WO1994005844A1

WO1994005844A1 - Adjusting moisture regain

Info

Publication number: WO1994005844A1
Application number: PCT/GB1993/001834
Authority: WO
Inventors: Thomas Cassidy; Raymond Jeffrey Harwood; Sarah Ann Down
Original assignee: De Montfort University
Priority date: 1992-08-29
Filing date: 1993-08-27
Publication date: 1994-03-17
Also published as: AU4971893A; GB2270091A; GB9218455D0; GB9317856D0

Abstract

There is disclosed a method and apparatus for adjusting the moisture regain of a textile material comprising travelling the material through a humidification chamber.

Description

ADJUSTING MOISTURE REGAIN

This invention relates to adjusting moisture regain of textiles and other moisture absorbing products.

It is desirable that textiles, whether in yarn or fabric form, should be presented with a "correct" moisture content, but since moisture content, or "regain", is affected by a number of factors, it is not easy to ensure the correct content when cones of yarn, for example, are sold to a knitter.

If the regain is too low, the knitter will experience difficulties in knitting the yarn. If it is too high, the knitter may well complain, buying the yarn by weight, that he is paying for water. Too high a moisture content causes mildew if yarn is stored for any length of time.

Yarn is stored sometimes in conditioning rooms or at least placed in such rooms for a time prior to use, but this represents an uneconomic dead time and an inefficient utilisation of expensively controlled storage space. It does not, moreover, solve the problem of producing yarn with the correct regain value in the first place so that a nominal kilogram cone will contain the correct length of yarn. The present invention provides methods and apparatus for adjusting moisture regain which can help to ensure that a textile material has the correct moisture content. The invention is also applicable to other products that contain moisture and are affected by changes in ambient conditions.

The invention comprises a method for adjusting the moisture regain of a material comprising travelling the material through a humidification chamber.

The material may be a textile material.

The textile material may be under tension during its travel - a low tension, consistent with tensions normally experienced in winding a yarn, for example, is found sometimes to accelerate take-up of moisture.

The adjustment may be controlled by controlling the conditions in the humidification chamber. Said conditions may be controlled in response to measurement of relative humidity in the chamber. In a small chamber, relative humidity may be controlled more quickly and easily than in a large air-conditioned room.

The regain of the material may be measured prior to adjustment, and the adjustment controlled to bring the regain to a desired level. The material may be travelled through the chamber at a speed such that there is a dwell time in the chamber which may be between one or a few seconds and two or three minutes. The shorter the dwell time, the faster the material can be processed for a given path length through the chamber. A longer path length gives increased throughput for the same dwell time but path length can be limited inter alia by constraints on the size and complexity of the chamber and associated equipment. The dwell time required will depend on the nature of the material and other features.

Where the material is a yarn, it may be travelled through the chamber on a rotating wrap arrangement. The wrapped yarn may be assisted to traverse lengthwise of the wrap arrangement. However, other dwell time arrangements may be used which are per se known for other purposes such for example as the relaxation of high bulk yarns.

The humidification chamber may be of adjustable length, and may comprise a telescoping tube arrangement. The length of the humidification chamber may be control¬ led in response to measurement of relative humidity of the chamber, or a measurement of the regain of the material prior to (feed-forward) or after (feedback) adjustment. There may be a flow of a humidifying material (usually, of course, moist air) relative to the material in the chamber.

The material may pass in countercurrent with the humidifying medium in the chamber.

The humidifying medium in the chamber may move past the material in a direction transverse to the direction of movement of the material through the chamber. The flow of humidifying medium may be controlled to control the region.

The material may be carried through the chamber by perforate support means, and may be held against deflection by the humidifying medium, for example by being carried through the chamber between perforate conveyor members. The material may comprise multiple ends of yarn or loose fibre fleece or tow arranged in ribbon or sheet form as it travels through the chamber.

The boundary layer of the humidifying medium at the material may be turbulent - this may be arranged by arranging that the flow of a humidifying medium through the chamber is turbulent. Turbulence may be effected by applied vibration such as ultrasonic vibration. A particularly effective way of controlling the adjustment of regain is to control the velocity of air flowing relatively to the material, particularly, in the case of a yarn, of the velocity of an airflow transverse to the yarn axis.

The material may be a yarn and the method carried out while the yarn is being rewound to cone.

The material, however, may be a fabric, which it will usually not be possible to wrap more than once around a rotary system, except, of course, in the case of narrow fabrics. For fabrics, however, the system can be scaled up as compared to yarns, and so a commensurate dwell time, even on the basis of a 180° wrap angle, can be readily provided for at satisfactory throughput rates, and certainly at conventional finishing treatment rates so that the fabric may be processed to adjust its regain as a final step in a finishing process.

The invention also comprises apparatus for adjusting the moisture regain of a textile material comprising a humidification chamber and transport means travelling the material through the chamber.

The humidification chamber may have an atomising, for example an ultrasonic, humidifier, and may comprise a relative humidity sensor in the chamber adapted to control the humidity therein via a control loop.

The transport means may comprise a rotary member carrying the material in the chamber for a dwell time, and, for yarn, the rotary member may comprise a wrap wheel, which may have a lengthwise traverse assist, traversing wraps of yarn lengthwise of the wheel.

The chamber may have condensate drainage means.

The apparatus may be comprised in a yarn winding machine.

The apparatus may comprise an adjustable-length humidifying chamber, which may comprise a telescoping tube arrangement, and may comprise control means controlling the length of the humidification chamber. Moisture measuring means connected to the control means may measure the relative humidity of the moisturising medium and/or the regain of the material.

The apparatus may comprise support means supporting the material as it travels through the chamber with a transverse flow of humidifying medium and may for example comprise perforate belt means. Whilst the humidifying medium will usually comprise moisture-laden air, other media may have advantages in certain situations such for example as moisture-laden nitrogen.

Embodiments of apparatus and methods for adjusting the moisture regain of a textile material according to the invention will now be described with reference to the accompanying drawings, in which :-

Figure 1 is a diagrammatic illustration of an arrangement for treating textile yarn;

Figure 2 is a diagrammatic illustration of an adjustable length humidification chamber and control means therefor;

Figure 3 is a part-cut-away perspective but diagrammatic view of a perforate ccnveyor arrangement with transverse humidifying medium flow;

Figure 4 is a diagrammatic section through a long dwell time arrangement for yarn;

Figure 5 is a diagrammatic section through another long dwell time arrangement for yarn; and Figure 6 is a diagrammatic section through a long dwell time arrangement for a fabric.

The illustrated method comprises travelling the yarn 11 through a humidification chamber 12. This is in contradistinction to conventional methods for adjusting regain of yarn in which yarn on package is placed in an air conditioned environment or, as a short cut, is simply dipped in water and allowed to drain off, or has moisture injected into it through perforations in the package.

The yarn 11 is under tension during its travel, the tension being the usual tension experienced in winding, and adjustable for example by a tension controlling device 13. It has been observed that yarn under such tension takes up moisture more readily than slack yarn.

The regain adjustment is controlled by control¬ ling the conditions in the humidification chamber 12 in response to the measurement of relative humidity in the chamber by an RH sensor 14.

It is found that a batch of yarn produced on a winding or spinning frame will be quite consistent as regards both package-to-package and within-package regain, and that it is sufficient, having determined the regain of a batch from a measurement, for example on a Streat (TM) moisture meter, of, say, three packages of the batch, to set and maintain the chamber RH to a level which, for a given dwell time, will adjust the regain to the desired value.

A typical measured regain will be 14-15%, adjustment being required, usually, to 17-18%. This is quickly, readily and uniformly achieved by the present method and apparatus.

The yarn 11 is travelled through the chamber 12 at a speed such that there is an adequate dwell time in the chamber. It is quite feasible to provide for dwell times of up to, say, three minutes even in high speed, and this will comfortably effect the required adjustment.

In the embodiment of Figure 1, the yarn 11 is travelled through the chamber 12 on a rotating wrap wheel 15 on which multiple wraps may be made, the yarn being assisted to traverse axially of the wheel 15 by a wrap separator 16 in the usual manner.

The yarn 11 may be treated while being rewound from cop 17 to cone 18, the apparatus being devised to be accommodated as part of or accessory to a conventional cone winder.

The humidification chamber 12 has an atomising humidifier 19 (using demineralised water), which is desirably of the ultrasonic type to produce a mist of very fine droplets directed into the chamber 12. Not all of the water introduced into the chamber will be taken up by the yam, and a condensate draining arrangement 21 is provided - this will naturally be important if the apparatus is to be incorporated in expensive cone winding equipment.

The control arrangement illustrated in the Figure comprises a computer 22 receiving RH signals from the RH sensor 14 and updating, say, every two seconds. A Streat (TM) moisture meter 23 equipped with electrodes adapted for contacting yarn cops and other types of package is connected to feed initial regain values directly into the computer 22 which is connected to control the humidifier 19 to operate so as to maintain relative humidity in the chamber 12 at a level predeter¬ mined by the computer 22 in accordance with the initial regain measurement from the moisture meter 23, and with software resident in the computer 22 setting a relative humidity level in the chamber appropriate to the throughput speed and the type and weight of the yarn 11, all of which will have been predetermined by experiment. An appropriate control philosophy would be simply to maintain chamber RH constant at 95%, but it would be possible to arrange for increase or decrease in chamber RH in accordance with, say, the measured regain of the yarn at input to or output from the chamber or with some other relevant variable.

Figure 2 illustrates a humidifying chamber 12 of adjustable length, comprising a telescoping tube arrangement. The length of the tube arrangement is varied by a ratchet and pinion arrangement 31 from a controller 32 in accordance with RH in the chamber 12 sensed by a meter 14 or with the regain in the material (yarn) 11 passing through the chamber 12 as measured by moisture meters 33 (at the chamber input - feed-forward control) or 34 (at the chamber output-feedback control).

Figure 3 illustrates an arrangement in which support means in the form of a pair of perforate conveyor belts 41 support and feed the material - here in the form of multiple ends of yarn 11 arranged between them in ribbon or sheet form through an eyelet board 42 while humidifying medium such as moisture-laden air or nitrogen is flowed transversely to the direction of travel of the yarns 11. The medium is supplied from a source through a plenum 43. The medium may flow at such a rate and/or be sufficiently disturbed by the perforate belts 41 and yarns 11 as to result in turbulent flow over the yarns 11, or turbulence may be encouraged by an ultrasonic vibrator 44 attached to vibrate the plenum 43.

The flow rate of the medium - air, for example at 95% RH - may be controlled so as always to be at least high enough for turbulent flow over the yarns 11 and optionally higher still in accordance with input or output measured regain.

Forms of control other than or in addition to those specifically described may of course be employed where appropriate such for example as temperature and atmospheric pressure control.

The arrangement of Figure 3 is suitable for the processing of loose fibre, fleece or tow as well as fabric. Discrete articles of textiles or indeed of other materials the moisture content of which needs to be adjusted such for example as articles of clothing, surgical dressings, foodstuffs such as biscuits, tobacco and grains may also be processed in such apparatus or such apparatus as may be adapted for such products.

Figure 4 illustrates an arrangement for processing yarn 51 which is fed at a known speed by rollers 52 into a primary chamber 53 with the aid of a jet 54 so as to form a plug 55. The jet air may be temperature and relative humidity controlled and the plug 55 contained in a perforate tube 56 that allows the jet air to escape therefrom into and thence from the chamber 53.

The plug 55 is carried from the bottom of the tube 56 through a second chamber 57 by a perforate conveyor arrangement 58. Air at controlled temperature and relative humidity is pumped into the second chamber 57 via a centrally-located inlet 57a so as to flow through the plug 55 on the conveyor 58.

From the conveyor arrangement 58 the yarn 51 is withdrawn from the plug 55 by feed rollers 59 which forward the processed yam to a winding operation. The height of the plug 55 in the perforate tube 56 and the position of the end of the plug 55 on the conveyor arrangement 58 are monitored for example by photo¬ sensitive arrangements, and controlled by adjusting the speed of the conveyor arrangement 58 and the rate of feed of yam 51 into the primary chamber 53 by the rollers 52.

Such an arrangement can easily provide a dwell time of two or three minutes while maintaining high yarn throughput speeds for efficient operation. The yarn 51 is under essentially zero tension during processing in the equipment of Figure 4. Figure 5 illustrates another arrangement in which the yarn 51 is wrapped around the outside runs of belts or bands 61 trained over pulleys 62 mounted on spiders 63 on a rotary shaft 64. The outer runs of the belts or bands 61 move slowly from the feed-in end 65 to the take-off end 66 from where the yarn 51 is withdrawn by feed rollers 67 to be fed to a winding operation as before. Such an arrangement is generally known for thermally processing yarn for shrinking, the pulleys 62 being at smaller radius on the shaft 64 at the take-off end 66 to accommodate such shrinkage. The arrangement is enclosed in a treatment chamber 67 supplied with controlled temperature and relative humidity air through an inlet 68 as before.

Figure 6 illustrates an arrangement suitable for processing a fabric 71 in which the fabric 71 passes through a treatment chamber 72 trained over rollers 73. A bottom set 73a of rollers is fixed in the while a top set of rollers 73b carries loops of the fabric 71 in between perforated plenum chambers 75 from which relative humidity controlled air is forced on to and through the fabric 71. The dwell time can be varied by varying the elevation of the top set of rollers 73b or the rate of feed of fabric, while the temperature, rate of feed and relative humidity of the treatment air can be controlled as aforementioned to bring about a desired change in the regain of the fabric 71.

Claims

1. A method for adjusting the moisture regain of a material such as a textile material comprising travelling the material through a humidification chamber.

2. A method according to claim 1, in which the material is under tension during its travel.

3. A method according to claim 1 or claim 2, in which the adjustment is controlled by controlling the conditions in the humidification chamber.

4. A method according to claim 3, in which said conditions are controlled in response to measurement of relative humidity in the chamber.

5. A method according to any one of claims 1 to 4, in which the regain of the material is measured prior to adjustment and the adjustment controlled to bring the regain to a desired level.

6. A method according to any one of claims 1 to 5, in which the material is travelled through the chamber at a speed such that there is a dwell time in the chamber of between one second and three minutes.

7. A method according to any one of claims 1 to 6, in which the material is a yarn.

8. A method according to claim 7, in which the yarn is travelled through the chamber on a rotating wrap arrangement.

9. A method according to claim 8 , in which the wrapped yarn is assisted to traverse lengthwise of the wrap arrangement.

10. A method according to any one of claims 1 to 7, in which the humidification chamber is of adjustable length.

11. A method according to claim 10, in which the humidification chamber comprises a telescoping tube arrangement.

12. A method according to claim 10 or claim 11, in which the length of the humidification chamber is controlled in response to measurement of relative humidity in the chamber.

13. A method according to claim 10, 11 or 12, in which the length of the humidification chamber is controlled in response to a measurement of the regain of the material prior to adjustment.

14. A method according to any one of claims 10 to 13, in which the length of the humidification chamber is controlled in response to a measurement of the regain of the material after adjustment.

15. A method according to any one of claims 1 to 14, in which there is a flow of a humidifying medium relative to the material in the chamber.

16. A method according to claim 15, in which the material passes in countercurrent with the humidifying medium in the chamber.

17. A method according to claim 15, in which the humidifying medium in the chamber moves past the material in a direction transverse to the direction of movement of the material in the chamber.

18. A method according to any one of claims 15 to

17, in which the flow of humidifying medium is controlled to control the regain.

19. A method according to any one of claims 15 to

18, in which the material is carried through the chamber by perforate support means.

20. A method according to any one of claims 15 to

19, in which the material is held against deflection by the humidifying medium.

21. A method according to any one of claims 15 to

20, in which the material is carried through the chamber between perforate conveyor members.

22. A method according to any one of claims 15 to

21, in which the material comprises multiple ends of yarn or loose fibre fleece or tow and is arranged in ribbon or sheet form as it travels through the chamber.

23. A method according to any one of claims 1 to 22, in which the boundary layer of the humidifying medium at the material is turbulent.

24. A method according to claim 23, in which the flow of a humidifying medium through the chamber is turbulent.

25. A method according to claim 22 or claim 23, in which turbulence is effected by applied vibration such as ultrasonic vibration.

26. A method according to any one of claims 1 to 25, in which the material is a yarn and is treated while being rewound to cone.

27. A method according to any one of claims 1 to 6, in which the material is a fabric.

28. A method according to claim 27, in which the fabric is treated as a final step in a finishing process.

29. Apparatus for adjusting the moisture regain of a textile material comprising a humidification chamber and transport means travelling the material through the chamber.

30. Apparatus according to claim 29, in which the humidification chamber has an atomising humidifier.

31. Apparatus according to claim 30, in which the humidifier is an ultrasonic humidifier.

32. Apparatus according to claim 29, in which the humidification chamber has a steam humidifier.

33. Apparatus according to any one of claims 299to

32, comprising a relative humidity sensor in the chamber adapted to control the humidity therein via a control loop.

34. Apparatus according to any one of claims 29 to

33, in which the transport means comprise a rotary member carrying the material in the chamber for a dwell time.

35. Apparatus according to claim 34, in which the rotary member comprises a wrap wheel for yarn.

36. Apparatus according to claim 35, in which the wrap wheel has a lengthwise traverse assist, traversing wraps of yarn lengthwise of the wheel.

37. Apparatus according to any one of claims 29 to

36, in which the chamber has condensate drainage means.

38. Apparatus according to any one of claims 29 to

37, comprised in a yarn winding machine.

39. Apparatus according to claim 29, comprising an adjustable-length humidifying chamber.

40. Apparatus according to claim 38 or claim 39, comprising control means controlling the length of the humidification chamber.

41. Apparatus according to claim 40, comprising moisture measuring means connected to the control means.

42. Apparatus according to claim 41, in which said moisture measuring means measure the relative humidity of the moisturising medium.

43. Apparatus according to claim 41, in which said moisture measuring means measure the regain of the material.

44. Apparatus according to claim 29, comprising support means supporting the material as it travels in the chamber with a transverse flow of humidifying medium.

45. Apparatus according to claim 44, in which said support means comprise perforate belt means.