CA2261073A1 - Method and apparatus for making plastic pipe without mechanical pressure on inner pipe wall - Google Patents
Method and apparatus for making plastic pipe without mechanical pressure on inner pipe wall Download PDFInfo
- Publication number
- CA2261073A1 CA2261073A1 CA002261073A CA2261073A CA2261073A1 CA 2261073 A1 CA2261073 A1 CA 2261073A1 CA 002261073 A CA002261073 A CA 002261073A CA 2261073 A CA2261073 A CA 2261073A CA 2261073 A1 CA2261073 A1 CA 2261073A1
- Authority
- CA
- Canada
- Prior art keywords
- wall
- pipe
- pipe wall
- walls
- mold tunnel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/0015—Making articles of indefinite length, e.g. corrugated tubes
- B29C49/0021—Making articles of indefinite length, e.g. corrugated tubes using moulds or mould parts movable in a closed path, e.g. mounted on movable endless supports
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/0013—Extrusion moulding in several steps, i.e. components merging outside the die
- B29C48/0015—Extrusion moulding in several steps, i.e. components merging outside the die producing hollow articles having components brought in contact outside the extrusion die
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/13—Articles with a cross-section varying in the longitudinal direction, e.g. corrugated pipes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
- B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
- B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D23/00—Producing tubular articles
- B29D23/18—Pleated or corrugated hoses
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
A method of making double wall plastic pipe (8) having inner (8) and outer (5) pipe walls adhered to one another without mechanically holding the inner pipe wall against the outer pipe wall comprises extruding separate streams of molten plastic into a mold tunnel (3) to form the inner and outer pipe walls and producing a positive gas pressure which acts internally of and forces the inner pipe wall (8) outwardly against the outer pipe wall (5) while the pipe is being formed in the mold tunnel (3).
Description
Title: METHOD AND APPARATUS FOR MAKING PLASTIC PIPE
WITHOUT MECHANICAL PRESSURE ON INNER PIPE WALL
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for making double wall plastic pipe.
BACKGROUND OF THE INVENTION
According to conventional methods of manufacturing double wall plastic pipe, the inner and outer pipe walls are formed separately from one another within a mold tunnel. A mechanical assist and principally a cooling plug is used to force the inner pipe wall against the outer pipe wall to secure the two pipe walls to one another. This slows 15 down production of the pipe through the drag created by the contact between the plug and the inner pipe wall and also produces distortions on the inner surface of the pipe wall. When the pipe is in use, these distortions are extremely detrimental as they create undesirable build up or collection areas for product passing through the pipe.
SUMMARY OF THE INVENTION
The present invention provides a method of making double wall plastic pipe where the inner and outer pipe walls are adhered to one 25 another without using mechanical pressure to hold the inner pipe wall against the outer pipe wall. In accordance with the present invention, separate streams of molten plastic are extruded into a mold tunnel to form the inner and outer pipe walls and the inner pipe wall is forced outwardly against the outer pipe wall by gas pressure produced internally of the inner 3 o pipe wall and acting on the inner pipe wall while the pipe is in the mold tunnel. The use of gas pressure internally of the inner pipe wall does not produce scratching or other type of marking on the inside surface of the inner pipe wall and further substantially produces production speed of the pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
WITHOUT MECHANICAL PRESSURE ON INNER PIPE WALL
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for making double wall plastic pipe.
BACKGROUND OF THE INVENTION
According to conventional methods of manufacturing double wall plastic pipe, the inner and outer pipe walls are formed separately from one another within a mold tunnel. A mechanical assist and principally a cooling plug is used to force the inner pipe wall against the outer pipe wall to secure the two pipe walls to one another. This slows 15 down production of the pipe through the drag created by the contact between the plug and the inner pipe wall and also produces distortions on the inner surface of the pipe wall. When the pipe is in use, these distortions are extremely detrimental as they create undesirable build up or collection areas for product passing through the pipe.
SUMMARY OF THE INVENTION
The present invention provides a method of making double wall plastic pipe where the inner and outer pipe walls are adhered to one 25 another without using mechanical pressure to hold the inner pipe wall against the outer pipe wall. In accordance with the present invention, separate streams of molten plastic are extruded into a mold tunnel to form the inner and outer pipe walls and the inner pipe wall is forced outwardly against the outer pipe wall by gas pressure produced internally of the inner 3 o pipe wall and acting on the inner pipe wall while the pipe is in the mold tunnel. The use of gas pressure internally of the inner pipe wall does not produce scratching or other type of marking on the inside surface of the inner pipe wall and further substantially produces production speed of the pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
- 2 -The above as well as other advantages and features of the present invention will be described in greater detail according to the preferred embodiments of the present invention in which:
Figure 1 is a schematic view of a pipe manufacturing apparatus;
Figure 2 is a sectional view showing preferred features of the pipe forming apparatus of Figure 1.
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
Figure 1 shows the general outlines of a pipe manufacturing apparatus which includes an extruder die 1 at the upstream end of the 15 apparatus and a pipe forming mold tunnel down stream of the extruder die. Double wall pipe P emerges from the downstream end of the mold tunnel. This pipe, as better seen in Figure 2 of the drawings, comprises a profiled and in this case, corrugated outer wall 6 with a flat inner wall 8 secured or adhered to the troughs of the outer wall. The adhesion occurs 20 because the two walls meet with one another in a molten state and once cooled remain secured to one another as is known in the art. However, unlike prior art methods, the method of the present invention does not use a mechanical assist to physically hold the inner wall against the outer wall while the pipe is in the mold tunnel. In accordance with the present 25 invention, gas pressure is produced to force the inner wall outwardly against the outer wall.
More specifically, Figure 2 shows the extruder die as having a first extrusion orifice 5 through which a stream of molten plastic is fed to
Figure 1 is a schematic view of a pipe manufacturing apparatus;
Figure 2 is a sectional view showing preferred features of the pipe forming apparatus of Figure 1.
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
Figure 1 shows the general outlines of a pipe manufacturing apparatus which includes an extruder die 1 at the upstream end of the 15 apparatus and a pipe forming mold tunnel down stream of the extruder die. Double wall pipe P emerges from the downstream end of the mold tunnel. This pipe, as better seen in Figure 2 of the drawings, comprises a profiled and in this case, corrugated outer wall 6 with a flat inner wall 8 secured or adhered to the troughs of the outer wall. The adhesion occurs 20 because the two walls meet with one another in a molten state and once cooled remain secured to one another as is known in the art. However, unlike prior art methods, the method of the present invention does not use a mechanical assist to physically hold the inner wall against the outer wall while the pipe is in the mold tunnel. In accordance with the present 25 invention, gas pressure is produced to force the inner wall outwardly against the outer wall.
More specifically, Figure 2 shows the extruder die as having a first extrusion orifice 5 through which a stream of molten plastic is fed to
3 o the rib forming profile on the inner surface of the mold tunnel 3 to form the outer pipe wall 6. Also provided is a second extrusion orifice 7 downstream of the first extrusion orifice 5 which feeds a second stream of molten plastic to form the interior pipe wall 8. In the preferred embodiment as shown, a small lip 4 is provided at the second extrusion 35 orifice to guide the inner wall forming stream of plastic outwardly towards the outer wall forming stream of plastic as the two streams leave the die head. However, it should be noted that this lip or guide is not required and although the lip applies a slight momentary pressure on the plastic, it is no way maintains pressure to hold the inner wall against the outer wall while the two walls are fusing together.
Pressure is however applied to force the inner wall 8 outwardly against the troughs of the outer wall 6 as the plastic starts to cure and harden in the mold tunnel. This pressure is created by gas or air pressure within the mold tunnel. In the particular arrangement shown, the die head has a passage 18 which opens to the outside atmosphere and a fan 17 is provided to push air into the mold tunnel through passage 18. A baffle 15 is provided interiorly of the inner pipe wall 8. Although there is sufficient clearance to avoid contact between the inner pipe wall and baffle 15, the baffle does act as a block to maintain much of this pressure on the upstream side of the baffle. This pressure is sufficient to hold the inner wall against the outer wall while the two walls cure with one another.
The pressure provided inside the inner pipe wall must be sufficient to hold the inner wall against outer wall overcoming the pressure within the pockets 9 between the inner pipe wall and the crests of 2 0 the outer pipe wall. In order to produce a positive securing of the two walls, the pressure inside the inner wall will generally be slightly greater than the pressure within the pockets.
After the pipe emerges from the mold tunnel where it is 2 5 sufficiently hardened to maintain its shape, a cap 19 can be applied to the end of the pipe and this cap again acts as a block to prevent escape of the gas or air pressure built up inside the pipe.
It should be noted that the positive air pressure can also be 3 o produced from the downstream end and forced towards the upstream end of the system in which case the end cap, the baffle and the path through the die head would not be used.
Figure 2 also shows the use of a cooling coil 13 which cools the air internally of the inner pipe wall. This decreases curing or hardening time for the inner pipe wall but in no way provides anything in the way of mechanical pressure against the inner pipe wall.
. . . ~ .
Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art, that variations may be made without departing from the 5 spirit of the invention or the scope of the appended claims.
Pressure is however applied to force the inner wall 8 outwardly against the troughs of the outer wall 6 as the plastic starts to cure and harden in the mold tunnel. This pressure is created by gas or air pressure within the mold tunnel. In the particular arrangement shown, the die head has a passage 18 which opens to the outside atmosphere and a fan 17 is provided to push air into the mold tunnel through passage 18. A baffle 15 is provided interiorly of the inner pipe wall 8. Although there is sufficient clearance to avoid contact between the inner pipe wall and baffle 15, the baffle does act as a block to maintain much of this pressure on the upstream side of the baffle. This pressure is sufficient to hold the inner wall against the outer wall while the two walls cure with one another.
The pressure provided inside the inner pipe wall must be sufficient to hold the inner wall against outer wall overcoming the pressure within the pockets 9 between the inner pipe wall and the crests of 2 0 the outer pipe wall. In order to produce a positive securing of the two walls, the pressure inside the inner wall will generally be slightly greater than the pressure within the pockets.
After the pipe emerges from the mold tunnel where it is 2 5 sufficiently hardened to maintain its shape, a cap 19 can be applied to the end of the pipe and this cap again acts as a block to prevent escape of the gas or air pressure built up inside the pipe.
It should be noted that the positive air pressure can also be 3 o produced from the downstream end and forced towards the upstream end of the system in which case the end cap, the baffle and the path through the die head would not be used.
Figure 2 also shows the use of a cooling coil 13 which cools the air internally of the inner pipe wall. This decreases curing or hardening time for the inner pipe wall but in no way provides anything in the way of mechanical pressure against the inner pipe wall.
. . . ~ .
Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art, that variations may be made without departing from the 5 spirit of the invention or the scope of the appended claims.
Claims (3)
1. A method of making double wall plastic pipe having inner and outer pipe walls adhered by curing to one another without mechanically holding the pipe wall against the outer pipe wall, said method comprising extruding separate streams of molten plastic into a mold tunnel to form the inner and outer walls and producing a positive pressure by a gas internally of and forcing the inner wall outwardly against the outer wall while the pipe is in the mold tunnel, the gas being cooled to decrease curing time of the pipe walls.
2. The method of Claim 1, wherein the gas is cooled by a cooling device located interiorly of the inner pipe wall within the mold tunnel, said method including moving the inner pipe wall past the cooling device without any contact between the inner pipe wall and the cooling device.
3. The method of Claim 1, including forming the outer pipe wall with a profiled surface and forming the inner pipe wall with a flat profile and wherein the positive pressure internally of the inner pipe wall is greater than any pressure produced as a result of air trapped between the inner and outer pipe walls.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/CA1997/000332 WO1998052739A1 (en) | 1997-05-20 | 1997-05-20 | Method and apparatus for making plastic pipe without mechanical pressure on inner pipe wall |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2261073A1 true CA2261073A1 (en) | 1998-11-26 |
Family
ID=4173215
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002261073A Abandoned CA2261073A1 (en) | 1997-05-20 | 1997-05-20 | Method and apparatus for making plastic pipe without mechanical pressure on inner pipe wall |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0927099A1 (en) |
| CA (1) | CA2261073A1 (en) |
| DE (1) | DE29723138U1 (en) |
| WO (1) | WO1998052739A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2412066A1 (en) * | 2002-11-18 | 2004-05-18 | Manfred A. A. Lupke | Pipe molding apparatus with mold tunnel air turbulence |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT188510B (en) * | 1951-08-14 | 1957-01-25 | Huber & Drott | Method and device for the production of shrinkable tubes |
| FR1088125A (en) * | 1953-11-27 | 1955-03-03 | Process for the continuous production of tubular complex articles from extrudable materials and fibrous materials, and the articles obtained | |
| US3286305A (en) * | 1964-09-03 | 1966-11-22 | Rexall Drug Chemical | Apparatus for continuous manufacture of hollow articles |
| FR2171844B1 (en) * | 1970-05-14 | 1974-05-24 | Lefebvre Pierre | |
| DE2523975A1 (en) * | 1975-05-30 | 1976-12-16 | Veba Chemie Ag | DEVICE FOR MANUFACTURING LOW-TENSION PIPES FROM THERMOPLASTIC PLASTIC |
| DE2753103A1 (en) * | 1977-11-29 | 1979-06-07 | Roehm Gmbh | METHOD AND DEVICE FOR THE PRODUCTION OF A FILM-COATED HOLLOW PROFILE STRAND FROM PLASTIC |
| US4211525A (en) * | 1978-12-05 | 1980-07-08 | Rohm Gmbh | Apparatus for making stretched, hollow shaped strands having corrugated intermediate supports |
| US4305703A (en) * | 1980-09-12 | 1981-12-15 | Lupke Manfred Arno Alfred | Composite die assembly for use in the production of thermoplastic tubing |
| CA1172813A (en) * | 1982-06-16 | 1984-08-21 | Lupke, Manfred A. A. | Apparatus for producing multi-walled thermoplastic tubing |
| JPS59138418A (en) * | 1983-01-27 | 1984-08-08 | Toyobo Co Ltd | Manufacture of plastic pipe by blow forming and apparatus therefor |
-
1997
- 1997-05-20 WO PCT/CA1997/000332 patent/WO1998052739A1/en not_active Application Discontinuation
- 1997-05-20 CA CA002261073A patent/CA2261073A1/en not_active Abandoned
- 1997-05-20 DE DE29723138U patent/DE29723138U1/en not_active Expired - Lifetime
- 1997-05-20 EP EP97921550A patent/EP0927099A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE29723138U1 (en) | 1998-08-06 |
| EP0927099A1 (en) | 1999-07-07 |
| WO1998052739A1 (en) | 1998-11-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |