Patent TW-200842766-A (TW)
Title: Microwave-controlled controller for automatically stopping ignition and shutting off gas path at gas leakage
Inventor: TSAI SCOTT
IPC: F23N1/00
Filed: 2007-04-19
Abstract: In a microwave-controlled controller for automatically stopping ignition and shutting off gas path at gas leakage, the controller is divided into three parts, namely, a detection and transmission part, a receiving and ignition control part, and a gas supply valve part. The detection and transmission part is installed near a gas appliance, such as on a wall in the kitchen or inside a counter, and uses a gas sensor, either a hot wire sensor or a semiconductor sensor, to detect the gas concentration in the space around the gas appliance. Through determination by signal amplification and potential comparison, the detected gas concentration signal, such as "exceeded" or "normal", is encoded into a digital code having a specific format and then transmitted the same into air in the form of microwave. In the event the gas concentration is determined as being exceeded, an alarm will be produced. The receiving and ignition control part is installed inside the gas appliance for receiving the signal from the detection and transmission part through a microwave receiver. The received microwave signal is demodulated and decoded and then transmitted to a control unit. In the event the received signal indicating an exceeded gas concentration, the ignition is automatically prohibited and the gas supply valve is driven to shut off the gas path, lest the gas should keep leaking; otherwise, an electronic igniter is driven to ignite normally. The gas supply valve part is installed at an outlet of gas supply, such as a gas outlet on an LP gas cylinder or a gas outlet at a natural gas shunt switch, to connect to the receiving and ignition control part inside the gas appliance via a conductor. When it is determined the gas concentration is exceeded, the receiving and ignition control part will send a signal via a gas supply valve driving unit thereof to drive the gas supply valve to shut off the gas path. When the problem of exceeded gas concentration has been removed, a user can push an operating button on the top of the gas supply valve to open the gas path again. Since the gas sensor being used at its working temperature has a service life about 15,000 hours, the controller of the present invention adopts PWM power supply to extend the service life of the gas sensor. For example, when the duty cycle of power supply is 20%, the service life of the gas sensor can be extended to five times or about 8.5 years. Thus, the gas sensor can match the normal usable life of the gas appliance. An object of the present invention is to avoid gas explosion and fire possibly caused by negligent ignition by a user when the ambient gas concentration is high due to loosened, broken, poor connected gas pipe of the gas appliance and unsuccessful ignition. And, the controller of the present invention can shut off the gas path of the gas supply at the same time to prevent the gas from leaking continuously and ensure the safe use of the gas appliance. The present invention also applies microwave control technique to enable installation of the high power consuming detection and transmission part at an outer side of the gas appliance, so that the consumer would not worry about the safety in using an electrically connected gas range.