Improved injection device

An injection device 10 with an outer housing 12 receiving a syringe 14 with a barrel 16 for containing medicament, a stopper 18, plunger rod 38, and needle 20. A needle shield 22 is axially moveable relative to the outer housing between a forward needle covering position and a rearward needle exposing position. The needle shield is biased 24 forwardly toward the needle covering position. A locking sleeve 28 is movable between a forward non-locking position and a rearward locking position. When the plunger rod is moved forwards, a locking member 66 moves from a first position to a second position. In the second position, the locking member selectively limits movement of the locking sleeve. In a first configuration, the needle shield covers the needle, the locking sleeve is in the non-locking position and the needle shield can slide rearwardly within the locking sleeve. In a subsequent configuration, the needle shield is in the needle covering position and the locking sleeve is in the locking position, so the needle is prevented from moving rearward by interference with the locking sleeve. The locking member may comprise shunt arms which are engageable with protrusions on the plunger rod.