Note: Descriptions are shown in the official language in which they were submitted.
2 ~ 6
PROCESS AND APPARATUS FOR THE PRODUCTIQN OF WOUND TUBES
BACKGROUND OF THE INVENTION
The present invention relates to a process and an
apparatus for the production of wound tubes of plastic. A strip
of plastic is wound at a winding angle onto a cylinder and the
adjacent windings are bonded together by filling the gap
between them. A process similar to the present invention is
described in British Patent 1,514,321. According to this prior
art, prefabricated strips of plastic in a deformable condition
are wound onto a cylinder and the windings are welded together.
In addition, ~he cylinder has a rubber coating and is heated
before winding~ and the tube can be drawn off after cooling.
This is a slow, discontinuous process of low profitability.
On the other hand, a process and an apparatus are known
from U.S. Patent 4,082,597, wherein a continuous conveyor belt
is first wound onto a cylinder. A curing resin is then applied
to the winding. After the resin has cured to give the tube, the
conveyor belt end is removed and returned. Continuous
operation of this process is, however, costly, since the
cylinder must be relatively long, and the production rate is
limited because of the return of the conveyor belt.
It is also known to feed an extruded strand or band onto a
~;nd;ng drum (see, e.g., U.S. Patents 3,658,625, 3,917,500,
3,926,223 and 4,033,808, and German Patent 3,827,486). This
technique is also not completely satisfactory.
The problem is to improve the technique for producing
wound plastic tubes by simplifying the procedure and the
apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS0- Figure 1 shows a first apparatus with drivable cylinder
in side view,
Figure 2 shows the apparatus according to Figure 1 in
plan view,
Figure 3 shows a section along line A-B of Figure 2,
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Figure 4 shows a section along line C-D of Figure 2,
Figures 5 to 7 show sections through various embodiments of the tube,
Figure 8 shows another embodiment with stationary cylinder in side
view,
Figure 9 shows the apparatus according to Figure 8 in plan view,
Figure 10 a third embodiment with a stationary cylinder in side
view, and
Figure 11 the apparatus according to Figure 10 in front view.
D CRIPTION OF THE INVENTION
The above problem is solved by the present invention. A poly-
urethane reaction mixture is cast on a linearly moving supporting
Film tape and upon curing forms a strip. The adjacent windings are
bonded by filling the gap with a polyurethane reaction mixture and
the tuhe so formed is continuously stripped from the cylinder.
The special advantage of the new process lies in the fact that
it can be carried out continuously, that the strip can be produced
immediately before winding, and that the strip, on being wound onto
the cylinder, is surprisingly already so far cured that pressure can
be exerted against the last winding and the tube being formed can be
continuously pushed away from the cylinder. This could not have
been foreseen, since there is powerful friction between the windings
and the cylinder.
It is obvious that before or after applying the reaction mix-
ture to the supporting film, inorganic or organic reinforcing
materials in the form of strips, films, cloths, or reinforcements
of cut fib~rs or powders can be fed and embedded in the reaction
mixture. Reinforcing materials or fillers in powder form can also
be incorporated in one of the reaction components or in the reaction
mixture before its application. Alternatively, such reinforcing
materials can be spread beforehand onto the supporting film.
Finally, such reinforcing materials can be strewn onto and allowed
to sink into the reaction mixture after it has been applied to the
supporting film. Materials suitable as fillers include chalk,
slate flour, quartz flour, spar, aluminium hydroxide, wood flour,
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comminuted plas-tics, and recycled materials (such as crushed glass or
powdered plastics). Additional strips of plastic film or metal foil
can also be laid under, embedded or laid on and co-processed during
the casting of the strip. If strips of film are embedded, the strips
used are suitably perforated, so that the reaction mixture is able to
pass through. The winding angle, i.e. the angle between the support-
ing film feed and the axis of the cylinder, is less than 90. The
supporting film preferabl~y consists of a readily separable plastic,
such as polyethylene, polypropylene or polytetrafluoroethylene, or
of paper coated with a release agent, for example silicone. A metal
sheet can also be used as the supporting film, in which case a soap
solution can for example be used as the release agent. Due to the
rigidity of the metal sheet it can be used as a continuous belt or
can be re-used as a finite strip. Instead of a supporting film
strip it is also possible to use a continuous conveyor belt which
must be of such a length that the strip produced from the reaction
mixture is already sufficiently solid on leaving the conveyor belt.
The filling of the gap between the windings is preferably
carried out with the same polyurethane reaction mixture by means of
a second casting device, that is preferably at the highest point of
the cylinder or of the winding.
The stripping from the cylinder of the tube being produced is
carried out preferably by guides positioned in the take-off direct-
ion in accordance with the winding angle and which press against
the last-applied winding. These guides are, for example, pressure
pads or rollers.
It was surprising that the plastic strip just produced by
. : casting and the material curing in the gaps already possess suffi-
cient strength so that they are not damaged by the pressure required
to strip the tube. If necessary, removal aids can also be used
that act on the part of the tube that has already left the cylinder.
According to a further embodiment of the process, the support-
ing film tape has, at least on the side facing away from the take-
off direction, an edge projecting beyond the width of the strip.
This has the advantage that upon winding an overlap is formed,
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so that the cylinder shell itself is completely covered by the sup-
porting film tape and the casting material required for closing the
gaps cannot soil the cylinder shell.
According to a further development of the process, the support-
ing film tape is folded up at the edges like a trough and the poly-
urethane reaction mixture is cast into the trough so formed. Before
the strip is wound, the edge facing away from the take-off direction
is laid flat and the edge pointing in the take-off direction is
folded under the strip formed. In this way, a plastic strip with
precisely formed edges and constant width is obtained. If the edges
of the supporting film are folded upwards by more than 90, a cham-
fering of the strip which forms can be produced.
Alternatively it is possible to cut off the edge facing in the
take-off direction, which is advantageous inasmuch as there is
present one film thickness less, compared with the under-folding.
Preferably the supporting film tape is removed after the tube
has left the cylinder. This is important in particular when the
supporting film tape would interfere with the use of the tube. The
tape must be removed and led away by means of the cylinder, prefer-
ably through a hollow axis.
Such profiles can also be formed during the filling of the gapswith the aid of contour-providing means, for example a co-rotating
double V-belt drive.
According to a further development of the new process, when
the gaps are filled, profiles provided with undercuts are inserted.
Such profiles can be used as spacers or anchoring means, for
example, for a tube jacket. They consist for example of plastic,
: metal or stiff fiber products or of the gap composition itself.
It is also possible to wind several strips over each other
and to fill the gaps with a polyurethane reaction mixture. As a
result, higher strengths of the tube are obtained. Such strips can
be wound in layers in opposite directions, and still other layers
can be applied between the layers of strips, for example an inter-
mediate layer of a polyurethane reaction mixture or a polyurethane
- 35 rigid foam layer for thermal insulation. In both cases appropriate
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reaction mixtures, which cure on the cylinder, are preferably used.
Obviously, in such intermediate layers, reinforcing inlays also can
be worked in, for example windings of rovings or fiber fabrics or the
like. When applying several layers of strips, it is usually neces-
sary that from the second layer onwards the supporting film tapes bepeeled off.
Polyurethane casting materials suitable for the present invent-
ion are known are are described, e.g., in the "Kunststoff Handbuch",
Volume VII, Polyurethane, Carl-Hanser-Verlag (1966), on page 241, in
Table 31, right-hand column. Optionally, the system can be acceler-
ated by addition of 0.5 to 2 g of amine catalysts, e.g., N,N-di-
methylcyclohexylamine.
One apparatus for the production of wound tubes from a strip of
plastic by bonding the windings of this strip requires a cylinder
provided with a rotary drive with a take-off device for the tube.
The novelty of the apparatus can be seen in the fact that 1) an
unwinding station for a supporting film tape is arranged before this
cylinder, 2) a casting device for a polyurethane reaction mixture is
arranged over the transport path of the supporting film tape, and
3) another casting device is provided over the cylinder for filling
the gap between the windings. By this means, the plastic strip only
needs to be produced immediately before the winding process, as a
result of which storage and other operations are omitted. This mode
of production permits the use of strips which, if fully cured, could
no longer be wound. This is possible with the new apparatus since,
by taking into account the winding rate, the time that the strip
requires for transportation from the feed point of the reaction
mixture to the winding-up point can be adjusted, by choosing the
distance of the feed point from the winding-up point, so that the
strip is still sufficiently deformable during the winding.
An alternative embodiment of the apparatus is characteri~ed by
a stationary cylinder with an opening in its shell. A friction
roller, which acts on the windings of the strip, is arranged in
the opening. In addition, an unwinding station for a supporting
film tape is arranged before the cylinder and a casting device for
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a polyurethane reaction mixture is located over the transport path
of the supporting film tape. Finally, another casting device is
located above the cylinder for filling the gap between the windings.
Preferably with both embodiments, guides for the tape to
be wound are associated with the cylinder as take-off devices,
which are adjusted to the winding angle. These guides consist
of pressure pads, rails or rollers which press the strip or the
windings and thereby the tube being formed away from the
cylinder. In the second embodiment, with stationary cylinder,
these guides are largely unloaded when the friction rollers are
so adjusted that they transport the windings both radially and
axially, that is at the winding angle. Further take-off aids
can be provided on the tube already produced.
Naturally, for peeling off the supporting film tape, a
peeling device may be provided. It can be arranged at the end
of the cylinder. Alternatively, the supporting film tape to be
peeled off is led away backwards through the cylinder.
Both the unwinding station for the supporting film and the
casting device must lie on the transport path determined by the
winding angle.
If the supporting film tapes are turned up at the sides
like a trough, appropriate folding devices must be provided.
If the edge facing away from the take-off direction has to be
laid flat and the edge pointing in the take-off direction
folded under the strip formed, guides for this must be
provided. If the edge protruding in the take-off direction has
to be cut off, a cutting device must be provided.
If, during filling of the gap, profiles provided with
undercuts are to be inserted, a feeding device for these
profiles must be provided.
If several strips are to be wound to one tube, an
unwinding station for a supporting film tape as well as a
casting device must be provided for each strip. Whether for
the lowest tape layer another casting device for filling the
gap between the wind;ngs ;s prov;ded or one cast;ng dev;ce
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which casts over the whole area of the gaps and windings
depends on the desired tube structure. -If further intermediate
layers, for example a polyurethane foam insulating layer, are
to be applied, an appropriate device for applying a foamable
reaction mixture is provided over the cylinder. If an
intermediate layer is requ;red~ a feed device must be provided
before the ~eed device or feed position for the next layer of a
stripj at such a distance that the reaction mixture can cure
beforehand to a load-bearing form.
Reference will now be made to the drawings.
In Figures 1 and 2, the apparatus has a cylinder 2,
mounted on one side and rotatable by means of a rotary drive 1.
The cylinder's shell 3 has the internal diameter of the tube 4
to be produced. An unwinding stat;on 6 for a supporting f;lm
tape 7, which is led over a guide roller 8, is arranged at an
angle ~ of 80 to the axis 5 of the cylinder 2. Over the
supporting film tape 7, a second unwinding station 9 for a
reinforcing fabric 10 and a guide roller 11 are provided. A
folding device 12 serves to fold up the edges 13, 14 of the
supporting film tape 7 and to guide the upfolded edges 13, 14
laterally ;n the region of a casting clevice 15, arranged over
it, for a polyurethane reaction mixture 17 which forms a strip
16. The folding device 12 is of such a form that, shortly
before the cylinder 2, the edge 13 facing the take-off side of
the tube 4 is again laid flat and the edge 14 is folded by 180
under the strip 16 and accordingly no longer stands up. There
are arranged above the periphery of the cylinder shell 3,
corresponding to the winding angle ~, on a frame which is not
shown, guides in the form of pressure pads 18 and rollers 19,
which lie against the first winding 20. Over the highest point
o~ the cylinder 2, there is arranged a further casting device
21, which fills the gap 22 between the windings 20 with a
polyurethane reaction mixture 23. In addition, take-off ~ids,
which are not shown, are associated with the tube 4 which has
already been produced. The peeling device for the supporting
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film tape 7, which must be provided statically at the free end of the
cylinder 2 by means of a bracket reaching through the axis 5, is not
shown for the sake of improved clarity.
In Figure 3, in the folding device 12, there can be seen the
supporting film tape 7 with its upfolded edges 13 and 14 which form
a trough 24 in which the solidifying strip 16 lies. The edge 14 is
folded further inwards, so that the strip 16 receives a chamfer.
In Figure 4, the strip 16 is already cured, the left-hand edge
13 of the supporting film 7 standing up above the strip 16, while
the right-hand edge 14 is partly peeled from the underside of the
strip 16 and folded by 180 underneath it.
In Figure 5, windings 31 are shown, the strip 32 being chamfered
on one side. A profile 34 with undercuts 35 is laid over the gap
formed, and also cast into the gap material 36.
In Figure 6, a profile 41 is likewise cast into the gap material
42. But here the profile 41 has a semicircular cross-section.
In Figure 7, two layers of strips 51, 52 are arranged over
each other.
In Figures 8 and 9, a cylinder 62 is mounted on a stand 61.
The shell 63 of the cylinder 62 has an opening 64 in the wall there-
of. A friction roller 65 lies in the interior of the cylinder and
presses against the interior of the windings 66 of the strip 67
through the opening 64 and causes these to rotate around the
cylinder 62. Counter-pressure rollers 68 press from outside at
this same point against the windings 66. The unwinding station for
the supporting film tape, the folding device and the casting device
correspond to those of the apparatus according to Figures 1 and 2
; ~ and are omitted here. The gap 69 between the windings 66 is filled
with the same casting material as that from which the strip 67 is
produced.
In Figures 10 and 11 a cylinder 72 is fastened as the stator
to a stand 71. The shell 73 of the cylinder 72 has an opening 74
through which a continuous steel ribbon 75 serving as a release
sheet leaves the interior of the cylinder and an opening 76 through
which the steel ribbon reenters the interior and then returns to
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opening 74. This steel ribbon 75 surrounds the shell 73 for more
than one winding 77. A casting device 79 for a polyurethane react-
ion mixture is arranged above the steel ribbon 75. A continuous
conveyor belt 80 is arranged upstream of the cylinder 72, above which
S another polyurethane casting device 81 is arranged. The polyurethane
strip 82 is formed on the moving conveyor belt 80 and is fed on to
the steel ribbon 75, being driven by means of a roller 83. The gap
84 between the windings 85 is filled with the same composition as
that employed for the formation oF the strip 82. A double V-belt 78
determines the contour of the filli.ng for the gap 84.
The invention is further illustrated but is not intended to be
limited by the following examples in which all parts and percentages
are by weight unless otherwise specified.
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EXAMPLES
Process ExamPle 1
The apparatus according to Figures 1 and 2 was used~ The
cylinder 2, 1000 mm in diameter, rotates at 1 rpm. At the same
time, the strip 16 is fed to it at a winding angle of 86. To
produce this strip, the supporting film 7, which has a
polyethyléne coating, is unwound from the unwinding station 6
and transported via a guide roller 8 in the direction of the
cylinder 2. It is led into the folding device 12, which folds
up the edges 13 and 14 of the supporting film 7, so that a
trough 24 is formed. In this trough 24 a reinforcing strip 10
of glass fiber weave is fed from an unwind;ng station 9 via a
guide roller 11, and a polyurethane reaction mixture is poured
onto it by means of a casting device 15. Suitable reaction
mixtures are described below. The reaction mixture forms the
strip 16. The folding device lays the edge 13 flat again and
folds the edge 14 by 180 under the strip 16. On winding onto
the cyl;nder 2, the last winding 20 lies on the flattened edge
13 of the previous winding 20. The winding-on process is
20 assisted by guides in the form of pressure pads 18 and rollers
19, which simultaneously provide for the forward movement in
the direction of the axis of the cylinder 2 of the continuous
tube 4 being produced. The gap 22 formed between the wind;ngs
20 when winding on is filled with a polyurethane reaction
mixture 23 by means of a second casting device 21. After
leaving the ylinder 2, the supporting film 7 is removed. The
tube 4 is transported in the axial direction by means of
additional take-off aids and the continuous run then cut up
into desired tube lengths~
Process Example 2
The apparatus according to Figures 8 and 9 was used.
The plastic strip 67 is produced and guided as in Process
Example 1. The windings 66 lying round the shell 63 of the
cylinder 62 are driven by the friction roller 65, so that the
tube being produced rotates about the stationary cylinder 62,
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the friction between the shell 63 and the windings 66 being
reduced by lubricants. The gap 69 between the windings 66 is
also filled according to Process Example 1.
Composition Example 1
Polvol 1: a polyol mixture having an OH number of about 355 and
a viscosity at 25 of about 1200 mPa.s, consisting of
a~ 60 parts of a so-called polymer polyol prepared by
polymerizing 20 parts of a 40:60 mixture of styrene
and acrylonitrile in a polyether of OH value 36, that
has been obtained by addition of a mixture of 83%
propylene oxide and 17% ethylene oxide to
trimethylolpropane,
b) 10 parts of diethylene glycol,
c) 10 parts of dipropylene glycol,
d) 20 parts of a polyether of OH value 790 that has been
obta;ned by addition of 3.75 moles of propylene oxide
to ethylenediamine,
e) 3 parts of a paste consisting of 50% zeolite
(potassium/sodium aluminosilicate) and 50% castor
oil, and
f) 0.15 parts of dibutyltin dil,aurate.
1s~5~n3~ 1: a polyisocyanate with an NCO content oF about
31.5% and a viscosity at 25C of 200 mPa.s, prepared by
phosgenation of an aniline-formaldehyde condensate.
The reaction mixture of 100 parts of Polyol 1 and 97 parts
of Isocyanate 1 yields a hard and heat-stable polyurethane
product with a resistance to heat of about 110C.
Composition Example 2
Isocvanate 2: a polyisocyanate/polyether prepolymer with an NCO
content of about 20% and a viscosity at 25~C of about 1500
mPa.s, prepared by reacting 36 parts of the polymer polyol used
to produce Polyol 1 w;th 64 parts of Isocyanate 1.
The reaction mixture of 100 parts of Polyol 1, 0.10 parts
of dibutylt;n dilaurate and 150 parts of Isocyanate 2 yields a
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medium-hard, viscoplastic polyurethane product with high impact
resistance.
Composition Example 3
Polyol 2: a polyol mixture of OH value 56 and a viscosiky at
25C of 840 mPa.s, consisting of
a) 91 parts of a polyether of OH value 36 that has been
obtained by addition of a mixture of 83% propylene
oxide and 17% ethylene oxide to trimethylolpropane,
b) 0.9 parts of a polyether of OH value 150 that was
obtained by addition of a mixture of 87% propylene
oxide and 13% ethylene oxide to propylene glycol, and
c) 0.9 parts of a solution of alkali acetate in
diethylene glycol.
Isocvanate 3: a polyisocyanate mixture with an NCO content of
28 % and a viscosity at 25C of 300 mPa.s, consisting of
a) 100 parts of a semiprepolymer, having an NCO content
of 24.5%, that was prepared by reaction of
i) 100 parts of a mixture of
1) 80 parts of 4,4'-diisocyanato
diphenylmethane,
2) 10 parts of tri- and higher-functional
polyisocyanates of the diphenylmethane
series with
ii) 12.5 parts of a polypropylene glycol of OH value
485, and
b) 100 parts of a polyisocyanate that was prepared by
phosgenation of an aniline-formaldehyde condensate
and which has an NCO content of 31.5% and a viscosity
at 25C of 60 mPa.s.
The isocyanate index was adjusted by varying the amount of
the polyisocyanate mixture. 100 parts of the mixture per 100
parts of Polyol 2 corresponded to an isocyanate index of about
670; and 200 parts of Isocyanate 3 per 100 parts of Polyol 2 to
an isocyanate index of about 1330.
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The reaction mixture of 100 parts of Polyol 2, 0 to 2
parts of a solution of alkali acetate in diethylene glycol and
from 100 to 200 parts of Isocyanate 3 yielded a
polyisocyanurate product which could be varied from soft to
hard via alteration of the isocyanate index. The product is
high-temperature stable (>200C).
Although the invention has been descr;bed in detail in the
foregoing for the purpose of illustration, it is to be
understood that such detail is solely for that purpose and that
variations can be made therein by those skilled in the art
without departing from the spirit and scope of the invention
except as it may be limited by the claims.
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