| 摘要 |
PROBLEM TO BE SOLVED: To provide a defense device which solves the problems that a muddy stream unabsorbed by a sewage main pipe covers a road surface everywhere upon a downpour because of undeveloped preparation of the sewage main pipe incapable of catching up with urbanization, that those involved in management of a subway or the like are anxious about when the muddy stream inflows from a ventilation hole formed in the road surface as the abnormal weather is repeated, and that a defence means depending on an electric power or a sensor can do nothing when it comes to its breakage, and to provide the defense device which does not need the electric power or the sensor and is completely automatically opened and closed. SOLUTION: The automatic and low-costed device without a need for the electric power or without a danger of breakage or deterioration is structured under a ventilation grating formed in the road surface in a manner that it is open at a normal time and is horizontally closed only upon flooding due to the downpour. The device includes a tank, which goes around the four sides of the ventilation hole, to receive the intruded water. A float linked with an open/close door is disposed in the tank so that the float may go up and down by the buoyant force of the intruded water. The float is linked with the door above it by the intermediary of a pulley. When the intruded water leaves by discharging the water through a safety valve which discharges a predetermined safe amount of water, the door is automatically opened. COPYRIGHT: (C)2005,JPO&NCIPI
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