| 摘要 |
PURPOSE: A fire detector unit is provided which are fabricated with low cost and good efficiency, and assure a desirable electromagnetic shield on a part of an electric circuit. CONSTITUTION: According to the fire detector unit, a base(20) is made of a molded plastic, and has a labyrinth wall(30) which projects on the circumference of the base to define therein a smoke chamber, and the labyrinth wall permits an entry of smoke particles but prohibiting the entry of an ambient light into the smoke chamber. A light projector(61) is carried on the base and directs an incident light from a light emitting element(51) into the smoke chamber. A light collector(62) is carried on the base and collects a light scattered by the smoke particles in the smoke chamber to a light receiving element(52), and the light receiving element generates an electric signal indicative of the amount of the light received. Fire detecting circuits are connected to receive the electric signal so as to provide a fire warning signal based upon the electric signal. And a circuit board(50) mounts the light emitting element, the light receiving element, and electronic components forming the fire detecting circuit. A metal-made electromagnetic shield protects the light receiving element from electromagnetic radiation noises. The electromagnetic shield is integrally molded into the base and has a ground terminal for connection with a ground line of the circuit board. And the circuit board is fixed to the base by means of metal-made terminal pins which are integrally molded into the base and are electrically connected to the fire detecting circuit. And the terminal pins projects through the circuit board for connection with an external line so as to transmit the fire warning signal. |
