capable of temporarily displacing the locking member as it enters the needle shield cavity the locking member must also exhibit sufficient rigidity to resist displacement so that the needle cannula once entrapped cannot easily be re exposed by pivoting the needle shield and deflecting the locking member in accordance with a preferred embodiment of the invention the locking member 60 is integral with a sidewall of the needle shield 26 these elements are preferably constructed from a semi rigid plastic material such as polypropylene the locking member includes a base portion 60 a and three end portions 60 b it includes a tapered body that is thickest where it adjoins the wall of the needle shield the base portion is relatively rigid and substantially more resistant to deflection than the end portions this is due to several reasons including the relative thickness of the two portions the location of the base portion and the gaps between each of the end portions fig8 13 show in sequence the needle cannula 30 entering the cavity 58 of the needle shield 26 becoming trapped within the shield and engaging the locking member upon attempted pivoting of the needle shield 26 about the hinge pin from the needle cannula protective position referring first to fig8 the needle cannula 30 is shown entering the cavity 58 of the needle shield as the needle shield is pivoted from the position shown in fig5 to the protective position the angular orientation of the locking member 60 away from the cavity opening is clearly shown the locking member forms an angle a as shown in fig8 with the sidewall of the.