GB2118982A - Processing tow, particularly for filter rod manufacture - Google Patents

Abstract

A continuous tow is processed, particularly opened prior to incorporation into cigarette filter rods, by engaging it with at least one pin roller (58, 60), which is driven at such speed that the filaments of the tow (50) are separated without excessive stretch or substantial breakage. Several pin rollers (58, 60) may operate on the tow in series and their speeds and the spacing, lengths and inclination of their respective pins may differ. Fluid additive, such as plasticiser, may be applied to the tow (50) from a chamber (94, 96) inside the pin roller (58, 60). <IMAGE>

Description

SPECIFICATION Processing tow, particularly for filter rod manufacture This invention relates to processing a fibrous tow, particularly but not exclusively in the production of filter rod for the tobacco industry.

A conventional process for producing cigarette filters comprises withdrawing filter tow, comprising a bundle of substantially continuous filaments, from a source, such as a bale, passing it through tow opening apparatus designed to laterally spread and deregister or "bloom" the tow and compressing it to form a stream having the cross section of the completed filters. A plasticiser such as triacetin is usually sprayed onto the filaments while they are spread out. The compressed stream of filaments may be enclosed in a continuous wrapper or may be set by means of steam or some other source of heat to form a continuous rod which is then cut at regular intervals to produce the final filters.

Tow opening apparatus generally includes means for stretching the filaments of the tow, as well as for laterally separating them. For example, so-called threaded rollers designed to spread the tow and to stretch it longitudinally may be used.

Such rollers and the associated tow opening apparatus are disclosed in U.S. Patent Specification No. 3032829, to which reference is directed for details. Threaded rollers are used in the Amcel 103 and Molins T05 tow opening units.

Tow opening apparatus is intended particularly to separate the filaments of a tow which has been subjected to crimping. Materials from which cigarette filters are produced, such as cellulose acetate, are commonly subjected to a precrimping operation; this increases the effectiveness of the filtering action. However, in order to fully realise the advantages of crimping it is desirable to separate (or deregister) the crimped filaments so that the crimps of adjacent filaments are not in registry. One problem with conventional tow opening apparatus is the amount of stretch to which the filaments are subjected in order to achieve satisfactory deregistration is such that there is a risk of permanently removing at least some crimp. It is an object of the present invention to achieve an effective tow opening process without excessive stretch of the filaments.

According to one aspect the invention provides a method of processing a continuous tow which includes a plurality of preferably substantially continuous filaments, preferably crimped monofilaments, comprising moving the tow past a conveyor having a plurality of relatively sharp projections which at least partially penetrate the tow, and controlling the speed of at least one of the tow and the conveyor so that the filaments of the tow are separated by relative movement of the projections and the tow. Where the filaments are crimped the filaments are deregistered by the separation. Preferably the tow is maintained at a controlled speed and under a controlled tension.

The projections should be sufficiently widely spaced to allow adequate penetration of the tow but are preferably arranged in staggered rows so that as many filaments as possible across the width of the tow are contacted by or at least affected by a projection. Thus the width of the tow may be effectively divided into a large number of sections by the projections. The projections provide anchorage points for the filaments of the tow and the relative movement of the tow relative to the projections causes crimp deregistration.

The conveyor may be a roller or band carrying an array of pins or needles. The tow preferably passes partly around or along the surface of the conveyor. The tow could be passed between a pair of opposed conveyors carrying projections, so that it passes through the nip between intermeshing projections.

The relative speed of the tow and the projections and the nature of the projections should be such that there is no substantial breakage of filaments. Generally, the higher the relative speed of the projections and the tow the more likely breakage is to occur. Similarly, if the nature or orientation of the projections is such as to oppose the relative movement particularly effectively then again breakage is more likely to occur. Thus, for example, if the projections are pins they may be inclined in the direction of movement of the tow relative to the carrying conveyor, in which case possible breakage of the filaments may be minimised, or they may be inclined against that direction, in which case such breakage is more likely.It may be noted, however, that if the relative speed of the projections and the tow is increased, and also if the nature and orientation of the projections is such as to grip the tow more effectively, then the deregistration of the tow may be more effective, notwithstanding that breakage of filaments may occur. In order to minimise the risk of breakage yet retain full and effective separation or deregistration the tow may be processed in stages, i.e. it may be moved past a plurality of conveyors arranged in series and each carrying projections. Thus at an initial stage the effective action of the projections on a first conveyor may be slight by driving the conveyor at a speed which is close to that of the tow and by arranging its pins such that they are trailing.At a later stage, however, where the tow is already partially deregistered and thereby more able to withstand more severe action the relative speed of a conveyor may be increased and the orientation of the projections changed to more effectively grip the tow. The number and density of the projections on a conveyor surface and their lengths may also be increased as the filaments of the tow become partially separated.

The speed of the tow relative to the conveyor carrying the projections may be controlled by independent drive conveyors, e.g. conventional drive rollers, or may be controlled by another conveyor carrying projections. Thus, the tow may be moved past two or more conveyors carrying projections, the conveyors being arranged in series and driven at different speeds. In this arrangement, or in the arrangement where only a single conveyor carrying projections is used, the tow is subjected to stretch by the applied tension.

It is believed that with the present invention the amount of stretch which it is necessary to apply to the tow will be somewhat lower than with at least some conventional systems. For example, in known tow opening apparatus the ratio of controlled speeds respectively at the input to the apparatus and at its output are typically in the range 1.3-1.8:1. This ratio is a measure of the stretch applied to the tow. In apparatus in accordance with the present invention it is believed that tows can be successfully processed with a corresponding operating ratio preferably in the range 1.1-1.3:1 or even below 1.1:1.

According to another aspect of the invention the conveyor carrying the projections is used to apply a fluid additive e.g. a plasticiser, to the passing tow. Thus the conveyor may include an internal manifold to which plasticiser is supplied and a series of passages through which plasticiser passes onto the tow. In a preferred arrangement at least some of the projections are hollow pins or needles through which plasticiser can be applied not only to that surface of the tow in contact with the conveyor but at a level somewhat beyond that and therefore within a layer of the tow not in direct contact with the surface of the conveyor.

Such pins or needles could be of different lengths to apply fluid additive to different layers of the tow.

According to another aspect of the invention a conveyor for processing tow comprises a rotatable surface having tow engaging means and at least one aperture for supplying fluid additive from an internal manifold to the tow, and an internal stationary shield for preventing passage of fluid additive to the outer surface of the conveyor except in the vicinity of the tow. Thus the conveyor may be a pin drum carrying hollow needles and the shield may be part cylindrical having an aperture adjacent that part of the drum around which the tow passes.

The projections carried by a conveyor according to the invention may be arranged, e.g.

angled, to laterally spread the tow. Alternatively the conveyor itself may be constructed to produce this effect, e.g. having a crowned surface or possibly a flexible surface constrained to move such that the tow is spread. For example, a flexible cylindrical roller rotating about a curved axis might be used.

Whilst the invention has been described primarily with reference to processing tow suitable for incorporation in cigarette filters it is in principle applicable to processing tow generally, whether for production of continuous rod or otherwise, where a separating effect is desired.

The invention also provides a method of processing a continuous tow by moving it past a series of projections which penetrate the tow, the relative speed of the tow and the projections and the tension applied to the tow being such that filaments are deregistered without substantial breakage of filaments. In a preferred arrangement the tow comprises crimped filaments and the movement and tension are controlled such that a substantial part of the crimp is retained in the tow after processing. When the tow comprises filaments having visco-elastic properties, e.g.

cellulose acetate, the method may be such that the stretch ratio applied to the filaments during processing is in the range 1.0-1.3:1.

The invention also includes tow opening or processing a continuous tow by passing it through fibrillating apparatus, comprising at least one driven pin roller for example, to separate and deregister adjacent filaments without substantial breakage thereof.

The invention also includes a tow opening or blooming apparatus, particularly for preparing tow in filter rod manufacture, for performing any of the methods of the invention.

The invention will be further described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows one form of tow preparing apparatus including a pin roller, Figure 2 is a detail view of part of the pin roller, Figure 3 is a sectional view of part of a pin roller, Figure 4 shows part of a machine for preparing filter tow, Figure 5 shows part of another machine for preparing filter tow, Figure 6 is a sectional view of part of a pin roller suitable for use in the machine of Figure 5, Figure 7 shows part of a further machine for preparing filter tow, Figure 8 shows a different form of pin conveyor suitable for use in tow preparing apparatus, Figure 9 is a radial section of part of another pin roller, and Figure 10 is a longitudinal sectional view of a further pin roller.

Figure 1 shows tow preparing apparatus in which a band or stream of tow 10, comprising for example crimped, substantially continuous monofilaments, is drawn from a bale or similar source by a pair of driven rolls 12, 14. The upper roll 12 has a rubber surface and the lower roll 14 has a ground steel surface. The nip pressure between the rolls 12, 14 may be adjustable, for example by use of hydraulic or pneumatic means urging the rolls together. Downstream of the rolls 12, 14 the tow stream 10 passes partly around a driven larger drum or roller 1 6 carrying an array of pins 18 projecting from its surface. Beyond the pin roller 1 6 the tow passes over a delivery roll 20 and to further processing apparatus. An opposed upper roll (not shown) may co-operate with the roll 20. If the tow 10 is of filter material such as cellulose acetate fibres, for example, the further processing apparatus may include a machine for making continuous filter rod.

The peripheral speed of the pin roller 16 may be somewhat greater than that of the rolls 12, 14 so that the pins 1 8 penetrating the tow 10 move in reflation to its fibres and tend to drive it forward, thereby stretching the tow. The amount of stretch depends on the density and distribution of pins 18, and on their nature (e.g. length, diameter or width) and inclination, as well as on the speed of the roller 1 6.

Figure 2 shows one preferred arrangement of the pins 18 in the periphery of the roller 16. The pins lie in rows 22 which are inclined by a small angle to their direction of movement (shown by the arrow 24). Furthermore, the pins within adjacent rows are staggered with respect to one another. On each side of the roller 16 there is a flange 26 (only one of which is shown) which projects radially so that its surface is flush with the tips of the pins 18. The width of the roller 16 (between the flanges) may be approximately 200-250 mm to accommodate a typical width for the stream of tow 10. The diameter of the roller 1 6 could be typically 1 50 mm. The average spacing between pins 18 may be in the range 1 10 mm. The roller 1 6 need not have a flange 26.

Figure 3 is an enlarged section of part of the peripheral portion of the roller 1 6, showing one of the pins 18. In particular, it shows that each of the pins 1 8 is forwardly inclined relative to the direction of rotation of the roller 1 6. The axis of the pin 18 makes an angle a with the adjacent surface of the roller 1 6. Note that in this preferred arrangement the front face of the tapered outer end of the pin 18 is also inclined to the surface at an angle of less than 900. Although in the arrangement of Figure 1, where there is only one pin roller 16, it is normaliy preferable for the angle a to be less than 900 the angle may, depending on the required pin action on the tow be typically in the range 450 to 1350, so that the pins could be arranged at right angles to the surface or trailing.The pins 1 8 may typically project 2-10 mm from the surface of the roller 1 6.

The material of the roller 1 6 may be aluminium. The cylindrical portions of the pins 18 may be fixed in corresponding cylindrical bores in the roller 1 6 by an adhesive and are preferably secured in the manner disclosed in British Patent Specification No. 1298561. The inner ends of the pins 18, which may, as shown, project beyond the inner surface of the periphery of the roller 16 may be encased in a moulded sleeve of plastics material (not shown). Instead of being embedded directly in the surface of the roller the pins 1 8 could be mounted on staves attached to the outer surface of a carrier roller or on a belt wrapped around the roller.

Figure 4 shows part of a machine for processing filter tow. The machine may, for example, be arranged for delivery of processed tow to a continuous rod filter making machine such as a Molins PM SN. The tow 30 passes from a bale or other source between normally undriven control rolls 32, 34 to a first pair of opposed cooperating pin rollers 36, 38. The rollers 36, 38 may be similar to the roller 1 6. However the pins are arranged on the rollers 36, 38 such that they intermesh. Accordingly, a similar and effective pin action on the tow can be achieved with reduced pin density on each roller.On the other hand, it shpuid be noted that the length of the region of the tow contacted by pins is generally shorter between a pair of opposed pin rollers than with a single pin roller (where the tow can wrap partly around the roller) unless, of course, the tow is partly wrapped around one roller of a pair of opposed pin rollers.

The pins on the rollers 36, 38 are preferably trailing, i.e. their angle a is greater than 900.

Downstream of the rollers 36, 38 the tow 30 passes between a second pair of opposed cooperating pin rollers 40, 42 which are similar to the rollers 36, 38 except that the pins are preferably forwardly inclined, i.e. the angle a is less than 900. Beyond the rollers 40, 42 is a conventional plasticising chamber 44 in which the processed tow 30 is impregnated with plasticiser. A pair of driven delivery rolls 46, 48, which may include opposed steel surfaces, draws the tow 30 from the plasticising chamber 44 and delivers it towards further processing apparatus (e.g. a Molins PM5N machine).

The rolls 46, 48, the rollers 40, 42, and the rollers 36, 38 are preferably all driven at slightly different speeds. In the case where the tow 30 is delivered to a continuous rod filter making machine the rolls 46, 48 are preferably driven at a speed V equal to or slightly greater than the line speed of the rod making machine.The pin rollers 36, 38 are driven at a peripheral speed which is generally slightly less than V so that tension in the tow 30 is maintained between the rolls 46, 48 and pin rollers 36, 38. The pin rollers 40, 42 are driven faster than the pin rollers 36, 38, typically at 1.2 V, so that there is some temporary stretching of the tow 30 between the pin rollers 36, 38 and 40, 42, which increases the effective action of the pins of the respective rollers on the tow by providing tension which promotes slip between the pins and the tow to cause the required deregistration of the crimp in the tow.

Note that the trailing pins of the rollers 36, 38 and the forwardly inclined pins of the rollers 40, 42 help in this respect. The stretch imparted to the tow between the pin rollers 36, 38 and 40, 42 is generally less than that imparted in conventional systems and is such that more of the crimp in the tow is retained in the final filter rod.

As in conventional systems the rolls 32, 34 are preferably undriven and serve to pretension the tow 30 by means of the nip pressure applied and to present it more evenly to the first pair of pin rollers 36, 38.

Each of the pairs of pin rollers 36, 38 and 40, 42 should be separable for periodic cleaning of tow fibres from the nip and from the pins.

Figure 5 shows part of another machine for processing filter tow and for passing it to a continuous rod filter making machine. A stream of filter tow 50 is withdrawn from a tow bale 52 through a pair of rolls 54, 56 by first and second pin rollers 58,60. Upstream of the rolls 54,56 the tow stream 50 is laterally spread and partially deregistered by conventional air banding jets 62, 64.

From the rolls 54, 56 the tow 50 passes under and partially around the first pin roller 58 and subsequently over and partially around the second pin roller 60. The pin rollers 58, 60 may each be similar to the pin roller 1 6. However, the angles a of the pins on the roller 58 are preferably 900 or more and the angles a on the roller 60 are preferably 900 or less. The spacing of the pins on the roller 60 may be slightly less than that on the roller 58 since the tow 50 reaching the roller 60 has already been acted on by the roller 58 and is already partially deregistered. Similarly the pins on the roller 60 may project further than the pins on the roller 58. Downstream of the roller 60 the tow 50 passes to a continuous filter rod making machine having a garniture 66 for forming a continuous rod on a garniture tape 68 and for sealing the rod in a continuous paper web 70.The tow 50 is received in a unit 72 which includes a converging guide and which preferably also includes one or more air transport jets to convey the tow 50 and maintain tension between the unit 72 and the pin roller 60. The unit 72 may, for example, be similar to the unit 40 disclosed in British patent specification no. 1588506.

The pin roller 58 is driven through a transmission line 74 leading from the drive for the garniture tape 68 (i.e. from the drive for the rod making machine). The line 74 includes a positively infinitely variable gearbox (PIV) 76 (or other ratio device). The ratio of the PIV 76 depends on the nature of the filter rod to be produced and on the completeness of the blooming or deregistration process on the tow 50; generally the ratio is fixed for a particular apparatus and particular tow type and will be about 1:1. Drive to the second pin roller 60 is through a transmission line 78 including a second PIV 80. The ratio of the peripheral speed of the roller 60 to that of the roller 58 is controlled by the PIV 80; typically this ratio would be 1.2:1.

The differential speed and relative slip of the pins of the rollers 58, 60 relative to the tow 50 causes deregistration of the tow and prepares it for incorporation in the filter rod. In addition, the rollers 58 and 60 apply plasticiser to the tow.

Plasticiser contained in a tank 82 is withdrawn by a pump 84 driven by a transmission 87 leading from the drive for the rod-making machine (so that plasticiser is withdrawn at a speed related to the speed of production of filter rod). The pump 84 delivers plasticiser to a conduit 86 which supplies plasticiser under pressure to branch conduits 90, 92 which respectively lead to chambers 94, 96 within the pin rollers 58, 60.

The pump 84 is preferably of positive displacement type.

The surfaces of the pin rollers 58, 60 may be provided with holes intermediate the pins through which plasticiser may be supplied to the outer surface of the rollers for impregnation in the tow 50. Thus the roller 58 may supply plasticiser to the upper regions of the tow 50 and the roller 60 supply plasticiser to the lower regions.

Another possible arrangement is shown in Figure 6 where the surface of the roller 60 is provided with modified pins 98 which have bores 100 so that the pins resemble hypodermic needles. The outer ends of the pins 98 are preferably angled away from the leading face, as shown, so that there is less tendency for the bores 100 to clog and to ease penetration of the pins 98 into the tow 50. The lengths of the pins 98 may vary so that different layers of the tow may be positively supplied with plasticiser passing through bores 100. Either or both of the rollers 58, 60 could be provided with pins 98 which could be used in conjunction with conventional solid pins and/or with apertures 101 in the surface of the roller.

Metering of plasticiser to the region of the roller which is in contact with the tow 50 is achieved by use of a stationary sleeve or shield 102 including an aperture 104 where it is required to deliver plasticiser, as indicated in Figure 6. The pressure drop of the plasticiser in the pins 98 (and/or apertures 101) is useful for ensuring even distribution of flow between the pins (and/or apertures); however, in order to achieve adequate flow in some circumstances it might be necessary to heat the plasticiser to reduce its viscosity and thereby reduce the system fluid pressure.

Not all the plasticiser supplied by the rollers 58, 60 will be captured by the tow. This is partly because the width of the tow stream 50 will vary so that at least some of the outer pins or apertures of the rollers 58, 60 will not always be in contact with tow. Collecting means for uncaptured plasticiser is indicated diagrammatically at 104 in Figure 5. Additional shields around the rollers 58 and 60 may be required to direct the plasticiser thrown off the respective rollers or from the tow to the collecting means. The collected plasticiser may be filtered and returned to the plasticisertank 82.

The rollers 58 and 60 could be provided with needles similar to those disclosed in British patent specification nos. and 1 582262 for supplying plasticiser to the tow.

As an alternative arrangement to that depicted in Figure 5 the tow may be passed around pin rollers basically similar to the rollers 58 and 60 but without the internal piasticiser supply and with a conventional plasticiser chamber located between the pin roller 60 and the unit 72 of the rod making machine.

Figure 7 shows an arrangement in which a stream of filter tow 110 is drawn from a source (not shown) by a pair of pretension rolls 112, 114 (similar to the rolls 12, 14) and passed alternately over and under first, second, third, and fourth pin rollers 11 6, 118, 120, and 122. Downstream of the fourth pin roller 122 the tow 110 passes through delivery rolls 124, 126 (again similar to the rolls 12, 14).

The pins of the rollers 116, 118, 120, and 122 differ in type and orientation and in their spacing.

Generally the spacing, projecting length, and diameter of the pins on the rollers 116, 118, 120, and 1 22 decreases in that order. The pins are trailing on the rollers 116 and 118, more so on the roller 116, and are forwardly inclined on the rollers 120 and 122, more so on the roller 122.

Typical values for the pin spacing, angle a, and projecting length are as follows: Projecting Roller Pin spacing Pin angle a pin length 116 8 mm 1350 6 mm 118 6mm 1100 5mm 120 5 mm 800 4 mm 122 4 mm 700 3 mm The diameters of the pins may reduce from about 1.5 mm on the roller 116 to about 1 mm or less on the roller 122. The overall diameter of each of the rollers 116 etc. is about 1 50 mm and the lengths of tow between the rollers are typically in the range 100 to 500 mm.

Drive for the rolls 112, 114 and 124, 126 and for the pin rollers 116, 118, 120, and 122 is derived from the downstream apparatus (e.g. a continuous rod making machine) and a transmission line 128 leading to a PIV 130. The output of the PIV 130 leads directly to transmissions 132, 134, and 136 respectively for the rolls 124, 126, pin roller 122 and pin roller 120, and indirectly, through a second PIV 138, to transmissions 140, 142 and 144 respectively for the pin roller 118, pin roller 116, and rolls 112, 114.The relative speeds of the rolls 124, 126 and rollers 122 and 120 are therefore set as a group (by the transmissions 132, 134, and 136), as are the relative speeds of the rollers 118, 11 6 and rolls 112,114 (by transmissions 140, 142, and 144). The ratio of speeds between these groups is controllable by the PIV 138 and the overall ratio of speed to the main drive is controllable by the PIV 1 30. One possible combination of speeds is as follows: Rolls 124, 126 V Pin Roller 122 1.6 V Pin Roller 120 1.2 V Pin Roller 118 0.7 V Pin Roller 11 6 0.6 V Rolls 112, 114 0.9 V, where V is determined by the tow type and filter construction and is approximately the linear speed of the downstream processing machine (i.e.

the rod making machine).

Thus the overall stretch ratio between the rolls 112,114 and the rolls 124,126 is low (1.1 :1).

However, considerable relative slip between the pins of the respective rollers 11 6, 11 8, 120, and 122 occurs, causing a combing and deregistering effect on the tow 110 and separation of its filaments. The arrangement and orientation of the pins is such that crimp in the tow is substantially retained. As the tow becomes progressively deregistered by passing the upstream rollers it is possible to increase the pin density and the speed of the downstream rollers and to reduce the pin angle a without permanently removing crimp from the tow.

It would be possible to provide increased control of the relative speeds of the various rolls and rollers by arranging one or more additional PlVs in one or more of the transmissions 1 32, 1 34, 1 36, 140, 142, and 144. Alternatively, it is possible that only one PIV may be necessary; in that case the transmissions 1 32, 1 34 and 1 36 may be driven from the transmission 128 by way of a fixed ratio gearbox replacing the PIV 130, the PlV 138 remaining to vary the speeds of the transmissions 140, 142, and 1 44. Another possibility is that the PlV 138 is omitted and the PIV 1 30 retained to offer different filter specifications.

A conventional plasticing chamber, as indicated at 146, may be arranged downstream of the pin roller 1 22. Alternatively, one or more of the rollers 116,118, 120, and 122 may be supplied with plasticiser for application to the tow 110 in a manner similar to that depicted in Figure 5.

A conventional air banding jet to laterally extend the tow may be located in one or more of the spaces between the pin rollers 11 6, 118, 120, and 122, or elsewhere adjacent the tow stream 11 0. One such air banding jet is indicated at 148 in Figure 7.

As shown in Figure 7 the projecting lengths of the pins progressively decrease in the order of the rollers 11 6, 118, 120, 122. For tows which require considerable pin action to achieve the required deregistration of the filaments the projecting lengths of the pins on the rollers may be the same or may increase in the order 116, 118, 120, 122. This can achieve a more progressive deregistration. Similarly the speeds of at least the first and second rollers 116, 11 8 may be closer to that of the tow. Of course more pin rollers can be provided if it is required to process the tow even more progressively.

Referring to Figure 8, a stream of tow 1 50 may be contacted by a pin conveyor 1 52 comprising an endless band 1 54 passing around rollers 1 56 and 1 58, the band carrying a series of slats or staves 1 60 having rows of projecting pins 1 62.

This type of conveyor, known in the textile industry as a lattice conveyor, has the advantage of a potentially long region of contact with the tow. A conveyor similar to the conveyor 152 could replace one or more of the pin rollers in the previously-described embodiments. Another possible type of pin conveyor which may be used comprises one or more staves carrying pins, the staves being moved on a path which intermittently brings them into contact with the tow. For example the staves could follow a square-motion path, or could be given a motion similar to that of one of the elements 3 shows in British Patent Specification No. 278489.

Control of the width of the tow band may also be achieved by use of pins which are angled relative to a plane perpendicular to the axis of rotation of the pin roller. For example, as shown in Figure 9, which is a radial section through part of a pin roller 200, pins 202 may be angled slightly toward the nearer end of the roller so that the pins diverge from the median transverse plane of the roller. This helps to prevent the tow band width decreasing; preferably this width remains substantially equal to the width of the pin roller.

The pins 204 at the extreme edges of the pin roller 200 or those adjacent the flange 26 in Figure 2) may be angled slightly inwards, i.e.

away from the edge, to prevent tow fibres riding over the edge.

Other possible ways of controlling the width of the tow on a pin conveyor are to use slightly crowned rollers (as indicated by the dotted line 206 in Figure 9) or to use a flexible cylindrical roller 210, as shown in Figure 10. The roller 210 is rotated about a curved axis 212 and engages the tow on its concave side 214. Use of a flexible curved cylindrical roller rotating about such a curved axis has the advantage over a crowned roller that the peripheral speed at the surface can be the same along the whole length of the roller.

The flexibility of the roller should be such that it allows sufficient curvature to be effective but should not be so great that the pins cannot be securely anchored and engaged by the tow with sufficient force to be effective.

Claims (31)

Claims

1. A method of processing a continuous tow which includes a plurality of filaments, comprising moving the tow past a conveyor having a plurality of relatively sharp projections which at least partially penetrate the tow, and controlling the speed of at least one of the tow and the conveyor so that the filaments of the tow are separated by relative movement of the projections and the tow.

2. A method as claimed in claim 1, wherein the tension in the tow moving past the conveyor is controlled.

3. A method as claimed in claim 1 or claim 2, wherein the relative speed of the tow and the conveyor is such that no substantial breakage of tow filaments occurs.

4. A method as claimed in any preceding claim, including the step of applying a fluid additive to the tow while it is engaged by said conveyor.

5. A method as claimed in claim 4, wherein the fluid additive is supplied from said conveyor.

6. A method as claimed in any preceding claim, wherein the tow is processed in stages by moving it past a plurality of conveyors carrying projections.

7. A method as claimed in claim 6, wherein the tow is moved past an upstream and downstream conveyor and the relative speeds are controlled such that the speed difference between the tow and the downstream conveyor is greater than the speed difference between the tow and the upstream conveyor.

8. A method as claimed in any preceding claim, wherein the speed of the tow is controlled at positions upstream of and downstream of said conveyor or conveyors.

9. A method as claimed in claim 8, wherein the ratio of the speed of the tow at said downstream position to the speed of the tow at said upstream position is less than 1.3:1.

10. A method as claimed in any preceding claim, wherein downstream of said conveyor or conveyors the tow is formed into a continuous rod.

11. Apparatus for performing the method according to any preceding claim, comprising a path for tow, at least one conveyor having a plurality of relatively sharp projections for engaging the tow on said path, and means for moving the tow relative to the conveyor so that the projections are moved relative to the tow on said path.

12. Apparatus as claimed in claim 11, including means for moving the tow on said path at a first speed and means for moving the conveyor so that said projections move on said path at a second speed.

13. Apparatus as claimed in claim 11 or claim 12, wherein the conveyor is endless and carries an array of projections in staggered rows.

14. Apparatus as claimed in any of claims 11, 12, or 13, wherein said path and the conveyor are arranged such that the tow and the conveyor remain in contact along a substantial length of said path.

15. Apparatus as claimed in any of claims 11 to 14, including at least one pair of opposed conveyors having intermeshing projections, said path passing between said conveyors.

16. Apparatus as claimed in any of claims 11 to 15, including a plurality of said conveyors arranged at spaced positions along said path, so that the tow is processed in stages by said conveyors.

17. Apparatus as claimed in claim 16, wherein the relative spacing of projections on a conveyor at an upstream stage is greater than that on a conveyor at a downstream stage.

1 8. Apparatus as claimed in claim 16 or 17, wherein the penetration into the tow of projections on a conveyor at an upstream stage differs from that on a conveyor at a downstream stage.

19. Apparatus as claimed in any of claims 16 to 18, wherein the average angle subtended between a projection and the surface of the conveyor extending from the projection in a direction of movement of the conveyor is greater for a conveyor at an upstream stage than for a conveyor at a downstream stage.

20. Apparatus as claimed in any of claims 16 to 19, including drive means for moving said conveyors at different speeds.

21. Apparatus as claimed in any of claims 11 to 20, including a conveyor having laterally inclined projections for controlling the width of the tow on said path in the vicinity of said conveyor.

22. Apparatus as claimed in claim 21, wherein the conveyor comprises a crowned roller with laterally outwardly-inclined projections at least at axially-outer locations.

23. Apparatus as claimed in claim 21, wherein the conveyor comprises a substantially cylindrical flexible member, constrained to rotate about a slightly curved longitudial axis.

24. Apparatus as claimed in any of claims 11 to 23, wherein the conveyor is arranged to supply fluid additive to the tow on said path.

25. Apparatus as claimed in claim 24, wherein the conveyor includes a plurality of passages through which fluid additive may be supplied from an internal manifold.

26. Apparatus as claimed in claim 25, including a stationary shield arranged between said passages and said manifold, said shield having an aperture allowing communication between the manifold and said passages in a region corresponding to said path.

27. Apparatus as claimed in claim 25 or 26, wherein at least some of the passages pass through said projections.

28. Apparatus as claimed in any of claims 24 to 27, including at least two of said conveyors arranged at spaced positions on said path, each of said conveyors being arranged to supply fluid additive to tow on said path.

29. Apparatus as claimed in any of claims 11 to 28, wherein the conveyor includes projections of different lengths to penetrate the tow by different amounts.

30. A method of processing a continuous tow, substantially as herein described with particular reference to Figures 1 to 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, or Figure 10.

31. Apparatus for processing a continuous tow, substantially as herein described with particular reference to Figures 1 to 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, or Figure 10.