GB1574531A

GB1574531A - Open-end spinning

Info

Publication number: GB1574531A
Application number: GB1269577A
Authority: GB
Original assignee: Barmag Barmer Maschinenfabrik AG
Current assignee: Oerlikon Barmag AG
Priority date: 1976-03-27
Filing date: 1977-03-25
Publication date: 1980-09-10
Also published as: CS209436B2; JPS6113005B2; GB1574533A; JPS61179325A; DE2613263A1; GB1574532A; JPS6330412B2; JPS6330411B2; JPS61179324A; DE2613263B2; IT1078000B; GB1574534A; CS215121B2; BR7701876A; JPS52140640A; CS215122B2

Description

(54) OPEN-END SPINNING (71) We BARMAG BARMER MASCHINENFABRIK AKTIENGESELLSCHAFT, a body corporate organised under the laws of Germany, of Remscheid-Lennep, Federal Republic of Germany, 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: This invention relates to a method of open-end spinning.

In one method of spinning (Melliand Textilberichte 1975, Volume 9, page 690 et seq), a card sliver composed of staple fibres is separated into its individual fibres by means of a rapidly rotating carding roller and then transferred to a rotating cylindrical sieve drum. On the inside of this drum is a suction pipe which opens along a generatrix of the internal surface of the drum. The air suction produced by this pipe forces the staple fibres against the external surface of the sieve drum and should in addition hold the fibres on the above mentioned external generatrix of the drum. The rotation of the sieve drum introduces a moment of torsion into the spinning web, whereby the individual fibres are grouped together to form a bundle along the line of yarn formation and formed into a yarn by a true twist.The disadvantage of this arrangement is that the individual fibres only have an unstable position on the aforesaid generatrix. They will depart from this generatrix and the spinning process will break down if the speed of rotation of the sieve drum, the current of air produced by suction and the denier of the spun yarn are not correctly adjusted to each other or are subject to fluctuations. Moreover, the air current produced by suction counteracts the rotation of the yarn forming on the generatrix because on one side of this bundle the current flows in opposite direction to the rotation.The same principle has also been described in German Offenlegungsschrift No. 2361 313, in which air suction is again provided to produce an air current which has a powerful component of flow against the direction of the moving surface but which opposes the forces of torsion which effect twisting of the yarn.

A process for spinning textile fibres has been disclosed in German Offenlegungsschrift No. 2449 583, in which the fibres are twisted into a sliver in the nip between two sieve drums rotating in the same sense about parallel axes. Inside each of these drums is an air suction device, the open end of which is directed towards the nip in which the yarn is formed. The air currents force the fibres against the walls of the drums in the region of the nip.

This method has the disadvantage that one of the sieve drums as well as the current of suction associated with this drum oppose the desired twisting of the sliver. Here again, stable conditions are difficult to achieve and only exist if the sliver or yarn is kept on the line of yarn formation by draw-off rollers arranged transversely to the nip.

It is an object of the present invention to provide a process which obviates the disadvantages described above. In particular, it is intended that the sliver should not be subjected to opposing forces of torsion by the moving surfaces or air currents. In addition, a more stable operating point should be obtained without the aid of thread guide elements and substantially independently of the given operating parameters.

According to the invention there is provided a method of spinning fibres to form a yarn, in which the fibres are twisted together between two adjacent air permeable surfaces which are moved in opposite directions and penetrated by respective air currents, wherein in the yarn formation zone the vectors of movement of the moving surfaces and of the air currents taken together encircle the line of yarn formation in a single sense of rotation.

The invention also provides an apparatus for spinning fibres to form a yarn, comprising two air permeable surfaces adapted to move in opposite directions, between which surfaces the fibres bundle is formed along a line in use of the apparatus, air suction devices on those sides of the moving surfaces which are remote from the yarn, each air suction device being arranged in front of the said line, based on the direction of movement of the surface behind which it is arranged.

In contrast to German Offenlegunsschrift No. 2449 583, in which it is necessary to form a nip between the moving surfaces, this is unnecessary although possible with the method and apparatus according to the invention. The suction devices according to the invention are arranged on both sides of the line of yarn formation and intersect only very slightly, if at all, in the zone between the moving surfaces where the line of yarn formation is to be situated. The surfaces moving in opposite directions may be formed by sieve belts moving in opposite directions or by sieve drums rotating in the same sense.

The forces acting on the fibres preferably also have components in the direction of feed of the yarn. This can be achieved particularly advantageously by means of sieve drums having the form of hyperboloids since such drums both orientate the individual fibres in the direction of the sliver which is to be formed and transport the fibres and the sliver. This is especially so if the sliver is clamped between the end plates of the hyperboloids. The distance between the sieve drums or moving surfaces in the region of the yarn outlet is preferably not smaller than the diameter of sliver which is to be formed. The distance is limited upwardly by the speeds of rotation obtainable since a large distance between the drum surfaces and the axis of the yarn and high yarn draw-off rates necessitate very high circumferential velocities of the sieve drums.

The invention can be used very advantageously for producing a yarn from fibres of different origins, for example natural fibres and synthetic fibres obtained from different raw materials or synthetic fibres differing in their properties may be mixed.

This combined mixing and spinning process may be used to produce core/sheath yarns with core fibres differing from the external fibres if the core fibres are carried to the line of yarn formation in front of the external fibres.

The moments of torsion exerted on the fibres or sliver by the apparatus of the invention should preferably be relatively small and the apparatus should not be used in all cases of very thick yarns or high twists for producing the entire moment of torsion required for twisting the yarn. In the case of such yarns additional twisting devices are therefore advantageously employed.

The invention will now be described with reference to the accompanying drawings, in which: Fig. I is an overall view of the spinning process; Fig. 2 is a sectional view of one embodiment in which the fibres are fed in from both sides; Fig. 2a is a similar view of another embodiment; Fig. 3 is a plan view of one form of the spinning process according to the invention showing a delivery action exerted on the sliver; Fig. 4 and Fig. 4a show two embodiments of a spinning apparatus which use the same principle as Fig. 3; Fig. 5 is a perspective view of an embodiment of spinning apparatus similar to Fig. 1 but using a needle; Fig. 6 is a perspective view of a spinning apparatus with a fibre feed device; Fig. 6a is a section through a spinning apparatus of Fig. 6; and Fig. 6b shows a modified fibre feed device.

Fig. 1 shows schematically sieve belts 1 and 2 which move in opposite directions 11 and 12. Air currents 3 and 4 which pass through the sieve belts are produced by air supply means 13 and 14. The individual fibres 5 are delivered to one or both sieve belts. Consider fibres which are first pressed against the sieve belt 2 by the air current 3. When these fibres enter the zone of the air current 4, they are pressed against the sieve belt I by this current. Since the belt 1 moves in the opposite direction to belt 2, these fibres are then carried back into the region of the first air current. This circular motion causes the fibres to be rolled up into a yarn or sliver 8.The vectors of motion of the sieve belts I and 2 and of the air currents 3 and 4, taken together, encircle the line of yarn formation 9 in the same sense, thereby ensuring that the sliver 8 has a stable position on the line of yarn formation 9. The resulting yarn 10 is continuously pulled out of the zone between the surfaces of the sieves by winding devices (not shown).

The embodiment shown in Fig. 2 comprises cylindrical sieve drums 1 and 2 which rotate in the same sense so that their surfaces move in opposite directions in the region of the line of yarn formation 9. On both sides of this line, suction devices 13 and 14 are arranged in their interior of the drums 1 and 2 respectively. Each of these suction devices produces an air current 3 or 4 penetrating the respective sieve drum.

The individual fibres are fed to the apparatus by a fibre feed device 6 or a fibre feed device 7 or both. The fibre feed devices 6 and 7 are in the form of channels each ending in a curved plate which terminates adjacent a respective one of the sieve drums 1 and 2. Transport of the individual fibres in the fibre feed devices can be effected by an injector 15. Each of the fibre feed devices 6 and 7 may have a carding roller of known construction arranged in front of it.

The individual fibres which have been transferred to the sieve drums 1 and 2 in the region of the air currents 3 and 4 by the fibre feed devices 6 and 7 are pressed against the drum surfaces by the air currents and carried into the zone of the line of yarn formation 9. The open ends of the suction devices overlap only slightly in the region of this line 9.

The directions of the vectors of movement of the drums indicated in Fig. 2 and the directions of the air currents combine to convert the individual fibres into a sliver along the line of yarn formation 9. The sliver formed along the line 9 is removed from the spinning zone, for example by means of a winding device, and may subsequently be subjected to further twisting by means of a suitable twisting device, optionally after the spinning device, to impart the desired twist. This twisting device may, for example, comprise three shafts rotating in the same sense and arranged at the corners of an isosceles triangle. Friction discs are mounted in the sequence of their sense of rotation on these shafts, the discs overlapping at the centre of the isosceles triangle.The sliver is passed through the centre of this triangle and the friction discs both twist the sliver and transport the sliver or the resulting yarn.

The narrowest gap between the sieve drums 1 and 2, which lies in the plane containing the axes of the sieve drums, is approximately equal to the diameter of the yarn which is to be formed, but at the yarn outlet it is preferably slightly smaller and in the region of the fibre inlet it is about 2 to 3 times greater than the diameter of the yarn to be formed. For the manufacture of cotton yarn Nm 10, the preferred measurements of the narrowest gap are 0.1 mm in the region of the yarn outlet and 0.5 mm in the region of the fibre inlet. For a cotton yarn Nm 20, the distance between the sieve rollers is preferably between 0.2 mm and 0.8 mm.

Fig. 2a shows an apparatus similar to that of Fig. 2 but in Fig. 2a fibres are supplied only through the fibre feed channel 6. It should be noted, however, that a second feed channel could also be provided in this case, as in Fig. 2. A particular feature of the apparatus shown in Fig. 2a is that the opening of a suction device 13 is arranged in front of the plane connecting the axes of the two rollers 1 and 2. An edge 16 of the opening, which determines the position of the line of yarn formation, is situated in front of the said plane, based on the direction of movement of the roller 1 which carries the fibres into the nip, by a distance equal to up to 10 times the diameter of the yarn. Another feature of the arrangement of Fig. 2a is that the area defined by the opening of a suction device 14 in the roller 2 slightly overlaps the area defined by the opening of the suction device 13.The distance between the edge 16 of the opening of the suction device 13 and an edge 17 of the opening of the suction device 14 in the region of overlap is equal to up to 10 yarn diameters. This arrangement of the openings of the suction devices ensures that the line of yarn formation will be situated before the narrowest part of the nip. This is advantageous, not only for stabilizing the line of yarn formation but also for increasing the moment of torsion to be introduced.

The principle of combined twisting and transport of the slivers is illustrated in Fig. 3. This shows the sieve belts 1 and 2 moving in parallel planes in the directions 11 and 12. The distance between the sieve belts is adapted to the diameter of the yarn. The suction devices 13 and 14 are arranged on the two sides of the line of yarn formation 9 optionally with slight overlapping of their openings. The maximum width of the overlap is 10 times the diameter of the yarn. The diameter refers, as before, to the completely twisted yarn, and is calculated according to the following formula:

wherein P is the specific gravity and Nm (metric number) the fineness of the yarn, measured in metres per gram.The individual fibres 5 are fed on to the belt 2 and may in addition be fed on to the belt 1, and they are forced against the belts by the suction devices. The slivers are then twisted on the principle already described above.

At the same time, the sieve belts 1 and 2 have a component of movement in the direction of transport. Viewed in top plan view, the sieve belts intersect at an angle 2a. The edges 16 and 17 of the openings of the suction devices 13 and 14, which edges define the line of yarn formation 9, are arranged on the bisector of this angle 2a or with a slight shift parallel thereto, so that the openings overlap. This shift from the bisector of the angle may also be up to 10d, where "d" is the yarn diameter. It should be mentioned that the air currents produced by the suction devices 13 and 14 may also have a component of movement in the direction of transport.

The principle shown by Fig. 3 can be realised in practice by the sieve drums of Fig. 4, which are formed as hyperboloids 31 and 32. These hyperboloids are so arranged that their axes lie in parallel planes or that each of them has a generating straight line parallel to the line of yarn formation 9. This means that if the two axes are projected on a plane, the angle between them is twice the angle fi at which each of the generating straight lines intersects its hyperboloid axis. The vectors of movement 11 and 12 of the surface velocities of the circumferential surfaces of the hyperboloids in the narrowest gap formed between the two parallel generating straight lines intersect at an angle 2a, which has already been defined.

The hyperboloids are so arranged that the narrowest gap between the adjacent generating straight line is substantially rectangular. The hyperboloid 31 is displaceable on the support 22 by means of a mounting 21 and is pivotal about an axis 24. It is therefore possible to adjust the width of the gap and/or to set the hyperboloid 31 at such an angle of inclination that the narrowest gap tapers towards the yarn outlet. The frictional forces exerted by the sieve drums on the sliver which is in the process of being compressed to a yarn consequently increase with progressive compression of the sliver. Excessive moments of torsion and forces of tension liable to tear the sliver are thereby prevented from acting on the sliver.At the same time, the tapering of the gap towards the yarn outlet ensures that sufficient torsion can be exerted to produce the required twist on the yarn leaving the spinning device. The dimensions of the narrowest gap are adjusted so that in the region where the fibres 20 are introduced the gap is twice as great whilst in the region of the yarn outlet it is smaller than the yarn diameter.

The drums 31 and 32 are driven in the directions 11 and 12 by drive motors 18 and 19. The suction devices 13 and 14 are situated on the insides of these drums, and the openings of the suction devices extend over part of the internal circumference of the drums 31 and 32 and end shortly before, on or behind the line of yarn formation 9. Slight overlapping is again preferred, the area of overlap being situated before the narrowest gap, on the fibre feed side. The fibre feed device (not shown in Fig. 4 consists of a channel extending into the narrowest gap between the drums 31 and 32 and having an opening in the form of a slit which extends over at least part of the length of the gap. The completely formed yarn is drawn off by winding devices 23 at a draw-off rate of Va, optionally via a delivery mechanism.

In operation, the surface velocity of the drums is carefully adjusted to the required twist and to the required yarn draw-off rate, and at the same time a compromise must be reached to allow for the amount of yarn tension which can be tolerated. The draw-off rate is particularly limited by the fact that the yarn must not be exposed to excessive tension but at the same time it must not become slack.

The desired value am depends on the envisaged use of the yarn.

Experiments carried out with an apparatus according to the invention having two slightly overlapping suction devices provided the following results: Two hyperboloids maximum diameter: 85 mm Width of gap: 0.3 mm Overlap of suction devices 0.9 mm Angle of intersection of the vectors of movement 2a 140 Yarn: Cotton, nominal staple 28 mm g m y = 1.54- No 24 gr a metric = metric twist multiplier = 120 (am is mainly a practical coefficient specific to the particular application of the yarn, used for calculating the twist T of the yarn according to the formula T = aHNm.) am is obtained from the particular use of the yarn. Experience has shown a suitable value to be between 100 and 150.

Draw-off rate Va = 300 m/min.

The factor varied in the experiment was the speed of rotation of the hyperboloids (u in m/min). This was done in such a manner that both hyperboloids had the same peripheral velocity at the point of yarn outlet. The properties measured were the yarn tension (P, measured in pond) at which the yarn was drawn from the apparatus, the twist per metre value (T, measured in twists per metre) actually achieved in the finished yarn, and the breaking length (km), and they were calculated within the optimum ranges determined by the following formulae: 4.25 x 10-3 xam xVa < U < 0.95 Va #γ x sin a cos a as the wider range and 4.25 x 10-3x am x Va x sin a + Va x cos a < u < 0.85 x Va g cos a as the narrower range.

It was found that advantageous surface velocities u could be obtained within the following ranges: 132 m/min < 220 m/min < u < 746 m/min < 833 m/min.

The experimental results are shown in the following Table:

u(m/min) 100 200 400 600 800 900 P (p) 55 32 28 22 19 15.7 T (I/m) 375 505 630 680 730 795 BREAKING LENGTH 5.7 9.2 11.8 11.2 10.2 8.4 (km) a (metric) 76.5 103 128.6 138 149 162 The experimental results show that excessively high circumferential velocities and excessively high twist reduce the strength of the yarn. Both these factors are deleterious for further processing. In the region of the lower limit, on the other hand, the twists produced were so low that sufficient strength could not be obtained.

The circumferential surfaces of the hyperboloids could, for example, be cut off in the normal planes along the lines 36 and 37 to produce an asymmetric structure.

This would be advantageous in cases where no tension was to be exerted on the resulting yarn.

Fig. 4a shows a spinning apparatus similar to that of Fig. 4. In Fig. 4a beadings 34 and 35 are placed on the end faces of the hyperboloid sieve drums on the outlet sides. These beadings serve to grip the sliver which is already fully twisted at this stage. In the region of the line of yarn formation, the hyperboloid sieve drums have a component of movement which causes twisting and another component of movement which transports the resulting sliver and the individual fibres. The transporting action is assisted by the beadings 34 and 35.

Such additional increase in the torque may be advantageous when a high torque is required to produce the necessary twist, as in the case of coarse fibres or a very high twist. In these cases, an additional false twister 33 may also be provided downstream of the spinning device.

It should also be mentioned with reference to Fig. 2 that the fibres may be supplied either from the fibre feed device 6 or from the fibre feed device 7 or from both. By supplying fibres from both feed devices 6 and 7 it is possible to produce mixed fibre yarns if fibres from one source are supplied through the fibre feed device 6 and fibres from another source are supplied through the fibre feed device 7. The spinning apparatus represented in Fig. 2 can therefore be used for both mixing and spinning individual fibres. The fibre feed devices 6 and 7 may be staggered in relation to the line of yarn formation or additional fibre feed devices may be provided behind the devices 6 and 7. In this way, it is possible to spin yarn in which the core differs from the external fibres in the origin of the individual fibres and the structure.In this way it is possible, for example, to produce fancy yarns with a core and sheath effect, (e.g. yarns having a core of man-made fibres for high strength and a sheath of natural fibres to improve other properties such as the appearance, handle, and moisture absorption).

As can be seen from Fig. 4 for example, the core of the yarn may be formed from a continuous filament for example a continuous synthetic filament supplied from above on the line of yarn formation 9 and passing between the surfaces. This method can be used to produce a spun yarn in which the core is made up of continuous filaments and the sheath is of staple fibres. The continuous filament is advantageously a textured filament with a three-dimensional crimp of the kind obtained, for example, by false twist texturing or air jet texturing.

In applying the invention to thick yarns and particularly thick yarns which are to be highly twisted, it has been found that the twist is not uniform over the crosssection of the yarn. It has been found that the more internally situated filaments of the sliver have a smaller number of twists per metre than the more externally situated filaments. To achieve uniform twisting across the section of the fibre even in the case of thick yarns, an additional torque may be introduced into the sliver by means of a rotating needle. In Fig. 5, which is otherwise similar to Fig. 1, the yarn 10 which has just been formed is continuously pulled out of the zone between the sieve surfaces 1 and 2 on one side of the sieve belts by winding devices (not shown).

A needle 123 rotatably mounted in bearings 124 and 125 is situated on the other side of the apparatus. The needle is driven by a motor 127 via a belt 128 and a pulley 126 in the direction in which the vectors of movement of the surfaces 1 and 2 and of the air current 3 and 4 encircle the line of yarn formation 9. The needle can be shifted axially (this is not shown in the figure) so that it can dip to varying extents into the region in which the fibres 5 are brought to the line of yarn formation 9.

Experiments have shown that it is most effective to dip the needle into the sliver to a depth of about 30 mm. In these experiments, the diameter of the needle was 1.5 mm and the needle tapered to a cone at its outer end over a length of about 10 mm.

The speed of rotation of the needle was 60,000 revs/min. A twist of 600 turns per metre could be achieved under these conditions. The yarn draw-off rate was 100 n/min.

It should be noted that the needle may also advantageously be mounted in two pairs of rotatable support rollers at least one of which is driven, the needle being held in the nip of each pair of support rollers by magnetic forces.

The needle 23 may be hollow, as shown in the drawing. A core yarn 30 can then be supplied through the needle 23. By being supplied inside the needle, this yarn forms the core of the complete yarn to be formed, and as such has a major influence in the textile properties, particularly the strength and elongation of the completed yarn. It should be mentioned here that the needle could be used with all the embodiments of the invention described in this specification.

Figs. 6 and 6a illustrate a spinning apparatus having a fibre feed device 45. The spinning apparatus comprises cylindrical rollers 41 and 42. The circumferential surfaces of the cylindrical rollers are perforated. The rollers are both driven to rotate in the same sense. The rollers contain air suction devices, of which the suction pipe connections 43 and 44 are shown in Fig. 6. The fibre feed device comprises a housing which, in the representation in Fig. 6 has been cut in a tangential plane. This housing is placed against the roller 41 in the narrowest gap between the rollers 41 and 42. A delivery roller 47 and a carding roller 48 are rotatably mounted in the housing of the fibre feed device and driven by motors and transmissions not shown in the drawing.

The delivery roller 47 pulls a sliver 46 into the fibre feed device and into the region of the circumference of the carding roller 48. The carding roller 48 is provided with teeth 53 on its circumferential surface. The teeth 53 serve to separate the individual fibres of the sliver 46 and carry them over the circumference of the carding roller to a channel inlet slot 51. The individual fibres are thrown into the inlet slot 51 by the centrifugal force and by the air current from an injector 49 which produces a vacuum in the channel inlet slot 51. Inside the inlet slot 51, these individual fibres are aligned substantially parallel to the axis of the carding roller.

The fibre feed channel becomes narrower both in the direction parallel to the axis of the carding roller and in its cross-section. The mouth 52 of the fibre feed channel is therefore situated parallel to the gap between the two rollers 41 and 42 and has length which is adjusted depending on the staple length. The length of the mouth 52 is at least one third of the air permeable length of the rollers 41 and 42. The mouth 52 is only a few millimetres (1 to 5 mm) wide.Due to the fact that the cross-section changes its form from the inlet slot 51 to the mouth 52 and diminishes in crosssectional area and due to the effect of the air currents from the injector 49, the individual fibres are turned and accelerated so that they are orientated to lie substantially in the same plane as the line of yarn formation and encounter this line, spaced apart from each other, at an angle of less than 30 . The fibres are then twisted together to produce the finished yarn 10. It should be mentioned that additional air channels may open into the fibre feed channel between the inlet slot 51 and the mouth 52. These air channels are so arranged that they reinforce the vacuum in the inlet slot 51, and favour the acceleration separation, turning and orientation of the fibres in the manner described above.

Fig. 6a also shows that the fibre feed channel has ribs 54 fanning out from the channel inlet slot 51. The ribs merge with the wall in gentle transitions, (see section) and low enough not to touch the opposite wall or opposite ribs. The ribs have the effect of causing the fibres to lie in a plane parallel to the line of yarn formation. In the end region 55 of the mouth 52, the plane in which the mouth lies is not parallel to the plane of the narrowest gap between the rollers 41 and 42 but at an angle thereto of 20 . This enables the air current produced in the fibre feed channel to escape against the direction of movement of the yarn 10 at the narrowest gap. The individual fibres are thereby stretched and orientated.If it is desired to use the apparatus of Fig. 6a to spin a core/sheath yarn, this can be done by adding an additional fibre feed device (indicated in dashed lines in Fig. 6a) to feed the sheath fibres, the core fibres being fed by the feed device indicated in solid lines.

Fig. 6b shows another embodiment of the fibre feed device, which has the advantage of promoting the orientation of the individual fibres parallel to each other and to the line of yarn formation and of promoting the stretching of the fibres. The structure of the fibre feed device is similar to that shown in Fig. 6a except that the mouth 52 of the channel is shifted by a considerable distance from the inlet slot 51 in the direction of yarn formation. The rear boundary 56 of the feed channel should make an angle E of less than 60 with the line of yarn formation while the front boundary 55 makes an angle S of less than 45" with the line of yarn formation.

Attention is drawn to our co-pending application Nos, 7911911, (Serial No.

1,574,533), 7911912 (Serial No. 1,574,534) and 7930910 (Serial No. 1,574,532) which are divided from this application and which include in their specifications material common to this application.

Claims

WHAT WE CLAIM IS:

1. A method of spinning fibres to form a yarn in which the fibres are twisted together between two adjacent air permeable surfaces which are moved in opposite directions and penetrated by respective air currents, wherein in the yarn formation zone the vectors of movement of the moving surfaces and of the air currents taken together encircle the line of yarn formation in a single sense of rotation.

2. A method according to claim 1, wherein the vectors of movement of the surfaces lie in planes parallel to the line of yarn formation.

3. A method according to either preceding claim wherein in the region of fibre feed, the distance between the surfaces at the line of yarn formation is not smaller than the thickness of the yarn which is to be formed.

4. A method according to any preceding claim, wherein the distance between the surfaces diminishes towards the yarn outlet along the line of yarn formation.

5. A method according to any preceding claim, wherein the distance between the surfaces at the yarn outlet is smaller than the diameter of the yarn being produced.

6. A method according to any preceding claim, wherein the distance between the surfaces in the region of the fibre feed is more than twice the yarn diameter.

7. A method according to any preceding claim, wherein the surfaces are cylindrical.

8. A method according to any preceding claim wherein the said vectors of movement have a component in the direction of delivery of the yarn.

9. A method according to any preceding claim, wherein the fibres are supplied in two parts, one from each side of a plane perpendicular to the said surfaces at the line of yarn formation.

10. A method according to Claim 9, wherein the two parts each consist of fibres which differ from one another in at least one property.

11. A method according to any preceding claim, wherein a plurality of fibre feed means is provided in the direction of the line of yarn formation over the range of operation of the surfaces.

12. A method according to any preceding claim wherein a continuous filament is supplied as a core filament on the line of yarn formation.

13. A method according to Claim 12, wherein the core filament is threedimensionally crimped.

14. A method according to Claim 1, wherein the vectors of movement of the surfaces cross over in the narrowest gap formed between them, and the boundary line determining the line of yarn formation lies substantially on the bisector of the angle of intersection.

15. A method according to any preceding claim, wherein a driven rotating needle is mounted coaxially to the twisting line in the region where the individual fibres encounter the surfaces, and the yarn being formed is additionally driven by the needle in the sense of rotation of the yarn.

16. A method according to Claim 15, wherein a core filament is carried into the axis of twist at constant velocity through a concentric longitudinal bore in the needle.

17. A method of spinning fibres, substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.

18. An apparatus for spinning fibres to form a yarn, comprising two air permeable surfaces adapted to move in opposite directions, between which surfaces the yarn is formed along a line in use of the apparatus, and air suction devices on those sides of the moving surfaces which are remote from the fibre bundle, each air suction device being arranged in front of the said line based on the direction of movement of the surface behind which it is arranged.

19. An apparatus according to claim 18, wherein the moving surfaces are perforated surfaces of bodies of rotation, a suction device being arranged in each of the bodies of rotation, the mouth of each suction device extending over part of the internal circumference and in the direction of the said line.

20. An apparatus according to claim 19 when in use, wherein the mouths of the suction devices overlap by a width of up to ten times the yarn diameter.

21. An apparatus according to claim 20, when in use, wherein the area of overlap, viewed in the direction of fibre feed, is arranged in front of the narrowest gap.

22. An apparatus according to claim 21, when in use, wherein the area of overlap is arranged in front of the narrowest gap by an amount equal to ten times the yarn diameter.

23. An apparatus according to any one of claims 19 to 22, wherein the axial distance and/or the position of the axes of the bodies of rotation is adjustable.

24. An apparatus according to any one of claims 19 to 23, wherein the axes of the bodies of rotation are arranged to cross each other in such a manner that the narrowest gap diminishes towards the yarn outlet.

25. An apparatus according to any one of claims 19 to 24, wherein the diameter of the bodies of rotation continuously decreases towards the yarn outlet.

26. An apparatus according to any one of claims 18 to 25, wherein a respective fibre feed device is arranged on each side of a plane perpendicular to the said surfaces at the line of yarn formation.

27. An apparatus according to any one of claims 18 to 25, wherein a plurality of fibre feed devices is arranged along the line of yarn formation.

28. An apparatus according to any one of claims 18 to 27, wherein the moving surfaces are the surfaces of hyperboloidal bodies whose axes are arranged to cross over each other so that the line of yarn formation is parallel to a generating line from each of the hyperboloids, a fibre feed channel being provided whose mouth lies parallel to the line of yarn formation.

29. An apparatus according to claim 28, wherein discs are mounted on the said bodies at the yarn outlet end, the diameter of the discs being greater than the diameter of the cross-section of the hyperboloids.

30. An apparatus according to claim 28 or 29, wherein the hyperboloidal bodies are asymmetric in such a manner that they have no plane of symmetry perpendicular to their axis.

31. An apparatus according to claim 30, wherein the said bodies have a smaller diameter at the yarn outlet than in the region of fibre input.

32. An apparatus according to Claim 31, when in use, wherein the circumferential velocity u of the surfaces of the hyperboloids at the yarn outlet is within the range represented by the formula: am X Va Va

4.25 x 10-3 x < u < 0.95 v/xsina cosa wherein: am, V and a are as hereinbefore defined, and y is the density of the fibres.

33. An apparatus according to Claim 32, wherein the circumferential velocity of the surfaces of the hyperboloids is within a range represented by the formula: amx Va x sin a Va

4.25 x 103 x ----- + V a x cos a < u < 0.85 x cos a

34. An apparatus according to any one of Claims 18 to 33, comprising a needle which is drivable in the sense of yarn twisting by a motor, the needle being mounted in such a manner that its axis lies on the line of yarn formation and its tip extends into the region of the fibre feed.

35. An apparatus according to Claim 34, wherein the needle is hollow and means are provided for supplying a core fibre through the needle.

36. An apparatus according to Claim 19 or any one of Claims 20 to 35 as dependent on Claim 19, wherein to feed fibres to the yarn formation line, a fibre feed device is provided which comprises a housing with a cylindrical chamber whose axis, viewed in normal projection, is perpendicular to the axes of the bodies of rotation and in which a rotatably driven carding roller is mounted, a channel for introducing a card sliver which channel opens into the chamber, a fibre feed channel extending substantially from the carding roller to the narrowest gap between the bodies of rotation and having a rectangular fibre inlet slot which connects the chamber with the fibre feed channel, and the long side of which extends along the axial length of the carding roller, the said fibre feed channel having an opening the width of which is substantially equal to the width of the narrowest gap and the length of which is at least one third of the axial length of the air permeable wall of the bodies of rotation and the opening plane of which is inclined to the narrowest gap at an angle of between 0 and 20 towards the yarn outlet and means for producing a vacuum in the fibre inlet slot and for producing an air current from the fibre inlet slot to the mouth the surface area of the cross section of the fibre feed channel diminishing between the fibre inlet slot and the mouth.

37. An apparatus according to claim 36, wherein ribs are arranged in a fan formation in the fibre feed channel on at least one of the boundary surfaces which extend from the broad side of the fibre inlet slot to the long side of the mouth, the height of the said ribs being less than the width of the mouth.

38. An apparatus according to claim 36 or 37, wherein the front boundary of the fibre feed channel makes an angle of less than 45 , and the rear boundary makes an angle less than 600, with the line of yarn formation.

39. An apparatus according to any preceding claim, with a twister arranged downstream of the apparatus.

40. An apparatus according to claim 41, wherein the twister is adapted to impart a component of movement in the direction of yarn delivery.

41. An apparatus for spinning fibres to form a yarn, substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.