| 摘要 |
PROBLEM TO BE SOLVED: To provide a drainage trap wherein its valve is normally kept open, a valve structure for preventing a backflow from water holes is simplified so as to facilitate setting and maintenance, which is high in reliability on sealing performance in the case of sealing the water holes, and low in cost. SOLUTION: In the drainage trap provided with cover plates 20, 120 and 220 boring a plurality of trough-holes 24, 124 and 224 into them, valve seats 25b and 125b are respectively arranged to the through-holes 24, 124 and 224 and, at the same time, bore hole small rooms 27, 127 and 227 for storing floats 28, 128 and 228 are arranged to the lower parts of the valve seats in a vertically movable manner in the cover plates 20, 120 and 220. The water holes 26 and 126 in the valve seats can be sealed by coming into contact with the valve seats 25b and 125b with the upper motion of the floats 28, 128 and 228.
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