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Liquid level control with capacitive sensors

  • US 5,145,323 A
  • Filed: 11/26/1990
  • Issued: 09/08/1992
  • Est. Priority Date: 11/26/1990
  • Status: Expired due to Term
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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