Fremgangsmåde til fremstilling af filtre for tobaksrøg og apparat til udøvelse af fremgangsmåden

1336433 Tobacco-smoke filters BRITISHAMERICAN TOBACCO CO Ltd 4 Oct 1971 [7 Oct 1970] 47706/70 Heading A2C Additive is introduced into a rod of tobaccosmoke filter material through holes pierced in the rod. The rod may be of extruded polyethylene or polypropylene foam material, and the additive, which affects the rod locally in the region of the holes to modify the filtration characteristics or to modify the smoke flavour, may be a solution or dispersion of organic or inorganic acidic or alkaline material or a slurry, e.g. of carbon, alumina, finely divided metals such as zinc, or small beads of ionexchange material. Specific substances mentioned are manganese dioxide, zinc oxide or acetate, polyethylene imines, lithium chloride, sodium carbonate, trisodium phosphate, ethylenediamine diacetate and zeloites, and for smoke flavour modification, menthol, sweetening agents etc. As shown, a rod 1 of wrapped filter material is pierced by reciprocating needles 5 and then passed through a bath 3 in which additive is maintained at a level 15 such that the rod is partially immersed. The rod need not be wrapped if it has an impervious outer surface. Suction is applied through a hood 23 fitting over the rod so that additive is drawn into the rod through the lower holes. On emerging from the bath the rod may be dried and cut into filter lengths, or it may be pierced with further holes and passed through a second bath containing a different additve before being dried and cut. The needles 5 may be operated simultaneously or alternately, or they may be offset and operated simultaneously. Aternatively, a single needle may be passed right through the rod, or holes may be pierced by a pair of spiked wheels or by a single spiked wheel with spikes slightly longer than the diameter of the rod, or the rod may be pierced by small holes arranged in bands or rings or at random. Alternative arrangement of both comprises a first chamber in which the rod is subjected to vacuum and a second chamber in which the rod is totally submerged in additive which may be pressurised, the rod entering and leaving the chambers through O-ring seals.