NZ232390A - Spinning bulky yarns on a ringframe - Google Patents

Description

23*390 Patents Form 5 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No. 232390 5 February 1990 IMPROVEMENTS TO SPINNING PROCESSS& To FTapojcC. &uu*.s YAgN*S> WE, WOOL RESEARCH ORGANISATION OF NEW ZEALAND INC of Springs Road, Lincoln, Canterbury, New Zealand being a Society Incorporated in New Zealand under the Incorporated Societies Act 1909, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement ... " "OFFICE F Q 1 3 0 1 » L.0 i o J I The present invention relates to the manufacture of yarns, threads, twines and like materials. More particularly the invention relates to the manufacture of yarns in which a high degree of bulk is desired.

In textile yarns of all kinds it is frequently desirable to have a high bulk characteristic: that is, it is desired that the yarn shall have a high volume for a given mass of fibre. Such yarns have a low density and are soft to the touch and have good covering power in end-products such as knitwear and carpets, imparting a luxurious appearance and handle. In the case of knitwear the high volume of air entrapped within the structure of bulky yarn contributes to a large amount of thermal insulation.

A major contributing factor to yarn bulk is fibre crimp- Animal fibres such as wool can have a very high level of crimp, depending upon the breed of the sheep and the diameter of the fibres. Consequently wools to be spun into knitting yarns are frequently selected because of their crimp characteristics. Synthetic fibres are frequently crimped by artificial means such as texturising as part of the manufacturing process, and it is known also to crimp natural fibres by artificial means.

Crimped fibres can, however, be straightened by the application of relatively weak tensile forces such as those encountered in textile processing. In the case of staple fibres the forces encountered in drafting, spinning and winding can straighten the crimp.

Similarly, in the case of bulked, continuous filament (bcf) yarns the forces exerted in knitting can straighten the crimp. Crimped fibres straightened by such forces will recover their crimp on subsequent relaxation of the structure (yarn or cloth) provided, in the case of knitted cloth, the knit construction is not too tight. However, yarns which depend upon fibre crimp for their bulk, and in which the bulk can be temporarily destroyed by the application of a relatively weak tensile force, have a low initial elastic modulus which is undesirable.

It is also known to manufacture bulky yarns by including in a blend of fibres a minor proportion of fibre which can be made to shrink in length substantially by the application of heat and/or moisture. The shrinkable fibres then tend to migrate towards the axis of the yarn whilst the non-shrinkable fibres are caused to bulge away from the axis, creating a voluminous sheath. Such yarns retain a high initial elastic modulus, depending upon the proportion of shrinkable fibres present, and remain bulky throughout the textile manufacturing process. However, the shrinkable fibres have to be manufactured in a separate process and blended intimately and uniformly with the bulk of the fibre with which they may not be totally compatible.

Yarns made by the worsted and semi-worsted spinning systems tend to be the least bulky of yarns spun from staple fibres because of the steps taken to straighten and parallelise the fibres during processing and high draft ratios used in spinning. Woollen-spun yarns, on the other hand, retain a very much more randomised fibre geometry, by virtue of their method of manufacture, in which virtually all of the fibres reverse direction in the yarn at least once, but more frequently twice or more, creating loops of fibre both within the yarn structure and on its surface, and thus contributing to yarn bulk. For this reason woollen-spun yarns are often preferred for knitwear and carpet manufacture. However, the woollen process is considerably more costly than the worsted and semi-worsted processes for the manufacture of fine count yarns (generally yarns finer than about 250 tex).

It is also known to bulk wool yarns by felting. The yarn is subjected to a controlled degree of felting, either in a batch process or continuously on a single end of yarn, so that a degree of length shrinkage occurs in the yarn. In the early stages of felting fibres migrate longitudinally within the yarn structure in a direction dependant upon the direction which the fibre scales protrude. This causes some fibres (or parts of fibres) to tighten within the yarn structure whilst other fibres (or parts of fibres) loosen and bulge from the yarn axis. However, the felting process needs to be carefully controlled since overfelting can result in reduced bulk, and the felting process is an added cost.

It is also well known that the bulk of a spun yarn depends upon the twist inserted during the spinning process. The function of twist in a yarn is to bind the fibres together in such a way that when the yarn is subjected to tensile stress, the tension of individual fibres has a component directed towards the axis of the yarn which produces pressure between adjacent fibres and consequent high inter-fibre frictional forces from which is derived yarn tensile strength. The inter-fibre frictional forces so developed increase with increasing yarn twist, constraining the fibres towards the yarn core, and there is a commensurate decrease in yarn bulk. Conversely at low levels of yarn twist the constituent fibres are less constrained, with more freedom to bulge from the yarn core, particularly when the fibres are heavily crimped, but the inter-fibre frictional forces are reduced and the yarn has little tensile strength to withstand the rigours of subsequent processing.

It is also known to spin yarns having two components, comprising a pre-spun core, which may be a fine staple fibre yarn or a synthetic yarn, and a covering sheath of fibre, loosely twisted around the core. The core provides the yarn so formed with the necessary tensile properties whilst the covering sheath provides bulk. Such yarns, however, are relatively expensive to manufacture since it is a two-stage process in which the core has first to be spun and there is a limitation on the count it is possible to spin. The sheath is also susceptible to slipping along, or being stripped from, the core in subsequent processing.

An object of the present invention is to engineer a yarn structure which in effect embodies two levels of twist, there being high twist between fibres comprising the core of the yarn to provide tensile strength and low twist between fibres near the periphery of the yarn to provide high bulk.

Thus in one aspect of the invention there is provided a method of spinning high bulk worsted and semi-worsted yarns directly on a ringframe, using ordinary fibres which can be 100% wool, 100% synthetic, any blend of the two or any other fibre, in. which the yarn comprises a core of tightly spun fibres surrounded by a bulky sheath of loosely spun fibres, the core and the bulky sheath being mechanically connected by each including different parts of the same individual fibres.

The yarn structure is generated by spinning a first part of each constituent fibre into the yarn core with the normal level of spinning twist, then spinning a second part of each fibre around the core by overfeeding, and with a much reduced level of twist relative to the extent of the second part of each fibre. Thus each fibre in the yarn contributes both to the core and to the bulky sheath around that core. By virtue of this the bulky sheath and the core are mechanically connected and cannot be displaced or separated during subsequent processing.

A further object of the present invention is to provide a method and apparatus by which bulky yarns may be spun on a ringframe.

Further objects and advantages of the invention are to provide a bulky yarn, spun on a worsted or semi-worsted system in which the bulk is stable in subsequent processing, the yarn having a high initial elastic modulus and no special additional process is required to develop the bulk.

According to another aspect of the invention there is provided a method of generating a bulky yarn structure during a spinning operation, the method including the steps of: providing a driven roller means adapted to control the feed of fibres between front rollers of a drafting system and a point at which twist is first inserted between the fibres; dimensioning the roller means relative to length of the fibres and its surface speed relative to the delivery speed of the front drafting rollers so that part of each fibre is overfed into the forming yarn- Ac cording to yet another aspect of the invention there is provided a means of overfeeding part of each fibre in a yarn to the point at which twist is inserted between the fibres, the means including a driven roller means dimensioned to overfeed part only of each fibre at a controlled rate, and to delay the insertion of twist between the fibres to a point some distance downstream of front drafting rollers.

According to yet another aspect of the invention there is provided a bulky yarn which has a high initial elastic modulus and in which the bulk is stable in subsequent processing and requires no special additional process to develop the bulk.

The roller means can be covered with rubber or other material having a medium to high coefficient of friction with the fibres being spun, and dimensioned and so positioned on the ringframe that a stream of the fibres is in contact with an arc of one roller, the distance between the nip of the front drafting rollers and the point at which the stream of fibres leaves the roller surface being less than the mean length of the fibres.

The roller means can be a single roller which is contacted over an arc by the stream of fibres or it can a roller pair forming a lightly loaded nip.

Further aspects of the invention which should be considered in all its novel aspects will become apparent from the following description which is given by way of example only.

The present invention will now be described with reference to the accompanying drawings in which:- Figure 1: depicts diagrammatically in cross-section the basic elements of a type of ring spinning machine including a design of means according to the present invention; Figure 2: shows in detail one means according to the invention and how the second part of each fibre is overfed into the yarn; and Figure 3; shows in detail the path occupied by a typical fibre within the yarn structure.

Referring now to Figure 1 a roving 1 is delivered through a pair of back drafting rollers 2, a pair of apron rollers 3 and a pair of front drafting rollers 4 to ©merge as a twistless strand fed over the driven rollers 5 below which the strand is twisted to form a yarn 7 which passes on through a pigtail 8 onto a package 9 mounted on a spindle 10 via a ring and traveller mechanism 11.

The driven rollers 5 are driven with a surface speed preferably 50% to 200% greater than the delivery speed of the front draft rollers 4 and are lightly loaded.

Referring now to Figure 2, the front drafting rollers 4 and the driven roller 5 rotate in the directions indicated. Fibres emerging from the nip of the front drafting rollers 4 sure dragged forward, by-virtue of contact with each other and with the surface of roller 5, into the forming yarn 7. The roller 5 is dimensioned and positioned so that the major proportion of fibres are long enough to be securely twisted into the yarn 7 at the leading end and simultaneously still nipped at the trailing end between rollers 4. In this condition slippage occurs between such fibres and roller 5. When the trailing end of a fibre is released from the nip of rollers 4 it is now free to move forward at least at the surface speed of roller 5 and is overfed into the yarn 7. This condition is illustrated by fibre 12 in Figure 2. The yarn 7 then has a tightly spun core 13 covered by a sheath 14 of loosely spun fibre ends which provides the bulk of the yarn.

Referring now to Figure 3 there is illustrated the path in the yarn structure of a typical fibre 15 showing the leading end of the fibre firmly twisted into the yarn core with its trailing end loosely twisted into the sheath around the core. The trailing end of the fibre is then twisted into the yarn with a lower twist per unit fibre length. Thus by this invention there is provided a method and apparatus by which bulky yarns can be spun on a ringframe.

Particular examples of the invention have been described and it is envisaged that modifications and variations can be made without departing from the scope of the appended claims.

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Claims (10)

WHAT WE CLAIM IS:

1. A method of spinning high bulk worsted and semi-worsted yarns directly on a ringframe, using ordinary fibres which can be 100% wool, 100% synthetic, any blend of the two or any other fibre, in which the yarn comprises a core of tightly spun fibres surrounded by a bulky sheath of loosely spun fibres, the core and the bulky sheath being mechanically connected by each including different parts of the same individual fibres.

2. A method as claimed in claim 1 wherein the yarn structure is generated by spinning a first part of each constituent fibre into the yarn core with the normal level of spinning twist, then spinning a second part of each fibre around the core by overfeeding, and with a much reduced level of twist relative to the extent of the second part of each fibre so that each fibre in the yarn contributes both to the core and to a bulky sheath around that core.

3. A method for spinning high bulk worsted and semi-worsted yarns directly on a ring frame substantially as hereinbefore described with reference to the accompanying drawings.

4. A method of generating a bulky yarn structure during a spinning operation, the method including the steps of: providing a driven roller means adapted to control the feed of fibres between front rollers of a drafting system and a point at which twist is first inserted between the fibres; dimensioning the roller means relative to the length of the fibres and its surface speed relative to the delivery speed of the front drafting rollers so that part of each fibre is overfed into the forming yarn.

5. A method of generating a bulky yarn structure as claimed in claim 4 and substantially as hereinbefore described with reference to the accompanying drawings.

6. An apparatus for overfeeding part of each fibre in a yarn to the point at which twist is inserted between the fibres, the apparatus including a driven roller means dimensioned to overfeed part only of each fibre at a controlled rate, and to delay the insertion of twist between the fibres to a point some distance downstream of front drafting rollers.

7. An apparatus as claimed in claim 6 wherein the „ i roller means is covered with rubber or other material having a medium to high coefficient of friction with the fibres being spun, and dimensioned and so positioned on a ringframe that, in use, a stream of the fibres is in contact with an arc of a roller of the driven roller means, the distance between the nip of the front drafting rollers and the point at which the stream of fibres leaves the roller surface being less than the - 13 - ' >> 232390 mean length of the fibres.

8. An apparatus as claimed in claim 6 or claim 7 wherein the roller means is a single driven roller which is contacted over an arc by the stream of fibres or is a roller pair forming a lightly loaded nip.

9. An apparatus as claimed in claim 6 and substantially as hereinbefore described with reference to the accompanying drawings.

10. A bulky yarn manufactured by using the method of claims 1, 2 or 4. WOOL RESEARCH ORGANISATION OF NEW ZEALAND INC By Their Attorneys BALDWIN, SON & CAREY