Trane International Inc.

American Standard Inc.

Jerry E Brown

Joel C VanderZee

Ronald W Okoren

Jeffrey J DeGroot

Steven K Klingemann

Charles E Nelson

Two vertically offset thermistors for sensing a fluid such as oil and refrigerant in a compressor shell are monitored by a method that takes into account rapidly changing conditions within the shell. The system can determine the fluid's sump temperature, high/low liquid levels, and can determine whether the thermistors are sensing the fluid as a liquid, gas, or a mixture of the two, such as a foam or mist of liquid and gas. For greater accuracy, thermistor readings can be dithered and filtered to provide temperature or voltage values having more significant digits than the readings originally processed through a limited-bit A/D converter. For faster response, limited microprocessor time is conserved by sampling thermistor readings at strategic periods that enable the microprocessor to identify certain conditions and temperatures via simple delta-temperature ratios and undemanding equations rather than resorting to exponential functions or lookup tables to determine time constants.

Method for sensing a fluid in a compressor shell

Method for sensing the liquid level in a compressor

A scroll compressor has a discharge check valve assembly comprised of a valve and a valve cage. The valve is maintained open within the assembly by the flow of discharge gas from the scroll set during the normal course of compressor operation and is essentially unaffected by momentary gas backflow and/or momentary pressure pulsations that can repetitively occur in the discharge pressure portion of the compressor shell during such operation. At the same time, the valve is quickly responsive to close the discharge port to gas backflow upon compressor shutdown. A dash pot volume, defined between the discharge valve and its cage, is vented to the discharge pressure portion of the compressor shell and is such that the valve is maintained open and does not chatter in the face of momentary gas backflow and/or pressure pulsations yet closes quickly when the compressor shuts down to prevent the backflow of high pressure gas to the scroll set.

Discharge check valve in a scroll compressor

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La Crosse, WI, United States of America

Jerry E Brown