GB912579A - Improvements in underwater breathing apparatus - Google Patents

Abstract

912,579. Underwater breathing-apparatus. BISSET, C. O. June 13, 1960 [July 13, 1959], No. 24017/59. Class 81 (2). Underwater breathing-apparatus comprises a mask which covers the nose leaving the mouth exposed and means providing a substantially constant air pressure within the mask above the ambient water pressure and controlled automatically by the water pressure. The mask 4 includes a window 6 and is held airtightly over the eyes and nose by a strip 8. A regulating valve comprising a casing 3 is mounted on the mask, the interior of the casing communicating with the interior of the mask. A compressed-air cylinder 1 is connected by a tube 5 to a short tube 9 which passes through the casing wall. Within the casing, a sleeve, mounted over the outlet end of the short tube, guides movement of a valve stem of a valve member 13 which is urged by an adjustable spring 18 to close the short tube outlet. The valve stem bears against one arm of a bell-crank lever 16, the other arm of which is attached to a diaphragm 23 which separates the casing interior from the ambient water. The valve is so adjusted by the spring that it is closed by movement of the diaphragm when the pressure in the casing and the mask is just above the ambient water pressure. If the pressure in the casing falls relative to the water pressure due to the driver descending to a greater depth or inhaling, the diaphragm moves to open the valve so that air is introduced to restore the differential pressure between the mask and the water to the amount, slightly in excess of the water pressure, which is determined by the adjustment of the spring.