Disposable syringe with automatic needle retraction

#The present invention relates generally to medical instruments, and more particularly to a safety-disposable medicinal syringe. Still more particularly, the present invention relates to a disposable syringe having a releasable needle hub which, when released, is actuated by ambient air pressure into retraction into an evacuated plunger, carrying the needle with it.

#A problem for doctors, nurses, and other health care personnel who use or handle medicinal syringes is accidental puncture of the skin by the needle. The problem can be very serious if the needle has been used. Potentially fatal diseases, such as hepatitis or Acquired Immune Deficiency Syndrome (AIDS), can be contracted if the needle has been used on an infected subject.

#The syringe needle is typically covered with a removable sheath prior to and following use to prevent accidental contact, but the act of replacing the sheath after use can still result in accidental skin puncture. Also, if the sheath is not securely repositioned, the danger exists that personnel subsequently involved in disposal of the device may become infected by accidental puncture.

#FIG. 1 is an exploded pictorial view of a syringe of a preferred embodiment of the invention.

#FIG. 2 is a vertical cross-sectional view of the syringe of FIG. 1 prior to use.

#FIG. 3 is a vertical cross-sectional view of the syringe of FIG. 1 following use and actuation of the automatically retractable needle of the invention.

#While the invention is satisfied in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention, with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and is not intended to limit the scope of the invention to the embodiments illustrated.

#The embodiment shown as syringe assembly 10 in FIGS. 1-3 includes a hypodermic needle 14 that is inserted and mounted into a needle hub 16 in such a manner that the interior bore of the needle communicates with the exterior of the hub via a transversely extending hole 22 in the hub. Hub 16 is releasably attached to the interior of syringe barrel 12 in such a manner that it forms a circumferential seal around the inner periphery of the barrel at its distal end a. Barrel 12 and hub 16 may be made of plastic, glass, or other materials suitable to the intended use of the device.

#Slidably disposed within the barrel 12 is a hollow plunger tube 20 made of plastic, glass, or the like, which is sealed at its distal and proximal ends by a barrier seal member 28 and a cap 21, respectively. Cap 21 may be, for example, a thin round disc-like member having a circular boss 61 protruding therefrom and receivable within the interior of plunger 20. Alternatively, the cap may have a circular wall extending from the disc surface and adapted for receiving the exterior of the plunger therewithin. Other means of mounting a cap on the proximal end of plunger 20 will no doubt be readily apparent to those skilled in the art. During or after the process of sealing cap 21 to plunger tube 20, the air is removed from the sealed interior of the plunger, leaving a vacuum 24 within the plunger tube 20. Cap 21 may be made of plastic, rubber, glass, metal or the like.