Semi disposable auto injector

1. An automatic injection device comprising:

a reusable driving assembly having a forward injection end and an engagement element; and

a disposable cassette assembly including an injectable liquid to be injected at an injection site,

wherein said disposable cassette assembly is removably insertable into said reusable driving assembly at said forward injection end and is removably retained within said reusable driving assembly by snap fit engagement therewith, said snap fit engagement being effected at least partially by said engagement element, which is displaced rearwardly by insertion of said disposable cassette assembly in said reusable driving assembly,

and wherein said disposable cassette assembly further comprises:

a cassette housing element;

a syringe including a needle; and

a needle guard element,

said cassette housing element, said syringe and said needle guard element being arranged such that prior to insertion of said disposable cassette assembly into said reusable driving assembly, said syringe is locked against axial displacement relative to said cassette housing element.

2. An automatic injection device according to claim 1 and wherein:

said needle guard element has arms formed with notches;

said engagement element is a needle guard deploying element, having fingers formed with inwardly directed protrusions; and

said insertion of said disposable cassette assembly into said reusable driving assembly produces rearward displacement of said needle guard deploying element, thereby enabling engagement of said inwardly directed protrusions of said needle guard deploying element with said notches of said arms of said needle guard element.

3. An automatic injection device according to claim 2 and wherein:

said reusable driving assembly also includes a needle guard deploying spring;

said arms have rearward facing edges;

said needle guard deploying element has a forward-facing surface; and

said rearward displacement of said needle guard deploying element causes engagement of said rearward facing edges of said arms of said needle guard element of said disposable cassette assembly with said forward facing surface of said needle guard deploying element, against an urging of said needle guard deploying spring.

4. An automatic injection device according to claim 1 and wherein:

said reusable driving assembly has at least cocked and uncocked operative orientations;

said reusable driving assembly includes a safety catch element having engaged and disengaged operative orientations; and

said snap fit engagement occurs only when said reusable driving assembly is in said cocked operative orientation and when said safety catch element is in said engaged operative orientation.

5. An automatic injection device according to claim 1 and wherein:

said cassette housing element, said syringe and said needle guard element being arranged such that prior to insertion of said disposable cassette assembly into said reusable driving assembly, said syringe is locked against axial displacement in a first direction relative to said cassette housing element by engagement with said cassette housing element and is locked against axial displacement in a second direction, opposite to said first direction, relative to said cassette housing element by engagement with said needle guard element.

6. An automatic injection device according to claim 5 and wherein said syringe comprises a prefilled syringe.

7. An automatic injection device according to claim 5 and wherein:

said reusable driving assembly has a needle insertion operative orientation; and

said cassette housing element, said prefilled syringe and said needle guard element are arranged such that subsequent to insertion of said disposable cassette assembly into said reusable driving assembly but prior to said reusable driving assembly being in said needle insertion operative orientation, said syringe is locked by said cassette housing element and said needle guard element against axial displacement in either direction relative to said cassette housing element, but said syringe is not locked against axial displacement relative to said needle guard element at at least some other times.

8. An automatic injection device according to claim 7 and wherein:

when said reusable driving assembly is in said needle insertion operative orientation, said syringe moves axially forwardly together with said cassette housing element relative to said needle guard element, thereby exposing said needle at said forward injection end of said reusable driving assembly.

9. An automatic injection device according to claim 7 and wherein:

said cassette housing element and said needle guard element are arranged such that prior to both said disposable cassette assembly having been inserted into said reusable driving assembly and said reusable driving assembly being in said needle insertion operative orientation, said relative axial displacement between said cassette housing element and said needle guard element is prevented.

10. An automatic injection device according to claim 7 and wherein said cassette housing element is arranged such that upon said reusable driving assembly being in said needle insertion operative orientation, resulting axial displacement of said syringe produces outward displacement of a portion of said cassette housing element into engagement with a forward base element of said reusable driving assembly, thereby limiting a penetration depth of said needle.

11. A disposable cassette assembly for use with a reusable driving assembly in an automatic injection device, said disposable cassette assembly comprising:

a cassette housing element;

a syringe including a needle; and

a needle guard element,

said cassette housing element, said syringe and said needle guard element being arranged such that prior to insertion of said disposable cassette assembly into said reusable driving assembly, said syringe is locked against axial displacement in a first direction relative to said cassette housing element by engagement with said cassette housing element and is locked against axial displacement in a second direction, opposite to said first direction, relative to said cassette housing element by engagement with said needle guard element,

and wherein said disposable cassette assembly is adapted to be inserted into said reusable driving assembly by axially pushing said disposable cassette assembly into said reusable driving assembly along a longitudinal axis of said reusable driving assembly, wherein said longitudinal axis extends through both a rearward end and a forward injection end of said reusable driving assembly.

12. A disposable cassette assembly according to claim 11 and wherein said syringe comprises a prefilled syringe.

13. A disposable cassette assembly according to claim 12 and wherein:

said reusable driving assembly has a needle insertion operative orientation; and

said cassette housing element, said syringe and said needle guard element are arranged such that subsequent to insertion of said disposable cassette assembly into said reusable driving assembly but prior to said reusable driving assembly being in said needle insertion operative orientation, said syringe is locked by said cassette housing element and said needle guard element against axial displacement in either direction relative to said cassette housing element, but said syringe is not locked against axial displacement relative to said needle guard element at at least some other times.

14. A disposable cassette assembly according to claim 13 and wherein said cassette housing element and said needle guard element are arranged such that prior to both said disposable cassette assembly having been inserted into said reusable driving assembly and said reusable driving assembly being in said needle insertion operative orientation, said relative axial displacement between said cassette housing element and said needle guard element is prevented.

15. A disposable cassette assembly according to claim 13 and wherein when said reusable driving assembly is in said needle insertion operative orientation, said syringe is configured to move axially forwardly together with said cassette housing element relative to said needle guard element, thereby exposing said needle at said forward injection end of said reusable driving assembly.

16. A disposable cassette assembly according to claim 13 and wherein said cassette housing element is arranged such that upon said reusable driving assembly being in said needle insertion operative orientation, resulting axial displacement of said syringe produces outward displacement of a portion of said cassette housing element into engagement with a forward base element of said reusable driving assembly, thereby limiting a penetration depth of said needle.

17. A disposable cassette assembly according to claim 11 and wherein:

said disposable cassette has a pre-use operative orientation, which is suitable for storage; and

in said pre-use operative orientation, said needle guard element is locked to said cassette housing element by snap fit engagement of protrusions of said needle guard element in slots formed in said cassette housing element.

18. A disposable cassette assembly according to claim 11 and wherein said disposable cassette assembly is removably insertable into said reusable driving assembly at a forward injection end and is removably retained within said reusable driving assembly by snap fit engagement therewith.