BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a weaving machine having driven projectiles or rapiers, to a weft yarn feeder for a weaving machine, and to a method for inserting a weft yarn into a weaving machine. 
         [0002]    When weaving fabrics, there exist so called heavy duty applications meaning that coarse yarn qualities are woven such as heavy synthetic yarns or heavy synthetic bands, e.g. made from polypropylene. Special weaving machines are employed for heavy duty applications and also special weft yarn feeders designed to process such yarn qualities. Up to now it was considered to be sufficient to control the unavoidable yarn balloon occurring when withdrawing the weft yarn from the storage body of the yarn feeder with the insertion element of the weaving machine by a passive balloon breaker, e.g. a so-called balloon breaker cone as known from U.S. Pat. No. 5,769,132 A. However, newer and wider weaving machines for heavy duty applications have been developed which, e.g. have a weaving width of more than 5 meters and operate with considerably increased weaving speed. On such newly developed weaving machines, it has been found that a passive balloon breaker does not work satisfactorily enough because weft yarn very frequently becomes entangled in the region between the withdrawal rim of the storage body and the balloon breaker. 
         [0003]    U.S. Pat. No. 5,778,943 A relates to a weft yarn feeder equipped with a controllable output brake for the weft yarn. The output brake comprises a conical brush ring fixed to a housing bracket of the yarn feeder such that the bristles of the conical output brake cooperate with the rounded withdrawal rim of the storage body directly at the front end of the storage body. However, for heavy duty applications, the known yarn feeder does not work properly because the weft yarn may form entangled yarn loops between subsequent insertions in the region upstream from the entrance into the output brake. 
         [0004]    U.S. Pat. No. 3,411,548 A (FIGS. 8 and 13) relates to a weft yarn feeder for a projectile weaving machine. The stationary storage body has a conical withdrawal rim which directly continues from a cylindrical region of the storage body where the yarn store is stored intermediately for being taken off by the projectile. A circumferentially closed brush ring is supported at the housing of the yarn feeder such that the ends of the inwardly projecting bristles contact the withdrawal rim in order to generate a desirable yarn tension during each insertion. In order to vary the yarn tension generated by the brush ring during each insertion in adapt action to the weaving cycle, the brush ring is moved back and forth parallel to the axis of the storage body. In one embodiment, an end flange forms the front end of the stationary storage body. The outer diameter of the end flange is larger than the diameter of the storage body in the region where the yarn store is stored intermediately. The brush ring cooperates with the end flange. The brush ring can even be moved axially in relation to the withdrawal rim until the bristles are completely lifted from the withdrawal rim and do not impart any tensioning action on the weft yarn. In a heavy duty application, the weft yarn tends to get entangled around the front end of the storage body. 
         [0005]    It is an object of the invention to provide a weaving machine, a yarn feeder, and a method for inserting a weft yarn which avoids the drawbacks encountered with heavy duty applications, i.e. allow fabrics to be woven from very coarse yarn qualities without operation disturbances caused by entangled weft yarn. 
         [0006]    This object is achieved by the features of this invention. According to the present invention, there is provided a weaving machine equipped with a weft yarn feeder having a stationary storage body for intermediately storing a yarn store. The weft yarn feeder includes a passive hollow balloon breaker functionally associated with a withdrawal rim of the storage body. In addition, several yarn control elements are provided at the weft yarn feeder, which yarn control elements are distributed in a circumferential direction with intermediate distances in between and which can be adjusted actively by a drive from an outer rest position in an end phase of an insertion into an inner operative position upstream from the withdrawal rim and into a mechanical engagement on the weft yarn taken off from the yarn store without completely stopping the weft yarn. 
         [0007]    The weaving machine processes coarse yarn qualities with an extremely low quota of disturbances even in heavy duty applications when weaving fabric with considerable weaving width and extremely high weaving speed because the actively controlled yarn control elements, acting in addition to the passive balloon breaker on the region of the storage body between the yarn store and the withdrawal rim, assure that at the end of an insertion, and prior to the start of a subsequent insertion, the weft yarn is prevented from becoming entangled. The mechanical influence of the yarn control elements, i.e. of at least one of the yarn control elements, on the withdrawn weft yarn reliably suppresses a balloon formation in the region of the yarn control elements and assures that after the insertion the weft yarn does not get slacky and that the front most windings in the yarn store do not lose their correct order. The yarn control elements only impart the mechanical influence on the weft yarn beginning with the end phase of the insertion but are held in their rest position during the main part of the insertion. The balloon suppressing effect of the yarn control elements then also assists the balloon suppressing effect of the passive balloon breaker to assure that the weft yarn follows an orderly path inside the balloon breaker during the end phase of the insertion and after the insertion of the weft yarn has stopped. When a subsequent insertion is started, the yarn control elements are already brought into the rest positions such that the weft yarn takes an orderly, unobstructed course from the yarn store over the withdrawal rim into the balloon breaker. The high acceleration of the weft yarn in the start phase of the subsequent insertion is not at all negatively influenced by the yarn control elements. Controlling the weft yarn beginning with the end phase of the insertion by the yarn control elements reliably prevents the weft yarn from becoming entangled. This avoids operation disturbances and undesirable fabric faults even in the case of very coarse yarn qualities such as band-shaped yarns made from polypropylene. 
         [0008]    In the yarn feeder, the temporary engagement of the actively controlled yarn control elements beginning with the end phase of insertion is of assistance for the balloon suppressing effect of the passive balloon breaker and assures that no critical entanglements occur neither when an insertion is terminated nor before the subsequent insertion is started. 
         [0009]    According to the method, the interaction between the actively controlled yarn control elements and the withdrawn weft yarn is only limited and begins at the end phase of an insertion, while during the main part of the insertion, the weft yarn can be withdrawn without disturbance by the yarn control elements with full speed and high acceleration. The yarn control elements are controlled such that they add an additional balloon suppressing action to the given balloon suppressing action of the passive balloon braking when the weft yarn is decelerated and finally brought to a stop because then the passive balloon breaker cannot generate any influence on the weft yarn in the region between the yarn store on the storage body and the withdrawal rim. The engagement of the yarn control elements first starts in the end phase of the insertion and is actively terminated shortly before the start of the subsequent insertion. The engagement must, in any case, not stop the weft yarn but has to create a mechanical obstacle only which prevents the weft yarn section between the yarn store and the withdrawal rim from becoming slack and avoids that the front most windings in the yarn store lose their orderly placements on the storage body and inadvertently travel further forward while the weft yarn is decelerated abruptly. 
         [0010]    In a preferred embodiment, the yarn control elements are distributed regularly in circumferential direction in a common plane which is perpendicular to the axis of the storage body. This arrangement assures that with certainty at least one of the yarn control elements, or preferably several of the yarn control elements, will mechanically engage on the weft yarn. 
         [0011]    Expediently, two to four yarn control elements may be provided such that the intermediate distance between adjacent yarn control elements is larger in circumferential direction than the circumferential dimension of each yarn control element. As the weft yarn rotates during withdrawal around the front end of the storage body, even such a small number of yarn control elements suffice to assure that the mechanical engagement takes place accordingly. 
         [0012]    In an expedient embodiment, the yarn control elements are aligned with a region of the storage body upstream from the withdrawal rim, which region defines the maximum diameter of the storage body and which extends continuously in circumferential direction. Preferably, this region has a larger diameter than another region of the storage body provided for carrying the yarn store. The circumferentially continuous region of the storage body provides a smooth and continuous guiding and supporting surface for the rotating weft yarn. 
         [0013]    In an expedient embodiment, each yarn control element is a pin which is movable substantially radially with respect to the axis of the storage body. In order to avoid that the pin stops in the operative position completely, the withdrawal movement of the weft yarn, the free end of the pin forms a gap with the storage body in the operative position which gap is wider than the yarn thickness. Due to centrifugal force tending to lift the weft yarn from the storage body in the end phase of the insertion, the weft yarn then comes into mechanical engagement with at least one of the yarn control elements. 
         [0014]    Expediently, the yarn control element is driven by a linear drive such as a pneumatic cylinder or a solenoid. In some cases, the drive may only fulfill a stroke of the yarn control element in one direction against the force of a spring which acts the opposite direction. Alternatively, the linear drive could actively control the yarn control elements in both moving directions. 
         [0015]    In a preferred embodiment, the yarn control elements and a common drive for all yarn control elements or separate drives are arranged in a ring body surrounding a front end of the storage body with radial distance. The ring body not only serves as the carrier for the yarn control elements and the drive or the drives but also fulfills a supplemental balloon suppressing function during the insertion. 
         [0016]    The part of the yarn control element which engages in the operative position at the weft yarn is either rigid in circumferential direction or is flexible. If the part is rigid, the part has to keep a certain distance from the storage body in the operative position of the yarn control element. If the part is flexible, the part even may contact the storage body in the operative position of the yarn control element because then this part will yield when the weft yarn is passing beneath. 
         [0017]    In a preferred embodiment, the ring body is arranged such in a housing bracket of the weft yarn feeder that the ring body can be adjusted in the direction of the axis of the storage body. The housing bracket comprises a linear adjustment mechanism for the ring body allowing the ring body to be optimally placed in relation to the storage body and/or the withdrawal rim. Expediently, the passive balloon breaker is removably arranged at the ring body. As such, the ring body fulfills several tasks. 
         [0018]    In an alternative embodiment, the yarn control element is either designed as a brush having bristles, or fingers pointing towards the storage body, or carrying a foam material layer or a felt layer. In the case of bristles or fingers, the bristles may be oriented either substantially radially with respect to the axis of the storage body or may be inclined in the direction in which the weft yarn is rotating during withdrawal. 
         [0019]    In another preferred embodiment, the yarn control element may be a leaf spring. The leaf spring can be bent in the direction which the weft yarn is rotating during withdrawal. The drive for adjusting the leaf spring between the rest position and the operative position may be either a radial linear drive or a pivot drive for pivoting the leaf spring. 
         [0020]    In another preferred embodiment, the yarn control element may be designed as a pivot arm or a pivotable brush having fingers or bristles oriented towards the storage body. In both cases the drive may be a pivot drive like a pneumatic piston, a solenoid or an electric step motor. 
         [0021]    For the method, it is important that the yarn control elements are brought into the operative position first beginning with the end phase of the insertion, i.e. as soon as or before the withdrawn weft yarn is decelerated abruptly. The yarn control elements then mechanically engage on the weft yarn until the weft yarn comes to a stop caused by the stoppage of the insertion element, i.e. the projectile. It is, however, expedient to keep the mechanical engagement of the yarn control elements on the weft yarn even longer, namely, to a point in time shortly before the start of the subsequent insertion, i.e. to return the yarn control element into the rest position first some milli-seconds prior to the start of the subsequent insertion. 
         [0022]    In relation to the angle of rotation of 360° of the main shaft of the weaving machine, the yarn control elements should mechanically engage at the weft yarn for the last about 30° to 70° of the insertion and only up to 5° to 10° ahead of the start of the subsequent insertion. During the main period of the insertion, the yarn control elements then will be held in the rest positions where they do not impart any mechanical influence on the weft yarn. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0023]    Embodiments of the invention will be explained with reference to the drawings, in which: 
           [0024]      FIG. 1  is a schematic illustration of a projectile weaving machine equipped with at least one yarn feeder, 
           [0025]      FIG. 2  is a longitudinal section of an embodiment of a yarn feeder as schematically shown in  FIG. 1 , in a first operative phase, 
           [0026]      FIG. 3  is a part of the sectional illustration of  FIG. 2 , in second operative position, 
           [0027]      FIG. 4  is a perspective view of a component of the weft yarn feeder of  FIGS. 2 and 3 , 
           [0028]      FIG. 5  is a detail variant partial in sectional illustration, 
           [0029]      FIG. 6  is another detail variant, 
           [0030]      FIG. 7  is another detail variant, 
           [0031]      FIG. 8  is another detail variant, 
           [0032]      FIG. 9  is another detail variant, and 
           [0033]      FIG. 10  is a schematic diagram illustrating an insertion, e.g. in the weaving machine of  FIG. 1  indicating the rotation of a main shaft of the weaving machine and strokes of actively controlled yarn control elements. 
       
    
    
     DETAILED DESCRIPTION  
       [0034]    A weaving machine W, schematically shown in  FIG. 1 , comprises a weaving shed  1  having a reed la driven by a main shaft  2  of the weaving machine. One of a plurality of projectiles  3  serves as an insertion element E for inserting a weft yarn Y into the weaving shed  1 . The weft yarn Y is intermediately stored in a yarn store  7  on a stationary storage body  6  of a weft yarn feeder F which takes off the weft yarn Y from a storage bobbin B. The weft yarn feeder F has a housing  4  and a winding-on-element  5  which can be driven for rotation by a motor  16  in relation to the stationary storage body  6  which might have substantially the form of a drum. A housing bracket  9  supports a hollow passive balloon breaker  8  (e.g. a balloon breaker cone) aligned with the storage body  6  such that the withdrawn weft yarn Y has to pass through the passive balloon breaker  8 . Furthermore, several yarn control elements  11  are provided which can be actively driven by either a common or by separate drives  10  as it will be explained in more detail with respect to  FIGS. 2 ,  3  and  4 . 
         [0035]    The weaving machine W, in particular, is a weaving machine for heavy duty applications. The weft yarn feeder F is also prepared (e.g. anti-abrasive coating on the storage body, powerful motor, robust sensor, etc.) for heavy duty applications meaning for a relatively coarse and/or stiff weft yarn Y, e.g. a weft yarn such as a band of synthetic material like polypropylene. 
         [0036]    In a not shown alternative, the weaving machine W could be a rapier weaving machine with drivable rapiers as insertion elements E. 
         [0037]    The weft yarn feeder F in  FIG. 2  comprises in the housing  4 , the drive motor  16  in the housing  4  for driving a main shaft  15  which in the right side section of  FIG. 2  is hollow and carries the winding-on element  5 . The stationary storage body  6  is substantially conventional and is supported on the main shaft  15 . The storage body  6  has a circumferential and axial region  12  intended for carrying the yarn store  7  (not shown in  FIG. 2 ). This region  12  might consist of spaced apart axial rods between which conventional advance elements operate in order to transport the windings in the yarn store  7  forward and to separate the windings from each other. A sensor device  17  is arranged partly in the storage body  6  and at the lower side of the housing bracket  9 . The sensor device  17 , e.g. serves to control the drive motor  16 . The region  12  is substantially cylindrical and is continued by another cylindrical circumferentially continuous region  13  which in the shown embodiment defines the largest diameter of the storage body  6 . At the front end of the storage body  6 , a withdrawal rim  14  is provided with a diameter which decreases in withdrawal direction, i.e. is conically tapered or is rounded convexly. 
         [0038]    The front end of the storage body  6  is surrounded by a ring body  18  which is supported via a slider  19  in the housing bracket  9 . As adjustment mechanism  20  allows the position of the ring body  18  to be adjusted parallel to the axis of the storage body  6 . 
         [0039]    In this embodiment, the passive hollow balloon breaker  8  is removably fixed by the big diameter end to the ring body  18 . In another not shown embodiment, the passive balloon breaker  8  could be fixed to the housing  4 , or the housing bracket  9 , or to another not shown support. The ring body  18  forms a circumferential continuous gap around the region  13 . The gap width is, e.g. a multiple of the thickness of the weft yarn Y which is to be processed. The ring body  18  here even extends in axial direction beyond the front end of the storage body  6 . 
         [0040]    According to the invention, a plurality of actively controlled yarn control elements  11 , e.g. arranged at the ring body  18 , is distributed with circumferential intermediate distances, preferably regularly, around the front end of the storage body  6 . Examples of the number of yarn control elements  11  are two, three or four. The number, however, could even be larger than four. The yarn control elements in  FIGS. 2 and 3  are oriented radially to the axis of the storage body  6  and can be actively driven in a radial direction between an operative position ( FIG. 2 , P 2 ) and a rest position ( FIG. 3 , P 1 ) by a common drive or by separate linear drives such as pneumatic cylinders, solenoids, or electric linear motors, etc. represented by the indicated drive  10  supported on the ring body  18 . 
         [0041]    In  FIGS. 2 and 3 , the yarn control element is a rigid pin  22 . In the operative position P 2  in  FIG. 2 , the free end of the pin  22  maintains a predetermined distance from the region  13  of the storage body  6  so that a gap x is kept open with a width a slightly larger than the thickness of the weft yarn Y processed by the weft yarn feeder F and the weaving machine W. 
         [0042]    In a not shown embodiment, the pin  22  could instead be flexible in circumferential direction and also axial direction of the storage body  6 . In this case, it is possible that the pin  22  even slightly contacts the region  13  of the storage body  6  in the operative position P 2 . 
         [0043]      FIG. 2  shows that the ring body  18  has a smooth, substantially cylindrical inner surface  21  such that the ring body  18  also fulfills a balloon suppressing function for the withdrawn weft yarn Y. In the rest position P 1  in  FIG. 3 , the yarn control element  11  is moved outwardly so that the free end is either substantially flush with the cylindrical surface  21  or is even set back to a small extent. 
         [0044]    The respective drive  10  is controlled in relation to the weaving cycle of the weaving machine  2  such that the yarn control elements  11  are brought into the operative positions P 2  first in the end phase of a insertion and before the weft yarn is stopped by a stoppage of the projectile  3 , are then kept in the operative positions to a point in time shortly before the start of the subsequent insertion and are then moved into the rest positions P 1  before the subsequent insertion starts and are finally kept in the rest positions P 1  over the major part of the insertion. 
         [0045]      FIG. 4  illustrates the ring body  18  serving at the carrier for the drives  10 , which in this case are linear drives  23 , and receiving the yarn control elements  11 . In this case, there are three yarn control elements  11  regularly distributed in a common plane about the extension of the ring body  18  such that the intermediate distance between adjacent yarn control elements  11  is larger than the circumferential dimension of the respective yarn control element  11 . 
         [0046]    The ring body  18  carries the slider  19  and e.g. is prepared with fastening holes  24  for removably fixing the passive hollow balloon breaker  8 . 
         [0047]      FIG. 10  illustrates one insertion P within a rotation of 360° of the main shaft  2  of the weaving machine W. The insertions, e.g. starts at 150° and is terminated at 340°. The remaining angular range within the 360° revolution of the main shaft  2  is used for cutting the weft yarn, for beating up the inserted weft yarn by the weaving reed, for carrying out the shed change, for transmitting the weft yarn to a projectile  3  and e.g. also for selecting the respective weft yarn. Some degrees prior to the start of the insertion P, e.g. at 145°, the yarn control elements  11  are actively moved from the operating positions P 2  into the rest positions P 1  and are then kept in the rest positions P 1  up to, e.g. 310°. At 310 , for example, the yarn control elements  11  are again actively moved into the operative position P 2  so that the yarn control elements  11  remain in the operative positions P 2  for the last about 30° to about 70° of the insertion P. Expediently, the yarn control elements  11  are further kept in the operative positions P 2  up to again about 145° before the subsequent insertion P or are actively moved into the rest positions P 1  some milli-seconds prior to the start of the subsequent insertion P. 
         [0048]    The yarn control element  11  in the embodiment of  FIG. 5  is a brush  25  having bristles or fingers  26  oriented toward the region  13  of the storage body  6 .  FIG. 5  illustrates the rest position. The drive  10  is a linear drive  23 , e.g. a pneumatic cylinder with a piston  23 ′ acting, e.g. against a return spring  29 . In  FIG. 5 , the bristles or fingers  26 , which are flexible, are oriented substantially radially with respect to the axis of the storage body. 
         [0049]      FIG. 6  illustrates a similar embodiment in which the brush  25  has flexible bristles or fingers  26  which are inclined in relation to a radial orientation in the rotating direction  27  of the withdrawn weft yarn. Alternatively, instead of the flexible fingers or bristles  26 , a layer of felt or foam material  26  could be provided on the brush  25 . 
         [0050]    In the embodiment of  FIG. 7 , the yarn control element  11  is a leaf spring  28  which is either curved or straight and is inclined in the direction  27  of rotation of the withdrawn weft yarn. The drive  10  is a linear drive  23 , e.g. a solenoid which is adapted to move the yarn control element  11  in both directions between the rest position and the operative position. In the operative position as shown in  FIG. 7 , there might be a small gap between the free end of the leaf spring  28  and the region  13 . Alternatively, the leaf spring  28  may even contact the region  13 . 
         [0051]    In the embodiment of  FIG. 8 , the yarn control element  11  is a rigid or flexible pivot arm  30  fixed to a pivot axis  31 . The drive  10  is a pivot drive  32  like a rotary solenoid, a pneumatic piston, a step motor, or the like. At least in the operative position, the pivot arm  13  might be inclined in the direction  27  of the rotation of the withdrawn weft yarn. 
         [0052]    As a not shown alternative embodiment, the leaf spring  28  of  FIG. 7  could instead be moved by a pivot drive  32  between both positions. 
         [0053]    In  FIG. 9  the yarn control element  11  is a pivotably supported small brush  33  having several flexible bristles  34 . The bristles  34  can be pivoted by a pivot drive  32 , e.g. into contact with the region  13  of the storage body  6 .
A projectile-weaving machine is equipped with a weft yarn feeder having a stationary storage body for intermediately storing a yarn store consisting of windings, the weft feeder comprising a passive hollow balloon breaker functionally associated to a withdrawal rim of the storage body. In addition to the passive balloon breaker, several yarn control elements are separated in circumferential direction for being actively moved by a drive from an outer rest position into an inner operative position which without totally stopping withdrawn weft yarn are brought into a mechanical engagement on the weft yarn upstream from the withdrawal rim and starting with an end phase of an insertion on the weft yarn while the weft yarn is taken off from the yarn store over the withdrawal rim.