Retractable needle syringe

A retractable-needle syringe comprising:

• a barrel;
• a plunger axially slideable within the barrel for drawing medicament into a medicament chamber defined within the barrel and for injecting medicament into a patient, the plunger having a retraction lumen therein;
• a locking tip engaged at a distal end of the plunger within the retraction lumen, the locking tip being initially secured against a loading force or an injection force applied by a user, but moveable in response to application of a post-injection force by the user to allow sliding retraction of the locking tip within the retraction lumen;
• a false wall initially engaged within the barrel near a distal end of the barrel, the false wall being moveable in a distal direction in response to the application of the post-injection force by the user;
• a needle hub initially secured by the false wall against the loading force or the injection force applied by the user, the needle hub being engageable with the locking tip to provide a retraction assembly comprising the locking tip, the needle hub, and a needle, and the needle hub being releaseable from the false wall, upon the application of the post-injection force by the user;
• the needle projecting from the distal end of the barrel, the needle being secured to the needle hub;
• a unitary propellant release structure provided distally of the needle hub within the barrel, wherein the unitary propellant release structure comprises a channel defined within a distal portion of the barrel, the channel comprising a base, an inner wall and an outer wall, with a seal extending between upper edges of the inner and outer walls to contain a propellant within the unitary propellant release structure;
• and
• a rupturing member moveable to rupture the unitary propellant release structure upon the application of the post-injection force by the user to thereby drive retraction of the retraction assembly into the retraction lumen,
• wherein the needle hub comprises a tapered sealing portion on an inner surface of the needle hub at a proximal portion of the needle hub, a proximal end of the tapered sealing surface being wider than a width of the tapered sealing surface at any point distal to the proximal end of the tapered sealing surface, and wherein the locking tip of the plunger comprises a central projection with a tapered surface that is complementary to the tapered sealing portion of the needle hub, so that the tapered sealing portion and the tapered surface can be brought together into sealing contact upon the application of the post-injection force;
• and
• wherein the false wall comprises a central aperture extending axially therethrough, and a radially-outwardly projecting channel defined circumferentially on an interior portion of the central aperture, and wherein the needle hub comprises radially outwardly projecting engagement features for initially sealingly engaging with the channel, the engagement features being displaceable from the channel in response to the application of the post-injection force by the user.