Abstract:
A service unit for the automatic servicing of work stations of a textile machine for manufacturing cheeses, in particular for an open-end rotor spinning machine. The service unit comprises a pneumatic auxiliary yarn supply and removal device with a pivotably supported yarn supply tube and a yarn cutting device.  
     The yarn cutting device is arranged on a centering and guide sheet in such a manner that it is positioned in the operating position of the centering and guide sheet adjacent the yarn catch device of a tube plate supported in a freely rotatable manner in a creel of the respective work station.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of German Patent Application DE 10141046.8, filed Aug. 22, 2001, herein incorporated by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a service unit for a textile machine for producing cheeses, in particular for an open-end rotor spinning machine.  
         BACKGROUND OF THE INVENTION  
         [0003]    Service units are known in the textile industry and have been successfully used in various forms for many years.  
           [0004]    For example, German Patent Publication DE 44 43 818 A1 discloses a service unit having a series of yarn manipulating elements for grasping and restarting the spinning of a yarn end run up onto a winding bobbin as well as an auxiliary yarn transport device. The auxiliary yarn transport device has a yarn supply tube that can be pivoted into various work positions. A yarn cutting device is integrated into the yarn supply tube a distance from its mouth. The yarn supply tube can be switched in a defined manner either to a compressed-air connection or to a suction-air connection so that an auxiliary yarn is available and removable by the auxiliary yarn transport device.  
           [0005]    Moreover, a yarn placing device is arranged on the supply tube holder. The yarn placing device makes it possible to control the transfer of the yarn produced in the open-end spinning device to a yarn catch device arranged adjacent one of the tube plates of the creel. The yarn placing device consists substantially of a pivotably supported yarn guide sheet as well as a yarn retention element. The yarn guide sheet comprises a yarn guide element with a yarn guide notch and a yarn placing slot.  
           [0006]    The yarn guide sheet, that can be driven via a thrust piston transmission, is supported in its end position from the inside on one of the creel arms. As a result of this support, the creel is driven somewhat in the “open” direction such that even in the most unfavorable circumstances the empty tube held between the creel arms in rotatable tube plates by friction is insufficiently clamped, so that a relative movement can occur between the tube and the tube plate. Such a relative movement between the tube and the tube plate or between the tube and the yarn catch device arranged on the tube plate is extremely undesirable during the yarn transfer.  
           [0007]    Moreover, the position of the yarn cutting device is disadvantageous in this known device. Therefore, as a consequence of the arrangement of the yarn cutting device inside the yarn supply tube, a relatively large distance to the supply tube mouth and therewith also to the yarn catch devices of the tube plate is given, such that a relatively long yarn end remains after the winding of the yarn start reserve which yarn end can be secured only with great difficulty. Thus, the yarn start reserve is often again destroyed during the winding process.  
           [0008]    Moreover, German Patent Publication DE 199 17 969 A1 discloses another service unit. The service unit of German Patent Publication DE 199 17 969 comprises a pivot arm upon which a yarn supply tube as well as a so-called manipulator with a head element that can be shifted in the direction of the creel are arranged. The manipulator acts during the yarn transfer with a device arranged on the head end on a guide sheet arranged in the creel in the “closed” direction and, therewith, reliably prevents a damaging relative movement from being able to occur between the yarn catch device arranged on the tube plate and between the empty tube during the yarn transfer. Therefore, the empty tube is fixed between the tube plates with such a contact force that it is ensured that the yarn catch device arranged on the tube plate rotates in an angularly synchronous manner with the empty tube. Moreover, a device in the form of a yarn guide edge arranged on the head element ensures that the yarn produced in the open-end spinning device is first transferred to a yarn catch device arranged on the tube plate and that the caught yarn is subsequently placed in a defined manner on the empty tube.  
           [0009]    In this service unit, the yarn cutting device is moved up closer to the mouth of the yarn supply tube; however, the yarn cutting device is integrated into the supply tube so that even the previously recognized problems with unsecured yarn ends are not able to be completely eliminated.  
         SUMMARY OF THE INVENTION  
         [0010]    It is accordingly an object of the present invention to improve the known service units such that a yarn produced in the open-end spinning device is placed on an empty tube held in the creel in an unobjectionable manner and such that reliable fixing of the yarn end is ensured.  
           [0011]    Accordingly, the present invention addresses this problem by providing a service unit for automatically servicing a work station of a textile machine for manufacturing cheeses, wherein the the service unit comprises a pneumatic auxiliary yarn supply, a removal device with a pivotably supported yarn supply tube, and a yarn cutting device arranged on a centering and guide sheet in an operating position of the centering and guide sheet adjacent a yarn catch device of a tube plate supported in a freely rotatable manner in a creel of the work station.  
           [0012]    The present invention has the particular advantage that the yarn to be placed on an empty tube held between the tube plates of a creel is separated immediately adjacent to the yarn catch devices of the tube plate. In this manner, a relatively short yarn end is produced that is, for the most part overwound by the yarn start reserve and is securely fixed on the tube.  
           [0013]    In another embodiment of the present invention, the centering and guide sheet carrying the yarn cutting device can be moved by a thrust piston transmission into an operating position immediately adjacent to the tube plate comprising the yarn catch device. In this operating position, the centering and guide sheet extends over a centering shoulder on the creel with a centering slot so that the yarn cutting device is always precisely positioned. Thus, the yarn cutting device is always arranged immediately adjacent to the yarn cutting device of the tube plate.  
           [0014]    In yet another embodiment of the present invention, the yarn cutting device comprises a hook-shaped main body partially open to the inside. A fixed edge comprising a cutting edge having essentially a 45° angle as viewed from the side is integrated into the main body.  
           [0015]    Such a design ensures on the one hand that the yarn produced in the open-end spinning device and still removed at first via the yarn supply tube is drawn over the cutting edge as soon as it has been grasped by the yarn catch device of the tube plate and is cut. On the other hand, such an arrangement of the edge ensures that the operating personnel do not inadvertently come in contact with the edge and injure themselves.  
           [0016]    Further details of the present invention can be gathered from a non-limiting exemplary embodiment presented in the following description with reference made to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic view of one half of an open-end spinning device with a service unit that automatically services the work stations of the spinning machine.  
         [0018]    [0018]FIG. 2 is an enlarged view of the yarn manipulating elements of a service unit wherein the auxiliary yarn supply device is in a position such that a yarn that has been restarted to be spun can be placed on an empty tube held in the winding device of a work station.  
         [0019]    [0019]FIG. 3 is an enlarged side view of the auxiliary yarn supply device and yarn cutting device of the present invention.  
         [0020]    [0020]FIG. 4 is a top view of the yarn cutting device of FIG. 3.  
         [0021]    [0021]FIG. 5 is a front view of the yarn cutting device of FIG. 3. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    [0022]FIG. 1 is a schematic view of one half of a known open-end spinning machine  1 . The open-end spinning machine generally comprises a plurality of similar work stations  2 , each of which is provided with a spinning device  3  and a winding device  4 . Sliver  6  placed in a spinning can  5  is spun in spinning device  3  to yarn  7 . The yarn  7  is subsequently wound on winding device  4  to a cheese  8 . As indicated in the figures, winding device  4  comprises a creel  9  for rotatably holding a tube  10 . The winding device  4  also comprises winding drum  11  for driving tube  10  and cheese  8 . Open-end spinning machines  1 , that are usually designed in two rows, often comprise a bobbin transport device  12  between the work-station rows, via which device  12  the finished cheeses  8  are removed.  
         [0023]    A service unit  16 , referred to as a spinning-start carriage, is arranged on or on top of spinning machine  1  such that it can travel on guide rails  13 ,  14  and support rails  15 . Drive assembly  17  of service unit  16  comprises rollers  18  and support wheels  19 . The supply of service unit  16  with electric energy occurs via a drag chain or, as indicated in FIG. 1, via sliding contact device  20 . Such a service unit  16  patrols along work stations  2  of open-end spinning machine  1  and intervenes automatically when there is a need for action at one of work stations  2 .  
         [0024]    A need for action is present, for example, when a yarn break has occurred at one of work stations  2  or when a cheese has reached its prescribed diameter at one of the work stations and must be replaced by an empty tube  10 .  
         [0025]    In such an instance, service unit  16  runs to the respective work station  2 , assumes a position thereat and as in the case of a “normal” yarn break searches for the torn yarn end run up on the circumferential surface of cheese  8  with its yarn search nozzle  21 . After a cleaning of spinning device  3 , the yarn end that has been prepared in the interim is spun again in the spinning device onto a yarn ring rotating there.  
         [0026]    As set forth below, the operating process becomes somewhat more difficult if a full cheese  8  must first be replaced with an empty tube  10  and a spinning start subsequently begun again.  
         [0027]    [0027]FIG. 2 shows a service unit  16  with the most important yarn manipulating elements necessary for carrying out the previously cited instances of operation. As has already been indicated previously, service unit  16  comprises, among other things, pivotably supported yarn search nozzle  21  whose suction slot can be placed on the outer circumference of cheese  8  and can take up torn yarn ends. Moreover, ejection and drive arm  22  with drive roller  23  arranged on one end is present. In addition, service unit  16  is equipped, as is known, with a yarn catch sheet  25 , a yarn drawing-in device  26 , a yarn supplier  27  with supplier pincers  28  and yarn separating device  29  as well as with a controllable yarn withdrawal device comprising a drivable withdrawal roller  30  as well as of pivotably arranged pressure roller  31 . A creel opener  32 , pressure lever  33  and auxiliary yarn supply and removal device  34  are built as further operating elements into service unit  16 .  
         [0028]    Auxiliary yarn supply and removal device  34  comprises, for example, tube system  35  connected via flexible connection element  36 , such as a hose, to supply tube  37  that can be pivoted into various positions. Supply tube  37  is fixed for its part to pivot arm  38  supported such that it can be pivoted in a defined manner about pivot axis  39 .  
         [0029]    Tube system  35 , into which auxiliary yarn  45  withdrawn from storage bobbin  44  can be fed, comprises in its entrance area a suction-air connection  40  that can be switched on in a defined manner via valve  41  and comprises compressed-air connection  46  that can be controlled via valve  47 . Moreover, a first yarn separating device  42  can be arranged in the upper area of tube system  35 .  
         [0030]    In addition, thrust piston transmission  48  is fixed on pivot arm  38 , to the piston rod  49  of which transmission a centering and guide sheet  50  is fixed to the end which sheet  50  comprises yarn cutting device  51  of the present invention.  
         [0031]    FIGS.  3  to  5  show yarn cutting device  51  of the present invention in detail.  
         [0032]    [0032]FIG. 3 is a side view of the front part of a creel arm of creel  9 . It shows yarn supply tube  37  and centering and guide sheet  50  carrying yarn cutting device  51 . The creel arm comprises centering shoulder  55  on its end. In addition, tube plate  52  is rotatably supported on the creel arm in such a manner that it can rotate freely about axis of rotation  60 . This tube plate is provided on its outer circumference with yarn catch device  53 . Empty tube  10  is clamped in, as is customary, between shown tube plate  52  and a corresponding, opposite tube plate of a second creel arm (not shown).  
         [0033]    As FIG. 3 shows, main body  56  is designed in a hook-like manner, that is, main body  56  is partially open downwards. Edge  57  is fixed inside the opening of the main body, cutting edge  58  of which edge  57  runs, as shown, at essentially an angle of 45°.  
         [0034]    [0034]FIG. 5 shows that centering and guide sheet  50  also comprises yarn guide slot  59  in addition to centering slot  54 . Yarn  7  guided in yarn guide slot  59  is guided in such a manner for creating a yarn start reserve by laterally shifting centering and guide sheet  50  that the yarn end cut by yarn cutting device  51  is overwound and as a result is fixed on tube  10 .  
         [0035]    When a cheese  8  has attained its prescribed diameter, service unit  16  runs to the respective work station  2 , assumes a position thereat and replaces the full cheese  8  with an empty tube  10 . Service unit  16  then restarts the spinning of spinning device  3  of the respective work station  2 .  
         [0036]    At the beginning of the spinning start, process supply tube  37  of pivot arm  38  carrying auxiliary yarn supply device  34  is standing on suction nozzle  21  in a rear position (not shown). The mouth of supply tube  37  is standing in such a manner in the area of the suction intake slot of suction nozzle  21  that an auxiliary yarn  45  supplied via auxiliary yarn supply device and exiting out of the mouth of supply tube  37  can be immediately grasped by suction nozzle  21 . Pivot arm  38  is thereupon pivoted into its front position indicated in FIG. 2. A yarn strand (not shown) is produced that is grasped, as is known by one skilled in the art, by the previously described yarn manipulating elements of service unit  16 . The yarn is subsequently prepared, as is customary, and spun in open-end spinning device  3  on a yarn ring rotating there.  
         [0037]    Yarn  7  produced in open-end spinning device  3  is at first removed by suction, following auxiliary yarn  45 , via yarn supply tube  37 . The mouth of yarn supply tube  37  is standing at this time in the area of creel  9 . That is, the mouth of yarn supply tube  37  is positioned offset somewhat above axis of rotation  60  of the creel.  
         [0038]    Yarn  7  is brought into the area of yarn catch device  53  arranged on tube plate  52  of creel  9  by actuating thrust piston transmission  48  arranged on pivot arm  38  and actuating centering and guide sheet  50  arranged on piston rod  49  of thrust piston transmission  48  and is grasped by said device  53 . Yarn catch device  53  rotating in direction R subsequently ensures that yarn  7  caught in yarn catch device  53  slides over cutting edge  58  of yarn cutting device  51  and is cut at that time.  
         [0039]    While the cut free yarn end is removed by suction and disposed of by yarn supply tube  37 , a thrust piston transmission (not shown) arranged parallel to axis of rotation  60  assures a lateral shifting of centering and guide sheet  50 , that had been slightly raised previously, and as a consequence the creation of a yarn start reserve (not shown). That is, yarn  7  guided in yarn guide slot  59  of centering and guide sheet  50  is wound under lateral displacement in such a manner onto empty tube  10  that the yarn start reserve produced overwinds the yarn end and as a result secures it on tube  10 .  
         [0040]    It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.