Patent Publication Number: US-2007123830-A1

Title: Safety syringe

Description:
FIELD OF THE INVENTION  
      This invention relates generally to medical devices and more particularly to an improved hypodermic syringe for safely administering injections.  
     BACKGROUND OF THE INVENTION  
      Needlestick injuries have become of serious concern because of possible transmission of blood borne diseases. Blood borne diseases may also be transmitted by sharing and reusing needles. Syringes have been developed to protect a user from needlestick injuries by retracting the needle into the syringe after a hypodermic injection is performed. See, for example, U.S. Pat. Nos. 4,950,241 and 5,538,507. These syringes, however, have certain shortcomings.  
      Accordingly, there is a need for an improved syringe that may be used for safe and accurate injections. There is another need for an improved syringe that substantially reduces the chance of contamination through needlestick injuries. There is a still further need for an improved syringe that contains the contaminated needle after injection and renders it inaccessible for reuse. The present invention fulfills these needs and provides other related advantages.  
     SUMMARY OF THE INVENTION  
      The present invention resides in an improved hypodermic syringe that substantially prevents needlestick injuries and reuse of the needle. The syringe comprises, generally, a cylindrical barrel releasably connected with a hub of a hypodermic needle assembly, the hypodermic needle assembly comprising an anchor fixedly attached to a hypodermic needle and releasably mounted inside the hub, and a plunger slideably mounted in the cylindrical barrel. In the process of injection, a mechanical coupling is effected between the plunger and the anchor. When the plunger is retracted proximally from the barrel after an injection, the needle is carried by the anchor inside the barrel as a result of the coupling between the anchor and the plunger.  
      The anchor has flexible legs capable of gripping the plunger, by means of outward facing snap elements at the proximal end of the flexible legs that engage a retaining snap edge in the plunger. The plurality of flexible legs also include stop means to substantially prevent the hypodermic needle and anchor assembly from moving into the barrel during the penetrating force of the needle into the patient.  
      Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings illustrate the invention. In such drawings:  
       FIG. 1  is a perspective view of a hypodermic needle assembly according to the invention;  
       FIG. 2  is a sectional view of the hypodermic needle assembly of  FIG. 1 , illustrating an anchor releasably mounted in a hub and a hypodermic needle threaded through and fixedly attached to the anchor;  
       FIG. 2A  is a sectional view of the anchor of  FIG. 2 , illustrating a substantially cylindrical distal portion and a plurality of flexible legs terminating in outwardly facing snap elements and including stop means;  
       FIG. 2B  is a similar view to  FIG. 2 , the enlarged encircled portion illustrating a sealing lip defined between the hub and anchor;  
       FIG. 3  is a perspective view of a syringe including the hypodermic needle assembly of  FIGS. 1 and 2  releasably mounted on the distal end of a syringe barrel with a plunger slideably mounted into the syringe barrel;  
       FIG. 4  is a sectional view of the syringe barrel and plunger of  FIG. 3 ;  
       FIG. 5  is a partial sectional view of the syringe of  FIG. 3 , illustrating a distal portion of the plunger within a portion of the syringe barrel;  
       FIG. 6  is a similar view to  FIG. 5 , illustrating a more distal position of the plunger;  
       FIG. 7  is a similar view to  FIGS. 5 and 6 , illustrating the distal portion of the plunger at a fully distal position within the syringe barrel with the flexible legs of the anchor within the plunger;  
       FIG. 8  is a similar view to  FIGS. 5-7 , illustrating the outwardly facing snap elements of the flexible legs engaged with a snap edge of the plunger;  
       FIG. 9  is a similar view to  FIGS. 5-8 , illustrating full retraction of the plunger, the anchor and needle pulled inside the syringe barrel;  
       FIG. 10  is a perspective view of the syringe barrel of  FIG. 4 , with a portion of the barrel cutaway to reveal the distal portion of the plunger;  
       FIG. 11  is a perspective view of the plunger;  
       FIG. 12  is an enlarged partial perspective view of the distal portion of the plunger, illustrating the snap edge of the plunger;  
       FIG. 13  is another enlarged partial perspective view of the distal portion of the plunger; and  
       FIG. 14  is a sectional view of the syringe of  FIG. 3 , illustrating the plunger at different working steps within the syringe barrel.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      As shown in the drawings for purposes of illustration, the present invention is concerned with an improved syringe, generally designated in the accompanying drawings by the reference number  10 . The syringe  10  comprises, generally, a cylindrical barrel  12  having a conical distal portion  13  for releasable connection with a hypodermic needle assembly  14 , the hypodermic needle assembly  14  comprising a needle  16  fixedly attached to an anchor  18  adapted for coupling to a plunger  20  slideably mounted in the barrel  12  so that when the plunger  20  is retracted proximally from the barrel  12 , the needle  16  is carried by the anchor  18  (hereinafter “needle and anchor assembly”) inside the barrel  12  as a result of the coupling between the anchor  18  and the plunger  20 . As used herein, the phrase “needle and anchor assembly” refers to the needle carried by the anchor.  
      The coupling mechanism according to the invention for effecting the coupling between the anchor  18  and the plunger  20  comprises the anchor with a plurality of flexible legs  22  terminating proximally with outward facing snap elements  24  that snap under and engage a snap edge  26  in a distal end  29  of the plunger  20 .  
      In accordance with the present invention, and as illustrated with respect to a preferred embodiment in  FIGS. 1-14 , the syringe  10  enables a user to safely and accurately administer injections while substantially reducing the risk of needlestick injury. The improved syringe is simply constructed, and relatively inexpensive. The improved syringe requires no change to current safety syringe injection techniques. After injection, the syringe barrel harbors the needle post-retraction for safe transport and disposal thus rendering the needle inaccessible for reuse.  
      As shown in  FIGS. 1-2B , the hypodermic needle assembly  14  comprises a conforming hub  30  that may be pressed against the barrel conical distal portion  13  ( FIG. 3 ) for frictional and releasable connection therewith. The anchor  18  may be releasably mounted coaxially in the hub and the needle  16  threaded through and fixedly attached to the anchor  18 . In typical manner, the needle is provided on its distal extremity with a sharpened penetrating end (not shown) in order to be able to insert the needle in the body.  
      As shown in  FIGS. 1, 2  and  2 B, the hub  30  contains a longitudinal distal bore  32  that makes it possible to close-fittingly mount it around a distal portion of the anchor. The hub defines a sealing lip  38  that substantially prevents fluid leakage between the anchor  18  and hub  30 . As shown in  FIG. 2A , the anchor  18  comprises a substantially cylindrical distal portion  34  containing a longitudinal bore  36  through which the needle  16  is threaded and fixedly attached and a proximal portion defined by the plurality of flexible legs  22 . The diameter of the bore  36  in the anchor  18  corresponds to the diameter of the needle threaded therethrough to fix the needle in the bore without substantially any clearance between the bore and the needle. Anchor bore diameters may thus be sized to permit needles with different diameters to be placed therein.  
      As shown in  FIGS. 2A and 2B , the anchor  18  extends radially outwardly from the substantially cylindrical portion of the anchor to define a radial edge  39  before extending proximally to the plurality of flexible legs. The plurality of flexible legs  22  terminate in the outward facing snap elements  24  and include outward facing notches  40  in approximately the middle of the flexible legs for purposes as hereinafter described. As shown in  FIGS. 5-8 , the outward facing notches  40  are disposed inside the hub between the distal end of the syringe barrel and the substantially cylindrical part of the anchor until the needle and anchor assembly are retracted as hereinafter described. During forward movement of the plunger as a result of the distally oriented force exerted on the needle, the radial edge  39  of the anchor becomes blocked by the sealing lip  38  to substantially prevent movement of the needle and anchor assembly from the barrel to avoid the needle from penetrating further into the body of the patient  
      As is known in the art, the syringe barrel  12  has the conical distal end  13  that may be formed concentric to the axis of the barrel and a proximal open end  42 . A flange  44  may extend radially from the proximal open end to prevent slipping of the barrel through the finger.  
      As shown in  FIGS. 10-13 , the plunger  20  has a substantially cylindrical distal end portion  29  having a small recessed opening  28  in a side thereof and an inward funnel  33  at the tip for guiding the plurality of flexible legs of the anchor into the plunger. A substantially circular opening  35  at the bottom of the narrower part of the funnel  33  defines the snap edge  26  for coupling with the snap elements  24  of the anchor.  
      The substantially cylindrical distal end portion  29  of the plunger  20  is received in the distal end portion of the barrel  13  when the plunger  20  is at its distal position as shown in  FIG. 4 . A plunger gasket  46  substantially prevents leakage of the syringe. A medication or the like (not shown) for injection is disposed inside the barrel  12  between the plunger gasket  46  and the distal end of the barrel  13 .  
      In use, a suction needle (not shown) is placed on the syringe  10  by sliding a conventional needle hub (not shown) onto the distal portion of the barrel  13 . The suction needle (not shown) can be placed in the liquid and the injection liquid drawn into the syringe by retracting the plunger  20 . After removing the conventional needle hub from the distal portion of the syringe barrel, the hypodermic needle assembly  14  is placed on the syringe barrel  12  by sliding the hub  30  onto the distal end of the syringe barrel  13 . The medication is then administered to the patient in the usual way, by inserting the distal extremity of the needle into the patient and the medication discharged into the patient by displacing the plunger  20  toward its distal end position as shown beginning in  FIG. 5 . Once the medication is expelled, continued displacement of the plunger  20  at its distal end position pushes the plunger toward the snap elements  24  of the anchor  18 . As the plunger is further displaced toward its distal end portion, the flexible legs  22  of the anchor bend radially inwardly because of their flexible construction as shown in  FIG. 6  to fit into the distal end of the plunger  29 . When the plunger is fully displaced at its distal end position as shown in  FIG. 7 , the snap elements  24  move past the snap edge  26  and expand to snap under the snap edge  26  of the plunger as shown in  FIG. 8 , thus effecting an operational coupling between the plunger  20  and the anchor  18 .  
      The plurality of notches  40  substantially prevent movement of the anchor and needle assembly into the barrel when there is a proximal force on the needle (i.e. the penetrating force of the needle into the patient). As shown in  FIGS. 6-8 , the plurality of notches are closer to each other when the anchor is coupled to the plunger thereby permitting the anchor and needle assembly to retract through the distal end portion of the barrel following penetration as shown in  FIG. 9 . When the plunger is retracted proximally after the liquid has been injected (See  FIG. 9 ), the plunger carries the anchor and the needle fixedly connected (i.e. the needle and anchor assembly) thereto along inside the barrel as a result of the coupling between the end portion of the plunger and the anchor. The needle is therefore harbored inside the barrel for safe transport and disposal, thus minimizing needlestick injuries and reuse of the syringe. Each of these working steps is shown in  FIG. 14 .  
      Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications 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.