| 摘要 |
PROBLEM TO BE SOLVED: To detect a water level accurately in a simple structure so as to discharge drainage surely. SOLUTION: A cover unit 2 is tightened to a main unit 1 opening an inflow port 4 in an upper part and an outflow port 5 in a lower part, a drain reservoir vessel having a drain accumulated part 3 in the inside is formed. The inflow/ outflow ports 4, 5 are connected to a drainage discharge pipe 6. The drainage discharge pipe 6 is provided with an automatic valve 7 in a secondary side of the outflow port 5. An ultrasonic wave transceiver 8 is mounted in a bottom part outer surface of the main unit 1 and connected to a control arithmetic device 9. The automatic valve 7 is also connected to the control arithmetic device 9. The control arithmetic device 9 controls the ultrasonic wave transceiver 8 at each prescribed time, radiates an ultrasonic wave toward upward from a bottom part outer surface of the main unit 1, detects a water level of the drain accumulated part 3 from the time till returning after reflected by the water level, generates an open control signal to open the automatic valve 7 when the water level reaches a prescribed high level, and generates a close control signal to close the automatic valve 7 when the water level reaches a prescribed low level.
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