WO2005007951A1

WO2005007951A1 - Heating arrangements

Info

Publication number: WO2005007951A1
Application number: PCT/IB2004/002250
Authority: WO
Inventors: Geoffrey Naylor; Bipin Chauhan
Original assignee: Rieter Textile Machinery France
Priority date: 2003-07-19
Filing date: 2004-07-09
Publication date: 2005-01-27
Also published as: CN1826437A; GB0316947D0; EP1646741A1

Abstract

A heating arrangement in a textile machine for texturing textile yams by false twisting, heating and cooling the false twisted yarns, comprising yarn feeding devices, a heating device with a heated surface, a cooling zone and a false twisting device, wherein the feeding devices are operable to feed a yarn along a substantially longitudinal yarns path from a start point to an end point in contact with the heated surface, through the cooling zone and the false twisting device, characterised in that the heated surface is curved along the substantially longitudinal yarn path with a radius or major radius in the range 50 to 500m.

Description

HEATING ARRANGEMENTS

This invention relates to heating arrangements in textile machines, and in particular to heating arrangements in machines for texturing textile yarns by false twisting, heating and .cooling the false twisted yarns, and winding up such yarns. Additionally, this invention relates to methods of heating textile yarns, and in particular to methods of false twisting, heating and cooling textile yarns, and winding up such yarns. Textile machines of this type are well known. Conventionally, in many false twist texturing machines, the heating of the yarns is performed by passing the yarns in contact with the surface of a heated plate. Parallel grooves are formed in the surface of the plate so as to guide the yams and prevent interference of one yam with an adjacent yarn. Such a plate is formed having a curvature of relatively large radius in the longitudinal direction of the passage of the yarns over the surface, so that the tension in the yarns keeps the yarns in contact with that surface and maintains control of the long lengths of yam. This arrangement facilitates the transfer of heat from the heated surface to the yams, thereby keeping to a minimum the length of the heater required to raise the temperature of the yarns to that desired for correct processing. For heaters of between 0.2m and 3m hrlength, typical curvatures lie in the range of 5m to 20m radius.

It is an aim of the textured yarn producers to maximise the production of textured yarn from any texturing machine, by increasing the machine speed and hence the throughput speed of the yarn. It is also desirable to minimise the length of the heater by maximismg the rate of heat transfer from the heater to the yam. One of the limitations to increasing the speed of the machine is the 'surge speed', a yarn throughput speed at which dynamic threadline instability occurs. This speed is affected by yarn tension, the rate of twist insertion and machine configuration. At this speed, the high rotational speed of the twisting yarn tends to create uncontrolled vibrations in the running yam, and this causes rapid variations in tension and in the twist level inserted in the yam by the twisting unit, thereby producing unacceptable yarn. It has always been regarded as essential that the vibrations in the yam be minimised throughout the heating and cooling zones so as to raise the surge speed as much as possible. To this end, and to maximise the heat transfer to the yarn, the yarn is controlled by being maintained in contact with the heater surface by virtue of the yarn tension and the longitudinal curvature of the heater. Alternatively, for high temperature and non-contact heaters, guides have been located on the heater to provide a curved or sinuous path for the yarn on or adjacent the heated surface.

EP 0900866 (ttie contents of which are herein incorporated by reference) discloses improved heating arrangements in which the yarn is fed through a heating zone in contact with a substantially flat heated surface. This arrangement gives rise to a number of advantageous properties, principally the ability to increase the yam throughput speed beyond that possible with conventional heating arrangements. The improved performance of the heating arrangements of EP 0900866 is ascribed to a yam stabilising vibration which is induced in the yarn at higher yam throughput speeds, and acts to stabilise the passage of yam at such high speeds. The substantially flat heated surface in the heating arrangements of EP 0900866 are contrasted with conventional heating arrangements which employ conventional longitudinally curved heaters, which conventional arrangements cannot sustain a high surge speed and do not permit the creation of a yam stabilising vibration. However, there are some problems associated with the technique of EP 0900866. In particular, it has been found that manufacturing tolerances do not permit the production of a perfectly flat heater. Furthermore, it has been found that such manufacfairing variations can give rise to deleterious effects during yarn texturing. This is because the ya cannot follow the contours of the heated surface in region where surface imperfections give rise to a deviation from perfect flatness: rather, an air gap develops between the heated surface and the yam in such regions. The presence of an air gap gives rise to different and uncontrolled heat transfer characteristics, which in turn gives rise to a degradation in the performance of the heating arrangement. The present inventors have found that even a 0.25mm deviation from perfect flatness gives rise to an air gap which is sufficiently large air gap to degrade the performance of the heating arrangement Therefore, the present inventors have identified a need for a heating arrangement that permits high-surge speeds, but whose performance is not affected by variations in shape, (caused by manufacturing tolerances) in the way that the performance of heating arrangements of EP 0900866 is affected. The present invention satisfies the above described need and, furthermore, provides a heating arrangement in a textile machine in which the surge speed is higher than would be the case with a conventional contact heater arrangement or guided non-contact heaters, to allow processing at these higher speeds without detriment to the yam properties, and to minimise the temperature settings and hence the power consumption of the heater.

According to a first aspect of the invention there is provided a heating arrangement in a textile machine for texturing textile ya s by false twisting, heating and cooling the false twisted yams, comprising yam feeding devices, a heating device with a heated surface, a coolmg zone and a false twisting device, wherein the feeding devices are operable to feed a yam along a substantially longitudinal ya path from a start point to an end point in contact with the heated surface, through the cooling zone and the false twisting device, characterised in that the heated surface is curved along the substantially longitudinal yarn path with a radius or major radius in the range 50 to 500m. In this way a heating arrangement is provided which does not suffer from uncontrolled variations in heating performance due to uncontrolled gaps existing between, the heated surface and the yam. Without wishing to be limited by any particular theory, it is believed that circular or near circular motion over a slowly varying curved surface aids in the maintenance of contact between the yam and the heated surface. Surprisingly, it has been found that a range of curved surfaces of relatively large radius or major radius can support a high surge speed and permit the occurrence of a yam stabilising vibration of the type generally described in EP0900866. A further advantage is that high temperatures may be utilised with the heating arrangements of the present invention. The heating arrangements of the present invention can exhibit advantageous properties even when operating in conditions in which the yam stabilising vibration is not induced. In particular, improvements in processing speeds of up to 30% are possible in comparison to conventional curved heating arrangements even under conditions where the yam stabilising vibration is not induced.

The radius or major radius may be greater than or equal to 75m, preferably in the range 75 to 200m, most preferably in the range 90 to 110m. The heated surface may be circular along the substantially longitudinal yam path and be described by a single radius. Alternatively, the heated surface may be elliptical along the substantially longitudinal yam path, and in which instance the heated surface along said ya path is described by a major radius and a minor radius. ^■ The heating device may have a groove in Hie heated surface for receiving a running yam therein. The bottom of the groove may have a radius of between O.Sxxtm and 4mm. Alternatively, the bottom of the groove may be flat. The groove may be in a downwardly facing heated surface of the heating device. The yam may be unsupported over a length of between 25 and 35cm immediately prior to its contact with the heatmg device, and preferably over a length of substantially 28cm.

Yarn guides may be located on the outside of the heating device. The cooling zone may be arranged so that the yarn path through at least a section of the cooling zone extends in a direction which is different from that of the substantially longitudinal yam path at the end point. The cooling zone may be inclined to the plane of the heating surface. The heating device may be substantially horizontal and the cooling zone may extend downwardly from the heating device to the false twisting device, The substantially longitudinal yam path may be substantially horizontal and the cooling zone inclined downwardly from the heating device to the false twisting device. The coolmg zone may be inclined at between 10* and 60° to the horizontal. Preferably the yam path between the heating device and the false twisting device is curved. The yam path in the cooling zone may be curved. The cooling zone may comprise a cooling device in the form of a tube having yarn guides disposed adjacent the inlet and outlet ends thereof and positioned to guide a running yam in a substantially helical path along the outer surface of the tube. In operation, a running yam may make a plurality of turns around the surface of the cooling tube between the inlet and outlet guides. A cooling fluid may be passed through the cooling tube.

The heated surface may be convex along the substantially longitudinal ya path with respect to yam fed therethrough,

The heated surface may be concave along the substantially longitudinal yam path with respect to yam fed therethrough, in which instance the heating arrangement may further comprise means operable to provide a clearance between the yam and the level of the heated surface along the substantially longitudinal yarn path. According to a second aspect of the invention there is provided a method of texturing textile yams by false twisting, heating and cooling the false twisted yams comprising the steps of: feeding a yam along a substantially longitudinal yam path in contact with a heated surface, the heated surface being curved along the substantially longitudinal yam path with a radius or major radius in the range 50 to 500m feeding the yarn through a cooling zone; and feeding the yam through a false twisting device.

The radius or major radius may be greater than or equal to 75m, preferably in the range 75 to 200m, most preferably in the range 90 to 110m.

The heated surface may be circular along the substantially longitudinal yam path and be described by a single radius.

The yam may be fed along the substantially longitudinal yam path at a speed of -greater than 1200 m in"¹. An advantageous feautre of the invention is that such speeds can be achieved whilst maintaining twist levels traditionally associated with throughputs of around 900 m min"'.

A yam stabilising vibration may be induced in the yam along the substantially longitudinal yam path.

The invention will now be described with reference to the accompanying drawings, in which'. Figure 1 is a threadline diagram of a first embodiment of a machine;

Figure 2 shows an alternative yam path on the cooling tube of the machine of Figure 1 ;

,„ Figure 3 shows alternative groove versions of the heater of the machine of Figure 1; and

Figure 4 is a threadline diagram of a second embodiment of a machine.

Referring to Figure 1, there is shown a textile machine 10, comprising a first frame or creel 11 and a second frame 12. Mounted in the first frame or creel 11 are several packages 13 of supply yam. Also mounted on the first frame 11 is a first feed device 14 in the form of a feed and nip roller pair. Mounted on the second frame 12 is a second feed device 15, also in the form of a feed and nip roller pair, and a false-twist device 16. The frames 11, 12 are spaced from each other to provide an operator's aisle 17 between thera. Above the operator's aisle 17 is a substantially horizontally disposed first heating device 18 and, in a cooling zone C, a cooling device 19 mounted on the second frame 12. Figure 1 shows the cooling device 19 in its operating position. The heating device 18, which may have a length of between 0.2 and 1.5m, has a downwardly facing, longitudinally curved, heated surface 20 in which there is a groove (not shown). To reduce the length of heating device required for adequate heating of the yam 23, the heatmg device 18 may operate at a temperature above the melting point of the yam 23, ie, above 150^aC, typically above 260^βC, and up to 800°C. The cooling device 19 is in the form of a tube, and has guides 37 disposed adjacent the inlet and outlet ends thereof to guide the running ya 23 in a helical path, making from one half to three turns as it travels the length of the cooling tube 19. There may be additional guides located on the tube 1 along the helical yam path to aid the stability of the yarn 23 in this region. Alternatively, as shown, in Figure 2, such additional guides 38 may be used to reverse the direction of the helical path of the yam 23 so that for ease of threading it makes no or only one turn around the tube 19 whilst maintaining the path length and process control. A cooling fluid may be passed through the tube 19. This may be effected by withdrawing air from the tube 1 through an aperture adjacent the otherwise sealed inlet end, cooler air entering the tube at the open outlet end. Alternatively, the cooling fluid may be supplied from a cooling fluid supply device to circulate through the cooling tube 19. In either case the flow of fluid serves to enhance the cooling effect and thereby reduces the length of the cooling device 19 required for adequate cooling of the yam 23. The cooling device 19 may be inclined downwardly towards the false-twist device 16 at an angle between 10° and 60° to the horizontal, thereby aligning the incoming ya 23 to pass over the surface of the first working friction disc 24 of the false-twist device 16 at the desired angle. A yam guide 26 which is mounted adjacent the inlet end of the cooling tube 19 may, for threading purposes, 'drop-down' a track (not shown) adjacent the cooling tube 1 in the manner of a sledge on the track 31 as explained below. Alternatively, the cooling tube 19 may be mounted so as to be pivotal about its outlet end 25 downwardly to a threading position. With either arrangement, the ya 23 is able to be threaded over the yam guide 26 in its lowered position and the guide 26 can then be raised or the tube 19 can be pivoted upwardly to restore the machine 10 to its operating configuration. At this stage of threading the yam 23 will extend in a straight line between the first yam feed device 14 and the ya guide 26, The yam 23 is then passed over a twist stopping yam guide 28 on a sledge 29 which is pushed either pneumatically or by means of a rod so as to slide upwardly along a sledge track 31 extending between the first yam feed device 14 and the inlet end 32 of the first heating device 18. The heater door 42 is open at this stage, and this movement of the sledge 29 places the yam 23 in contact with guides 40, 41 accurately located on outside of the casing of heater 18 so as in turn to accurately align the yam 23 in the groove in contact with the downwardly facing heated surface 20. Even when the heater door 42 is closed, the yam 23 is visible as it passes over the yam guides 40, 41 so that, in operation, the accurate alignment of the yam 23 within the heater 18 can be verified. After passing through the falseJwist device 16, the yam 23 passes through the second feed device 15, via an optional second heating device 33, to a package winding mechanism 34 located in take-up section 35. The second heatmg device 33, if fitted, and the take-up section 35 are disposed in the second frame 12, the take-up section facing the first frame 11 across title operator's aisle 17. In this qase the packages 36 of textured yam are removed from the machine 10 by the operator or by an automatic doffing mechanism (not shown) operating in the operator's aisle 17. The invention is equally applicable to alternative configurations of machine, for example three frame machines or machines in which the first heater 18 is at substantially the same height as the first feed device 14 and the sledge 29 and track 31 dispensed with, Referring now to Figure 3, there is shown alternative forms of the groove 21 in the heated surface 20 of the first heater 18. In the first case shown uppermost in the Figure, the groove 21 is relatively narrow, the bottom of the groove 21 being of comparable radius to that of the yam 23, eg, a 0.5mm radius. Such a groove 21 is typical of the grooves provided in the conventional heaters of longitudinally curved form currently in* use. However, in the second case shown on the lower left of the Figure, the groove 21 is relatively wide, the bottom of the groove 21 being of larger radius than that of the yam 23, eg. up to 4mm radius. In the third case shown on the lower right of the Figure, the groove 21 is 'fiat bottomed'. In the second and third cases the yam 23 i$ more able to vibrate laterally than in the first case, and such vibrations may be controlled by the choice of the shape of the groove 21 in relation to the yam 23 being processed. The vibrations will occur naturally due to the action of the false-twist device, but also may be induced by means of a vibrator device or air jet, thereby providing further control. This vibration continuously brings the running yam 23 into contact with parts of the heated surface of the _ _m groove 1 which have not been cooled by the travel of the immediately preceding length of ya 23, thereby enhancing the transfer of heater from the heated surface 20 to the yam 23. This enhanced vibration may also assist in cleaning the surface of the groove 21, in reducing the possibility of the ya 23 sticking that surface if a yam break occurs, and in entraining from the heater 18 fumes which would otherwise accumulate adjacent the downwardly facing surface 20. Furthermore, a more uniform texturing of the yam 23 is believed to be a consequence of the enhanced vibration of the yam 23 on the heater 18 tending to mask the transient variations, of tension in the yam 23 as it issues from the supply package 13 in the creel 11. The distance between the twist stopping yam guide 28 and the guide 40 on the heater door is between 25 and 35cm, preferably substantially 28cm. Too large a distance would provide too greater a length of unsupported yarn 23 leading to process instability, whereas too small a distance would tend to inhibit the vibrations in the ya 23. It has been found in the case of the longitudinally substantially flat heater 18 coupled with the control of the yam 23 in the cooling zone C of the present invention that, contrary to what has previously been believed, the lack of the longitudinal curvature or lateral sinuous yam path which is provided in conventional heaters does not reduce the surge speed or the transfer of heat to the yam 23. Surprisingly, it has been found that an increase in the surge speed of up to 200m/min can be obtained using the present arrangement compared with the use of a conventional longitudinally curved heater of similar dimensions and heating capabilities with or without the generally desirable straight yam path through the heater and coolmg zone, This may be due to being able to run at higher yam tensions since the near-molten yam is not dragged over a hot and substantially curved longitudinal surface or in a sinuous path around hot ya guides. Improved yam properties are believed to be a consequence of this. Furthermore, it has been found that increasing the yam throughput speed through the heater 18, whilst maintaining the heater temperature constant, can produce an increase in the temperature of the yarn 23 on exit fro the heater 18. This effect is opposite to that experienced with conventional contact heaters. The favourable effects on surge speed and heat transfer in the present case are believed to result from the increased lateral vibration in the yam 23 on the present heater 18. Advantageously, this vibration is restricted in the cooling zone due to the cooling tube 1 . It is believed that the inclination of the cooling tube 19 to the plane of the heater surface 20 and the curvature of the yam path around the tube 19 assists in the action of the cooling device 1 as a vibration restricter and also as a tension break, separating the high ya tension that exists in the region of the false twist device from the relatively low yam tension that is observed in the yam path through the heating device. However, it is possible that guide wraps might be used in the cooling zone which deflect the yarn away from the path followed by the yam out of the heater and thus restrict vibration in the cooling zone. Such guide wraps might be employed in a cooling arrangement in which the overall yam path through the cooling arrangement is colinear with the ya path out of the heater. Alternatively still, it may be possible to employ a form of vibration damping device/ tension breaker which is positioned between the heater and the cooling zone. It is believed that the increase in lateral vibration breaks the static friction and provides a mechanism for the dissipation of twisting energy, at a distance remote from the region of twist creation by the twist unit 16, which is isolated from these phenomena by the close control afforded by the helical path around the cooling tube 19,

The present inventors have discovered that curved heating arrangements employing a certain range of radii can exhibit a number of advantageous properties. Firstly, the heating problems noted above in respect of EP 0900866, which are caused by small air gaps present due to surface imperfections in the heater, are solved by the present invention. Without wishing to be limited by any particular theory, it is believed that circular or near circular rotation over a slowly varying curved surface aids m the maintenance of contact between the yam and the heated surface. As noted above, prior art heating arrangements employing curved heated surfaces (typically of a radius in the range 5 to 20m) cannot suppor high surge speeds, and, at high yam throughputs, give rise to uncontrolled yam vibrations of a deleterious and destructive nature. In view of this prior art, it is surprising that a range of curved heated surfaces (of relatively large radius or major radius) can support a high surge speed and permit the occurrence of a yam stabilising vibration, It is believed that the use of heated surfaces having a relatively large radius of curvature results in a relatively low pressure between die heated surface and the yarn, which reduces the constraining and damping force acting on the yam, which in turn permits the yam stabilising vibration to occur, It should be noted that the low pressure between the heated surface and the yam provides advantages even when the yarn stabilising vibration is not being induced, since low pressure conditions associated with the large radii of curvature provided by the present invention cause less filament damage. The ya stabilising vibration will not be present if the yam throughput speed is reduced below a critical value, which is dependent on factors such as the type of yam used and the rotational speed applied to the yam. Furthermore, it should be noted that there is a distinct range of radii over which these advantageous features can be enjoyed. If the radius of curvature is too large, the heated surface begins to approach flatness and becomes prone to the heating problems associated with EP 0900866. If the radius of curvature is too small, then there are start-up problems, and a high pressure between the yam and the heated surface which constrains the yam, leads to breakages and inhibits or prevents the ability to induce a yam stabilising vibration. A radius of about 100m has been found to be the most preferred value, particularly in combination witih heater lengths in the range 1.2 - 1,5m, preferably about 1.3m.

The arrangement shown in Figure Z is suitable for processing relatively heavy yam such as polyester. It is advantageous to employ a slightly modified arrangement in order to texture somewhat lighter yams such as nylon. Polyester yam is usually in the range 78 to 167 decitex whereas nylon has a lower average decitex, usually in the range

22 to 78 decitex. The finer nylon yams have a lower breaking strength and therefore to process these yams a lower frictional drag is advantageous. In preferred embodiments for texturing nylon, some of the guide and cooling tube wrap - which is Important to maintain stability when texturing polyester ya s - is reduced. It has been found that, although nylon has a higher specific heat capacity than polyester, nylon yam can be untwisted at a higher temperature than polyester. This feature, together with the feature that nylon yam has a lower average decitex than polyester yarn, enables the use of a shorter cooling zone, thereby reducing frictional drag. Figure 4 shows a second embodiment of a textile machine 40. The second embodiment of a textile machine 40 shares many common features with the textile machine 10 shown in Figure 1, and identical numerals have been used to denote such shared features. The principal differences are that the second embodiment of a textile machine 40 utilises a shorter coolmg tube 19, giving rise to a shorter cooling zone C. Also, the cooling tube 19 of the second embodiment is inclined at a shallower angle with respect to the heater 19. There are numerous further variations which are within the scope of the invention. For example, it may be possible to utilise a heating device having a concave curved heated surface instead of a convex curved heated surface. In such an arrangement, yam guides at either end of the heated surface can be employed to ensure that the yam is raised slightly above the level of the heated surface, typically less than 0.5mm. ϊn such instances, it is believed that the yam stabilising vibration will occur both laterally and up and down with respect to the heated surface so as to bring the yam down into contact with the heated surface in a controlled manner. Alternatively, it may be possible to utilise a concave heated surface in which the yam is in direct contact with the heated surface at either end, with contact between the ya and the heated surface in the region between the ends of the heated surface being caused through the yam stabilising vibration.

Claims

_ mC AIMS

1. A heating arrangement in a textile machine for texturing textile ya s by false twisting, heating and cooling the false twisted yams, comprising yam feeding devices, a heating device with a heated surface, a cooling zone and a false twisting device, wherein the feeding devices are operable to feed a yam along a substantially longitudinal yam path from a start point to an end point in contact with the heated surface, through the coolmg zone and the false twisting device, characterised in that the heated surface is curved along the substantially longitudinal yam path with a radius or major radius in the range 50 to 500m.

2. A heating arrangements according to claim 1 in which the radius or major radius is greater than or equal to 75m, preferably in the range 75 to 200m, most preferably in the range 90 to 110m.

3. A heating arrangement according to claim 1 or claim 2 in which the heated surface is circular along the substantially longitudinal yam path and is described by a single radius.

4. ■ A hearing arrangement according to any of claims 1 to 3 wherein the heating device has a groove in the heated surface for receiving a running yam therein.

5. A heating arrangement according to claim 4 wherein the bottom of the groove has a radius of between 0.5mm and 4mm.

6. A heating arrangement according to claim 4 or claim 5 characterised in that the groove is in a downwardly facing heated surface of the heating device.

7. A heating arrangement according to any one of claims 1 to 6 characterised in that yam guides are located on the outside of the heating device.

8. A heating arrangement according to any one of claims 1 to 7 characterised in that the yam is unsupported over a length of between 25 and 35cm immediately prior to its contact with the heating device.

9. A heating arrangement according to any previous claim wherein the cooling zone is arranged so that the yam path through at least a section of the cooling zone extends in a direction which is different from that of the substantially longitudinal yam path at the end point

10. A heating arrangement according to any one of claims 1 to 9 characterised in that the substantially longitudinal yam path is substantially horizontal and the cooling zone is inclined downwardly from the heating device to the false twisting device.

11. A heating arrangement according to any one of claims 1 to 10 characterised in that the yam path in the cooling zone is curved.

12. A heating arrangement according to any one of claims 1 to 11 characterised in that the cooling zone comprises a cooling device in the form of a tube, and in that the tube has yam guides disposed adjacent the inlet and outlet ends thereof and positioned to guide a running yam in a substantially helical path along t . outer surface of the tube.

13. A heating arrangement according to any one of claims 1 to 12 in which the heated surface is convex along me substantially longitudinal yam path with respect to yam fed therethrough.

14. A heating arrangement according to any one of claims 1 to 1 in which the heated surface is concave along the substantially longitudinal yarn path with respect to yam fed therethrough.

15. A method of texturing textile yams by false twisting, heating and cooling the false twisted yams comprising the steps of: feeding a yam along a substantially longitudinal yam path in contact with a heated surface, the heated surface being curved along the substantially longitudinal yam path with a radius or major radius in the range 50 to 500m; feeding the yam through a cooling zone; and feeding the yam through a false twisting device.

16. A method according to claim 15 in which the radius or major radius is greater than or equal to 75m, preferably in the range 75 to 200m, most preferably in the range 90 to 110m.

17. A method according to claim 15 or claim 16 in which the heated surface is circular along the substantially longitudinal yarn path and is described by a single radius.

18. A method according to any of claims 15 to 17 in which the yam is fed along the substantially longitudinal yam path at a speed of greater than 1200 m min^*1.

19. A method according to any of claims 15 to 18 in which a ya stabilising vibration is induced in the yam along the substantially longitudinal yam path.