Tobacco smoke filter

Abstract

The invention provides a method of producing a tobacco smoke filter or filter element comprising: • heat treating a continuously advancing longitudinally extending strand of material; • cooling the heat treated continuously advancing strand; and • forming a longitudinally extending outer layer of tobacco smoke filtering material around the continuously advancing strand, to form a continuously advancing rod comprising a longitudinally extending strand (1a) of material and a longitudinally extending outer layer (2a) of tobacco smoke filtering material engaged around the longitudinally extending strand (1a). An apparatus for carrying out the method, and products of the method, are also provided.

Claims

1. A method of producing a tobacco smoke filter or filter element comprising: heat treating a continuously advancing longitudinally extending preformed strand of material; cooling the heat treated continuously advancing longitudinally extending preformed strand of material; and forming a longitudinally extending outer layer of tobacco smoke filtering material around the continuously advancing longitudinally extending preformed strand of material subsequent to said cooling, to form a continuously advancing rod comprising the longitudinally extending preformed strand of material and the longitudinally extending outer layer of tobacco smoke filtering material engaged around the longitudinally extending preformed strand of material; wherein the preformed strand is formed at least 15 minutes before the longitudinally extending outer layer of tobacco smoke filtering material is formed around the continuously advancing longitudinally extending preformed strand of material; and in which the continuously advancing longitudinally extending preformed strand of material is under tension during the heat treatment.

2. A method according to claim 1 in which the longitudinally extending preformed strand of material does not comprise a tobacco smoke filtering material.

3. A method according to claim 1 in which the preformed strand of material is a single filamentary element.

4. A method according to claim 1 in which the continuously advancing longitudinally extending preformed strand of material has a non-circular cross section.

5. A method according to claim 1 in which the preformed strand of material is advanced longitudinally through a positioning apparatus prior to formation of the longitudinally extending outer layer of tobacco smoke filtering material around the preformed strand of material.

6. A method according to claim 5 in which the positioning apparatus guides the advancing preformed strand of material in a direction which is substantially the same as a direction in which the preformed strand of material advances after formation of the longitudinally extending outer layer of tobacco smoke filtering material around the preformed strand of material.

7. A method according to claim 1 in which the preformed strand of material is an extruded material.

8. A method according to claim 1 in which the preformed strand of material comprises extruded cellulose acetate.

9. A method according to claim 1 in which the preformed strand of material and/or the outer layer of tobacco smoke filtering material includes a pigment.

10. A method according to claim 1 in which the preformed strand of material is of a contrasting colour to the outer layer of tobacco smoke filtering material.

11. A method according to claim 1 further comprising a step of applying a wrapper around the continuously advancing rod.

12. A method according to claim 1 further comprising a step of cutting the continuously advancing rod into single or multiple length filters or filter elements.

13. A method of producing a tobacco smoke filter or filter element comprising: heat treating two or more continuously advancing longitudinally extending preformed strands of material; cooling the heat treated continuously advancing longitudinally extending strands of material; and forming a longitudinally extending outer layer of tobacco smoke filtering material around the continuously advancing longitudinally extending strands of material subsequent to said cooling, to form a continuously advancing rod comprising the longitudinally extending preformed strands of material and the longitudinally extending outer layer of tobacco smoke filtering material engaged around the longitudinally extending preformed strands of material; wherein the preformed strands are formed at least 15 minutes before the longitudinally extending outer layer of tobacco smoke filtering material is formed around the continuously advancing longitudinally extending preformed strands of material; and in which each continuously advancing longitudinally extending preformed strand of material is under tension during the heat treatment.

14. A method according to claim 13 in which the longitudinally extending preformed strands of material do not comprise a tobacco smoke filtering material.

15. A method according to claim 13 in which each of the preformed strands of material is a single filamentary element.

Description

(1) The present invention will now be illustrated with reference to the attached drawings in which:

(2) FIG. 1 is an end view of a tobacco smoke filter produced according to an aspect of the invention; and

(3) FIG. 2 is a schematic side elevation view of an example of an apparatus for forming the filter of FIG. 1.

(4) FIG. 1 shows one end of a filter (or element or rod), made by a process according to the invention. The filter comprises an outer layer 2a (substantially annular layer) of white-coloured plasticised cellulose acetate filamentary tow filtering material (formed from a multitude of plasticised cellulose acetate filaments which are bonded together to form a tobacco smoke filtering material). The outer layer (2a) is engaged around (and intimately surrounding) a strand (inner core) 1a having a heart shaped cross section which comprises a single extruded element formed from red-coloured (pigmented) plasticised cellulose acetate [i.e. a strand which is a single filamentary element (formed from plasticised cellulose acetate)]. The extruded cellulose acetate is impervious to smoke flow and therefore has no tobacco smoke filtering capability). The outer layer of white-coloured plasticised cellulose acetate filamentary tow 2a is encased in a plugwrap 3a. It will be appreciated that strand 1a is of heart shaped cross section. The contrast between the centrally located red heart-shaped strand and the white surrounding outer layer of filtering material provides an attractive and distinctive end appearance. Plugwrap paper 3a may be perforated (not shown) or air-permeable to provide a ventilated filter.

(5) It will be appreciated that the filter of FIG. 1 may be joined at its upstream end to a wrapped tobacco rod (not shown) by means of, for example, a full tipping overwrap which surrounds and engages the full length of the filter and the adjacent end only of the wrapped tobacco rod, to form a filter cigarette. The filter of FIG. 1 may also be attached to a tobacco rod to form a filter cigarette by other means known in the art, such as ring tipping.

(6) FIG. 2 shows a schematic side elevation view of an apparatus of the invention, for forming filters according to FIG. 1.

(7) A band of cellulose acetate tow 10 is drawn through funnel 15, which has an internal wall converging downstream. In passing through the funnel 15 the tow 10 is gathered and largely condensed therein. The tow 10 is further gathered and condensed into rod form as it enters and passes through a gathering device in the form of a rod making and wrapping garniture 20.

(8) A longitudinally extending strand of red-coloured (pigmented) plasticised cellulose acetate having heart shaped cross section (1a) is pre-formed by extruding plasticised cellulose acetate through a die, by methods well known in the art. It will be appreciated that various methods of making such shaped and pigmented strands are known in the art. The preformed longitudinally extending strand 1a is continuously advanced from a holder in the form of bobbin 8 through a heat treatment station 9 where it is exposed to steam at a temperature of 120° C. The strand 1a has a cross section of width (at its broadest point) 2.4 mm.

(9) The heat treated strand 1a is then advanced through a cooling station 9a where it is cooled using air to approximately 18° C. It will be appreciated that the action of advancing (i.e. pulling) the strand from bobbin 8 has the effect that the continuously advancing (longitudinally extending) strand of material 1a is under tension (and straightened) during the heat treatment and cooling. Pre-processing the strand by heating it (in heat treatment station 9) and cooling it (in cooling station 9a), preferably under tension, prior to forming the outer layer greatly reduces or eliminates the bowing or bending effect caused by storage of the pre-formed strand on bobbin 8.

(10) The heat-treated and cooled strand 1a is then continuously advanced by additional rollers (not shown) which are motorized (coupled and synchronized to the main machine motor) in order to pull the strand towards a positioning apparatus 55 which includes a positioning channel in the form of a hollow tube 56 of internal diameter 2.5 mm. The additional rollers (not shown) pull the strand 1a so it enters apparatus 55 and funnel 15, and are required because the moving tow is unable to pull the strand simply through frictional forces. Prior to entrance of the strand to apparatus 55, it may be passed through a unit to spray flavour solution onto the strand or may be passed through a sensor to detect strand breakage (so that the machine automatically stops). These additional units are not shown.

(11) The strand 1a continuously advances from (i.e. exits) tube 56 and is drawn directly into engagement with the longitudinally advancing gathering (and largely condensed) tow 10 in funnel 15. The strand 1a travels with the tow to and through the rod making and wrapping garniture 20, where the tow 10 is further gathered and condensed into rod form around strand 1a such that the strand 1a is incorporated in a product continuous rod including a longitudinally extending strand of material 1a (extending longitudinally of the rod) and a longitudinally extending outer layer of filtering material (formed by tow 10) engaged around the longitudinally extending strand. It will be appreciated that tow 10 forms outer layer 2a in FIG. 1. The positioning apparatus 55 guides the advancing strand 1a in a direction which is substantially the same as the direction in which the strand 1a advances after formation of the longitudinally extending outer layer around the strand, thereby guiding the advancing strand 1a into the correct position so the longitudinally extending outer layer 2a of tow 10 is formed around the strand with the strand located centrally within the outer layer.

(12) On start up of the apparatus, the tow is threaded through the machine and funnel 15 into the garniture 20, and the free end of strand 1a is threaded through stations 9, 9a and tube 56 of positioning apparatus 55, and stuck to the tow upstream of funnel 15. Thus, once the apparatus is started, the advancing tow continuously entrains the strand 1a which is being drawn (advances it) under tension continuously from the bobbin 8 through stations 9, 9a and positioning device 55 to tow 10.

(13) Wrapping paper 28 is drawn continuously from reel 30 and fed continuously into the garniture 20, the paper 28 and the tow incorporating the strand 1a being carried continuously through the garniture by a delivery device in the form of endless conveyor belt 32. In the garniture 20, the tow is shaped to rod form, and the paper 28 is wrapped around and secured with a lapped and stuck seam; member 34 applies a line of adhesive to one edge of paper 28, before the overlapping edges are bought into engagement. The continuously produced wrapped rod 36 passes to a cutter 38 which severs the rod 36 into individual lengths 40 each of which include a continuous element 22. The lengths 40 may be single filter or filter elements (such as those of FIG. 1), but, more usually, will be multiple double or higher multiple (usually quadruple or sextuple) lengths for subsequent use, as is well known.