| 摘要 |
A method, a mandrel (10) and a device for removing coreless rolls (15) of a plastic film. The mandrel (10) comprises a tubular body having a plurality of radial holes (17), conformed with a chamber (16) for distributing pressurised air, in which a piston (22) suitable for being magnetically coupled with an external drive member (27) slides. When a roll (15) must be removed, pressurised air is supplied to the fore end of the mandrel (10), and escapes from all the holes (17) to expand the internal turns of the roll (15) which can be taken off without friction. As the roll (15) advances along the mandrel (10), the magnetically driven piston (22) progressively reduces the volume of the air chamber (16) preventing at the same time the air to escape from the holes (17) that progressively come to lie on the rear side of the mandrel (10), with consequent saving of compressed air.
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