Importance

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Abstract

A valve for selectively allowing the return of oil from a discharge plenum to a suction plenum includes a passage which is selectively opened or blocked by a valve spool. The valve spool sees a pressure from a discharge pressure location upstream of a discharge check valve on one face, and a discharge pressure from a discharge plenum on an opposed face. While the compressor is running, the two pressures should be relatively equal. The face which sees the pressure from the chamber upstream of the check valve is larger than the face which sees the pressure from the discharge plenum. Thus, when the compressor is running, the valve spool is biased to a first position at which it allows oil return from the discharge plenum to the suction plenum. However, upon shutdown of the compressor, the pressure in the chamber upstream of the discharge valve drops. The valve spool will be driven to a second position at which it blocks communication for oil return.

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First Claim