FLUENT MATERIAL LEVEL CONTROL SYSTEM

• US 3,602,251 A
• Filed: 07/22/1969
• Issued: 08/31/1971
• Est. Priority Date: 07/22/1969
• Status: Expired due to Term

• Current Assignee: John Carroll Hill
• Original Assignee: John Carroll Hill
• Inventors: Hill, John Carroll
• Primary Examiner(s): Cohan, Alan
• Assistant Examiner(s): Matthews, David R.
• Application Number:
  US04/843,511
• Time in Patent Office: 770 Days
• Field of Search: 137/386,387,392 340/244,244C
• US Class Current: 137/392
• CPC Class Codes: F16L 2101/30 Inspecting, measuring or testing
• CPC Class Codes: G05D 9/12 characterised by the use of electric means
• CPC Class Codes: Y10T 137/7306 Electrical characteristic sensing

Abstract

A system for detecting, indicating and controlling the level of a fluent material in a container. This system applies alternating current to two electrodes in a container, the electrically conducting paths through the electrodes to the container being included in a voltage divider network. A solid-state circuit controls a pump and motor in response to the output of the voltage divider network to regulate the level of the material in the container.

Claims

1. Apparatus for controlling the level of a fluent material in a container, said apparatus comprising:

means for applying alternating electrical power to said apparatus;

a variable impedance voltage divider network connected directly across said electrical power-applying means, said voltage divider network including;

said container;

the fluent material within said container;

a plurality of electrodes located within said container at spaced levels; and

at least one resistor;

the electrical signal output of said voltage divider network being uniquely dependent upon the level of the fluent material in said container;

a demodulator circuit connected to said voltage divider network to convert the alternating current output signals thereof to direct current signals;

a threshold detector for generating first and second indicating signals responsive to the direct current output signals of said demodulator circuit, said first and second indicating signals being nonuniquely dependent upon the level of the fluent material in said container;

means for producing control signals in response to said first and second indicating signals; and

means responsive to said control signals for adjusting the level of the fluent material in said container;

said control signal-producing means and said level-adjusting means being connected in series across said electrical power applying means.

2. The apparatus recited in claim 1, wherein:

said control signal-producing means includes a triode AC switch in series with said fluent material level-adjusting means across said electrical power-applying means, said triode AC switch being turned on in response to said first indicating signal to thereby cause said level-adjusting means to operate, and being turned off in response to said second indicating signal to thereby inhibit operation of said level-adjusting means.

3. The apparatus recited in claim 1, wherein:

said electrodes are two in number, the first electrode being suspended within said container adjacent the bottom thereof, the second electrode being suspended within said container adjacent the top thereof.

4. The apparatus recited in claim 1, wherein:

said threshold detector has a predetermined hysteresis characteristic whereby said first indicating signal is produced when the fluent material in said container is below a first predetermined level and said second indicating signal is produced when the fluent material in said container is above a second predetermined level higher than said first predetermined level, one of said first and second indicating signals being produced by said threshold detector when the fluent material is between said first and second predetermined levels, the determination of the indicating signal to be produced being dependent upon the immediate past history of the level of the fluent material in said container.

5. The apparatus recited in claim 4, wherein:

said threshold detector produces said first indicating signal when the fluent material is between said first and second predetermined levels immediately after having been below said first predetermined level, and produces said second indicating signal when the fluent material is between said first and second predetermined levels immediately after having been above said second predetermined level.

6. The apparatus recited in claim 4 and further comprising a power supply connected to said electrical power-applying means, said power supply providing operating power voltages to said threshold detector.

7. The apparatus recited in claim 6, wherein:

said threshold detector comprises;

a first transistor having its base coupled to the output of said demodulator circuit;

a second transistor having its base coupled to the collector of said first transistor, the base of said first transistor being coupled to the collector of said second transistor, the output of said power supply being coupled to the emitters of both said first and second transistors;

the collector of said second transistor being coupled to said control signal-producing means.

8. Apparatus for indicating changes in the level of a fluid within a container, said apparatus comprising:

means adapted for applying alternating electrical power to said apparatus;

a variable impedance voltage divider network connected directly to said electrical power-applying means, said voltage divider network including;

said container;

the fluent material within said container;

a plurality of electrodes located within said container at spaced levels; and

at least one resistor;

the electrical signal output of said voltage divider network being uniquely dependent upon the level of the fluent material in said container;

a demodulator circuit connected to said voltage divider network to convert the alternating current output signals thereof to direct current signals;

a threshold detector for generating first and second indicating signals responsive to the direct current output signals of said demodulator, said first and second indicating signals being nonuniquely dependent upon the level of the fluent material in said container.

9. The apparatus recited in claim 8 and further comprising a power supply connected to said electrical power-applying means, said power supply providing operating power voltages to said threshold detector.

10. The apparatus recited in claim 8, wherein:

said demodulator circuit and said voltage divider network having mutually proportional output signals, the value of said output signals being dependent upon the level of fluent material within said container, said output signals having a first predetermined value determined by a first predetermined level of the fluent material, a second predetermined value determined by a second predetermined level of the fluent material and a third predetermined value intermediate said first and second predetermined values and when the level of the fluent material is between said first and second predetermined levels;

said threshold detector producing said first indicatiNg signal in response to the signal of first predetermined value from said demodulator circuit and thereafter continuing to produce said first indicating signal when the level of the fluent material changes from said first predetermined level and until said level reaches said second predetermined level, said threshold detector producing said second indicating signal in response to said signal of second predetermined value from said demodulator circuit and thereafter continuing to produce said second indicating signal when the level of the fluent material changes from said second predetermined level and until said level reaches said first predetermined level.