Multiple telescoping screw-driven pump mechanism with anti-rotation of innermost screw keyed to reservoir plunger in fluid delivery device

Abstract

A fluid delivery device has a syringe barrel-type reservoir with plunger and plunger driver assembly comprising nested, telescopic screws comprising an innermost screw keyed to a first side of the plunger or intermediate pusher to prevent rotation. In a fully retracted position, the nested screws do not extend into the reservoir. The nested screws all have right handed threads and employ the same pitch in their respective inner thread and outer thread designs. The outermost screw is connected to a motor for controllable rotation. The decreasing torque ratios from the outermost to innermost screw member and anti-rotation feature allows the innermost screw to advance the plunger into the reservoir before the adjacent concentric screw member commences rotating and advancing within its corresponding screw, and so on, to translate the plunger and expel fluid in a fluid chamber defined on the other, second side of the plunger.

Dependencies are inferred from the claim text.