Abstract:
An apparatus and method for guiding and cutting a continuously advancing yarn during a package doff in a yarn winding apparatus wherein the advancing yarn is wound on a driven bobbin tube. In this process, the yarn is guided by means of a movable yarn guide along a direction substantially parallel to the axis of the tube. Downstream of the yarn guide, a suction device is arranged, which includes a pneumatic suction inlet end and a cutter. The suction device cooperates with a transfer device, so as to cut the yarn during the package doff and receive the loose end of the advancing yarn. To facilitate a protective processing of the yarn during the package doff, during the catching, and during the winding of initial layers on a tube driven by a drive roll, the yarn guide is arranged in the path of the yarn upstream of the driven tube and the suction device downstream of the driven tube.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus and method for guiding and cutting a continuously advancing yarn during a package doff in a yarn winding apparatus. 
     The apparatus and method are known from EP 0 311 827. In textile machines, for example, a crimped yarn is continuously wound to a package. After the package is fully wound, same is doffed. To this end, it is necessary to first cut the yarn, so that the full package with the loose yarn end can be replaced with a new empty tube. During the doff, the yarn end of the continuously advancing yarn is received and removed by a pneumatic suction device. After the package is doffed, the yarn is caught by means of a catching device and wound on the new tube. 
     In the apparatus disclosed in EP 0 311 827 and by the known method, the yarn is guided, after the package is fully wound, by means of a movable yarn guide outside the winding range to a suction device laterally arranged next to the winding range. After the package is doffed and the new tube is ready for catching the yarn, the yarn guide swings back to the winding range. To transfer or respectively catch the yarn, same is deflected by means of a transfer device between the suction device and the yarn guide, and presented for catching to the catching device. 
     The known apparatus and the known method have the disadvantage that at the end of the winding cycle, the loose yarn end on the fully wound package lies there against in an undefined manner, which complicates locating the loose yarn end in particular during further processing. 
     Furthermore, the deflection of the yarn by the transfer device for purposes of catching the yarn leads to considerable loopings which result, when compared to the winding tension, in major tension fluctuations of the yarn. Such fluctuations in the tension may lead to a formation of laps on preceding feed elements. 
     It is accordingly an object of the present invention to provide an apparatus and a method of the initially described type which ensure that the yarn is guided as gently as possible while doffing the package, catching the yarn, and winding initial layers thereof. 
     A further object of the invention is to ensure that after cutting the yarn, the loose yarn end lies against a tie-off wind on the full package. 
     SUMMARY OF THE INVENTION 
     The above and other objects and advantages of the present invention are achieved by the provision of a yarn winding apparatus which comprises a bobbin tube mounting device for rotatably supporting a bobbin tube, and with the mounting device being movable between a winding position wherein the bobbin tube is in contact with a drive roll so as to rotate the tube, and a withdrawn position wherein the bobbin tube is separated from the drive roll. A yarn traversing device is provided for traversing the advancing yarn along a winding range on a bobbin tube which supported by the mounting device at the winding position to form a wound package. Also, a yarn guide is mounted upstream of the bobbin tube located at the winding position so as to be movable by a drive along a direction parallel to the axis of the bobbin tube, and a cutting and suction device is mounted downstream of the bobbin tube. Further, a transfer device is mounted for movement to an operative position wherein, when the bobbin tube mounting device moves a full package to its withdrawn position, the transfer device deflects the advancing yarn into contact with the cutting and suction device. 
     The cutting and suction device is located in a transfer plane which is within the winding range, and the yarn guide is movable into the transfer plane. Also, the transfer device includes a gripping arm having a free end which is within the transfer plane when the transfer device is moved to its operative position. 
     The yarn guide and the suction device are arranged within the winding range. In this connection, the winding range is the range on the tube which is covered by the traversed yarn. This allows the yarn to be cut with relatively little deflection and to recatch same thereafter. Thus, no significant yarn tensions occur during the doffing phase. The suction device is arranged preferably stationarily. In the case of a suction device constructed for movement substantially parallel to the package there is the possibility of placing the loose yarn end with the tie-off wind in any desired position within the winding range. Furthermore, the additional mobility of the suction device imparts a high flexibility to the configuration of the catching device. 
     In a particularly advantageous embodiment of the apparatus, the yarn guide and the suction device may be arranged in a transfer plane, so that the loose yarn end on the full package can be reliably deposited on the tie-off wind. Furthermore, a simple swing movement of the transfer device permits the yarn to be guided into the cutter of the suction device. In this process, only one deflection is needed in the transfer plane. The gripping arm of the transfer device engages the yarn as it advances between the package that is already raised and the yarn guide. This arrangement has furthermore the advantage that when raising the package from the drive roll, the transfer device causes the yarn to remain safely guided in the yarn guide. Preferably, the transfer plane is formed as a normal plane of the package and includes the tie-off wind of the package. 
     The inlet end of the suction device and the cutter may be arranged one after the other in the transfer plane. This ensures that the yarn is already engaged by the pneumatic suction inlet opening before entering into the cutter. Thus, after being separated in the cutter, the end of the advancing yarn is safely received and removed. To this end, the cutter has preferably a cutting blade which cooperates with the gripping arm of the transfer device such that the yarn is cut clean and safely by the cutting blade. 
     To guide the yarn safely into the opening of the suction inlet, it is advantageous to make same slotted in the direction of the advancing yarn and arranged in alignment with a cutting blade of the cutter. 
     For catching the yarn, the yarn guide and the suction device are arranged relative to each other such that the catching device extends in the path of the yarn between the yarn guide and the suction device. This arrangement facilitates catching of the yarn in the catching device without additional auxiliary means alone by the movement of the yarn guide. To this end, the yarn is deflected only in the longitudinal direction parallel to the tube. By an additional, equidirectional movement of the suction device it is also made possible to minimize the deflection of the yarn. 
     In the winding apparatus of the present invention, wherein the tube is mounted between two clamping plates arranged on a package holder, and the catching device is formed on one of the clamping plates, it is possible to catch the yarn in a simple manner. To this end, the yarn is obliquely guided over the front edge of the clamping plate, so that the yarn automatically drops into a catching slot arranged in the front edge of the clamping plate. Furthermore, the arrangement of the yarn guide and the catching device is advantageous in such a manner that the yarn and the clamping plate perform an equidirectional movement. This prevents the yarn from sagging and, thus, from undergoing an excessive fluctuation in tension. 
     In the case of the previously described operations concerning doffing a package, catching the yarn, and winding first layers thereof, it is presumed that at the beginning of the package doff, the yarn is guided on a traversing yarn guide by means of an auxiliary device, and that it is subsequently received by the yarn guide. In this instance, it is preferred to provide the yarn guide with a drive which moves the yarn guide in the longitudinal direction parallel to the tube, and the movement of the yarn guide is performed in each direction at a variable speed. In this case, the drive may, for example, be a linear drive. 
     In a particularly advantageous further development of the invention, the yarn guide is realized by a traversing yarn guide of a yarn traversing device. To this end, the traversing yarn guide may guide the yarn outside and inside the winding range in the longitudinal direction parallel to the tube. This embodiment has the advantage that no additional control unit is needed for controlling the traversing device. All operations during the winding, during the package doff, and during the catching are controlled via a controller of the traversing device. 
     After the yarn has been caught and initial layers thereof have been wound on the tube, the actual winding cycle starts, i.e., the winding of the package. After the package is fully wound, the yarn is taken over by the suction device for purposes of initiating the package doff. To this end, the traversing yarn guide that guides the yarn stops in a transfer plane. The transfer device then guides the yarn into the suction device. After the package is doffed and the empty tube is clamped in the package holder between the clamping plates, the threadup of the yarn is started. To this end, the tube is initially accelerated to a rotational speed necessary for the threadup. As soon as the rotational speed is reached, the drive of the traversing yarn guide will be activated, and the traversing yarn guide guides the yarn to a catching position, in which the yarn advances obliquely across a catching plane of the catching device, for example, a front edge of the clamping plate. 
     The drive of the yarn guide may be controllable by a controller, which is connected to a sensor that senses the rotational speed of the tube. This construction is especially advantageous, when it comes to catch the yarn by means of the catching device without a time delay, immediately after reaching the winding speed necessary for the winding, and to wind the yarn on the tube. To this end, the rotational speed of the tube is continuously sensed. As soon as a predetermined winding speed is reached, the drive of the yarn guide will be activated. The yarn guide then performs the corresponding movements for catching the yarn and for winding initial layers of same on the tube. The winding speed corresponds to the rotational speed of the tube, which generates a circumferential speed on the tube that is substantially equal to the yarn speed. 
     This embodiment also presents the possibility of advancing the sequence of motions of the yarn guide even to the acceleration or deceleration phase of the tube. This will be especially advantageous in cases, in which the yarn is initially caught in the catching device on a larger diameter than the tube diameter. For purposes of maintaining a substantially constant winding speed of the yarn, it will therefore be necessary that the catching device operating at the rotational speed of the tube be driven during the catching at a lower speed than the winding speed. 
     The sensor may be designed to sense the position of the catching groove in the catching device. This has the advantage that the yarn is caught by the catching device without a significant delay immediately upon reaching a catching position of the yarn guide. Since the yarn continues to be guided in the suction device until it is caught, this embodiment will result in a reduction of the amount of yarn that goes to waste. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the apparatus of the present invention as well as the method are described in more detail with reference to the embodiments illustrated in the attached drawings, in which: 
     FIG. 1 is a schematic view of a first embodiment of a yarn winding apparatus according to the invention during a package doff; 
     FIG. 2 is a schematic view of the apparatus of FIG. 1 during the catching of the yarn; 
     FIG. 3 is a schematic view of a further embodiment of the apparatus according to the invention during a package doff, and 
     FIG. 4 is a schematic view of the apparatus of FIG. 3, during the catching of the yarn. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show a first embodiment of an apparatus in accordance with the invention within a winding apparatus as may be used, for example, in a texturing machine. The following description will therefore apply to FIGS. 1 and 2, unless otherwise specified. 
     The winding apparatus comprises a rotatable package holder  26 , which is mounted on a swing axle  40  secured to a machine frame  41 . On the free ends of the fork-shaped package holder  26 , two opposite clamping plates  27  and  28  are mounted for rotation. Between the clamping plates  27  and  28  a bobbin tube  13  extends for receiving a package. To this end, the clamping plates  27  and  28  are each provided with a conical centering extension which extends in part into the tube end. With these extensions, the tube  13  is centered between the clamping plates  27  and  28 . A drive roll  29  lies against the surface of tube  13 . The drive roll  29  is mounted on a shaft  31 . The shaft  31  is connected at its one end to a motor  30 . The drive roll motor  30  drives roll  29  at a substantially constant speed. By frictional engagement via drive roll  29 , the tube  13  is accelerated to a winding speed, so that the yarn  1  on tube  13  is wound to a package. To this end, a traversing yarn guide  6  is arranged in the path of the yarn upstream of drive roll  29 . The traversing yarn guide is connected to a drive, which oscillatingly drives the traversing yarn guide  6  within the winding range. The traverse drive may be formed by a cross-spiralled roll or a belt drive. 
     Between the yarn guide  6  and tube  13  a movable yarn guide  18  is arranged. The yarn guide  18  is connected to a drive  19  which reciprocates the yarn guide  18  in a plane parallel to the tube  13  such that the yarn guide  18  can be positioned both inside the winding range and outside the winding range. The drive  19  is connected to a controller  8 . The controller  8  may optionally be connected to a sensor  32  arranged on package holder  26 . The sensor  32  is arranged in the region of clamping plate  27  and senses the position of a groove  21  of a catching device  14 . The catching device  14  is formed on clamping plate  27 . The sensor  32  may, for example, be a pulse generator which releases per revolution a signal as a function of the catching groove  21 . These pulses are converted in controller  8  for evaluating the position of the catching groove and the rotational speed of tube  13 . The tube  13  is clamped between plates  27  and  28  such that the clamping plates  27  and  28  rotate without slip at the rotational speed of tube  13 . 
     A suction device  37  is arranged on the side of the tube  13  opposite to the traversing device. The suction device  37  comprises a cutter  38  and a suction inlet end  39 . The suction inlet end  39  is arranged between cutter  38  and tube  13 , and possesses a slotted suction opening  46  which is in alignment with a cutting blade  47  of cutter  38 . 
     In the situation shown in FIG. 1, a package doff is imminent in the winding apparatus. To initiate the package doff, the yarn guide  18  is brought by means of drive  19  to a transfer plane in the winding range. At the same time, an auxiliary device (not shown) removes the yarn  1  from traversing yarn guide  6 , and inserts same into the yarn guide  18 . The auxiliary device may be constructed in a simple manner as a ramp which is entered into the winding range parallel to the movement of traversing yarn guide  6 . Advantageously, the ramp is connected to the yarn guide  18 , so that the yarn sliding on the ramp automatically drops into the guide groove of yarn guide  18 . 
     While the yarn guide  18  is positioned in the transfer plane, a tie-off wind  23  is wound in the form of a bead on the package  24 . To doff the package, the package holder  26  is rotated in the winding apparatus such that the package  24  separates from the surface of drive roll  29 . Thus, the package  24  is no longer actively driven. The yarn  1  is further wound as tie-off wind  23 . A transfer device  42  arranged on the side of the winding range is now activated. The transfer device  42  comprises a gripping arm  43  which extends with its free end through the transfer plane. The gripping arm  43  is rotatably supported on a swing axle  25  and moved parallel to the transfer plane by means of a drive not shown. The gripping arm  43  is dimensioned such that its free end engages the yarn between the yarn guide  18  and the package  24  and guides the yarn  1  in the transfer plane to the suction device  37 . The suction  37  extends in this instance within the path of motion that is described by the free end of gripping arm  43 . This allows to accomplish that the yarn  1  enters into cutter  38  and is cut by cutting blade  47 . Shortly before or simultaneously, the yarn  1  enters into the slotted opening  46  of suction inlet end  39 . The end of the advancing yarn is thus removed by suction directly after the cutting. The loose yarn end of the package is deposited on the tie-off wind  23  by the package  24  as it slows down. After cutting the yarn, the transfer device  42  returns to its starting position. 
     In the situation shown in FIG. 2, the package is already doffed, and the continuously advancing yarn is guided by the suction device  37  and the yarn guide  18 . For the sake of clarity, the transfer device is not shown in FIG.  2 . 
     The yarn  1  is continuously removed by means of a suction current through suction opening  46  in suction inlet end  39 . The package  24  has been replaced with a new empty tube which is driven by drive roll  29 . To thread the yarn  1  for winding on empty tube  13 , it is guided by the suction device  37  through yarn guide  18 . The yarn guide  18  is brought by drive  19  to a catching position outside the winding range. This catching position of the yarn guide  18  is selected such that the yarn  1  advances obliquely across the front edge of clamping plate  27 , which faces the tube. Before that, the tube  13  is accelerated by the drive roll  29  lying against its circumference to a winding speed that is predetermined by the drive roll. 
     When a sensor  32  is used, same generates a pulse each time the catching groove  21  passes by. This pulse is supplied to controller  8 . The controller  8  includes an evaluation unit which determines from the pulses entering per unit time the momentary rotational speed of clamping plate  27  and, thus, of tube  13 . At the same time, each pulse indicates the position of catching groove  21 . After tube  13  reaches the winding speed, and the catching groove  21  is in a position that is necessary for a reliable catching, the drive  19  of controller  8  is activated to move yarn guide  18  to its catching position. The yarn  1  is now caught by catching device  14  in clamping plate  27 . 
     After the yarn  1  is caught by catching device  14 , it is cut by a cutter  45  arranged between the yarn suction device  37  and the clamping plate  27 . After the catching, the yarn guide  18  is deflected by drive  19  from its catching position to wind a yarn reserve on the tube. To this end, the yarn guide  18  is moved in direction toward the tube center. After the yarn reserve is wound, the yarn  1  is transferred to traversing yarn guide  6 . To this end, it would likewise be possible to use an auxiliary device in the form of a ramp. Winding proceeds now in a new cycle. 
     Shown in FIGS. 3 and 4 is a further embodiment of a winding apparatus according to the invention, as may be used for winding in a texturing machine. In this embodiment, the yarn  1  is guided by traversing yarn guide  6  for doffing a package, for catching the yarn, and for winding initial layers thereof. Since the construction of the winding apparatus differs from that shown in FIG. 1 essentially only by the traversing device, identical numerals are used for structural elements of the same function. To this extent the description with reference to FIGS. 1 and 2 is herewith incorporated by reference. 
     A traversing device  22  is constructed as a so-called belt drive traversing system. In this traversing system, a traversing yarn guide  6  is attached to an endless belt  33 . The belt  33  extends between two deflection pulleys  34 . 1  and  34 . 2  parallel to tube  13 . In the belt plane a drive pulley  35  partially looped by the belt is arranged parallel to the deflection pulleys  34 . 1  and  34 . 2 . The drive pulley  35  is mounted on a drive shaft  44  of an electric motor  36 . The electric motor  36  drives the pulley  35  oscillatingly, so that the traversing yarn guide  6  reciprocates in the region between the deflection pulleys  34 . 1  and  34 . 2 . The electric motor  36  is controllable via controller  8 . The controller  8  connects to the sensor  32  which is arranged on package holder  26  and senses the groove  21  of the catching device  14 . 
     In FIGS. 3 and 4, the winding apparatus is shown in different operating situations. FIG. 3 shows the winding apparatus at the end of a winding cycle. After the package  24  is fully wound, the traversing yarn guide  6  is positioned in a transfer plane, and remains in this transfer plane. A tie-off wind  23  is now wound on the package  24 . At the same time, the package holder  26  is rotated with the package  24  out of its operating position. A transfer device  42  now starts to act, in that a gripping arm  43  enters with its free end into the yarn path between the full package  24  and the traversing yarn guide  6 . The gripping arm  43  swings from its idle position to a transfer position. In this process, it engages the yarn  1  and guides same in the transfer position to the suction device  37 . In the cutter  38  the yarn is then cut and taken into suction inlet end  39 . The loose yarn end is deposited on the package in the region of the tie-off wind. The package  24  can now be replaced with an empty tube. In this connection, it is of advantage that the sensor is mounted on the package holder and, thus, signals the standstill of the package in that it discontinues to generate pulses. Thus, it is possible to use the sensor signal for activating a doffing device. After the package  24  is replaced with a tube, the threadup operation starts. 
     FIG. 4 shows the beginning of the threadup operation. The continuously advancing yarn is guided by the suction device  37  and the traversing yarn guide  6 . To this end, the yarn is sucked into an opening of the suction inlet end  39 . The traversing yarn guide  6  is moved in direction of clamping plate  27  to a catching position outside the winding range. The tube  13  is accelerated by drive roll  29  in circumferential contact with same to a predetermining winding speed. Each time the catching groove  21  passes by, the sensor  32  generates a pulse which is supplied to controller  8 . The controller  8  comprises an evaluation unit which determines from the pulses entering per unit time the momentary rotational speed of the clamping plate and, thus, of the tube. At the same time, each pulse indicates the position of catching groove  21 . After tube  13  has reached the winding speed and the catching groove occupies a dependable position for catching the yarn, the controller  8  activates the electric motor  36  such that same moves the traversing yarn guide  6  to the catching position. The yarn  1  now intersects the catching plane of catching device  14 , so that it is caught by catching groove  21 . The yarn  1  is caught in catching groove  21  and cut with a cutting blade integrated in the catching device or in clamping plate  27 . Such a clamping plate is disclosed, for example, in EP 0 403 949 which is herewith incorporated by reference. 
     After catching the yarn, the traversing yarn guide  6  is moved from the catching position to the winding range. In this process, the yarn  1  is wound on the tube  13  outside the winding range to a yarn reserve wind. The winding of the yarn reserve wind could be performed by a traversing yarn guide that remains in one position. In this instance, the yarn reserve wind will have a number of parallel winds. However, the traversing yarn guide  6  may also be moved at a speed defined by electric motor  36  to the winding range, so that side-by-side winds are produced in the yarn reserve wind. As soon as the yarn guide reaches the winding range, the winding cycle starts. The traversing yarn  6  is then driven oscillatingly within the winding range by the yarn traversing device  22 . The increasing diameter of package  24  is facilitated by a swing movement of package holder  26 . To this end, the package holder  26  has biasing forces which generate on the one hand between the package  24  and the drive roll  29  a contact pressure that is necessary to drive the package, and facilitate on the other hand a swing movement of the package holder  26 .