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CA-3144813-C - MULTI-PORT COEXTRUSION PRE-DIE HAVING A MONOLITHIC THROUGH-STIFFENER THAT MAY BE OBTAINED BY ADDITIVE MANUFACTURING

CA3144813CCA 3144813 CCA3144813 CCA 3144813CCA-3144813-C

Abstract

The invention relates to a pre-die (1) intended to extrude jointly a plurality of elastomeric compounds along one flow direction (X1) in order to form a profile member, said pre-die comprising for this purpose, superimposed in a stacking direction (Z1) transverse to the flow direction (X1), a first port (11), a second port (12) separated from the first port (11) by a first partition (15), then a third port (13) separated from the second part (12) by a second partition (16), said pre-die also comprising a stiffener (20) which is formed as one piece with the first partition (15) and the second partition (16) and which extends through the second port (12) while having a leading edge (21) that divides the flow of the elastomeric compound passing through said second port (12).

Inventors

  • Christophe GOARANT

Assignees

  • COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN

Dates

Publication Date
20260505
Application Date
20200728
Priority Date
20190730

Claims (15)

  1. CA 3144813-34 - CLAIMS 1. A pre-die intended for jointly extruding a plurality of elastomeric compounds along a common direction called the "flow direction" for the purpose of assembling said elastomeric compounds into a co-extruded profile, said pre-die comprising for this purpose, in superposition along a first direction transverse to the flow direction, called the "stacking direction", a first channel provided for conveying a first elastomeric compound, a second channel provided for conveying a second elastomeric compound and separated from the first channel by a first partition, and a third channel provided for conveying a third elastomeric compound and separated from the second channel by a second partition, the first, second, and third channels each having a cross-section, said pre-die comprising at least one stiffener formed in one piece with the first and second partitions and extending so as to cross at least the second channel along the direction of transverse stacking to the direction of flow, thus presenting, at least in the passage section of said second channel, a leading edge which allows the elastomeric mixture using the second channel to bypass said stiffener by splitting into two sub-flows which flow, in said second channel, on either side of said leading edge.
  2. 2. The pre-die according to claim 1, wherein the stiffener, in one piece, also passes through at least one of the first and third channels, so as to present, in the passage section of each of the first, second and third channels concerned, a leading edge which allows the elastomeric mixture taking the channel concerned to bypass said stiffener by splitting into two sub-flows which flow, in said channel concerned, on either side of said leading edge and therefore on either side of said stiffener.
  3. 3. The pre-die according to claim 1 or 2, in which the stiffener extends, along the flow direction, between the leading edge and a trailing edge, so as to present, on either side of said leading edge, respectively a first flow surface called CA 3144813-35 - "intrados", and a second flow surface called "extrados", which each join the leading edge to the trailing edge, and in which said stiffener has a section, delimited by the intrados and the extrados, which forms, with respect to a chord which connects in a straight line the leading edge to the trailing edge, a biconvex profile.
  4. 4. The pre-die according to claim 3, wherein the stiffener section has an upstream bulge such that the biconvex profile is thicker in an upstream half of the chord, on the leading edge side, than in a downstream half of said chord, on the trailing edge side.
  5. 5. The pre-die according to any one of claims 1 to 4, wherein the stiffener extends, along the stacking direction, from a first end plane to a second end plane, and wherein said first and second end planes are inclined with respect to the flow direction in an orientation which makes said end planes converge towards each other in the direction downstream of the flow, such that said first and second end planes can cooperate respectively with a first beveled bearing face and a second beveled bearing face of a cassette receiving the pre-die, in order to ensure automatic centering of the pre-die within said cassette, as well as retention of said pre-die within the cassette in the direction of the flow.
  6. 6. The pre-die according to any one of claims 1 to 5, wherein the first, second, and third lanes, and consequently the first and second partitions, extend widthwise along a second direction transverse to the flow direction, referred to as the "lateral direction," which is also transverse to the stacking direction, the pre-die comprising several stiffeners distributed so as to be spaced apart along said lateral direction, each of said stiffeners being formed as a single unit with the first and second partitions, and extending along the stacking direction so as to cross at least the second lane. CA 3144813-36-
  7. 7. The pre-die according to any one of claims 1 to 6, wherein the first, second and third lanes, and consequently the first partition and the second partition, extend in width along a second direction transverse to the flow direction, referred to as the "lateral direction", which is also transverse to the stacking direction, the pre-die being divided, in width along the lateral direction, into a plurality of individual modules, each comprising a portion of the width of the first partition and a portion of the width of the second partition, and consequently a portion of the width of the first lane, the second lane, and the third lane, said individual modules being joined in pairs, reversibly, edge to edge, along the lateral direction, and wherein at least one of said individual modules comprises said stiffener formed in one piece with the portion of the first partition and the portion of the second partition of the individual module concerned.
  8. 8. The pre-die according to claim 7, wherein the individual modules are butted together along joint planes arranged obliquely such that said joint planes each form, in projection into the plane formed by the flow direction and the lateral direction, a non-zero angle with respect to the flow direction, called "yaw angle", so that the individual modules lock each other in the direction of flow.
  9. 9. The pre-die according to claim 7 or 8, wherein the individual modules each have an alignment groove which extends from one edge to the other of the individual module concerned in the lateral direction, so that said individual modules can be aligned on the same common key, engaged in all of said alignment grooves.
  10. 10. The pre-die according to any one of claims 1 to 9, wherein the first partition has a thickness, measured along the stacking direction, of between 3 mm and 30 mm and the second partition has a thickness, measured along the stacking direction, of between 3 mm and 30 mm. CA 3144813-37-
  11. 11. The pre-die according to any one of claims 1 to 10, wherein the first partition and the second partition have at least one step at which the second track and the third track are both folded back towards the first track in the stacking direction, so as to be able to form a longitudinal groove in an extruded profile which is intended to form a tread for a tire, and wherein the stiffener extends, in the second and third tracks, vertically relative to said step.
  12. 12. The pre-die according to any one of claims 1 to 11, wherein a single-piece assembly formed by the first partition, the second partition and said stiffener is obtained by additive manufacturing.
  13. 13. The pre-die according to claim 12, wherein additive manufacturing is carried out by successive layers created progressively along a manufacturing direction which corresponds to the flow direction, from a base plane normal to said flow direction, at least a part of the first partition and/or at least a part of the second partition having an inclination with respect to the flow direction, and therefore with respect to the manufacturing direction, so that the superposition of the successive layers forms steps, and wherein the pre-die permanently retains, along said steps formed by the superposition of the successive layers, an arithmetic roughness of between 4 µm and 30 µm which corresponds to a raw additive manufacturing roughness defined by said steps.
  14. 14. The pre-die according to any one of claims 1 to 13, wherein downstream ends of the first partition and/or the second partition have a composite structure comprising, on the one hand, a permanent base which is an integral part of the partition concerned, and which is made at the same time as the partition and the stiffener in the same original material as said partition, and on the other hand, an end piece called a "refillable end piece", which is obtained by first grinding down the end of the partition to remove material and thus form the permanent base, and then adding material to said permanent base to form an end piece, integral with said base, CA 3144813-38 - end piece which therefore protrudes downstream, relative to the permanent base, in the direction of flow.
  15. 15. The pre-die according to any one of claims 1 to 14, wherein the stiffener extends in one piece beyond the second track, through at least one of the first and third tracks, and wherein constituent portions of said stiffener which appear in the tracks concerned and form said leading edge in the passage section of said tracks concerned, have a cylindrical shape generated by a constant base section which sweeps, through the different tracks concerned, the same straight generatrix, parallel to the stacking direction.

Description

MULTI-WAY COEXTRUSION PRE-DIE WITH A MONOLITHIC THROUGH-THROUGH STIFFENER THAT CAN BE OBTAINED BY ADDITIVE MANUFACTURING 5 [0001] The present invention relates to the field of co-extrusion processes, and more particularly to the co-extrusion processes of complex profiles, in which a plurality of elastomeric mixtures, that is to say mixtures formed on the basis of elastomers, from several extruders, are extruded simultaneously through the same die, so as to bring together said elastomeric mixtures in a profile which is said to be "complex" because said profile obtained thus presents, in the same section, an assembly of several adjacent zones, typically an assembly of several layers, which have distinct compositions corresponding to the plurality of elastomeric mixtures. [0002] Such coextrusion processes are notably used to produce treads in the form of complex profiles for use in tire manufacturing. 15 [0003] Such processes usually require relatively complex tooling, which includes, following a head to which the extruders are connected, a preformer which includes several paths allowing the different elastomeric mixtures from the extruders to be conveyed and progressively shaped, and to converge said elastomeric mixtures towards a mouth which opens into a die, which die gives the section of the profile its final shape. [0004] Generally, such equipment is heavy and bulky, especially since it must be able to withstand very high pressures, necessary to convey the elastomeric mixtures, which are quite highly viscous, through channels whose cross-section 25 of passage can sometimes be relatively narrow and can therefore cause significant pressure losses. [0005] In addition, such tooling is often expensive to produce, and especially to develop, since it is necessary, each time one wishes to experiment with a change in geometry or dimension of one of the paths of the pre-die, to machine a new corresponding pre-die. Generally, this machining is carried out by electroerosion, by a wire cutting process, which is certainly relatively precise and allows for the creation of complex shapes, but which is relatively long to set up. [0006] The objects assigned to the invention therefore aim to remedy the aforementioned disadvantages and to propose a new co-extrusion tooling which is compact, inexpensive and quick to manufacture, and which limits energy consumption during extrusion operations. [0007] The objects assigned to the invention are achieved by means of a pre-die intended to jointly extrude a plurality of elastomeric mixtures along a common direction called the "flow direction" in order to assemble said elastomeric mixtures into a co-extruded profile, said pre-die comprising for this purpose, in superposition along a first direction transverse to the flow direction, called the "stacking direction", a first channel provided for conveying a first elastomeric mixture, a second channel provided for conveying a second elastomeric mixture and separated from the first channel by a first partition, and then a third channel provided for conveying a third elastomeric mixture and separated from the second channel by a second partition, said pre-die being characterized in that it comprises at least one stiffener which is formed in one piece with the first partition and the second partition and which extends so as to cross at least the second channel in the direction of stacking transverse to the direction of flow, thus presenting, at least 20 in the passage section of said second channel, a leading edge which allows the elastomeric mixture taking the second channel to bypass said stiffener by splitting into two sub-flows which flow, in said second channel, on either side of said leading edge and therefore on either side of said stiffener. [0008] Advantageously, the presence of a stiffener according to the invention makes it possible to reinforce 25 and structurally stiffen the partitions delimiting the channels, without hindering the flow of the elastomeric mixtures, which makes it possible to produce relatively thin partitions, and therefore to reduce the bulk of the pre-die while maximizing the passage area of the channels in a given tool volume. In this way, pressure losses can be reduced, and therefore extrusion can be operated using a lower supply pressure, 30 which reduces energy consumption. [0009] Furthermore, the pre-die arrangement proposed by the invention is particularly suited to manufacturing said pre-die by additive manufacturing, in three-dimensional printing, which allows the pre-die to be produced quickly at a lower cost, and where appropriate to modify said pre-die locally by carrying out machining operations and then 5 additive manufacturing operations, so that the pre-die can be easily and quickly developed by successive iterations during the machining development phase, without having to manufacture a completely new pre-die each time. [0010] Other objects, features and advantages of the invention will become