Patent Publication Number: US-6209300-B1

Title: Apparatus for pneumatic condensing of a drafted fiber strand and method of making and using same

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims the priority of German application 199 01 148.6, filed in Germany on Jan. 14, 1999, and German application 199 23 396.9 filed in Germany on May 21, 1999, the disclosure of which is expressly incorporated by reference herein. 
     The present invention relates to an apparatus for pneumatic condensing of a drafted fiber strand in a condensing zone arranged downstream of a front roller pair of a drafting apparatus, which condensing zone is limited in transport direction of the fiber strand by the nipping line of a delivery roller pair, said nipping line forming a twist block, and said delivery roller pair comprising a perforated suction roller, in whose inside a suction slit is arranged which extends essentially in transport direction to the nipping line. 
     An apparatus of this type is prior art in German published patent application 41 39 067. In the case of this apparatus, an apron pair is arranged around the front roller pair of the drafting apparatus, which apron pair guides the fiber strand exiting from the front roller pair into the condensing zone. The bottom apron of this apron pair is also guided over the bottom roller of the delivery roller pair. The upper roller of the delivery roller pair has suction openings and is thus in the form of a suction roller. The suction roller is not surrounded by the upper apron of the apron pair. 
     This apron pair, which loops the front roller pair of the drafting apparatus, requires, for a faultless drafting clamping of the fiber strand at the drafting apparatus, high pressures, which are higher than pressures in standard drafting apparatuses and which pressures diminish the life duration of the apron pair. In the zone where the fiber strand is double-guided by the apron pair, no condensing as yet takes place, as this can occur at the earliest at the suction roller. Because the bottom apron of the apron pair loops the bottom roller of the front roller pair as well as the bottom roller of the delivery pair, no differing peripheral speeds for an eventual tension draft between the front roller pair and the delivery roller pair can be set. 
     It is known from U.S. Pat. No. 4,488,397 that downstream of the actual drafting apparatus a condensing element in the form of a suction roller is arranged. This suction roller comprises, however, for the drafted fiber strand, a peripheral groove, so that no nipping point, which would clamp the fiber strand, can be formed with the suction roller. The twist block should rather more be effected in that the fiber strand loops the suction roller at a certain angle, so that the spinning twist, retroactive back to the drafting apparatus, is increasingly lost. In the area of the looping, the perforation of the suction roller is not suctioned, so that in this area also no pneumatic condensing takes place. Rather, the condensing takes place mechanically by means of the V-shaped ring groove. 
     It is an object of the present invention to utilize the entire distance between the front roller pair of the drafting apparatus and the delivery roller pair for the condensing of the fiber strand, and to create the possibility of setting a tension draft. 
     This object has been achieved in accordance with the present invention in that the suction roller is disposed directly downstream of the front roller pair and in that the fiber strand loops the suction roller up to the nipping line at an angle of at least 45°. 
     As there is no apron pair present in the condensing zone, the condensing effect can begin directly downstream of the drafting apparatus. As a result of the relatively large looping of the suction roller, the condensing zone is sufficiently long. In addition, it is possible to drive the front roller pair and the delivery roller pair at different peripheral speeds. 
     It has been shown that it is favorable for the condensing effect when a drafting plane, defined by the drafting apparatus, at least approximates a tangential plane guiding the fiber strand to the suction roller. The fiber strand is thus not deflected on its way from the front roller pair of the drafting apparatus to the suction roller. 
     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 
     FIG. 1 is a partly sectional side view of an area of an apparatus constructed according to a preferred embodiment of the is present invention, 
     FIG. 2 is a view in the direction of arrow II of FIG. 1; 
     FIG. 3 is a view similar to FIG. 1 of another embodiment of the present invention; and 
     FIG. 4 is a view similar to FIG. 1 having a suction roller with a large diameter to which two nipping rollers are arranged. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The drafting apparatus  1  only partly shown in FIGS. 1 and 2 comprises a front roller pair  2  and an apron roller pair  3  arranged upstream thereof. Further roller pairs are not shown. The apron roller pair  3  guides in a known way a bottom apron  4  and an upper apron  5 . 
     The front roller pair  2  comprises a front bottom roller  6 , which extends in machine longitudinal direction and is driven. At each spinning station, a front top roller  7  is flexibly or elastically pressed onto the front bottom roller  6 , whereby two front top rollers of adjacent spinning aggregates jointly form so-called top roller twins. The front roller pair  2  of the drafting apparatus  1  forms a front nipping line  8 , at which the drafting of the fiber material is ended. 
     A sliver or roving  9  is guided through the drafting apparatus  1  in transport direction A and drafted to the desired degree of fineness. Downstream of the front nipping line  8 , a drafted, but still twist-free fiber strand  10  is present. 
     The drafted fiber strand  10  is guided downstream of the drafting apparatus  1  through a condensing zone  11 , where pneumatic condensing takes place. The purpose of the condensing is to bundle the fiber strand  10  so that it is smaller in diameter and less hairy, as outwardly projecting edge fibers are rolled in around the core strand. A thread or yarn  20  formed from the strand and emerging from the condensing zone  11  is more tear-resistant, more even and relatively smooth as compared to yarn formed without such condensing. 
     The condensing zone  11  is bordered on its exit side by a nipping line  12 , which is defined by a delivery roller pair  13 . This nipping line  12  serves at the same time as a twist block for the spinning twist retroactive from a twist device (not shown), for example a ring spindle. 
     The delivery roller pair  13  comprises as a bottom roller a driven suction roller  14 , which, on its periphery, at least in the fiber guiding area, is perforated and thus air-permeable. The suction roller  14  is arranged directly downstream of the front roller pair  2  of the drafting apparatus  1 . Arranged directly at the suction roller  14  is a nipping roller  15 , whose clamping pressure is weaker than the clamping pressure at the front roller pair  2 . The nipping roller  15  forms the upper roller of the delivery roller pair  13  and is so arranged that the fiber strand  10  to be condensed loops the suction roller  14  in the condensing zone  11  at an angle α of at least 45°. 
     It is favorable when the tangential plane, the so-called drafting plane  16 , formed by the nipping lines of the apron roller pair  3  and the front roller pair  2 , also forms the tangential plane which guides the fiber strand  10  to the suction roller  14 . The fiber strand  10  which is to be condensed is thus not deflected between the front nipping line  8  and the suction roller  14 , but rather only then, when it is transported onto the periphery of the suction roller  14 . 
     It has been shown that this has a favorable effect on the quality of the thread  20  to be spun. 
     The suction roller  14  is supported in a way not shown on a stationary suction tube  17  extending in machine longitudinal direction. In the inside of each suction roller  14 , the suction tube  17  comprises a suction opening  18  directed against the condensing zone  11 , at which suction opening  18  a suction slit  19 , decisive for the condensing effect, is arranged. The suction slit  19  is significantly wider than the condensed fiber strand  10  and extends essentially in transport direction A, or at a slight angle to transport the direction A. The suction slit  19  begins at the latest there, where the fiber strand  10  is disposed onto the suction roller  14 , and extends up to the nipping line  12 . Thus the condensing effect is maintained in any case up to the nipping line  12 . 
     Downstream of the nipping line  12 , the condensed fiber strand in the form of a forming yarn  20  is fed in delivery direction B to a ring spindle (not shown). The spinning twist imparted by the ring spindle is retroactive to the nipping line  12 . 
     Because the suction roller  14  is directly downstream of the front roller pair  2 , the condensing of the fiber strand  10  takes place directly downstream of the front nipping line  8 . Because the fiber strand  10  loops the suction roller  14  at an angle of at least 45°, the condensing zone  11  is sufficiently long. 
     As, in contrast to the above mentioned prior art, no inevitable coupling as regards a drive is present between the front bottom roller  6  and the suction roller  14 , the drives can be created independently of one another as required. It is therefore possible to run the delivery roller pair  13  at a higher speed than the front roller pair  2 , so that the fiber strand to be condensed experiences a low tension draft. 
     The embodiment of the present, invention according to FIG. 3 differs from the embodiment shown in FIGS. 1 and 2 only in that the suction roller  14  takes up a somewhat different position in relation to the front roller pair  2  of the drafting apparatus  1 . For this reason a repeat description of the individual components is not necessary. 
     According to FIG. 3, the drafting plane  16  of the drafting apparatus  1  is no longer the tangential plane which guides the fiber strand  10  to the suction roller  14 . This has the advantage that the suction roller  14  can be advanced nearer to the front nipping line  8 , so that the condensing effect for the drafted fiber strand  10  begins earlier. However, a slight deflection for the fiber strand  10  before reaching the suction roller  14  must be accepted. 
     In the embodiment of the present invention shown in FIG. 4 a suction roller  23  is provided whose diameter is significantly larger compared to the diameters of the front roller pair  2  of the drafting apparatus  1 . Thus the curve of the roller surface in the area of the condensing zone  11  can be advantageously reduced. The suction roller  23  forms, together with a nipping roller  15  which borders the exit side of the condensing zone  11 , the delivery roller pair  24 . 
     Due to the large diameter of the suction roller  23 , the condensing zone  11  is bordered also on its entry side by a nipping roller  21 , so that the condensing zone  11  is now located between two nipping lines  22  and  12 . The looping of the suction roller  23  again measures an angle of at least 45°. 
     As in the above embodiments of the present invention, the suction roller  23  is also supported on a stationary suction tube  25 , which comprises a suction opening  26  directed against the condensing zone  11 . The suction opening  26  is in contact with a suction slit  27 , which extends essentially between the two nipping lines  22  and  12  in transport direction A of the fiber strand  10  to be condensed. 
     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.