Decorating machine particularly for the decoration of ceramic products and method for realising a belt for decorating said ceramic products

1. A decorating machine for decoration of ceramic products, comprising:

a closed loop belt ( 3 ) for the transfer of a decoration ( 9 ) on a receiving surface ( 11 ) of a ceramic product;

a plurality of conveyor rollers ( 2 ) about which said closed loop belt ( 3 ) is wound and moved in rotation;

at least one of said plurality of conveyor rollers ( 2 ) comprises a central portion ( 12 ) and two end portions ( 14 ) opposite one another, at least one of said two end portions ( 14 ) being free in rotation with respect to the other said end and central portions ( 12 , 14 );

characterised in that each of said two end portions ( 14 ) has a variable diameter; said variable diameter reaching a maximum diameter (D) in a remote position with respect to a flank ( 18 a ) of each of said two end portions ( 14 ) close to the central portion ( 12 );

characterised in that the closed loop belt ( 3 ) comprises a central portion thin in thickness and defining respective lateral edges ( 19 ) constrained to flat cooperating belts ( 20 ) tensioned on said two end portions ( 14 ); interaxes of said flat cooperating belts ( 20 ) defining a distance (A) between the interaxes of flat cooperating belts shorter than a distance (B) defined between the maximum diameters (D) of said opposite two end portions ( 14 ).

2. The decorating machine according to claim 1 , characterised in that said maximum diameter (D) reaches the maximum in an intermediate position ( 16 ) of each of the two end portions ( 14 ).

3. The decorating machine according to claim 1 , characterised in that the at least one of the plurality of conveyor rollers ( 2 ) has a respective central portion ( 12 ) that is motorized.

4. The decorating machine according to claim 1 , characterised in that the at least one of the plurality of conveyor rollers ( 2 ) has respective end portions ( 14 ) that are motorized and connected to a differential means ( 26 ).

5. The decorating machine according to claim 1 , characterised in that the at least one of the plurality of conveyor rollers ( 2 ) has respective opposite end portions ( 14 ) connected to distinct motorisations; striking means being arranged on said flat cooperating belts ( 20 ) to determine the position in the direction of advancement and control means maintaining the synchronisation between said flat cooperating belts ( 20 ).

6. The decorating machine according to claim 5 , characterised in that said flat cooperating belts ( 20 ) are elastically deformable lengthwise and the inside surface thereof is provided with a high coefficient of friction.

7. The decorating machine according to claim 1 , characterised in that said end portions have a metal surface with a glossy finish.

8. The decorating machine according to claim 1 , characterised in that said closed loop belt ( 3 ) comprises a central zone consisting of a tubular, unwelded and electrically conductive polymeric film.

9. The decorating machine according to claim 8 , characterised in that said flat cooperating belts ( 20 ) in the untensioned state, have a peripheral development that is smaller than the peripheral development of the said closed loop belt ( 3 ).

10. The decorating machine according to claim 1 , characterised in that said lateral edges ( 19 ) and said flat cooperating belts ( 20 ) are connected by interposition of a fabric strip ( 21 ).

11. The decorating machine according to claim 10 , characterised in that said closed loop belt ( 3 ) comprises a central zone consisting of a tubular, unwelded and electrically conductive polymeric film; and further characterised in that said fabric strip ( 21 ) has a higher melting temperature than the melting temperature of the said polymeric film and the fabric strip is welded to the said polymeric film by means of hot-melt adhesive ( 27 a ) thermofused under pressure.

12. The decorating machine according to claim 11 , characterised in that said fabric strip ( 21 ) is made of polyester fabric.

13. The decorating machine according to claim 8 , characterised in that said polymeric film is of a thickness ranging between 0.02 mm and 0.1 mm and is obtained using “blown film” technology.

14. The decorating machine according to claim 8 , characterised in that said polymeric film is made of polymer charged with carbon black and/or nanotubes of carbon.

15. The decorating machine according to claim 8 , characterised in that said polymeric film has a surface electrical resistivity ranging between 0.5 KΩm and 20 KΩm.

16. The decorating machine according to claim 8 , characterised in that said polymeric film is made of polyethylene.

17. The decorating machine according to claim 8 , characterised in that said polymeric film has been made to be hydrophilic in the external surface by means of plasma treatment.

18. The decorating machine according to claim 8 , characterised in that said flat cooperating belts ( 20 ) in the untensioned state have an internal diameter (H) ranging between 0.99K and 0.90K, K being the internal diameter of the said tubular polymeric film.