Method and apparatus for regulating out variations in the sliver weight on devices for processing fibre slivers

A method of and apparatus for regulating out variations in the sliver weight on processing machines such as cards, carding engines, draw frames and the like wherein a first measuring device measures either the absolute cross-section or the relative variations of cross-section relative to a predetermined fixed desired value of a fibre sliver issuing from the machine. The first measuring device forms a corresponding first test signal. An additional measuring device is arranged at a point upstream of the first measuring device with respect to the direction of travel of the fibre material. The additional measuring device produces a second test signal corresponding to the relative variations in the cross-section of the fibre material relative to an average value for these variations formed over a predetermined period. The first and second test signals are used for controlling at least one regulating device which controls the cross-section of the fibre sliver.

CROSS-REFERENCE TO RELATED APPLICATION 
The present application is related to application Ser. No. 33,448 entitled 
"DEVICE FOR OBTAINING A CONTROL SIGNAL CORRESPONDING TO THE DENSITY OF A 
FIBRE WEB LYING ON A FIBRE-CARRYING ELEMENT OF A CARD," filed on Apr. 26, 
1979 by Werner Grunder and Ernst Loch, which discloses a measurement 
device which can be used in conjunction with the present invention 
disclosed herein. 
BACKGROUND OF THE INVENTION 
This invention relates to the regulation of variations in the sliver weight 
on cards, carding engines, draw frames and the like. 
There is a need in the processing of textile fibres to be able to 
compensate for unavoidable irregularities in intermediate products by 
means of correcting devices. Such irregularities can be produced by 
properties of the material, properties of the machinery, by the personnel 
or by chance. In the final analysis, the better the intermediate products 
the better the finished products and the finished products can either be 
reduced to a better price or can produce less waste or scrap and thus save 
costs. 
For economic reasons, stages of manufacture with a maximum yield, i.e. with 
a large amount of processed fibre per unit time are particularly suitable 
for the use of correcting devices. The card and the draw frame provide 
optimum properties for cotton spinning mills. Various measuring and 
regulating devices for card and draw frame slivers are also already known. 
A measuring device is usually provided at the machine outlet to 
continuously measure the fibre sliver delivered with respect to its 
cross-section and to produce a signal by means of which the amount of 
fibre supplied can be controlled by means of a regulating device in such a 
way that a weight of sliver which is as constant as possible per unit 
length (i.e. a sliver count which is as constant as possible) is 
delivered. 
The apparatus which has been conventional up until now has a closed control 
circuit. However, owing to the relatively long path of the fibre between 
the regulating position and measuring position, such known apparatus has a 
dead time which makes it impossible in principle to regulate out errors 
which are shorter than the path of the fibre between the regulating 
position and measuring position. On the card with measurements on the 
take-off calenders and regulation of the speed of the feed roller, this 
path of the fibre corresponds to about 4 meters sliver length. In 
subsequent processing, the card slivers are, however, drafted by 100-fold 
to 1000-fold so that errors of at least 400 to 4000 meters length are 
still contained in the finished yarn in spite of regulating apparatus. Any 
significant reduction in these residual errors, therefore, denotes a 
technical progress toward improvement in the quality of the textile end 
product. 
The draw frame which usually follows a card has until now also been 
subjected to similar restrictions with regard to regulation in the closed 
control circuit. Although in this case the distance between regulating 
position and measuring position is smaller, it is still sufficiently large 
for considerable dead times to exist, and thus residual errors remain in 
the sliver. Since virtually none of the subsequent processing operations 
allows regulating out, the residual errors also act, in the final 
analysis, as quality-impairing count variations in the finished product. 
Some proposals for improvement are known, in particular for reducing the 
correction length on cards, carding engines and draw frames. However, 
these known proposals are burdened with considerable disadvantages. For 
example, the following measures have been considered on cards and found 
disadvantageous: 
(a) various means of regulating the drafting mechanism, and the drawing of 
the drafting mechanism at the outlet of the card being modified in 
opposition to the variations in the cross-section of the sliver. 
Disadvantages of this measure are that it is mechanically complicated and 
expensive, particularly in the case of subsequent regulator modification; 
(b) regulation of the drawing between the doffer and take-off calender is 
disadvantageous in that it involves considerable interventions into the 
card, has a small control region, is unflexible, and results in difficult 
servicing; 
(c) measuring the weight of the fibre material introduced at the card inlet 
in the open control circuit. This approach is disadvantageous because the 
measuring member is complicated and imprecise owing to a poor opening with 
regard to short deviations, and has high sensitivity to differences in the 
opening of the flocks in the feed sliver. 
In draw frames, one method of reducing the correction length which has been 
considered is the measurement of the entering fibre slivers and evaluation 
in an open control circuit. In the present state of the art, this 
measurement can be made virtually only with a mechanical measuring member 
or an isotopic measuring member. Disadvantages of this method are that an 
isotopic measuring member encounters pyschological resistance and demands 
additional safety measures. With a mechanical measuring member, the marked 
compression of the entering slivers is disadvantageous in regard to the 
subsequent drafting. In addition, an open control circuit demands very 
precise conformity between the characteristic of the measuring member and 
regulating member, which is virtually unobtainable for long and large 
deviations from the desired value of the feed sliver. 
SUMMARY OF THE INVENTION 
An object of the present invention is to permit the correction length to be 
reduced, while avoiding these disadvantages. 
To achieve this and other objects according to the present invention, there 
is provided a method of regulating out variations in the sliver weight on 
cards, carding engines, draw frames and the like with a first measuring 
device for measuring the absolute cross-section or the relative variations 
of cross-section relative to a predetermined fixed desired value of the 
fibre sliver issuing from the machine outlet and for forming a 
corresponding test signal, wherein an additional measuring device is 
arranged at a point upstream of the first measuring device with respect to 
the direction of travel of the fibre material, and produces a second test 
signal corresponding to the relative variations in the cross-section of 
the fibre material with respect to an average value for these variations 
formed over a limited period, the first and second test signals being used 
for controlling at least one regulating device controlling the 
cross-section of the fibre sliver. 
The present invention also provides a device for carrying out this method 
which comprises a first measuring device for measuring the absolute 
cross-section or the relative variations in cross-section relative to a 
predetermined fixed desired value of the fibre sliver issuing at a machine 
outlet and for forming a corresponding first test signal, a second 
measuring device which is arranged upstream of the said first measuring 
device with respect to the direction of travel of the fibre material, 
which second measuring device is arranged to provide a second test signal 
reproducing the relative variations in the cross-section of the fibre 
material relative to an average value of these variations formed over a 
limited period, and regulating devices for controlling the cross-section 
of the fibre sliver by means of the first and second test signals.

DETAILED DESCRIPTION OF THE INVENTION 
The card of known design shown in FIG. 1 consists of a cylinder 1, a 
licker-in 2, flats 3, doffer 4, a pair of take-off rollers 5 and take-off 
calenders 15. The supplied fibre material 9 is metered in by means of a 
feed roller 14 and disperses as a fibre coating over the covering of the 
cylinder. A web is taken from the cylinder by the doffer 4, is removed 
from the doffer 4 by the take-off rollers 5 and is combined to form a card 
sliver 20 in a funnel which can advantageously be designed in a known 
manner as a first measuring device 10. It is then taken off by the 
take-off calender 15. Thereafter, it passes into a fibre sliver take-up 
device 21. 
The first measuring device 10 transmits a first test signal U.sub.1 to a 
signal evaluator 12 and an additional test signal U.sub.2 is also fed to 
this signal evaluator 12 by another measuring device 11a which can also be 
constructed in a known manner. The first test signal U.sub.1 corresponds 
to the absolute value or the variations about a fixed predetermined 
desired value of the cross-section of the fibre sliver, while the 
additional test signal U.sub.2 contains only the relative variations in 
the fibre coating located on the cylinder, relative to an average value of 
these variations formed over a limited period. Since the licker-in 2 and 
the cylinder 1 rotate at higher speed, U.sub.2 has a dead time of only a 
few hundredths of a second with respect to the amount of fibre fed by the 
feed roller 14. 
Numeral 11a denotes an alternative arrangement of the second measuring 
member, namely in the region of the licker-in 2. In this case, the 
corresponding test signal U.sub.2a is fed to the signal evaluator 12 
instead of the signal U.sub.2. This arrangement has the advantage that the 
measuring position for the second test signal U.sub.2a determines the 
amount of fibre material more precisely on the feed roller 14. However, it 
can only be produced if it is possible to fit the measuring device 11a at 
this position. 
Another variation of the arrangement of the measuring device is denoted by 
numeral 11b, which is also shown in FIG. 1. This arrangement has the 
advantage that a test signal U.sub.2b can be determined before the amount 
of fibre supplied has passed the feed roller 14. 
The first test signal U.sub.1 and the second test signal U.sub.2 (or 
U.sub.2a or U.sub.2b) are superimposed on each other in the signal 
evaluating device 12 in such a way that a resulting combined signal 
U.sub.3 or U.sub.4 (FIG. 2) containing portions of both signal magnitudes 
is formed. In a first design according to FIG. 1, the combined signal 
U.sub.3 enters a regulating member 13, preferably a regulatable direct 
current motor which drives the feed roller 14 or a controllable gear 
mechanism driven by the doffer 4 which drives the feed roller 14. Thus, 
the speed of the feed roller 14 is controlled according to the magnitude 
of the combined signal U.sub.3. The amount of fibre material 9 submitted 
to the card is metered in such a way that a regulated fibre coating is 
deposited on the covering of the cylinder 1 and is then taken by the 
doffer 4 and the take-off rollers 5 as a uniform fibre web and combined to 
form the sliver 20. 
In the variation according to FIG. 2, the combined signal U.sub.4 is fed to 
a regulating member 17 which is also controlled in its resultant speed, 
but controls the speed of the take-off calender 15, the take-off rollers 
5, and the take-up device 21. Further, as a variation, the doffer 4 may 
also be controlled depending upon the magnitude of the combined signal 
U.sub.4. The amount of fibre material taken off the cylinder 1 or doffer 4 
is metered in such a way that the fibre sliver 20 has a count which is as 
uniform as possible. 
In the variation according to FIG. 2, it is advantageous if a measuring 
member arrangement according to the variation shown with the sensor 11c is 
selected, and a signal U.sub.2c is produced instead of U.sub.2b so that 
the distance to the regulating position remains small. 
FIG. 3 shows the application of the method according to the invention and a 
corresponding device on a drafting mechanism. The drafting mechanism 
consists essentially, in a manner known per se, of three pairs of drafting 
rollers. This includes a pair of take-in rollers 18, a pair of cylinders 
19 and a pair of cylinders 16. Preliminary drafting is adjusted between 
the pair of take-in cylinders 18 and the pair of cylinders 19 by selecting 
suitable speeds, and the main drafting is adjusted between the pair of 
cylinders 19 and the pair of cylinders 16. 
A first measuring device 30 determines the cross-section of the issuing 
draft sliver 23 and emits a corresponding signal U.sub.5. A second 
measuring device 31 or 31' is arranged upstream of the first measuring 
device 30, as close as possible to the regulating position, inside, 
upstream of or downstream of the drafting zone where it is possible to fit 
a measuring member, for example between the pair of take-in rollers 18 and 
the pair of rollers 19, or, when viewed in the direction of the entering 
card slivers 23, upstream of the pair of take-in rollers 18. The test 
signal U.sub.6 of the second measuring device is fed with a test signal 
U.sub.5 to the signal evaluating device 12 in the manner already 
described. The resulting combined signal U.sub.7 or U.sub.8 controls the 
speed of either the upstream pair of cylinders 16, or preferably, the pair 
of take-in rollers 18 and the downstream pair of cylinders 19. The main 
drafting can therefore be changed between the pairs of rollers 19 and 16. 
The device is advantageously arranged in such a way that the speed of the 
pair of rollers 16 is unchangeable. The yield of drafter silver 22 is 
therefore constant and the silver receiving device 21' can operate at a 
constant speed. In this case, the speed of the pair of take-in rollers 18 
and the downstream pair of cylinders 19 can be influenced via the 
regulating member 13 by the combined signal U.sub.7. It is also 
conceivable to regulate the preliminary drafting. In this case, the 
regulating member 13 influences only the speed of the pair of take-in 
rollers 18. 
Complicated fitting conditions or other reasons may however make it 
necessary to regulate drafting by varying the delivery rate via a 
regulating member 17 and only the upstream pair of cylinders 16 is usually 
variable in speed. If preliminary drafting is regulated, the downstream 
pair of cylinders 19 can be driven with the same percentage of variation 
in speed. 
When regulating drafting by varying the delivery rate, it is necessary to 
coordinate the fibre silver receiver 21 with the variable delivery of the 
drafter silver. However, it is also important here to form a combined 
signal U.sub.7 or U.sub.8 from the signals U.sub.5 from a first measuring 
device 30 in the region of the silver delivery and the signals U.sub.6 
from a second upstream measuring device 31, as near as possible to the 
regulating position, so that both short and long variations in 
cross-section can be compensated. 
When arranging the second measuring device 31 upstream of the regulating 
position, a delay line known per se and not therefore shown here is 
arranged between the measuring member 31 and the signal evaluator 12. 
It is to be understood, of course, that the elements shown in block diagram 
form can relate to a variety of devices constructed in a known manner to 
perform the functions discussed herein. For example, various arrangements 
are well-known for combining a pair of input signals to form a particular 
output signal containing portions of the signal magnitudes of both input 
signals, as is done by the signal evaluator 12. This can include adding of 
dc levels if the input signals and output signal are all dc voltages, or 
other known arrangements for combining in the event that ac signals are 
involved. Similarly, although the regulator 13 has been discussed in terms 
of being a dc motor, it is, of course, understood that other known 
regulators could be used. 
While I have shown and described several embodiments in accordance with the 
present invention, it is understood that the same is not limited thereto 
but is susceptible of numerous changes and modifications as known to a 
person skilled in the art, and I therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are obvious to one of ordinary skill in the 
art.