Patent ID: 7811143

Claim:
A shaft seal pressure compensation system for equalizing pressure across a shaft seal of an underwater device, the system comprising in combination: a variable volume gas container responsive to a pressure differential between an external ambient pressure and an internal pressure within said variable volume gas container for adjusting the volume of said variable volume gas container so that said internal pressure equals said ambient pressure; a motor housing defining an enclosed internal space; a motor within said enclosed internal space and having a shaft extending from said internal space outwardly of said motor housing and terminating at an external location of said motor housing; a shaft seal between said motor housing and said shaft for making sealing contact between said shaft and said motor housing; said variable volume gas container being pneumatically connected to said motor housing to allow air to freely exchange between said variable volume gas container and said motor housing for pressurizing said enclosed internal space of said motor housing so that it equals said ambient pressure, thereby equalizing the pressure across said shaft seal.