GB901334A - Improvements in breathing apparatus - Google Patents

Abstract

901,334. Respiratory apparatus. POWER, MINISTER OF. Dec. 11, 1958 [Sept. 12, 1957], No. 28759/57. Class 81 (2). A closed circuit breathing apparatus includes in a single unit a source of liquid oxygen or air and a cooler to which purified expired air is fed to evaporate and warm the liquid oxygen or air, the transference of heat taking place progressively between a number of successive layers of vaporized oxygen or air each of which encloses the liquid oxygen or air. The unit 7 comprises coaxially arranged nested containers 18, 19, 20, 21 the innermost container 18 containing liquid air or oxygen in a microporous absorbent 25 such as microcellular polyvinyl chloride which may be interleaved with metal foil heat conductors. Expired air purified in the carbon dioxide absorbent canister 4 passes from the breathing bag 9 to a sump 11, in which condensed water vapour collects, and thence through a space 24 between the two outermost containers 20, 21. Heat is transferred from the gas in the space 24 to evaporate liquid air or oxygen in the innermost container 18 and warm the resulting gas which passes through spaces 22, 23 between the three inner containers 18, 19, 20 and flows through a pipe 34, disposed outside the containers or in the outermost space 24, to join the cooled expired gas in a pipe 6 connected with the mouthpiece 1. The unit 7 has a liquid gas filler pipe 28 and an overflow pipe 27 both of which may be closed by air-tight caps. The purifier 4 contains a carbon dioxide absorbent chemical 13a disposed between coaxially arranged perforated cylinders 12, 13. Expired gas enters the inner cylinder 12, flows radially through the chemical 13a into a space 14 surrounding the outer cylinder and thence to the breathing bag 9. A spring-pressed rubber ring 15 is pressed axially against the chemical and a thimble or plug 17a prevents expired gas bypassing the chemical in the region of the rubber ring. The purifier alternatively may be connected so that gas passes through it radially inwardly. A relief valve 37 comprises a plate (not shown) of magnetic material normally held closed against a non-magnetic seat by a magnet the portion of which is adjustable relative to the plate to vary the magnetic force acting on the plate. Specification 733,473 is referred to.