Patent ID: 8690825

Claim:
A safety syringe, comprising: a barrel having a front-end opening, a rear-end opening and a plurality of elastic support units disposed in an inner side of the front-end opening; a plunger having a jostling portion at a front-end thereof, a first coupling portion disposed at a top of the jostling portion, and a rubber ring mounted around a lower portion of the jostling portion; wherein the front-end of the plunger is inserted into the barrel from the rear-end opening of the barrel; and an injection head unit comprising a first needle seat, a second needle seat, and a needle; wherein the first needle seat has an inner tube for holding the second needle seat, and the needle is mounted in a front-end of the second needle seat, and a second coupling portion is disposed in a rear-end of the second needle seat; when the first needle seat is mounted on the front-end opening of the barrel, the rear-end of the second needle seat is propped by the plurality of elastic support units; and when the first coupling portion is pushed to couple with the second coupling portion, the plurality of elastic support units is jostled out of the second needle seat by the jostling portion, and then the second needle seat and the needle are pulled into the barrel responsive to pulling the plunger; wherein the first coupling portion is a cone-like body, and the second coupling portion is a cone-like cavity having a bump protruding into the cone-like cavity; engagement between the cone-like body and the cone-like cavity forces contact between an inclined side of the cone-like body and the protruding bump to apply a stress to a side of the second needle seat so that when the second needle seat and the needle are pulled into the barrel, the needle is forced to incline as a result of the stress applied to the second needle seat.