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Medication delivery system with improved dose accuracy

  • US 7,500,959 B2
  • Filed: 10/04/2001
  • Issued: 03/10/2009
  • Est. Priority Date: 10/05/2000
  • Status: Expired due to Fees
First Claim
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1. A method of configuring motorized injection device having a piston rod that pushes a piston in a medication cartridge to expel medication from the cartridge and having an actuator that drives the piston rod, the method comprising the steps of:

  • a. calculating a relationship between movement of the actuator and expected movement of the piston rod;

    b. moving the actuator an amount expected to move the piston rod a predetermined distance;

    c. measuring the actual distance the piston rod moves when the actuator is moved in step b;

    d. determining the error between actual movement of the piston rod and expected movement when the actuator is moved a predetermined distance, wherein expected movement is a value calculated from design specifications and actual movement is a value measured from a calibration procedure;

    e. programming a processor to control the actuator to compensate for the error of step d so that the piston rod is moved by a desired amount even though the actuator is moved by a greater or lesser amount than would be expected to move the piston rod by the desired amount.

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