Abstract:
A yarn texturing machine for texturing and winding a yarn, wherein the feed system withdraws the yarn from a texturing device and advances it to a takeup device. Between the feed system and the takeup system, a yarn accumulation or free space is provided for the purpose of receiving the yarn that has slackened during a package doff due to an overfeed. To withdraw the yarn reliably from the feed system, a conveying nozzle is positioned between the feed system and the free space, and the conveying nozzle includes at least one nozzle bore that is directed in the direction of the advancing yarn, so that an air stream directed through the bore toward the yarn generates a tension on the yarn in the direction of its advance. Subsequently, the yarn is blown into the free space.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of international application No. PCT/EP99/06388, filed Aug. 31, 1999, and designating the U.S. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a yarn processing machine for processing and winding an advancing yarn, and more specifically, to a yarn texturing machine of the type disclosed in EP 0 633 213. 
     The known texturing machine comprises a texturing device and a takeup device. In this machine, a feed system withdraws the yarn from the texturing device and advances it to the takeup device. In the takeup device, the yarn is wound to a package. In particular in machine types with an automatic package doff, time phases occur with a momentary yarn overfeed in the feed system upstream of the takeup device, since the takeup device receives the yarn at a regular speed only during the winding time. As soon as the yarn is removed for purposes of preparing the package doff from a traversing device that reciprocates the yarn in the takeup device, the advancing speed adjusted by the feed system is often greater than the receiving speed of the takeup device. During a package doff, a so-called tie-off bead is wound, after the yarn has been lifted out of the traversing system. Subsequently, the yarn is cut and taken over by a suction device. In this instance, the receiving speed of the takeup device is dependent on the receiving capability of the suction device. In the phases, during which the receiving speed of the takeup device is less than the advancing speed of the feed system, an overfeed of the yarn occurs, which leads to a slack in the yarn between the takeup device and the feed system. 
     To avoid the formation of laps on the feed system, a yarn accumulator for receiving the slack yarn is used in the known texturing machine. In this connection, the yarn accumulator is arranged in the direction of the advancing yarn directly downstream of the feed system. Consequently, there is a risk that a slack in the yarn, which forms when there is a difference between the advancing speed of the feed system and the receiving speed of the takeup device, propagates to the feed system and leads to the formation of laps due to electrostatic effects. 
     It is therefore an object of the invention to further develop the texturing machine of the initially described kind such that the slack in the yarn as occurs during a package doff is reliably accumulated. A further object of the invention is to assist the package doff in such a manner that the yarn can be reliably taken over by the suction device during the doffing phase. 
     SUMMARY OF THE INVENTION 
     The above and other objects and advantages of the present invention are achieved by the provision of a yarn processing apparatus which includes a yarn processing device, such as a texturing device, through which the yarn is advanced. A feed system withdraws the advancing yarn from the processing device and conveys the yarn to a takeup device, and a yarn conveying nozzle is located between the feed system and the takeup device. The yarn conveying nozzle generates an air stream which engages the advancing yarn with a component of movement extending in the direction of the advancing yarn, so that the air stream generates a tension on the yarn upstream of the yarn conveying nozzle and causes an accumulation of slack to be formed in a free space positioned downstream of the yarn conveying nozzle. 
     The invention is distinct from the apparatus disclosed in DE 22 54 736, wherein a yarn is injected directly upstream of a takeup device into a chamber arranged laterally of the yarn by means of an injection nozzle opposite to the chamber. The relatively strong deflection, that is increased by yarn guides on the lower and upper chamber walls, causes the yarn to be held under tension by the looping friction between the takeup device and the chamber. This effect is contrary to the invention. In the texturing machine of the present invention, a tension is generated on the yarn in its direction of advance. With that, a slack in the yarn toward the takeup device is possible. During the package doff, this slack is desired for purposes of assisting in the transfer of the yarn from the fully wound package to the suction device. This all the more, since greater looping frictions on the yarn could result in that the suction device does not engage the yarn or is unable to hold it. Thus, the invention shows a way of temporarily storing a slack yarn between the feed system and the takeup device without significantly increasing the looping friction and without a risk of lap formation. 
     Besides the conveying effect, the conveying nozzle is able to lead to a deflection of the slack yarn. In this connection, it has shown that it is favorable to arrange the nozzle bore of the conveying nozzle at an angle less than about 30°, preferably less than about 20°. 
     The conveying nozzle may include a second nozzle bore which is arranged with the first bore to define a plane which intersects or contains the advancing yarn, and to also define an angle which is bisected by the advancing yarn when viewed in a direction perpendicular to the plane. This construction causes a high tension to be generated on the yarn. At the same time, the arrangement of two opposite nozzle bores facilitates a relatively smooth advance of the yarn despite the air stream. In this connection, it is preferred to arrange the nozzle bores relative to each other such that their center axes form an angle less than about 60°, preferably less than about 40°, which is bisected by the advancing yarn. 
     In the production of a textured yarn, the yarn tension in the apparatus of the present invention remains unchanged in the zones upstream of the feed system during the package doff. The yarn delivered by the feed system is withdrawn under tension. This effect is supported in particular by the further development of the invention wherein a rotatably driven conveying roll is positioned in the yarn path upstream of the conveying nozzle, such that the yarn partially loops about its circumference. A conveying roll upstream of the conveying nozzle causes the yarn tension to be increased toward the feed system according to the Eitelwein law (F 1 =F o *e :*a ). Between the feed system and the conveying roll, no slack occurs in the yarn. The conveying nozzle blows the yarn into the free space. In so doing, the yarn forms, for example, a loop in the air. 
     Thus, the conveying effect of the conveying nozzle F 0  is increased up to the factor e :*a . In this connection, it is advantageous to operate the conveying roll by a turbine drive or an electric drive, so that the circumferential speed is greater than the yarn speed. 
     With the use of a turbine drive, the conveying roll and conveying nozzle can advantageously be combined into one unit wherein the nozzle bores are formed directly downstream of the point of departure of the yarn from the conveying roll. The turbine drive and the nozzle bore are supplied by a common compressed air supply. 
     In one embodiment of the conveying nozzle, the yarn is guided in a conveying gap, which is defined by two opposite sidewalls. One of the sidewalls accommodates one or two nozzle bores that terminate in the conveying gap. With that, the air stream is directed to the yarn in a concentrated manner. This construction of the apparatus in accordance with the invention is especially suitable for use inside the traversing triangle in a takeup device. The conveying gap formed transversely of the yarn advance offers the possibility of performing unhindered a transverse movement that is necessitated by the yarn traversing device, when the yarn is wound on a package. The air stream of the conveying nozzle is activated only at the start of the package doff. 
     To convey the yarn into the free space for receiving the slack, the yarn is guided along the sidewall which opposes the opening of the nozzle bore. 
     To deflect the yarn at the outlet of the conveying nozzle in a purposeful manner, it is proposed to arrange a guide plate in the extension of the sidewall which opposes the opening of the nozzle bore. The shape of the guide plate permits deflecting the air stream exiting from the conveying gap according to the laws of flow (Coanda effect). Therefore, in particular a guide plate curved in direction toward the free space results in that the air stream exiting from the conveying gap is deflected in a concentrated manner into the free space and leads to the deflection of the yarn. 
     To receive a yarn, in the event of a great difference between the receiving speed of the takeup device and the advancing speed of the feed system, it is desirable to utilize a bounce plate which defines the free space. In this instance, the slack yarn is accumulated within the free space on the bounce plate in the form of loops and coils. After the package is doffed, and the receiving speed of the takeup device is substantially greater than or equal to the advancing speed of the feed system, the accumulated yarn will be removed. 
     Since the slack in the yarn occurs only for a very short time during the package doff, the conveying effect of the conveying nozzle is likewise needed only for a short time. To this end, it would be possible to construct the conveying nozzle for movement, so that the yarn comes into the effective range of the nozzle only during a package doff. However, it would also be possible to mount the conveying nozzle stationarily inside the machine. In any event, it is preferred to activate the compressed air supply only during the package doff. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, several embodiments are described in more detail with reference to the attached drawings, in which: 
     FIGS. 1-3 are schematic views of a first embodiment of the texturing machine according to the invention; 
     FIG. 4 shows an embodiment of a conveying nozzle with a bounce plate; 
     FIG. 5 shows an embodiment of a conveying nozzle with a conveying roll upstream thereof; 
     FIGS. 6-8 show a further embodiment of a conveying nozzle with a conveying roll upstream thereof; and 
     FIGS. 9.1 and  9 . 2  show a conveying roll with an integrated conveying nozzle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 illustrate a first embodiment of a texturing machine according to the invention, with FIGS. 2 and 3 being each a cutout view of the machine shown in FIG.  1 . Thus, the following description applies to FIGS. 1-3 alike. 
     The texturing machine comprises a texturing device  1 . Inside this device, a feed system  9  withdraws a yarn  4  via a yarn guide  8  from a feed yarn package  5 . The feed system  9  advances the yarn  4  into a texturing zone. The texturing zone is formed between a false twist unit  13  and the feed system  9 . The texturing zone accommodates a heating device  10  and a cooling device  11  that are arranged one after the other in the path of the yarn. The false twist unit  13  imparts to the yarn a false twist that returns at least to the heating device  10 . In the heating device  10  and the cooling device  11  downstream thereof, the texturing in the yarn is set. 
     Subsequently, a feed system  2  withdraws the yarn from the texturing device  1  and advances it to a takeup device. The takeup device  3  consists of a package  15  and a friction roll  17 . The friction roll  17  lies against the circumference of the package  15  and drives the package  15  at a constant circumferential speed. In the yarn path upstream of the package  15 , a yarn traversing device  16  is arranged, which reciprocates the yarn substantially transversely to the yarn path, so the yarn is uniformly deposited on the package surface. 
     Between the feed system  2  and the takeup device  3 , a conveying nozzle  6  is arranged in the path of the yarn. FIG. 2 is a cross sectional view of the conveying nozzle  6 . The conveying nozzle  6  consists of two sidewalls  20  an  21 . The sidewalls  20  and  21  form between them a conveying gap  22 , through which the yarn  4  advances. The sidewall  21  accomodates two nozzle bores  23  and  29  (see FIG. 3) in such a manner that they terminate with their one end in the conveying gap  22 . At their opposite end, the nozzle bores  23  and  29  connect to a supply line  24 . The nozzle bores  23  and  29  terminate in the conveying gap at an angle β between the center axis  26  of the nozzle bore and sidewall  20 , note FIG.  4 . The angle β is less than about 30°, preferably less than about 20°. 
     At the outlet  44  of the conveying nozzle, a guide plate  25  extends from the sidewall  20 . The guide plate  25  has a curved shape that is directed away from the yarn path. 
     Between the outlet  44  of conveying nozzle  6  and a deflection bar  14 , a free space  7  is formed directly upstream of the takeup device  3 . 
     The feed system  2  consists of a feed shaft  18  and a pressure roll  19  lying against the circumference of the feed shaft  18 . The feed shaft  18  connects to a drive. For advancing the yarn  4 , same is nipped between the feed shaft  18  and pressure roll  19 . The rotation of the feed shaft  18  with freely rotatable pressure roll  19  causes the yarn  4  to advance at the circumferential speed of the feed shaft  18 . 
     FIG. 3 is a front view of conveying nozzle  6 . The nozzle bores  23  and  29  are shown in phantom lines. In the sidewall  21 , the nozzle bores  23  and  29  are arranged, preferably in one plane. Their center axes enclose an angle 2α. Advantageously, the intersection of the center axes coincides with the yarn path in conveying gap  22 . The angle 2α is less than about 60°, preferably less than about 40°, with the yarn advantageously representing the angle bisector. The sidewalls  21  and  20  of conveying nozzle  6  are interconnected via pin  27  and  28 . The pins may be threaded, so that the width of the conveying gap can be adjusted at the same time. 
     In the embodiment shown in FIGS. 1-3, the yarn  4  is first continuously wound to a package  15 . The winding speed or the receiving speed of the takeup device  3  is in this instance equal to the delivery speed or greater than the delivery speed of feed system  2 . In this phase, the yarn  4  advances through the conveying nozzle in a straight line to the deflection bar  14 . After the package  15  is fully wound, the package is doffed. To this end, it is necessary to lift the yarn  4  first out of the traversing device  16 . For a short time, the yarn is wound on the package  15  to a so-called tie-off bead. After winding the tie-off bead, the yarn  4  is cut by a device not shown and removed by suction. Now, the full package  15  is replaced with an empty tube. In this phase, the winding speed of the yarn in the takeup device  3  is less than the advancing speed of the feed system  2 . Thus, the feed system  2  causes the yarn  4  to be overfed. In the conveying nozzle  6 , the yarn  4  is subjected to an air stream generated by nozzle bores  23  and  29 . As a result of the configuration of nozzle bores  23  and  29 , the direction of blowing is oblique relative to the direction of the advancing yarn. This allows generating a tension on the yarn in its direction of advance. The guide plate  25  causes the flow at the outlet of the conveying gap to be deflected in the direction of free space  7 , so that in the instance of overfeeding, the yarn is guided as a loop in the air (shown in phantom lines). Thus, the excessive amount of yarn is received in free space  7 . 
     FIG. 4 shows a further embodiment of the apparatus according to the invention. This embodiment shows only a section of the machine, which is relevant to the invention. The conveying nozzle  6  is constructed, as has previously been described with reference to FIGS. 1-3. To this extent, the description of FIGS. 1-3 is herewith incorporated by reference. Furthermore, structural parts having the same function are identified in the following embodiments by like numerals. In the embodiment shown in FIG. 4, the free space  7  is bounded by a bounce plate  30 . In this connection, the blowing effect of conveying nozzle  6  blows the slack yarn into the free space  7 , until the yarn  4  impacts upon the bounce plate  30 . On the bounce plate  30 , the yarn will deposit in the form of loops or coils. After completion of the package doff, the yarn tangle becomes again undone by the action of the winding speed. This arrangement is especially suited for receiving a strong overfeed of feed system  2 . 
     FIG. 5 illustrates a further embodiment, as may be used in the machine of FIG.  1 . In this embodiment, the feed system  2  withdraws the yarn  4  from a texturing device and advances it to the takeup device not shown. The feed system  2  comprises the feed shaft  18  and pressure roll  19 . Between the feed system  2  and the deflection bar  14 , a conveying roll  31  extends in the path of the yarn. In this arrangement, the yarn partially loops about the circumference of conveying roll  31 . FIG. 5 shows a deflection of about 90°. The conveying roll  31  is driven by means of a drive  32 . In the path of the yarn, the conveying roll  31  is followed by conveying nozzle  6 . In this arrangement, the conveying nozzle [roll]  6  is located laterally of the yarn path opposite to the conveying roll  31 . The conveying nozzle consists of a housing  33 . The housing  33  accommodates a nozzle bore  23 , which connects to the supply line  24 . A pressure medium is supplied to the conveying nozzle  6  via supply line  24 . The conveying nozzle  6  is arranged such that the air stream generated by nozzle bore  23  generates a transverse force on the yarn, which has an essential component in the direction of advance. Thus, when the yarn  4  is overfed, it is blown into the free space  7 . This generates in the yarn length advancing from conveying roll  31  a tension (F o ), which leads in the yarn length between the conveying roll  31  and feed system  2 , due to the looping friction on the conveying roll  31 , to a tension (F 1 ) correspondingly increased under the laws of friction. Thus, the drive of the conveying roll  31  causes the tension to increase between the conveying roll  31  and the feed system  2  by the factor e μ*a  (F 1 =F 0 *e μ*a ), when the conveying roll  31  drivingly overtakes the yarn. Thus, the overfeed of the yarn  4  occurs only downstream of the conveying roll  31  in the region of free space  7 . The conveying roll  31  may be driven, for example, by an electric motor or by a turbine drive actuated by compressed air. 
     The conveying nozzle  6  is arranged relative the yarn path such that the center axis  26  of the nozzle bore  23  forms with the yarn path an angle β. The angle β is less than about 30°, preferably less than about 20°. This ensures that the longitudinal force generated by the air stream produces an adequate conveying effect on the yarn for receiving the overfeed. 
     In the embodiment shown in FIG. 5, the blowing direction and the free space  7  are configured relative the deflection bar  14  such that a slack yarn  4  has a lesser looping on deflection bar  14 . With that, the looping friction is further decreased, so as to assist during a package doff in the takeover of the yarn end by a suction device. 
     FIGS. 6-8 show a further embodiment, as could be used in the machine of FIG.  1 . In this embodiment, a nondriven conveying roll  31  and a conveying nozzle  6  extend between the feed system  2  and deflection bar  14 . FIG. 7 is a cross sectional view of the conveying nozzle  6 , and FIG. 8 is an axially sectioned view of the conveying nozzle  6 . Therefore, the description applies to FIGS. 6,  7 , and  8  alike. 
     The conveying nozzle  6  consists of a housing  34 . In the housing  34 , a groove-type yarn channel  35  is formed. The yarn channel  35  comprises essentially two parallel channel walls  36 ,  37 . The yarn  4  advances through the yarn channel  35  in the longitudinal direction. The channel walls  36  and  37  accommodate the nozzle bores  23  and  29 . They terminate in the yarn channel  35  such that an angle 2*α of less than about 30°, preferably less than about 20° is adjusted. The mouth of nozzle bores  23  and  29  is directed in the direction of the advancing yarn. Via bores  38 ,  39 ,  40 , the nozzle bores  23  and  29  connect to supply line  24 . 
     The nozzle bores  23  and  29  extend in one plane. 
     In this embodiment of conveying nozzle  6 , the air stream enters yarn channel  35  via nozzle bores  23  and  29 . By the yarn channel  35 , the air stream is concentrated, and it generates on the yarn a relatively high tension, thereby driving the roll  31  that is looped by the yarn. Due to the looping friction and the bearing friction of roll  31 , the yarn tension that is effective between the feed system  2  and the roll  31 , is smaller than the tension generated by the conveying nozzle  6 . During an overfeed of the yarn, same is blown into the free space  7  after leaving the yarn channel  35 . 
     FIGS. 9.1 and  9 . 2  illustrate a further embodiment of a conveying nozzle with a conveying roll, as could be used, for example, in the machine of FIG.  1 . In this connection, FIG. 9.1 is a cross sectional view and FIG. 9.2 a front view of the conveying roll. At its two ends, the conveying roll  31  is rotatably supported in a drive housing  41 . In the drive housing  41 , a turbine drive connects to conveying roll  31 . To this end, the conveying roll  31  comprises a plurality of turbine blades  42 . The drive of the turbine, via its blades  42 , occurs by a compressed-air jet from a nozzle bore  45  that is supplied by a compressed-air supply  43 . In the drive housing  41 , a nozzle bore  23  and  29  are arranged each on one side of the yarn  4 . The nozzle bores  23  and  29  receive compressed air from a compressed-air supply  43 . The nozzle bores  23  and  29  extend in the region of drive housing  41 , in which the yarn has just left conveying roll  31 . During an overfeed of yarn  4 , the conveying roll  31  and the air stream on the outlet side of the conveying nozzle advance the yarn  4  directly into an adjoining free space  7 . 
     In each of the illustrated embodiments, the conveying nozzle is stationarily arranged. However, it is also possible to construct the conveying nozzles for movement. In this case, the conveying nozzle swings into the yarn path only in the phase of the package doff, and subjects the yarn to an air stream. 
     In the illustrated embodiments, it is advantageous to activate the air stream of the nozzle only in the phase of the package doff. However, it is also possible to apply an air stream constantly to the yarn. In this instance, it may be advantageous to add a liquid to the air stream for treating the yarn. Furthermore, it may also be advantageous to operate the conveying nozzle with a gas. 
     Basically, it will be possible to combine each conveying nozzle  6  with a conveying roll  31 , if it is intended to reach a high yarn tension downstream of feed system  2 . 
     At this point, it should also be pointed out that the texturing machine shown in FIG. 1 is exemplary in its construction. Thus, the texturing device could comprise in addition a second heater with a preceding feed system for an aftertreatment of the yarn. Likewise, it would be possible to arrange an entanglement nozzle upstream of the takeup device for removing a residual twist in the yarn.