Tamper-alerting hypodermic syringe

Abstract

The inside surface of the glass tubular member of the hypodermic syringe cartridge is made rough along a strip which extends substantially the length of the cartridge. A piece of a solid but easily abradable material is retained on the circumference of the rubber drive piston, and the resiliency of the rubber drive piston squeezes the abradable material against the rough strip on the inside wall of the glass tubular member. As the drive piston is advanced to express fluid from the syringe, some of the abradable material becomes lodged in the rough surface where it remains even after the drive piston has been retracted to its original position. In another embodiment the marking substance is a fluid, paste, or liquid which is stored in a reservoir inside the drive piston and which is squeezed out of the drive piston by the compressive forces that act on the drive piston as it is being advanced.

Dependencies are inferred from the claim text.