GB1319862A - Tobacco-smoke filters - Google Patents

Abstract

1319862 Tobacco-smoke filter BRITISHAMERICAN TOBACCO CO Ltd 29 June 1971 [23 July 1970] 35783/70 Heading A2C The filter comprises a porous tube 1 extending within a tubular case 2 of smoke-impermeable material having longitudinal internal ribs 3 of flutings which directly support the tube I throughout its length, spaces 4, 6 within the tube 1 and between it and the case 2 being closed at opposite ends so that smoke entering one end of the filter is constrained to pass substantially radially through the tube 1 before reaching the other, outlet end. As shown, the space 4 is closed at the outlet end of the filter by a plug 5 of smoke-impermeable material, and the spaces 6 are closed at the other end by an inturned lip 7 of the case 2. The tube 1 is formed of smoke-filter paper; the case 2 is formed of a plastics material such as polyethylene or a copolymer material; and the plug 5 may be formed of extruded foam polyethylene, nyon or polyurethane, or of fibrous cellulose acetate rendered impermeable by use of a high concentration of plasticizer, or of wax. The tube 1 may comprise two or more layers of filter material sealed together at their ends, and the filter material may be impregnated with additives such as sodium carbonate, zinc acetate or polyethylene imine. The space 4 may be partly or wholly filled for example with granulated activated carbon or manganese dioxide, and its open end may house a conventional filter plug. Two or more filter sections may be used in series or tandem within a common case 2.