Patent GB-758418-A (GB)
Title: Improvements in or relating to breathable gas regulating devices
IPC: B63C11/22
Filed: 1954-08-24
Abstract: 758,418. Respiratory appliances. GARRETT CORPORATION. Aug. 24, 1954 [Sept. 8, 1953], No. 24575/54. Class 81(2). [Also in Group XXIX] A respirator regulating device comprises first passage means for conducting gas from a source to a point of use, second passage means for conducting expired gas from the point of use to a chamber in the device, a check valve for controlling fluid flow from the chamber on one side of which is a movable wall subjected on one side to the pressure of the surrounding fluid medium, valve means for controlling the flow of gas through the first passage means and means operably associated with the movable wall for opening the valve means upon reduction in pressure in the second passage means and the chamber to permit flow of gas through the first passage means. A regulator 11 is connected to a source of breathable gas in a tank 12 and to a face mask 15 by way of an inhalation conduit 13. Exhaled gases are conducted from the mask 15 by an exhalation conduit 14 to the regulator 11 and are thence vented to the ambient medium which may be gas or liquid. On exhalation a reduction of pressure is created in a chamber 18 of the regulator 11. A diaphragm 82 forming one wall of the chamber 18 moves inwardly of the chamber 18 and by means of connecting levers 110 raises a valve member 70 from its seat 69 so that gas can flow from the tank 12 to another chamber 17 in the regulator 11 and thence to the mask 15. On exhalation, expired gases pass from the mask 15 by way of exhalation conduit 14 to the chamber 18. - The diaphragm 82 is moved outwardly of the chamber 18 to cause the valve member 70 to be sealed and thus cut off the gas supply. Check valve 96 opens to allow the expired gases to be vented to the ambient medium through passages 101 in a bushing 89 provided in the centre of the diaphragm 82 and through passages 102 in the regulator cap 83. Breathable gas flows from the tank 12 through a shut-off valve 33 and a filter 35 to a recess 36 in a portion 28 of the regulator 11. The gas pressure is normally sufficient to unseat a spring-pressed closure member 39 of a gas reserve valve 40 so that gas flows from the recess 36 into a bore 41 of the gas reserve valve 40 and thence through a passage 58 to a recess 59 in the member 28. The recess 59 contains a slidable element 61 which is provided with bores 68 connected with the recess 59 and through which gas is conducted towards the valve member 70. The conical tip 72 of the valve member 70'is urged by a compression spring 74 against the seat 69 which is formed in the slidable element 61. A stronger compression spring 75 is provided to urge the slidable element 61 in a direction to oppose the force of the breathable gas entering the recess 59, and thus away from the valve member 70. The combined-effect of the compression springs 74, 75 is to ensure that uniform breathing resistance is maintained. In the event of pressure of breath . able gas in the tank 12 becoming low and thus failing to unseat the closure member 39 of the gas reserve valve 40, against a spring 54, the gas supply is cut off giving warning of the failure. The closure member 39 is then unseated by manual operation of a lever 50 which, through a cam device retracts a shaft 45 thus releasing the spring 54. The gas supply is thus continued while the user of the apparatus retreats. The mask 15 comprises a flange portion 120 to be held beneath the wearer's lips and bit portions 121 to be gripped between the teeth. It is connected with inhalation and exhalation conduits 13, 14 by a passage 118 leading to a cross-passage 115.