| 摘要 |
A device in casings (1) for sucking air containing impurities away from a region, under and near the casing, comprises a casing downwardly open, at least a suction opening (6) arranged inside the casing and connected to a suction member for generating an air flow from below, into the casing and out through the suction opening for conducting air away from the device, means (10-18, 28) for conducting a part of the air sucked from the interior of the casing back to the region of a lower edge of a side wall of the casing and members (23, 32', 34) for directing this air as a stream from a side edge towards the interior of the casing, so that secondary air flows into the casing are induced at its edge region. Said means comprises at least a second suction opening (10) separately arranged with respect to the first suction opening (6) for sucking in the air for said stream, all air sucked through the first suction opening being conducted away from the device. The second suction opening (10) is arranged closer to that side wall (4) of the casing which at the bottom is terminated by said edge than the first suction opening (6). The second suction opening (10) is arranged at a substantial height inside the casing, at least in the upper half of the casing. |
