Blood collection set

A needle assembly comprising:

• a needle cannula having opposed proximal and distal ends and a lumen extending therebetween;
• a hub having opposite proximal and distal ends, an inner ate with a passage extending between said proximal and distal ends of said hub, portions of said inner tube at said distal end of said hub being connected to said proximal end of said needle cannula such that the lumen through the needle cannula communicates with the passage through the inner tube, an outer tube surrounding the inner tube, a longitudinal slit extending through said outer tube from said proximal end to said distal end of said hub, the outer tube further comprising a pair of transverse wings disposed on opposite respective sides of the slit, the wings being deflectable toward one another for deflecting said outer tube into a position for narrowing said slit, a cylindrical space between said inner and outer tubes and extending proximally from said distal end of said hub;
• a first biasing element engaging portions of said outer tube on opposite respective sides of said slit, for widening said outer tube at said slit and increasing cross-sectional dimensions of said cylindrical space;
• a shield disposed within outer tube of said hub and telescoped over said inner tube and said needle cannula, said shield being cross-sectionally dimensioned to be clamped in a fixed position by said outer tube when said outer tube is biased against forces of said first biasing element to close said slit, said shield further being dimensioned to move relative to said outer tube when said first biasing element biases said slit open;
• a second biasing element captured between said hub and said shield and being operative for propelling said shield from a proximal position where said needle cannula is exposed to a distal position where said needle cannula is shielded.