Abstract:
The invention relates to a yarn feeding device with a stationary storage drum and an adjustable yarn pitch. The yarn feeding device comprises a motor housing, a drive shaft of a winding element and a storage drum. Said storage drum consists of meshing finger-shaped cages. The finger-shaped advance cage has an advance bushing that is eccentric and skew with respect to the drive shaft. A backturn detent for the take-up element is mounted in said advance cage. The backturn detent is furthermore interposed between the finger-shaped advance cage and the drive shaft.

Description:
FIELD OF THE INVENTION 
     The invention relates to a yarn feeding device. 
     BACKGROUND OF THE INVENTION 
     Yarn feeding devices operating with adjustable yarn separation and a backturn detent for the winding element are known in practice by prior notorious use and e.g. disclosed in WO/A-99/14149. Such yarn feeding devices predominantly are used for processing special yarn materials, e.g. for supplying the weft yarn when weaving filtering or bossing fabric webs for paper or cardboard production. Due to the elasticity or rigidity of the yarn material or due to certain mechanical conditions a tendency of a backturning motion of the winding element occurs counter to the winding on direction when the winding element stops. This might result in the formation of loops or kinks in the yarn or might lead to overlaps between the yarn windings on the storage drum and finally in operation failures. The backturn detent is provided between the motor housing and the drive shaft or in the supporting bearing of the stationary rod cage and prevents this undesirable backturn motion of the winding element. The yarn separation, i.e. the intermediate distance between respective two adjacent yarn windings on the storage drum in such cases with delicate yarn material is an extremely important measure to properly control the yarn. As the magnitude of yarn separation (pitch) is not the same for all yarn qualities and yarn types but is dependent on each yarn type or each yarn material, respectively, and individually depends on different factors, the magnitude of the yarn separation has to be adjusted in order to achieve optimum conditions for the respective yarn being processed. The yarn separation results from an advance motion in a direction oriented to the withdrawal end of the storage drum, which advance motion is imparted on to the yarn windings on the storage drum. For that function it is a common principle to rotate by the drive shaft an eccentric and skew cylinder inside the advance rod cage. The advance rod cage of the stationary storage drum is supported rotatably on said cylinder. The rotation of said cylinder generates a wobbling motion of the advance rod cage. Thanks to the wobbling motion the rods of the advance rod cage first move outwardly beyond the rods of the supporting rod cage, simultaneously are moved forward relative to the winding on location of the yarn, and finally re-enter inwardly behind the rods of the support rod cage, reverse their motion direction and return to their home position. In order to vary the magnitude of the yarn separation either the radial plane of the maximum eccentricity is rotated about the axis of the drive shaft relative to the plane of the skew inclination of the cylinder to vary the phase offset between those two radial planes, or the magnitude of the skewness position is varied at a given phase offset between the two radial planes. In case of the first, technically simpler method, a bushing carrying the skew cylinder surface is rotated on an eccentric element which either is provided on the drive shaft or even is formed at the drive shaft. In this case, for adjustments the bushing is held against rotation from outside and the drive shaft is rotated inside with the help of the winding element and in one or the other rotational directions. However, the mentioned backturn there only allows a rotation of the drive shaft in one direction of rotation, namely in the winding on direction. For this reason an adjustment of the yarn separation in the locked direction of rotation cannot be carried out by simply rotating the driving shaft by means of the winding element. 
     It is an object of the invention to provide a yarn feeding device of the kind as disclosed at the beginning at which the yarn separation despite the presence of a backturn detent can be increased or decreased by simply rotating the driving shaft. 
     As intended, the backturn detent prevents the undesired backturning motion of the winding element since the driving shaft is blocked in backturning direction by the backturn detent and the advance rod cage inside the stationary storage drum. According to this the desired safety effect of the backturn detent is reliably achieved. As for the adjustment of the yarn separation the advance rod cage has to be held while the drive shaft is rotated in one or the other direction of rotation. The locking action of the backturn detent in backturn rotational direction optionally even can be used to provide the relative rotation between the planes of the skew inclination position and the eccentricity. For that reason it is comfortably possible to increase or decrease the yarn separation despite the action of the backturn detent and only by rotating the drive shaft, e.g. by hand, and with the help of the winding element in the respectively required direction. Extremely comfortable and quick adjustments even can be carried out in the blocked direction of rotation without an auxiliary tool just with the help of the backturn detent. 
     The backturn detent can be provided in the advance support in a structurally simple and space saving manner. 
     As relative rotational movements between the drive shaft and the stationary advance rod cage occur between the inner race and the outer race of a usual ball bearing or between the bearing surfaces of a plain bearing, it is expedient to provide the backturn detent between the races or between the bearing surfaces, respectively. In this case expediently a conventionally available bearing just containing the backturn detent can be used. The backturn detent can be equipped by locking elements, similar to the free wheel assembly of a bicycle driving hub, which locking elements engage automatically only in case of or prior to the not desired rotational motion. As a consequence the backturn detent can be made as a rotational freewheel device locking automatically in one rotational direction or as a overtaking rotational clutch locking automatically in one rotational direction. Alternatively, the backturn detent may be located between the advance bearing and the drive shaft such that the advance bearing is supported by the backturn detent on the drive shaft or the adjustable element of the yarn separation mechanism respectively. 
     As a further alternative the backturn detent may be provided parallel to the advance bearing and at a side of the latter. The locking effect is imparted between the bearing races or the bearing surfaces, respectively, or directly between the element and the advance rod cage, which element is provided for rotational adjustment on the drive shaft. 
     For a comfortable and gradual adjustment of the yarn separation the axis of eccentricity and the axis of the skew inclination are adjustable in relation to each other and/or relative to the axis of the drive shaft. 
     The axis of the eccentricity and the skew inclination axis are adjusted in relation to each other in rotational direction of the drive shaft in each sense of rotation, in order to allow to use a rotational motion of the drive shaft for the adjustment, which rotational motion may be imparted manually. In this it is expedient to integrate the axis of eccentricity into the drive shaft and to constitute the axis of the skew inclination by a separate element mounted on the drive shaft for its rotational adjustments. 
     In a plain bearing even the bearing surfaces could be located skew or eccentrically with respect to the axis of the drive shaft. In this case the inner bearing sleeve is constituting the element necessary for the adjustment of the yarn separation, which element they can be rotated relative to the drive shaft. 
     The phase offset between the skew inclination position and the eccentricity is varied by relative rotational adjustments such that an increase or decrease or even a complete nullification of the yarn separation results. 
     In a structurally simple way a bushing is provided at a carrying surface of the drive shaft such that the bushing can be rotated on the drive shaft and can be fixed in the respective desired rotational position. The bushing constitutes an element of the yarn separation adjusting yarn mechanism which element can be adjusted by rotation. In this case either the carrying surface of the drive shaft or the counterstay surface of the bushing may be formed eccentrically. The respective other of both surfaces in this case then is located in a skew inclined position. 
     Expediently, the advance bearing is provided on the bushing without the possibility to be rotated. Furthermore, a rotational locking socket is provided for engagement of an adjustment tool in order to hold the bushing in case of an adjustment of the yarn separation and when the drive shaft is rotated relative to the bushing by means of the winding element. 
     An adjustable friction clutch between the bushing and the drive shaft allows a comfortable and simple handling. The friction connection of the friction clutch only needs to be strong enough so that the bushing reliably is taken with in case of normal rotation of the drive shaft, and just so strong that the backturn locking force is unable to overcome the friction force of the friction clutch. 
     At least two axially spaced apart roller bearings or plain bearings are provided to achieve a stable support of the advance rod cage. The backturn detent, however, only needs to be provided in one of both bearings. If desired, however, each bearing of the advance support could be equipped by backturn detents. 
     A simple handling of the yarn feeding device in case of an adjustment of the yarn separation is possible, if the adjustment tool is constituted by an on-board pin adjustable in the front end of the storage drum between an engaging position in the rotation locking socket and a passive position. In case that the pin is pre-loaded by a spring, e.g. towards its passive position, an adjustment process can be carried out easily, because the pin only need to be pressed counter to the spring force into its engaging position, before the drive shaft is rotated accordingly. Later, by spring force, the pin automatically returns into its passive position. 
     In order to avoid an excessive adjustment expediently a stop arrangement ought to be provided for limiting the relative rotational adjustment stroke of the bushing on the drive shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will be described with the help of the drawing. In the drawing: 
     FIG. 1 is a longitudinal axial section of components of a yarn feeding device, the yarn feeding device including an adjustable yarn separation and backturn detent. 
    
    
     DETAILED DESCRIPTION 
     A yarn feeding device F in FIG. 1 has a motor housing  1  containing an electromotor  2  driving a drive shaft W about an axis X in one selected direction of rotation. A winding element  3  is provided at drive shaft W, e.g. a winding tube, terminating outside of motor housing  1  and extending obliquely outwards from hollow drive shaft W. Winding element  3  in this case is incorporated into a so-called winding disk  4  which is carried by drive shaft W and is located between motor housing  1  and a storage drum  6  which storage drum is supported via the drive shaft W at motor housing  1 . Drive shaft W functions as the carrier of storage drum  6  and has, for this purpose, a coaxial extension  5 . 
     Storage drum  6  is combined from two interengaging rod cages, namely of a supporting rod cage  7  having axial rods  8  spaced apart in circumferential direction, and an advance rod cage  28  having axial rods  9  respectively provided in the interspaces between rods  8 . Support rod cage  7  has a stationary front end  24  and is located on a hub  10  which is supported rotatably on the extension  5  by a support bearing  11  (e.g. two roller bearings) coaxially with axis X of drive shaft W. 
     To hinder storage drum  6  against rotation with the rotating drive shaft W, co-operating permanent magnets  12 ,  13 , as well known, are provided in the motor housing  1  and in hub  10 , respectively (stationary storage drum). 
     The rods  9  of the advance rod cage  28  are provided at a common hub  14 . The hub  14  is supported by a bushing B rotatably seated on drive shaft W in an advance bearing  15  provided eccentrically and skew or inclined relative to the axis X of drive shaft W. The bushing B is seated on a support surface  16  which is cylindrical and located eccentrically relative to the axis X. Cylindrical support surface  16  is formed on extension  5  or is constituted by a not shown member provided on extension  5 . An eccenter axis X 1  of support surface  16  is distanced by a measure e from axis X. Another cylindrical support surface  17  is formed at the periphery of bushing B and is skew and inclined relative to axes X and X 1  (indicated by the dash dotted inclination axis X 2 ). 
     In the drawing the eccenter axis X 1  and the inclined axis X 2 , for illustration purposes only, are shown in the drawing plane. In order to achieve the yarn separation Z between the yarn windings of the yarn Y wound by winding element  3  onto storage drum  6 , however, a phase offset in rotational direction of drive shaft W has to be provided between the plane containing the axes X, X 1  and the plane containing the inclination axis X 2 . In order to increase, decrease or completely nullify the yarn separation Z the above-mentioned phase offset between the inclination axis X 2  and the eccenter X 1  is to be varied in the respective direction of rotation. A friction clutch R is provided between the bushing B and the drive shaft W, e.g. in the form of a spring package  19  loading the free front end of the bushing B which spring package  19  is pre-loaded by a tensioning screw  18  inserted into the set back free end of the drive shaft W. The spring package  19  couples the bushing B with a predetermined rotation resistance with the drive shaft W. 
     Furthermore, a rotation-locking socket  21  is provided in the advance bearing  15 , e.g. at a ring flange  20  which may, e.g., be coupled to the bushing B in rotational direction. 
     An on-board adjustment tool  22  is located in the stationary front end  24  of storage drum  6 . The adjustment tool  22  has the form of a pin which can be brought into an engaging position into rotation locking socket  21  counter to spring force from the shown passive position. In the shown embodiment the advance bearing  15  consists of two axially spaced apart roller bearings. Of the roller bearings the roller bearing  29  facing towards the free end of the drive shaft W is equipped with a backturn detent D. The roller bearing  29  comprises an inner race  25  and an outer race  26  and roller bodies  27  located therebetween. The backturn detent D is functionally integrated between the inner race and the outer race  25 ,  26 . Alternatively, the advance bearing  15  instead could include one or two plain bearings having co-operating slide surfaces. 
     Even though the detail structure of the backturn detent D is not shown, it is to be noted that it is a freely available rotational freewheel or an overtake rotational clutch (sprag clutch) containing locking elements which automatically move into a locking engagement when a rotation tends to occur in the undesired rotational direction. In the shown embodiment the backturn detent D is integrated into the advance bearing  15 . It is, however, possible to incorporate the backturn detent into the roller bearing shown in FIG. 1 on the left side, or even to equip both roller bearings with a respective backturn detent. Furthermore, it is possible, to provide the backturn detent D between the inner race  25  and the bushing B, or to provide it parallel to the respective bearing and at the side of the same. 
     Finally, a stop assembly  30  is provided between the bushing B and the drive shaft W for limiting the rotational stroke of the bushing B relative to drive shaft W. 
     In operation of the yarn feeding device F the rotating winding element  3  is supplying the yarn Y onto the storage drum  6 . Due to the skew and eccentric support surface  17  of the bushing B rotating with the drive shaft W the inner race  25  is carrying out a rotating wobbling motion. As the stationary support rod cage  7  is hindered by the co-operating permanent magnets  12 ,  13  to rotate with the drive shaft, also the advance rod cage  28  is hindered by the mutually inter-engaging rods  8  and  9  from rotating with the drive shaft. 
     Between the inner race  25  and the outer race  26  a rotational motion can take place in only one direction of rotation. At the same time tilting motions derived from the wobbling motion of the inner race  25  are transmitted into the rods  9  which effect the advance motion of the yarn windings and by this produces the adjusted yarn separation Z. 
     If the electromotor  2  is stopped a tendency of a backturn motion of the winding element  3  counter to the former winding on direction can occur, e.g. due to tension in the yarn Y. However, the backturn detent D then is coupling the inner race  25  to the outer race  26  and blocks the drive shaft W in this undesired direction of rotation against the hub  14  of the advance rod cage  28 . A backturn motion is prevented. 
     In case that the yarn separation Z is to be varied, i.e. is to be increased, decreased or completely to be nullified, first the electromotor  2  is stopped. Then the winding disk  4  is rotated manually and at the same time a frontally located button is pressed to insert the tool  22  into the rotation locking socket  21 . As a consequence of the friction connection of the friction clutch R the drive shaft W or the winding disk  4 , respectively, can no longer be rotated freely. As soon as the friction resistance of the friction clutch R is overcome, however, the support surface  16  can be rotated with the drive shaft W within the bushing B, while the bushing B is locked by the tool  22 . Within the rotational stroke determined by the stopping assembly  30  the respective desired adjustment of the yarn separation Z can be carried out. As soon as the tool  22  is set free, or the button is released which is provided in the front side  24  to actuate the tool  22 , respectively, the return spring moves the tool  22  back into the shown passive position, preferably assisted by a slight manual rotational movement of the winding disk  4  in one or the other direction of rotation. Then the yarn feeding device F again is ready to operate. 
     As an alternative for the shown adjustment tool  22  a separate adjustment tool could be inserted from outside between the interengaging rods  8 ,  9  or even through one of the rods into a then modified rotation locking socket  21  to allow to hold the bushing B against rotation. Basically, the backturn detent D is active in one direction of rotation of the drive shaft W and parallel to the adjustment tool  22 . This has the effect that also the backturn detent D supports the bushing B in this direction of rotation against rotation at advance rod cage  28  and, in turn, at the storage drum  6 . In case that a desired adjustment of the yarn separation Z needs only a rotational movement of the drive shaft W in the rotational direction locked by the backturn detent D, then adjustment tool  22  does not need to be actuated. Such adjustments can be carried out by using the locking function of the backturn detent D instead. 
     In case that the operational direction of rotation of the winding element  3  is to be reversed, either the roller bearing  29  containing the backturn detent D has to be reversed, or a respective roller bearing  29  is to be mounted containing a backturn detent acting in the opposite direction of rotation.