Method of producing a twisted yarn

A method of producing twisted yarn comprises precision doubling several single yarns in a precision assembly winder to form a precision package which is dyed or bleached. The yarn is thereupon twisted during withdrawal from the precision package.

LIST OF REFERENCES 
Applicants are aware of the disclosures of U.S. Pat. No. 4,020,998 
(corresponding to FR-A2 259 775), FR-A-2 283 976, NL-A-7501160, 
DE-A-2504403, GB-A-1491731, CH-A-594097, JP-A-50107239, SE-B-401163, 
SE-A-7500838 and DE-A-2537922. U.S. Pat. No. 4,020,998 discloses a method 
and an apparatus for winding bobbins preparatory to dyeing. FR-A-2 283 976 
discloses a bobbin dyeing apparatus. The other references are random 
examples of art in the field to which the present invention belongs. 
BACKGROUND OF THE INVENTION 
The present invention relates to a method of treating yarns, and more 
particularly to improvements in a method of producing a twisted yarn, 
especially a dyed or bleached yarn. 
In the making of dyed twisted yarns wherein the twisting operation is 
preceded by the step of doubling two or more single yarns, it is necessary 
to rewind the yarn three or four times, depending on the requirements 
regarding the run-off characteristics of the twisted yarn. The first 
rewinding operation takes place during doubling of two or more single 
yarns, the second rewinding operation takes place during twisting, and the 
third rewinding operation is carried out during lubricating which follows 
the dyeing step. If the twisted yarn is to exhibit exceptionally 
satisfactory run-off characteristics and should constitute a high-quality 
product, it is necessary to form a precision package upon completion of 
the twisting operation. 
Each rewinding of the yarn involves an additional expenditure and is likely 
to entail yarn breakage with the need for the making of additional knots 
which, in turn, create problems during further processing of the yarn. 
Furthermore, each rewinding operation invariably affects the quality of 
the surface of the yarn. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the invention is to provide a novel and improved method of 
treating yarns, especially of producing dyed or bleached twisted yarns, 
which necessitates fewer rewinding operations than the heretofore known 
methods. 
Another object of the invention is to provide a method which renders it 
possible to form a high-quality twisted yarn. 
A further object of the invention is to provide a method which renders it 
possible to effect a highly uniform dyeing of each and every portion of 
the yarn including the points where the sections of single yarns cross 
each other. 
An additional object of the invention is to provide a method which renders 
it possible to form a twisted yarn having a highly satisfactory surface, 
highly satisfactory run-off characteristics and fewer knots than a yarn 
which is twisted in accordance with heretofore known techniques. 
Still another object of the invention is to provide a yarn which is 
obtained in accordance with the above outlined method. 
An additional object of the invention is to provide a precision package of 
twisted or doubled yarn which is obtained in accordance with the above 
outlined method. 
One feature of the invention resides in the provision of a method of 
producing a twisted yarn. The method comprises the steps of precision 
doubling several single yarns to form a precision package, impregnating 
the precision package with a liquid medium (such as a dye liquor or a 
bleaching agent), and withdrawing and simultaneously twisting the thus 
impregnated yarn. 
The liquid medium can contain a dye liquor and a lubricating agent or a dye 
liquor and a softening agent. Alternatively, the yarn which has been dyed 
or bleached in the form of a precision package is contacted with a 
lubricating agent in the course of the twisting step. 
The method can further comprise the step of converting the twisted yarn 
into a precision package. 
Another feature of the invention resides in the provision of a precision 
package which is produced in accordance with the improved method, i.e., a 
precision package which contains several doubled single yarns or a 
precision package containing twisted yarn which has been bleached or dyed 
subsequent to the formation of a precision package consisting of several 
doubled single yarns. 
A further feature of the invention resides in the provision of twisted yarn 
which is produced in accordance with the above outlined method and 
constitutes a dyed or bleached doubled yarn, e.g., a precision package of 
such twisted yarn. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The improved method need not comprise more than three steps, namely a first 
step of precision doubling two or more single yarns to form a precision 
package, a second step of treating (especially impregnating) the precision 
package with a liquid medium, particularly a dye liquor (which can contain 
a lubricating agent or a softening agent) or a bleaching agent, and a 
third step of withdrawing and simultaneously twisting the dyed or bleached 
yarn. 
The precision doubling step involves the making of a homogeneous package 
having a constant winding ratio, a constant helix angle and uniform mutual 
spacing of the windings. The making of such precision package establishes 
optimal conditions for the dyeing or bleaching operation which can involve 
the outflow of a liquid medium through a hollow permeable core and 
simultaneous flow of such liquid medium inwardly from the exposed surfaces 
of the package. This will be readily appreciated since the dyeing or 
bleaching operation which constitutes a step of the improved method 
involves the step of contacting the liquid medium with several doubled 
single yarns prior to their twisting so that the crossing points which are 
formed in the course of the twisting operation contain yarn portions all 
of which have been dyed or bleached to the same extent. It has been found 
that the dyeing or bleaching of a doubled yarn is incomparably more 
uniform than if the dyeing or bleaching were to take place upon completion 
of the twisting step. The color shade of a dyed doubled yarn is 
surprisingly uniform from end to end. 
The density of a precision package exceeds considerably the density of a 
standard package. This renders it possible to increase the capacity of the 
yarn processing plant by between 30 and 40 percent without further 
investments and with pronounced reduction of the quantities of liquid 
medium. 
Another important advantage of the improved method is that the edge 
crimping of package flanges is eliminated or reduced to a minimum, and 
also that the percentage of waste due to deviations of density from the 
desired value is a small fraction of the percentage of waste which is 
produced if the dyeing or bleaching precedes the twisting operation. 
Since the making of a precision package entails an increase of density by 
up to 30 percent, the bulk of such package is a fraction of that of a 
standard package containing the same length of yarn. The making of a 
relatively small and compact precision package results in savings of 
energy in the course of the next-following (twisting) step. Still further, 
the yarn is subjected to lesser tensional stresses because the balloons 
are much smaller. Moreover, the precision doubling feed from the large 
spool diameter to the small diameter takes place without any noticeable 
reduction of yarn storage on the two-for-one spindle. 
The method further entails a substantial reduction of labor costs due to 
fewer and shorter periods of standstill, complete run-off and considerable 
length of the yarn and fewer knots. Moreover, the quality of the treated 
yarn is highly satisfactory, and the dyeing operation results in the 
making of voluminous round yarn which, when constituting an open-end yarn, 
is highly satisfactory for the making of stylish knit outer garments. 
Still another important advantage of the improved method is that it allows 
for substantial automation of plants for the making of dyed and twisted 
yarns.

EXAMPLE 
The first step involved the withdrawal of two or more open-end or ring-spun 
yarns in a precision assembly winder (also called doubler) to form a 
homogeneous precision package with a constant winding ratio and a constant 
helix angle as well as uniform spacing of the windings and a density 
exceeding by approximately 30 percent that of a random-wound bobbin. 
The second step was carried out immediately following completion of the 
first step and involved dyeing of the precision package. Such dyeing 
operation involved the utilization of a surprisingly small quantity of dye 
liquor. This is believed to be attributable to the much higher density of 
a precision package, i.e., to greater length of the yarn per unit volume. 
At any rate, the quantity of dye liquor per kilogram of yarn is much lower 
than in connection with the dyeing of twisted yarns. Furthermore, an 
autoclave can be used to dye 30-40 percent more yarn per cycle, without 
any additional investments, than in connection with the dyeing of twisted 
yarns. 
The second step can involve impregnating the precision package with a 
bleaching agent in lieu of dye liquor. 
The third step involved twisting of the doubled and dyed or bleached yarn 
directly off the precision package. The run-off characteristics of the 
dyed or bleached yarn were highly satisfactory which is believed to be 
attributable to a pronounced reduction of the number of knots. The run-off 
characteristics of the dyed yarn were improved still further by adding a 
lubricating agent to dye liquid during the last dyeing cycle. As stated 
above, the dimensions of the precision package (in comparison with a 
standard package containing the same length of yarn) are surprisingly 
small because the precision package is denser by up to 30 percent. 
Consequently, the diameter of the balloon is also smaller than that of a 
standard balloon which, in turn, enhances the output of the twisting 
machine. 
If the method is to result in the production of a sewing thread, the yarn 
is or can be contacted by a lubricating agent in the course of the 
twisting step. An additional step can involve conversion of twisted and 
lubricated yarn directly into a precision package of sewing thread. 
The improved method renders it possible to form threads from single yarns 
which are produced in open end spinning machines, friction spinning 
machines or air jet spinning machines. As concerns the overall cost and 
versatility, the improved threads are at least equivalent or superior to 
conventional ring-spun yarns having the same final yarn count. 
The term "precision package" is intended to denote a package of the type 
defined by the DIN nomenclature (reference may be had particularly to 
German DIN-Norm No. 61 801 of August 1975). Generally speaking, a 
precision package is a bobbin having layers of precision windings. This 
also embraces the data processor-controlled package and bobbin build. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic and specific aspects of our contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the appended 
claims.