Method and apparatus for winding textile yarns

A method and apparatus for winding textile yarns into core supported packages is disclosed, and which is characterized by the ability to produce relatively large packages which are adapted to permit a high speed unwinding by withdrawal of the yarn over one end of the package. The method and apparatus involves controlling the yarn traverse guide so as to include stroke modification cycles during which the traverse stroke is progressively contracted and then increased, with the stroke modification cycles being designed to produce a precisely cylindrical package end with a uniform distribution of hardness along the package. In one illustrated embodiment, a number of stroke modification cycles having a relatively large contraction alternate with a number of stroke modification cycles having a relatively small contraction. In addition, the speed of the yarn guide may be constantly accelerated and decelerated to avoid undesirable patterns, with the changes in speed being coordinated with the stroke modification cycles to provide a uniform yarn tension in the package.

The present invention relates to the winding of textile yarns into core 
supported packages, and more particularly the random winding of a 
cylindrical cross wound package of a textured yarn, such as a false twist 
textured filament yarn. In such winding operations, the end faces of the 
cylindrical package may lie in a normal plane (winding with straight end 
faces), or the end faces may be inclined relative to this normal plane 
(biconical winding). 
A randomly cross wound package in the context of the present invention is a 
cross wound package having a winding ratio which is constantly or 
periodically variable during the course of the winding cycle. The "winding 
ratio" is here understood to mean the ratio of the package speed 
(revolutions of the package per minute) to the traversing speed (number of 
double strokes per minute). Packages of the described type are described 
in DIN 61800 (German Industrial Standards), and they are commonly produced 
on the winding systems of yarn texturing machines. In such machines, the 
yarns receive crimp-elastic properties from their treatment, in particular 
the false twist texturing operation. 
It is known that the end areas of cylindrical packages often include bulges 
which result from an unavoidable deposit of an unduly large quantity of 
yarn in the area of stroke reversal. In order to avoid such bulges at the 
package ends, it is known to periodically modify the traverse stroke, by a 
periodic shortening and lengthening of the stroke in the area of these 
bulges. From investigations as to the unwinding behavior of packages, it 
has surprisingly been found that a flattening, i.e. a reduction in the 
bulge, of the cylindrical surface area of the cross wound package on the 
end opposite to the unwinding end of the package, results in substantially 
improved unwinding properties of the yarn. In this regard, such packages 
are commonly mounted on a creel, with the yarns being withdrawn in an 
axial direction over one end of the package. The unwinding end of the 
package is usually identified by a rounded edge on the supporting core or 
bobbin tube, and a yarn transfer tail which is used to connect the 
beginning of a yarn on one package with the end of a yarn on a successive 
package, is positioned at the opposite end, i.e. the end opposite the 
unwinding end. 
As noted above, a flattening of the surface area on the end opposite the 
unwinding end results in improved unwinding properties. In contrast 
thereto, bulged formations on the unwinding end of the package, have no 
disadvantageous unwinding consequences. This result was extremely 
unexpected, inasmuch as the opposite result would have been expected from 
experience with the unwinding behavior of yarns from conical packages. 
It should also be noted that the flattening of the cylindrical surface of 
the cross wound package in accordance with the present invention is not an 
inclined face, as is obtained in the production of biconical, cross wound 
packages by uniformly shortening the stroke of the traverse guide. Rather, 
the flattening is an intentionally produced uniform reduction of the 
diameter on at least the end of the cylindrical package which is opposite 
to the unwinding end of the package. Such packages may be produced in a 
winding system for cross wound packages, by providing the yarn traverse 
system with means for a periodic contraction and lengthening of the stroke 
of the traversing yarn guide (i.e. stroke modification), together with a 
ribbon breaking mechanism. The length of the modified strokes may be 
substantially decreased, for example, to about 20 mm contraction of the 
stroke at one or both ends of a basic stroke of the traversing yarn guide 
of about 250 mm. 
Packages which are produced in the above manner have however, relatively 
soft frontal surfaces. Depending on the type of further processing, the 
soft surfaces are undesirable since they are more easily damaged than hard 
packages. Thus in many instances, and in particular because of the 
resulting transport and handling problems, such packages have proven to be 
undesirable despite their favorable unwinding properties. However, in 
accordance with the present invention, the advantages of packages with 
flattened ends are maintained. In addition, unduly soft package ends are 
avoided, and a package with a desired controlled hardness together with 
excellent unwinding properties is produced. The present invention thus 
proceeds from the method disclosed in U.S. Pat. No. 4,325,517, in which 
the length of the traverse stroke is varied. 
It is accordingly an object of the present invention to provide a method 
and apparatus for winding yarns which is adapted to produce a package of 
relatively large diameter, and yet which insures a satisfactory overhead 
withdrawal of the yarn at high unwinding speeds, of for example, 1000 
m/min. 
This and other objects and advantages of the present invention are achieved 
in the embodiments illustrated herein by the provision of a winding method 
and apparatus which includes controlling the traverse of the yarn guide at 
at least one end of the package in a recurrent series of yarn deposit 
intervals, with each interval being divided into at least two segments, 
with the first segment comprising at least one stroke modification cycle 
in which the length of the strokes of the yarn guide is progressively 
decreased to a maximum contraction and then progressively increased, and 
with the second segment comprising at least one stroke modification cycle 
in which the length of the strokes of the yarn is progressively decreased 
to a minimum contraction and then progressively increased. Preferably, the 
minimum contraction is less than about 60 percent of the maximum 
contraction. 
The present invention may be advantageously used to produce cylindrical 
packages having either straight end surfaces, or inclined end surfaces 
(biconical packages), when viewed in their longitudinal section. 
In a preferred embodiment of the invention, several stroke modification 
cycles may occur within one or both of the segments of the yarn deposit 
intervals. Thus for example, within the yarn deposit segment having large 
stroke modification cycles, the cycles may be varied, and preferably 
reduced in stages, from one modification cycle to another. In the 
following segment with small stroke modification cycles, the small cycles 
are preferably less than 60 percent and most preferably less than 50 
percent, of the large stroke modification cycles. Within the second 
segment, the stroke modification cycles may be in groupings, with one 
grouping having the same modified stroke, and the subsequent groupings 
having progressively smaller modified strokes. In this manner, a package 
is formed with differing wound layers. During the yarn deposit segments 
having the large stroke modification cycles, a flattened and soft wound 
layer is formed at the ends. During the yarn deposit segments having the 
smaller stroke modification cycles, the flattened end areas of the package 
are substantially filled and covered with a hard layer, so that the hard 
layer protects the soft layer, and with the underlying soft layer 
providing for a certain amount of flattening, and as a result assuring 
good unwinding properties throughout the package. Thus a specific package 
is formed which externally has a good appearance, is easy to handle, and 
which has satisfactory unwinding properties. 
In another embodiment of the invention, the yarn deposit segments with the 
large stroke modification cycles, and the yarn deposit segments with the 
small stroke modification cycles directly follow each other. In this 
further embodiment, a single stroke modification cycle occurs within the 
yarn deposit segment having the large cycles, while several identical 
stroke modification cycles follow each other within the segments of small 
cycles. Preferably, a rest time, i.e. a time during which the traverse 
stroke is unchanged, is positioned between each of the stroke modification 
cycles of the second segments. As a result, it is provided that the time 
in which the yarn traversing system is operated with large stroke 
modification cycles may be maintained at a desired ratio to the time in 
which the yarn traversing system operates with the small stroke 
modification cycles. This ratio typically ranges from about 1.8 to 1 and 
1.2 to 1. This ratio is empirical, and an adherence to the ratio may be 
significant to achieve the desired unwinding properties. 
In a further embodiment of the present invention, both the large and the 
small stroke modification cycles may be reduced in steps from one yarn 
deposit interval to the next, with the largest small stroke modification 
cycle then amounting to more than 50 percent, preferably between 60 and 80 
percent of the smallest large stroke modification cycle. In this 
arrangement, two to ten steps, each with reduced stroke modification 
cycles, may follow each other. 
Another possibility of favorably effecting the package build, and of 
improving the unwinding properties of the yarn, is provided by the present 
invention in that the contraction and/or lengthening speeds of the stroke 
modification cycles i.e, the rate of the decrease in the stroke length 
and/or the rate of the increase in the stroke length, may be controlled. 
The control of the contraction and/or lengthening speeds of the cycles 
defined by the traversing yarn guide permits the adjustment of the time of 
the cycles irrespective of the magnitude of the cycles. Such control also 
permits a rest time of any desired length to be placed between two stroke 
modification cycles or between two yarn deposit intervals, without having 
to change the total duration of the yarn deposit interval, i.e., the 
duration of a yarn deposit interval including the rest time. 
A further aspect of the present invention provides that the stroke of the 
traversing yarn guide maintained between the stroke modification cycles, 
and which normally corresponds to the package length, may be temporarily 
narrowed or reduced. As a result, a further parameter for influencing the 
formation of a package with desirable unwinding properties is made 
available. The traverse stroke may be continuously varied between two 
outer and two inner limits, with the outer and inner limits also being 
varied. 
From the above, it will be seen that the present invention makes available 
a number of controllable process parameters for the build of a precisely 
cylindrical package, which has a uniform hardness over its length. For 
example, the extent of the contractions of the stroke of the traversing 
yarn guide, as well as the duration of the respective yarn deposit 
segments for the large and small stroke modification cycles may be 
selected. In addition, one or more of the following process parameters may 
be controlled, including the number of the stroke modification cycles per 
yarn deposit interval, the variation of the large and small stroke 
modification cycles within a yarn deposit interval and in the following 
yarn deposit interval, the contraction speed and lengthening speed of the 
stroke modification cycles, the duration and number of rest times, and the 
narrowing of the stroke of the traversing yarn guide between two stroke 
modification cycles or yarn deposit intervals, respectively. 
The selection of the above parameters depends on the type of yarn, its 
denier, its advancing and winding speed, the length and maximum diameter 
of the package, the angle at which the yarn is deposited on the package, 
as well as other conditions. The specific selection of the parameters is 
preferably made as a result of trials. 
The significance of the present invention resides in the fact that certain 
basic parameters, and a large number of secondary parameters as noted 
above, are made available so as to accomplish a satisfactory package build 
with good unwinding properties, in each instance. 
It is known that the quality of the yarn package also depends on the 
tension under which the yarn has been wound onto the package. A particular 
criterium for good unwinding properties is the uniformity of this tension 
over the yarn length and over the length of the package. The present 
invention also provides that the traversing speed may be varied for the 
purpose of breaking the patterns or ribbons, and may be changed between a 
minimum and a maximum value. To insure uniform yarn tension, the minimum 
value occurs at about the mid point of the yarn deposit segment having 
small stroke modification cycles, and the maximum value of the speed 
occurs at about the mid point of the yarn deposit segment having large 
stroke modification cycles. As a result, the reduction of the traverse 
speed which is produced by shortening the traverse stroke is compensated 
by an increase of the rate of double strokes defining the frequency of the 
traverse speed, i.e., the number of the reciprocal movements of the 
traversing yarn guide per unit of time. The ratio of double strokes is 
preferably controlled so that its maximum coincides with the maximum point 
of a large stroke modification cycle. 
Another possibility for making the yarn tension uniform in accordance with 
the invention, may be provided in that the circumferential speed of the 
package is temporarily and slightly reduced and increased in such a manner 
that the yarn tension remains constant. For this purpose, the 
circumferential speed should be varied only slightly as a result of the 
synchronization of the stroke modification and ribbon breaking functions 
provided by the present invention. 
Each stroke modification cycle may be defined as the time in which the path 
of the traverse stroke of the traversing yarn guide is shortened according 
to a predetermined law, from the maximum path of the traverse to a minimum 
path of the traverse, and then again lengthened to the maximum path of 
traverse. Thus, a number of modified strokes may occur within each stroke 
modification cycle. It is also possible and advantageous, to operate the 
traverse system with an intermediate traverse stroke, which is slightly 
narrowed or reduced, rather than at the maximum traverse stroke which 
substantially corresponds to the length of the yarn deposited on the 
package. This narrowing is particularly useful during the rest times 
between two stroke modification cycles. The narrowing, i.e., half the 
difference between the maximum traverse stroke and the intermediate 
traverse stroke preferably amounts to between about 20 and 50 percent of 
the smallest stroke modification cycle. 
Another possibility for obtaining a variation of the traverse stroke in 
accordance with the present invention resides in the fact that the package 
may be built with a so-called displacement of the stroke. In a stroke 
displacement, the length of the traverse stroke remains constant, but the 
traversing yarn guide is displaced relative to the package. Such 
displacement may occur either periodically, or after predetermined 
intervals and over a predetermined period of time. Also, the present 
method permits the formation of a package which consists of alternating 
soft and hard wound layers. For this purpose, there may be another 
stepwise variation of the maximum length of the yarn deposit, which is 
analogous to the above described method by which the large and small 
stroke modification cycles occur in steps and preferably within the 
individual yarn deposit segments.

Referring more particularly to the drawings, it will be understood that the 
present invention relates to a method and apparatus for winding textile 
yarns which includes means for supporting and rotating suitable package 
cores to wind a textile yarn therearound at a substantially constant rate, 
and a traversing yarn guide for guiding the yarn onto the rotating package 
core. Such textile winding apparatus are well known to persons skilled in 
the textile arts. 
In accordance with the present invention, the winding apparatus is provided 
with a controllable stroke reduction means, means for continuously varying 
the traverse motion speed of the traversing yarn guide, and control means 
for controlling the stroke reduction means and traverse speed varying 
means according to a predetermined program, and so as to provide a desired 
package configuration which has desirable unwinding characteristics. A 
specific embodiment of the apparatus is described below in conjunction 
with FIGS. 7 and 8. 
FIG. 1 illustrates the motion diagram of a winding method in accordance 
with one embodiment of the present invention. The upper portion of FIG. 1 
is a diagram illustrating that the traverse speed nC is continuously 
varied about a mean value nCM, for the purpose of breaking the repeating 
patterns or ribbons. The lower portion of FIG. 1 is a diagram which 
illustrates the stroke modification over time T, which preferably proceeds 
concurrently with the ribbon breaking, and so as to have a positive effect 
on the yarn tension. 
The stroke modification as illustrated includes the shortening of the 
traverse stroke H. In the case of cylindrical packages with straight or 
square front ends, the largest traverse stroke corresponds substantially 
to the package length. In the case of biconical packages, which have 
conical ends, the largest traverse stroke corresponds to the length of the 
yarn deposited on the package, note FIG. 2. In the context of the present 
description, the traverse stroke H may be also described as the stroke of 
the traversing yarn guide. The segmented arrows respectively indicate the 
position of the reversal points U of the traversing yarn guide, and thus 
indicate the contraction A of the traverse stroke H measured from the 
abscissa. A few such reversal points U are indicated in FIG. 1. In the 
case of a biconical package, the contraction A on one end of the package 
is half the difference between the greatest and the smallest stroke of the 
traversing yarn guide within a stroke modification cycle, which may also 
be described as a modified stroke. 
The method of the present invention involves the step of controlling the 
traverse of the yarn in a recurrent series of yarn deposit intervals as 
indicated in the lower portion of FIG. 1. Each such interval is divided 
into a number of yarn deposit segments, with two such segments being 
illustrated and advantageous. During the first yarn deposit segment of 
each interval, the length of the strokes H is progressively decreased to a 
relatively large contraction A max/max, which is the point of the greatest 
modified stroke, and the stroke is then progressively increased to define 
a stroke modification cycle. In addition, the first yarn deposit segment 
consists of several such stroke modification cycles, with successive 
cycles having different maximum contractions A. Very good results are 
achieved, when three such stroke modification cycles occur during the 
first yarn deposit segment, with the greatest modified stroke, i.e., the 
greatest contraction A max/max equaling 19.2 mm, and the smallest maximal 
contraction A max/min equaling 13.8 mm. Similarly, good results are 
achieved with four stepwise variations. During this yarn deposit segment, 
the smallest modified stroke A max/min should equal at least about 50 
percent, and preferably more than 60 percent of the greatest modified 
stroke A max/max. 
The first yarn deposit segment having large stroke modification cycles is 
followed by the second yarn deposit segment having relatively small stroke 
modification cycles. The two yarn deposit segments preferably have about 
the same duration, so that the yarn is wound in layers of about the same 
thickness during the two segments. However, it is possible to vary the 
thicknesses of these two layers, by which the hardness or softness of the 
package can be influenced. 
During the second yarn deposit segment of each interval, the stroke 
modification cycles are again varied by steps between A min/max and A 
min/min. As illustrated in FIG. 1, several groupings of stroke 
modification cycles may be employed, with the cycles of each grouping 
having the same magnitudes. Also, it is preferable that the smallest cycle 
A min/min of the small stroke modification cycles should amount to at 
least 50 percent, and preferably more than 60 percent of the largest of 
the small stroke modification cycles A min/max. In addition, the small 
stroke modification cycles A min are preferably less than about one third 
of the large stroke modification cycles A max, and preferably less than 
one fourth of the large cycles. Here again, the possibility of variations 
in these parameters may be employed to influence both the hardness of the 
package and its unwinding properties. 
As further indicated in the diagrams of FIG. 1, the stroke modification 
cycles occur synchronously with the ribbon breaking process, and the 
individual yarn deposit segments alternate one after another without an 
intervening rest time. To this end, the contraction speed of the stroke 
modification cycles from one yarn deposit segment to the next is so 
coordinated that a synchronization is obtained with the cycle of the 
ribbon breaking. The contraction speed of the stroke modification cycle is 
the shortening of the stroke of the traversing yarn guide per one 
reciprocal movement, i.e. double stroke, of the traversing yarn guide. The 
contraction speed is proportional to the angle of inclination or lead of 
the zig-zag lines shown in FIG. 1, which indicate the respective stroke 
reversal points U of the traversing yarn guide. Similarly, the lengthening 
speed is the increase of the stroke of the traversing yarn guide per one 
double stroke of the traversing yarn guide, and is proportional to the 
angle of inclination of the descending leg of the illustrated cycles. 
As the yarn deposit segment with the small stroke modification cycles 
proceeds, a switchover to a stroke modification cycle with the next 
smaller cycle occurs concurrently with a change in direction in the ribbon 
breaking cycle. In addition, during the period of time a ribbon breaking 
cycle is operative, the extent of the modified strokes remains constant. 
A biconical package formed in accordance with the method of the present 
invention, is illustrated schematically in FIG. 2. The package consists of 
a plurality of different built-up layers, with six such layers being 
illustrated. The wound layers which are produced during the yarn deposit 
segment of large stroke modification cycles have highly flattened but soft 
ends. These layers are illustrated by cross hatching. The wound layers 
which are produced during the yarn deposit segments having relatively 
small stroke modification cycles have hard ends, and are illustrated by 
section hatching. As can be seen, these hard wound layers substantially 
fill each of the flattened end areas of the previously wound layers, so 
that substantially hard wound layers come to lie and cover the ends of the 
package. It will also be noted that the package illustrated in FIG. 2 is 
biconically wound, and incorporates the modification of the invention 
illustrated in FIG. 3. 
The process illustrated in FIG. 3 differs from that of FIG. 1 only in that 
a further contraction B of the traverse stroke is superimposed upon the 
contractions A resulting from the stroke modification cycles. As the 
winding process proceeds, the contraction B increases proportionally to 
the build of the package, and so that the length of the yarn deposit on 
the package is progressively reduced in proportion to the package size. 
FIG. 4 is a motion diagram of another winding process in accordance with 
the present invention. The illustrated method has the advantage that the 
yarn layers which are produced in the yarn deposit segment of relatively 
large stroke modification cycles, and as a result have relatively soft 
ends, are very thin. After this yarn deposit cycle, the thin layers are 
bound in and held in place during the immediately following yarn deposit 
segment with relatively small stroke modification cycles. As a result, the 
homogeneity of the package with respect to its hardness can be improved to 
a further extent as compared to the package of FIG. 2. 
The lower portion of the diagram of FIG. 4 illustrates the end of the 
traverse stroke H. The upper half shows the traversing speed nC, in terms 
of double strokes per minute. As can be seen in the lower half of FIG. 4, 
the traverse stroke H varies continuously in its length. In addition, a 
uniform contraction B of the traverse stroke proceeds in time, which is 
necessary to produce a biconical package. It should here be noted that 
this contraction is in general identical on both ends of the package, so 
that a package is formed which is symmetrical to its centrally located 
normal plane. 
FIG. 4 also illustrates that contractions A as described above also 
proceed, and which result from the control of the traverse of the yarn 
guide in a recurrent series of yarn deposit intervals. The intervals are 
divided into two segments, with the first segment having a single 
relatively large stroke modification cycle A max and the second segment 
having a number of relatively small stroke modification cycles A min. The 
first and second segments alternate continuously. The small stroke 
modification cycles are identical within each of the second segments, and 
there are rest times between the stroke modification cycles of the second 
segment in which the traverse stroke is not shortened for the purpose of 
stroke modification. The largest contraction length of the large stroke 
modification cycles, i.e., the maximum modified stroke, is indicated at A 
max/max. In this embodiment, the large stroke modification cycles do not 
remain uniform, but decrease in steps, with the minimal large stroke 
modification cycle being indicated at A max/min. 
The largest small contraction length, i.e., the maximum small stroke 
modification cycle is indicated at A min/max. The lower half of FIG. 4 
also illustrates that the small stroke modification cycles similarly 
decrease in steps, with the minimum small stroke modification cycle being 
indicated at A min/min. 
The rest times between the small stroke modification cycles are of such a 
duration that the time ratio TG/TK is between about 1.8 and 1.2. A 
preferred value is about 1.5. TG represents T max in FIG. 4, which is the 
duration of the first yarn deposit segment having a single large stroke 
modification cycle (A max), and TK represents T min in FIG. 4 which is the 
duration of the second yarn deposit segment having small stroke 
modification cycles, less the rest time between the small stroke 
modification cycles. Thus TK is the sum of the individual stroke 
modification cycles within the second segment. 
As can further be seen in the lower half of FIG. 4, the contraction of the 
large stroke modification cycles between A max/max and A max/min, and the 
contraction of the small stroke modification cycles between A min/max and 
A min/min proceed in the same manner. As a result, A max/max and A min/max 
follow each other directly, and similarly A max/min and A min/min follow 
each other directly. 
As also will be noted in FIG. 4, the change of the traversing speed for the 
purpose of breaking a ribbon is synchronized with the contraction of the 
traverse stroke, so that the peak of the large stroke modification cycles 
coincides with the maximum traversing speed, whereas the minimum of the 
traversing speed is in the mid point of the second yarn deposit segment 
having small stroke modification cycles (A min). This synchronization 
permits the increase of the traversing speed for the purpose of ribbon 
breaking to be compensated by lowering the traversing speed which results, 
at a given rate of double strokes, from the contraction of the traverse 
stroke. In addition, change of the traversing speed for ribbon breaking 
purposes as is plotted in dashed lines I on the right side of the upper 
portion of the diagram, may be avoided. Such an asymmetrical law of motion 
has the disadvantage that the traversing speed is slowly reduced, and that 
there is a risk that possible ribbon areas may be passed very slowly, 
which in turn would not effectively eliminate the ribbon symptons. 
Preferably, the contraction length of the large stroke modification cycles 
A max ranges between about 10 to 20 mm. The contraction length of the 
small stroke modification cycles A min is between 2 and 5 mm. It should 
also be noted that in the course of a winding operation the stroke 
modification cycles need not remain uniform. In particular, the duration 
of the contraction legs may be increased. However, the time ratio TG/TK as 
defined above preferably remains constant. 
Another embodiment of the present invention is illustrated in conjunction 
with FIG. 5. This embodiment is characterized in that a change of the 
contraction and lengthening speeds of a stroke modification cycles permits 
the time ratio TG/TK to be not only predetermined, but also that a portion 
of the rest time to be predetermined. Further, the stroke modification 
cycles may be synchronized with the ribbon breaking in a desired fashion. 
The lower portion of the diagram again shows that a constant contraction B 
of the traverse stroke occurs in time, so as to produce a biconical 
package. There are also the contractions A which are defined by the stroke 
modification cycles. The stroke modification cycles are again divided into 
two segments of differing magnitude, which alternate constantly. The yarn 
deposit segment T max with a relatively large stroke modification cycle is 
followed by the yarn deposit segment T min having a relatively small 
stroke modification cycle and a rest time TT. The duration of T max is 
predetermined not only by the magnitude of the maximum modified stroke, 
but also by the selection of the contraction and lengthening speeds of the 
cycle. The duration of the stroke modification cycle within the second 
segment, i.e. T min minus TT, is similarly predetermined by a 
corresponding selection of the contraction and lengthening speeds in such 
a manner that there is a desirable synchronization with the ribbon 
breaking. The diagram of the ribbon breaking is shown in the upper half of 
FIG. 5, with the zig-zagged line indicating the traverse speed which is 
symmetrically varied about a mean traversing speed nCM. The parameters of 
the stroke modification are adapted so that the maximum modified stroke 
coincides with the highest traversing speed, and the end of each small 
stroke modification cycle coincides with the lowest traversing speed. As 
previously noted, this synchronization of ribbon breaking and stroke 
modification achieves a desirable uniformity of the yarn tension. 
The variability of the contraction and/or lengthening speeds of the stroke 
modification cycles with respect to each other, or from one yarn deposit 
segment to another, also results in the advantageous possibility of 
adapting the time sequence of the ribbon breaking and the time sequence of 
the stroke modification to each other. 
It has also been found that a particularly favorable and uniform package, 
with uniform hardness and good unwinding properties, may be achieved by an 
arrangement wherein the stroke modification does not always proceed from 
the traverse stroke ends which determine the length and the form of the 
package. Rather, the ends of the traverse stroke, i.e. the outer limits of 
the traverse stroke, are intermittently displaced in a direction toward 
the center of the package, preferably by an amount between 1 and 10 mm. In 
so doing, the stroke modification, or contraction length in the context of 
the present invention, forms from the displaced end of the traverse 
stroke. As a result, the outer limits of the yarn length deposited by the 
traversing system are temporarily narrowed or reduced. This narrowing 
preferably occurs during the yarn deposit segments having the small stroke 
modification cycles. It is also possible to displace the inner limits of 
the traverse stroke in the same or opposite direction, or to leave the 
inner limits. 
FIG. 6 illustrates a method of traversing the yarn which incorporates such 
a narrowing of the traverse stroke relative to the length of the yarn 
deposited on the package. Here, both the outer and inner limits of the 
traverse stroke are displaced, and as a result, it is provided that the 
modified stroke, which is the difference in length between the inner and 
outer limits of the traverse stroke, can be carried out over varying areas 
of the package length, and with changing magnitudes. 
The lower half of FIG. 6 again illustrates the end area of the traverse 
stroke H. The upper half illustrates the traversing speed nC, in terms of 
double strokes DH per minute. The method of ribbon breaking, i.e. the 
variation of the traversing speed nC for ribbon breaking purposes, is the 
same as the method described in conjunction with FIGS. 4-5. 
Again referring to the lower half of FIG. 6, the traverse stroke H varies 
continuously in length. On the one hand, there is the constant contraction 
B which occurs with time which is required to produce a biconical package. 
This contraction B permits the determination of the outer limit of the 
traverse stroke in FIG. 6, and it should be noted that the contraction B 
is the same on both ends of the package so that a package is formed which 
is symmetrical to a center normal plane. The traverse stroke between these 
ends of the package is described as the yarn deposit length, and this yarn 
deposit length or contraction B also determines the ends and the 
configuration of the package. 
In FIGS. 1, and 3-5, a method is described in which the traverse stroke is 
shortened on the basis of the yarn deposit length, whereas in FIG. 6 the 
yarn deposit length is narrowed, i.e. the outer limit of the traverse 
stroke is periodically located inwardly by an amount indicated at V. In 
FIG. 6, the stroke modification cycles are again divided into first and 
second yarn deposit segments as described above, wherein A max is the 
segment having large stroke modification cycles and A min within the 
segment having relatively small stroke modification cycles. Also, the two 
yarn deposit segments alternately follow each other, and during the first 
yarn deposit segment a large stroke modification occurs, and in the second 
yarn deposit segment several small stroke modification cycles occur. The 
maximum contraction length of the large cycles is indicated at A max/max, 
and the maximum small contraction length, i.e. the maximum contraction of 
the relatively small cycles is indicated at A min/max. As in the method of 
FIG. 5, the inner limit of the traverse stroke is continuously varied. 
In the method of FIG. 6, the yarn deposit length is also temporarily 
narrowed or reduced, and thus the outer limit of the yarn deposit is 
displaced inwardly, with the yarn length initially being considerably 
narrowed after the first yarn deposit segment having the large stroke 
modification cycles. The amount V of the narrowing may for example amount 
to 8 mm measured at one end of the package. The following yarn deposit 
segment with the small stroke modification cycles then occurs on the basis 
of this narrowed yarn deposit length, with the traverse stroke being 
carried out over the entire narrowed yarn deposit length during the rest 
times TT. Next, a yarn deposit segment with a large stroke modification 
cycle follows, with the total contraction length being less than the 
contraction length of the preceding large stroke modification cycle. In 
the next yarn deposit segment having short cycles, the amount V by which 
the yarn deposit length is narrowed, is reduced for example to about 6 mm. 
The stroke modification occurs on the basis of this yarn deposit length, 
and the modified stroke of the relatively small cycles is less than the 
stroke of the small cycles of the preceding segment. 
During the following yarn deposit segments, the large stroke modification 
cycles, the small stroke modification cycles, and the narrowing V of the 
deposit length are further reduced. Such a length of stroke modification 
having a narrowed yarn deposit length may then be followed by a length of 
stroke modification as shown for example in FIGS. 4 or 5. 
FIG. 7 shows an apparatus for winding a yarn onto a package by the method 
of this invention. In this regard, reference is made to FIG. 3 of U.S. 
Pat. No. 3,730,448, and essentially identical German Pat. No. 19 16 508. 
The numerals of FIG. 3 of U.S. Pat. No. 3,730,448 have been increased by 
100 for designating identical parts in FIG. 7 of this disclosure. 
Generally, FIG. 7 illustrates a package 102 which is being wound on bobbin 
tube 101. The package is driven by friction roller 105 mounted on shaft 
106. The shaft is driven by motor 50 via a frequency inverter 51. The 
traversing mechanism is generally indicated at 107, and comprises a yarn 
guide 108 mounted on one arm of a toggle lever 109 which is pivotably 
mounted on pin 110. Pin 110 is fixed to slide 111 which is driven by shoe 
113 riding in a helical or spiral groove 114 of cam drum 115. The shoe 113 
extends through a slot in the guide plate 112, so that the slide 111 is 
reciprocated along a direction parallel to this axis of the drum 115 by 
rotation of the drum. A slide block 117 is pivotally mounted to the other 
arm of the toggle lever by the pin 116, and a guide rail 118 is provided 
for receiving the slide block 117. The guide rail 118 is pivotably mounted 
on pivot axis 120, and a spring 122 extends between one end of the rail 
and the machine frame for biasing such end in a downward direction. 
As will be apparent, the traverse stroke of yarn guide 108 depends on the 
inclination of guide rail 118. For defining the inclination of guide rail 
118, there is provided a cam head 135 which is mounted on a bar 126. Bar 
126 preferably serves a series of side-by-side winding stations and has a 
central drive as further described below. The working surface 136 of cam 
head 135 acts on the guide rail 118 through the transmission cam 128 and 
the transmission element 129, and thereby determines the inclined position 
of the guide rail and hence the length of the traversing stroke. 
Transmission element 129 serves to produce packages 102 having biconical 
ends by diminishing the traverse stroke in dependency on the increasing 
diameter of package 102, and a further description of the element 129 may 
be obtained from the above-mentioned U.S. Pat. No. 3,730,448. For making 
packages having flat ends, the guide rail 126 is pulled and adjusted to 
the left in the manner described below, so that the working surface 137 of 
cam head 123 cooperates with the shoulder 138 on guide rail 118. In this 
position, transmission element 129 is out of operation because of the 
increased inclination of guide rail 118. 
The left hand portion of FIG. 7 schematically illustrates a preferred 
embodiment of means for driving and adjusting the bar 126. This drive 
means includes a program unit 18, an output-to-current converter 19, and 
an electromagnet 20, the magnetic force of which is transmitted to 
hydraulic control valve 21, to a spring 22, and to the cylinder and piston 
unit 23. The piston rod 24 of the unit 23 is connected to the end of 
adjusting bar 126. The assembly consisting of magnet 20, control valve 21, 
spring 22, and cylinder and piston unit 23 is mounted on a support slide 
25. 
As seen in FIG. 8, a unitary housing 26 is provided which mounts the 
electromagnet 20, the hydraulic control valve 21, the spring 22, and the 
cylinder and piston unit 23. The iron core 27 of magnet 20 acts upon the 
rod 28 of control valve 21. The rod 28 has three collars 29, 30, 31 for 
controlling the fluid connections between hydraulic pump 32, reservoir 33 
and the rear 34 of the cylinder and piston unit 23. The spring 22 acts 
upon the other side of rod 28 via a suitable support plate 35, and the 
other end of the spring 22 acts upon support plate 36 and piston 37 of 
cylinder and piston unit 23. The piston 37 is a differential piston, since 
the front face 38 is diminished by the area of piston rod 24. The front 
face 38 of piston 37 is permanently connected by duct 39 to pump 32. The 
rear 34 of piston 37 is connected to either the pump 32 via duct 40 or to 
reservoir 33 via duct 41. This connection is controlled by movement of 
collar 30 which connects duct 41 to either one of duct 40 and 42. 
One branch 43 of duct 42 leads to the rear 34 of the cylinder and piston 
unit 23. The other branch 44 serves to equalize the pressure on both sides 
of the hydraulic control valve. It should be noted that piston 37 in its 
outer left hand position lies upon a shoulder 45 of the cylinder. Thereby, 
the outermost stroke ends of the package are mechanically defined. 
As also shown in FIG. 8, the housing 26 is supported by a frame 25 which is 
mounted on two parallel rods 49. The rods 49 are in turn slidably mounted 
to the supports 46. The frame 25 is movable between two positions, the one 
being defined by the stop 47, and the other being defined by flange 48 
which is adapted to engage the adjacent support 46. 
In operation, any of the winding programs as shown in the preceding 
drawings and diagrams may be stored in the program unit 18. The program 
unit produces an output signal which corresponds to a certain stroke 
length according to one of the traverse programs provided by this 
invention. This output signal is transformed by transducer 19 into an 
electrical current activating the magnet 20. The magnetic force is 
transmitted to piston rod 28 of control valve 21, to spring 22 and to 
piston 37 and piston rod 24. 
The function of the control means may be described by reference to the 
position of the control valve 21 as shown in FIG. 8. A certain output 
signal may be related to a current generating a force on iron core 27 
pushing the piston rod 28 with collar 30 into the shown position. In this 
position, duct 42 is closed. Therefore, the front face 38 of the piston 37 
is acted upon by the fluid flow from pump 32, and the rear 34 is closed. 
Consequently, piston 37 and piston rod 24 are locked in the shown 
position. 
The change of the output signal of program unit 18 causing an increasing 
current to electromagnet 20 will lead to an increasing force of iron core 
27 to the right. Consequently, duct 42 will be opened to duct 41 leading 
to the reservoir 33. This will cause a pressure drop on rear 34 of the 
cylinder and piston unit 23, and the pump pressure on the front face 38 
will shift the piston 37 and rod 24 to the left. Thereby the spring 22 
will be compressed and the spring force will tend to shift rod 28 of 
control valve 21 to the left with a tendency of collar 30 to close duct 42 
with respect to the duct 41 and the reservoir. Thus, the force generated 
by the iron core 27 will be balanced by spring 22. If in turn the current 
is decreased, spring 20 will shift rod 28 to the left, and collar 30 will 
open duct 42 to branch 40 leading to the pump. Now, the pump pressure will 
act on both sides of piston 37. Since the active area on rear 34 is 
greater than active area on front face 38, the piston 37 will be moved to 
the right. Thereby, spring 22 is expanded and the spring force acting on 
rod 28 is released. Now, the magnetic force on iron core 27 will have a 
tendency to move rod 28 to the right and to cause collar 30 to close the 
connection between duct 42 and pump branch 40. 
It will be apparent from the above description that each input current to 
electromagnet 20 is related to a certain position of the piston 37, rod 24 
and consequently to bar 126 and the inclination of the guide rail 118. 
Thereby, the output of program unit 118 controls the stroke length of yarn 
guide 108. 
As mentioned above, housing 26 is mounted to a frame 25, and in the 
illustrated position where flange 48 abuts stop 47, the housing 26 and bar 
126 are adjusted such that cam head 135 on bar 125 is active to control 
the inclination of guide rail 118. In this position of frame 25 and 
housing 26, biconical packages 102 are thus produced. In the other 
position of the frame 25, where flange 48 abuts support 46, cam head 123 
of bar 126 cooperates with shoulder 138 on guide rail 118, and packages 
102 having flat ends are produced. 
In FIG. 7 it is also indicated that shaft 106 of friction roller 105 is 
driven by motor 50. Motor 50 is controlled by the output of the frequency 
converter 51. Cam drum 115 is driven by a motor 52 and the motor 52 is 
controlled by the program unit 53 which causes a changing traverse motion 
speed to prevent undesirable pattern formations in the yarn winding. 
Frequency converter 51 is, on the one hand, controlled by the output 
signal of program unit 18 representing the stroke modification pursuant to 
this invention, and on the other hand by the output of program unit 53 
representing the change of the traverse motion speed. Thereby, any 
variation of the tension of the yarn to be wound on package 102 caused by 
either stroke modification and/or change of traverse motion speed can be 
compensated by slight fluctuations of the peripheral speed of friction 
roller 105 and package 102. Timer 54 coordinates the outputs of the 
program units 18 and 53 for the stroke modification and the traverse speed 
modification in accordance with this invention, and particularly the above 
diagrams. 
From the above description, it will be apparent that the method and 
apparatus of the present invention is adapted to provide a stroke 
modification in the area of the package end where it is necessary or 
desired to obtain a good, uniformly hard package build up, and good 
unwinding properties. 
In the drawings and specification, there has been set forth a preferred 
embodiment of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.