Method and apparatus for plotting a trace pattern on the tread band of a tire

A method for plotting a trace pattern on the tread band of a tire, comprising the steps of:

• storing a base data sequence relative to a predetermined trace pattern in an electronic computer;
• storing a detection data sequence in the electronic computer, which data correspond to the geometrical conformation and surface of the radially external surface of a tire;
• processing said base data sequence depending on said detection data sequence, so as to create an application data sequence corresponding to the trace pattern to be reproduced on said tire surface;
• plotting said trace pattern by a laser beam on the radially external surface of the tire, as a sequential sum of a plurality of distinct elementary portions, through movement of the laser beam controlled by the electronic computer, based on said application data sequence, said plotting operation comprises the step of detecting the outer surface of the tire through a detection means directly connected to the electronic computer which is driving the laser beam for transmitting to said computer the sequence of the detection data to be stored, said method further including oscillating said laser beam, through optical reflection means, within a cone in which the vertex is at the beam emitting point, the axis of symmetry is perpendicular to the axis of rotation of the tire, the height of the cone being the same as the distance of the emission point from the tire surface and the diameter of the base circle of the cone is not greater than 40 cm.

A method for plotting a trace pattern on the tread band of a tire, comprising the steps of:

• storing a base data sequence relative to a single elementary portion of a trace pattern in an electronic computer;
• storing a detection data sequence in the electronic computer, which data correspond to the geometrical conformation and surface of the radially external surface of a tire;
• processing said base data sequence depending on said detection data sequence, so as to create an application data sequence corresponding to the trace pattern to be reproduced on said tire surface;
• plotting said trace pattern on the radially external surface of the tire, as a sequential sum of a plurality of distinct elementary portions, through movement of a laser beam controlled by the electronic computer, based on said application data sequence;
• dividing at least one of said elementary portions of the trace pattern into a series of two-dimension stratigrafies, each relating to a single focusing value of the laser beam.

An apparatus for plotting a trace pattern on the tread band of a tire comprising:

• a bearing structure for said tire provided with means for enabling tire movement around at least one pair of axes perpendicular to each other and intersecting at the center of symmetry of the tire, one of said axes being the axis of rotation of the tire, and means for enabling displacement of the axis of rotation of the tire at least in a direction perpendicular to said axis of rotation;
• at least one plotting instrument operatively connected to said bearing structure and arranged to act on the radially external surface of said tire for plotting a desired trace pattern thereon;
• an electronic computer means for:
• (a) storing a base data sequence relating to a predetermined trace pattern;
• (b) storing a detection data sequence corresponding to the geometrical conformation and surface extension of said tire surface;
• (c) processing said base data sequence depending on said detection data sequence, so as to create an application data sequence corresponding to the trace pattern to be reproduced on said tire surfaces;
• (d) driving said movement means for moving the tire as well as said plotting instrument in order to produce said trace pattern on said tire surface.