| 摘要 |
A check valve within a closed loop refrigeration system isolates the evaporator from the helical screw compressor. A normally open, solenoid operated valve is positioned within an unload line having one end coupled to a drive cylinder outboard chamber to the side of the piston opposite an inboard chamber which opens to compressor discharge pressure. The other end of the unload line is connected to the system low pressure side, downstream of the check valve. The same drive cylinder outboard chamber opens via a load line to the system high pressure side through a normally closed solenoid operated valve. Upon compressor shut down, the outboard chamber is vented to the system low pressure side, while the opposite side of the unloader drive cylinder piston sees the compressor high side, thus driving the slide valve to full unload position and eliminating the coil spring normally needed to drive the slide valve to that position.
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