GB847754A - Improvements in breathing apparatus - Google Patents

Abstract

847,754. Respiratory appliances. ROBERTSHAW-FULTON CONTROLS CO. Oct. 2, 1958. [Feb. 14,1958) No. 31519/58. Class 81(2). High altitude breathing apparatus, having a differential pressure-operated exhalation valve, has means for applying pressure to one side of the exhalation valve independently of the actuation of the inhalation valve. In the supply valve, oxygen is admitted under pressure to a conduit 30, Fig. 3, and passes to a flexible differential valve disc 40, the lower side of which is subjected to the same pressure through ducts 44, Fig. 4 and a metering orifice 48. A chamber 52 below a control diaphragm 56 is in communication with the interior of the face mask through an orifice 54, Fig. 3 and when the diaphragm is drawn down, on inhalation, it engages a lever 62, pivoted on a spring 74, Fig. 4, and opens a pilot valve 66 so as to exhaust the chamber 33 through duct 50. Consequently the valve member 40 moves away from its seating and oxygen flows from the supply and through ducts 34, Fig. 3, to the face mask. On exhalation, the diaphragm 56 is again raised so that the pilot valve is closed and pressure again builds up below the valve, member 40 to close it. A small flow of gas is permitted through orifice 94 to the space 92 above the diaphragm and when the apparatus is used at high altitudes, a closure member 88, actuated by an evacuated aneroid 97, closes an orifice 84 to seal the space 92, and the gas thereupon creates a pressure on the upper face of the diaphragm 56, with a resultant increase in the mask pressure. The altitude at which this device becomes operative may be set by a screw 106. At the same time, the pressure in the space 92 is communicated through a tube 120 to the pressure sensitive element of the exhalation valve so as to increase the exhalation pressure required to open it. A spring-loaded release valve 136 prevents excessive pressure in the chamber 92 and exhalation valve system.