Title of Invention

AN ARRANGEMENT FOR CONDENSING A FIBRE STRAND .

Abstract

A device for condensing a drafted fibre strand in a spinning machine. Condensing zone is arranged downstream of the front roller pair, through which the fibre strand is transported by means of an air-permeable transport belt. A sliding surface which guides the transport belt is arranged to the condensing zone where a suction slit is located, which is bordered by two lateral edges. The suction slit comprises a transverse fibre guiding edge which positions the fibre strand transversely to the direction of motion of the transport belt. The suction slit comprises further a widened starting area for seizing the transversely traversing fibre strand. During condensing, the fibre strand is somewhat rolled in along the fibre guiding edge. In order to ensure that this rolling only occurs in one twisting direction, only one edge (24,25) of the suction slit (16) designed as a fibre guiding edge (17). Despite the traverse motion (D,E) the fibre guiding edge (17) positions the fibre strand (62) transversely to the direction of motion (B) of the transport belt (13) from the widened starting area (26) to the end (27) of the suction slit (16).

Full Text

BACKGROUND AND SUMMARY OF THE INVENTION 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 sliding surface arranged to the condensing zone which sliding surface guides the transport belt, and also comprising a suction slit, bordered by two lateral edges, arranged in the sliding surface, which suction slit comprises a fibre guiding edge which positions the fibre strand transversely to the direction of motion of the transport belt, and which suction slit has a widened starting area for seizing the transversely traversing fibre strand. The purpose of the condensing zone arranged downstream of the drafting unit is to condense or bundle by means of lateral gathering of its lateral fibres the drafted, but still twist-free fibre strand, so that when the spinning twist is imparted, a so-called spinning triangle does not occur. The produced thread is then more tear-resistant, more even and less hairy. The transversing of the fibre strand serves to prevent the premature wear of the aprons and roller coatings which are part of the drafting unit. An arrangement of the above mentioned type is prior notorious use and is described in the older, but subsequently published German patent application 199 49 666.8. The known arrangement comprises a suction slit, which begins with a starting width, which seizes the not yet condensed fibre strand in its entire width and while in traverse motion. Directly after the fibre strand has been seized, the suction slit in the known arrangement in the form of a delta graduates to a narrower effective width into an overall transverse suction slit, whose fibre guiding edge continues an edge of the delta without any deflection. The not yet condensed fibre strand thus reaches, in an extreme position of the traverse motion, a lateral edge of the suction slit - at this point in delta form - which lateral edge is facing away from the actual fibre guiding edge. As the above mentioned lateral edge extends diagonally and, in relation to the direction of motion of the transport belt, in the opposite direction to the actual fibre guiding edge arranged downstream which serves the condensing process, the not yet condensed fibre strand is rolled in the area of the delta in another direction to the one later used in actual condensing at the fibre guiding edge. The twisting direction of the fibres changes during an extreme position of the traverse motion. This gives rise to erratic movement on the part of the fibres in the condensing zone and a periodical worsening of the yarn parameters. A similar disadvantage is shown in a non-generic arrangement according to German published patent application 44 26 278 A1, where a suction slit is arranged in the inside of a suction roller at a distance. The suction slit of a condensing zone begins with a relatively large initial width and tapers symmetrical in a delta-like way. The fibre strand is supposed to be disposed alternately on the right and on the left edge of the delta, whereby however, the disadvantage arises in that the fibre strand to be condensed is periodically rolled in in differing twisting directions. In German published patent application 196 23 824 an also non-generic arrangement is known, in which a suction slit is arranged on the inside of a suction roller, whereby only one lateral edge of the suction slit is designed as a fibre guiding edge. The fibre guiding edge only serves here, however, to permit two fibre strands traveling parallel at a relatively large distance to one another to run into two adjacent suction slits, and to reduce the distance of the then condensed fibre strands to one another, so that they are brought to an optimum distance from one another for the purpose of the spinning process. For this reason, the fibre guiding edge, which at the start is diagonal to the direction of motion of the suction roller, very soon graduates into a lateral edge parallel to the motion of direction, so that from this moment in time onwards the fibre strand is no longer positioned diagonally to the direction of motion of the suction roller. The order is such that in the case of an extreme position of the traverse motion, the relevant fibre guiding edge is touched by the fibre strand only over a very short distance. US 6,338,183 B1 discloses condensing arrangement for fibre strand downstream of a drafting unit of a spinning machine. The condensing zone comprises a stationary suction slit of transporting the fibre strand over it by an air permeable transporting element. The air stream is used for positioning the fibres of the fibre strands diagonally to the direction of the motion of the transport condensing the fibre strand. US 6,185,790 B1 discloses a condensing zone for condensing a drafted fibre strand arranged downstream of a drafting arrangement in a ring spinning machine. A perforated transport belt is provided for transporting the fibre strand over a suction slit of a sliding surface. The transport belt drives a nipping roller for limiting the condensing zone on its exists cites with he leaping point acting as a twist block. The nipping roller presses the fibre strands and the transport belt against the sliding surface of the condensing zone. It is an object of the present invention to avoid the rolling-in of the fibre strand in differing directions in an arrangement of the above mentioned type and to improve the quality of the yarn. This object has been achieved in accordance with the present invention in that only one lateral edge of the suction slit is designed as a fibre guiding edge, which, from the beginning, positions the fibre strand, despite its traverse movements, in the starting area up to the end of the suction slit, diagonally to the direction of motion of the transport belt. As only one lateral edge is designed as a fibre guiding edge, a change in the twisting direction during the condensing rolling in of the fibre strand is prevented. Furthermore, as the fibre strand, despite its traverse movements, reaches this one fibre guiding edge from the beginning at the widened starting area, the fibre guiding edge remains, despite the traverse movement, essentially constantly effective along its entire length. As the fibre strand is positioned diagonally to the direction of motion of the transport belt by the fibre guiding edge right up to the end of the suction slit, the fibre strand is prevented from any slight opening out again when it leaves the suction slit. Overall, each measure serves to improve the yarn parameters. In an advantageous embodiment of the invention, it is provided that the fibre guiding edge is more slanted in relation to the direction of motion of the transport belt in the widened starting area of the suction slit than in the remaining areas of the suction slit. How large the angle of the slant may be, must - depending on the delivery speed and the respective fibre material -m be ascertained by means of tests. The angle of the slant should not be so large that the fibre strand to be condensed can leave the fibre guiding edge and thus also the suction slit. The angle of the slant should be as large as permissible in order that the above mentioned widened starting area of the suction slit is as short as possible. As a result of a shorter starting area, constant ratios are maintained to as large an extent as possible during condensing in both extreme positions of the fibre strand to be condensed during traverse motion. The starting area of the suction slit should measure at maximum a quarter of the length of the suction slit. In practice it has been shown that the minimum slant of the fibre guiding edge downstream of the starting area measures an angle of between 3° and 20° to the direction of motion of the transport belt. 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 arrangement for condensing a fire strand; Figure 2 is a view in the direction of the arrow II of Figure 1 of the condensing zone; Figures 3 and 4, greatly enlarged, show only the contour of a suction slit according to the present invention, without the respective transport belt, whereby an extreme position of the traversing fibre strand is shown by a dot-dash line. 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 fibre strand 2 are shown in Figures 1 and 2. he 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 upstream thereof in transport direction A, are shown. The apron roller pair 5 guides a bottom 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 which is flexibly pressed thereagainst. The front roller pair 4 defines thus a front nipping line 10, which forms the end of the drafting zone. In the drafting unit 3, a sliver or alternatively a roving 11 is drafted in transport direction A in a known way to the desired degree of fineness. This drafting is at an end at the front nipping line 10, and from this point onwards, a drafted, but still twist-free fibre strand 2 is produced. In order to avoid the known and disadvantageous spinning triangel during twisting, the fibre strand 2 is condensed directly downstream of the front nipping line 10 in a condensing zone 12. The arrangement 1 for the condensing process comprises an air-permeable transport belt 13, which can be designed as a close-meshed, thin woven belt of polyamide threads, which belt transports the fibre strand 2 to be condensed through the condensing zone 12. The arrangement 1 comprises further a suction channel 14, which is designed as a hollow profile which acts under low pressure and which can extend over a plurality of spinning stations. On its outer contour facing the condensing zone 12, the suction channel 14 is designed as a sliding surface 15 for guiding the transport belt 13. In this sliding surface 15 a suction slit 16 is located, which is arranged slightly slanted in relation to the direction of motion B of the transport belt 13, so that the suction slit 16 comprises a fibre guiding edge 17 for the fibre strand 2 to be condensed. 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, and the fibre strand 2 is hereby somewhat rolled in. The suction channel 14 is connected to a low pressure source (not shown) via a low pressure conduit 18, which is located at a distance from the suction slit 16. If the suction channel 14 extends over a plurality of spinning stations, only one low pressure conduit 18 per machine section is required. The condensing zone 12 is bordered on its exit side by a nipping roller 19, which presses the fibre strand 2 and the transport belt 13 onto the sliding surface 15 and hereby defines a delivery nipping line 20, which acts in relation to the spinning twist to be imparted as a twist block. The nipping roller 19 drives the transport belt 13 and is in turn driven via a transfer roller 21 by the front pressure roller 9. Downstream of the delivery nipping line 20, the produced thread 22 receives its spinning twist, whereby it is fed in delivery direction C to a twisting element (not shown), for example a ring spindle. The delivery nipping line 20 acts in relation to the spinning twist as a twist block, so that the spinning twist does not retroact back into the condensing zone 12. On the side facing away from the suction slit 16, the transport belt 13 is tensioned by means of a tensioning element 23 , which for example can be designed as a stationary rod or a guiding roller. The tensioning element 23 is so arranged that the transport belt 13 is disposed with a slight pressure on the front bottom cylinder 8. As the transport belt 13 and the front bottom cylinder 8 travel in opposite directions at the point of contact, the transport belt 13 is cleaned of any adhering fibre fly. As can be seen from Figure 2, the fibre strand 2 to be condensed is traversed according to the directions D and E of the double arrow. These traverse movements serve to prevent the bottom apron 6, the upper apron 7 and the flexible coating of the front pressure roller 9 from premature wear. The traverse motion according to the directions D and E, however, makes it more difficult for the fibre strand 2 to be condensed to be reach the fibre guiding edge 17 reliably. Should the fibre strand 2 not reach the fibre guiding edge 17 during seizing by the suction slit 16, but rather instead reach the other lateral edge of the suction slit 16, as is the case in the above mentioned prior art, then a temporary and periodic rolling-in movement would take place in the fibre strand 2, said rolling-in movement going temporarily in the opposite direction to the desired rolling-in movement along the fibre guiding edge 17, and as a result, lowering the yarn quality. For this reason, a particular embodiment of the suction slit 16 is provided, as is described below according to the Figures 3 and 4. In the enlarged depiction of the suction slit 16 according to Figures 3 and 4, two extreme positions of the fed, traversing fibre strand 2 are indicated by dot-dash lines. According to Figure 3, the fibre strand 2 has reached its left extreme position and is beginning its traverse movement according to the arrow direction E. According to Figure 4, the traversing fibre strand 2 has reached its right extreme position and is begins its reverse movement according to the arrow direction D subsequently. The traverse lift measures overall approximately 5 to 6 mm, whereby in one minute, only a very few traverse movements take place. In the enlarged depiction of the suction slit 16 according to Figures 3 and 4, the two lateral edges 24 and 25 bordering the suction slit 16 can be seen, whereby it now must be ensured, that during condensing, the fibre strand 2 reaches the fibre guiding edge 17 as soon as possible in spite of the traverse movements. At the same time, it must be ensured that the traversing fibre strand 2 is actually seized by the suction slit 16. The suction slit 16 has initially on its upstream side a starting area 26, which must be at least as wide as the traversing lift. In longitudinal direction of the suction slit 16, however, the starting area 26 must be as short as possible, preferably only a quarter of the length of the suction slit 16. In contrast to Figures 3 and 4, if the starting area 26 of the suction slit 16 were to extend not to the right, but, as in prior art, to the left, then the traversing fibre strand 2 could be also seized, but would, however, be disposed temporarily on a lateral edge of the suction slit 16 arranged opposite to the fibre guiding edge 17, which lateral edge extends diagonally in the opposite direction. This would result in a disadvantageous way to a rolling-in of the fibre strand 2 at intervals in an undesired twisting direction. For this reason, the starting area 26 of the suction slit 16 according to Figures 3 and 4 is so designed, in accordance with the present invention, that the angle of the diagonal position of the fibre guiding edge 17 in the entry area 26 is increased. As a result, the fibre strand 2 to be seized and condensed actually reaches the guiding edge 28 in the starting area 26 sooner or later, whereby the guiding edge 28 increases the actual fibre guiding edge 17 towards the entry into the suction 16 and is hereby more slanted in relation to the direction of motion B of the transport belt 13 than the fibre guiding edge 17. The present invention ensures that the fibre strand 2 always reaches only the correct fibre guiding edge 17, and as quickly as possibly after it has been siezed. The fibre guiding edge 17 has an angle a in relation to the direction of motion B of the transport belt 13, which angle a measures in practical embodiments between 3° and 20°. The fibre guiding edge 17 hereby extends to the end 27 of the suction slit 16, whereby the end 27 occurs at approximately the same place as the delivery nipping line 20. This ensures that the condensed, and thus somewhat rolled in fibre strand 2 cannot fluff out again at the end 27 of the suction slit 16. If the slant of the guiding edge 28 were matched to a great extent to the angle a of the actual fibre guiding edge 17, then the starting area 26 would be enlarged as a result to such an extent that the fibre strand 2 in the extreme position as shown in Figure 3 would reach the fibre guiding edge 17 much too late, as in the arrangement according to the cited German published patent application 196 23 824. In its extreme positions, the fibre strand 2 would have one short path and one long path along the fibre guiding edge 17, which would result in periodically different yarn qualities. On the other hand, a starting area 26, which was too short, could result in the fibre strand 2 in its extreme position according to Figure 4, not travelling along the guiding edge 28 , but rather leaving same and thus the suction slit 16 under the action of the transport belt 13 in its direction of motion B. The optimum angle for the guiding edge 28 must in each case be ascertained by means of tests. WE CLAIM: 1. 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; - an air-permeable transport belt for transporting the fibre strand through the condensing zone; - a sliding surface arranged in the condensing zone for guiding the transport belt; and - a suction slit, bordered by two lateral edges arranged in the sliding surface, said suction slit comprises a fibre guiding edge for positioning the fibre strand transversely to the direction of motion of the transport belt, and said suction slit has a widened starting area for seizing the transversely traversing fibre strand, characterized in that the suction slit (16) in the starting area (26) is widened toward one side only such that it forms only one guiding edge (17) which guiding edge has a starting area (28) which is inclined at a greater angle to the direction of motion (B) of the transport belt (13) than the areas of the starting edge downstream thereof and positions transversely the fibre strand (2) to the suction slit (16). 2. An arrangement as claimed in claims 1 or 2, wherein the starting area (26) of the suction slit (16) takes up a maximum of a quarter of the length of the suction slit (16). 3. An arrangement as claimed in claims 1 to 3, wherein the lowest angle a of the slant of the fibre guiding edge (17) in relation to the direction of motion (B) of the transport belt (13) measures between 3° and 20°. Dated this 14th day of January, 2002 A device for condensing a drafted fibre strand in a spinning machine. Condensing zone is arranged downstream of the front roller pair, through which the fibre strand is transported by means of an air-permeable transport belt. A sliding surface which guides the transport belt is arranged to the condensing zone where a suction slit is located, which is bordered by two lateral edges. The suction slit comprises a transverse fibre guiding edge which positions the fibre strand transversely to the direction of motion of the transport belt. The suction slit comprises further a widened starting area for seizing the transversely traversing fibre strand. During condensing, the fibre strand is somewhat rolled in along the fibre guiding edge. In order to ensure that this rolling only occurs in one twisting direction, only one edge (24,25) of the suction slit (16) designed as a fibre guiding edge (17). Despite the traverse motion (D,E) the fibre guiding edge (17) positions the fibre strand (62) transversely to the direction of motion (B) of the transport belt (13) from the widened starting area (26) to the end (27) of the suction slit (16).

Documents:

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

22-CAL-2002-FORM-27.pdf

22-cal-2002-granted-abstract.pdf

22-cal-2002-granted-claims.pdf

22-cal-2002-granted-correspondence.pdf

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

22-cal-2002-granted-drawings.pdf

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

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

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

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

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

22-cal-2002-granted-others.pdf

22-cal-2002-granted-pa.pdf

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

22-cal-2002-granted-specification.pdf