Syringes are in common use today for hypodermic injection. Often these syringes are disposable syringes intended for only one use. However, these syringes are capable of repeated reuse if a user so desires. A serious problem today is that syringes are obtainable by intravenous drug addicts who repeatedly reuse and share the same syringe with other drug addicts without proper sterilization between each use. Hence, any blood-borne infectious disease that one such addict has is spread to those with whom he shares his syringes. This mechanism is thought to be a major cause of the spread of the current AIDS epidemic, as well as contributing to the spread of hepatitis, venereal disease, and other blood-borne diseases.
Recognizing the problem with the use of injectible drugs, several U.S. patents have addressed the problem by disclosing self-destructible syringes which render themselves unreusable.
U.S. Pat. No. 3,747,812, issued to Karman, et al. on July 24, 1973 discloses a syringe with a plunger shaft having a shear zone. This shear zone is utilized for breaking the shaft after a vacuum is produced following the withdrawal of fluids from a human body. To prevent reuse, the user of the syringe applies torque to the plunger, thereby breaking the shaft.
U.S. Pat. No. 3,478,937, issued to I, Solowey discloses a non-reusable syringe with a locking plunger. The upper end of the plunger has a collar unit which pushes through the collar at the top of the barrel on the downstroke. The collar expands, thereby locking the plunger and preventing reuse of this syringe after a single depression thereof.
U.S. Pat. Nos. 3,951,146; 3,998,224; and 4,391,273, issued to Chiquiar-Arias, disclose various forms of disposable, self-destructible syringes having blades attached to the piston which cut through the body of the syringe to prevent reuse, or sharp pins attached to the piston that puncture the body of the syringe.
U.S. Pat. No. 4,367,738, issued to Legendre, et al., discloses a non-reusable syringe having spikes attached to the shaft. The spikes pass inwardly through the body of the syringe and expand so as not to pass out backwardly.
Unfortunately, none of these prior-art patents have a feature in which the shaft of the plunger is disconnected from the piston of the syringe. In many cases, the disabling feature is not automatic. These prior-art devices allow the disabling feature to be neutralized by direct access or tampering prior to use. With these prior-art devices, the self-destructing feature is typically discretionary in the user.
It is an object of the present invention to provide a syringe that is self-destructing following a single use.
It is another object of the present invention to provide a self-destructible syringe that avoids tampering.
It is another object of the present invention to provide a disposable syringe to deter the spread of fatal infectious disease and to deter the theft and abuse of controlled substances.
It is still another object of the present invention to provide a self-destructible syringe that is relatively easy to manufacture, low in cost, and conventional in its single use.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.