US 4,061,442 AGranted

System and method for maintaining a liquid level

AssigneeBeckett Corporation

InventorsAnthony W. Clark, Rex G. Stubbs, Jr.

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Abstract

The specification discloses a technique for controlling a pump to maintain a body of liquid below a maximum liquid level. A low voltage high frequency signal is applied to a conductive first probe which extends to a desired maximum liquid level. The high frequency signal is also applied to an electronic detector and switching circuit in order to maintain the switching circuit in a first state when the liquid level does not contact the first probe. The effect of the application of the high frequency signal to the switching circuit is reduced when the liquid level contacts the first probe, thereby changing the switching circuit to a second state. A pump is then energized to lower the liquid level in response to the second state of the switching circuit. A second probe is then coupled to receive the high frequency signal. The second probe extends to a lower level than does the first probe, thereby maintaining the pump in an energized state until the liquid level falls below the second probe. A safety overflow probe and circuitry is provided to prevent overflow in case of malfunction of the system.

Claims9

Dependent claims

A liquid level control system for an air conditioner comprising:

first and second conductive probes suspended above a body of liquid and extending below a maximum desired level,
a third conductive probe suspended above the body of liquid and extending downwardly to said maximum desired level,
an oscillator normally coupled to said first and third probes for generating a high frequency signal,
electronic switching means coupled to said probes and said oscillator, said switching means being switched to a first state in response to said high frequency signal when the liquid level does not contact said third probe and being switched to a second state when the liquid level contacts said third probe,
means responsive to said second state of said switching means for coupling said second probe to said oscillator, wherein said switching means is maintained in said second state as long as the liquid level contacts said second probe,
pump means responsive to said second state of said switching means for lowering the liquid level of the body of liquid, and
a fourth safety overflow prevention conductive probe connected to terminate operation of said air conditioner if the liquid level rises to a predetermined oveflow level.

4 more elements

Dependencies are inferred from the claim text.