Abstract:
A retractable hypodermic safety syringe device is provided for encapsulating a needle after use to prevent accidental needlesticks. The retractable syringe device includes a syringe barrel having one or more locking tabs for securing a needle carrier. A hypodermic needle attached to the needle carrier. A plunger having a piston slideably mounted within the syringe body. Locking fingers on the needle carrier for receiving the plunger.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         REFERENCE TO A MICROFICHE APPENDIX  
         [0003]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0004]    1. Field of the Invention  
           [0005]    The present invention relates to a retractable hypodermic safety syringe. In particular, the present invention relates to a safety syringe for completely encapsulating a needle after use to prevent accidental needlesticks or reuse of the needle.  
           [0006]    2. Description of the Related Art  
           [0007]    Healthcare workers in the United States suffer over a half million needlesticks each year. From these needlestick injuries healthcare workers contract HIV, become infected with hepatitis C and hepatitis B, and acquire such infectious diseases as tuberculosis, syphilis, malaria, herpes, diphtheria, gonorrhea, typhus and Rocky Mountain spotted fever.  
           [0008]    Healthcare workers worldwide are concerned about accidental needlesticks resulting in life-threatening infections. Often, healthcare workers become patients after being injured by contaminated needles. These healthcare workers contract potentially deadly infections from needlestick injuries that are largely preventable.  
           [0009]    Many methods and devices have been created to reduce accidental needlesticks by contaminated needles. An example of such a device is shown in U.S. Pat. No. 4,790,822. This patent discloses a retractable hypodermic safety syringe that retracts the used needle into the barrel of the syringe after use. A disadvantage of this design, however, was the expense and the difficulty of manufacture related to the molded internal parts of the syringe barrel, such as shoulders. Another disadvantage included the close tolerances [on what parts?] Another disadvantage of this device was the inability to evacuate the entire contents of the cavity.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    Briefly, the present invention provides an improved retractable hypodermic safety syringe that allows the needle to be retracted into the syringe cylinder after an injection has been given without the practitioner contacting the needle, thereby avoiding contamination by infectious agents. The retractable syringe device is simple and convenient to use. Additionally, the retractable syringe device is easy to manufacture because there are few internal parts molded to the inside of the syringe barrel. Moreover, the device includes locking and releasing tabs that provide a positive locking mechanism without the need for close tolerance snap fittings. Further, the retractable syringe device provides a means for evacuating the entire contents of the syringe barrel and needle carrier cavity.  
           [0011]    The retractable syringe device includes a syringe cylinder, and a needle carrier for securing a hypodermic needle. A plunger snap coupling engages the needle carrier, allowing the needle carrier to be slid into the cylinder as the plunger is retracted to a locked position. As this snap coupling occurs, further pressure on the plunger also releases a set of positive locking tabs that secure the needle carrier to the syringe cylinder. This set of locking tabs insures that the needle carrier will not become dislodged during normal operation of loading and injecting medications. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0012]    A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which:  
         [0013]    [0013]FIG. 1 is an elevational view of the retractable hypodermic safety syringe of the present invention;  
         [0014]    [0014]FIG. 2 is a side elevational view of the device in FIG. 1;  
         [0015]    [0015]FIG. 3 is a side elevational view, partially in section, as viewed along line  3 - 3  of FIG. 2;  
         [0016]    [0016]FIG. 4 is a side elevational view, partially in section, of the device in FIG. 1;  
         [0017]    [0017]FIG. 5 is an expanded side elevational view, partially in section, of a portion of the device within circle  5  of FIG. 4;  
         [0018]    [0018]FIG. 6 is a side elevational view, partially in section, of the device in FIG. 1;  
         [0019]    [0019]FIG. 7 is an expanded side elevational view, partially in section, of a portion of the device within circle  7  of FIG. 6;  
         [0020]    [0020]FIG. 8 is a side elevational view, partially in section, of the device in FIG. 1;  
         [0021]    [0021]FIG. 9 is a side elevational view, partially in section, as viewed along line  9 - 9  of FIG. 8;  
         [0022]    [0022]FIG. 10 is an expanded side elevational view, partially in section, of a portion of the device within circle  10  of FIG. 8;  
         [0023]    [0023]FIG. 11 is a side elevational view of the device in FIG. 1;  
         [0024]    [0024]FIG. 12 is a side elevational view, partially in section, of the device in FIG. 11; and  
         [0025]    [0025]FIG. 13 is an expanded side elevational view, partially in section, of a portion of the device within circle  13  of FIG. 12. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    A retractable hypodermic safety syringe device  30  according to the present invention is shown in FIG. 1 prior to use. The retractable syringe device  30  includes a syringe barrel or body  1  for holding injectable fluids. A plunger  14  is inserted at one end of the syringe barrel  1 . The opposite end of the syringe barrel  1  includes a needle carrier  4  which receives a hypodermic needle  13  for injecting patients.  
         [0027]    The syringe barrel  1  includes locking tabs  3  for securing the needle carrier  4  to the syringe body  1  prior to retraction of the needle  13  into the syringe body. In the preferred embodiment, the locking tabs  3  are molded into the wall of the syringe body  1 . A notch  21  on the needle carrier  4  receives a lip portion  32  of the locking tabs  13  and secures the needle carrier  4  within the syringe barrel  1 . The syringe barrel  1  also includes a lower body portion  23  for abutting the needle carrier  4  on a front surface  7 . The combination of the locking tabs  3  and the lower body  23  works to retain the needle carrier  4  within the syringe barrel  1  during loading of the syringe and injecting of the fluid into a patient.  
         [0028]    Referring to FIGS. 2 and 3, the retractable syringe device  30 , is shown with the plunger  14  in the fully retracted position. The plunger  14  includes a piston  15  and a plunger snap  16  extending from the piston for engaging the needle carrier  4 . Outward travel of the plunger  14  within the syringe barrel  1  is limited by a plunger seal interference ring  26  located on the interior of the syringe barrel  1 . Typically, the syringe barrel is made from a mold which includes relief for the interference ring  26 . A plunger seal  24  secured to the plunger  14  includes a plunger wiping ring  25  which contacts the interference ring  26  when the plunger  14  is extracted during loading of the syringe barrel.  
         [0029]    The needle carrier  4  includes the notch  21  for receiving the locking tabs  3  to secure the needle carrier  4  to the syringe barrel  1 . The needle carrier  4  also includes a carrier seal  5  sized to be in an interference fit with the inner wall on the syringe body  1 . The carrier seal  5  prevents fluid from leaking out of the syringe barrel  1 . Fingers  9  for receiving the plunger snap  16  extend from a cavity  6  of the needle carrier  4 . The needle  13  includes a conical fitting  12  which is pressed and sealed onto a carrier conical fitting  8 .  
         [0030]    Referring to FIGS. 4 and 5, the plunger  14  is pushed into the syringe barrel  1  by means of a plunger grip  20  and a syringe body grip  2  until resistance is felt due to the contact of the snap  16  with the locking fingers  9 . The resistance occurs when the load is ejected from the syringe and when the syringe is being loaded with fluid. Upon feeling the resistance, the user appreciates that the plunger snap  16  is almost engaged by the FIG. 9 of the needle carrier  4 . At this point, the plunger piston  15  is moved into the geometrically matching cavity  6 , which purges the load (or air, if in fill mode) from the cavity  6 .  
         [0031]    As shown in FIGS. 6 and 7 when the injection is finished and it is desired to set the needle  13  to the safe position (as shown in FIG. 12) the user must apply sufficient pressure to the plunger grip  20  to spring the carrier locking fingers  9  open and allow the plunger snap  16  to pass through and lock behind the carrier locking fingers  9 . As shown in FIGS. 8-10, as the user continues to apply pressure to the plunger grip  20 , a plunger push surface  17  contacts a rear surface  11  of the needle carrier  4  until a plunger stop  19  on the plunger  14  contacts the syringe body grip  2 .  
         [0032]    At this point, the needle carrier  4  has moved sufficiently to allow the locking tabs  3  to release from the notch  10  of the needle carrier  4 . The locking tabs  3  are sprung to the position shown in FIG. 10, returning to their normal “as molded,” pre-loaded position. To insure the locking tabs  3  are ejected from the notch  10 , a carrier tab ejection surface  21  on the needle carrier  4  is used to push the locking tabs  3  outward as the needle carrier  4  is pulled back by the plunger  14 .  
         [0033]    For the device to work properly, the force to slide the needle carrier  4  and release the locking tabs  3  must be greater than the snap mechanism comprised of the plunger snap  16  and the fingers  9 . This insures that the locking tabs  3  do not disengage until the plunger grip  20  has had sufficient force applied to cause the snap engagement of the plunger snap  16  and fingers  9 . The force required for releasing the tabs  3  is much greater than what is felt in normal filling and dispensing of the load. As a result, the locking tabs  3  will stay engaged until the user desires release of the needle carrier  4 .  
         [0034]    Referring to FIGS. 9 and 10, as the needle carrier  4  is pushed by the plunger  14 , a carrier front surface  7  contacts a syringe body ramp  22  on the lower body portion  23 , which causes the lower syringe body  23  to flex outward. The force required to cause the flex and allow travel of the needle carrier  4  is greater than the force required to engage the plunger snap  16  and the carrier locking fingers  9 , thereby insuring the locking tabs  3  are held in place in the notch  10  until after this snap occurs. The deflection force of the lower syringe body  23 , as shown in FIG. 9, is applied by the distortion strain of the circular cross section geometry, as relieved by a syringe body slot  27 .  
         [0035]    Referring to FIGS. 11-13, with locking tabs  3  disengaged, the plunger  14  can now be pulled to the fully retracted position by the plunger grip  20  until the plunger wiping ring  25  passes the plunger seal interference ring  26 , indicating to the user the end of travel of the plunger  14 . At this point the plunger  14  can be broken at a plunger break-off notch  18 , leaving the plunger piston  15 , plunger seal  24 , needle carrier  4 , and needle  13  inside the syringe body  1 . This assembly is held in position by the plunger wiping ring  25  and the plunger seal interference ring  26 . The needle  13  is recessed a distance  28  to protect the user from needlesticks.