Note: Descriptions are shown in the official language in which they were submitted.
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Method and Device for Applying a Reinforcement to a Plastic Pipe
by way of a Wrap Welding Process
The present invention concerns a method and a device for producing a
reinforcement on a plastic pipe and a plastic pipe comprising a reinforcement.
Methods and devices for producing reinforced sleeves on plastic pipes
are known in the prior art. For example, it is known from DE 101 52 604 Al to
slide a
plastic pipe by one end onto a mandrel and to rotate it with the mandrel about
its
longitudinal axis, while during this rotation a layer of plastic is extruded
onto a
preformed sleeve region of the pipe to constitute a reinforcing sleeve that is
formed
onto the plastic pipe. This method does, in fact, reinforce the plastic pipe
against
one-time static loads. However, it provides very little reinforcement against
permanent static loads, which would also prevent the plastic from creeping.
Such
permanent loading occurs primarily in the sealing area of the sleeve when
another
plastic pipe is inserted in the sleeve and an annular seal presses with great
pressure
against the sleeve from the inside. Over time, this pressure can cause the
plastic
pipe to creep, causing leaks in the sleeve area.
It is, therefore, an object of some embodiments of the present invention
to provide a plastic pipe comprising a reinforcement at a connection site or
sleeve in
which there is an improved loading capacity with respect to permanent loads,
in order
to prevent the plastic from creeping. It is also an object of some embodiments
of the
invention to provide a method and a device for producing such a plastic pipe.
According to an aspect of the invention, there is provided a method for
producing a reinforcement on a plastic pipe, comprising the following steps:
providing
a plastic pipe that comprises at least one connection site for connection to
another
plastic pipe or to another connecting piece, said connection site having a
sealing
area, and applying a reinforcement band of plastic with one or more
reinforcing
materials with a high permanent tensile strength to said connection site in
said
sealing area that substantially or completely prevents the plastic of said
connection
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site from creeping in said sealing area wherein the reinforcement band is
applied by a
winding process with a prestress, and the reinforcement band is applied by a
device
moving synchronously with the production speed of the plastic pipe into the
longitudinal direction of the plastic pipe.
There is also provided a plastic pipe comprising at least one connection
site for connection to another plastic pipe or to another connecting piece,
said
connection site having a sealing area, wherein applied to said connection site
in said
sealing area is a reinforcement band of plastic with one or more reinforcing
materials
with a high permanent tensile strength that substantially or completely
prevents the
plastic of said connection site from creeping in the sealing area, whereby the
reinforcement band is applied by a winding process with a prestress and the
plastic
pipe is produced by means of such a method.
There is also provided a device for producing a reinforcement on a
plastic pipe, according to such a method, comprising a holding device for
holding a
plastic pipe having at least one connection site for connection to another
plastic pipe
or to another connecting piece, whereby the device is synchronously movable
with
the production speed of the plastic pipe in the longitudinal direction of the
plastic
pipe; and whereby said device includes an arrangement for conveying a
reinforcing
band of plastic with one or more reinforcing materials with a high permanent
tensile
strength; and an arrangement for winding said reinforcing band with a
prestress with
a winding process onto a sealing area of said connection site of said plastic
pipe.
The exemplary embodiments of the invention are described in more
detail below with reference to the following drawings.
Fig. 1 shows a plastic pipe with a reinforced sleeve according to the
present invention;
Fig. 2 shows a first exemplary embodiment of a device according to the
present invention for producing a reinforcement on a plastic pipe;
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Fig. 3 shows a second exemplary embodiment of a device according to the
present invention for
producing a reinforcement on a plastic pipe;
Fig. 4 shows a third exemplary embodiment of a device according to the present
invention for
producing a reinforcement on a plastic pipe;
Fig. 5 shows a fourth exemplary embodiment of a device according to the
present invention for
producing a reinforcement on a plastic pipe;
Fig. 6 shows an enlarged detail of the first and second exemplary embodiments;
Fig. 7 shows an enlarged detail of the third and fourth exemplary embodiments;
Fig. 8 shows an arrangement that can be used for an inventive device
alternatively to the arrangements
illustrated in Figs. 6 and 7;
Fig. 9 shows another arrangement that can also be used for an inventive device
alternatively to the
arrangements illustrated in Figs. 6 and 7;
Fig. 10 shows an arrangement for supporting and rotating a plastic pipe for
the first and third exemplary
embodiments;
Figs. 11 and 12 illustrate still another arrangement that can be used for an
inventive device alternatively
to the arrangements illustrated in Figs. 6 and 7;
Fig. 13 shows a reinforced sleeve according to the present invention;
Fig. 14 shows a device according to the present invention disposed downstream
of a corrugated pipe
plant equipped with an extruder.
Figure 1 represents a plastic pipe 1 with a corrugated outer wall and a smooth
inner wall. Plastic pipe 1
has a sleeve or connection site 3 [sic] for connection to another plastic pipe
3, which connection site 2 is
sealed with a gasket 4. In the area of gasket 4, connection site 2 of plastic
pipe 1 comprises a reinforcing
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band 5, which according to the present invention provides reinforcement not
only against one-time static
loads but also against permanent static loads, to prevent the connection site
2 from creeping in the region
of the gasket 4.
The reinforcing band 5 is made of plastic, particularly of thermoplastic
plastic, e.g. the material of the
plastic pipe, high-density polyethylene (HDPE) or polypropylene (PP), and
contains one or more
reinforcing materials that have a high and permanent tensile strength,
particularly natural fibers, synthetic
fibers, synthetic yarns, glass fibers, fiberglass fibers, Kevlar fibers,
carbon fibers, metal fibers or metal
wires. It is particularly advantageous in this regard to use simple or braided
yarns made of these
reinforcing materials or woven fabrics made of these reinforcing materials.
Most notably, flat woven
metal fabrics have proven to be especially suitable reinforcing materials for
the present invention. Not
only do woven metal fabrics have a high permanent tensile strength, but they
also exert relatively little
surface pressure against the plastic pipe, thereby preventing any incising if
the reinforcing material is
applied to the plastic pipe with a prestress.
The reinforcing materials are advantageously oriented in the longitudinal
direction of the reinforcing
band and can be applied one-sidedly to the plastic of the band. It is
advantageous, however, if the
reinforcing materials are coated with plastic on both sides or are embedded in
plastic. The proposed
reinforcing materials bring about a resistance to permanent static loads that
has not been achieved
heretofore, such that the plastic of pipes can be prevented from creeping in
the sealing areas of sleeves.
The use of braided steel ropes and woven metal fabrics is particularly
advantageous in this regard. This
makes it possible to ensure a permanent seal with plastic pipes that are more
than 2 m in diameter.
The reinforcing band 5 can be wound once around the connection site 2, in
which case the beginning and
the end of the reinforcing band 5 are joined. It is advantageous, however, to
wrap the reinforcing band
over itself more than once ¨ as indicated in Fig. 13 ¨ to achieve a self-
locking effect. The reinforcing
band 5 can in this case be wrapped about the connection site 2 in spiral
and/or overlapping fashion, the
end area of the wound reinforcing band being welded or glued directly to the
connection site or to the
immediately underlying winding of the reinforcing band 5. The reinforcing band
5 is advantageously
heat-welded to the connection site 2. It is also sufficient, however, if the
reinforcing band 5 is merely
glued to the connection site 2.
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The reinforcing band 5 can be applied to the connection site 2 by means of a
wrap welding process
described hereinafter. However, according to the present invention it is also
possible for the reinforcing
band 5 to be extruded directly onto the connection site 2 along with the
reinforcing material.
Figure 2 shows a first exemplary embodiment of a device 6 according to the
present invention for
producing a reinforcing band on a plastic pipe 1. Illustrated in the left-hand
portion of Fig. 2 is a feed
device 7, by which a plastic pipe [is] to be transferred with the aid of lever
arms 8 into the working
position 9 of the inventive device 6, depicted in the center of Fig. 2.
Alternatively to the lever arms 8
shown in Fig. 2, a lifting cross-conveyor can also be used. The plastic pipe 1
is held in working position
9 by support rollers 10, 11 and by upper pressure rollers 12, support roller
11 being driven by a motor 13
so that it is able to rotate plastic pipe 1. Device 6 further comprises an
arrangement for conveying a
reinforcing band 5 and an arrangement for welding the reinforcing band 5 to
the plastic pipe 1, which in
Fig. 2 are denoted jointly by reference numeral 14.
In Fig. 2, arrangements 14 are disposed fixedly in device 6, the winding-on of
reinforcing band 5 being
effected by rotating plastic pipe 1 one or more times. However, it is also
possible, as illustrated in Fig. 3,
for arrangements 14 to be guided around the plastic pipe 1 one or more times
while plastic pipe 1 remains
fixedly clamped in a clamping device 16. This rotational movement of
arrangements 14 can be achieved
by rotating them by means of a live ring or rotor 15, driven by a motor 17. In
Fig. 3, rotor 15 is connected
to motor 17 via a V-belt or drive belt 18. It is also possible, however, for
motor 17 to be installed directly
on the device 6, in which case a pinion mounted on the motor directly engages
teeth on the outer
circumference of the rotor 15.
Arrangements 14 must be able to rotate at least about 360 in this embodiment.
It is advantageous,
however, if multiple rotations about plastic pipe 1 are possible. Arrangements
14 can be driven reversibly
to permit easier powering via connector cables, which when permanently
connected cannot be wound
around the plastic pipe an arbitrary number of times.
The particular advantage of rotationally moving arrangements 14 around plastic
pipe 1 is that in this way,
inventive device 6 can be disposed immediately downstream of a corrugated pipe
plant or corrugator 19,
as illustrated in Fig. 14. The corrugator 19 is fed with plasticized plastic
by an extruder 20 equipped with
an injection head 21, to produce a plastic pipe 1. It is not possible to
rotate the plastic pipe 1 in this
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production process. Hence, the inventive device 6 provided with rotating
arrangements 14 makes it
possible for the first time to apply a reinforcing band 5 immediately after
the forming section of a
corrugator 19, thus enabling pip production on the whole to take place more
efficiently and with less
space consumption.
Since plastic pipe 1 moves slowly along the forming section as it is being
fabricated (cf. arrow 22 in Fig.
14), it is advantageous if device 6 can be moved by means of a motor 23 along
rails 25 synchronously
with the production speed of the plastic pipe 1. For precise manipulation, it
is advantageous in this case
to provide a clamping device 26. During the inventive wrap welding process,
device 6 thus moves from
the upstream end of the rails 25 to the downstream end of the rails 25. Device
6 is then moved by means
of motor 23 back to its upstream end to provide the next connection site 2
with a reinforcing band 5. It
should be noted here that the plastic pipes are produced in a continuous
process with the connection sites
built in, and after the plastic pipe has been fabricated it is severed in the
desired length, or cut to length,
to yield individual pieces of pipe.
Various ways of implementing arrangements 14 for producing or applying the
reinforcing band 5 are
depicted in Figs. 6 to 9 and in Figs. 11 and 12. Illustrated in Fig. 7 is a
drum 30 on which the reinforcing
band 5 is wound. Reinforcing band 5 is fed over a guide roller 31 and a
pressing roller 32 of a drive
device 33, which unwinds reinforcing band 5 from drum 30 to feed it to a work
area 34 on plastic pipe 1.
The drive unit 33 comprises a driven roller 35 and a counter-roller 36, which
is pressed against the driven
roller 35 by a pneumatic or hydraulic cylinder 37. The work area 34 is heated
by means of a hot air
blower 38 equipped with a hot air nozzle 39 to locally plasticize the plastic
pipe 1. The plastic of the
reinforcing band 5 is also plasticized by the hot air that is produced,
causing the reinforcing band 1 [sic]
to become welded to the plastic pipe 1 as the subsequent pressing rollers 40,
41 press the reinforcing
band 5 against the plastic pipe 1.
Figure 6 provides a more detailed view of a cutting device 42 of arrangement
14, which includes a cutter
43. When the reinforcing band 5 has been wound around the plastic pipe 1 to
the desired length, the
cutter 43 is traversed to the left through a cylinder to sever the reinforcing
band 5. Reinforcing band 5 is
held in place during this process by a metal counter-sheet 44. The end area of
the severed end of
reinforcing band 5 is then welded to the immediately underlying area of the
reinforcing band by means of
the hot air blower and pressing rollers 40, 41.
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Figure 8 illustrates another embodiment of an arrangement 14 for applying a
reinforcing band 5. In this
embodiment, plasticized plastic is extruded directly onto the plastic pipe 1,
the reinforcing material being
fed in separately. Wound onto a drum 46 is a plastic wire 48, which is fed
into a small-screw extruder 45.
Disposed in the small-screw extruder 45 are an extruder screw and a heater,
which plasticize the plastic
that is fed in. The plasticized plastic is fed via connecting neck 49 into a
crosshead 50 having a
cylindrical cavity that tapers to the nozzle 51. Also wound onto a drum 53 is
reinforcing material 47,
particularly natural fibers, synthetic fibers, synthetic yarns, glass fibers,
fiberglass fibers, Kevlar fibers,
carbon fibers, metal fibers or metal wires and yarns or woven fabrics made of
these reinforcing materials.
The reinforcing material is conveyed by a pushing device 54 into a conical
cavity in crosshead 50 and
exits through a separate channel of nozzle 51, whereupon it is enveloped by
the plasticized plastic. This
yields a reinforcing band, which is applied by pressing roller 52 to plastic
pipe 1. The hot air device need
only locally plasticize the plastic pipe 1, since the plastic of the
reinforcing band is already in the
plasticized state. Shortly before the end of the wrapping or extruding-on
process, the reinforcing material
is severed by a cutting device 55 to terminate the winding-on of the
reinforcing band 5.
The nozzle 51 of crosshead 50 can be configured as a round nozzle or a flat
nozzle. A round nozzle is
preferably used with reinforcing material that has a round cross section. For
a flat woven metal or
synthetic fabric, on the other hand, a corresponding flat nozzle is preferably
used.
Figure 9 illustrates a modification with respect to the arrangement shown in
Fig. 8. In this exemplary
embodiment the reinforcing material is fed in, not through the crosshead, but
from the outside instead.
Thus, the reinforcing material is first brought into contact with the plastic
pipe 1 by means of a guide (not
shown), and is then covered with plasticized plastic, which in this exemplary
embodiment emerges from
a wide-slit nozzle 54. The cutting device 55 and the pushing device 56 are not
disposed behind the
crosshead in this exemplary embodiment, but rather to the side of it.
Alternatively to the exemplary embodiments depicted in Figs. 8 and 9, the
feeding-in of reinforcing
material can also take place such that short-fiber reinforcing materials are
fed into the small-screw
extruder 45 along with the plastic. The drum 53 for the reinforcing material,
corresponding guides for the
reinforcing material and a cutting device can be dispensed with in this
exemplary embodiment.
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Still another exemplary embodiment of an arrangement 14 is illustrated in
Figs. 11 and 12. In contrast to
the exemplary embodiment depicted in Fig. 7, here the reinforcing band and the
plastic pipe 1 are
plasticized with a laser 58 and are then joined together by means of pressing
rollers 40, 41. The particular
advantage of using a laser is that the plastic to be plasticized can be warmed
in a very contained manner,
so that the overall thermal action is less than that which obtains with a hot
air apparatus. As illustrated in
Fig. 12, by beam focusing, the laser can also be used to cut the reinforcing
band 5, thereby reducing the
number of contrivances needed. Alternatively, however, a mechanical cutting
device can also be
provided.
In all of the above-described exemplary embodiments, it is advantageous if the
reinforcing band or
reinforcing material is applied to the plastic pipe with a prestress. A
tensile stress of more than 100 N to
1000 N ¨ depending on the diameter of the plastic pipe and the degree of
reinforcement ¨ can thus be
applied to the reinforcing band or reinforcing material during the wrapping
process. This can be
accomplished by having the arrangement that effects the rotating unwind the
reinforcing band or
reinforcing material under tensile stress, either the corresponding drum or
the reinforcing band or
material being braked under its own control by means of a holdback mechanism.
In the above-described exemplary embodiments, it is also conceivable to weld
reinforcing band 5 to
plastic pipe 1 only in preset lengths. This further reduces the energy
consumption and associated thermal
loading, with virtually no adverse effect on the reinforcement of the plastic
pipe 1 against permanent
static loads.
In the above-described exemplary embodiments it is advantageous to provide
computer control to drive
the individual motors, the cutting device, the heaters or lasers and the other
arrangements, to permit fully
automatic operation.
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