Patent Publication Number: US-2007100291-A1

Title: Safety syringe

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority of Taiwanese application no. 094138109, filed on Oct. 31, 2005.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a syringe, more particularly to a safety syringe that can be safely disposed.  
      2. Description of the Related Art  
       FIG. 1  illustrates a conventional safety syringe that includes a barrel  50 , a needle hub  60 , a hub connector  61 , a plunger  70 , an elastic piston  80 , and a pushing member  90 . The barrel  50  has a medicine-storing portion  501 , a needle-connecting portion  502  that is reduced in cross-section from the medicine-storing portion  501 , and a shoulder  503  formed between the medicine-storing portion  501  and the needle-connecting portion  502 . The hub connector  61  is mounted movably in the barrel  50 , and has front and rear end portions  611 ,  612 . The rear end portion  612  of the hub connector  61  abuts against the shoulder  503  of the barrel  50  and is provided with a first engaging member  610  therein. The needle hub  60  engages threadedly the front end portion  611  of the hub connector  61 . A needle  100  is coupled to a front end of the needle hub  60 . The plunger  70  extends into the medicine-storing portion  501  of the barrel  50 , and has a front end that is provided with a second engaging member  701 . The piston  80  is sleeved on the plunger  70 , is disposed rearward of the second engaging member  701 , is received in and is in frictional contact with the medicine-storing portion  501  of the barrel  50 , and has front and rear ends  801 ,  802 . The pushing member  90  extends radially from the plunger  70 , and abuts against the rear end  801  of the piston  80 . With further reference to  FIG. 2 , the plunger  70  is movable relative to the barrel  50  in a frontward direction from a first position, in which the first and second engaging members  611 ,  701  are spaced apart from each other, to a second position, in which the first and second engaging members  611 ,  701  engage each other. At this time, the hub connector  61  together with the needle hub  60  and the needle  100  may be drawn into the medicine-storing portion  501  of the barrel  50  by pulling the plunger  70 .  
      The aforementioned conventional safety syringe is disadvantageous in that, when the plunger  70  is moved to the first position, a gap exists between the front end  801  of the piston  80  and the rear end portion  612  of the hub connector  61 . As such, the conventional safety syringe still has medicine fluid residue left in the gap after use. Moreover, the gap contains trapped air, which decreases suction force of the conventional safety syringe when the plunger  70  is pulled. Further, the plunger  70  is easily moved to the second position when accidentally pushed.  
     SUMMARY OF THE INVENTION  
      Therefore, the object of the present invention is to provide a safety syringe that can overcome the aforesaid drawbacks of the prior art.  
      According to the present invention, a safety syringe comprises a barrel, a needle hub, a plunger, an elastic piston, and a pushing member. The barrel has a medicine-storing portion, a needle-connecting portion that is reduced in cross-section from the medicine-storing portion, and a shoulder that is formed between the medicine-storing portion and the needle-connecting portion. The needle hub extends into the needle-connecting portion of the barrel, and is provided with a first engaging member therein. The plunger extends into the medicine-storing portion of the barrel, and has a front end that is provided with a second engaging member. The elastic piston is sleeved on the plunger, is disposed rearward of the second engaging member, is received in and is in frictional contact with the medicine-storing portion of the barrel, and has a hollow body that has a rear end, and a restricting member that extends radially and inwardly from the rear end of the hollow body. The pushing member extends radially from the plunger. The plunger is movable together with the piston relative to the barrel to a first position, in which the pushing member is disposed rearwardly of and abuts against the restricting member, in which the piston abuts against the shoulder of the barrel, and in which the first engaging member is spaced apart from the second engaging member. The plunger is movable relative to the piston in a frontward direction from the first position to a second position, in which the piston abuts against the shoulder of the barrel and in which the first and second engaging members engage each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:  
       FIG. 1  is a fragmentary partly sectional view of a conventional safety syringe when a plunger thereof is moved to a first position;  
       FIG. 2  is a fragmentary partly sectional view of the conventional safety syringe when the plunger thereof is moved to a second position;  
       FIG. 3  is an exploded fragmentary partly sectional view of the preferred embodiment of a safety syringe according to this invention;  
       FIG. 4  is a fragmentary partly sectional view of the preferred embodiment when a plunger thereof is disposed at an initial position;  
       FIG. 5  is a fragmentary partly sectional view of the preferred embodiment when the plunger thereof is moved to a first position;  
       FIG. 6  is a fragmentary partly sectional view of the preferred embodiment when the plunger thereof is moved to a second position;  
       FIG. 7  is a fragmentary partly sectional view of the preferred embodiment when the plunger thereof is moved to a third position;  
       FIG. 8  is a fragmentary partly sectional view to illustrate a guiding piece of the preferred embodiment; and  
       FIG. 9  is a fragmentary partly sectional view to illustrate a plunger being guided by the guiding piece of the preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 3 , the preferred embodiment of a safety syringe according to this invention is shown to include a barrel  10 , a needle hub  20 , a plunger  30 , an elastic piston  32 , and first and second pushing members  315 ,  314 .  
      The barrel  10  has a medicine-storing portion  12  and a needle-connecting portion  13 . The medicine-storing portion  12  of the barrel  10  has opposite front and rear ends  15 ,  16 . The needle-connecting portion  13  of the barrel  10  is reduced in cross-section from the medicine-storing portion  12 . As such, a shoulder, which serves as the front end  15  of the barrel  10 , is formed between the medicine-storing portion  12  and the needle-connecting portion  13  of the barrel 10 . The barrel  10  is provided with a finger flange  14  that extends radially and outwardly from the rear end  16  of the medicine-storing portion  12  of the barrel  10 .  
      The needle hub  20  extends into the needle-connecting portion  13  of the barrel  10 , and is provided with a first engaging member  212  therein. In this embodiment, the first engaging member  212  is an annular tapered flange.  
      The safety syringe further includes a hypodermic needle  22  that extends from the needle hub  20 .  
      The plunger  30  extends into the medicine-storing portion  12  of the barrel  10 , and has opposite front and rear ends  312 ,  311 , and a middle portion  313  that interconnects the front and rear ends  312 ,  311  of the plunger  30 . The rear end  311  of the plunger  30  is disposed externally of the barrel  10 . The front end  312  of the plunger  30  is disposed in the barrel  10 , and is provided with a second engaging member  317 . In this embodiment, the second engaging member  317  is an annular projection.  
      The piston  32 , preferably made from a plastic material, is disposed rearward of the second engaging member  317 , is sleeved on the middle portion  313  of the plunger  30 , and is received in and is in frictional contact with the medicine-storing portion  12  of the barrel  10 . In this embodiment, the piston  32  has a hollow body  328  and a restricting member  326 . The hollow body  328  of the piston  32  has a front end  321 , and a rear end  322  that is opposite to the front end  321  of the hollow body  328 . The restricting member  326  extends radially and inwardly from the rear end  322  of the hollow body  328 , cooperates with the hollow body  328  to define an inner space  324  therebetween, and defines a rear opening  323  that is in spatial communication with the inner space  324  and that is defined by a tapered wall  327 .  
      The first pushing member  315  is disposed rearward of the second engaging member  317 , and extends radially from the middle portion  313  of the plunger  30 . In this embodiment, the first pushing member  315  is disposed externally of the piston  32  (see  FIG. 4 ), and has a tapered front end portion  318  and an annular rear end portion  319 .  
      The second pushing member  314  is disposed between the second engaging member  317  and the first pushing member  315 , and extends radially from the middle portion  313  of the plunger  30 . In this embodiment, the second pushing member  314  is received in the inner space  324  and is in frictional contact with the piston  32  (see  FIG. 4 ).  
      Referring to  FIG. 4 , at an initial position in which the medicine-storing portion  12  of the barrel  10  already contains medicine fluid  11 , the piston  32  is disposed at a distance from the shoulder  15  of the barrel  10 . The tapered front end portion  318  of the first pushing member  315  extends into the rear opening  323  (see  FIG. 3 ) and is in frictional contact with the tapered wall  327  of the restricting member  326  of the piston  32 . The annular rear end portion  319  of the first pushing member  315  abuts against the restricting member  326 . The second pushing member  314  is disposed in the inner space  324 . The first engaging member  212  and the second engaging member  317  are spaced apart from each other.  
      Referring to  FIG. 5 , the plunger  30  is movable together with the piston  32  relative to the barrel  10  in a frontward direction, as indicated by arrow (X), from the initial position to a first position, in which the medicine fluid  11  (see  FIG. 4 ) is discharged from the medicine-storing portion  12  of the barrel  10 , in which the front end  321  of the hollow body  328  of the piston  32  abuts against the shoulder  15  of the barrel  10 , in which the annular rear end portion  319  of the first pushing member  315  is disposed rearwardly of and abuts against the restricting member  326 , and in which the first and second engaging members  212 ,  317  are spaced apart from each other. The tapered front end portion  318  of the first pushing member  315  is still disposed in the rear opening  323  (see  FIG. 3 ) and is in frictional contact with the tapered wall  327  of the restricting member  326  of the piston  32 . The second pushing member  314  is still disposed in the inner space  324 . It is noted that, when the plunger  30  is at this position, there is no gap existing between the front end  321  of the hollow body  328  of the piston  32  and the shoulder  15  of the barrel  10 . As such, there is no medicine fluid residue in the medicine-storing portion  12  of the barrel  10 . Moreover, since no gap exists between the front end  321  of the hollow body  328  of the piston  32  and the shoulder  15  of the barrel  10 , there is no trapped air in the medicine-storing portion  12  of the barrel  10 . As such, suction force of the safety syringe of this invention is enhanced when the plunger  30  is pulled. Further, since the medicine fluid may be fully discharged from the medicine-storing portion  12  of the barrel  10  without resulting in the engagement between the first and second engaging members  212 ,  317 , the safety syringe of this invention is reusable.  
      Referring to  FIG. 6 , due to abutment between the front end  321  of the hollow body  328  of the piston  32  and the shoulder  15  of the barrel  10 , the plunger  30  is movable relative to the piston  32  in the frontward direction (X) from the first position to a second position, in which the tapered front end portion  318  and the non-tapered rear end portion  319  of the first pushing member  315  are received in the inner space  324  through the rear opening  323  in the restricting member  326  of the piston  32 , in which the second pushing member  314  is still disposed in the inner space  324  and abuts against the front end  321  of the hollow body  328  of the piston  32 , and in which the first engaging member  212  and the second engaging member  317  engage each other. At this time, the needle hub  20  and the hypodermic needle  22  may be retracted into the medicine-storing portion  12  of the barrel  10  by moving the plunger  30  relative to the barrel  10  in a rearward direction, as indicated by arrow (Y), opposite to the frontward direction (X), as best shown in  FIG. 7 , from the second position to a third position.  
      In this embodiment, when the plunger  30  is at the initial position (see  FIG. 4 ), a gap exists between the second pushing member  314  and the front end  321  of the hollow body  328  of the piston  32 . When the plunger  30  is moved to the first position (see  FIG. 5 ), the gap still exists between the second pushing member  314  and the front end  321  of the hollow body  328  of the piston  32 . When the plunger  30  is moved to the second position (see  FIG. 6 ), there is no gap between the second pushing member  314  and the front end  321  of the hollow body  328  of the piston  32 . In an alternative embodiment, when the plunger  30  is moved to the second position, the gap between the second pushing member  314  and the front end  321  of the hollow body  328  of the piston  32  is simply reduced.  
      It is noted herein that it requires a certain amount of force before the first pushing member  315  can be pushed into the inner space  324  through the rear opening  323  in the restricting member  326  of the piston  32 . As such, accidental movement of the plunger  30  to the second position can be deterred.  
      With further reference to  FIGS. 8 and 9 , the safety syringe further includes a guiding piece  40  for guiding movement of the plunger  30  in the medicine-storing portion  12  of the barrel  10 . In particular, the middle portion  313  of the plunger  30  is provided with a guide member  31  that has a cross-shaped cross-section, and that includes a pair of crossed pieces  33 . The finger flange  14  of the barrel  10  is formed with an engaging hole  140 . The guiding piece  40  is provided with an engaging protrusion  401  that engages the engaging hole  140  in the finger flange  14  of the barrel  10 , as best shown in  FIG. 8 , and is formed with a guiding groove  402  that receives slidably an edge  310  of one of the crossed pieces  33  of the plunger  30 , as best shown in  FIG. 8 .  
      With the formation of the inner space  324  in the piston  32  and the restricting member  326  on the rear end  322  of the hollow body  328  of the piston  32 , the aforesaid drawbacks associated with the prior art can be eliminated.  
      While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.