Abstract:
A hypodermic injection system with a retractable needle wherein the needle retracts within an interior cavity of a syringe plunger, such that the needle is confined within the plunger. A spring biases the needle rearwardly into the plunger, and a needle retainer releasably retains the needle against the bias of the spring. The plunger has a frangible end, which dissociates when the plunger engages the needle retainer, allowing the coiled spring to eject the needle into the interior cavity of the plunger. A body fluid sampling embodiment employs the same functional elements except the plunger is shorter and contains a linking that communicates with a vacuum container. The container allows fluid sampling and provides the structure to release the spring retracting the needle. The retractable needle embodiment is also employed with an insertion needle that guides a catheter tube below the skin of a patient and into the vein, and allows retraction of the insertion needle thereby avoiding accidental pricking of the health care worker by the insertion needle.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation of U.S. application Ser. No. 09/170,649 filed Oct. 13, 1998 now U.S. Pat. No. 6,179,812, which is a continuation of U.S. application Ser. No. 08/692,895 filed Jun. 20, 1996 now U.S. Pat. No. 6,096,005, which is a continuation-in-part of U.S. application 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 
   This invention relates generally to retractable needle systems and particularly to hypodermic syringes and intravenous catheter insertion devices that are suited for quickly and effectively removing the sharp insertion needle which poses a serious health threat. 
   BACKGROUND ART 
   Various types of retractable needle systems currently exist in the art, with the object being to provide a protective cover or cap over the possibly wound-inflicting insertion needle. Insertion needles found in intravenous catheter insertion devices and hypodermic syringes must be very sharp to quickly and easily puncture the skin and tissue of the patient in order to provide medication directly into the vascular system. Additionally, the insertion needle is usually very thin and hard to see, especially in low-light conditions. It is possible for doctors and nurses to accidentally prick themselves with the needle, either prior to or after an insertion into a patient. 
   Pricking oneself prior to the insertion of a solution does not present much of a health risk, since the needles to be used are normally sterilized. Also, the insertion needle usually comes with a needle cap which is secured over the top of the needle to prevent the accidental puncturing of skin. When the doctor or nurse removes the needle cap, exposing the needle, there is little risk of being injured by the needle. However, upon removal and placing the needle cap back onto the needle, the fingers can be pricked by a slight visual miscalculation or by a motorneuro mistake. The consequences of this type of accident are more extreme. 
   Since the insertion needle has already punctured the skin and tissue of the patient, blood and body fluid containing viruses or bacteria which may be found in the patient could possibly be transferred to the health care provider by a single accidental prick. 
   Various types of diseases previously known could be conveyed by such an accident, including hepatitis and cholera. 
   In the last decade, an even more menacing and lethal virus, the Acquired Immune Deficiency Syndrome, or AIDS virus, could be communicated by such accidental and catastrophic event. Since there is no known cure for AIDS at this time, a great deal of precaution is required to prevent the accidental prick of the health care provider by an insertion needle which has previously been used on a patient. 
   Many types of syringes of one type or another have been developed in an effort to address this problem yet allow the ease of use of more conventional hypodermic needles. 
   A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. However, the following U.S. patents were considered related: 
   U.S. Pat. No. 3,046,985, issued to C. Saenz on Jul. 31, 1962, discloses a dental syringe adapter for concealing a needle of the hypodermic syringe prior to use by a dentist. The needle is retained in a housing until a syringe plunger is depressed and the needle is pushed out of the protective housing instead of being captively retained within a syringe body. 
   U.S. Pat. No. 3,134,380, issued to T. Armao on May 26, 1964, discloses a hypodermic syringe needle having a shield which need not be removed prior to the use of the needle and which can be disposed of along with the needle itself. Holes are provided near the end of the shield to permit the escape of air as the shield is collapsed, allowing the needle to protrude through the protective caps. The cap is held in an extended position by a spring which yields upon injection. 
   U.S. Pat. No. 3,306,290, issued to H. S. Weltman on Feb. 28, 1967, discloses a retractable needle syringe which retracts the needle into a fluid-containing body and not into the syringe plunger. 
   U.S. Pat. No. 3,890,971, issued to T. A. Leeson on Jun. 24, 1975, discloses a safety syringe for one-time use, including a plunger which is lockable by detent members and a slidable needle cap which is also permanently lockable to prevent reuse. The needle cap slides over the exterior of the syringe barrel and over the fixed needle. 
   U.S. Pat. No. 4,367,738, issued to R. Legendre on Jan. 11, 1983, discloses a pre-filled syringe having spikes upon the plunger rods to prevent the withdrawal of the plunger from the syringe barrel. No means is disclosed for protecting the user from accidental pricking with the tip of the needle. 
   U.S. Pat. No. 4,416,663, issued to R. N. Hall on Nov. 22, 1983, discloses a self-sterilizing needle, wherein a capsule containing sterilizing fluid and having perforated ends of flexible material with elastic memory tendencies for self sealing after actual penetration by the forward end of the needle. The capsule is coaxially and slidably received over the forward end of the needle, with the forward exposed end of the needle slidably penetrating one end of the capsule and perforation for sterilizing of the needle. A syringe is provided for axially urging and positioning the capsule outward to its original position of rest. Then, the exposed end of the needle is again enclosed in the capsule for sterilization when the hypodermic penetration force is removed. 
   U.S. Pat. No. 4,631,057, issued to C. B. Mitchell on Dec. 23, 1986, discloses a needle coupled to a syringe barrel, wherein a needle guard is mounted on the barrel for movement from a retracted position in which the guard does not shield the needle, to an extended position in which the guard shields the needle. 
   U.S. Pat. No. 4,695,274, issued to R. L. Fox on Sep. 22, 1987, discloses a safety needle attachment wherein the needle is initially and entirely surrounded by a protecting jacket which is releasably interlocked with a holder. When the needle is to be used, an interlocker is released and the jacket is effectively telescoped over the holder to project the needle through a membrane over the end of the jacket to a working position. 
   U.S. Pat. No. 4,702,739, issued to N. M. Milorad on Oct. 27, 1987, discloses a hypodermic needle having a sleeve extending from a holder protectively covering the needle so that the sleeve can be placed against the body part where injection is to occur and with the needle tip proximate to the body part. By sliding the holder toward the body part, a detent restraint holding the sleeve in an extended position is overcome and relative retraction movement effected therewith. 
   U.S. Pat. No. 4,731,068, issued to J. E. Hesse on Mar. 15, 1988, discloses a non-reloadable syringe wherein the plunger is permitted to be withdrawn for purposes of loading the syringe and permitted to be urged forward to discharge the contents of the syringe. However, means is provided wherein subsequent retraction of the plunger assembly is inhibited to prevent further loading and use of the syringe. 
   U.S. Pat. No. 4,735,618, issued to J. Hagen on Apr. 5, 1988, discloses a protective enclosure for a hypodermic syringe needle formed by a tubular sleeve sized for friction fitting engagement over the barrel portion of the syringe. A needle guard portion is located at an opposed end, and pivotally removable arms operate to permit the needle to pass through a central channel of the needle guard. 
   U.S. Pat. No. 4,737,144, issued to P. V. Choksi on Apr. 12, 1988, discloses a syringe system comprising a tubular barrel and a sleeve mounted on the barrel to slide lengthwise from a retracted position in which the needle is exposed, to an extended position in which the sleeve extends protectively about the needle. 
   U.S. Pat. No. 4,737,150, issued to H. Baeumle on Apr. 12, 1988, discloses a tube-cannula syringe, the first cannula being disposed so as to be displaced relative to the second cannula, to be removable or displaceable in the longitudinal direction of the syringe. 
   U.S. Pat. No. 4,738,663, issued to David E. Bogan on Apr. 19, 1988, discloses a sleeve guide having a pair of fasteners with cavities formed in them that fit over the flange and which are located in hypodermic syringes for grasping in the user&#39;s fingers. The guide in the retracted position prevents the accidental pricking by the needle. 
   U.S. Pat. No. 4,743,233, issued to Michael B. Schneider on May 10, 1988, discloses a slidable sleeve over a syringe barrel that is connectable in a first position extending over a hypodermic needle and that is reconnectable in a second position along the syringe barrel to expose the needle for use. 
   U.S. Pat. No. 4,747,829, issued to J. Jacob et al., on May 31, 1988, discloses a pre-filled syringe with a retractable needle. A barrel of the syringe is removable within a casing from a remote pre-injection position to a forward injection position and back again. The barrel is moved forward allowing the needle to pass through an opening in a cap prior to injection. 
   U.S. Pat. No. 4,747,380, issued to W. W. Gloyer et al., on May 31, 1988, discloses a syringe having a hollow barrel formed at the distal end to receive an injection piston carried by the plunger member which allows the needle to also retract within the barrel by extracting the piston. 
   U.S. Pat. No. 4,747,831, issued to John C. Kulli on May 31, 1988, discloses a cannula insertion needle housing. The housing includes a latch mechanism for extending and retracting the needle. 
   U.S. Pat. No. 4,752,290, issued to J. J. Schramm on Jun. 21, 1988, discloses a tubular shield which is adapted to protect users from injury. The tubular shield cooperates with the raised surfaces on the body of the medical appliance to be protected. 
   U.S. Pat. No. 4,755,170, issued to T. A. Golden on Jul. 5, 1988, discloses a protective sealing device comprising a block with which a sharp end of the needle can be held within to prevent accidental puncture. Also disclosed is a retaining shield which can be retracted over the needle to prevent accidental puncture. 
   U.S. Pat. No. 4,772,272, issued to B. C. McFarland on Sep. 20, 1988, discloses a protective sleeve for a hypodermic needle which sleeve is completely dissociable from the hypodermic syringe. The protective sleeve is moved over the needle protecting position to the needle injection position solely by axial movement of the protective sleeve. 
   An International Patent Application filed by K. W. Gaarde and having a published number WO 89/00435, and a publication date of Jan. 26, 1989, shows a hypodermic syringe with a retractable needle in a needle holding mechanism which is integrally attached to a syringe body. 
   It is desirable that the insertion needle of the hypodermic needle or intravenous catheter device can be made available in a safe condition prior to insertion so that the health care provider will not accidentally prick his/her finger and require a new sterilized needle prior to the insertion into the patient. It is also a requirement that after insertion or sampling using the insertion needle, that the needle be safely and easily discarded without representing a continued health risk to anyone who may encounter the insertion needle, either on the premises of the health care facility, or in transit or arrival at the refuse collection area or disposal facility. 
   There is potentially a great interest in the health care industry to manufacture, sell, distribute, and use a hypodermic needle, an intravenous catheter insertion needle and a vacuum tube syringe that provides the type of safety as described above. It can be easily operated, proves to be completely reliable, and is easily and cheaply manufactured, yet still has a great deal of versatility for various applications using various needles in diameter and length and different sized vacuum tubes. 
   The features described above as being desirable for hypodermic syringes, intravenous catheter insertion devices and vacuum tube syringes are all provided for by the present invention. 
   SUMMARY OF THE INVENTION 
   The present invention is embodied in an approved hypodermic syringe system and intravenous catheter insertion device which is entirely safe prior to insertion or sampling due to a protective cover tip. Furthermore, after insertion or sampling, the hypodermic syringe system and intravenous catheter insertion device is entirely safe, since the health care provider, using one hand, can retract the insertion needle into a tamperproof isolation container which may then be easily and safely discarded, preventing the injury or transmission of any dangerous viruses or bacteria. In addition, both the hypodermic syringe system and intravenous catheter insertion device are easily manufactured, easy to use and provides visual and audible confirmation that the insertion needle has been safely retracted after use. 
   More particularly, the hypodermic injection system comprises a cylindrical syringe housing assembly, holding a retractable injection needle which can be safely, quickly and easily retracted within a specially designed syringe plunger. Furthermore, preferably the plunger is fixedly held after use within a specifically designed syringe barrel. The syringe barrel, plunger and needle assembly can be easily discarded without the dangers associated with an exposed needle or needle that can be easily uncapped. The needle is preferably held locked inside the barrel which is tamperproof. 
   In accordance with one aspect of the present invention, a medical device is provided that has a housing from which a needle projects for piercing the skin of the patient. After use, the needle is retracted so that it is shielded against inadvertent contact. The housing has a fluid cavity and a forward end. A dead-space area is in fluid communication with the fluid cavity and the needle, and is formed between the forward end of the housing and the rearward end of the needle. Preferably, but not necessarily, the dead-space area is part of the housing fluid cavity. A plunger is axially displaceable within the housing to expel fluid from the housing. A piston tip projects forwardly from the forward end of the plunger and is configured to cooperate with the dead-space area. A biasing element displaces the needle from the projecting position to the retracted position upon actuation of retraction. Displacing the plunger forwardly displaces the piston tip into the dead-space area to expel fluid from the dead-space area. In addition, when the plunger is displaced forwardly, the plunger operates to release the needle for retraction by the biasing element. 
   Preferably the device also includes a needle retainer for releasably retaining the needle in the projecting position. The needle retainer may comprise a frangible connection such that forward displacement of the plunger operates to fracture the frangible connection to effectuate release of the needle. In addition, the plunger preferably includes a cavity for receiving the needle after retraction. 
   Other aspects and advantages of the present invention will be apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principals of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of the hypodermic syringe of the present invention. 
       FIG. 2  is a partial cross-sectional view of the hypodermic syringe of the present invention shown with its plunger proximate to the needle housing. 
       FIG. 3  is a cross-sectional view of the hypodermic syringe of the present invention with the needle housing, needle, and needle cap shown exploded from the syringe barrel. 
       FIG. 4  is a cross-sectional view of the hypodermic syringe in the present invention shown with the syringe plunger in a partially depressed position within the syringe barrel. 
       FIG. 5  is a cross-sectional view of the hypodermic syringe of the present invention shown with the syringe plunger in a fully depressed position and the needle fully retracted. 
       FIG. 6  is a cross-sectional view of the second embodiment of the hypodermic syringe of the present invention. 
       FIG. 7  is an exploded view of the hypodermic syringe in the third embodiment. 
       FIG. 8  is a cross-sectional view of the hypodermic syringe of the third embodiment of the present invention shown with the plunger ready for use. 
       FIG. 9  is a cross-sectional view of the hypodermic syringe of the third embodiment of the present invention with the plunger in the fully depressed position and the needle fully retracted. 
       FIG. 10  is an exploded view of the hypodermic syringe in the vacuum tube blood sampling embodiment. 
       FIG. 11  is a full cross-sectional view of the hypodermic syringe in the vacuum tube blood sampling embodiment shown with the vacuum tube installed in the device and the hypodermic needle extended ready for use and the cap removed. 
       FIG. 12  is a full cross-sectional view of the hypodermic syringe in the vacuum tube blood sampling embodiment with the tube removed and the needle retracted ready for disposal. 
       FIG. 13  is an exploded view of the intravenous catheter insertion device of the present invention. 
       FIG. 14  is an exploded view of the intravenous catheter housing assembly of the present invention. 
       FIG. 15  is an exploded view of the spring housing assembly and insertion needle of the present invention. 
       FIG. 16  is a cross-sectional view of the intravenous catheter insertion device in the present invention shown with the plunger in a partially depressed position within the barrel. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The best mode for carrying out the invention is presented in the terms of a preferred, second, third, fourth and fifth embodiment. All five embodiments are similar in principle and function, however, variations in structure segregate the five. The preferred embodiment is shown in  FIGS. 1–6 , wherein like numerals represent like elements throughout, the complete hypodermic syringe  7  of this embodiment is best shown in exploded view as  FIG. 1 . The main components of syringe  7  are a standard injection needle  9  having a specifically mounted holder  11  including an enlarged lip  13 , located posteriorly thereto. A coiled spring  15  rides a shaft  17  of the injection needle  9  with an axially located passageway  19  therethrough. A cylindrical spring housing  21  includes a plurality of radial spaced resilient fingers  23  which include inwardly engaging inferiorly positioned hooks  25  on the posterior end  27  of the spring housing  21 . A sealing means or washer  29  is sized to be received within an inner cavity  31  of the spring housing  21 . 
   The injection needle  9 , including the enlarged lip  13  of the holder  11  can be forwardly positioned within the inner cavity  31  of the cylindrical spring housing  21 . A cross-shaped opening  33  in a forward end  35  of the spring housing  21  allows the shaft  17  of the injection needle  9  to extend through the cross-shaped opening  33 . The enlarged lip  13  is engaged by the hooks  25  when forwardly positioned within the spring housing  21 , causing the resilient fingers  23  and hooks  25  to flex around the enlarged lip  13  and engage a top surface  37  of the enlarged lip  13 . 
   The washer  29  provides a secure seal between the shaft  17  of the injection needle  9  and the inner cavity  31  of the spring housing  21 . Finally, a gasket or O-ring engages a circumferential groove  41 , located midway between the posterior end  27  of the spring housing  21 . This configuration can be more clearly shown in  FIG. 2 , and also in  FIG. 3 , partially exploded from the other components of the hypodermic syringe  7  of the present invention. 
   Also, shown in  FIG. 3  is a needle cap  43 , which engages a forwardly-positioned second circumferential groove  45  of the spring housing  21 . The spring housing  21  has radially-extending bayonet slots  47 , which provide locking engagement within bayonet slots  49  and a bayonet groove  51 , located within a tapered nose  53  of a syringe barrel  55 . Engagement between the spring housing  21  and the tapered nose  53  of the syringe barrel  55  is easily accomplished by aligning the bayonet tabs  47  with the bayonet slots  49  and pushing the spring housing  21  through the bayonet slots  49  and then rotating the bayonet tabs  47  within the bayonet groove  51  to provide locking engagement therebetween. The bayonet tabs  47  may have slanted edges (not shown) on opposing sides and the bayonet groove may have raised surfaces (not shown) to allow the slanted edges to pass by the raised surface in one direction of rotation. This effectively locks the spring housing  21  to the tapered nose  53  of the syringe barrel  55  in a racket-like manner. The first tapered inner wall  57  within the tapered nose  53  of the syringe barrel  55  provides sealing engagement between the spring housing  21  and the syringe barrel  55 , due to the tight fit of the O-ring  39  between the spring housing  21  and the first tapered inner wall  57 . 
   A plunger  59  is sized to be received within the syringe barrel  55  and engages a plunger piston  61  of a conventional type commonly used with syringe systems known in the art, except that a cylindrical cavity  71  extends therethrough, allowing a frangible end  65  to enter the cylindrical cavity  71  of the plunger piston  61 . The plunger piston  61  is positioned over the associated frangible end  65  and is supported by a rim  67 . The length of the plunger piston  61  is such that outwardly tapered shoulders  68  extend through and above the passageway  63  of the plunger piston  61 , joining the frangible end  65 . Between the outwardly tapered shoulders  68  and the frangible end  65  is a circumferential groove  69  of a defined thickness of approximately 0.031 inches (0.080 cm) which allows the frangible end  65  to dissociate from the outwardly tapered shoulders  68  upon a normal force on the frangible end  65  of approximately two pounds or less in the preferred embodiment. The circumferential groove  69  can, of course, simply be a thinner construction of material allowing frangibility. 
   The plunger  59  includes the cylindrical central cavity  71  running axially through the plunger  59  and adjacent to the frangible end  65 . The cylindrical cavity  71  has a diameter sufficient to allow the enlarged lip  13  and the holder  11  and the associated shaft  17  of the injection needle  9  to be injected into the cylindrical cavity  71  and need not be circular. Furthermore, the cylindrical cavity  71  can be evacuated so as to allow the vacuuming effect upon the dissociation of the frangible end  65  from the outwardly tapered shoulder  68 . 
   A plunger sleeve  73  defines the cylindrical cavity  71  while reinforcement ribs  75  provide support to the plunger sleeve  73  and are associated with the rim  67  to provide additional support when the plunger  59  is being depressed. A pushing plate  77  is located on a posterior end  82  of the plunger  59 . The pushing plate  77  is sized sufficient to allow the thumb of a normal person to properly depress the plunger  59  when associated with the syringe barrel  55 . 
   Also, finger retaining lips  79  are associated with the posterior end  81  of the syringe barrel  55  so as to allow the index finger and middle finger to grasp the finger-retaining lips  79  of the syringe barrel  55  while the thumb presses upon the pushing plate  77 . Grooves  83  or knurling may be etched within the finger-retaining lips  79  or upon the pushing plate  77  to provide a greater coefficient of friction between the fingers and thumb and the finger retaining lip  79  and pushing plate  77 , respectively. 
   Radially extending ratchet teeth  85  interrupt the reinforcing ribs  75  and are posteriorly located while being posteriorly flared to allow the ratchet teeth  85  to pass by an extending ratchet lip  88  defined by an interior wall  89  of the syringe barrel  55 . Upon full depression of the syringe plunger  59  within the syringe barrel  55 , the ratchet teeth  85  pass by the ratchet lip  88 . The ratchet teeth  85  flexibly pass by the ratchet lip  88  and prevent the extraction of the plunger  59  from the syringe barrel  55 . 
   In operation, the syringe  7  of the instant invention, functions very much like a conventional hypodermic syringe as found in the prior art. However, after injection, of the substance to be injected the hypodermic syringe  7  of the instant invention allows the dissociation of the frangible end  65  from the outwardly tapered shoulders  68  of the plunger  59  and the radial flexing of the resilient fingers  23  so that the hooks  25  release the enlarged lip  13  of the holder  11  of the injection needle  9 . 
   Since a circumferential space  91  exists between the resilient fingers  23 , and the inner wall  93  of the syringe barrel  55 , the resilient fingers  23  can flex, releasing the holder  11 . The resilient fingers will only flex when inwardly tapered surfaces  95  of the hooks  25  are engaged by the outwardly tapered shoulders  68  of the plunger  59 . Such engagement takes place when the plunger  59  is pushed through the syringe barrel  55  and the frangible end  65  abuts against the top surface  37  of the holder  11 . A normal force of less than 2 pounds exerted between the top surface  37  of the holder  11  and the frangible end  65  causes the frangible end  65  to dissociate from the outwardly tapered shoulders  68  of the plunger  59 . 
   With the resilient fingers  23  flexed radially outward, causing the hooks  25  to release the holder  11 , the compressed spring  15  exerts an ejecting force against the enlarged lip  13  of the holder  11 , propelling the injection needle  9  along with the holder  11 , as well as the dissociated frangible end  65  into the cylindrical cavity  71  of the plunger  59 . 
   The above operation makes a very distinctive click sound alerting the health care provider that the device is now safe. 
   Also, if the cylindrical cavity  71  is evacuated, a suction pulls the residual fluids into the cylindrical cavity  71 . Upon further depressions of the syringe plunger  59  into the syringe barrel  55 , the ratchet teeth  85  engage the ratchet lip  88 , preventing the plunger  59  from being extracted from the syringe barrel  55 . 
   The holder  11  can be a bright red or fluorescent color, while the plunger  59  and syringe barrel  55  can be manufactured from a transparent or translucent material so that the retracted position is readily identified in low light conditions and the needle is visibly safe for further handling, transport of discard. 
   Also, an interchangeable identification ring  101  can be positioned around the syringe barrel  55  so as to identify the hypodermic syringe for whatever purpose. 
   The plunger  59 , syringe barrel  55 , holder  11 , spring housing  21  and needle cap  43  can be made from a transparent or translucent plastic material. However, the spring housing  21  does not necessarily have to be transparent nor does the holder  11 . Such materials and their manufacturer are well known in the art and will not be further herein described. The plunger piston  61  can be formed of a neoprene material sufficient to provide a seal between the plunger piston  61  and the syringe barrel  55  and is also commonly known in the art and will not be hereinafter described in more detail. The shaft  17  of the injection needle  9  is of material known in the art as well. 
   The O-ring  39  can be of a elastomeric material, just as the washer  29  may also be of a resilient material, so as to provide a proper sealing effect well known in the art. It should be noted that the spring housing  21  must be formed of a durable plastic material which is resilient, so that the resilient fingers  23  properly and radially outwardly extend in association with the syringe plunger  59 . The syringe plunger must be of a more resilient or brittle material or have a proper thickness so as not to flex inwardly when the frangible end  65  dissociates from the plunger  59 . It is important that the plunger  59  remains sufficiently durable to cause the resilient fingers  23  to move radially outward when the inwardly tapered surfaces  95  of the hooks  25  engage the outwardly tapered shoulders  68  of the syringe plunger  59 . Specific examples of types of plastics and thicknesses are not required, as these can be readily determined by those ordinarily skilled in the art of plastics manufacture. 
   In the second embodiment, the mechanism responsible for ejecting the injection needle  9  can be fully positioned within the syringe plunger  59 . As shown in  FIG. 6 , some slight variations in structure are necessary to achieve similar if not identical results as described in the first embodiment of the invention. 
   The injection needle  9  is held within a frangible needle holder  105 , which includes a frangible cone  107 , which engages an enlarged section  109  of the injection needle  9 . The injection needle  9  has a length sufficient to extend well within the syringe barrel  55  and has an extraction end  111 , which can be engaged by extraction hooks  113  of similar design as shown in  FIGS. 1–5 . 
   A needle retractor housing  115  is located and held on an inward end of the syringe plunger  59 , specifically held in place by detents  117 , defined within the interior wall  119  of the cylindrical cavity  71  of the plunger  59 . The compressed spring  17  exerts force between the needle retracting housing  115  and the inner end  116  of the plunger  59 . The force exerted by the spring is not sufficient to force the needle retractor housing  115  past the detents  117 . 
   In operation the plunger  59  is pushed into the barrel  55  having outwardly tapered shoulders  121 , which break the frangible cone  107 , thereby releasing the enlarged section  109  of the injection needle  9 . Further downward pressure on the plunger  59  forces the needle retractor housing  115  past detentes  117 , allowing the spring  15  to expand, pushing the needle retractor housing  115  deep within the cylindrical cavity  71  and taking with it the injection needle  9 , because the hooks  113  grab the extraction end  111  as the needle retractor housing  115  is moved deeper into the cylindrical cavity  71  of the plunger  59 . It should be noted that an extra piston spacer  123  is required for proper operation, due to the injection needle  9  extending within the syringe barrel  55 . In other words, as shown in  FIG. 6 , a dead space is located at the forward end of the syringe between the rearward end of the needle  9  and the forward end of the barrel  55 . Fluid will remain in this dead space at the end of the injection stroke unless the plunger is configured to fill the dead space area at the end of the injection stroke to expel the fluid from the dead space area. Accordingly, a piston spacer  123  is attached to the forward end of the plunger  59  forward of and adjacent to the piston. The piston spacer  123  is configured to cooperate with the dead space area to expel fluid from the dead space area at the end of the injection stroke. 
   Besides the above-identified differences, the second embodiment of the invention functions substantially as the first and the materials necessary for each of the components are similar to those materials as described in the first embodiment of the invention. 
   The third embodiment of the invention is illustrated in  FIGS. 7–9  and consists of a syringe barrel  55 ′ having a partially open end  125  and a fully opened end  127 . The barrel  55 ′ has finger retaining lips  79 ′ on the partially opened end  125  providing a gripping surface for the user&#39;s fingers. Optionally, near the lips  79 ′, a color coded ring  101  of sufficient resiliency and diameter is slid over the exterior surface of the barrel  55 ′ and retained by friction to identify the particular syringe system. The open end  125  of the barrel contains bayonet slots  49 ′ and grooves  51 ′ or threads for connecting other elements to the open end. The barrel  55 ′ is transparent thus permitting the user to see the fluid inside, allowing expulsion of bubbles of air that may be within the liquid dispensed by the syringe. 
   A hollow syringe plunger  59 ′ is slidably received within the barrel  55 ′ and is sized to move linearly back and forth without restriction. The plunger  59 ′ has converging taper  135  on one end and an axial flange  136  on the other. The flange  136  has a radially thinned slender section  138  at the interface with the barrel  55 ′ which actually breaks away if forced outwardly when the plunger  59 ′ is in its fully closed position contiguous with the barrel  55 ′. 
   A resilient barbed stopper  140  is tightly pressed into the flange end of the plunger  59 ′ completely closing the end thereof allowing a hermetic seal inside the plunger. A frangible end  65 ′ is located on the tapered end  135 ′ of the plunger  59 ′ completing the hermetic seal inside. The plunger  59 ′ further contains an outwardly extending raised circumferential band  142  around the flange end and the barrel  55 ′ has an internal recessed girdle  144  in a similar location near the lips  79 ′. When the plunger  59 ′ is fully depressed and is recessed flush with the end of the barrel  55 ′, the band  142  snaps into the recessed girdle  144  locking the plunger  59 ′ into place. This prevents the plunger from being withdrawn and as the flange  136  is frangible, the closure becomes tamperproof even if an attempt is made to pry the flange  136  from the barrel  55 ′. 
   On the converging tapered end  135  of the plunger, a piston  61 ′ is positioned over a raised radial projection  146 . This piston is resilient in nature and seals the internal portion of the barrel  55 ′ allowing liquids to be drawn inside and forced out by the movement of the plunger  59 ′. Initially, the piston  61 ′ is located such that it is forward of the tapered end  135 , however, when the plunger  59 ′ is fully inserted into the barrel  55 ′, the piston  61 ′ is forced over the radial projection  146  into a secondary position sealing tightly against the inside of the hollow of the barrel  55 ′ and exposing the tapered end  135  of the plunger  59 ′. 
   An injection needle  9 ′ is positioned into the partially opened end  127  of the barrel  59 ′. This needle  9 ′ has an axial passageway inside and is sharp on the exposed end and flat on the other, or holder end. Spring holding means in the form of a holder  11 ′, coiled spring  15 ′ and spring housing  21 ′ retain the needle  9 ′ and attach combined elements to the barrel  55 ′. The holder  11 ′ has a raised lip  13 ′ on the end and the spring housing  21  is divided into two pieces  21   a  and  21   b  that are pressed together. The front portion  21   a  attaches to the barrel with bayonet tabs  47 ′ into the threads consisting of slots  49 ′ and grooves  51 ′ and partially retains the spring  15 ′. The rear portion  21   b  retains the balance of the spring  15 ′ and fingers  23 ′ and hooks  25 ′ are integrally formed therein in a frangible manner. The needle holder  11 ′ is held in place as the lip  13 ′ interfaces with the hooks  15 ′ on the fingers  23 ′ maintaining compressive tension on the spring  15 ′. 
   In operation, the fluid medication or pharmaceutical is drawn into the syringe  7 ′ in a normal manner by the vacuum created when the plunger  59 ′ is withdrawn. After injecting the liquid and the needle is withdrawn, the plunger  59 ′ is forced completely into the barrel  55 ′. As the tapered end  135  of the plunger approaches the end of the hollow barrel  55 ′, the piston  61 ′ is forced back over the raised projection  146  and simultaneously, the plunger converging taper end  135  forcibly breaks the frangible section between the resilient fingers  23 ′ of the rear portion  23   b  of housing  21 ′. This forcible bending outward of the resilient fingers  23 ′ releases the holders raised lip  13 ′ held by the hooks  25  at the end of the fingers  23 ′. This releasing movement permits the expansive force of the coiled spring  15 ′ to break the frangible end  65 ′ of the plunger  59 ′ and drive the needle  9 ′ frangible end  65 ′ and spring  15 ′ into the hollow of the syringe plunger  59 ′ fully retracting the needle  9 ′ and retaining it safely inside the syringe  7 ′. An audible clicking sound is heard when this action takes place. As previously described, the plunger  59 ′ is fully inserted into the barrel  55 ′ with the flange  136  flush with the open end  125  of the barrel  55 ′ and is unremovable due to the locking into place of the band  142  into the girdle  144 . As it is seen, the elements and function of this embodiment are basically the same with only slight differences in structure to accomplish secondary operable features. 
   In a fourth embodiment of the invention, the injection needle retracting mechanism is basically the same and the functional principal is identical except that instead of using the syringe  7 ″ for injecting fluids such as intramuscular absorbing medication or intravenous pharmaceuticals, the invention is directed to removing a fluid sample such as blood from the body. The usual method to accomplish this procedure is to employ a system that includes a hypodermic needle and a barrel including an interconnecting needle that pierces a vacuum container or vial drawing the sample into the container when the connection is made. The same problem exists with this system as it exposes a sharp hypodermic needle with only a removable cover for protection. The inside interconnecting needle is of little danger as it is completely surrounded by the barrel and is unaccessible to most parts of the medical practitioner&#39;s body, at least without a conscious effort. 
   The invention&#39;s embodiment for a device used in taking body fluid samples is illustrated in  FIGS. 10–12  and consists of the same hypodermic needle  9 ″, holder  11 ″, coiled spring  15 ″, spring housing  21 ″ complete with resilient fingers  23 ″ and hooks  25 ″ and all of the associated elements. The syringe barrel  55 ″ and the plunger  59 ″ however, differ somewhat in structure but retain the basic function. 
   The syringe barrel  55 ″ is cylindrical in shape and has a fully open end  125 ′ and an opposed partially opened end  127 ′. The open end  125 ′ may optionally contain a replaceable centering washer  129  that fits over the end  125 ′ and that has a predetermined inside diameter allowing a single barrel to be used with various diameter fluid sampling receptacles. Finger retaining lips  79 ″ are positioned away from the end  125 ′ in this embodiment serving to assist the user in handling and manipulating the device and allowing the washer  129  to be installed on the extreme end  125 ′. The partially opened end  127 ′ of the barrel contains the same tapered nose  53 ′ and tapered inner wall  57 ′ except a straight reduced bore section  131  is added extending the end slightly. On the inside surface of the barrel  55 ″, near the partially opened end  127 ′, are located a pair of circumferential snap release projections  133  that have a slightly smaller inside diameter, a radial shape, and that are positioned parallel and close to one another. These projections  133  are integrally formed with the plastic barrel  55 ″ and function as a retainer for the operating parts described later. 
   The material of the barrel  55 ″ may be opaque or translucent, however, transparent is preferred to allow the sampling vial to be viewed when it is disposed within the barrel. Additionally, a color-coded identifying ring  101 ″ may be slid over the exterior surface of the barrel  55 ″ and be retained by a slide fit to identify the size of the syringe system such as its needle diameter, length, etc. 
   A hollow syringe plunger  59 ″ is slidably received within the barrel  55 ″. This plunger is configured to contain a converging taper  135 ′ on one end and a hollow linking needle  137  on the other. The plunger&#39;s tapered end  135 ′ includes a resilient seal  139  that snaps over the plunger and becomes a closure between the plunger  59 ″ and in the straight reduced bore section  131  creating a tight hermetic seal with sufficient resistance to maintain the seal when slid linearly in the bore. 
   The linking needle  137  is held within the plunger  59 ″ through a compression fit and is parallel with the inside of the barrel  55 ″ as shown in  FIGS. 11 and 12 . A needle boot  141  is disposed over the needle  137  and stretches over a barbed projection  143  integral with the plunger holding the needle  137  on the inside and providing a gripping surface for the boot. The boot  141  is formed of a thin resilient material such as flexible silicone and is sized to enclose and protect the needle when stored. 
   The needle end of the plunger  59 ″ further contains an offset extended flange  145  almost the same diameter as the inside of the barrel  55 ″ creating a stop and centering the plunger in the barrel. 
   The middle portion of the plunger  59 ″ is considerably smaller in diameter than the barrel and defines a hollow plunger sleeve  73 ′ with a rim  67 ′ near the tapered end  135 ′. This rim  67 ′ is basically the same structure as the preferred embodiment except the outer edge is tapered sharply permitting the tip of the rim  67 ′ to be held in place between the peripheral snap release projections  133  located inside the barrel  55 ″. When the plunger  59 ″ is urged toward the partially open end  125 ′ of the barrel, the rim  67 ′ has sufficient resiliency to overcome its captivity between the projections and snap away from the containment. A similar snap action takes place when it is originally installed. 
   A sampling fluid vacuum container  147 , vial or “B-D VACUTAINER” as it is sometimes known in the medical field is inserted inside the open end  125 ′ of the barrel  55 ″. The container  147  has a resilient perforatable seal  149  on one end and is domed shaped on the other much like a test tube. The container  147  is well known in the art and widely used to receive and store body fluid samples. The container is normally fabricated of glass or transparent thermoplastic and is evacuated on the inside allowing the fluid to displace the vacuum eliminating the problem of expelling trapped air. 
   The spring holding means associated with and positioned on the barrel  55 ″ is as previously described using the same hypodermic needle  9 ″, holder  11 ″, and coiled spring  15 ″. The spring housing  21 ″ is slightly different and is preferably formed in two pieces that are pressed together. The front portion  21   a ′ interfaces with the partially open end  125 ′ of the barrel  55 ″ and holds part of the spring  15 ″; the rear portion  21   b ′ of the housing retains the balance of the spring  15 ″. The fingers  23 ″ and hooks  25 ″ are also integrally formed with the rear portion  2   b′.    
   In operation, the container  147  is inserted loosely into the barrel  55 ″ and the hypodermic needle  9 ″ is inserted, usually intervenously into the patient. The container  147  is urged forward into the barrel  55 ″ where the linking needle  137  pierces the container seal  149  and the vacuum within draws the fluid into the container. The container  149  may be removed and replaced if another sample is required however, when finished, the container is urged further into the barrel  55 ″ toward the partially open end  127 ′ by the practitioner thumb while grasping the lips  79 ″ with the fingers. This compressive force overcomes the resistance of the snap release projections  133  holding the extended flange  145  allowing the plunger  59 ″ to slide forward. The plunger converging tapered nose end  53 ′ forcibly spreads the resilient fingers  23 ″ of the rear portion  21   b ′ of the housing  21 ″ radially outward to release the holder&#39;s raised lip  13 ″. Thus, permitting the expansive force of the coiled springs  15 ″ to break the frangible end  65 ′ and extend the needle  9 ″ and holder  11 ″ into the hollow syringe plunger  59 ″. This triggered movement fully retracts the needle  9 ″ into the hollow center of the plunger  59 ′ and retains it in that position by the continual urging of the coiled spring  15 ″ thus repositioning the needle  9 ″ into a permanently protected and harmless location. An audible clicking sound is emitted when this action is completed and the container  147  may then be removed. Any liquid on the needle is again harmlessly retained inside the syringe  7 ″ and disposal may be safely achieved. A color coded ring  101 ″ as shown in FIGS.  1  and  4 – 6 , may optionally be used in this embodiment if desired. 
   The fifth embodiment of the invention is an intravenous catheter insertion device illustrated in  FIGS. 13–16 . Referring now to  FIGS. 13 and 14 , the main components of the intravenous catheter insertion device  150  is a catheter hub  152  comprising a flexible catheter sleeve  154  having an interior shaft  156  with an axial passageway wherein a standard insertion needle  9 ′″ is concentrically located. The insertion needle  9 ′″ is mounted in a spring housing assembly  21 ′″ which engages a barrel  55 ′″. A plunger  59 ′″ having an external ring portion  151  sized to be received within the barrel  55 ′″ for sealing purposes defines a partially open or closed longitudinal cavity  71 ′ extending therethrough, allowing a frangible end  65 ″ to enter the longitudinal cavity  71 ′ of the plunger  59 ′″. For ease of manufacturing, the longitudinal cavity  71 ′ may have a longitudinal slot  155  along a top side. 
   Between the frangible end  65 ″ and the longitudinal cavity  71 ′ are outwardly tapered conical shoulders  68 ′ having a circumferential groove  69 ′ of a defined depth which allows the frangible end  65 ″ to dissociate from the outwardly tapered conical shoulders  68 ′ as described in the preferred embodiment. The circumferential groove  69 ′ can, of course, simply be a thinner construction of material allowing frangibility. 
   A pushing plate  77 ′ is located on a posterior end  164  of the plunger  59 ′″. The pushing plate  77 ′ is sized sufficient to allow the thumb or palm of a normal person to properly depress the plunger  59 ′″ when associated with the barrel  55 ′″. Also, a finger retaining area  158  is associated with the posterior end  156  of the barrel  55 ′″ so as to allow the index finger and thumb to grasp the finger retaining area  158  of the barrel  55 ′″ as the palm presses upon the pushing plate  77 ′. 
   An extending rachet tab or tabs  160  are posteriorly located on plunger  59 ′″ while being posteriorly flared to allow the rachet tab  160  to pass by a complementing recess or radial groove  162  defined by an interior wall  89 ′ of the barrel  55 ′″. Upon full depression of the plunger  59 ′″ within the barrel  55 ′″, the rachet tab  160  flexibly passes by the complementing recess or radial groove  162  providing locking engagement thereby preventing the extraction of the plunger  59 ′″ from the barrel  55 ′″. Also shown in  FIG. 14  is a catheter needle cap  166 , which engages a forwardly-positioned circumferential flange  168  of the catheter hub  152  to prevent accidental pricking by insertion needle  9 ′″ prior to use. Optionally, the needle cap  166  can directly engage a forward portion of the spring housing assembly  21 ′″. In order to removably secure the needle cap  166  to the spring housing assembly  21 ′″, an external engagement groove may be present on the forward portion of the spring housing assembly  21 ′″ (similar to that present in the preferred embodiment). 
   As shown in  FIG. 15 , the needle holder  11 ′″ is affixed to a distal end of insertion needle  9 ′″ for placement in a first end of spring housing assembly  21 ′″. An opening  171  in a second end of the spring housing assembly  21 ′″ is sized to receive a housing plug  170  having a front end aperture  172  to allow passage of the shaft  17 ′ of the insertion needle  9 ′″ and a circular cavity  176  having a diameter that allows the spring  15 ′″ to be coiled when the housing plug  170  is forwardly positioned within the spring housing assembly  21 ′″. 
   As shown in  FIG. 16 , the needle holder  11 ′″ is retained by resilient fingers  23 ′″ of the spring housing assembly  21 ′″ by radially inwardly positioned hooks  25 ′″ sized to engage and hold the end of needle holder  11 ′″. The spring  15 ′″ is positioned axially within the cylindrical spring housing assembly  21 ′″ and concentrically located around insertion needle  9 ′″. The housing plug  170  compresses the spring  15 ′″ within spring housing assembly  21 ′″ with the shaft  17 ′ of insertion needle  9 ′″ passing through a central opening  172  of housing plug  170 . The housing plug  170  is permanently affixed to spring housing assembly  21 ′″ by sonic welding, bonding, Luer lock or other techniques known in the art. The coiled spring  15 ′″ is now positioned axially within spring housing assembly  21 ′″ between the retained needle holder  11 ′″ and affixed housing plug  170 . 
   As shown in  FIG. 13 , the barrel  55 ′″ has internal ratchet teeth  161  sized and positioned to receive an external circumferential locking groove  167  of the spring housing assembly  21 ′″, and a transparent viewing lens  153  for the doctor or nurse to view blood, indicating that the insertion needle  9 ′″ and catheter sleeve  154  are located properly under the skin. The spring housing assembly  21 ′″ has external extending tabs  169  that slide into complementary longitudinal slots  175  of the barrel  55 ′″ for insuring proper alignment of the insertion needle  9 ′″ when the spring housing  21 ′″ assembly is engaged with the barrel  55 ′″. 
   In operation, the intravenous catheter insertion device  150  functions very much like the hypodermic syringe  7  of the preferred embodiment. However, after injection of the insertion needle  9 ′″ and catheter sleeve  154  below a patient&#39;s skin, the insertion needle  9 ′″ is withdrawn when the health care provider sees blood in the viewing window  153  wherein the plunger  59 ′″ is pressed into barrel  55 ′″ allowing for the dissociation of the frangible end  65 ″ from the outwardly tapering shoulders  68 ′ of the plunger  59 ′″ and the radial flexing or breaking of the resilient fingers  23 ′″ allowing release of the needle holder  11 ′″ of the insertion needle  9 ′″. 
   As shown in  FIG. 16 , a circumferential space  91 ′ exists between the resilient fingers  23 ′″ and the inner wall  93 ′ of the barrel  55 ′″, allowing the resilient fingers  23 ′″ to flex or break which releases the needle holder  11 ′″. The resilient fingers  23 ′″ will only flex or break when inwardly tapered surfaces  95 ′ of the hooks  25 ′″ are engaged by the outwardly tapered conical shoulders  68 ′ of plunger  59 ′″. As previously described and shown in the preferred embodiment, engagement takes place when the plunger  59 ′″ is pushed through the barrel  55 ′″ and the frangible end  65 ″ abuts against the end surface  174  of the needle holder  11 ′″ which abuts against a solidly compressed spring. A normal force of less than two pounds exerted between the end surface  174  of the needle holder  11 ′″ and the frangible end  65 ″ causes the frangible end  65 ″ to dissociate from the outwardly tapered shoulders  68 ′ of the plunger  59 ′″. 
   When the resilient or frangible fingers  23 ′″ flex radially outward, the hooks  25 ′″ release the needle holder  11 ′″ causing the compressed spring  15 ′″ to exert an expansive force against the needle holder  11 ′″, propelling the insertion needle  9 ′″ along with the needle holder  11 ′″, as well as the dissociated frangible end  65 ″ into the longitudinal cavity  71 ′ of the plunger  59 ′″. 
   Similar to the other embodiments, the above operation makes a very distinctive clicking sound alerting the health care provider that the device is now safe. 
   Although not shown, the longitudinal cavity  71 ′ may be evacuated by application of a sealing plug exterior to plunger  59 ′″ so as to allow a vacuuming effect upon the dissociation of the frangible end  65 ″ from the outwardly tapered shoulder  68 ′ of plunger  59 ′″. Furthermore, the needle holder  11 ′″ can be a bright or fluorescent color, while the plunger  59 ′″ and barrel  55 ′″ can be manufactured from a transparent or translucent material so that the retracted position is readily identified in low light conditions and the insertion needle  9 ′″ is visibly safe for further handling, transport or discard. 
   Additionally, although not shown, it may be envisioned that the frangible end  65 ″ may be replaced with the plunger  59 ′″ defining an aperture of sufficient size to allow the needle holder  11 ′″, insertion needle  9 ′″, and compressed spring  15 ′″ to be propelled into longitudinal cavity  71 ′ when the resilient fingers  23 ′″ flex or break when inwardly tapered surfaces  95 ′ of the hooks  25 ′″ are engaged by the outwardly tapered conical shoulders  68 ′ of plunger  59 ′″, therefore performing the same operation as described above. 
   Upon further depression of the plunger  59 ′″ into the barrel  55 ′″ the rachet tab  160  engages the rachet lip  162 , preventing the plunger  59 ′″ from being extracted from the barrel  55 ′″. Additionally, at the end of resilient fingers  23 ′″ are engaging members  178  that engage grooves  180  located at the end of outwardly tapered conical shoulders  68 ′ of plunger  59 ′″ further preventing the plunger  59 ′″ from being removed or extracted from barrel  55 ′″. 
   Besides the above-identified differences, the fifth embodiment of the invention functions substantially as the preferred embodiment and includes all variations described in the all of the above-described embodiments. The materials necessary for each of the components of the fifth embodiment are similar to those materials as described in the first embodiment of the invention. 
   It should be appreciated from the foregoing description that the present invention describes an improved hypodermic syringe and intravenous catheter insertion device with a retractable needle which is simple in construction, yet completely effective in retracting a needle once the needle has served its purpose in the injection or removal of fluids below the surface of the skin. The retractable needle system of the present invention can be conveniently assembled from a minimum number of separate parts, all of which can be manufactured with relatively inexact precision, all of which are configured to facilitate compact and efficient operation. The retractable needle system of the present invention can be fully and safely operated by the use of one hand to retract the needle and allow for safe handling, transport and discard. 
   Although the present invention has been described in detail with reference only to the presently-preferred embodiment, it will be appreciated by those of ordinary skill in the art that various modifications can be made without departing from the invention. Accordingly, the invention is limited only by the following claims.