Patent Publication Number: US-6336259-B1

Title: Apparatus and method for condensing a drafted fiber strand

Description:
This application claims the priority of German application 199 24 527.4, filed in Germany on May 28, 1999. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to an apparatus for condensing a drafted fiber strand in a condensing zone arranged downstream of the front roller pair of a drafting unit, which condensing zone comprises a stationary sliding surface having a suction slit extending essentially in transport direction of the fiber strand, and a perforated transport belt which transports the fiber strand over the sliding surface, on which transport belt a nipping roller, bordering the exit side of the condensing zone, is disposed. 
     In the case of an apparatus of this type (German published patent application 197 08 410), the nipping roller is the upper roller of a delivery roller pair, whose bottom roller is looped by the transport belt. The bottom roller in turn is driven by a further drive roller which extends in machine longitudinal direction, so that at the end of the condensing zone three rollers in total are arranged one over the other. This design, which requires a separate drive shaft und gearing from the headstock of the ring spinning machine, is considerably complicated and, in particular, does not permit already existing ring spinning machines to be retrofitted with a condensing zone. 
     It is an object of the present invention to simplify the complicated drive design for the transport belt, thus creating an opening for existing ring spinning machines not having a condensing zone to be retrofitted with same. 
     This object has been achieved in accordance with the present invention in that the nipping roller drives the transport belt, the nipping roller in turn being driven by a friction roller, which is pressed, by means of a loading spring, to the nipping roller and also to a roller of the front roller pair. 
     A friction drive of this type is very simple and makes it possible in particular to maintain to a great extent the peripheral speed of the front roller pair also at the nipping roller. This takes into consideration the fact that the fiber strand has left the drafting unit and should not be additionally drafted in the condensing zone. In addition, a friction drive of this kind is suitable for retrofitting existing ring spinning machines having no condensing zones with same. 
     Although it is possible that the friction roller, as well as the nipping roller, is disposed at the same time on the driven bottom roller of the front roller pair, it is particularly purposeful when the friction roller is disposed on the upper roller of the front roller pair. It is then possible to arrange the loading spring at the top arm of the drafting unit, which results in a very simple design. 
     In the case of an apparatus of this type (German published patent application 197 08 410), the nipping roller is the upper roller of a delivery roller pair, whose bottom roller is looped by the transport belt. The bottom roller in turn is driven by a further drive roller which extends in machine longitudinal direction, so that at the end of the condensing zone three rollers in total are arranged one over the other. This design, which requires a separate drive shaft and gearing from the headstock of the ring spinning machine, is considerably complicated and, in particular, does not permit already existing ring spinning machines to be retrofitted with a condensing zone. 
     The nipping roller can also be designed in a variety of ways. The nipping roller can have a flexible coating, which is provided for the drive effected by the friction roller as well as for the drive of the transport belt. The nipping roller can alternatively be so designed that the flexible coating has two areas, one for the drive effected by the friction roller and one for the drive of the transport belt. The two areas can have in addition different diameters, so that the area with an enlarged diameter driving the transport belt effects a certain tension draft on the fiber strand. 
     The friction roller, which is advantageously designed as a pressure roller, can have a fitted collar. This makes it possible to design the friction roller simultaneously as a cleaning device for the nipping roller and/or for the upper roller of the front roller pair. The cleaning device can, for example, comprise a lamellar ring fitted onto the collar of the friction roller. 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a part sectional schematic side view through an apparatus for condensing a fiber strand, constructed according to a preferred embodiment of the 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 friction wheel and the nipping roller; 
     FIG. 4 is a view in the direction of the arrow IV of FIG. 3; 
     FIG. 5 is a view similar to FIG. 3 of a friction roller comprising a cleaning device; and 
     FIG. 6 is a view in the direction of the arrow VI of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The apparatus for condensing a drafted fiber strand  12  shown in FIGS. 1 and 2 is a component part of a ring spinning machine. The apparatus is connected to a drafting unit  1  present at each spinning station of the ring spinning machine, of which essentially only the front roller pair  2  and the apron roller pair  3  arranged upstream of the front roller pair  2  in transport direction A are shown. A bottom apron  4  and an upper apron  5  can be seen. 
     The front roller pair  2  comprises a driven bottom cylinder  6  extending in machine longitudinal direction, and an upper roller  7  arranged at each spinning station. The upper rollers  7  of two adjacent spinning stations are joined together to form a pressure roller pair by means of a joint axle  8  in a way not further shown, as is mostly the case in operating machines. The upper roller  7  comprises a flexible coating  9 , which presses against the bottom cylinder  6 . The upper rollers  7 , joined together to form a pressure roller pair, are mounted in a top arm  10  (indicated only) by means not shown. 
     In the drafting unit  1 , a sliver or roving  11  is drafted to the desired degree of fineness and transported through the drafting unit  1  in transport direction A. Directly downstream of the front roller pair  2 , a ready drafted fiber strand  12  is present, which is to be further condensed by means of bundling in a condensing zone  13  downstream thereof. In this condensing zone  13 , the fiber strand  12  is not yet provided with a spinning twist. During condensing, the outermost fibers of the fiber strand  12  are deposited on the core strand, so that the thread  25  leaving the condensing zone  13  is less hairy, and thus smoother and hereby also more tear-resistant. 
     The condensing zone  13  comprises a suction device  14 , which is formed essentially by a hollow section  15  extending over a plurality of spinning stations. A suction connection  16  is arranged for a plurality of spinning stations, which leads to a vacuum source (not shown). In the hollow section  15 , one suction slit  17  is applied per spinning station, which suction slit  17  faces the fiber strand  12  to be condensed and which extends essentially in transport direction A. The width of the suction slit  17  is significantly larger than the diameter of the condensed fiber strand  12 . 
     The outer contour of the hollow section  15  forms a stationary sliding surface  18  for an air-permeable transport belt  19 , which is advantageously designed as a very fine-pored and thin woven belt, and which transports the fiber strand  12  over the sliding surface  18  and the suction slit  17 . 
     The condensing zone  13  is bordered on an exit side by a nipping roller  20 , which presses the fiber strand  12  and the transport belt  19  against the sliding surface  18  and which acts hereby as a twist block for the thread  25  to be subsequently twisted. The axle  21  (indicated only) of the nipping roller  20  can also be mounted in the top arm  10  in a way not further shown here. 
     The nipping roller  20  comprises a flexible coating  22 , which can be designed similarly to the flexible coating  9  of the upper roller  7 . The nipping roller  20  forms, together with the hollow section  15 , a nipping point  24 , so that the condensing zone  13  is located entirely between a nipping point  23  of the front roller pair  2  as well as the above mentioned nipping point  24 . In order that the condensing effect does not lessen before the nipping point  24  is reached, the suction slit  17  is guided at least to the nipping point  24 . From this point on, the thread  25  to be twisted is fed in delivery direction B to a ring spindle (not shown). 
     The speeds of the fiber strand  12  should be essentially the same at the two nipping points  23  and  24 . This can be achieved in that, according to the present invention, the drive is derived from the front roller pair  2  and transferred by means of a friction roller  26  to the nipping roller  20 . 
     The friction roller  26 , whose axle  27  is also mounted in a way not shown in the top arm  10 , presses against the upper roller  7  of the front roller pair  2  as well as against the nipping roller  20 . The axle  27  of the friction roller  26  is loaded with a loading spring  29  affixed in the top arm  10 . 
     In the specific embodiment shown in FIGS. 1 and 2, the friction roller  26  has an elastomer coating  28 , which can correspond to the flexible coatings  9  and  22  of the upper roller  7  and the nipping roller  20 . In the case of this embodiment, it is also provided that the flexible coating  22  of the nipping roller  20  has an area which is provided for the drive by the friction roller  26  as well as for the drive of the transport belt  19 . The friction drive  26 , which thus receives its drive from the upper roller  7 , drives the nipping roller  20 , which in turn drives the transport belt  19 . 
     In the embodiments described below, those components which are identical with those in FIGS. 1 and 2, shall not be described again, and the identical components shall be denoted by the same reference numbers. 
     In the embodiment to be described according to FIGS. 3 and 4, the only changes in contrast to the variations described above are essentially a differently designed upper roller  30  of the front roller pair  2 , a differently designed nipping roller  32  as well as a differently designed friction roller  35 . The upper roller  30  differs from the upper roller  7  only in a somewhat extended flexible coating  31 . 
     The nipping roller  32  now has two different areas  33  and  34  of the flexible coating, whereby these two areas  33  and  34  have in addition two different diameters, which does not necessarily have to be the case. The area  34  with the smaller diameter serves the drive by the friction roller  35 , while the area  33  with the larger diameter is arranged at the spinning area and drives the transport belt  19 . Due to these differing diameters it is possible to apply a small tension pull to the fiber strand  12  to be condensed in the condensing zone  13 . 
     The friction roller  35  is narrower in this embodiment of the present invention than the variations described above and is made of steel, even on its outer periphery. The friction roller  35  is knurled or fluted on its peripheral area, so that a good frictional effect is attainable. The friction roller  35  is hereby pressed against the area  34 . A separation of drive and spinning area is thus provided. 
     The embodiment according to FIGS. 5 and 6 corresponds to a great extent to the embodiment according to FIGS. 3 and 4, whereby only a somewhat modified friction roller  36  is provided. 
     The friction roller  36  is again designed as a pressure roller and is provided with a fitted collar  37 . This collar  37  serves to take up a lamellar ring  39 , which acts as a cleaning device  38 . 
     The friction roller  36 , as in the embodiment according to FIGS. 3 and 4, also presses here with a knurled or fluted steel ring against an area  34  of the nipping roller  32  as well as against an extended area of the flexible coating  31  of the upper roller  30 , whereas a lamellar ring  39  is arranged at the spinning area, the outer diameter of the lamellar ring  39  corresponding to the area  33  of the nipping roller  32  with the enlarged diameter. Due to the different peripheral speeds between the lamellar ring  39  and the area  33 , the lamellar ring  39  acts with light pressure as a cleaning device  38 . 
     In a way not shown, the flexible coating  31  of the upper roller  30  can be provided with different diameters in such a way that the lamellar ring  39  also cleans the periphery of the upper roller  30  during operation. 
     In all embodiments the suction slit  17  is shown as extending in transport direction A. However, it should be noted that it was found out that favorable condensing results are obtained with a design in which the suction slit  17  deviates from the transport direction A by an angle of about 5° to about 12°. 
     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.