| 摘要 |
PURPOSE:To call the attention of an user only when the air filter is clogged actually and cleaning or the like has become necessary by a method wherein a luminous body is provided in front of the air filter and a light receiving body is provided at a position, pinching the air filter and opposing to the luminous body, while a resistor is connected to the light receiving body in parallel and a push-button switch is connected to the same in series. CONSTITUTION:When the push-button switch 13 is closed, a circuit, consisting of a D.C. voltage source 11, a current restricting resistor 10, the light receiving body 9 and the luminous body 8, is formed to continue the light emission of the luminous body 8. In this case, when the amount of dust 14, adhered to the air filter 4, is increased and the filter 14 is clogged, the amount of light, arriving at the light receiving body 9 from the luminous body 8, is decreased to a degree set in the current restricting resistor 10, the light of the luminous body 8 is put off. According to this method, the timing of cleaning of the air filter may be indicated to the user. |
