Importance

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Abstract

An assembly is described for accurately and precisely controlling the position of a plunger in a syringe to deliver precise fluid volumes. The assembly includes a motor coupled to a lead screw that drives a bearing block along a linear guide rod to move the plunger of the syringe in a linear fashion. The position of the plunger is accurately controlled by attaching a digital encoder to the rotating motor shaft. The encoder and associated electronics output to a controlling processor that generates a series of regular pulses, typically 300 to 500 responsive to each motor revolution. Utilizing appropriate gear ratios of the motor and the lead screw, the number of pulses per full syringe stroke in typical applications can be on the order of one hundred thousand. The final position and the motion of the plunger (velocity and acceleration) can be controlled to within a few encoder pulses, thus precisely controlling the rate of delivery of the fluid and the volume of the fluid actually delivered by the syringe. A closed positive feedback system is utilized to detect positional errors and obtain improved precision and accuracy.

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First Claim