Patent ID: 7921866

Claim:
A first stage pressure regulator for a two-stage underwater breathing apparatus, which first stage regulator is adapted to be connected to a source of high pressure breathable gas, and comprises: an inlet adapted to be connected to the source of high-pressure gas and an outlet for gas having a lower pressure than the incoming gas; a high pressure gas chamber communicating with said inlet and a low pressure gas chamber connected with said outlet; the low pressure gas chamber communicating with the high pressure gas chamber through a regulating valve; a balance chamber interposed between the low pressure gas chamber and a chamber communicating with the ambient or between the low pressure chamber and directly the ambient; said low pressure gas chamber being sealingly separated from the balance chamber by a first movable wall; said balance chamber being sealingly separated from the ambient exposed chamber or directly from the ambient by a second movable wall; said first and said second movable walls being mechanically and rigidly interconnected by a stem which is designed to transfer a force exerted on said movable walls; said first movable wall being further connected by force transfer means to a closing element of the regulating valve interposed between the high pressure gas chamber and the low pressure gas chamber; a diaphragm relief valve being provided for relieving an overpressure build up in the balance chamber and being located between said balance chamber and said ambient exposed chamber or between said balance chamber and directly the ambient; wherein the second movable wall for separating the balance chamber from the ambient exposed chamber or directly from the ambient is formed by a disk-shaped piston which is slideably guided along the peripheral walls that delimit the balance chamber and by an elastically deformable diaphragm, which overlies the side of the piston facing toward the ambient exposed chamber or facing toward directly the ambient and forms with said piston the diaphragm relief valve; wherein the elastically deformable diaphragm is operable to deflect away from the piston and thereby break a seal formed directly therebetween that forms the diaphragm relief valve to allow overpressure in the balance chamber top escape therefrom.