Abstract:
A safety hypodermic syringe in which the needle hub of the needle assembly has two sliding grooves respectively coupled to respective small stub rods in the socket at the front side of the barrel so that the needle assembly is moved backwards and received inside the barrel upon a return stroke of the plunger after the service of the safety hypodermic syringe and after a rotation of the plunger through an angle relative to the barrel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to a hypodermic syringe and, more particularly, to a safety hypodermic syringe, which enables the needle assembly to be automatically received inside the barrel upon a return stroke of the plunger after a rotary motion of the plunger.  
           [0003]    2. Description of the Related Art  
           [0004]    When disposing of a disposable hypodermic syringe after its service, the person handling the disposable hypodermic syringe may be injured by the protruding needle cannula accidentally. In order to eliminate this problem, safety hypodermic syringes are developed. These safety hypodermic syringes enable the needle assembly to be pulled backwards with the plunger and received inside the barrel after the service. Exemplars of these safety hypodermic syringes are seen in Taiwan Patent Publication Nos. 189436; 356013; 463639; 414085; 384709; 359621; 492328; 467752; 475449; 480185; 497976; 430565; 471322; 332433; 394027; and 447310, and U.S. Pat. Nos. 5,385,557; 4,747,830; 4,677,980; 5,242,400; 4,986,813; 4,947,863; 5,533,975; 5,171,300; 4,944,723, . . . etc.  
           [0005]    [0005]FIG. 1 shows a safety hypodermic syringe according to the prior art. According to this design, the safety hypodermic syringe comprises a barrel  11 , the barrel  11  having a front socket  12  and two raised portions  121  protruding from the inside wall of the front socket  12 , a needle hub  13  mounted in the front socket  12 , the needle hub  13  having two angled crevices  131  extended to the front side and respectively coupled to the raised portions  121  of the front socket  12 , and a bottom retaining hole  132 , and a plunger and stopper assembly  14  inserted into the barrel  11  from the rear side, the stopper assembly  14  having a front engagement tip  141  adapted to engage the bottom retaining hole  132  of the needle hub  13 . FIG. 2A shows the safety hypodermic syringe assembled. This design of safety hypodermic syringe is seen in U.S. Pat. No. 5,273,543. It has drawbacks as outlined hereinafter.  
           [0006]    1. The raised portions  121  of the front socket  12  are respectively stopped at the end of the rear horizontal section of the angled crevices  131  when the safety hypodermic syringe assembled. When removing the needle hub  13  from the front socket  12  after the service of the hypodermic syringe, the user must rotate the needle hub  13  with the plunger  14  in the assigned direction. When rotating the plunger  14  in the wrong direction, the connection between the needle hub  13  and the raised portions  121  of the front socket  12  is reinforced, unable to remove the needle hub  13  from the raised portions  121 .  
           [0007]    2. Because the contact  15  between the needle hub  13  and the front socket  12  is a planar contact, the outer diameter of the needle hub  13  must be made to be press-fitted into the inner diameter of the front socket  12  to prevent a leakage. Due to high friction resistance between the outside wall of the needle hub  13  and the inside wall of the front socket  12 , the user must employ much effort to the plunger  14  to pull the needle hub  13  and the needle cannula  133  back to the inside of the barrel  11  after the service of the safety hypodermic syringe (see FIG. 2B).  
           [0008]    There are known other designs of safety hypodermic syringes that use a screw joint to secure the neck hub in position. These designs are seen in U.S. Pat. Nos. 4,944,723; 4,978,340; 5,171,300; 4,947,863; 4,986,813. Other needle hub positioning designs are seen in Taiwan Patent Publication Nos. 492328; 356013; 359621; 463639, etc., and U.S. Pat. Nos. 5,242,400; 4,747,830; 5,098,390; 5,370,619; 4,911,693, etc. These prior art designs still cannot eliminate the aforesaid drawbacks.  
           [0009]    Therefore, it is desirable to provide a safety hypodermic syringe that eliminates the aforesaid drawbacks.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a safety hypodermic syringe, which enables the needle assembly to be conveniently received inside the barrel after the service of the safety hypodermic syringe. It is another object of the present invention to provide a safety hypodermic syringe, which enables the needle assembly to be automatically received inside the barrel upon a return stroke of the plunger after a rotary motion of the plunger.  
           [0011]    To achieve these and other object of the present invention, the safety hypodermic syringe comprises a barrel, the barrel comprising a body and a socket at a front side of the body; a needle assembly, the needle assembly comprising a needle hub mounted in the front socket of the barrel, the needle hub having a bottom coupling hole, and a needle cannula forwardly extended from the needle hub outside the barrel; and a plunger and stopper unit, the plunger and stopper unit comprising a stopper fitted into the body of the barrel, and an elongated plunger backwardly extended from the stopper to the outside of the barrel and adapted to reciprocate the stopper in the body of the barrel, the stopper having a front engagement tip adapted to engage the bottom coupling hole of the needle hub for enabling the needle assembly to be pulled backwards with the plunger and stopper unit and received inside the body of the barrel. The socket of the barrel has at least one small stub rod protruding from the inside wall. The needle hub of the needle assembly comprises at least one sliding groove formed in the periphery and respectively coupled to the at least one small stub rod of the socket, for enabling the needle assembly to be pulled backwards with the plunger and stopper unit and received inside the body of the barrel after a rotary motion of the plunger relative to the barrel. The at least one sliding groove each has two distal open ends through which the at least one small stub rod of the socket is moved in and out of the at least one sliding groove when the plunger and stopper unit and the barrel are rotated relative to each other, and a positioning portion on the middle between the two distal open ends for engagement with the at least one small stub rod of the socket. Further, the sliding grooves of the needle hub can be made having a substantially U-shaped profile, or a V-shaped profile. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is an exploded view of a safety hypodermic syringe according to the prior art.  
         [0013]    [0013]FIG. 2A is a sectional side assembly view in an enlarged scale of the prior art safety hypodermic syringe shown in FIG. 1.  
         [0014]    [0014]FIG. 2B is similar to FIG. 2A but showing the plunger moved backwards.  
         [0015]    [0015]FIG. 3 is a perspective exploded view of a safety hypodermic syringe according to the present invention.  
         [0016]    [0016]FIG. 4 is a perspective exploded view of an alternate form of the safety hypodermic syringe according to the present invention.  
         [0017]    [0017]FIG. 5 is an enlarged view in an enlarged scale of a part of the needle hub according to the present invention.  
         [0018]    [0018]FIG. 6 is a bottom view of FIG. 5.  
         [0019]    [0019]FIG. 7A is a schematic drawing showing one example of the sliding groove of the needle hub according to the present invention.  
         [0020]    [0020]FIG. 7B is a schematic drawing showing another example of the sliding groove of the needle hub according to the present invention.  
         [0021]    [0021]FIG. 8 is a sectional assembly view in an enlarged scale of a part of the safety hypodermic syringe according to the present invention, showing the needle hub positioned in the socket of the barrel.  
         [0022]    [0022]FIG. 9 is a schematic side view of the present invention, showing a status of the use of the safety hypodermic syringe.  
         [0023]    [0023]FIG. 10 is a sectional view in an enlarged scale of the safety hypodermic syringe according to the present invention, showing the status of the hypodermic syringe after injection.  
         [0024]    [0024]FIG. 11 is a sectional view taken along line  11 - 11  of FIG. 10.  
         [0025]    [0025]FIG. 12A is a schematic side view of the present invention, showing the plunger rotated clockwise relative to the barrel after injection.  
         [0026]    [0026]FIG. 12B is a schematic side view of the present invention, showing the plunger rotated counter-clockwise relative to the barrel after injection.  
         [0027]    [0027]FIG. 13 is a schematic drawing of the present invention, showing the needle assembly received inside the barrel upon a back stroke of the plunger and stopper unit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    Referring to FIG. 3, a safety hypodermic syringe in accordance with the present invention is shown comprised of a barrel  2 , which comprises a body  21 , a socket  22  at the front side of the body  21 , and at least one, two example, two small stub rods  23  symmetrically protruded from the inside wall of the socket  22 , a plunger and stopper unit  3 , which comprises a stopper  32  fitted into the body  21  of the barrel  2  and an elongated plunger  31  axially extended from the rear side of the stopper  32  and adapted to reciprocate the stopper  22  in the body  21  of the barrel  2 , and a front engagement tip  33  shaped like a truncated cone and forwardly protruded from the front side of the stopper  32  at the center and having at least one, for example, two planes  331  at two sides, and a needle assembly  4 , which comprises a needle hub  41  mounted in the front socket  22  of the barrel  2  and a needle cannula  42  forwardly extended from the needle hub  41  outside the barrel  2 . The needle cannula  42  may be formed integral with the front side of the needle hub  41 . Alternatively, the needle hub  41  and the needle cannula  42  can be independent members fastened together (see FIG. 4). Further, a rubber ring  45  may be fastened to the periphery of the needle hub  41  as shown in FIG. 4. Further, the needle hub  41  has a bottom coupling hole  43  and two planes  431  symmetrically disposed in the bottom coupling hole  43  at two sides corresponding to the planes  331  of the front engagement tip  33 .  
         [0029]    Referring to FIGS. 5 and 6 and FIG. 3 again, the needle hub  41  comprises two smoothly curved sliding grooves  44  symmetrically disposed at two sides and respectively coupled to the small stub rods  23  in the socket  22  of the barrel  2 . Each sliding groove  44  has two distal open ends  441  and a positioning portion  442  disposed on the middle at the lowest point. The sliding grooves  44  may be made having a substantially U-shaped profile as shown in FIG. 7A, or a substantially V-shaped profile as shown in FIG. 7B. Each sliding groove  44  symmetrically downwardly curves from the respective two distal open ends  441  to the respective positioning portion  442 .  
         [0030]    Referring to FIG. 8, when fastening the needle hub  41  to the socket  22  of the barrel  2 , one open end  441  of each sliding groove  44  is respectively attached to the small stub rods  23  inside the socket  22  of the barrel  2 , and then the needle hub  41  is rotated in the socket  22  in one direction through an angle, enabling the small stub rods  23  to be respectively moved to the positioning portions  442  of the sliding grooves  44  and firmly secured thereto by means of friction resistance. Preferably, the socket  22  is a tapered socket having an inner diameter gradually reduced from the rear side (the side connected to the body  21  toward the front side (the side remote from the body  21 ), and the needle hub  41  is a stepped conical member having an outer diameter fitting the inner diameter of the socket  22 . The connection between the socket  22  and the needle hub  41  becomes firmly when the needle hub  41  pulled forwards relative to the socket  22 .  
         [0031]    Referring to FIG. 9, when pulling the plunger  31  forwards in the barrel  2 , the stopper  32  forces the liquid medicine out of the needle cannula  42 .  
         [0032]    Referring to FIGS.  10 ˜ 13 , when the plunger  31  moved to the front limit position and the liquid medicine completely (or approximately completely) forced out of the safety hypodermic syringe, the front engagement tip  33  of the plunger and stopper unit  3  is press-fitted into the bottom coupling hole  43  of the needle hub  41 , keeping the planes  431  of the needle hub  41  abutted against the planes  331  of the front engagement tip  33 . When rotating the plunger  31  clockwise (see FIG. 12A) or counter-clockwise (see FIG. 12B), the needle hub  41  is rotated with the front engagement tip  33  relative to the socket  22 , thereby causing the needle assembly  4  to be moved axially backwards toward the inside of the body  21  of the barrel  2  and disengaged from the stub rods  23  of the socket  22 , and therefore the needle assembly  4  is completely received inside the body  21  of the barrel  2  when the plunger  31  pulled backwards to the rear side of the barrel  2  (see FIG. 13).  
         [0033]    A prototype of safety hypodermic syringe has been constructed within the features of FIGS.  3 ˜ 13 . The safety hypodermic syringe functions smoothly to provide all the features discussed earlier.  
         [0034]    Although particular embodiments of the invention have 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.