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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
• • 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
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/92—Measuring, controlling or regulating
• • 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
  • B29C2948/00—Indexing scheme relating to extrusion moulding
  • B29C2948/92—Measuring, controlling or regulating
  • B29C2948/92504—Controlled parameter
  • B29C2948/92704—Temperature
• • 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
  • B29C2948/00—Indexing scheme relating to extrusion moulding
  • B29C2948/92—Measuring, controlling or regulating
  • B29C2948/92819—Location or phase of control
  • B29C2948/92857—Extrusion unit
  • B29C2948/92876—Feeding, melting, plasticising or pumping zones, e.g. the melt itself
  • B29C2948/92895—Barrel or housing
• • 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
  • B29C48/0012—Combinations of extrusion moulding with other shaping operations combined with shaping by internal pressure generated in the material, e.g. foaming
• • 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
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
  • B29L2023/22—Tubes or pipes, i.e. rigid

Definitions

• the present invention relates to a device for extruding a thermoplastic polymer into a tube, and to an extruder head for use in such an extruding device .
• thermoplastic polymer undergoes an extrusion process (under the influence of changes in pressure and orientation) such that the tube formed by extrusion meets set quality standards.
• quality standards relate to the correct diameter and wall thickness, waviness (internal smoothness of the tube) and the impact resistance.
• the polymer is stretched in axial as well as peripheral direction at one or more positions (for instance in the conical gap and/or compression gap) .
• the polymer does not react uniformly, which can be caused by material differences as a result of for instance welding (joining together) at an earlier stage before or during the extrusion and/or as a result of temperature differences in axial, and particularly peripheral direction.
• the European patent application 153,511 describes such a device .
• the invention relates to providing a solution to this problem and provides for this purpose a device for extruding a thermoplastic polymer into a tube, comprising means for annular feed of the tube material for extrusion to an extruder head which comprises an extruder head gap with an inner wall and an outer wall, wherein the inner wall and/or the outer wall of the diverging conical gap and/or of the converging part of the compression gap is provided with guide structures running in axial direction for tube material.
• the invention is based on the insight that, by making use of these guide structures in the inner and/or outer wall of the extruder head gap, flow of the extruding material in axial direction is enhanced and decreased or slowed in tangential direction. This enhanced flow in axial direction and reduced flow in peripheral direction while the material is passing through the extruder head gap results in the above stated problems being alleviated or avoided.
• the guide structures according to the invention running in axial direction can be applied at one or more locations in the extruder head gap.
• the extruder head gap comprises a diverging conical gap which is bounded by an inner cone and an outer cone, in which a wall of the inner cone and/or the outer cone bounding the conical gap is provided with guide structures running in axial direction for the tube material. Arranging of these guide structures in the conical gap is particularly recommended because stretch and flow in peripheral direction can occur to a greater extent because of the diverging conical gap .
• Another advantageous location for arranging the guide structures according to the invention is the compression gap of the extruder head.
• the material for extruding does after all have a relatively high speed in the compression gap, whereby an axial guiding is very advantageous in avoiding the described adverse effects.
• the guide structures according to the invention can consist of recessed parts. This means that in the wall of the inner cone and/or the outer cone there are arranged grooves through which extruding tube material can pass. The material in the recessed parts themselves and the adjoining material will thus be able to flow to a lesser extent in peripheral direction.
• the guide structures can also consist of raised parts, i.e. ribs and the like standing away from the wall of the inner cone and/or outer cone . These raised parts prevent material flowing between the raised parts from flowing in peripheral direction. Combinations of recessed and raised parts are also possible.
• the guide structures extend along the whole axial length of the conical gap. It is however also possible for the guide structures to extend along only a part of this axial length of the conical gap.
• the guide structures extend along only a part of the axial length of the conical gap, successive guide structures can then be applied which are then preferably disposed mutually offset along the periphery. If the guide structures herein connect to each other with mutual overlap, any form of peripheral . flow is practically avoided. An even and uniform flow is obtained along, around or through the guide structures if in further preference the guide structures have a rounded form in cross-section.
• the tube of thermoplastic polymer to be produced with the device according to the invention may in some conditions not possess a uniform thickness along the periphery.
• An improved uniform peripheral thickness is obtained if, as proposed in EP 153,511, heating/cooling means are arranged locally, and particularly at the position of the so-called mould land, along the periphery.
• heating/cooling means are arranged locally, and particularly at the position of the so-called mould land, along the periphery.
• the flow behaviour at this position is thereby influenced and can be controlled toward a more homogeneous peripheral thickness .
• this automatic temperature control is then found to act less effectively in obtaining a uniform peripheral thickness.
• these separately controllable heating/cooling means at the position of the so-called compression gap of the extruder head.
• a relatively large pressure drop in this compression gap and the extruding material will have a relatively high transporting speed, whereby, under the influence of different temperatures prevailing along the periphery, the thickness of the tubes can be controlled in more effective manner.
• the device of the type stated in the preamble further comprises a compression gap which follows the conical gap of the extruder head and which is bounded by a compression inner wall and a compression outer wall, wherein the compression inner wall and/or compression outer wall is provided with separately controllable heating/cooling means distributed over the periphery and received in peripheral segments.
• the peripheral wall thickness of the tube can be controlled more precisely if in further preference an end gap of the extruder head which is bounded by an end gap inner wall and an end gap outer wall is provided with separately controllable heating/cooling means distributed over the periphery in the end gap inner wall and/or end gap outer wall and received in peripheral segments .
• the heating/cooling means can be arranged in the inner wall, outer wall or both walls of the compression gap. For simplicity of construction however, it is recommended that the heating/cooling means are arranged in the outer wall .
• peripheral segments which are provided with separately controllable heating/cooling means depends on the desired result, and particularly on the wall thickness of the tubes.
• the number of peripheral segments generally amounts to 2-12, preferably 4-10, and in practice 8 peripheral segments suffice .
• peripheral segments at the position of the compression gap are arranged offset over the periphery relative to the segments at the position of the end gap. It is hereby possible to influence the flow behaviour along the length of the extrusion device at two locations, but along the periphery at a plurality of locations, by adding heat or extracting heat. It is thus possible, particularly in the production of polyolefin tubes, for instance PE or PP tubes, to guarantee a relatively highly uniform wall thickness at relatively large wall thicknesses .
• the device for extruding a thermoplastic polymer according to the invention it has further been found that at the exit from the extruder head and the transition to the calibration tube at the position of the outlet gap of the extruder there occurs so-called burr growth, i.e. an accumulation occurs of substances from the tube material, contamination and also filler. These accumulating materials have an adverse effect on the appearance and quality of the outer surface of the extruded tube.
• the invention provides a solution for this burr growth problem. This is achieved in that an outlet gap of the extruder is provided with means for avoiding burr growth.
• the means for avoiding burr growth comprise a constriction arranged in the outer wall of the outlet gap.
• the means for avoiding burr growth comprise an inner wall extended axially relative to the outer wall .
• the means for avoiding burr growth are therefore intended to ensure that the extruded tube still makes contact with the wall as it exits the outlet gap. Because this contact is ensured, the formation of burr growth is also reduced or avoided.
• the invention relates to an extruder head evidently intended for use in the above stated device for extruding a thermoplastic polymer into a tube. Mentioned and other features of the device according to the invention will be further elucidated hereinbelow on the basis of a number of embodiments which are given only by way of example without the invention being deemed limited thereto.
• figures 1, 2 and 5 each show a schematic and broken-away view of a device for extruding a thermoplastic polymer into a tube; figure 3 shows a cross-section of guide structures according to the invention; figure 4 shows a detail IV of figure 1; and figure 6 shows a variant of detail VI of figure 5.
• the device according to the invention is described in general sense in EP 153,511. Only details relevant to the understanding of the present invention will be further described hereinbelow.
• FIG. 1 shows a device 1 for extruding thermoplastic polymer into a tube.
• This thermoplastic polymer can consist of PVC, polyolefin, such as polyethylene and polypropylene, and the like.
• Device 1 comprises a feed block 2 for adding material as according to arrow 3. From the feed block the tube material is fed to an extruder head gap of an extruder head, and in particular to a conical gap 4 diverging in axial direction.
• Conical gap 4 is bounded by a conical outer wall 5 and a conical inner wall 6.
• Conical outer wall 5 has a smooth surface.
• Conical inner wall 6 is provided with guide structures 7 running in axial direction. These guide structures consist in this case of recessed parts 8 and 9 (see figure 3b) .
• Recessed parts 8 and recessed parts 9 each extend respectively over an upstream and a downstream part of the axial length of conical gap 4. Recessed parts 8 and ' 9 overlap each other and are arranged offset in peripheral direction.
• Inner cone 10 connects onto a breaker plate section 11 which comprises breaker plates 22 which are arranged distributed over the periphery and between which the material for extruding flows. The material then passes through a compression section 13 and the extruded tube leaves device 1 via a mould land section 14.
• FIG 2 shows another device 15 according to the invention.
• the conical inner wall 6 has a guide structure 16 which runs in axial direction and takes the form of a raised part as shown in figure 3a.
• Conical inner wall 6 is provided with guide structures 17 which have the same form as guide structures 16 on the conical outer wall. Both guide structures 16 and 17 extend over the whole axial length of the conical gap.
• Figure 5 shows another device 17 according to the invention. Use is made in this case of a feed block 18 for feeding three tube materials. Materials 19 and 20 for the outer wall and material 21. This material 21 can optionally be provided with a foaming agent, whereby the tube will obtain a foamed intermediate layer. Feed block 18 is adapted in known manner such that the three materials enter the conical gap 22 as three layers.
• conical outer wall 5 and conical inner wall 6 are both provided with guide structures 23 and 24 which each extend over a part of the axial length of conical gap 22 and connect to each other mutually offset along the periphery.
• guide structures 23 and 24 which each extend over a part of the axial length of conical gap 22 and connect to each other mutually offset along the periphery.
• any possible guide structure can be applied, in particular the guide structures with a cross-section as shown in figure 3.
• These guide structures are recessed or raised parts and have a rounded form over the cross-section which enhances guiding of the tube material flowing past and does not disturb it.
• FIG 4 shows detail IV of the device 1 of figure 1 on larger scale.
• compression section 13 the extruding thermoplastic polymer passes through a compression gap 23.
• a high axial pressure drop occurs in this gap, whereby the material has a relatively high axial speed.
• Compression gap 23 is bounded by a compression inner wall 24 and a compression outer wall 25.
• Compression outer wall 25 is constructed from eight peripheral segments 26 which are each provided with electric heating means 27. These heating means are connected to a control unit (not shown) .
• This control unit drives the heating means 27 separately depending on the peripheral thickness of the tube being extruded in device 1.
• the flow through compression gap 23 can hereby be controlled axially over the periphery subject to the on-line produced tube.
• compression gap 23 can also be provided with guide structures as described for the conical gap with reference to figures 1, 2 and 3. Reference is made in this respect to figure 6.
• Figure 6 shows the end of a device 28 according to the invention at the position of its end gap 29. At that position in the mould land section 14 there are arranged segments 30 as according to figure 4 which are distributed over the periphery and which are each provided with heating means 31. In this case also there are eight peripheral segments 30 present. The orientation of peripheral segments 30 is chosen such that they are arranged offset over the periphery relative to the peripheral segments 26 at the position of compression gap 23.
• Figure 6 further shows that at the position of end gap 29 the inner wall 32 is extended axially relative to outer wall 33. Extruded tube material will therefore lie against the outer wall 33 until it leaves device 28. The formation of burr growth is hereby avoided.
• Figure 5 shows similar means 34 for avoiding burr growth in the form of an annular constriction 35.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=19773660

Family Applications (1)

Country Status (3)

Families Citing this family (4)

Family Cites Families (7)

• 2001
  • 2001-07-03 NL NL1018450A patent/NL1018450C2/nl not_active IP Right Cessation
• 2002
  • 2002-07-02 EP EP02743982A patent/EP1401628A1/de not_active Withdrawn
  • 2002-07-02 WO PCT/NL2002/000432 patent/WO2003004247A1/en not_active Ceased

Non-Patent Citations (1)

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