| 摘要 |
PURPOSE:To prevent water within a bathtub whose temperature has been once raised from being cooled directly with external air by fitting a switching tap having a switching mechanism set so that it is closed when the temperature becomes less than a predetermined temperature, to a hot water feed pipe. CONSTITUTION:A switching tap 6 is fitted at the intermediate of a hot water feed pipe 2 between a portion which is near to a burner 7 and heated, and an upper port 3. In the switching tap 6 a shape memory alloy coil holder 11 and a keep spring holder 13 are combined. A shape memory alloy coil 10 is accommodated in a shape memory alloy coil holder 11. One end of the shape memory alloy coil 10 makes contact with the periphery of an opening part 11b, and the other end makes contact with a packing 16 of a keep plate 14. The shape memory alloy coil 10 elongates when its temperature becomes higher than a predetermined temperature. When the temperature of water becomes less than a predetermined temperature and the shape memory alloy coil 10 loses a holding force, the keep plate 14 is pressed against the peripheral side of an opening 11c by the operation of a keep spring 12 and hermetically adheres thereto. The interior of the hot water feed pipe 2 is closed and circulation of water due to convection within the hot water feed pipe 2 is stopped.
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