Importance

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Abstract

An isolation valve is provided for use in a pneumatic system having an air compressor operable in normal and unloading modes, an air dryer, a reservoir of charged air, and a governor. The isolation valve includes a housing provided with an internal cavity and having a first port to the cavity communicating with a first port of the compressor, a second port to the cavity communicating with an inlet port of the dryer, and a third port to the cavity communicating with a port of the governor. A pneumatically responsive primary valve member is mounted within the cavity for movement between open and closed positions with respect to the housing second port. The primary valve member is provided with an internal passage having one end in communication with the housing third port and a second end in communication with the housing cavity. A pneumatically responsive secondary valve member is mounted within the passage for movement between blocking and unblocking positions. The secondary valve member is in the blocking position and the primary valve member is in the open position when the compressor is in the normal mode. The secondary valve member is in the unblocking position and the primary valve member is in the closed position when the compressor is in the unloading modes.

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First Claim