US Patent 7204760 Constant velocity joint vent

A vent valve for use in a constant velocity joint having a vent aperture in communication with a joint cavity comprises a body portion having a first end and a second end and a plurality of escape pathways extending therebetween. An umbrella shaped flexible retention cap is disposed adjacent the first end of the body portion and the plurality of escape pathways, wherein the retention cap is operative in a normally closed position to cover the plurality of escape pathways and seal the joint from external contaminants, and in response to internal pressure created in the joint cavity functions to bellow outward and expose the plurality of escape pathways to permit air to escape from the cavity.