Measuring and testing – Liquid level or depth gauge – Float
Reexamination Certificate
1999-04-12
2002-04-02
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Float
C073S319000, C073SDIG005
Reexamination Certificate
active
06363785
ABSTRACT:
DESCRIPTION
1. Technical Field
This invention relates to systems and methods for determining the relative location of items with respect to one another. More particularly, it relates to methods and apparatus for detecting and reporting the relative location of an indicating unit traveling along the length of an elongate detector. In a preferred embodiment, this invention senses the position of a magnetic indicating unit relative to an elongate detector thereby determining and reporting the location of one or more fluid interfaces within a multi-phase fluid reservoir.
2. Background Art
Many instances arise in both industrial and residential settings wherein the location of a reference point is desired to be detected and reported for evaluation. Many alternative methods may be employed for such purposes; an example is a video camera that either transmits or records a visual image of items that an operator desires to monitor. One drawback of such a system is that an operator is required to observe the image, make an evaluation, and then report that information for further processing if so required. With the advent of computers used as controllers for various processes, it is desirable to have automatic reporting systems that indicate relative locations of different components in a system. In a residential setting, an example would be a garage door that opens and closes by traversing tracks. In the event that the operation of such a door were to be automated, it would be necessary for the controller to know the relative position of the door with respect to the tracks thereby indicating its open or closed configuration, or its relative position somewhere in between. Such detection and reporting may be achieved by placing an elongate stationary detector along the track of the garage door and installing an indicating unit upon the traveling door in a position that travels adjacent to the length of the detector. By detecting and reporting the location of the indicating unit, a controller for the system can ascertain the door's position and take action based thereon.
A linear relative location detecting and reporting system of the present invention finds a myriad of applications in industrial settings. In manufacturing processes, there are many instances in which human operators or automated controllers must know real time relative positions of certain parts in an apparatus. One particularly applicable situation is found in automated manufacturing processes wherein assembly lines are employed. By being able to detect the relative position of a conveyor within the manufacturing process, the degree of advancement or completion of a given task is detectable and reportable for control and evaluation purposes.
One particular industrial application and environment in which such a detection system has been found to be desirable is in liquid reservoirs wherein the position of fluid interfaces are desired to be detected. By detecting the interfaces between phases of fluids, the level, and normally the volume of one or more fluids present in a reservoir or container may be calculated.
In some circumstances, the interface will be between two fluids, each in a different state. The lower fluid will normally be in a liquid state and the upper fluid will typically be in a gaseous state. These conditions are common to most fluid filled tanks. Examples of such situations include containers for gasoline, water, crude oil, and liquid chemicals that are often retained in holding tanks. In each case, the lower phase of a fluid interface is liquid and the upper phase is usually air that fills the remainder of a partially filled tank. A detector may be similarly utilized in less contained environments such as in subterranean reservoirs and in flood plane areas to measure water level conditions.
There are several known devices that are employed in liquid reservoirs for detecting interfaces, and in turn liquid levels of both single and multi-phase liquids. Two such examples have been previously invented and patented by a common inventor of the present invention in U.S. Pat. Nos. 4,976,146 and 5,347,864 for Liquid Level Measuring Apparatuses issued to Senghaas. Each of those systems, however, employ different apparatus and methods of operation than is presently being disclosed. In each, a plurality of reed switches are installed upon an elongate support or back board in an angled configuration with respect to the length of that board. The apparatus of the two Senghaas Patents '146 and '864 each employ reed switches arranged in a vertical series, but each switch is significantly angled with respect to horizontal.
The reed switches operate in response to magnetic forces applied thereto. When no magnetic force or same pole magnetic forces are applied to each of two leads of the switch, the reed portions are biased away from one another thereby keeping the switch open and preventing current from being transmittable thereacross. Oppositely, when magnetic forces of opposite or north and south poles are applied to the leads of the reed switch, the two reeds of the switch are attracted to one another thereby closing the switch and accommodating the transmission of applied current thereacross. The overlapped configuration of adjacent switches accommodates a cancellation affect that is utilized for achieving an error correcting procedure, but which is no longer required in the present invention.
Each of the '146 and '864 inventions employ one or more toroidal magnets that surround the series of angled vertical switches and move relative thereto in an up and down direction. The use of such toroidal magnets slidably fitted about a series of detection switches have also been employed in such earlier examples as the Hall-Cell Liquid Level Detector disclosed in U.S. Pat. No. 4,361,835 issued Nov. 30, 1982 to Nagy. While reed switches were not employed in the '835 patent, Hall-Cell sensors were alternatively used as detectors responsive to the influence of toroidal or donut-shaped magnets moved up and down the length of a series of such Hall-Cells.
The measuring devices of the earlier Senghaas patents, like the present invention, have a common physical constraint because of the environment in which they are most commonly utilized. That environment is installation in liquid containing tanks, and more specifically in large above ground holding tanks for crude oil, water and the like that have been constructed to accept liquid level measuring devices that are inserted through a pre-formed aperture in the top of the tank. Because of the high cost associated with modifying this aperture, it is important that new devices developed for employment in such applications and settings be constructed to satisfy the criteria and limitations of these tanks and the existing measuring device receiving apertures.
In some instances, the tops or covers of such tanks rise and fall together with the level of liquid contained therein. Therefore, sliding movement of the lid about the measuring device must be facilitated. To alter this preexisting configuration of the tanks would be exceedingly expensive and prohibitive to the employment of measuring devices that deviate from these constraints. Therefore, these apertures dictate the maximum diameter or width of measuring devices that may be inserted therein. As a result, the size of the aperture also governs the width of the support board upon which the reed switches are mounted in both the previously known measuring devices and that of the present invention.
Because of performance limitations of components employed in the earlier measuring apparatuses of the '146 and '864 patents, it was necessary that the reed switches be angularly positioned with respect to horizontal on their supporting back boards. Specifically, the actuating toroidal magnets heretofore available had a limited strength and therefore required a more substantial lead area, sometimes achieved through elongation of the reed switch leads, in order for the switch to be influenceable to a closed
Gold John H.
Kolonko, Jr. Peter T.
Michalec Jerzy
Senghaas Karl A.
Senghaas Peter
Kilpatrick & Stockton LLP
Worth Willie M.
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