Abstract: A needle protective device for a syringe having a barrel has a needle hub and a sleeve. The needle hub detachably connected to the barrel has an anti-rotation device. The anti-rotation device is formed on the needle hub. The sleeve is mounted slidably on the barrel and has an inner wall, a detent and an anti-rotation seat. The detent is formed at the inner wall of the sleeve. The anti-rotation seat is formed inside the sleeve and selectively engages the anti-rotation device of the needle hub so that the needle can be attached to the barrel. After injecting liquid material, the barrel is pulled out of the sleeve, the needle hub enlarges size after being stopped by the detent in the sleeve so the barrel can be detached from the needle hub that is held in the sleeve. Consequently, detaching the barrel from the needle hub is easy.

Abstract: An needle assembly includes a barrel having a front opening, a rear opening in communication with the front opening, a front blockage formed and an annular rear stop formed on an inner periphery of the barrel to be adjacent to the rear opening. A needle hub is movably received inside the barrel and having a stop ring securely mounted around the needle hub. The needle hub is alternately positioned by the front blockage and the rear stop. A needle is securely mounted at a distal end of the needle hub to be extended out of the barrel when the stop ring is positioned by the front blockage and to be received inside the barrel when the stop ring is positioned by the rear stop. A tube is connected to the needle hub to be in communication with the needle hub.

Abstract: A safety syringe has a barrel, a retractor, a needle hub and an outer sleeve. The barrel has a plunger mounted slidably in the barrel, a front end and a threaded protrusion formed on the end and has a through hole. The retractor is hollow, engages the threaded protrusion and has a first connector. The needle hub has an enlarged end having a needle longitudinally extending through the needle hub and a second connector corresponding to and connecting detachably with the first connector. The outer sleeve is mounted slidably around the needle hub, is mounted detachably and slidably around the retractor and the barrel to mount in detachably and has a front end, a cavity, an inner surface, a positioning protrusion and an annular protrusion mounted in the inner surface. The syringe is assembled easily and conveniently.