GB494500A - Improvements in or relating to gas mask filters - Google Patents

Abstract

494,500. Respiratory filters. SOC. ITALIANA PIRELLI. May 24, 1938, No. 15523. Convention date, July 3, 1937. [Class 81 (ii)] In a gas-mask filter containing two or more masses of active material of different filtering characteristics in series and including a mass which deteriorates on exposure to the atmosphere, for example a mass for the absorption of carbon monoxide, means are provided for byepassing the deterioratable mass as regards the path of air breathed through the filter. As shown, the filter comprises a canister 1 subdivided into a number of compartments for the different active masses by perforated diaphragms 3, 4, 5, 6 spaced by beads 7, 8, and held in position by spring 9. The upper mass may be active carbon, and the next lower a mass for protection against arsine. The lowest and byepassable mass is disposed in an annular cartridge, the ends of which are closed by perforated diaphragms 10, 11, the diaphragm 11 being pressed upwardly by spring 12. The cartridge is removable from the canister, being held therein by a lid 13 formed with a flange 17 adapted to engage a co-operating flange on the end of the canister. Openings 16 are formed in the cover and when these are closed, e.g. by rubber plugs, the air breathed in passes through a central hole 15 in the lid and passage 14, the active mass within the cartridge being thereby byepassed. The byepassable mass is placed in circuit by opening holes 16 and closing hole 15. To isolate the mass from the atmosphere, the diaphragm 10 may be covered by a disc of waterproof paper or fabric adapted to be torn away. Alternatively, the cartridge may be closed by apertured diaphragms adapted for relative rotation whereby the apertures may be brought into and out of register with one another. The rotatable diaphragm is accessible for manipulation through the passage 14 or may be formed with manipulating means extending therethrough.