| 摘要 |
To detect fluid leakage in a hydraulic directional control valve, a plate is installed between the valve and its mounting subplate. Passages through the plate connect with the pressure inlet and tank ports of the valve, while the load ports of the valve are blocked by the plate. Leaking fluid flows out of the tank port and passes through an orifice across which a pressure differential develops in proportion to the leakage rate. The pressure differential is applied to a piston which retracts an indicator knob within the plate when an unacceptable leakage rate is present. A modified form of the invention detects the combined leakage rate in the valve and the load which it controls. Rather than blocking the load ports, the modified plate has passages which connect with the load ports of the valve to deliver fluid to the load. An orifice is located in the passage of the plate which connects with the pressure inlet port of the valve. When the load is held at its travel limit, fluid leakage in the valve or load creates a pressure differential across the orifice to effect movement of the piston and retraction of the indicator knob.
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