Conventional methods of yarn formation by friction spinning use fibres in the form of a fibre sliver delivered to a spinning system by a pair of feed rollers. The feed rollers are separated by means of a rapidly rotating pinned opening roller. Fibres leaving the rapidly rotating pinned opening roller are subsequently transported by an air flow along a tube or duct known as a transfer channel. On exiting the transfer channel, fibres are directed onto the surface of a perforated roller. A suction force is applied to the interior of the perforated roller so that perforations on its outer surface allow for a suction force along its length. The perforated roller's suction force permits effective collection of the in-coming fibres upon its surface as they exit the transfer channel from the feed rollers. In a typical conventional arrangement there is provided, at a distance of some 0.1-0.2 mm from the perforated roller, a plasma coated solid roller. The solid roller is positioned and mounted co-axially with respect to the perforated roller and on top of it so that both the solid and perforated rollers rotate in the same direction.

In use, fibres exiting from the transfer channel land on the surface of the perforated roller and join the end of a forming yarn or yarn arm. The yarn arm rotates/twists between the solid and perforated rollers as a result of the relative motion and frictional contact between the fibres and the roller surfaces. Rotation of the yarn arm is responsible for insertion of a twist in the yarn. In this way, a continuous yarn forming process occurs. It is of note that in conventional friction spinning systems fibres land and twist simultaneously within the same area of the spinning machine/system. Accordingly, there is little control over the positioning of the fibres

with respect to one another on either the roller surface or in the yarn itself, consequently fibres can become buckled and/or looped within the yarn structure.

A serious problem associated with the prior art is that, as a result of fibres simultaneously landing and twisting on the perforated roller, yarn strength is reduced. Yarn strength is dependent on the proportion of aligned fibres. Thus, a system and method that could improve the overall number and control the positioning/orientation of fibres positioned substantially in parallel, would offer immediate advantage over the prior art methods and would overcome one of the major technical limitations of current practices in the friction spinning process.

A further problem associated with the lack of control of fibre alignment by fibres landing and twisting simultaneously within the spinning machine/system, is an inherent difficulty to control the quality of the ultimate product. For instance, fibre density can vary because of bunching and lead to non-uniform properties of a yarn such as variable absorbency.

The present invention provides an elegant and inventive solution to the problems associated with yarn produced by friction spinning by providing a system which separates fibre deposition and yarn twisting into discrete and independent operations. The system of the invention, in contrast to the prior art, provides for the formation of an intermediate and continuous ribbon of fibres subsequent to fibre deposition and prior to twisting of the fibre ribbon. In this way the orientation of fibres can be controlled and a quality controlled product achieved.

It is therefore an object of the invention to improve the strength and uniformity of the properties of yarn produced by friction spinning.

It is further object of the invention to improve the spinning of fine yarn counts.

In its broadest aspect, the invention comprises a friction spinning system suited to the production of a single and/or bi-component yarn structure compose from any fibre type including, and without limitation, technical fibres such as alginate and other super absorbent fibres for use especially, but not exclusively, for application in medical woven and/or knitted wound dressing structures.

According to a first aspect of the invention there is provided a friction spinning system for producing yarn, the system comprising: (i) means for feeding fibres on to a surface; (ii) means for forming a consolidated ribbon of said fibres on said surface; and (iii) means for taking off said ribbon from said surface in the form of a yarn, said take-off means including yarn twisting means located downstream of said surface whereby, in use, twisted yarn forms between said surface and said yarn twisting means.

Preferably, the fibre feeding means includes a transfer channel and means for directing an air flow along said channel.

Preferably, the fibre feeding means further includes at least one fibre opening roller.

Preferably, said ribbon forming means comprises a pair of deposition rollers which contact each other to form a positive nip.

Preferably, one of said rollers is perforated and means are provided for applying inwardly directed suction to the perforations of the roller.

Preferably, the rollers are arranged one above the other.

Preferably, the fibre feeding means are such as to direct fibre on to said perforated roller in advance of said nip.

Preferably, the yarn twisting means comprises at least a pair of twisting rollers.

Preferably said second roller deposition is not perforated.

Preferably said stream of fibres is continuous.

It will be appreciated that unlike conventional rollers the said pair of first and second deposition rollers operate in contact so as to form a positive nip. Moreover, the fibre deposition or landing zone is located adjacent and to the rear of a nip-line of said first and second deposition rollers. By continuous deposition of fibres onto said first deposition roller, a ribbon of fibres is formed immediately behind the nip-line and is the fibre ribbon is positioned by means of the suction force on the outer surface of said first deposition roller. Counter rotation of said first and second deposition rollers causes a ribbon of fibres to pass continuously between the roller nip whereby said ribbon is compacted prior to emerging beyond the interface of said first and second deposition rollers.

Preferably said system further comprises at least a pair of second twisting rollers ideally the second twisting rollers are co-axially mounted with respect to one another.

Preferably said twisting rollers are positioned and mounted so as to be co-axial with respect to said deposition rollers and are provided at a pre-selected distance therefrom. Ideally said twisting rollers are mounted perpendicular to a roller-nip.

It will be appreciated that a yarn is formed as the yarn twist propagates along the nip- line of the deposition rollers so that the deposition rollers nip the emerging fibre ribbon into a coherent or single bundle form. Fibres produced by the system of the invention are highly orientated in the direction of yarn take-off. A high proportion of straight fibres, free from proportion of straight fibres, free from loop or entanglements result in the final yarn thus increasing yarn strength and quality.

Preferably the fibres are of a length in the range 5-150mm and ideally 30-65mm.

Preferably the fineness of the fibre is in the region of 1-15 expressed as linear density weight gm/10,000 metres (dtex) and more ideally as 1.5-5 dtex.

Preferably the fibres for use in the system comprise highly absorbant material, ideally algenate and more ideally super-absorbant material selected from the group comprising: viscose, rayon, polyamide, cotton or polypropylene.

It will be appreciated that the system of the invention is applicable to man-made or natural fibres and the nature of fibre it is not intended to limit the scope of the application.

According to a second aspect of the invention there is provided a method for producing yarn, the method comprising: (i) feeding fibres on to a surface; (ii) forming a consolidated ribbon of said fibres on said surface; and (iii) taking off said ribbon from said surface in the form of a yarn, said taking off including the formation of a twisted yarn downstream of said surface.

According to a third aspect of the invention there is provided a friction spun yarn having a high proportion of straight fibres substantially free from loops and entanglements.

According to a fourth aspect of the invention there is provided a product produced by the method of any the invention.

Preferably, the friction spun yarn of the third aspect of the invention and the product of the fourth aspect of the invention are for use in medical woven and/or knitted wound dressing structures.

Preferably, the friction spun yarn of the third aspect of the invention and the product of the fourth aspect of the invention comprise a single and/or bi-component yarn structure product produced by the system of the first aspect of the invention and/or by the method of the second aspect of the invention.

The invention will now be described by way of example only with reference to the following Figures wherein; Figure 1 illustrates a conventional friction spinning system, Figure 2 illustrates a friction spinning system according to the present invention, and Figure 3 illustrates a diagrammatic representation of Figure 2.

With reference to Figure 1 there is shown a conventional friction spinning machine 1, comprising a feeding roller 2 rotating in direction A and feeding fibre 4 to a spiked fibre opening roller 6 rotating in opposed direction B. Fibres are separated into single strands 8 and carried in an air flow duct 10 towards rollers 12 and 14. Roller 14 is perforated on its surface and an internal suction force allows for collection of fibre strands. Roller 12 is a plasma coated solid roller which rotates in the same direction as perforated roller 14. The rollers 12 and 14 are mounted along side each other in non-abutting relationship typically being set to be 0.1-0.2 mm apart. Fibres landing between the rotating rollers 12 and 14 at area 16 join the end of yarn arm 18.

Yarn arm 18 is rotating due to the relative motion of rollers 12 and 14 and frictional contact between the fibres and the roller surfaces, the yarn arm 18 emerges in yarn take off direction C. In this way a continuous yarn forming process is achieved in which fibres land and are deposited the surfaces of rollers 12 and 14 and the yarn simultaneously twists. In order to overcome the problems associated with simultaneous deposition and twisting of yarn fibres as herein before discussed, the

system of the present invention provides for these two processes to be conducted as discrete and independent operations.

In the system according to the present invention, with reference to the representation of Figure 2, there is shown an air flow duct 10 feeding a continuous separated stream of fibres 8 towards rollers 24 and 22. Fibres are separated in a conventional manner by a process similar to that of Figure 1 by means of a feeder roller and spiked fibre opening roller (not shown). Roller 22 is perforated and provided with a suction force so as to collect fibres on its surface, however unlike conventional roller arrangements roller 22 is positioned so as to be in contact the surface of roller 24 along region 26.

The area of contact 26 of the rollers creates a positive nip, thus the fibre deposition/landing area is located behind the central axis of rollers 22 and 24 and in front of the roller nip. Rollers 22 and 24 and mounted in side by side relationship with perforated roller 22 being positioned beneath roller 24. Moreover, rollers 22 and 24 are adapted so as to counter rotate in directions D and E. By the continuous landing of fibres on rollers 22 and 24, a ribbon of fibres 26 is formed immediately behind the nip-line and is held to the surface of roller 22 by the suction force.

Counter rotation of rollers 22 and 24 in directions D and E causes ribbon 26 to continuously pass between the roller nip whereby the ribbon is consolidated to some extent before it emerges at point 30. The ribbon 26 is then passed to a pair of twisting rollers 32 and 34 which are mounted a discrete distance along the direction of yarn take off F. Twisting rollers 32 and 34 are mounted perpendicular to the roller nip and a yarn 20 is formed as the twist runs up in to the roller nip so as to roll the emerging ribbon 26 in to yarn 20. The twisting rollers are mounted co-axially with respect to rollers 22 and 24 and yarn 20 is formed as the twist propagates along the nip line thus rolling up ribbon 26 into a coherent form.

With reference to Figure 3 there is shown a plan view of the system of the present invention wherein the continuous stream of fibres 8 form ribbon 26. Ribbon 26 is

then twisted by twisting rollers 32 and 34 which counter rotate in directions G and H thus forming yarn 20 which is collected on spool 36.

The present invention therefore provides a system for producing yarn with aligned fibres that are highly orientated in the direction of yarn take-off. A high proportion of straight fibres, free from proportion of straight fibres, free from loop or entanglements result in the final yarn thus increasing yarn strength and quality.