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
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/695—Flow dividers, e.g. breaker plates
  • B29C48/70—Flow dividers, e.g. breaker plates comprising means for dividing, distributing and recombining melt flows
  • B29C48/705—Flow dividers, e.g. breaker plates comprising means for dividing, distributing and recombining melt flows in the die zone, e.g. to create flow homogeneity
• • 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
  • B29C48/05—Filamentary, e.g. strands
• • 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
  • B29C48/30—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
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films

Definitions

• the present invention concerns an extrusion head for tubular articles made of plastic materials.
• the production of tubes through polymers of various kinds is generally carried out by means of hot extrusion of the selected plastic material.
• the extrusion head has a critical role, because such a head determines the geometry of hot flows of the material subjected to the extrusion with important final qualitative features of the obtained articles.
• extrusion heads of different kinds are known, which comprise a part associated to an extruder flange, a central part, and a terminal part connected to a spinneret , which causes the molten polymer to fit to the size of the article to be produced.
• Heads having a spiral distribution have some constructional difficulties due to the machining complexity and manufacturing difficulties for their surface treatments, i.e. chromium plating.
• the object of the present invention is to avoid the prior art drawbacks. Therefore the subject matter of the present invention is an extrusion head for tubular articles made of plastic material, which, articles, are of simple construction, and efficient operation, because by achieving a perfect flow distribution of the material an optimal mechanical quality of the final product is obtained.
• an extrusion head comprising a body with at least a first part operatively associated to a flange of an extruder, a central part and a terminal part operatively connected to a spinneret for tubular articles made of plastic material
• said first part has a plurality of conduits for the passage of the material to be extruded in the fluidic state from the inside to the outside of said head, said conduits communicating to the outside through holes associated to a corresponding number of distribution channels provided in the central part of said body and adjacent to a cylindrical surface of said central part, wherein the internal geometry of these distribution channels is such that the fluid pressure distribution along the separation lines between said channels and said cylindrical surface creates a plurality of fluidic threads, each thread having the same flow rate, said fluidic threads being able to generate on the terminal part of said head a homogeneous tubular article.
• the extrusion head for tubular articles made of plastic material according to the invention is characterized by the features of claim 1.
• each distribution channel consists of two branches forming an arc on said cylindrical surface of said central part, where the width and the depth of said branches are at a maximum in proximity of each hole, gradually decreasing away from these holes and vanishing at their tip.
• the head according to the invention is advantageously used in the production of multilayer articles, because due to the sequential arrangement of a plurality of component parts, said head achieves the production of multilayer tubes with a number of layers corresponding to said plurality of component parts.
• a further advantageous application of the extrusion head according to the invention is the production of multifilament and short fiber synthetic fibers because the dimensions of said component parts of said head can be designed in order to produce layers of a constant size.
• the extrusion head according to the present invention is highly versatile because the plastic materials to be used comprise at least those selected from polyolefins, PVC, polycarbonate, methacrylate, EVOH, polystirol, nylon, PET.
• Figure 1 is a partially sectioned perspective view showing the extrusion head for tubular articles made of plastic material according to the present invention.
• Figure 2 is a lateral view of the extrusion head shown in Figure 1.
• Figure 3 is a horizontally sectioned view of the extrusion head according to the present invention.
• Figure 4 is a schematic view of a plane development of the distribution channels machined on the extrusion head according to the present invention.
• Figure 5 is a partially sectioned lateral view of the extrusion head shown in
• the extrusion head 1 for tubular articles comprises a substantially cylindrical body, preferably including a first part 2 which is connected to a flange of an extruder, a central part 3 being adjacent to said first part 2 and a terminal part 4, which connects said head 1 to a spinneret
• the first part 2 has a central internal duct 5 which allows the passage of the molten polymer from the extruder body to the head.
• a duct 5 splits into a plurality of ducts 6, e.g. three ducts as shown in figure 1 , which lead the polymer in fluidic state from the inside to the outside of the head 1.
• conduits 6 communicate with the outside at the beginning of said central part 3 of the head 1 through corresponding holes 7.
• These holes 7 communicate in turn with a corresponding number of distribution channels 8 abutting to a cylindrical surface of the said part 3 through their own perimetrical curved lines, each channel consisting of two branches 12, which form an arc on said cylindrical surface of the part 3. More precisely the width and the depth of said branches 12 are at the maximum in proximity of each hole 7, gradually decreasing away from these branches and vanishing at their tip; the mathematical rule governing the development has been calculated by imposing particular physical conditions which will be better illustrated hereinafter.
• the number of distribution channels 8 and as a consequence of ducts 6 will increase with the diameter of head 1 , thus allowing the length of the head to be reduced.
• Individual thermoregulation devices of the ducts may optionally be provided in order to compensate the flow rate of each duct.
• the depth, width and the curvature of branches 12, hence their geometry, is determined as above indicated by means of computation, which imposes that the pressure distribution of the fluid along the curved lines 9 of separation between said distribution channels 8 and said cylindrical surface generates a plurality of fluidic threads, each one of the same flow rate.
• the computation is correlated to the diameter and the width of the instant head, hence there will be different kinds of geometry for each head in a head family.
• Such a pressure distribution finally, generates a tube with a substantially constant thickness at every single point on the terminal part 4 downstream to the central part 3.
• the terminal part 4 as already pointed out is associated to a spinneret 10, which can advantageously be of reduced size due to the optimal geometry of the tube obtained by said terminal part 4. Furthermore also said part 4 can be clearly shorter than the corresponding terminal parts of the prior art heads, because for the above mentioned reason this head does not serve to homogenize the melt.
• the present head l ean be made of any material and be subjected to various surface treatments e.g chromium plating.
• the plastic material in the molten state travels through the ducts 5,6 and flows into the distribution channels 8 through the holes 7.
• the pressure drop created by the geometry of the distribution channels generates a plurality of fluidic threads with the same flow rate on the perimetrical lines 9 of said channels 8 and these fluidic threads hence produce a perfectly homogeneous tubular article on the terminal part 4.
• the above illustrated technical solution can be used treating different plastic material such as polyolefins, PVC, polycarbonate, methacrylate, EVOH, polystyrene, nylon, PET achieving optimal results, because the results obtained with this head are independent from the used polymer.
• plastic material such as polyolefins, PVC, polycarbonate, methacrylate, EVOH, polystyrene, nylon, PET achieving optimal results, because the results obtained with this head are independent from the used polymer.
• the head 1 according to the present invention can also be advantageously used in order to produce multilayer tubes: this solution is becoming more and more requested by the market for enviromental reasons related to the declining use of materials which are not reusable and to the use of recycled materials. In such a case the component parts 2, 3, 4 of the head body are repeated once for each layer to be carried out.
• the first part 2 being a structure made of single channels, easily solves the main problem of the multilayer heads, i.e. the intersection of flows of different polymers.
• the central part 3 is repeated several times on the cylindrical bodies which will be mounted coaxially one inside the other, on the internal parts of which distribution channels calculated on basis of the desired final thickness will be carried out.
• the terminal part 4 allows the various layers to be overlapped and the dimensions of the final article to be obtained according to the desired diameters and thicknesses.
• An alternative use of the head for multilayer tubular articles consists of its application in the field of multifilament or short synthetic fibers: in this case such a multilayer head is used as to obtain single layers of constant thickness.

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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)

Family

ID=11444282

Family Applications (1)

Country Status (4)

Family Cites Families (4)

• 2000
  • 2000-03-01 IT IT2000MI000406A patent/IT1316700B1/it active
• 2001
  • 2001-02-26 AU AU58254/01A patent/AU5825401A/en not_active Abandoned
  • 2001-02-26 WO PCT/EP2001/002209 patent/WO2001064420A2/en not_active Ceased
  • 2001-02-26 EP EP01931485A patent/EP1214184A2/en not_active Withdrawn

Non-Patent Citations (1)

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