US Patent 11065381 Infusion pump device and method for use thereof

A patch pump including a medicament reservoir having an inner surface defining an elongate piston engagement pathway, an electric motor having a rotary drive output element, a piston replaceably axially fixed to the electric motor. The piston having an outer surface arranged for sealing engagement with the inner surface of the medicament reservoir, the piston also including a rotary to longitudinal drive converter receiving a rotary drive input from the rotary drive output element of the electric motor and providing a longitudinal drive to the reservoir, thereby driving the medicament reservoir in longitudinal motion relative to the piston in which the elongate piston engagement pathway defined by the inner surface of the medicament reservoir is displaced axially and in sealing engagement with the outer surface of said piston.