Roller unit for laying cables in a plant for laying cables and plant for laying cables comprising the roller unit

Roller unit for laying cables (11, 12, 13), comprising a frame (23, 23′) where at least one pair of sliders (25, 25′) are positioned, disposed in sequence and aligned parallel to a laying direction (S1, S2) of the cables (11, 12, 13), wherein said sliders (25, 25′) are each provided with at least one pair of wheels (28, 28a, 28b) supporting a cable (11, 12, 13) to be laid, and wherein said sliders (25, 25′) are hinged to said frame (23, 23′) and rotatable around respective axes of rotation (A, A′) so as to vary the inclination thereof with respect to said frame (23, 23′) and therefore to vary the radius of curvature of the cable (11, 12, 13) supported, said roller unit being characterized in that said wheels (28, 28a, 28b) are provided with an annular groove (32) to support the cables, delimited by containing wings (33) and able to define a contact and sliding surface of at least one of said cables (11, 12, 13), wherein at least said annular support groove (32) is made of or covered by a material of great hardness and low rolling friction, said minimum hardness being equal to 90 Shore D (dry as molded) or 75 Shore D (conditioned at 23° C. and 50% relative humidity) and an elastic modulus not lower than 5000 Mpa (dry as molded) in the case of thermoplastic material, said annular groove (32) of said wheels (28, 28a, 28b) is made of or covered by a plurality of interchangeable sectors (34) made of said material with great hardness and low rolling friction.