Patent Publication Number: US-7591153-B2

Title: Yarn delivering apparatus having a yarn return operating mode

Description:
This application is a continuation of PCT/EP2005/010754 filed Oct. 6, 2005. 

   The invention relates to a yarn delivering apparatus which is adapted particularly for use in knitting machines or other yarn consuming machines which return yarn from time-to-time. Such machines are, for example, flat knitting machines having a reciprocating carriage; at least at one of the reversal points of the carriage a short yarn return delivery may take place. Yarn return delivery may also occur in flat knitting machines which have several knitting cams and yarns and where individual cams may be switched to idling for one or several strokes. 
   Further, frequent yarn return deliveries may occur in circular knitting machines, particularly when using the “fully-fashioned” technique. In such a technique not only are yarns inserted and dropped, but for certain knitted sections it may be required to rotate the knitting cylinder once or several times in the reverse direction to a greater or lesser extent. Such an operation, in which the knitting cylinder is rotated repeatedly forward and backward, is referred to as “shuttling”. A yarn return delivery of 0.5 meter or more may occur. The yarn delivering apparatuses must take into account such yarn return deliveries. 
   German Patent Document DE 40 32 402 C2 describes a storage feeder for use in flat knitting machines, and combined with a separate dynamic yarn storing device. The yarn discharged by the storage feeder is guided to the flat knitting machine by a yarn storing device. The latter is formed by a long lever to which a torque is applied and which has a yarn eyelet at its free end. The lever is pivotally supported. Further, in the yarn path a yarn brake and a yarn tension sensor are arranged. The yarn quantity delivered back upon carriage reversal is taken up by first applying the controlled yarn brake, so that no further yarn can be withdrawn from the yarn storage feeder. Thereafter a torque is applied to the pivotal lever, as a result of which the lever takes up the yarn, delivered back by the flat knitting machine, by pulling lengthwise a yarn loop which has an acute angle. 
   Upon the subsequent carriage reversal, first the yarn reserve is consumed, and then the yarn brake is released for withdrawing yarn from the yarn storage feeder. 
   Such a mode of yarn storage is adapted particularly for yarn storage feeders where the knitting machine takes the yarn from the yarn storage feeder. This, however, is counter to the principle sought for the positive feeders to allocate a predetermined yarn quantity to the knitting machine. 
   An intermediate yarn storage is also feasible with the yarn delivering apparatus according to German Patent Document DE 37 32 102 C1 which discloses an electronically controlled positive feeder having a yarn delivering wheel around which the yarn is looped. The yarn running to the knitting machine is guided over a yarn storing device which includes a lever supported for a pivotal motion through almost 360°. The yarn passes through the eyelet of the lever. Within the circle described by the yarn eyelet, several yarn supporting elements are arranged which define a polygonal yarn storing device. In case between the yarn delivering wheel and the adjoining machine yarn remains which is not taken up by the machine, such a yarn quantity is deposited by the lever on the yarn supporting elements. 
   Such a mode of yarn delivery is adapted in particular for yarn delivery at a constant yarn tension. 
   Further, German Patent Document DE 34 29 193 C1 describes a device for unwinding yarns from a yarn spool and winding yarns thereon, wherein the yarn is guided by a winder finger on the yarn spool. The winder finger is mounted on a shaft which is concentric to the yarn spool and which is driven by an electric motor. The winder finger circulates about the outer periphery of the yarn spool. The electric motor may be controlled according to requirements in such a manner that the yarn is unwound from the yarn spool or wound back thereon. For the control, a yarn tensioning roller is provided by means of which the yarn tension is monitored. When yarn return delivery is required, the winder finger rewinds the yarn until the yarn tensioning roller is reset into its normal position by the tensioned yarn. 
   Yarn spools are, as a rule, combined on spool creels from which the yarns, as needed, are withdrawn only in a passive manner even for long sections. To involve the yarn spools in the active winding and unwinding steps is undesirable in many cases and is not even possible for larger distances between the yarn spools and the knitting machine. 
   It is accordingly an object of the invention to provide a yarn delivering apparatus which may process occasionally occurring yarn return deliveries in up-to-date knitting machines and other textile machines. 
   The above object is achieved with a yarn delivering apparatus which may include a yarn delivering wheel which, by means of a drive, may be rotated in two opposite directions for delivering the yarn. The yarn run is essentially tangential. A first direction of rotation serves as forward rotation in the normal operation for yarn delivery in a yarn delivering direction to a yarn consuming station. The reverse rotation serves in the yarn return operation for retrieving the yarn which returns from the yarn consuming station in the yarn return direction. Such yarn portion is then wound back onto the yarn delivering wheel. The yarn becoming free at the intake side of the yarn delivering wheel is intermediately buffered in a yarn storing device which, as viewed in the normal yarn delivering direction, is positioned upstream of the yarn delivering wheel between a yarn brake (if such is provided) and the yarn delivering wheel. The arrangement of the yarn storing device upstream of the yarn delivering wheel and in the immediate vicinity thereof preserves, on the one hand, the direct delivering conditions between the yarn delivering wheel and the knitting machine, so that the yarn delivering wheel may allocate the desired yarn quantity to the knitting machine or withdraw such quantity therefrom. On the other hand, the yarn is stored without having an appreciable influence on the tension in the wound yarn and in the portion between the yarn delivering wheel and the yarn consuming station. 
   The yarn storing device has preferably a yarn storing surface which is concentric to the yarn delivering wheel and which may be either a coherent, uninterrupted surface or an interrupted surface composed, for example, of several individual surfaces. Such individual surfaces may be, for example, supporting regions of pins or the like. The arrangement concentric to the yarn delivering wheel makes possible a uniform winding and unwinding, at a uniform tension, of the yarn delivered back from the yarn delivering wheel at its intake side. Preferably, with the yarn storing device a yarn laying device is associated which deposits the yarn, emanating from the yarn delivering wheel, on the yarn storing surface and withdraws the yarn therefrom. The yarn laying device may be a yarn guiding eyelet which is guided, for example, by a suitable lever along a path concentric to the yarn delivering wheel. Such an arrangement ensures a uniform winding and unwinding of the yarn without any appreciable tension fluctuations. Particularly in case of elastic yarns, the latter are prevented from being intermediately stored in different extended states. Further, the yarn, when it is again guided onto the yarn delivering wheel from the yarn storing device, is prevented from running onto the yarn delivering wheel with different, that is, with fluctuating tensions in the yarn winding. Thus, in an overall sense, the above-described concentric arrangement enhances the quality of the knitted fabric. 
   With the yarn laying device preferably a yarn layer drive is associated which is independent from the drive of the yarn delivering wheel. Both drives may be, for example, electric motors controlled by a control device which moves the yarn laying device and the yarn delivering wheel coordinated with one another. The control device distinguishes preferably among several operating conditions, for example, as defined in claim  10 , according to which the control deice causes the yarn laying device and the yarn delivering wheel to move in the reverse direction at coordinated rpm&#39;s, so that the returned yarn is deposited on the yarn storing device without pulling new yarn into the yarn storing device. When resuming normal operation, first the thus-formed yarn reserve-is used up as the yarn delivering wheel and the yarn laying device rotate in the forward direction with coordinated rpm&#39;s. When the yarn reserve is consumed, the yarn laying device stops, for example, in a fixed position, and the yarn delivering wheel continues its forward rotation at unreduced speed. From the moment the yarn laying device stops, the yarn delivering wheel takes the yarn from the yarn spool. 
   The advantage of the above-described device resides in that an associated knitting machine may shuttle as frequently as desired without consuming any yarn. During each shuttle step the yarn is wound on the yarn storing device and then unwound therefrom. The speed of the yarn laying device and that of the yarn delivering wheel are coordinated with one another such that during the shuttle operation no yarn is supplied from the yarn spool and thus the total yarn quantity present in the yarn delivering apparatus does not increase. In the shuttle operation of the knitting machine, the yarn quantity of the yarn delivering apparatus oscillates between a maximum value and a minimum value which may differ from one another by more than 1 meter. 
   The drive for the yarn delivering wheel and that for the yarn laying device are constituted by respective electric motors, particularly by position-regulated electric motors. As an alternative, it is, however, feasible to provide a drive and a clutch arrangement between the yarn delivering wheel and the yarn laying device for connecting the yarn laying device with the yarn delivering wheel with fixed rpm&#39;s in each instance during charging and discharging the yarn storing device. In such a case the drive for the yarn laying device is composed of a drive/clutch/brake combination. Because of a better possibility of control, however, it is preferred to provide the yarn laying device with its own electric motor drive. 
   During normal operation the yarn delivering wheel is driven preferably with a predetermined speed which may be derived from the operating speed or rpm of the knitting machine. The yarn delivering wheel and the knitting machine are sought to be driven in synchronism in a given rpm ratio. Such an operation is referred to as a positive operation. In such an operation the yarn delivering wheel allocates the desired yarn quantity to the knitting machine and thus determines the loop size of the knitted fabric. To compensate for dynamic occurrences during starting and stopping of the yarn delivering wheel, between the yarn delivering wheel and the knitting machine a yarn storing device with a small storage capacity may be provided. Such a yarn storing device, however, does not serve for the intermediate storage of the returned yarn; for such a purpose its capacity is definitely insufficient. It is provided merely for buffering tension peaks which may otherwise appear during switch-on steps (starting and stopping of the yarn delivering wheel). As the simplest solution, such a yarn storing device is formed by a thin, light and resilient lever which holds a yarn loop. 
   The yarn return delivery may likewise be performed with a predetermined rpm of the yarn delivering wheel. It is, however, preferable to effect the yarn return delivery with tension control, that is, by controlling the yarn tension. In such an operation, during the shuttling of the knitting machine, the yarn delivering apparatus is continuously switched between positive drive and tension-controlled drive (positive drive for the normal operation and tension control for the yarn return operation). 
   The yarn laying device as well as the yarn delivering wheel are preferably coupled to angular position sensors. The control device is preferably provided with a counter or another monitoring device which counts the angular steps traveled by the yarn laying device, and preferably also counts the angular steps traveled by the yarn delivering wheel, particularly during the yarn return operation. In the alternative, the angle traveled by the yarn laying device as well as the yarn delivering wheel may be registered in a different manner. The control device thus monitors the quantity of the yarn intermediately buffered in the yarn storing device. The control device may switch over to normal operation with the yarn laying device at rest, when the entire forward-registered path has been traveled in reverse, or, in the alternative, when the yarn laying device has reached a fixed position. As the yarn laying device approaches its fixed position, its normal speed may be gradually braked to zero to prevent abrupt tension changes at the intake side of the yarn delivering wheel. In this manner the yarn running onto the yarn delivering wheel is relieved of stress. In cooperation with the pattern storing device of the knitting machine care can be taken that such a gradual braking takes place only when the shuttling operation is terminated, in order to avoid a gradual filling of the yarn storing device which would otherwise occur. 
   Control of the yarn delivering apparatus occurs preferably by the machine control, particularly its pattern storing device. The latter supplies data relating to the yarn quantities to be delivered which correspond to the rpm of the yarn delivering wheel, as well as relating to the moments of delivery start and delivery termination. The yarn delivering apparatus converts these values in a possibly error-free manner. It is also feasible to operate the yarn delivering apparatus in a self-learning manner. For this purpose, for,example, the yarn tension is, in a test run, held at a nominal value by tension control. In such a proceeding the rpm&#39;s of all the yarn delivering wheels of all the active yarn delivering apparatuses are monitored and a suitable mean value is determined as the nominal value for the subsequent positive operation. 
   During the positive operation, it is furthermore feasible to monitor the self-setting yarn tensions by a yarn tension sensor and if such tension deviates from a nominal value, to effect a follow-up setting of elements of the knitting machine. Such follow-up settings may also be limited to instances where the deviation exceeds a threshold value. Elements of the knitting machine to undergo follow-up setting may be the knitting cams or the product pull-off device. It is also possible to dispense with the follow-up setting of the knitting machine or its elements, and in case the yarn tension exceeds or falls below the threshold values of the yarn tension, to generate an alarm signal or a switch-off signal. 
   The yarn laying device may further be utilized for significantly improving the dynamics of the yarn delivering wheel. In this connection it has been found that in case of a sudden yarn requirement from zero speed to a high delivery speed, not only the drive and the yarn delivering wheel, but the entire yarn length from the yarn spool to the yarn consuming station have to be accelerated. In this procedure the yarn has to be accelerated and furthermore, the friction of adhesion has to be overcome. The yarn running onto the yarn delivering wheel on its intake side brakes the yarn delivering wheel. The acceleration of the yarn delivering wheel can be significantly improved by providing that the yarn laying device, shortly before such an acceleration phase, produces a small yarn reserve on the yarn storing device. Further, the yarn laying device, upon starting of the yarn delivering wheel, is also accelerated for supplying the yarn delivering wheel first with yarn from the yarn storing device and for delivering yarn to the yarn delivering wheel from the yarn spool only when the yarn laying device approaches its fixed position. The yarn storing device serves in this connection to positively disconnect the yarn delivering wheel, during its acceleration phase, from the yarn spool. 
   It is also feasible to effect an early start or stop of the yarn delivering wheel in anticipation of an abrupt increase or decrease in the yarn requirement (pattern in advance). In this manner the inertia of the yarn delivering wheel and connected components may be compensated for up to a certain degree, and yarn tension peaks or yarn tension drops may be reduced at the beginning or the end of yarn delivery. 

   
     Further details of advantageous embodiments or further developments are disclosed in the drawing, the description or the claims. In the drawing, which illustrates embodiments of the invention, 
       FIG. 1  is a front elevational view of a yarn delivering apparatus according to the invention, 
       FIG. 2  is a longitudinal sectional and partially schematic view of the yarn delivering apparatus according to  FIG. 1 , 
       FIG. 3  is a schematic perspective view of the yarn delivering apparatus according to  FIGS. 1 and 2 , 
       FIG. 4  is a schematic illustration of the yarn delivering apparatus of  FIGS. 1 to 3  in normal operation, 
       FIGS. 5 to 9  show the yarn delivering apparatus of  FIG. 4  in different positions in the yarn return delivery operation, 
       FIG. 10  shows, a modified embodiment of the yarn delivering apparatus, and 
       FIG. 11  shows the yarn delivering apparatus of  FIG. 4  in a phase of start preparation before normal operation. 
   

     FIG. 1  shows a yarn delivering apparatus which serves, for example, for delivering hard (poorly elastic) or elastic yarns to flat knitting machines or circular knitting machines. The yarn delivering apparatus  1  is particularly adapted for delivering yarn to knitting machines which have a strongly fluctuating yarn requirement over time and/or which occasionally perform yarn return delivery. The yarn delivering apparatus  1  has, as also shown, for example, in  FIG. 2 , a carrier  2  on which a drive  3  is mounted for a yarn delivering wheel  4  shown as a hexagonal structure. In practice the yarn delivering wheel  4  may have several wings which form, for example, a hexagon. The drive  3  is, for example, an electric motor  5 , whose armature  6  is connected with a drive shaft  7  carrying the yarn delivering wheel  4 . For example, at its other end, the armature  6  may be coupled with an angular position sensor  8  which serves for detecting the actual angular position of the armature  6 . The electronic circuit  9  of the angular position sensor  8  is connected to a control device  11  which serves for controlling the stator windings  12  of the electric motor  5 . 
   The yarn delivering wheel  4  has a particularly low-inertia construction for permitting large rotational accelerations thereof. For this purpose, the yarn delivering wheel  4  has a number of identically structured, radially differently oriented wire yokes  13 ,  14 ,  15  (and additional, un-numbered yokes) which are supported by a hub  16  mounted on the drive shaft  7 . The wire yokes are generally U-shaped having a central portion  17  for the yarn winding and further having, particularly at their sides oriented toward the drive  3 , a radially outward directed projection  18  for the yarn winding. The projection  18  constitutes the intake side  19  of the yarn delivering wheel  4 . 
   At the intake side  19  of the yarn delivering wheel  4  a yarn laying device  21  is provided which forms part of a yarn storing device  22 . The yarn storing device  22  further comprises a preferably frustoconical yarn storing surface  23  which tapers away from the yarn delivering wheel  4  and which is concentric to the drive shaft  7 . The yarn storing surface  23  is preferably significantly shorter in the axial direction of the drive shaft  7  than the portions  17  of the wire yokes  13 ,  14 ,  15 . 
   The yarn laying device  21  bridges the axial distance between the yarn storing surface  23  and the intake side  19  of the yarn delivering wheel  4 . For this purpose, the yarn laying device  21  has a tubule  24  which is made, for example, of ceramic and which constitutes a yarn eyelet. The tubule  24  is carried by a circulating lever  25  which is supported on the carrier  2  by at least one bearing  26  for rotation about an axis concentric to the drive shaft  7 . 
   With the circulating lever  25  a yarn layer drive  27  is associated, comprising a position-regulated electric motor  28 . The drive shaft  29  of the latter is connected with the circulating lever  25  by a gearing composed of two gears  31 ,  32 . The electric motor  28  is controlled by the control device  11 . For this purpose the control device  11  is connected by means of signal-carrying conductors  33  and control conductors  34  with the electric motor  28  for controlling the windings thereof. Corresponding signal-carrying conductors  35  and control conductors  36  are also provided for the electric motor  5 . 
   With the yarn layer drive a locking device  37  may be associated for locking the circulating lever  25  in a fixed position. The locking device  37  may be actuated by an electromagnet  38  controlled by the control device  11 . In case the yarn laying device  21  executes more than one revolution, the locking device  37  assumes its releasing state. For this purpose, for example, an abutment pin  38  a is provided which is movable by the electromagnet  38  between a locking position and an abutting position. 
   Further, the carrier  2  supports a yarn tension sensor  39  for detecting the tension of the yarn running therethrough. The yarn runs at an obtuse angle over a yarn supporting pin  42  forming a part of the yarn tension sensor  39 . The yarn supporting pin  42  is coupled with a force-measuring device  43  which delivers a yarn tension measuring value to the control device  11  or any other suitable device. The yarn tension sensor  39  may be, as illustrated in  FIG. 1 , accommodated in a partial housing  44 , on the frontal face of which a display  45  and several operating elements  46 ,  47  may be arranged. As may be observed particularly in  FIG. 2 , the yarn path defined by the partial housing  44  and the yarn supporting pin  42  is oriented at an obtuse angle to the rotary axis of the yarn delivering wheel  4 . 
   As shown in  FIG. 3 , the yarn laying device  21  serves in particular to wind the yarn  41  onto the yarn storing surface  23  and to unwind the yarn  41  therefrom. In such an operation the yarn  41  is guided by a yarn intake eyelet  48  before it reaches the yarn storing surface  23 . The yarn  41  may first run through a yarn brake  49  shown schematically only in  FIG. 4 . The yarn brake  49  is preferably an uncontrolled yarn brake which sets a constant yarn-pulling force. If required, however, a controlled braking force may be applied to the brake elements of the yarn brake  49 . For this purpose, the brake elements are provided, for example, with an electric setting device (for example, an electric motor, an electromagnet, a piezo setting device or the like) controlled by the control device  11 . The latter controls the yarn brake  49  preferably in such a manner that the braking force is increased when the yarn laying device  21  charges or empties the yarn storing device  22 , whereas the braking force is reduced when the yarn storing device is empty and the yarn delivering wheel pulls yarn from the yarn spool to the knitting machine in the positive operational mode. 
   Preferably, upstream of the yarn brake  49  a non-illustrated intake stopper is positioned which operates preferably optically. However, a simple mechanical stopper formed as a sensor lever may also be used. A yarn monitoring ahead of the yarn delivering wheel.  4  is preferred to a monitoring after the yarn delivering wheel  4 . The yarn tension sensor  39  is not well adapted for yarn monitoring, since even in normal operation, occasionally zero yarn tension magnitudes may appear. Further, it should be prevented in any event, that a ruptured yarn is fed into the machine. 
   It is further feasible to utilize the yarn laying device  21  as a stopper, that is, for monitoring the yarn. For this purpose, the force exerted by the yarn to the yarn laying device is monitored. If, as the yarn delivering wheel rotates, the force drops to an insufficient value or to zero, such an event is evaluated as a yarn rupture. In practice this may be realized, for example, by holding the yarn laying device  21  by the yarn a few millimeters away from the abutment (pin  38   a ), but elastically tensioned theretoward. If the yarn laying device abuts the pin  38   a , such an event is detected by a suitable sensor and is evaluated as a yarn rupture. 
   The yarn delivering apparatus of  FIGS. 1 to 3  operates in accordance with the functional description which follows. 
   The yarn delivering apparatus has several operational modes.  FIG. 4 , which is a substantially schematized representation for a succinct showing of conditions, illustrates the normal operation. The yarn storing surface  23  is shown only in broken lines for distinguishing it from a surface with yarn and a surface without yarn. In  FIGS. 4 to 9  only a single wire yoke  14  of the yarn delivering wheel  4  is provided with a reference numeral for better following the rotation of the yarn delivering wheel  4 . Further, the end of the referenced wire yoke  14  is shown blackened. Also, of the yarn laying device  21  only the tubule  24  is illustrated. 
   In the normal operational mode the yarn laying device  21  is at rest; it is in alignment with the yarn intake eyelet  48 . The yarn delivering wheel  4  rotates, for example, counterclockwise, in the direction of arrow  50 . The yarn  41  runs to a yarn consuming station in a yarn delivery direction as indicated by the arrow  52  tangentially away from the yarn delivering wheel  4  over a yarn tension sensor  39 . As particularly well seen in  FIG. 3 , the yarn is looped several times around the yarn delivering wheel  4  and is thus fed in an essentially slip-free manner. However, slip-causing means, such as yarn lifting pins or the like may also be provided. Yarn slippage may also be effected by a slip clutch arranged between the drive shaft  7  and the yarn delivering wheel or by reducing the extent of yarn loop-around on the yarn delivering wheel  4 . For example, slippage may be generated by merely positioning very few yarn turns about the yarn delivering wheel  4 . It is also feasible to have the yarn contact the yarn delivering wheel  4  by less than an entire loop (for example, a ¾ loop-around). The control device  11  determines the rpm of the yarn delivering wheel  4  and thus sets the speed of yarn delivery and the quantity of the yarn delivered. This mode of operation is termed as the positive operational mode (with tangential yarn take-off). 
   When the yarn requirement of the associated knitting machine drops to zero, the yarn delivering wheel  4  stops, and thus no more yarn is delivered. From a stopped state a normal operation may be resumed at any time according to  FIG. 4 . 
   When the knitting machine or other machine begins to release the yarn  41 , that is, it begins to feed it back, the yarn delivering apparatus begins its return delivery operation. The yarn delivering apparatus immediately determines a reduction in the yarn tension at the yarn supporting pin  42  and attempts to reinstate the yarn tension by reversing the drive  3 . The latter thus executes a clockwise reverse rotation as indicated by arrow  53  shown in  FIG. 5 , and the yarn delivering wheel  4  takes up the yarn  41  in the return delivery direction as indicated by the arrow  54 . The yarn  41  runs tangentially onto the yarn delivering wheel  4 . As depicted in  FIG. 5 , the yarn delivering wheel  4  has already executed a 30° reverse turn which may be observed by comparing the positions of the wire yoke  14  in  FIGS. 4 and 5 . For preserving the yarn tension before the yarn delivering wheel  4 , the control device  11  has triggered the operation of the yarn laying device  21 , so that the tubule  24 , as shown in  FIG. 5 , has been moved approximately 15° clockwise. In this manner the yarn length shown in  FIG. 5  between the intake eyelet  48  and the wire yoke  14  exactly equals the sum of the yarn length present according to  FIG. 4  between the intake eyelet  48  and the wire yoke  14  plus the back-fed yarn length. The motion of the yarn laying device  21  is effected preferably not with tension control, but “positively”, that is, in accordance with a computed travel path determined from the detected reverse rotation of the yarn delivering wheel. No means are provided for detecting the yarn tension at the yarn laying device  21 . If required, however, a tension-controlled actuation of the yarn laying device  21  is also possible. 
   Upon a continued return feed of the yarn  41  the conditions according to  FIGS. 6 to 9  prevail. As seen in  FIG. 6 , the tubule  24  of the yarn laying device  21  deposits the yarn  41  on the yarn storing surface  23 . During yarn return delivery, the yarn laying device  21  runs significantly slower than the yarn delivering wheel  4 . As depicted in  FIG. 6 , the yarn laying device  21  has executed an approximately one-quarter turn, while the wire yoke  14  and thus the yarn delivering wheel  4  have turned by more than one-half revolution. 
   As shown in  FIG. 7 , a continued return delivery results in a gradual circulation of the yarn laying device  21  about the yarn storing surface  23  as the yarn delivering wheel  4  rotates, and the yarn storing surface  23  first receives one turn of yarn ( FIG. 8 ) and further turns ( FIG. 9 ), if required. Based on the conicity of the yarn storing surface  23 , the yarn turns are deposited in the yarn storing device  22  side-by-side and are thus preferably not superposed. The rpm ratio of the yarn laying device  21  to the yarn delivering wheel  4 , that is, the respectively traveled angles are computed by the formula 
             α   β     =       r   1       r   2             
where α is the angle traveled by the yarn laying device,
     β is the angle traveled by the yarn delivering wheel,   r 1  is the diameter of the yarn storing device and   r 2  is the diameter of the yarn delivering wheel.   
   This arrangement ensures that no yarn is pulled through the yarn intake eyelet  48 . In addition, the yarn brake  49  may be applied for preventing such yarn pull-off. xxx 
   When the knitting machine stops the return delivery of yarn, the return delivery operation is terminated; this may occur, for example, in the position of the yarn laying device  21  and the yarn delivering wheel  4  shown in  FIG. 9 . If the knitting machine starts to take yarn, the yarn delivering apparatus changes into a modified normal operational mode in which yarn is no longer taken back in a tension-controlled manner, but rather, yarn is delivered to the knitting machine again in a quantity-controlled manner, that is, by means of predetermined rpm&#39;s set for the yarn delivering wheel  4 . During this operation the directions indicated by arrows in  FIGS. 9 to 5  are reversed. The yarn laying device  21  and the yarn delivering wheel  4  thus rotate clockwise in accordance with the above-defined angle and rpm ratio, whereby the yarn laying device  21  takes yarn off the yarn storing surface  23  and supplies it to the intake side  19  of the yarn delivering wheel  4 . Again, no yarn is pulled through the yarn intake eyelet  48 . This modified operational mode continues until the yarn storing device  22  is emptied, that is, until the tubule  24  has assumed its position in the vicinity of the yarn intake eyelet  48 , as shown in  FIG. 4 . 
   Upon reaching this point, the yarn laying device  21  stops, while the yarn delivering wheel  4  continues to rotate unchanged. Thus, first a true normal operation is obtained. While in the modified normal operation only the yarn wound on the yarn storing surface  23  is again taken up and delivered to the yarn delivering wheel and thus to the knitting machine, yarn is now pulled off against the effect of the yarn brake  49 . The yarn return operation and the modified normal operation may alternate arbitrarily often. No yarn is pulled from the yarn spool through the yarn brake  49  either during the yarn return operation or during the modified normal operation. 
   While according to the starting point in the preceding description the yarn layer drive  27  operates in an accurate position-regulated manner, it has to be noted that this does not necessarily need to be the case. It is also feasible to utilize an electric motor  28  which is not position-regulated and to monitor merely the position of one of the two gears  31 ,  32 . In the simplest case it may suffice to provide on the gear  32  or also on the gear  31  one or more markers (bore holes) or magnets which are detected by optical sensors or, respectively, by magnetic sensors (Hall sensors). When the yarn delivering wheel  4  rotates in the reverse direction, the position or rotation of the yarn delivering wheel is detected, and the motor  28  is energized for moving the yarn laying device  21 . The motor  28  may be supplied with a controlled current for generating a predetermined torque which should be smaller than the torque required for pulling yarn through the yarn brake  49 . In this manner the yarn storing device  22  takes up yarn only from the yarn delivering wheel  4 . When the yarn delivering wheel  4  reverses its direction of rotation to again empty the yarn storing device  22 , it works against the slight tension of the yarn laying device  21 . Such a tension may also be reduced by reducing the current supplied to the motor  28 . When the yarn laying device  21  reaches its position (fixed position), for example, marked by the Hall sensor and the magnets on the gear  31  (or also on the gear  32 ), the yarn laying device  21  is braked to a stop, that is, it is arrested in its fixed position, and the yarn delivering wheel  4  pulls off new yarn from the yarn spool while overcoming the force of the yarn brake  49 . 
   As a departure from the above description, it is to be noted that the modified normal operation which consumes the stored yarn reserve, as well as the normal operation which pulls yarn off the upstream-arranged spool, may proceed in a tension-controlled manner as controlled by the yarn tension sensor  39 . 
   A modified embodiment of the yarn delivering apparatus  1  is schematically illustrated in  FIG. 10 . The modification resides in the configuration of the yarn storing surface  23  which, in this embodiment, is divided into individual surfaces  55 ,  56 . These surfaces are formed by individual pins  57 ,  58  which are arranged as a crown in the vicinity of the yarn delivering wheel  4 . In other respects the previous description applies. 
   The yarn delivering apparatus  1  makes possible a particularly rapid start and stop of yarn deliveries. For such a purpose a dynamic operational mode may be used which will now be described in conjunction with  FIG. 11 . As a starting point of the dynamic operational mode, prior to yarn delivery in the yarn storing device  22 , a smaller yarn reserve is built up, for example, as shown in  FIG. 11 . The yarn reserve may even be smaller. It could be built up by rotating the yarn laying device  21  into the illustrated position during standstill of the yarn delivering wheel  4 , for example, by a few degrees in a clockwise direction. During such a step, the yarn  41  is pulled through the yarn intake eyelet  48  and over the yarn storing surface  23 . This may always occur preventively when the yarn delivering wheel  4  stops at the end of its normal operation. It may occur, controlled by the pattern storing device of the knitting machine, merely when a highly dynamic start, that is, an abrupt increase in the yarn requirement is expected. 
     FIG. 11  shows the yarn delivering apparatus in its state of preparation for a high-dynamic start. If now a starting signal is emitted by the knitting machine for the yarn delivering apparatus  1 , the yarn laying device  21  and the yarn delivering wheel  4  are simultaneously accelerated in a counterclockwise direction (arrows  50 ,  51   a ). By means of the acceleration of the yarn laying device, the yarn delivering wheel  4  is first temporarily, that is, during its run-up phase, relieved of the load of the yarn which is otherwise pulled by the yarn delivering wheel  4  and which extends to the yarn spool. Thus, during the run-up phase, the yarn delivering wheel  4  merely has to overcome its own inertia and that of the yarn winding carried thereby. When the yarn delivering wheel  4  reaches its nominal rpm, for example, after a one-half or three-quarter revolution, the yarn laying device  21  arrives in its fixed position underneath the yarn intake eyelet  48  and is gradually, that is, softly, arrested there, until it comes to standstill. Such an operational mode avoids yarn tension peaks between the yarn delivering wheel  4  and the knitting machine in case of a sudden yarn requirement. 
   A yarn delivering apparatus  1  comprises a yarn delivering wheel  4  having a drive  3 , as well as a yarn storing device  22  having a yarn laying device  21  which is provided with its own yarn layer drive  27 . A control device  11  controls both drives  3 ,  27 , providing for a pure positive operation of the yarn delivering wheel  4  on the one hand, and a yarn return delivery during shuttling of the knitting machine, on the other hand. Further, such a configuration improves the dynamics of the yarn delivering apparatus  1 . 
   
     
       
         
             
           
             
                 
             
             
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               yarn delivering apparatus 
             
             
                 
                2 
               carrier 
             
             
                 
                3 
               drive 
             
             
                 
                4 
               yarn delivering wheel 
             
             
                 
                5 
               electric motor 
             
             
                 
                6 
               armature 
             
             
                 
                7 
               drive shaft 
             
             
                 
                8 
               angular position sensor 
             
             
                 
                9 
               circuit 
             
             
                 
               11 
               control device 
             
             
                 
               12 
               stator winding 
             
             
                 
               13, 14, 15 
               wire yokes 
             
             
                 
               16 
               hub 
             
             
                 
               17 
               portion 
             
             
                 
               18 
               projection 
             
             
                 
               19 
               intake side 
             
             
                 
               21 
               yarn laying device 
             
             
                 
               22 
               yarn storing device 
             
             
                 
               23 
               yarn storing surface 
             
             
                 
               24 
               tubule 
             
             
                 
               25 
               circulating lever 
             
             
                 
               26 
               bearing 
             
             
                 
               27 
               yarn layer drive 
             
             
                 
               28 
               electric motor 
             
             
                 
               29 
               drive shaft 
             
             
                 
               31, 32 
               gears 
             
             
                 
               33, 35 
               signal carrying conductors 
             
             
                 
               34, 36 
               control conductors 
             
             
                 
               37 
               locking device 
             
             
                 
               38 
               electromagnet 
             
             
                 
               38a 
               abutment pin 
             
             
                 
               39 
               yarn tension sensor 
             
             
                 
               41 
               yarn 
             
             
                 
               42 
               yarn supporting pin 
             
             
                 
               43 
               force measuring device 
             
             
                 
               44 
               partial housing 
             
             
                 
               45 
               display 
             
             
                 
               46, 47 
               operating elements 
             
             
                 
               48 
               yarn intake eyelet 
             
             
                 
               49 
               yarn brake 
             
             
                 
               55, 56 
               individual surfaces 
             
             
                 
               57, 58 
               pins 
             
             
                 
               52 
               yarn delivery direction (arrow) 
             
             
                 
               54 
               yarn return delivery direction (arrow) 
             
             
                 
               51a, 50 
               forward rotation (arrow) 
             
             
                 
               51, 53 
               reverse rotation (arrow)