US Patent RE40399 Low charge protection vent

A vent is included into a scroll compressor for protecting a refrigerant system in the event of loss of charge. The vent selectively taps an entrapped compression chamber to a housing chamber which surrounds the motor. In the event of a low charge, the gas in the compression chamber will be at a high temperature, and will heat the motor when the vent opens. The vented heated gas will then actuate a temperature protection device on the motor, causing the motor to stop rotation. In further embodiments, the compression chamber which supplies the tapped fluid is the discharge port.