Abstract:
A safety hypodermic syringe is disclosed to include a barrel, which has a front connector with a breakable connection portion connected to the peripheral wall of the barrel, a needle assembly connected to the front connector, a flexible stopper fitting the inner diameter of the barrel, a plunger, which has a stopper holder that holds the flexible stopper and a barbed retaining flange disposed at the front side for engaging two hollow retaining wings of the front connector when the plunger is pushed further forward after the service of the safety hypodermic syringe such that the front connector is separated from the barrel and received with the needle assembly to the inside of the barrel upon a return stroke of the plunger.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a hypodermic syringe and more particularly, to a safety hypodermic syringe that prevents vibration of the needle assembly and leakage of the contained fluid medicine. 
         [0003]    2. Description of the Related Art 
         [0004]    A hypodermic syringe is an important medical instrument adapted for use to inject or withdraw liquid medicines. In recent years, the spreading of AIDS and many other diseases that are difficult to treat causes many contamination accidents. In order to prevent contamination, self-destructive safety hypodermic syringes are developed. 
         [0005]    A safety hypodermic syringe is known comprising a needle assembly, a medicine barrel, a plunger, and an outer barrel. The needle assembly is fastened to the front side of the medicine barrel. The plunger is axially movably coupled to the medicine barrel and mounted with the medicine barrel inside the outer barrel. After the service of the hypodermic syringe, the plunger is pulled backwards to carry the needle cannula or the needle assembly backwards to the inside of the medicine barrel. This design of safety hypodermic syringe is functional, however it has a complicated structure and comprised of a big number of parts, resulting in a high manufacturing cost. 
         [0006]    Taiwan Patent Publication No. 540385, issued on Jul. 1, 2003, discloses a safety hypodermic syringe entitled “Two Piece Type Retractable Safety Hypodermic Syringe”. According to this design, the safety hypodermic syringe comprises a barrel, a plunger inserted into the barrel, a needle holder provided at the front side of the barrel to hold a needle, and a block with a through hole installed in the needle holder. The barrel has a tear groove on the front wall around the needle holder. After engagement of the head of the plunger with the needle holder, the plunger is pulled backwards to break the tear groove, causing the needle holder and the needle to be carried with the plunger backwards to the inside of the barrel. According to this design, the thin tear groove on the front wall of the barrel may be broken accidentally during injection or transportation of the safety hypodermic syringe, thereby causing a leakage of the fluid medicine. 
         [0007]    Further, according to conventional designs, a residual amount of the applied liquid medicine will be left in the tubular front neck of the barrel and the hub of the needle assembly after the stopper has been pushed to the front limit position and stopped at the front wall of the barrel. 
         [0008]    Therefore, it is desirable to provide a safety hypodermic syringe that eliminates the aforesaid drawbacks. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been accomplished under the circumstances in view. According to one embodiment of the present invention, the safety hypodermic syringe comprises a barrel, the barrel comprising a fluid chamber, and a front connector suspending in a front end thereof, the front connector defining an axially extending fluid passage in communication between the fluid chamber and the atmosphere, the front connector having two retaining portions protruded from the periphery thereof at two sides, a connection portion extending around the periphery of a rear end thereof and connected to the periphery of the barrel, and a tearing groove formed on the connection portion; a needle assembly, the needle assembly comprising a hub and a needle cannula forwardly extending from the hub, the hub having an axial hole disposed in fluid communication with the needle cannula and a rear coupling portion capped on the front connector of the barrel and engaged into the tearing groove; a plunger, the plunger comprising a shank, a front extension rod forwardly axially extending from a front end of the shank, and a retaining portion at the front extension rod; and a flexible stopper fitting the diameter of the fluid chamber of the barrel, the stopper having a longitudinal chamber through which the front extension rod of the plunger passes, and a front center through hole forwardly extending from the longitudinal chamber to a front side thereof and stopped in front of the retaining portion of the plunger; wherein when pushed the plunger forwards after the service of the safety hypodermic syringe, the retaining portion of the plunger is forced into engagement with the retaining portions of the front connector and the tearing groove is broken to separate the front connector from the barrel for enabling the broken front connector and the needle assembly to be pulled with the plunger backwards to the inside of the barrel upon a return stroke of the plunger at this time. 
         [0010]    The retaining portions of the front connector are hollow retaining wings; the retaining portion of the plunger is a barbed retaining flange for engaging the hollow retaining wings of said front connector. 
         [0011]    The coupling portion of the hub of the needle assembly has a beveled outer surface disposed in contact with the connection portion of the front connector of the barrel. 
         [0012]    According to another embodiment of the present invention, the safety hypodermic syringe comprises a barrel, the barrel comprising a fluid chamber, and a front connector suspending in a front end thereof, the front connector defining an axially extending fluid passage in communication between the fluid chamber and the atmosphere, the front connector having two hollow retaining wings protruded from the periphery thereof at two sides, a connection portion extending around the periphery of a rear end thereof and connected to the periphery of the barrel, and a tearing groove formed on the connection portion; a needle assembly, the needle assembly comprising a hub and a needle cannula forwardly extending from the hub, the hub having an axial hole disposed in fluid communication with the needle cannula and connected to the front connector of the barrel; a plunger, the plunger comprising a shank, a front extension rod forwardly axially extending from a front end of the shank, and a barbed retaining flange around the periphery of a front end of the front extension rod; and a flexible stopper fitting the diameter of the fluid chamber of the barrel, the stopper having a longitudinal chamber through which the front extension rod of the plunger passes, and a front center through hole forwardly extending from the longitudinal chamber to a front side thereof and stopped in front of the barbed retaining flange of the plunger; wherein when pushed the plunger forwards after the service of the safety hypodermic syringe, the barbed retaining flange of the plunger is forced into engagement with the hollow retaining wings of the front connector and the tearing groove is broken to separate the front connector from the barrel for enabling the broken front connector and the needle assembly to be pulled with the plunger backwards to the inside of the barrel upon a return stroke of the plunger at this time. 
         [0013]    The barrel further has an inside annular stop flange extending around an inside wall near a rear end thereof; the plunger has a head connected between the shank and the front extension rod, the head having a front flange and a rear flange for engagement with the inside annular stop flange of the barrel after a return stroke of the plunger after the service of the safety hypodermic syringe. The plunger further has a neck connected between the shank and the head for breaking to separate the shank from the head after engagement of the front flange and rear flange of the head with the inside annular stop flange of the barrel, and a stopper holder formed integral with the front extension rod for holding the stopper. The stopper holder has a front retaining skirt and a rear retaining skirt respectively extending around the periphery thereof; the flexible stopper having an inside annular flange formed in a rear side of the longitudinal chamber and disposed in contact with the periphery of the stopper holder between the front skirt and the rear skirt. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1   a  is an exploded view of a safety hypodermic syringe according the present invention. 
           [0015]      FIG. 1   b  corresponds to  FIG. 1   a  when viewed from another angle. 
           [0016]      FIG. 2  is a perspective assembly view of the safety hypodermic syringe according to the present invention. 
           [0017]      FIG. 3   a  is a top view in an enlarged scale of the safety hypodermic syringe according to the present invention. 
           [0018]      FIG. 3   b  is a sectional view in an enlarged scale of the front part of the barrel of the safety hypodermic syringe according to the present invention. 
           [0019]      FIG. 4  is a sectional view of the present invention, showing a standby status of the safety hypodermic syringe. 
           [0020]      FIG. 5  is a schematic sectional view of the present invention, showing the barrel of the safety hypodermic syringe filled with a liquid medicine for injection. 
           [0021]      FIG. 6  is a schematic sectional view of the present invention, showing the status of the hypodermic syringe after injection. 
           [0022]      FIG. 7  is a schematic sectional enlarged view of a part of the present invention, showing the barbed retaining flange of the plunger engaged with the retaining wings of the conical front connector of the barrel. 
           [0023]      FIG. 8  is a schematic sectional enlarged view of a part of the present invention, showing the conical front connector disconnected from the peripheral wall of the barrel. 
           [0024]      FIG. 9  is a schematic sectional enlarged view of the present invention, showing the needle assembly received inside the barrel after a return stroke of the plunger. 
           [0025]      FIG. 10  is a schematic sectional enlarged view of the present invention, showing the neck of the plunger broken, the needle assembly with the front part of the plunger left inside the barrel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Referring to  FIGS. 1   a ˜ 4 , a safety hypodermic syringe in accordance with the present invention is shown comprised of a barrel  1 , a needle assembly  2 , a plunger  3 , and a stopper  4 . 
         [0027]    The barrel  1  comprises a fluid chamber  11  adapted to hold a liquid medicine, a finger flange  12  extending around the periphery of the rear end thereof for the holding of the hand, and a conical front connector  14  suspending inside the front end thereof. The conical front connector  14  defines an axially extending fluid passage  13  in communication between the fluid chamber  11  and the atmosphere, having two retaining portions, for example, two hollow retaining wings  141  protruded from the periphery at two sides, a connection portion  16  extending around the periphery of the bottom (inner) end thereof and connected to the peripheral wall  15  of the barrel  1 , and a tearing groove  17  formed on the connection portion  16 . When the user pushed the plunger  2  further forwards after the service of the safety hypodermic syringe (after injection), the connection portion  16  is broken along the tearing groove  17 , and therefore the conical front connector  14  is separated from the barrel  1 . 
         [0028]    The barrel  1  further has an inside annular flange  18  extending around the inside wall thereof near the finger flange  12 . 
         [0029]    The needle assembly  2  comprises a hub  22  and a needle cannula  21  fastened to the hub  22 . The hub  22  has an axial hole  23  disposed in fluid communication with the axial center through hole of the needle cannula  21 , and a rear coupling portion  24  capped on the conical front connector  14  of the barrel  1  and engaged into the tearing groove  17 . The rear coupling portion  24  has a beveled outer surface  241  disposed in contact with the connection portion  16 . 
         [0030]    Because the rear coupling portion  24  is capped on the conical front connector  14  of the barrel  1  and engaged into the tearing groove  17  with the beveled outer surface  241  disposed in contact with the connection portion  16 , the needle assembly  2  is held positively in position and can stop leaking of the contained fluid medicine out of the barrel  1  in case the tearing groove  17  is broken accidentally. Therefore, the hub  22  of the needle assembly  2  has the functions of: (1) preventing biasing of the conical front connector  14  to cause breaking of the tearing groove  17  upon an external force, and (2) stopping the contained fluid medicine from leaking out of the barrel  1  when the tearing groove  17  is broken accidentally. 
         [0031]    The plunger  3  comprises a radially ribbed shank  32 , a thumb rest  31  at the rear end of the shank  32 , a head  33  at the front end of the shank  32 , a neck  37  connected between the shank  32  and the head  33 , a front extension rod  34  axially forwardly extending from the center of the front side of the head  33 , a front tip  361  axially forwardly extending from the front end of the front extension rod  34 , a barbed retaining flange  36  extending around the periphery between the front extension rod  34  and the front tip  362 , and a stopper holder  35  formed integral with the front extension rod  34 . The stopper holder  35  comprises a front retaining skirt  351  and a rear retaining skirt  352  respectively extending around the periphery of the front extension rod  34  for holding the stopper  4 . 
         [0032]    The stopper  4  is made out of a flexible material, for example, rubber. The outer diameter of the stopper  4  fits the diameter of the fluid chamber  11  of the barrel  1 . The stopper  4  has a longitudinal chamber  41 , which accommodates the front skirt  351  of the stopper holder  35  of the plunger  3  to secure the stopper  4  to the stopper holder  5 , allowing axial displacement of the stopper  4  relative to the stopper holder  5 , an inside annular flange  42  formed in the rear side of the longitudinal chamber  41  and disposed in contact with the periphery of the stopper holder  35  between the front skirt  351  and the rear skirt  352 , and a front center through hole  43  forwardly extending from the longitudinal chamber  41  to the front side at the center for the passing of the front extension rod  34  of the plunger  3 . 
         [0033]    During the assembly process of the present invention, the stopper  4  is fastened to the front extension rod  34  of the plunger  3  to have the barbed retaining flange  36  stopped at the front side of the stopper  4  and the inside annular flange  42  be disposed in contact with the periphery of the stopper holder  35  between the front skirt  351  and rear skirt  352  of the stopper  4 , and then the stopper  4  is inserted with the plunger  3  into the fluid chamber  11  of the barrel  1  from the rear side, and then the rear coupling portion  24  of the hub  22  of the needle assembly  2  is capped on the conical front connector  14  of the barrel  1  and engaged into the tearing groove  17  with the beveled outer surface  241  disposed in contact with the connection portion  16 .  FIGS. 2 and 4  show the safety hypodermic syringe assembled. 
         [0034]    After the safety hypodermic syringe has sucked in the fluid medicine for injection, as shown in  FIG. 5 , push the plunger  3  to move the stopper  4  forwards along the fluid chamber  11  and to further squeeze the fluid medicine out of the conical front connector  14  and the needle assembly  2  into the patient&#39;s body. 
         [0035]    When the stopper  4  reached the connection portion  16  of the conical front connector  14  as shown in  FIG. 6 , the barbed retaining flange  36  of the plunger  3  is stopped at the rear end of the fluid passage  13  and the front tip  361  is inserted into the fluid passage  13  of the barrel  1 , expelling residual fluid medicine out of the conical front connector  14  of the barrel  1 . 
         [0036]    After the service of the safety hypodermic syringe as shown in  FIG. 7 , push the plunger  3  further forwards to force the barbed retaining flange  36  into engagement with the retaining wings  141  of the conical front connector  14 . Because the stopper  4  is stopped at the connection portion  16  of the conical front connector  14  at this time, pushing the plunger  3  further forwards causes forward displacement of the plunger  3  relative to the stopper  4  to move the rear skirt  352  over the inside annular flange  42  into the longitudinal open chamber  41  of the stopper  4  as shown in  FIG. 8 . When continuously pushing the plunger  3  forwards at this time, the tearing groove  17  will be forced to break, causing disconnection of the conical front connector  14  from the peripheral wall  15  of the barrel  1 . At this time, the broken safety hypodermic syringe becomes useless. 
         [0037]    Thereafter, the plunger  3  is pulled backwards. At this time, as shown in  FIG. 9 , the stopper  4 , the broken conical front connector  14 , and the attached needle assembly  2  are carried with the plunger  3  into the inside of the fluid chamber  11  of the barrel  1  to have the front flange  331  and rear flange  332  of the head  3  be respectively stopped at the front and rear sides of the inside annular stop flange  18  of the barrel  1 . 
         [0038]    After the needle assembly  2  has been received inside the fluid chamber  11  of the barrel  1 , the user can bias the shank  32  against the inside wall of the barrel  1  to break the neck  37 , as shown in  FIG. 10 , keeping the needle assembly  2  and a part of the plunger  3  and the stopper  4  inside the fluid chamber  11  of the barrel  1 . 
         [0039]    A prototype of safety hypodermic syringe has been constructed with the features of  FIGS. 1˜10 . The safety hypodermic syringe functions smoothly to provide all the features discussed earlier. 
         [0040]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.