Syringe spring retainer

1. A spring retainer for a syringe that comprises a barrel, a plunger, a spring and a retractable needle, said spring retainer comprising a housing having first and second body members adapted to releasably maintain said spring in a compressed state until rotational disengagement of said first and second body members allows decompression of said spring to facilitate retraction of said retractable needle into said barrel, wherein the second body member is adapted to be engageable by said plunger so that depression of said plunger triggers said rotational disengagement of said second body member relative to said first body member, wherein said second body member further comprises circumferential ramps arranged so that decompression of said spring forces engagement of said ramps by tabs to facilitate rotation of said second body member relative to said first body member.

2. The spring retainer of claim 1 , wherein the first body member comprises two or more projections capable of slidably engaging respective slots in said plunger to guide rotation of said plunger in use.

3. The spring retainer of claim 2 , wherein said second body member comprises one or more recesses arranged so as to be releasably engageable by respective tabs on said first body member.

4. A syringe comprising a barrel, a plunger, a spring, a spring retainer, and a retractable needle which is capable of coupling with said plunger for retraction of said needle into said barrel, said spring retainer comprising a housing having a first body member that comprises two or more projections capable of slidably engaging respective slots in said plunger to guide rotation of said plunger in use and a second body member, said first and second body members adapted to releasably maintain said spring in a compressed state until disengagement of said first and second body members allows decompression of said spring to facilitate retraction of said retractable needle into said barrel, wherein the second body member is adapted to be engageable by said plunger so that depression of said plunger triggers rotational disengagement of said first body member and said second body member.

5. The syringe of claim 4 , wherein said second body member comprises one or more recesses arranged so as to be engageable by respective tabs on said first body member.

6. The syringe of claim 5 , comprising one or more plunger elements that engage respective complementary mating portions on said second body member.

7. The syringe of claim 6 , wherein the one or more plunger elements comprise two shoulders engageable with respective shoulder ramps on said second body member.

8. The syringe of claim 7 , arranged so that upon engagement between said two shoulders and respective shoulder ramps on said second body member, rotation of said shoulders selectively rotates said second body member relative to said first body member thereby disengaging said tabs from said recesses which disengages said first body member and said second body member to allow decompression of said spring.

9. The syringe of claim 8 , wherein said second body member further comprises circumferential ramps arranged so that decompression of said spring forces engagement of said ramps by said tabs to facilitate rotation of said second body member relative to said first body member.

10. The syringe of claim 9 , arranged so that rotation of said second body member is capable of assisting rotation of said plunger into a final, inoperable position.

11. The syringe of claim 4 , having said retractable needle mounted thereto, whereby in use said spring is maintained in a compressed state by said spring retainer until at or near completion of depression of said plunger when injecting material from said syringe.

12. The syringe of claim 11 , arranged so that said plunger and said retractable needle are coupled at or near completion of depression of said plunger.

13. The syringe of claim 4 , arranged so that disengagement of said first and second body members of said housing can facilitate rotation of said second body member relative to said first body member.

14. The syringe of claim 13 , arranged so that rotation of said second body member is capable of assisting rotation of said plunger, when said retractable needle is coupled therewith, into a final, inoperable position.

15. The syringe of claim 14 , wherein said first body member comprises two or more projections capable of bearing against respective abutments in respective slots in said plunger to maintain said plunger in said final, inoperable position.

16. A spring retainer for a syringe that comprises a barrel, a plunger, a spring and a retractable needle, the spring retainer comprising a housing having first and second body members adapted to releasably maintain the spring in a compressed state until rotational disengagement of the first and second body members allows decompression of the spring to facilitate refraction of the retractable needle into the barrel, wherein the second body member is adapted to be engageable by said plunger so that depression of said plunger triggers said rotational disengagement of said first body member and said second body member and wherein the first body member comprises two or more projections capable of slidably engaging respective slots in the plunger to guide rotation of the plunger in use.