Device for preparing a reinforcing strip intended for the manufacturing of a tyre, said device making it possible to prepare a wavy reinforcing strip from a flat reinforcing strip , said device comprising: - a carousel that is able to guide a plurality of fingers in a generally circular movement about a carousel axis (AC), - a rotary star wheel that is rotatable about a star-wheel axis (AE), said rotary star wheel bearing a plurality of rotary rollers having axes parallel to the star-wheel axis, said rollers being distributed in a concentric circle with respect to the star-wheel axis, - means for synchronizing the generally circular movement of the fingers and the rotation of the star wheel, - guide means for guiding the flat reinforcing strip entering the device, in which: - the star-wheel axis and the carousel axis are spaced apart from and substantially parallel to one another, said fingers being able to bear against a first face of the strip, said rollers being able to bear against a second face of the strip, - each of the fingers is borne by a support that pivots with respect to the carousel such that the finger can take up a bearing position in which it bears against the first face of the strip and a spaced-apart position in which it is away from the first face of the strip and from said common plane, - the generally circular movement imparted on the fingers by the carousel has an intersecting portion (PI) in which the synchronizing means allow the fingers and the rollers to move in a common plane perpendicular to the star-wheel axis, the fingers and the rollers being interposed in said intersecting portion so as to impose waves on the strip that extend in said common plane. - a carousel that is able to guide a plurality of fingers in a generally circular movement about a carousel axis (AC), - a rotary star wheel that is rotatable about a star-wheel axis (AE), said rotary star wheel bearing a plurality of rotary rollers having axes parallel to the star-wheel axis, said rollers being distributed in a concentric circle with respect to the star-wheel axis, - means for synchronizing the generally circular movement of the fingers and the rotation of the star wheel, - guide means for guiding the flat reinforcing strip entering the device, - the star-wheel axis and the carousel axis are spaced apart from and substantially parallel to one another, said fingers being able to bear against a first face of the strip, said rollers being able to bear against a second face of the strip, - each of the fingers is borne by a support that pivots with respect to the carousel such that the finger can take up a bearing position in which it bears against the first face of the strip and a spaced-apart position in which it is away from the first face of the strip and from said common plane, - the generally circular movement imparted on the fingers by the carousel has an intersecting portion (PI) in which the synchronizing means allow the fingers and the rollers to move in a common plane perpendicular to the star-wheel axis, the fingers and the rollers being interposed in said intersecting portion so as to impose waves on the strip that extend in said common plane. <EOS>