Abstract:
A safety medical device having a sharpened needle is provided. After use, the needle is retracted so that the contaminated needle is shielded to prevent inadvertent contact with the contaminated needle. In one embodiment, the device includes a barrel and a plunger that is slidable within the barrel. The sharpened needle is operable between a projecting position and a retracted position. In the projecting position, the needle projects forwardly from the front end of the barrel. In the retracted position, the needle is shielded to prevent inadvertent contact with the needle. When the plunger is displaced forwardly to expel fluid from the barrel, the plunger actuates retraction so that the needle is automatically retracted after use. The needle may be included as an element of a needle assembly that is connectable with the barrel. The needle assembly includes a spring for biasing the needle toward the retracted position and a connector for attaching the needle to the barrel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of co-pending U.S. application Ser. No. 08/692,895 filed Jun. 20, 1996, still pending, which is a continuation-in-part of Ser. No. 08/381,203 filed Jan. 31, 1995, now abandoned, which is a continuation of U.S. application Ser. No. 08/127,962 filed Sep. 27, 1993, now U.S. Pat. No. 5,407,431, which is a continuation-in-part of U.S. application Ser. No. 08/017,832 filed Feb. 16, 1993, now abandoned, which is a continuation of U.S. application Ser. No. 07/656,305 filed Feb. 15, 1991, now U.S. Pat. No. 5,188,599, which is a continuation-in-part of U.S. application Ser. No. 07/378,275, filed Jul. 11, 1989, now U.S. Pat. No. 4,994,034. Each of the foregoing applications is hereby incorporated herein by reference as if fully set forth herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to retractable needle medical devices and, more particularly, to a mechanism for retracting a contaminated needle in order to render a needle-bearing medical device safe after use. 
     BACKGROUND OF THE INVENTION 
     Various types of medical devices include a needle for insertion into the skin of a patient. Such needles are inserted into the skin to serve various diagnostic or therapeutic purposes. For example, a traditional injection syringe is provided with a needle for facilitating a passageway into the patient for injecting fluid into, or withdrawing fluid from, the patient. A traditional phlebotomy apparatus is provided with a needle for withdrawing fluid from a patient and transmitting the withdrawn fluid into an evacuated receptacle. A catheter stylet is provided with a needle for piercing the skin and supporting a catheter cannula on the stylet while the cannula is guided into a desired position within the patient. Each of the aforementioned needle-bearing medical devices can cause transmission of various pathogens, most notably the Human Immune Virus (HIV), due to an accidental needle stick of an uninfected person after the needle is withdrawn from the patient. 
     It would be desirable to provide a needle retraction mechanism for permanently and reliably retracting a used or contaminated needle into the needle-bearing medical device in order to render the medical device in a safe condition after use. It would further be desirable to provide such a mechanism in a configuration that does not interfere with the customary uses of needle-bearing medical devices, is resistant to undesired activation by forces normally encountered in the use of such medical devices, and can be easily operated without a significant change in the techniques employed by the medical professionals who use needle-bearing medical devices. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, there is provided a needle retention mechanism for mounting a needle to a medical device such that the needle can be retracted into the medical device subsequent to use thereof to reduce the risk of infection from an inadvertent prick. The needle retention mechanism comprises a spring housing positioned in the forward end of the device having a front alignment aperture for allowing the needle to extend therethrough from within the spring housing. A spring is positioned within the spring housing for exerting a rearward bias upon the needle. The rear of the spring housing comprises a needle retainer having axially extending resilient fingers for retaining the rearward end of the needle against the bias exerted by the spring. An actuating member is positioned within the device and has an engagement surface formed thereon for operatively engaging the rear of the spring housing to flex the resilient fingers outward in order to allow the spring to propel the needle into the interior of the device. The actuating member further has a needle receiving cavity formed therein for receiving the retracted needle. 
     In accordance with another aspect of the present invention, the needle retention mechanism can be adapted for retaining needles upon such medical devices as hypodermic syringes, catheter insertion devices, phlebotomy devices, and other hand-held needle-bearing instruments. In the hypodermic syringe, the actuating member provides a piston for withdrawing or injecting fluid into or from a patient. In the phlebotomy device, the actuating member is positioned within a barrel for supporting a rearward extending linking needle for piercing an evacuated fluid collection vial. In the catheter insertion device, the actuating member is fitted with a porous vent plug so that the actuating member cavity provides a blood flashback chamber for ensuring proper placement of a catheter within a patient. 
     Other aspects and advantages of the present invention are made apparent in the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of a first embodiment of the present invention wherein the device is a hypodermic syringe and is shown with a syringe plunger in a partially depressed position within a syringe barrel; 
     FIG. 2 is a fragmentary cross-sectional view of the front end of the first embodiment of the present invention in FIG. 1 but showing the plunger proximate to a needle housing at the forward end of the syringe; 
     FIG. 3 is a cross-sectional view of the first embodiment of the present invention in FIG. 1 but showing the syringe plunger in a fully depressed position and the needle fully retracted; 
     FIG. 4 is a cross-sectional view of a second embodiment of the present invention wherein the device is a hypodermic syringe and is shown with a plunger in a rearward position and ready for use; 
     FIG. 5 is a cross-sectional view of the second embodiment of the present invention of FIG. 4 but showing the plunger in the fully depressed position and the needle fully retracted; 
     FIG. 6 is an exploded view of the rear portion of a spring housing in accordance with the present invention; 
     FIG. 7 is a cross-sectional view of a third embodiment of the present invention wherein the device is a vacuum tube blood sampling device and is shown with a vacuum tube installed in the device and a hypodermic needle extended and ready to use; 
     FIG. 8 is a cross-sectional view of the third embodiment of the present invention of FIG. 7 but with the vacuum tube removed and the needle retracted and ready for disposal of the device; 
     FIG. 9 is a cross-sectional view of a fourth embodiment of the present invention wherein the device is an intravenous catheter insertion device and is shown with a plunger in a partially depressed position within the barrel; 
     FIG. 10 is an exploded view of the fourth embodiment of the present invention of FIG. 9; 
     FIG. 11 is a sectional view of a fifth embodiment of the present invention wherein the device is a catheter insertion device; 
     FIG. 12 is an enlarged fragmentary cross-sectional view of the front end of the fifth embodiment of the present invention of FIG. 11 but showing the protective cap and the catheter removed; and 
     FIG. 13 is an enlarged fragmentary sectional view of the rear end of the fifth embodiment of the present invention of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, there is shown a syringe  20  for injecting fluid into, or withdrawing fluid from, a patient. The syringe  20  includes a hollow barrel  22 . The rear end of the barrel  22  has an opening  22   a  formed therein for receiving an operating member, or plunger  24 , in slidable engagement within interior cavity  21  of the barrel  22 . The forward end of the barrel  22  is reduced in diameter and has an opening  22   b  formed therein for receiving a spring housing  26 . A needle  25 , having an axially located passageway therethrough, is axially positioned within the spring housing  26 , and extends from the forward end of the spring housing  26 . The forward end of the needle  25  has a pointed tip  28  for piercing the skin of a patient. 
     The barrel  22  has retaining flanges  41  on the rear end providing a gripping surface for the user&#39;s fingers. Optionally, in a forward position from lips  41 , a color coded ring  44  of sufficient resiliency and diameter is slid over the exterior surface of the barrel  22  and retained by friction to identify a particular syringe system. The color coded ring  44  is retained over the barrel  22  in circumferential groove  45 . Alternatively, the ring  44  can be retained on the barrel  22  by friction. The barrel  22  is transparent, thus permitting the user to see the fluid inside so that air bubbles can be detected and expelled before the fluid is dispensed by the syringe  20 . 
     The plunger  24  is slidably positioned as a piston within the barrel  22 . The plunger  24  includes a sleeve  27  defining a central cylindrical receptacle  38  for receiving the needle  25  and needle retaining member  35  during retraction of the needle  25 , and for thereafter containing the needle. Reinforcement ribs  29  extend radially outward from the sleeve  27  for maintaining the plunger  24  and the sleeve  27  in central alignment within the barrel  22  during use of the syringe  20 . An annular sealing member  36  is positioned about the forward end of the sleeve  27 , forming a sliding fluid seal with the interior of the barrel  22 . 
     One or more radially extending ratchet teeth  49  interrupt the reinforcing ribs  29  and are posteriorly located while being outwardly flared to allow the ratchet teeth  49  to pass by a ratchet lip  58  on the inside of the finger retaining lip  41  of the syringe barrel  22 . Upon full depression of the plunger  24  within the barrel  22 , the ratchet teeth  49  pass by the ratchet lip  58 . The ratchet teeth  49  flexibly pass by the ratchet lip  58  and thereafter prevent extraction or free movement of the plunger  24  from the barrel  22 . 
     The forward end of the plunger  24  is sealed by a frangible end member  40 . The frangible end member  40  is preferably integrally formed with the sleeve  27  such that a thin supporting rim  42  connects the frangible end member  40  with the forward end of the sleeve  27 . The frangible end member  40  is dissociable from the end of the plunger  24  upon application thereon of a rearwardly-directed force, preferably of less than about 0.9 kg (2 pounds), sufficient to fracture the supporting rim  42 . 
     The spring housing  26  includes a nose portion  32  having a bore  34  formed therein for holding the needle  25  in axial alignment. A washer  31  is positioned within the spring housing  26  about the rearward opening of bore  34 , forming the forward interior surface of the spring housing  26  and providing a fluid seal about the shaft of the needle  25 . In addition, an O-ring  53  is fitted between the spring housing  26  and the inner surface of the barrel  22  to provide a fluid-tight seal between the spring housing  26  and the barrel  22 . 
     A needle retaining member  35  is mounted to the rearward end of the needle  25  by positioning the rearward end of the needle  25  within an axial passageway through the retaining member  35 . The retaining member  35  provides an enlarged lip or outwardly extending rim relative to the diameter of the needle. The tip  28  of the needle is in fluid communication, through needle  25  and retaining member  35 , with the interior cavity  21  of the barrel  22 . 
     Within the spring housing  26 , the needle  25  is surrounded by a spring  33 . The spring  33  is compressed within the spring housing  26  so as to exert an expansive force between the forward interior surface of the spring housing  26  and a forward surface of the needle retaining member  35 . A plurality of latching projections or fingers, of which fingers  37   a  and  37   b  are representative, extend rearwardly from the nose portion  32  of the spring housing  26  substantially parallel to the needle  25 . The fingers  37   a  and  37   b  have hooks  39   a  and  39   b  formed upon the respective rear ends thereof. The hooks  39   a  and  39   b  are formed to have radially inward extending forward surfaces for engaging the needle retaining member  35  by mutual abutment between the rear surface of the retaining member  35  and the respective forward surfaces of the hooks  39 . The hooks  39  are formed to have rear surfaces, or shoulders, which are angled outwardly toward the cavity  21 . An annular shoulder  46  is formed at the forward end of the plunger  23 . The annular shoulder  46  has a slope that is complementary to or mates with the outwardly angled surfaces of the hooks  39 , in order to effect outward deformation of the fingers  37  when retraction of the needle  25  is desired. The interior of the barrel  22  is circumferentially flared in the vicinity of the hooks  39  to allow the fingers  37  to flex, or break, outwardly when the fingers  37  are deformed by the shoulder  46  of the plunger. 
     Attachment means, such as bayonet tabs  23   a  are formed in the exterior of the spring housing  26  for engaging the spring housing  26  with mating bayonet slots  23   b  formed within the forward end of the barrel  22 . The bayonet tabs  23   a  and slots  23   b  may have complementary cambered surfaces (not shown) to allow the tabs  23   a  to be permanently locked into position within the slots  23   b  in a ratchet-like manner. In the use of the syringe  20 , a selection of spring housings  26  having needles of various gauges may be provided for attachment to a uniformly-sized barrel  22  prior to use. After use, the selected spring housing  26  will be locked to the syringe  20  to prevent access to the retracted needle  25 . 
     In alternative embodiments, other attachment means may be provided for the spring housing  26  and the barrel  22  such that the spring housing  26  can be attached and removed from the barrel  22 . For example, it may be desirable to use different needle gauges for filling the syringe  20  from a puncturable vial and for giving the patient an injection. In such an alternative embodiment, the spring housing  26  and the barrel  22  can be provided with complementary threaded surfaces for removably attaching needles  25  of various gauges. Such threaded surfaces may be compatible with standard needle fittings, so that a standard needle housing can be used for filling the syringe. The spring housing  26  can subsequently be attached to the forward end of the barrel for giving the injection to a patient. 
     During an injection, the user depresses a pushing plate  47  attached to the rear of the plunger  24 . In this arrangement, the plunger  24  is pushed into the barrel  22  in order to expel the contents of cavity  21  through needle  25 . Referring now to FIG. 2, the forward end of the syringe  20  is shown with the plunger  24  advanced within the barrel  22 . At the completion of an injection stroke, the frangible end member  40  abuts against the rear surface of the needle retaining member  35 . If a second injection is to be given, or if the syringe  20  is to be used to withdraw fluid from the patient, the plunger  24  may then be withdrawn within the barrel  22 , while the frangible end member  40  remains intact upon the end of the plunger  24 . 
     When retraction of the needle  25  is desired, the plunger  24  is pressed firmly into the barrel, so that the supporting rim  42  for the frangible end member  40  is fractured and the frangible end member  40  is dissociated from the end of the plunger  24 . The force required to dissociate the frangible end member  40  is significantly higher than the normal force applied to the plunger  24  during an injection, so that undesired retraction is guarded against in use. When the frangible end member  40  is dissociated from the end of the plunger  24 , an opening is formed through the forward end of the plunger  24  into the receptacle  38 . 
     When the frangible end member  40  is dissociated from the end of the plunger  24 , the plunger  24  may be advanced forward beyond the position shown in FIG. 2, so that the annular shoulder  46  of the plunger  24  abuts against the rearward sloping surfaces of the hooks  39 . The diameter of the barrel  22  in the vicinity of the hooks  39  is sufficiently large to permit the fingers  37  to flex or break radially outward, so that the forward surfaces of the hooks  39  are moved radially outward to release the needle retaining member  35 . Then, the expansive force exerted by the spring  33  propels the needle retaining member  35  and needle  25  into the receptacle  38 , and indicated in the syringe  20  shown in FIG.  3 . 
     A second embodiment of the invention is illustrated in FIGS. 4-6 and consists of a syringe  220  comprising a barrel  222 . The barrel  222  has a reduced diameter opening  222   b  at the front end and an opening  222   a  at the rear end. The barrel  222  has finger retaining flanges  241  near the rear end of the barrel  222  providing a gripping surface for the user&#39;s fingers. 
     A plunger  224  is slidably received within the barrel  222  and is sized to move linearly back and forth. The plunger  224  has a converging taper  246  on the front end and a flange  247  on the rear end. The flange  247  has a radially thinned slender section at the interface with the plunger  224  which breaks away if forced outwardly when the plunger  224  is in its fully depressed position. In addition, the shaft of the plunger  224  has a longitudinal slot or channel  248  formed therein to facilitate molding the plunger and the flange  247  as a single unit. 
     A frangible end member  240  is formed on the tapered end of the plunger  224 . The plunger  224  further contains an outwardly extending raised circumferential band  249  around the end near the flange  247 . Additionally, the barrel  222  has an internal recess  250  in a similar location near the flanges  241 . When the plunger  224  is fully depressed and is recessed flush into the rear end of the barrel  222 , the band  249  snaps into the recess  250  locking the plunger  224  into that location. This prevents the plunger  224  from being withdrawn and, as the flange  247  is frangible, the closure is rendered tamper-proof even if an attempt is made to pry the flange  247  from the barrel  222 . 
     A sealing member  236  is positioned on the converging tapered end of the plunger  224 . The sealing member  236  provides a resilient sliding seal for the internal cavity  221  of the barrel  222  allowing liquids to be drawn inside and forced out by reciprocating movement of the plunger  224 . Initially, the sealing member  236  is positioned such that a first circumferential groove  252   a  formed in the interior of the sealing member  236  is held upon a radial projection  251  formed about the exterior of the tapered end of the plunger  224 . When the plunger  224  is fully depressed into the barrel  222  to effect retraction of the needle, the sealing member  236  is forced over the radial projection  251  into a secondary position wherein a second circumferential groove  252   b  in the sealing member is received and held upon the radial projection  251 , as indicated in FIG.  5 . As can be appreciated, the sealing member is initially seated upon the plunger such that a forward surface of the sealing member is positioned in the forward direction beyond the rear of the converging taper  246  of the plunger  224 . The exterior periphery of the forward portion of the sealing member is shaped to conform with the forward interior surface  221   a  of the cavity  221 . Hence, when the plunger  224  is initially fully depressed into the barrel  222 , but retraction has not yet been effected, the forward surface of the sealing member mates with the interior forward surface of the barrel so that substantially the entire contents of the cavity  221  is forced into the needle and ejected. Then, when retraction is effected, the sealing member is forced to move rearwardly upon the plunger in order to accommodate flexing the fingers  237  by forward motion of the plunger  224 . 
     A spring housing  226  comprising a nose portion  232  and a needle retainer  256  is attachable to the forward end of the barrel  222 . The axial cavity thus provided in the spring housing  226  is coextensive with an opening in the nose portion  232  to accommodate the needle  225  and its associated spring  233 . The front portion  232  of the spring housing  226  attaches to the barrel  222  using bayonet tabs  223   a  and slots  223   b . The needle retainer  256  forms the rear portion of the spring housing  226  and retains the needle  225  therein by abutment with the rear of a needle retaining member  235  fixed to the rearward end of the needle. 
     The cooperative relationships among the needle retaining member  235 , the spring  233 , and the needle retainer  256  are best shown in the exploded view of FIG.  6 . The needle retainer  256  includes rearward extending fingers  237  having hooks  239  formed toward the rear ends thereof. The fingers  237  are preferably flexible to permit outward movement for releasing the needle retaining member  235 . It should be appreciated that the fingers  237  could be fractured when moved outwardly by the plunger to release the needle retaining member  235 . The forward interior surfaces of the hooks  239  provide an engaging surface or stop  254 , which extends radially inward for overlapping abutment with the rear surface of the needle retaining member  235 . Accordingly, the needle retaining member  235  is held against the hooks  239  on the fingers  237  in relation to the expansive force exerted by the spring  233 . 
     The hooks  239  are formed to have rearward facing canted or wedge-shaped surfaces  339 ; which extend outwardly at a rearward angle, for mating with a complementary tapered surface on the forward end of the plunger. When the fingers  237  are deformed or flexed radially outwardly, the hooks  239  move out of abutment with the rear surface of the retaining member  235 . Upon this occurrence, the expansive force of spring  233  against the front surface of the retaining member  235 , immediately thrusts the needle retaining member  235  and hence, the needle  225 , rearwardly toward the back or rear portion of the syringe  220  and into the plunger. 
     The latching projections or fingers  237  within its associated hooks  239  of the needle retainer  256  are preferably joined together to form an annular latching member or rim  254  with a circular opening at the rear end. The needle retainer  256  is provided with longitudinal grooves  255  or score lines extending axially along the outside to facilitate breakage and separation of the fingers  237 . The continuous rim  254  provides a seal with the rearward surface of the needle retaining member  235 , so that fluid is kept out of the interior of the spring housing  226 . Additionally, a radially-protruding shoulder  257  is formed around the exterior of the needle retainer  256  for abutment with a complementary ridge  260  on the interior of the nose portion  232  of the spring housing  226  (as best shown in FIGS. 4 and 5) to secure the needle retainer  256  to the nose portion  232  and to prevent the needle retainer  256  from being pushed rearward by the expansive force of the compressed spring  233 . 
     In operation, fluid is drawn into the syringe  220  in a normal manner by the vacuum created when the plunger  224  is withdrawn within the barrel. After injecting the fluid, the needle  225  is withdrawn from the patient and the plunger  224  is forced completely into the barrel  222 . As the tapered end of the plunger  224  is forcibly depressed against the forward end of the hollow barrel  222 , the sealing member  236  is forced back over the raised projection  251 , and the frangible end of the plunger is broken off. Simultaneously, the plunger&#39;s ( 224 ) converging tapered surface  249  forcibly breaks apart or moves radially outwardly the resilient fingers  237  of the needle retainer  256 . This forcible bending outward of the resilient fingers  237  releases the retaining member  235  held by the hooks  239  at the end of the fingers  237  of the needle retainer. This releasing movement permits the expansive force of the coiled spring  233  to drive the needle  225 , frangible end  240 , and spring  233  into the hollow of the syringe plunger  224 , thereby fully retracting the needle  225  and retaining it safely inside the syringe  220 . An audible clicking sound is heard when this action takes place. The plunger  224  is then fully inserted into the barrel  222  with the flange  247  flush with the open rearward end  222   a  of the barrel  222  and is unremovable due to the locking into place of the rim  249  into the grove  250 . 
     In a third embodiment, the invention is directed to removing fluid samples, such as blood, from the body of a patient. A phlebotomy device  320  used in taking body fluid samples in accordance with the present invention is illustrated in FIGS. 7 and 8 and comprises a hypodermic needle  325 , coiled spring  333 , and a spring housing  326  having resilient fingers  337  and hooks  339 , in an arrangement as described in connection with the first and second embodiments. 
     The barrel  322  is cylindrical in shape and has a fully open end  322   a  and an opposed reduced-diameter end  322   b . The open end  322   a  may optionally contain a replaceable centering washer  380  that fits over the open end  322   a  and that has a predetermined inside diameter allowing a single barrel  322  to be used with various diameter fluid sampling receptacles  381 . Finger retaining flanges  341  are positioned away from the open end  322   a  to assist the user in handling and manipulating the device  320  and allowing the washer  380  to be installed on the extreme open end  322   a . The reduced diameter end  322   b  of the barrel  322  includes a reduced tubular bore section  382 . 
     A hollow plunger  324  is slidably received within the barrel  322 . The plunger  324  is configured to provide a converging tapered surface  346  on the front end and on its rear end to hold a hollow linking needle  384 . The tapered end of the plunger  324  includes a resilient sealing member  336 , that snaps over the plunger  324 , which slides within the reduced tubular bore section  382 , to create a tight hermetic seal with sufficient resistance to maintain the seal when slid linearly in the bore section  382 . 
     On the inside surface of the barrel  322 , near the reduced-diameter end  322   b , are located a pair of circumferential projections  383  that are formed about the interior of the barrel. These projections  383  are integrally formed with the barrel  322  and function as a retainer for a radial flange  387  formed on the plunger  324 , the flange  387  being snap released from the projections as the plunger moves forward. 
     The linking needle  384  is held within the plunger  324  through a compression fit and is axially aligned within the barrel  322  as shown in FIGS. 7 and 8. A needle boot  385  is disposed over the needle  384  and stretches over a barbed projection  386  integral with the plunger  324  for holding the linking needle  384  and providing a gripping surface for the boot  385 . The boot  385  is formed of a thin resilient material, such as flexible silicone, and is sized to enclose and protect the linking needle  84  when the device  320  is stored. 
     During operation of the device  320 , a fluid sampling receptacle  381 , such as a container, vial or “VACUTAINER” as it is known in the medical field, is inserted inside the open end  322   a  of the barrel  322 . The receptacle  381  has a resilient perforatable seal  390  on one end, its inner end, and has a closed dome shaped on the other, much like a test tube. The receptacle  381  is normally fabricated of glass or transparent thermoplastic and is evacuated on the inside allowing the sampled fluid to displace the vacuum. 
     In operation, the hypodermic needle  325  is inserted, usually intravenously, into the patient. The receptacle  381  is then urged forward into the barrel  322  so that the linking needle  384  pierces the perforatable seal  390  and the vacuum within the receptacle  381  draws the fluid into the receptacle  381 . The receptacle  381  may be removed and replaced if another sample of fluid, such as blood, is required. When finished withdrawing fluid, the device  320  is withdrawn from the patient. To effect needle retraction, the receptacle  381  is then urged further into the barrel  322  toward the partially open end  322   b  by the practitioner&#39;s thumb while grasping the flanges  341  with his or her fingers. This compressive force overcomes the resistance of the projections  383  holding the extended flange  387 , thereby allowing the plunger  324  to slide farther forward. The tapered outer edge of rim  346  on plunger  324  forcibly spreads the resilient fingers  337  of the needle retainer  356  radially outward to release the needle retaining member  335 . In this arrangement, the expansive force of the coiled spring  333  pushes the needle  325  and retaining member  335  into the hollow plunger  324 . This triggered movement fully retracts the needle  325  into the hollow center of the plunger  324  and retains it in that position by the continual urging of the spring  333 . An audible clicking sound is emitted when this action is completed and the receptacle  381  may then be removed. The needle  325  is thus harmlessly retained inside the device  320  and disposal of the device may be safely achieved. 
     A fourth embodiment of the invention is an intravenous catheter insertion device  420  as illustrated in FIGS. 9 and 10. Referring now to FIG. 10, the catheter  500  comprises a catheter hub  501  having an interior shaft  503  with an axial passageway. A flexible catheter sleeve  502  is attached at the front end of the catheter hub  501 . The catheter  500  is positioned with the front end of a standard insertion needle  425  concentrically located within the axial passageway of the shaft  503 . The rearward end of the insertion needle  425  is mounted in a spring housing  426  which engages a barrel  422 . A plunger  424 , having an offset extended flange  487  sized to be received within the barrel  422  for sealing purposes, is received within the rear of the barrel. For ease of manufacturing, the longitudinal cavity  438  within the plunger may have a longitudinal slot  448  formed along a side of the plunger  424 . The forward end of the plunger  424  has a frangible end member  440  formed thereon. 
     Between the frangible end member  440  and the longitudinal cavity  438  are outwardly tapered conical shoulders  520  having a circumferential space or annular groove  521  of a defined depth which facilitate the frangible end member  440  being dissociated from the outwardly tapered conical shoulder  520 . The circumferential groove  521  can, of course, simply be provided by a thinner wall of material allowing frangibility. A flange  447  is formed on the rear end of the plunger  424 . The flange  447  is sized to allow the thumb or palm of the user to properly depress the plunger  424  when positioned within the barrel  422 , as shown in FIG.  9 . 
     An extending band or rachet tab  449  is rearwardly located on plunger  424 , and is rearwardly flared to allow the rachet tab  449  to pass by a mating groove  450  formed in an interior wall of the barrel  422 . Upon full depression of the plunger  424  within the barrel  422 , the rachet tab  449  flexibly passes by the mating recess or groove  450 , facilitating a locking engagement and thereby preventing the extraction of the plunger  424  from the barrel  422 . 
     As best shown in FIG. 9, spring housing  426  comprises a front portion  432  and a rear portion provided by a needle retainer  456 . A needle retaining member  435  is affixed to the rearward end of insertion needle  425  for positioning within spring housing  426 . An opening  510  in the front end of the rear portion  456  of spring housing  426  is sized to receive the portion  432  of spring housing  426 . Portion  432  has an aperture therein to align the insertion needle  425  and also has a cylindrical cavity  514  formed therein having a diameter to receive spring  433  coiled about the needle  425 . 
     The needle retaining member  435  is retained by resilient fingers  437  of the spring housing  426  by radially inwardly positioned hooks  439  thereof sized to engage and hold the rear end of needle retaining member  435 . The spring  433  is positioned axially within the cylindrical spring housing  426  and concentrically located around insertion needle  425 . The front portion  432  compresses the spring  433  within spring housing  426  with the shaft  513  of insertion needle  425  passing through the forward aperture of the portion  432 . The portion  432  is permanently affixed to the rear portion  456  of spring housing  426 , as by sonic welding, bonding, or other known techniques. 
     As best shown in FIG. 10, the barrel  422  has internal ratchet teeth  516  sized and positioned to receive an external circumferential locking groove  517  of the spring housing  426 . Barrel  422  also comprises a transparent viewing window  523  for the doctor or nurse to view fluid as it enters the barrel  422 , which indicates that the insertion needle  425  and catheter sleeve  502  are located properly in a blood vessel of a patient. The spring housing  426  has external extending tabs  518  that are positionable into complementary longitudinal slots  519  of the barrel  422  for insuring proper alignment of the insertion needle  425  when the spring housing  426  is engaged with the barrel  422 . 
     In operation, the intravenous catheter insertion device  420  functions as follows. After positioning the insertion needle  425  and catheter sleeve  502  below a patient&#39;s skin in a vessel, the insertion needle  425  is withdrawn after the health care worker sees blood in the viewing window  523 . As can be appreciated, the portion of the barrel between the rear of the spring housing and the forward end of the actuating member provides a flashback chamber beneath the viewing window  523 . To retract needle  425 , the plunger  424  is pressed into barrel  422  causing the dissociation of the frangible end member  440  from the outwardly tapering shoulders  520  of the plunger  424 . Such continued motion of the plunger causes the resilient fingers  437  to flex or break, thereby resulting in release of the needle retaining member  435 . Accordingly, the compressed spring  433  exerts an expansive force against the needle retaining member  435 , propelling the needle retaining member and insertion needle  425 , as well as the dissociated frangible end member  440  into the longitudinal cavity  438  of the plunger  424 . The above operation makes a very distinctive clicking sound, thereby assuring the health care worker that the device  420  is now safe. 
     As shown in FIG. 9, a circumferential chamber  461  adjacent the resilient fingers  437  by the inner diameter of the barrel  422 , allowing the resilient fingers  437  to flex outwardly or break, thereby facilitating release of the needle retaining member  354 . The resilient fingers  437  will only flex or break when the tapered surfaces of the hooks  439  are engaged by the tapered conical shoulders  520  of plunger  424 . 
     In an alternative embodiment, the frangible end member  440  may be eliminated. In such an embodiment, the plunger  424  defines an aperture of sufficient size to allow the needle retaining member  435 , insertion needle  425 , and compressed spring  433  to be propelled into longitudinal cavity  438  when the resilient fingers  437  are flexed or break. 
     Returning to FIG. 10, upon further depression of the plunger  424  into the barrel  422 , the rachet tab  449  engages the radial groove  450 , thereby preventing the plunger  424  from being extracted from the barrel  422 . 
     A fifth embodiment of the present invention is shown in FIGS. 11-13. The device  620  may be referred to as a trocar or stylet. The device  620  includes a hollow barrel  622  of varying cross section with a spring housing  626  mounted in the front end of barrel  622 . The spring housing  626  comprises a nose portion or front alignment member  632  and a rear portion providing a needle retainer  656 . A needle  625  extends from the front end of the spring housing  626 . A catheter  700  is mounted upon the needle. The catheter  700  includes a tapered flexible cannula  725  positioned as a sleeve over the needle  625 . The tip or front end of the needle  625  extends beyond the front end of the cannula  725 . The catheter  700  further includes a catheter hub  701  attached to the distal or rear end of the cannula  725 . The exterior of the alignment member  632  is contoured to mate with the interior of the catheter hub  701  and removably holds the catheter  700  and its associated hub  701  in frictional engagement therewith before the catheter  700  is inserted for use in the patient. 
     Finger ridges  728  are formed on opposite sides of the forward end of the barrel  622 . The ridges  728  are contoured to allow a doctor or other health care professional to comfortably grip the device  620  near the forward end thereof, preferably between the thumb and forefinger of the doctor&#39;s preferred hand. 
     Cap retaining ridges  729  are formed upon the forward end of the barrel  622 , in front of the finger ridges  728 , for retaining the cap  724  upon the device  620 . Preferably, cap  724  is retained in snap-fit engagement thereon by a retaining groove  730  formed on the interior surface of the hollow cap  724 . The cap  724  extends forward from the front end of the barrel  622  to surround and protect the needle  625  prior to use of the device  620 . 
     Referring now to FIG. 12, the front or forward end of the barrel  622  is shown in greater detail. The front end of the barrel  622  has an axial bore  731  formed therein. The axial bore  731  is sized to receive the front alignment member  632 . The front alignment member  632  is firmly engaged within the forward portion of the axial bore  731  by a friction fit. The positioning of the alignment member  632  within the front portion of the axial bore  731  may be further secured by epoxy or ultrasonic welding. The alignment member  632  is generally cylindrical and has a cylindrical axial cavity  714  with a reduced diameter portion  733  providing an opening adapted to accommodate the needle  625 . The reduced diameter portion  733  also provides an internal annular surface  734 , which functions as an abutment for the forward end of a compressed spring  633 . 
     The rear end of the front alignment member  632  abuts against a reduced diameter portion  735  of the axial bore  731  through the forward end of the barrel  622 . The needle retainer  656  of spring housing  626  is firmly held in the reduced diameter portion  735  of barrel  622 . The forward end of the rear portion  656  of spring housing  626  abuts against the rearward end of the front alignment member  632 . The rear end of the spring housing  626  is provided with a latch means, such as a plurality of fingers  637  formed at the rear end of the spring housing  626 . The fingers  637  extend rearwardly from the spring housing  626  into an outwardly tapered portion  661  of the interior of the barrel  622 . The fingers  637  have hooks  639  integrally formed at their ends. The hooks  639  extend radially inward for retaining the needle  625  in position, as described above. In the present preferred embodiment, four fingers  637  are employed, but more or less latching projections  637  may be used depending on the size of the device  620 , the nature of the spring  633 . 
     The needle  625  includes a needle shaft  713  and an increased diameter head  630  attached thereto. The head  630  of the needle  625  functions as a cooperating latch member with the latching projections on fingers  637 . The needle head  630  includes an enlarged portion having an annular forward surface  737  which provides an abutment for the rear end of spring  633 . Hence, the spring  633  is maintained in compression between the forward surface of the needle head  630  and the rearward interior surface of the front alignment member  632 , to bias the needle  625  toward the rear of the device  620 . 
     The needle head  630  further includes an abutment surface  738 , which is formed as a lip or rim that is maintained in abutment with the hooks  639  of fingers  637 . As should be appreciated, when the fingers  637  are deformed or flexed radially outward, the engaging surfaces of the hooks  639  would be moved out of abutment with the abutment surface  738  of the needle head  630 . Upon this occurrence, the compressive force of spring  633  against the forward surface of the needle head  630 , would immediately thrust the needle head  630 , and hence the needle  625 , through an aperture  741  in the forward end of plunger  624  toward the rear of the device  620 . 
     A plunger  624  is slidably positioned within the barrel  622  for effecting such disengagement of the fingers  637  to free the needle head  630  and, thereby, fully retract the needle  625  into the device  620 . The forward end  740  of the plunger  624  is contoured or wedge shaped to mate with cooperating wedge shaped surfaces  739  of the hooks  639 . Such an arrangement facilitates the spreading of the fingers  637  to release the needle head  630 . More specifically, the plunger  624  preferably has a tapered forward end  740  which engages complementary sloping faces  739  of the hooks  639 , when the plunger  624  is urged forward within the barrel  622 . The forward motion of the plunger  624  causes the fingers  637  to spread radially outward by flexing or breaking, thus releasing the head  630  of the needle  625 . 
     An O-ring  742  is held in an annular recess  743  around the front end of the plunger  624  to be in sliding engagement between the plunger  624  and the interior of the barrel  622 . The O-ring  742  helps to maintain the aperture  741  in alignment with the needle head  630  for unhindered retraction of the needle  625 . Alternatively, the plunger  624  may be formed to fit within the barrel  622  and to maintain alignment therein by an integral sliding seal. 
     Referring now to FIG. 13, a vent plug  757  is positioned within the opening of the rear end of plunger  624  and is adapted to seal the rear of receptacle  638 . The vent plug  757  is preferably formed of a resilient porous material that allows air to escape from within the receptacle  638  during a blood return. The vent plug  757  is preferably adapted to become clogged when wet so as to prevent any leakage of blood from the rear end of the device  620 . Hence, a flashback chamber is provided by the central cavity of the actuating member. In alternative embodiments, the rear end of the receptacle  638  may be sealed with a solid sealing member, as long as the receptacle  638  is of sufficiently large volume that blood return is not significantly hindered by the back pressure produced therein when the volume is reduced by the influx of blood. 
     Prior to, and during insertion of the device  620  into the patient, the plunger  624  is maintained at a fixed, partially depressed position within the barrel  622 , so that the needle  625  is not prematurely retracted. Additionally, it is preferable for the plunger  624  to remain locked within the barrel  622 , at a second or forward position after the needle  625  is retracted into the device  620 , in order to prevent access to the contaminated or used needle. Both of these objectives are attained by the dual-position locking mechanism provided at the rear end of the device  620 , as shown most clearly in the enlarged view in FIG.  13 . 
     The rear of the barrel  622  has an open end  622   a  to receive the plunger  624  within the barrel  622  during assembly of the device  620 . The plunger  624  has first locking tabs  649   a  thereon, which extend outward from the exterior of the plunger  624 , as in the form of a rim or tooth. The first locking tabs  649   a  extend slightly beyond the internal diameter of the barrel  622  and have sloping forward surfaces  751   a  thereon, to allow the tabs  649   a  to be forced or press-fitted into an internal circumferential groove  650  formed in the interior surface of the barrel  622 . A lip  753  is formed in the interior of the barrel  622  between groove  650  and the open end  622   a  of the barrel  622 . Second locking tabs  649   b  are formed on the exterior of the plunger  624  around its circumference, the second locking tabs  649   b  being located to the rear of the first locking tabs  649   a . When the plunger  624  is positioned within the barrel  622  during assembly of the device  620 , the lip  753  is caught between the rear surfaces of the first locking tabs  649   a  and the forward surfaces  751   b  of second locking tabs  649   b . Hence, the plunger  624  is held at a first fixed position within the barrel  622  for initial use of the device  620  in insertion of the catheter  700 . 
     The forward surfaces  751   b  of the second locking tabs  649   b  are angled or ramped to mate with complementary angled rearward surfaces  756  of the lip  753 . To retract the needle  625 , the plunger  624  is pushed or urged forward within the barrel  622  with sufficient force to cause the second locking tabs  649   b  to enter the barrel  622  by virtue of a radial deforming force exerted mutually between the angled surfaces  751   b  of the second locking tabs  649   b  and the angled surfaces  756  of lip  753 . Continued forward motion of the plunger  624  within the barrel  622  is eventually halted by abutment of the rear end of the barrel  622  with an enlarged annular flange  647  forming the rear end of the plunger  624 . When the plunger  624  is urged forward into the barrel  622 , the second locking tabs  649   b  snap into the groove  650 , thus producing a distinct audible and tactile sensation indicating that needle retraction has been effected. 
     The force required to effect retraction is sufficiently high to minimize undesirable premature retraction, yet sufficiently low that the average person can effect retraction with one hand. Referring again to FIG. 11, the forward end of the device  620  is gripped during use, between the thumb and a forefinger of the dominant hand, with the rear of the device  620  aligned with the palm. In order to effect retraction, the doctor merely flexes the gripping thumb and finger firmly toward the palm while maintaining a natural grip on the device  620 . Hence, the doctor does not need to be distracted from attending to the inserted catheter  700  in order to render the device  620  in a safe condition with the needle  625  retracted and to receive confirmation that the safety feature has been activated. Alternatively, needle retraction can be effected by any other technique for applying the predetermined actuating pressure to the rearwardly protruding flange  647  of the plunger  624 . 
     When the plunger  624  has moved the latching projections or finger  637  to unlatch or release the needle head  630 , the needle  625  is freed for retraction. As the head  630  of the needle  625  is freed, the spring  633  forces or shoots the needle head  630  and the attached needle  625  into the barrel  622 . Of course, the device  620  is dimensioned to permit the entire length of the needle  625  to be received into the device  620  so that no portion of the needle  625  protrudes from the front alignment member  632  after retraction. 
     It will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the claims.