Abstract:
A top roller carrier for drafting systems in spinning machines with at least one pair of feed rollers, one pair of apron rollers and one pair of output rollers as top rollers and with holding devices for the top rollers, and wherein the top rollers are rotatably mounted on the ends of axles which are held centrally between the top rollers. According to the present invention, a common holding device is provided for the axle of the output rollers and the axle of the apron rollers and is movably connected to the top roller carrier and fixes the two axles at a rigid spacing with respect to one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of German patent application 10 2005 005 382.3, filed Feb. 5, 2005, herein incorporated by reference. 
   FIELD OF THE INVENTION 
   The invention relates to a top roller carrier for drafting systems in spinning machines and, more particularly, to a top roller carrier with at least one pair of feed rollers, one pair of apron rollers and one pair of output rollers as top rollers and with holding devices for the top rollers, wherein the top rollers are rotatably mounted on the ends of axles which are held centrally between the top rollers. 
   BACKGROUND OF THE INVENTION 
   Top roller carriers are generally used as a carrying and loading arm for pairs of top rollers and can be lifted relative to the bottom rollers mounted so as to be secured to the machine. 
   In drafting systems, it is known to carry out an adaptation, which is necessary for reasons concerning textile technology, to the fibre material or the staple length of the fibre material and, for this purpose, to change the spacing between the clamping lines formed by the pairs of rollers of the drafting system. This spacing is also called the field width. It is known, for this purpose, to configure the top roller carrier for the field width adjustment in such a way that the spacings between the top rollers can be adjusted. German Patent Publication DE 43 35 889 C2, for example, shows a top roller carrier for drafting systems of spinning machines, in which the top rollers are mounted in holders by slides. The slides can be adjusted separately from one another for the field width adjustment, in each case, in the longitudinal direction of the top roller carrier. A holder for top aprons is associated with the apron roller. Configured in the top roller carrier is an elastic hollow body, which is loaded with pressure, pneumatically or alternatively hydraulically. The pressure acts via a base plate of the hollow body on plungers and loads the feed and the output roller and also the apron roller and the holder for the top apron with a force, which presses against the bottom rollers and allows the top rollers to act as pressure rollers. 
   The German Utility Model G 92 14 598 U1 describes a top apron holder for spinning machine drafting systems with an apron guide, which deflects the top apron and tensions it under the pressure of a spring. The apron guide is held on a central piece of the top apron holder. 
   A load carrier for drafting systems of spinning machines is known from the generic German Patent Publication DE 39 37 667 A1, in which the axles of the top rollers are each fastened in holders, which can be displaced independently of one another in longitudinal guides of the top roller carrier for the field width adjustment. The drafting system is a three roller drafting system, in which the top rollers are configured as pressure roller twins. The pressure on the top rollers is applied by the holders acting like a spring element because of their shape. The holders are not set up to vary the pressure force. 
   The holders of the known top roller carriers, as they are described in the above-mentioned documents, have the common drawback that they require a large number of individual parts and require time-consuming field width adjustments that are prone to faults for the apron and output roller. 
   Swiss Patent Publication CH 656 647 A5 shows an apron drafting system, which is used in a spinning machine and has three pairs of rollers consting, in each case, of top and bottom rollers. The top rollers are held in the top roller carrier, which is arranged so as to be pivotable about a pivot pin with respect to the machine stand. 
   The box-shaped top roller carrier contains a guide arrangement for the top roller pins. Holding down devices, which are spring-loaded in their longitudinal central region and with which approximately the same gap contact pressure is to be achieved for all the pairs of rollers, engage thereon. The top roller carrying pins are guided for this purpose in guide slots of the top roller carrier. The play always occurring in this case between the top rollers and guide edges counteracts an exact adjustment of the clamping point and leads to wear problems. The spacing of the top rollers from one another in the longitudinal direction of the top roller carrier cannot be changed for this reason. An adjustment of the field widths, such as is necessary during adaptation to the fibre material to be respectively processed, is not possible. 
   Both British Patent Publication GB 691615 and U.S. Pat. No. 3,256,570 show three-roller drafting systems for spinning machines, in which the top roller carrier has slots which are spaced apart from one another in the longitudinal direction of the top roller carrier for guiding the top roller carrying pins or the axles of top rollers. 
   It can be inferred from British Patent Publication GB 691615 that, to change the spacing of the top rollers guided by the top roller carrier, the top roller carrier present has to be replaced by a top roller carrier, in which the arrangement or the spacing of the slots differs according to the changed requirements. For a fibre material change mentioned as an example, of cotton to viscose, it is described as sufficient to hold two or three alternatively usable or replaceable top roller carriers in readiness. A replacement of this type of the top roller carrier including disassembly and installation of the top rollers is very laborious. 
   In the drafting system of U.S. Pat. No. 3,256,570, all three top rollers are carried respectively at their axle ends by a frame-like top roller carrier. The guides of the top roller carrying pins are also affected by play as in the apron drafting system of Swiss Patent Publication CH 656 647 A5 and particularly prone to wear because of the top roller carrier pins co-rotating with the top roller. U.S. Pat. No. 3,256,570 describes how the pivoting up of the top roller carrier can be facilitated in magnetically held top rollers and gives absolutely no indication as to how the spacings apart of the top rollers could be changed. This is also only possible by means of a very laborious replacement of the top roller carrier in the drafting system of U.S. Pat. No. 3,256,570. 
   SUMMARY OF THE INVENTION 
   The object of the invention is to improve the known top roller carriers. 
   The object is achieved according to the invention by means of a top roller carrier for drafting systems in spinning machines with at least one pair of feed rollers, one pair of apron rollers and one pair of output rollers as top rollers and with holding devices for the top rollers, and wherein the top rollers are rotatably mounted on the ends of axles which are held centrally between the top rollers. According to the present invention, a common holding device is provided for the axle of the output rollers and the axle of the apron rollers and is movably connected to the top roller carrier and fixes the two axles at a rigid spacing with respect to one another. 
   Advantageous configurations of the top roller carrier are described more fully herein. 
   The holding device according to the invention movably connected to the top roller carrier combines the axle receivers for the output roller and the apron roller in one component. The position of the axle receivers in the holding device and therefore the position of the axles of the output roller and the apron roller with respect to one another can be produced with a high degree of manufacturing precision. In this manner, an extraordinarily exact positioning of the clamping points of the apron roller and output roller can be achieved and maintained. The parallelism of the output roller and apron roller is always ensured. The addition of conventional safety spacings can be dispensed with. Such conventional safety spacings are taken into account, for example, in the adjustment of the desired field width, because the achievable accuracy in the field width adjustment can only be inadequate. Manufacturing and assembly inaccuracies, which can add up with multi-part holders, allow an oblique position of the top rollers, which disadvantageously influences the adjustment of the field widths. Additions in the form of safety spacings are to counteract this. The holding device according to the invention reduces the number of components for the holding device compared to conventional holding devices. In order to be able to load the holding device with a force in the direction of the bottom rollers, only a single common mechanism, for example a spring mechanism, is necessary. The force loading of the output roller and apron roller can take place separately from other top rollers like the feed roller. The outlay occurring during a change in the significant field width adjustment between the apron roller and feed roller is small. The outlay required during production and assembly is lowered as less and only simpler parts are required. 
   The holding device advantageously comprises a top apron deflection device, the top apron deflection device being configured as a vane, which ends at the free end with a deflection edge. The number of components on the top roller carrier is thereby further reduced. The orientation of the top apron deflection device with respect to the apron roller is very precise and cannot disadvantageously change due to the effect of assembly tolerances or the summation of manufacturing tolerances of a plurality of components. The deflection edge cannot be deflected from the parallel orientation by poor adjustment or fibre materials which are difficult to draw. A deflection of this type would disadvantageously lead to number fluctuations or even to aprons running off axially. The degree of opening remains the same. 
   If the deflection edge is configured as a chromium-plated metal bar and if the metal bar is fastened to the vane, only a little friction occurs during the deflection process, and the deflection edge is only subjected to low wear. The apron slippage is minimised by the low-friction deflection edge. 
   Maintenance intervals can be increased. The apron roller only has to be disassembled rarely or not at all. 
   An apron tensioner is preferably associated with the holding device and is oriented axially parallel to the top rollers and movable relative to the holding device. This embodiment allows a simple flexible tensioning of the top aprons. An excellent apron synchronisation is ensured. 
   The required contact force can easily be applied with a holding device, which has a head part, and in which, by a force acting from above, a loading force can be exerted on the apron rollers and output rollers configured as a top roller, by means of the head part. If the head part is configured as a separate component which can be longitudinally displaced relative to the holding device, the division of the pressure force over the apron roller and the output roller can be changed. 
   Both a head part, which is configured as a pressure plate, over which an elastic hollow body is arranged, and wherein the force sufficient for generating the loading pressure can be generated, pneumatically or hydraulically, with the aid of the hollow body, and also a head part, over which a spring is arranged in the top roller carrier, by means of which spring the head part can be loaded with the force, allow a regulated loading of the output roller and the apron roller with a pressure force. With uniform pressure distribution owing to the non-interrupted pressure plate, the wear can be reduced, the service life increased and the maintenance intervals can be lengthened. To apply the loading pressure to the output roller and apron roller, only a single device is necessary for the two rollers. A common adjustable force loading of output roller and apron roller separately from other top rollers like the feed roller, is possible. 
   A holding device consisting of plastics material can be produced particularly economically, has only a low weight, is resistant to corrosion and satisfies the elasticity demands on the holding device. Polyoxymethylene, designated POM, is distinguished by a high degree of hardness, stiffness and toughness and is particularly suitable for this application. If the plastics material is electrically conductive, an uncomplicated discharge of electrostatic charges is ensured. Thus disturbances in the spinning operation caused by electrostatic charge are avoided. 
   Time-consuming field width adjustment work prone to errors for the apron and output roller is dispensed with. Only a simple adjustment for the feed roller is required. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the invention are described below with the aid of the figures, in which: 
       FIG. 1  shows a simplified partial view of a top roller carrier with a holding device in a side view, partially in section, 
       FIG. 2  shows the holding device of  FIG. 1  in the view A-A, partially in section, 
       FIG. 3  shows a plan view of the top apron deflection device of the holding device of  FIG. 1  in the view I-I, partially in section, 
       FIG. 4  shows the deflection edge of the top roller deflection device with metal bar, in a side view, 
       FIG. 4A  shows a deflection edge of the top roller deflection device with the metal bar in an alternative position, in a side view, 
       FIG. 5  shows a simplified partial view of a top roller carrier with a spring-loaded holding device in a side view, partially in section. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 , shows a part of a top roller carrier  1 , which carries a holding device  2 . Top roller carriers of this type are used on drafting systems of spinning machines. The holding device  2  has axle receivers  3 ,  4  for the axles  5 ,  6  of the pair of apron rollers and the pair of output rollers. The position of the pair of apron rollers and the pair of output rollers is indicated in each case by an apron roller  7  and an output roller  8 . The two axle receivers  3 ,  4  are part of the one-piece holding device  2 . The holding device  2  consists of the elastic plastics material POM. Because of the elasticity, the axles  5 ,  6  can be pressed in a simple manner into the axle receivers  3 ,  4  during assembly. The axles  5 ,  6  are reliably held in the snap-on connection. The pair of apron rollers and the pair of output rollers together with the pair of feed rollers, not shown in  FIG. 1 , form the top rollers of the drafting system. The associated bottom rollers  9 ,  10  are positioned in such a way that their rotational axes  11 ,  12  are offset with respect to the rotational axes  13 ,  14  of the output roller  8  and the apron roller  7 . The rotational axis  11  of the bottom roller  9 , in the view of  FIG. 1 , is not vertically beneath the rotational axis  13  of the output roller  8 , but offset slightly to the right. The rotational axis  12  of the bottom roller  10 , on the other hand, is offset slightly to the left with respect to the rotational axis  14  of the apron roller  7 . If the apron roller  7  and the output roller  8  are loaded with pressure and pressed against the bottom rollers  9 ,  10 , horizontal force components occur. The horizontal force component, which acts on the output roller  8  is directed to the left in the view of  FIG. 1  and is called a forward biasing force. The horizontal force component, which acts on the apron roller  7  is directed to the right in the view of  FIG. 1  and is called a rearward biasing force. The forward biasing force and rearward biasing force are substantially the same in the embodiment shown in  FIG. 1 , so only a small or hardly any horizontal force component acts on the holding device  2 . There is therefore an almost friction-free coupling of the holding device  2  movably connected to the top roller carrier  1  to the top roller carrier  1 . A stable position of the apron roller  7  and the output roller  8  with respect to the bottom rollers  9 ,  10  is established. 
   The pressure loading of the apron roller  7  and the output roller  8  takes place pneumatically. A head part which is configured as a pressure plate  15  and on which the base plate  16  of an elastic hollow body  17  rests is arranged on the holding device  2 . By loading the hollow body  17  with compressed air, the holding device  2  is pressed downwardly, the pressure is transferred to the apron roller  7  and the output roller  8  and the apron roller  7  and the output roller  8  are pressed on the bottom rollers  9 ,  10 . The pressure plate  15  is displaceable in the longitudinal direction of the top roller carrier  1  relative to the holding device  2 . If the pressure plate  15  in the view of  FIG. 1  is displaced to the left, the pressure on the output roller  8  is increased, and the pressure on the apron roller  7  becomes less. If the pressure plate  15  is displaced to the right, the pressure on the output roller  8  reduces and the pressure on the apron roller  7  becomes greater. In this manner, the pressure distribution on the apron roller  7  and the output roller  8  can be designed so as to be variable. 
   The holding device  2  has an elongated hole  18 , the edges  19 ,  20  of which in each case run on the radius R TR , which is placed round the pivot point of the top roller carrier  1 . A hollow bolt  21  is guided in the elongated hole  18  and is rigidly connected to the top roller carrier  1  by means of screws  22 . Owing to the interaction of the elongated hole  18  and the hollow bolt  21 , the holding device  2  can be positioned independently of the level which the top roller carrier  1  adopts. The metallic hollow bolt  21  reinforces the U-shaped, downwardly open body of the top roller carrier  1 . 
   The holding device  2  has an top apron deflection device configured as a vane  23 , via which the top apron  24  is guided, toward the axle receivers  3 ,  4 . The free end of the vane  23  has a spacing R from the rotational axis  14  of the apron roller  7 . The spacing R is, for example, 35 mm, in an embodiment for the processing of short-staple fibre material. The free end forms the deflection edge  25  for the two top aprons  24 ,  26  of the pair of apron rollers. The width of the vane  23  is matched to the greatest required spindle division. In the direction of action of the force, by means of which the top aprons  24 ,  26  are tensioned, the vane  23  is configured so as to be very stiff. In the vertical direction, the deflection edge  25  at the free edge of the vane  23  can be moved without a large exertion of force. Therefore, the degree of opening X can be easily adjusted for the opening widths required in each case. The form of the vane  23  can be seen in  FIGS. 2 and 3 . The position of the top apron  26  is shown in  FIG. 2  by dashed lines. The vane  23  has a lug  27  on which a piston  28  applies a contact force. The contact force is transferred to the piston  28  from the base plate  16 . The piston  18  is movably guided in a bore  29  of the holding device  2 . 
     FIG. 4  shows an alternative embodiment to the vane  23  shown in  FIGS. 1 to 3 . The vane  30  has a receiver  31  for a chromium-plated replaceable metal bar  32 . The receiver  31  is configured in such a way that the metal bar  32  can be positioned alternatively in two different positions.  FIG. 4  shows a first position of the metal bar  32  in which the spacing R 1  from the rotational axis  14  of the apron roller  7  is produced.  FIG. 4A  shows a second position of the metal bar  32 , in which the spacing R 2  is produced. The spacing R 2  is smaller than the spacing R 1 . Because it is possible to replace the metal bar  32 , the position of the deflection edge  25  can be adapted by a suitable selection of the metal bar  32  and/or by the selection of the position of the metal bar  32  to the respective production conditions in such a way that an optimum spinning geometry is ensured. The position of the deflection edge  25  can be selected such that an adequate spacing is ensured between the output roller  8  and top apron  24 . A quality-impairing brushing of the top apron  24  on the output roller  8  is reliably avoided. The chromium-plated metal bar  32  is particularly resistant to wear and brings about low-friction deflection of the top aprons  24 ,  26 . The apron slippage and the wear of the top aprons  24 ,  26  is reduced. 
   The holding device  2  has a vertically oriented and downwardly open slot  33  between the vane  23  and the axle receiver  3 . The slot  33  is used as a guide link for the carrier axle  34  of an apron tensioner  35 . A guide element  36 ,  37  is fastened, in each case, as shown in  FIG. 2 , on either side on the carrier axle  34 . The guide elements  36 ,  37  hold the top aprons  24 ,  26  in the desired position and prevent their axial displacement. The gap  38  between the vane  23  and the lower side of the holding device  2  is slightly smaller than the diameter of the carrier axle  34 . When installing the carrier axle  34 , the vane  23  is deflected because of its elasticity and the carrier axle  34  can easily be pressed into the slot  33 . The carrier axle  34  is prevented in this manner from falling out of the holding device  2 . 
   A spring element  39  presses from below against the carrier axle  34 . The top aprons  24 ,  26  are tensioned by means of the carrier axle  34  with a selectable force. The position of the tensioned top apron  26  is shown by dashed lines in the view of  FIG. 2 . The top apron  24  adopts a corresponding mirror-inverted position on the left-hand side of the holding device  2 , but is not shown in  FIG. 2 . The top rollers and the bottom rollers together with axles are also not shown in  FIG. 2 . 
   The holding device  2 , on each side, has a knob  66 , with which the holding device  2  is secured in the top roller carrier  1 . 
     FIG. 5  shows a top roller carrier  40  with a holding device  41 , which is loaded by means of a spring force in order to generate the force, required for the spinning process, of the apron roller  42  and the output roller  43  on the bottom rollers  44 ,  45 . The bearings of the bottom rollers  44 ,  45 ,  46  and the top rollers configured as feed rollers  47  are not shown in  FIG. 5  for reasons of simplification. The axle receiver  48  configured as a snap-on connection holds the axle  50  of the apron roller  42 . The axle receiver  49  holds the axle  51  of the output roller  43 . The forward biasing force of the output roller  43  and the rearward biasing force of the apron roller  42  substantially balance each other out in the embodiment of  FIG. 5 , so only a slight or even no horizontal force component acts on the holding device  41 , as is also the case in the holding device  2  shown in  FIG. 1 . A head part configured as a pressure plate  52  is arranged on the holding device  41 . The pressure plate  52  consists of steel. The pressure plate  52  is suitable both for holding devices for processing short-staple fibre material and for holding devices, which are to be used for processing medium-staple or long-staple fibre material. 
   The holding devices can be replaced simply and rapidly. The pressure plate  52  and the holding device  41  fastened to it are pivotally connected to a pressure plate  54  by means of a snap-on connection and a bolt  53 . The pressure plate  54  can be pivoted about a pivot axle  55  rigidly connected to the top roller carrier  40 . The compression spring  56  is supported, on the one hand, on a transverse pin  57  of the pressure plate  54  and, on the other hand, on a support disc  58 . The support disc  58  rests on an eccentric element  59 . The eccentric element  59  is rotatably mounted on a pivot axle  60 . The pivot axle  60  is rigidly connected to the top roller carrier  40 . By rotating the eccentric element  59 , the force can be adjusted, with which the compression spring  56  loads the pressure plate  54  and therefore, via the holding device  41 , the apron roller  42  and the output roller  43 . The pressure plate  54  is configured such that the holding device  40  is loaded with a substantially constant force, even if the height position of the top roller carrier  40  is adjusted within a specific range. This range may be about 6 mm. A compression spring  61  loads the vane  65  with a specific force directed downwardly. The vane  65  is used to deflect the top apron  62  of the apron roller  42  and the other top apron and the associated other apron roller, neither of which are shown in  FIG. 5 , and which in each case form a pair with the top apron  62  and the apron roller  42 . An apron tensioner  63 , as shown in  FIG. 1 ,  2  or  4 , is used to tension the top apron  62  and the top apron arranged in a mirror-inverted manner with respect thereto. The apron tensioner  63  can be moved up and down in the slot  64  and is pressed upwardly by a spring element, not shown. 
   The operating position of the top roller carrier  40  shown in  FIG. 5  is secured by means of the lever  67 . 
   The holding devices, configured in each case for the processing of short-staple, medium-staple or long-staple fibre material, can be replaced easily and simply. 
   The apron guides can be configured to rotate in a smooth-running manner, so the apron slippage can be further reduced. 
   In the scope of the invention, further embodiments of top roller carriers are possible. For example, instead of the vanes  23 ,  30 ,  65  shown in the figures, which form a one-piece part with the holding device  2 ,  41 , a vane can be used, which is configured as a separate part and fastened to the holding device  2 ,  41 .