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Variable step rate precision pumping apparatus

  • US 5,932,987 A
  • Filed: 04/14/1998
  • Issued: 08/03/1999
  • Est. Priority Date: 04/14/1998
  • Status: Expired due to Term
First Claim
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1. Apparatus for dispensing liquids using a stepper motor pump that has first and second windings which, upon being energized, step the pump by a predetermined angular step the quantity of liquid dispensed by the pump being determined by the angular step size, the apparatus comprising a controller for generating first and second digital signals in response to an input indicating a predetermined liquid dispense rate;

  • means for converting the first and second digital signals to corresponding first and second analog signals; and

    means for driving the first and second windings of the stepper motor pump at a selected rate within a predetermined range of rates with the first and second analog signals to dispense liquid, the controller having means for varying the first and second digital signals to vary the step size of the pump to control the amount of liquid dispensed.

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