GB1317172A - Respirators - Google Patents

Abstract

1317172 Respirator M L AVIATION CO Ltd 7 May 1971 [21 May 1970 9 Oct 1970] 24714/70 and 48184/70 Heading A5T A respirator comprises a hood 1, for completely covering the head, an oro-nasal mask 13 and a mechanical blower (6) Figure 1 (not shown) for passing air through a first non- return valve 21 to the mask 13 and through a second non-return valve 20 to the hood 1 at a rate greater than required for respiration so that the excess flows out between the edge of the hood and the body of the wearer. Filtered air passes from the mechanical blower (6) along a pipe 10 and splits between branch pipe 11 leading to the interior of the hood 1 and branch pipe 12 leading to the mask 13. An oxygen inlet pipe 16 communicates with the mask 13 so that the respirator can be used at high altitudes. The pressure of the oxygen supply causes first valve 21 to close so that air from the blower passes only into the hood 1. The first valve 21 contains a valve plate 30, operating against a seating 31, and which is connected to a second plate 33 by a light spring 32. A second, stronger spring 35 connected only to the second plate 33 is brought into operation by a piston 44 which is depressed by the oxygen supply pressure. The oxygen pressure causes the stronger spring to press the valve plate 33 firmly against its seating 31. A latch 42 is provided to lock the piston 44 in the down position in case the oxygen supply fails. In a variant of valve 21 the latch 42 contains a notch (52) Figure 4 (not shown) to allow controlled escape of oxygen to the mask when the oxygen regulator 28 fails. The hood 1 has an excess pressure relief valve (15) Figure 1 (not shown) which limits the total pressure of air inside the hood.