阅读说明：本技术 用于基于弹性体混合物生产的成型条带的挤出设备 (Extrusion device for profiled strips produced on the basis of elastomer mixtures ) 是由 H·因克 A·勒托卡特 C·乌吉耶 于 2019-04-04 设计创作，主要内容包括：一种用于生产成型条带(例如由通过共挤的弹性体混合物制成的胎面)的挤出设备(1),包括用于向挤出机头供给弹性体混合物的多台挤出机(10,20,30,40,50,60),所述挤出机头包括分配通道,用于将来自每台挤出机的弹性体混合物的流体经由专用分配通道输送到模具,所述模具限定第一共挤型材的形状。根据本发明,所述设备包括至少一个第二挤出机头(2’),所述第二挤出机头(2’)能够取代第一挤出机头连接到所述设备的挤出机(10,20,30,40,50,60),并且其生产成使得来自所述设备的至少两台挤出机的弹性体混合物的流体在到达模具(3’)之前被输送到共用的分配通道(5c)中,所述模具(3’)限定第二共挤型材的形状。(An extrusion apparatus (1) for producing profiled strips, for example treads made of elastomer mixture by coextrusion, comprises a plurality of extruders (10,20,30,40,50,60) for supplying the elastomer mixture to an extruder head comprising a distribution channel for conveying the fluid of the elastomer mixture coming from each extruder via a dedicated distribution channel to a die defining the shape of a first coextrusion profile. According to the invention, the apparatus comprises at least one second extruder head (2 '), which second extruder head (2') can be connected to the extruders (10,20,30,40,50,60) of the apparatus in place of the first extruder head, and which is produced in such a way that the fluids of the elastomer mixtures from at least two extruders of the apparatus are conveyed into a common distribution channel (5c) before reaching a die (3 '), the die (3') defining the shape of the second coextruded profile.)

1. An extrusion apparatus (1) for manufacturing profiled element strips, such as treads (100,200), based on elastomeric compounds by co-extrusion, said apparatus (1) comprising a first extruder head (2) and a plurality of extruders (10,20,30,40,50,60) supplying the elastomeric compounds to said first extruder head (2), said first extruder head (2) comprising a distribution duct allowing the fluid of the elastomeric compounds coming from each extruder to be directed to a die (3) via a dedicated distribution duct, so that the various elastomeric compounds extruded by the extruders do not join together before reaching said die (3), said die (3) defining the shape of a first co-extruded profiled element, said apparatus (1) being characterized in that it comprises at least one second extruder head (2',2 ", 2"'), the second extruder head (2',2 ", 2"') is connectable to the extruders (10,20,30,40,50,60) of the apparatus in place of the first extruder head (2), and the second extruder head (2',2 ", 2"') is produced such that the fluids of elastomeric compounds from at least two extruders of the apparatus are guided into a common distribution duct (5c,5d) before reaching the die (3',3 ", 3"'), which die (3',3 ", 3"') defines the shape of the second co-extrusion element.

2. The plant (1) according to the preceding claim, wherein said common distribution duct is a duct that: which extends in a direction substantially perpendicular to the direction of fluid flow of the elastomeric compound from the at least two extruders.

3. The apparatus according to any of claims 1 and 2, characterized in that the extruders (10,20,30,40,50,60) are arranged on both sides of the head with respect to a symmetry plane (P) through the outlet orifice of the die.

4. The apparatus according to any one of claims 1 to 3, characterized in that the two longitudinal flows coming from the two extruders (50,60) merge together in a longitudinal collecting duct (6), the longitudinal collecting duct (6) opening into a common distribution duct (5 c).

5. The apparatus according to any one of claims 1 to 3, characterized in that the two longitudinal flows coming from the two extruders (40,60) merge together in a transverse collecting duct (7), the transverse collecting duct (7) leading to a common distribution duct (5 d).

6. The apparatus according to any of claims 1 to 3, characterized in that the three longitudinal flows from the three extruders (40,50,60) merge together via a longitudinal collecting duct (6) and a transverse collecting duct (7) into a common distribution duct (5 c).

7. The apparatus according to any one of the preceding claims, wherein the first extruder head (2), the second extruder head (2',2 ") are directly connected to the extruder (10,20,30,40,50,60), respectively, without an elastomeric compound transfer duct therebetween.

8. The apparatus according to any of the foregoing claims, characterised in that the common distribution duct is located in a second extruder head (2',2 ", 2"') opposite the outlet of the die (3',3 ", 3"').

9. The apparatus according to any of the preceding claims, characterized in that the extruders (10,20,30,40,50,60) are identical.

10. The apparatus according to any one of the preceding claims, wherein the first extruder head (2) and/or the second extruder head (2',2 ", 2"') respectively comprise a set of a plurality of removable plates arranged side by side.

11. A method for manufacturing a profiled element strip, such as a tread (100,200), based on a plurality of elastomeric compounds of different composition, by coextrusion with a plurality of extruders (10,20,30,40,50,60), said plurality of extruders (10,20,30,40,50,60) supplying the elastomeric compounds to interchangeable extruders heads (2,2',2 ", 2"'), said method being characterized in that:

-selecting and introducing a first extruder head (2) suitable for the profiled element to be coextruded into a support provided for this purpose in the apparatus, said first extruder head being connected to the extruders of the apparatus to direct the fluid of elastomeric compound from each extruder to the die (3) via a dedicated dispensing duct;

-locking the first extruder head in position using a quick-fit device;

-co-extruding a strip of elements;

-removing the first extruder head (2) and replacing it with another extruder head, so as to form a second extruder head (2',2 ", 2"') suitable for a new forming element and capable of directing the fluid of elastomeric compound coming from at least two extruders of the apparatus into a common dispensing duct (5c,5d) before reaching the dies (3',3 ", 3"').

Technical Field

The present invention relates to the field of extrusion of elastomeric compounds for the manufacture of tyres. More particularly, the present invention relates to the manufacture of strips of coextruded composite profiled elements based on elastomeric compounds, such as strips forming a tire tread.

Background

It is known that tire treads are produced in the form of composite profiled elements by co-extruding elastomeric compounds (most of which have different compositions) using a plurality of extruders connected to a common extruder head. As is known, an extruder is formed by a cylinder or barrel which is stationary and inside which there is an archimedes screw coaxial with the longitudinal axis of the barrel and driven to rotate about said axis. The purpose of the extruder is to homogenize the rubber compound introduced therein and to push said compound towards the outlet die of the extruder head. In the case of complex products, the outlet die receives a plurality of elastomeric compounds of different composition arranged side by side and joined together before the outlet. The die includes an exit orifice whose geometry determines the profile of the coextruded rubber strip. Such a profile may be defined between stationary profiled vanes cooperating with rotating rollers or with stationary walls.

For the manufacture of treads using the coextrusion method, it is usual to use one extruder for each type of elastomeric compound (type indicates the composition of the compound) the size of which (diameter of the extrusion screw) is chosen according to the volume of compound extruded. For example, in the case of a tread with an outer 80% of the volume for running and with the addition of a sublayer representing about 15% of the volume and two side edges representing the remaining 5% in total, three extruders are generally used: the larger first extruder had a screw diameter of 250mm, the second for the sublayer had a screw diameter of 200mm and the third mini extruder had a diameter of 120 mm.

There is now a method of improving tire performance by using more complex treads containing a greater number of components (e.g., up to seven different components) with very variable volume ratios between the components. Each component has its own well-defined characteristics, for example the tread portion on the outer side of the profiled strip comprises an elastomeric composition comprising silica (which has good rolling resistance characteristics), supported by elastomeric strips of different composition having shock-absorbing characteristics, a small piece of conductive elastomeric compound strip being inserted in the two aforesaid strips, all of which is supported by a sublayer having good adhesion characteristics to the component radially on the inner side of the green tyre, and by side edges made of a compound different from the aforesaid compound or even a compound containing mixed scrap. Therefore, since each compound has different characteristics from the other compound, it is obviously necessary to increase the number of extruders in order to manufacture such a complex tread.

FIG. 1 shows an example of a prior art extrusion apparatus in which one extruder is used for each product making up the tread shown in FIG. 2. The longitudinal axes of the extruders making up the apparatus are in different planes and converge towards a common extruder head. It can be seen that a plant like this with seven extruders, arranged one above the other, is very bulky.

Such a complex plant represents a significant investment in the manufacture of tyres and it is therefore advantageous to be able to exploit its potential. In other words, the aim is to produce not only a complex co-extruded tread (for example with seven components) but also a less complex co-extruded tread (for example comprising three components) using the same apparatus.

Document DE102012111439 describes an extrusion apparatus which uses five adjacent extruders on the same side of the same extruder head, wherein two of the five extruders are arranged on the same plane and cooperate to produce the same product. Admittedly, this arrangement does allow to optimize the space available on the extruder head side. However, the apparatus does not provide sufficient flexibility to enable it to adapt to structural variations of the co-extruded product which require easy variation of the amounts of the components.

Disclosure of Invention

It is an object of the present invention to overcome the drawbacks described herein and to propose a structurally optimized extrusion device which is highly flexible in use, being able to easily switch from the extrusion of complex products to the extrusion of simpler products using all the extruders which make up the device.

This object is achieved by the present invention which proposes an extrusion apparatus for manufacturing strips of profiled elements (for example treads) based on elastomeric compounds by co-extrusion, comprising a first extruder head comprising a distribution duct which allows the fluid of elastomeric compound from each extruder to be directed to a die via a dedicated distribution duct so that the various elastomeric compounds extruded by the extruders do not join together before reaching the die, and a plurality of extruders which supply the elastomeric compounds to the first extruder head, the apparatus being characterized in that it comprises at least one second extruder head which can be connected to the extruders of the apparatus in place of the first extruder head and which is produced so that the elastomeric compounds from at least two extruders of the apparatus are compounded The flow of substance is directed into a common distribution conduit before reaching the die which defines the shape of the second co-extruded element.

In other words, the apparatus of the invention comprises, on the one hand, a number of extruders chosen in such a way as to be able to produce, by using a first extruder head, a complex product having a number of components equal to the number of extruders of the apparatus, and, on the other hand, a second extruder head produced in such a way that, when installed in the position of the first extruder head, at least two extruders work in cooperation. This makes it possible to manufacture both highly complex strips of co-extruded elements of the tyre tread type and simpler products, using the same apparatus.

Preferably, the common distribution conduit is a conduit that: which extends in a direction substantially perpendicular to the direction of fluid flow of the elastomeric compound from the at least two extruders. Such a solution makes it possible to obtain a better cohesion between the two compounds and to avoid any problems at the interface between them.

Advantageously, the extruders are arranged on both sides of the head with respect to a plane of symmetry passing through the exit orifice of the die. This solution allows a better balance of the fluids coming from the various extruders.

In a variant of the invention, the two longitudinal flows coming from the two extruders merge together in a longitudinal collecting duct which leads to a common distribution duct.

In another variant of the invention, the two longitudinal flows coming from the two extruders are merged together in a transverse collecting duct which leads to a common distribution duct.

In a further variant, the three longitudinal flows from the three extruders are merged together into a common distribution duct via a longitudinal collection duct and a transverse collection duct.

Preferably, the extruder heads (in this case the first extruder head), respectively the second extruder head, are directly connected to the extruder, without an elastomer compound delivery duct between the two. More preferably, each of said first and second extruder heads is arranged to be able to be connected in turn directly to an extruder, without an elastomeric compound delivery duct being present between said extruder and the extruder head in question. Thus, the screw end of each extruder essentially reaches the corresponding inlet hole in the extruder head, which greatly reduces the pressure drop. The remaining volume can thus be used to form a wider inlet duct in the extruder head than in the prior art extruders, so that the degree to which the compound is heated can be reduced and the productivity of the machine can be increased.

Advantageously, said common distribution duct is located in a second extruder head opposite the outlet of the die. Thus, the flows from the different extruders are brought together as early as possible into a common distribution pipe before the outlet of the die, so that a better cohesion between the compounds is possible.

Preferably, the extruders are identical. Thus, maintenance of the apparatus is made easier.

Advantageously, the extruder head (whether it is the first extruder head and/or the second extruder head) comprises a set of a plurality of removable plates arranged side by side. This structure comprising a removable plate makes it possible to obtain an extruder head with a simplified and flexible structure.

The object of the invention is also achieved by a method for manufacturing a profiled element strip (for example a tread) based on a plurality of elastomeric compounds of different composition by coextrusion using a plurality of interchangeable extruders feeding the elastomeric compounds to the extruder heads, said method being characterized in that:

-selecting a first extruder head suitable for the profiled element to be coextruded and introducing it into a cradle provided for this purpose in the apparatus, said first extruder head being connected to the extruders of the apparatus in order to direct the fluid of elastomeric compound from each extruder to the die via a dedicated dispensing duct;

-locking the first extruder head in position using a quick-fit device;

-co-extruding a strip of elements;

-removing the first extruder head and replacing it with another extruder head, so as to form a second extruder head suitable for a new forming element and capable of directing the fluid of elastomeric compound coming from at least two extruders of the apparatus into a common dispensing duct before reaching the die.

Drawings

The invention will be better understood from the rest of the description supported by the following drawings:

figure 1 is a schematic perspective view of an extrusion apparatus according to the prior art;

figure 2 is a perspective view of a first example of a tread;

figure 3 is a perspective view of a second example of a tread;

figure 4 is a perspective view of the extrusion apparatus of the invention;

FIG. 5 is a schematic view of a longitudinal section of the apparatus of FIG. 4;

fig. 6 is a schematic view of a longitudinal section of an extrusion apparatus according to a first exemplary embodiment of the present invention;

fig. 7 is a schematic view of a longitudinal section of an extrusion apparatus according to a second exemplary embodiment of the invention;

fig. 8 is a schematic view of a longitudinal section of an extrusion apparatus according to a third exemplary embodiment.

Identical or similar elements have the same reference numerals in the various figures. Therefore, the description of these elements will not be repeated systematically.

Detailed Description

Fig. 1 shows an extrusion apparatus according to the prior art, which uses a plurality of extruders A, B, C, D, E, F, G which converge together in the same extruder head T to produce by co-extrusion a complex shaped product forming a tire tread 100'. The tread 100' is more clearly visible in fig. 2, wherein the individual components forming the tread have been identified by letters corresponding to the extruder from which they came. Thus, the sub-layer comes from extruder a, the adjacent layer above the sub-layer comes from extruder B, and the outer layer comes from extruder C. The two profiled elements from extruder E, F complete the outer layer which additionally contained two conductive inserts from extruder D. The assembly is finally completed by two side edges coming from the extruder G.

The extrusion apparatus of the present invention may be embodied in a variety of ways. The apparatus is capable of producing complex shaped products of the type shown in figure 2, but also simpler shaped products of the type shown in figure 3.

Fig. 4 shows an extrusion apparatus 1 of the invention comprising a plurality of extruders 10,20,30,40,50,60 for producing profiled products by coextrusion in a common extruder head 2. The shaped product obtained is a tread 100 and comprises a plurality of components (6 in the example shown) made of elastomeric material coming from different extruders. The extruders 10,20,30,40,50,60 are schematically shown, only their respective screws being described, but it will be understood that, in a well-known manner, the screw of each extruder rotates within a cylindrical barrel equipped with an elastomeric compound feed inlet and an outlet to the extruder head 2. The screw of each extruder is driven to rotate about its longitudinal axis by a motor located at the other end of the screw opposite the end that reaches the extruder head, so as to rotate the screw within its respective barrel, in order to supply the extruder head with the elastomeric compound that has been homogenized and is ready to be shaped by said head.

The extruders 10,20,30,40,50,60 are arranged on both sides of the extruder head 2 and the longitudinal axes of the screws are located in the plane of symmetry P of the tread 100. When the product is a symmetrical product, the plane of symmetry P is a vertical plane passing through the centre of gravity of the strip, whereas in the case of an asymmetrical product, said plane passes through the centre of inertia of the product. Extruders located on both sides of the extruder head refer to extruders facing each other by being disposed on both sides of a vertical plane perpendicular to the symmetry plane P and passing through the center of the extruder head 2. This arrangement can balance the flow from each extruder through the extruder head.

In operation, when supplying each extruder with elastomeric compounds, the various compounds extruded by the extruders 10,20,30,40,50,60 flow without mixing along the distribution duct provided for this purpose in the extruder head 2 (in this case the first extruder head 2) and converge towards the die 3 which finally shapes the product (in this case the tread 100).

Thus, each elastomeric compound coming from one of said extruders 10,20,30,40,50,60 passes through the first extruder head 2 along a distribution duct dedicated to it, and for each elastomeric compound coming from one of the extruders of the apparatus 1 it is allowed to be conveyed to the die 3 separately from the other elastomeric compounds coming from the other extruders, so that it cannot come into contact with any other elastomeric compound coming from the other extruders and conveyed by the other dedicated distribution ducts before reaching the die 3.

For example, different elastomeric compounds like this are compounds based on elastomers or rubbers used for manufacturing tread components, such as: a first material made of 100% natural rubber to form a sublayer, then a second material made of 100% synthetic rubber, for example containing silica, to form the outer part of the tread, and a third material free of silica but having absorbing properties, then a fourth material and a fifth material to form the lateral edges and made for example of a compound of natural/synthetic rubber (comprising 20% to 80% natural rubber), the sixth material being a conductive compound, containing a mixture of natural/synthetic rubber and carbon black.

As shown in fig. 4 to 8, the extruders 10,20,30,40,50,60 are arranged with their longitudinal axes 11, 21, 31, 41, 51, 61 parallel to each other and perpendicular to the side walls 22 and 23 of the extruder heads 2,2',2 ", 2'", three extruders 10, 30, 50 being located on the right side of the vertical middle plane of the extruder heads and the other three extruders 20, 40,60 being located on the left side of said plane. The right side extruder and the left side extruder face each other; they are located in pairs at the same height with their longitudinal axes in the same plane. However, the right side extruder may be disposed at a different height than the left side extruder. In one variation, the longitudinal axes of the extruders are not parallel, but are angled with respect to each other, and the longitudinal axes of two adjacent extruders may be angled at a different angle than the longitudinal axes of the other two adjacent extruders. In another variant, it is possible to envisage the number of extruders on the right side being different from the number of extruders on the left side of the head.

The extruder head 2 consists of a stack of several plates, seven in the example shown in fig. 5: the plates 2a, 2b, 2c, 2d, 2e, 2f, 2g are parallel to each other and to the side walls 22, 23 of the extruder head and perpendicular to the longitudinal axis of the extruder 10,20,30,40,50, 60. The plates 2a to 2g have a length equal to or slightly shorter than the length of the side walls 22, 23 of the head and define between them transverse distribution ducts 5a, 5b, 5c,5d, 5f, 5g which convey the elastomeric compound coming from the extruder of the plant towards the outlet die 3. The plates 2a to 2g are detachable and fixed together, for example by screw fixation (not depicted) to the side walls of the extruder head. The apparatus of fig. 2 may manufacture the six-component tread 100 of fig. 4.

According to the invention, the apparatus comprises a second removable extruder head which allows the fluid of elastomeric compound coming from at least two extruders of the apparatus to be directed into a common distribution duct before reaching the outlet die.

In a first exemplary embodiment and more clearly visible in fig. 6, the second extruder head 2' is produced in the following manner: the two extruders 50 and 60 facing each other are fed into the longitudinal collecting duct 6 by the outlet holes of their respective barrels being connected to the inlet holes 52 and 62 in the second extruder head 2', respectively. Each extruder 50,60 feeds, towards the second extruder head 2', respectively, a flow of material F50 and F60 entering the head in the direction of the longitudinal axis of the extruder, the two flows F50 and F60 merging together in a collecting duct 6 and then abruptly changing direction together, substantially perpendicular to the longitudinal axis of the extruders 50,60, along a common transverse distribution duct 5c towards the die 3'. In the example of fig. 6, the two longitudinal flows F50 and F60 merge together and form the same transverse flow, and the combined flow Fc of the material is obtained by the combination of the two aforementioned flows. With respect to the extruders facing each other, it should be understood that each of the extruders 50 and 60 is mounted at an inlet aperture 52, 62, respectively, of the second extruder head 2', the inlet apertures 52 and 62 facing each other in the extruder head 2', or being located on both sides of the middle plane of the extruder head.

In a second exemplary embodiment of the invention, as shown in fig. 7, a second extruder head 2 "is produced in the following manner: the two superimposed extruders 40 and 60 feed into a transverse collecting duct 7 in direct communication with a common transverse distribution duct 5d in which the flows of compound join together and flow together along said distribution duct before reaching the die 3 ". More specifically, each extruder 40,60 feeds the second extruder head 2 "with streams F40 and F60, respectively, entering the head along the longitudinal axis of the extruder. Longitudinal flows F40 and F60, respectively, abruptly change direction upon contact with plate 2d, substantially perpendicular to the longitudinal axis of extruders 40, 60. The two flows join together at the inlet aperture 42 and flow along a common transverse distribution duct 5d towards the mould 3. In the example of fig. 7, the two longitudinal flows F40 and F60 merge together and form the same transverse flow, and the combined flow Fc of the material is obtained by the combination of the two aforementioned flows. By stacked extruders is meant that the extruders 40 and 60 (referring to their longitudinal axes) are arranged in horizontal or inclined planes, but at a vertical distance from each other. The respective inlet apertures 42, 62 of the second extruder head 2 "are thus located at a vertical distance from each other on the same side of the extruder head 2", viewed in relation to the middle plane of the second extruder head 2 ".

In a third exemplary embodiment of the invention as shown in fig. 8, a second extruder head 2 "' is produced in the following manner: the two extruders 50 and 60 facing each other feed into the longitudinal collecting duct 6 and the two superimposed extruders 40,60 feed into the longitudinal collecting duct 7, which means that the combined flows from the three extruders form one and the same flow directly into the common transverse distribution duct 5 c. The fluid thus obtained flows along the distribution duct 5c before reaching the die 3 "'. More specifically, each extruder 50,60 feeds, respectively, to the second extruder head 2 "', the streams F50 and F60 entering the head along the longitudinal axis of the extruder, the two streams F50 and F60 merging together in a longitudinal collecting duct 6 and then abruptly changing direction together, substantially perpendicularly along a common transverse distribution duct 5c towards the die 3"'. The longitudinal flow from extruder 40 and a portion of the fluid exiting extruder 60 change direction upon exiting the extruder substantially perpendicular to the longitudinal axis of the extruder and merge with the flow from the longitudinal collection conduit, resulting in three longitudinal flows merging in a common transverse conduit 7. The same flow Fc obtained by combining the three flows F50, F60 and F40 flows along the distribution duct 5c to reach the die 3 "'.

Thus, when feeding the same material (referred to as elastomeric compound of the same composition) to two extruders 50 and 60 facing each other, or to two extruders 40,60 in stack, or to any combination of extruders facing each other and of extruders in stack, it is possible to obtain a simpler coextruded product (since it contains less components) using the same equipment as that capable of producing a more complex coextruded product. When the six extruders of the apparatus of fig. 4 are made to cooperate in pairs, it is possible to produce a tread 200 (as shown in fig. 3) comprising three components a, b and c.

According to an advantageous aspect of the invention, the extruder head is interchangeable and is directly connected to the extruder 10,20,30,40,50,60 without any elastomeric compound transfer duct between the two. The choice of making two extruders cooperate is therefore made by fitting the appropriate extruder heads and then operating the extruders according to the geometry of the product to be obtained. The amount of product delivered to the die is adjusted by adjusting the rotational speed of the extruder screw. Furthermore, the extruders 10,20,30,40,50,60 are fed directly to the extruder head 2 (i.e. the first extruder head) or separately to a second extruder head (when the latter replaces the first), thereby significantly limiting the pressure drop.

According to an advantageous aspect of the invention, the flows of compounds F50 and F60 or F40 and F60, respectively, to be coordinated are made to converge as early as possible at the bottom of the extruder head or opposite part thereof to reach the outlet via the dies 3',3 ". This has the advantage that a good cohesion between the two compounds forming a single component avoids debonding problems at the interface between the two materials.

According to another advantageous aspect of the invention, the extruders 10,20,30,40,50,60 of the plant 1 are identical. For example, they have an extrusion screw with a diameter of 100 mm. This means that they can easily cooperate to meet the requirements of the product to be manufactured. Thus, maintenance of the apparatus is made easier.

Furthermore, the arrangement "facing each other" is advantageous in that it reduces the size of the space tool (in particular the extruder head), thereby providing better ergonomics, while enabling it to reduce its weight.

In a variant of the invention, all the extruders 10,20,30,40,50,60 of the plant 1 are extruders using archimedes screws. In another variant of the invention, at least two extruders of the apparatus 1 are positive-displacement extruders, for example of the positive-displacement counter-rotating twin-screw type with closely meshing screw flights comprising mating profiles.

In operation, a first extruder head 2 is selected and introduced into a cradle provided for this purpose in the apparatus 1, said first extruder head 2 being capable of manufacturing a complex tread 100 based on a plurality of elastomeric compounds of different composition by co-extrusion of the elastomeric compounds from the extruders 10,20,30,40,50, 60. The first extruder head is locked in place using a quick-fit device (not shown in the figures). An extrusion operation is performed. When it is desired to change the type of tread (structure, composition), a second extruder head 2',2 "is selected and introduced into the cradle provided for this purpose in the apparatus 1, said second extruder head 2', 2" being adapted to the new tread 200 by co-extrusion of the elastomeric compounds from the extruders 10,20,30,40,50,60 based on a plurality of elastomeric compounds of different compositions, and then locked in position using a quick-fit device. The new tread 200 contains fewer components than the first tread, but is fed from the same extruders, some of which deliver the same compound to a common distribution conduit within the extruder head before reaching the exit die.

Other variations and embodiments of the invention may be envisaged without departing from the scope of the claims of the invention.

Thus, it is possible to arrange more than six extruders on both sides of the extruder head or even on the other faces of the extruder head, at least two of the extruders working with different compounds and the others working with the same elastomeric compound, provided that said faces are not designated on the one hand for the extrusion die to reach the outlet of the compound and on the other hand for the gripping part of the head so that it can move around.

Advantageously, whatever the number of extruders included in the plant 1, the invention allows to use a same set of multiple extruders 10,20,30,40,50,60 for manufacturing complex first molding elements, or second molding elements that are simpler than said complex molding elements, depending on whether they are used in conjunction or in conjunction with said same set of multiple extruders:

a first extruder head 2 for forming complex first forming elements and defining, for each extruder of a group of multiple extruders, from said extruder up to the die 3, a dedicated flow path for the elastomeric compound concerned, said flow path being realized by a respective dedicated distribution duct and being isolated from the other paths taken by the fluids of elastomeric compound coming from the other extruders of said same group of multiple extruders, so that the fluids of elastomeric compound always separate from each other on the path up to the die 3, said fluids merging at the die 3 to form a first forming element;

-or a second extruder head 2',2 "', for forming a simpler second forming element, and wherein at least two paths from at least two extruders of said same group of multiple extruders, respectively, converge in a confluence zone, located inside said second extruder head, upstream of the die 3', 3"' in the flow direction, at a distance from said die, so that at least two flows of the respective elastomeric compounds converge together before reaching said die, then follow together a same shared path realized by a respective common distribution duct from their confluence zone up to said die, so that said two extruders share said distribution duct, compared to the first extruder head.