GB663202A - Improvements in or relating to respirators - Google Patents

Abstract

663,202. Respiratory appliances. FILETI, A. Dec. 20, 1948, No. 32898/48. [A Specification was laid open to inspection under Sect. 91 of the Acts, June 21, 1949.] Class 81 (ii) A respiratory device for supplying gas to a mask or mouthpiece comprises a casing having two chambers, each connected individually to the mouthpiece, one chamber being supplied with gas through a valve controlled in accordance with the pressure in the other chamber. In one form described a diaphragm 8<SP>1</SP>, Fig. 1, is open to the atmosphere through an orifice 9<SP>1</SP> on one side and to the mouthpiece 13, through a tube 10<SP>11</SP> and ducts 5<SP>1</SP>, 6<SP>1</SP>, on the other. Its movements are communicated by a rod 4 to a valve member 3 to control the flow of gas from a supply pipe 9, through an orifice in a plate 5 to a chamber 2<SP>1</SP> and thence through a tube 101 to the mouthpiece. Thus the flow of gas is controlled in accordance with the variations in pressure at the mouthpiece and it is not influenced by the pressure drop in the supply pipe thereto, so allowing the use of a narrower bore pipe than hitherto. The diaphragm 8<SP>1</SP> may be biassed by a leaf spring 311, adjusted by a screw 11<SP>1</SP>, and the control valve may be set slightly open, to a desired extent, by means of a plunger 6, sealed by a rubber pad 7, coacting with the valve member 3 and set by a cam surface on a hand wheel 10. In a modification the flow of gas is controlled electrically by the pressure responsive diaphragm. The diaphragm 8, Fig. 2, when bowed inwards by the user's inspiration, causes a push rod 22 to make electrical contact with a member 25 and complete a circuit through a solenoid 27 which attracts an armature 28 and this, through linkage 29, opens the supply valve 3. The contact device 25 is made with carbon granules so that the current flowing, and thus the extent of opening the valve, is proportional to the degree of suction in the chamber 1. A similar arrangement in which the control is effected pneumatically instead of electrically is described with reference to Fig. 3 (not shown); in this the power for operating the mechanism is taken from the compressed gas itself. In these two arrangements it is possible to dispense with a pressure reducing valve and to use a high pressure valve in the control mechanism. Such a valve may comprise a closed ellipse of tubing, as shown in Fig. 5, with opposed outlets tending to close each other under the distorting influence of the internal pressure. The valve is opened by exerting a lateral compressing force 48 on the sides of the ellipse.