Process for unwinding a thread from a reel in looms, and arrangement used therefor

Process for unwinding a thread from a reel in looms, wherein the thread (6) is guided through a thread guide (4) placed behind the reel, characterized thereby that the distance (L) between said thread guide (4) and said reel (3) is adjusted automatically mainly during the weaving process.

The present invention relates to a process for unwinding a thread from a 
reel in looms, as well as to arrangements that are used for realizing the 
process according to the invention. 
It is known that in looms a thread guide, being mostly a thread eyelet, 
placed behind every reel along which the weaving thread is unwound from 
the reel. The distance between the reel and the thread guide can be 
adjusted herein in advance depending on the size of the reel in order to 
provide a smooth unwinding. The distance between the reel and the thread 
guide remains constant during the weaving process. 
It has been determined experimentally that at high speeds of thread 
unwinding, relatively many thread breaks occur near the reel and the 
thread guide. It has been observed from tests and measurements that the 
forces arising upon unwinding the thread give rise in the weaving thread 
to stress peaks that may lead to the abovesaid thread breaks. 
It also appeared from tests that there is an optimal distance between the 
reel and the thread guide, whereby the stress peaks or variations are 
minimal or are kept constant, and whereby the course of the stress in the 
thread as a function of time remains relatively constant. Said tests 
showed as well that this optimal distance depends on the diameter and the 
type of the reel, i.e. on the type of yarn and on the way of winding up 
the yarn. 
In order to eliminate the above mentioned disadvantage of thread breaks, 
the invention provides a method for unwinding a thread from a reel 
according to which the stress variations in the threads are optimized 
i.e., minimized. For that purpose the invention consists in a method for 
unwinding a thread from a reel in looms, according to which the thread is 
guided through a thread guide and according to which the distance between 
the thread eyelet and the reel, mainly during the weaving process, is 
adjusted automatically. As will appear further on, it is clear that such a 
process can be brought about according to several variants. Preferably and 
mostly, adjusting occurs either directly or indirectly as a function of 
the thread stress. The present invention also relates to the arrangements 
for realizing said method.

In FIG. 1 the course of the stress S in the thread is represented versus 
time t by means of two curves 1 and 2, of which curve 1 represents the 
course in the case of a badly chosen distance between the reel and the 
thread guide, whereas curve 2 applies to an optimally adjusted distance L. 
It is clear that variations or peaks of stress such as those occuring in 
curve 1 have to be avoided in order to exclude thread breaks. It is 
remarked that in this FIG. 1, starting from a determined situation of 
unwinding, the time t1 equals the time that is needed for arriving again 
at said substantially same situation of unwinding. So, in the FIGS. 2 and 
3 various arrangements are represented wherein one aims at automatically 
adjusting the distance L between a reel 3 and a thread guide 4 in an 
optimal or almost optimal way. 
In the embodiment according to FIG. 2 the arrangement in addition to reel 3 
and thread guide 4 consists of a mechanism (not specifically represented 
in the figure) for adjusting the distance L between the reel 3 and the 
thread guide 4; a measuring device 5 for measuring the course of the 
stress in the thread 6, and a processing unit 7 providing the coupling 
between the measuring device 5 and said mechanism for adjusting the 
distance L. In general, the distance L is increased with increasing 
tension in the thread. However, the optimum distance may vary depending on 
the winding method on the reel and the kind of thread used. The processing 
unit 7 is equipped with built in logics so as to adjust the distance L in 
such a way that the stress variations in the thread 6 be minimal or at 
least be maintained as constant as possible. It is clear that herein the 
measuring device 5 can equally well consist of a means to measure the 
length of unwound thread passing the device or a stress meter as a 
stress-variation meter. 
The process followed herein can simply be deduced from the schematical 
representation of FIG. 2 and consists in directly adjusting the distance L 
between the thread guide 4 and the reel 3 as a function of the thread 
stress S by measuring the stress in the thread 6 and by automatically 
adjusting the distance L as a function of the measured stress S. This 
process offers the advantage that the slightest stress variation is 
immediately determined and corrected. 
In FIG. 3 an arrangement is represented wherein the distance L between the 
reel 3 and the thread guide 4 is adjusted indirectly as a function of the 
stress in thread 6. Herein, the optimal distance L is determined in 
advance as a function of the diameter of a determined type of reel 3. 
Thereby a parameter 8 is obtained, which is put in a processing unit 9. 
Said processing unit 9 is then controlled by means of a measuring device 
10, that continuously measures the diameter D of the reel 3 during the 
weaving process. As has been said above, the processing unit 9 controls a 
mechanism for adjusting the distance L between the reel 3 and the thread 
guide 4. Generally, the distance L decreases as the diameter of the reel 
decreases, however, the optimum distance may vary, depending on the 
winding method on the reel and the kind of thread used. 
Such a dependency of the distance L upon the diameter D of the reel is 
represented in FIG. 5. 
Summarizing, the method followed herein shows the feature that the distance 
L between the thread guide 4 and the reel 3 is adjusted by determining the 
momentary diameter D of reel 3 and by automatically adjusting the distance 
L as a function of the determined diameter, wherein thus a parameter 8 or 
a functional relation is used from which is expected that an optimal 
course of stress is obtained when it is applied. 
Determining the diameter D does not necessarily take place by means of the 
direct measurment thereof as is represented in FIG. 3. 
According to a variant, the diameter D can also be determined from other 
measuring values, e.g. by means of transfer functions. Preferably the time 
T of unwinding the reel is then measured, from which the diameter is 
calculated by means of a previously fixed transfer function D=f(T). 
According to another embodiment the distance L is adjusted directly as a 
function of the measured time T of unwinding. 
According to still another variant, the distance L is adjusted as a 
function of the amount of thread 6 taken off which could be directly 
measured by a suitable means known in the art. Measuring device 5, for 
example, could be a length measurer. 
FIG. 4 provides an arrangement which is a combination of the arrangements 
according to FIGS. 2 and 3. So, the processing unit 11 provides the 
coupling of both measuring devices 5 and 10 for the stress and the reel 
diameter D respectively, with the mechanism for adjusting the distance L 
between reel 3 and the thread guide 4. Further, the above-said parameter 8 
is put in the processing unit 11. 
The process applied to this arrangement mainly shows the feature that it 
consists in measuring the stress S in the thread 6, measuring the diameter 
D of reel 3, and adjusting the distance L between said reel 3 and the 
thread guide 4 as a function of the measured stress S as well as of the 
measured diameter D. This process offers the advantage that the 
information on the diameter allows a quick adjustment when the reels are 
changed, whereas the information on the stress provides an additional 
adjustment. It is also possible to adapt the distance L as a function of 
the diameter D during the weaving process such that the additional 
adjustment becomes minimal. It is still possible to store the former 
measured distances L in a memory. This allows, e.g., upon changing reels 
to bring the thread eyelet directly to a position where said thread eyelet 
stood optimally at the preceding change of reels. 
It is clear that also in the embodiment according to FIG. 4 the measurement 
of diameter can be replaced by the measurement of unwinding time, wherein 
of course a suitable timer 10a and a suitable processing unit has to be 
applied as illustrated in FIG. 11. 
It is also possible upon starting up the machine to impose to the eyelet a 
determined motion and to adapt this motion to every start in such a way 
that the stress peaks during starting-up are minimised. 
Obviously, the reel 3 as well as the thread guide 4 in the above-said 
arrangements can be adjusted. The mechanism for regulating the distance L 
and for adjusting the thread guide 4 in itself can be made according to 
many variants. According to a possible embodiment, the thread guide 4 is 
placed on a telescopic arm, that can be extended, e.g., by means of some 
worm or the like built in said arm. 
Adjusting the position of said thread guide 4 with regard to reel 3 
preferably occurs by a usual proportionally integrating differentiating 
adjustment (PID-adjustment). 
As is represented in FIG. 6, adjusting the distance L preferably occurs by 
a suitable construction of the reel stand. The reel stand 12 is formed 
herein by telescopic arms 13 and 14, to which are mounted the reels 3 and 
15 respectively. In the same way also the thread guide 4 can be fixed to a 
telescopic arm 16. By a suitable adjustment of the various telescopic 
arms, the distance L can be adjusted as aforesaid. The telescopic arm 
embodiment allows that in the case of a transition between two successive 
reels 3 and 15, an optimal distance L1 and L2 can be maintained between 
the respective reels and the thread guide 4. 
In the FIGS. 7 to 9 another mechanism for adjusting the aforesaid distance 
L is represented. It consists of a reel arrangement 17 comprising two 
reels 3 and 18 respectively, and a thread guide 4 arranged symmetrically 
with regard to them and comprising an elongated thread-guiding opening 19. 
The thread guide 4 is rotatably fixed between its both ends 20 and 21 in 
such a way that when the distance between the end 20 and the reel 3 grows, 
the distance between the end 21 and the reel 18 is reduced, and 
conversely. At the beginning of the first reel 3, the end 20 is placed at 
the optimal distance L1 as represented in FIG. 7. When reel 3 is unwound 
the end 20 finds itself at an optimal distance L2, and also the end 21 has 
come to the optimal distance L1 from reel 18. When the reels are changed, 
thread 6 moves from the end 20 to the end 21, which has the advantage that 
the optimal distance L1 of the full reel 18 is reached immediately so that 
no sudden adjustment of the thread guide 4 is necessary. FIG. 9 represents 
the new situation. 
Of course, the revolving thread guide 4 of the embodiment according to 
FIGS. 7 to 9 is equipped with the necessary control means for adjusting 
the right rotation thereof. This means is e.g. a step motor or the like, 
which rotates the spindle 22 in a regulated way, optionally with the help 
of a belt transmission. 
In one embodiment, the reels 3 and 18 can be mounted telescopically, e.g. 
as is represented in FIG. 10. In addition to the telescopic arms 23 and 24 
whereby the reels 3 and 18 can be moved, also a telescopic arm 25 can be 
provided for moving the revolving thread guide up and down. Adjustment of 
the distance L is achieved by a suitable combination of motions made by 
the various components. 
The present invention is by no means limited to the embodiments represented 
in the accompanying drawings and described by way of examples, but such an 
arrangement can be realized in any form without departing from the scope 
of the invention.