GB2034776A - Yarn Making Process - Google Patents

Abstract

In a process for making a yarn of cotton, or of man-made fibres having fibre lengths in the cotton range, a roving of the cotton or other fibre is twisted with a thin fixing thread or filament in a direction opposite to the twist of the roving, which initially has a low degree of twist. The twisting of the roving and the thread or filament is performed in such manner that the roving is completely untwisted and is given a twist in the direction opposite to its initial twist.

Description

SPECIFICATION Yarn-Making Process This invention relates to a process for making a yarn of cotton, or of man-made fibres having fibre lengths in the cotton range, in which a first-stage twisted fibre structure, for example a staple roving, is twisted with a thin fixing thread or filament. Such yarns are, for example, Ondé yarns.

However, attempts at making such a yarn so as to keep the soft properties of a staple roving have not produced the desired result so far, because cotton, or man-made fibres having a fibre length in the cotton range are, in comparison, smooth and short and, for this reason, a generally high degree of twist is needed for the yarn to be produced with the necessary tensile strength.

While it is true that Ondé yarns may be produced with a certain degree of fluffiness, this is only possible with complex twisting operations.

In a paper dated the 26th September 1978 presented at The National Fibers Conference in Colony Square Hotel, Atlanta, Georgia, United States of America, a suggestion was made for drafting a normal twisted roving in a normal three roll drafting system with a degree of draft of 1 5 to 40. The drafted and then untwisted staple fibres, generally parallel to one another, are fed into a hollow shaft of an upright spindle, on which a filament bobbin is mounted. From the bobbin the filament is run to the outlet of the drafting system, where, because of the rotation of the spindle and the tangential run-in of the filament, it is wound helically around the untwisted staple fibres running continuously through the hollow shaft.

This process cannot, however, be used with cotton fibres, as is in fact noted by the writer of the paper. The main reason for this is that cotton fibres are not long enough, and do not have a large enough gripping length to enable them to be moved across the gap between the outlet of the drafting system and the position of the first strongly gripping filament turn without loss of cohesion within the untwisted fibre structure. The only possible solution would seem to be that of mixing the cotton with another fibre material having a very much longer staple.

German Offenlegungsschrift No. 2,149,426 describes a two-material yarn made by twisting one yarn of staple fibres with a continuous yarn of rubber or an unstretched plastics material, such as polyamide or polyester, which relies on adhering the component parts of the composite yarn by thermal means.

One aim of the present invention is so to increase the tensile strength of cotton, or manmade fibre, yarns, which have a soft or low degree of twist, that, without further processing, they may undergo subsequent steps for making woven and knitted materials.

According to the invention, a process for making a yarn of cotton, or of man-mads fibres with fibre lengths in the cotton range, in which a first-stage twisted fibre structure is twisted with a thin fixing thread or filament, is characterised in that the first-stage twisted structure, having a low degree of twist, is twisted with the fixing thread or filament in such a way that the first-stage twisted structure is completely untwisted and is then given a twist opposite to its original twist direction.

In one embodiment of the process of the invention, the first-stage twisted structure, for example a staple roving, has a degree of twist which is insufficient for processing it into the finished product, for example by weaving or knitting or the like. This first-stage twisted structure is run into a doubling frame at the same time as the fixing thread or filament, the doubling frame being so operated that the first-stage twisted structure is given a twist which is of opposite direction to its original twist.

Such an operation makes it possible for the fixing thread or filament to be placed round the first-stage twisted structure with the desired high degree of twist, so that, generally speaking, the end twist of the structure can be freely chosen as desired.

The process of the invention is especially useful because the starting material may be a first-stage twisted structure which has, generally speaking, a low degree of twist and in which the final degree of twist is only dependent on how high the joining-up effect of the fixing thread is to be and what degree of fluffiness and/or tensile strength is desired in the finished product.

In one embodiment of the process according to the invention, the twisting in the opposite direction is performed to the extent that the firststage twisted structure has the same degree of twist as originally, but in the opposite direction.

In carrying out the process according to the invention, it is possible to use for example, a ring spinning machine and its drafting system for producing the first-stage twisted structure, the final roller pair in the drafting system then being used as a supply system for running in the fixing thread or filament to the first-stage twisted structure.

Yarns produced by the process according to the invention have a surprisingly high tensile strength. Because of the fixing thread twisted round the staple fibre structure, the staple fibres are forced together when acted upon by a tensile force so that the friction between them is increased and the pull is no longer taken up by the fixing thread alone; it is in fact, to a great degree, taken up by the forced-together staple fibres.

In one embodiment of the process according to the invention, the fixing thread is in the form of a wholly or partly elastic thread or filament, the stretch property of which is fixed or locked for the time being. This elastic thread may be acted upon, for example, by heat and/or moisture, so that its elastic property is restored with the development of a spring force which has the effect of making the resulting yarn shorter in length and more fluffy. However, the yarn may be stretched or drafted again in opposition to this spring force. If this spring force, which initially is locked, is only made effective subsequently in a fabric produced with the yarn, the fabric will have the property of being able to be stretched, so that it can be pulled out again to its original size.

In a further development of the invention the elastic thread, which is kept in a non-elastic condition, is run in with a variable degree of pulling force. When the elastic condition of the thread is restored, there will be varying degree of shrinkage, in the longitudinal direction of the yarn, which may be desired for producing speciai fashion effects.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 is a diagrammatic perspective view of one embodiment of apparatus for performing the process of the invention, Figure 2 is a side view of a yarn produced by the process according to the invention, and Figure 3 is a view similar to Figure 2 of another yarn produced by the process according to the invention.

Referring to Figure 1, a first-stage twisted structure or roving 2, produced for example on a roving frame, is drawn from a bobbin 1 via guides 3 and 4 by a supply system 7 comprising nip rollers 5 and 6 driven in the directions indicated by the arrows. The supply system 7 also draws a fixing thread 10 from a further bobbin 9 via a guide 8 and the guides 3 and 4. This fixing thread may be a spun yarn, a multi-thread yarn or, generally, a thread- or filament-structure which is unable to undergo any further drafting, although it may, if necessary, be elastic in its longitudinal direction. The roving 2 and the fixing thread 10 are united at the nip of the supply system 7.

From the supply system 7 the roving 2, united with the fixing thread 1 0, passes to the ring traveller 13 of the spindle 11 of a twisting frame, which is of conventional design and, for this reason, not shown in detail. The spindle 11 is turned in the direction indicated by the arrow and produces, with the help of the ring traveller 1 3 (which travels around the ring 1 2 in the same direction as, but more slowly than the spindle 11), a twist in the staple roving which is of opposite direction to its original twist. The roving 2 is therefore first untwisted and then twisted up again in the opposite direction. The fixing thread 10 has the same direction of twist, but it has a higher degree of twist than the roving 2 by an amount equal to the degree of untwisting of the roving.

Figure 2 is a view of the yarn 14 produced from a staple fibre roving 2 and a fixing thread 10, from which it will be clearly seen that the fixing thread 10 and the staple fibre roving 2 have the same direction of twist, but are twisted to different degrees. If the yarn 14 is acted upon by a tensile force, the force will first take effect on the fixing thread 10, which will be pulled more tightly around the staple fibre roving 2. The separate fibres of the roving 2 will therefore be forced together and the friction forces between them will be increased with the result that the pull will now be taken up by the staple fibre structure as well.

In one example of the above described process, the roving 2 had a count of 6 Nm, was made up from 27 mm cotton fibres, and had a left-hand twist of 1 25 turns per metre (tpm). The fixing thread 10 was a 60 dtex polyamide filament. The spindle 11 of the twisting frame gave the combined roving 2 and thread 10 a right-hand twist of 250 tpm. The staple fibre in the finished yarn then had a right-hand twist of 125 tpm and the fixing thread a right-hand twist of 250 tpm, i.e. twice the degree of twist as the staple fibres.

Figure 3 shows a yarn 1 5 made up from a staple fibre roving 16 and a fixing thread 17 which, in this case, is able to undergo shrinkage and has a high modulus of elasticity. After the twisting together of the roving 1 6 and the thread 17, for example in the twisting frame of Figure 1, the yarn is acted upon by moisture and heat, causing shrinkage of the fixing thread 10 in its longitudinal direction and giving the staple roving 1 6 a pronounced fluffy appearance. The fixing thread, however, will still keep a certain degree of stretch, that is to say it may be pulled out again to its original length, when the yarn will have the appearance shown in Figure 2. In one example of such a yarn, the fixing thread 1 7 was a twisted thread made up from a polyurethane elastomer of 78 dtex and a texturised polyamide of 44 dtex, the two being doubled together at a rate of 900 tpm.

Claims (6)

Claims

1. A process for making a yarn of cotton, or of man-made fibres with fibre lengths in the cotton range, in which a first-stage twisted fibre structure is twisted with a thin fixing thread or filament, characterised in that the first-stage twisted structure, having a low degree of twist, is twisted with the fixing thread or filament in such a way that the first-stage twisted structure is completely untwisted and is then given a twist opposite to its original twist direction.

2. A process as claimed in claim 1, in which the twisting takes place in the opposite direction until the first-stage twisted structure has substantially the same degree of twist as originally, but in the opposite direction.

3. A process as claimed in claim 1 or 2, in which the fixing thread or filament is a wholly or partly elastic member, the stretch property of which is locked during the twisting operation and then subsequently restored so as to produce a spring force which causes the yarn to shorten and become more fluffy.

4. A process as claimed in claim 3, in which the elastic member with locked elastic properties is run in with a varying degree of pulling force.

5. A process as claimed in claim 1, substantially as herein described with reference to the accompanying drawing.

6. Yarn when produced by the process claimed in any of the preceding claims.