Low radial profile needle safety device

1. A needle safety device for an injection device having a generally cylindrical barrel with a distal end having a hub from which a cannula extends, the needle safety device comprising:

an outer tube within which the barrel is slideably receivable, the outer tube having a distal end, a proximal end spaced from the distal and a longitudinal axis along which the outer tube is movable in a distal extended direction and in a proximal retracted direction opposite the distal extended direction;

a track formed in an inner surface of the outer tube;

a collar within the outer tube and movable relative thereto, the collar attachable to the distal end of the barrel and having a radially outwardly extending collar pin slideably engaging the track;

a cannula shield within the outer tube, the cannula shield able to receive the cannula therein,

a cap removably attached to the outer tube, the cannula shield fixedly attached to the cap, the cap having diametrically-opposed, longitudinally-extending arms received in a releasable friction fit in corresponding recesses in an outer surface of the outer tube and a distal end having an annular bore within which a radially outwardly extending disk-like flange of the cannula shield is fixedly received; and

a biasing member within the outer tube applying in the distal direction a biasing force to the outer tube,

wherein the cannula is in the cannula shield and entirely within the outer tube when the collar is attached to the distal end of the barrel and the collar pin is in a pre-injection position in the track spaced from the proximal end of the outer tube,

wherein the cannula extends beyond the distal end of the outer tube when the collar is attached to the distal end of the barrel, the cannula shield and cap are removed from the outer tube and the collar pin is in a full-insertion position in the track proximal to the distal end of the outer tube; and

wherein the cannula is irreversibly retained entirely within the outer tube when the collar is attached to the distal end of the barrel and the collar pin is in a locking position in the track between the pre-injection position and the full-insertion position.

2. The needle safety device according to claim 1 , wherein the track comprises:

a first track segment extending between the pre-injection position and the full-insertion position, a part of the first track segment guiding the collar pin to slideably move simultaneously in translation and rotation only in the distal direction and in a first rotational direction about the longitudinal axis, when an applied force greater than the biasing force moves the outer tube in the proximal direction;

a second track segment contiguous with the full-insertion position of the first track segment, a part of the second track segment guiding the collar pin to slideably move simultaneously in translation and rotation only in the proximal direction and a second rotational direction opposite the first rotational direction when the biasing force moves the outer tube in the distal direction; and

a third track segment contiguous with the second track segment, a part of the third track segment forming the locking position in which the collar pin is irreversibly retained.

3. The needle safety device according to claim 2 wherein the part of the first track segment is a generally arcuate first-track-segment second portion and the first track segment further comprises:

an axially-extending first-track-segment first portion within which the collar pin is constrained to move only in translation in the distal direction parallel to the longitudinal axis of the outer tube, when an applied force greater than the biasing force moves the outer tube in proximal direction, the first-track-segment first portion preceding and contiguous with the first-track-segment second portion; and

a first-track-segment third portion contiguous with the first-track-segment second portion and within which the collar pin is constrained to move only in translation in the distal direction, when an applied force greater than the biasing force moves the outer tube in proximal direction.

4. The needle safety device according to claim 2 wherein, the part of the second track segment is a generally arcuate second-track-segment second portion and the second track segment further comprises:

an axially-extending second-track-segment first portion within which the collar pin is constrained to move only in translation in the proximal direction when the biasing force moves the outer tube in the distal direction, the second-track-segment first portion preceding and contiguous with the second-track-segment second portion.

5. The needle safety device according to claim 2 , wherein the part of the third track segment is a third-track-segment second portion angled with respect to the longitudinal axis of the outer tube and the third track segment further comprises:

an axially-extending third-track-segment first portion within which the collar pin is constrained to move only in translation in the proximal direction when the biasing force moves the outer tube in the distal direction, the third-track-segment first portion preceding and contiguous with the third-track-segment second portion; and

a third-track-segment third portion which is contiguous with the third-track-segment second portion and extends axially in the distal direction and circumferentially in the second rotational direction forming a lock preventing axial movement of the collar pin.

6. The needle safety device according to claim 1 , wherein the biasing member surrounds the cannula shield.

7. The needle safety device according to claim 1 , wherein the outer tube is disposed in the cap, and the cap is releasably retained by the outer tube.