Medical device with a lockable needle shield

Claim 1

A medical device comprising: a barrel having proximal and distal ends; a needle extending from the distal end of the barrel and terminating in a point; a shield coaxially and rotationally mounted on said barrel, said shield being axially movable between a retracted position in which said needle point is exposed and an extended position in which said needle point is covered; means associated with said barrel and said shield and responsive to a combined rotational is axially distal movement of said shield, when said shield is at an extended and unlocked position, for locking said shield on said barrel at said extended position and for preventing subsequent rotational and axial movement of the shield on the barrel, said means including a collar at the distal end of the barrel, said collar forming a raised annulus around an outside surface of the barrel, said collar having a first locking surface and a second locking surface and at least one slot extending through said collar between said surfaces, said means further including at least one locking protuberance extending inwardly from an interior surface of said shield, said protuberance being sized to pass through the slot in said collar when the shield is in said extended position and, upon rotation of said shield, said protuberance being adapted to engage the first locking surface of said collar thereby preventing retrograde axial movement of said shield with respect to said barrel; means associated with the shield for guiding the movement of the shield from the retracted to the extended position and for facilitating the function of the means for locking the shield on said barrel at said extended position; and means associated with the shield for preventing movement of the shield from its retracted position toward the extended position but being responsive to rotation of said shield with respect to said barrel for permitting such movement, said means for preventing including a locking projection extending inwardly from the interior of said shield and spaced rotationally from said means for guiding, said projection adapted to engage said slot when the shield is in its retracted position and, upon rotation of said shield with respect to said barrel, to become removed from said slot whereby said shield is unlocked for movement to its extended position.