Method for producing a coil

A method for producing a coreless coil of strand-like material in which the strand-like material, which may be wire, insulated or non-insulated cable, glass fiber or the like, is wound in several layers on a substantially cone-shaped winding spool. The layers are inclined with respect to the longitudinal axis of the winding spool. The first pair of layers each contain N.sub.1 windings. The second pair of layers each contain N.sub.2 =N.sub.1 +.DELTA.N windings, where N is a constant value. In this manner, the number of windings for consecutive layer pairs is increased until the total number of possible windings for a predetermined winding pitch is reached. The layers of each pair are wound by a take-up apparatus that moves in a first direction for winding one of the layers of a pair and in a second opposite for direction for winding the other layer of the pair. A coreless coil produced by such a method, an apparatus for carrying out the method, and an apparatus for unwinding a coreless coil also are disclosed.

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.sub.1a having a predetermined number of windings 
N.sub.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.sub.1 is smaller than 
the maximum number N.sub.max of windings that can be applied to the spool 
at a predetermined winding pitch; (c) winding a second layer L.sub.1b onto 
the first layer L.sub.1a by reversing the movement of the take-up 
apparatus in a second direction opposite the first direction, with the 
second layer L.sub.1b, having substantially the same number of windings 
N.sub.1 as the first layer L.sub.1a ; and (d) winding additional layers 
L.sub.2a, L.sub.2b, L.sub.3a, L.sub.3b, . . . L.sub.xa, L.sub.xb and so 
forth onto winding layers L.sub.1a and L.sub.1b such that the additional 
layers have a number of windings N.sub.2, N.sub.3 . . . N.sub.x, 
respectively, that increases for each additional layer by a substantially 
constant winding factor .DELTA.N until the maximum number N.sub.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.sub.1a is wound with N.sub.1 number of windings. When the number 
N.sub.1 is reached, the direction of movement the take-up roll is reversed 
and a layer L.sub.1b is wound back to the starting point of the first 
layer L.sub.1a. Layers L.sub.1a and L.sub.1b have essentially the same 
number of windings N.sub.1. The next layer L.sub.2a, which is wound in the 
same direction as the layer L.sub.1a, has a number of windings N.sub.2 
&gt;N.sub.1, where the difference between the number N.sub.2 and the number 
N.sub.1, corresponds to the winding factor .DELTA.N. 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.sub.3 for the layers L.sub.3a and L.sub.3b is again increased by 
the winding factor .DELTA.N 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.degree. and 16.degree. is 
provided, more preferably, between 13.degree. and 15.degree.. 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.degree., the intersection line of the 
cone in a cross-section that includes the longitudinal axis of the winding 
spool is inclined by 8.degree. 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.degree. 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.degree. and 
12.degree.. 
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 "overhead" 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.degree. 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.sub.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.sub.max now, is 
correspondingly reduced by the substantially constant winding value 
.DELTA.N, 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.sub.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.sub.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.sub.2 =N.sub.1 +.DELTA.N windings is wound onto the first 
pair where .DELTA.N is a substantially constant winding value. Additional 
pairs of layers of windings then are wound, with each pair containing a 
number of windings N.sub.3, N.sub.4 . . . N.sub.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.

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.sub.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.sub.1b. 
The number of windings or the winding number N.sub.1 of layer 1 therefore 
is 4. Following this convention, the layer L.sub.2 is wound, with the 
number of windings N.sub.2 in this layer calculated from the equation: 
EQU N.sub.x =N.sub.x-1 +.DELTA.N 
where 
N.sub.x is the number of windings in layer X; and 
N.sub.x-1 is the number of windings in the preceding layer, 
EQU i.e. layer X-1. 
In the present case, .DELTA.N=4, i.e. it is coincidentally equal to the 
number N.sub.1 of the first layer L.sub.1. According to this equation, the 
layer L.sub.2a receives 8 windings, which are wound in conjunction with 
movement of roll 21 in the direction of the arrow 22. The layer L.sub.2b 
also receives 8 windings, which are wound as roll 21 moves in the 
direction of the arrow 23. For the next layer L.sub.3a, N.sub.3 =N.sub.2 
+.DELTA.N or 8+4=12 windings, the layer L.sub.4a (not referenced) has 16 
layers, the layer L.sub.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.sub.x =N.sub.x-1 -.DELTA.N. 
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.degree. 
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.