Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 022274~1 1998-01-20
METHOD AND APPARATUS FOR THE MANUFACTURE OF A
CORRUGATED ENVELOPING PIPE WITH A FLUID PIPE HOUSED
S THEREIN
BACKGROUND OF THE rNVENTION
Field of the Invention
The invention relates to a method for the m~nllf~cture of a corrugated en-
veloping pipe with a fluid pipe housed therein, a tube of thermoplastic
plastics being produced continuously in a direction of production, a fluid
pipe being inserted in the tube in the direction of production with play to-
15 wards the tube, the tube and the fluid pipe housed therein being conveyedin the direction of production, and the tube being provided with cross
grooves. The invention further relates to an apparatus for putting the
method into practice, comprising an extruder, which comprises a crosshead
having a pipe die head, through which a passageway for the fluid pipe
20 passes in the direction of production, and which comprises an ~nmll~r die
enclosing the passageway, a molding machine, which is disposed down-
stream of the pipe die head in the direction of production, and which com-
prises half shells completing each other in a molding path to form a closed
mold moved in the direction of production and on their inside having a pro-
25 filed shape corresponding to the cross grooves of the corrugated envelopingpipe, and which is provided with a device for the deformation of the tube
on the profiled shape, the pipe die head finishing before the molding path.
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Background Art
It is known from heating and sanitary technics to protect fluid pipes of the
most varying materials, i.e. plastic materials, by means of corrugated en-
5 veloping pipes. In this way, damages to the surfaces of fluid pipes areavoided. Should there be any damage, the fluid pipe - similar to electric
lines - can easily be replaced. The defective pipe is removed, a new fluid
pipe is inserted. In practice, fluid pipes of this type are pulled or slid into
the corrugated enveloping pipe exclwsively subsequently. This way of
10 m~nllf~cture requires an intensive second operation after the production of
the corrugated enveloping pipe and involves limited lengths of pipes, which
results in a correspondingly high number of joints and possible waste dur-
ing installation.
15 EP 0 683 032 A teaches a method of'the generic type in which to manu-
facture a corrugated enveloping pipe conventionally and to slit it length-
wise subsequently. A fluid pipe, which has play towards the corrugated
enveloping pipe, is inserted in the slit up corrugated enveloping pipe. Then
the corrugated enveloping pipe is welded again. The requirements involved
20 in terrns of industrial instrumentation are very complicated. Further, there
is the risk of the comparatively thin-walled corrugated enveloping pipe af-
ter the welding job no longer possessing the original rigidity.
A method or an apparatus for the manufacture of corrugated enveloping
25 pipes with a cable inserted is known from DE 22 61 530 B. In this case the
pipe extrusion head of the crosshead for the corrugated enveloping pipe has
an internal mandrel which extends as far as into the molding path and
closes a chamber of excess pressure within the tube extruded from the pipe
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die head, air being blown into this chamber for the tube to be pressed
against the profiled shape of the shel:ls. Deformation of the tube on the
molding machine takes place according to the so-called blowing method. A
continuous passageway for electric cables is provided in the pipe die head
5 and the intern~l mandrel. Owing to the design specified, only a compara-
tively small portion of the inside cross-sectional area of the corrugated en-
veloping pipe can be used for the electric cables. That is why this known
method and this known apparatus are not suitable for having a fluid pipe
inserted into the corrugated enveloping pipe during the latter's manufacture.
10 For the reasons mentioned, this method has not given a good account of
itself in practice.
It is known from WO X6/05570 to place a fluid pipe into a pipe of heat in-
s~ ting material that has been slit lengthwise before and to provide the
15 surface of the slit with glue. In a crosshead of an extruder, a coating of ap-
propriate plastic material is then injection-molded around the pipe of heat
insulating material equipped with the fluid pipe and provided with ribs in a
molding machine by means of half shells completing each other to form a
closed mold moved in the direction of production, a vacuum being pro-
20 duced in the mold. In this case, direct insertion of a fluid pipe into a ther-
mally plastic tube produced for the m~nllf~cture of a corrugated enveloping
pipe is not provided and is not feasible either.
SUMMARY OF THE INVENTION
It is the object of the invention to create a method of the generic type, by
means of which the inside cross-sectional area of the corrugated enveloping
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pipe can be filled substantially by the at least one line, and to specify an
appal~lus for putting the method into practice.
In the method of the generic type, this object is attained by the features
5 which consist in that the cross grooves are produced exclusively by low
pressure, relative to atmospheric pressure, acting on the outside of the tube.
In an app~lus of the generic type, this object is attained by the features
wherein for the deformation of the tube on the profiled shape, solely a de-
vice for the generation of low pressure, relative to atmospheric pressure, is
10 provided on the inside of the half shells.
Owing to the exclusive use of vacuum deformation, any measures to be
taken on the pipe die head or in the molding machine become unnecessary,
which otherwise require part of the inside cross-sectional area of the corru-
15 gated enveloping pipe during the latter's manufacture and the sim~llt~neousinsertion of the fluid pipe. To a great extent the inside cross-sectional area
of the corrugated enveloping pipe can be filled by the fluid pipe. This en-
sures that the corrugated enveloping pipes, when placed, will not require
any unnecessary space and that no unnecessary material requirements are
20 involved.
It is of special, advantageous importance that prior to the insertion, the
fluid pipe inserted in the tube is equipped with a parting agent. As a result
it is possible to approximate the outside diameter of the fluid pipe to the
25 inside diameter of the corrugated enveloping pipe, because during the ex-
trusion of the tube, the latter may touch the line coated with the parting
agent.
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The app~alus for putting the method into practice has no internal mandrel,
i.e. the inside cross-sectional area of the tube is free at least to a great ex-tent during deformation. When a parting agent applicator is provided up-
stream of the annular die in the direction of production, this ensures the
inside cross-sectional area of the tube to be entirely free.
Further features, advantages and details of the invention will become ap-
parent from the ensuing description of an exemplary embodiment, taken in
conjunction with the drawing.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is an illustration of a fluid pipe housed in a corrugated enveloping
pipe,
Fig. 2 is an illustration of an apparatus for the manufacture of a corru-
gated enveloping pipe with a fluid pipe housed therein, and
Fig. 3 is a longitudinal section through a pipe die head and part of a
downstream molding machine of the apparatus according to Fig. 2,
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows a corrugated enveloping pipe 1 with a so-called fluid pipe 2,
25 i.e. a hot or cold water pipe or a pipe for any other free flowing substances.
This is used in particular in heating ~md sanitary technics, where the fluid
pipe 2, which consists of the most varying materials, such as interlaced
polyethylene (XLPE), polypropylene (PP), polybutene (PB) and the like, is
CA 022274~1 1998-01-20
to be protected against external impairments by a protecting tube, namely a
corrugated enveloping pipe 1. The corrugated enveloping pipe 1 is a con-
ventional corrugated pipe provided with cross grooves 3 for reinforcement
and which is pliable on the one hand, having high summit compressive
5 strength at a low weight on the other hand. As seen in Fig. 1, the outside
diameter d of the continuously smooth fluid pipe 2 is only slightly smaller
than the inside diameter D of the corrugated enveloping pipe 1. Approxi-
mately 0.65 D < d < O.9S D applies, 0.7 D < d < 0.95 D applying l,rerela-
bly.
Fig. 2 illustrates an apparatus for the manufacture of such a corrugated en-
veloping pipe 1 with a fluid pipe 2 inserted. It comprises an extruder 4 pro-
vided with a so-called crosshead 5 so that the extruder itself is not in the
straight direction of production 6, but, relative to the direction of produc-
15 tion 6, opens sidewards into the crosshead 5. Relative to the direction ofproduction 6, the crosshead 5 (details of which are still to be described be-
low) is topped by a feeding device 7 for the fluid pipe 2 to be supplied
continuously. A tube 8 of thermoplastic plastics is extruded from the
crosshead 5 in the direction of production 6, concentrically enclosing the
20 fluid pipe 2. This tube 8 is deformed to constitute the so-called corrugated
pipe 1 in a downstream molding machine 9 by so-called vacuum treatment.
Molding machines 9 of the generic type are generally known for instance
from German patents 12 03 940 and British patent 971 021.
25 Details of the crosshead 5 and, in part, of the molding machine 9 can be
seen in Fig. 3. The crosshead 5 comprises a pipe die head 10, which is dis-
posed concentrically of the direction of production 6 and comprises an ex-
terior supporting ring 12 and an interior filler piece 13. The exterior sup-
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porting ring 12 is mounted on a connecting piece 14 of the extruder 4. The
filler piece 13, which - relative to the central longitudinal axis 15 - is radi-ally tightly fixed in the supporting ring 12, comprises an ~nn~ r collar 16
which projects in the direction of production 6 and on which an internal die
5 mandrel 17 is axially and radially tightly mounted by means of screws 18.
By means of an adjusting ring 20, a die casing 19 is fixed to the supporting
ring 12 likewise concentrically of the axis 15. The adjusting ring 20 com-
prises an ~nn~ r collar 21, which projects inwards radially to the axis 15
and which encloses an ~nmll~r flange 22 of the die casing 19. It is tightly
10 joined to the supporting ring 12 by screws 23, the die casing 19 thus being
tightly connected with the supporting ring 12 in the direction of the axis 15.
An ~nn~ r gap 25 is formed between the periphery 24 of the ~nnlll~r
flange 22 and the adjusting ring 20. Adjusting screws 26 are disposed in the
adjusting ring 20 at uniform angular distances radially to the axis 15, bear-
15 ing against the periphery 24. By adjustment of these adjusting screws 26,the die casing 19 is aligned radially to the axis 15 and thus relative to the
supporting ring 12. A die channel 27 is formed between the internal die
mandrel 17 and the die casing 19, its radial width being modifiable over the
circulnferellce by the mentioned adjustability of the die casing 19. A melt
20 channel 28, which extends from the extruder 4 through the connecting
piece 14 and the supporting body 11, opens into this die channel 27. Di-
rectly before the molding machine 9, the die channel 27 finishes in an an-
nular die 29 from which discharges l:he tube 8 of thermoplastic plastics - as
mentioned.
The pipe die head 10 is hollow throughout in the direction of the axis 15,
i.e. the interior filler piece 13 as well as the internal die mandrel 17 are an-nular, enclosing a cavity which extends concentrically of the axis 15 and
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forms a passageway 30 for the fluid pipe 2. On the inlet side 31 for the
fluid pipe 2, a parting agent applicator 32 is mounted on the pipe die head
10. It has a tubular insert 33 which is placed into the supporting body 11. A
flange 34 of the insert 33 bears against the supporting body 11, to which it
S is fixed by means of screws 35. The tubular insert 33 is provided with two
~nn~ r dividing walls 36, 37, which extend concentrically of the axis 15
and are spaced from each other in the direction of production 6 and which
are in sealing contact with the external wall 38 of the fluid pipe 2 fed into
the passageway 30 concentrically of the axis 15, thus defining a parting
10 agent application chamber 39. A parting agent supply conduit 40 leads
from outside through the supporting body 11 into this parting agent appli-
cation chamber 40. Since the passageway 30 is closed externally, a pres-
sure compensation duct 41 discharges from this passageway 30 after the
applicator 32 - seen in the direction of production 6.
The molding machine 9 conventionally comprises a table 42 on which halfshells 43, 43' are disposed which join to folm two so-called chains 44, 44'.
At their rear end seen in the direction of production 6, the chains 44, 44' are
guided along deflection wheels servi.ng as so-called feed rollers 45. During
20 circulation of the chains 44, 44', the individual half shells 43, 43' are moved
in a molding path 47 corresponding to the arrows 46, 46', where two half
shells 43, 43' at a time are united to form a pair of shells, pairs of shells,
successive in the direction of production 6, again lying close together. At
the front end, seen in the direction of production 6, of the table 42, return
25 rollers 48 likewise serving as deflection wheels are rotatably mounted, the
chains 44, 44' being deflected around them and returned to the feed rollers
45. The pairs of shells are moved by a drive (not shown) in the direction of
production 6 through the molding path 47.
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On their inside, the half shells 43, 44 are provided with a profiled shape 49
which corresponds to the shape of the cross grooves 3. They further com-
prise vacuum columns 50 which are connected with the inside of the half
S shells 43, 43' by way of vacuum slits S 1. The vacuum slits S 1 finish in the
profiled shape 49. In the vicinity of lhe inlet 52 of the molding path 47, the
table 42 is provided with a first vacuum supply system 53, by which low
pressure from a vacuum device, for instance a vacuum pump, is ~mi~te~ to
the vacuum columns 50 of the half shells 43. In the direction of production
10 6, this vacuum supply system 53 is followed by a second vacuum supply
system 54 which, basically in the same way, admits low pressure - relative
to atmospheric pressure - to the vacuum columns 50 and thus to the slits 51
and the insides of the half shells 43, 43'.
15 As seen in Fig. 3, the tube 8 of thermoplastic plastics is extruded from the
~nmll~r die 29 at a radial distance to the fluid pipe 2. Since the external
wall 38 of the fluid pipe is coated with a thin layer of a temperature-
resistant parting agent, the thermoplastic tube 8 cannot stick or weld on the
fluid pipe 2. Parting agents of this type are commercial. It is even conceiv-
20 able to use water as a parting agent, which evaporates and thus forms aparting layer. Upon entry of the tube 8 in the molding path 47, it is sucked
into the profiled shape 49 on the insides of the half shells 43, 43' due to the
low pressure, the profile of the cross-grooves 3 thus being conferred to it.
In this case, the first vacuum supply system 53 serves to suck the tube 8
25 into the profiled shape 49, i.e. to deform the tube 8. The subsequent, sec-
ond vacuum supply system 54 then serves to stabilize the deformed tube 8,
i.e. to keep it in the deformed condition. The fluid pipe 2, the tube 8 and
the half shells 43, 43' in the molding path 47 have almost the same speed in
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- 10-
the direction of production 6, i.e. there is no important difference of speed
in the direction of production 6 between the corrugated enveloping pipe 1
that forms from the tube 8 and the fluid pipe 2. Since due to the pure vac-
uum treatment, the pipe die head 10 does not reach into the molding path
5 47 during the deformation of the tube 8, the fluid pipe 2 can have a great
outside diameter d relative to the inside diameter D of the corrugated en-
veloping pipe 1. Additionally, the fluid pipe 2 cannot be rigid radially to
the axis 15, because it need not be compressed during its entry, together
with the tube 8, into the molding path 47; no space is required for m~chine
10 parts such as components of the pipe die head 10. In the molding path 47,
the tube 8 is cooled down conventionally to such an extent that leaving the
molding path 47 is the already inherently stable corrugated enveloping pipe
1 having cross grooves 3 and housing the fluid pipe 2.
15 In a cooling bath 55 disposed downstream of the molding machine 9, this
corrugated enveloping pipe 1 is further cooled by an appropliate coolant 56
which is directed onto the corrugated pipe 1 by nozzles 57 (roughly out-
lined). The coolant can be air or water. Cooling baths of this type are
known and general practice.
A belt or Caterpillar delivery mech~ni~m 58 is disposed downstream of the
cooling bath 55 in the direction of production 6, conveying the corrugated
enveloping pipe 1 in the direction of production 6. Belt of Caterpillar de-
livery mech~nism~ 58 of this type are also known and common practice.
Downstream of the delivery mechanism 58, provision is made for a cutter59 which is equipped for instance with a cutting-off saw 60, the saw 60,
during execution of a cutting operation, traveling as usual along with the
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corrugated enveloping pipe 1 and the fluid pipe 2 contained therein by a
length a in the direction of production 6 from a position shown in solid
lines in Fig. 2 into the position shown by dashes. Cutting the corrugated
enveloping pipe 1 together with the fluid pipe 2 takes place in lengths that
5 can be rolled up on a downstream take-up roller 61.
