GB482137A - Improvements relating to filters for use in respirators and the like - Google Patents

Abstract

Respiratory and other air filters comprise, as the component for removing suspended particles and droplets, an intimate mixture of fibres, including 5-30 per cent by weight of opened mineral fibres, for example chrysotile or crocidolite asbestos, such fibres being very fine or of small average diameter compared with the other fibrous constituent. The other constituent is preferably combed wool but may comprise cotton, cellulose, or other vegetable fibres, natural or artificial silk, hair, or glass or slag wool. A preferred mixture comprises 80 per cent of dry combed merino wool noils and 20 per cent of white chrysotile asbestos of average fibre length one inch and diameter one to two microns. In an example asbestos is thoroughly opened up and a lap formed from the fibres is fed, together with a lap of combed merino wool noils, to a picker which feeds them in correct proportions to a carding engine. The lap delivered from the carding engine is folded on itself to form a layer two to three inches thick from which discs or pads are cut or stamped out, the waste being returned to the carding engine. The pads are placed in filter cells or containers of diameter slightly smaller than themselves and are held under slight pressure between gauzes or the like. The filters may comprise gas-absorbing material such as charcoal as an additional component. The Provisional Specification refers to the mixing of combed wool with opened asbestos fibres in bulk to produce a loosely matted mixed product, and states that a product comprising the mixed fibres may be wrapped around a perforated tubular or gauze core.