GB885353A - Pressure regulating system - Google Patents

Abstract

885,353. Respiratory appliances. BENDIX CORPORATION. May 6, 1960 [May 14, 1959], No. 16145/60. Class 81 (2). A pressure-regulating arrangement, primarily for use at high altitudes, has an exhaust valve which is biased towards the closed position by a pressure which is increased in accordance with the increase in the internal pressure in the system. The main housing 12 is mounted on the mask 10 and air is admitted to it through a duct 17 leading to a chamber 18, below a main valve 16, but this has a bleed duct 19 leading to the upper face of the diaphragm 16 so that the pressure above it normally holds the valve closed. The interior of the mask, and associated space 28, is connected through a duct 29 to the space 23, below a demand diaphragm 27 and, on inhalation, this diaphragm is deflected downwards so that a lever 25 opens a pilot valve 24 and exhausts the space 20, whereupon the main valve 16 is opened by the supply pressure and oxygen passes to the face mask. In order to increase the mask pressure with increasing altitude a pressure is applied to the outer face of the demand diaphragm 27 by oxygen received through a choke tube 39. At low altitudes this pressure only rises to a value sufficient to raise a valve 43 against a light spring 50 and this ensures that the mask pressure is only slightly above atmospheric, to prevent the admission of external air. At higher altitudes, however, an evacuated aneroid 51 presses with increasing force on the valve 43 and the pressure applied to the diaphragm 27 is increased accordingly. The pressure existing above the diaphragm 27 is also communicated through a duct 65 to a diaphragm 66 which is mechanically connected to the exhaust valve 61. Consequently, at high altitudes, this valve is held closed against the excess mask pressure above ambient pressure and there is no tendency for oxygen to be continuously lost through this valve, but it is merely opened by the additional pressure produced by exhalation. The spring 70 is employed to balance the initial internal pressure at low altitudes, before the aneroid 51 becomes effective.