Abstract:
A hypodermic syringe provides a simple mechanism for manually retracting its needle into the syringe after injection has been completed. The syringe preferably has an elastomeric barrel to exert a radial bias to seal on a retractable needle carrier and the plunger. Attachment components on the plunger and needle carrier engage such that withdrawal of the plunger releases the needle carrier for withdrawal into the syringe barrel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a provisional conversion application and claims priority to commonly owned and prior filed provisional application No. 60/401,742 filed on Aug. 6, 2002 and entitled “Safety Syringe.” 

   FIELD OF THE INVENTION 
   The present invention relates to medical devices and more particularly to hypodermic syringes designed to provide cross contamination protection to others by way of a retractable needle assembly that prevents accidental contact with the needle after use. 
   BACKGROUND OF THE INVENTION 
   Inadvertent needle stick injuries from used syringes may present a significant health hazard to others if infectious blood products are transmitted. Such accidental needle sticks may spread hepatitis, AIDS and other communicable diseases to health care workers and patients. In certain instances, the resulting disease may be life threatening. Further, the emotional distress from the fear of contracting such diseases can be significant. Still further, in the event of a stick, series of diagnostic blood tests may have to be performed to determine if cross-contamination has occurred in a needle stick injury. In many cases, the victim often is required to receive injections of gamma globulin to prevent further infection and to cure the patient. This is uncomfortable, inconvenient, and expensive to the victim. 
   According to the prior art, the usual technique has been to, after use of the needle, to break off the needle and dispose of the needle and syringe in a “sharps” container for secured disposal such as by incineration or stabilization in, for example, plastic of concrete. 
   Efforts have been made to develop syringes which attempt to prevent inadvertent sticks. In Chen, U.S. Pat. No. 6,432,082 issued Aug. 13, 2002, there is disclosed a safety syringe having a needle holder which is retractable into the barrel of the syringe. The needle holder is secured to the syringe barrel by a frangible component. After use, the uses forces the plunger to couple with the needle holder and withdraws the plunger to rupture the frangible component so that the portion of the holder mounting the needle (cannula) can be withdrawn into the barrel. A drawback of this design is that the frangible portion of membrane must be manufactured to tolerances such that (1) the pressure imposed by the plunger during aspiration of the medicine into or injection of the medicine out of the syringe does not rupture the seal and (2) still provide for rupturing the portion during withdrawal of the plunger without the plunger first separating from the needle holder. It is submitted that such requirements contribute to the expense of such a device. Further, the inability of the health card provider to rupture the portion will cause frustration and abandonment of the operation to withdraw the needle. 
   In Jenson, U.S. Pat. No. 5,540,660 issued Jul. 30, 1996 there is disclosed another syringe where a needle holder is captured by the plunger for withdrawal into the syringe barrel. In one embodiment of this disclosure, the plunger makes and interference fit into a tapered sleeve such that withdrawal of the plunger withdraws the sleeve and needle into the barrel. A drawback of this arrangement is that it would be difficult to aspirate medicine into the syringe without creating an interference fit between the plunger and sleeve thus disabling the syringe before injection of the medicine. In another embodiment an snap connection is utilized to couple the plunger to a needle holder. In either embodiment, close tolerances must be adhered to during manufacture to provide the seal between the sleeve and needle holder. Further, for either embodiment, an arcuate cannula is required to prevent re-use of the device. 
   Mazur, U.S. Pat. No. 5,205,824 issued Apr. 27, 1993 discloses another syringe where the needle holder is retained at the end of the syringe barrel only by the friction between the o-rings and the barrel which, it is believed, would (1) make secure attachment of the needle to the holder difficult since the holder may tend to rotate as the needle is threaded thereon. Further there remains a risk that insertion of he needle into a bottle of medicine for aspiration of medicine into the syringe would dislodge the needle holder and interfere with the seal. 
   There is a need for a safety syringe which is easy and inexpensive to manufacture, which provides for withdrawal of the needle into the barrel of the syringe, which can be re-used if desired, which has a positive coupling to provide for attachment of the needle and retention of the needle during aspiration and injection, which provides for a positive stop during withdrawal of the needle to indicate full withdrawal of the needle and which overcomes the drawbacks noted above. 
   SUMMARY OF THE INVENTION 
   There is, therefore, set forth according to the present invention, a safety hypodermic syringe designed to provide cross contamination protection to others by way of a retractable needle assembly obviating accidental contact with the needle to another person and which is of simple and inexpensive construction. 
   Toward this end the safety syringe is disclosed which includes a hollow barrel having a forward and rear end. Proximate the forward end a first retention structure is provided which may be in the form of a circumferential groove or ridge or other suitable structure. A first coupling structure is also provided at the first end. Proximate said rear end is a second retention structure which may also be in the form of a circumferential groove or ridge. 
   A needle carrier is disposed at said forward end and has a third retention structure configured to engage with the first retention structure to releaseably retain the needle carrier at the forward end and to engage the second retention structure to retain said needle carrier in a position withdrawn into the barrel. To prevent the needle carrier from rotating in the barrel at the first end, the barrel and needle carrier have cooperative coupling structures which may be embodied as engaging tabs or teeth. Also provided is a mounting for mounting a needle such as a threaded or luer lock connection as is known in the art. 
   A plunger is disposed in the barrel and has a head to slideably seal within the barrel for aspiration of fluid into an out of the barrel. At the head and at the needle carrier are cooperative attachment components which, when engaged, attach the needle carrier to the plunger for withdrawal thereof. Withdrawal of the plunger disengages the third retention structure from the first retention structure to release the needle carrier to be withdrawn a position in the barrel where the third retention structure engages the second retention structure to retain the needle carrier with its needle in the withdrawn position. 
   The barrel may be rigid but is preferably fashioned from an elastomeric material such as plastic or the like to be radially biased at least in the regions of the first and second retention structures for engagement with the third retention structure. The barrel may also be rigid with an elestomeric liner. 
   Accordingly, the health care provider positions the plunger adjacent the needle carrier and secures the needle to the needle carrier. The needle is inserted into a vial of fluid and the plunger is withdrawn to aspirate the fluid to be injected into the barrel. The needle is withdrawn from the vial and, for example, inserted into a patient. The plunger is pushed through the barrel to aspirate the fluid from the barrel through the needle into the patient. At the forward end the plunger is positioned such that the cooperative retention structures on the head and needle carrier engage to capture the needle carrier to the plunger. Thereafter the plunger is withdrawn disengaging the needle carrier from the forward end of the syringe barrel and continued withdrawal of the plunger withdraws the needle carrier and needle to a position nested within the barrel whereat the needle carrier engages the second retention structure to retain the needle carrier within the barrel. In this position the needle is safely withdrawn into the barrel to prevent inadvertent sticks. The syringe may then be disposed of in a sharps disposal container. If desired, the syringe may be sterilized and re-used. 

   
     DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages will become better understood with reference to the description, claims and drawings wherein: 
       FIG. 1  is a front perspective view of the syringe without a needle; 
       FIG. 2  is a side, perspective, partial section view of the needle carrier; 
       FIG. 3  is a side section view of the needle carrier mounted in the barrel of the syringe of  FIG. 1 ; 
       FIG. 4  is a side view of the plunger for the syringe of  FIG. 1 ; 
       FIG. 5  is an end view of the plunger of  FIG. 4 ; 
       FIG. 6  is a section view of the fluted shaft of the plunger of  FIG. 6  taken along line  6 — 6 ; 
       FIG. 7  is a side section view of the syringe with the plunger in a first position; 
       FIG. 8  is a side section view showing capture of the needle carrier by the plunger and withdrawal into the barrel; and 
       FIG. 9  is a perspective, partial cutaway view of the barrel for the syringe. 
   

   DESCRIPTION 
   Turning to the drawings,  FIG. 1  shows the safety syringe  10  according to the present invention. The syringe  10  includes a barrel  12  which may be cylindrical and rigid such as by being manufactured from a hard plastic. Alternatively and preferably, the barrel may be constructed from an elastomeric or elastically deformable material such as such as vinyl, soft polyurethane or other elastically, radially biased, deformable plastic. The deformable plastic should be somewhat elastic but still able to retain its overall cylindrical shape and should be selected to withstand sterilization processes. Still alternatively, the barrel  12  may be rigid with an interior, elastic, lining. Thus, the elastic characteristic permits the barrel  12  to impose a radial bias against expansion and to be contractile to a degree. 
   To provide for aspiration of the desired amount of fluid, e.g. medicine, into the barrel  12 , the barrel should transparent or semi-transparent and include graduation markings to indicate volume within the barrel  12 . 
   The syringe  10  also includes a needle carrier  14 , the details of which will hereafter be described. 
   To provide for aspiration of fluid into an out of the syringe barrel  12 , the syringe  10  includes a plunger  16 , the details of which will hereafter be described. 
   The barrel  12  is hollow and preferably cylindrical having a forward end  18  and rear end  20 . At the rear end  20  a pair of finger loops  22   a, b  may be mounted to the barrel  12  to receive the fingers of the health care provider using the syringe  10 . 
   With reference to  FIGS. 3 , and  7 - 9 , the barrel  10  includes proximate the forward end  18  a rearward facing, circumferential shoulder  24  which defines a first coupling structure the purposes of which will hereinafter become evident. The shoulder  24  may have teeth  26 , tabs, notches or other cooperative structure to engage with structure on the needle carrier  14  to prevent coaxial rotation thereof relative to the barrel  12 . 
   Disposed rearward of the shoulder  24  inside the barrel  12  is a first retention structure  28  illustrated as one or more circumferentially arranged, radial projections fashioned within the barrel  12 . As shown in the drawings, the first retention structure  28  may be a continuous, circumferential ridge or projection. Alternatively the first retention structure my be discontinuous. 
   Disposed proximate the rear end  20  of the barrel  12  and inside thereof is a second retention structure  30 . The second retention structure  30  has a construction similar to the first retention structure  28 . The second retention structure  30  is disposed such that, as hereinafter described, the needle carrier  14  and attached needle can be fully withdrawn into the barrel  12 . 
   In an alternative embodiment, the first and second retention structures  28 ,  30  may be embodied as continuous or discontinuous circumferential grooves in the inside wall of the barrel  12 . 
   Turning to  FIGS. 2 and 3 , an embodiment of the needle carrier  14  is shown. The needle carrier  14  is generally cylindrical to be received at the forward end  18  of the barrel  12 . In a cylindrical first portion  32  there is disposed a third retention structure  34  shown as embodied as a circumferential depression  36  dimensioned to closely receive the first and second retention structures  28 ,  30  of the barrel  12  to releasably retain and capture the needle carrier  14  therein. Where the first and second retention structures  28 ,  30  are grooves or depressions, the third retention structure  34  would be a projection to be received into the grooves. 
   The first portion  32  transitions to a smaller diameter second portion  38  at a circumferential, axially and forwardly directed, surface  40  defining a second coupling structure. The surface  40  is cooperatively configured to engage with the first coupling structure of the shoulder  24  and its teeth  26  to couple the needle carrier  14  to the barrel  12  against axial rotation. Thus the surface  40  includes teeth  42  as well. It should be noted that the first and second coupling structures could have any suitable configuration for coupling thereof such as one or more interlocking tabs, pins, or the like. 
   At the forward end of the needle carrier there is defined a mounting structure suitable for mounting of a needle  42  ( FIGS. 7 and 8 ) or cannula. Accordingly the forward end of the needle carrier includes an axially projecting, hollow, nipple  44 . The nipple  44  is supported by a radial substrate  46  which extends to a cylindrical wall  48  which extends axially spaced from the nipple  44 . The inside surface of the wall  48  includes threads  50 . The needle  42  has an exteriorly threaded cap  52  which is received over the nipple  44  and is threaded into the wall  48  with cooperating threads. The cap  52  and threads  50  define a standard luer lock connection for the needle as is known in the art. As shown in  FIG. 7 , when the needle  42  is mounted to the needle carrier  14 , a fluid passageway is defined through the nipple  44  and needle  42  for fluid to be aspirated into and from the syringe barrel  12  thought the needle  42 . 
   Opposite the nipple  44  the needle carrier  14  has a first attachment component  70  adapted for coupling the needle carrier  14  to the plunger  16 . With reference to  FIG. 3 , the first attachment component is defined as an ellipsoidal recess  72  defined in the needle carrier  14  and which intersects with the hollow of the nipple  44 . The recess  72  opens to the inside of the barrel  12  through a reducing neck  74  defined by a circumferential, and radially inwardly directed nose  76 . At spaced locations, e.g. at 90 degree intervals, radially directed, deformable wings  78  extend into the recess  72 . Each wing includes a radial slot  80 . 
   To provide for aspiration of fluid and for withdrawing the needle carrier  14 , the syringe  10  also includes the plunger  16  as shown in  FIGS. 4-6 . The plunger  16  includes at one end a thumb loop  54  to receive the thumb of the health care provider for manipulation of the plunger  16 . A shaft  56  extends between the thumb loop  54  and a plunger head  58 . The shaft  56  may be orthogonally fluted or of any other suitable shape. 
   At the head  58  there are disposed axially spaced and radially extending first and second seals  60   a, b  which are, when the barrel  12  is rigid, elastically deformable to engage and seal against the inside surface of the barrel  12 . Where the barrel  12  is elastomeric or includes an elastomeric lining the seals  60   a, b  may be rigid. 
   Forward of the seals  60   a, b , the head  58  includes a radially extending stop  62 . Forward of the stop  62  is a radially extending, deformable disk  64  of a size to (1) deform to pass through the neck  74  and to expand to engage into the slots  80  for coupling the needle carrier  14  to the plunger  16 . The disk  64  defines a second attachment component for the syringe  10 . Forward of the disk is an end piece  66  which is adapted to be received into the recess  72 . 
   With the foregoing in mind the operation of the syringe  10  will now be described. The syringe  10  is assembled with the needle carrier  14  disposed in the forward end  18  of the barrel  12 . In this position the first retention structure of the barrel, e.g. the radially projecting projection, is received into the depression of the needle carrier  14  defining the third retention structure. The elastomeric character of the barrel  12  constricts to retain the components. Thus, to displace the needle carrier  14 , i.e. disengage the first and third retention structures, a first axial displacement force is required. This force may act to locally expand the barrel  12  or, if the barrel  12  is rigid, compress the first portion  32  of the needle carrier  14  or both. In a preferred embodiment the interference retention of the needle carrier  14  in the barrel  12  is with a force F 1  greater than that required for insertion of the needle into a medicine vial, patient or other intended use. That is, during aspiration, the needle carrier  14  remains retained by the engagement of the first and third retention structures. 
   As manufactured, the plunger  16  is retained in the barrel  12  for example in the position as suggested in FG  7  in readiness for aspiration of medicine into the syringe  10 . 
   The needle  42  is threaded onto the needle carrier  14 , also as suggested in FIG.  7 . The needle carrier  14  is retained against rotation during the mounting of the needle  42  by the coupling between the shoulder teeth  26  and the teeth of the surface  40 . Once the needle  42  is secured to the needle carrier  14 , the needle  42  is inserted into a medicine vial, for example, and the plunger  16  is withdrawn in the barrel  12  to aspirate medicine into the barrel  12 . The seals  60   a, b  seal the plunger head  58  within the barrel  12 . Any air remaining in the barrel  12  is aspirated from the barrel  12  by forward movement of the plunger  16 . 
   The needle  42  is then inserted into the patient and the medicine is aspirated from the barrel  12  by forward motion of the plunger  16  and injected into the patient. The elastomeric character of the barrel  12  helps seal against the plunger  16 . At the end of the injection, the plunger  16  is displaced to cause the head  58  to approach the needle carrier  14 . The disk  64  deforms to pass through the neck  47  and ultimately snap outward to engage into the slots  80  of the wings  78  to thereby attach the needle carrier  14  to the plunger  16  as shown in FIG.  8 . The stop  63  engages the needle carrier  14  to limit and guide the insertion of the head  58  components into the recess  72 . The plunger  16  may then be withdrawn with a force greater than F 1  to overcome the retention force offered by the engagement by first and third retention structures  28 ,  32  to dislodge the needle carrier  14  for withdrawal into the barrel  12 . Continued withdrawal of the plunger  16  pulls the needle carrier  14  into the barrel  12 . When the second retention structure  30  is engaged by the third retention structure  34  of the needle carrier  14 , the needle carrier  14  is retained within the barrel  12 . With the needle carrier  14  in the withdrawn position, the needle  42  is nested within the barrel  12  from the open forward end  18  preventing inadvertent sticks by the needle  42 . 
   As can be appreciated, the force F 2  necessary to separate the plunger from the needle carrier  14  must be greater than F 1  in order for the plunger to withdraw the needle carrier  14 . 
   To re-use the syringe, it would be sterilized by suitable means such as an autoclave (steam or suitable gas) and the plunger would be re-positioned to locate the needle carrier  14  such that the first and third retention structures engage as do the teeth  26  and  43 . The needle  42  is removed. The needle holder nipple  44  is held while the plunger is withdrawn with a force sufficient to overcome force F 2  thereby releasing the plunger  16  from the needle carrier  14  for re-use thereof. 
   It should be noted that the present invention is subject to many modifications without departing from scope of the invention as expressed in the claims. For example, the barrel  12  need not be cylindrical. Further, only a portion of the barrel  12  may be elastomeric or coated with an elastomeric liner.