US Patent 7517385 Gas separation device and method of use

A gas separation device for separating oxygen gas from air includes a compressor; a concentrator; a measurement mechanism; and a flow control mechanism that includes a valve assembly for providing fluid flow control, the valve assembly having a motor; a valve body; and a plunger within the valve body and reciprocally driven by the motor, wherein the valve body including a fluid inlet, a fluid outlet, and a flow chamber therebetween, the flow chamber including a flow chamber wall and a flow chamber outlet, the plunger including a flexible member reciprocating within the flow chamber outlet to provide variable flow control therethrough, the flexible member including a lip seal engageable with the flow chamber wall during reciprocation of the plunger and flexible member to provide a seal therebetween.