Liquid level control with capacitive sensors
First Claim
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1. An apparatus for controlling liquid levels, said apparatus comprising:
- a pump including an outer case;
a motor drivingly connected to said pump;
first sensor means for detecting the presence of liquid and mounted at a first vertical position, said first sensor means producing a first signal indicative of the presence of liquid at said first position;
second sensor means for detecting the presence of liquid and mounted at a second vertical position, which is different than said first vertical position, said second sensor means producing a second signal indicative of the presence of liquid at said second position; and
means for activating said motor, said activating means operably coupled to said first and second sensor means, said activating means starting said motor to drive said pump when both of said first and second signals are produced by said first and second sensors, said activating means for continuing operation of said motor while at least one of said first and second signals are being produced, and said activating means stopping said motor when both said first and second signals are no longer produced;
said first and second sensor means each including a capacitive circuit having two capacitive electrodes, one of said electrodes of said first and second sensor means including said pump outer case.
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Abstract
The present invention is a liquid level control system for selectively activating and deactivating a pump according to the liquid level indicated by capacitive sensors. Activating circuitry starts the pump motor when both upper and lower sensors indicate the presence of liquid. The pump motor continues operation until both of the capacitive sensors indicate the absence of liquid, in which case the pump is shut off. The circuitry of the present invention operates reliably over a wide range of operating conditions.
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Citations
19 Claims
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1. An apparatus for controlling liquid levels, said apparatus comprising:
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a pump including an outer case; a motor drivingly connected to said pump; first sensor means for detecting the presence of liquid and mounted at a first vertical position, said first sensor means producing a first signal indicative of the presence of liquid at said first position; second sensor means for detecting the presence of liquid and mounted at a second vertical position, which is different than said first vertical position, said second sensor means producing a second signal indicative of the presence of liquid at said second position; and means for activating said motor, said activating means operably coupled to said first and second sensor means, said activating means starting said motor to drive said pump when both of said first and second signals are produced by said first and second sensors, said activating means for continuing operation of said motor while at least one of said first and second signals are being produced, and said activating means stopping said motor when both said first and second signals are no longer produced; said first and second sensor means each including a capacitive circuit having two capacitive electrodes, one of said electrodes of said first and second sensor means including said pump outer case. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for controlling liquid levels, said apparatus comprising:
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a pump; a motor drivingly connected to said pump; an upper sensor means for detecting the presence of liquid and mounted at a first vertical position, said upper sensor means producing a first signal indicative of the presence of liquid at said first position; a lower sensor means for detecting the presence of liquid and mounted at a second vertical position, which is vertically below said first vertical position, said lower sensor means producing a second signal indicative of the presence of liquid at said second position; means for latching said motor in an active state for driving said pump, and means for activating said latching means, said activating means operably coupled to said upper and lower sensor means, said activating means including means for starting activation of said motor when both of said first and second signals are produced by said first and second sensors, said activating means including means for continuing activation of said motor while at least one of said first and second signals are being produced, and said activating means including means for stopping activation of said motor when both said first and second signals are no longer produced; said continuing means including a divider circuit having at least one non-unitary temperature coefficient resistor and a gating means coupled to said divider circuit, said gating means for operably activating said latching means whereby changes in ambient temperature do not affect the activation of said motor. - View Dependent Claims (17, 18)
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19. An apparatus for controlling liquid levels, said apparatus comprising:
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a pump; a motor drivingly connected to said pump; first sensor means for detecting the presence of liquid and mounted at a first vertical position, said first sensor means producing a first signal indicative of the presence of liquid at said first position; second senor means for detecting the presence of liquid and mounted at a second vertical position, which is different than said first vertical position, said second sensor means producing a second signal indicative of the presence of liquid at said second position; and means for activating said motor, said activating means operably coupled to said first and second sensor means, said activating means starting said motor to drive said pump when both of said first and second signals are produced by said first and second sensors, said activating means for continuing operation of said motor while at least one of said first and second signals are being produced, and said activating means stopping said motor when both said first and second signals are no longer produced; said first and second sensor means each including a capacitive circuit having two capacitive electrodes; said activating means including means for minimizing the occurrence of false triggering caused by high temperatures.
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Specification