Apparatus for cross-winding a traveling yarn

In a yarn cross-winding apparatus of the type wherein a driven winding drum peripherally drives a bobbin and a traversing yarn guide applies yarn in a cross-wound fashion to the bobbin periphery, the problem of increased yarn winding density at the opposite ends of the bobbin is avoided by forming opposite peripheral end areas of the winding drum, whereat cross-winding yarn reversal occurs, with oppositely angled intersecting grooves forming a plurality of relatively staggered yarn engagement locations over the circumferential and axial extent of the peripheral end areas of the drum. The yarn engagement locations guide the yarn onto the bobbin at its opposite ends to resist deviation of the yarn from its cross-winding angle at the location of yarn cross-winding reversal.

BACKGROUND OF THE INVENTION 
The present invention relates to apparatus for cross-winding a traveling 
yarn on a bobbin, and more particularly, to yarn winding apparatus of this 
type wherein the bobbin is peripherally driven by a winding drum and a 
yarn guide traverses the traveling yarn along the bobbin to apply the yarn 
thereon in a cross-wound fashion. 
In yarn cross-winding apparatus of the aforementioned type, a common 
disadvantage is the tendency of yarn to be wound more densely at the ends 
of the bobbin, which is particularly problematic in the production of dye 
bobbins wherein the yarn winding density should be as low as possible to 
facilitate the yarn dyeing process. To achieve this objective, yarn should 
be wound with an appropriately sharp crossing angle. However, the use of a 
relatively sharp crossing angle for this purpose tends to cause the yarn 
to draw axially inwardly with respect to the lengthwise extent of the 
bobbin at its opposite ends whereat the reversal of yarn cross-winding 
occurs. As a result, the yarn windings compact at the axial ends of the 
bobbin so that the effective axial extent of the yarn windings on the 
bobbin is shorter than that prescribed by the traversing yarn guide and, 
in turn, only the central extent of the yarn windings on the bobbin have 
the desired low density with the axial ends of the bobbin being more 
densely formed than desirable. Further, this problem cannot be compensated 
by enlarging the yarn traversal, which only serves to form the densified 
windings of yarn at a greater spacing from one another. The yarn windings 
at the opposite ends of the bobbin still tends to move axially inwardly 
with a relatively flattened reversal angle so that the yarn is still more 
densely wound at the bobbin ends. 
West German Offenlegungsschrift 22 42 507 discloses a yarn winding 
apparatus of the aforementioned type wherein the winding drum which 
frictionally drives the bobbin is formed with a central peripheral area 
which is substantially smooth and with peripheral areas at the opposite 
ends formed with concentric or helical grooves to assist in applying the 
yarn to the ends of the bobbin during winding. However, the use of such an 
arrangement of grooves on the winding drum requires that the winding drum 
and the traversing yarn guide must be synchronized with one another so 
that a groove of the winding drum is properly located at the point of yarn 
contact with the bobbin when the traversing yarn guide reaches each 
opposite end of its traversing movement. As a result, certain set 
translation ratios must be maintained between the winding drum and the 
traversing yarn guide and, in turn, the possible range of selective 
adjustment of the desired yarn cross-winding angle is reduced. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide an improved 
winding drum for a yarn cross-winding apparatus of the aforementioned type 
which provides the advantage of applying yarn to a bobbin without 
significant deviation from the desired yarn cross-winding angle at the 
bobbin ends while also enabling a reasonably large range of selective 
adjustment of a desired cross-winding angle. 
Briefly summarized, the winding drum of the present invention has a 
generally smooth peripheral area centrally along the winding drum with two 
peripheral areas spaced from one another at opposite ends of the central 
peripheral area for contact respectively with opposite end areas of the 
bobbin whereat reversal of the cross-winding of the yarn occurs. Each of 
the spaced peripheral areas defines a plurality of yarn engagement 
locations spaced with respect to one another over the circumferential and 
axial extents of the spaced peripheral area for guiding the yarn onto the 
bobbin at its opposite end areas to resist deviation of the yarn from its 
cross-winding angle at the location of yarn cross-winding reversal. In 
this manner, at any translation ratio between the winding drum and the 
yarn guide and any cross-winding of the yarn, the yarn will automatically 
enter an appropriate yarn engagement location at the respective ends of 
the winding drum upon each reversal of the traversing movement of the yarn 
guide at each opposite end of the bobbin without any need for any 
relatively precise correlation between the translation ratio and the 
arrangement of the yarn engagement locations. 
Preferably, each of the spaced peripheral areas of the winding drum has 
respective peripheral grooves oppositely formed obliquely to the axis of 
the winding drum for intersecting one another so that each intersection of 
the grooves forms a respective yarn engagement location. In the preferred 
embodiment, two sets of such grooves form each peripheral area, one set of 
grooves extending parallel to one another at a common oblique angle to the 
drum axis and the other set of grooves extending parallel to one another 
at a common oblique angle substantially oppositely to that of the first 
set of grooves for crossing relation therewith. The yarn engagement 
locations at the groove intersections may be optimized for any desired 
yarn count by suitable adjustment of the width and depth of the groove as 
well as the angularity of the lateral walls defining each groove. 
Moreover, the winding geometry of the bobbin may be influenced by the 
positioning of the yarn engagement loctions. This result is particularly 
possible in that it is not necessary that the two sets of parallel grooves 
by formed at the same oblique angle relative to the axis of the winding 
drum. However, as will be understood, if the angle of inclination of the 
first set of parallel grooves is inversely equal to the angle of 
inclination of the second set of parallel grooves to the bobbin axis, the 
yarn engagement locations are formed precisely in a geometric diamond 
pattern about the periphery of the winding drum. As a result, the yarn 
engagement locations are arranged in a series of axially extending rows 
which are parallel to one another and to the axis of the winding drum. At 
the same time, the yarn engagement locations of each row are staggered 
axially with respect to each adjacent row. 
Because of this arrangement of the yarn engagement locations, as the 
traversing yarn guide passes each grooved peripheral area at the 
completion of each traversing stroke of the guide, the yarn immediately 
engages automatically in a yarn engagement location depending upon the 
position of the yarn guide, even though the appropriate yarn engagement 
location may not be located exactly adjacent the yarn as it exits the yarn 
guide. Accordingly, it is not necessary to synchronously coordinate the 
yarn guide are the yarn engagement locations on the winding drum to insure 
that a yarn engagement location is always located at the precise point of 
yarn application to the bobbin when the yarn guide reverses its traversing 
movement. 
In the preferred embodiment, the spaced peripheral areas of the winding 
drum are provided with a coating of a frictional material in which the 
intersecting grooves are formed to produce the yarn engagement locations. 
Typically, the frictional coating is a thermoplastically deformable 
material rather than a metal so that a more economical formation of the 
grooves in the frictional coating is possible. For example, the 
application of the frictional coating and the formation of the grooves and 
yarn engagement locations may advantageously be performed in one step.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the accompanying drawings, a yarn cross-winding apparatus 
according to the preferred embodiment of the present invention is shown in 
pertinent part, conventional features and components of the apparatus 
being omitted for sake of simplicity. Basically, the apparatus includes a 
winding drum 4 mounted on a shaft 5 which is driven in conventional 
fashion by a drive motor or other suitable means (not shown). A bobbin 
tube 2 is rotatably supported in a bobbin holder 3 of conventional 
construction. A yarn 16 to be wound about the bobbin tube 2 is trained 
through a yarn guide 14 mounted on a yarn guide rod 15 which is driven by 
a drive motor or other suitable drive (not shown) to actuate a traversing 
movement of the yarn guide 14 back-and-forth along the length of the 
bobbin tube 2. At the start of a winding operation, the bobbin tube 2 is 
held by the bobbin holder 3 in peripheral surface contact with the winding 
drum 4 to be driven thereby simultaneously with the traversing of the yarn 
guide 14 to initiate the cross-winding of the yarn 16 on the tube 2. As 
the cross-windings of the yarn 16 build progressively on the bobbin tube 
2, as indicated at 1, the bobbin holder 3 maintains the yarn windings 1 in 
surface driven contact with the winding drum 4. 
As best seen in FIG. 1, a series of intersecting grooves 9, 10 are formed 
in the periphery of the winding drum 4 in the areas of the opposite ends 
6, 7 thereof which respectively contact the opposite ends of the would 
bobbin 1 whereat the reversal of the cross-winding of the yarn 16 under 
the traversing movement of the yarn guide 14 occurs. The predominant 
lengthwise area 8 of the winding drum 4 intermediate the end areas 6, 7 
has a smooth periphery substantially identical in cicumference and 
diameter to the outermost circumference and diameter of the non-grooved 
portions of the end areas 6, 7. Preferably, the end areas 6, 7 of the 
winding drum 4 have a peripheral coating 13 of a frictional material which 
may be, for example, a plastic, rubber or a rubber-like material. The 
frictional coating 13 permits the grooves 9, 10 to be produced during the 
step of forming the coating 13 on the ends 6, 7 of the winding drum 4. By 
way of example, the coating 13 may be press-fitted or shrink-fitted onto 
the ends 6, 7 of the winding drum 4. 
As shown in FIG. 1, the grooves 9 are formed at each end of the winding 
drum 4 as a series of spaced parallel grooves each extending at an obtuse 
angle inclined rightwardly with respect to the axis, i.e. the shaft 5, of 
the winding drum 4, while the grooves 10 are likewise formed at each end 
of the winding drum 4 as a series of spaced parallel grooves extending at 
an obtuse angle leftwardly with respect to the axial shaft 5 of the 
winding drum 4. As a result, the two sets of parallel grooves 9, 10 
intersect at each end of the winding drum 4 to form a yarn engagement 
location 11 at each intersection. The spacing of the respective grooves 9, 
10 leave a plurality of knob-like projections 12 extending outwardly 
intermediate the yarn engagement locations 11. As shown, the respective 
obtuse angles at which the set of paralle grooves 9 and the set of 
parallel grooves 10 are formed are identical but inverse or opposite to 
one another relative to the axis of the winding drum 4. Additionally, the 
relative spacing of the grooves 9 and the relative spacing of the grooves 
10, as shown is substantially identical. Accordingly, the yarn engagement 
locations 11 are arranged at each end 6, 7 of the winding drum 4 in linear 
rows which extend axially relative to the winding drum 4 in parallel 
relation to one another and at circumferential spacings about the 
periphery of the drum, leaving the knob-like projections 12 in a diamond 
pattern with each projection 12 having a substantially diamond-shaped 
cross section. Of course, as will be recognized, the respective angles at 
which the grooves 9 and the grooves 10 are formed may be different from 
one another and the spacing of the grooves, as well as their width and 
depth, may be varied as desired, whereby the orientation and arrangement 
of the yarn engagement locations 11 and the size and shape of the 
knob-like projections 12 would be correspondingly varied. Further, the 
configuation of the knob-like projections 12 may be varied by subsequent 
processing operations to form the projections 12 with any desired shape, 
for example, a round or elliptical cross-section as well as a cylindrical 
or conical contour. 
The width and depth of the grooves 9, 10 should be selected in relation to 
the count of the yarn 16 with which the winding drum is to be untilized, 
so that the grooves 9, 10 are of sufficient size for easy entry and exit 
of the yarn 16. While the cross-section of the grooves 9, 10 may be 
considerably larger than the cross-section of the yarn to achieve this 
purpose, the yarn may tend to catch or lodge within the grooves if the 
cross-section of the grooves is the same as or less than the yarn 
cross-section. 
The operation of the present invention may thus be understood. In FIG. 1, 
the traversing yarn guide 14 is shown in the rightwardmost point of its 
traversing path adjacent the rightwardmost end 6 of the winding drum 4 
whereat the yarn guide 14 has completed its rightward traversing movement 
and is reversing to traverse leftwardly with respect to the winding drum 4 
and the wound bobbin 1. As the yarn 16 exits the guide 14, the yarn 16 is 
directed between two of the knob-like projections 12 and thereby the 
winding direction of the yarn 16 changes at the corresponding yarn 
engagement location 11 between the projections 12 as the guide 14 reverses 
its traversing direction. The two knob-like projections 12 substantially 
fix the disposition of the yarn 16 and prevent it from being drawn axially 
away from the end of the wound bobbin 1 despite the leftward movement of 
the yarn guide 14 and the angular change in the winding direction of the 
yarn. As a result, the yarn 16 is deposited by the winding drum 4 onto the 
wound bobbin 1 in substantially the desired cross-winding pattern, thereby 
imparting a substantially uniform density to the entire body of yarn wound 
on the bobbin tube 2, which as aforementioned is particularly advantageous 
in the formation of dye bobbins. 
With reference now to FIG. 2, the yarn winding apparatus is shown as viewed 
along line II--II of FIG. 1, with the wound bobbin 1 and its bobbin holder 
3 in end elevation and the winding drum 4 in cross-section. As seen, the 
bobbin holder 3 acts through the bobbin tube 2 to hold the wound bobbin 1 
in peripheral surface contact with the winding drum 4. The winding drum 4 
along with its drive shaft 5 is shown sectioned in the area of its 
rightward end 6, whereby the friction coating 13 about the end 6 of the 
winding drum, the intersections of the grooves 9, 10 in the friction 
coating 13 forming the yarn engagement locations 11, and the knob-like 
projections 12 can be seen. As in FIG. 1, the yarn guide 14 is shown at 
the completion of the rightward stroke of its traverse. The yarn 16 is 
directed tangentially to the winding drum 4 in contact with the grooved 
periphery at a yarn engagement location 11 in advance of the passage of 
the yarn 16 tangentially onto the periphery of the wound bobbin 1. As is 
apparent, the yarn 16 loops about a knob-like projection 12 and is thereby 
retained at the yarn engagement location 11 in the desired cross-wound 
disposition determined by the traversing movement of the yarn guide 14 so 
as to be deposited on the periphery of the wound bobbin 1 substantially in 
such disposition. Thus, as aforedescribed, the knob-like projections 12 
which define the yarn engaement locations 11 prevent the yarn 16 from 
undesirably being drawn axially inwardly away from the ends of the wound 
bobbin 1, which otherwise would occur in the case of a conventional 
winding drum 4 having an entirely smooth periphery. Of course, within the 
intermediate region of the traversing movements of the yarn guide 14 in 
the region of the smooth central area 8 of the winding drum 4, the guiding 
and application of the yarn 16 onto the wound bobbin 1 is controlled 
entirely by the yarn guide 14 in a usual manner. 
While the yarn winding apparatus of the present invention has herein been 
described with respect to a preferred embodiment thereof for winding a 
cylindrical cross-wound bobbin, it will be understood by those persons 
skilled in the art that a winding drum according to the present invention 
may also be utilized for winding conical cross-wound bobbins of any 
conicity. In such embodiments, it is contemplated to be abvantageous, 
because of the conicity of the bobbin, that the grooved peripheral areas 
at opposite ends of the winding drum have different arrangements of the 
yarn engagement locations from one another in order to accommodate the 
winding geometry of conical cross-wound bobbins. This may be achieved, for 
example, by differently positioning the parallel rows of grooves relative 
to the axis of the winding drum at the respective peripheral end areas 
thereof. 
It will therefore by readily understood by those persons skilled in the art 
that the present invention is susceptible of a broad utility and 
application. Many embodiments and adaptations of the present invention 
other than those herein described, as well as many variations, 
modifications and equivalent arrangements will be apparent from the 
reasonable suggested by the present invention and the foregoing 
description thereof, without departing from the substance or scope of the 
present invention. Accordingly, while the present invention has been 
described herein in detail in relation to its preferred embodiment, it is 
to be understood that this disclosure is only illustrative and exemplary 
of the present invention and is made merely for purposes of providing a 
full and enabling disclosure of the invention. The foregoing disclosure is 
not intended or to be construed to limit the present invention or 
otherwise to exclude any such other embodiments, adaptations, variations, 
modifications and equivalent arrangements, the present invention being 
limited only by the claims appended hereto and the equivalents thereof.