Title of Invention

AN ARRANGEMENT IN A SPINNING MACHINE FOR CONDENSING A FIBRE STRAND

Abstract

An arrangement in a spinning machine for condensing a fibre strand (2), comprising a condensing zone (12) arranged down stream of a front roller pair (4) of a drafting unit (3), also comprising an air-permeable transport belt (13), which transports the fibre strand through the condensing zone (12), also comprising a suction channel (14) arranged to the condensing zone, also comprising a sliding surface (15) arranged to the suction channel which sliding surface guides the transport belt, and also comprising a suction slit (16), bordered by two lateral edges, one of which edges is designed as a slanted fibre guiding edge (17) which positions the fibre strand transversely to the direction of motion (A) of the transport belt, characterized in that the suction slit (16) comprises a widened area (28) which is wider than a preceding middle area (26) while retaining the fibre guiding edge (17).

Full Text

BACKGROUND AND SUMMARY OF THE INVENTION An arrangement in a spinning machine for condensing a fibre strand The present invention relates to an arrangement in a spinning machine for condensing a fibre strand, comprising a condensing zone arranged downstream of a front roller pair of a drafting unit, also comprising an air-permeable transport belt which transports the fibre strand through the condensing zone, also comprising a suction channel arranged to the condensing zone, also comprising a sliding surface arranged to the suction channel which guides the transport belt, and also comprising a suction slit, bordered by two lateral edges one of which edges is designed as a slanted fibre guiding edge which positions the fibre strand transversely to the direction of motion of the transport belt arranged. When a drafted fibre strand is imparted its spinning twist directly downstream of the front roller pair, then a so-called spinning triangle occurs at the nipping line of the front roller pair. This happens because the drafted fibre strand leaves the drafting unit having a certain width and is then 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 thread. As a solution to this problem, a so-called condensing zone has, in recent times, been arranged directly downstream of the drafting zone of a drafting unit, said condensing zone being in turn bordered by a nipping line. The thread is imparted its twist only after leaving the condensing zone. The fibres are bundled or condensed in the condensing zone, whereby the fibre strand is so narrow when it leaves the last nipping line that the feared spinning triangle does not occur. The spun thread is stronger, more even, and less hairy. An arrangement of the above mentioned type is prior art in US patent 6,223,514. In this publication it is stated that between the stationary sliding surface of the suction channel and the underside of the transport belt which runs over the sliding surface, fibre fly and trash can settle, whereby the prior art discloses that the trash occurs, for example, in that single fibres of the fibre strand to be condensed, in particular the short fibres, reach inwards through the perforation of the transport belt with their front ends into the area of the suction slit. Experience has shown that single fibres can also reach the underside of the transport belt laterally. It is an object of the present invention to prevent to a large extend the accumulation of fibre fly at the end of the suction slit in an arrangement of the above mentioned type. This object has been achieved according to the present invention in that the suction slit is provided in its end area with an area wider than that of a middle area arranged upstream thereof, while maintaining the fibre guiding edge. Due to the embodiment of the present invention, there is an increased volume of throughput air at the end area of the suction slit, so that at this point fibre accumulations do not occur at all, or at least do not occur so easily. Maintaining the fibre guiding edge extending transversely to the direction of motion of the transport belt prevents the fibre strand losing the desired condensing effect. This is already achieved when the fibre guiding edge extends in the end area of the suction slit exactly in the direction of motion of the transport belt. In principal it is, however, correcter when the fibre guiding edge retains its transverse position to the end of the suction slit, with the widened area being provided exclusively on the side of the suction slit facing away from the fibre guiding edge. In order to prevent any fibres which may separate from the fibre strand from getting caught on the outer edge of the suction slit, an unbroken graduation for the widened area from the middle area of the suction slit to its end area is advantageoully provided. It is further possible that the widened area has an essentially circular design. As a starting point for a practical rule of calculation, it can be given that the widened area should measure approximately double the width of the middle area. of the suction slit. If a suction slit measures 1.5 to 2 mm in its middle area, then the widened area in the end area of the suction slit should measure between 2.5 and 3.5 mm. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 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 wherein: Figure 1 is a partly intersectional side view of an arrangement for condensing a fibre strand, Figure 2 is a view in the direction of the arrow II of Figure 1 of the actual condensing zone, having a suction slit according to the present invention, Figures 3 to 6 are, in enlarged form, several embodiments for a suction slit according to the present invention. DETAILED DESCRIPTION OF THE DRAWINGS Of a spinning machine, in particular a ring spinning machine, only the area of an arrangement 1 for condensing a drafted, still twist-free fibre strand 2 is shown in Figures 1 and 2. The arrangement 1 is located directly downstream of a drafting unit 3, of which only the front roller pair 4 as well as an apron roller pair 5 arranged in transport direction A upstream of the front roller pair 4 are shown. The apron roller pair 5 guides a lower apron 6 and an upper apron 7. The front roller pair 4 comprises a driven front bottom cylinder 8 as well as a front pressure roller 9 pressed flexibly thereagainst. The front roller pair 4 defines a front nipping line 10, which forms the end of the drafting zone of the drafting unit 3. In the drafting unit 3, a sliver or a roving 11 is drafted in the known way to the desired degree of fineness in transport direction A. This drafting process ends at the front nipping line 10, and from this line on a drafted, but still twist-free fibre strand 2 is present. In order to avoid the known and disadvantageous spinning triangle when the spinning twist is being imparted, the fibre strand 2 is condensed directly downstream of the front nipping line 10 in a condensing zone 12. The arrangement 1 provided for condensing comprises an air-permeable transport belt 13, which can, for example, be designed as a closed-meshed, thin woven belt made of synthetic fibres and which transports the fibre strand 2 to be condensed through the condensing zone 12. The arrangement 1 also comprises a suction channel 14, which is designed as a hollow profile with prevailing low pressure and which extends over a plurality of spinning stations. The suction channel 14, for the purpose of guiding the transport belt 13 is, on its outer contour facing the condensing zone 12, designed as a sliding surface 15. A suction slit 16 is located in the sliding surface 15, which suction slit 16 is arranged slightly transversely to the direction of motion B of the transport belt 13, so that in relation to the fibre strand 2 to be condensed, the suction slit 16 comprises a fibre guiding edge 17. The fibre strand 2 travels along this fibre guiding edge 17 during condensing, whereby the fibres located in the fibre strand 2 are bundled or condensed transversely to the direction of motion B of the transport belt 13, whereby the fibre strand 2 is rolled in somewhat. The suction channel 14 is connected via a vacuum connection 18, which is located at a distance to the suction slit 16, to a vacuum source (not shown). If the suction channel 14 extends over a plurality of spinning stations, only one vacuum connection 18 need be provided per machine section. The condensing zone 12 is limited on its outer side by a nipping roller 19, which presses the fibre strand 2 and the transport belt 13 to the sliding surface 15 while defining a delivery nipping line 20, which acts as a twist block in relation to the spinning twist to be imparted. The nipping roller 19 drives the transport belt 13 and is in turn driven via a transfer wheel 21 by the front pressure roller 9. Downstream of the delivery nipping line 20, the produced thread 22 receives a spinning twist, as the thread 22 is fed in delivery direction C to a twist element (not shown), for example a ring spindle. The delivery nipping line 20 serves as a twist block to the spinning twist, so that the spinning twist cannot retroact back into the condensing zone 12. The transport belt 13 is tensioned by means of a tensioning element 23 on the side facing away from the suction slit 16, which tensioning element 23 can, for example be designed as a stationary rod or also as a guiding roller. The tensioning element 23 is arranged hereby in such a way that the transport belt 13 is disposed with a slight pressure on the front bottom cylinder 8. Because the transport belt 13 and the front bottom cylinder 8 rotate in opposite directions at the line of contact, the transport belt 13 is hereby cleaned of any fibre fly which has adhered thereto. As can be seen in Figure 2, the starting area 24 of the suction slit 16 is provided with a widened area 25, which serves the purpose of reliably seizing the fibre strand 2, which traverses slightly tranversely to the direction of transport A, despite the narrow suction slit 16. In the middle area 26, the suction slit 16 has a relatively narrow width of, for example, between 1.5 to 2 mm. It has been shown that in the condensing zone 12, single fibres from the fibre strand 2 get in sideways under the transport belt 13 and become caught between the underside of the transport belt 13 and the sliding surface 15, in particular in the end area 27 of the suction slit 16. On the other hand, other fibres can penetrate into the perforations of the transport belt 13. These fibres, which are not bound into the thread 22, can, in time, block the perforations of the transport belt 13, thus causing a reduction in the condensing effect at some spinning stations, which in turn results in a thread 22 having a different hairiness at some spinning stations. In order to avoid fibre fly accumulations at the end area 27 of the suction slit 16, this end area 27 is provided with a widened area 28 which is wider than the preceeding middle area 26 of the suction slit, and which is located solely on the side of the suction slit 16 facing away from the fibre guiding edge 17, as shown in the embodiment in Figure 2. This widened area 28 measures approximately twice the width of the middle section 26. Due to this widened area 28, there is a significantly greater volume of through air in the end area 27 of the suction 16, so that here any occuring fibre fly accumulations most probably reach the inside of the suction channel 14 and thus subsequently also the suction removal. As the fibre guiding edge 17 extends slightly slanted in relation to the direction of motion B of the transport belt 13 up to the end of the suction slit 16, there is no risk that the condensing effect already in the fibre strand 2 is lost due to the widened area 28. In the following greatly enlarged embodiments of suctions slits 16, the fibre guiding edge 17, as well as the starting area 24, the middle section 26 and the end area 27 can be identified. In the embodiment according to Figure 3, the widened area 328 is so designed that it extends from the middle section 26 in a smooth, unbroken graduation 329. Thus fibres do not tend to settle on the side edges of the suction channel 16. In the end area 27 of the suction slit 16 according to Figure 4, the widened area 428 is circular in shape. Thus any small deflecting radii in the end area 27 of the suction slit 16 are avoided, so that the risk of fibre fly settling is reduced from a geometric point of view. The widened area 528 in the end area 27 of the suction slit 16 as shown in Figure 5 deviates from the embodiments described up to now in that here the fibre guiding edge 17 comprises an end piece 530 in the end area 27, which extends in exactly the same direction of motion B as the transport belt 13. In this embodiment also, there is not yet the tendency for the condensed fibre strand 2 to widen again at the end area 27 of the suction slit 16. More practical are embodiments in which the fibre guiding edge 17 extends slanted to the end of the suction slit 16, whereby the this slant must not extend in a constant angle. The embodiment according to Figure 6 corresponds to a large extent to that in Figure 2, that is, the suction slit 16 also comprises a widened area 625 at its starting area 24, which serves to seize the traversing fibre strand 2 at this point. Such a widened area 625 at the starting area 24 can be provided at any of the shown suction slits 16. WE CLAIM: 1. An arrangement in a spinning machine for condensing a fibre strand (2), comprising a condensing zone (12) arranged down stream of a front roller pair (4) of a drafting unit (3), also comprising an air-permeable transport belt (13), which transports the fibre strand through the condensing zone (12), also comprising a suction channel (14) arranged to the condensing zone, also comprising a sliding surface (15) arranged to the suction channel which sliding surface guides the transport belt, and also comprising a suction slit (16), bordered by two lateral edges, one of which edges is designed as a slanted fibre guiding edge (17) which positions the fibre strand transversely to the direction of motion (A) of the transport belt, characterized in that the suction slit (16) comprises a widened area (28) which is wider than a preceding middle area (26) while retaining the fibre guiding edge (17). 2. An arrangement as claimed in claim 1, wherein the widened area (28) is located only on the side of the suction slit (16) facing away from the fibre guiding edge (17). 3. An arrangement as claimed in claims 1 or 2, wherein an unbroken graduation (329) from the middle area (26) of the suction slit (16) to its end area (27) is provided for the widened area (328). 4. An arrangement as claimed in any one of the claims 1 to 3, wherein the widened area (428) is essentially circular in form. 5. An arrangement as claimed in any one of the claims 1 to 4, wherein the widened area (28) measures approximately double the width of the middle are (26) of the suction slit (16). An arrangement in a spinning machine for condensing a fibre strand (2), comprising a condensing zone (12) arranged down stream of a front roller pair (4) of a drafting unit (3), also comprising an air-permeable transport belt (13), which transports the fibre strand through the condensing zone (12), also comprising a suction channel (14) arranged to the condensing zone, also comprising a sliding surface (15) arranged to the suction channel which sliding surface guides the transport belt, and also comprising a suction slit (16), bordered by two lateral edges, one of which edges is designed as a slanted fibre guiding edge (17) which positions the fibre strand transversely to the direction of motion (A) of the transport belt, characterized in that the suction slit (16) comprises a widened area (28) which is wider than a preceding middle area (26) while retaining the fibre guiding edge (17).

Documents:

34-cal-2002-granted-abstract.pdf

34-cal-2002-granted-assignment.pdf

34-cal-2002-granted-claims.pdf

34-cal-2002-granted-correspondence.pdf

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

34-cal-2002-granted-drawings.pdf

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

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

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

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

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

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

34-cal-2002-granted-pa.pdf

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

34-cal-2002-granted-specification.pdf

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