Medical syringe - has piston connected to rod via thin partition which breaks to prevent second use

摘要

A medical syringe, designed to be used once only, consists of a barrel with a cylindrical inner chamber, and a piston (15) which fits into the chamber and is connected to a hollow rod (16) via a thin partition (32). The piston also has a seal element (19) made from a base (25) and a cylindrical skirt (26) round it on the opposite side to the rod. The partition (32) is thick enough to withstand the force (F1) applied to the rod to fill the syringe, but it breaks under the effort required to push the piston down the barrel. As a result the rod applies a pressure directly against the piston, but it cannot be withdrawn for a second filling. ADVANTAGE - Design simplicity and low cost is obtd. while preventing second use.