Plunger assembly for patient infusion device

A device for delivering fluid to a patient comprising; a set of output orifice (70); a reservoir (30) including an outlet connected to a set of outlet and a side wall (32) extending along a longitudinal axis towards the outlet (36) and a plunger assembly (40) held in the reservoir and movable along the longitudinal axis (33) of the tank to the tank outlet, including the piston assembly, a first lateral segment (200) extending laterally of the longitudinal axis of the reservoir and contacting the wall side of the tank, including the first lateral segment (200): two blocks (208) movable laterally relative to the longitudinal axis (33) of the tank (30), a spring (202) separating pressure and laterally two blocks outside to frictionally engage the side wall (32) of the reservoir and prevent longitudinal movement of the first lateral segment from the outlet (36) of the reservoir (30) and an actuator (204) arranged to overcome the spring of the first lateral segment and joining pressure blocks laterally upon actuation; a second lateral segment (220) positioned between the first lateral segment and the tank outlet, extending the second lateral segment (220) laterally relative to the longitudinal axis of the reservoir and contacting the side wall of the tank and longitudinally spaced from the first lateral segment ( 200) and a longitudinal segment (240) extending substantially parallel to the longitudinal axis of the reservoir and connecting the first and second lateral segment (200, 220) including longitudinal segment (240), a spring (242) pressure separates the first and second lateral segments (200, 220), longitudinally and an actuator (244) arranged to overcome the spring pressure and joining the first and second lateral segments (200, 220) longitudinally upon actuation.