| 摘要 |
PURPOSE:To obtain a drain valve for preventing freezing which is employable both for pressurized water and for non-pressure water with no capacitive restriction by filling a cylinder bore in which a valve opening piston is disposed and a freezing chamber communicating therewith with water. CONSTITUTION:When the outside air temperature is about 0 deg.C, water does not freeze and a valve hole 2a is closed by a valve member 13a under valve closing force of a spring 17. When the outside air temperature becomes below 0 deg.C, at first water in a minor freezing chamber 20 defined in a small pipe 19 begins to freeze to choke the communication through the pipe 19, and then water in the pipe 19 freezes, and thereafter, water in a freezing chamber 12 defined in a cylindrical member 10 which readily releases heat and in a cylinder bore 2 communicating with the freezing chamber 12 begins to freeze from the foward toward the rearward into ice 22, and a magnificient force caused by cubin expansion obtained by transformation from water into ice urges a piston 15 rearwardly to open the valve, so that water in piping and a water inlet port 5 which is not yet solidly frozen at the time is ejected through the valve hole 2a to a water outlet port 7.
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