| 摘要 |
PURPOSE:To prevent a solenoid valve for disconnecting a gas flow passage from being brought into a heated condition resulting from consumption of a useless power, by a method wherein the presence of leak fuel gas is detected as a change in an electrical resistance value. CONSTITUTION:In the operation of the titled gas flow shutting-off device, with a switch SW1 energized, a plug P is connected to a service power outlet, and through adjustment of a resistor VR1 of a gas sensor 4, the device may be brought into a condition in which an output signal is prevented from being produced at an output terminal 16 of a gas detector 2. When gas leak occurs, a coil L1 of the gas sensor 4 is oxidized, a potential difference between output terminals 14 and 15 is changed resulting from a change in the balanced condition of a bridge, and a transistor TR1 is energized through an amplifying circuit 5 and a signal processing circuit 6. This causes exciting of a relay RL to energize switches SW2 and SW3, and an alarm lamp LP2 and an alarm buzzer BZ are actuated. Energization of the transistor TR1 results in energization, in order, of transistors TR3 and TR4 to causes a solenoid valve SV to make electrical connection, resulting in disconnection of the flow through a gas flow passage. |
