Retractable needle assembly and syringe utilizing the same

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.