ELECTRICALLY CONDUCTIVE TYRE AND APPARATUS FOR EXTRUDING SECTIONS MADE CONDUCTIVE

The tire has two outer layers (31, 31) with circumferential, electrically-conductive strip inserts (11, 12). At the layer interface (310), the widths of the facing strips (E, e') in contact, differ by a factor of ten or more. Strips are located with respect to the equatorial plane, such that the strips touch at numerous points, to assure electrical connection. Independent claims are included. To make the tire, each tread layer is separately extruded, unvulcanized. The extruder nozzle has a roller throat. The unvulcanized conducting strips are inserted in each layer by coextrusion using a micro-extruder, its nozzle against the roller of the main extruder. Equipment carrying out the method and the extrusion nozzle used, are also claimed. Preferred features: The non-conductive layers are inner and outer parts of the tread (3). Connection is made between the ground and the crown reinforcement of the tire belt plies. The latter contain wire cords calendered into conductive rubber. The non conductive sections comprise tread plies and a triangular section strip (62) separating carcass reinforcement from edges of the crown reinforcement. All three layers are bonded together. One tread section has an insert (11) with differing widths (E, e) at either end of its cross section. The other has a rectangular insert (12), each end having width e', equal to e. The external tread section or band, has the insert with differing widths.