Pneumatic analogue decompression instrument

Claim 1

In a decompression meter for use in SCUBA diving including a submersible housing providing an ambient pressure gas chamber and a time-constant gas chamber and a passageway communicating with said gas chambers, the combination of a gas diffusion membrane assembly closing the passageway to the free flow of gas from one said chamber to the other and providing gasketing between separate parts of the meter housing, said assembly consisting of a. an imperforate air-permeable sheet of polymeric material, b. a first reinforcing screen of plastic material covering one side of the imperforate sheet, c. gasket means for the meter housing comprising an annular band of plastic bonding material carried on the periphery of the first reinforcing screen and bonded to the imperforate sheet, d. a second reinforcing plastic screen contacting and covering the other side of the imperforate sheet and bearing against the housing around the time-constant gas chamber end of the passageway to prevent gas pressure differential displacement of the imperforate sheet and reinforcing screens in the direction of the ambient pressure gas chamber, and e. a perforate metal disc air-tightly joined around its periphery to the housing by an annular solder seal and covering the time-constant chamber side of the first reinforcing screen and bearing in compression against the opposed annular surface of the gasket means around its periphery to prevent gas leakage around the edge of the membrane and also to prevent gas pressure differential displacement of the imperforate sheet and the reinforcing screens in the direction of the time-constant gas chamber.