| 摘要 |
PROBLEM TO BE SOLVED: To make a main body case small-sized and secure watertightness and alarm sound pressure by providing a means which radiates a sound wave signal generated by an alarm means in a ventilation passage and boring a through hole in part of a sound source. SOLUTION: An air vent and sound radiation hole 31 is arranged on the case main body 30. A net 38 is arranged at the center part of the hole 31 to prevent relatively large dust, etc., from entering it. A resonance space 32 is formed deep in the hole 31. Further, a ventilation filter 33, a metal thin plate 36, and a piezoelectric element 35 are arranged further inside. The vibration of the piezoelectric element 35 is conducted to the metal thin plate 36 and then conducted to the ventilation filter 33. The metal thin plate 36 and ventilation filter 33 are adhered, so the vibration is conducted directly and the sound wave signal is not attenuated. Then the piezoelectric element 35 and metal thin plate 36 have through holes 37 bored in the center. Consequently, air can be circulated between the inside and outside of the main body case 30 through the ventilation filter 33. Consequently, air can be sent to an air battery. |
