Patent ID: 8118781

Claim:
A fluid infusion system for infusing a medication fluid comprising: a reservoir pre-filled with the medication fluid and adapted for use with a pump drive system having a linear actuation member provided with one or more first protrusions, the reservoir comprising: a proximal end closed by a pierceable membrane and adapted to connect to an infusion set; an open distal end; a cylindrical wall longitudinally extending along an axis from the proximal end to the distal end, and a piston adapted to be slideably mounted within the reservoir along a longitudinal axis and forming a fluid-tight barrier inside the reservoir; the piston comprising at least one peripheral sealing portion wherein the piston is adapted to engage the linear actuation member by axially displacing the linear actuation member relative to the piston and wherein the engagement is adapted to release when an axial disengagement force exceeds a predefined limit, wherein the at least one peripheral sealing portion is made of a material of a first stiffness, and the piston further comprises a core member of a material having a stiffness larger than said first stiffness, the core member comprising one or more connective members being adapted to cooperate with said one or more protrusions of the linear actuation member, and that said one or more connective members are adapted to be substantially rigid in the axial direction while being resilient in a radial direction, thereby forming a releasable connection with the linear actuation member, and wherein the connective members and the protrusions being formed to provide a snap fit engagement or a friction fit engagement.