Measuring and testing – Liquid level or depth gauge – Float
Reexamination Certificate
1999-01-22
2002-01-08
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Float
Reexamination Certificate
active
06336362
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to remote liquid level monitoring of propane storage tanks via the public telephone network or other means of telecommunications, like radio frequency; from a remotely located tank to a host computer located at the propane suppliers' site or to a computer at a centralized location. Such reporting from remote monitors is triggered by previously programmed expected events, or periodically programmed to occur in a timely manner.
BACKGROUND OF THE INVENTION
The quantity of liquid propane stored and remaining on customer propane tanks should be accurately and frequently measured by the propane dealer to maintain control of his customer's needs, his [dealer's] inventory, and control and schedule delivery of propane to his customers. Additionally, the dealer, being responsible for the safety of propane usage by his customers, needs to prevent, as much as possible, his customer from running out of gas. The standard practice for propane dealers to keep track of their customers' propane consumption is to, whether or not propane is needed, periodically visit each tank and visually read a gauge located on the tank. This industry practice results in a high operating costs and highly inefficient practices.
It is an industry standard that all propane gas suppliers dispatch several route-drivers every day to check the level of propane gas in their tanks for each route, replenishing the tanks should they be low and meet certain criteria. The criteria for refilling low tanks is determined by several factors, including customer's preference of maximum quantity of propane gas put in the tank each time it is refilled, in order to keep payments low. Also, seasonal changes require changing the frequency and quantities of propane dispensed to each customer. As a consequence, propane suppliers must meet numerous legal requirements and customer demands.
A number of tanks today are fitted with gauges for reading levels in a tank, as well known in the art. A common type of gage is the float gage which has a float that rests on the surface of the fluid being measured. The float is usually connected with other members which move with the float as the fluid level changes. Movement of the float and attached members is sensed by a gage, typically through a magnetic coupling, to provide on-site indication, either visual or otherwise, of the fluid level. A similar system is described in U.S. Pat. No. 5,357,815, incorporated herein by reference, which utilizes a float and a pointer assembly which pivots about an axis in response to the float's level in a tank to allow for on site inspection of the level in the tank. Other systems have been devised to remotely measure liquid levels in tanks, such as that described in U.S. Pat. No. 4,788,648, incorporated herein by reference, which utilizes differential pressure measurements to calculate the level. Another system is described in U.S. Pat. No. 5,111,201, incorporated herein by reference, which utilizes radio transmissions to transmit level information from a float attached to a potentiometer which varies voltage to correspond to liquid level in a tank. Other representative systems include those described in U.S. Pat. Nos. 5,023,806, 5,265,032, and 5,305,639 each of which is incorporated herein by reference.
Despite the existence of these systems, there is a need in the art for a system which is readily received by and/or retrofitted on to standard tanks which provides an accurate reading that can be transmitted to a host system to accurately monitor the level in a tank.
SUMMARY OF THE INVENTION
The present invention comprises a system, methods, and devices to efficiently and remotely monitor a physical condition such as a liquid level of a tank.
The subject system comprises a combination of various electronic modules and mechanical assemblies that interactively will: (1) periodically or continuously sense and monitor one or more physical conditions such as, but not limited to liquid or gas level in a tank, pressure, temperature, flow, displacement, orientation, light (color, intensity, direction), and sound; (2) based on the sensed physical condition, or upon the occurrence of an event, determine what actions to take based on an embedded set of instructions and threshold parameters; (3) transmit appropriate information from a remote site to a host system by one or more means of communications such as, but not limited to radio waves, telephone lines, cable TV circuits, electrical power grid, light signals, sonar signals through water mains, etc.; (4) analyze and make predictive projections based on the information sent and received.
The sensor unit, to sense the level of the liquid in the tank and report it, preferably includes an electronic circuit to decode specific markings on a disc. The disc is magnetically coupled to a master magnet connected to the float within the tank. The master magnet rotates as a function of the level of liquid in the tank. A slave magnet secured to the disc rotates in turn with the master magnet. The disc comprises specifically placed markings to be optically read by appropriate sensors. These markings are preferably located in concentric circles, or tracks, about the disc.
In one embodiment, a plurality of tracks are marked so that the sensors read a binary representation of the angular position of the disc. The marking can be accomplished with dark and light sections, reflective and non-reflective sections, and/or a cut-away section with or without a reflective surface underneath. These contrasting markings provide the binary representations of “on” and “off” or “0” and “1”. The markings are preferably arranged such that the binary representations change as the disc rotates according to a Gray-coded scale. Gray-coding is also referred to as “cyclic binary code” or reflective code (i.e., a sequence of code values is employed around the disc such that transitions between each Gray-code representation of angular position is accomplished with only a single bit change between each angular position). A sample Gray-coded position indicator is described in U.S. Pat. No. 3,824,587, incorporated herein by reference. This type of coding is preferred for accuracy. For example, as light from a source reflects off a light section, such may represent “1”, whereas when light is absorbed by a dark section, such may represent a “0”. If, for example, four tracks are utilized to represent position, and the light sections radially overlap on adjacent ends about a 360° range (or somewhat less), the binary combinations representing position would include the binary combinations of 0000, 1000, 1100, 0100, 0110, 0011, and 0001. More tracks would provide more combinations as a function of 2
(#of tracks)
, and therefore, a greater accuracy. The number of tracks is a matter of design choice as a function of preferred accuracy. The Gray-scale optically sensed pattern is decoded into a combination of 2 out of 8 audible tones which frequencies are derived as a function of an oscillator frequency and the values listed in
FIG. 11
,
182
,
183
.
In addition to the above-noted binary decoded angular representation, greater accuracy can be provided utilizing additional concentric tracks with a colorimetric optically sensed pattern. The pattern preferably utilizes color tracks having variant concentric shading. The tracks may be located anywhere on the disc and, in the example shown in
FIG. 4
, are presented as a pair of inner concentric tracks. These patterns would provide a greater degree of accuracy, but often the color-sensing devices therefor are more expensive than the binary sensors noted above. The color-coded disc may have light-transmitting or light-reflecting colored information arranged in such a pattern that coded information can be electronically constructed by colorimetric means using an optical sensor or photosensor such as a photodiode, phototransistor, or photocell; and which resolution and accuracy of the positional information increases as a function of the r
Garber Charles D.
Saliwanchik Lloyd & Saliwanchik
Williams Hezron
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