Abstract:
An apparatus and a method for guiding and cutting a continuously advancing yarn during a package doff in a takeup device. In this connection, a movable yarn guide guides the yarn substantially parallel to a package or a winding tube, which is driven by a drive roll. The yarn guide is followed by a suction device, which consists of a pneumatic suction inlet end and a cutting device. The suction device cooperates with a transfer device for purposes of cutting the yarn during the package doff and receiving the loose end of the advancing yarn. To protect the yarn during the package doff, the yarn guide extends in the yarn path upstream of the driven tube, and the suction device downstream thereof. For catching the yarn and winding initial layers thereof on a new winding tube that is driven by the drive roll, the yarn is guided in a yarn guide groove provided on the circumference of the drive roll or on the circumference of the new winding tube so that the yarn is protected within the contact zone between the accelerating winding tube and the drive roll.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for guiding and cutting a continuously advancing yarn, and winding initial layers thereof during a package doff in a takeup device, as well as to a method of guiding and cutting a continuously advancing yarn. An apparatus and method of this general type 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 completely wound, it is doffed. To this end, it is necessary that the yarn be first cut, 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 completion of the package doff, the yarn is caught by means of a catching device and wound on the new tube. 
     In the apparatus and method disclosed in EP 0 311 827, the yarn is guided by a movable yarn guide outside of the winding range to a suction device laterally adjacent the winding range, after the package is fully wound. After completion of the package doff, and once the new tube is ready for catching, the yarn guide is pivoted back to the winding range. To transfer or catch the yarn, a transfer device deflects the yarn between the suction device and the yarn guide and offers it to the yarn catching device for engagement. 
     The known apparatus and method have the disadvantage that at the end of a winding cycle , the loose yarn end lies against the fully wound package in an undefined manner, which complicates locating the loose yarn end in particular in the further processing. 
     Furthermore, the deflection of the yarn by the transfer device for engaging the yarn leads to considerable looping, which results in major tension fluctuations in the yarn in proportion with the winding tension. Such tension fluctuations may lead to lapping on upstream feed elements. 
     It is accordingly an object of the invention to provide an apparatus and method of the initially described kind, so as to ensure that during a package doff, when the yarn is guided and caught, and when first layers thereof are wound, the yarn is guided as gently as possible with little deflection. 
     A further object of the invention is to ensure after cutting the yarn that the loose yarn end lies against a tie-off bead of the full package, and that the advancing yarn is threaded on a new tube without substantial slack. 
     SUMMARY OF THE INVENTION 
     The invention is characterized in that the yarn guide and the suction device are arranged within the winding range at the beginning of the package doff. In this connection, the winding range is the range on the tube, which is covered by the traversed yarn. Thus, the yarn can be cut with relatively little deflection and be taken over by the yarn suction device, so t hat no significant fluctuations occur in the yarn tension during the doffing phase. Preferably, the suction device is stationary. In the case of a suction device that is constructed for movement substantially parallel to the package, it is possible to place the loose yarn end with the tie-off bead in any desired position within the winding range. 
     To ensure that when the package is replaced with the empty tube, the yarn is reliably removed by the suction device, the drive roll or the tube includes a circumferential groove. Before the tube is brought into circumferential contact with the drive roll, the yarn is guided by the yarn guide, the yarn guide groove, and the suction device. This prevents the yarn advancing between the surfaces of the new tube and the drive roll from being clamped and braked by the new tube, as long as the latter has not yet reached its predetermined rotational speed. The yarn can then be transferred, without slacking, from the full package to a new tube. The suction device receiving the yarn ensures in the doffing phase an undisturbed yarn path in the devices upstream of the takeup device. The yarn guide groove may be formed radially extending in the circumferential direction on the circumference of the drive roll or on the circumference of the tube, so that during the acceleration of the tube the yarn is reliably guided without being clamped. 
     In a particularly advantageous further development of the apparatus, the yarn guide groove of the drive roll is formed in the circumferential portion of the drive roll or tube, which is contacted by the full package. This permits minimizing the deflections and deviations of the yarn during the doffing phase and, thus, the fluctuations of the yarn tension. 
     When the yarn guide groove is provided in the tube, it advantageously extends in the region of the tube, which is covered by the wound yarn. 
     In a particularly preferred development of the invention, the yarn guide groove is made with a groove depth T, which is at least greater than the yarn diameter. In this instance, the yarn guide groove has a groove width B, which is substantially greater than the groove depth. This yarn guide groove that is made relatively shallow with a great width ensures that the yarn does not leave the guide groove due to its natural dynamics. When the unwound tube is in contact with the drive roll, it is made sure that the yarn advances freely through the guide groove. Both the small groove depth and large groove width further effect that the yarn guide groove on the circumference of the drive roll or on the circumference of the tube does not significantly affect the buildup of the package during the winding cycle. 
     In another advantageous further development of the invention, the yarn guide groove is designed and constructed such that the groove depth T is greater than the groove width B. This narrow yarn guide groove permits holding the yarn safely in the yarn guide groove. In addition, the package buildup remains unaffected during the entire winding cycle. In order that the yarn enters the narrow groove, the traversing yarn guide may guide the yarn across the groove slowly at a reduced traversing speed. 
     In another, advantageous further development of the invention, a plurality of narrow grooves are arranged close to one another. The yarn need not be exactly positioned and yet enters one of the narrow grooves safely. Since the package buildup is defined by a cross wind, its formation is not disturbed even in the presence of a plurality of yarn guide grooves arranged side by side. 
     In a particularly advantageous further development of the apparatus, the cutting device, the yarn guide, the yarn guide groove on the circumference of the drive roll, and the suction device are arranged in a transfer plane. This permits depositing the yarn at first as a tie-off wind on the full package and transferring it to the suction device without substantial deflection. Furthermore, a simple swing motion of a transfer device enables the yarn to enter the cutting device of the suction system. In this instance, a deflection is needed only in the transfer plane. The gripping arm of the transfer device engages the yarn in its advance between the previously raised package and the yarn guide. This development has furthermore the advantage that when the package is raised from the drive roll, the transfer device keeps the yarn safely guided in the yarn guide. Preferably, the transfer plane is formed as a normal plane of the package and contains the tie-off wind of the package. In this normal plane, the yarn guide groove is provided on the drive roll. However, it is also possible to design and construct the yarn guide groove obliquely to the axis of the drive roll. This imparts to the yarn a wobbling motion, which leads to an improved cohesion of the yarn layers, when the tie-off wind is wound. 
     In the previously described operations for doffing the package, catching the yarn, and winding initial layers thereof, there exists the possibility that an auxiliary device removes the yarn from a traversing yarn guide at the beginning of the package doff, and that subsequently the yarn guide of the auxiliary device receives the yarn. In this instance, the yarn guide is constructed preferably with a drive, which moves the yarn guide in the longitudinal direction parallel to the tube, and performs the movement of the yarn independently of direction at a variable speed. In this instance, the drive could be realized by a linear drive. 
     In a particularly advantageous further development of the invention, the function of the yarn guide of an auxiliary device is assumed and performed by a traversing yarn guide of a traversing device. To this end, the traversing yarn guide is capable of guiding the yarn outside and inside the winding range in the longitudinal direction parallel to the tube. This development has the advantage that no additional auxiliary device and its control are needed. All operations during the winding, package doff, and catching are controlled via a controller of the traversing device. 
     Once the yarn is caught and wound in first layers on the tube, the actual winding cycle starts, i.e. winding of the package. Once 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 reciprocates the yarn, stops in a transfer plane. At first, a tie-off bead is wound on the full package. To this end, the full package has previously been raised from the drive roll. Subsequently, the transfer device guides the yarn into the suction system. Once the package is doffed, and the empty tube is clamped in the package holder between the clamping plates, the threading of the yarn will start. Before the new tube is placed onto the drive roll, the traversing yarn guide and the yarn guide groove in the drive roll guide the yarn between the tube and the drive roll. The tube is placed onto the drive roll and accelerated to a rotational speed necessary for threading the yarn. Once the rotational speed is reached, the drive of the traversing yarn guide is activated, and the traversing yarn guide leads the yarn to a catching position, in which the yarn advances obliquely over a catching plane of the catching device, for example, a front edge of the clamping plate. 
     The method of the present invention distinguishes itself by a fast and precise doffing of the package. In particular, the guidance of the yarn upstream and downstream of the catching device permits a very accurate positioning of the yarn, so that while the package is doffed, the yarn is safely guided without a substantial slack, and caught by the catching device. 
     For catching the yarn on the new tube, the yarn guide is moved with the yarn to a catching position which is outside the winding range, so that the yarn slides out of the guide groove and crosses a catching plane of the catching device. This allows a great freedom of variation for the catching device. In addition, it is possible to avoid unnecessary yarn loopings. 
     The use of the apparatus according to the invention in a false twist texturing machine is especially advantageous, since the false twist machine comprises a plurality of takeup devices, which perform a package doff after each wound package without a manual operation. A false twist texturing machine equipped with the apparatus of the present invention thus possesses the previously described advantages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, both the apparatus and the method of the present invention are described in greater detail, with reference to the attached drawings, in which 
     FIG. 1 is a schematic view of an embodiment of an 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 a yarn; and 
     FIGS. 3 and 4 are schematic views of further embodiments of the yarn guide groove. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     FIGS. 1 and 2 illustrate a first embodiment of an apparatus according to the invention within a takeup device, as may be used, for example, in a texturing machine. Therefore, the following description will apply to FIG.  1  and FIG. 2, unless otherwise specified. 
     The takeup device comprises a swinging package holder  26 , which is supported on a pivot shaft  40 . The pivot shaft  40  is mounted to a machine frame  41 . At the free ends of the fork-shaped package holder  26 , two opposite clamping plates  27  and  28  are mounted for rotation. Clamped between the clamping plates  27  and  28  is a tube  13  for receiving a package. To this end, the clamping plates  27  and  28  comprise each a conical centering extension that extends in part into the tube end. With that, the tube  13  is centered between the clamping plates  27  and  28 . A drive roll  29  lies against the surface of tube  13 . A yarn guide groove  48  radially extending in the circumferential direction is arranged on the circumference of the drive roll  29 . The yarn guide groove  48  has a small depth, which makes it essentially possible to receive an advancing yarn, without clamping it between the surfaces of the drive roll  29  and the empty tube in contact therewith. The drive roll  29  is mounted on a drive shaft  31 . At its one end, the drive shaft  31  connects to a drive roll motor  30 . The motor  30  drives the drive roll  29  at a substantially constant speed. Via frictional engagement, the tube  13  is thus accelerated by means of the drive roll  29  to a winding speed, so that a yarn  1  is wound to a package on the tube  13 . To this end, a traversing yarn guide  6  is arranged in the yarn path upstream of the drive roll  29 . The traversing yarn guide connects to a traverse drive, which oscillatingly drives the traversing yarn guide  6  within the winding range. 
     In the present embodiment, the traversing yarn guide  6  guides the yarn  1  for purposes of doffing a package, catching the yarn, and winding initial layers thereof. 
     A yarn traversing device  22  is designed and constructed as a so-called belt-type traversing system. In this traversing system, the traversing yarn guide  6  is mounted to an endless belt  33 . The belt  33  extends between two deflection pulleys  34 . 1  and  34 . 2  parallel to the tube  13 . In the plane of the belt, a drive pulley  35  that is 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 oscillatingly drives the drive pulley  35 , so that the traversing yarn guide  6  reciprocates in the region between the deflection pulleys  34 . 1  and  34 . 2 . The electric motor is controllable by a controller  8 . 
     On the side opposite to the traversing system toward the tube  13  or drive roll  29 , a suction device  37  is arranged. The suction device  37  consists of a cutting device  38  and a suction inlet end  39 . In the illustrated embodiment, the suction inlet end  39  is arranged between the cutting device  38  and the tube  13 . The suction inlet end  39  possesses a slot-shaped suction orifice  46 , which is arranged in alignment with a cutting blade  47  of the cutting device  38 . 
     FIGS. 1 and 2 show the takeup device in different operating situations. FIG. 1 shows the takeup device 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. The traversing yarn guide  6  remains in this transfer plane. A tie-off wind  23  is now being produced on the package  24 . At the same time, the package holder  26  swings with the package  24  out of the operating position. This activates a transfer device  42  arranged laterally of the winding range. The transfer device  42  has a gripping arm  43 , which extends with one free end through the transfer plane. The gripping arm  43  is mounted for rotation on a pivot shaft  25 , and is moved by a drive (not shown) parallel to the transfer plane. The gripping arm  43  is dimensioned such that its free end engages the yarn between a yarn guide  6  and the package  24 , and guides the yarn  1  in the transfer plane to the suction device  37 . The suction device  37  lies within a path of motion that is described by the free end of gripping arm  43 . With that, it is realized that the yarn  1  enters the cutting device  38  and is cut by blade  47 . Shortly before or at the same time, the yarn  1  enters the slot-shaped orifice of suction inlet end  39 . The end of the advancing yarn is thus removed by suction immediately after cutting. On the package, the loose yarn end is deposited in the region of the tie-off wind. At the same time, the yarn enters the yarn guide groove  48  of drive roll  29 . This permits replacing the full package  24  with an empty tube. Once the package  24  has been replaced with a tube, the threadup sequence will start. After cutting the yarn  1 , the transfer device  42  returns to its initial position. 
     FIG. 2 illustrates the beginning of the threadup operation. The continuously advancing yarn is guided by the suction device  37 , yarn guide groove  48 , and traversing yarn guide  6 . For the sake of clarity, the illustration of the transfer device was omitted in FIG.  2 . To this end, the yarn end is taken into a suction orifice of the suction inlet end  39 . As soon as the yarn  1  is guided by the traversing yarn guide  6  and the yarn guide groove  48  within the contact range between the tube  13  and the drive roll  29 , the tube  13  is brought into circumferential contact with the drive roll  29 . The tube  13  is accelerated by the drive roll  29  in circumferential contact therewith to a winding speed that is predetermined by the drive roll. Once the tube  13  has reached the winding speed, the controller  8  activates the electric motor  36  such that it moves the traversing yarn guide to a catching position. The yarn  1  slides out of yarn guide groove  48  and now crosses the plane of a catching device  14 , so that it engages a catching groove  21 . The yarn is caught with catching groove  21  and cut with a blade integrated in the catching device or clamping plate  27 . Such a clamping plate is known, for example, from EP 0 403 949, which is herewith incorporated by reference. 
     After the catching, the traversing yarn guide  6  is moved from its catching position to the winding range. In so doing, the yarn  1  is wound on the tube  13  to a yarn reserve wind outside of the winding range. In this instance, the yarn reserve wind could be formed by a traversing yarn guide  6  that remains in one position. If so, the yarn reserve wind will comprise a number of parallel winds. However, it is also possible to move the traversing yarn guide  6  at a speed defined by the 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 will start. The traversing yarn guide  6  is then driven by the traversing device  22  for oscillation within the winding range. The rotated position of the package holder  26  follows the increasing diameter of package  24 . To this end, the package holder  26  comprises biasing means, which generate on the one hand, between the package  24  and the drive roll  29 , a contact pressure which is necessary to drive the package, and enable on the other hand a swing motion of the package holder  26  for the package doff. 
     The embodiment of the invention as shown in FIGS. 1 and 2 is not limited to guiding the yarn by the traversing yarn guide during the doffing procedure. When a different kind of traversing device is used, which is driven, for example, by a cross-spiraled shaft, it is possible to use a separately driven auxiliary yarn guide. To this end, the yarn guide is arranged for movement between the traversing yarn guide and the tube. A drive permits reciprocating the yarn guide in a plane parallel to the tube  13  such that the yarn can be transferred from the traversing yarn guide at the end of the winding cycle. Subsequently, the yarn guide is moved to the transfer plane, so that the package doff starts as previously described. The drive of the yarn guide is likewise controllable by the controller shown in FIGS. 1 and 2. 
     The further sequence is identical with the foregoing description, with the traversing yarn guide being replaced with the yarn guide. After catching the yarn and winding initial layers thereof, the yarn is returned to the traversing yarn guide. 
     FIGS. 3 and 4 schematically illustrate further embodiments of the yarn guide groove. Shown in FIGS. 3 and 4 are a drive roll  29  with a tube  13  in contact therewith. The tube  13  is clamped between the clamping plates  27  and  28 . The clamping plates  27  and  28  are connected to a swinging package holder (not shown). The drive roll  29  in contact with the circumference of tube  13  is driven by the drive roll motor  30  at a predetermined winding speed. As a result, the tube  13  in contact with the circumference of drive roll  29  is initially accelerated, until the desired rotational speed is reached. 
     In FIG. 3, the tube  13  comprises in its center region on the circumference a yarn guide groove  48 . The yarn guide groove  48  has a depth T and a width B. The groove depth T is somewhat greater than the yarn diameter, so that a yarn advancing in the yarn guide groove  48  between the tube  13  and drive roll  29  is guided without being clamped. In proportion with its depth T, the yarn guide groove  48  has a substantially greater width B. Preferably, the sides of the groove are made gentle, so that a very wide yarn guide groove results with a small depth. This development of the yarn guide groove, which could likewise be arranged on the circumference of the drive roll, affects the package buildup very little during the winding of the yarn. 
     In the embodiment shown in FIG. 4, the drive roll  29  contains a plurality of yarn guide grooves  48  that extend parallel side by side. In this embodiment, the yarn guide grooves have a small width B and a relatively great depth T. This results in a very narrow yarn guide groove, wherein the groove width B is smaller than the groove depth T. Due to the very narrow yarn guide groove, the package buildup remains unaffected. The arrangement of a plurality of yarn guides allows to accomplish that despite the very small groove width, the yarn is able to enter one of the grooves quickly and reliably. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.