Ball joint-style, non-fixed coupling between a pusher plate and plunger in a syringe barrel

A fluid delivery device with a syringe barrel having a reservoir chamber that can contain fluid and a plunger that translates within the chamber along a longitudinal reservoir axis thereof to expel fluid from the chamber and out of the syringe barrel via an outlet, the fluid delivery device further comprising:

• a pusher dimensioned to translate within the barrel, the plunger having a front face directed toward the outlet and a rear face directed toward a front face of the pusher;
• and
• an extending mechanism coupled to a rear face of the pusher to controllably translate the pusher within the chamber along the longitudinal reservoir axis, the extending mechanism configured to extend the front face of the pusher to abut at least a portion of the rear face of the plunger to move the plunger;
• wherein the perimeter of the syringe barrel, the plunger and the pusher have the same elliptical cross-sectional shape;
• and
• wherein the extending mechanism comprises telescopic nested screws rotated controllably to extend and retract the pusher, the rear face of the pusher is connected to a distal end of one of the nested screws, the distal end of the screw comprising an anti-rotation feature configured to cooperate with another anti-rotation feature provided on the rear face of the pusher.