Adjustable penetration depth syringe

1. A syringe with adjustable penetration depth, comprising:

a tubular syringe barrel;

a plunger positioned within the syringe barrel;

a hub bearing a needle and attached to a distal end of the syringe barrel, the hub being removable from the syringe barrel;

a movable collar having an open proximal end received over the hub, a distal end wall having an opening through which the needle protrudes, and a sidewall extending proximally from the distal end wall, the sidewall having an interior surface engaging the hub; and

a retaining feature on the collar engaging the hub and retaining the collar at a plurality of axial positions; wherein

the collar travels with respect to the hub along a path defined by the retaining feature on the interior surface of the sidewall engaging the hub, exposing a greater length of the needle as the collar travels toward the plunger;

the collar is retained in a fixed position at a first or second axial position;

the collar rotates without axial movement when the retaining feature on the collar is engaged to one of a plurality of slots on the hub; and

the plurality of slots is not visible when the collar contacts the syringe barrel.

2. The syringe according to claim 1 , wherein the hub bearing the needle is snap-fit to the syringe barrel and the syringe is configured to be provided pre-assembled to a user.

3. The syringe according to claim 1 , further comprising indicia on the hub representing a penetration depth of the needle, said indicia being visible through an opening in the sidewall of the collar.

4. The syringe according to claim 1 , wherein the hub includes a plurality of laterally extending protrusions defining the plurality of slots at distinct axial positions on the hub.

5. The syringe according to claim 4 , wherein the retaining feature includes a tab adapted to engage one of the plurality of slots on the hub when the collar is rotated.

6. The syringe according to claim 5 , wherein

at least one of the plurality of slots includes a depression; and

when the tab of the collar engages the depression, the collar is locked from further rotation.

7. The syringe according to claim 6 , wherein the collar is locked at a distal most position on the collar.

8. The syringe according to claim 6 , wherein when the collar is locked, a tactile indication is provided.

9. The syringe according to claim 6 , wherein the collar is prevented from clockwise rotation when locked.

10. The syringe according to claim 4 , wherein the plurality of slots on the hub are spaced at substantially 1 mm increments, providing for the first axial position at which 8 mm of needle length protrudes from the distal end wall of the collar, and the second axial position at which 4 mm of needle length protrudes from the distal end wall of the collar.

11. The syringe according to claim 4 , wherein each of the plurality of slots is substantially perpendicular to an axis of the syringe.

12. The syringe according to claim 1 , wherein

the hub includes an axially extending channel;

the retaining feature includes a tab; and

the axially extending channel engages the retaining feature of the collar to allow axial movement.

13. The syringe according to claim 12 , wherein the axially extending channel is substantially parallel to an axis of the syringe.

14. The syringe according to claim 12 , wherein the collar travels axially without rotating when the tab on the collar is engaged to the axially extending channel on the hub.

15. The syringe according to claim 1 , further comprising a visual indicator to indicate a locked after-use position.

16. The syringe according to claim 1 , further comprising an internally facing flange or detent on the collar that engages the hub to provide a locking action to prevent proximal or rotational movement of the collar after use.