Liquid level controller

• US 3,916,213 A
• Filed: 08/26/1974
• Issued: 10/28/1975
• Est. Priority Date: 08/26/1974
• Status: Expired due to Term

• Current Assignee: Frank Kenneth Luteran
• Original Assignee: Frank Kenneth Luteran
• Inventors: Luteran, Frank Kenneth
• Primary Examiner(s): Hohauser, Herman
• Application Number:
  US05/500,317
• Time in Patent Office: 428 Days
• Field of Search: 73/34R,34C 307/118 137/392 340/244C
• US Class Current: 307/118
• CPC Class Codes: G01F 23/244 comprising oscillating circuits
• CPC Class Codes: G05D 9/12 characterised by the use of electric means
• CPC Class Codes: Y10T 137/7306 Electrical characteristic sensing

Abstract

A liquid level control system for sump pit and tank level control utilizing solid state sensing control of conductive liquids. A pair of electrodes are disposed in the liquid at the two levels at which level control is desired. The electrical circuitry generates a high frequency signal from the power line frequency and the attenuation of the high frequency signal by the conductive fluid acts to energize circuits to activate pumps and accessories.

Claims

1. A system for controlling the level limits of a conductive fluid in an enclosure comprising:

a. a first conductive probe disposed in the enclosure and contacting the fluid at the lower limit of the fluid level, b. a second conductive probe disposed in the enclosure and contacting the fluid at the upper limit of the fluid level, c. high frequency electrical means capacitively coupled to the first and second probes and producing a current flow through the probes, a maximum current flowing when the probes are in contact with the fluid and a minimum current flowing when the probes are in non-contact with the fluid, d. first detector means connected to the first probe and producing an output signal that is inversely related to the current flow through the first probe, e. second detector means connected to the second probe and producing an output signal that is inversely related to the current flow through the second probe, f. a start switch connected to the first detector output and activated when the first probe is in non-contact with the fluid, the start switch latching in the conductive state when activated, g. a stop switch connected to the second detector output and activated into conduction when the second probe is in noncontact with the fluid, h. DC voltage means supplying electrical energy to the high frequency electrical means, the start switch and the stop switch, i. driver means serially activated by the start and stop switches, and controlling pump means, the start and stop switches acting in conductive cooperation to activate the driver which controls the pump to maintain the fluid level within the limits determined by the location of the probes.

2. The combination of claim 1 wherein the high frequency electrical means includes a transistorized multi-vibrator and the DC voltage means includes a half wave rectifier circuit energized from the 60 cycle power input.

3. The combination of claim 1 wherein the first and second detector means include a diode rectifier and filter capacitor to produce a DC output signal equal to the peak value of the high frequency input signal.

4. The combination of claim 1 wherein the start switch includes an SCR serially connected between the stop switch and the input to the driver means.

5. The combination of claim 1 wherein the stop switch includes a transistor serially connected between the DC voltage means and the start switch.

6. The combination of claim 1 wherein the driver means includes a TRIAC activated by simultaneous conduction of the start and stop switches.

7. A system for controlling the level limits of a conductive liquid in an enclosure comprising:

a. a first electrically conductive probe disposed in the enclosure at the lower level limit of the fluid, b. a second electrically conductive probe disposed in the enclosure at the upper level limit of the fluid, c. high frequency signal means connected to the probes and producing a current flow through the probes, the current decreasing when the probes are in non-contact with the fluid and increasing when the probes are in contact with the fluid, d. electrical conductive means connecting the fluid in the container to the power ground lead, e. DC energy means connected to the 60 cycle power and providing a DC voltage to the high frequency generating means, f. first detector means for measuring a change in current flow through the first probe, g. second detector means for measuring a change in current flow through the first probe, h. driver means having a control input and activating a pump for changing the liquid level in the enclosure, i. logic means activating the driver means when the detector means measure a decrease in probe currents and deactivating the driver means when the detector means measure an increase in probe currents.

8. The combination of claim 7 wherein the driver includes a TRIAC which is serially connected to the pump.

9. The combination of claim 7 wherein the logic means includes a stop switch which operates instantaneously with the change in current through the second probe and a start switch which latches in one state when the first probe current changes.

10. The combination of claim 9 wherein the stop switch is in a conductive state when the second probe is in non-contact with the fluid and is nonconductive when the second probe is in contact with the fluid and the start switch latches into a conductive state when the first probe changes from a contacting to a non-contacting state and the start switch is non-conductive when both probes are in the fluid contacting state.

11. The combination of claim 10 wherein the stop and start switches are serially connected to the control input of the driver means.