Title of Invention

AN AIR-PERMEABLE TRANSPORT BELT FOR TRANSPORTING A FIBRE STRAND TO BE CONDENSED.

Abstract

An air-permeable transport belt in the form of a woven belt for transporting a fibre strand to be condensed over a suction slit of a condensing zone of a spinning machine, the transport belt comprising longitudinal threads extending in the transport direction of the fibre strand, while also comprising cross threads extending transversely to the transport direction of the fibre strand, characterized in that the clearance (x) between two longitudinal threads (20) is larger than the clearance y between two cross threads (21).

Full Text

BACKGROUND AND SUMMARY OF THE INVENTION A transpon belt for transporting a fibre strand to bo oondonsed The present invention relates to an air-permeable transport belt in the form of a woven belt for transporting a fibre strand to be condensed over a suction slit of a condensing zone of a spinning machine, the transport belt comprising longitudinal threads extending in the transport direction of the fibre strand, while also comprising cross threads extending transversely to the transport direction of the fibre strand. When a drafted fibre strand is imparted a spinning twist directly downstream of a front roller pair of a drafting unit, then a so-called spinning triangle occurs at the nipping line of the front roller pair. This arises because the drafted fibre strand leaves the drafting unit having a certain width and is then subsequently twisted to a thread having a relatively small diameter. The spinning triangle comprises lateral fibres, which are not properly bound into the twisted thread and thus contribute little or nothing to the tensile strength of the spun yarn. Recent times have seen a move towards arranging a so-called condensing zone downstream of the drafting zone of the drafting unit, which condensing zone is in turn bordered by a nipping line on its exit side. The thread is only then imparted its spinning twist subsequently. In the condensing zone, the fibres are bundles or condensed, whereby the fibre strand is so narrow when it leaves the last nipping line that the feared spinning triangle does not occur. The spun yarn is thus more even, stronger and less hairy. There are many varying embodiments of condensing zones which serve to condense the fibre strand, whereby embodiments in which a fibre strand to be condensed is transported over a suction slit of the condensing zone by means of an air-permeable transport belt have proved to be advantageous. A transport belt of the above mentioned type is prior art in German published patent application 198 37 182. The known transport belt is woven from thin synthetic threads, so that, as a result of its method of fabrication, it is by its very nature air-permeable. Both the longitudinal threads and the cross threads have each the same distance between them and have also the same diameter. Transport belts of this type in the form of woven belts must fulfill various requirements. For one, the openings formed by the longitudinal threads and the cross threads must be sufficiently large so that the necessary volume of air-flow is guaranteed for the condensing process. The weave openings must, however, on the other hand, be small enough to prevent the single fibres of the fibre strand to be transported and condensed from being sucked through the weave openings and thus ending up as fibre loss. The long-term aim has been to find a suitable compromise between the two contradictory requirements. It is an object of the present invention to create an air-permeable transport: belt designed as a woven belt of the above type, which on the one hand guarantees a large throughput of air and which on the other hand prevents the loss of fibres through suction removal. This object has been achieved in accordance with the present invention in that the clearance between two longitudinal threads is greater than the clearance between two cross threads. In this embodiment of the woven belt rectangular openings occur, whose smaller sides extend in transport direction and whose larger sides extend tranversely to the transport direction. Due to the relatively small clearance in transport direction, the fibre loss is significantly reduced, while the sufficiently high air throughput is still guaranteed due to the larger clearance in transverse direction, as the cross section of the rectangular openings of the transport belt according to the present invention can measure the same as that of the square cross section of the known transport belt. The clearance between two cross threads can be reduced with the resulting reduced loss of fibres, while, to balance this, the clearance between two longitudinal fibres can be increased. The cross threads are formed during weaving by a thick warp, while in the case of the longitudinal threads, there is a relatively reduced weft insert. In an embodiment of the present invention, the clearance between two longitudinal threads is larger than their diameter. In this way, a free airflow cross section of the transport belt of more than 30% is achieved. These measures can be supported further in that the diameter of the longitudinal threads as well as the diameter of the cross threads is smaller than 0.08 mm. This achieves a very homogenous airflow, which results in a good condensing effect and in good yarn quality. As the transport belt slides over a sliding surface, the transport belt is subjected to a certain amount of wear. Because, due to the suction removal, fibre fly, or parts adhering to the fibre material can settle over time on the transport belt, the transport belt should be washable. For this reason, it is advantageous when the longitudinal threads and the cross threads are both made from PEEK (polyetheretherketone). This produces a transport belt which has a high level of resistance to abrasion, and which barely shrinks when washed. In order to avoid points of impact for the circulating transport belt, the woven belt can be an endless belt. Even one point of impact, however small, which occurs due to overlapping, forms a miniature gap in which fibres can settle. This is avoided when the woven belt is endless. BRIEF DESCRIPTION OF THE/DRAWINGS These and further obejcts, 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 wherein: Figure 1 is a partly intersectional side view of the area of a condensing zone, Figure 2 is a view in the direction of the arrow II of Figure 1 of the condensing zone, whereby several components have been omitted, Figure 3 is, in greatly enlarged dimensions, a partial view of Figure II of a woven transport belt according to the present invention. DETAILED DESCRIPTION OF THE DRAWINGS Figures 1 and 2 show in the area of the present invention a section of a spinning machine, in particular a ring spinning machine. The end area of a drafting unit 1 with its front roller pair 2 and an apron pair comprising a bottom apron 3 and an upper apron 4, arranged upstream thereof, can be seen. The front roller pair 2 comprises a driven bottom cylinder 5 which is continuous in machine longitudinal direction, as well as a pressure roller 6> arranged to each spinning station. The front roller pair 2 forms a front nipping line 7 of the drafting unit 1 and ends the drafting zone arranged upstream thereof. In the drafting unit 1 a sliver or a roving 8 is fed through in the known way in transport direction A and drafted to the desired degree of fineness. A drafted but still twist-free fibre strand 9 is then present directly downstream of the front nipping line 7. If the fibre strand 9 were to be imparted its spinning twist immediately, then the feared spinning triangle would occur at the front nipping line 7. For this reason, the drafted fibre strand 9 is bundled or condensed by means of lateral gathering in a condensing zone 10 arranged downstream of the drafting zone, so that when the spinning twist is imparted at a later stage, the spinning triangle does not occur. A suction channel 11 is located in the condensing zone 10 in the form of a hollow profile, which suction channel 11 is subjected to low pressure and which extends over a plurality of spinning stations, as can be seen in Figure 2. The suction channel 11 extends preferably over a machine section and is provided at a suitable place with a low pressure connection 12, which leads to a vacuum source (not shown). In the area of the condensing zone 10, the outer contour of the suction channel 11 is designed as a sliding surface 13, over which an air-permeable transport belt 14 is guided in a gliding manner. In the case of the transport belt 14, a thin and close-meshed woven belt is involved here, which is described in more detail below, and which transports the fibre strand 9 to be condensed through the condensing zone 10. The fibre strand 9 is hereby sucked against the transport belt 14. On the side facing away from the condensing zone 10, the transport belt 14 is guided over a tensioning element 15, which at the same time aligns the transport belt 14 in lateral direction. In the sliding surface 13 a suction slit 16, covered by the transport belt 14, is located, which suction slit 16 extends slightly transversely to the transport direction A, so that during condensing, the fibre strand 9 is imparted an additional light false twist along an edge of the suction slit 16, which increases the overall condensing effect. The end of the condensing zone 10 is defined by a nipping roller 17, which drives the transport belt 14 by means of friction. The nipping roller 17 is pressed against the transport belt 14 and the suction channel 11 and forms a so-called delivery nipping line 18, which acts as a twist block against the spinning twist in such a way that the fibre strand 9 is, in the condensing zone 10, free from any spinning twist. The suction slit 16 reaches almost to the delivery nipping line 18. Directly downstream of the delivery nipping line 18 the produced thread 19 receives its spinning twist, whereby it is fed in delivery direction B to a twisting device (not shown), for example a ring spindle. As the transport belt 14 transports the fibre strand 9 on its upper side and travels over the suction slit 16 with its lower side, there is a risk that single fibres of the fibre strand 9 get through the openings in the weave and thus into the inside of the suction channel 11 and then on into the suction removal. Some of these lost fibres and the dust which adheres hereto can, however, get caught in the transport belt 14 and thus impair the condensing effect, which in time can lead to a change in the character of the spun yarn. For this reason, the transport belt 14, in the form of a woven belt, is designed as described below with the aid of the greatly enlarged Figure 3. The weave of the transport belt 14 comprises longitudinal threads 20 extending in transport direction A, as well as cross threads 21 extending transversely to transport direction A. These longitudinal threads 20 and the cross threads 21 often consist of a polyamide, but PEEK (polyetheretherketone) can be used advantageously in the present invention. The latter material is particularly resistant to abrasion. The longitudinal threads 20 and the cross threads 21 are so woven with each other that the clearance x between two adjacent longitudinal threads 20 is larger than the clearance y between two adjacent cross threads 21. The distance x can measure several times that of the distance y. This creates in the weave openings small rectangular openings 22, whose shorter side corresponds to the clearance y and extends in transport direction A, and whose longer side extends transversely to the transport direction A and corresponds to the distance x. In this design, rectangular openings 22 have a cross section, which in size corresponds to the square cross section of the previously known weave openings, which were more susceptible to fibre trash. By reducing the clearance y, the danger of trash fibres is significantly reduced, while at the same time the enlargement of the clearance x between two longitudinal threads 20 ensures a sufficiently large volume of air throughput through the transport belt 14. It has been shown to be advantageous when the clearance x between two longitudinal fibres 20 is larger than their diameter dL. This diameter lies advantageously below 0.08 mm and corresponds to the diameter dQ of the cross threads 21. In Figure 3, four adjacent fibres 23 of the fibre strand 9 are shown, from which can be seen that in the case of the woven belt according to the present invention, the fibres 23 have a reduced tendency to be sucked through the weave openings as trash. The volume of air throughput necessary for condensing, however, does not have to be reduced. CLAIMS 1. An air-permeable transport belt in the form of a woven belt for transporting a fibre strand to be condensed over a suction slit of a condensing zone of a spinning machine, the transport belt comprising longitudinal threads extending in the transport direction of the fibre strand, while also comprising cross threads extending transversely to the transport direction of the fibre strand, characterized in that the clearance (x) between two longitudinal threads (20) is larger than the clearance(y)between two cross threads (21). 2. A transport belt according to claim 1, wherein the clearance (x) between two longitudinal threads (20) is larger than their diameter (dL). 3. A transport belt according to claims 1 or 2, wherein the diameter (dL, dQ) of the longitudinal threads (20) as well as of the cross threads (21) is smaller than 0,08 mm. 4. A transport belt according to any one of the claims 1 to 3, wherein the longitudinal threads (20) and the cross threads (21) are made from PEEK (polyetheretherketone). 5. A transport belt according to any one of the claims 1 to 4, wherein the transport belt is endlessly woven. An air-permeable transport belt in the form of a woven belt for transporting a fibre strand to be condensed over a suction slit of a condensing zone of a spinning machine, the transport belt comprising longitudinal threads extending in the transport direction of the fibre strand, while also comprising cross threads extending transversely to the transport direction of the fibre strand, characterized in that the clearance (x) between two longitudinal threads (20) is larger than the clearance y between two cross threads (21).

Documents:

39-CAL-2002-(27-12-2011)-CORRESPONDENCE.pdf

39-CAL-2002-FORM-27.pdf

39-cal-2002-granted-abstract.pdf

39-cal-2002-granted-assignment.pdf

39-cal-2002-granted-claims.pdf

39-cal-2002-granted-correspondence.pdf

39-cal-2002-granted-description (complete).pdf

39-cal-2002-granted-drawings.pdf

39-cal-2002-granted-examination report.pdf

39-cal-2002-granted-form 1.pdf

39-cal-2002-granted-form 18.pdf

39-cal-2002-granted-form 2.pdf

39-cal-2002-granted-form 26.pdf

39-cal-2002-granted-form 3.pdf

39-cal-2002-granted-form 5.pdf

39-cal-2002-granted-priority document.pdf

39-cal-2002-granted-reply to examination report.pdf

39-cal-2002-granted-specification.pdf

39-cal-2002-granted-translated copy of priority document.pdf