It is a kind of for being used together with syringe to provide the device of safety injector, which includes: that can be unfolded with the sheath (100 of the syringe needle (126) at least partly covering syringe 300 500) And for by with sheath deployment mechanism (104 304 504) interaction carrys out the sheath actuator (102 of deployment sheath 302 502) Wherein, sheath is configured to fix relative to syringe needle, until syringe plunger (116 316 516) until reaching sheath point of release on inner stroke at it, and wherein, sheath actuator be configured for after sheath point of release when sheath actuator is mobile relative to syringe plunger deployment sheath.
