Spinning device and method of making yarn

Abstract

A spinning device is provided in which at least one sliver is opened to single fibers and the single fibers are deposited on a moveable collecting surface in the form of a spread out fiber veil. During transport on the collecting surface, the fiber veil is condensed transversely to its direction of movement to a fiber strand. The now roving-like fiber strand is transported through a nipping line and twisted to a thread by a twisting nozzle. On the side facing away from the fiber veil, a suction opening is arranged at the perforated collecting surface, one side edge of said suction opening extending in the direction of movement of the collecting surface while the other side edge is arranged hereto at an acute angle.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] This application claims the priority of Germany, filed Dec. 13, 2001, the disclosure(s) of which is (are) expressly incorporated by reference herein.

[0002] The present invention relates to a spinning device comprising an opening roller for opening at least one sliver to single fibers, a driven, air-permeable collecting surface arranged directly adjacent to the opening roller and in the direction of motion of the single fibers for taking over the single fibers in the form of a wide fiber veil, a suction opening for condensing the fiber veil to a narrow fiber strand, said suction opening being covered by the collecting surface and tapering by means of two side edges in the direction of motion of the collecting surface from a starting width corresponding to the width of the fiber veil to a narrow suction slit, a nipping line provided at the end area of the suction opening for nipping the condensed fiber strand, and a twisting nozzle directly downstream of the nipping line for twisting the fiber strand to a thread.

[0003] A spinning device of this type is prior art in U.S. Pat. No. 6,058,693. This spinning device operates with a suctioned opening roller, whereby the purpose of the suction is to keep the surface speed of the opening roller low, so that the single fibers, while being combed from at least one sliver, are not accelerated greatly. If this were not the case, there would be the risk that the end speed of the spun thread would increase endlessly, as the fiber material in the case of the known spinning device is sucessively accelerated during transport. The opening roller transfers the single fibers at a relatively low speed to a collecting surface which moves at a somewhat faster speed; the suction opening arranged thereto tapers in the direction of motion of the collecting surface in such a way that the single fibers are laterally condensed and the original fiber veil is finally bundled to a roving-like fiber strand. Nowhere during this entire process is the fiber material bunched. The condensing process ends at the latest at the nipping line, and thereafter, in order to form a thread, the fiber strand is given its spinning twist by means of a twisting nozzle. A thread is produced which has a similar character to that known from so-called air jet spinning. The spun thread does not, therefore, have an absolutely pure open-end character.

[0004] The side edges of the suction opening of the known spinning device extend each at an acute angle to the direction of motion of the collecting surface and approach each other in a V-shape. The direction of motion of the collecting surface generates on the single fibers of the fiber veil a transport component towards the nipping line on the one hand, while on the other hand on the edge areas of the fiber veil, as a result of the transversely extending side edges, a transverse component is generated, which strives to roll in the single fibers travelling along the side edges. As both side edges extend transversely in relation to the direction of motion of the collecting surface, the lateral fibers of the fiber veil are rolled in in different directions of torsion. This has a negative effect, in particular in the end area of the suction opening, which tapers to a sucion slit.

[0005] It is an object of the present invention to improve the above described arrangment while retaining the advantages thereof, namely in that a counter-rolling in of the single fibers located at the edges of the fiber veil is prevented.

[0006] This object has been achieved in accordance with the present invention in that one side edge of the suction opening extends in the direction of motion of the collecting surface and the other side edge is arranged at an acute angle to the direction of motion of the collecting surface.

[0007] On that side edge of the suction opening, which extends in the direction of motion of the collecting surface, the single fibers are now no longer rolled in, as the transverse movement caused by the movement of the collecting surface is no longer present. The entire condensing is thus effected by the other side edge extending at an acute angle to the direction of motion of the collecting surface, whereby rolling in of the single fibers is now only possible in one direction of torsion, and becomes more intensive the more the fiber veil is condensed to a narrow and roving-like fiber strand. The condensed fiber strand, when it reaches the nipping line and before it receives its spinning twist, thus has a very uniformly pre-twist character. The pre-twist is above all present in the core of the fiber strand, that is, exactly there, where, in the case of a twist being imparted by means of a twisting nozzle, the twist does not reach the entire fiber strand.

[0008] In an advantageous feature of preferred embodiments of the present invention, the one side edge, which extends in the direction of motion of the collecting surface, enables the collecting surface to be provided outside of the area of the suction opening along its side edge extending in its direction of motion with a reinforcement to prevent deformation.

[0009] Such a reinforcement is then practical when the nipping line is not formed by means of a separate nipping roller pair, but rather in that a nipping roller is disposed directly onto the collecting surface. The suctioned collecting surface itself should be as thin-walled as possible, so that the suction bore holes are as short as possible. Thanks to the one side edge, extending transversely, of the suction opening, the nipping line, which can cause deformation in the collecting surface, can be deposited in the area of the straight edge, where reinforcements are possible in the interior without the suction being impaired hereby. A reinforcement of this type contributes to the good concentric running of the collecting surface, insofar as this is in the form of a tranport roller.

[0010] It is practical when the suction opening in the area of its starting width is provided with side edges parallel to one another, and directly downstream thereof with side edges which form an acute angle to one another, and in the area of the nipping line again is provided with side edges parallel to one another which form the narrow suction slit. The single fibers, created by the opening roller, can thus be transfered in a controlled manner initially in their entire width onto the collecting surface, so that a spread fiber veil is formed. Only then is the fiber veil condensed to a fiber strand. Subsequently, at the suction slit, which borders the suction opening, there is a sufficiently bundled fiber strand.

[0011] It can be practical when the suction opening is successively connected to a plurality of suction chambers at different pressure levels. At the end area of the nipping line, where, because of the closeness of the single fibers to one another condensing is particularly intensive, a particularly strong low pressure is needed. The entire rest area of the collecting surface can be suctioned normally. It may be additionally provided that the collecting surface in the area of the transfer of the single fibers from the open roller is more strongly suctioned.

[0012] In a further advantageous feature of preferred embodiments of the present invention it is provided that a cover is arranged adjacent to the collecting surface which covers the fiber veil and fiber strand without touching it and which cover is adapted to the extenion of the side edges of the suction opening. On the one hand this creates in the area of the side edges a transverse air stream which condenses the fiber veil laterally, while on the other hand the spinning arrangement can be cleaned by an air stream without the spinning process being disrupted.

[0013] The side edge, which extends in an acute angle towards the direction of motion of the collecting surface, does not by any means have to be straight. Rathermore, in order to achieve a more compact design, it can be practical that the acute angle of said side edge not extending in the direction of motion of the collecting surfaces is continuously enlarged and thus has a curved gradient.

[0014] These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings.

[0015] Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a side view of a spinning arrangement constructed according to preferred embodiment of the present invention;

[0017] FIG. 2 is a view of the spinning arrangement in the direction of the arrow II of FIG. 1; and

[0018] FIG. 3 is a view similar to FIG. 2 of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] The spinning arrangement according to FIGS. 1 and 2 comprises a feeding device 1, to which at least one sliver 2 is fed in feed direction A. The feeding device 1 is arranged directly upstream of an opening device 3, which opens the at least one sliver 2 to single fibers 4. The single fibers 4 are subsequently transfered to a collecting surface 6 of a transport roller 5. The open single fibers 4 are taken up on the collecting surface 6 in the form of a wide fiber veil 7 and laterally condensed to a fiber strand 9 in a way to be described below.

[0020] The condensed fiber strand 9 is lightly pressed against a nipping line 8 by means of a nipping roller 10 onto the collecting surface 6. Directly downstream thereof, a twisting nozzle 11 is arranged, in which the twist of the thread 12 to be spun is generated. The thread 12 is withdrawn in withdrawal direction B by a delivery roller pair 13.

[0021] The feeding device 1 comprises a feed roller 14, which is driven in rotational direction C. A feed table 15 is arranged at the feed roller 14, said feed table 15 being hinged around a swivel axle 16 and being pressed against the feed roller 14 by the pressure of loading spring 17. A feed funnel 18 is arranged upstream of the feed roller 14, which feed funnel 18 advantageously comprises a plurality of feed channels in the case of a plurality of slivers 2 being fed hereto. Alternatively, a broad band sliver of fiber material is also possible.

[0022] The opening device 3 comprises an opening roller 19, which is driven in the same rotational direction D as the feed roller 14. The periphery of the opening roller 19 comprises a toothed combing structure 20, the front of teeth of the combing structure having an advantageous negative front angle.

[0023] The opening roller 19 has an effective width X, which corresponds to the width of the fed sliver 2 or slivers 2.

[0024] In the inside of the opening roller 19, a suction device 21 is located, which is connected to a vacuum source (not shown). By means of a perforation located on the periphery of the opening roller 19, suction is generated against the sliver 2 to be opened, which sucks the sliver 2 deep into the toothed combing structure 20, even when the opening roller 19 is driven at a relatively low speed. The suctioned area 22 extends over an angle of 45° to 90°, that is, as far as the single fibers 4 are to be transported on the periphery of the opening roller 19.

[0025] The transport roller 5 is driven in rotational direction E. Its effective width Y corresponds to the width of the transfered fiber veil 7. The transport roller 5 is provided with a perforation on its periphery, which permits suction from the outside inwards. The suction area 23 of the transport roller 5 begins approximately there where the suction area 22 of the opening roller 19 ends. The suction opening 24 belonging to the suction area 23 comprises side edges 25 and 26, which are denoted in FIG. 2 by dash lines, whereby it can be seen that the suction area 23 tapers in the direction of motion of the collecting surface 6. The side edges 25 and 26 of the suction opening 24 thus form means for condensing the single fibers 4 transversely to their direction of motion to a roving-like fiber strand 9.

[0026] The nipping roller 10 comprises a base body, which is provided on its periphery with a flexible coating. The axle 27 of the nipping roller 10 is swivellingly mounted (not shown), so that the nipping roller 10 can be pressed lightly against the collecting surface 6.

[0027] The nipping roller 10, which, in the embodiments according to FIGS. 1 and 2, is arranged parallel to the axis of the transport roller 5, defines together with the transport roller 5 a nipping line 8 for the condensed fiber strand 9. The suction area 23 condenses to a fiber strand 9 the initially spread out fiber veil 7 transversely to its direction of motion, in conditions similar to be found in a classical drafting unit, so that the fiber strand 9 can, in this form, enter the twisting nozzle 11 in a way known in so-called air jet spinning. The fiber strand 9 is thus spun to form a thread 12.

[0028] The delivery roller pair 13 arranged downstream of the twisting nozzle 11 delivers the spun thread 12 in delivery direction B to a winding device (not shown), where the thread 12 is wound to a cross package.

[0029] The geometrical arrangement of the spinning device is such that the collecting surface 6 of the transport roller 5 is so closely adjacent to the periphery of the opening roller 19 that the single fibers 4 can be easily transfered at the end of the suction area 22 in the form of a fiber veil 7 to the collecting surface 6. The circumferential speed of the transport roller 5 is somewhat greater than the speed of the in-coming single fibers 4.

[0030] The effective width X of the opening roller 19 and the effective width Y of the transport roller 5 is so chosen that either a very wide sliver 2, or a plurality of normal slivers 2, or a broad band sliver can be fed. It is advantageously provided that the fiber veil 7 comprises in its width a number of single fibers 4 which approximately corresponds to the number of fibers present in the cross section of the thread 12.

[0031] The transport roller 5 should have a sufficiently large diameter of approximately 100 to 150 mm, so that the tapering of the suction area 23 does not have to occur too spontaneously.

[0032] The nipping roller 10, as well as the delivery roller 13 should have the largest possible diameters because of the expected wear which occurs at high spinning speeds. The nipping roller 10 need not be pressed strongly against the collecting surface 6, as the nipping roller 10 does not perform any drafting funtion, as opposed to the delivery roller of a classical drafting unit. The nipping roller 10 simply regulates the condensed fiber strand 9, which subsequently enters the twisting nozzle 11.

[0033] Thanks to its perforation, the peripheral speed of the opening roller 19 is less than those opening rollers used in open-end rotor spinning. As the end of the sliver 2, the so-called fiber beard, is pulled deep into the toothed combing structure 20, an intensive combing takes place. Because of the negative front angle of teeth, the single fibers 4 at the end of the suction area 22 are transfered very quickly to the collecting surface 6, as a negative front angle strives to convey the transported single fibers 4 outwards.

[0034] The peripheral speed of the transport roller 5 is, as mentioned above, somewhat greater than the speed of the single fibers 4 accelerated by the opening roller 19. The peripheral speed of the delivery roller pair 13 is in turn greater than the peripheral speed of the transport roller 5. This means that the single fibers 4 are constantly accelerated somewhat during the entire spinning process, which is advantageous for their parallel position.

[0035] The fiber veil 7 desposited on the collecting surface 6 is initially quite wide; on the transport roller 5 however, it is successively narrowed and thus to a large extent condensed, so that it can enter the twisting nozzle 11 easily.

[0036] To this point in the description of the drawings, the spinning arrangement according to the present invention corresponds to a large extent to that of the above described prior art. In the case of the known spinning device, the side edges of the suction opening extend V-shaped towards one another in such a way that both side edges form an acute angle in the direction of motion of the collecting surface. This results in the disadvantage described above.

[0037] In the spinning arrangement according to the present invention, it is provided, in contrast to the spinning arrangement described above, that the side edge 25 of the suction opening 24 extends in the direction of motion of the collecting surface 6 and that the other side edge 26 is arranged at an acute angle α thereto. In this embodiment, the side edges 25 and 26 extend in a V-shape towards one another, but with the advantage that, at the edge of the fiber veil 7, only those single fibers 4 which travel along the side edge 26 are rolled in by the transverse force generated by the collecting surface 6. When the fiber veil 7 is bundled to a fiber strand 9, all single fibers 4 are rolled in in the same rotational direction. This is advantageous with regard to the quality of the spun thread 12.

[0038] The starting width of the suction opening 24 defines the effective width Y of the transport roller 5 and the collecting surface 6 and corresponds initially to the width of the fiber veil 7 taken up from the opening roller 19. The end area of the suction opening 24 is just a relatively narrow suction slit 28, which is adapted to the fiber strand 9 to be condensed.

[0039] The side edge 25 extending exactly in the direction of motion of the collecting surface 6 makes it possible, in an advantageous embodiment, to provide the edge area of the transport roller 5 directly adjacent to the side edge 25, but still outside of the suction area 23, with a reinforcement 29, for example, by means of applying a side rim. In this way, the nipping roller 10 can not only press against the collecting surface 6 from the outside, but can also press against the area provided with the reinforcement 29 which prevents the collecting surface 6 from deforming due to the nipping pressure of the nipping roller 10.

[0040] As can be seen from FIG. 2, the side edge denoted with the number 26 actually comprises three consecutive side edges 30, 31, 32. The side edge 30 is located directly downstream of the opening roller 19 and extends parallel to other side edge 25, so that the suction opening 24 initially has a constant width for the proper take-over of the fiber veil 7. Only subsequently, along the side edge 31, does the actual bundling to a fiber strand 9 take place. In the end area of the suction opening 24, the side edges 25 and 32 extend again parallel to one another.

[0041] As can be seen from FIG. 1, the suction opening 24 is successively connected in a plurality of suction chambers 33, 34, 35 to differing levels of pressure. The middle suction chamber 34, which takes up the largest area, has a normal, relatively slight low pressure, while the suction chambers 33 and 35, belonging to the end areas of the suction opening, have a relatively strong low pressure. At the suction chamber 33, the single fibers 4 must be taken from the opening roller 19 and transfered to the collecting surface 6, while an increased low pressure is required at the suction chamber 35, as here the fiber veil 7 is, to a large extent, already condensed to a roving-like fiber strand 9.

[0042] Furthermore, it can be seen in FIG. 1 that a cover 36 is arranged adjacent to the collecting surface 6, which cover 36 covers the fiber veil 7 or the fiber strand 9 without touching it and which is adapted to the line of the side edges 25 and 26. On the one hand, this prevents the spinning process from being disrupted when a known traveling clearer is activated, while on the other hand in the area of the side edges 25 and 26 a transverse air stream is generated, which supports the pushing together of the single fibers 4 to fiber strand 9.

[0043] The variation according to FIG. 3 as described below deviates from the embodiments 1 and 2 described above in several details.

[0044] According to FIG. 3, a very wide feed roller 314 is provided, with which a sliver 302 is fed in feed direction A in the form of a broad band sliver. The opening roller 319 is also suctioned and designed as a slow-speed roller.

[0045] The single fibers 304 released from the sliver 302 reach the collecting surface 306, which rotates somewhat faster than the opening roller 319, in the form of a spread-out fiber veil 307. As explained above, a perforated transport roller or an air-permeable transport belt, for example a sieve belt or a lattice belt, can be involved. In particular in the latter case it is practical to design the transport belt as a relatively stiff skeleton and to provide it with a fine-perforated covering.

[0046] In the embodiment according to FIG. 3, the side edge 325 of the suction opening 324 extends again parallel to the direction of motion of the collecting surface 306, while the other side edge 326 is again arranged thereto at an acute angle α, deviating, however from the embodiment according to FIGS. 1 and 2 in such a way that the acute angle α becomes increasingly larger. The side edge 326 is thus designed as a continuously curving edge. The suction opening 324 also ends here in a narrow suction slit 328, which is adapted to the condensed fiber strand 309.

[0047] Deviating from the embodiment according to FIGS. 1 and 2, the variation according to FIG. 3 does not show a nipping roller directly disposed on the collecting surface 306, but rather a nipping roller pair 310, which has no direct contact with the collecting surface 306. Here the necessary nipping line 308 is formed by the nipping roller pair 310, through which the fiber strand 309 travels. Downstream thereof is again a twisting nozzle 311, in which the thread 312 receives its final spinning twist. The thread 312 is then withdrawn by a delivery roller pair 313 and fed in delivery direction B to a winding device (not shown).

[0048] It should be expressly mentioned at this point that such features, which differ on the one hand in FIGS. 1 and 2 and on the other hand in FIG. 3, can be exchangeable. For example, in the embodiment according to FIG. 3, a cover for the fiber veil 307 is possible, and in addition the suction area can be divided into different suction chambers. On the other hand it is possible in the embodiment according to FIGS. 1 and 2 to provide a separate nipping roller pair for the nipping line 8, or to design the collecting surface 6 as the surface of an air-permeable transport belt.

[0049] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

1. Spinning arrangement comprising: an opening roller for opening at least one sliver to single fibers, a driven, air-permeable collecting surface arranged directly adjacent to the opening roller and in the direction of motion of the single fibers for taking over the single fibers in the form of a wide fiber veil, a suction opening for condensing the fiber veil to a narrow fiber strand, said suction opening being covered by the collecting surface and tapering by two side edges in the direction of motion of the collecting surface, from a starting width corresponding to the width of the fiber veil to a narrow suction slit, a nipping line, provided at the end area of the suction opening for nipping the condensed fiber strand, and a twisting nozzle arranged downstream of the nipping line for twisting the fiber strand to a thread, wherein one side edge of the suction opening extends in the direction of motion of the collecting surface and the other side edge is arranged at an acute angle (α) to the direction of motion of the collecting surface.

2. A spinning arrangement according to claim 1, wherein the collecting surface is provided outside of the area of the suction opening with a reinforcement against deformation along the side edge extending in the direction of motion of said collecting surface.

3. A spinning arrangement according to claim 1, wherein the suction opening is provided in the area of its starting width with side edges parallel to one another, directly downstream thereof with side edges enclosing an acute angle (α) and in the area of the nipping line with parallel side edges which form the narrow suction slit.

4. A spinning arrangement according to claim 2, wherein the suction opening is provided in the area of its starting width with side edges parallel to one another, directly downstream thereof with side edges enclosing an acute angle (α) and in the area of the nipping line with parallel side edges which form the narrow suction slit.

5. A spinning arrangement according to claim 1, wherein the suction opening is successively connected to various levels of pressure in a plurality of suction chambers.

6. A spinning arrangement according to claim 2, wherein the suction opening is successively connected to various levels of pressure in a plurality of suction chambers.

7. A spinning arrangement according to claim 3, wherein the suction opening is successively connected to various levels of pressure in a plurality of suction chambers.

8. A spinning arrangement according to claim 4, wherein the suction opening is successively connected to various levels of pressure in a plurality of suction chambers.

9. A spinning arrangement according to claim 1, wherein a cover, adapted to the course of the side edges of the suction opening is arranged adjacent the collecting surface, said cover covering the fiber veil and the fiber strand but not coming into contact therewith.

10. A spinning arrangement according to claim 2, wherein a cover, adapted to the course of the side edges of the suction opening is arranged adjacent the collecting surface, said cover covering the fiber veil and the fiber strand but not coming into contact therewith.

11. A spinning arrangement according to claim 3, wherein a cover, adapted to the course of the side edges of the suction opening is arranged adjacent the collecting surface, said cover covering the fiber veil and the fiber strand but not coming into contact therewith.

12. A spinning arrangement according to claim 4, wherein a cover, adapted to the course of the side edges of the suction opening is arranged adjacent the collecting surface, said cover covering the fiber veil and the fiber strand but not coming into contact therewith.

13. A spinning arrangement according to claim 5, wherein a cover, adapted to the course of the side edges of the suction opening is arranged adjacent the collecting surface, said cover covering the fiber veil and the fiber strand but not coming into contact therewith.

14. A spinning arrangement according to claim 1, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

15. A spinning arrangement according to claim 2, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

16. A spinning arrangement according to claim 3, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

17. A spinning arrangement according to claim 4, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

18. A spinning arrangement according to claim 5, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

19. A spinning arrangement according to claim 9, wherein the acute angle (α) of the side edge not extending in the direction of motion of the collecting surface becomes increasingly larger in a travel direction of said fiber vail.

20. A spinning arrangement according to claim 1, wherein a separate nipping roller pair is provided for the nipping line.

21. A spinning arrangement according to claim 2, wherein a separate nipping roller pair is provided for the nipping line.

22. A spinning arrangement according to claim 3, wherein a separate nipping roller pair is provided for the nipping line.

23. A spinning arrangement according to claim 4, wherein a separate nipping roller pair is provided for the nipping line.

24. A spinning arrangement according to claim 5, wherein a separate nipping roller pair is provided for the nipping line.

25. A spinning arrangement according to claim 9, wherein a separate nipping roller pair is provided for the nipping line.

26. A spinning arrangement according to claim 14, wherein a separate nipping roller pair is provided for the nipping line.

27. A method of making yarn utilizing a spinning arrangement comprising: an opening roller for opening at least one sliver to single fibers, a driven, air-permeable collecting surface arranged directly adjacent to the opening roller and in the direction of motion of the single fibers for taking over the single fibers in the form of a wide fiber veil, a suction opening for condensing the fiber veil to a narrow fiber strand, said suction opening being covered by the collecting surface and tapering by two side edges in the direction of motion of the collecting surface, from a starting width corresponding to the width of the fiber veil to a narrow suction slit, a nipping line, provided at the end area of the suction opening for nipping the condensed fiber strand, and a twisting nozzle arranged downstream of the nipping line for twisting the fiber strand to a thread, said method comprising: controlling said fiber vail during travel over said collecting surface with one side edge of said vail extending in a direction of travel of said vail on said collecting surface and an opposite side edge of said vail extending at an acute angle to the direction of travel of said vail on said collecting surface, whereby condensing of said fiber vail during travel over the collecting surface is in one direction of torsion, and applying a spinning twist to said fiber vail downstream of the collecting surface.

28. A method according to claim 27, wherein said controlling said fiber vail during travel over said collecting surface includes configuring the suction opening to have one side edge extending in the direction of motion of the collecting surface and the other opposite side edge extending at an acute angle to the direction of motion of the collecting surface.