Abstract:
A plunger engagement section for safety hypodermic syringe includes a protruding portion at the plunger engagement section accommodated by a barrel. The protruding portion fills an entire space at an interior of a needle holder when the plunger is pushed forward, thereby overcoming a drawback or prior inventions as failing to completely inject a medical solute contained.

Description:
RELATED APPLICATION  
       [0001]    This application is a continuation-in part of U.S. application Ser. No. 09/993,572, filed on Nov. 27, 2001 and currently patented. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    (a) Field of the Invention  
           [0003]    The invention relates to a plunger engagement section for safety hypodermic syringe, and more particularly, to a plunger engagement section for safety hypodermic syringe that provides a novel structure in conjunction with the application Ser. No. 09/993,572.  
           [0004]    (b) Description of the Prior Art  
           [0005]    According to the aforesaid prior invention disclosed, a safety hypodermic syringe comprises a barrel, a needle holder, and a locating ring. The needle holder has a front engagement section press-fitted into the inside of a front small inner diameter section of the barrel, and a springy rear expansion section. The expansion section has a front side edge corresponding to a rear side of a shoulder of the barrel, and a rear side edge stopped at a protruding inner edge of a large inner diameter section of the barrel. The locating ring has an outside wall with an outer diameter slightly larger than a neck at the inner diameter section of the barrel. When the neck is inserted into the needle holder, the expansion section of the sleeve is expanded to butt at the large inner diameter section of the barrel, and therefore locating effects are provided by expanding the rear edge of the expansion section at the protruding edge. Hence, such type of safety hypodermic syringe adopts a locating mechanism formed by the needle holder, the locating ring and the barrel, so as to locate the needle holder at an end portion of the barrel and to perform an injection after placing in a needle.  
           [0006]    For that a hollow chamber of the barrel is disposed with a needle holder, the needle holder is necessarily provided with a hollow tubular section for connecting to the needle. However, a space in an interior of the tubular section is prone to residual dosage and hence wastage of a portion of the medical dosage contained in the hollow tubular section. Furthermore, for barrels having smaller capacities, errors occurred by the hollow tubular section are likely to result in after-effects of insufficient dosages.  
         SUMMARY OF THE INVENTION  
         [0007]    The primary object of the invention is to provide a plunger engagement section for safety hypodermic syringe, so as to thoroughly inject a medical solute contained at an interior of a hollow tubular section of a needle holder thereof, and to further overcome drawbacks as failures of completely injecting medical solutes or uneven dosage concentrations.  
           [0008]    To accomplish the aforesaid object, the plunger engagement section for safety hypodermic syringe comprises a protruding portion at a front end of the plunger engagement section accommodated by a barrel. In order to thoroughly inject a medical solute contained in the barrel, the protruding portion fills an entire space within a hollow tubular section at an interior of a needle holder of the syringe during injection, thereby overcoming a drawback as failing to completely inject the medical solute. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 shows a conventional exploded elevational view illustrating a safety hypodermic syringe of a prior invention.  
         [0010]    [0010]FIG. 2 shows an exploded elevational sectional view illustrating the locating ring, the needle holder and the barrel of the prior invention.  
         [0011]    [0011]FIG. 3 shows a sectional view illustrating the locating ring, the needle holder and the barrel of the prior invention.  
         [0012]    [0012]FIG. 4 shows an exploded elevational view according to the invention.  
         [0013]    [0013]FIG. 5 shows a sectional schematic view according to the invention.  
         [0014]    [0014]FIG. 6 shows an operational schematic view according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    To better understand the technical contents of the invention, detailed descriptions shall be given with the accompanying drawings hereunder.  
         [0016]    Referring to FIG. 1 showing an exploded elevational view of the prior invention, wherein the safety hypodermic syringe comprises a barrel  1 , a needle holder  2 , a locating ring  3 , a plunger  4 , a needle  5 , and a needle shield  51 .  
         [0017]    [0017]FIGS. 2 and 3 show an exploded elevational view and a sectional view of unassembled structures of the locating ring  3  and the needle holder  2 .  
         [0018]    The barrel  1  is a hollow tubular section having a hollow chamber  10  at an interior thereof. The hollow chamber  10  is has a front portion thereof as a small inner diameter section  11 , and a rear portion thereof as a large inner diameter section  12 . Between the small inner diameter section  11  and the large diameter section  12  is a shoulder  13 . At an appropriate position approaching the shoulder  13 , the large inner diameter section  12  has a flange  14  in a complete ring shape. The flange  14  is provided with a wedge-shaped rear beveled plane  141  for facilitating passing through of the needle holder  2 .  
         [0019]    A middle portion of an outer wall  210  of a hollow tubular section  21  of the needle holder  2  is disposed with a coaxial outer ring  22  in an outward direction. The coaxial outer ring  22  has a joining section  221  at a front portion thereof and an expansion section  222  at a rear portion thereof. The joining section  221  is for locating purposes when inserted into the small inner diameter section  11  of the barrel  1 . The expansion section  222  has a front edge  223  and a rear edge  224 , with the front edge  223  stopped at the shoulder  13  of the barrel  1  for locating purposes and the rear edge  224  corresponded at the flange  14  at the large inner diameter section  12  of the barrel  1 . In addition, between the expansion section  222  and the outer wall  210  of the hollow tubular section  21  is an in-ring space  225 .  
         [0020]    The locating ring  3  has an outer wall  31  and an inner wall  32 . The outer wall  31  is disposed to slide within the large diameter section  12  of the barrel  1 . The inner wall  32  is disposed to slide around the outer wall  210  of the hollow tubular section  21  of the needle holder  2  as shown in FIG. 3. The outer wall is  31  is formed with a neck portion  311  at a front end thereof, and the neck portion  311  is further formed with a beveled plane at a front end thereof for favoring inserting into the in-ring space  225  of the needle holder  2 , and has an outer diameter slightly larger than the inner diameter of the expansion section  222  of the needle holder  2 . The inner wall  32  has a first fastening portion  321  and a second fastening portion  322  at front and rear ends thereof, respectively. The first fastening portion  321  is for corresponding with a first fastening portion  211  at a rear end of the hollow tubular section  21  of the needle holder  2 . The second fastening portion  322  is for coordinating with an engagement section  41  at the front end of the plunger  4 . Wherein, the first fastening portion  211  is a complete ring provided at the outer wall  210  of the hollow tubular section  21  in an outward direction, and the first fastening portion  321  is provided at the inner wall  32  of the locating ring  3  in an inward direction. Note that sections of the first fastening portions  211  and  321  are wedge-shaped in opposite directions for facilitating secure fastening as well as blocking disengagement.  
         [0021]    The safety hypodermic syringe according to the invention utilizes a locating structure relationship of the needle holder  2  and the locating ring  3  that correspond with the flange  14  at the large inner diameter section  12  of the barrel  1 , so as to locate the needle holder  2  at an end portion of the hollow chamber  10  of the barrel  1 . Thus, an injection can be performed when the needle  5  is inserted and joined into the hollow tubular section  21  of the needle holder  2 . However, the hollow chamber  20  within the hollow tubular section  21  is prone to residual dosage and hence wastage of a portion of a medical solute contained. Furthermore, for a barrel  1  having a smaller capacity, residual dosage incurs insufficient dosage and produces an error in the intended dosage.  
         [0022]    Therefore, referring to FIGS. 4 and 5 showing an exploded elevational view and a sectional schematic view according to the invention, to overcome the aforesaid drawback, the invention further comprises a protruding portion  42  at the engagement section  41  of the plunger  4 . The protruding portion  42  is a cylindrical body having dimensions corresponding to the hollow chamber  20  within the hollow tubular section of the needle holder  2 .  
         [0023]    Referring to FIG. 6 showing a plunger according to the invention being pushed forward, when the plunger  4  is pushed forward to having completed injection, the engagement section  41  at the front end of the plunger  4  is extended into the locating ring  3  and corresponded with the second fastening portion  322 . Meanwhile, the protruding portion  42  fills the space of the hollow chamber  20  within the hollow tubular section  21 , thereby overcoming medical dosage wastage or uneven concentration of medical solutes by thoroughly injecting a medical solute contained in the barrel  1 .  
         [0024]    It is of course to be understood that the embodiment described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.