Unidirectional blunting apparatus for hypodermic needles

Claim 1

A needle assembly comprising: a tubular needle having a proximal end, a sharpened distal tip, and a lumen extending longitudinally therethrough; a needle hub attached to the proximal end of the needle and defining a longitudinally extending bore which fluidly communicates with the lumen of the needle; a blunting member having a proximal end and a blunt distal end, the blunting member being movable relative to the needle from a non-blunting position whereat the distal end is located within the lumen at a prescribed distance proximal to the distal tip, to a blunting position whereat the distal end protrudes from the distal tip; and a positioning member attached to the blunting member and comprising: a body attached to the proximal end of the blunting member; and a series of pliable engagement fins extending outwardly from the body in spaced relation to each other and sized relative to the bore so as to be proximally deflected when distally advanced into the bore thereby frictionally engaging the needle hub; the engagement fins being initially advancable into the bore to a first position whereat at least some of the engagement fins frictionally engage the needle hub to maintain the blunting member in the non-blunting position, and thereafter further advanceable into the bore to a second position whereat additional ones of the engagement fins frictionally engage the needle hub to maintain the blunting member in the blunting position; the frictional engagement of the engagement fins to the needle hub being operable to deter proximal movement of the blunting member subsequent to its distal advancement to the blunting position thereby minimizing the risk of inadvertant penetration trauma caused by the distal tip of the needle.