Level sensing system

Disclosed is a system for sensing the level of a body of liquid within a container. The system includes a shaft secured parallel to a vertical axis of said container, said shaft having a magnetically responsive digital switch. Further provided is a toroidally-shaped reference element situated circumferentially about the shaft and secured at fixed level thereto, the reference element having a magnetic axis which is co-directional with the axis of the shaft. Also provided is a toroidally-shaped measuring sensing element also situated circumferentially about said shaft and vertically above said reference element but without securement thereto, said sensing element having a magnetic axis co-directional with the axis of said shaft and having a polarity of the magnetic axis which is repulsive in relationship to the magnetic axis of the reference element. The measuring element may possess a circumferential interior formed of a material having a negative buoyancy relative to the specific gravity of the level of the liquid to be measured. The reference and sensing elements will repel each other as long as they are within the magnetic proximity of each other, thusly causing the sensing element to float above the level of the reference element. The relative buoyancy of said sensing element will increase as a function of the level of the body of liquid of said sensing element, thereby causing the distance between said sensing and reference elements to change relative to changes in the level of the body of liquid, which changes are monitored by the magnetic actuation of the digital switches.

BACKGROUND OF THE INVENTION 
The present invention relates to a system for the measurement of changes in 
the level of a body of liquid within a container. More particularly, the 
present invention is concerned with the use of float elements to 
selectively actuate one or more of a plurality of digital switches. 
The prior art in the instant area is not well-defined and, to the knowledge 
of the inventor, does not deal with the problem of measurement of liquid 
levels in the manner set forth herein. Also, the prior art, as known to 
the inventor, is not capable of measurement of specific gravity of the 
liquid whose liquid level is being measured. 
Prior art float measurement means employing magnetic fields as the 
actuation means for digital switches appear in U.S. Pat. No. 3,200,645 
(1965) to Levins, entitled Electric Position Sensor; U.S. Pat No. 
3,419,695 (1968) to Dinkelkane, entitled Float Switches Assembly; and U.S. 
Pat. No. 3,646,293 (1972) to Howard, entitled Electrical Signal Generator 
and Liquid Level Indicator, all of the above being classified in U.S. 
Class 200, subclass 84C. 
The above prior art, and other art known to the inventor, does not set 
forth a system making use of the forces of negative buoyancy of the 
sensing element, magnetic repulsion between sensing elements, and specific 
gravity of the sensed medium to produce output data suitable for 
translation into information regarding liquid level and specific gravity 
of the measured liquid. It is to this end that the present invention is 
addressed. 
SUMMARY OF THE INVENTION 
The instant invention comprises a system for sensing the level of a body of 
liquid within a container. The system comprises a shaft secured parallel 
to a vertical axis of said container, said shaft having therein a vertical 
plurality of magnetically responsive digital switches. Further provided is 
a toroidally-shaped reference element situated circumferentially about 
said shaft and secured at fixed level thereto, said reference element 
having a magnetic axis which is co-directional with the axis of said 
shaft. Further provided is a toroidally-shaped measuring and sensing 
element also situated circumferentially about said shaft and vertically 
above said reference element but without securement thereto, said sensing 
element having a magnetic axis co-directional with the axis of said shaft 
and having a polarity of said magnetic axis which is repulsive in 
relationship to said magnetic axis of said reference element. Said 
measuring element is formed of a material having a negative buoyancy 
relative to the specific gravity of the level of the liquid to be 
measured. 
Said reference and sensing elements will repel each other as long as they 
are within the magnetic proximity of each other, thereby causing said 
sensing element to float above the level of said reference element. The 
relative buoyancy of said sensing element will increase as a function of 
the level of the body of liquid above said sensing element, thereby 
causing the distance between said sensing and reference elements to change 
in direct relation to changes in the level of the said body of liquid, 
which changes are monitored by the magnetic actuation of said digital 
switches. 
It is accordingly an object of the present invention to provide a negative 
buoyancy system for the sensing of the level of a body of liquid held 
within a container. 
It is another object to provide a sensing system that will monitor both 
change and rate of change of the level of a body of liquid held within a 
container. 
It is a further object to provide a sensing means which will monitor 
changes both of liquid level and of specific gravity of the measured 
liquid. 
The above and yet other objects and advantages of the present invention 
will become apparent from the hereinafter set forth detailed Description 
of the Invention, the Drawings, and claims appended herewith.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the perspective view of FIG. 1, there is shown a 
container 10 having a bottom 14. 
Vertically oriented within said container 10 and optionally secured to said 
bottom 14 is shaft 12. Within said shaft 12 is disposed a plurality of 
digital switching elements 28, 30 and 32, such as reed switches. Each of 
said switching elements are magnetically responsive. 
Further provided is a toroidally-shaped, reference element 16 situated 
circumferentially about said shaft 12 and secured at surface 15 to said 
shaft 12. Said reference element 16 is provided with a magnetic axis which 
is co-directional with the axis of said shaft 12. 
Further provided is a toroidally-shaped, measuring and sensing element 22 
also situated circumferentially about said shaft 12 and vertically above 
said reference element 16, however, without securement thereto. Said 
measuring element 22 is provided with a magnetic axis which is 
co-directional with the axis of said reference element. However, its 
polarity is repulsive in relationship to the magnetic axis of said 
reference element 16. This repulsive relationship of the respective 
magnetic axes of elements 16 and 22 is represented by the letters "NN" in 
the figures. 
Said measuring element 22 is provided with a hollow circumferential cavity 
24 formed of a material having a negative buoyancy relative to the 
specific gravity of the liquid 26 to be measured. In a common embodiment, 
the material of circumferential cavity 24 may simply be that of air, 
however, it is to be borne in mind that cavity 24 may be formed of any 
material having a lesser specific gravity than the specific gravity of the 
liquid which is to be measured. 
As may be noted in FIG. 2, the mutual magnetic repulsion between reference 
element 16 and sensing element 22 will cause sensing element 22 to be 
suspended above reference element 16 at a level indicated as .DELTA.Z=1 
when liquid 26 is at level Z1, this being the level below that of the top 
of reference element 16. 
In FIG. 3, liquid 26 is shown at level Z2, this being a level above the 
bottom of sensing element 22 but below the top thereof. Under this 
condition, the combined effect of the negative buoyancy of sensing element 
22 and of magnetic repulsion will lift sensing element 22 to a level of 
.DELTA.Z=3. 
In FIG. 4, liquid 26 is shown at level Z3. This level of liquid 26 will 
create a greater external pressure upon the top of sensing element 23 
which, in turn, will bring about a greater differential in pressure 
between the external surface of element 22 and the internal pressure 
within circumferential cavity 24. Accordingly, the higher the level of 
liquid 26, the greater will be the pressure differential between the 
inside and the outside of sensing element 26. 
Therefore, an increase in the level of liquid 26 will cause sensing element 
22 to elevate upward in direct relationship to the increase of the level 
of the liquid. This may be noted in FIG. 4 in that, as the level of liquid 
26 increases from Z2 to Z3, the vertical displacement .DELTA.Z between 
elements 22 and 16 increases from three units to five units. 
In FIG. 5, it may be seen that as the level of the liquid rises to level 
Z4, the vertical displacement between elements 22 and 16 increases yet 
further to .DELTA.Z=6. This phenomenon may be also viewed as the effect of 
the enhanced pressure in container 10 acting to squeeze elements 22 and 26 
further apart in direct relationship to an increase in the level of liquid 
26. 
The above discussed buoyancy, that is, the relationship between the 
internal pressure within element 22 and the exterior pressure thereon is 
also affected by the specific gravity of the liquid to be measured. Where 
the specific gravity is greater, the weight upon sensing element 22 will 
increase more rapidly as the liquid level increases, thereby magnifying 
the above-described phenomenon. Accordingly, at greater specific 
gravities, the displacement of Z between sensing element 22 and reference 
element 16 will occur more rapidly than would be the case with lower 
specific gravity liquids. Conversely, the increase in Z portrayed in FIGS. 
3 thru 5 will occur more slowly where the liquid is of a lower specific 
gravity. 
The above described changes are monitored by said digital switches 28 thru 
32 and the inputs thereof fed to appropriate microprocessing means. 
It is to be appreciated that a plurality of sensing elements 22 may be 
employed within a given application. 
Accordingly, while there have been shown and described the preferred 
embodiment of the present invention, it will be understood that the 
invention may be embodied otherwise than as herein specifically 
illustrated or described and that within said embodiments certain changes 
in the detail and construction, and the form of arrangement of the parts 
may be made without departing from the underlying idea or principles of 
this invention within the scope of the appended claims.