| 摘要 |
The arrangement comprises a cover (10) with an inner chamber (12) and a plain-edged opening (18) feeding into the chamber. At least one suction passage (38) is connected to the cover and communicates with the chamber. An opening (16) is provided in the cover to accommodate a drill and is opposite to the plain-edged opening. An air feed is provided for the cover chamber and a device prevents air feed to the chamber via the drill opening. |
