Patent ID: 7635356

Claim:
An injection device, comprising: an outer housing inside which is located: a barrel for holding a dose of a medicament; a needle at one end the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing; a plunger, axially moveable within the barrel; an inner housing; and an energy source in communication with said inner housing, wherein the inner housing is moveable by the energy source and operates in three modes, namely a first mode in which the inner housing is in contact with and acts on the barrel other than via said medicament such that, in use, the plunger and barrel move axially so as to move at least part of said needle out of the outer housing, wherein in the first mode the inner housing moves with the plunger and the barrel, wherein in the first mode the inner housing, the plunger and the barrel move relative to the outer housing, and wherein in the first mode the inner housing is intermediate the outer housing and at least a portion of the plunger; a second mode in which the inner housing is in direct contact with and acts on the plunger to move the plunger axially but not the barrel such that, in use, said plunger moves axially into said barrel so as to expel medicament through the needle, wherein in the second mode the inner housing moves with the plunger, and wherein the inner housing is intermediate the outer housing and at least portions of both the barrel and the plunger; and a third mode in which the inner housing acts on neither the plunger nor the barrel such that, in use, the plunger and barrel retract relative to the inner housing and the outer housing in order to retract the needle into the outer housing, and wherein as a result of said plunger and barrel retracting said needle is retracted such that said at least part of said needle moved out of the outer housing in said first mode is retracted into the outer housing.