Yarn processing apparatus

Abstract: In the feeding of an elastomeric yarn (10) having a very low modulus of elasticity, for example for forming a composite yarn (50) from the elastomeric yarn (10) and a relatively inelastic yarn (22) such as nylon, the elastomeric yarn is fed from a supply package (12) in a relaxed form, through a precisely controlled tensioning device (90). The tensioning device (90) includes a driven reel (91) carrying several turns of the elastomeric yarn (10) and a tension detector means comprising a pivoted arm (93) biased by a torque motor acting on a lever (97) which is pivoted (98), rotation of the lever (97) controlling a stepper motor drive to the tensioning reel (91). Since the drive to the tensioning reel (91) is continuously adjusted in response to the actual instantaneous tension in the elastomeric yarn (10), the tension can be maintained precisely throughout the supply from the package (12) which can therefore be connected nose to tail with a second reserve package (12') for high speed continuous feeding of the elastomeric yarn.

Description: This invention relates to a yarn processing apparatus according to the preamble of claim 1. Such an apparatus is known from EP-A-0 400 838. An elastomeric yarn alone is difficult or impossible to use in conventional knitting or weaving machinery. However, when combined with a relatively inelastic yarn to form a composite yarn, it can be knitted or woven into a fabric having good elastic properties. An elastomeric yarn may consist typically of a long chain polymer having a high percentage content of segmented polyurethane. Such yarns are variously known as Spandex, or Elastane or may be of the type known as LYCRA (registered trade mark). The relatively inelastic reinforcing yarn may comprise a nylon (polyamide) or polyester yarn. The inclusion of elastomeric yarn in textile fabric produces a fabric with a wide range of total extension and resistance to stretch with complete recovery. Elastomeric threads of the kind referred to are characterised by a total extension of around 700% with complete recovery. Such threads have to be anchored in the fabric in such a way that they are normally extended to about 50% of their maximum extension when the fabric is at rest. The elastomeric threads then exert a high level of resistance to stretching of the fabric, thus providing support and/or improved fit of a garment made from the fabric. Unless some special effect is required, it is essential that all the elastomeric threads in a piece of fabric have the same percentage extension to within very closely controlled limits, to ensure a regular surface and even stretch characteristics in the fabric. It is very difficult in practice to achieve this high level of accuracy since the elastomeric yarn has a very high total extension and a low modulus of elasticity (ratio of stress to strain during extension) making it difficult to combine with conventional, relatively inelastic textile yarns. A method which has hitherto been widely used is to wrap the elastomeric yarn while extended to about 50-60% of its total extension with an inelastic yarn such as nylon, under accurately controlled conditions which maintain the extension of the elastomeric yarn within very narrow limits. The composite yarn can then be fed into a knitting or weaving machine through conventional tensioning devices which maintain the inelastic yarn at full extension. This in turn maintains the extension of the elastomeric yarn within the narrow limits achieved in the wrapping process. For example, US-A-3281087 describes a tensioning arrangement for core spun elastomeric yarn which is drawn from a reel through powered draw off rollers, the speed of the draw off rollers being controlled so as to slightly exceed the take-up speed of a winding mandrel onto which the yarn is fed, the arrangement being that no tension can be detected in the core spun yarn between the powered draw off rollers and the mandrel. Elastomeric yarn and an inelastic yarn such as nylon have very different extensometric properties as illustrated in the typical load/extension graph shown in Figure 1. The low modulus of elasticity (stress/strain characteristic) of the elastomeric yarn indicates that very small changes in load cause large changes in extension. The control of tension by the type of device used for nylon and similar inelastic yarns is therefore impossible with elastomeric yarns. It has been the practice to maintain the elastomeric yarn in extended condition within acceptable limits of extension throughout its processing through from extrusion to the wrapping procedure used to maintain the extension. A supply package of elastomeric yarn is driven at a fixed speed at the peripheral surface of the yarn package. The elastomeric yarn is unrolled off the side of the supply package so as to retain substantially constant extension. A take-up or receiving package is similarly driven, but at a higher speed, at its peripheral surface. The extension of the yarn is thus governed by the difference in surface or peripheral speeds of the supply and take-up packages by this method. In US-A-3657873, an elastomeric yarn is tensioned using powered draw off rolls which are also used to twist the elastomeric yarn with a less elastic covering yarn. A tensioning device comprising a braked friction roller is interposed between the elastomeric yarn supply package and the draw off rolls. The braking of the braked feed roller is controlled by a spring loaded arm which detects the tension in the thus supplied elastomeric yarn and adjusts the braking force accordingly. However it is believed that this method does not enable precise control of the tensioning because of the very high percentage elongation (up to 700%) to which elastomeric threads may be subjected. The braking of the friction roller takes place in response to the tension of yarn which has already passed over the roller, and there is no intervention in the drive speed of the actual pull off feed rollers. The desire for higher speeds of production and processing has not been fully met by the prior yarn supply means described, particularly in combination with the relatively slow conventional core wrapping techniques. In order to explain these disadvantages, reference will be made to Figure 2 of the drawings. Figure 2 (prior art) illustrates a known wrapping procedure in which the supply package 3 of elastomeric yarn 1 is peripherally driven at a first speed by contact with a driving roller 4 and is taken up by a take-up package 6 driven in the same manner by a driving roller 7, but at a higher peripheral speed than the supply package. These surface or peripheral speeds and thus the extension of the elastomeric yarn between the supply package 3 and take-up package 6 can be maintained within very close limits. An inelastic nylon wrapping yarn is unrolled from a rotating package 8. The number of turns per unit length of the nylon wrapping yarn 2 about the elastomeric yarn 1 is governed chiefly by the speed of rotation of the package 8 providing the inelastic nylon yarn 2 but is also governed by the speed of rotation of the take-up package 6. There is a clear practical limit to the speed at which a usefully sized package bobbin 8 of nylon 2 can be rotated in order to maintain an acceptable level of wrapping turns. As a result, the production output speed of composite yarn 5 by this prior core wrapping method is very low, typically 20-25m per minute. Although somewhat greater output speeds, for example 500m per minute or more, may be achieved by a composite yarn manufacturing procedure set forth in the specification of our prior European Patent Application EP-A-0 400 838, there is still a problem in supplying the elastomeric yarn at a sufficiently high supply rate. At the relatively high output speed obtainable by the method of EP-A-0 400 838, the elastomeric yarn is rapidly unrolled from a supply package. When the supply package is exhausted, a new one has to be fitted, entailing quite frequent stoppage of the supply package spindle. Since the elastomeric yarn is conventionally fed under constant controlled extension from the supply package, it is unrolled off the side of the rotating supply package 3 and there is no means of replenishing the package without stopping the supply package spindle. It is an object of the present invention to provide an improved means for supplying elastic or elastomeric yarn in a controlled manner. As a secondary object, a continuous supply of elastomeric yarn may be made possible for high speed processing such as production of composite yarn. Tensioning apparatus is known, for example from US-A-4953367 for use with circular knitting machines having a number of supply means for yarn. The yarn tension is monitored at each of the supply stations and the tension is compared with a reference value dependent on measured signals from all the measuring circuits. A feedback system controls the speed of a stepper motor driving each individual yarn tensioner in response to the control signal. This enables the yarn to be supplied to a multi-station knitting machine with consistent tension at each of the yarn supply stations. However the yarn involved is a normal knitting yarn which is being supplied to apparatus for its final utilisation. The apparatus described in US-A-4953367 is not disclosed for use with elastomeric thread of very high total extension. The present invention was developed to improve the supply rate of elastomeric yarn particularly but not exclusively for the manufacture of composite yarn in the way described in our prior European Patent Application EP-A-0400838. However, it is to be understood that the supply means of the invention can be used for supply of elastomeric yarn to other apparatus for composite yarn manufacture such as for example one in which two yarns are combined by air or other fluid jet intermingling, for example as set out in GB-A-1 487 674 (E. I. Du Pont De Nemours and Company). According to the present invention there is provided a yarn processing apparatus for combining a relatively inelastic yarn with an elastomeric yarn having a high total extension and a low modulus of elasticity; the yarn processing apparatus including:- a supply means for supplying the relatively inelastic yarn to a combining station; a supply package for the elastomeric yarn in which the elastomeric yarn is provided in a relaxed form; tensioning means receiving the elastomeric yarn from the supply package and arranged to impart a predetermined tension sufficient to extend the elastomeric yarn to 50-60% of its maximum total extension and to feed the thus tensioned elastomeric yarn to the combining station; characterised in that the yarn processing apparatus is continuously operable; the supply package for the elastomeric yarn is non-driven; a further non-driven supply package is provided for the elastomeric yarn, with the leading end of the yarn being connected to the trailing end of the yarn of the supply package for continuous supply of the elastomeric yarn to the tensioning means; the tensioning means comprise a rotary driven tensioning reel adapted to receive a plurality of turns of said elastomeric yarns over end from the non-driven supply package via an intake; each supply package is inclined at the same angle with respect to the intake of the tensioning means; tension detector means are disposed between the reel and the combining stations and provide a signal in response to the actual instantaneous tension detected in the elastomeric yarn; drive control means are provided to control the drive to the tensioning reel in response to said instantaneous tension signal so as to provide substantially constant tensioning of the elastomeric yarn, throughout the continuous operation of the yarn processing apparatus, irrespective of which of the supply packages is connected to the reel. The invention will now be described in more detail with reference to the accompanying drawings in which Figure 1 is a graphical representation of load and extension traces of a typical elastomeric yarn and a typical relatively inelastic nylon yarn, Figure 2 (prior art) is a diagrammatic illustration of a known supply means and yarn wrapping apparatus for manufacturing composite yarn, Figure 3 is a diagrammatic illustration of controlled yarn supply means according to the present invention applied to a machine for manufacturing composite yarn, Figure 4 is a detail view on an enlarged scale of a yarn supply tensioning device of the type used in the apparatus of Figure 4, Figure 5 is a graph of a conventional extension draft ratio versus tension of the elastomeric yarn, Figure 6 shows portions of test recordings of yarn feed tension under conditions of controlled extension of the yarn (prior art), Figure 7 shows portions of test recordings of yarn feed tension with tension control, Figure 8 shows portions of test recordings of yarn feed tension without tension control, Figure 9 is a detailed view of a composite yarn which may be produced by the apparatus of Figure 4. Figures 1 and 2 of the accompanying drawings have already been referred to in relation to the prior art. Figure 3 illustrates the present invention applied to a machine for manufacturing composite yarn as set out in EP-A-0 400 838, by way of example only. However, a supply means for the elastomeric yarn has been provided incorporating a tension device 90 having specific characteristics which make it possible to supply an elastomeric yarn at a very precisely regulated tension. It is known from US-A-4953367 to use a tensioning device in supplying conventional non-elastic yarns into knitting machines which require the yarn to be fed at variable speeds according to the pattern being knitted. A form of feedback is used in such a knitting yarn tensioner in such a way that, where the demand for the yarn drops, the rate of feeding is automatically caused to drop, and when the demand for the yarn increases the feed speed is automatically increased. It has been found as a result of the present invention that a tensioning device based on the known knitting yarn feed device could be adapted to meet the requirements regarding the supply of elastomeric yarn at precisely controlled tension. Referring to Figures 3 and 4 of the drawings, incoming yarn 10 is fed from a supply package 12 or 12' via input guides 94 and 95 onto a motor driven reel 91. The yarn is passed a few times around the reel before passing through a guide eyelet 92 of a pivotally mounted tension control arm 93. The arm 93 is pivoted at 96 against the action of an electric torque motor which acts on the arm 93 by means of a pivoted lever 97 connected at 98 to the torque motor. Angular movement of the arm against the bias of the torque motor causes an increase or decrease in the drive speed to the driven reel 91. The reel 91 may be driven by example by a stepper motor and the speed of the motor may be increased if the detected tension in the yarn 10 increases and may be decreased if the detected tension in the yarn 10 decreases. The arm 93 and lever 97 act as a tension detector. The tension desired can be set by means of a potentiometer 99 which adjusts the load of the torque motor acting on the arm 93 through the lever 97. A predetermined tension 10 at the arm guide will give a known delivery rate of the elastomeric yarn 10 to other processing apparatus, in the example illustrated the yarn texturising machine employed to produce a composite yarn by the process described in EP-A-0 400 838. The tension required can be calculated from the graph of Figure 6 based on data previously obtained. The tensioning device 90 thus creates and controls tension in the elastomeric yarn 10 between the tension control arm 93 and for example the drafting rollers 68, 70. The tension is effectively maintained within very narrow limits. Since the yarn 10 is not extended in the package 12, 12', it can be provided in a relaxed condition and the supply can be taken over end from the package. This enables a plurality of packages 12, 12' to be connected nose to tail. The drawing shows a pair of adjacent packages thus connected. The packages are mutually inclined so as to converge symmetrically towards the guide 94 on the tension device 90. The distance between the packages 12, 12' and central guide 94 is such as to maintain a constant flow in the ballooning yarn as it is fed over end from the stationary package 12, such distance being typically 15cm. The first or running package 12 of elastomeric yarn has a tail of yarn from the lower end tied or otherwise attached to the leading end of yarn 10' from the upper end of the second or reserve package 12'. When the yarn 10 is fully drawn off from the first package 12, over end drawing off of yarn 10' immediately and automatically follows from the second package 12'. An operator can then replace the package 12 by a fresh loaded package and tie the leading end of its yarn to the trailing end or tail of the second package 12'. Thus, continuous and uninterrupted supply of elastomeric yarn is able to take place with adequate time available for changing the packages. Apart from yarn breakage, no stoppage of the supply of yarn need occur and this has clear advantages where the processing of the elastomeric yarn is to be carried out at high speed. It will be appreciated that more than two packages may be employed using nose to tail connection. In the apparatus shown in Figure 3, a relatively inelastic nylon yarn is separately supplied and is twisted with the elastomeric yarn to form a composite yarn. Incompletely drawn nylon yarn 22 (partially orientated yarn) is provided from a first yarn package 24 through a guide tube 60 and is fed alongside the elastomeric yarn 10 via drafting rollers 68, 70 to a guide 40 from which the two yarns are twisted together by a twisting head 42 during their passage in a downwardly inclined direction adjacent an electric heater 38 as described in EP-A-0 400 838. As described in relation to the elastomeric yarn 10, the inelastic nylon yarn 22 is supplied from package 24 connected nose to tail with one or more further packages such as the second reserve package 24'. The yarn combining apparatus is described in our prior European patent EP-A-0 400 838 to which reference may be made. The guide 40 is a "twist-stop-pulley" acting as a guide to bring the yarns together and preventing migration of twist in an upstream direction towards the drafting rollers 68, 70. From the twisting head 42, the twisted composite yarn is fed into a nip provided by an "apron" feeder including an endless belt 84 about rollers 79, 81 and cooperating with a driven roll 77. The twisted composite yarn 50 passes to a driven take-up package 54 after passing round a lubricating oil roller 78. An additional plain friction roller type guide 76 guides the composite yarn between the heater 38 and twisting head 42. The apron feeder 77, 84 can be replaced if desired by a pair of nip rollers. Typically, in the apparatus illustrated, the elastomeric yarn 10 is fed to the guide 40 at a relatively low speed such as 125m per minute and the relatively inelastic nylon yarn 22 is fed at a higher speed such as 385m per minute. The speed is increased during passage of the yarns against the heater 38 so as fully to draw the partially orientated nylon yarn and the twisted yarn emerges from the apron feeder 77, 84 at about 500m per minute. Higher output speeds up to 900m per minute may be envisaged to take advantage of the continuous supply of elastomeric yarn by the supply means of the invention. In the event of breakage, detectors and cutters are provided in the supply of each of the yarns, so that a break in one yarn will be accompanied by cutting of the other yarn to avoid wastage. It will be appreciated that the processing of the elastomeric and non-elastic yarns may take the form of a relatively conventional wrapping about the elastomeric yarn which becomes a core yarn or a twisting process in which the yarns 10, 22 are twisted approximately equally as shown in Figure 9. Figures 6, 7 and 8 show test results obtained by measurement of tension under different conditions. Figure 7 shows test traces made using the supply means of the present invention whereas Figure 8 shows similar traces made without the device 90. Figure 6 shows traces made when the supply of elastomeric yarn is made at constant extension, rather than using a relaxed supply. Figure 6 (prior art) shows a test tension trace in respect of an elastomeric yarn (22 d'tex Lycra T146) obtained by means of a tension measuring head responsive to the tension of the yarn 1 running between the supply package and take-up package and an operating extension of 200%. In this test example, the readings A were taken when the supply package spool was at half size. In readings B the supply package was almost finished. In both cases the mean tension lies between 1.75gm and 2.00gm. On carrying out test C, from the commencement of a new package, the mean tension remained between 1.60gm and 1.90gm throughout. Comparing Figures 7 and 8, it has proved possible, using the supply means of the invention, to maintain a constant mean tension in the run of yarn 10 between the device 90 and the draft rollers 68, 70 throughout the drawing off of yarn from the outside to the inside layers on a supply package 12. Without the automatic compensation of tension provided by the tensioning device 90, tension would tend to increase substantially as the diameter of the supply package 12 decreased as later described with reference to Figure 8. In carrying out the test which resulted in the trace of Figure 7, the head of a tension measuring apparatus was inserted at a position 100 in the run of elastomeric yarn between the tensioning device 90 and the draft rollers 68, 70. A trace of measurements of tension made throughout the drawing off of yarn from the package 12 and through the transfer to the second or reserve package 12'. As will be seen from the trace recording shown in Figure 7, a mean tension was maintained between 1.50gm and 2.00gm throughout trace X and trace Z, corresponding to the middle and outer layers of the supply package. For a short period of about 24 seconds, just before the transfer from supply package 12 to the reserve package 12', tension increased as shown in trace Y due to the innermost layer of yarn gripping the tube of the supply package 12. An abrupt change in tension took place as the slack length of yarn 10' of the leading end of package 12' was taken up. The feeding device immediately adjusted the tension of the elastomeric yarn of the second package 12' maintaining the level of 1.50gm to 2.00gm again. It will be seen that the trace of Figure 7 compares closely with that of the pre-extended yarn trace of Figure 3, previously referred to. The elastomeric yarn can be used to produce very satisfactory quality products. Referring to Figure 8, this shows the traces of a similar apparatus to that shown in Figure 9 but with the tensioning device 90 omitted. Initially, the trace X' was of a low mean value, about 0.60gm. By the end of the first package 12, tension had risen to 2.00gm mean value and after transfer to a new package 12', the tension dropped very substantially and was subject to considerable irregularities. This is particularly noticeable in trace Z'. Such a range of tension and its irregular nature resulted in a composite yarn being produced which was quite unacceptable for knitting or weaving purposes. It is to be understood that the selected recording portions X, Y, Z and X', Y' and Z' have been taken from full recordings of considerably greater length but are closely representative of them.

Claims: Yarn processing apparatus for combining a relatively inelastic yarn (22) with an elastomeric yarn (10) having a high total extension and a low modulus of elasticity; the yarn processing apparatus including:- a supply means for supplying the relatively inelastic yarn to a combining station; a supply package (12) for the elastomeric yarn in which the elastomeric yarn is provided in a relaxed form; tensioning means (90) receiving the elastomeric yarn from the supply package and arranged to impart a predetermined tension sufficient to extend the elastomeric yarn to 50-60% of its maximum total extension and to feed the thus tensioned elastomeric yarn to the combining station (42); characterised in that the yarn processing apparatus is continuously operable; the supply package (12) for the elastomeric yarn (10) is non-driven; a further non-driven supply package (12') is provided for the elastomeric yarn, with the leading end of the yarn (10') being connected to the trailing end of the yarn (10) of the supply package (12) for continuous supply of the elastomeric yarn (10,10') to the tensioning means; the tensioning means (90) comprise a rotary driven tensioning reel (91) adapted to receive a plurality of turns of said elastomeric yarn (10,10') over end from the non-driven supply package (12 or 12') via an intake (94); each supply package (12,12') is inclined at the same angle with respect to the intake (94) of the tensioning means (90); tension detector means (93,97) are disposed between the reel (91) and the combining station (42) and provide a signal in response to the actual instantaneous tension detected in the elastomeric yarn (10,10'); drive control means (97,98) are provided to control the drive to the tensioning reel (91) in response to said instantaneous tension signal so as to provide substantially constant tensioning of the elastomeric yarn, throughout the continuous operation of the yarn processing apparatus, irrespective of which of the supply packages (12,12') is connected to the reel (91). Yarn processing apparatus according to claim 1 further characterised in that the tension detector means comprises a pivoted arm (93), the pivoting movement of the arm being resisted by biasing means (97,98) comprising a torque motor (98) and the movement of the arm providing said instantaneous tension signal to a stepper motor arranged to drive the tensioning reel (91).

Inventors: PICKETT DAVID GRAHAM, PICKETT, DAVID GRAHAM
Applicants: JONES STROUD & CO LTD
Application year: 1992
Main classification: B65H59
IPC codes: B65H59, D02G3