Abstract:
The method for producing cheeses of the random winding type, wherein the workstations of an automatic cheese winder comprise a winding device with a yarn guide drum and a creel, both supported in an axially shiftable relation to each other, the creel holding the cheese in a rotatable manner and the yarn guide drum driving the cheese through frictional engagement, a ribbon disturbance device and an edge displacement device. The ribbon disturbance device causes a slippage by a defined adjustment of the bearing pressure of the cheese on the yarn guide drum. Relative movements between the yarn guide drum and the creel are initiated in the area of ribbon winding zones which counteract a stroke change caused by the ribbon disturbance during the winding of the yarn onto the cheese.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the benefit of German Application DE P 10020664.6 filed Apr. 27, 2000, herein incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a method for producing cheeses of a random winding type, particularly in a winding machine having a yarn guide drum and a creel that are mounted to be axially shiftable relative to each other and a ribbon disturbance device such that the relative movement between the yarn guide drum and the creel when the cheese enters a ribbon winding zone counteracts a stroke change caused by the ribbon disturbance device.  
           [0003]    Automatic cheese winders having winding heads with yarn guide drums mounted in an axially shiftable manner are known, e.g., in German Patent Publication DE 43 36 312 A1. The yarn guide drum is connected to a drive shaft that also comprises the rotor of the bobbin drive device. Moreover, this known winding device comprises an edge displacement mechanism with which the yarn guide drum can be axially moved back and forth in a reciprocating, traversing manner as required with a constant stroke length.  
           [0004]    German Patent Publication DE 198 29 597 A1 describes a method of producing cross-wound cheeses in a “random” type of winding process. In order to avoid ribbon-like pattern windings the bearing pressure of the cheese on the yarn guide drum can be reduced and the cheese loaded at the same time with a braking moment. Thus, the angular velocity of the cheese is constantly detected and processed in a control device in such a manner that at or shortly before a ribbon winding zone is reached, the angular velocity of the cheese is lowered to a non-critical angular velocity by a defined adjusting of the bearing pressure with which the cheese rests on the yarn guide drum. A device for performing this method is disclosed in German Patent Publication DE 198 29 597 A1.  
           [0005]    Cheeses produced in accordance with the previously described method are characterized by a clearly improved ribbon resolution as well as by a very good flow behavior even at high unwinding speeds in subsequent production processes.  
           [0006]    However, the reduction of the bearing load of the cheese on the yarn guide drum in the ribbon winding zones results in a slight impairment of the visual appearance of such cheeses. In particular, as a result of the reduction of the bearing load in the ribbon winding zones, a slight reduction of the displacement width of the yarn traversed by the yarn guide drum can occur in these areas, which becomes visible as rings on the ends of the bobbins of the cheeses.  
         SUMMARY OF THE INVENTION  
         [0007]    It is accordingly an object of the present invention to improve the known devices for random winding in order to overcome the disadvantages discussed above and manufacture cheeses in which the external appearance corresponds to their high manufacturing quality.  
           [0008]    The objective is achieved by the present invention which produces a cheese with the desired visual appearance by using a winding station having a yarn guide drum and a creel mounted in an axially shiftable manner relative to each other and a ribbon disturbance device such that when a cheese enters a ribbon winding zone, relative movements between the yarn guide drum and the creel counteracts a stroke change caused by the ribbon disturbance device.  
           [0009]    The method of the present invention has the particular advantage that the stroke change occurring in the ribbon winding zones by a ribbon disturbance device during the placement of yarn windings is immediately compensated by the simultaneous introduction of a relative movement between the yarn guide drum and the creel.  
           [0010]    A preferred embodiment of the present invention provides that the stroke losses occurring on account of the ribbon disturbance process during the placement of yarn windings are compensated in a simple manner by an axial oscillation of the yarn guide drum with an adjustable amplitude. This assures that the cheeses produced have neither rings nor other optical impairments on their bobbin flanks.  
           [0011]    Preferably, the oscillation of the yarn guide drum takes place simultaneously with the slippage regulation causing the ribbon disturbance. Thus, as soon as the drive device for the creel lift-off device is activated by the winding-head computer to reduce the bearing pressure between the cheese and the yarn guide drum, the drive for axial displacement, or oscillation, of the yarn guide drum, is automatically activated.  
           [0012]    In addition to the frequency of the oscillation, the amplitude of the oscillation of the yarn guide drum is very important for an unobjectionable bobbin flank of the cheese. Since both the frequency and the optimum amplitude of the oscillation are a function of different bobbin parameters, e.g., the yarn material, the bobbin hardness, etc., it is preferable if both the frequency and also the amplitude of the oscillation can be adjusted in a defined manner.  
           [0013]    The frequency of the oscillation is relatively low, e.g., between about 0.1 and about 3 hertz with about 0.5 hertz being especially advantageous.  
           [0014]    Since the magnitude of the amplitude of the oscillation is very significant for the later appearance of the bobbin flank of the cheese, the amplitude is preferably selected to reliably assure that the stroke loss resulting from the ribbon disturbance is regained during the later traversing of the yarn.  
           [0015]    The yarn guide drum oscillation in accordance with the present invention occurs independently of the operation of a standard edge displacement device of the winding head.  
           [0016]    In a preferred embodiment in which the standard edge displacement device is already in operation at the winding head, a superimposing of the standard edge displacement motion and the yarn-guide-drum oscillation occurs in accordance with the present invention. Hence, the amplitude of the standard edge displacement motion is increased by the amplitude of the yarn guide drum oscillation.  
           [0017]    In the preferred embodiment, a stepping motor which drives the edge displacement device is programmed so that it can operate continuously in one direction or in a reversing manner during which the angle of rotation of the stepping motor can be adjusted in a defined manner. Thus, the present invention provides a simple way to adjust the frequency as well as the magnitude of the amplitude of the oscillation of the yarn guide drum in a defined manner without having to expand the hardware of the winding head, which is associated as a rule with not-insignificant expense.  
           [0018]    Further details, features and advantages of the present invention will be understood from the following disclosure of exemplary embodiments with reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a perspective view of a workstation of an automatic cheese winder illustrating a device required for carrying out the method in accordance with a preferred embodiment of the present invention.  
         [0020]    [0020]FIG. 2 shows a front view of the workstation of FIG. 1 in partial section. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    [0021]FIG. 1 shows winding head housing  2  of a workstation of an automatic cheese winder which workstation is designated in its entirety by reference numeral  1 . Workstation  1  comprises devices for carrying out a ribbon disturbance process, a standard edge displacement as well as a yarn-guide-drum oscillation in accordance with the present invention. In particular, a yarn-guide drum  3  driven by electromotor  27  is mounted in an axially shiftable manner in winding head housing  2  of workstation  1 . Cheese  4  is held in creel  5  that is connected to pivot shaft  6  in such a manner that they rotate in unison. Pivot shaft  6  is arranged parallel to the axis of yarn guide drum  3  and mounted on winding head housing  2  in a limited pivotable manner, as indicated by arrow S. Yarn guide drum  3  drives cheese  4  via friction.  
         [0022]    Creel  5  comprises, as is customary, two bobbin arms  7 ,  8  provided with rotatably mounted bobbin plates. A tube, or bobbin, is held between the bobbin plates, a yarn  33  is wound onto the tube in order to form cheese  4 . At least one of bobbin arms  7 ,  8  can be pivoted away with the bobbin plate to the side away from the cheese in a manner not shown in detail, so that a full cheese can be removed from creel  5  and an empty tube can be inserted. The ribbon disturbance device is essentially a torque transmitter, designed as creel lifting device  22 , which controls pivot shaft  6  of creel  5 . The torque transmitter includes a connection disk  9  connected to pivot shaft  6  in such a manner that connection disk  9  and pivot shaft  6  rotate in unison, and gear  10  pivotably mounted coaxially to pivot shaft  6 . Connection disk  9  is provided with connection bolts  11  facing toward gear  10 . Corresponding connection bolts  12  are provided on gear  10  and face toward connection disk  9 . Identical spring elements  13  in the form of spiral springs are inserted between connection bolts  11  of connection disk  9  and between connection bolts  12  of gear  10  and are used as transmission elements that are opposingly deformed upon a relative rotation of gear  10  and connection disk  9 .  
         [0023]    Gear  10  meshes with pinion  14  of a stepdown gearing whose outer rim  15  is connected via drive pinion  16  to stepping motor  17 . Since drive pinion  16 , outer rim  15  and pinion  14  are rotatably mounted on winding head housing  2 , and stepping motor  17  is fixedly attached to the winding head housing  2 , then every rotational movement of stepping motor  17  is transmitted via the stepdown gearing with a ratio, for example, of about 1:25, to gear  10 . Stepping motor  17 , adjustable to individual steps of, for example, approximately 1.8 degrees, is controlled by winding head computer  18  and is thus capable of executing a predetermined number of rotations or a predetermined number of individual steps to produce a torque on creel  5 . The change in the torque produced on creel  5  changes the contact pressure of cheese  4  on yarn-guide drum  3 , resulting in an adjustable contact pressure.  
         [0024]    The angular velocity of cheese  4  and the angular velocity of yarn guide drum  3 , determined by the number of revolutions, are continuously monitored by sensors  23  and  24 , that are connected via corresponding signal leads  25 ,  26  to winding head computer  18 , which controls the contact pressure between cheese  4  and yarn guide drum  3 . Using the data collected from sensors  23 ,  24  and known construction data of the winding machine, the winding head computer  18  can continuously calculate the winding parameters of cheese  4 .  
         [0025]    When the diameter of cheese  4  approaches a ribbon winding zone, that is, an area in which the number of revolutions of the yarn guide drum is, for example, a whole-number multiple of the number of revolutions of the cheese in slippage-free operation, a slippage regulation is initiated that causes a ribbon disturbance. In particular, the angular velocity of cheese  4  is reduced from an instantaneous angular velocity calculated for the diameter of cheese  4  to a lower angular velocity.  
         [0026]    The reduction of the angular velocity of cheese  4  and the continued retention of the lower angular velocity occurs by simultaneously applying a constant braking moment to cheese  4  by a bobbin brake  20  which is connected to winding head computer  18  by signal lead  21 , and reducing the bearing pressure between cheese  4  and yarn guide drum  3  by a defined lifting of creel  5 . The desired number of revolutions of cheese  4  can be exactly regulated by appropriately raising or reducing this bearing pressure by having gear  10  rotated by stepping motor  17  into a position corresponding to a calculated bearing pressure of cheese  4  on yarn guide drum  3 . Thus, ribbon windings on cheese  4  can be avoided. A control program in winding head computer  18  regulates the bearing pressure as a function of the bobbin travel of the cheese  4  and/or of the diameter of cheese  4  by adjusting stepping motor  17 . The control program calculates the required position of stepping motor  17 , expressed in positive or negative steps, based on the previously described sensor data fed to the winding head computer  18  during the entire bobbin travel.  
         [0027]    Yarn guide drum  3 , driven by reversible electromotor  27 , is mounted so that it can shift axially relative to creel  5  by edge displacement mechanism  28 , as has already been discussed. Such an edge displacement mechanism is disclosed in German Patent Publication DE 43 36 312 A1.  
         [0028]    Edge displacement mechanism  28  includes stepping motor  29 , connected via control lead  37  to winding head computer  18 , eccentric plate  30  and lifting element  31  which acts on drive shaft  32  of yarn guide drum  3 . Eccentric plate  30  is rotated in accordance with the adjustment angle of stepping motor  29  and pivots lifting element  31 , preferably designed as a double lever, which axially shifts drive shaft  32  and yarn guide drum  3  therewith against the force of a spring element (not shown).  
         [0029]    Stepping motor  29  is programmed to be operated not only in a continuously rotating manner, as is customary in standard edge displacement devices, but also in an alternating manner by presettable degrees of angle. Thus, the adjustment angle of stepping motor  29  and the resulting amplitude of the oscillations of yarn guide drum  3  can be adjusted in a defined manner in both directions. The eccentricity of the eccentric plate  30  is preferably selected so that both the maximum amplitude of the standard edge displacement movement as well as the maximum amplitude of the yarn-guide-drum oscillation can be obtained.  
         [0030]    A winding station having the devices discussed above can be operated by the following method in accordance with the present invention to avoid ribbon windings. During the winding process a yarn  33  drawn off from a presenting bobbin (not shown) is backwound to a large-volume cheese  4 . As is customary, yarn  33  is checked during the backwinding by a yarn cleaner (not shown) for any yarn errors and cleaned up, if necessary. Cleaned yarn  33  is subsequently wound by yarn guide drum  3  in crossing layers onto a tube, or bobbin, rotatably supported in creel  5 , to form cheese  4 . Cheese  4  rests against yarn guide drum  3  with a presettable bearing pressure. Thus, yarn guide drum  3 , in whose yarn guide groove  37  yarn  33  slides, drives the tube or cheese  4  by frictional engagement.  
         [0031]    When cheese  4  has attained a diameter at which the creation of a ribbon formation is expected, a slippage regulation is initiated by winding head computer  18 , activating creel-lifting device  22  and bobbin brake  20 . Creel lifting device  22  assures that the bearing pressure of cheese  4  of yarn guide drum  3  is reduced, which results in a reduction of the angular velocity of cheese  4 , thereby creating a slippage between cheese  4  and yarn guide drum  3 . The number of revolutions of cheese  4  is lowered as a result thereof to a value that is non-critical for the cheese diameter present.  
         [0032]    Since the reduction of the bearing pressure also results in a slight loss of stroke when the yarn is placed, edge displacement mechanism  28  is activated at the same time in the manner in accordance with the present invention. Stepping motor  29  is controlled via winding head computer  18  such that it moves back and forth in an alternating manner by an adjustable angle of rotation and oscillates bearing shaft  32  via eccentric plate  30  and lifting element  31 , causing yarn guide drum  3  to oscillate axially, as is indicated in FIG. 2 by double arrow  36 . The stroke losses produced during the traversing of the yarn due to the lesser bearing pressure of cheese  4  are immediately compensated by this oscillation  36  of the yarn guide drum. The frequency and amplitude of the oscillation of the yarn guide drum  3  can be adjusted by an appropriate controlling of stepping motor  29 .  
         [0033]    As has already been indicated above, yarn-guide-drum oscillation  36  in accordance with the present invention occurs either in addition to the standard operation of the edge displacement mechanism  28  or when the standard edge displacement mechanism  28  of the particular winding head is not engaged. When yarn-guide-drum oscillation  36  in accordance with the present invention occurs in addition to the standard operation of the edge displacement mechanism  28 , a superimposing of the amplitudes of the two axial yarn-guide-drum movements occurs in some instances. In any case, the yarn-guide-drum oscillation  36  in accordance with the present invention assures that only high-quality cheeses are produced with respect to the behavior of the operating sequence and the appearance. Hence, the cheeses produced in accordance with the method of the present invention exhibit in every instance unblemished bobbin flanks without grooves or other visual impairments.  
         [0034]    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.