Abstract: A retractable safety syringe includes a retractable needle hub holding a needle and having a first guiding means; and a hollow barrel having a second guiding means set correspondingly to the first guiding means; and a collapsible plunger comprising of a first plunger element having a protrusion releasably coupled with a second plunger element having a longitudinal slot with a pinched zone to curb the movement of said protrusion; and a spring disposed between the needle hub and hollow barrel and acts between the needle hub and the hollow barrel. The uncoupling of the collapsible plunger triggers the retraction mechanism to enable the needle hub to retract into the barrel by the decompression force of a spring. The reliability of retraction is further improved by a longitudinal slot and a protrusion to facilitate the retreating of the collapsible plunger in an orderly way.

Abstract: A retractable safety syringe includes a retractable needle hub holding a needle and having a first guiding means; and a hollow barrel having a second guiding means set correspondingly to the first guiding means; and a collapsible plunger comprising of a first plunger element having a protrusion releasably coupled with a second plunger element having a longitudinal slot with a pinched zone to curb the movement of said protrusion; and a spring disposed between the needle hub and hollow barrel and acts between the needle hub and the hollow barrel. The uncoupling of the collapsible plunger triggers the retraction mechanism to enable the needle hub to retract into the barrel by the decompression force of a spring. The reliability of retraction is further improved by a longitudinal slot and a protrusion to facilitate the retreating of the collapsible plunger in an orderly way.

Abstract: A medically safety injector comprises a needle hub attached by a needle, a hollow barrel for engaging with the needle hub and guiding the needle hub to retract into the hollow barrel, and a plunger combination settled in the hollow barrel. The plunger combination comprises a retractable plunger and a hollow shank partially telescoped with the retractable plunger, wherein at least one raised portion is formed on an outer wall of the retractable plunger and at a telescoping portion for engaging at least one depression formed on an inner wall of the hollow shank so that when the plunger combination continuously receives a pushing force after the medically safety injector is used to perform the injection operation, the retractable plunger can smoothly retract into the hollow shank. Consequently, space in the hollow barrel originally occupied by the retractable plunger or hollow shank is freed for accommodating the retracted needle hub.

Abstract: A safety injector comprises a needle hub attached by a needle, a hollow barrel for engaging with the needle hub and guiding the needle hub to retract into the hollow barrel, and a plunger combination settled in the hollow barrel. The plunger combination comprises a retractable plunger and a hollow plunger partially telescoped with the retractable plunger, wherein at least one raised portion is formed on an outer wall of the retractable plunger and at a telescoping portion for engaging at least one depression formed on an inner wall of the hollow plunger so that when the plunger combination continuously receives a pushing force after the safety injector is used to perform the injection operation, the retractable plunger can smoothly retract into the hollow plunger. Consequently, a space in the hollow barrel can be spared for accommodating the retracted needle hub.

Abstract: A safe medical-drug injector with a collapsable plunger combination thereof is proposed. The injector includes a hub connected with a needle, a hollow barrel, and a collapsable plunger combination including a hollow cannula and a retractable plunger that is telescoped with the hollow cannula. At least a stress adjustable notch is formed at the core of the retractable plunger or in an upper edge of the hollow cannula, and at least one raised portion is formed on an outer lateral side of the retractable plunger near the stress adjustable notch to be correspondingly embedded with at least a depression formed on an inner lateral side of the hollow cannula. The engagement between the raised portion and the depression is released to make the retractable plunger drawn back to the hollow cannula when a following press is applied on the hollow cannula after the safe medical-drug injector completes an injection.

Abstract: This invention of a prepacked automatic retractable safety syringe comprises a needle hub with a needle tube and a rubber washer, a cap, a barrel, a spring, a vial, and a retractable plunger. To prevent or reduce injuries of needle stab and protect medical staffs, a forward action of the vial plus the needle hub compressed by the retractable plunger can drive a sliding movement between slides on the needle hub and snap hooks on the barrel via the spring's force to complete automatic retraction of the needle hub as well as the vial when an injection is finished.