| 摘要 |
The outer tube (3) has a ring of peripherally distributed air inlet apertures (5). A skirt (6) is connected at least at its upper end with the outer tube and surrounds the outer tube concentrically and is spaced from it in the area of the air inlet apertures. The skirt beneath the air inlet apertures has at least one air suction aperture (8). The skirt is cylindrical and the air suction aperture comprises a ring of peripherally distributed air suction slots. The skirt beneath the ring of slots is connected via a base ring (9) with the outer tube. The skirt is connected at its upper end with the outer tube by a closed cover ring (7). The skirt forms a downwardly open bell. |
