Safty hypodermic syringe and needle holder for same

A safety hypodermic syringe comprising a barrel having a front end and a rear end, a plunger moved in said barrel between the front end and rear end of said barrel, a needle holder mounted in the front end of said barrel, and a needle cannula fastened to said needle holder, said needle holder comprising a hollow cylindrical body, said hollow cylindrical body comprising a front hub, which holds said needle cannula, and a rear coupling structure adapted to receive a front end of said plunger, wherein said needle holder comprises at least one movable unit and at least one engagement unit respectively connected to said hollow cylindrical body, said at least one movable unit being alternatively shifted between an extended-output status where said at least one movable unit are disengaged from said at least one engagement unit, and an inwardly squeezed status where said at least one movable unit are respectively forced by external force into engagement with said at least one engagement unit;

• said barrel comprises an inside stop flange, which supports said needle holder in the front end of said barrel when said at least one movable unit is respectively shifted to said extended-out status, and an inside engagement wall portion, which secures said needle holder to said inside stop flange when said at least one movable unit is respectively shifted to said extended-out status and forces said at least one movable unit inwardly from said extended-out status to said inwardly squeezed status when said plunger is moved to the front end of said barrel.