Patent Publication Number: US-6669666-B2

Title: Safety syringe

Description:
BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
    
    
     DETAILED DESCRIPTION 
     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&#39;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  &amp;  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.