Note: Descriptions are shown in the official language in which they were submitted.
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YARN MAKING PROCESS AND APPARATUS
BACKGROUND OF THE INVENTION
( 1 ) Field of the Invention
The present invention relates to the synergistic combination of an air shield
and a
tension gate apparatus and a process for operating the synergistic combination
in a relax
zone during yarn production. Both the air shield and the tension gate
apparatus are
incorporated into a relax zone in the production of yarn to increase the
stability of the
yarn on the relax rolls, especially at process speeds greater than 4,000
meters per minute.
In particular, the present invention relates to that portion of yarn
production wherein the
yarn is relaxed to control its shrinkage without decreasing the yarn stability
on the relax
rolls. Typical processes that have apparatus for relaxing the yarn during
production are
spin-drawing, draw-twisting, draw-winding, and draw-bulking processes.
(2) Prior Art
It is known to use air shields in a relax stage of yarn production. It is also
known
to employ a tension gate in a relax zone.
U.S. Patent 5,240,667 to Andrews, Jr., et al., discloses a nylon yarn
production
process having a relax zone between pairs of rollers. Specifically, one pair
of rolls
operate at a process speed approximately 11 % lower than the speed of another
pair of
rolls. Between the roll pairs are a pair of snubbing pins which act to
increase the tension
on the yarn advancing onto the pair of rolls following the pins. This patent
discusses
wind-up speeds of over 2,000 yards per minute and preferably 2,400 yards per
minute.
Whereas the present invention is looking at speeds over 3,500 meters per
minute and
preferably over 5,000 meters per minute. The snubbing pins employed at the
speeds
mentioned in the Andrews, Jr., et al. patent are suitable for nylon, however
at the
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increased speeds of the present invention, snubbing pins are not suitable for
polyester in
that they abrade and fray the polyester such that it is of poor mechanical
quality. This
patent does not teach the use of air shields.
The following patents relate to employing an air shield during yarn
production.
Generally these patents teach employing an air shield, with or without holes,
near a pair
of godet roll. None of these patents teach employing the air shield with a
tension gate.
Japanese Patent 58-26767 to Ishihara Masatoshi, et al. assigned to Toray
Industries, Inc., describes air shield plates used to prevent yarn vibration
thereby
enhancing the quality of the wound yarn in high speed winding applications.
This patent
employs restricting guides as well as the air shield plates in Figure 2 of JP
58-26767.
Japanese Patent 62-116477 to Ohata Takahiro, et al. assigned to Teijin Seiki
Company, Ltd., discloses an air shield plate positioned between a pair of
godet rolls to
prevent the occurrence of vibration of the yarn.
Korean Patent Applications 94-4689 and 94-4690 by Baek, et al. and assigned to
Cheil Synthetics, Inc., both relate to employing mufti-hole air shield plates
near the first
godet roll to be used at high speeds above 6,000 meters per minute to prevent
air flow
thereby reducing fiber breakage and ensure high productivity of the process.
Japanese Patent 2761789 to Takashi moue, and assigned to Teijin Seiki, Co.,
Ltd., describes an air shield type device. Specifically, two godet rolls are
employed
where yarn moves excessively on the roll surfaces. Each godet pair consists of
a driven
roll and a separator roll. The air shield is a single plate mounted between
the rolls with
one edge in close proximity to the driven godet roll surface. The plate is
perforated with
multiple holes which break up the deflected air stream that bounces off the
plate and
reduces the incidence of roll wrap.
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Despite all of the prior art listed above, there is still a need in the
marketplace to
improve the yarn stability and the frays and breaks that occur during textile
fiber
manufacturing. This need increases as the windup speed increases. There is
also a need
in the art to provide greater relax on the rolls without losing the stability
of the yarn as it
traverses the rolls. Both of these needs are satisfied by the present
invention.
SUMMARY OF THE INVENTION
The present invention relates to the combination of a tension gate and an air
shield. Not only is the combination not known in the prior art, but the
combination gives
a synergistic effect over using either an air shield alone or a tension gate
alone. The air
shield can be any blocking type plates with or without perforations.
Furthermore, these
air shields may be placed in close proximity to the pair of relax rolls
following the
tension gate present in the relax zone of a fiber producing process. The
plates are
positioned on the inside of the threadline so that the airflow is
substantially reduced
around the threadline. The tension gate can be one or more air drag devices,
one or more
liquid drag devices, one or more solid surface contact devices, or a
combination of any
of these, as disclosed by the inventor in U.S.S.N. 09/613,225 filed on July
10, 2000. The
preferred embodiment of the present invention is with a tension gate
comprising one or
more rolls in the relax area of the fiber production process with air shields
positioned on
the inside of the fiber string up (threadline) between the pair of rolls
following the
tension gate.
In the broadest sense, the present invention comprises, for use in a
relaxation
zone of a fiber production process, an air shield and a tension gate.
Likewise, the present invention relates to a process for producing fibers in a
relax
zone comprising the steps of introducing a tension gate in the relaxation
zone; and
introducing an air shield around the pair of rolls (relax rolls) following
said tension gate
in the fiber relaxation zone.
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BRIEF DESCRIPTION OF THE DRAWINGS
The drawings are to aid one skilled in the art in understanding the present
invention and its related concepts as well as the scope of the invention.
However, the
drawings are in no way meant to limit the scope of the invention or impose any
limitation on the invention beyond that set forth in the claims.
Figure 1 shows a schematic of the combination of an air shield and a tension
gate
apparatus with the air shield positioned inside the threadline between the two
rolls
following the tension gate.
Figure 2 shows a second schematic of the combination of an air shield and a
tension gate apparatus where the tension gate has an additional threadline
drag device.
Figure 3 is a side schematic view of the rolls following the tension gate,
with the
air shield positioned inside the threadline between the two rolls.
Figure 4 is a graph of process speed versus yarn stability on the relax rolls.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Applicant has filed a patent application on tension gates and their use in a
relaxation zone in a fiber production process. U.S.S.N. 09/613,225 to
DeBenedictis, et
al. filed July 10, 2000 is hereby incorporated by reference.
The present invention is the combination of air shields and tension gate
devices.
Current processes such as a spin draw process, draw twisting process, draw-
winding
process, or draw bulking process include a relax zone and thus the process and
apparatus
of the present invention can be employed in such a relax zone. Any melt-spun
polymer
employed with any of the above processes such as polyesters, polyamides
(nylons),
polyolefins, polyketones, polyetherketones, polyphenylene sulfide, and
polyarylates can
be employed with the present invention. Typical polyesters are polyethylene
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terephthalate, polybutylene terephthalate, polypropylene terephthalate,
polyethylene
naphthalate, or a mixture of any of these, or copolymers of any of these
polyesters with
up to about 15% by weight of polyolefins, poly-alkylene glycol, or other
copolyesters
such as polyethylene terephthalate isophthalate. Typical nylons are nylon 6
and nylon
66. Typical polyolefins are polyethylene, polypropylene, polybutylene, or a
mixture of
these. Combinations of any of these polymers, or any one of these polymers
with other
polymers like polyethylene or polypropylene, in the form of a bicomponent or
heterofil
fiber are also within the scope of the present invention.
As the relax level increases, yarn tension in the relax zone decreases, and
this
causes the yarn to become unstable on the rolls downstream of the relax zone.
As
process speeds increase, stability becomes worse, at a constant relax ratio,
due to the
increase in centrifugal force on the yarns on the relax rolls. Thus as process
speeds are
increased, relax level must be decreased to maintain stability. Unstable yarn
is defined
as yarn moving, or swaying across the roll surface due to low tension. Highly
unstable
yarn can lead to a reduction in mechanical quality, and in severe cases, to
breakouts
(yarn breakage).
When the process or apparatus of the present invention is used in any of the
yarn
production processes having a relax zone, a higher level of relax and a
resulting lower
hot air shrinkage can be achieved as compared to conventional processes and
apparatuses. By using the present invention at higher processing speeds one
can achieve
the same level of relax under high speed conditions versus more conventional
low speed
conditions, or one could maintain the process speed but increase the level of
relax such
that the hot air shrinkage is greatly improved (reduced), or both can be done
simultaneously.
The tension gate of the present invention partitions a relax zone in a
conventional
process into a relax zone and a small stretching zone. Different devices, when
positioned
in a conventional relax zone can create a partition. Tension gates can be
created by
applying drag to the yarn, by means of air drag, liquid drag, or drag produced
by pulling
the yarn over a solid surface. Air drag can be applied to the yarn by
employing one or
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more interminglers or a counter-current air-flow device, for example. The air
pressure
for the air drag device is typically from 5 to 50 psi, and more typically 10
to 40 psi and
preferably between about 10 to 30 psi. The air pressure blowing across the
threadline
can be directly related to the amount of tension the intermingler places on
the threadline.
The higher the air pressure, the higher the tension.
Liquid drag can be introduced by employing one or more finish applicators (a
finish applicators is a device well known to those in the textile industry, as
it applies a
liquid finish or coating to the yarn), or by drawing the yarn through a pool
of liquid, for
example. Applying liquid at a rate of about 4 - 7 ml. per min. for 1000 denier
yarn is
typical. The application rate varies with the process speed, denier, and
desired tension,
as well as other factors known to those skilled in the art.
Solid surface drag can be introduced by contacting the yarn with one or more
solid surfaces (like rolls) over or around which the yarn traverses, but
because the yarn
does not have multiple wraps on a roll, traversing and swaying yarn on the
tension gate
device is not a problem, and does not cause yarn breakage. In situations where
it is
desirable to achieve only a low tension gradient (e.g. 5 mg/d) across a free-
wheeling roll
or rolls, or situations where it is desirable to limit the tension gradient
across such rolls,
it may be necessary to assist the rotation of one or more tension gate rolls.
In other
words, a free-wheeling roll has sufficient bearing friction and air drag that
it may be
difficult to achieve a tension gradient of only about 5 mg/d, because the
total rolling
resistance may exceed the tension gradient. To achieve a low tension gradient,
it may be
desirable to assist the rolls in their rotation by employing a turbine drive
wherein air is
employed to help drive the rolls. Operating the rolls with turbine drives or
with very
sensitive secondary assistance such as electric motors is well within the
scope of the
skilled artisan and within the present invention.
A tension gate is a device which when used in a relax zone of a yarn
production
process has an outlet yarn tension greater than the inlet yarn tension thus
creating a
tension differential. Additionally, tension gates of the present invention
comprising one
or more rolls are non-multiwrap yarn roll devices. The tension differential is
generally
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greater than 5 milligrams per denier (mg/d) such that if the yarn is a 1,000
denier yarn,
then the tension gate of the present invention is 5 grams, whereas if the yarn
has a 2,000
denier, then the tension gate is at least about 10 grams. For the present
invention a
preferred embodiment is a tension gate or a process having a tension
differential of at
least about 7 mg per denier, and more preferable greater than about 9 mg per
denier. Use
of the tension gate and process of the present invention in the relax zone of
a yarn
production system allows higher levels of relax and corresponding significant
reductions
in hot air shrinkage of the yarn at the same processing speeds.
If we assume that a significant improvement in process speed is 10%, or if we
assume that a significant increase in the relax level is 15%, then a tension
gate which has
about 7 mg per denier of tension differential between the yarn leaving the
tension gate
versus the yarn entering the tension gate achieves the significant
improvement. This is
the preferred embodiment. Of course, good stability can result even when the
process
speed is improved less than 10% and/or the relax level is increased less than
15%. Such
results are not characterized as a "significant improvement", but are within
the scope of
the present invention.
Figure 1 schematically illustrates the present invention comprising the
combination of a tension gate and air shields. Referring to Figure 1,
reference 10
generally indicates the apparatus of the present invention positioned in a
relax zone of a
fiber production process. The relax zone has a pair of draw rolls 12,14 spaced
apart and
a fiber threadline 16 is multiply wrapped around the draw rolls 12,14. After
the draw
rolls, the threadline 16 proceeds to the tension gate device 18 and from the
tension gate
device to a pair of relax rolls 20,22 (thus rolls 20,22 follow the tension
gate in the
threadline path). The pair of relax rolls have an air shield generally
indicated by
reference numeral 24 mounted adjacent the rolls 20,22 and are spaced
approximately 1
cm from the rolls. The shield 24 may be perforated or solid as known in the
art. The air
shield 24 is supported by a support frame (not shown) that may be secured to
the
supporting framework (also not shown) for the rolls 20,22. The air shield is
positioned
inside of the threadline 16 so that airflow is blocked from blowing across the
threadline
and creating movement on the rolls 20,22. The air shield 24 comprises at least
one plate
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(thin and flat - substantially two dimensional) and preferably a pair of
plates 26,28. The
plates may be made from any material capable of being perforated or being
solid such as
metal, like aluminum or copper for example (virtually any metal will perform
equally
well); plastic like polycarbonate, polyester, polyamide, all of which are well
known in
the art; wood, rubber; or a combination of these. Preferably the spaced apart
plates
26,28 are positioned between the relax rolls 20,22 and within each tangent
line
connecting the outer surface of each roll, and thus within the threadline 16.
The plates
blocks the flow of air generated by the rotation of the rolls 20,22 and any
airflow caused
by fans or blowers in a production facility, for example. By virtue of the
fact that the air
shield 24 is positioned approximately 1 cm from rolls 20,22 and are also about
the same
distance from the threadline 16, a quiescent zone adjacent the air shield 24
is created
thus significantly reducing any disruption of the movement of the threadline
on rolls
20,22 induced by air currents.
The tension gate device 18 can be of any device discussed in the prior patent
application of the inventor such as one or more air drag devices, one or more
liquid drag
devices, one or more solid surface contact devices, or a combination of two or
more of
any of these. With respect to Figure 1, the tension gate device comprises a
pair of rolls
30,32. The yarn exiting the tension gate 18 has a greater tension than the
yarn entering
the tension gate.
In operation of the Figure 1 device, a threadline 16 coming from the draw
stage
(not shown), for example, is multiple wrapped about the pair of rolls 12,14.
The
function of the rolls 12,14 is not a part of the present invention and depends
upon the
type of process in which the relax zone is present (the relax zone includes
the rolls 12,14
the tension gate 18 and the rolls 20,22). The roll pair 12,14 have a process
speed
(velocity) that is faster than the roll pair 20,22, and thus during operation
the yarn
relaxes. Therefore the rolls 12,14 could be a pair of draw rolls in a spin-
drawing
process, or a pair of rolls in a draw-twisting process, or a pair of rolls in
a draw-winding
process, or a pair of rolls in a draw bulking process. Upon exiting the pair
of rolls 12,14
the threadline 16 enters the tension gate 18. The tension gate in Figure 1
comprises a
pair of rolls 30,32 which increase the tension on the threadline compared to
the tension
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of the threadline entering the tension gate. The threadline 16 then proceeds
to a pair of
rolls 20,22 that may be a pair of relax rolls, for example. The threadline is
multiply
wrapped about the rolls 20,22 and exits the rolls to further processing or
winding.
Adjacent the rolls 20,22 are the plates 26,28 and the threadline 16 passes in
close
proximity to the outside surface of the plates. Because the plates 26,28 are
positioned
inside of the threadline created by the multiple wraps of the yarn or fiber
16, as shown in
Figure 3, the air shield 24 does not interfere with string-up, for example.
The tension
gate 18 increases the tension from the inlet of the tension gate to the outlet
of the tension
gate on the threadline 16 by virtue of the speed of rotation of the rolls
30,32. The first
roll 30 in the tension gate may typically rotate at a speed less than the
rolls 12,14. The
second roll 32 of the tension gate has a rotational speed higher than the
first roll 30 and
preferably at the same speed or slightly less than the speed of the rolls
20,22 thereby
maintaining a tight wrap about rolls 20,22 thereby increasing the stability on
these rolls.
Figure 2 illustrates a second modification of the present invention in which
an air
drag device or a liquid drag device 34 is employed in combination with the
pair of rolls
30,32 in the tension gate. This combination of devices to produce a tension
gate device
18 is disclosed in the patent application of the inventor previously
referenced. The
operation of the Figure 2 device is substantially similar to that of the
Figure 1 device
with the obvious exception that the threadline 16 upon leaving the rolls 12,14
passes first
through the air or liquid drag device 34 then onto the pair of rolls 30,32.
The air or
liquid drag device 34 provides tension to the threadline 16 coming from that
portion of
the relax zone located between the rolls 12,14 and the tension gate 18, for
example.
With reference to Figure 3, a side view of rolls 20,22 is illustrated.
Positioned
between the rolls 20,22 is the plate 28 which is inside the threadline, thus
permitting the
viewer to see the wraps of the threadline about the rolls 20,22 and extending
outside of
the plate 28 (the plate 28 is positioned inside of a tangent line of the rolls
20,22). With
the wraps positioned outside of the plate 28, the plate does not interfere
with string-up of
the apparatus. When viewing Figure 3, the threadline 16 comes from the tension
gate on
the top of the right side of roll 20, wraps around the rolls 20,22, and exits
from the top of
the left-hand side of roll 20, for further processing or wind-up.
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The roll pairs 12,14 and 20,22 can be the same or different sizes.
Additionally,
the pair of rolls 12,14 or the pair of rolls 20,22 are not necessary the same
size either.
For example roll 12 can be a driven roll and roll 14 a smaller separator roll,
similarly roll
20 can be a driven roll and roll 22 a smaller separator roll.
Exam~,les
Polyester polymer was extruded through a spinneret, spun, drawn and relaxed in
a conventional spin-draw process. The spun ~ yarn IV was 0.88 (measured in
orthochlorophenol at 25° C.).
The spun yarn was drawn in a two-stage process. The final draw rolls had a
temperature of 242° C. The yarn was relaxed 9.62% between these draw
rolls and a pair
of relax rolls at 240° C.
The initial conditions were a spinning speed of 678 mpm and a final draw speed
of 3658 mpm. The final draw speed was increased in 250 mpm increments to
create the
lines in Figure 4, with an increase in the spinning speed to maintain constant
yarn
physical properties (tenacity and elongation). The throughput was adjusted
(increased) to
maintain a final drawn denier of 1000. The yarn stability of the wraps on the
relax rolls
was recorded as a function of the draw roll speed.
A subjective scale is used to define the yarn stability. A rating of 1
(excellent) is
defined as extremely stable with no threadline movement or swaying, while a
rating of 5
(extremely poor) is defined as sufficient yarn movement that the threadline
immediately
breaks. A rating of 3.0 to 3.5 is considered the maximum level of instability
permitted in
a manufacturing process. Acceptable preferred stability is from 1.0 to 2.5.
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Example 1
Run 1 had no tension gate or air stripper between the relax rolls (control).
Run 2 had a tension gate consisting of 2 air driven rollers as schematically
shown
in Figure 1. The break angle over the first roll was 161 degrees, and the
break angle of
the second roll was 175 degrees. This created a tension gate of 55-70 grams.
Run 3 utilized air stripper plates between the pair of relax rolls, positioned
about
1 cm. from the rolls.
Run 4 combined both the tension gate of run 2 and the air stripper plates of
run 3.
Figure 4 shows the yarn stability on the first set of rolls following the
tension
gate as a function of draw speed for these runs. In particular, the draw speed
is
measured on the draw rolls just prior to the tension gate, measured in meters
per minute
(mpm). From this Figure the process speed corresponding to a yarn stability
rating of 3
is shown in Table 1.
Table 1
Run S eed, m m Increase over run
1
1 4,180
2 4,540 360
3 4,460 260
4 I 5,280 - T- -1 ~-100 - -
It was believed that the combination would not yield a result significantly
better
than the air shield alone or the tension gate alone because once the yarns on
the relax
rolls were stable, only a minor improvement at best could be expected. The
best that
could be expected was that the combination of the tension gate and air
stripper would be
additive, i.e. a speed increase of 620 mpm, while maintaining a stability
rating of 3.
Surprisingly it was 60% higher at 1,100 mpm, thus illustrating a synergistic
effect.
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Example 2
Using the configuration of Example 1, Run 4, an additional tension gate was
added prior to the two roll tension gate as illustrated in Figure 2. This
tension gate was
an air intermingles operating at a pressure of 30 psig. A draw speed of 5000
mpm was
used, with a relax ratio of 8.91 % onto the relax rolls at a temperature of
150° C (the draw
rolls were maintained at 242° C).
At 5,000 mpm, the threadline stability improved from 3.0 to 2.75 when the air
was supplied to the intermingles.
Thus it is apparent that there has been provided in accordance with the
invention
a process and an apparatus that fully satisfies the objects, aims, and
advantages set forth
above. While the invention has been described in conjunction with specific
embodiments thereof, it is evident that many alternatives, modifications and
variations
will be apparent to those skilled in the art in light of the foregoing
description.
Accordingly, it is intended to embrace all such alternatives, modifications
and variations
as fall within the spirit and the broad scope of the claims.
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