A roller-type compression incision cutting unit for packaging material comprising:
- a drive roller having a first shaft and defining a first axis and including a projecting compression incision cutting profile;
- the roller being adapted to rotate about the first axis and comprising first and second supporting elements on opposite ends of the first shaft respectively;
- a driven counter-roller having a second shaft and defining a second axis parallel with the first axis, the second shaft having a first end portion adjacent a first end thereof and a second end portion adjacent a second, opposite, end thereof, the counter-roller including an outer surface with an abutting counter-profile configured to cooperate with the projecting compression incision cutting profile, wherein the counter-roller, including the outer surface, is driven in rotation on the second axis when the second shaft is rotated;
- a first gear wheel fitted on the first shaft supporting the drive roller;
- a second gear wheel fitted on the second shaft supporting the counter-roller, the first gear wheel meshing with the second gear wheel for directly transmitting motion, in a synchronized fashion, between the drive roller and the counter-roller;
- first and second thrust assemblies respectively mounted on the first and second end portions of the second shaft and respectively in direct and continuous rolling contact with the first and second supporting elements,
- the first thrust assembly comprising:
- a single first bearing between the first supporting element and the first end portion of the second shaft;
- and
- a first rolling thrust ring encircling the first bearing and, concentrically with the outer surface, being in direct and continuous rolling contact with the first supporting element, the first rolling thrust ring being made of metal;
- the second thrust assembly comprising:
- a single second bearing between the second supporting element and the second end portion of the second shaft;
- and
- a second rolling thrust ring encircling the second bearing and, concentrically with the outer surface, being in direct and continuous rolling contact with the second supporting element, the second rolling thrust ring being made of metal;
- wherein the first and second bearings have respective first and second internal parts, respective first and second external parts and respective first bearing balls and second bearing balls, the first and second external parts being in contact with the respective first and second rolling thrust rings, the first internal and external parts of the first bearing being in rolling contact with the first bearing balls and the second internal and external parts of the second bearing being in rolling contact with the second bearing balls;
- wherein the first and second internal parts are rigidly fixed to the first and second end portions of the second shaft, respectively;
- and
- wherein the first and second rolling thrust rings are effective to rotate about the second axis driven in rotation by the first and second supporting elements of the drive roller respectively by friction, in such a way as to keep a speed of rotation of the driven counter-roller independent of a speed of rotation of the first and second rolling thrust rings, to allow the rotation of the counter-roller to be driven only by the directly transmitted motion of the meshing first and second gear wheels.