Braking band of a disc brake disc

1. A braking band of a disc for disc brake, said disc defining a rotation axis (A-A), which defines an axial direction (X-X) either coinciding with or parallel to said rotation axis (A-A) of the disc, a radial direction (R-R) substantially orthogonal to the axial direction (X-X), and a circumferential (C-C) or tangential (C-C) direction, substantially orthogonal to the axial direction (X-X) and to the radial direction (R-R), said braking band comprising a first plate and a second plate, arranged mutually facing each other so as to form a gap, wherein

at least either said first plate or said second plate comprises a radially inner edge, facing said rotation axis (A-A) of the disc, and a radially outer edge substantially coaxial with said radially inner edge and facing opposite with respect to said rotation axis (A-A) of the disc,

said braking band further comprises a group of connecting fins which connects said first plate and said second plate, defining a module (M) repeated according to said circumferential direction (C-C),

said group of connecting fins comprises a first fin which connects said first plate and said second plate, and a second fin which connects said first plate and said second plate, wherein

said first fin extends along a first longitudinal direction between said radially inner edge and said radially outer edge forming:

a circumferentially arched first length of said first fin, said circumferentially arched first length of said first fin having a first concavity (R 13 ) which extends along the entire extension of the circumferentially arched first length of said first fin in said first longitudinal direction;

a circumferentially arched second length of said first fin, said circumferentially arched second length of said first fin having a second concavity (R 14 ) which extends along the entire extension of the circumferentially arched second length of said first fin in said first longitudinal direction, said second concavity (R 14 ) having opposite direction with respect to said first concavity (R 13 );

a circumferentially arched third length of said first fin, said circumferentially arched third length of said first fin having a third concavity (R 15 ) which extends along the entire extension of the third length of said first fin in said first longitudinal direction;

a circumferentially arched fourth length of said first fin, said circumferentially arched fourth length of said first fin having a fourth concavity (R 16 ) which extends along the entire extension of the third length of said first fin in said first longitudinal direction, said fourth concavity (R 16 ) having opposite direction with respect to the said third concavity (R 15 );

and wherein said second fin extends along a second longitudinal direction between said radially inner edge and said radially outer edge forming:

a circumferentially arched first length of said second fin, said circumferentially arched first length of said second fin having a fifth concavity (R 17 ) which extends along the entire extension of the first length of said second fin in said second longitudinal direction;

a circumferentially arched second length of said second fin, said circumferentially arched second length of said second fin having a sixth concavity (R 18 ) which extends along the entire extension of the second length of said second fin in said second longitudinal direction, said sixth concavity (R 18 ) having opposite direction with respect to the said fifth concavity (R 17 );

a circumferentially arched third length of said second fin, said circumferentially arched third length of said second fin having a seventh concavity (R 19 ) which extends along the entire extension of the third length of said second fin in said second longitudinal direction;

a circumferentially arched fourth length of said second fin, said circumferentially arched fourth length of said second fin having an eighth concavity (R 20 ) which extends along the entire extension of the fourth length of said second fin in said second longitudinal direction; said eighth concavity (R 20 ) having opposite direction with respect to said seventh concavity (R 19 ); and wherein

said first fin has a length that is shorter than the length of said second fin.

2. The braking band of claim 1 , wherein said group of connecting fins constituting said module (M) delimits at least one ventilation channel, which defines a longitudinal channel direction substantially coinciding with a longitudinal development axis of said at least one ventilation channel.

3. The braking band of claim 2 , wherein said at least one ventilation channel extends along the longitudinal channel direction between a radially inner mouth and a radially outer mouth forming a first widened length, a bottleneck and a second widened length.

4. The braking band of claim 3 , wherein said bottleneck is interposed between said first widened length and said second widened length.

5. The braking band of claim 3 , wherein a radially outer portion of said first fin and a radially outer portion of said second fin delimit a radially outer channel length which leads into said radially outer mouth.

6. The braking band of claim 3 , wherein a radially outer portion of said first fin and a radially outer portion of said second fin delimit an outlet bottleneck at said radially outer mouth so as to accelerate a flow exiting from the ventilation channel.

7. The braking band of claim 2 , wherein said longitudinal channel direction is not parallel to the radial direction (R-R).

8. The braking band of claim 1 , wherein

said first fin comprises a radially inner length of said first fin which extends radially internally with respect to said circumferentially arched first stretch of said first fin, and

said second fin comprises a radially inner length of said second fin which extends radially internally with respect to said circumferentially arched first stretch of said second fin.

9. The braking band of claim 8 , wherein said radially inner length of said first fin and said radially inner length of said second fin diverge in radially outer direction (RO).

10. The braking band of claim 8 , wherein

said first fin and said second fin both extend to a same radially outer circumferential level; and/or wherein

said radially inner length of said second fin comprises a curved connecting wall facing the rotation axis (A-A) of the disc and a radially inner recess wall facing the rotation axis (A-A) of the disc, wherein said radially inner recess part is substantially parallel to the circumferential direction (C-C).

11. The braking band of claim 1 , wherein the direction of said first concavity (R 13 ) is complementary with the direction of said third concavity (R 15 ) and the direction of said second concavity (R 14 ) is complementary with the direction of said fourth concavity (R 16 ).

12. The braking band of claim 1 , wherein the direction of said fifth concavity (R 17 ) is complementary with the direction of said seventh concavity (R 19 ) and the direction of said sixth concavity (R 18 ) is complementary with the direction of said eighth concavity (R 20 ).

13. The braking band of claim 1 , wherein the body of said first fin comprises an axial connecting portion which extends to axially connect said first plate with said second plate, and a longitudinal tongue which extends axially along a portion of an axial distance between said first plate and said second plate forming a tongue surface axially facing said gap, preventing said longitudinal tongue from forming a connection in axial direction (X-X) between said first plate and said second plate.

14. A disc for disc brake, said disc defining a rotation axis (A-A), which defines an axial direction (X-X) either coinciding with or parallel to said rotation axis (A-A) of the disc, a radial direction (R-R) substantially orthogonal to the axial direction (X-X), and a circumferential (C-C) or tangential (C-C) direction, substantially orthogonal to the axial direction (X-X) and to the radial direction (R-R), said disc comprising a disc bell and a braking band, said braking band comprising a first plate and a second plate, arranged mutually facing each other so as to form a gap, wherein

at least either said first plate or said second plate comprises a radially inner edge, facing said rotation axis (A-A) of the disc, and a radially outer edge substantially coaxial with said radially inner edge and facing opposite with respect to said rotation axis (A-A) of the disc,

said braking band further comprises a group of connecting fins which connects said first plate and said second plate, defining a module (M) repeated according to said circumferential direction (C-C),

said group of connecting fins comprises a first fin which connects said first plate and said second plate, and a second fin which connects said first plate and said second plate, wherein

said first fin extends along a first longitudinal direction between said radially inner edge and said radially outer edge forming:

a circumferentially arched first length of said first fin, said circumferentially arched first length of said first fin having a first concavity (R 13 ) which extends along the entire extension of the circumferentially arched first length of said first fin in said first longitudinal direction;

a circumferentially arched second length of said first fin, said circumferentially arched second length of said first fin having a second concavity (R 14 ) which extends along the entire extension of the circumferentially arched second stretch of said first fin in said first longitudinal direction, said second concavity (R 14 ) having opposite direction with respect to said first concavity (R 13 );

a circumferentially arched third length of said first fin, said circumferentially arched third length of said first fin having a third concavity (R 15 ) which extends along the entire extension of the third length of said first fin in said first longitudinal direction;

a circumferentially arched fourth length of said first fin, said circumferentially arched fourth length of said first fin having a fourth concavity (R 16 ) which extends along the entire extension of the third length of said first fin in said first longitudinal direction, said fourth concavity (R 16 ) having opposite direction with respect to the said third concavity (R 15 );

and wherein said second fin extends along a second longitudinal direction between said radially inner edge and said radially outer edge forming:

a circumferentially arched first length of said second fin, said circumferentially arched first length of said second fin having a fifth concavity (R 17 ) which extends along the entire extension of the first length of said second fin in said second longitudinal direction;

a circumferentially arched second length of said second fin, said circumferentially arched second length of said second fin having a sixth concavity (R 18 ) which extends along the entire extension of the second length of said second fin in said second longitudinal direction, said sixth concavity (R 18 ) having opposite direction with respect to the said fifth concavity (R 17 );

a circumferentially arched third length of said second fin, said circumferentially arched third length of said second fin having a seventh concavity (R 19 ) which extends along the entire extension of the third length of said second fin in said second longitudinal direction;

a circumferentially arched fourth length of said second fin, said circumferentially arched fourth length of said second fin having an eighth concavity (R 20 ) which extends along the entire extension of the fourth length of said second fin in said second longitudinal direction; said eighth concavity (R 20 ) having opposite direction with respect to said seventh concavity (R 19 ); and wherein

said first fin has a length that is shorter than the length of said second fin.

15. A disc brake comprising a disc according to claim 14 and at least one brake caliper.