要 |
An on/off, protective circuit has a pressure line with an inlet for connection to a pressure source and an outlet for connection to the pressure port of a hydraulic system, such as a reciprocating conveyor. A relief valve is spring biased into a closed position and openable by pressure in the pressure line to short circuit pressure from the pressure line to a return line when an on/off valve is in an off position. The spring biasing of the relief valve causes residual pressure in the pressure line. To prevent communication of the residual pressure out through the pressure outlet and into the hydraulic system and thereby prevent creeping movement in the system, a check valve is provided in the pressure line downstream of the relief valve. The check valve has a valve plug positioned to be closed by pressure in the pressure line. The check valve also has a pilot chamber which is supplied with pressure when the on/off valve is in an on position to open the check valve and allow pressure to be supplied to the hydraulic system. When the on/off valve is in its off position, the pilot chamber of the check valve is connected to return to allow the residual pressure in the pressure line and a biasing spring to maintain the check valve closed.
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