Single-use syringe

An operable syringe assembly comprising:

• a barrel having an inside surface describing a chamber for retaining fluid, said barrel having an open barrel end and a distal barrel end having a passageway therethrough in fluid communication with said chamber;
• a plunger rod having an elongate body portion, a proximal end, and a distal end;
• a stopper at said distal end, said stopper being slidably positioned in fluid-tight engagement in said barrel;
• a locking element positioned in said barrel between said elongate body portion of said plunger rod and said inside surface of said barrel, said locking element including a proximally and outwardly facing locking barb, a distally and inwardly facing resisting edge and an inwardly facing driving edge, said driving edge adapted to interact with said body portion of said plunger rod to move said locking element along said barrel as said stopper is advanced distally along said barrel, said resisting edge and said barb adapted to prevent proximal motion of said plunger rod with respect to said barrel after initial distal motion of said stopper to expel fluid through said passageway wherein proximal motion of said plunger rod with respect to said barrel causes said resisting edge to engage said plunger rod causing said locking element to move in a proximal direction wherein said locking barb engages said inside surface of said barrel to prevent further movement and allowing only distal movement of said plunger rod with respect to said barrel;
• and
• barrier means on said elongate body portion for limiting the delivery volume of said syringe assembly by establishing the maximum proximal position of said locking element with respect to said elongate body portion.

A syringe assembly having single use features comprising:

• a plastic barrel having an inside surface describing a chamber for retaining fluid, said barrel having an open proximal end and a distal barrel end having a passageway therethrough in fluid communication with said chamber;
• a plunger rod including an elongate body portion having a longitudinal recess, a proximal end, and a distal end, and a stopper at said distal end, said stopper being slidably positioned in fluid-tight engagement in said barrel, said body portion extending outwardly from said proximal open end;
• a metal locking element positioned in said barrel between said longitudinal recess of said plunger rod and said inside surface of said barrel said recess acting as a pathway for the longitudinal motion of said locking element relative to said elongate body portion, said element having a proximal portion and a distal portion, said locking element including a proximally and outwardly facing locking barb, a distally and inwardly facing resisting edge and an inwardly facing driving edge at said proximal portion of said element, said driving edge adapted to interact with said longitudinal recess of said plunger rod to move said locking element along said barrel as said stopper is advanced distally along said barrel by force applied to said plunger rod, said resisting edge and said barb adapted to prevent proximal motion of said plunger rod with respect to said barrel after initial distal motion of said stopper to expel fluid through said passageway wherein subsequent proximal motion of said plunger rod with respect to said barrel causes said resisting edge to engage said longitudinal recess causing said locking element to move in a proximal direction wherein said locking barb engages said inside surface of said barrel to prevent further movement and allowing only distal movement of said plunger rod with respect to said barrel;
• and
• barrier means in said longitudinal recess for limiting the delivery volume of said syringe assembly by establishing the maximum proximal position of said locking element with respect to said elongate body portion.