US Patent 9446193 Dosing unit for an infusion pump device

A dosing unit for an ambulatory infusion pump device is presented. The dosing unit comprises a cylinder pump with a cylinder and a piston arranged in the cylinder. The piston has a shaft with a first threaded segment interacting with a threaded portion of the cylinder and can be displaced along a longitudinal axis of the cylinder by rotating the piston in regard to the cylinder around the axis. Furthermore, the piston allows for the relative or absolute determination of the longitudinal and/or rotational displacement of the piston in regard to the cylinder. In one embodiment, the piston shaft comprises a second segment provided with optically detectable markings that allow the monitoring of the longitudinal and/or rotational displacement of the piston in regard to the cylinder.