Retractable needle assembly and syringe utilizing the same

1. An injection device comprising:

a barrel;

a hollow plunger having a portion structured and arranged to move within the barrel;

the plunger comprising:

a proximal end;

an outer surface arranged axially behind the proximal end; and

a space disposed in the hollow plunger;

a needle unit;

the space being sized and configured to receive therein a distal portion of the needle unit prior to the plunger reaching a substantially fully depressed position;

at least one releasable retaining member which releasably retains the needle unit in an initial position and that is movable to a position arranged outside the outer surface of the plunger; and

a safety system that one of:

automatically causes the needle unit to retract into the plunger when the plunger reaches the substantially fully depressed position; and

utilizes a frangible or breakable seal arranged within the plunger,

wherein, during movement of the plunger to the substantially fully depressed position, the space is structured and arranged to receive therein a portion of the distal portion of the needle unit and receives therein the distal portion of the needle unit prior to the needle unit being contacted and prior to the at least one releasable retaining member being contacted, and

wherein, in the substantially fully depressed position, the at least one releasable retaining member is each of:

arranged outside the space; and

in contact with the outer surface, and

wherein the injection device further comprises each of:

a locking arrangement that is structured and arranged to lock the needle unit to the frangible or breakable seal; and

a plugging system spaced from the locking arrangement and that is structured and arranged to plug a distal end of a lumen of the needle unit so as to prevent medication from passing into the lumen.

2. The injection device of claim 1 , wherein the injection device is a single-use syringe.

3. The injection device of claim 1 , wherein the barrel comprises a cylindrically shaped internal space structured and arranged to receive therein a medicine.

4. The injection device of claim 3 , wherein the barrel further comprises a proximal opening within which the needle unit is at least one of:

press fit; and

in sealing engagement therewith.

5. The injection device of claim 1 , wherein the plunger comprises a piston arranged at a proximal area of the plunger and an actuating end arranged in front of the piston.

6. The injection device of claim 5 , wherein the plunger further comprises at least one of:

the piston being an elastomer or rubber piston;

a hollow space sized and configured to receive therein the needle unit in its entirety; and

a locking member adapted to lock with a locking member arranged on the barrel.

7. The injection device of claim 1 , wherein the barrel, the plunger, and a hub portion of the needle unit each comprise a synthetic resin material.

8. The injection device of claim 1 , wherein the needle unit comprises a generally cylindrical hub and a hollow needle projecting from the hub.

9. The injection device of claim 8 , wherein the needle comprises at least one of metal and stainless steel.