An injection device (210) is described. A housing (212) receives a syringe andincludes a return spring (226) for biasing the syringe from an extendedposition in which its needle (218) extends from the housing to a retractedposition in which the it does not. A drive spring (230) acts on a first driveelement (232) and a second drive element (234) acts upon the syringe toadvance it from its retracted position to its extended position and dischargeits contents through the needle. The first drive element is capable ofmovement relative to the second once a nominal decoupling position has beenreached. A release mechanism is activated when the-first drive element isfurther advanced to a nominal release position, to release the syringe (214)from the action of the drive spring, whereupon the return spring restores thesyringe to its retracted position. A locking mechanism (337, 375) confines thereturned syringe in its retracted position.
