Abstract:
A spinning device for producing a spun yarn by a circulating air flow in a housing has an adjustment device ( 17 ) for controlling the angular position of the fiber ends wrapped around a spindle head, and in turn, the angular position of the fibers wrapped around the produced yarn, by adjusting a linear component of an air flow into the spinning device as a function of the yarn withdrawal speed, whereby a yarn is produced of a required yarn strength even during a spinning start phase in the process of making the spun yarn.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of German patent application 102 01 577.5, filed Jan. 17, 2002, herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a spinning device for producing a spun yarn by means of a circulating air flow. 
     A spinning device for producing a spun yarn by means of a circulating air flow is known from German Patent Publication DE 199 26 492 A1. A sliver to be spun is drawn into a nozzle body and passes a sliver guidance device. The sliver guidance device has sliver guide elements, which are spaced apart from each other and permit the free passage of a core fiber bundle. The sliver is subjected to an air flow circulating around the sliver at the inlet opening of a spindle. The free fiber ends of the sliver are wrapped around the conical spindle head by the circulating airflow at the inlet opening of the spindle. In the course of drawing the sliver into the hollow spindle, these fiber ends wrap themselves in a spiral shape to form wrapped fibers around the sliver, whereby a yarn is produced from the sliver and removed through the hollow spindle. 
     German Patent Publication DE 40 36 119 C2 also shows a device for producing a spun yarn by a circulating air flow by which free fiber ends of the sliver are wrapped around a conical spindle head at the inlet opening of the spindle by the circulating air flow. With this spinning device, the sliver guidance device is located inside the running fiber strand, so that the fibers of the sliver are arranged at the circumferential surface of the sliver guidance device. 
     Continuously increasing demands in regard to productivity and yarn properties are made on modern spinning frames. Such spinning devices, known from above-referenced. German Patent Publication DE 199 26 492 A1, or in another embodiment from above-referenced German Patent Publication DE 40 36 119 C2, are suitable for achieving high production speeds, along with good yarn properties. It is all the more bothersome if in the course of starting the processes at high withdrawal speeds, such as are employed during normal spinning operations, repetitions of the start of the spinning process are often made necessary because, at these high yarn speeds the spinning start process takes place relatively uncontrolled and with a greatly reduced assurance of a satisfactory spinning start. 
     It is known from rotor spinning to clearly lower the withdrawal speed during the spinning start process in comparison with the spinning operation in order to achieve a more easily controlled spinning start process and therefore greater spinning start assurance. However, if an attempt is made to utilize this type of operation from rotor spinning and to operate a circulating air flow spinning device at a lowered withdrawal speed of the yarn in the spinning start phase, a yarn is temporarily created thereby whose yarn strength could be unsatisfactory. Such yarn sections of reduced strength constitute undesired weak points. This increases the danger of yarn breaks and considerably reduces the interference-free processing of the yarn. In the least advantageous case a yarn break may occur already in the spinning start phase. This has very disadvantageous consequences with regard to the intention of achieving a good yarn quality along with high productivity when employing the air spinning method. It is therefore customary to perform the spinning start process at the high withdrawal speeds of the normal spinning operation and in the course of this start process to accept the disadvantages of frequent repetitions of the spinning start process. 
     The above described problems cannot be overcome by the known prior art, such as disclosed in German Patent Publications DE 199 26 492 A1 or in DE 40 36 119 C2. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to further develop the above mentioned prior art to provide improved devices for producing a spun yarn employing a circulating air flow. 
     Basically, the spinning device of the present invention produces a spun yarn by a circulating air flow, and for this purpose comprises a housing having an inlet opening for receiving a sliver, at least one sliver guidance element arranged downstream of the inlet opening, a hollow spindle through which a formed yarn is withdrawn, the spindle having a conical spindle head, and openings in the area of the spindle inlet for injecting into the housing a circulating air flow comprised of a linear airflow component essentially in a yarn traveling direction and a twisting airflow component essentially in a helical orientation about the yarn for wrapping free fiber ends of the sliver helically around the spindle head to subsequently be wrapped around the yarn at an acute angle in respect to the yarn traveling direction as the yarn is drawn off through the spindle. In accordance with the present invention, an adjustment device is provided for adjusting at least the linear airflow component as a function of the withdrawal speed of the yarn and controlling a helical wrapping angle of the fiber ends around the spindle head and the acute angle of wrapping of the fibers around the yarn; and a control device is provided for controlling the adjustment device between a setting for the spinning start process and at least one setting for normal spinning operations. For example, the injector effect of air nozzles or the vacuum in the housing can contribute to forming the air flow. At least a part of the air flow in the yarn running direction can be formed by air entering the inlet opening of the housing together with the sliver. 
     In accordance with one embodiment of the present invention, the adjustment device includes a positionable cover for the inlet opening such that the position of the cover determines the cross section of the inlet opening. The greater the cross section of the inlet opening, the greater the amount of air entering the housing together with the sliver, and therefore the proportion of the linear component of the circulating air flow in the area of the spindle head. If the cross section is reduced, the amount of air is correspondingly reduced. The linear component of the air flow is advantageously set by controlling the cross section of at least one air inlet opening for this air flow. A control of the air drawn in through the inlet opening offers the advantage that no additional amount of air needs to be made available to be blown into the housing. 
     An alternative embodiment for setting the linear component of the air flow is provided by a bypass of the inlet opening of the fiber conduit in the housing, which is directed in the yarn traveling direction, and whose cross section can be adjusted by means of the adjustment device. In spinning frames with a plurality of work stations, considerable costs can be avoided by means of the mutual advantage of these embodiments by not having to provide additional amounts of air. 
     In a further alternative embodiment, the housing has at least one injection conduit, which is directed in the yarn traveling direction and is connected with the compressed air source. The adjustment device is equipped for setting the air pressure of the supplied air. In this manner, the adjustment of the linear component of the air flow occurs in a particularly simple and rapid manner through the regulation of the pressure of the air supplied by the compressed air source. In particular, no mechanical devices are required, whose function could be reduced or hampered by dust or flying fibers. 
     The linear component of the air flow is advantageously set in such a way that the angle at which the wrapped fibers have been placed around the withdrawn yarn lies in the range between 20° to 35°, preferably at 27°. It is possible to empirically determine how the adjustment device must be set in each individual case for achieving the greatest yarn strength possible, and to store the appropriate settings, for example in a data memory of a control device, for retrieval and use in connection with identical spinning parameters. For this purpose, the control device includes a data memory for storing yarn data and is connected to a line through which the yarn data can be input to the memory. The adjustment device can be controlled as a function of the yarn data. 
     The provision of a single drive mechanism for each spinning station makes it possible to be able to immediately perform every spinning start process at each spinning station in the manner in accordance with the invention independently of other spinning stations of the spinning frame. Downtimes are reduced in this way. 
     It is possible by means of the invention to prevent an impermissible drop of the yarn strength during the spinning start process, which is performed with a clearly reduced withdrawal speed in comparison with the normal spinning operation which ensues following the spinning start. The assured reliability of the spinning start process is increased. The tendency toward faults in the further processing of the yarn can be reduced. A high productivity, along with good yarn quality, can be achieved by means of the invention. 
     When using the device in accordance with the invention in connection with batch changes, it is possible in some cases to omit the exchange of the housing, or portions of the housing, for meeting the new yarn parameters. 
     Further details, features and advantages of the present invention will be explained and understood from the following description of preferred embodiments of the invention with reference to the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial schematic elevational view, partially in longitudinal section, of a spinning device in accordance with the present invention, depicting the device during the spinning start phase, 
     FIG. 2 is another schematic view, similar to that of FIG. 1, of the present spinning device but depicting only a smaller portion thereof during normal spinning operations, 
     FIG. 3 is a simplified enlarged cross-sectional view of the spindle head of the present spinning device depicting a basic representation of the formation of the air flow in the area of the spindle head, 
     FIG. 4 is a perspective view of the spindle head of the present spinning device, depicting a greatly simplified basic representation of the position of the free fiber ends of the sliver wrapped around the spindle head during the spinning start phase, 
     FIG. 5 is another perspective view of the spindle head of the present spinning device, depicting a greatly simplified basic representation of the position of the free fiber ends of the sliver wrapped around the spindle head during the normal spinning operation, 
     FIGS. 6 to  9  are actual photographs of yarn structures produced by the spinning device of the present invention at different settings and withdrawal speeds, 
     FIGS. 10 and 11 are schematic elevational views, partially in longitudinal section, of further spinning devices in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The spinning station  1  represented in a partial view in FIG. 1 has a housing  2 , in which an air nozzle body  3  is mounted. A sliver  6  delivered by an arrangement of drafting rollers  4 ,  5  passes through a sliver conduit  8  and sliver guidance elements  9  and is conveyed to the inlet opening  10  of a hollow spindle  11 . Air nozzles  12  formed in the nozzle body  3  blow air in the area of the inlet opening  10  of the spindle  11 , forming an air flow circulating around the sliver  6  and the spindle head  13 , which applies a twisting effect to the sliver  6 . Free fiber ends  14  of the sliver  6  are wrapped around the sliver  6 , as well as the spindle head  13 . An air flow  30  is generated in the sliver conduit  8 , or in the air gap  15  between the wall of the sliver conduit and the sliver  6  by the injector effect of the air blown in through the air nozzles  12 , as well as by the sliver  6  entering the inlet opening  7  at high speed. The air flow  30  moves in the longitudinal direction of the sliver  6  toward the spindle head  13  and forms a linear component of the air flow circulating around the spindle  11 . The yarn  16  formed from the sliver  6  is withdrawn through the spindle  11 . In the process, the free fiber ends  14  wrapped around the spindle head  13  are taken along and wrapped around the yarn  16 . 
     A further understanding of the basic structure and operation of the spinning station  1  can be taken from German Patent Publication DE 199 26 492 A1, or the corresponding U.S. Pat. No. 6,209,304, or from German Patent Publication DE 40 36 119 C2, or the corresponding U.S. Pat. No. 5,159,806, incorporated herein by reference. 
     A cover  18  which can be positioned by means of an adjustment device  17 , is associated with the inlet opening  7 . The adjustment device  17  acts via a toothed rack  19  on the cover  18 . A gear wheel, not represented, in a gear housing  20  acts together with the toothed rack  19 . The gear wheel is driven by an actuating motor  22  via an operative connection  21 . The actuating motor  22  is controlled by a control device  23 . The control device  23  controls a motor  25  through a line  24 , as well as a motor  27  through a line  26 . The control device  23  is connected through a line  28  with further elements, not represented for reasons of simplicity, of the spinning station and the spinning frame. The motor  25  drives the drafting rollers  4 ,  5 , and the motor  27  drives the withdrawal rollers  29 ,  29 A. 
     FIG. 1 shows the adjustment device  17  at the spinning station  1  during a spinning start phase of the spinning operation, with the cover  18  in a lifted position. It is possible in this manner to draw in a maximum amount of air through the inlet opening  7 , and through the sliver conduit  8 , which passes through the sliver conduit  8  in the form of an air flow  30  and which, as represented in FIG. 3, acts as a linear component of the circulating air flow  31 . The circulating air flow  31  wraps the free fiber ends  14  around the spindle head  13 . 
     FIG. 2 shows the spinning station during normal spinning operations. During normal spinning operations, the yarn traveling speed, i.e., the yarn withdrawal speed, is considerably higher in comparison with the spinning start phase. In this case, the cover  18  is in a lowered position. As a result, the air gap  15  has become narrower, and the amount of air drawn in through the inlet opening  7 , and through the sliver conduit  8 , is decreased in comparison with the setting represented in FIG.  1 . 
     The principle of the formation of the air flow in the area of the spindle head  13  can be understood from FIG. 3. A stronger air flow  30 , such as generated by the cover  18  in the raised position in accordance with the representation in FIG. 1 during the spinning start phase, combines with the air flow  32  comprised of air blown in through the air nozzle  12 , to collectively form the air flow  31  circulating around the spindle head  13 , both in respect to the strength as well as the direction of the air flow  31 . The direction of the circulating air flow  31  defines the position of the free fiber ends  14  wrapped around the spindle head  13 . In addition to indicating the air flow direction, the strength of the air flows  30 ,  31 ,  32 ,  33 ,  34  is indicated in FIG. 3 by the length of the arrows representing each of the air flows  30 ,  31 ,  32 ,  33 ,  34 . 
     The air flow  33 , which is created by the cover  18  in the lowered position in accordance with FIG. 2 during normal spinning operations, combines with the air flow  32  comprised of air blown in through the air nozzle  12 , to form the air flow  34  circulating around the spindle head  13 . The air flow  34  has a different direction than the air flow  31 . This respective direction determines the position of the free fiber ends  14  during normal spinning operations. The air flow  34  forms an acute angle α with respect to a line parallel to the center axis  35  of the yarn, which is greater than the angle α formed by the air flow  31  with respect to the same line parallel to the center axis  35 . Accordingly, the position of the free fiber ends  14  wrapped around the spindle head  13  is different during the spinning start phase than during normal spinning operations. 
     The change in the position of the free fiber ends  14  on the spindle head  13  of the spindle  11  are shown in perspective views in FIGS. 4 and 5. The direction, or position, of the free fibers ends  14  during the spinning start phase, when the stronger air flow  30  is present, can be seen in FIG. 4, while the direction, or position, of the free fibers ends  14  during normal spinning operations when the air flow  33  is present can be seen in FIG.  5 . The free fiber ends  14  wrapped around the spindle head  13  are represented longer than in actuality, for illustrative purposes of making the different positions clearer. 
     The yarn  36  represented in FIG. 6 was produced in accordance with the present invention at a withdrawal speed of 100 m/min and with a large opening during the spinning start phase with the cover  18  in the raised position represented in FIG.  1 . The yarn  36  has wrapped-around fibers which predominantly lie at an angle β of approximately 22° with a line parallel with the center axis of the yarn  36 . The strength of the yarn  36  was measured to be 15.5 cN/tex. In FIG. 6, the angle β is indicated by a horizontal line  70  and an obliquely extending line  71  representing the position of the wrapped-around fibers. 
     In each of FIGS. 7 to  9  the position of the wrapped-around fibers is similarly indicated by obliquely extending lines  72 ,  73  and  74 . 
     The yarn  37  represented in FIG. 7 was produced in accordance with the present invention at a withdrawal speed of 300 m/min and with a narrow opening during normal spinning operations with the cover  18  in the lowered position represented in FIG. 2, has wrapped-around fibers which predominantly form an angle β of approximately 27° with a line parallel with the center axis of the yarn  37 . The strength of the yarn  37  was measured to be 13.4 cN/tex. The cross sectional area of the inlet opening formed for the air drawn into the housing  2  in the raised position of the cover  18  is called the large opening, and the cross sectional area of the inlet opening formed in the lower position of the cover  18  is called the narrow opening. 
     FIG. 8 shows a yarn  38  which was produced at a withdrawal speed of 300 m/min, instead of 100 m/min, with a large size of the opening unchanged from that used in producing the yarn of FIG.  6 . The wrapped-around fibers form an angle β of approximately 12°. The strength of the yarn  38  was measured to be 9.9 cN/tex. 
     FIG. 9 shows a yarn  39  which was produced at a withdrawal speed of 100 m/min, instead of 300 m/min, with a narrow size of the opening unchanged from that used in producing the yarn of FIG.  7 . The wrapped-around fibers form an angle β of approximately 52°. The strength of the yarn  39  was measured to be 10.7 cN/tex. 
     In each case, the clear decrease in yarn strength in comparison with yarn produced in accordance with the invention shows the result of yarn production in accordance with the known prior art where, for example, the withdrawal speed in the spinning start phase was lowered to 100 m/min in comparison with the withdrawal speed of 300 m/min during normal spinning operations. By dropping the withdrawal speed to a lower speed value it is intended for the spinning start process to run in a more controlled manner in order to increase the spinning start assurance in this manner. However, the reduced strength values of yarn produced in this manner do not satisfy the requirements and lead to the above mentioned defects, or disadvantages. 
     FIG. 10 shows an alternative embodiment of the present invention. A sliver  40  is transported through the arrangement of drafting rollers  41 ,  42  and enters the housing  44  through the sliver conduit  43 . In the housing  44 , the sliver  40  is subjected to the action of a sliver guidance element  45  and a circulating air flow. The circulating air flow is generated by blowing air into the housing  44  through the air nozzles  46 ,  47 . The circulating air flow wraps the free fiber ends  48  around the spindle head  49  of the hollow spindle  50 . In turn, the free fiber ends  48  are placed around the yarn  51  in the form of wrapped-around fibers. 
     The housing  44  has a passage, embodied as a bypass  52  of the sliver conduit  43 . The bypass  52  can be closed by means of a cover  53 . The cover  53  can be pivoted by means of the adjustment device  54 . The pivoting movement is generated with the aid of a lifting cylinder  55 , which is pneumatically actuated via lines  56 ,  57 . A switching arrangement  58  charges the lines  56  and  57  alternatively with compressed air supplied from a compressed air source  59 . The switching arrangement  58  is actuated by a control device  60 , with which it is connected via a line  61 . 
     The bypass  52  is open in the representation of FIG. 10, so that air is drawn in through the sliver conduit  43 , as well as through the bypass  52 , and enters the circulating air flow as the linear component. This open setting of the bypass corresponds to the “large opening” setting of the sliver conduit  8  of the device represented in FIG. 1 as it is employed in the spinning start phase. 
     If the lifting cylinder  55  is charged with compressed air through the line  57 , the piston of the lifting cylinder  55  moves upward in the representation in FIG. 10 until the cover  53  takes up the position indicated by dashed lines. The inflow of air through the bypass  52  is thereby stopped, and air is only drawn in through the sliver conduit  53 . This setting corresponds to the “narrow opening” setting of the sliver conduit  8  in the device represented in FIG. 2, such as it is used in normal spinning operations. 
     FIG. 11 shows another alternative embodiment of the invention. A sliver  40  runs through an arrangement of drafting rollers  41 ,  42  and enters a housing  63  through a sliver conduit  62 , is subjected to the effects of a circulating air flow and is drawn off through a spindle  50 . The circulating air flow wraps the free fiber ends  48  around the spindle head  49 . When drawing off the yarn  51 , the free fiber ends  48  are wrapped around the yarn  51  in the form of wrapped-around fibers. In contrast to the housing  44  represented in FIG. 10, the housing  63  has an air injection conduit  64  extending parallel with the sliver conduit  62 . Compressed air is blown in through the injection conduit  64 . For this purpose, the injection conduit  64  is connected through a line  65  with a compressed air source  65 . The control of the air pressure is performed by means of an adjustment device  66 . The adjustment device  66  is controlled through a line  67  by a control device  68 . The compressed air is injected during the spinning start phase, wherein the air pressure is set such that the wrapped-around fibers lie at a desired angle β around the yarn  51 , or that the desired yarn strength is achieved. The setting corresponds to a “large opening” setting of the sliver conduit  8  in the device represented in FIG. 1, such as is used in the spinning start phase. If, however, the compressed air supply is blocked, the setting corresponds to the “narrow opening” setting of the sliver conduit in the device as represented in FIG. 2, as it is employed in normal spinning operations. 
     For the spinning start process, the “large opening” setting is set, for example at a withdrawal speed of 100 m/min. Following the start of spinning, the withdrawal speed of the yarn  16 ,  51  is increased to, for example, 300 m/min for a normal spinning operation and the “narrow opening” setting is set. One setting of the adjustment device  17 ,  54 ,  66  is sufficient for normal spinning operations. 
     Alternatively to the examples as described, it is possible by means of a regulation of the air pressure to adapt the linear component of the air flow following the spinning start process in intermediate steps or continuously during the increase of the withdrawal speed in such a way that a desired high yarn strength is maintained during the respective increases. Accordingly, a continuous, or alternatively also stepped displacement of the positionable cover  18  can also take place during the increase in yarn withdrawal speed. 
     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.