Abstract:
The present invention relates to a syringe ( 10 ) for administering injections of medicinal fluids to a patient or withdrawal of fluid, such as blood from a patient. More specifically the present invention is a syringe device ( 10 ) for injecting medication or withdrawing fluid, wherein after use the needle ( 60 ) is shielded ( 15 ) against inadvertent contact to prevent needle sticks.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to syringes for administering injections of medicinal fluids to a patient or withdrawal of fluid, such as blood from a patient. More specifically, the invention relates to such devices having a retractable needle feature for rendering the device non-reusable and safely disposable. This application claims priority to U.S. Provisional Application No. 60/169,430, which incorporate herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    Various types of medical devices employ a needle for piercing the skin of a patient for diagnostic or therapeutic purposes. One such device is a hypodermic syringe. Handling of such needle-bearing medical devices after the needle is withdrawn from the patient can result in transmission of various pathogens, most notably human immune virus (HIV), to uninfected medical personnel, due to an inadvertent needle stick. Accordingly, it is desirable to provide a device for injecting medication or withdrawing fluid, wherein the needle is retracted into the housing of the device after use. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0003]    All of the objects of the present invention are more fully set forth hereinafter with reference to the accompanying drawings, wherein:  
         [0004]    [0004]FIG. 1 is a cross-sectional view of a first needle-bearing medical device, in which the needle is retractable after use;  
         [0005]    [0005]FIG. 2 is a cross-sectional view of the medical device illustrated in FIG. 1, in which medicine is aspirated into the device;  
         [0006]    [0006]FIG. 3 is a cross-sectional view of the medical device illustrated in FIG. 1, illustrating the device just prior to retraction of the needle;  
         [0007]    [0007]FIG. 4 is a cross-sectional view of the medical device illustrated in FIG. 1, illustrating the device after retraction;  
         [0008]    [0008]FIG. 5 is a cross-sectional view of the medical device illustrated in FIG. 1, illustrating the device after retraction;  
         [0009]    [0009]FIG. 6 is a cross-sectional view of a second needle-bearing medical device, in which the needle is retractable after use;  
         [0010]    [0010]FIG. 7 is a cross-sectional view of the medical device illustrated in FIG. 6, illustrating the device after retraction;  
         [0011]    [0011]FIG. 7A is an enlarged fragmentary view of the medical device illustrated in FIG. 7;  
         [0012]    [0012]FIG. 8 is a partially broken away perspective view of the medical device illustrated in FIG. 6;  
         [0013]    [0013]FIG. 8A is an enlarged fragmentary perspective view of the portion designated A of the medical devices illustrated in FIG. 8;  
         [0014]    [0014]FIG. 8B is an enlarged fragmentary perspective view of the portion designated B of the medical devices illustrated in FIG. 8;  
         [0015]    [0015]FIG. 9 is a partially broken away perspective view of the medical device illustrated in FIG. 6, illustrating the device after retraction;  
         [0016]    [0016]FIG. 10 is a partially broken away exploded perspective view of the medical device illustrated in FIG. 6;  
         [0017]    [0017]FIG. 11 is a cross-sectional view of a third needle-bearing medical device, in which a shield covers the needle after use;  
         [0018]    [0018]FIG. 12 is a plan view of the medical device illustrated in FIG. 11;  
         [0019]    [0019]FIG. 13 is a perspective view of the medical device illustrated in FIG. 11;  
         [0020]    [0020]FIG. 14 is a cross-sectional view of the medical device illustrated in FIG. 11, illustrating the device just prior to advancement of the shield;  
         [0021]    [0021]FIG. 15 is a cross-sectional view of the medical device illustrated in FIG. 11, illustrating the device after the shield is advanced;  
         [0022]    [0022]FIG. 16 is a cross-sectional view of a fourth needle-bearing medical device, in which a shield covers the needle after use;  
         [0023]    [0023]FIG. 17 is a cross-sectional view of the medical device illustrated in FIG. 16, illustrating the device just prior to advancement of the shield;  
         [0024]    [0024]FIG. 18 is a cross-sectional view of the medical device illustrated in FIG. 16, illustrating the device after the shield is advanced;  
         [0025]    [0025]FIG. 19 is an enlarged fragmentary cross-sectional view of the medical device illustrated in FIG. 16;  
         [0026]    [0026]FIG. 20 is an enlarged fragmentary cross-sectional view of the medical device illustrated in FIG. 17;  
         [0027]    [0027]FIG. 21 is a cross-sectional view of a fifth needle-bearing medical device, in which the needle is retractable after use;  
         [0028]    [0028]FIG. 22 is a cross-sectional view of the medical device illustrated in FIG. 21, illustrating the device after retraction;  
         [0029]    [0029]FIG. 23 is a fragmentary cross-sectional view of a sixth needle-bearing medical device, in which the needle is retractable after use;  
         [0030]    [0030]FIG. 24 is an enlarged fragmentary cross-sectional view of the medical device illustrated in FIG. 23;  
         [0031]    [0031]FIG. 25 is a fragmentary cross-sectional view of a seventh needle-bearing medical device, in which the needle is retractable after use;  
         [0032]    [0032]FIG. 26 is a fragmentary cross-sectional view of an eighth needle-bearing medical device, in which the needle is retractable after use;  
         [0033]    [0033]FIG. 27 is a cross-sectional view of the medical device illustrated in FIG. 26, illustrating the device just prior to retraction;  
         [0034]    [0034]FIG. 28 is a cross-sectional view of the medical device illustrated in FIG. 26, illustrating the device after retraction;  
         [0035]    [0035]FIG. 29 is a cross-sectional view of a ninth needle-bearing medical device, in which the needle is retractable after use;  
         [0036]    [0036]FIG. 30 is a cross-sectional view of the medical device illustrated in FIG. 29;  
         [0037]    [0037]FIG. 31 is a cross-sectional view of the medical device illustrated in FIG. 30, illustrating the device after a fluid specimen has been obtained;  
         [0038]    [0038]FIG. 32 is a cross-sectional view of the medical device illustrated in FIG. 29, illustrating the device after retraction;  
         [0039]    [0039]FIG. 33 is a cross-sectional view of the medical device illustrated in FIG. 30, illustrating the device after the fluid specimen has been expelled;  
         [0040]    [0040]FIG. 34 is an enlarged perspective view of a piston of the device illustrated in FIG. 30;  
         [0041]    [0041]FIG. 35 is an exploded perspective view of the device illustrated in FIG. 30;  
         [0042]    [0042]FIG. 36 is a fragmentary cross-sectional view of a tenth needle-bearing medical device, in which a shield covers the needle after use;  
         [0043]    [0043]FIG. 36A is an enlarged fragmentary cross-sectional view of the portion designated A of the medical device illustrated in FIG. 36;  
         [0044]    [0044]FIG. 36B is an enlarged fragmentary cross-sectional view of the portion designated B of the medical device illustrated in FIG. 36;  
         [0045]    [0045]FIG. 37 is a cross-sectional view of the medical device illustrated in FIG. 36;  
         [0046]    [0046]FIG. 38 is a cross-sectional view of the medical device illustrated in FIG. 36, illustrating the device just prior to advancement of the shield;  
         [0047]    [0047]FIG. 39 is a cross-sectional view of the medical device illustrated in FIG. 36, illustrating the device after the shield is advanced;  
         [0048]    [0048]FIG. 40 is an exploded perspective view of the medical device illustrated in FIG. 36;  
         [0049]    [0049]FIG. 41 is a cross-sectional view of an eleventh needle-bearing medical device, it which the needle is retractable after use;  
         [0050]    [0050]FIG. 42 is a cross-sectional view of the medical device illustrated in FIG. 41, illustrating the device after retraction; and  
         [0051]    [0051]FIG. 43 is an enlarged fragmentary cross-sectional view of the medical device illustrated in FIG. 41. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0052]    First Device  
         [0053]    Referring now to FIGS.  1 - 5 , a syringe  10  having a retractable needle  60  is illustrated. The syringe includes a needle retainer  40  for releasably retaining the needle during use. A plunger  35  is operable to aspirate medicine into the syringe and expel medicine from the syringe into a patient. At the end of an injection stroke, the plunger  35  engages the needle retainer  40  to release the needle for retraction. A spring  55  then displaces the needle  60  rearwardly so that the contaminated needle is shielded within the syringe  10 .  
         [0054]    The syringe  10  includes a generally cylindrical hollow barrel  20 . The rearward end of the barrel is open for receiving the plunger  35 . The forward end of the barrel is generally closed, having a reduced diameter opening through which the needle  60  projects. A pair of retaining holes  22  are formed in the side of the barrel adjacent the forward end of the barrel. The retaining holes  22  cooperate with the needle retainer  40  to retain the needle  60  prior to retraction. A pair of lockout openings  24  are formed in the side of the barrel adjacent the rearward end of the barrel (see FIG. 5). The lockout openings  24  cooperate with a pair of locking arms  50  to lock the needle in a retracted position.  
         [0055]    An axially elongated stem  30  is disposed within the barrel  20 . The stem cooperates with the plunger  35  to effectuate aspiration and expulsion of medicine into and out of the syringe. Specifically, the stem  30  includes a seal  32  disposed at the rearward end of the stem. The needle  60  is fixedly attached to the stem  30  by an adhesive, such as epoxy, so that the forward sharpened tip of the needle projects forwardly from the stem, and the rearward end of the needle projects into an opening at the rearward end of the stem, adjacent the seal  32 . The stem is generally hollow, and a spring disk  34  is attached to the stem within the hollow portion of the stem. The spring disk  34  provided bearing surface against which the rearward end of the spring  55  bears.  
         [0056]    The plunger  35  is an axially elongated generally hollow cylinder having an open forward end and a closed rearward end. The interior of the plunger  35  forms a cavity  37  for receiving medicinal fluid. The diameter of the cavity  37  is sized to cooperate with the exterior diameter of the seal  32  on the stem  30  to provide a fluid tight seal between the plunger and the stem. The forward end of the plunger  35  forms a rim for engaging the needle retainer  40  as described further below. A thumb pad  39  is formed at the rearward end of the plunger  35  to facilitate manual operation of the plunger. Specifically, the thumb pad  39  forms a surface that the user can press against to advance the plunger to expel fluid from the syringe.  
         [0057]    The needle  60  is operable between an extended position in which the sharpened tip of the needle is exposed for use and a retracted position in which the sharpened tip is shielded within the barrel to prevent inadvertent contact with the sharpened tip. The spring  55  circumscribes the needle  60 , and biases the needle and attached stem  30  rearwardly toward the retracted position. The needle retainer  40  releasably retains the needle and attached stem in the extended position.  
         [0058]    The needle retainer  40  comprises at least one and preferably two radially deformable arms  42 . The ends of the arms  42  form latches that engage the retaining holes  22  in the barrel to retain the needle against the bias of the spring  55 . The needle retainer arms  42  are connected to the stem  30 , and preferably are integrally formed with the stem. At least a portion of the needle retainer arms  42  extend transverse the central axis of the barrel  20 . This transverse portion of each needle retainer arm forms an engagement surface that cooperates with the forward rim of the plunger  35 , as discussed further below.  
         [0059]    Configured in this way, the device operates as follows. FIG. 1 illustrates the syringe  10  as it is shipped. A needle cover  15  encloses the forward end of the needle  60  to maintain the sterility of the needle. Referring to FIG. 2, the needle cover  15  is removed, and medication can be aspirated into the syringe from a vial by inserting the sharpened tip into the vial and displacing the plunger  35  rearwardly. The fluid tight seal between the seal  32  and the interior of the plunger  35  create a vacuum as the plunger is displaced rearwardly. In response, fluid flows from the vial through the needle and into the plunger cavity  37  that is in fluid communication with the needle. This procedure for aspirating the syringe  10  is essentially the same as the procedure for aspirating a typical non-safety syringe. However in the present instance, the medicine is aspirated into the plunger  35 , rather than into the barrel  20 , as occurs in a typical non-safety syringe.  
         [0060]    After medicine is aspirated into the syringe, the medicine can be injected into a patient by pressing against the thumb pad  39  to displace the plunger  35  forwardly. The medicine flows from the plunger cavity  37  through the needle  60  and into the patient. The distance from the rearward end of the seal  32  to the actuation surface of the needle retainer  40  is the same as the distance from the rim of the plunger to the end wall of the cavity  37  in the plunger. In this way, at the end of the injection stroke (i.e. substantially all of the medication is expelled from the plunger cavity  37 ), the rim of the plunger  35  engages the needle retainer arms  42 , displacing the arms radially inwardly so that the arms disengage the retaining holes  22  in the barrel  20 , as shown in FIG. 3.  
         [0061]    Referring to FIG. 4, after the needle retainer  40  is released, the spring  55  displaces the stem  30  rearwardly. Since the needle  60  is attached to the stem  30 , the needle is displaced rearwardly along with the stem. Further, since the plunger is in engagement with the stem  30 , the plunger is also displaced rearwardly along with the stem.  
         [0062]    Referring now to FIG. 5, a cross-sectional view that is taken through a plane orthogonal to the view in FIG. 4. This view shows the details of the locking feature of the syringe  10 . Specifically, at least one, and preferably two radially deformable locking arms  50  project radially outwardly from the stem  30 . The distance between the rearward end of the seal  32  and the locking arms  50  is greater than the distance from the forward rim of the plunger to the rearward wall of the plunger cavity  37 , so that at the end of the injection stroke the plunger does not engage the locking arms.  
         [0063]    When the stem  30  is disposed in the forward position, the locking arms  50  are displaced radially inwardly relative to the position illustrated in FIG. 5, and are in engagement with alignment grooves  26  formed in the interior of the barrel. The alignment grooves  26  are axially extending grooves that are substantially parallel to the axis of the barrel. As the stem  30  and needle  60  are retracted from the extended position, the locking arms  50  engage the alignment grooves  26  to guide the retraction of the stem and needle. The grooves and locking arms prevent the locking arms from rotating relative to the barrel. The alignment grooves intersect the lockout openings  24 , so that at the end of retraction, the locking arms before radially outwardly into engagement with the lockout openings  24 .  
         [0064]    Second Device  
         [0065]    Referring now to FIGS.  6 - 10 , a second safety medical device is illustrated. The device  110  is a syringe having a retractable needle  160 , so that after use the contaminated needle is protected against inadvertent contact.  
         [0066]    The syringe  110  includes a cylindrical barrel  120  having a generally open forward end and a generally open rearward end. The forward end of the barrel  120  forms a socket  122  for receiving a slotted collar  130  that releasably retains a needle carrier  140 . A plunger  150  is axially displaceable within the barrel. At the end of an injection stroke, the plunger  150  engages the needle carrier  140  to automatically actuate retraction of the needle  160 .  
         [0067]    The needle  160  has a sharpened tip that is operable between an extended position and a retracted position. In the extended position, the needle projects forwardly from the barrel  120  to facilitate an injection of medication. In the retracted position, the sharpened tip of the needle is enclosed within the barrel  120  to prevent inadvertent contact with the contaminated sharpened tip of the needle. A spring  155  biases the needle  160  toward the retracted position.  
         [0068]    As showed in FIG. 10, preferably the needle  160  is bonded to a needle hub  162 , forming a needle assembly similar to standard needle assemblies that are presently used in the medical profession. The needle hub has a connector, such as a Luer connector for attaching the needle assembly to the needle carrier  140 .  
         [0069]    The needle carrier  140  is adapted to engage the needle assembly and releasably retain the needle assembly against the bias of the spring  155 . The needle carrier  140  includes A connector  146  such as a Luer connector that is configured to cooperate with the needle hub  162  to provide a fluid tight seal between the needle hub and the needle carrier. The needle carrier further includes a pin  142  that cooperates with the slotted collar  130  to releasably retain the needle  160  in the extended position, as discussed in greater detail below. In addition, preferably the needle carrier comprises a second pin circumferentially spaced from the pin  142  shown in FIG. 10, whereby the two pins are symmetrically disposed about the circumference of the needle carrier, and both pins cooperate with the collar  130 .  
         [0070]    A sealing ring  144  is attached to the rearward end of the needle carrier  140  to provide a fluid tight seal between the needle carrier and the barrel  120 . The sealing ring  144  prevents fluid from leaking out the forward end of the barrel  120 . In this way, the sealing ring  144  forms the forward wall for the fluid cavity within the barrel in which the medication is contained.  
         [0071]    The needle carrier  140  is a generally cylindrical element having a through bore that operates as a fluid passage between the interior of the barrel and the needle. In this way, when a needle assembly  160 , 162  is attached to the needle carrier, the needle is in fluid communication with the fluid cavity within the barrel.  
         [0072]    The spring  155  is disposed between the slotted collar  130  and the needle carrier  140  biasing the needle carrier rearwardly. The spring  155  circumscribes the needle carrier  140 , and the rearward end of the spring engages a circumferential flange projecting radially outwardly from the rearward end of the needle carrier adjacent the sealing ring  144 .  
         [0073]    Referring to FIGS. 8A and 8B, the details of the slotted collar  130  are illustrated in greater detail. As shown in FIG. 8A, the slotted collar  130  is a generally cylindrical collar engaged with the socket  122  at the forward end of the barrel  120  to fixedly attach the collar to the barrel. Specifically, the socket  122  comprises an annular ridge  123  at the forward end of the barrel and an annular flange  124  axially spaced from the forward ridge. The ridge  123  and flange  124  operate to retain the collar within the socket  122 . In addition, preferably, the slotted collar  130  comprises in alignment key  131  that aligns the slotted collar at a predetermined circumferential position relative to the barrel  120 . The alignment key  131  cooperates with an axial groove formed in the socket  122  of the barrel. Although the connection between the slotted collar  130  and barrel has been described above as a snap fit or press it engagement, the slotted collar can be fixedly attach to the barrel in a number of other ways. For instance, the slotted collar can be bonded to the barrel  120 , such as by epoxy.  
         [0074]    The slotted collar  130  comprises at least one, and preferably two pin slots  132  that cooperate with retaining pins  142  attached to the needle carrier  140 . The pin slots  132  are disposed transverse the axis of the syringe. Referring to FIGS. 8A and 8B, an axial groove  134  intersects the pin slots  132 . The rearward edge of the pin slot  132  forms a shoulder that engages the pin  142  to retain the needle carrier, as shown in FIG. 8B. The depth of the axial groove  134  is greater than the length of the pin  142  that projects into the pin slot  132 . Therefore, when the needle carrier  140  is twisted so that the pin  142  is circumferentially aligned with the axial groove  134 , the needle carrier  140  is free to move axially rearwardly relative to the collar  130 .  
         [0075]    Accordingly, the syringe  110  operates as follows. Prior to use the user selects a needle assembly attaches it to the needle carrier  140 . A dose of medication is then aspirated into the syringe by displacing the plunger rearwardly. The plunger  150  includes a piston  152  that forms a fluid-tight seal with the interior wall of the barrel. Therefore, displacing the plunger rearwardly forms a vacuum within the barrel, so that medicine is drawn into the barrel with the plunger is displaced rearwardly.  
         [0076]    At the end of the injection stroke, the plunger  150  engages the needle carrier  140 . Continued forward axial displacement of the plunger  150  drives the needle carrier  140  forwardly. The engagement between the pins  142  and the angled pin slots  132  operate like a cam and follower, causing the needle carrier to rotate until the pins are aligned with the axial grooves  134 . The spring  155  then drives the needle carrier  140  and attached needle  160  rearwardly into the retracted position. In addition, since the plunger  150  is engaged with the needle carrier  140 , the plunger  150  is also displaced rearwardly as the needle is retracted. Preferably, the barrel includes a locking rib  126  projecting radially inwardly from the interior wall of the barrel, adjacent the rearward end of the barrel. The locking rib  126  engages the plunger, acting as a stop to impede continued rearward displacement of the plunger. In this way, the locking rib  126  prevents the plunger, needle carrier  140  and needle  160  from being displaced out the rearward end of the barrel by the spring.  
         [0077]    Third Device  
         [0078]    Referring now to FIGS.  11 - 15 , a third device  310  is illustrated. The device  310  is a syringe having a shield  330  for covering a needle  360  after use. The syringe includes a barrel  320  and a plunger  340  that are similar to commonly used non-safety syringes. However, the barrel  320  and plunger  340  are configured so that at the end of the injection stroke continued axial force on the plunger releases the shield  330 , and a spring  355  displaces the shield  330  forwardly over the used needle  360  to shield the contaminated needle against inadvertent contact.  
         [0079]    The barrel  320  is a generally hollow cylinder having a generally closed forward end with a reduced diameter opening forming a fluid passage, and a rearward end that is substantially open for receiving the plunger  340 . The plunger  340  includes a piston  344  in fluid-tight engagement with the interior wall of the barrel for aspirating medicine into the syringe and injecting medicine into a patient from the syringe. A connector  322  is formed on the forward end of the barrel  320 , and is configured to attach the needle  360  to the barrel. Preferably, the connector  322  is a threaded Luer connector.  
         [0080]    The needle  360  is fixedly attached to a needle hub  362  to form a needle assembly similar to those commonly used with non-safety medical devices. Specifically, the needle hub  362  is adapted to cooperate with the connector  322  to attach the needle assembly to the barrel  320 . Preferably, the needle hub comprises a female Luer connector providing a fluid tight seal between the needle assembly and the barrel. In this way, the needle assembly is readily attachable to the barrel by the user so that the needle is in fluid communication with the interior of the barrel.  
         [0081]    The barrel  320  includes a shield lock  324  adjacent the connector  322 . The shield lock  324  is a circumferential flange that operates to retain the shield  330  in an extended position after use. The shield lock  324  can be integrally formed with the barrel  320 , however in the present instance, the shield lock  324  is formed on the outer surface of a collar disposed around the Luer connector  322 . A flange  326  projects radially outwardly from the outer surface of the barrel  320  adjacent the rearward end of the barrel.  
         [0082]    The shield  330  is a generally cylindrical sleeve overlying the barrel  320 , so that the shield and barrel are preferably coaxial. The shield is operable between two positions, a retracted position and an extended position. In the retracted position, the needle  360  is exposed for use. In the extended position, the shield encloses the sharpened tip of the needle to prevent inadvertent needlesticks. A spring  355  disposed between the barrel and the shield biases the shield towards the extended position. Specifically, the spring is disposed between the flange  326  at the rearward end of the barrel, and an annular flange  334  projecting radially inwardly from the interior of the shield  330 , as shown in FIG. 11.  
         [0083]    At least one, and preferably two, shield latches  332  attached to the rearward end of the shield  330  releasably retain the shield in the retracted position. The shield latches  332  are radially deformable arms that engage the circumferential flange  326  formed at the rearward end of the barrel  320 . The latches  332  have rearward facing actuations surfaces that are angled transverse the axis of the syringe. The actuations surfaces cooperate with a button cap  345  on the plunger  340  to release the shield  330 , as discussed further below.  
         [0084]    The plunger  340  is axially displaceable within the barrel. A piston  344  attached to the forward end of the plunger forms a fluid tight seal with the interior surface of the barrel. The rearward end of the plunger  340  comprises a thumb pad  342  projecting radially outwardly. The button cap  345  is attached to the thumb pad  342 .  
         [0085]    The button  345  is a generally cylindrical cup-shaped element having an interior diameter that corresponds to the diameter of the thumb pad  342 . The button cap is operable between a first position and a second position. A detent  347  projects radially inwardly from the inner surface of the button cap to impede displacement of the button cap from the first position to the second position. The detent  347  cooperates with the thumb pad  342  to provide sufficient retention force to prevent the button cap from being displaced into the second position in response to forward axial force applied to the button cap to displace the plunger forwardly during an injection stroke.  
         [0086]    Referring to FIG. 12, the syringe is illustrated in a position in which the plunger is completely inserted into the barrel so that the piston  344  engages the front wall of the barrel. This is the position of the plunger at the end of an injection stroke. In FIG. 11, the button cap  345  is shown in its first position. In this position, the forward rim of the button cap does not engage the shield latches  332 . At the end of the injection stroke, the button cap  345  can be displaced into the second position by applying sufficient forward axial force to the button cap to overcome the retention forced provided by the engagement between the detent  347  and the thumb pad  342 .  
         [0087]    Referring to FIG. 14, as the button cap  345  is displaced into the second position, the forward rim of the button cap engages the actuations surfaces of the shield latches  332  deforming the shield latches radially outwardly out of engagement with the flange  326 . The spring  355  then displaces the shield  330  forwardly into the extended position to cover the needle  160 . The shield includes a shield retainer  335  in the form of a pair of radially deformable latches formed in the side wall of the shield, as shown in FIG. 13. As the shield  330  is displaced forwardly, the shield retainer engages the shield lock  324  at the forward end of the barrel  320  to lock the shield in the extended position, thereby preventing re-exposure of the needle  160 .  
         [0088]    Referring now to FIGS.  16 - 20 , a fourth safety medical device is illustrated. The device is a combination safety needle assembly  420  and syringe  410 . The syringe  410  is the same as commonly used non-safety hypodermic syringes. The needle assembly  420  is adapted to cooperate with the syringes  410  that are presently available so that they can be used with a safe needle assembly without modification. Specifically, the needle assembly  420  includes a needle  430  having a sharpened tip and a shield  440  that extends over the needle after use to prevent inadvertent contact with the contaminated needle.  
         [0089]    The syringe  410  includes a hollow cylindrical barrel  415  and a plunger  417  reciprocally displaceable within the barrel to infuse medicine into the barrel or expel fluid out of the barrel. The forward end of the barrel  415  comprises a connector  419  such as a Luer connector for attaching the needle assembly to the barrel prior to use. In the present instance, the plunger  417  is illustrated as a standard plunger used in connection with hypodermic syringes, in which the plunger comprises an axially elongated plunger rod and a piston attach to the forward end of the plunger rod. However, it may be desirable to use the needle assembly  420  with syringes that are used for drawing blood specimens and inserting guide wires. Specifically, the plunger may include a bore for receiving a guide wire, along with a valve for preventing fluid from leaking into the bore from the syringe. During use, a guide wire is inserted through the plunger and is fed through the needle  430  into a patient.  
         [0090]    The needle assembly  420  includes a needle hub  425  for attaching the needle assembly  420  to the barrel  415 . The needle hub  425  includes a connector, such as a Luer connector that cooperates with the connector  419  of the barrel to form a fluid-tight seal between the needle assembly and the syringe. The needle  430  is fixedly attached to the needle hub  425 .  
         [0091]    The  440  is operable between a retracted position, in which the needle is exposed for use as shown in FIG. 17, and an extended position in which the shield covers the sharpened tip of the needle as shown in FIG. 18. A spring  435  biases the shield  440  toward the extended position. A shield retainer  445  releasably retains the shield  440  in the retracted position against the bias of the spring  435 .  
         [0092]    The shield retainer  445  comprises at least one, and preferably two, radially deformable arms  447 . The arms  447  comprise an actuation portion disposed transverse the central axis of the syringe. The forward ends of the arms form latches that cooperate with retainer openings  442  formed in the forward end of the shield  440 . The ends of the arms  447  form a radially projecting flange  440  that cooperate with first and second locking ridges  426 ,  427  formed on the needle hub  425 . Specifically, the first and second locking ridges  426 ,  427  are formed in the inner surface of the needle hub  425  projecting radially inwardly.  
         [0093]    The locking ridges  426 ,  427  have a tapered forward edge and a perpendicular rearward edge, so that the locking ridges operate as one-way locks allowing the locking flange  449  of the retainer arms  447  to be displaced rearwardly relative to the needle hub, but not forwardly. In this way, the locking ridges  426 ,  427  cooperate with the locking flange  449  to retain the retainer arms  447  in first and second axial positions.  
         [0094]    The forward edge of the needle hub  425  forms a rim configured to cooperate with the actuation portion of the retaining arms  447 . During use of the device, the shield retainer  445  is disposed so that the locking flange  449  engages the first locking ridges  446  as shown in FIGS. 16 and 19. Referring to FIGS. 17 and 19, after use, pulling the shield rearwardly displaces the shield retainer  445  rearwardly relative to the needle hub  425 . This displaces the locking flange  449  into engagement with the second locking ridges  427  thereby substantially permanently locking shield retainer  445  in a rearward position. In addition, pulling the shield rearwardly after use displaces the retaining arms  447  into engagement with the forward rim of the needle hub  425 , so that the needle hub displaces the arms radially inwardly out of engagement with the openings  442  in the shield. The spring  435  then displaces the shield  440  forwardly into the extended position to cover the needle as shown in FIG. 18.  
         [0095]    Fourth Device  
         [0096]    Referring now to FIGS.  16 - 20 , a fourth safety medical device is illustrated. The device is a combination safety needle assembly  420  and syringe  410 . The syringe  410  is the same as commonly used non-safety hypodermic syringes. The needle assembly  420  is adapted to cooperate with the syringes  410  that are presently available so that they can be used with a safe needle assembly without modification. Specifically, the needle assembly  420  includes a needle  430  having a sharpened tip and a shield  440  that extends over the needle after use to prevent inadvertent contact with the contaminated needle.  
         [0097]    The syringe  410  includes a hollow cylindrical barrel  415  and a plunger  417  reciprocally displaceable within the barrel to infuse medicine into the barrel or expel fluid out of the barrel. The forward end of the barrel  415  comprises a connector  419  such as a Luer connector for attaching the needle assembly to the barrel prior to use. In the present instance, the plunger  417  is illustrated as a standard plunger used in connection with hypodermic syringes, in which the plunger comprises an axially elongated plunger rod and a piston attach to the forward end of the plunger rod. However, it may be desirable to use the needle assembly  420  with syringes that are used for drawing blood specimens and inserting guide wires. Specifically, the plunger may include a bore for receiving a guide wire, along with a valve for preventing fluid from leaking into the bore from the syringe. During use, a guide wire is inserted through the plunger and is fed through the needle  430  into a patient.  
         [0098]    The needle assembly  420  includes a needle hub  425  for attaching the needle assembly  420  to the barrel  415 . The needle hub  425  includes a connector, such as a Luer connector that cooperates with the connector  419  of the barrel to form a fluid-tight seal between the needle assembly and the syringe. The needle  430  is fixedly attached to the needle hub  425 .  
         [0099]    The  440  is operable between a retracted position, in which the needle is exposed for use as shown in FIG. 17, and an extended position in which the shield covers the sharpened tip of the needle as shown in FIG. 18. A spring  435  biases the shield  440  toward the extended position. A shield retainer  445  releasably retains the shield  440  in the retracted position against the bias of the spring  435 .  
         [0100]    The shield retainer  445  comprises at least one, and preferably two, radially deformable arms  447 . The arms  447  comprise an actuation portion disposed transverse the central axis of the syringe. The forward ends of the arms form latches that cooperate with retainer openings  442  formed in the forward end of the shield  440 . The ends of the arms  447  form a radially projecting flange  440  that cooperate with first and second locking ridges  426 ,  427  formed on the needle hub  425 . Specifically, the first and second locking ridges  426 ,  427  are formed in the inner surface of the needle hub  425  projecting radially inwardly.  
         [0101]    The locking ridges  426 ,  427  have a tapered forward edge and a perpendicular rearward edge, so that the locking ridges operate as one-way locks allowing the locking flange  449  of the retainer arms  447  to be displaced rearwardly relative to the needle hub, but not forwardly. In this way, the locking ridges  426 ,  427  cooperate with the locking flange  449  to retain the retainer arms  447  in first and second axial positions.  
         [0102]    The forward edge of the needle hub  425  forms a rim configured to cooperate with the actuation portion of the retaining arms  447 . During use of the device, the shield retainer  445  is disposed so that the locking flange  449  engages the first locking ridges  446  as shown in FIGS. 16 and 19. Referring to FIGS. 17 and 19, after use, pulling the shield rearwardly displaces the shield retainer  445  rearwardly relative to the needle hub  425 . This displaces the locking flange  449  into engagement with the second locking ridges  427  thereby substantially permanently locking shield retainer  445  in a rearward position. In addition, pulling the shield rearwardly after use displaces the retaining arms  447  into engagement with the forward rim of the needle hub  425 , so that the needle hub displaces the arms radially inwardly out of engagement with the openings  442  in the shield. The spring  435  then displaces the shield  440  forwardly into the extended position to cover the needle as shown in FIG. 18.  
         [0103]    Fifth Device  
         [0104]    Referring now to FIGS.  21 - 22 , a fifth safety medical device is illustrated. The device is a needle assembly  510  that is operable in connection with a number of standard medical devices having a cooperating connector, such as the syringe  410  illustrated and described above. However, the needle assembly  510  is particularly suited for use in connection with a medical device for inserting a guidewire  515  into a patient.  
         [0105]    The needle assembly  510  comprises a housing that is preferably formed of two pieces, namely a rear housing  520  and a forward housing  525 . The needle assembly also includes a needle  445  that is operable between a projecting position in which the sharpened tip of the needle is exposed for use, and a retracted position in which the sharpened tip is protected against inadvertent contact. A spring  540  biases the needle rearwardly toward the retracted position, and a latch  435  releasably retains the needle in the extended position against the bias of the spring.  
         [0106]    The spring  540  is bonded directly to the needle  545  along the length of the needle forward of the rearward end of the needle. Preferably the spring is bonded to the needle by epoxy. The rearward edge of the spring bears against the latch  535 , thereby retaining the needle  545 . A manually actuable pushbutton  537  is attached to the latch  535 . The latch  535  has an opening that is larger than the diameter of the spring  540 . Accordingly, depressing the pushbutton downwardly aligns the spring with the opening in the latch, thereby allowing the needle to retract rearwardly.  
         [0107]    The forward end of the housing is generally, closed having a reduced diameter opening through which the needle  545  extends. A nose seal  527  is disposed within the housing adjacent the forward opening, so that upon retraction, the nose seal seals the forward opening to prevent fluid from leaking out of the needle assembly.  
         [0108]    A generally cylindrical needle chamber  530  is disposed within the housing extending between the rear housing  520  and the forward housing  525 . The rearward end of the rear housing  520  is generally opened forming a connector such as a Luer fitting  522  for attaching the needle assembly  510  to a medical device. An end wall  524  adjacent the Luer fitting  522  has a reduced diameter opening through which fluid and/or a guidewire  515  can pass.  
         [0109]    A valve  550  is attached to the rearward end of the needle  545 . The valve operates to prevent residual fluid in the needle from spitting out the forward end of the needle as the needle is retracted. In addition, the valve  550  includes rearward facing tapered surfaces for aligning a guidewire with the opening at the back end of the needle to thread the guide wire through the needle.  
         [0110]    Sixth Device  
         [0111]    Referring now to FIGS. 23 and 24, a sixth safety medical device is illustrated. The device is a hypodermic syringe  610  having a retractable needle  660 . The syringe includes a needle retainer  640  releasably retaining the needle  660  in an extended position. A plunger  630  is configured to cooperate with the needle retainer to release the needle  660  after use.  
         [0112]    The syringe  610  includes a hollow generally cylindrical barrel  620  having an open rearward end for receiving the plunger  630 . The forward end of the barrel  620  tapers inwardly forming a nose. The plunger  630  is axially displaceable within the barrel, and forms a fluid-tight seal with the interior wall of the barrel.  
         [0113]    The plunger is hollow, having a cavity  632  for receiving the needle  660  after it is retracted. The forward end of the plunger has an opening sized to receive the needle after it is retracted. A disassociable plunger  634  seals the opening at the forward end of the plunger to prevent fluid from entering the cavity  632  during aspiration of medicine into the barrel or expulsion of the medicine during an injection stroke. In the present instance, the plunger  634  frictionally engages the plunger. Alternatively, the plunger may be frangibly attached to the plunger. In either instance, the connection between the plunger and the plug is greater than the hydraulic pressure applied to the plug during an injection stroke.  
         [0114]    The needle  660  has a sharpened tip for piercing a patient, and is operable between a projecting position in which the sharpened tip is exposed for use and a retracted position in which the needle is disposed within the plunger cavity  632  to protect the contaminated needle against inadvertent contact. A spring  655  bonded to the needle biases the needle toward the retracted position. The needle retainer  640  releasably retains the needle  660  against the bias of the spring.  
         [0115]    The needle retainer comprises a bore. A needle seal  635  disposed within the bore of the needle retainer provides a fluid-tight seal between the seal and the needle retainer. The seal  635  is a cup shaped element having a substantially open forward end and a substantially closed rearward end. A fluid passageway extends through the closed rearward end of the seal  635 . The spring  655  biases the needle  660  against the closed end of the seal  635  so that the needle abuts the fluid passageway, whereby the bore of the needle is aligned with the fluid passageway of the seal.  
         [0116]    A circumferential rib  637  projects radially outwardly around the circumference of the seal  635  and into engagement with the bore of the needle retainer. The rib  637  provides a fluid-tight seal between the seal  635  and the bore of the needle retainer so that the fluid from the barrel does not leak out of the barrel between the needle retainer and the seal. In addition, the needle retainer  640  comprises a circumferential flange  644  forming a snap fit with a recess in the nose of the barrel formed to receive the needle retainer. The engagement between the flange  644  and the interior wall of the barrel forms a fluid-tight seal so that fluid does not leak from the barrel between the needle retainer and the wall of the barrel.  
         [0117]    The needle retainer  640  comprises a plurality of axially elongated radially deformable fingers  642 . The ends of the fingers form hooks or latches that engage the needle seal  635 . Since the needle  660  abuts the needle seal  635 , the needle retainer retains the needle along with the needle seal. The rearward surface of the fingers  642  taper radially outwardly, and the forward end of the plunger  630  is tapered to cooperate with the tapered surfaces of the fingers. In this way, at the end of an injection stroke, the tapered surfaces of the plunger  630  engage the tapered surfaces of the fingers  642 , and operate like a wedge to deform the fingers radially outwardly out of engagement with the needle seal  635 . As the plunger is displaced forwardly, the plug  634  at the end of the plunger engages the needle seal  635  and the needle seal dislodges the plug from the opening of the plunger, thereby providing access to the cavity. Accordingly, after the needle retainer releases the needle seal, the spring  655  propels the needle, needle seal, and plug rearwardly into the cavity of the plunger.  
         [0118]    Seventh Device  
         [0119]    Referring now to FIG. 25, a seventh safety medical device is illustrated. The device is a hypodermic syringe  710  having a retractable needle  760 . The syringe  710  is similar to the syringe illustrated in FIGS. 23 and 24. Specifically, the syringe  710  has a barrel  720 , plunger  730  and needle retainer  740  that are configured substantially similarly to the barrel  620 , plunger  630  and needle retainer  640  of the syringe illustrated in FIGS. 23 and 24, and described above.  
         [0120]    The syringe  710  in FIG. 25 differs from the syringe  610  in the following ways. The syringe  710  includes an axially elongated needle seal  735  having a bore for receiving the needle, and the needle is fixedly bonded to the needle seal within the bore. The needle seal includes a circumferential rib  737  forming a fluid-tight seal between the needle seal and the bore of the needle retainer  740 , similar to the previous syringe  610 .  
         [0121]    The syringe  710  also comprises an actuator  750  disposed in the forward end of the barrel. The actuator  750  is a disk-like member having a tapered surface  752  projecting from its forward face. The tapered surface  752  is configured to cooperate with the needle retainer to deform the needle retainer fingers  742  radially outwardly to release the needle. The actuator is disposed between the forward end of the plunger  730  and the rearward end of the needle retainer  740 . Accordingly, at the end of the injection stroke, the plunger engages the actuator  750  displacing the actuator axially forwardly so that the tapered surface  752  engages the needle retainer  740  to release the needle. In addition, the plug  734  sealing the opening to the cavity  732  of the plunger engages the needle seal  735 , which dislodges the plug as the plunger is displaced forwardly. Therefore, after the needle is released by the needle retainer, the spring  755  displaces the needle rearwardly into the retracted position in the cavity of the plunger so that the sharpened tip of the needle is protected against inadvertent contact.  
         [0122]    Eighth Device  
         [0123]    Referring now to FIGS.  26 - 28 , an eighth safety medical device is illustrated. The device is a hypodermic syringe  810  having a retractable needle  860 . The syringe is similar to the syringe illustrated in FIG. 25. Specifically, the syringe  810  has a barrel  820 , plunger  830  and needle seal  835  that are configured substantially similarly to the barrel  720 , plunger  730  and needle seal  735  of the syringe illustrated in FIG. 25, and described above.  
         [0124]    The syringe  810  in FIGS.  26 - 28  differs from the syringe  710  in the following ways. The syringe  810  includes a collet-type needle retainer  840  and a retaining collar  850  that cooperates with the needle retainer. Specifically, the needle retainer comprises a plurality of axially elongated fingers  842  having engagement surfaces that engage the side of the needle seal  835 . The fingers  842  are biased radially outwardly away from the needle seal  835 . The retaining collar  850  retains the fingers  842  inwardly into engagement with the needle seal, to retain the needle against the rearward bias of the spring  855 . Specifically, the retaining collar  850  has an internal diameter that is the substantially the same or less than the combined diameter of the needle seal  835  and the thickness of the fingers  842 . In this way, the fingers  842  operate like a collet to frictionally engage the needle seal.  
         [0125]    At the end of an injection stroke, the plug  834  at the forward end of the plunger is dislodged by the needle seal  835 . The opening at the forward end of the plunger  830  is larger than the diameter of the needle retainer  840  when the needle retainer is in engagement with the needle seal. Accordingly, as the plunger is displaced forwardly, the plunger advances over the needle retainer driving the retaining collar  850  forwardly. As the retaining collar  850  is displaced forwardly, the fingers  842  are released so they displace radially outwardly releasing the needle. The spring  855  then propels the needle rearwardly into the plunger so that the sharpened tip of the needle is protected against inadvertent contact, as shown in FIG. 28. In addition, the interior of the plunger adjacent the opening preferably tapers radially outwardly. The outer surface of the fingers  842  engage the inner tapered surface of the plunger to impede rearward displacement of the plunger, thereby locking the plunger in the barrel.  
         [0126]    Ninth Device  
         [0127]    Referring now to FIGS.  29 - 35  a ninth safety medical device is illustrated. The device is a fluid sampling device  910  having a retractable needle  960 . The device is particularly suited for drawing samples of blood from a patient&#39;s artery.  
         [0128]    The device  910  includes a housing  920  and a needle  960  projecting forwardly from the housing. A spring  955  biases the needle rearwardly toward a retracted position in which the sharpened tip of the needle is enclosed within the housing. A needle retainer  955 , in the form of a latch that engages an aperture or socket  921  in the housing, releasably retains the needle in the extended position. The needle retainer  955  is integrally formed with a mounting stem  952  that is disposed within the housing. A piston or seal  970  is mounted on the mounting stem  952 .  
         [0129]    The piston  970  forms a fluid-tight seal with the interior of a cylindrical barrel  940  that is disposed within the interior of the housing. As shown in FIGS.  30 - 32  , the barrel  940  is displaceable relative to the housing  920  to form a variable size fluid chamber. The fluid chamber is in fluid communication with the needle  960 .  
         [0130]    Preferably a check valve  980  is disposed within the piston  970 . The check valve  980  allows fluid to flow into the fluid cavity but impedes fluid flow out of the fluid chamber through the needle  960 . In the present instance, the check valve is a ball-type check valve.  
         [0131]    Specifically, the check valve comprises an inlet port  982  for receiving fluid from the needle  960  an a discharge passage  984  for discharging fluid into the fluid chamber. A frustoconical valve seat is formed adjacent the inlet port  982 . When the piston  970  is displaced rearwardly relative to the barrel, a check ball  986  seats in the valve seat to prevent fluid from flowing out of the chamber through the needle.  
         [0132]    Retraction of the needle  960  is actuated by manually pressing a button, which disengages the needle retainer  955  latch from the housing  920 . The spring  965  then propels the needle retainer  955 , mounting stem  952  and barrel  940  along with the fluid sample, rearwardly. As the barrel  940  is displaced rearwardly, a circumferential flange  944  on the exterior of the forward end of the barrel engages an internal annular flange  932  that projects radially inwardly from a sleeve  930  that telescopingly engages the housing  920 . As the barrel is further displaced rearwardly, the sleeve  930  is also displaced rearwardly until a pair of locking tines  957  connected to the mounting stem  952  engage locking windows  926  in the housing, which impedes further rearward movement of the sleeve and barrel, as well as the needle and mounting stem. Preferably, the locking tines  957  engage axial alignment grooves  925  in the interior of the housing, which prevent the stem  952  from rotating relative to the housing during retraction. The telescoping sleeve  930  permits usage of a shorter housing, while providing a sufficiently long enclosure for containing the used needle.  
         [0133]    Referring now to FIGS. 33 and 34, after the needle  960  is retracted, the fluid can be expelled from the fluid chamber in the barrel  940 . Specifically, the rearward end of the barrel has a reduced diameter opening through which the fluid can be expelled. The rearward end of the barrel forms a connector  942 , such as a Luer fitting for cooperating with a diagnostic device such as a blood gas analyzer. The opening in the rearward end of the barrel is sealed by a vent cap  945 . The vent cap  945  engages the Luer fitting to form a fluid-tight seal. In addition, the vent cap includes a porous plug  948  that permits air to flow out of the barrel, and prevents blood from leaking out of the opening at the rear of the barrel. In this way, a blood sample can be withdrawn and maintained in a sealed condition and injected into a diagnostic device without contamination by air.  
         [0134]    Tenth Device  
         [0135]    Referring to FIGS.  36 - 40 , a tenth safety medical device is illustrated. The device  1010  is a syringe having a shield  1040  for covering the needle after use is illustrated. The shield  1040  circumscribes the barrel  1020  of the syringe. A spring  1055  biases the shield  1040  forwardly. As shown in FIG. 36A, a detent  1025  formed in the side of the barrel cooperates with a recess  1049  in the shield to retain the shield in a retracted position against the bias of the spring, so that the needle  1050  is exposed for use. The forward end of the syringe barrel is generally open.  
         [0136]    A separate cap or nose piece  1030  is attached to the forward end of the syringe barrel. The cap has a reduced diameter opening forming a tip in the form of a Luer fitting  1032 . In this way, the cap encloses the forward end of the syringe barrel so that the forward end is substantially closed.  
         [0137]    The cap  1030  is attached to the forward end of the barrel by a plurality of annular interference seals  1034  as shown in FIG. 36B, so that the cap or nose piece forms a snap fit connection with the syringe barrel. Referring to FIG. 38, at the end of the injection stroke, the piston at the forward end of the plunger  1035  engages the nose piece. Continued advancement of the plunger displaces the nose piece forwardly, thereby driving the shield forwardly, which in turn releases the engagement between the detent on the syringe barrel and the recess on the shield. The spring then advances the shield over the needle so that the sharpened tip of the needle is enclosed within the shield to prevent inadvertent contact with the contaminated needle. Preferably, as shown in FIG. 39, the shield includes locking tabs  1042  that prevent retraction of the shield after use.  
         [0138]    Eleventh Device  
         [0139]    Referring now to FIGS.  41 - 43 , an eleventh safety medical device is illustrated. The eleventh device is a syringe. This ninth alternate embodiment is similar to the embodiments illustrated in FIGS.  21 - 23 , which are described further above. As shown in FIG. 41, the device includes a needle retainer for releasably retaining the needle in an extended position against the bias of a spring so that the sharpened tip of the needle extends forwardly from the syringe barrel. The needle retainer is in the form of a disk having a central portion or hub that is frangibly attached to an annular outer portion. The central hub of the needle retainer is attached to the rearward end of the needle. At the end of the injection stroke, the forward end of the plunger engages the needle retainer. Further advancement of the plunger causes the outer annular portion of the needle retainer to detach from the central hub that is attached to the needle. In addition, a plug or seal at the forward end of the plunger is displaced, establishing an opening leading to the hollow interior of the plunger. After the needle retainer is fractured, the needle is released so that the spring propels the needle and attached hub rearwardly into the housing, and more specifically into the plunger. In addition, preferably the plunger includes a plurality of radially deformable resilient latching arms that provide a one-way lock to impede withdrawal of the plunger after actuation of retraction. The latches engage an annular shoulder on the interior surface of the syringe barrel.  
         [0140]    The terms and expressions which have been employed are used as terms of description and not of limitation. There is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof. It is recognized, however, that various modifications are possible within the scope and spirit of the invention.