Multiple telescopic screw driven pump for preventing rotation of innermost screw in fluid delivery device

A fluid delivery device having a syringe barrel-type reservoir with a plunger and a plunger driver assembly including nested telescopic screws including an innermost screw, the innermost screw including a plunger and a plunger driver assembly, the plunger driver assembly including a plunger and a plunger, the plunger driver assembly including a plunger and a plunger, the plunger and the plunger, the plunger and the plunger, and the plunger. The innermost screw is keyed to a first side of the plunger or intermediate pusher to prevent rotation. In the fully retracted position, the nesting screw does not extend into the reservoir. The nested screws are each provided with a right-hand thread and adopt the same pitch in their respective internal and external thread designs. The outermost screw is connected to a motor for controllable rotation. The torque ratio and anti-rotation feature that decreases from the outermost to innermost screw members allows the innermost screw to advance the plunger into the reservoir