Dynamic lead screw thread engagement system and method

A system for aligning threads of a lead screw with threads of a screw drive mechanism, the screw drive mechanism operating to translate rotational motion of the lead screw into linear motion when their threads are fully engaged with each other, the system comprising:

• a motor coupled to the lead screw that selectively rotates the lead screw;
• a plunger driver coupled to the screw drive mechanism to selectively engage a syringe plunger for movement of the plunger in response to movement of the screw drive mechanism;
• a position sensor that provides a position signal representative of an axial position of the screw drive mechanism along the lead screw;
• a release device that disengages the threads of the screw drive mechanism from engagement with the threads of the lead screw thereby allowing an operator to move the screw drive mechanism to a selected position along the lead screw at which the threads of the screw drive mechanism may be re-engaged with the threads of the lead screw;
• and
• a processor that receives position signals from the position sensor and controls the motor to rotate the lead screw to a predetermined rotational position based on the position signals;
• wherein, the processor receives a position signal from the position sensor indicative of the position at which an operator is re-engaging the threads of the screw drive mechanism with the threads of the lead screw;
• and
• the processor controls the motor to rotate the lead screw to a rotational position at which the threads of the lead screw are aligned with the threads of the screw drive mechanism at the selected position.