A shearing device (1) for fragmenting a metal strip into multiple pieces, said device comprising:
- two counter-rotating drums positioned facing each other, respective axes of rotation of the two drums being parallel to each other;
- a drive device connecting the two drums and synchronising a speed of rotation of the two drums;
- and
- a pair of blades, first and second blades of the pair of blades being carried by a respective drum of the two drums,
- the first and second blades of the pair of blades cooperating with a shearing effect during rotation of the two drums for cutting, the first and second blades having, starting from cutting edges (4) of the first and second blades, flat overlapping faces (5,6) that overlap with one another and face each other at least locally during shearing between the first and second blades,
- the first blade of the pair of blades being attached transversely to the respective drum at an angle with respect to an axis of rotation of the respective drum and in such a way that a plane which is co-planar with said overlapping face (5,6) of the first blade forms an angle with the axis of rotation of the respective drum, a cutting edge of the first blade and the axis of rotation of the respective drum being non-coplanar,
- the second blade of the pair of blades being attached transversely to the respective drum at an angle with respect to an axis of rotation of the respective drum and in such a way that a plane which is co-planar with said overlapping face (5,6) of the second blade forms an angle with the axis of rotation of the respective drum, a cutting edge of the second blade and the axis of rotation of the respective drum being non-coplanar,
- the first and second blades of the pair of blades carried by the two drums having opposite diagonal orientations and in such a way as to produce progressive shearing,
- wherein said overlapping face of each blade of the first and second blades has a double inclination with respect to the respective drum in such a way that the plane which is co-planar with said overlapping face does not intersect the axis of rotation of the respective drum over an active width of the respective drum, said plane intersecting the axis of rotation of the respective drum at a point located outside of a segment of the axis corresponding to the active width of the respective drum,
- wherein each blade of the pair of blades has a rectilinear cutting edge defined at an intersection of the overlapping face and an outer face of the blade,
- wherein said double inclination of the first blade prevents the rectilinear cutting edge of the first blade from impacting the second blade during shear cutting,
- wherein said double inclination of the second blade prevents the rectilinear cutting edge of the second blade from impacting the first blade during shear cutting, and
- wherein said double inclination is determined with respect to the rectilinear cutting edge of each blade parallel to the axis of rotation of the respective drum as follows:
- a first inclination of the overlapping face is obtained by rotation of each blade about an axis of rotation which is contained in a plane coplanar with the overlapping face, radial and perpendicular to the axis of rotation of the respective drum, and in such a way as to obtain the progressive shearing, the rotation ranging from 10° to 20°, and
- a second inclination is obtained by rotation of each blade about an axis of rotation which is contained in a plane coplanar with the overlapping face and is parallel to the cutting edge of the blade, the rotation ranging from 4.5° to 14.5°.