Device for centering and clamping a flexible foil

Claim 1

A device for centering and clamping a flexible foil having a round opening, comprising a bell-shaped hub which rotates the foil in the plane of its major surface, which hub has a cylindrical inner bore whose diameter is slightly greater than the diameter of the opening in the foil, and also has an end surface on which the foil is positioned, the opening in the foil permitting the insertion of an expanding mandril having a conical surface and a cylindrical portion insertable into the inner bore of the hub, thereby keeping the foil positioned on the end surface of the hub with a flange having a contact surface which is parallel to said end surface, and after the device further comprising an expanding cone, which can be inserted into the expanding mandril, for expanding the expanding mandril so far that the cylindrical portion of the expanding mandril is urged against the wall of the cylindrical inner bore of the hub, thereby enlarging the opening in the foil to the diameter of the inner bore, characterized in that the expanding cone (12) expands the expanding mandril (3) via at least one resilient element (6), the force that can be transmitted to the expanding mandril (3) by the resilient element (6) at the location of the transition between the conical (4) and cylindrical portion (5) of said mandril being greater than the force required for widening the opening in the foil (1) but smaller than the force necessary for a substantial elastic deformation of the expanding mandril (3) beyond the cylindrical inner bore of the hub (9), which bore terminates at the end surface (11), and that the expanding cone (12) comprises a cone flange (14) which presses the flange of the expanding mandril (3) onto the foil (1), thereby pressing said foil onto the end surface (11) of the hub (9) with a force which suffices to transmit the driving torque for the foil.

Claim 2

A device for centering and clamping a flexible foil having a round opening, comprising a bell-shaped hub which rotates the foil in the plane of its major surface, which hub has a cylindrical inner bore whose diameter is slightly greater than the diameter of the opening in the foil, and also has an end surface on which the foil is positioned, the opening in the foil permitting the insertion of an expanding mandril having a conical surface and a cylindrical portion insertable into the inner bore of the hub, thereby keeping the foil positioned on the end surface of the hub with a flange having a contact surface which is parallel to said end surface, and after the device further comprising an expanding cone, which can be inserted into the expanding mandril, for expanding the expanding mandril so far that the cylindrical portion of the expanding mandril is urged against the wall of the cylindrical inner bore of the hub, thereby enlarging the opening in the foil to the diameter of the inner bore, characterized in that the expanding cone (12) expands the expanding mandril (3) via at least one resilient element (6), the force that can be transmitted to the expanding mandril (3) by the resilient element (6) at the location of the transition between the conical (4) and cylindrical portion (5) of said mandril being greater than the force required for widening the opening in the foil (1) but smaller than the force necessary for a substantial elastic deformation of the expanding mandril (3) beyond the cylindrical inner bore of the hub (9), which bore terminates at the end surface (11), and that the expanding cone (12) comprises a cone flange (14) which presses the flange of the expanding mandril (3) onto the foil (1), thereby pressing said foil onto the end surface (11) of the hub (9) with a force which suffices to transmit the driving torque for the foil.