Patent ID: 6871802

Claim:
In a valve unit having a valve body presenting an inlet adapted for coupling with a source of pressurized gas pressurized at a first level and an outlet adapted for coupling with a restricted gas receiver, a shiftable valve member having a passageway therein and located between said inlet and outlet and shiftable between a closed, gas flow-blocking position and an open position permitting flow of gas from said source to said receiver, the improvement comprising: a spring operably coupled with said member and biasing the member toward the open position thereof; separate first and second operating surface areas forming a part of said member, said first area exposed to said pressurized gas and said second area exposed to said pressurized gas through said passageway, said first and second surface areas being oriented and correlated relative to said valve body to normally maintain said member in the closed position thereof against the bias of said spring, there being a modulating gas chamber formed between at least a part of said second operating surface area and adjacent portions of said valve body, and a passage formed in said valve body and communicating said outlet and said modulating gas chamber; an actuator operably coupled with said passage and normally blocking communication between said outlet and said modulating gas chamber, said actuator operable upon actuation thereof to open said passage and thereby drain gas from said modulating chamber through said passage to reduce the gas pressure within the modulating gas chamber and permit movement of said member to the open position thereof under the influence of gas pressure exerted against said first surface area; and a gas flow restriction in said passageway operable to substantially limit the flow rate of gas between said modulating gas chamber and said passageway, said first and second operating surface areas, modulation chamber, passage and spring being correlated so that gas from said source is delivered to said receiver at a generally constant pressure over a substantial part of the time gas flows from the source to the receiver by flow of said gas into and out of said modulation chamber.