| 摘要 |
The ring foresight has an insert (3,4) within the foresight tunnel (1) to determine its size. At least two plates (6) of a given width extend from them, as far as the tunnel (1) through the foresight ring. An adjustment unit (13) alters the width of the plates (6), using a spreader (13) as a U-shaped plate with legs which can be spread apart to widen the plates (6).
|
