Note: Descriptions are shown in the official language in which they were submitted.
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Method of operation and construction to place parallel fibres under required
equal
tension.
The invention is concerned with a mode of operation and a construction for the
unwinding of yarn reels, bobbins and spin cakes from a creel (rack with reels)
and
placing these yarns under the same correct tension as each other for the
purpose of
supplying them to a machine for further processing.
For the manufacture of textile products, especially the processing of high-
quality
industrial fibres such as glass fibres, "ARAMIDE" fibres and carbon fibres, it
is
important that the tension of the fibres in the end product are all the same
as each other.
After all, during the manufacturing of a semifinished product or an end
product the
fibres are generally introduced with a particular prestressing force, this
prestressing
force fades away as a result of shrinkage after the product is finished. If
the f bres were
to have different diameters, as is often the case with spun threads, the
fading away of the
strength after the product is finished leads to different rate of shrinkage
.of the eparate
threads, whereby the flatness of the product is adversely~affected.. ~ ~ . . .
..,
If during the process the fibres are fixed by irripregnation with
synthetic~resin, .as is:usual .
for the manufacture of so-called prepregs, unidirectional material or, the
vYinding under.
tension round a (temporary) carrying core, it can be advantageous to
bring.them to a:
level of prestress to be further determined.
The correct and equal tension of all the fibres is extremely important if the
tensile
strength of the fibres is critical for the correct working of the end product,
as is the case
with wound synthetic flywheels, high-pressure tanks, and synthetic rotors for
ventilators
and generators, among other things.
It is exactly these applications whereby the creel is directly coupled to the
construction
that takes care of the processing of the fibres into the semifinished product
or end
product.
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2
Up until now, by preference people carry this out by equipping each individual
end
paint with a precise (electronically controlled) brake that regulates the exit
force.
The braking of such a creel is more expensive as the exit force of several end
points
must be regulated. It must be noted that it is not possible with this
equipment to regulate
S the exit tension, but only the exit force. The braking mentioned is usually
generated by
measuring the deflection of a so-called dancer roller around which the fibre
is led
strengthening or weakening the working of the brake based an this measurement.
Only
with very homogenous fibres of equal diameters is the strength in the fibre a
measure for
the tension in the fibre.
The operating method in question does not have the above mentioned
disadvantages of
the current technical possibilities and can be advantageously implemented in
situations
where there is a need for an exact tension regulating, where many exit points
are
required simultaneously and with a high degree of accuracy, such as the
manufacture of
wide prepregs for the aircraft industry, printed circuit board manufacture and
the
manufacture of extremely lightweight sandwich panels. ~In those cases it is
not unusual
for a~fbre bundle width of lmm to contain 1,000 to 1,500 fibre bundles.
The airn .of the invention in question is, in a simple and inexpensive way, to
bring about
20: ~ that the .out-fed.fibres .all have the same tensile-
,stress;within,:narrovv.tolerances
independent: of the randomly fluctuating force with which they: are -
introduced.
While. the invention is also suitable for the transport'and :tensioning of
materials with a
more continuous structure such as on a production line for paper, plastics,
composite
materials or textiles, the invention will be further explained here by means
of it's
preferred application in the sphere of fibre transport.
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'.' i ~J V
3
SUMMARY OF THE INVENTION
The method of operation
From experiments it appears that the coefficient of friction f in the case of
sliding
friction between a textile fibre and the surface of a roller shows a greater
constancy than
that of a stationery friction. Thus a small difference of speed between fibre
and dxiving
roller appears to have a stabilising effect on the transfer of a constant
drive power. With
many pairings of materials this drive power is less than the maximum drive
power that
can be transferred without slippage. Also, to avoid this phenomenon and remain
holding
full grip a so-called Anti-Blocking System (ABS) has been developed for the
motor
industry for the purpose of being able to use the maximum braking power for as
long as
possible.
In the mode of operation according to the invention the very aim is to limit
the drive
power to a maximum level that can be compared to a similar maximum level of
the
adjacent fibre bundles. According to the theory of elasticity tension in warp
fibres or
fibres of a prepreg or fabric can only arise in the case of an equal
elasticity of the warp
threads of fibres. According to this reasoning it is so that if the passage of
the,end
. : 20 . .~ product via a roller can take place slip=free with a peripheral
velocity v2 and the supply
... .. . . ; ; : : of all warp threads can take.place slip-free. with a
velocity vl, the elasticity between out- . ~ ~ .
feed and supply for all warp fibres is equal.
This reasoning likewise goes for slipping rollers if v~ is the velocity of the
fibre supply
and v2 the velocity of the fibre out-feed. The speed of the rollers thereby
becomes
unimportant. In that case the value of the elasticity s = (v2 - vl)/ vl. The
fact is that the
product is transported over the out-feed roller with the same velocity at
every point
where the fibre touches the circumference of the roller. We call this the
production
velocity v2.
So at each point on the circumference of this roller a surface can be imagined
tls.at lies in
the rotation axis of the roller and that is also at right angles to the
sectional plane of the
product so that the condition of equal relative velocity is fulfilled.
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Equal tension of each and every fibre requires an equal elasticity to be
determined
beforehand, so that at the start of the production process a vertical plane
must exist
where all fibres are supplied with each of them travelling at the same
velocity v f .
Because transport of fibres by means of transporting them over a roller can
only take
place without slippage if the fibre tension before the roller and after
leaving the roller is
virtually the same, the fibre tension is by preference built up from 'nil', at
any rate
virtually nil.
As is well known this construction can be realised by drawing the fibres over
a number
of stationary rods. For example this is described in the American patent
US3253803.
The building up the required tension then takes place by partly encircling the
rod
according to the formula F2 = Fl x e~'°', whereby a is the angle at
which the fibres cover
the surface of the rod.
Because the coefficient of friction f depends on the properties of the
material between
the elements that cause the friction, here the fibre and the rod surface, and
can therefore
only be influenced to ~a limited extent, a higher friction required can be
achieved by
increasing the encircled section a of the rod. In the application in question
the fibre
bundles are lying next to each other so that the circumference of the rod is
only usable to
a limited extent.
The invention in question then also includes the increasing of the angle of
contact by the
application of more rods whereby the bundles of f bre can go round each rod to
a
0
maximum of almost 180 .
A further improvement to the invention is created by rotating the rods in the
direction of
the transport with a peripheral velocity that is marginally smaller than the
velocity of the
fibre.
This is possible with the aid of a design that strongly resembles the mode of
operation
described above on the understanding that the peripheral velocity of the
rollers in this
case is marginally higher then the required velocity of the bundles. Such a
mode of
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operation is described in the American patent I1S5957359 in which the tension
decreases through the part encircling of one roller. The patent mentioned
makes use of
the partial encirclement of only one roller over which the fibres slip whereby
the tensile
strength in the fibres is reduced whereby a tensile strength difference
between the fibres
lying next to each other of a maximum of approximately 100% can be equalised.
In
addition by partly encircling a subsequent roller it can be assumed that the
fibres should
not slip over this last roller because of a greater (part} encirclement of the
roller. This is
at the least dubious because in the case that no slippage of the fibres takes
place on this
roller the fibres will move over the roller following a helical line. In any
case with this
well-known construction it is only possible to create a relatively very
limited final
tension. In addition this well-known construction has the disadvantage that
all fibres
must be manually introduced one by one over the set of rollers. .
The invention in question does not have these disadvantages because each fibre
or
bundle of fibres has as it were its own imaginary surface across the entire
installation in
which all the necessary processing takes place. What is new is the idea that
with the use
of several rollers the tension in different fibres that at the start of the
process may have
very large differences in value from each other, irrespective of the starting
tension and
the differences from each other, after a particular number of rollers and
remaining in
their own flat plane, is reduced to a tension level that is virtually nil. The
tension
differences to be reconciled, the required accuracy, the coefficient of
tension and the
total (part) encirclement determine the number of rolls. The number of fibres
that are
simultaneously available in the process has no effect on the process, but only
on the total
required pair and the strength of the construction. The invention consists of
the fact that
this tension reduction can be used in the first part by transporting the
fibres to the second
part, a slip lock unit, out of which they are, in the third part, transported
across a number
of rollers and each brought to the required equal tension. The slip lock unit
is
constructed such that the fibres cannot slip in the unit. Control of this
tension can be
simply carried out automatically by measuring the result of a measuring xoller
under
prestress preferably resting at right angles to the fibres moving over it and
hereupon
changing the total (part encirclement of the rollers of the first processing
phase in such a
way that the result of the measuring roller returns to the required state. The
in absolute
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6
values very small difference in tension before the unit manifests itself as a
very small
difference in velocity. Because the starting velocity preceding the third part
is near
enough the same for all the fibres, and the take-off velocity for all fibres
is the same for
each one because of the nature of the process to be next carried out (for
example a
wrapping machine, an impregnation process or loom), the final tension of all
the fibres
is near enough the same. The absolute difference between each of the tensions
before
the slip lock unit is determined by the difference in tension at the start of
the process, the
number of rollers, the coefficient of friction f and the angle of contact a
across all rollers
and can therefore b reduced to a required minimum. So with the invention it is
possible
to make a construction whereby for a large number of fibres with an arbitrary
Level of
tension and an arbitrary difference in tension between them the tension of the
fibres is
reduced simultaneously to near enough tension free, which in the slip lock
unit is
converted into a near enough equal velocity of the each and all of the fibres.
From the
slip lock unit, in a well-known way, by applying a difference in velocity, the
tension on
all the fibres can be increased again if required. If people do not want to
increase tension
it is possible in the following process to have the slip lock unit driven by
the tensile
strength on the parallel fibres between the slip lock unit and the following
process. In
that case as well the tension of each fibre will not vary. Because of the
equal elasticity
between the slip lock unit and the place where the fibres become connected to
each
other in the following process in the construction the final tension for all
fibres is the
same to a high degree of accuracy.
The invention also provides an improvement to a slip lock unit by applyzng an
endless
belt with elastomer properties, which is transported over one part of the
circumference
of a roller. The fibres are pressed onto the roller by the belt, without a
great deal of
deforming arising in the fibres or in the belt or the surface of the roller.
The large
surface nevertheless makes it possible to apply a large frictional force to
the fibres. The
small deformations make it possible to transport the fibres through the unit
without
slippage and at a constant and known velocity, whereby the unit is not very
sensitive to
the tensions present in the fibres.
In summary the mode of operation consists of the following three processing
phases:
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1. Reducing the tension of the fibres from an arbitrary individual stress
level to a
stress level of nil or near enough nil.
2. Slippage free transport of the fibres through a slip lock unit at a known
velocity
determined in advance.
3. Building up the tension of each fibre equally from the nil stress level to
the
xequired collective stress level.
By means of this mode of operation it can be realised that all the bundles of
fibres lying
next to each other are brought from an arbitrary stress level to a stress
level of near
enough nil, whereby a new mutually identical tension situation is realised and
by means
of a slip lock unit an identical transit of the bundles of fibres is achieved.
The building
up of the tension after the unit must take place by degrees with the aid of a
number of
rollers that, as a consequence of a deliberate difference in velocity from the
bundles of
fibres, slows these down until the correct tension is achieved. Because the
distance to be
travelled is the same for all bundles, identical elasticity comes into being
whereby an
identical tension is guaranteed. Collectively processing the bed offibre
bundles
obviously requires sufficient stiffness of the rollers. The diameter of these
rollers is
therefore preferably chosen to be not too small. This also has the consequence
that the
bending stress of the individual fibres in the bundles of fibres remains
fractionally low
sa that breakage of fibres in the construction is ruled out and the ends of
the fibres even
after any preceding breakage will simply be carned along in the fibre bundle
package
and therefore not cause any snags (the rolling up of individual fibres in a
bundle of
fibres as a consequence of the frictional working of stationery guiding
elements)_
The construction
The invention further encompasses an arrangement for the execution of the mode
of
operation described above. Such an arrangement is according to the invention
provided
with a first part (de-tensioner) with at least one but preferably a number of
cylinder
shaped rotating elements (rollers) of which each roller can rotate on its own
axle with a
peripheral velocity that according to a preferred realisation is higher than
the required
transport velocity whereby the fibres to be transported are preferably led
round the
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8
rollers in a loop in order to realise an encirclement of these rollers whereby
a greater
total angle of contact can be achieved than would be possible with only one
roller, and a
second part (slip lock unit)with at least one roller with a rigid or at least
relatively non-
distortable surface wherein a part of the transport, by pairing with an
accompanying
S pressure element, preferably consists of an endless transport belt or a
roller with
compressible surface that exerts a frictional force on the fzbres between the
surfaces so
that they are transported without slippage at the transport velocity of the
roller with a
rigid surface and therefore determines the velocity of the transport of the
fibres, and a
third part (tensioner) provided with rollers whether revolving or not around
which by
preference the surrounding fibres are drawn so that a build up of the tension
of the fibres
is obtained.
In order to guarantee good working of the de-tensioner and the tensioner it is
important
that the transport velocity of the rollers of the de-tensioner is always
greater than the
I S transport velocity of the slip lock unit and the transport velocity of the
rollers of the
tensioner are always smaller than the transport velocity of the slip lock
unit. This can be
simply realised by choosing that the diameter of tine rollers of the de-
tensioner is greater
than that of the roller of the slip lock unit and the diameter of the rollers
of the tensioner
is smaller than that of the roller of the slip lock unit and at the same time
keeping the
speed of revolution of all the rollers the same.
In order to realise the good working of the arrangement in a simple way it is
preferably
constructed of two parallel frame plates connected to each other via spacer
blocks and
equipped with an identical pattern of bearings in which the rollers mentioned
can be
2S lowered.
One arrangement with a very good ease of operation and suitable for a large
diversity of
frictional properties can be achieved by the (part) encirclement of a larger
number of
identical rollers whereby aII the uneven numbered rollers are placed on a
first part of the
frame above each other at a distance from each other that is twice the
diameter of one
roller and all the even numbered rollers are placed on the second part of the
frame above
each other all at the same distance whereby through the approaching of the
first part of
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the frame by the second part of the frame the even numbered rollers can pass
over the
uneven numbered rollers without them touching each other in such a way that
the
rotation axles of all the rollers maintain there parallelism, all with each
other.
With such a form of construction of the invention through the maximum
distancing of
the frame parts from each other a passage between the set of uneven rollers
and even
rollers exists through which the one-off throughput of fibres is considerably
simplified.
With the approaching of the first part of the frame by the second part of the
frame
gradually a (part) encirclement of all the rollers comes into being that
through a further
approach can be increased to a value that is determined by the product of the
number of
rollers and half the circumference of one roller.
The arrangement also provides reduction in wear and tear to the fibre and to
the
equipment as a consequence of the continuous slippage between the cylinder
shaped
elements and the fibres, by driving the cylinder shaped elements in the third
part of the
arrangement with a transfer velocity that is slightly less than the required
throughput
velocity of the fibres.
Further wear and tear can be avoided advantageously by providing the rollers
with a
wear-resistant layer for example achieved by hardening the surface. One
important
positive consequence of the preferred construction according to the invention
is also that
through the slippage between the bundles of fibres and roller surfaces a
particular
maximum friction by the cylinder on the bundle of fibres can be transferred
and
therefore the amount of the slippage is unimportant for the correct working of
the
arrangement. This means that the rollers that rotate in relation to the fibre
bundles with
slippage do not have to be completely round and can therefore be constructed
simply
and cheaply.
Because the diameter of all the rollers can be chosen freely the construction
based on the
preferred arrangement of the invention is insensitive to the arising of the
snags
mentioned earlier and breakage of the fibres during their passage through the
construction is ruled out.
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d"~ V i / i V L.. LUU~! / U a a r ,,j ...
The invention is discussed below using the illustrations. These illustrations
must only
serve as explanations about the invention in question and must not be taken as
restrictive.
5
Figure 1 shows a schematic illustration of the physical principle upon which
the
invention is based.
Figure 2 shows a schematic illustration of the entire construction according
to the
essence of the invention.
10 Figure 3 shows a schematic illustration of the de-tensioner and the slip
lock unit
according to the invention, whereby the construction is in a state whereby
ribbons,
threads, filaments, fibres or bundles can be simply transported in the
construction.
Figure 4 shows a schematic illustration of the de-tensioner and the slip lock
unit
according to the invention, whereby the two parts of the frame are moved
towards each
other with respect to the position in Figure 3 and the ribbons, threads,
filaments, fibres
or bundles are in contact with a part of the circumference of the rollers.
Figure S shows a schematic illustration of the de-tensioner and the slip Iock
unit
according to the invention, whereby the two frame parts are moved further
towards each
other with respect to the position in Figure 4 and the ribbons, threads,
filaments, fibres
or bundles are in contact with a larger part of the circumference of the
rollers.
Figure 6 shows a schematic illustration of the tensioner according to the
invention.
Figure 1 shows a bundle of fibres that is moving over a driven roller at a
particular
velocity (v). The bundle of fibres partly encircles the roller at an angle
(a). The roller
2S rotates in the direction shown at the peripheral velocity (w x R). The
coefficient of
friction of the roller surface amounts to (f). F1 is the tensile force in the
bundle of fibres
before the roller. F2 is the tensile force in the bundle of fibres after the
roller.
Now one of three situations can arise:
1. (wxR)>v
The peripheral velocity of the roller is greater than the velocity of the
bundle of
fibres. In this case the tension in the bundle of f bres is reduced. Because
the
sliding friction is independent of the sliding velocity the difference in
velocity
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11
between fibre and roller surface is not important. This situation arises at
the
location ofthe de-tensioner.
(F1>F2).
2. (cc X R) = v
The peripheral velocity of the roller is equal to the velocity of the bundle
of
fibres. Now slippage free transport of the bundle of fibres takes place. This
situation arises at the location of the slip lock unit.
(F I=F2).
3. (c~ X R) < v
The peripheral velocity of the roller is less than the velocity of the bundle
of
fibres. In this case the tension in the bundle of fibres is increased. Also in
this
situation the difference in velocity has no effect on the friction between the
fibre
and the roller surface. This situation arises at the location of the
tensioner.
4. (Fl<F2).
Figure 2 shows in which way a single fibre coming from one of the exit points
(30i to
30iii inclusive) and in the virtual plane represented by the illustration goes
through all
the processing steps via a free-turning roller (31 ) that serves to make the
(part)
encirclement for all parallel fibres the same to the de-tensioner in the
construction. This
is a first processing step by transporting the fibre alternatively left and
right over the
rollers (16) and (5) whereby because of the slippage of the fibre with respect
to the
periphery of the roller, the force in the fibre is further reduced by each
partial loop until
a negligible force remains. The sum of the remaining forces of a1I parallel
fibres can be
determined using a measuring roller (32) that is pressed more or less at right
angles on
the fibres that are travelling from the de-tensioner to the slip lock unit and
of which the
depression or the pressing force determines this remaining force.
Tn the slip lock unit the fibres are pressed between the roller (7) and the
endless belt (11)
so that the transport velocity of all fibres is determined by the peripheral
velocity of the
roller (7). In the next and third processing step, the so-called tensioner, by
equal
lengthening of all parallel fibres as a consequence of the alternately left
and right pulling
of the fibres with slippage over a number of rollers (25) and (29) an equal
and desired
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12
tension is built up in all the fibres. The tensile force mentioned is supplied
by the
following process, for example by a warp beam winding device.
This tension results in a sum of the forces of all the fibres, which force can
simply be
determined on the basis of a measuring roller {33) that is pressed more or
less at right
angles on the fibres that are travelling from the tensioner to the next
process and of
which the depression or the pressure force determines the remaining force in
the f tires.
Figure 3 is a schematic illustration of the de-tensioner and the slip lock
unit in a state
whereby the ribbons, threads, filaments, fibres or bundles (I2) can be fed
easily through
the construction. The fibres (12) come from a supply (not shown) and are
transported
between the rollers (5, 16). The fibres are then led over a roller (7),
whereby the fibres
are pressed onto the surface (8) ofthe roller by a belt (11). This combined
action of
roller (7) and belt (11) forms a slip lock unit. 'The belt (11) is tensioned
by rollers (9).
The rollers (5) are supported on bearings connected to frame part (1) and the
rollers (16)
are supported on bearings connected to frame part (2). Both frame parts can
move with
respect to each other whereby a guide (3) only permits one degree of freedom.
Figure 4 is a schematic illustration of the de-tensioners and the slip lock
unit in a state
whereby the ribbons, threads, fibres or bundles (12) are fed through the
construction and
whereby the frame parts (I, 2) have been moved towards each other as compared
with
the situation in Figure 3. The fibres (12) now make contact with a part of the
surface (6,
17) of the rollers (5, 16). The peripheral velocity of the rollers (S, 16) is
greater than the
throughput velocity of the fibres, whereby the arbitrary forces in the fibre
bundles from
the various exit reels are decreased by partially looping round a first
slipping rotating
roller, which decrease is continued by the following slipping rotating rollers
so that the
bundles of fibres are transported with a minimal and negligible level of force
and
thereby also a minimal and negligible relative difference in forces between a
precisely
cylindrical rotating roller (7) with a peripheral velocity determined before
hand and kept
constant on the one hand and an endless transport belt (11) covered with a
material that
offers sufficient resistance against slippage placed and supported against the
roller on
the other hand whereby a slippage-free drive of the bundles of fibres (13), by
now
brought to a very low tension, is achieved.
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13
Figure 5 is a schematic illustration of the de-tensioner and the slip lock
unit in a state
whereby the ribbons, threads, fibres or bundles (12) are transported by the
construction
and whereby the frame parts (1, 2} have been moved closer to each other than
the
situation in Figure 4. The fibres (12) now make contact with greater part of
the surface
(6,17) of the rollers (5,16). The angle of the encircled arc a of the fibres
on the rollers
has become greater, whereby per roller, under constant conditions, more
tension is built
up in the fibres.
Figure 6 is a schematic illustration of the tensioner, whereby the ribbons,
threads,
filaments, fibres or bundles (24) are in contact with a part of the
circumference (26) of
rollers (25). The rollers have a peripheral velocity that is less then the
throughput
velocity of the fibres (24) whereby the tension in the fibres is increased by
each roller
according to the principle shown in Figure 1. As a consequence of the
lengthening of the
fibres between the slippage-free supply and take-off over an equal distance
for all the
bundles, the tension of all the fibres is and remains equal. Obviously, where
the tension
is momentarily higher a momentarily greater elasticity will come into being
with a lower
normal force in the (part) encirclement as a result, which immediately has a
decrease in
the friction and therewith the tension as a consequence. The fibres (27} leave
the
construction to be further dealt with by a process that is not described here.
In this
arrangement also the frame parts (21) and (22) can move in relation to each
other,
whereby the guide (23) only permits one degree of freedom.
