US Patent 7195028 Self-contained oxygen generator

A self-contained oxygen generator containing a PSA unit and a flowmeter in the outlet line. The flowmeter provides a signal which represents the flow rate of the oxygen in the outlet line. A leakage circuit with a calibrated orifice and a solenoid valve are also located on the outlet line. In response to a signal from the flowmeter, the solenoid can be actuated so as to provide a calibrated leakage at the outlet of the PSA. This calibrated leakage is useful when overall oxygen usage is too low.