Injection device

An injection device comprising an outer housing (30) adapted to house the following: a cylinder for containing a volume of a medicament; a needle (10) at one end of the cylinder, with the needle and the cylinder such that at least part of the needle is axially displaceable in and out of the housing (30) outside but is biased to be normally wholly within the housing; and a plunger (8) axially displaceable within the cylinder, further comprising the injection device: a housing (7) disposed between the inner housing and the outer barrel and plunger; and a source (1; 40) of energy in communication with the housing (7) inside, being movable device between two positions, namely a first position in which the device acts on the barrel such that, during the use, the piston and the cylinder can be displaced axially thus to move at least part of the needle out of the outer casing; and a second position in which the device acts on the plunger but not on the cylinder, so that, in use, the plunger can move axially within the cylinder so as to expel medicament through the needle; characterized in that the housing (7) inside displaceable by the energy source between three positions, namely the first position, in which the inner housing has one or more tabs (7B) flexible radially in communication with the cylinder so which, during use, the plunger and cylinder can be displaced axially thus to move at least part of the needle out of the outer casing; the second position, in which the inner housing has one or more tabs (7A) flexible radially in communication with the plunger but not the barrel, so that, in use, the plunger is axially displaceable in the cylinder to expel drug through the needle; and a third position in laque said flanges (7A, 7B) flexible radially to the inner housing are not in communication with either the piston or the cylinder, so that, in use, the plunger and cylinder can be retracted to retract the needle into the outer housing.