A - Human Necessities
61
B
128/83
A61B 5/15 (2006.01)
Patent
CA 1109745
SYRINGE ABSTRACT Improved disposable syringe for taking arterial blood samples for blood gas testing and for administering epi- dural anaesthesia, wherein the syringe plunger has a compressible elastomeric tip member which has a peripheral annular wiper extending axially forwardly toward the syringe floor and radially outwardly at an acute angle to the longitudinal center line of the barrel and plunger to form an excellent seal with the inner surface of the syringe barrel while at the same time providing only a gentle pressure against such surface and hence an exceptionally low resistance to axial movement of the tip member and plunger. The tip member and barrel floor are designed so that when the tip member is moved to its furthest point forwardly into engagement with the floor of the syringe barrel, e.g., to eject air and excess liquid anti-coagulant, a sea]. is formed between the forward end of the tip member and the portion of the barrel floor immediately adjacent the needle opening in such floor upon initial contact of the tip member with such floor to prevent further flow of liquid out of such barrel and thereby trap a predetermined amount of the liquid in a space of predetermined volume remaining between the tip member and barrel floor. The trapped liquid acts as a stop to prevent deformation and com- pression of the tip member against the barrel floor The plunger and tip member are also designed so that when the tip member initially engages the barrel floor as aforesaid to seal the needle opening and further forwardly directed axial force on the plunger is substantially restricted to that portion of the tip member which is behind the trapped liquid with a minimum of force being applied to the portion of the tip member located behind the needle opening whereby distortion of such tip member into such opening is minimized. This, in combination with the aforesaid liquid stop minimizes the intake of air upon release of inward force on the plunger after it has been moved to its for- wardmost position against the barrel floor to eject air and excess anti-coagulant prior to taking a blood sample.
298486
Ridout & Maybee Llp
Sims Portex Inc.
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