Unwinder with automatic switching of the unwinding roll

An unwinder of a thin ply product wound on a roll, of the type with automatic switching of the unwinding roll with a spare roll, said unwinder comprising:

• a first roll-holder assembly equipped with a first unwinding rod for a respective roll, on which the roll is adapted to be supported, and which has an axis of rotation that is transverse to the direction of movement of the ply unwound from the roll;
• a second roll-holder assembly equipped with a second unwinding rod for a respective roll, on which the roll is adapted to be supported, said second rod being parallel to said first unwinding rod of the first roll-holder assembly, said second roll-holder assembly facing said first roll-holder assembly in an unwinding zone, wherein of said two roll-holder assemblies, one assembly holds the unwinding roll and the other assembly holds the spare roll to be switched;
• a ply splicing assembly placed above said first and second facing roll-holder assemblies;
• a ply accumulation unit to allow automatic switching between a roll being unwound in one said roll-holder assembly and a spare roll provided in the other roll-holder assembly;
• a transversal position correction system for the side edges of the plies on the rolls present in said roll-holder assemblies;
• wherein said transversal position correction system for the side edges of the plies of the rolls present in said roll-holder assembly comprises a device for aligning a side edge of the leading edge of the ply on the spare roll with a corresponding side edge of the ply on the unwinding roll when both rolls are in said unwinding zone, which in turn comprises
• a device for verifying the alignment of said side edges of the spare roll and the unwinding roll, and
• a device for correcting any misalignment detected.