A single-usage disposable hypodermic syringe comprising a needle cannula, a needle locking base, a barrel, a plunger and a finger flange wherein:
- a tubular housing encloses from the tip of the needle cannula to the rear end of the barrel and snaps at an appropriate location, the front of the tubular housing is a cone shape and the rear end of which is a finger flange;
- an empty space is reserved inside the needle locking base, a ball plug is fixed inside the empty space in an appropriate position, from where the internal space of the barrel is connected to through a channel which is smaller in diameter than the ball plug, the needle locking base is securely mounted on a connecting base which is located in the tapered end of the barrel;
- a channel opening, which joins with the empty space, is opened at the center of the ball plug, said empty space is linked to the channel of the needle cannula, a rubber plug located at the front end of the plunger, is connected to a projected member in a direction pointing to the needle cannula, as the plunger is pushed forward, the projected member also advances and is driven into the channel, the projected member continues to move inside the channel until the dosage of medication is finished, at this time the projected member is in contact with the ball plug and blocks the channel opening, no more medication can be injected accordingly, the empty space is appropriately designed such that the ball plug seals off the channel to the needle cannula and therefore the syringe can no longer be reused, the shape of the rubber plug is preferably made to match the upper part of the barrel and snap onto the plunger, the projected member of the plunger ensures that the rubber plug is secured with the plunger, the rubber plug is made to be able to slide smoothly inside the plunger;
- to avoid the plunger from being mistakenly used, such as the plug being pushed first and the plunger loses its primary function, a projecting plate is mounted on a pivot on the edge of the finger flange, the projecting plate is a small square plate having a sharp end pointing at the barrel, the length of the projecting plate is able to shield the plunger partially but does not affect its forward movement, the plunger is made to have a "Y" shape and in the rear portion of the plunger a triangular plate is installed, when the syringe is new, the projecting plate is facing toward the center of the plunger, the projecting plate is restricted by the triangular plate and cannot move forward during injection, only when the projecting plate is rotated that the syringe is able to accept medication, the tubular housing is used to cover up the needle cannula and the syringe is ready to be disposed.