Patent Publication Number: US-2006010656-A1

Title: Adjustment device for drafting device drafting distances

Description:
The present invention relates, according to the preamble to the independent Patent Claims  1 ,  11 , and  12 , to a housing with a pair of rollers mounted inside it, a drafting device with a housing of this type, as well as a textile machine with a corresponding drafting device.  
      Drafting devices are used in textile technology for the drafting or drawing of fibre slivers in spinning machines. Following the drawing process, the fibre slivers which are drawn in the drafting devices are spun by means of a spinning process to form a yarn. The invention described hereinafter is concerned with the adjustment, or adjustability, of the drafting devices referred to, i.e. the adjustability of the drafting distances in a drafting device. A drafting device consists of at least two pairs of rollers, but for preference of three or four pairs of rollers. A fibre sliver running through the drafting device is drawn by the different rotation speeds of the pairs of rollers. The drawing or drafting takes place between two pairs of rollers following in succession, i.e. in the area between the nip lines of the two pairs of rollers. The distance between two such nip lines is also referred to as the nip or grip distance. Located within such a nip distance is a drafting zone, in which the fibres of the fibre sliver are drawn against one another. Three-roller drafting devices with a preliminary drafting zone and a main drafting zone are widespread. In order to achieve optimum guidance and optimum drawing of the fibres in the drafting devices, the nip distances of the individual drafting zones must be adjusted to the staple length of the fibres which are to be processed. In the drafting zones, the optimum nip or grip distance is slightly longer than the longest fibres which are to be processed (by about 2 mm). In order to adjust the nip distances to the staple fibres to the optimum amount, the drafting zones must accordingly be adjustable steplessly or at least in very small steps (step length approx. 1 mm); this applies in particular to the preliminary drafting zone. The adjustability of the nip distance in the preliminary drafting zone is of particular importance because it is here that genuine drawing or drafting processes of 1.1 to 5 times are carried out, without an additional external fibre guide (such as an apron) being present. For the main drafting zone (with drafting or drawing procedures of about 10 to 100 times), adjustability of the nip distance is likewise of advantage, even if in this case the fibre guidance is guaranteed by the aprons which are usually present. It is sufficient in this case, however, if the nip distance is adjustable in from two to a maximum of five steps.  
      It is generally usual (e.g. with ring-spinning drafting devices), when adjusting the nip distance, always to move two axles of a roller pair (see in this connection, for example, DE 1 123 959 or DE 1 122 885). That is to say, both the driven roller as well as the loaded top roller are moved together. These devices demonstrate the disadvantage of conventional drafting devices. The adjustment of the pairs of rollers when the fibre material which is to be processed is changed is associated with a considerable amount of work. This applies in particular if the main drafting or drawing distance must he changed, since in this case both the lower as well as the upper aprons and all upper apron cages must be replaced.  
      One possible arrangement for this problem is disclosed by DE 489 810, although only for single-apron drafting devices which were used in earlier times. The adjustable upper intake roller disclosed in DE 489 810 is mounted on a guided carriage and is pressed by means of screws against the lower roller which pertains to it. Thanks to the simple design of single-apron drafting devices and the absence of an upper apron, the adjustment of the upper roller was easy to carry out.  
      With modern double-apron drafting devices, adjustability of this kind is no longer possible, since the upper roller carries an apron.  
      With the device according to DE 1 122 885, both rollers of the pair of inlet rollers are moved. This can be derived from their Description, since the device is intended to be suitable for the processing of short-staple and long-staple fibres, i.e. from cotton to wool. Because it must be possible for widely differing nip distances to be adjusted in order for such suitability to be attained, the text cannot disclose anything other than the joint adjustment of upper and lower rollers. The use of such a single-apron drafting device for the processing of short-staple as well as long-staple fibres is no longer conceivable in modern machines. Long aprons would be necessary for this, which, with the present-day speeds of high-speed drafting devices (speeds greater than 100 m/min), would begin to flutter.  
      A further device for the adjustment of pairs of rollers is disclosed by EP 362 477 A1. The device which is disclosed in this, however, relates to what are referred to as drafting or drawing frames. Drafting or drawing frames do not contain any aprons, since they are only required to achieve far fewer draftings. In return, however, they exhibit very high delivery speeds of up to 1000 m/min at the delivery roller pair. The contact pressure at the nip line between two rollers is also very high, in order that it can be ensured that nipping or gripping is still sufficient at these speeds and with these large fibre masses. With high speeds and pressures of this type, the use of aprons is excluded, since a very high amount milling work occurs at the apron, as a result of which the apron would become too hot due to the poor heat dissipation.  
      The present invention is therefore based on the problem of improving the adjustability of the nip distance to modern high-speed drafting devices (outlet speeds greater than 100 m/min).  
      This problem is resolved by the features in the independent Patent Claims  1 ,  11 , and  12 .  
      In the Claims and the following Description, mention is made of “bottom roller” and “top roller”. These designations of the two rollers, which are generally conventional in textile technology, are derived in particular from the arrangement of the drafting device, which as a rule is horizontal. The spatial arrangement of the drafting device and of the rollers is, however, absolutely not of significance to the present invention. On the contrary, in particularly preferred application possibilities of the invention, provision is even expressly made for the drafting device to be arranged essentially perpendicularly. Attention is therefore expressly drawn to the fact that the terms “bottom roller” and “top roller” throughout the application are not to be interpreted in respect of their spatial position, restricting them to “top” or “bottom”. The term “bottom roller” can, as a rule, be understood to mean the cylinder of the roller pair. This is for preference made of metal (such as steel). The “top roller” as a rule exhibits an elastic covering (e.g. rubber).  
      It has been demonstrated that, in particular with high-speed drafting devices, the nip distance can be adjusted simply by an axle being moved, without any disadvantageous effects being determined on the yarn quality or the spinning result. The adjustment of the nip distances is thereby substantially simplified. If only one roller is moved, a cage can be used for the rigidly mounted roller, which does not need to be changed in the event of adjustment. This too simplifies the adjustment. In order to keep the nip or grip forces between the two rollers constant during the adjustment, it is advantageous if the loading force on the nip point can be automatically or manually adjusted. In order for the aprons to exhibit sufficient tension in every position to which they are adjusted, the apron may exhibit a tensioning device at the movably mounted roller. If both rollers have an apron, then both aprons may each exhibit a tensioning device. It would also be conceivable, however, for particularly elastic or extendible aprons to be used, as a result of which no apron tensioning devices would have to be used. And even if the aprons must be replaced because a tensioning device or the elastic properties are not present, a considerable time saving is still achieved, because only one roller needs to be moved.  
      Advantageous embodiments and forms of the invention are to be found in the dependent Claims. 
    
    
      The invention and the concepts of the invention are explained hereinafter on the basis of the embodiments represented in the Figures. Attention should be expressly drawn to the fact, however, that the invention and the concept of the invention are not restricted to the embodiments shown in the examples. These show:  
       FIG. 1  An adjustable pair of rollers according to the invention  
       FIG. 2  An adjustable pair of rollers according to the invention with an apron tensioning device  
       FIG. 3 A  housing for an adjustable pair of rollers according to the invention  
       FIG. 4 A  spinning position of a textile machine with a drafting device, which exhibits an adjustable pair of rollers according to the invention 
    
    
       FIG. 1  shows an adjustable pair of rollers  2  according to the invention. The rollers of the pair of rollers  2  are naturally mounted in an appropriate housing, although for the sake of overview this is not represented in the Figure. The pair of rollers  2  consists of a bottom roller  4  and a top roller  5 , which are in contact at what is referred to as the nip line  6 . The top roller  5  is rigid in its arrangement. The bottom roller  4 , by contrast, is arranged so as to be movable about the axis of the top roller  5 , with the result that the nip line is movable (see positions shown as dotted lines and arrow in  FIG. 1 ). As a result of the movement of the bottom roller  4  (see arrow), the nip line  6 , and therefore also the nip distance from the preceding roller pair to the next roller pair (not represented) can be shortened or lengthened. In order for the bottom roller  4  to be arranged axial-symmetrically about the rigidly arranged top roller  5 , no adjustment of the top roller  5  is provided for. As a result, not only can a readjustment be carried out more quickly, but the mounting of the top roller  5  can also be simpler in design. In addition to this, the adjustability according to the invention of the roller pair allows for a single cage  9  and a single top apron to be used. Hitherto, with the adjustment devices according to the prior art, it was not only necessary for both rollers to be moved, but it was also necessary, as well as the cage  9 , for the apron to be replaced (in order to adjust to the new nip distance). Due to the fact that the roller  5  is arranged to be rigid, this requirement for replacement no longer applies, as a result of which a considerable saving of time can be achieved.  
      In  FIG. 1 , aprons  8  are applied to both the rollers. The aprons are tensioned by the reversing rail  10  or the cage  9 . For the adjustability of the bottom roller  4 , it is necessary for the apron  8  of the bottom roller  4 , as represented, to be extendible, or to be tensioned by means of an appropriate tensioning device (see  FIG. 2  following). As mentioned earlier, the top roller  5  is arranged in a rigid manner (i.e. its axle is not movable). According to the invention, however, it would also be conceivable for the rigid axle of the top roller  5  to be capable of movement in the plane  7 , which is formed by the two axes of the rollers. A displaceable mounting of this type would be sensible provided that the fibre material to be drawn or passing the nip line is compressed in a constant and uniform manner at the nip line  6  (a loading means which can be used for this purpose is represented in  FIG. 3  described hereinafter). An axis which is displaceable in this manner would have the effect that a deflection of the top roller  5  would not lead to any displacement of the nip line  6 .  
       FIG. 2  shows the adjustable pair of rollers  2  according to the invention and according to  FIG. 1 , whereby an additional apron tensioning device  13  is provided for. This apron tensioning device  13  is intended in particular for aprons  8  which are not elastic, or not sufficiently elastic, to compensate for the different nip distance lengths due to extension. The apron tensioning device  13  shown can be designed as a tensioning spring. Other tensioning devices are also conceivable, however. It may of course be necessary for such a tensioning device to be provided for the apron of the top roller (not shown), if this is also not sufficiently elastic. If elastic properties or suitable tensioning devices are not present, the bottom apron can, according to the invention, also simply be replaced.  
      According to the invention as described heretofore, and as represented in particular in  FIGS. 1 and 2 , it is not essential to the invention that the roller  5 , mounted rigidly or only movable in the plane  7 , exhibits an apron  8 , although this is shown in the Figures.  
       FIG. 3  shows a housing  1  with a roller pair  2  mounted according to the invention. The housing  1  is represented in diagrammatic form. As well as a pair of rollers  2 , adjustable according to the invention, the mounting for a further pair of rollers  14  may also be exhibited. It is also conceivable that a further, third pair of rollers are mounted in the housing  1 . In this arrangement it can very readily be appreciated that the axle of the top roller  5  is not arranged rigidly, but is mounted in a moveable manner in the housing, in the plane formed by the two axles of the rollers  4  and  5 . The top roller  5  is subjected to load by means of a loading means  12  (represented in this case by a spring). For preference, the loading means  12  are adjustable. There are two possibilities represented in the Figure for the movement of the nip line: In one case, provision is made for a curved longitudinal hole  11 . A second variant shows a straight longitudinal hole  11  (represented as a broken line). For the latter variant, an adjustment of the top roller  5  is also necessary, which in this case is assured by the longitudinal hole  18 . In addition, provision can be made in the lower part of the housing  1  for a reversing rail  10 . The reversing rail  10  is required for the tensioning of the bottom apron (apron not shown). For preference, the pair of rollers  2  and the pair of rollers  14  represent the main draft zone of a drafting device, whereby a further pair of rollers would then be provided for in the housing  1  in front of the pair of rollers  4  (intake roller pair of a three-roller drafting device). In a further variant of the invention (not shown), however, it would be conceivable for the housing  1  to accommodate only the pair of rollers  4  mounted according to the invention, and for other pairs of rollers of the drafting device to be mounted in other ways.  
       FIG. 4  shows a spinning position of a textile machine which is equipped with an apron drafting device  3 . The apron drafting device  3  exhibits a pair of rollers  2 , which according to the invention are adjustable (represented in diagrammatic form only on the basis of the arrow at the bottom roller). Apart from this, it is also conceivable according to the invention that instead of the bottom roller, the top roller according to the invention is adjustable. The invention is particularly well-suited for double-apron drafting devices. The roller pair  2 , with the adjustable roller  4  according to the invention, forms the main drafting zone  15  of the apron drafting device  3 . The Figure shows a spinning position with a spinning box  20 , which is producing a yarn  17  by means of an air-spinning method. To do this, in the first instance a fibre sliver  19  is guided through the apron drafting device  3 , in which it runs through the preliminary drafting zone  16  and the main drafting zone  15 . The fibre structure  21  which is drafted in this way is then conducted into the spinning box  20 , where, by means of an air flow  23  around the mouth of a spindle  22 , the drafted fibre structure  21  is spun to form a yarn  17 . The invention is naturally also well-suited for spinning positions which manufacture a yarn by means of another spinning method. For example, instead of the air spinning process, a ring spinning process may be used. The invention is particularly well-suited for spinning machines with several spinning positions, whereby the spinning positions are independently equipped with individual drives (i.e. the drive is not effected by means of long shafts, which drive several spinning positions simultaneously). For preference, with three-roller drafting devices two pairs of rollers are equipped with an adjustment device according to the invention.  
      The invention is not restricted to the possibilities and embodiments explicitly mentioned. Rather, these variants are intended to serve as incentives for the person skilled in the art to implement the idea of the invention in the most favourable possible manner. Accordingly, further advantageous applications and combinations can be derived from the embodiments described, which likewise reproduce the concept of the invention and are intended to be protected by this Application. Some of the disclosed features have been described in combination in this Description, and are claimed in combination in the following Claims. It is, however, also conceivable for individual features of this Description to be claimed alone or in another combination in application of the concept of the invention. The Applicants therefore expressly reserve the right to make provision for other combinations in the application of the concept according to the invention.  
     LEGEND  
     
         
           1  Housing  
           2  Roller pair  
           3  Apron drafting device  
           4  Bottom roller  
           5  Top roller  
           6  Nip or grip line  
           7  Plane of the two roller axles  
           8  Apron  
           9  Cage  
           10  Reversing rail  
           11  Longitudinal hole  
           12  Loading means  
           13  Apron tensioning device  
           14  Additional roller pair  
           15  Main drafting zone  
           16  Preliminary drafting zone  
           17  Yarn  
           18  Longitudinal hole for top roller  3   
           19  Fibre structure  
           20  Spinning box  
           21  Stretched fibre structure  
           22  Spindle  
           23  Air flow