Assembly for use in a drug delivery device

摘要

The present invention relates to a piston for a cartridge for a drug delivery device comprising: at least one annular sealing surface to radially abut against an inner side wall of a cartridge, a distal surface to confine a drug receiving volume of the cartridge, a thrust receiving surface adapted to receive a thrust exerting plunger of a drug delivery device for displacing the piston in a proximal direction relative to the side wall, wherein the thrust receiving surface comprises numerous centering elements protruding from the thrust receiving surface towards the plunger and wherein the centering elements comprise an outer shape and geometry that matches with a corresponding receptacle of the plunger, and wherein the centering elements are arranged and aligned on the circumference of an imaginary annular or circular structure.

主权项

1. A piston and plunger combination for use in a drug delivery device comprising,
a) a piston having a body comprising a distal end face and a proximal thrust receiving surface, wherein the piston further comprises a radial sealing surface that is configured to engage an inner sidewall of a cartridge to provide a leak proof seal; b) a plurality of centering elements protruding proximally from the proximal thrust receiving surface, c) a plunger having a distal facing end face; and d) a receptacle on the distal facing end face having a geometric shape and depth, where the geometric shape of the receptacle is a substantially U- or V-shaped groove of circular geometry as viewed in a plane parallel to the distal facing end face, wherein the plurality of centering elements are arranged on the proximal thrust receiving surface in a pattern that matches the geometric shape of the receptacle and protrude outwardly from the proximal thrust receiving surface a distance less than or equal to the depth of the receptacle such that the distal facing end face is in contact with the proximal thrust receiving surface when the plunger and piston abut, wherein each of the plurality of centering elements when as viewed in a plane parallel to the proximal thrust receiving surface comprise an arcuate shape.