EP2489382A1 — Auto-injector

USPTO Abstract

An Auto-injector (1) for administering a dose of a liquid medicament (M) comprises: - an elongate case (12), - a carrier subassembly comprising a tubular carrier (7) slidably arranged inside the case (12), the carrier (7) adapted to contain a syringe (3) with a hollow injection needle (4), a drive spring (8) and a plunger (9) for forwarding load of the drive spring (8) to a stopper (6) of the syringe (3), wherein the syringe (3) is lockable for joint axial translation with the carrier (7), - a control spring (19) arranged around the carrier (7) for translating the carrier (7) in a proximal direction (P) for advancing the needle (4) beyond a proximal end of the auto-injector (1), - a trigger button (13) for releasing the control spring (19) on actuation. The drive spring (8) biases the plunger (9) in the proximal direction (P) against the carrier (7). At least one resilient arm (15) is arranged on either the carrier (7) or the plunger (9) and in a ramped engagement to the other of the carrier (7) or the plunger (9) so as to disengage them under load of the drive spring (8). A peg (14) is arranged to be coupled to the case (12) at least after actuation of the trigger button (13) so as to be positioned to support the resilient arm (15) preventing disengagement of the carrier (7) from the plunger (9) and thus release of the drive spring (8) when the carrier (7) is in a distal position. The peg (14) is arranged to remain in position when the carrier (7) is translated for advancing the needle (4) so as to pull the resilient arm (15) away from the peg (14) thus allowing deflection of the resilient arm (15) due to the ramped engagement under load of the drive spring (8) for disengaging the plunger (9) from the carrier (7) and releasing the drive spring (8) for drug delivery when the carrier (7) has reached a predefined position during needle advancement.