Machine and process for the production of logs of paper material

A rewinding machine for the production of logs of paper material, comprising:

• a winding station in which a paper web is fed and, in sequence, more tubular cores, and in which station winding are arranged a first, a second and a third winding roller cooperating with each other to wind a predetermined amount of said paper web onto each core, the machine further comprises the winding station having a fourth winding roller which is connected to respective moving means adapted to arrange it in a first inoperative position until the diameter of a log in the winding station is lower than a first predetermined value and a second operating winding position when the diameter of the log being formed is equal to said first predetermined value, said moving means being controlled to maintain the fourth roller in the second operating winding position until the diameter of the log reaches a second final value higher of the first predetermined value such that, in a first phase, which ends with the attainment of said first predetermined value of the diameter of the log being formed, the winding of the web on the cores is realized by said first, second and third winding roller, and, at a subsequent phase, the log is completed in cooperation by the four winding rollers until said second final value of the diameter of the log is reached.

A Process for the production of logs of paper material, comprising:

• supplying a paper web and, in sequence, more tubular cores in a winding station of a rewinding machine, in which winding station are arranged a first, a second and a third winding roller cooperating with each other to wind a predetermined amount of said paper web onto each core, wherein, in said winding station, a fourth winding roller which is arranged in a first inoperative position until the diameter of a log in the winding station is lower than a first predetermined value and a second operating winding position when the diameter of the log being formed is equal to said first predetermined value, said fourth winding roller being maintained in the second operating winding position until the diameter of the log reaches a second final value higher of the first predetermined value such that, in a first phase, which ends with the attainment of said first predetermined value of the diameter of the log being formed, the winding of the web on the cores is realized by said first, second and third winding roller, and, at a subsequent phase, the log is completed in cooperation by the four winding rollers until said second final value of the diameter of the log.