WO2011036451A1

WO2011036451A1 - Tow cutter

Info

Publication number: WO2011036451A1
Application number: PCT/GB2010/001787
Authority: WO
Inventors: Graham Penrose
Original assignee: Filtrona International Limited
Priority date: 2009-09-23
Filing date: 2010-09-22
Publication date: 2011-03-31
Also published as: WO2011036452A1; CN102573533A; PL2480100T3; EP2480100B1; MY174700A; KR20180000349A; EP2480100A1; KR101853778B1; KR20120071390A; CN102573533B; LT2480100T

Abstract

An apparatus for continuously cutting filamentary tow (2) into fibres and condensing the cut fibres to rod form, the apparatus comprising: a tow inlet feeder and a cut fibre exit gas jet arranged in-line and separated by ledgers (58); a knife blade (60) rotatably mounted for periodic passage between adjacent ledgers (58) to intersect tow (2) passing therepast and cut it into fibres; and a unit for separating air from the cut fibres and condensing the latter to rod form including an air permeable f rusto-conical screen (21) formed of a mesh having openings of size 0.088 mm to 0.841 mm.

Description

TOW CUTTER

The present invention relates to the cutting of filamentary tow into short, e.g. staple fibres, e.g. for subsequent formation into tobacco smoke filter rods.

UK Specification No. 1 ,221 ,346 describes a process for the production of filter rods of staple fibre in which a band of tow incorporating a bonding agent is fed continuously by a stuffer jet to a rotary cutter, a fan downstream of the cutter drawing the fibres away from the cutter in an airstream perpendicular to the tow feed path and then impelling the fibres in the airstream parallel to the tow feed path to a unit where the fibres are separated from the airstream and condensed to rod form for filter production. This is a commercial process, but its rate of throughput is not as high as is desirable, and various attempts to increase the rate of operation have led to undesirable lack of uniformity in the cut fibre length and/or in the distribution of the fibres in the rod product.

UK Specification No. 2,101 ,642 describes a process for the production of filter rods of staple fibre in which a band of tow is cut into fibres and condensed into rod form using a wire mesh screen having openings 0.12 mm square. Again, the rate of throughput is not as high as is desirable.

There is a need for an apparatus which can produce filter rods from tow cut into short e.g. staple fibres at increased speed, for example speeds in excess of 200 - 250 m/min. The present invention provides in-line apparatus for continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, the apparatus comprising: a tow inlet feeder and a cut fibre exit gas (e.g. air) jet arranged in-line and separated by ledgers; a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres; and a unit for separating air from the cut fibres and condensing the latter to rod form including an air permeable frusto-conical screen formed of a mesh (e.g. a wire mesh) having openings of size0.088 mm to 0.841 mm (mesh size 170 to mesh size 20). The screen may be formed of a mesh (e.g. a wire mesh) having openings of size 0.105 mm to 0.841 mm (mesh size 140 to mesh size 20), for example having openings of size 0.125 mm to 0.354mm (mesh size 120 to mesh size 45), for example 0.210 mm to 0.297 mm (mesh size 70 to mesh size 50), for example 0.250 mm (mesh size 60). The screen may have openings of size 0.13 mm to 0.25mm. Preferably the unit for separating air from the cut fibres and condensing the latter to rod form (which includes the air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm) is attached directly to the outlet of the fibre exit gas jet (or the outlets of each fibre exit jet, if more than one jet is present). In one example, the air permeable frusto-conical screen is formed of a mesh of mesh size 100 (having openings of size 0.1 8 mm). The air permeable frusto-conical screen may be formed of a mesh of mesh size 60 (having openings of size 0.25 mm), 70 (having openings of size 0.21 mm) or 80 (having openings of size 0.17 mm) etc..

The air permeable frusto-conical screen tapers inward, longitudinally, from a wider inlet to a narrower outlet. The stream of air and cut fibres from the knife blade is carried, by means of the fibre exit gas jet acting in-line with the tow feed, away from the knife blade and into the air permeable frusto-conical screen, where it proceeds (longitudinally) from screen inlet to outlet. Air is separated from the fibres by escaping through the tapering mesh (walls) of the frusto-conical screen, and the cut fibres exit the screen outlet for condensation to rod form. Preferably the unit for separating air from the cut fibres and condensing the latter to rod form [which includes the air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm (mesh size 170 to mesh size 20), for example 0.13 to 0.25mm] is attached directly to the outlet of the fibre exit gas jet. In one example, the air permeable frusto-conical screen is formed of a mesh of mesh size 100 (having openings of size 0.148 mm). The air permeable frusto-conical screen may be formed of a mesh of mesh size 60 (having openings of size 0.25 mm), 70 (having openings of size 0.21 mm) or 80 (having openings of size 0.17 mm) etc.. The upstream (tow inlet) ledger may be annular with the material (filamentary tow) path extending longitudinally therethrough. The downstream (fibre exit) ledger may be annular with the material (cut fibre) path extending longitudinally therethrough. Any tow feed to the ledgers (e.g. the upstream ledger) may be used, but a stuffer jet or jets may be preferred. The apparatus may comprise two or more knife blades rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres. The invention also provides an in-line method of continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, the method comprising: feeding the tow continuously (e.g. longitudinally) to a rotary knife blade whose rotary path periodically intercepts the path of the tow; and carrying, by means of an exit gas jet acting in-line with the tow feed, the resulting cut fibres away from the knife blade and

(longitudinally) through an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm (mesh size 170 to mesh size 20), thereby separating air from the cut fibres; and condensing the cut fibres to rod form. The screen may be formed of a mesh (e.g. a wire mesh) having openings of size 0.105 mm to

0.841 mm (mesh size 140 to mesh size 20), for example formed of a mesh (e.g. a wire mesh) having openings of size 0.125 mm to 0.354mm (mesh size 120 to mesh size 45), for example 0.210 mm to 0.297 mm (mesh size 70 to mesh size 50), for example 0.250 mm (mesh size 60). The screen may have openings of size 0.13 mm to 0.25mm. The air permeable frusto-conical screen tapers inward, longitudinally, from a wider inlet to a narrower outlet. The stream of air and cut fibres from the knife blade is carried, by means of the fibre exit gas jet acting in-line with the tow feed, away from the knife blade and into the air permeable frusto-conical screen, where it proceeds (longitudinally) from the screen inlet to the screen outlet. Air is separated from the fibres by escaping through the tapering mesh (walls) of the frusto-conical screen, and the cut fibres exit the screen outlet - for example, for condensation to rod form. Preferably, the air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm (mesh size 170 to mesh size 20), for example 0.13 to 0.25mm, is included in a unit for separating air from the cut fibres and condensing the latter to rod form. A wholly in-line path is thus provided for the passage of the tow to the cutter, and of the cut fibres therefrom to the unit for separating air from the cut fibres and condensing the latter to rod form. The unit may be attached directly to the outlet of the fibre exit jet, thus permitting minimum travel of the cut fibres prior to rod formation.

In a further aspect, the present invention provides in-line apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas (e.g. air) jet arranged in-line and separated by ledgers, and a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, the knife blade including one or more venting holes. The apparatus may comprise two or more knife blades rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres. The venting holes allow passage of gas (air) through the (or each) knife blade in the direction in which the tow is travelling, enabling an increase in production line speeds. The venting holes may be of 1 to 5 mm in diameter.

In another aspect, the present invention provides in-line apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas (e.g. air) jet arranged in-line and separated by ledgers, and a knife blade (e.g. a knife blade including one or more venting holes) rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, the knife blade having a cutting edge of profile angle 15 to 50 degrees (see Fig 4). Preferably the cutting edge is of width 15mm to 57mm (see Fig 4). Preferably, the cutting edge has a profile angle (also referred to as cutting angle) of 20 to 48 degrees, for example 32 degrees or 45 degrees). The cutting edge may be straight (i.e. present a straight edge to the tow passing therepast as it cuts) or curved (i.e. present a curved edge of to the tow passing therepast as it cuts). The knife blade may be of thickness (in the direction the tow is passing), 0.1 to 0.23 mm, preferably 015mm (6 thousands of an inch) or 0.2 mm (8 thousands of an inch). The applicants have found that providing a knife blade of the defined profile angle (and optionally width) allows increased air flow through the cutter, thereby allowing increased machine speed while maintaining cut fibre (staple fibre) length, and without unduly increasing PD variation in the resulting rod formed from the cut fibres. In other words, the applicants have found that the defined knife blade is of a shape that minimizes disruption of air through the ledgers, yet provides an efficient cutting operation. The apparatus may comprise two or more knife blades rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres.

A unit for separating air from the cut fibres and condensing the latter to rod form (including an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm (mesh size 170 to mesh size 20), e.g 0.13 to 0.25mm) may be attached directly to the outlet of the fibre exit jet, thus permitting minimum travel of the cut fibres prior to rod formation. The knife blade may be made of, for example, any blade material suitable for the cutting of fibre or textile materials - e.g. steel (either carbon steel or stainless steel), tungsten carbide etc. The upstream (tow inlet) ledger may be annular with the material (filamentary tow) path extending longitudinally therethrough. The downstream (cut fibre exit) ledger may be annular with the material (cut fibre) path extending longitudinally therethrough. Any tow feed to the ledgers may be used, but a stuffer jet or jets may be preferred.

In a further aspect, the present invention provides in-line apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas (e.g. air) jet arranged in-line and separated by ledgers, and a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, and a ventilator for one (or each) ledger. Preferably the ventilator is for the downstream (cut fibre exit) ledger. The downstream ledger may be annular with the material (cut fibre) path extending longitudinally therethrough. Preferably the ventilator is in the form of one or more ventilation holes (e.g. through the annular walls of the downstream ledger), which allow a flow of air laterally (e.g. radially inwards e.g. radially inwards through the annular walls of the downstream ledger) into the (inlet end of) cut fibre exit jet. The ventilator(s) allow increased air flow through the cutter, thereby allowing increased machine speed while maintaining cut fibre (staple fibre) length, and without unduly increasing PD variation in the resulting rod formed from the cut fibres. A ventilator may additionally or alternatively be provided for the upstream (tow inlet) ledger. The apparatus may comprise two or more knife blades rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres.

A unit for separating air from the cut fibres and condensing the latter to rod form (including an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm (mesh size 170 to mesh size 20), e.g. 0.148 to 0.25mm) may be attached directly to the outlet of the fibre exit jet, thus permitting minimum travel of the cut fibres prior to rod formation. The upstream (tow inlet) ledger may be annular with the material (filamentary tow) path extending longitudinally therethrough. Any tow feed to the ledgers may be used, but a stufferjet or jets may be preferred.

In apparatus according to aspects of the invention, a single (e.g. ventilated) knife blade may be mounted, e.g. on a rotary disc, for co-operation with a single pair of ledgers, but other arrangements are possible. For example, two longitudinally spaced pairs of ledgers could be provided, with a corresponding pair of (e.g. ventilated) knife blades being mounted (usually in circumferential register) on the rotary disc. In other embodiments, a plurality of (e.g. ventilated) knife blades or blade pairs may be spaced circumferentially around the rotary disc to provide for a corresponding plurality of cutting actions per revolution of the disc. Apparatus according to aspects of the invention may comprise two or more knife blades rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres.

The applicants have surprisingly found that the apparatus according to aspects of the invention can be operated satisfactorily at higher throughput rates than the apparatuses previously proposed and used. The present invention provides in-line apparatus for continuously cutting filamentary tow into fibres and condensing the cut fibres to (e.g. continuously issuing) rod form, and/or in-line apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, which may, for example, deliver the cut fibres to a unit for separating air from the cut fibres and condensing the latter to (e.g. continuously issuing) rod form. The invention also provides in-line method(s) of continuously cutting filamentary tow into fibres and condensing the cut fibres to (e.g. continuously issuing) rod form. The continuously issuing rod (of filtering material, formed from the cut fibres e.g. by methods or using apparatus of the invention) may be cut into individual filter or filter elements for subsequent use. More usually, however, the continuously issuing rod (of filtering material, formed from the cut fibres e.g. by methods or using apparatus of the invention) is first cut into double or higher multiple (usually quadruple or sextuple) filter or filter element rod lengths for subsequent use. When the initial cut is into quadruple or higher rod lengths, the multiple lengths are subsequently cut into double lengths for further cigarette or filter assembly. If the filter is for direct application to a cigarette, the multiple rod lengths are subsequently cut into double rod lengths and the double length filter rod is assembled and joined (e.g. by ring tipping or full tipping overwrap) between a pair of wrapped tobacco rods with the combination being severed centrally to give two individual cigarettes, as is well known in the art. The present invention includes double and higher multiple (length) filter rods and/or filter element rods.

Thus, according to the present invention in a further aspect there is provided a double or higher multiple length filter or filter element comprising a filter rod produced (e.g. formed from cut fibres) according to the method or methods described above, or produced (formed) using apparatus (or apparatuses) defined above.

According to the invention in a still further aspect there is provided a method of manufacture of a smoking article (e.g. a filter cigarette) comprising a step of applying (e.g. joining) a tobacco smoke filter comprising a filter rod produced (e.g. formed from cut fibres) by a method and/or apparatus of the invention [or a filter including a filter element comprising a filter rod produced (e.g. formed from cut fibres) by a method and/or apparatus of the invention] to a wrapped rod of smoking material (e.g. tobacco). The filter may be a single filter, or, preferably, a filter which forms part of a multiple length filter rod (e.g. a multiple rod of 2, 4, or 6 filters in end-to-end relationship). In a filter cigarette according to the invention, a filter (e.g. filter rod) made by the method and/or apparatus of the invention (or a filter which includes filter element (e.g. filter rod) made by a method and/or apparatus according to the invention) is joined to a wrapped tobacco rod with one end towards the tobacco.

The filter or filter element comprising a filter rod produced (e.g. formed from cut fibres) may, for example, be joined to the wrapped tobacco rod by ring tipping (which engages around just the adjacent ends of a (wrapped) filter and rod to leave much of the filter wrapper exposed) or by a full tipping overwrap (which engages around the full filter length and adjacent end of the tobacco rod). Any filter or filter cigarette according to the invention may be unventilated, or may be ventilated by methods well known in the art, e.g. by use of a pre-perforated or air-permeable plugwrap and/or laser perforation of plugwrap and tipping overwrap. The invention is illustrated, by way of example only, by the accompanying drawings, in which:

Figure 1 is a diagrammatic elevation view of a complete filter rod production apparatus according to the invention;

Figure 2 is a similar enlarged view of the air separation and rod formation portion of the apparatus of Figure 1 ;

Figure 3 is a diagrammatic side elevation view, partly in section, of a tow cutting device according to the invention suitable for use in the Figure 1 apparatus; and

Figure 4 is a diagrammatic profile view of a knife blade according to the invention suitable for use in the apparatus of Figures 1 to 3. In the illustrated filter rod production method and apparatus described below, the rod is made from cellulose acetate continuous filamentary tow plasticised with glyceryl triacetate; this is the preferred material for cigarette filter production, but a variety of other materials can be used. Referring to the drawings, from a bale 1 of continuous filamentary cellulose acetate tow, the tow 2 is drawn upwardly first through an air banding jet 4, thence over a cylindrical guide 5, traction being given by rollers 3. The tow 2 then passes to rollers 6 which rotate faster than rollers 3 and thereby stretch the tow between them and rollers 3. A further air banding jet 7 forms the tow into a band which form it retains as it passes into box 10 where it is sprayed over the whole of its width with glyceryl triacetate in known manner. The banding jets 4 and 7 are of known form and comprise a slot through which the tow passes, having on one side a wall, divided by narrow slits to the outer side of which compressed air is supplied. This air passes through the slits and impinges upon the tow. On the other side of the slot is an undivided wall which retains the tow while the air impinges upon it. Rollers 11 hold the tow in band form until it enters the cutting device 13 according to the invention. A rotary knife cutter within the cutting device is driven by a belt, not shown, which is driven, via an infinitely variable gear, from the main-shaft of a plug-maker 20, as are rollers 3, 6 and 1 1 via other such gears. By varying the relative rates of rotation of the cutter and the rollers 11 the length of the fibres may be varied. By varying the relative rates of rotation of the rollers 3, 6 and 11 the weight per unit length of the rod may be varied e.g. by varying the rate of rotation of rollers 3 relatively to rollers 6, the percentage crimp of the filaments entering the cutting device 13 is altered. The cutting device 13 is described hereinbelow with reference to Figs. 3 and 4.

The combined delivery stream of air and fibre from cutting device 3 passes through exit 18 into a unit where the fibres are separated from the airstream and

condensed to rod form (for filter production) which includes an air permeable, e.g.

perforate, frusto-conical screen 21. The screen 21 has an inlet (e.g. which may be connected directly to exit 18) and an outlet, the inlet being of wider diameter than the outlet, and walls made of the air permeable, e.g. perforate, material (e.g. wire mesh). The screen 21 is a 60 mesh screen, having openings of size 0.25 mm. Most of the air escapes through the openings in the wall of screen 21 ; however, the frusto-conical form ensures that the velocity of the air inside the cone is not unduly reduced by passage of air through its walls. The remainder of the air (passing through the screen outlet) deposits the fibres on a tape 22 and then passes out of holes in a surrounding heating block 24. The latter has a bore 25 through which the tape passes. The bore has a cross section corresponding to the cross section desired in the rod, e.g. it is circular. It holds the tape 22 so as to envelop the staple fibres in the rod 31. The heating block 24 is of substantial metallic construction so that the tape is held around the fibres in a constant configuration. It is preferred that the fibres remain in suspension until they meet the tape 22. However, it is undesirable that an excessive air flow be used for this purpose as fibres may be blown into the atmosphere instead of being deposited. The rate of flow may be increased by blocking off a part of the screen 21 next to the exit 18.

The tape which is driven by drum 26 and is trained about tension rollers 27 and 28 and guide rollers 29 and 30, carries the fibres now held in the form of the rod 31 through the heating block 24, wherein they are heated by steam coming from a source (not shown) via pipe 33. A plenum chamber within the heating block 24 serves to distribute the steam evenly around the whole of the periphery of the tape enclosing the fibres. Upon passing from the heating block the tape, containing the rod formed from the fibres, passes through cooling enclosure 36 where it is cooled by air supplied to pipe 37. The latter connects with channels inside the cooling enclosure which distribute the air about the tape enclosing the rod, thereby cooling and hardening it so that at the exit of the cooling enclosure a firm rod is delivered. The tape 22, folding from the circular to the flat form, is separated from the rod as it passes on to the drum 26. The continuous rod 31 may pass to a cut-off 42 in which it is cut into equal length rods which are deposited upon a delivery band 35, or first to a wrapping garniture where the fibrous rod is wrapped with a paper wrapper in known manner and thence to the cut-off.

If the edges of the tape 22 as they envelop the fibrous material do not meet perfectly, fibres press between them and form a ridge. To eliminate this a ridge remover 41 can be provided between the heating block and the cooling enclosure. This comprises a narrow blade arranged between the edges of the tape. It presses upon the fibres protruding between the edges of the tape to return them into the body of the rod.

In this embodiment the function of the steam is to heat the cellulose acetate and glyceryl triacetate so that the solvent action of the glyceryl triacetate upon the cellulose acetate is accelerated. Thus solvent welding of the cellulose acetate fibres occurs. In the case of other fibrous materials or other bonding constituents the heating effect of the steam may accelerate the bonding by causing fusion or polymerisation. Figures 3 and 4 illustrate a cutting device and a blade according to the invention which could be used for the cutting device 13 of Figs 1 and 2.

In the Figure 3 device tow inlet stuffer jet 50, supplied with pressurised air via conduit 52 and jacket 54, draws tow 2 from rollers 11 through the relatively restricted circular orifices 56 of annular ledgers 58. A knife blade 60 is mounted on a rotary disc 62 so that its circular travel path passes between ledgers 58 once per rotation to intersect the tow and thereby cut the tow into substantially uniform fibre lengths, this fibre length being the longitudinal distance by which the tow is advanced per revolution of the disc 62. In aspects of the invention (not shown) it is possible to have more than one blade 60 mounted on the rotary disc 62, in which case the fibre length would depend on the number of blades mounted on the disc (and it will appreciated that for uniform fibre length the blades would have to be spaced equidistantly around the disc perimeter). The downstream ledger 58 is disposed at the inlet end of fibre exit jet 64 which is supplied with pressurised air via conduit 66 and jacket 68 so that the cut fibres are immediately swept from the downstream annular ledger to the widened exit 18 of jet 64. The annular downstream ledger 58 includes ventilation holes 77 in the walls of the ledger each of which functions as a ventilator to allow air to flow laterally (i.e. radially inwardly) through the annular walls of the ledger into the restricted circular orifice 56 of downstream ledger 58 and, from there, longitudinally (i.e. in the direction of the flow of the cut fibres/tow) on into the inlet end of fibre exit jet 64. The ventilation holes 77 allow increased air flow through the cutting device, thereby allowing increased machine speed while maintaining cut fibre (staple fibre) length, and without unduly increasing PD variation in the resulting rod formed from the cut fibres. It is believed that when, in the course of its rotation, the knife blade 60 is placed fully between upstream and downstream ledgers 58 it stops (or greatly reduces) the air flowing through the ledgers, in turn restricting the last cut fibres from being properly pulled (swept) through (the restricted circular orifice of downstream ledger 58 and) to the widened exit 18 of jet 64 (and on to cone 21 etc.); without wishing to be bound by theory, it is believed that the provision of ventilators (e.g. ventilation holes 77) may enable a small amount of air to be drawn laterally inwards through the downstream ledger 58 when the knife is in this position, thereby allowing the last cut fibres to flow through to the cone 21 and on to rod formation.

As shown in Fig. 3, the exit 18 of jet 64 may be connected directly to the inlet of air permeable frusto-conical screen 21 of the apparatus of Figs. 1 and 2.

Figure 4 is a diagrammatic profile view of knife blade 60. The knife blade 60 is made of steel in a single section of thickness 8 thousands of an inch. The blade 60 includes a base portion 91 (of width 57mm) which includes mounting holes 92, 93 allowing the blade 60 to be fixed (using e.g. screw or similar) firmly onto the rotary disc 62 (see Fig 3) for cutting, and enabling ready removal of a worn/broken blade from disc 62 and replacement with another blade 60. The base portion 60 extends into a narrower cutting portion 95 which includes cutting edge 96 which has a cutting width 97 of 32 mm and a cutting depth 98 of 20 mm resulting in a profile angle or cutting angle 99 of 32 degrees. In general, the cutting angle 99 may be between 15 to 50 degrees, for example 32 degrees (as shown in Fig 4), 45 degrees etc. As shown in Fig 4, the cutting edge 96 may have a profile radius 100 - that is, it may present a curved cutting edge 96 to the tow. In the Figure 4 embodiment the profile radius 100 is 110 mm. Alternatively the cutting edge may be straight (as shown by dotted line 01 in Fig 4). In the Fig 4 embodiment the maximum cutting width 97 is 57mm, corresponding to the width of the base portion 91. The minimum practical cutting width 97 is around 15mm. It will be seen from Fig 4 that, for a given cutting depth 98, the cutting angle increases as the width of blade decreases. When mounted on the rotary disc 62 and rotated (in the clockwise direction as one looks at Fig 4) the circular travel path of the cutting portion 95 passes between ledgers 58 such that the cutting edge 96 is presented to, and intersects, the longitudinally advancing tow 2 (at an angle of 90° to the direction in which the tow is advancing) once per rotation, thereby cutting the tow into substantially uniform fibre lengths. The blade 60 of Figure 4 will pass stably between the ledgers 58 at the desired machine speeds (if the knife blade is unstable it can chip or smash) and is able to last for a reasonable time before it requires resharpening or replacement.

The cutting device 13 is preferably run at such a speed relative to the speed of the tow that the fibres cut from it are about the same length (e.g. 6 to 12 mm) as the diameter of the rod to be produced (e.g. about 8mm). The length of the fibres can, however, be varied, e.g. from 3mm to 50mm. Preferably, the apparatus is coated on surfaces which come into contact with the tow and with the plasticiser with a substance which prevents adhesion.

In one embodiment of the invention the knife blade 60 mounted on a rotary disc 62 includes one or more venting holes of 1 -5 mm diameter. The (or each) venting hole allows passage of gas (air) through the (or each) knife blade in the direction in which the tow is travelling, thereby enabling an increase in production line speeds. In a further embodiment, a plurality of (e.g. ventilated) knife blades or blade pairs may be spaced circumferentially around the rotary disc to provide for a corresponding plurality of cutting actions per revolution of the disc.

The rods made as described above are deformation-resistant in that they may be handled by known cigarette filter rod handling devices without an unacceptable distortion. A paper wrapping may however facilitate some steps in the subsequent utilisation of the rods. If such a rod is desired it may be made by providing the plug-maker 20 with an additional drum similar to the drum 26 and garniture and roller system. The garniture is located downstream of the cooling enclosure and before the cut off. It is used to wrap paper around the continuous rod 31 as it comes from the cooling enclosure and adhere it around the rod by means of a lapped and stuck seam. The two tapes, i.e. the tape 22 and the tape passing through the garniture, will have a substantially identical linear speed, though the tape 22 may be run slightly faster than the garniture tape so as to prevent any tensile breakage in the fibrous rod as it is transferred from the cooling enclosure to the garniture. Other materials such as fibres of paper pulp may be incorporated with the fibres cut from the filaments of the tow by feeding them simultaneously with the latter into the cutter 13 so that together they are dispersed in air, become blended, enter the heating enclosure and are bonded into a homogeneous rod. Various filamentary tows such as polypropylene, polyethylene, cellulose triacetate, nylon or viscose may be used where their particular physical or chemical properties are needed, but for cigarette filters secondary cellulose acetate is preferred. Other bonding constituents such as fusible resins and fibres may be used instead of solvent plasticisers. Other plasticisers such as triethylene glycol diacetate may be used in place of glyceryl triacetate. Alternatively or additionally, water soluble binder systems may also be used.

Whilst the method and apparatus illustrated in Figures 1 and 2 employ a heating block to activate a bonding constituent on the fibres to yield a bonded rod, this is not essential. For example, the fibre (with or without bonding constituent) from the outlet of cone 21 could be deposited instead on a strip of conventional plug-wrap and passed through a conventional wrapping garniture to yield a wrapped rod.

In all rod formation embodiments according to the invention, there may be continuous in-line travel of the filter material through the tow preparation, tow cutting, and fibre rod information stages.

To take account of the longitudinal movement of the tow being cut, and hence facilitate a cleaner cut and more uniform cut fibre length, the ledgers may be oscillated along the tow path. In another embodiment, the apparatus of Figs. 1, 2 and 3 may further comprise a ventilator (e.g. ventilation holes similar to ventilation holes 77) for the upstream ledger 58, in addition to a ventilator for the downstream ledger .

Claims

1. An apparatus for continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, the apparatus comprising: a tow inlet feeder and a cut fibre exit gas jet arranged in-line and separated by ledgers; a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres; and a unit for separating air from the cut fibres and condensing the latter to rod form including an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm.

2. An apparatus according to claim 1 wherein the unit for separating air from the cut fibres and condensing the latter to rod form is attached directly to the outlet of the fibre exit jet.

3. An apparatus according to claim 1 or claim 2 wherein the air permeable frusto- conical screen is formed of a mesh of mesh size 60 or mesh size 100.

4. An apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas jet arranged in-line and separated by ledgers, and a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, the knife blade including one or more venting holes.

5. An apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas jet arranged in-line and separated by ledgers, and a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, the knife blade having a cutting edge of profile angle 15 to 50 degrees.

6. An apparatus according to any of claims 1 to 3 or claim 5 wherein the knife blade includes one or more venting holes.

7. An apparatus according to any of claims 4 to 6 for continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, further comprising a unit for separating air from the cut fibres and condensing the latter to rod form, the unit including an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm.

8. An apparatus according to claim 7 wherein the unit for separating air from the cut fibres and condensing the latter to rod form is attached directly to the outlet of the fibre exit jet.

9. An apparatus according to claim 7 or claim 8 wherein the air permeable frusto- conical screen is formed of a mesh of mesh size 60 or mesh size 100.

10. An apparatus for continuously cutting filamentary tow into fibres and delivering the cut fibres in a continuous stream, the apparatus comprising a tow inlet feeder and a cut fibre exit gas jet arranged in-line and separated by ledgers, and a knife blade rotatably mounted for periodic passage between adjacent ledgers to intersect tow passing therepast and cut it into fibres, and a ventilator for one (or each) ledger.

11. An apparatus according to claims 10 wherein the knife blade includes one or more venting holes.

12. An apparatus according to claims 10 or 1 1 for continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, further comprising a unit for separating air from the cut fibres and condensing the latter to rod form, the unit including an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm.

13. An apparatus according to claim 12 wherein the unit for separating air from the cut fibres and condensing the latter to rod form is attached directly to the outlet of the fibre exit jet.

14. An apparatus according to claim 12 or claim 13 wherein the air permeable frusto- conical screen is formed of a mesh of mesh size 60 or mesh size 100.

15. An in-line method of continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form, the method comprising: feeding the tow continuously to a rotary knife blade whose rotary path periodically intercepts the path of the tow; and carrying, by means of an exit gas jet acting in-line with the tow feed, the resulting cut fibres away from the knife blade and through an air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm, thereby separating air from the cut fibres; and condensing the cut fibres to rod form.

16. A method according to claim 15 wherein the air permeable frusto-conical screen formed of a mesh having openings of size 0.088 mm to 0.841 mm is included in a unit for separating air from the cut fibres and condensing the latter to rod form.

17. A method of continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form substantially as hereinbefore described with reference to Figures 1 to 3.

18. An apparatus for continuously cutting filamentary tow into fibres and condensing the cut fibres to rod form substantially as hereinbefore described with reference to Figures 1 to 3.

19. A double or higher multiple length filter or filter element comprising a filter rod produced by a method according to any of claims 15 to 17, or produced using an apparatus according to any of claims 1 to 14 or 18.

20. A method of manufacture of a smoking article comprising a step of applying a tobacco smoke filter comprising a filter rod produced by a method according to any of claims 15 to 17, or produced using an apparatus according to any of claims 1 to 14 or 18, or a filter including a filter element comprising a filter rod produced by a method according to any of claims 15 to 17, or produced using an apparatus according to any of claims 1 to 14 or 18, to a wrapped rod of smoking material.

21. A filter cigarette comprising a filter rod produced by a method according to any of claims 15 to 17, or produced using an apparatus according to any of claims 1 to 14 or 18, or a filter including a filter element comprising a filter rod produced by a method according to any of claims 15 to 17, or produced using an apparatus according to any of claims 1 to 14 or 18 joined to a wrapped tobacco rod with one end towards the tobacco.

22. A knife blade substantially as hereinbefore described with reference to Figure 4.