An injection device (110) comprises a housing (112) adapted to receive asyringe (122) having a discharge nozzle (118) , an actuator (114) and a drive(120) acted upon by the actuator which acts upon the syringe to advance itfrom a retracted position in which the discharge nozzle is contained withinthe housing to an extended position in which the discharge nozzle extends fromthe housing. There is a locking mechanism (HS) in communication with theactuator and activatable to be moved from a locked position in which theactuator is prevented from releasing the drive to an unlocked position inwhich the actuator is operable to act upon the drive to advance the syringe.The locking mechanism or the housing includes integrally formed biasing means(210) adapted to return the locking mechanism to a locked position when it isnot activated. There is no need for separate springs to be used to bias thereleasable locking mechanism out of the housing.
