| 摘要 |
<p>The drainage device has a drainage chamber (14) solidly cast into a concrete slab (10). A cylindrical insert (20) in the form of a disc rotatable about the chamber axis is fitted in the concrete slab. A square frame (30), rotatable in a cylindrical component (31), is also fitted in the disc to take a grid. When the flags are relaid, the square sides of the grid frame may be set parallel to the flag joint lines by rotating the frame. As there is an eccentric inner cylinder (24) to take the cylinder (31) formed at the cylindrical insert (20), it is however also possible to cause the square sides of the grid to coincide with the co-ordinates of the flag joints by rotating the cylindrical insert in the concrete slab.</p> |
