| 摘要 |
<p>A perforating unit (1) for producing ventilated cigarettes (4), wherein a laser beam (13), emitted by a laser source (13a) along an axis (7), is reflected and focused by a movable reflecting and focusing assembly (14) and a reflecting element (16), both rotating about the axis (7), to produce a focused beam (35; 36) directed on to given points of a succession of cigarettes (4) traveling about both the axis (7) of the beam (13) and about their own axis (8); the movable assembly (14) presenting at least one diffracting optical element (49; 68) for dividing the focused beam (35; 36) into a given number of identical further beams (52; 71) to form, on each cigarette (4), a number of rings (2) of ventilation holes (3) equal to the aforementioned given number. <IMAGE></p> |
