| 摘要 |
The overflow has a shutter (3) attached to a horizontal axis (6) which is weighted below the axis (13) so that it is closed in the resting position. It has a frame (1) which supports the axis and allows it to rotate freely. The shutter rests against stops (9) in the frame when closed and against stops (8) when open. When closed the shutter forms a dam and when open allows the required amount of water to pass through before closing automatically. A grid positioned upstream of the overflow retains any solids. A valve (5) which rests against watertight seals (16) prevents any backflow of water from downstream. However, when the shutter rocks the valve opens to allow flood water to flow downstream. |
