Protective device for cannula used to draw blood

A protective device for a cannula used to draw blood, the device comprising:

• an elongated sheath open at one end and including a longitudinal slot;
• stop means at the other end of the sheath;
• a piston disposed in the sheath to be longitudinally slidable between an extended position against the stop means and a retracted position away from the stop means, the piston having a bore extending through it in the direction in which the piston slides;
• means for securing an elongated cannula in the piston bore so the cannula extends longitudinally through the bore with one end of the cannula in the sheath and the scarf end of the cannula extending outwardly away from the sheath when the piston is in the extended position;
• slidable means rigidly secured to the piston and extending away from the piston through the longitudinal slot in the sheath so the slidable means and the sheath may be manipulated with one hand to move the piston away from the stop means to the retracted position so the outwardly extending scarf end of the cannula moves to a safely enclosed position within the sheath;
• and
• longitudinally extending detent means adjacent the end of the slot near the end of the sheath with the stop means for releasably holding the piston in the extended position adjacent the stop means and so the piston can be moved with one hand from the extended to the retracted position without rotating the piston relative to the sheath.