A pneumatically amplified conservation valve controls a flow of gas, such as oxygen, to a hospital patient. A sense tube monitors pressure variations as a result of exhalation by the user. The exhalation pressure variation deflects a diaphragm which closes a check valve that serves to vent gas through...http://www.google.fr/patents/US4575042?utm_source=gb-gplus-shareBrevet US4575042 - Pneumatically amplified conservation valve
