| 摘要 |
Means for aligning the device include a ball holder (17) placed on a base (4) in such a way that it is movable in all directions in a horizontal plane during the positioning phase of the spindle (6), a spherical ball (13) freely rotatably mounted in the ball holder (17), and a substantially vertical quill (10) that is axially movable within the ball (13) and supports the tool driving spindle. Said spherical ball (13) has weights that balance the weight of the means for translating the quill (10) and that of said quill and said spindle when the latter are in the lower aligned position, so that said weights return the centre of gravity (G) of the assembly substantially into alignment with the axis (x, x') of the quill (10), whereas the electrical means (28, 29) for driving the spindle (6) are arranged in the quill (10) and thus locate the centre of gravity thereof on said axis (x', x) and close to the centre (C) of the spherical ball (13) when said quill is in the lower aligned position. Furthermore, means for generating a planar air cushion between the base (4) and the ball holder (17) include jets (47) arranged in the base (4) opposite the ball holder (17) for feeding a film having a uniform thickness, and clamping means include nozzles (62) separate from the cushion-forming jets (47) and capable of being connected to a vacuum source.
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