| 摘要 |
<p>The cowl covers the top end of the air venting pipe. It is supported from the latter by ribs forming extensions of the pipe wall. The cross-section of the ribs (2) is such as to offer high resistance to inwards flowing air, but low resistance to outwards flowing air. The ribs can be of curved cross-section, concave towards the outside, while their width in the peripheral direction can be roughly equal to that of the intervening gaps (9). There can be eight ribs round the pipe, their edges protruding beyond its walls, while the cowl is formed by a plate protruding beyond the ribs.</p> |
