Abstract: The invention concerns a process and apparatus for the coextrusion of rubber mixtures, comprising a main extruder (1) with an extrusion head (10) having at least two flow channels (14, 15), each for a rubber mixture (A, B), the channels opening into an extrusion orifice (18) through which the two rubber mixtures (A, B) are propelled. The extrusion orifice (18) is delimited by a first wall (111) and a second wall (161). The apparatus also comprises at least one micro-extruder (2) for a third rubber mixture (C), whose extrusion head (22) is provided at its end with a nozzle (23) passing through the two flow channels (14, 15) such that the third rubber mixture (C) is inserted into each rubber mixture (A, B) upstream from the extrusion orifice (18).

Abstract: A tire having a tread composed of two non-conductive layers, each layer containing a circumferential insert of conductive mix, the inserts having a wider interface at the interface of the two layers. An apparatus for extruding a layer, provided with a conductive insert, including a main extruder for extruding a non-vulcanized, non-conductive layer, and a micro-extruder having an extrusion head, provided at its end with a nozzle, for extruding a conductive insert in the layer.

Abstract: A tire having a tread consisting of two circumferential layers of non-conductive material, each layer containing a circumferential insert made of a conductive mix and having on the contact surface between the two layers a circumferential footprint, the first of these layers having on the said surface a circumferential footprint with a circular path of width e, the second layer having on the said surface a circumferential footprint of width e′ lying across and having crests on either side of the circular path of the first layer, such that circumferentially between the two paths there are numerous points of contact which ensure electrical connection between the two conductive elements. The second layer with its insert is extruded from a main extruder for the extrusion of the portion of a tread in the unvulcanized condition, and a micro-extruder whose extrusion nozzle is fitted with a cutting edge and whose extrusion orifice is directed against a conveyor associated with the main extruder.

Abstract: The invention concerns a process and apparatus for the coextrusion of rubber mixtures, comprising a main extruder (1) with an extrusion head (10) having at least two flow channels (14, 15), each for a rubber mixture (A, B), the channels opening into an extrusion orifice (18) through which the two rubber mixtures (A, B) are propelled. The extrusion orifice (18) is delimited by a first wall (111) and a second wall (161). The apparatus also comprises at least one micro-extruder (2) for a third rubber mixture (C), whose extrusion head (22) is provided at its end with a nozzle (23) passing through the two flow channels (14, 15) such that the third rubber mixture (C) is inserted into each rubber mixture (A, B) upstream from the extrusion orifice (18).