| 摘要 |
A shaft which can expand and retract in order to position and grip mandrels onto which materials in the form of a web are wound, which comprises semi-cylindrical shells, which can move radially, defining the external surface of the shaft, and a control means actuated by compressed air in order to move the said shells radially, the shaft being characterised in that the said control means comprises two pistons 18, 18' solidly attached to a central hollow shaft 20 provided with an axial bore 21 for supplying the two chambers E, E', in which the said pistons move, with compressed air, these pistons interacting with tapered rings 22, 22', 22" in order to move the said shells 32, 32' radially. <IMAGE>
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