CONTROLLING THE RETRACTION OF A NEEDLE IN AN AUTO RETRACTABLE SYRINGE

摘要

Means to control the retraction of an auto-retractable safety syringe to minimise splashback or splatter is disclosed. The end of a hollow plunger (11) is covered by a sealing member (14) that, upon retraction, is dislodged so that the needle assembly and seal enters the hollow plunger. Three methods by which the auto-retraction is controlled are disclosed. Firstly there is provided a taper within the inside of the hollow plunger which creates varying resistance of movement to the sealing member. Secondly there is provided a bleed hole (15) at the upper end of the plunger, whereby the air is allowed to escape. Thirdly, there is provided on or more grooves (16) in the periphery of the plunger seal so that air is allowed to be released, thereby reducing the pressure in the plunger and hence the possibility of splashback.