Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-07-09
2001-12-25
Ham, Seungsook (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S901000
Reexamination Certificate
active
06333512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical gauges, and more particularly to optical gauges for determining the level of a medium in a container, such as the level of fuel in a fuel tank.
2. Description of the Related Art
Prior art liquid level gauges, such as fuel gauges for motor vehicles, usually include a float that rides on an upper surface of the fuel in a fuel tank. The float is typically connected to one end of a pivot arm while the other end of the pivot arm typically includes a wiper mechanism that brushes against a resistor strip when the arm is rotated due to a change in fuel level in the tank. The wiper mechanism, when rotated, causes a change in electrical resistance which is displayed at a convenient location in the passenger compartment of the vehicle. Ideal fuel level measurement conditions would require the vehicle to remain stationary or travel along a flat, horizontal surface at a constant velocity in order to eliminate any fuel sloshing in the tank. However, it is not possible to achieve ideal measurement conditions in the real world. Variations in velocity, acceleration and centrifugal forces, road roughness, response of the vehicle's suspension, and other factors may cause the fuel to slosh in the tank in an unpredictable manner. When sloshing occurs, float movement becomes erratic and may result in false measurements of the actual fuel level in the tank.
Moreover, liquid level gauges with moving parts that are linked together, such as float and pivot arm assemblies, resistance strips, etc., are subject to wear. Worn parts may result in mechanical and/or electrical breakdown of the gauge or, at the very least, inaccurate liquid level detection.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved liquid level gauge that addresses the aforementioned disadvantages.
According to the invention, an optical gauge for measuring a level of a liquid in a container comprises an elongate, tubular member having a central axis and a bore extending parallel to the central axis, with the bore being adapted to receive liquid that may be present in the container. A light source is positioned for projecting radiant energy at least into the bore along a length of the tubular member. An elongate light collector is spaced from the light source and extends along the length of the tubular member for receiving, at least indirectly, radiant energy from the light source. The light collector has opposite ends and is formed such that radiant energy incident on a length of the light collector is transmitted to the light collector ends. A light blocking member is located within the bore and extends between the light source and at least a portion of the elongate light collector for blocking at least a portion of the radiant energy from the light collector. The light blocking member is movable with respect to the light collector in response to change in liquid level within the tubular member for varying the position of the radiant energy incident on the light collector to thereby vary the amount of radiant energy transmitted to the light collector ends. At least one photosensor is positioned proximal at least one of the light collector ends for detecting the amount of radiant energy transmitted thereto. With this arrangement, the amount of radiant energy received by the light collector and detected by the at least one photosensor is indicative of the liquid level.
In one embodiment of the invention, the light blocking member comprises one or more floats that ride along an upper surface of the liquid in the tubular member.
In a further embodiment of the invention, the light blocking member comprises an upper surface of the liquid.
In yet a further embodiment of the invention, the light blocking member comprises the liquid itself.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
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Ham Seungsook
Hill Bradford
Wirthlin Alvin R.
LandOfFree
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