Abstract:
Apparatus and process for winding filamentary material in a  figure 8  configuration including a rotatable spindle for retaining a mandrel upon which the filamentary material is wound; a traverse mechanism for controlling the laying of wound coils on the mandrel; and controlling the advance of the wound layers on the mandrel in accordance with the rotation of the spindle and the movement of the traverse mechanism to vary the angular displacement of the wound coil so that the number of crossovers of succeeding layers of the wound coils increases as the winding process progresses, thereby increasing the density of the wound coils.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to method and apparatus for the winding of coils of filamentary material in a figure 8 winding configuration and, more particularly, to such method and apparatus in which the density of the wound coil or package is controlled to increase the density of the wind. The invention has application to figure 8 winding configurations and in particular to figure 8 winding configurations of filamentary material in which a radial hole (payout hole) is produced from the innermost wind to the outermost wind, thereby enabling the filamentary material to be withdrawn from inside the wound coil through the payout hole to eliminate kinking or bird-nesting of the filamentary material as it is paid out. The winding techniques are known in the winding trade as REELEX® or REELEX II® winding processes and are the subject of trademark and patent protection by Windings, Inc., the assignee of the present invention. 
   2. Related Art 
   Known technology for winding filamentary material in a figure 8 configuration on a mandrel produces figure 8 coils substantially evenly spaced radially around the mandrel. Each layer of the wound coil is produced by advancing the figure 8s in either a plus direction (plus ADVANCE or upper ratio), or in the minus direction (minus ADVANCE or lower ratio). A plus or negative ADVANCE refers to changing the speed of rotation of the mandrel with respect to the movement of the traverse which is feeding the filamentary material to the mandrel. This concept was introduced as early as 1956 in U.S. Pat. No. 2,767,938; Taylor, Jr.; “Winding Flexible Material”; assigned to Windings, Inc. the assignee of the present invention. 
   The ADVANCES have also been referred to as “gear ratios”, which can be actual mechanical gears (prior technology), or more recently, “electronic gears”. In the latter method, for example, computer-generated signals control the rotation of the spindle on which the mandrel is mounted with respect to the movement of the traverse to obtain the desired ADVANCE. The wound layers of filamentary material are produced by alternating between the aforementioned positive or negative ratios. In the REELEX® or REELEX II® winding technique of Windings, Inc. a portion of the wound coil is devoid of the figure 8s to generate the aforementioned radial payout hole for deploying the wound filamentary material. 
   In prior or known winding techniques the ADVANCES are set and remain fixed throughout the production of the entire wound coil. Because the number of figure 8s in each layer is constant (in alternating layers) it is apparent they are spaced circumferentially further apart as the coil diameter increases as the winding process continues. This has the effect of decreasing the density of the wound coil as the diameter of the coil increases. For example, if the figure 8s are spaced 36 degrees apart in one of the layers (10 figure 8s in the particular layer), the figure 8s will be approximately 2.4 inches apart (along the circumference of the wind) on the surface of a mandrel that is 8 inches in diameter. The figure 8s will be 4.8 inches apart when the coil reaches 16 inches in diameter and 6.6 inches apart when the coil reaches 21 inches in diameter. A similar result is of course obtained with other spacing of the figure 8s and mandrels of different diameter. 
   SUMMARY OF THE INVENTION 
   The present invention produces windings of filamentary material in a figure 8 configuration using programmed winding techniques resulting in windings having increased density over figure 8 windings using prior art winding techniques, thereby enabling substantially more filamentary material to be wound for the same diameter of filamentary material wound with prior art winding techniques. 
   It is a feature of the present invention to program the radial spacing of the figure 8 crossovers in a figure 8 winding configuration of filamentary material such that the number of figure 8 crossovers is increased per layer of wound coil, whereby the density of the wound coils is increased. 
   It is an advantage of the present invention that increasing the density of a wound coil provides a smaller diameter coil for a given length of filamentary material. Alternatively, a significant increase in the length of filamentary material can be wound in a figure 8 configuration for a given diameter of wound coil or a smaller diameter for a given length of FM. 
   It is a further object of the present invention to provide a package of filamentary material wound in a figure 8 configuration and wherein the number of crossovers of the filamentary material in succeeding layers increase so that the density of the wound coil increases with increasing diameter of the package, whereby the length of material wound for a given diameter of the package is greater than if the number of cross-overs remained constant. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects, features and advantage of the invention are readily apparent from a consideration of the following description of the best mode of carrying out the invention when taken in conjunction with the following drawings representing a preferred embodiment of carrying out the invention; 
       FIG. 1  illustrates the figure 8 crossovers in the center of a partial coil of filamentary material wound in a figure 8 configuration in accordance with prior art winding techniques and wherein the crossovers are in the center of the coil; 
       FIG. 2  is a section of the partial coil of  FIG. 1  taken along lines A-A of  FIG. 1 ; 
       FIG. 2A  illustrates the extra bend in a partial coil of filamentary material due to the radial spacing of the coil in the winding process; and 
       FIG. 3  shows, in block diagram format, a preferred embodiment of winding apparatus for carrying out the programmed density concept of the invention. 
       FIGS. 4A and 4B , respectively show (1) a cross section of a package of filamentary material wound according to prior art winding techniques using non-programmed winding, i.e. constant angle spacing of the crossovers of the coils in the package of wound filamentary material; and (2) a cross section of a package of filamentary material wound according to the programmed density teachings of the present invention, i.e. programmed radial spacing of the figure 8 crossovers. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   By reducing the radial displacement of the figure 8s as the diameter of the wind increases during the winding of filamentary material, an increase in the density of the wind and, particularly, in the outer diameters of the wind, can be achieved when compared to prior methods of winding in the figure 8 configuration, i.e. constant radial spacing of the wind. For example by way of explanation, in a coil of filamentary material wound to a 21 inch diameter, if the radial spacing were maintained at 36 degrees separation, the coils will be approximately 2.4 inches apart along the circumference of the coil at a diameter of 8 inches. The circumferential coil spacing will be 4.8 inches when the coil diameter reaches a 16 inch diameter and 6.6 inches apart when the coil reaches 21 inches in diameter. The starting coil separation of 2.4 (36 degrees) inches for an 8 inch coil diameter can be reduced to an angular (radial) displacement of 13 degrees. This means that 27 figure 8s can be placed in the last layer. The difference in the wound length for that layer is significant. For constant ADVANCE the amount of filamentary material wound according to the prior art winding techniques mentioned herein, is approximately 110 feet, whereas with the programmed technique of the invention the amount of wound filamentary material is 297 feet. 
   Crossovers  11 ,  12 ,  13  and  14  are shown in the partial section of a coil  10  wound in a figure 8 configuration shown in  FIG. 1  along a center line X of the wound coil. The angle β formed by the center axis X and the coils  15 ,  16 ,  17  and  18  is a function of the pattern of the figure 8 configuration, which in turn is a function of the traverse motion, the diameter to which the figure 8 pattern is being wound, and other factors. It is believed apparent from  FIG. 1 , that the smaller the angle β, then the less crossovers per layer of the wind, and conversely, the greater angle β is, the more crossovers per layer of the wind  10  This is because as angle β becomes smaller the spacing between the filamentary material becomes smaller. That is, the density of the wind decreases or increases in dependence on whether the angle beta is increased or decreased. 
   The section of the wound coil  10  of  FIG. 1  along lines A-A shown in  FIG. 2A  shows mandrel surface  20  with the wound material  22  approaching out of the paper and returning into the page at  24 . The next coil of filamentary material is shown approaching out of the paper at  26 . The radial displacement φ is calculated by taking into consideration the need not to deform the wound material. Strand  26  is placed at a point where the strand  22  is already in contact with the surface  20  of the mandrel (or the layer below it if it is not the surface of the mandrel). If strand  26  were close to strand  22  (i.e. angle φ were decreased) strand  22  would have an extra bend in it as shown in  FIG. 2B . 
   The angular displacement φ in  FIG. 2   a  can be calculated from the equation (1):
 
φ=COS −1 ( Rm /( Rm+D ))
 
where: Rm=Radius of the mandrel
 
   D=Diameter of the cable 
   Because the angle φ is viewed at a plane (Section A-A) other than the axis of the coil, it is adjusted by taking into account the angle β ( FIG. 1 ). Angle β is a function of the shape of the pattern of the figure 8 configuration, which is, in turn, a function of the traverse motion, the diameter of the figure 8 wind, and other factors as mentioned above with respect to the description of  FIG. 1 . Therefore angle β can be almost any angle, but a typical angle would be approximately 24 degrees (This angle is typical of most industrial wire winding machines using an 8 inch mandrel). The displacement angle between figure 8s on the mandrel (individual coil layer) is then calculated by the equation (2):
 
φ/cos[24]=φ
 
   This angle is the minimum angle that is usually used to set the winding ADVANCE. Although the ADVANCE could be entered as an angular displacement, the usual entry parameter in the winding control system is in the form of a percent speed increase or decrease of the traverse motor speed when compared to the spindle motor speed of rotation. Therefore an UPPER RATIO could be a number such as 4.0%. It takes two spindle revolutions (720 degrees) to create one figure 8. This upper ratio of 4.0% then has the effect of advancing the traverse by 28.8 degrees for two revolutions of the spindle (720 degrees×0.040=28.8 degrees). A typical calculation to determine the minimum ADVANCE is as follows:
 
Rm=4 inches (Mandrel diameter assumed to be 8 inches)
 
D=0.242 inches
 
   Therefore φ=19.447 degrees and the minimum figure 8 displacement on the mandrel would be 21.287 degrees. To create a 21.287 degree ADVANCE, the traverse must have a speed ADVANCE (plus or minus), when compared to the spindle, of 2.96% (or spindle to traverse ratio of 2 to 1.0296 and 2 to 0.9704, respectively). 
   To illustrate the effect of a density change as the coil diameter increases it is helpful to perform a simple calculation. Because in the above example, each figure 8 is displaced around the circumference by 21.287 degrees, there is room for 16.9 figure 8s in each layer if there were no payout hole (360 degrees/21.287 degrees). In coils with large payout holes, the size of the payout hole is approximately 90 radial degrees (i.e, greater than 80 radial degrees and often larger than 110 radial degrees). By removing figure 8s to accommodate the payout hole, (25% of them for 90 degrees is arbitrarily chosen for this example) the number of figure 8s is 12.675. 
   Each loop of the figure 8 is approximately the shape of a circle and because there are two loops per figure 8, each figure 8 is made up of approximately 4.189 feet on the surface of a typical 8 inch diameter mandrel (two loops times 8 inches×Pi/12). With 12.675 figure 8s per layer of the coil, the length of cable placed on the mandrel will be 53.093 feet (12.675 loops×4.189 feet). At the last layer of this exemplary wind, the coil is approximately 15 inches in diameter. Using the same number of figure 8s in this final layer, the length of cable wound is 99.549 feet. 
   In accordance with the method outlined herein, i.e. one that increases the number of figure 8s as the diameter of the wound coil increases, and by using formulas (1) and (2) for a layer diameter of 14 inches, 17.306 figure 8s can be placed in the last layer instead of 12.675 figure 8s without increasing the number of figure 8s as is the case with prior art figure 8 winding techniques. It is also noted that another benefit of the method of the present invention is that the diameter of the last layer is 14 inches instead of 15 inches. This enables the wound coil of filamentary material to be contained in a smaller package, thereby enhancing the storage transportability of the wound package and commensurately lowering the packaging costs. 
   The primary advantageous features of the invention reside in the fact that the same amount of filamentary material can be contained in a smaller container or package. Alternatively, a greater amount of filamentary material can be contained in a given size package. In the above example the length of filamentary material wound in the last layer is 126.855 feet which is over 27% more than with a wind in which the density of the figure 8s is not programmed as with the present invention. As a matter of fact all layers of the wound filamentary material after the first wound layer will have more wound material in it such that less layers are needed for a given length of desired wound filamentary material (Thus the 14 inch diameter instead of 15 inches). 
   Prior to the use of the programmed density method described herein, the ADVANCE(S) were constant throughout the winding of the coil of filamentary material (the plus and minus ADVANCE may not have been equal to one another, but once chosen, they remained unchanged throughout the winding of the coil). It is apparent that as the layers of filamentary material are wound upon each other, the radius R of the coil increases and the increase in radius can be calculated by knowing the diameter of the material being wound. It is evident that the coil radius for the strand  26  ( FIG. 2A ) is larger than the strand ( 22 ) by an amount equal to the diameter (D) of the filamentary material. By solving the equations 1 and 2 (by Computer), or by providing a “look-up chart” (in a computer) the ADVANCES can be reduced to an appropriate amount to maintain a figure 8 spacing that provides increased density while not adding extra bends in the wound material. 
   The accompanying Table illustrates the difference between the previous winding method and the programmed density approach of the present invention. The tabulations in the Table assume a 1000 foot coil of filamentary material that is 0.33 inches in diameter wound on an 8 inch diameter mandrel, using 21 inch endforms and a traverse width of 12 inches. The coil is wound using an average (of the upper and lower) ADVANCE that starts at 6.50%. This leaves 46.8 degrees between figure 8s and a distance, on the circumference of the mandrel, of 3.267 inches. These are not minimum numbers, but numbers that are likely to produce a good figure 8 coil with increased density and without bending of the filamentary material resulting in damage to it. Ratios that are too low will produce an uneven coil. In the Table the ratios are reduced from the average 6.50% to 1.30% by the time the coil reaches 21 inches. In this example the ratio never actually reaches the 1.3% mark because the coil never reaches 21 inches because of the effect of the density adjustment. In this example the ratios are reduced by 0.26% with each layer. This reduction rate is ultimately dependent on the cable diameter. 
   
     
       
             
             
             
             
             
             
           
             
             
             
             
             
             
           
         
             
               TABLE 
             
             
                 
             
             
                 
                 
               (3) 
                 
               (5) 
                 
             
             
                 
                 
               No Density 
                 
               Density 
             
             
                 
                 
               Program- 
                 
               Program- 
             
             
               (1) 
               (2) 
               ming 
               (4) 
               ming 
               (6) 
             
             
               Layer 
               Layer 
               Length/ 
               Cumulative 
               Length/ 
               Cumulative 
             
             
               Number 
               Dia. 
               Layer 
               Length 
               Layer 
               Length 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               1 
               8 
               32 
                32 
               32 
                32 
             
             
               2 
               8.66 
               35 
                67 
               36 
                69 
             
             
               3 
               9.32 
               38 
               105 
               41 
               109 
             
             
               4 
               9.98 
               40 
               145 
               46 
               115 
             
             
               5 
               10.64 
               43 
               188 
               51 
               206 
             
             
               6 
               11.3 
               46 
               233 
               57 
               263 
             
             
               7 
               11.96 
               58 
               281 
               63 
               326 
             
             
               8 
               12.62 
               51 
               332 
               71 
               397 
             
             
               9 
               13.28 
               53 
               386 
               79 
               476 
             
             
               10 
               13.94 
               56 
               442 
               88 
               563 
             
             
               11 
               14.6 
               59 
               501 
               98 
               661 
             
             
               12 
               15.26 
               61 
               562 
               110 
               771 
             
             
               13 
               15.92 
               64 
               626 
               123 
               864 
             
             
               14 
               16.58 
               67 
               693 
               136 
               1034* 
             
             
               15 
               17.24 
               69 
               762 
               158 
               1191  
             
             
               16 
               17.9 
               72 
               835 
               180 
               1372  
             
             
               17 
               18.56 
               75 
               909 
               208 
               1579  
             
             
               18 
               19.22 
               77 
                987* 
               242 
               1821  
             
             
               19 
               19.88 
               80 
               1067  
               286 
               2107  
             
             
               20 
               20.54 
               83 
               1149  
               345 
               2452  
             
             
                 
             
           
        
       
     
   
   By interpolation it is evident that the coil diameters differ by approximately 2.9 inches. Theoretically, at 20 inches the amount of filamentary material that can be wound using the programmed density method of winding is more than twice that which can be wound by the prior techniques or a coil of 1000 ft. could be 16.58 inches in diameter (layer #14) instead of 19.22 inches in diameter (layer #18) for the same length of filamentary material and using the programmed density techniques of the present invention. The ADVANCE started at 6.5% and finished at 3.38%. 
   Description of Typical Winding Machine with Programmed Density 
   With respect to the block diagrammatic illustration of a winding machine  28  as shown in  FIG. 3 , computer  30  tracks the displacement of spindle  31  and traverse  32  usually with encoders  33  and  34 , but other devices such as potentiometers or resolvers can be used. The necessary ADVANCES are entered either with an input device  30 A such as thumb-wheel switches, a keypad, computer keyboard, an internally stored data base, or downloaded from a database through serial communication (none shown in  FIG. 3 ). The ADVANCES are calculated from the diameter of the filamentary material  29 , the diameter of the mandrel  31 A and the distance of the traverse  32  from the surface  31 A of spindle  31 . Various parameters of the winding process are displayed via display  30 B. 
   The ADVANCES generally consist of two numbers-one for a plus ADVANCE and one for a minus ADVANCE and do not need to be equal. The computer  30  reads the position of the spindle  31  and traverse  32  and provides a reference signal  41  to the traverse motor  38  via the traverse drive  40  that results in an ADVANCE to the traverse  32 . The computer  30  switches the sense of the ADVANCE (plus or minus) when it is time to make the payout hole in the winding. The aforementioned operations are known to those skilled in the winding art. 
   The spindle motor  33  is controlled by spindle drive  42  by a reference signal  43  from computer  30  in a manner known to the winding art. 
   The traverse  32  is driven with a simple crank arm  35  and connecting rod  36 . When this arrangement of a crank arm  35  and connecting rod  36  is driven at a constant RPM (of the crank arm  36 ) by the traverse motor  38  and cam box  39 , there is distortion created in the motion of the actual wire distributor (traverse  32 ). The cam box  39  normally uses an arrangement of cams to remove the aforementioned distortion. 
   The computer  30  receives input of the respective position of the traverse motor  38  and the spindle motor via encoders  34  and  33 , respectively, through counter circuitry  44 . The programmed density process in accordance with the invention is carried out by either programming the computer to solve equations (1) and (2) as defined above, or to provide a “look-up” table in the computer so that the necessary ADVANCES can be provided to the traverse motor  38  and/or the spindle motor  33 . 
   The actual physical layout of the winding machine  29  is of no importance to the present invention as there are numerous ways of building a winding machine depending upon what features are most desirable. For example, mechanical cams provide the most speed. Dual and single belt traverses have other advantages. Electronic cams can provide a certain amount of flexibility, but have speed limitations. For example, electronic cams can be used to wind standard spools, but the method described herein does not apply to spools. A screw and a nut arrangement can provide high accuracy but has a serious speed limitation. DC motors can be used as well as AC motors, steppers or servos. The traverse  32 , if driven by a mechanical cam, can be driven with a standard rotary motor (DC, AC, stepper, servo). Electronic cams can use a servo motor or linear motor. No matter what the details of the winding machine  29  are, the process of density compensation of the invention is the same. 
     FIGS. 4A and 4B , respectively show: (1) a cross section of a package of filamentary material wound according to prior art winding techniques using non-programmed winding, i.e. constant angle spacing of the crossovers of the coils in the package of wound filamentary material; and (2) a cross section of a package of filamentary material wound according to the programmed density teachings of the present invention, i.e. programmed radial spacing of the figure 8 crossovers. 
   With respect to  FIG. 4A , it is evident that without programmed density control, the angle alpha between adjacent crossovers  50 - 51 ,  52 - 53 ,  54 - 55 ,  56 - 57 ,  58 - 59  and  59 - 60  is a constant angle. That is in the prior art winding techniques using non-programmed density control, the crossovers in a given group of crossovers (for example crossovers within group  50 ), are aligned with one another. It is also evident from  FIG. 4A  that the crossovers are spaced circumferentially further apart as the diameter of the wind  61  increases. This results in an effective decrease in the density of the wound coil as the diameter of the coil increases. The priort winding technique produces a payout hole  62  as shown in the  FIG. 4A  in a region devoid of crossovers. 
   The crossover “pattern”  64  of individual crossovers  64 A- 64 I (all inclusive) is formed in a package  63  of filamentary material wound in a figure 8 configuration and wherein the number of crossovers of the filamentary material in succeeding layers from the center  63 A of the package  63  increase so that the density of the wound coil increases with increasing diameter of the package, whereby the length of material wound for a given diameter of the package of wound material, is greater than if the number of cross-overs remained aligned as in the package  61  of  FIG. 4A . Unlike the package of  FIG. 4A , formed by a non-programmed density winding technique and wherein the crossovers in successive layers of the wind are aligned, it is apparent that in the embodiment of the invention represent by  FIG. 4B , the crossovers  64 A- 64 I are “scattered”, i.e. they are not aligned. This non-alignment of the crossovers in a wound package of filamentary material enables the wound package to be more dense, and thereby the same length of filamentary material can be wound in a smaller diameter, or alternatively a greater length of filamentary material can be wound with a lesser diameter than that formed by a prior art winding technique not using the programmed density winding technique of the present invention. 
   Therefore, it is desired that the present invention not be limited to the embodiments specifically described, but that it include any and all such modifications and variations that would be obvious to those skilled in this art. It is our intention that the scope of the present invention should be determined by any and all such equivalents of the various terms and structure as recited in the following annexed claims.