Abstract:
The invention relates to a method for inserting weft yarn material, comprising an insertion system in a loom. According to the invention, for every insertion the insertion system (A) is supplied with a substantial part of the weft yarn required for the insertion in a loose and substantially tension-free manner so as to be intermittently pulled off. A tubular package of adjacent windings is produced from the weft yarn material on an inner mechanical support (S) by way of an at least substantially continuous winding process and is conveyed forward in withdrawal direction. For an insertion, a number of windings that corresponds at least approximately to the weft yarn section intended to be inserted is detached or set free from the support while maintaining its tubular configuration without yarn tension. The weft yarn material is withdrawn directly inwardly from the frontmost winding and then further along the tube axis (X).

Description:
[0001]     This application is a divisional of U.S. patent application Ser. No. 10/399,296 filed Oct. 14, 2003, the disclosure of which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a yarn feeding device for a weaving machine, and to a method of inserting weft yarns into a weaving machine.  
       BACKGROUND OF THE INVENTION  
       [0003]     According to known methods a winding package consisting of contacting or separated and spaced apart windings is formed on a storage body. The insertion system pulls the yarn from the winding package over the front end of the storage body. The windings on the storage body may be advanced forward by different advance assemblies. The storage body is axially longer than the winding package. During withdrawal a yarn balloon is formed which generates significant yarn tension variations and a considerable yarn tension which both delay the insertion. In order to achieve high insertion speeds a considerable energy input thus is needed in the insertion system. On the other hand this means a high mechanical load for the weft yarn. The most important drawback is the long insertion time dictated by this method, i.e. the time period between the start of the insertion and the arrival of the then stopped weft yarn at the opposite fabric edge. The basically very high efficiency potential of modem weaving machines cannot be used satisfactorily due to the long insertion time of such known insertion methods. Furthermore, other methods are known according to which the insertion system does not directly withdraw the weft yarn from the winding package on a storage body but instead weft yarn material is presented for the insertion system in loose and substantially tensionless condition. The influence of a yarn balloon is avoided thereby such that higher insertion speeds can be achieved with low energy input while the weft yarn material is treated with respect. For example, a weft yarn portion is presented by mechanical means in zigzag form or loop form. The mechanical means release the weft yarn portion in synchronism with the withdrawal motion. The method needs high efforts in terms of the devices but is too slow for modem weaving machines because of the mass inertia of the mechanical elements and a plurality of very precisely controlled movements of the mechanical elements.  
         [0004]     There are further methods according to which the weft yarn is presented by mechanical means in a single large loop to the insertion system. The loop is released with the start of the insertion. In this case an undesirably large space is needed and the achievable insertion speeds are limited.  
         [0005]     Finally, it is known to present the weft yarn section to the insertion system loosely and substantially without tension in random configuration in the interior of a cavity. The random configuration of the weft yarn section easily might lead to disturbances due to weft yarn breakages and yarn tension variations during the withdrawal.  
         [0006]     It is an object of the invention to provide a method and a yarn feeding device, as mentioned above, which allow to achieve optimal short insertion times with low energy consumption and high operational safety in highly efficient modem weaving machines.  
         [0007]     Said object is achieved by the features of the yarn feeding device and method as disclosed herein.  
         [0008]     Surprisingly, the winding package portion set free from the support for the withdrawal in orderly arranged windings shows a tendency, among others, due to the inherent inertia property and the form stability of the windings, to safely remain in a tubular configuration in the free space even without any mechanical inner suspension and such that the weft yarn during withdrawal first runs inwardly from the tube without forming any balloon and then runs further centrally and consumes the windings from the tube in a clean fashion, even up to the last in-fed winding which may still be supported on the support. The released winding package section does not collide. The windings do not tend to entangle or to collapse, provided that the withdrawal is carried out rapidly and in a timewise precisely controlled adaptation to the release of the winding package section. Astonishingly short insertion times can be achieved by the method. The astonishingly short insertion times allow to optimally use the capabilities of modern weaving machines in terms of high yarn speeds and high insertion frequencies. The released yarn package section may be supported from the outer side. Such a suspension, however, is more a safety measure. Expediently, the winding on speed of the substantially continuous winding process may be matched with the insertion frequency and the length of the respective inserted weft yarn section such that each insertion substantially consumes the released winding package section before a subsequent winding package section is released. Even in case of extremely high yarn speeds it can be seen that the centrally withdrawn weft yarn does consume the first winding in withdrawal direction substantially radially inwardly and without any ballooning and that the tubular configuration of the windings in the released winding package section is maintained till the end of the insertion with optimum yarn geometry. The released winding package section may contain a number of yarn windings which substantially correspond to the weft yarn length which is to be inserted, or may contain a larger number corresponding to several weft yarns which are to be inserted one after the other.  
         [0009]     It may be expedient to overlap the withdrawal timewise with the release of the winding package section such that the released winding package section or the windings at the withdrawal side of the winding package section, respectively, have as little time as possible to leave the tubular configuration of the orderly arranged windings.  
         [0010]     The method can be carried out in a simple way if the windings in the winding package section are set free by axial overfilling of the inner support beyond the withdrawal side end of the support. The released windings are consumed during the withdrawal before the released winding package section can collide or get into a state of disorder. The overfilling is carried out by continuous winding on of new weft yarn material.  
         [0011]     Alternatively or additively the windings may be released by advancing the winding package on the support beyond the withdrawal side end of the support. In this case advance assemblies of any suitable kind may be employed.  
         [0012]     In order to maintain the tubular configuration of the released yarn package section as stably as possible, and in order to optionally even use the natural adhesion between the contacting windings, the winding package and the released winding package section may be conveyed in withdrawal direction obliquely upwards.  
         [0013]     A further alternative may be to release the windings in the winding package section released for withdrawal by a respective conveying movement or adjusting movement of at least a part of the support. In this case mechanical adjusting devices of the support may be employed.  
         [0014]     It is important for the course of the method to extend the tendency of the released winding package section to remain freely in space without inner mechanical suspension as long as possible. This tendency also depends on the form stability of the yarn material and the windings and from the at least preliminarily inherent form stability of the winding package section. The form stability is good when the windings are wound on the support with a curvature of the yarn material which at least substantially corresponds to the smallest natural and unforced capability of the weft yarn material to store a curvature. Said capability to store the curvature may be explained as follows: a section of the weft yarn material is laid on a smooth surface. Both ends of the section are brought towards each other as close as possible. By this the weft yarn section receives a certain curvature. If then both ends are released, the weft yarn section will relax into a residual curvature representing the smallest natural capability to store a curvature. Surprisingly, it has been found that different weft yarn materials behave only slightly differently or behave even very similarly. In case that the weft yarn material in the winding package is wound at least substantially with the smallest natural capability to store a curvature, then the windings in the released winding package section will not have a considerable tendency to increase or decrease the winding radius themselves such that the released winding package section maintains the tubular configuration formed by the winding process on the inner support relatively long even if there is no further support from inside. Any adhesion between the equally formed contacting windings can support this effect.  
         [0015]     In case of insertion methods employing an insertion system which itself cannot precisely measure the length of the respective inserted weft yarn section it may be expedient to mechanically measure the weft yarn section between the insertion system and the winding package section remaining on the support. For that purpose mechanical systems may be employed which are controlled in adaptation to the weaving cycles.  
         [0016]     The yarn feeding device is designed predominantly but not restrictive for the measurement of the weft yarn length for a weaving machine which is unable to measure the weft yarn length by itself, e.g. a jet weaving machine. In order to hardly influence the formation of the yarn winding package and the release of the yarn winding package section by the measurement or the definition of the correct weft yarn length for each insertion, the engaging stop element is moved into the stop position without using a separate drive, but by the forward moving yarn winding package only. The stop element is brought into the engagement position just in front of a winding just generated on the support and in a position suitable for measuring the length without interfering with the conveying movement of the winding package. Then the stop element drifts with the forwardly conveyed winding package until finally the stop position is reached where the stop element defines the end of the withdrawn weft yarn length. In order to bring the stop element later again into the home position, a power drive is provided which moves the stop element exclusively in the moved away release position and substantially opposite to the withdrawal direction while at the same time yarn windings can be withdrawn without hindrance by the moved away stop element. This results in a stepwise method run during which the power drive always returns the stop element while the yarn package moves the stop element forward. In the engaging stop position the stop element is responsible for the termination of the insertion.  
         [0017]     Expediently, the stop element functionally co-operates with a yarn clamp which is responsible for the start of the insertion and which is controlled in timewise adaptation to the operation movements of the stop element. The yarn clamp holds the weft yarn firmly while the disengaged stop element is returned to the home position. The yarn clamp releases the weft yarn first precisely at the start of the insertion cycle. The insertion then is terminated when the engaging stop element has reached the stop position and is caught at the stop position, before the yarn clamp again holds the yarn in preparation for the return motion of the stop element.  
         [0018]     When the stop element terminates the insertion in the engaging stop position, the weft yarn may be subjected to a significant longitudinal tension between the stop element and the insertion system or between the stop element and even the weaving machine. The longitudinal tension acts backwards at least towards the stop element. The weft yarn section between the yarn clamp adjusted into the clamping position and holding the yarn and the stop element as well will remain under longitudinal tension. In case that then the stop element would be moved from the engaging stop position into no longer engaging the release position, the tension depending friction of the weft yarn at the moving stop element could disturb the tubular configuration of the yarn winding package. Furthermore, the unavoidably occurring relaxation of the tensioned yarn during the movement of the stop element into the release position also could cause a disorder of the tubular configuration of the yarn windings. However, by means of the auxiliary drive the yarn clamp holding the yarn can be adjusted such that by an adjustment travel of the yarn clamp in the direction towards the stop element still positioned in the engaging stop position the weft yarn section extending therebetween becomes gradually relaxed and will be totally relaxed as soon as the stop element then moves into the release position for the next insertion. This adjustment of the yarn clamp avoids damages to the tubular configuration of the yarn winding package. Basically, it also may be expedient, to move the yarn clamp out of the moving space of the yarn at least in the final phase of an insertion, e.g. with the help of a further actuator or even with the same auxiliary drive. This minimises the danger that the yarn might be caught by the yarn clamp. Under certain conditions it might suffice to move a shield for a short while over the clamping region of the yarn clamp, or to provide a deflector at the yarn clamp or adjacent to the clamping region of the yarn clamp which deflector then guides the yarn sidewardly past the clamping region, namely at the sides from which the yarn normally enters the clamping region.  
         [0019]     In order to move as little mass as possible during the movement of the stop element in withdrawal direction by the yarn winding package, a hinge should be provided between the stop element and the power drive of the stop element. Furthermore, the stop element ought to be guided in its moving direction in order to have precise positioning at least in the stopping position which is important for measuring the yarn length. The guidance either may be achieved by a defined hinge axis perpendicular to the withdrawal direction and/or a guiding curve in the support or even in a structure adjacent to the support at the outer side, which guiding curve then may extend exactly in this direction.  
         [0020]     A power drive on a magnetic basis is constructionally simple and functionally safe. A stationary solenoid pulls or pushes the at least partially magnetically conductive stop element in the released position back into the home position by using the hinge. Alternatively, for the same purpose other drives might be employed instead.  
         [0021]     A correct positioning of the stop element in the stop position may be achieved by a stop provided in the guiding notch either in the support or in the outwardly located adjacent structure. The yarn winding package moves the stop element in conveying direction against the stop.  
         [0022]     Since by an abrupt stop of the withdrawn weft yarn in the stop position of the stop element unavoidably a whiplash effect or sudden stretching occurs in connection with a momentary yarn tension rise in this technique, conventionally a controlled yarn brake (end-of-insertion-brake) is employed which dampens the tension rise. Such controlled yarn brakes are expensive and need a complicated control system. For this reason and according to the invention in a structurally simple way the yarn instead is dampened at the stop position of the stop element precisely at the location where the whiplash effect or the stretching effect occurs, namely at the stop element; The dampening is carried out by deflecting the stop element counter to a predetermined elastic counter force essentially in circumferential direction of the support and by the energy which is transferred on the stop element by the stop the weft yarn. By deflecting the stop element counter to the elastic counter force the weft yarn is decelerated gradually and energy will be dissipated to significantly alleviate or remove the weft yarn tension peak. For this reason a controlled yarn brake can be omitted here.  
         [0023]     The above-mentioned function e.g. can be achieved by using a stop element which itself is designed for an elastic return behaviour, e.g. with a springy hinge portion such that the stop element is deflected like a bending spring only under the energy increase of the whiplash effect to alleviate the yarn tension rise. Alternatively a sidewardly positioned retainer could be provided for the stop element in the support or in the structure adjacent to the support. The retainer then is temporarily dislocated sidewardly under the force of the weft yarn counter to the predetermined counter force and together with the sidewardly moving stop element in order to dissipate energy. As soon as the whiplash effect is over the retainer or stop element, respectively, is returned in circumferential direction into the predetermined correct length defining stop position.  
         [0024]     The yarn clamp which is responsible for the start of the insertion has considerable importance since the point in time of the release of the weft yarn has to be adapted very precisely to the operation of the weaving machine and since only a very short time should expire between the command to start the insertion and the actual release of the weft yarn. For that reason the yarn clamp is used as the trigger of the insertion. The yarn clamp should occupy as little space in the yarn path and should act just as close in front of the front end of the support that the released yarn package section can be set free for the insertion with the desired size and without any mechanical interference. The adjustability of the yarn clamp in withdrawal direction, either in a linear or a pivoting motion, is important in order to relax the weft yarn section provided between the yarn clamp holding the yarn and the stop element positioned in the stop position after the insertion, and, under certain conditions, to move a yarn disturbing part of the yarn clamp at least substantially out of the yarn moving area. A step motor is e.g. a useful rotational drive. A solenoid assembly can be used as a linear drive.  
         [0025]     An effective clamping at a small spot and with precisely adjusted clamping force may be achieved by a notch-like clamping region in a slim protrusion of the yarn clamp. The clamping force is mechanically generated by spring force. This can be done, because the clamping action for the yarn is of timewise secondary importance since then the weft yarn is caught by the stop element anyway. The spring force has to assure that the clamping force is sufficient for safely holding the weft yarn back even under tension produced by the insertion system.  
         [0026]     Of importance is, however, that the yarn clamp releases the weft yarn precisely at the desired point in time and as rapidly as possible, when an insertion is to be introduced. This can be achieved by a switching solenoid in a functionally simple way. The armature of the switching solenoid is in an initial position with an intermediate predetermined distance from a bolt tightly holding the weft yarn while the switching solenoid is excited. Thanks to the intermediate distance the armature has sufficient time to overcome the static starting friction and to convert the increasing magnetic force in high speed and to build up high kinetic energy and to accelerate strongly before the armature hits the bolt. The switching solenoid then does not need to overcome the spring force by accelerating the armature from speed zero, but overcomes the counter force of the spring abruptly by the then accelerated and by the high kinetic energy of the armature. This results in an abrupt release of the clamped weft yarn. In practice, release times in a range of only one millisecond can be achieved.  
         [0027]     While the yarn winding package has the tendency to keep the tubular configuration for a longer time in its released section which is no longer suspended from the inner side, it may be expedient, to then support the yarn winding package from the outer side at least in certain regions on guiding surfaces. The suspension from the outer side maintains the tubular configuration and allows during withdrawal to withdraw the weft yarn from the first winding radially inwardly and then along the prolongation of the axis of the support such that no balloon is formed which could cause a delay and could dissipate energy, and such that the desired high insertion speeds or the short insertion times, respectively, are achieved.  
         [0028]     The guiding surfaces could be formed such that they suspend at least the lower half of the released yarn winding package section. In some cases even a bigger part or even the entire yarn winding package section may be suspended. In this case the guiding surfaces could be formed by surface parts or rods or the like in order to generate as low friction as possible on the released yarn winding package section, or to generate friction only there where it might be expedient, e.g. at an upper location at the front most windings in withdrawal direction in order to prevent that those windings may inadvertently tilt forwardly.  
         [0029]     Alternatively or additively at least a part of the guiding surface may be inclined upwardly in withdrawal direction. This contributes to maintain the released yarn winding package section compact and dense while it moves forwards, and even during withdrawal of the yarn.  
         [0030]     A further alternative may be to move the guiding surface together with the forwardly conveyed yarn winding package in order to keep friction influences between the guiding surface and the yarn winding package as low as possible. This may be achieved, e.g. by a caterpillar structure of driven guiding surfaces which hold and convey the yarn winding package from the outer side like spaced apart gear wheels. At the end of an insertion even the last yarn winding on the support may be consumed up to the stop element in the stop position. The undesirable whiplash effect or stretching effect could then lead to an undesirable increase of the weft yarn tension. For that reason a hold-back element with the shape of a lamella or a brush could be provided on top of the yarn winding package. The element co-operates with the front end of the support to slow down the weft yarn speed before the weft yarn comes to a total standstill at the stop element. This element has to be adjustable such that it comes into action only at the respective desired point in time, namely at the end of the insertion, but does not influence the released yarn winding package section during the remaining time period.  
         [0031]     In a structurally simple way the support is designed as a rod cage. The fingers of the rod cage may have individual eccentric adjustment devices with a common adjusting eccentric which is accessible from the front side of the support. In this way diameter variations of the rod cage can be made comfortably. Since the support for carrying out the method has a relatively small diameter, approximately corresponding to the smallest natural and unforced capability of the weft yarn material to store a curvature, a simple eccentric adjustment device is enough, because a diameter variation corresponding to the length of one yarn winding only requires a relatively small radial adjustment stroke.  
         [0032]     Here two possibilities can be realised. The adjusting eccentric either is rotated in the carrier and displaces the finger outwardly or inwardly, or the adjusting eccentric is rotated in the finger and is displaced within the carrier together with the finger and via the eccentric portion.  
         [0033]     An outer diameter between about 20 mm and about 50 mm is expedient for the support, preferably between about 30 mm to about 40 mm. This is a diameter range corresponding to the smallest natural and unforced capability to store a curvature of most of the weft yarn materials processed nowadays.  
         [0034]     Since, of course, any disturbance of the tubular configuration of the yarn winding package is to be avoided in order to achieve a yarn winding package as homogenous and stable as possible, and also a stable, homogenous released yarn winding package section, it may be expedient to provide the stop element at the lower side of the support where the gravitation force contributes towards avoiding disturbing influences of the stop element.  
         [0035]     The yarn clamp should substantially be aligned in the direction of the stretched out yarn with the region at which the stop penetrates into the support.  
         [0036]     According to a very important aspect of the invention the operational safety of the method can be improved significantly by a loop-suppressing body centrally provided at the support and projecting substantially in alignment with the support axis in withdrawal direction such that its free end is positioned at a location with a distance in front of the support. The basic advantages of the method are extremely high insertion speeds or short insertion times, respectively. This positive effect results from the fact that the yarn during withdrawal out of the frontmost winding of the released winding package section directly runs substantially radially inwardly and first then in axial direction into the weaving machine, and without any balloon formation. This yarn movement is carried out with very high speed and a high dynamic. Since the windings in the released winding package section are not supported from the inner side but remain so to speak freely in the space, particularly in case of lively yarn quality occasionally snarls may be formed which would lead to fabric faults if inserted while twisted or which then could cause disturbances in the insertion system, respectively. The snarl suppressing body supports the yarn run there where the yarn runs substantially radially inwards from the frontmost winding and then further in axial direction. In this region the suppressing body hinders by its structural presence that a snarl may get twisted. Instead the untwisted snarl will be pulled open again. The contact occurring during the running dynamic of the yarn with the suppressing body significantly also calms the yarn which then moves relatively linearly in axial direction into the insertion system.  
         [0037]     Expediently, the snarl suppressing body has a coat surface which is rotationally symmetrical and which is tapered towards the free end. This assures that a formed snarl will slide off there and hinders that the snarls gets twisted. The shape also hinders that the snarl even might tend to wrap and tighten around the body under the withdrawal tension.  
         [0038]     Structurally simple the snarl suppressing body is a pin, preferably a conical pin. The pin offers an ideal possibility for placing a withdrawal sensor there for registering each withdrawn winding.  
         [0039]     The outer diameter of the pin should, at least close to its free end, only amount to a fraction of the diameter of the support.  
         [0040]     The free end should markedly project beyond the front side of the support in order to function also in the region in which the yarn is running inwardly from the released winding package section. Preferably, the free end even is located in withdrawal direction downstream of the position of the yarn clamp in order to reach into an area downstream where snarls are no longer formed and where no danger exists that a snarl could get twisted and could form a knot.  
         [0041]     The coat surface should be smooth and should have a low coefficient of friction, optionally the coat surface should have a low friction overlay. Low friction has the meaning that the surface should generate only low friction with the yarn material. This is because the suppressing body only by its bodily presence and extension substantially in withdrawal direction has to effect that snarls which are in process of being generated cannot be twisted. The body should impose as little mechanical and delaying load as possible on the yarn.  
         [0042]     Expediently the forward advancing movement of the winding package is initiated by means of a predetermined conicity of the support. The cone-conveying principle leads to the advantage of directly contacting yarn windings which then also may stick to each other in the released yarn winding package section. Furthermore, this is a low cost and safe solution.  
         [0043]     Alternatively an advancing principle employing a wobbling element in the support may be used which is driven in synchronism with the winding the element, does not rotate but generates a wobbling motion due to its inclined axis which wobbling motion is transferred onto the first yarn winding exiting from the winding element and being formed on the support. The first yarn winding then pushes further the downstream yarn windings.  
         [0044]     As a further alternative the yarn winding package can be advanced axially with so-called yarn separation generated by driven advancing elements. The advancing elements are placed between the fingers or rods of the rod cage and use e.g. a common drive hub which has a skew axis in relation to the axis of the support or the drive axis of the winding element, respectively.  
         [0045]     Basically, the yarn winding package section when presented for withdrawal without tension and loosely, is released by overfilling the support. As an alternative, the support may be pulled back in relation to the yarn winding package and opposite to the withdrawal direction in order to release the yarn winding package section at the right moment. In this case an assisting strip member may contribute to release the yarn winding package from the pulled back support in compact form and in tubular configuration.  
         [0046]     According to a further alternative an auxiliary support is associated to the front side of the support. The auxiliary support is used to first form a yarn winding package supported from the inner side. Thereafter, the auxiliary support is coaxially pulled away from the support in order to release the yarn winding package section which is intended to be inserted. In this case the pull-back of the auxiliary support can be assisted by a stripper member which may be of advantage to keep the released yarn winding package section in compact shape.  
         [0047]     The stretching effect or whiplash effect at the end of an insertion into a jet weaving machine fed by weft yarns originating from a measuring feeding device is a mechanical consequence of the abrupt deceleration of the inserted weft yarn at the stop element. In order to avoid damages, in practice controlled yarn brakes are employed which start to brake in advance before the weft yarn is caught at the stop element and which gradually decelerate the weft yarn. Controlled yarn brakes of this kind need a precise electronic control system and are complicated and costly. According to an important aspect of the invention the stop element itself which is responsible for the whiplash effect or the stretching effect when reaching the stop position, is used for dampening or attenuating the yarn tension rise at the end of an insertion. That is, the attenuation is carried out in the weft yarn exactly at the location where the undesirable yarn tension rise would come from. For that purpose the stop element can be deflected counter to a predetermined elastic force and over a dampening stroke substantially in circumferential direction of the support. In more detail, the stop element is adjusted from a first catching position in which it starts to decelerate the weft yarn over the dampening stroke into a second catching position and is loaded by the reaction force from the weft yarn, such that energy is dissipated before the weft yarn is totally stopped. The stop element then is returned by the predetermined elastic force. In toto this allows a very good yarn control resulting without yarn breakage in a finally linearly stretched weft yarn.  
         [0048]     For this case it may be expedient to provide at least one hinge region between the linear drive which controls the stop element between the engaged position and the released position, and the support. The hinge region allows the sideward movability or this degree of freedom of the stop element without the necessity to accordingly move the linear drive as well. The damping element movably arranged with a predetermined moving direction in a stationary guide can yield against spring force. The damping element is moved by the stop element by the reaction force of the weft yarn counter to the spring force and over the dampening stroke, such that energy is dissipated and that the yarn is braked gradually without suffering from a significant yarn tension rise. The damping element does not need to move strictly in circumferential direction of the support, but could instead move obliquely in a direction approximately corresponding with the orientation of the resulting yarn reaction force at the stop element. The orientation results from the substantially circumferential force of the yarn extending between the last winding at the withdrawal side and the stop element and the substantial axial force of the downstream yarn portion. The automatic return of the damping element after the compensation of the yarn tension peak offers the advantage to then also pull back the weft yarn at least for a small distance.  
         [0049]     In an alternative embodiment the yarn winding package already is formed with several yarn windings which are larger than adjacent ones and which define engagement locations for a respective one out of a plurality of stop elements. The stop elements may be formed like hooks and can e.g. be turned and move together with the yarn winding package such that they sequentially may engage in the enlarged windings. This particularly expedient when the yarn winding package is formed with a size which represents a weft yarn length for several subsequent insertions. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0050]     Embodiments of the invention will be explained with the help of the drawings wherein:  
         [0051]      FIG. 1  is a schematic illustration of the course of a method according to the invention, i.e. a method for inserting weft yarn sections into a weaving machine,  
         [0052]      FIG. 2  is a perspective schematic illustration explaining the so-called smallest unforced capability of a weft yarn material to store a curvature,  
         [0053]      FIG. 3  is a detail variant,  
         [0054]      FIG. 4  is a further detail variant,  
         [0055]      FIG. 5  is a further detail variant, prior to the start of withdrawal,  
         [0056]      FIG. 6  is the detail variant of  FIG. 5  after the start of withdrawal,  
         [0057]      FIG. 7  is a perspective view of a yarn feeding device,  
         [0058]      FIG. 8  is a radial section belong to  FIG. 7 ,  
         [0059]      FIG. 9  is a radial section similar to the radial section of  FIG. 8  of another embodiment, in a home position of a movable stop element,  
         [0060]      FIG. 10  is a radial sectional view similar to  FIG. 9  of the same embodiment in another position of the stop element,  
         [0061]      FIG. 11  is a detail section in the plane XI-XI in  FIG. 10 ,  
         [0062]      FIG. 12  is a schematic illustration of a further embodiment,  
         [0063]      FIG. 13  is a longitudinal section of a yarn clamp as it is used e.g. in  FIG. 7 ,  
         [0064]      FIG. 14  is a diagram showing by means of different curves the operation of several components in relative association during the method,  
         [0065]      FIG. 15  is a perspective front view of a detail of  FIG. 7 ,  
         [0066]      FIG. 16  is a detail of  FIG. 15 , in a perspective view and with enlarged scale,  
         [0067]      FIG. 17  is a schematic view of a method and device variant,  
         [0068]      FIG. 18  is a top view of a detail of a yarn feeding device of  FIG. 17 ,  
         [0069]      FIG. 19  is a perspective view of a further detail,  
         [0070]      FIG. 20  is a detail variant in a perspective view, and  
         [0071]      FIG. 21  is a further variant in a perspective view. 
     
    
     DETAILED DESCRIPTION  
       [0072]     In  FIG. 1  endless weft yarn material Y, e.g. coming from a not shown yarn supply, is pulled into a rotating winding element W which is moved by a drive M with a substantially continuous rotational winding movement R. The weft yarn material Y is wound by the winding element W on an inner mechanical support S in subsequent or adjacently placed windings T as a tubular winding package which moves forward on the support S by a speed V in the direction of an arrow. The windings T then are set free in a winding package section B beyond the end of the support S in withdrawal direction and further in the direction of the axis X from the support S, while they maintain the tubular configuration. In the set free winding package section B the windings T 1  are conveyed forward loosely and substantially without tension. Due to inertia and the form stability of the winding package the windings T 1  remain free in the space. Approximately in alignment with the axis X an insertion system A of a weaving machine L is provided which insertion system A withdraws the weft yarn Y intermittently (indicated by single arrows C) and inserts each weft yarn Y into a weaving machine L. Between the insertion system A and the winding package section B set free from the support S at one side and/or in the region of the end of the support S at the other side, mechanical assemblies H and G may be provided for measuring the respective correct weft yarn length for an insertion. Those assemblies H, G are controlled in adaptation to the weaving cycles. The weft yarn Y withdrawn from the set free winding package section B essentially coaxial to the axis X consumes the respective first winding in withdrawal direction without any balloon formation and runs substantially radially inwards and then further axially, e.g. such that finally all windings T 1  of the set free winding package section B may be consumed at the end of the insertion. Subsequently, the next following winding package section for the next following insertion is set free.  
         [0073]     The winding package consisting of the windings T and the winding package section B are of round or polygonal tubular configuration. At least in the winding package section B the windings T 1  are more or less densely contacting each other, are arranged in good order and have substantially the same form. The diameter D of the winding package is selected such that the winding curvature corresponds at least approximately to the smallest natural and unforced capability of the weft yarn material to store a curvature.  
         [0074]      FIG. 2  illustrates what is meant by the smallest natural and unforced capability to store a curvature. A section E of the weft yarn material Y is laid on a smooth surface  5 . Both ends  3 ,  4  of the section A are moved in the direction of the arrows  1  to each other and then are released. The section E returns by its inherent elasticity in the direction of the dotted arrows  2  to the shown position in which the section has a residual curvature the radius RN of which corresponds to the smallest natural and unforced capability of this weft yarn material to store a curvature. This radius RN of the curvature corresponds approximately to half of the diameter D of the winding package in  FIG. 1 .  
         [0075]      FIG. 3  explains schematically another variant for carrying out the method. The inner support S on which the weft yarn winding package is formed by a substantially continuous winding process has rearward stationary elements  6  and frontward (in withdrawal direction) located elements  8  which can be displaced inwardly and which e.g. are connected via respective hinges  7  with the elements  6 . By means of a corresponding control system for the movement in the direction of the dotted arrow  9  the windings T 1  which are pushed forward during the winding process are set free for withdrawal similar as shown in  FIG. 1  by displacing the elements  8  of support S inwardly.  
         [0076]     In  FIG. 4  the support S includes e.g. cage-like provided elements  10  on a carrier  11  carrying the elements  10 , and, in some cases, also a stationary retainer  12 . By pulling back the carrier  11  in the direction of the arrow  13  a desired number of windings is set free from the support S for withdrawal. Alternatively, it may be possible to set free the windings by pushing the retainer  12  forward.  
         [0077]      FIGS. 5 and 6  show a further variant of the method. The support S consists of a stationary support section S 1  on which the winding element W forms the winding package with the windings T, T 1  with the help of a substantially continuous winding movement R. In withdrawal direction in front of the support section S a further, e.g. coaxial auxiliary support S 2  is provided. The auxiliary support S 2  is inwardly open and includes rod-shaped elements  15  constituting a cage-like configuration connected to a carrier  14 . The elements  15  prolong the support section S 1  in withdrawal direction as long as the carrier  14  remains in the position as shown in  FIG. 5 . In some cases a stationary stripper member may be provided, although this member is not necessary in any case. As soon as by overfilling the support section S 1  a predetermined number of windings T 1  is formed on the support part S 2  in tubular configuration the carrier  14  together with the element  15  is pulled away rapidly in the direction of the arrow  17 . By this action the windings T 1  are set free. From the first winding in withdrawal direction the weft yarn Y then runs inwardly and in withdrawal direction through the stripper member  16  and the carrier  14  which are formed with inner through openings.  
         [0078]     In  FIG. 6  the windings T 1  already are set free. The support section S 2  is adjusted into the right end position. By the withdrawal of the weft yarn Y indicated by the arrow C the set free windings T 1  are successively consumed back to the support section S 1 . After that the support part S 2  again is returned into the position shown in  FIG. 5 , such that by overfilling the support section S 1  again windings T 1  may be brought into the tubular configuration and can be pushed off from the support part S 1 .  
         [0079]     With the method variants of  FIGS. 3-6  also the assemblies H, G for measuring the weft yarn length may be used, e.g. for an insertion system A which is not able to measure the inserted weft yarn length by itself, e.g. in case of a jet weaving machine. The assembly H, e.g. directly co-operating with the support S, may be a controlled stop device with a stop element used to terminate an insertion by catching the weft yarn material Y, while the other assembly G may be controlled yarn clamp which initiates the start of an insertion by an opening stroke.  
         [0080]     In all above described method variants the winding package produced by the winding process is pushed forwards by the winding process itself. Alternatively or additively even advance elements or advance assemblies may be employed which convey the windings forward. It is even possible to operate on the support S with a separation (pitch) between adjacent yarn windings.  
         [0081]     For safety&#39;s sake (in  FIG. 1  indicated in dotted lines) a mechanical (or pneumatic) guiding surface arrangement F may be provided for the winding package section B set free from the support S. The guiding surface arrangement acts on the set free windings, however, exclusively from outside. The suspension by the guiding surface arrangement F is not a must, may, however, be of advantage in order to prevent collapsing or lowering of the set free winding package section B. Furthermore, it is possible, to provide means which engage at the set free winding package section B exclusively on top and from the outer side which means suppresses that the first windings T 1  at the withdrawal side in the set free winding package section B may tilt forward. Those means as well as the suspension by the guiding surface arrangement S do not have any influence on the balloon free consumption of the windings T 1  during the central inward withdrawal of the weft yarn Y in the direction of the axis X of the winding package section B. The diameter D e.g. may lie in a range of about 30 mm. Special yarn qualities, however, may demand a larger or even a smaller diameter D. Experience has shown that a wide variation of yarn qualities and yarn counts have a very similar smallest natural and unforced capability to store a curvature corresponding to a radius of the curvature of about 15 mm.  
         [0082]     The method is not only intended for jet weaving machines but may as well e.g. be employed with gripper weaving machines, rapier weaving machines and projectile weaving machines.  
         [0083]      FIG. 7  illustrates a yarn feeding device  18  for carrying out the method. Several details of the yarn feeding device  18  are shown in  FIGS. 8, 9 ,  10 ,  11  and  13 . The yarn feeding device  18  of  FIG. 7 e .g. serves for feeding weft yarn Y into a jet weaving machine, e.g. an air jet weaving machine, the insertion system A of which is unable to measure the weft yarn length by itself. For this reason the assemblies H, G are provided in the yarn feeding device  18 .  
         [0084]     The driving motor M of the winding element W is received in a housing. The winding element W rotates in relation to the stationary support S which is formed as a kind of a rod cage having circumferentially distributed, freely ending rods  19  extending substantially parallel to the withdrawal direction X. The assembly H is provided at the lower side of the support S and will be described in detail with the help of  FIGS. 8-10 , while the assembly G is provided downstream of support S and is constituted by a controlled yarn clamp  20 .  
         [0085]     The yarn clamp  20  is pivoted backwards and forwards by means of an auxiliary drive  21  and about a pivot axis  21 ′ oriented perpendicular to the withdrawal direction X. The yarn clamp  20  comprises a tubular projection  41  and a notch-shaped clamping region  42  for the weft yarn. The projection  41  extends from outside and perpendicular to the pivot axis  21 ′ essentially below a prolongation of the support axis. A double arrow  22  indicates how the yarn clamp  22  is adjusted back and forth by means of the auxiliary drive  21 . The rotational auxiliary drive  21  includes, e.g., a rapidly responding step motor. Alternatively, a linear drive assembly could be provided which reciprocally displaces the yarn clamp  20  parallel to the withdrawal direction and corresponding to the double arrow  22 . Guiding surfaces F axially overlap the support S and serve for the yarn winding package or the set free yarn winding package section, respectively. The guiding surfaces F, in this embodiment, are arranged at the lower side and at both sides in order to guide and support the set free yarn winding package section, if necessary.  
         [0086]     Basically, it may be expedient to remove the yarn clamp  20  in the end phase of an insertion temporarily from the moving space of the yarn, e.g. by means of a separate, not shown, actuator or even by means of the auxiliary drive  21 , e.g. into a position Q in  FIG. 7 . Alternatively, a shield could be moved for a short while above the clamping region  42 . As a further alternative, a permanent deflector could be provided there. Those measures hinder that the yarn can be caught accidentally by the yarn clamp  20  at the end of an insertion.  
         [0087]      FIG. 8  is radial section of a variant of the yarn feeding device  18 . In this embodiment, the assembly H is provided below the support S and is constituted by a stopping device having a movable stop element  24 . The rods  19  of the support S are provided in a stationary carrier  23  in a freely cantilevering fashion. The winding element W rotates around the support SW. The carrier  13 , e.g. is rotatably supported on the driving shaft of the winding element W; however, not shown solenoid arrangements hinder the carrier  23  from rotating with the driving shaft such that the carrier  23  remains stationary.  
         [0088]     The stop element  24  is pin-shaped and is connected via a hinge  28  having a hinge axis perpendicular to the withdrawal direction X with an armature  25  of a solenoid drive  26  (linear drive) by which the stop element  24  is reciprocally movable in the direction of the double arrow  27  between the shown release position and an engagement position. In the engagement position the free end of the stop element  24  engages into a cut-out or a longitudinal guide  13  of one rod  19 . At the left end in  FIG. 8  of the longitudinal guide  31  a stop  32  is provided which defines a stop position in which the engaging stop element  24  hinders that weft yarn will be further withdrawn from the windings on the support S. The free end of the stop element  24 , e.g., is reciprocally movable in the direction of the double arrow  21  in the hinge  28 . A stop  30  defines the home position of the stop element  24  shown in  FIG. 8 . In the home position the stop element can be brought from the shown release position upwardly into the longitudinal guide  31  such that it will be placed in front of the yarn exiting from the winding element W and behind at least a first yarn winding in withdrawal direction which first yarn winding already is placed on the support S. Thanks to the hinge  28  during the further formation of the yarn windings the stop element  24  is carried along by the axially growing yarn winding package until it is caught in the stop position at stop  32 . The insertion is terminated as soon as the withdrawn weft yarn is caught at the stop element  24 . After the termination of the insertion the stop element  24  again is pulled back by the solenoid drive  26  into the release position such that the yarn winding package can further overfill the support S or such that again weft yarn can be withdrawn. For returning the stop element  24  in the home position shown  FIG. 8 a  power drive  33  is provided, which is stationary with respect to the stop element  24  and which may be, e.g., a controlled solenoid  33 . The solenoid  33  only is active when the stop element  24  has to be returned. The stop element  24  only has to control the end of an insertion. The start of an insertion is controlled by the yarn clamp  20 .  
         [0089]      FIGS. 9 and 10  show a detail variant having a stop element  24  the hinge  28  of which is constituted by an elastic hinge section  28 ′ which provides movability in all directions. The hinge section  28 ′ consists, e.g., of an elastomeric part. The adjustment of the stop element  24  from the stop position shown in  FIG. 10  back into the home position shown in  FIG. 9  is carried out by the inherent elasticity of the hinge section  28 ′, so to speak, automatically. The spring action in the spring section  28 ′ ought to be as weak as possible in order to resist as little as possible the yarn winding package conveying the stop element  24  forward. A permanent magnet  33  can be provided for safety&#39;s sake in order to ensure in co-action with a magnetic section  35  the home position of the stop element  24  as shown in  FIG. 9 .  
         [0090]     Adjacent to the support S or the rods  19 , respectively, in this embodiment a stationary structure  34  is provided distant from the spaced apart from the outer sides of the rods  19  and includes a longitudinal guide  31 ′ for the stop element  24 . Within rod  19  or in-between two rods  19  a cut-out  39  is provided as a longitudinal guide or as a passing path for the stop element  24 . Within the structure  34  as a stop  32 ′ a retainer  36  is provided which defines a damping element and which will be explained with the help of  FIG. 11 . The retainer  36  has to define the stop position of the stop element  24  and constitutes in co-operation with the stop element  24  a damping device of the yarn feeding device  18 .  
         [0091]     The sectional view in  FIG. 11  shows that the longitudinal guide  31 ′ is a slot guiding the engaging stop element  24  while the yarn winding package conveys the stop element  24  forward. In a lateral guide notch  38  substantially oriented in circumferential direction of the support S or oriented in a direction which is oblique in relation to the withdrawal direction, the retainer  36  is displaceable counter to the force of a spring  37 . The retainer  36  on the one hand forms the stop  32 ′ for defining the stop position, and on the other hand constitutes a damping element which elastically can be displaced by the reaction force of the decelerated weft yarn via the stop element  24  from a first catching position k over a damping stroke into a second catch position I. During this stroke kinetic energy will be dissipated such that a yarn tension rise at the end of an insertion is moderated or even avoided.  
         [0092]     In a not shown alternative embodiment the stop element  24  itself could be displaced substantially in circumferential direction of the support S with a counter force and resiliently and could directly constitute the damping device.  
         [0093]      FIG. 12  shows a back-holding element  39  associated to the support S (a lamella or a brush) which extends obliquely downwards in withdrawal direction for co-operation with the front end of the support S or the weft yarn, respectively, which weft yarn just is in progress to be caught at the stop element  24  in the stop position. The back-holding element  33  is adjustable, e.g., in the direction of a double arrow  40  back and forth in order to act indeed only towards the end of an insertion on the yarn to reduce the yarn speed.  
         [0094]      FIG. 13  illustrates the structure of the controlled yarn clamp  20  of  FIG. 7 . The tube-shape projection  41  is secured to a housing  47  receiving the solenoid drive  48 ,  49  serving to adjust the yarn clamp from the shown clamping position into the not shown passive position. The notch-shaped clamping region  42  is defined by a boundary surface  43  of an outwardly open notch of the projection  41  and a clamping surface  44  provided at a shoulder of a bolt  45  which is slideably received in the projection  41 . The bolt  45  is loaded in clamping direction by the force of a spring  46 . The spring  46 , finally, serves to hold the weft yarn Y. A plunger-shaped armature  49  is provided in the solenoid drive  48 . The armature rests in the initial position as shown in  FIG. 13  as long as the solenoid  48  is not excited. In this initial position the armature  49  is spaced apart from the bolt  45  by an intermediate distance  50 . The intermediate distance  50  allows that the armature  49  upon excitement of the solenoid  48  accelerates rapidly and then hits with full vehemence against the bolt  45  such that the held weft yarn Y is released abruptly (opening time in the range of one millisecond).  
         [0095]     The yarn clamp  20  is adjusted from the clamping position shown in  FIG. 13  into the passive position by means of a trig signal transmitted from the weaving machine. By this adjustment the weft yarn Y is released for withdrawal in order to start the insertion cycle. On the other hand, e.g., the stop element  24  is pulled back from the engaging stop position at the point in time after the yarn clamp  20  is brought into the clamping position by a signal generated from a not detailed shown control system of the yarn feeding device. In some cases even a signal of the control device of the yarn feeding device may be used to control the yarn clamp  20 . An adjustment of the stop element  24  from the home position into the engagement position as well may be controlled by a signal of the control device of the yarn feeding device, e.g., as soon as the counted number of wound on yarn windings reaches a target value. A Hall sensor HS ( FIG. 8 ) placed in the stationary part of the yarn feeding device may e.g. serve to count the wound on yarn windings. The Hall sensor may be aligned to a permanent magnet PM provided at the winding element W.  
         [0096]     The method carried out with the yarn feeding device  18  will be explained with the help of the diagram of  FIG. 14  for two subsequent insertion cycles (notch I′). The horizontal axis shows the time t or the rotational angle of the weaving machine, respectively, while the vertical axis among others represents the travel strokes of the assemblies H, G in two opposite direction.  
         [0097]     The horizontal lower parts of the notch I′ represent times during which no yarn consumption takes place, while arc-shaped parts of the curve represent respective insertions during which the predetermined weft yarn lengths are inserted by the insertion system A into the weaving shed of the weaving machine.  
         [0098]     The curve II indicates the substantially radial adjustment of the assembly H, i.e. of the stop element  24 , between the release position a and the engagement position b. The curve III indicates the adjustment of the assembly G, i.e., of the clamping surface  44  relative to the boundary surface  43  of the yarn clamp  20  in longitudinal direction of the projection  41  between the clamping position d and the passive position c. The curve IV indicates the travel of the stop element  24  in the assembly H in and counter to the withdrawal direction between the home position f similar as shown in  FIG. 8  and the stop position e similar as shown in  FIG. 10 . The curve V indicates the adjustment of the assembly G, i.e. of the yarn clamp  20 , in the direction of the double arrow  22  in  FIG. 7 , i.e., in and counter to the withdrawal direction between a position g in which the yarn clamp  20  is furthest from the support S over an intermediate position h into a position i in which the yarn clamp  20  is closest to the support S.  
         [0099]     According to curve II the stop element  24  in the release position and prior to an insertion, is adjusted at a point in time t 1  into the engagement position b, more precisely according to curve IV in the home position f close to the winding element W. Now successively new yarn windings are formed such that according to curve IV the stop element  24  conveyed by the windings gradually reaches the stop position e until the point in time t 3 . When at the point in time t 1  the stop element  24  is adjusted into the engagement position b, the yarn clamp  20  still is in the clamping position d according to curve III, such that the yarn clamp  20  still holds the weft yarn. During this time period the yarn clamp  20  still is in the position g with the largest distance from the support S and according to curve V. For example, at point in time t 2  a trig signal is transmitted. The yarn clamp  20  now is adjusted into the passive position c. The insertion starts. In the passive position the yarn clamp  20  gradually is moved into the intermediate position h and according to curve V such that the yarn clamp  20  will reach the intermediate position h at point in time t 4 . At point in time t 3  the insertion is to be terminated. The stop element  24  has reached the stop position e and stops, according to curve IV, such that the weft yarn is caught. The insertion has ended. At point in time t 4  the yarn clamp  20  again is adjusted into the clamping position d according to curve III such that the yarn clamp  20  again holds the yarn. Thereafter the closed yarn clamp  20  is moved from the intermediate position h according to curve IV into the position i closest to the support S such that the yarn clamp relaxes the yarn section between the stop element  24  and yarn clamp  20 . After the relaxation of the yarn in point in time t 4  the stop element  24  is moved into the release position according to curve II. This movement is carried out without significant friction on the yarn and without jerking motions of the yarn, because the yarn already is relaxed. As soon as the stop element  24  has reached the release position, the stop element  24  is brought by the power drive  33  according to curve IV from the stop position e into the home position f close to the winding element W until the home position f is reached in point in time t 1 . Then the stop element  24  again is adjusted into the engagement position b (curve II) before at point in time t 2  the next insertion will start. After the stop element  24  has been brought into the release position at point in time t 5  in curve II, the yarn clamp  20  is moved according to curve V in withdrawal direction from the position i closest to the support S gradually into the position g in which the yarn clamp (according to curve III) holds the yarn until the point in time t 2 , i.e., the start of the insertion.  
         [0100]     According to curve V the yarn clamp  20  first is adjusted gradually from the position g into the intermediate position h such that the yarn clamp  20  reaches the intermediate position h at point in time t 4 . Only then the further adjustment into the position i is carried out and after the stop element  24  has been adjusted into the release position.  
         [0101]     Alternatively, the yarn clamp  20  may, different from the curve V, remain approximately in the position g between the points in time t 2  and t 3 . The yarn clamp  20  then will be adjusted first after point in time t 4  in one stroke into the position i such that it reaches the position i at point in time t 5  or shortly before.  
         [0102]     In case of only one stop element  24  the releasably weft yarn length only can be an integer multiple of the circumferential length of the support S (diameter D′). In order to adapt the weft yarn length to the weaving width of the weaving machine the diameter D′ has to be variable. For this purpose and according to  FIGS. 15 and 16  the support S is designed with a variable diameter. The rods  19  are, preferably in groups, provided at fingers  51  which are radially movable in guides of the stationary carrier  23 . The respective radial adjustment position of the fingers  51  is fixed by at least one fastening screw  52 . Each finger  51  has an individual eccenter adjustment device  53  allowing to steplessly vary the diameter D′ of the support S. The eccenter adjustment device comprises an adjusting eccentric portion  55  penetrating a cut-out  56  in the finger  51 . The function of the adjusting eccentric portion  55  will be explained with reference to  FIG. 16 .  
         [0103]     The eccentric portion  55  is rotatably supported about the axis  57  in carrier  23  in  FIG. 16 , and particularly by means of a rotatable portion  58  (secured in place by a not shown safety element engaging into circumferential groove  61 ). The adjusting eccentric portion  55  comprises an eccentric portion  59  the eccentric axis of which is offset in relation to the rotation axis  57 , and a handle  60  for the engagement of a turning tool. The eccentric portion  59  engages into the cut-out  56  which extends substantially in circumferential in the finger  51 , preferably in a sliding fit. By turning the adjusting eccentric portion  55 , e.g. over a limited rotational range of 180°, the entire adjusting range for each finger  51  is defined. An adjustment is carried out after first loosening the fastening screw  52 . A new adjustment position is fixed by again tightening the fastening screw  52 .  
         [0104]     Alternatively (not shown) the adjusting eccentric portion  55  only could be supported rotatably in finger  51  such that it engages with its eccentric portion  59  into a cut-out in the carrier  23  which cut-out is similar to the cut-out  56 .  
         [0105]      FIG. 17  indicates schematically how according to the method a number of windings is formed in the yarn winding package. The number of windings corresponds to several weft yarn lengths. For defining the length of each weft yarn section several stop elements  24 ′ are provided which expediently move together with the yarn winding package in withdrawal direction and which can be brought into engagement into selected windings T′. The windings T′ are formed larger than the adjacent windings T, e.g. with the help of a device  62  which preliminarily is placed close to the winding element W (double arrow  63 ) and which then forms one larger winding T′. A respectively selected of the stop elements  24 ′ engages into one of the enlarged windings T′ in order to terminate the insertion of all of the windings T′ located downstream in withdrawal direction. Later, this stop element  24 ′, e.g. is returned by a turning motion into a release position, as soon as the next insertion starts, which next insertion then will be terminated by the subsequent engaging stop element  24 ′.  
         [0106]     In  FIG. 18  the stop elements  24 ′ are formed like hooks and are held in rotatable bearings  65 . The stop elements  24 ′ can be turned between the engagement positions and the released positions back and forth by means of gear rims. An arrow  64  indicates the movement of the stop elements  24 ′ together with the forwardly conveyed yarn winding package in  FIG. 17 .  
         [0107]     In the yarn path downstream of the yarn clamp  20  a controlled yarn brake may be provided (not shown).  
         [0108]     In case of a weaving machine the insertion system of which automatically is capable of mechanically defining the weft yarn length (projectile weaving machine or rapier weaving machine) the assemblies H, G may be omitted.  
         [0109]     During withdrawal of the yarn from the set free winding package section B the yarn of the frontmost winding first runs directly substantially radially inwards before running further substantially in axial direction. Depending on the adhesion between the yarn windings and the elasticity and the liveliness of the yarn material occasionally almost a full winding may move inwardly or the yarn may run spiralling inwardly from the frontmost winding, respectively. This could mean that occasionally a snarl is formed which then, in case of a lively yarn material, might have the tendency to fully get twisted at the location where the yarn crosses. Due to the high withdrawal speed such a snarl could result in a knot or may not be removed but would be inserted. This could cause a fabric fault or an insertion disturbance. For this reason a snarl suppressing body  70  is provided in  FIG. 19  which eliminates the above-mentioned effect. The rods  19  at the fingers  51  which are mounted in the support S at the carrier  23  about which the winding element W rotates, e.g. in the direction of the arrow, define a support surface having a certain axial length and the above-mentioned diameter D′. The snarl suppressing body  68 ,  70  is stationarily secured by a foot part  69  at support S within the rods  19 . The snarl suppressing body  68 ,  70  may be easily removably inserted or even screwed in. The snarl suppressing body  68 ,  70  extends substantially in the direction of the axis of the support beyond the front end of the support S, i.e. beyond the front end defined by the rods  19 , and has a free end  71 . In the shown embodiment a tapered rotation symmetrical pin  70  is provided the diameter of which is significantly smaller than the diameter of the supporting surface. At least the free end  71  has a diameter which only is a fraction of the diameter of the supporting surface. The pin  70  may be linearly conical or may have a concave or convex generatrice. It even may be formed like a pointed cone or as a cylinder. The coat surface  72  of the pin ought to be smooth, in some cases it even might carry a low friction overlay in order to generate as little friction resistance for the yarn as possible. In the shown embodiment the snarl suppressing body  68  reaches with its free end  71  in withdrawal direction beyond the position of the yarn clamp  20 . The yarn clamp  20  is positioned in the withdrawal path of the yarn from the support S outside of the support axis and substantially aligned with the stop element  24  such that the yarn running off from the stop element  24  safely reaches the clamping section  42 .  FIG. 19  also shows the guiding slot  31  for the stop element  24 .  
         [0110]     The free end  71  of the pin  70  of the snarl suppressing body  68  does not need to be necessarily downstream of the yarn clamp  20 . It is possible to place the free end  71  exactly at the position of the yarn clamp  20 , or even between the yarn clamp  20  and the support S. In each case the snarl suppressing body  68  ought to project beyond the front end of the support S in order to be able to hinder that snarls get twisted and occasionally even form knots on their way downstream.  
         [0111]     In operation the withdrawn yarn at least sometimes may contact the coat surface  72 . In case that a snarl is in progress which has the tendency to twist about its crossing location, e.g. in case of lively yarn material, this is hindered by the bodily presence of the snarl suppressing body  68 . A snarl cannot get twisted but will be opened and consumed or removed. Surprisingly, a particularly positive effect of the snarl suppressing body  68  is a very calm run behaviour of the yarn into the insertion system.  
         [0112]     The snarl suppressing body  68  may consist of plastic material or metal. Instead of a pin several parallel or conically converging wire section or the like could be employed. As mentioned, the conical pin  70  could be formed with a concave or convex generatrice of its coat surface  72 .  
         [0113]     Advantageously, the snarl suppressing body  68  may be used to place a reliable yarn withdrawal sensor ( FIGS. 20 and 21 ) for detecting the withdrawn windings. In  FIG. 20 a  reflecting surface  73  (e.g. a mirror) is placed on or in the coat surface  72 . The surface  75  co-acts with an optoelectric sensor  74 ,  75 . In  FIG. 21 a  lateral passage  76  is formed in the pin  70 . A detection beam of a light emitting sensor  74 ′,  75 ′ is directed through the lateral passage  76 . In  FIG. 20  each winding is detected once (one count) per passage, in  FIG. 21  each winding is detected twice (two counts) per passage.