Unit for feeding and cutting into lengths a strip of wrapping material

A unit for feeding and cuffing into lengths a strip of wrapping material, applicable to a cigarette packer, comprising:

• a cutter device comprising a first roller and a second roller, rotatable in an opposite direction to the first roller;
• the first roller having a first blade and a second blade occupying diametrically opposed positions, the second roller having a first blade and a second blade occupying diametrically opposed positions;
• the first and the second rollers combining at an area of substantially tangential proximity to establish a cutting zone that can be occupied alternatively by the first blades of the first and the second rollers and by the second blades of the first and the second rollers;
• the first blades, being cyclical in operation, for dividing the strip transversely into single leaves of predetermined length and the second blades being cyclical in operation, for impressing at least one transverse tear-off line on each leaf;
• control means for controlling a timing of a stroke of the second blades relative to the strip, between each two successive transverse dividing strokes made through the strip, so as to adjust a position of the transverse tear-off line on the leaf;
• wherein the first roller and the second roller rotate at a constant angular speed and the strip wraps around and engages a circumferential surface portion of one of the first roller and the second roller, and wherein the control means, acting directly on the strip, produces a periodic variation in a linear speed of the strip relative to a peripheral speed of the roller around which the strip wraps to cause the strip to slip on the circumferential surface of that roller for cyclically controlling a position of the strip with respect to the second blades before reaching the cutting zone.