US 3,995,169 AGranted

Optical liquid level gauge

OwnerLouis D. Oddoninventor

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Abstract

An optical liquid level gauge is described for sensing and indicating the height of a liquid within a container, such as within a fuel tank. The gauge includes an optical liquid probe that has a plurality of U-shaped light pipes to be inserted into a tank. Each of the light pipes terminates in a U bend with the U bends of such light pipes being staggered in position relative to one another so as to be positioned at different liquid height indication levels within the tank. A source of light is provided for transmitting light into a first arm of each of the light pipes, and sensors are provided at the end of the second arm of each of such light pipes for detecting the amount of light transmitted from one end of the pipe to the other. The U bend of each pipe has a geometrical design which assures that when liquid is not present in the tank it transmits substantially all of the light received by it from the first arm of the light pipe into the second arm thereof for sensing by the sensor associated therewith. The design of the U bend is such, though, that when the liquid within the tank is at a height submerging the U bend, light received by the U bend from the first arm of the light pipe will be refracted out of such light pipe, rather than passed to the second arm thereof. The sensor associated with the end of the second arm of each light pipe is connected with a display providing a visual indication of whether or not liquid is present at the U bend and, hence, at the liquid level in the container represented by such U bend.

Claims10

Dependent claims

A liquid level gauge for indicating exteriorly of a liquid container, the height to which liquid has displaced an ambient medium within said container comprising:

a. a plurality of continuous U-shaped light pipes, each of which has distinct first and second arms which are separated from one another except for a connection therebetween at one end by a U-bend integral therewith, said light pipes being adapted for insertion into said container with the U-bend of each positioned therewithin generally at a desired liquid height indication level;
b. a source of light at the end of said first arm of each of said light pipes for transmitting light thereinto;
c. sensing means at the end of the second arm of each of said light pipes for detecting the amount of light transmitted through said pipe from its first end to said second end;
d. each of said light pipes being continuous and free of light absorptive discontinuities between said ends, and the geometry of each of said light pipes at the U-bend thereof relative to the indices of refraction of the material of said pipe and said liquid providing refraction of a measurably greater amount of light from said U-bend of said pipe when said U-bend is submerged in said liquid than when said U-bend is in said medium;
and
e. display means responsive to said sensing means detecting an amount of light transmitted through one of said light pipes indicative of refraction of said measurably greater amount of light from the U-bend thereof by indicating the presence of liquid at the liquid height indication level represented by the position of said U-bend in said container.

3 more elements

Dependencies are inferred from the claim text.