| 摘要 |
A modular three block assembly provides unloading control for a hydraulic cylinder functioning to variably position a slide valve on a helical screw rotary compressor. A first compressor block is fixedly and sealably mounted within the hermetic compressor outer casing and has through holes leading to a first tube connected to a source of oil under discharge pressure forming the hydraulic fluid for the hydraulic cylinder, a second tube connected to the hydraulic cylinder and a third tube to the suction tube returning low pressure vapor to the compressor suction side. A needle valve block is fixedly mounted to the external face of the compressor block and bears within longitudinal through passages paired needle valves determining the load and unload flow rates for the hydraulic fluid passing through said compressor block through holes. A solenoid valve block face connected to the needle valve block carries a three position solenoid valve assembly for controlling flow through the various passages leading to the internal tubes. Flow distribution plates of gasket material are interposed between the blocks at the block interfaces to seal the block interfaces and to provide lateral flow distribution between the various passages through the blocks interconnecting the tubes and under control of the solenoid valve assembly. Elimination of external tubing insures oil of low viscosity for proper operation at compressor start up and significantly reduces complexity and cost to the control system.
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