ES366885A1 - Tobacco smoke filter - Google Patents

Abstract

A tobacco-smoke filter element 30 comprises an axially extending tubular outer member 34 and, within said member 34, an axially extending hollow inner member 36 comprising an axially extending air permeable wall, the outer surface of said wall being in engagement with the inner surface of the outer member 34 at a first axial position (e.g. at end portion 38) so as substantially to preclude axial passage of smoke between the members 34, 36, and at a second axial position the inner surfaces of the said wall being in engagement (e.g. at edges 42) so as substantially to preclude axial passage of the smoke between them at the second position, the arrangement being such that smoke passing axially of the element must travel through said wall of the inner member 36 and be filtered thereby. Granular filtering material 52, such as activated carbon or silica gel, may be enclosed within a downstream cavity 48 in the member 36 and retained therein by a permeable disc 50 or a plug 51. The outer member 34 may be formed from plastics, paper, cardboard or bonded fibres, and the inner member 36 may be formed from filter paper, bonded fibres such as crimped cellulose acetate fibres, porous plastics, plastics foam or blends of paper fibres with thermoplastic fibres especially secondary cellulose acetate fibres. The material of the inner member may incorporate active carbon or flavours. Alternative forms of crimp in the inner member 36 to the Z shaped crimp shown in Fig. 1 include Y shaped, cruciform ribs and helically arranged cruciform ribs (Figs. 5, 6 and 7 not shown). Another form (Fig. 8, not shown) has its end portion 42 closed by twisting. A separate outer member 34 may be dispensed with and its function performed by a stiff tipping overwrap 32. In one form of apparatus for producing the filter elements 30, a strip of filter paper is fed from a roll 62 through a tubular garniture 64 to form a tube 68 the overlapping or butting edges of which are sealed together by molten plastics material applied by a nozzle 74. The tube 68 then passes through a crimper 80 where stripes of molten plastics material 76 round the inside of the tube 68, previously applied to the filter paper before folding by a dispenser 78, seal the crimps to produce a continuous rod 86 of crimped inner members 36. The molten plastics material may be replaced by heat seal or liquid adhesives in which case the jaws of the crimper 80 are heated. The rod 86 is overwrapped with a strip of heat seal paper from a reel 88 by a garniture 90 and sealed by a heater 96 before being divided into multiple length filter rods 102 by a cut-off 100. The inner member 36 may alternatively be formed from a laminate that includes a thermoplastic layer that becomes the inner layer of the formed tube, or may be formed from a web or strip by helical winding. In another form of apparatus (Fig. 9, not shown) an opened, crimped, continuous filamentary cellulose acetate tow (132), having triacetin droplets distributed on its surface, is supplied to an air nozzle (134) through which it is drawn by compressed air and forwarded over a mandrel into a jet (140) supplied with steam to produce a tube (156) or bonded cellulose acetate filaments. The tube (156) is then passed through a crimper (144) where it is formed into a crimped tube (160) which is subsequently wrapped by a paper strip (174) by a garniture (162). Optionally, the paper strip (174) is formed into a trough around the crimped tube (160) and granular material is dropped from a hopper (176) so as to flow around the tube (160) to fill the spaces between it and the strip (174) before passing to the garniture (162) for sealing to form a composite rod.