Abstract: A needle guard for a hypodermic syringe to prevent repuncture by a used needle. The needle guard comprises a flexible double-walled membrane which is shaped to define a closed toroidal chamber which, under atmospheric pressure, is conical in shape and defines a hollow interior with an opening thereto for passage of the needle. The toroidal chamber is partially evacuated and folded inwardly upon itself with a needle passing through the opening for normal use of the needle. Upon release of the partial vacuum, the entrance of air into the toroidal chamber effects expansion of the needle guard into the shape of a cone with the needle contained within the hollow interior thereof so that needle-stick or re-use of the needle may be prevented.

Abstract: The invention features a needle guard for a hypodermic syringe that will prevent repuncture by a used needle. The needle guard has a flexible membrane that expands when pressure actuated to cover and protect the injecting tip of the syringe needle. The membrane is characterized by a small, unobtrusive profile in the inactivated state.