Safety syringe

This invention is an improvement of U.S. Pat. No. 5,533,975 (hereinafter called “prior art”) also invented by the present inventor.

The prior art disclosed a safety syringe for automatically tilting a used needle when retracted into the syringe to prevent re-protrusion of the needle outwardly. A cylindrical recess 125 is recessed in the front portion of the syringe 1 provided with two wedged extensions 126 formed on the recess 125 for retarding two bars 225 diametrically formed on a cylindrical portion 224 of the shank portion 22 of the needle assembly, thereby preventing rotation of the shank portion when rotatably coupling the needle portion 21 and the shank portion 22 . However, such a cylindrical recess 125 will be accumulated with liquid medicine to form a “dead pool” which can not be completely injected into a patient, causing waste of the medicine.

The present inventor has found the drawbacks of the prior art and invented the present improved safety syringe.

The object of the present invention is to provide a safety syringe including: a syringe cylinder having a plurality of sleeve ribs formed in a sleeve portion of the syringe cylinder, a needle device having a needle detachably coupled on an shank portion which is provided with a plurality of shank ribs on the shank portion to be engaged with the sleeve ribs in the sleeve portion, with the needle device retractable in and automatically biased in the syringe cylinder to prevent outward protruding of used needle; whereby upon external connecting and rotative coupling of the needle on the shank portion, the shank portion will be locked without being rotatable, thereby enhancing a smooth coupling of the needle on the shank portion of the needle device.

Another object of the present invention is to provide a safety syringe including an annular extension annularly formed on an inside wall of the syringe cylinder adjacent to a rear end of the syringe cylinder and at least a ratchet tooth formed on a front portion of a plunger slidably held in the syringe cylinder; whereby the annular extension provides a stopper for preventing a rearward releasing of the plunger from the cylinder since the ratchet tooth on the plunger will be locked against the annular extension when accidentally pulling the plunger rearwardly outwardly.

FIG. 1 is a sectional drawing showing a shank portion of a needle device separated from a syringe cylinder of the present invention.

FIG. 2 is a sectional drawing of the present invention when assembled from FIG. 1 .

FIG. 3 is a sectional drawing showing the engagement of the needle device with the plunger when finishing an injection in accordance with the present invention.

FIG. 4 shows a retracted and tilted needle in a syringe cylinder of the present invention.

FIG. 5 is an illustration showing the prevention of an outward releasing of the plunger from the syringe cylinder.

FIG. 6 shows another embodiment of the plunger means having ratchet tooth formed thereon.

As shown in FIGS. 1 ˜ 5 , the safety syringe of the present invention comprises: a syringe means 1 ; a needle device 2 detachably secured on the syringe means 1 ; and a plunger means 3 slidably held in the syringe means 1 .

The syringe means 1 includes: a syringe cylinder 11 having an interior 10 for filling liquid medicine therein, a sleeve portion 12 formed on a front portion of the cylinder 11 having a sleeve hole 12 a formed through the sleeve portion 12 , a shoulder portion 13 formed in between the sleeve portion 12 and the cylinder 11 , a syringe handle 14 formed on a rear end of the cylinder 11 , and an annular extension 15 annularly formed on an inside wall of the cylinder 11 adjacent to the syringe handle 14 .

The sleeve portion 12 has a plurality of sleeve ribs 12 b longitudinally formed on an inside wall of the sleeve hole 12 a , and a shallow recess 12 c recessed in a rear portion of the sleeve portion 12 and having a diameter of the shallow recess 12 c slightly larger than the diameter of the sleeve hole 12 a (FIG. 4 ).

The needle device 2 includes: a hollow needle 21 having a needle hole 20 formed through the needle 21 and having a coupling sheath 21 a secured to a rear portion of the needle 21 and formed with female threads 21 b in the coupling sheath 21 a ; a shank portion 22 detachably secured in the sleeve hole 12 a of the sleeve portion 12 to be coupled with the coupling sheath 21 a of the needle 21 ; and a locking head portion 23 formed on a rear end of the shank portion 22 having a discharge slot 24 formed in the locking head portion 23 and in the shank portion 22 to be fluidically communicated with the needle hole 20 of the hollow needle 21 for passing the liquid medicine through the relevant holes 24 , 20 to be injected into a patient's body.

The shank portion 22 includes: a shallow disk portion 22 a formed on a rear end of the shank portion 22 to be engaged with the shallow recess 12 c when securing the shank portion 22 in the sleeve portion 12 , a plurality of shank ribs 22 b longitudinally formed on a circumference of the shank portion to be engaged with the sleeve ribs 12 b in the sleeve portion 12 , a packing ring 22 c disposed about the shank portion 22 and engaged with the inside wall of the sleeve hole 12 a and forwardly retarded by the rib ends of the sleeve ribs 12 b when mounting the shank portion 12 in the sleeve portion 12 for preventing leakage during injection of the needle 21 , and a stem portion 22 d formed on a front portion of the shank portion 22 having a pair of projections 22 e circumferentially formed on the stem portion 22 d for engaging the female threads 21 b formed in the coupling sheath 21 a of the needle 21 for externally connecting the coupling sheath 21 a of the needle with the shank portion 22 previously secured in the sleeve portion 12 of the syringe cylinder 11 .

The plunger means 3 includes: a plunger 31 secured on a front end portion 34 of a plunger rod 35 slidably held in the syringe cylinder 11 , a biasing socket 32 recessed in the plunger 31 for engaging the locking head portion 23 of the needle device 2 through a guiding port 33 formed in the plunger 31 after finishing the injection, and at least a ratchet tooth 35 b formed on a rear portion of a circular disk 35 a (having arcuate front edge portion on the disk 35 a ) formed on a front portion of the plunger rod 35 , with the ratchet tooth 35 b operatively retarded against the annular extension 15 formed in the cylinder 11 when pulling the plunger rod 35 rearwardly outwardly (FIG. 5) for preventing a rearward releasing of the plunger means 3 from the cylinder 11 after finishing the injection.

When assembling the hollow needle 21 of the present invention, the coupling sheath 21 a of the needle 21 is rotated to engage the female threads 21 b therein with the projections 22 e on the stem portion 22 d , the shank ribs 22 b will be engaged and retarded by the sleeve ribs 12 b in the sleeve portion 12 to prevent from a rotation of the shank portion 22 , thereby allowing a smooth rotation of the coupling sheath 21 a about the shank portion 22 until firmly securing the sheath 21 a (of the needle 21 ) on the shank portion 22 which is already secured in the sleeve portion 12 of the syringe means 1 .

The cylindrical recess 125 and the extensions 126 as provided in the front portion of the syringe of the prior art are now eliminated, indicating that there is no “dead pool” formed in the front portion of the syringe cylinder of the present invention and thereby exhausting all liquid medicine in the cylinder after completing the injection without wasting the liquid medicine and being superior to the prior art.

After completing the injection, the locking head portion 23 of the needle device 2 as engaged with the biasing socket 32 in the plunger will be simultaneously retracted into the cylinder 11 and will be automatically tilted from the axis X (from FIG. 3 to FIG. 4) for a safe protection of the syringe.

The ratchet tooth (or teeth) 35 b as recessed or formed in a rear portion of the circular disk 35 a of the plunger means 3 can be plural ratchet teeth 35 b (the number and shapes of teeth being not limited) circumferentially formed in a front portion of the plunger rod 35 as shown in FIG. 6 or may be formed as an annular ratchet tooth 35 b annularly formed on a front portion of the plunger rod 35 as shown in FIG. 5 .

The arcuate front edge portion of the circular disk 35 a on the front end portion of the plunger rod 35 may be smoothly inserted into the interior 10 of the syringe cylinder 11 by passing through the annular extension 15 when assembling the plunger means 3 in the cylinder 11 . However, when rearwardly pulling the plunger rod 35 as shown in FIG. 5, the ratchet tooth (or teeth) 35 b will be retarded or locked on the annular extension 15 to thereby prevent from an outward rearward releasing of the plunger means 3 from the cylinder 11 , especially when coupled with a tilted needle 21 thereon (FIGS. 4 & 5 ).

Accordingly, the present invention really provides a safety syringe to prevent from a forward protruding of a used needle as retracted in the syringe cylinder (FIG. 4 ); and also to prevent from a rearward releasing of the plunger 31 coupled with the used needle 21 from the cylinder 11 (FIG. 5 ). The used needle 21 will be well “trapped” in the cylinder 11 for absolutely ensuring the safety protection of a syringe (for preventing from sticking injury of a used needle to a nurse, a doctor, a hospital cleaner or housekeeper, etc.)

The present invention may be modified without departing from the spirit and scope of the present invention.

The present invention may be used for hypodermic injection and may also be modified to be used for intravenous injection.