Device for detection of imminent gas depletion of a liquified gas tank and gas lighter equipped with this device

A device for detecting the imminent depletion of gas in a gas tank for liquified gas, said device comprising:

• a tank adapted to hold liquified gas;
• a fiber optic bundle, said bundle having two ends, one end of which forms an observation surface and is viewable from the exterior of said tank and the other end of which has a flat surface and is disposed inside of said tank;
• a transparent element having at least two surfaces, one of which is flat, the flat end of said transparent element being disposed against the flat end of said fiber optic bundle and in optical contact therewith;
• and
• at least one dioptric element disposed on the other surface of said transparent element, said dioptric element having lateral walls which form an angle, preferable obtuse, with said other surface of said transparent element, the dimensions of said dioptric element being such that it is capable of being covered nearly completely by a meniscus formed of a liquid gas condensate, so long as there is gas remaining in said tank, said meniscus thus preventing any total reflection of the rays directed thereto by the fiber optic bundle.