| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the occurrence of a step at a main entrance even if the whole inside of a house is made barrier-free, since a step between a throating door sill of this door and an outdoor floor has never been architecturally eliminated in an outdoor to indoor door, particularly, an entrance door-cum- fireproof door of an apartment house. SOLUTION: The step can be eliminated when necessary by applying a spring (operation) to the throating door sill. Normally, the step is caused between the throating door sill and a floor, and even if a fireproof door is arranged, the function of the fireproof door can be carried out as usual. Thus flat throating door sill may be formed as a fixed type, when it is formed as a cassette type by considering maintenance, the throating door sill can be easily restored by replacing this cassette frame at failure time.
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