Suodin, jossa on virtaavaa ainetta läpäisevä kuituainemassa

1,273,418. Making filter elements. PHILIP MORRIS Inc. 20 June, 1969 [24 July, 1968], No. 31438/69. Headings B1D and BIT. [Also in Divisions A2, B5 and B6] Continuous filter rod particularly for cigarette filters but suitable also for filtering liquid or other gaseous media is produced by extruding a thermoplastic material such as polyethylene through a tubular die 28 to form a tube of greater diameter than the intended final diameter, advancing a fibrous tow 14 of filter material through a nozzle 38 so that it does not come immediately into contact with the hot extrudate, and subsequently contracting the tube in a portal gland 42 at the entrance to a cooling chamber 40. The tow, which may be of cellulose acetate, a polyalkene, polyethylene or paper, is treated with a plasticizer, e.g. triacetin, and may contain filtrant or flavourant particles, e.g. charcoal. It is partially compressed in a horn 26 to a cylindrical form of slightly larger diameter than the final internal diameter of the tube so as to be radially compressed as the tube is finally sized, the tow being bonded to the tube either as a result of the inner wall of the latter being still plastic, or by the plasticizer in the tow. The cooling chamber 40, which contains water and a succession of sizing plates 48-58 to provide progressive cooling and hardening of the tube, is followed by a puller unit 64 and cutter (not shown). The tube, which is kept in contact with the sizing plate apertures by the provision of vacuum in the chamber 40, may have a cylindrical or polygonal outer surface, or a surface with longitudinal flutings.