GB2175926A - Method and apparatus for producing staple yarn - Google Patents

Abstract

A tow 1 from drafting means 2 is converted into a soft yarn by passing it through a succession of twisting means, 3 to 9, in which the direction of twisting changes from one twisting means to the next so that a plurality of twist reversals, preferably six, is effected. The twisting means 3 to 9 are preferably friction twisters. <IMAGE>

Description

SPECIFICATION Method and apparatus for producing staple yarn The present invention relates to a method of and apparatus for producing staple yarn.

It has hitherto been known to roughen the surface of yarn in order to expose the ends of fibres comprising the yarn, and then to wrap those fibres round the body of the roughened yarn. Examples of such devices are disclosed in GB 2,093,079, 2,119,820 and 2,131,842.

The manufacture of fasciated yarns is also known, in which wrapper fibres of the yarn are tightly wrapped around the surface of the yarn. However, fabrics made with such fasciated yarns have a harsh feel, presumably because there are only a few wrapper fibres which are each tightly wrapped around the yarn structure.

It is an object of the present invention to provide an improved staple yarn in which the outer fibres of the yarn are well intermingled with one another, and in which the finished fabric will have a softer feel than is the case with fasciated yarns.

In accordance with one aspect of the present invention, there is provided a method of forming yarn, comprising taking a tow and subjecting it to a sequence of twist reversals in order to effect intermingling of the outer fibres of the tow.

A further aspect of the present invention provides apparatus for forming a yarn, comprising a succession of twisting means of opposite hand to effect a sequence of twist reversals on a strand being twisted thereby, means for feeding a strand to one end of said succession of twisting means, and means for withdrawing said strand after treatment by said succession of twisting means.

The invention also provides a yarn formed by the process or apparatus of the above two aspects of the invention.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawing in which: Figure 1 is a schematic diagram of a yarn manufacturing apparatus in accordance with the present invention; Figure 2 is a schematic view of one form of friction twister for use in the apparatus shown in Fig. 1; and Figure 3 is a schematic sectional view taken on the line Ill-Ill of Fig. 2.

Fig. 1 shows a tow 1 being advanced from a drafting section 2 to a friction twister 3 in which twist in a first direction is imparted to the incoming tow.

The twisted tow is then advanced to a sec ond friction twister 4 of opposite hand, where opposite twist is imparted to the yarn being formed from the tow 1. There is thus a reversal of twist between the first two friction twisters 3 and 4.

A further reversal of twist is undergone by the yarn as it passes from the second friction twister 4 to a third friction twister 5 operating in the same sense as the first friction twister 3.

From then on the yarn passes successively through a fourth friction twister 6, a fifth friction twister 7, a sixth friction twister 8, and a seventh. friction twister 9 so that, in all, the yarn undergoes six reversals of twist.

On passing through each of the friction twisters 3, 4, 5, 6, 7, 8 and 9, the outer fibres of the yarn become intermingled with one another and at each of the friction twisters the intermingling effect is relatively small in magnitude but embraces a high proportion of the outer fibres of the yarn. By the time the yarn leaves the seventh friction twister 9 to be forwarded by delivery rolls 10 to a winder comprising a package drive roll 11 and a package 12, the yarn has a much higher proportion of its fibres intermingled than is the case with a conventional fasciated yarn, and as a result the yarn has a much softer feel, particularly when converted into fabric.

Fig. 2 shows a typical friction twister of the type which can be used with the embodiment of Fig. 1 and the friction twister there illustrated comprises a pair of friction twisting rollers, only one of which (13) can be seen in Fig. 2. Fig. 3 illustrates in more detail the fact that the roller 13 is solid and co-operates with a foraminous roller 14 having an internal masking sleeve 15 provided with a slot 16 so that when suction is applied to the interior of the masking sleeve 15, by virtue of a suction duct 17 (Fig. 2), air is sucked in through the slot 16 to attract the yarn 18 down into the nip between the two friction twisting rollers 13 and 14.

As shown in Fig. 3, the direction of rotation of the two friction twisting rollers is common so that the foraminous roller 14 tends to drive the yarn 18 into the nip while the solid roller 13 tends to lift it out of the nip. The result of the intimate contact of the yarn 18 with the cylindrical surfaces of the two friction twisting rollers 13 and 14 is frictional twisting of the yarn in an anti-clockwise direction as viewed in Fig. 3.

Any other form of friction twister may be used in order to generate the desired number of twist reversals. For example, both of the rollers 13 and 14 may be suction drums as illustrated for the righthand roller 14 in Fig. 3.

Alternative possibilities include manufacturing the suction drums as skew hyperboloidal rollers defining a substantially straight line friction zone for the tow 1 being transformed into the yarn 18. Disc or belt twisters may be used.

The present invention provides a considerable number of twist reversals in order to de rive the desired softness of the finished yarn, but the duplication of the friction twisting means must be balanced against the constructional cost and complexity of the equipment.

Thus, in practice, less than six twist reversals may be used, but it is considered that two twist reversals will constitute the absolute minimum in accordance with the invention.

More than seven friction twisters may give even better results than are derived with the embodiment shown, but the penalty for this is the increased cost of the equipment.

One way of economising on the cost of the installation is to rely on reversal of the yarn part-way through the multi-twisting process and on passing it back along the opposite side of the nip between the two friction twisting rollers such as 13 and 14 in Fig. 3. Thus the seven friction twisting means illustrated in Fig. 1 could be used to give fourteen passes of the yarn through friction twisting means, with a reversing roller at the righthand end of the array to guide the yarn back towards the opposite side of the nip of the friction twister 9. This will result in thirteen twist reversals.

Claims (14)

1. A method of forming yarn, comprising taking a tow and subjecting it at every part along its length to a sequence of twist reversals in order to effect intermingling of the outer fibres of the tow.

2. A method according to claim 1, wherein the tow is drafted before being subjected to the first twist reversal.

3. A method according to either of the preceding claims, wherein the twist reversals are effected using a succession of friction twisters.

4. A method according to claim 3, wherein each said friction twister comprises a pair of similarly rotating friction members defining a nip in which the tow becomes twisted to form a yarn.

5. A method according to claim 3 or claim 4, wherein said friction twisters are arranged in relation to the direction of feed of the tow such that the tow makes two passes through each of said friction twisters.

6. A method according to any one of the preceding claims, wherein there are six twist reversals in said sequence.

7. Apparatus for forming a yarn, comprising a succession of twisting means of opposite hand to subject all of the yarn to a sequence of twist reversals on a strand being twisted thereby, means for feeding a strand to one end of said succession of twisting means, and means for withdrawing said strand after treatment by said succession of twisting means.

8. Apparatus according to claim 7, wherein each said twisting means comprise a friction twister.

9. Apparatus according to claim 8, wherein said friction twisters each include a pair of rotating friction members, at least one of which has a foraminous surface with suction means therewithin to draw the strand into a friction twisting nip between the said members.

10. Apparatus according to claim 9, wherein only one of the friction twisting members is perforated and provided with said suction means.

11. Apparatus according to any one of claims 7 to 10, wherein said means for feeding a strand to the succession of twisting means comprise drafting means.

12. A method of forming yarn, substantially as hereinbefore described with reference to the accompanying drawing.

13. Apparatus for forming yarn, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.

14. A yarn made by the method of any one of claims 1 to 6 and 12 or using the apparatus of any one of claims 7 to 11 and 13.