Signals and indicators – Indicators – Liquid level
Patent
1987-05-06
1988-11-29
Stephan, Steven L.
Signals and indicators
Indicators
Liquid level
73290R, 73327, 116DIG5, G01F 2302
Patent
active
047873299
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns a device that is capable of detecting the imminence of gas depletion in a luquified gas tank. It also concerns a refillable gas lighter equipped with this device.
DESCRIPTION OF THE PRIOR ART
In its French patent application No. 2,524,980, the Applicant has described a device for detecting a liquid level in a tank, this device comprising a transparent element, one end of which is placed in said tank at the level to be detected, has a refractive index such that the light rays which are propagated there are refracted at the interface when this is immersed in the liquid, and in the opposite case, they are reflected by total reflection. In this device, the transparent element consists of a fiber optic bundle, and the end placed approximately at the level to be detected consists of a transparent unit, one flat surface of which is applied against a first end of said fiber bundle, and the other surfaces of which are such that the incident rays transmitted by the bundle can be subject to at least one total reflection there and be transmitted in the reverse direction by this bundle to its second end when the transparent unit is not immersed. The second end of the fiber bundle is attached to one of the walls of the tank, in a manner such that it is visible from the outside or inside of the latter.
Such device can, in particular, be used to advantage in a gas lighter, to ascertain whether the level of liquified gas, in the tank, has gone down below a certain threshold. However, it does not make it possible to determine with sufficient accuracy from what moment only a quantity of gas remains in the tank corresponding to a few lightings by the gas lighter, for example, about ten, so as to warn the user of the imminent depletion of the gas, so that he can refill his lighter.
SUMMARY OF THE INVENTION
The purpose of this invention is to remedy this disadvantage by improving the previously patented device such that it is possible to detect the imminent depletion of the gas in the tank.
The invention is based on the known fact that, when a vessel contains a liquified gas, the walls of the vessel are covered, due to a condensation phenomenon, with a thin film of gas in the liquid phase, such that, a meniscus of liquid tends to form in the sections forming a reflex angle.
If, inside of the tank, the external surface of the transparent unit of the device of the prior art comprises a reflex angle, the pathway of the incident light rays being displaced in parallel with the fiber bundle will be modified by the presence of the layer of liquid in that angle. In fact, instead of being subject to a total reflection on that surface, as would be the case in the absence of liquified gas on the outside, the corresponding light rays will pass through that surface, enter the meniscus of liquid gas, be refracted there in order to come out again and be lost inside of the tank.
On the observation surface of the fiber optic bundle (end of this bundle placed on the outside of the tank), the area corresponding to these rays, and consequently, to the meniscus of liquified gas will thus be dark. It will remain so as long as there is still liquid gas in the tank and will become light only when the liquid phase disappears, which will constitute a signal to the user that the end of the gas is imminent, and will indicate to him that it is time to refill the tank of his lighter.
According to the invention, the observation surface of the fiber optics bundle, which is situated at the outside end of the tank will thus contain at least one area which will be lighted only when the tank is drained of gas in the liquid phase.
Consequently, the subject of the invention is a device for detecting the imminent gas depletion of a tank of liquified gas, comprising a bundle of fiber optics, one end of which constitutes the observation surface, is visible from the outside of the tank, and the other end, which is placed inside of the tank, is in optical contact with a flat surface of a transparent element, includin
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S. T. Dupont Company
Stephan Steven L.
Will Thomas B.
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