Device for rewinding and forming a paper roll and related method

A device for rewinding and forming a paper roll in a rewinding machine comprising three rollers (12, 13, 14) with axes parallel to each other and perpendicular to a paper feeding direction (11), wherein two lower and upper winding rollers (12, 13) supported on a frame (100) cooperate with a third swinging roller (14) pressing on a roll or log (11′) being formed, a paper (11) being wound on the upper winding roller 13 is provided with a series of transverse piercing and weakening lines spaced according to regular intervals along its longitudinal development and a finished roll (11′) exiting from an output opening defined between the lower roller (12) and the third roller (14), cores (111) for said rolls (11′) being fed one after the other by a conveyor (16) and inserted by a pusher (17) within a channel (18) obtained below the upper roller (13), wherein mechanical tearing means are placed in the upper roller (13) along its development facing towards the side of the paper facing towards the upper winding roller (13) in order to positively act directly at a piercing line and to cause the tearing of the paper (11), wherein said mechanical tearing means comprise at least three longitudinal bars (21) housed in longitudinal seats (43) in the cylindrical shell of the upper winding roller (13) and radially distributed by a constant angle (α) along the development thereof, each of them being selectively movable from a tearing position, projecting with respect to the shell of the upper winding roller (13), to a neutral position, not projecting, and in that said upper winding roller (13) is provided with an independent motor (41) for setting the rotation speed independently of the feeding speed of the paper (11) and of the lower winding roller (12).