Title of Invention

DEVICE FOR MUNUFACTURING A DOUBLE -WALLED THERMOPLASTIC PIPE WITH A CONNECTING SLEEVE

Abstract The invention relates to a device for manufacturing a double- walled thermoplastic pipe with a connecting sleeve. When the pipe is manufactured by using this device, there forms an ap- proximately annular space (A), which is defined by an extrusion head (1), a first flexible tube (2), which is extruded into a molding tunnel (4), and a second flexible tube (5), which is extruded into the first flexible tube (2). The invention envis- ages connecting the space (A) to a compressed-gas reservoir (24), so that pressure changes in the space (A) are attenuated by the compressed-gas vessel (Fig. 1).
Full Text Device for manufacturing a double-walled thermoplastic pipe
with a connecting sleeve
The invention relates to a device for manufacturing a double-
walled thermoplastic pipe with a connecting sleeve.
A device of this type is known for example from DE 101 10 064
Al. The device has a number of molds guided on a path, which
form a molding tunnel, which has in at least a first portion a
corrugated molding wall and in at least a second portion a
Sleeve recess corresponding to the connecting sleeve. An extru-
sion head of the device has a first die for the extrusion of a
tirst flexible tube into the molding tunnel and a second die,
arranged downstream in the direction of movement of the molds
In the molding tunnel, for the extrusion of a second flexible
tube. Arranged between the two dies is a first gas channel,
which is connected to a first compressed-gas control device for
generating a pressure p1 or p2 in the space between the two
tubes by the compressed gas emerging from the mouth of the
first gas channel. A second gas channel, which opens out down-

2
stream of the second die in the direction of movement of the
molds of the molding tunnel, is connected to a second com-
prsssed-gas control device, in order to generate a pressure p3,
lying above atmospheric pressure, on the inner side of the
second flexible tube by the compressed gas emerging from the
mouth of the second gas channel. The two compressed-gas control
devices are controlled In an open-loop or closed-loop manner by
means of a control device.
With the device, the first flexible tube is extruded into the
molding tunnel. In the first portion of the molding tunnel, the
first flexible tube is brought into a corrugated form and, in
the second portion of the molding tunnel, it is expanded to
form the connecting sleeve. The second flexible tube is ex-
truded into the first flexible tube and pressed against the
corrugation troughs of the first flexible tube, so that a com-
posite pipe comprising an outer tube and an inner tube fused
with the latter is formed. While the first flexible tube is
being brought into the corrugated form and the second flexible
tube is being extruded into the first flexible tube, the space
between the two tubes is subjected to a pressure p1 lying above
atmospheric pressure (the space between the two flexible tubes
is referred to hereafter as space A). The pressure p1 is set at.
such a level that, after the cooling of the flexible tubes
fused together at the corrugation troughs, the inner tube is
not curved inward or outyrard between these points. After the
cooling of the flexible tubes, it is intended that atmospheric
pressure will be established there. Moreover, the pressure p1
produces the corrugated form of the first flexible tube.

3
If the first flexible tube is to be expanded in the second
portions to form the connecting sleeve, the pressure p2 is set
in the space A. The pressure p2 must not be too low, otherwise
the first flexible tube would not expand, or not expand ade-
quately to form the connecting sleeve. If, on the other hand,
the pressure p2 is too great, the first flexible tube is
stretched during extrusion, so that it has a thinner wall
thickness at the beginning of the formation of the connecting
sleeve and a thicker wall thickness at the end of the connect-
ing sleeve.
During the extrusion of the second flexible tube into the first
flexible tube which has been expanded to form the connecting
sleeve, the second flexible tube is subjected to a pressure p3
above atmospheric pressure from the inside and pressed against
the first flexible tube. As a result, it is ensured that fusion
of the two flexible tubes is achieved over their full surface
area in the region of the connecting sleeve.
Once the connecting sleeve has been formed by the two flexible
tubes and the second flexible tube is extruded again against
the corrugation troughs of the first flexible tube in a further
first portion of the same, the space A is again subjected to
the pressure p1
The closed-loop or open-loop control of the pressures p1, p2
and p3 takes on special significance, since curvatures of the
inner flexible tube and/or irregularities in the wall thickness
Of the connecting sleeve can be avoided to the greatest extent
by suitable setting of the pressures. In the case of the device
described above, closed-loop control of the pressures p1 and

4
p2, to which the space A is subjected, in particular proves to
be difficult. This space is in this case bounded by the extru-
sion head and the two flexible tubes, it being intended that
the first flexible tube either lies against the corrugated
molding wall or against the sleeve recess. Since the diameter
of the sleeve recess is greater than the diameter of the corru-
gated molding wall, the volume of the space A depends on the
respective stage of the process. Consequently, the volume
changes at the beginning end at the end of the manufacture of
the connecting sleeve. In particular in the case of large pipe
diameters, the changes in volume in the space A influence the
pressures p1 and p2 to such an extent that maintaining them
imposes very great demands on the pressure control.
Furthermore, the temperature in the space A also influences the
pressure prevailing there. The temperature depends on the
amounts of heat that are supplied to and removed from the space
A. The amounts of heat in turn depend on the surface areas of
the space A via which the amounts of heat are transferred.
Consequently, the different form of the molds in the first
portion (corrugated) and the second portion also influences the
pressure prevailing in the space A.
Therefore, the object underlying the invention is to improve
the device for manufacturing a double-walled thermoplastic pipe
with a connecting sleeve in such a way that, in the first por-
tion of the molding tunnel, a curvature of the inner tube is
avoided during the cooling of the. flexible tubes and, in the
second portion of the molding tunnel, satisfactory expansion of
the first flexible tube to form a connecting sleeve is made
possible.

5
According to the invention, this object is achieved by the
features of claim 1, In this case, the pressure controller is
connected to said first gas channel by a compressed-gas line
which is connected to an additional compressed-gas reservoir
for gas exchange. The compressed-gas reservoir can consequently
communicate with the space A via the compressed-gas line and
via the first gas channel. If, for example on account of an
increase in volume of the space A, the pressure there drops,
there is immediately a pressure equalization between space A
and the compressed-gas reservoir, which attenuates the pressure
drop in the space A. This makes it possible in a simple way to
avoid to the greatest extent undesired pressure gradients in
the space A, which would otherwise have to be equalized by the
compressed-gas control device, which however would involve much
more, sophisticated closed-loop control. According to the inven-
tion, the pressure is controlled in a closed-loop or open-loop
manner in a complete system, the volume of which is substan-
tially made up by the volume of the space A and the volume of
the compressed-gas reservoir. This leads to an evening-out of
the pressure profile in the space A, so that in particular the
undesired curvatures at the inner wall of the double-walled
pipe can be avoided.
In a preferred embodiment, the compressed-gas reservoir is
formed as a separate vessel. Consequently, a compressed-gas
line with customary flow cross sections can be used for the
connection of the compressed-gas control device to the first
gas channel, the size of the vessel determining the extent of
the attenuation of the pressure changes in the space A. The
additional compressed-gas reservoir may also be formed by the

6
widening of the flow cross section of the compressed-gas line,
at least in partial regions of the compressed-gas line.
The separate vessel is preferably connected to the compressed-
gss line by a T-shaped sleeva. This allows a device known from
the art to be modified in a simple way, in that the compressed-
gas line provided there is cat and the T-shaped sleeve with a
compressed-gas vessel is inserted there.
The compressed-gas vessel may be releasably connected to the T-
sleeve. It is therefore possible, for example, in a trial phase
of the device to analyze the influence of the sise of the sepa-
rate vessel on the quality of the pipe wall in a simple way, in
order to determine the optimum vessel volume for the process.
The compressed-gas vessel may comprise two supply lines and be
connected in series with the compressed-gas line. It is also
possible to connect the compressed-gas vessel parallel to the
compressed-gas line, that is to say to connect the compressed-
gas vessel to the compressed-gas line by a bypass.
In a preferred embodiment, the compressed-gas reservoir is
arranged in the vicinity of the first gas channel. An arrange-
ment of this type allows the flow resistances between the com-
pressed-gas reservoir and the space A to be minimized, so that
a rapid pressure equalization can take place between the com-
pressed-gas reservoir and the space A.
The compressed-gas control device preferably has a pressure
gage, which is arranged upstream of the compressed-gas reser-
voir. Consequently, the pressure gage does not directly detect

7
pressure equalizations between the compressed-gas vessel or
reservoir and the space A, but only the pressure of the com-
plete system, the volume of which is, as already described
above, substantially made up by the volume of the compressed-
gas reservoir and of the space A.
A safety valve may be connected between the compressed-gas
control device and the first gas channel. The valve is prefera-
bly formed as a spring-actuated valve, which closes under a
specific pressure, In this way it is possible to avoid inadmis-
aible excess pressures in the space A, for example if there is
a defect of the compressed-gas control device.
The outer diameter of the molding wall in the first portion,
which corresponds to the pipe diameter of the pipe to be manu-
factured, may be greater than 500 mm, preferably greater than
800 mm. In particular in the case of large pipes, it has proven
to be expedient to use the gas-pressure reservoir according to
the invention. As the pipe diameter becomes greater, the volume
decrease or increase for the space A becomes greater when a
changeover is made from the manufacture of the connecting
sleeve to the manufacture of the corrugated pipe wall or a
changeover is made from the manufacture of the corrugated pipe
wall to the manufacture of the connecting sleeve. As the pipe
diameter becomes greater, the decrease or increase in the heat
transfer surface areas o£ the apace A also becomes greater when
there is a changeover between manufacture of the connecting
sleeve and manufacture of the corrugated wall.
In a preferred embodiment, the volume of the reservoir is
greater than 10 liters (standard liters). The volume is pref-

8
erably greater than 20 liters. In order that the system to be
controlled, comprising the compressed-gas reservoir, the gas-
pressure line, the first gas channel and the space A, does not
become too slow-acting, in a preferred embodiment the volume of
the compressed-gas reservoir is less than 50 liters. Prefera-
bly, it may also be less than 40 liters.
Alternatively or additionally, the compressed-gas control line
for generating the pressure p3 on the inner side of the second
flexible tube may comprise a pressure controller which is con-
nected to the second gas channel via a compressed-gas line
which is connected to a second, additional compressed-gas res-
ervoir for gas exchange.
The invention is explained in more detail on the basis of an
embodiment represented in the drawing, in which:
Fig. 1 shows a longitudinal section through part of an
extrusion head of the device according to the inven-
tion before the manufacture of a connecting sleeve;
Fig. 2 shows a longitudinal section through part of the
extrusion head and the (Holding tunnel during the ex-
trusion of the second flexible tube into the first
flexible tube, expanded into the connecting sleeve;
Fig. 3 schematically shows a control of the pressures pl, p2
and p3; and
Fig. 4 shows a view of the compressed-gas control devices
with a compressed-gas reservoir.

9
Figures I and 2 show an extrusion head 1 of the device accord-
ing to the invention in various process steps. In the step
represented in Fig. 1, a first flexible tube 2 is extruded
through a first die 3 of the extrusion head 1 into a first
portion of the molding tunnel 4 and brought into a corrugated
form. A second flexible tube 5 is extruded through a second die
6 of the extrusion head 1 into the first flexible tube 2 and
pressed against corrugation troughs 7 of the first flexible
tube 2. Arranged downstream of the extrusion head 1 in the
direction, of production. Is a calibrating mandre1 8 for the
second flexible tube 5.
While the first flexible tube 1 is being brought into the cor-
rugated form and the second flexible tube 5 is being pressed
against the corrugation troughs 7 Of the first flexible tube 2
and fused with them, the space between the two flexible tubes 2
and 5, space A, is subjected to a pressure p1 lying above at-
mospheric pressure. The pressure is generated by a compressed
gas which emerges from a first gas channel 9, arranged on the
extrusion head 1 between the two dies 3 and 6.
The pressure p1 is set such that, after the cooling of the two
flexible tubes 2 and 5, atmospheric pressure is established in
the intermediate spaces 10 between the two flexible tubes, so
that the second flexible tube does not have any curvatures at
the points of connection with the corrugation troughs 7 of the
first flexible tube 2. It must be ensured that, in the process
step represented in Fig. 1, compressed gas constantly flows
into the space A to maintain the pressure p1, since the inter-
mediate spaces 10 filled with the pressure p1 extract com-
pressed gas from the space A.

10
Fig. 2 shows a process situation in which the second die 6 of
the extrusion head 1 has already reached a sleeve recess 11 of
the molding tunnel 4, while the first flexible tube 2 is still
being extruded into the sleeve recess 11 . In the space A be-
tween the two flexible tubes 2 and 5 there is then a substan-
tially constant pressure p2, which is less than p1. With the
pressure p2, the first flexible tube 2 is pressed over its full
surface area against the sleeve recess 11.
As Fig. 2 reveals, the pressure p2 is set such that the first
flexible tube 2, extruded from the first die 3, is raised to-
ward the sleeve recess 11, but not inflated to the extent that
there is excessive stretching, which leads to a small wall
thickness of the flexible tube 2 in the region of the beginning
and middle of the sleeve recess 11 and a build-up of the ther-
moplastic material, and consequently an enlargement of the wall
thickness, at the end of the sleeve recess 11 that is remote in
the direction of production.
In order effectively to fuse the second flexible tube 5 with
the first flexible tube 1 which has been expanded to form the
connecting sleeve, in the process situation represented in Fig.
2 the second flexible tube 5 is subjected to a pressure p3
above atmospheric pressure from the inside via a second gas
channel 12. The pressure p3 is set such that optimum fusing of
the second flexible tube 5 with the first flexible tube 2 is
ensured.
If Figures 1 and 2 are compared, it becomes clear that the
volume of the space A varies, depending on the process step,
and changes during the process. The size of the surface areas

11
of the space A via which the amounts of heat are transported
also changes in the course of the process. Both the changing of
the volume and the changing of the size of the heat-transfer
surface areas have an influence on the pressure in the chamber
A. However, the pressure changes caused as a result are attenu-
ated or partly equalized by the pressure cushion in the pres-
sure reservoir according to the invention.
Fig. 3 shows the control of the pressures p1, p2 and p3 by
compressed-gas control devices 13 and 14 connected to the first
gas channel 9 and the second gas channel 12, by means of a
control device 15 for the time-dependent switching of the com-
pressed-gas control devices 13 and 14.
A compressed gas for generating the pressures p1, p2 and p3 is
supplied to the compressed-gas control devices 13 and 14 via a
compressed-gas feed 16. The compressed-gas control device 13
serves for generating the pressure p1 and the pressure p2 by
the gas emerging from the mouth of the first, gas channel 9 into
the space A, while the compressed-gas control device 14 is
provided for generating the pressure p3 to which the second
flexible tube 5 is subjected from the inside by the compressed
gas emerging from the mouth of the second gas channel 12. A
compressed-gas line 26 connects the compressed-gas control
device 13 to the first gas channel.
This time-dependent switching of the compressed-gas control
devices 13 and 14 takes place by the control device 15. By
means of a device not described any further here, the control
device 15 receives signals via a signal supply line 17, on the
basis of which the pressures p1, p2 and p3 can be set variably

12
over time in dependence on the position of the forming tunnel
in relation to the extrusion head. This allows the compressed-
gas control devices to set specific pressure values for p1, p2
and p3 in dependence on the relative position of the molding
tunnel.
In Fig, 4, an embodiment of the compressed-gas control devices
13 and 14 for the time-dependent switching of the pressures p1,
p2 and p3 is represented. The compressed gas required for set-
ting the pressures p1, p2 and p3 is supplied via the com-
pressed-gas feed 16. This is connected via branches to pressure
controllers 18 and 19, Downstream of the pressure controllers
18 and 19, the gas pressure emerging from the latter is meas-
ured by pressure gages 20 and 21, respectively, and indicated
to an actuating unit (not represented in detail in Fig. 4)
inside the pressure controllers 13 and 19. Since, as Fig. 4
reveals, the actuating units are operated with the aid of the
compressed gas provided by the compressed-gas feed 16 , but at a
lower pressure value, pressure reducers 23 and 24 are required.
Arranged downstream of tlie pressure controller 16 and the pres-
sure gage 20 is a compressed—gas vessel 24, which is connected
by a T-sleeve 25 to a compressed-gas line 26. The compressed-
gas line 26 connects the pressure controller 18 to the first
gas channel 9.
In the Case of the embodiment represented here, the compressed-
gas control device controls via the pressure controller 18 the
pressure in a system which comprises the compressed-gas line
26, the vessel 24, the first gas channel 9 and the space A. An
approximately equal pressure prevails in the compressed-gas

13
vessel 24 and in the space A, since they can communicate with
each other without any appreciable flow resistances. Conse-
quently pressure changes in the space A are attenuated by the
pressure cushion in the compressed-gas vessel. Attenuation of
this type facilitates the suitable control of the pressures p1
and p2 and consequently the manufacture of doubls-walled pipes
with a connecting sleeve.

14
List of Reference Numerals
1 extrusion head
2 first flexible tube
3 first die
4 molding tunnel
5 second flexible tube
6 second die
7 troughs
8 calibrating mandrel
9 first gas channel
10 intermediate space
11 sleeve recess
12 second gas channel
13 compressed-gas control device
14 compressed-qas control device
15 control device
16 compressed-gas feed
17 signal supply line
18 pressure controller
19 pressure controller
20 pressure gauge
21 pressure gauge
22 pressure reducer
23 pressure reducer
24 compressed-gas vessel
25 T-sleeve
26 compressed-gas Line
A Space between flexible tubes 2 and 5

15
Claims
1. A device for manufacturing a double-walled thermoplastic
pipe with a connecting sleeve, comprising
A) a molding tunnel (4), which is formed by at least a
succession of molds guided on a path, and which has in
at least a first portion a corrugated molding wall and
in at least a second portion a sleeve recess (11) cor-
responding to the connecting sleeve,
B) an extrusion device provided with an extrusion head
(1), the extrusion head (1) having a first die (3) for
the extrusion, of a first flexible tube (2) into the
molding tunnel (4) and a second die (6), arranged
downstream in the direction of movement of the molds
in the molding tunnel (4), for the extrusion of a sec-
ond flexible tube (5),
C) a first gas channel (9), arranged between the two dies
(3) and (6), and a second gas channel (12), opening
out downstream of the second die (6) in the direction
of movement of the molds of the molding tunnel (4),
D) a compressed-gas control device (13), connected to the
first gas channel (9), for generating a pressure p1 or
p2 in 3 space (A) between the two flexible tubes (2,
5) by the compressed gag emerging from the mouth of
the first gas channel (9), the compressed-gas control
device (15) comprising a pressure controller (18),
E) a compressed-gas control device (14) , connected to the
second gas channel (12), for generating a pressure p3
lying above atmospheric pressure on the inner side of
the second flexible tube (5) by the compressed gas

16
emerging from the mouth of the second gas channel
(12),
F) a control devics (15) for controlling the compressed-
gas control devices (13) and (14),
characterized in that the pressure controller (18) is con-
nected to the first gas channel (9) via a compressed-gas
line (26), which is connected to an additional compressd-
gas reservoir (24) for gas exchange.
2. The device as claimed in claim 1, characterised in that
the compressed-gas reservoir (24) is formed as a separate
compressed-gas vessel (24)
3. The device as claimed in claim l, characterized in that
the compressed-gas reservoir (24) is formed by an exten-
sion of the flow cross section at least in partial regions
of the compressed-gas line (26).
4. The device as claimed in claim 2, characterized in that
the separate compressed-gas vessel (24) is connected to
the compressed-gas line (26) by a T-shaped sleeve (25) .
5. The device as claimed in claim 4, characterised in that
the compressed-gas vessel (24) is releasably connected to
the T-shaped sleeve (25).
6. The device as claimed in claim 2, characterised in that
the compressed-gas vessel (24) comprises two supply lines
and is connected in series with the compressed-gas line
(26).

17
7. The device as claimed in claim 2, characterized in that
the compressed-gas vessel (24) comprises two supply lines
and is connected in parallel with the compressed-gas line
8. The device as claimed in anyone of claims 1 to 7 , charac-
terized in that the compressed-gas reservoir {24) is ar-
ranged in the vicinity of the first gas channel (9).
9. The device as claimed in anyone of claims 1 to 8 , charac-
terised in that the compressed-gas control (13) has a
pressure gage (20), which is arranged upstream of the com-
pressed-gas reservoir (24).
10. The device as claimed in anyone of claims 1 to 9, charac-
terized in that a safety valve is connected between the
compressed-gas control device (13) and the first gas chan-
nel (9) .
11. The device as claimed in anyone of claims 1 to 10, charac-
terized in that the outer diameter of the molding wall (4)
in the first portion is greater than 500 mm, preferably
greater than 300 mm.
12. The device as claimed in anyone of claims 1 to 11, charac-
terized in that the volume of the compressed-gas reservoir
(24) is greater than 10 liters, preferably greater than 20
liters.

18
13. The device as claimed in anyone of claims of 1 to 12,
characterised in that the volume of the compressed-gas
reservoir (24) is less than 60 liters, preferably less
than 50 liters,
14. The device as claimed in anyone of claims 1 to 13, charac-
terized in that the compressed-gas control device (14)
comprises a pressure controller (l9), the pressure con-
troller (19) being connected to the second gas channel
(12) via a compressed-gas line which is connected to a
second, additional compressed-gas reservoir for gas ex-
change.

The invention relates to a device for manufacturing a double-
walled thermoplastic pipe with a connecting sleeve. When the
pipe is manufactured by using this device, there forms an ap-
proximately annular space (A), which is defined by an extrusion
head (1), a first flexible tube (2), which is extruded into a
molding tunnel (4), and a second flexible tube (5), which is
extruded into the first flexible tube (2). The invention envis-
ages connecting the space (A) to a compressed-gas reservoir
(24), so that pressure changes in the space (A) are attenuated
by the compressed-gas vessel (Fig. 1).

Documents:

00005-kolnp-2006-abstract.pdf

00005-kolnp-2006-claims.pdf

00005-kolnp-2006-description complete.pdf

00005-kolnp-2006-drawings.pdf

00005-kolnp-2006-form 1.pdf

00005-kolnp-2006-form 2.pdf

00005-kolnp-2006-form 3.pdf

00005-kolnp-2006-international publication.pdf

00005-kolnp-2006-pct forms.pdf

00005-kolnp-2006-priority document.pdf

5-KOLNP-2006-ABSTRACT-1.1.pdf

5-KOLNP-2006-ABSTRACT.pdf

5-KOLNP-2006-AMENDED CLAIMS.pdf

5-KOLNP-2006-CANCELLED PAGES.pdf

5-KOLNP-2006-CLAIMS.pdf

5-KOLNP-2006-CORRESPONDENCE-1.1.pdf

5-KOLNP-2006-CORRESPONDENCE-1.2.pdf

5-kolnp-2006-correspondence.pdf

5-KOLNP-2006-DESCRIPTION (COMPLETE)-1.1.pdf

5-KOLNP-2006-DESCRIPTION (COMPLETE).pdf

5-KOLNP-2006-DRAWINGS-1.1.pdf

5-KOLNP-2006-DRAWINGS.pdf

5-KOLNP-2006-FORM 1-1.1.pdf

5-KOLNP-2006-FORM 1.pdf

5-kolnp-2006-form 18.pdf

5-KOLNP-2006-FORM 2-1.1.pdf

5-KOLNP-2006-FORM 2.pdf

5-kolnp-2006-form 26.pdf

5-KOLNP-2006-FORM 3.pdf

5-KOLNP-2006-FORM 5-1.1.pdf

5-KOLNP-2006-FORM 5.pdf

5-KOLNP-2006-FORM-27.pdf

5-KOLNP-2006-OTHERS.pdf

5-KOLNP-2006-PETITION UNDER RULE 137.pdf

5-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-00005-kolnp-2006.jpg

Thumbs.db


Patent Number 242315
Indian Patent Application Number 5/KOLNP/2006
PG Journal Number 35/2010
Publication Date 27-Aug-2010
Grant Date 23-Aug-2010
Date of Filing 02-Jan-2006
Name of Patentee MANFRED ARNO ALFRED LUPKE
Applicant Address 92 ELGIN STREET THORNHILL, ONTARIO L3T 1W6 CANADA
Inventors:
# Inventor's Name Inventor's Address
1 MANFRED ARNO ALFRED LUPKE 92 ELGIN STREET THORNHILL, ONTARIO L3T 1W6 CANADA
2 STEFAN A. LUPKE 32 VINTAGE LANE THRONHILL, ONTARIO L3T 1X6 CANADA
PCT International Classification Number B29C 49/00, 49/78
PCT International Application Number PCT/1B2004/003361
PCT International Filing date 2004-06-23
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 103 35 518.9 2003-07-31 Germany