| 摘要 |
<p>Two or more perforation rollers (1, 2) are provided, each carrying pins (8), and arranged in relation to one another so that the pins of each form a corresponding set of perforations in the film which is offest relative to a set of perforations formed by the, or each other perforation roller. The perforation rollers (1, 2) may be located on opposite sides of the film or the perforation rollers (1, 2) are located on the same side of the film and a furnish roller (4) is provided to support the film and feed it past the perforation rollers. A registration control system (10, 12) is provided which monitors the pattern of perforations in the film and generates a correction signal corresponding to any misalignment. The registration control system preferably comprises a visual inspection system, for example, a video camera (10), which produces an image of the perforations and a controller (12) which analyses the image on-line to generate said correction signal. The pins (8) are preferably heated to assist perforation of the film and to ensure consistent perforation size and shape.</p> |
