Abstract:
A yarn splicing device for producing a knot-free yarn connection, particularly with elastic yarns, comprises a splicing body ( 25 ) formed with a splicing channel ( 26 ) to receive the yarns to be spliced and having at least one compressed air inlet opening ( 29 ) for pneumatic splicing of their constituent fibers. Yarn clamping devices ( 43, 44 ) and cutting devices ( 41, 42 ) are provided adjacent the splicing channel. Preparatory nozzles ( 53, 54 ) act to prepare the yarn ends for splicing and pneumatically hold the yarn ends to be spliced. Restraining devices ( 49; 50 ) are arranged along the splicing extent of the yarn between the clamping devices ( 43; 44 ) and the preparatory nozzles ( 53; 54 ) to pneumatically resist contraction of the yarn ends up to the preparatory nozzle ( 53; 54 ). The number of unsuccessful yarn splicing attempts with elastic yarns thereby can be reduced.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of German patent application DE P 10124832.6 filed May 22, 2001, herein incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a yarn splicing device for producing a knot-free yarn connection in a spicing channel of a splicing body and, more particularly, to a splicing device adapted for splicing an elastic yarn. 
     BACKGROUND OF THE INVENTION 
     Such yarn splicing devices commonly comprise a splicing body formed with a splicing channel for receiving an upper yarn and a lower yarn to be spliced with one another and at least one inlet opening into the splicing channel for injecting compressed air thereinto for pneumatically splicing constituent fibers of the yarns. Respective clamping devices clamp the upper yarn adjacent one end of the splicing channel and the lower yarn adjacent an opposite end of the splicing channel. Likewise, respective cutting devices cut an end of the upper yarn to a defined length adjacent the opposite end of the splicing channel and cut an end of the lower yarn to a defined length adjacent the one end of the splicing channel. A preparatory nozzle adjacent the upper yarn cutting device prepares the end of the upper yarn for splicing and pneumatically holds the upper yarn end while being prepared, and a like preparatory nozzle adjacent the lower yarn cutting device prepares the end of the lower yarn while pneumatically holding it. 
     Such yarn splicing devices are described, e.g., in German Patent Publication DE 40 05 752 A1 or DE 44 20 979 A1. The attempt is being made to adapt pneumatic yarn splicing devices to a growing range of threads and yarns in order to be able to produce knot-free connections with great tensile strength and a good appearance for all applications. These yarn connections should differ as little as possible from the tensile strength and the appearance of the main length of the thread or yarn. The pneumatic splicing is carried out in a splicing channel or conduit. The yarns to be connected are placed into this splicing channel in opposite directions and in an overlapping manner. The yarn ends are subjected in preparatory nozzles, also called opening tubes, to a suitable pneumatic or pneumatic/mechanical pre-treatment for the opening and parallelization of their constituent fibers. The yarn ends are subsequently intermingled in the splicing channel of a splicing body, that is designated in German Patent Publication DE 44 20 979 A1 as a splicing head, with the aid of compressed air to a knot-free yarn connection. Such a splicing can achieve approximately the same yarn strength as the main length of the yarn and represents an almost yarn-like connection of two yarn ends. The time of the actual splicing process is usually approximately 15 to 40 ms, depending on the particular splicing conditions. 
     Presently, elastic and highly elastic yarns, e.g., for socks, underwear and sports clothing, are being processed to a great extent. These yarns frequently comprise a highly elastic core yarn whose material consists, for example, of spandex fiber. Elastic and highly elastic yarns can cause significant problems during the splicing process. Defective splices or even no splice connection frequently occur. The cause of this resides in the elastic behavior of the yarn in the yarn splicing device. 
     After a yarn break the so-called upper yarn is grasped by a pivotable suction nozzle and placed into the yarn splicing device in a tensioned state by pivoting the suction nozzle. The same process is used with the so-called lower yarn. Both the upper yarn and the lower yarn are clamped under tension in a clamping device and their ends are severed by a cutting device. In order to draw the yarn ends into the adjacent preparatory nozzles by suction immediately after the cutting and to hold them there until the actual splicing process, compressed air is usually blown into the preparatory nozzles before the cutting action, which air is directed away from the mouth of the preparatory nozzles onto the yarn end and produces a suction action. In the case of elastic and highly elastic yarns, the contractive relaxation of the elastic yarn end when freed by the yarn cutting action is so great that the yarn ends are no longer held by the suction draw in the preparatory nozzles and may possibly even be drawn entirely out of the preparatory nozzles. This hinders or prevents the preparatory opening of the yarn ends as well as the subsequent splicing process. Unsuccessful splicing attempts and therewith repetitions of the entire yarn connecting process occur. The suction action exerted by the preparatory nozzles can not be reinforced as desired in order to increase the holding power since this, on the one hand, causes a greater consumption of compressed air, which is undesired for economic reasons, and on the other hand, can result in an adverse effect on the quality of the splice. As is known, a substantially more protective, better and more uniform opening of the yarn ends takes place at rather low pressures of the preparatory air. 
     The described deficiencies can not be eliminated with the known yarn splicing devices existing in accordance with the present state of the art. 
     SUMMARY OF THE INVENTION 
     Thus, the present invention seeks to address the problem of improving the known yarn splicing devices to enable them to reliably splice elastic yarns. 
     The present invention addresses this problem by providing a yarn splicing device of the type described above with restraining devices arranged between each yarn clamping device and its associated yarn preparatory nozzle for pneumatically retarding the contraction of elastic yarn ends up to the yarn preparatory nozzles after cutting of the yarn ends. 
     In this manner, the contraction of the elastic yarn ends is sufficiently reduced and the withdrawal of the yarn ends from the preparatory nozzles is successfully counteracted by the restraining devices acting pneumatically on the yarn between the clamping devices and the preparatory nozzles. The preparation of the yarn ends for splicing and the splicing process itself are no longer disturbed or prevented by the yarn contraction. Standstill times caused by repetitions of the splicing process are avoided. Bulky, additional mechanical clamping devices in the area of the splicing body are not necessary. The action of the restraining device begins extremely rapidly upon actuation. Standard yarn consisting of different raw materials that are wound instead of elastic yarns on a work site in accordance with the invention can be processed without disadvantage as regards the yarn joining process or the quality of the yarn connection. 
     The restraining devices are preferably arranged between the splicing body and the preparatory nozzle. Compared with an alternative design in which the restraining device is arranged between the splicing body and the clamping device, thus creating more space for the restraining device, there is less play available given the selection of the position of the restraining device, but the contraction of the stretched yarn can be shortened to an especially great extent. 
     The restraining device is preferably designed as a suction nozzle comprising elements that prevent the drawing in by suction of the yarn end. This reliably avoids the situation that the yarn end can be drawn out of the preparatory nozzle by the drawing in by suction of the yarn end into the restraining device. This can be brought about in an advantageous manner by a tubular suction nozzle with an air-permeable cover on the suction intake. A design of the cover as a grate with grate rods running largely transversely to the path of the yarn, together with the tensioning of the yarn caused by the preparatory nozzle, prevents the drawing in of the yarn into the restraining device and acts preventively against a clogging of the cover, as can readily occur with a wire mesh. If the control device associated with the yarn splicing device is set up in such a manner that it continuously activates the restraining device at the latest during the cutting of the yarn and up to actuation of the splicing device, a reliable course of the splicing process is assured. 
     If the preparatory nozzle and the restraining device are connected at the same time to a source of compressed air, the control expense is especially low since no switching times that differ from one another must be observed. The loading of the preparatory nozzles and of the restraining device with compressed air for the injection of air and to produce the particular suction effect can take place with a single, joint switching process. The preparatory nozzle and the restraining device can be connected to the same source of compressed air, which permits an especially simple construction as regards compressed-air lines and switching elements. Alternatively, the preparatory nozzle and the restraining device can be connected to two sources of compressed air with different strengths, which makes a controlling of the holding power of the restraining device readily possible. In another alternative embodiment the restraining device can be connected to a vacuum source in order to produce the suction action. 
     A friction surface is advantageously arranged adjacent to the restraining device in such a manner that the yarn rests on the friction surface when the restraining device is actuated. This supports and increases the restraining action on the yarn without any damage being caused to the yarn. 
     The yarn splicing device in accordance with the present invention can also be used in open-end spinning machines. As is known, it is also customary in such textile machines to prepare the yarn end in an appropriate preparatory nozzle before the new spinning start. 
     The invention permits the desired quality of the splice to be observed and the number of unsuccessful splicing attempts to be lowered. This achieves an increase in the yarn quality and in the productivity of the winding head and of the entire textile machine. 
     The present invention will be further explained in detail with reference to exemplary embodiments shown in the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side elevational view of a winding head of a cheese-producing bobbin winding machine with a pneumatic yarn splicing device in accordance with the present invention. 
     FIG. 2 is a simplified perspective view of the yarn splicing device of the present invention. 
     FIGS. 3 and 5 are simplified front elevational views of the same embodiment of the yarn splicing device as FIG. 2, showing different phases of the yarn-end preparation. 
     FIG. 4 is a cross-sectional view of the yarn splicing device of FIG. 2, taken through the restraining device thereof along section line A—A of FIG.  3 . 
     FIG. 6 is another simplified front elevational view of another embodiment of the yarn splicing device of the present invention, shown in a phase of the yarn-end preparation. 
     FIG. 7 is a cross-sectional view of the yarn splicing device of FIG. 6, taken through the restraining device thereof along section line B—B thereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the accompanying drawings and initially to FIG. 1, a winding head  1  is schematically shown as part of a textile machine for producing cheeses. Such textile machines, also called cheese winders, comprise a plurality of such winding heads arranged adjacently to one another. The design and operation of such winding heads are already known to those persons skilled in the art, so that only a summary description thereof is believed to be necessary. 
     A yarn  3  is drawn off from unwinding bobbin  2  and guided over balloon breaker  4  and yarn eyelet  5  to yarn tensioner  6 . Yarn splicing device  7  is arranged between yarn tensioner  6  and cleaner  8 . During the normal yarn winding process, yarn  3  assumes the path of travel designated by reference numeral  30 . Yarn scissors  9  are associated with cleaner  8  which interrupts the yarn travel and actuates severing of the yarn  3  when cleaner  8  determines an inadmissible deviation from given quality values of yarn  3 . After yarn scissors  9 , yarn  3  travels through paraffin waxing device  10  and over guide element  11  onto grooved drum  12  that drives a cheese  13  and at the same time effects the winding of yarn  3  thereon in a cross winding form. Cheese  13  is carried in cheese holder  14 . 
     In the exemplary embodiment of FIG. 1, the course of the yarn travel between unwinding bobbin  2  and cheese  13  is shown to be interrupted. Such an interruption of the travel of the yarn occurs if the yarn is torn (a so-called yarn break) or has been cut by yarn scissors  9 . Further interruptions of the course of the yarn travel can occur due to a change of unwinding bobbin or when the cheese has attained its pre-set diameter. 
     The connecting of the yarn ends of upper yarn  31  running to cheese  13  and of lower yarn  32  drawn off from unwinding bobbin  2  takes place in yarn splicing device  7 . In order not to disturb the travel of the yarn during normal winding operation, yarn splicing device  7  is set back from travel path  30  of yarn  3 . Thus, in order to make a yarn connection, the yarn ends must be placed into yarn splicing device  7 . Pivoting nozzle  15  with suction slot  16  is provided for inserting upper yarn  31  into yarn splicing device  7 . In order to grasp the yarn end of upper yarn  31 , pivoting nozzle  15  pivots about its rotary articulation  17  into the position shown in dotted lines. The end of upper yarn  31  trailing from the cheese  13  is drawn by suction through suction slot  16  from the surface of cheese  13 , which is driven during the grasping process counter to the normal direction of rotation during yarn winding. Then, pivoting nozzle  15  pivots back into the initial position. The suctioned end of upper yarn  31  is guided thereby in circular arc  18  and placed into guide element  11 , paraffin waxing device  10 , yarn scissors  9 , yarn cleaner  8  and also yarn splicing device  7 . Lower yarn  32  is similarly grasped by suction tube  19  below yarn tensioner  6 . To this end, suction tube  19  pivots out of its resting position about its rotary articulation  21  into the position indicated in dotted lines. Suction intake opening  20  stands after this pivoting procedure in the dotted-line position in front of yarn  3  and draws it out of opening yarn tensioner  6 . Then suction tube  19  pivots about rotary articulation  21  in circular arc  22  back into its resting position. Lower yarn  32  is placed thereby into open yarn tensioner  6  and into yarn splicing device  7 . The control of these motions of the pivoting nozzle  15  and suction tube  19  takes place by means of control device  59 . 
     FIG. 2 shows the construction of yarn splicing device  7  of the invention in perspective. Yarn splicing device  7  comprises splicing body  25  fastened by screws  23  on air distributor block  24 . The splicing body  25  is formed with splicing channel  26 . The splicing device further comprises preparatory nozzles  27 ,  28  arranged above and below splicing body  25  in air distributor block  24 . Inlet openings  29  for compressed air empty into splicing channel  26 . Yarn baffles  39 ,  49  are arranged adjacent to splicing channel  26  to support the insertion of the yarn ends into yarn splicing device  7  by pivot nozzle  15  and suction tube  19 . The entry area of preparatory nozzles  27 ,  28  is arranged in the immediate vicinity of cutting devices  41 ,  42 . Yarn clamping devices  43 ,  44  are disposed adjacent to cutting devices  41 ,  42 . The course of the yarn travel is only partially indicated in FIG.  2 . 
     The operation of the yarn splicing device in accordance with the present invention is explained below with reference to FIGS. 3 to  7 . In the view of FIG. 3, the yarn ends have already been inserted into channel  26  of splicing device  7  but have not yet been prepared and also not yet cut. Pivot nozzle  15  has received upper yarn  31  on the surface of cheese  13  with its suction slot  16  and has pivoted with upper yarn  31  into the lower position shown. Suction slot  16  has moved during this pivoting motion on circular arc  18  indicated in FIG. 1, during which upper yarn  31 , guided by yarn baffles  40 ,  46 , has been placed into upper yarn clamping device  44 , which at this stage is open, into splicing channel  26 , and also into the lower yarn cutting device  41 , which also is open at this stage. 
     Lower yarn  32  drawn off from unwinding bobbin  2  has been correspondingly placed by suction intake opening  20  pivoting upward on circular arc  22  indicated in FIG. 1 into opened lower clamping device  43 , into splicing channel  26  and into opened upper cutting device  42 , during which upper yarn  31  has been guided by yarn baffles  39 . 
     Thereafter, the clamping devices  43 ,  44  are closed, whereupon upper yarn  31  and lower yarn  32  assume the path shown in FIG. 3 in which the yarns at least partially traverse the mouths of preparatory nozzles  27 ,  28  and of restraining devices  35 ,  36  and are held thereby under the suction action generated by the blowing in of compressed air into preparatory nozzles  27 ,  28  and restraining devices  35 ,  36 . 
     Lower yarn  32  held fast in lower clamping device  43  is subsequently cut by actuating cutting device  42 . The yarn remnant is removed by suction tube  19 . Upper yarn held fast in upper clamping device  44  is also cut in a corresponding manner by cutting device  41 . The holding action of pivot nozzle  15  and of suction tube  19  is cancelled by the cutting. Since preparatory nozzles  27 ,  28  are already loaded with compressed air at the time of the actuating of cutting devices  41 ,  42 , the yarn ends are immediately drawn into preparatory nozzles  27 ,  28  and assume the position shown in FIG.  5 . 
     Restraining devices  35 ,  36  are designed as suction nozzles and are covered with grates  47 ,  48  so that upper yarn  31  and lower yarn  32  can not be drawn by suction into restraining devices  35 ,  36 . Restraining devices  35 ,  36  are connected simultaneously with preparatory nozzles  27 ,  28  to a source of compressed air, not shown for reasons of simplicity. Upper yarn  31  and lower yarn  32  are drawn by the blowing in of compressed air and the suction action produced thereby and are pressed against the grate rods of grate  47 ,  48  as can be seen from FIG.  4 . This pressure force effects a restraining of the elastic yarn ends and thus counteracts and retards their tendency to contract from the previously stretched condition of the yarns, whereby the length by which the yarn ends held by clamping devices  43 ,  44  can be reduced. 
     Separating tab  37  shields lower yarn  32  from the flow of intake air of preparatory nozzle  27  and screens upper yarn  31  from the flow of intake air of restraining device  35  and in this manner prevents an undesired influencing of the yarn position. In a corresponding manner, separating tab  38  shields upper yarn  31  from preparatory nozzle  28  and shields lower yarn  32  from restraining device  36 . The grate rods of grate  47  and or grate  48  run largely transversely to the course of the yarn of upper yarn  31  and lower yarn  32 . This arrangement deters upper yarn  31  and lower yarn  32  from being drawn into the associated restraining devices  35 ,  36 . 
     The preparation of the yarn ends of upper yarn  31  and lower yarn  32  for the splicing operation and the ensuing course of the splicing operation takes place in a known manner. Further explanations for the yarn joining process can be gathered, e.g., from German Patent Publications DE 40 05 752 A1 or DE 44 20 979 A1, or their corresponding U.S. Pat. Nos. 5,115,629 and 5,829,706, which are incorporated herein by reference. 
     FIG. 6 shows an alternative design of the subject matter of the present invention. Yarn splicing device  58  comprises air distributor block  57  to which splicing body  25  with splicing channel  26  is fastened by screws  23 . Restraining device  49  and associated preparatory nozzle  53  for upper yarn  33  are located on the same side of splicing body  25  and likewise restraining device  50  and associated preparatory nozzle  54  for lower yarn  34  are located on the same side of splicing body  25 . The contraction of the stretching of upper yarn  33  and lower yarn  34  is minimized by this arrangement. Grates  51 ,  52  cover the respective suction intakes of restraining devices  49 ,  50  and prevent a drawing in of the yarn ends of a yarn loop into the suction intakes of restraining devices  49  or  50 . Even in the embodiment in accordance with FIG. 6, the rods of grates  51 ,  52  advantageously run transversely to the direction of travel of upper yarn  33  and of lower yarn  34 . 
     During the severing of lower yarn  34  by cutting device  42 , the preparatory nozzle  54  and restraining device  50  are connected to a source of compressed air (not shown for reasons of simplicity). The compressed air is blown into preparatory nozzle  54  and restraining device  50  by air nozzles  60 . After the separation the tensioned, elastic lower yarn  34  would otherwise contract without restraining device  50  and possibly be drawn out of preparatory nozzle  54  or even out of splicing channel  26 . However, the end of lower yarn  34  is held fast by restraining device  50  acting pneumatically on lower yarn  34 . The holding action of restraining device  50  is reinforced by friction surface  56 . Due to the suction action of preparatory nozzle  54  and of restraining device  50 , lower yarn  34  rests on friction surface  56 , as shown in FIG. 7, and the friction becomes active in an advantageous manner. If restraining device  50  is no longer loaded with compressed air, lower yarn  34  rises off of friction surface  56  again on account of the yarn tension. A corresponding effect occurs with respect to upper yarn  33 , via the coordinated actions of cutting device  41 , preparatory nozzle  53 , restraining device  49  and friction surface  55 . 
     The invention is naturally not limited to the exemplary embodiments shown in FIGS. 1 to  7 . Alternatively, for example, in another embodiment (not shown) restraining device  35 ,  36 ,  49 ,  50  can be connected to a vacuum source and the suction action generated by loading with vacuum. 
     Further information about the drive, support and mounting of device parts as well as the control and linkage can be gathered, to the extent not explained in detail here, e.g., from the cited publications, which are incorporated herein by reference, and the known state of the art cited therein. 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.