Method for producing a coil
This application is a continuation of application Ser. No. 07/612/148, filed on Nov. 13, 1990, now abandoned which is a continuation of application Ser. No. 07/326,610 filed on Mar. 21, 1989, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a coil, skein or bunch of strand-like stock, for example, wire, insulated or non-insulated cable, glass fiber or the like, and more particularly to an improved method for producing such a coil and apparatus for carrying out the improved method. 
     Frequently during the processing of strand-like stock, such as wire, the need arises for further processing of the wire that cannot be carried out at the same coil location, often, not even in the same plant, in which the wire itself was manufactured. The strand-like stock must then be prepared in a suitable way for transport and brought to the location where the further processing occurs. Several problems or disadvantages have arisen as result of the preparation required for transportation of the stock. Commonly, the winding material is wound on winding cores or spools for transportation together with the wound material. Therefore, a large number of spools must be stored at the corresponding locations or plants, which requires a considerable investment cost. Further, considerable costs arise because the empty spools must be transported back from the processing point to the original production plant. Moreover, the spools also increase the transport weight of the wound stock, which produces an increase in transportation costs. 
     In order to avoid the aforementioned problems and disadvantages, a need has developed in the industry for strand-like stock, such as wire or cable, that is not wound on spools, but rather transported and delivered as skeins or bunches that substantially are comprised only of the actual strand-like material itself and possibly a cover or other packaging for the coil. This type of coil is usually referred to as a one-way packaged coil. 
     A method for producing a one-way packaged coil is disclosed in DE-OS 3520195. In this known method a cone-shaped winding spool is used. The strand-like stock is wound on the cone-shaped spool in individual layers parallel to one another. An adhesive then is provided, which binds the individual windings and layers to one another. When further processing occurs, the wire is unwound from the inside. 
     There are number of serious disadvantages that result from employing this method and the coil that results therefrom. First of all, use of an adhesive in the production of the coil is disadvantageous because it makes the method complicated and expensive. In addition, the adhesive can disrupt further processing of the coil and, therefore, in some circumstances it must initially be removed. Furthermore, entanglement of the wire layers can occur, despite the use of adhesive, especially, when approaching the end of the unwinding process as the adhesive forces between the individual layers degenerate, resulting in several windings coming loose at once. 
     The invention is directed to a method for producing a coil that can be carried out more simply and inexpensively than heretofore possible, while at the same time providing a stable coil that can be transported and processed without incurring the disadvantages and problems of the prior art. Advantageous apparatus for carrying out the method of the invention and for unwinding a coil also are disclosed. 
     SUMMARY OF THE INVENTION 
     The invention accomplishes these goals by providing a method of producing a coil of strand-like material wound in layers on a substantially cone-shaped surface of a winding core or spool having a cone aperture angle, with the layers being inclined with respect to the cone-shaped surface of the winding spool and in which a take-up apparatus is employed that moves approximately parallel to the longitudinal axis, comprising the steps of (a) beginning the winding process at a starting diameter on the portion of the winding spool having the smallest diameter; (b) initially winding a first layer L 1a  having a predetermined number of windings N 1  onto the substantially cone-shaped surface of the winding spool at an acute angle relative to the substantially cone-shaped surface which is greater than one-half of the cone-aperture angle by moving the take-up apparatus in a first direction, where the number N 1  is smaller than the maximum number N max  of windings that can be applied to the spool at a predetermined winding pitch; (c) winding a second layer L 1b  onto the first layer L 1a  by reversing the movement of the take-up apparatus in a second direction opposite the first direction, with the second layer L 1b , having substantially the same number of windings N 1  as the first layer L 1a  ; and (d) winding additional layers L 2a , L 2b , L 3a , L 3b , . . . L xa , L xb  and so forth onto winding layers L 1a  and L 1b  such that the additional layers have a number of windings N 2 , N 3  . . . N x , respectively, that increases for each additional layer by a substantially constant winding factor ΔN until the maximum number N max  of windings are wound on the winding spool wherein the first, second, and additional pairs of layers form a double-cone shape. 
     Thus, the method of the invention is carried out such that at least one layer L 1a  is wound with N 1  number of windings. When the number N 1  is reached, the direction of movement the take-up roll is reversed and a layer L 1b  is wound back to the starting point of the first layer L 1a . Layers L 1a  and L 1b  have essentially the same number of windings N 1 . The next layer L 2a , which is wound in the same direction as the layer L 1a , has a number of windings N 2  &gt;N 1 , where the difference between the number N 2  and the number N 1 , corresponds to the winding factor ΔN. The substantially constant winding factor is added to the following windings, until the layers extend between the coil flanges, to ensure the desired double cone-shaped structure of the coil results. This means that the winding number N 3  for the layers L 3a  and L 3b  is again increased by the winding factor ΔN and so on for further layers. 
     According to one embodiment of the invention, the winding factor may lie in the range between 2 and 6, preferably between 3 and 5. With this winding factor, a cone aperture angle of between 12° and 16° is provided, more preferably, between 13° and 15°. The cone aperture angle is understood as being the total opening angle of the winding spool during the winding process. This means that with a cone aperture angle of, for example, 16°, the intersection line of the cone in a cross-section that includes the longitudinal axis of the winding spool is inclined by 8° with respect to the longitudinal axis. Winding the layers onto the substantially cone-shaped surface of the winding spool at an angle greater than this angle, i.e., greater than one-half the cone aperture angle or 8° in this example, ensures that the advantageous double-cone coil shape results. According to a further embodiment of the invention, the winding factor lies in the range between 6 and 12, preferably between 7 and 11. With this winding factor, a preferred cone aperture angle lies in range between 0° and 12°. 
     In accordance with the method of the invention, the winding process may be carried out with different winding pitches, i.e., the space in between two windings of the same layer, depending upon the diameter of the winding stock. A winding pitch of 1.5 to 3.0 is advantageous because in this range small deviations of the wire height when wire is being taken up and unwound do not adversely influence the stability of the coil. 
     The method for producing one-way packaged coils of strand-like stock of the invention has considerable advantages over the method known in the art. Through the specially controlled winding process of the invention, it is possible to provide coils formed in the shape of a double cone. This shape enables the individual windings to support each another, which results in a coil structure that is much more stable for transport, and obviates use of an adhesive. 
     Furthermore, the method of the invention provides a completed coil that can be unwound in a particularly simple and reliable manner. In principle, the coil of the invention can be unwound from either the inside or from the outside. When unwinding from the inside, the coil is typically arranged such that the longitudinal axis of the coil is vertical and the larger inside diameter of the coil is located at the bottom. If the wire then is withdrawn from the interior of the coil, each winding is supported by the winding below, due to the angle of inclination provided by the cone-shaped winding spool. In this manner, the wire winding cannot fall downwardly and become entangled. 
     Unwinding from the outside of the coil also can be accomplished with the coil of the invention, which was not possible with coils heretofore known in the art. According to this aspect of the invention, the coil may be arranged with its longitudinal axis in the vertical direction and the smaller inside diameter of the coil at the bottom. Subsequently, an unwinding disc may be placed on the coil whose diameter is equal to or larger than the outside diameter of the coil. The unwinding disc preferably can rotate. The strand-like stock, for example, wire or cable, is then withdrawn from above or &#34;overhead&#34; as the stock is passed over the disc. Unwinding of the coil in this manner also enables the windings to support one another. Each winding is supported from the winding below because the winding diameter is larger than the diameter of the previously unwound winding and, hence, the upper winding cannot slip downwardly. 
     The double-cone shape of the coil ensures that, regardless of whether the coil is unwound from the inside or the outside, it remains in a very stable condition, which makes it possible to arbitrarily interrupt and restart the unwinding process, without fear that the winding will slip and the strand-like material tangle during the standstill. The high stability of the coil also substantially simplifies transport of the coil. 
     The method of the invention can be employed with very different types of strand-like material. The method is particularly suited for winding wire. Furthermore, it was discovered that the method of the invention is particularly well-suited for simultaneously winding several twisted or untwisted stranded cables. Being able to perform these functions is a particular advantage of the invention, since simultaneously winding several cables, which must later be unwound and separated again, is an important aspect of cable manufacturing. Furthermore, the invention enables the winding of finished stranded cables and also of insulated cable and the like. In addition, glass fibers also can be wound by the method of the invention. 
     In accordance with one embodiment of the invention, the winding spool can rotate during the winding process. In this case, an upwardly and downwardly moving take-up or traverser roll may be employed for guiding the strand-like stock to the respectively desired height or location on the spool. Due to the rotation of the winding spool, a twist-free winding of the stock may be effectuated. It should be noted that in this embodiment, the rotary speed of the winding spool must vary according to the position of the take-up apparatus to ensure that for a constant wire feed speed, each diameter of the winding spool has the same tangential speed. 
     According to a further embodiment of the invention, the winding spool may be stationary during the winding process. In this case, the take-up apparatus revolves around the spool to wind the strand-like around the winding spool in accordance with the winding method of the invention. The strand-like stock then, in general, has a twist, since the stock is rotated by 360° for each winding. This twisting can be undone when unwinding the spool, by unwinding or fly-off in the correspondingly opposing direction. If the twisting is desired for further processing, e.g. for producing stranded cables, the twist can be increased by one further revolution per winding during take-off. 
     According to another aspect of the method of the invention, parallel layers of windings can be applied after reaching the maximal winding number N max , i.e. as soon as the first layer reaches the flange of the winding spool lying opposite the starting flange. In each of the parallel layers, the number of windings is substantially equal. In this manner, the advantageous, inclined form of the outer winding layers is maintained. When the first parallel winding layer reaches the maximum diameter of one of the spool flanges, the windings may continue such that the coil forms an outer cylindrical shape. For this purpose, the take-up apparatus is controlled in essentially the same way as in the start of the winding process, but the winding number, which is equal to N max  now, is correspondingly reduced by the substantially constant winding value ΔN, which is the number of additional windings that was added to the initial winding layers. This feature of the invention produces the advantage of better utilization of the volume of the coil. 
     An apparatus for carrying out the method of the invention is disclosed as comprising (a) a substantially cone-shaped winding core having first and second axially spaced flanges arranged substantially perpendicular to the longitudinal axis of the winding core; (b) a take-up apparatus movable in at least first and second opposite directions to guide the strand-like material at respective predetermined heights as the material is wound onto the winding spool in layers; (c) a counter for counting the number of windings wound within the layers on the winding core; (d) a comparator operably connected to the counter for generating an output signal when a predetermined number of windings N is wound within a layer on the winding spool, the signal being operably connected to the take-up apparatus for reversing the direction of movement of the take-up apparatus; and (e) an adder for summing a predetermined value to the number of windings last counted by the counter to determine the new value of windings N to be wound in the next layer. 
     The coil of the invention may be formed from strand-like material, selected from the group consisting essentially of wire, insulated stranded cable, non-insulated stranded cable and glass fiber. The coil may include a substantially cone-shaped packaging for the coil, such as a paper cover or the like, which may be applied to the winding apparatus before the winding process starts instead of being applied to the coil after the winding process is complete. The cover has first and second axially spaced, removable flanges that are arranged substantially perpendicular to the longitudinal axis of the cover. If such a cover is used, the strand-like material is wound in layers on the cover and the layers are inclined with respect to the substantially cone-shape surface of the cover. A first pair of layers of windings, each containing a predetermined number of windings N 1 , is wound onto the substantially cone-shaped surface at an acute angle relative to the substantially cone-shaped surface which is greater than one-half of the cone aperture angle of the cover. N 1  is smaller than the maximum number of windings that can be applied to the cover at a predetermined winding pitch. A second pair of layers of windings each containing N 2  =N 1  +ΔN windings is wound onto the first pair where ΔN is a substantially constant winding value. Additional pairs of layers of windings then are wound, with each pair containing a number of windings N 3 , N 4  . . . N x , respectively, that increases for each additional layer by N until the windings extend from the first flange to the second flange wherein the first, second, and additional pairs of layers form a double-cone shape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a schematic partially cross-sectional view through winding apparatus for carrying out the method of the invention. 
     FIG. 2 schematically illustrates the winding or take-up process of the invention. 
     FIG. 3 shows a coil produced according to the method of the invention. 
     FIG. 4 is a schematic representation of the structure of the various layers of the coil of FIG. 3. 
     FIG. 5 shows the coil of the invention packaged for delivery. 
     FIG. 6 shows the unwinding of the coil of the invention from the outside without use of any auxiliary unwinding apparatus. 
     FIG. 7 shows the unwinding of the coil of FIG. 5 from the outside in conjunction with a special take-off device. 
     FIG. 8 shows the unwinding of several coils of the invention. 
     FIG. 9 shows an arrangement of several coils of the invention prepared for transport. 
     FIG. 10 shows unwinding of the coil of the invention from the inside of the coil. 
    
    
     DETAILED DESCRIPTION 
     The method of the invention and a winding apparatus for carrying out the method are described in conjunction with FIGS. 1-4, which illustrate an embodiment provided with a rotating winding spool. The winding apparatus comprises the actual winding core 1, which is conically shaped and has a cone aperture angle schematically indicated at 2. The winding apparatus further comprises a first flange 3 and second flange 4, both of which are perpendicular to the longitudinal axis 5 of the rotatable winding core 1. The two flanges are disc-shaped and have no conical surfaces. The second flange 4 is removable such that the winding apparatus can be removed from the finished coil. Furthermore, the winding apparatus may be taken apart to simplify removal thereof. 
     A thin packaging cover 10 may be applied to the winding apparatus and is adapted to conform to the contour of the apparatus. The thin cover 10 may be formed, for example, of paper and may remain after completion of the coil to increase the rigidity of the coil for transport or to facilitate unwinding from the outside. Cover 10 includes spaced flanges 10a, 10b, as shown in FIG. 1, and a substantially conical surface 10c lying parallel against the corresponding conical surface 6 of winding core 1. As is readily apparent to those of ordinary skill in the art, flanges 10a, 10b are removable, such as by cutting, tearing or the like, or are bendable to facilitate unwinding of the coil, if necessary. 
     Take-up or winding of the strand-like stock, in the present case a wire or cable 12, begins at the flange of the winding spool that is arranged on the part of the spool that has the smallest diameter. The wire 12 first is loosely passed over the second flange 4. The take-up process then begins with the winding 20, which represents the first winding wound on the spool. Take-up occurs in conjunction with a take-up or traverser roll 21, which is controlled in its upward and downward movement for guiding the wire 13. The wire is fed at a substantially constant speed to the rotating spool 1. The control of the take-up roll is best illustrated schematically in FIG. 2. Take-up begins with application of the layer L 1a , which in the present case comprises four windings vertically wound as the roll 21 moves in the direction of the arrow 22. The windings are wound onto the substantially cone-shaped surface 6 of the winding core 1, or surface 10a of the cover 10 if provided, at an angle greater than one-half of the cone-aperture angle 2. This ensures that the outer surface 44 of the inner coil portion 40 (see FIG. 4) tapers toward the inner surface 41, which follows the incline of conical surface 6 (or 10c if cover 10 is provided) to form a double cone shape, the advantages of which are discussed subsequently. 
     Then the take-up roll reverses its direction and winds four more windings as it moves back in the direction of arrow 23 to form the layer L 1b . The number of windings or the winding number N 1  of layer 1 therefore is 4. Following this convention, the layer L 2  is wound, with the number of windings N 2  in this layer calculated from the equation: 
     
         N.sub.x =N.sub.x-1 +ΔN 
    
     where 
     N x  is the number of windings in layer X; and 
     N x-1  is the number of windings in the preceding layer, 
     
         i.e. layer X-1. 
    
     In the present case, ΔN=4, i.e. it is coincidentally equal to the number N 1  of the first layer L 1 . According to this equation, the layer L 2a  receives 8 windings, which are wound in conjunction with movement of roll 21 in the direction of the arrow 22. The layer L 2b  also receives 8 windings, which are wound as roll 21 moves in the direction of the arrow 23. For the next layer L 3a , N 3  =N 2  +ΔN or 8+4=12 windings, the layer L 4a  (not referenced) has 16 layers, the layer L 5a  has 20 layers, etc. The number of windings is increased by a constant amount for each new layer wound in the same direction or movement of roll 21. This constant amount can be varied according to the particular configuration the coil desired. The conical shape that results from this process, as illustrated in the figures, is the aggregate result of a number of windings about the core, and represents the general geometric shape that a winding so produced tends towards after a number of windings. 
     The continuation of the winding process is more clearly shown in FIGS. 3 and 4. The winding process continues in the manner described above, until the number of windings is so large that the windings reach the opposing first flange 3. As soon as this point is reached, the following layers are wound with the same number of windings to produce parallel layers. This is schematically illustrated by the parallel dashed lines 25 shown in FIG. 3. 
     Winding of the parallel layers continues until the outer edge of the second flange 4 is reached. At this point, the winding process either may end or continue by applying a respectively reduced number of windings, essentially opposite from the beginning of the winding process of the invention such that the coil receives an outer cylindrical form. The end of the wire 26 is then returned to the starting point of the process by a few large pitch windings 49 such that the end 26 lies next to the beginning of the wire 12. 
     The schematic configuration of the wire windings is best illustrated in FIG. 4. The wire coil consists of an inner portion 40, which is formed in a double cone shape, i.e. it tapers at its inner surface as a cone and widens at its outer surface as a cone. This double cone form provides an essential advantage in that during unwinding in the upright or vertical position, as the wire reaches the inner layers, which are always critical during unwinding, the diameter of the coil windings increases in the downward direction thereby supporting the windings from falling downward, regardless of whether unwinding is performed from the inside or outside. This is quite advantageous because it enables provision of a commercial coil product that does not depend on the specific requirements of a particular customer, i.e., whether unwinding must occur from the inside or outside of the coil. 
     In addition to double cone portion 40 in the illustrated embodiment, a parallel winding portion 42 is formed by the invention whose diameter also increases in the downward direction. It is noted, however, that provision of parallel portion 42 is not necessary, as it is readily possible to configure the coil with only the double cone portion. 
     In the region 43, which adjoins the parallel region 42, the layers are arranged such that a cylindrical outer coil form results. This form can be achieved by exactly reversing the winding process that led to formation of the first portion 40 of the winding, i.e., N x  =N x-1  -ΔN. Provision of outer coil portion 43 of the winding may be optional. 
     A coil produced in accordance with the method of the invention is illustrated in FIG. 5 in a condition ready for delivery. As noted above, the coil may include a paper or cardboard packaging cover 10, which provides additional stability. Furthermore, an outer cover 50 formed of, for example, plastic foil, may be provided to protect the coil from dirt during transport. Further stability for transport may be achieved with bands 51, which are placed around the coil as shown in FIG. 5. To simplify mounting of these bands, corresponding channels may be provided in the winding spool. Further, plastic or steel bands 52 may be circumferentially arranged around the coil to provide for even further stability. 
     FIG. 6 shows how the winding material can be taken off or unwound from the coil without the need for any further unwinding apparatus. This occurs as the coil is set in the upright position such that the end with the smaller inside diameter of the coil faces downwardly. Naturally, any packaging such as covers 10, 50 and bands 51, that would interfere with unwinding is first removed. Although not necessary as indicated by FIG. 7, flange 10a has been removed from the coil shown in FIG. 6. The wire 56 then can be withdrawn from above, preferably, through an eyelet (not shown). 
     In the same manner it also is possible to unwind the coil from the inside. However, for inside take-off, in order to take advantage of the double cone effect, the coil is placed such that the portion with the larger inside diameter faces downwardly. Thus, the coil is rotated 180° with respect to the illustrated coil position of FIG. 6. This type of inside take-off is shown in FIG. 10, which illustrates the wire 95 being withdrawn from the middle 96 of the coil. As is readily apparent to those of ordinary skill in the art, inside take-off requires removal of flange 10b (if cover 10 is provided) and any other packaging that might hinder unwinding. Thus, flange 10b and the portion of the foil 50 present at the small diameter end of the coil have been removed from the coil shown in FIG. 10. 
     FIG. 7 illustrates unwinding of the coil of FIG. 5 in conjunction with a take-off apparatus. Take-off apparatus 60, which comprises a core 61 and a rotatable disc 62, is inserted into the cardboard section 10 of the coil. Rotatable disc 62 includes a circular ridge 64 at its outer circumference. Unwinding occurs via the disc by drawing the strand-like stock wound on the coil through an eyelet 65 arranged along the longitudinal axis of the coil. As unwinding occurs from the outside via disc 62, removal of flange 10a is not necessary. The eyelet is connected to further unwinding apparatus in a manner that is not shown. 
     As is recognizable from FIG. 7, the individual windings are taken off consecutively one after the other and each subsequent winding in this region of the coil has a larger diameter than the previously unwound winding. Downward slippage of the windings thereby is avoided and, therefore, entanglement of the strand-like material, in particular, by a stoppage of the unwinding process, cannot arise during unwinding. 
     Although unwinding of the coil from the outside is a preferred form of unwinding of the coil of the invention, as discussed above, it also is possible to unwind the wire from the inside, depending on the needs of the customer. Thus, inside unwinding, which is possible with the coil of the invention, also lies within the scope of the invention. 
     FIG. 8 illustrates how two coils formed according to the invention can be connected to one another to provide a transition, without a loss of time in the unwinding process, from a first coil 70 to a second coil 71. As shown in FIG. 8, the end of the wire 12 leading to the outside of coil 70 is connected to the end of the wire 26 of coil 71, which also leads to the outside. When the first coil 70 is unwound, the unwinding process continues with the second coil 71 without interruption. A third or fourth coil also can be connected in the same manner. 
     FIG. 9 illustrates how several coils produced according to the invention can be prepared for transport. As shown therein, the coils 90 can be arranged on a pallet 91 without any further auxiliary apparatus. To provide the coils with sufficient stability, bands 92 may also be provided in a manner similar to bands 51, as discussed above.