Plunger sub-assembly for a prefilled medicament injector, a prefilled medicament injector and method for assembling a prefilled medical injector

A plunger sub-assembly for a pre-filled medicament injector for expelling a dose of a medicament, comprising:

• a container holding a medicament, the container comprising a cylindrical container body extending along a central axis between a medicament expelling distal end and a proximal end, wherein an axially slideable piston is arranged within the container body to seal the container proximally, and wherein the proximal end of the container body comprises a proximally facing rim surface,
• a plunger arranged along the axis and configured for driving the piston distally relative to the proximally facing rim surface, the plunger being distally movable from a start position where the plunger is not cooperating with the proximally facing rim surface until an end position relative to the container where the plunger cooperates with the proximally facing rim surface thereby preventing the plunger from moving further distally, the piston assuming an end of dose position relative to the proximally facing rim surface when the plunger assumes the end position, and
• an adjustable blocking structure associated with the plunger and the container to provide an axial blocking structure for the plunger in the end position,
• wherein the adjustable blocking structure comprises a tolerance compensating element configured to cooperate with the plunger and to cooperate with the proximally facing rim surface, wherein the tolerance compensating element is rotatable relative to the plunger to adjust the piston end of dose position relative to the proximally facing rim surface,
• wherein the tolerance compensating element is so configured that, when the plunger assumes the end position,
• the plunger engages directly with the piston, whereas the tolerance compensating element directly engages both the plunger and the proximally facing rim surface
• wherein one of the plunger and the tolerance compensating element comprises a contour system comprising a plurality of circumferentially disposed stop surfaces that are arranged axially offset relative to each other, and wherein the other of the plunger and the tolerance compensating element comprises a counter stop surface arranged to axially engage a selective one of the plurality of circumferentially stop surfaces, and
• wherein, when in an initial assembly configuration, the tolerance compensating element and the plunger are positioned relative to each other to rotationally align the counter stop surface with a selective one of the plurality of circumferentially disposed stop surfaces to thereby adjustably control the end position of the plunger relative to the container, enabling the counter stop surface to axially abut the selected one of the plurality of circumferentially disposed stop surfaces.