Method for controlling the discharge of fluids during a process for vulcanization and molding of a green tire and tire for vehicle wheels

1. A method for controlling the discharge of fluids during a process for vulcanisation and moulding of a green tyre, said fluids being interposed between a radially external surface of a pressing bladder and a radially internal surface of the green tyre, comprising:

building said radially internal surface of the green tyre, wherein the building comprises winding a continuous elongated element of elastomeric material into a plurality of coils confining circumferential grooves along a rolling direction of the tyre; and

disposing said circumferential grooves into fluid communication with discharge channels present in said radially external surface,

wherein “L” represents a half-width in an axial direction of a belt structure associated at a radially external position with a carcass structure of the green tyre, as measured from the equitorial plane of the green tyre,

wherein “H” represents a section height of the green tyre, as measured from a radially inner most bead area of the tyre, said circumferential grooves extending only throughout two discrete axially-opposed portions of the radially internal surface of the green tyre, each discrete axially-opposed portion of the radially internal surface of the green tyre being defined by a region on the internal surface of the tyre extending from 90% of the respective “L” half-width of that discrete portion's axial side of the tyre to 20% of the respective “H” section height of that discrete portion's axial side of the tyre; and

wherein the discharge channels present in the radially external surface of the pressing bladder extend only throughout two discrete axially-opposed portions of the bladder, each discrete axially-opposed portion of the bladder being defined by, during the moulding, being in contact with a respective one of the regions on the internal surface of the tyre extending from 90% of the respective “L” half-width of that discrete portion's axial side of the tyre to 20% of the respective “H” section height of that discrete portion's axial side of the tyre.

2. The method as claimed in claim 1 , wherein the discharge channels comprise a plurality of secondary channels recessed into a cross section of the pressing bladder and disposed in a reticular structure across said radially external surface and defining a plurality of cells, and

wherein a cross-sectional area of the secondary channels is less than a cross-sectional area of other channels in the cross-section of said radially external surface.

3. The method as claimed in claim 1 , wherein the discharge channels comprise a plurality of main channels, each of said main channels extending from a radially internal portion of the radially external surface of the pressing bladder in an inflated configuration, to an equatorial portion of said pressing bladder.

4. The method as claimed in claim 3 , wherein the discharge channels comprise a plurality of secondary channels disposed in a reticular structure defining a plurality of cells, and wherein the secondary channels are in fluid communication with the main channels.

5. The method as claimed in claim 3 , wherein the discharge channels comprise a plurality of secondary channels disposed in a reticular structure defining a plurality of cells, wherein at least some of the secondary channels intersect at least some of the main channels.

6. The method as claimed in claim 2 , wherein the reticular structure of the secondary channels comprises contiguous polygons.

7. The method as claimed in claim 6 , wherein the polygons have at least one pair of sides that meet at an obtuse angle.

8. The method as claimed in claim 2 , wherein each cell encloses an area between 0.5 mm 2 and 500 mm 2 .

9. The method as claimed in claim 2 , wherein the secondary channels have a width between 0.15 mm and 2 mm.

10. The method as claimed in claim 2 , wherein the secondary channels have a depth greater than 0.2 mm and less than or equal to 1.5 mm.

11. The method as claimed in claim 3 , wherein the main channels have a width between 0.3 mm and 4 mm.

12. The method as claimed in claim 3 , wherein the main channels have a depth between 0.5 mm and 3 mm.

13. The method as claimed in claim 1 , wherein the circumferential grooves have a width between 0.05 mm and 2 mm.

14. The method as claimed in claim 1 , wherein the circumferential grooves have a depth between 0.05 mm and 1 mm.