An autoinjector having a plunger biasing means

摘要

An autoinjector comprising an outer housing in which is mounted a syringe comprising a barrel 100 for holding a volume of medicament, a needle at one end of the barrel and a plunger 8 axially-moveable in the barrel 100, the autoinjector further comprising an inner housing 7 intermediate the outer housing and the syringe and an energy source in communication with said inner housing 7, wherein the inner housing 7 is moveable by the energy source between three positions, namely a first position in which the inner housing 7 is in communication with the barrel 100 such that, in use, the plunger 8 and barrel 100 are moveable axially so as to move at least part of said needle out of the outer housing; a second position in which the inner housing 7 is in communication with the plunger 8 but not the barrel 100 such that, in use, said plunger 8 is moveable axially into said barrel 100 so as to expel medicament through the needle; and a third position in which the inner housing 7 is in communication with neither the plunger 8 nor the barrel 100 such that, in use, the plunger 8 and barrel 100 are able to retract in order to retract the needle into the outer housing, characterised in that the plunger 8 includes biasing means 200 for axially biasing the barrel, before activation of the energy source, to a position forward of the part of the inner housing 7 which acts on the barrel in said first position.