Rosenberg, Klein & Bilker
Safety syringe with retractable standard needle
 A safety syringe with retratable standard needle, including a syringe barrel, a plunger and an injection needle. A commonly used standard needle holder is replaceably connected with a second needle holder, whereby a user can conveniently replace the injection needle with another type of injection needle as necessary. A first needle pulling member is formed on the needle holder or the plunger, having at least one rotatable click. A second needle pulling member is formed on the plunger or the needle holder, having a detent. When the piston of the plunger is pushed to the bottom, the detent is easily and firmly engaged and hooked with the click. Thereafter, the injection needle and the needle holder can be together pulled into the barrel so as to ensure that the injection needle will not impale medical personnel or other persons. 
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Wen-Neng
Liu