Improvements in filters for protection against gas, dust, arsines, toxic fumes and liquids sprayed in the atmosphere

摘要

468,084. Air-filters. DUNEME, L. March 16, 1936, No. 7846. [Class 8 (ii)] [Also in Group VI] In filters, employed in closed chambers for protection against noxious liquid and solid particles and gases in the atmosphere, and comprising several filtering elements in series, at least one element is constituted by a portion of a band adapted to be wound from one spool to another in steps to expose successive portions of the band for use as preceding portions are exhausted. As shown a gas-mask filtercanister 6 of curved formation comprises a band 1 in series with a pleated paper filter 2 and active carbon or like material which may be enclosed in a separate container within the canister. The band 1 may be of paper, fabric, mineral wool or impregnated felt and is arranged to be wound from a spool 3 upon a spool 4 by means of a key, the spools being enclosed in chambers defined by walls 11, 12 and having tensioning means. In front of the filter 2 the band is guided upon and pressed against flanges upstanding from the base of the canister and from a top wall thereof removable for refilling. The edges of the band may be strengthened or compacted by the application of strips of the material known under the Registered Trade Mark " Cellophane," which may be stretched before apply-. ing, or by impregnation with gum, wax, or solid paraffin. Transverse strips of " Cellophane " may also be used to mark off the band in sections, for consecutive use. The filters 1, 2, may be clogged in known manner to reduce the pore size, the band 1 being less heavily treated than the filter 2. The canister may have transparent windows and the band may be coloured, for example black and white in alternate sections, or otherwise marked to facilitate correct positioning thereof. Air enters the canister through an aperture 13, and leaves through an aperture 20. In a modification, several bands may be arranged on separate pairs of spools one behind the other for successive use, the ends of the bands having apertures or comprising the stiffening strips only to present no filtering surface before and after use. In a further modification a folded paper filter, employable in place of the band, is arranged behind it and is connected at its ends to one side of the canister which side has a second inlet orifice. The inlet of the filter not in use is closed by a plug.