Abstract:
The present invention is a safety syringe for use with a plurality of interchangeable needles. The plurality of needles may be inserted by the user into the safety syringe for use. In operations, the user selects the desired needle, e.g., a needle having a particular gauge or size or of a particular type. The user inserts the needle ( 14 ) into a safety syringe ( 10 ) comprising a barrel ( 6 ), a needle assembly area ( 18 ) located within or attached to the barrel and a plunger ( 66 ). The needle couples to the syringe by a number of means. For instance, a locking mechanism ( 20, 22 ) may be used by which a needle hub located within the needle assembly has an area adapted to mate with a corresponding area on the needle. Or, the needle may be formed as part of a separate needle assembly, whereby the user will place the entire needle assembly onto the end of the syringe barrel. During use, the user operates the syringe like other safety syringe, using one hand to depress the plunger, which ultimately causes a spring to propel the needle into the barrel of the syringe.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority under U.S. law to U.S. Patent Application No. 60/120,622 filed Feb. 18, 1999, entitled “Interchangeable Needle Safety Syringe,” which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to the art of safety syringes and more particularly to a safety syringe with an interchangeable needle which reduces the likelihood of unintentional puncture or pricking of human skin.  
       BACKGROUND OF THE INVENTION  
       [0003]     In recent history, the transmission of contagious diseases, particularly those brought about exclusively by the co-mingling of human body fluids, has been of great technological interest. One of the particular problems has been associated with the use and disposal of hypodermic syringes, particularly among healthcare professionals. There have been various devices developed for the destruction of the needles or cannula used in such syringes. Additional devices have been developed for capping of syringes, while fixed needle safety syringes have also been designed, all of which attempt to minimize the likelihood of accidental puncture. The accidental puncture or pricking of a finger, or any other part of the body, after the treatment of a patient with a contagious disease, particularly a deadly contagious disease, results in a high likelihood of transmission of that disease. Various syringes have been developed in the prior art to attempt to minimize the likelihood of accidental puncture after patient treatment.  
         [0004]     One such device is described in U.S. Pat. No. 4,973,316 to Dysarz wherein a needle is retracted into the barrel of the syringe after the use thereof. Another such device is described in U.S. Pat. No. 4,921,486 to DeChellis, et al.  
         [0005]     Other references describing devices relating to needle retraction in a syringe include U.S. Pat. No. 4,994,034 to Bostich et al., U.S. Pat. No. 4,838,869 to Allard, and U.S. Pat. No. 5,114,410 to Batlle, GB 2 197 792 to Powers et al., WIPO 90/06146 to Nacci et al., and WIPO 90/03196 to Utterberg et al. Additionally, U.S. Pat. No. 5,407,431 to Bostich, et al, describes a safety syringe with an interchangeable needle. While all such devices seek the same goals of preventing accidental puncture and providing user flexibility, considerable room for improvement exists.  
       SUMMARY OF THE INVENTION  
       [0006]     These as well as other objects are accomplished by a hypodermic syringe having a barrel with a plunger movable therein to inject a fluid through a hollow needle thereof. A hollow needle hub is housed in a passageway within a needle assembly to which is releasably attached a replaceable needle. Positioned between the passageway within the needle assembly and a shelf on an internal wall of the syringe barrel is a deformable base, with integral flexible supports. The deformable base forms a liquid tight seal with the barrel, at the needle end of the barrel. The deformable base houses a head of the needle hub, forms a liquid tight seal with the base, and is in contact with energy storage means within the passageway in the needle assembly. The plunger has a thin, rupturable web on an end thereof which is part of a boot covering the end of the plunger, the boot, including the web, being liquid impermeable for forcing a liquid from the barrel upon movement of the plunger. Upon completion of an injection, the boot covered plunger contacts the deformable base, and upon application of force at the plunger, moves such base downward. Continued application of force causes flexible supports to flex and move over the sidewall of the needle assembly, permitting the deformable base to move the head of the needle hub downward until further movement of the needle hub is blocked by the passageway in the needle assembly. With the needle hub blocked by the passageway, continued force at the plunger causes the deformable base to move around the needle hub. As the deformable base moves further, the needle hub begins to protrude from the deformable base and come into contact with a web on the boot of the plunger.  
         [0007]     Continued force causes the head of the needle hub to tear the web of the boot, positioning the needle hub just inside a hollow portion of the plunger. The torn portion of the web creates a flap just inside the hollow plunger. As the plunger moves the deformable base still further, the needle hub eventually looses contact with the deformable base, which triggers a release of energy from the energy storage means in the passageway, projecting the needle hub with its changeable needle attached thereto into the hollow portion of the plunger. Once inside the plunger, the needle hub is trapped by its enlarged head behind a flexible catch within the plunger. Final movement of the plunger causes the plunger to become substantially locked in the barrel and causes a liquid tight seal to be created between the plunger and the syringe body. A closing member placed on the front of the needle assembly completely seals the syringe to prevent residual fluids from escaping. Completion of the needle retraction also automatically highlights an indicia such as a biohazard label which alerts persons handling the device that the syringe has been used and represents a potential biohazard.  
         [0008]     In multiple alternative embodiments presented later, various methods are taught to effect changeability of the needle. For these embodiments, concepts of operation of the retractable needle may be substantially the same, or other means of causing the needle to retract may be used. Rather than focusing on the retraction method, these embodiments focus on various ways of allowing needles of varying gauges to be used with same basic syringe body. One embodiment generally accomplishes this by forming a head on the needle that can mate with, in a detachable fashion, a needle hub that is formed as part of the syringe body, simply attached to the syringe body or otherwise associated with the syringe body. By way of example, the needle head may be formed with threads for mating with corresponding threads inside the needle hub. Or, snap-lock ridges may be inscribed on the needle head and needle hub so that the two can mate in a locking fashion. Many different mating connections can be used, so long as the needle head can be detachably inserted into the needle hub without causing the spring or other propellant means to trigger during the installation process. In other words, one cannot require substantial force for detachably inserting and removing the different sizes and types of needles because otherwise the act of interchanging needles will cause the syringe to trigger, this rendering it useless.  
         [0009]     Other methods may be used for forming an interchangeable needle while accomplishing this objective. For instance, in stead of simply inserting the head into a mating needle hub, the needle hub itself could be detachably connected to the syringe body. This would allow the user simply to unscrew one complete needle hub assembly and replace it with another. One advantage to this approach is that the needle hub could be formed so as completely to contain the mechanism for restraining the needle against the bias of the spring or other propelling means. Another advantage is that the assembled needle hub and needles may be larger and thus easier for the user to deal with than simply just another gauge needle. Additionally, because the needle hub can be formed with a ledge or the like to support a needle guard that will surround the needle before use and prevent sharps injuries, one can leave a guard on the needle hub while installing the entire assembly onto the rest of the syringe body.  
         [0010]     This invention accordingly aims to provide a hypodermic safety syringe having one, more or combinations of the following advantages: 
        the ability to minimize the likelihood of accidental puncture.     the ability to use an interchangeable needle, before syringe utilization, for selection of the optimum needle type and gauge for patient procedures and effectiveness and to provide a syringe which also provides automatic indication that the syringe represents a biohazard after utilization.     the ability to, after utilization with a patient, captures and isolates the used needle so as to render such needle harmless.     the ability to a hypodermic syringe which is operable utilizing only one hand.     to provide such a syringe which automatically, upon the end of an injection, retracts the interchanged needle to prevent its reuse, while sealing the needle within the body of the syringe to prevent leakage of residual fluids.     to provide a simple device, which is manufacturable in high volumes.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a cross-sectional view illustrating a completed assembly of the needle hub, base, barrel, needle assembly, and energy storage means of a syringe of this invention.  
         [0018]      FIG. 2  is a sectional view of a replaceable needle head and needle of this invention.  
         [0019]      FIG. 2A  is an enlarged view of the encircled area in  FIG. 2 .  
         [0020]      FIG. 3  is a sectional view of a replaceable needle head and a filter needle of this invention.  
         [0021]      FIG. 4  is a sectional view of an alternative embodiment of a replaceable needle head and needle of this invention.  
         [0022]      FIG. 5  is an isolated sectional view of the barrel of this invention.  
         [0023]      FIG. 5A  is a cross-sectional view along line  5 A- 5 A of  FIG. 5 .  
         [0024]      FIG. 6  is a side view of the needle hub.  
         [0025]      FIGS. 6A, 6B , and  6 C are enlarged partial side views of the end of the needle hub of this invention illustrating alternate embodiments of sealing mechanisms.  
         [0026]      FIG. 7  of the drawings is an elevational side view of the energy storage means.  
         [0027]      FIG. 8  is a cross-sectional subassembly view illustrating the assembly of the needle hub and base.  
         [0028]      FIG. 9  is a cross-sectional subassembly view illustrating the assembly of the needle hub, base, and barrel.  
         [0029]      FIG. 10  is isolated sectional view of the needle assembly of this invention.  
         [0030]      FIG. 10A  is an isolated sectional view of the guard edge of the needle guard.  
         [0031]      FIG. 11  is an isolated sectional view of a plunger in accordance with this invention.  
         [0032]      FIG. 12  is a cross-sectional view of the plunger of this invention, showing assembly of the plunger boot and the plunger seal on the plunger.  
         [0033]      FIG. 13  is a cross-sectional view of the syringe of this invention in an operable pre-activation state.  
         [0034]      FIG. 14  is an elevational view of the needle guard, showing the needle assembly closing member tethered, for example, to the tip of the needle guard.  
         [0035]      FIG. 14A  is an enlarged view of the encircled area of  FIG. 14 .  
         [0036]      FIG. 15  is a cross sectional view of the completed assembly of the syringe, including the needle guard.  
         [0037]      FIGS. 16, 17 ,  18 ,  19 ,  20 ,  21 ,  22 ,  23 ,  24 , and  24 A are cross-sectional views of the syringe of this invention showing the sequence of operation, after the injection cycle.  
         [0038]      FIG. 25  is a graph depicting the Force/Balance relationship upon which the syringe operation is based.  
         [0039]      FIGS. 26, 26A ,  27 ,  27 A,  28 ,  28 A,  29 ,  30 ,  31 , and  32  are sectional views of an alternative embodiment of the interchangeable needle head and needle and subassembly of the needle hub, base, barrel, needle assembly, and energy storage means of a syringe of this invention, where no supports are utilized in the subassembly and the needle hub is blocked in the passageway.  
         [0040]      FIGS. 33, 33A ,  34 ,  34 A,  35 ,  35 A,  36 ,  37 ,  38 , and  39  are sectional views of another alternative embodiment of the interchangeable needle head and needle and subassembly of the needle hub, base, barrel, needle subassembly, and energy storage means of a syringe of this invention, where no base supports are utilized in the subassembly, a shelf on the needle assembly contacts the end of the barrel, a taper on the base mates with a taper in the body, and is blocked in the needle hub in the needle assembly.  
         [0041]      FIGS. 40, 40A ,  41 ,  42 ,  42 A,  43 ,  44 ,  45 ,  46 ,  47 ,  47 A, and  48  are sectional views of an alternative embodiment showing a replaceable nose and needle assembly cooperating with an assembly of the needle hub, base, barrel, needle assembly, and energy storage means of a syringe of this invention.  
         [0042]      FIGS. 49, 49A ,  50 ,  51 ,  51 A,  52 ,  53 ,  54 ,  55 ,  55 A,  56  and  56 A are sectional views of an alternative embodiment of a replaceable nose and needle assembly and subassembly of the needle hub, base, barrel, needle assembly, and energy storage means of a syringe of this invention.  
         [0043]      FIG. 57  is an elevational view of the syringe prior to needle retraction.  
         [0044]      FIG. 58  is an elevational view of the syringe subsequent to needle retraction wherein an indicia has been revealed. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]     Before describing the drawings and embodiments in more detail, several terms are described below in an effort to clarify the terminology used in this document. Additional and fuller understanding of these terms will be clear to persons skilled in this art upon reading this entire document: 
        “Needle assembly”: refers to the area on the end of the syringe in which the needle, spring or base are assembled. The needle assembly can be a separate, physical piece that is attached to or associated with the rest of the syringe body. Alternatively, the needle assembly could be just the section of the syringe body near which the needle, spring, or base are partially or completely located.     “Needle head”: refers to the end of the needle that is associated with the syringe and which has an enlarged area. The enlarged area may be formed as part of the needle itself, or may be an additional piece fitted to the needle end. The enlarged area may be formed of plastics, metal or other suitable materials.     “Needle hub”: refers to a device that mates with the needle head. The device may be a separate, generally elongated device placed in the needle assembly area between, e.g. a base an one end of the needle assembly. Alternatively, the needle hub may be formed as part of the base, needle assembly or other component located in that area.     “Attached to”: means that physical parts are actually attached, possibly with an intermediate member between them, either by welding, gluing, snap-lock fit, screws or other attachment mechanisms known in the art. The attachment is designed to be semi-permanent in that the user does not normally remove the physical parts that are said to be attached.     “Associated with”: means that the devices in question are permanently or detachably coupled. Associated with is intended to be broader in scope than “attached to,” and covers devices that users may or may not be able to remove.        
 
         [0051]     In accordance with this invention it has been found that a syringe may be provided for normal operation which permits changing a needle subsequent to use, but which, upon completion of normal operation and continued movement of a plunger, results in a triggering of a needle hub with the interchangeable needle to project such needle harmlessly into the plunger and body of the syringe.  
         [0052]     Once trapped inside the plunger and body of the syringe, the needle is no longer subject to accidental pricking or poking of human tissue thus minimizing the likelihood of transfer of a contagious disease which may be carried by fluids contained on the surface of or within such needle. To prevent possible leakage of residual fluids in the needle, the syringe is sealed after use, and after such use an automatic indication is given that the syringe represents a biohazard. Various other advantages and features will become apparent from a reading of the following description given with reference to the various figures of drawing.  
         [0053]      FIG. 1  is a cross-sectional view illustrating a subassembly of a needle hub  2 , base  4 , barrel  6 , needle assembly  8  and an energy storage means  10  of a syringe  1  (shown in  FIG. 13 ) of this invention in a normal pre-injection position. In a preferred embodiment, energy storage means is a spring  10 . Base  4  is shown as a deformable body, but could be formed of multiple pieces, e.g. one piece that is deformable (such as an o-ring or the like) and others rigid. Needle assembly  8  is affixed to the barrel  6  by guiding the threaded end of needle hub  2  through the center of passageway  15  and inserting needle assembly  8  into the front of barrel  6 , until mating shelf  17  on needle assembly  8  contacts and is positioned against the top edge of the barrel  6 . Permanent joining between the needle assembly  8  and the barrel  6  can be accomplished by ultrasonic welding around the circumference of barrel  6  at overlap  7  between the two parts, or any other permanent attaching means can be used. Attachment of the needle assembly  8  to the barrel  6  creates a liquid tight seal between the two parts. As a result of this assembly step, the end of the needle assembly  8  is positioned just in contact with engaging flanges  19  of supports  21  thus preventing movement of the base  4  and the needle hub  2  contained therein for normal syringe use. If the needle hub  2  is formed as part of a single molded syringe barrel  6 , then the needle head  2  could be molded with a ridge or the like against which flanges  19  could bear. A preferred material for the base  4  is an elastomer. Supports  21  are illustrated in the preferred embodiment as a pair of opposing semicircular cantilevered beams, however, it is envisioned according to this invention that supports  21  could be connected and unitary, divided up further, or in some embodiments, be eliminated all together.  
         [0054]      FIG. 2  shows a sectional view of a replaceable needle head  12  and needle  14  of this invention. Fixed and sealed into a cavity  13  of the needle head  12  is the needle  14  by means of adhesive  16 , or other means of fixing needle hub  2  to needle head  12 . Female threads  18  are illustrated for releasably attaching, or detaching, the needle head  12  to the needle hub  2 , fixed within the passageway  15  of the needle assembly  8 . A bevel  20  of the needle head  12  mates with a bevel  22  in the needle hub  2  to create a liquid tight seal between the two parts. Alternate embodiments of sealing mechanisms are illustrated in  FIGS. 6A, 6B , and  6 C. Fins  23  on needle head  12  (as shown in  FIG. 2 ) mate with slots  25  in a needle guard  27  as seen in  FIG. 14 , which releasably fix the needle guard  27  to the needle head  12  and prevent rotation of needle head  12  in the needle guard  27 .  
         [0055]     This invention provides for releasably attaching a variety of types and styles of needles to the needle hub  2  within the passageway  15  because the configuration of the needle hub  2  and needle head  12  remain constant and allow mating of needles  14  of various lengths and features to the syringe  1 . For example, needles  14  ranging from a 18 gauge to a 26 gauge of various lengths may be used with this invention. Additionally, filter needles which are not intended to be retractable work with this invention as prescribed in standard syringe practice. Moreover, the interchangeable needle safety syringes of this invention may be compatible with syringes of other manufacturers including those made by Retractable Technologies and New Medical Technologies, Inc.  
         [0056]      FIG. 2A  is an enlarged view of the encircled area of  FIG. 2  showing fins  23  and recess  29  on fin  23  used for releasably fixing the needle guard to the needle head  12 .  
         [0057]      FIG. 3  shows a sectional view of a replaceable needle head  26  and a filter needle  24 . Adhesive  28  or other satisfactory means binds the needle  24  to the needle head  26 . A filter  30  is positioned between the needle  24  and the needle head  26  to protect from any debris entering the barrel during the syringe fill cycle. The uncontaminated filter needle is not retracted into the syringe but is removed and thrown away after use and replaced by another replaceable needle which is generally retractable.  
         [0058]      FIG. 4  is an alternative embodiment of a needle  14  disposed within the needle head  12 . The needle head  12  is the same as the needle head  12  shown in  FIG. 2 .  FIG. 4  shows an example of a different length and gauge needle  14 , where the needle shaft is shorter than the needle shaft shown in  FIG. 2 .  
         [0059]      FIG. 5  shows an isolated section view of the barrel  6 .  FIG. 5A  is a cross-sectional view along line  5 A- 5 A of  FIG. 5  showing a finger support flange  40  of the barrel  6  of this invention. Referring to  FIGS. 5 and 5 A, an undercut  42  for locking the plunger into the barrel is shown at the finger support flange  40  of barrel  6 . At the opposite end of the barrel  6 , a base shelf  3  and a base relief shelf  44  are illustrated. These internal offsets receive the base in the case of shelf  3 , while the function of the shelf  44 , is to provide room for base expansion as the base  4  is deformed and travels over hub  2  during operation.  
         [0060]      FIG. 6  shows an isolated view of the needle hub  2 . Top  46 , flange  48 , spring contactor  50 , hub catch receiver  52  and hub block  54  are illustrated. Needle hub  2  male threads  56  and bevel  22  are also illustrated and are used to releasably attach the needle head  12  to needle hub  2 , while also creating a liquid tight seal between the two parts.  
         [0061]      FIGS. 6A, 6B , and  6 C illustrate alternate embodiments for sealing mechanisms of needle hub  2  to the needle head.  FIGS. 6A and 6B  represent seals  51  and  53  formed as integral and unitary parts of the needle hub  2 , while  FIG. 6C  illustrates seal  55  as an O-ring seal.  
         [0062]      FIG. 7  is an elevational view of the energy storage means  21  illustrated as a spring  10 .  
         [0063]      FIG. 8  shows an assembly step accomplished by inserting the needle hub  2  into the base  4 . Once inserted, a base wedge  58  is positioned for a substantially mating engagement over a flange  48  of the needle hub  2  which blocks needle hub  2  movement in both directions when inserted in the barrel  6 . A liquid tight seal between the needle hub  2  and a needle hub seal  60  on the base  4  as shown in  FIG. 8  is created at the needle hub  2 . With the needle hub  2  blocked into the base  4 , the next assembly step is accomplished.  
         [0064]      FIG. 9  shows the next step of the assembly process, where the subassembly in  FIG. 8  is inserted into the front end of the barrel  6  as shown in  FIG. 9 , until the base  4  contacts and is positioned against the base shelf  3 . When the base  4  is completely inserted as shown in  FIG. 9 , the base  4  is compressed circumferentially in the direction of the needle hub  2 , and a liquid tight seal is produced between the base  4  and the barrel  6 , and needle hub  2  is restrained from movement.  
         [0065]      FIG. 10  shows an isolated sectional view of the needle assembly  8  of this invention. The passageway  15  is shown and is defined within the needle assembly  8 . A circular grove  64  on the needle assembly  8  serves as a guide for positioning the needle head  12 . A rotating shelf  17  contacts and is positioned against the edge of the barrel  6 . In an alternative embodiment, the needle assembly  8  is transparent providing for viewing a joint between the needle hub  2  and the needle head  12  after the needle  14  is changed.  
         [0066]      FIG. 10A  shows the circular groove  64  on the needle assembly  8  that serves as an indicator that needle head  12  is in proper position when a guard edge  65  on the guard  27  (shown in  FIG. 14 ) is over the center of the groove  64 .  
         [0067]      FIG. 11  of the drawings is an isolated sectional view of a plunger  66  in accordance with this invention. A capturing means  68  is illustrated for capturing the needle hub  2  with interchangeable needle  14  attached thereto into hollow  82  of plunger  66 . A plunger boot termination  70  is also illustrated and is designed to receive and mate with rupturable boot  72 .  
         [0068]     A plunger seal  74  and the boot  72  are placed onto the plunger  66  as shown in  FIG. 12 . The boot  72  is preferably placed onto plunger  66  so that a web  76  is just at the end of the plunger.  
         [0069]     The plunger  66  is then inserted into the barrel  6 . The thickness of the web  76  and the tear grooves are selected to withstand normal operating pressures within the syringe  1 , yet allow relative ease in the puncturing of the web  76  by the needle hub  2 . The preferred material for boot  72  is an elastomer. In an alternative embodiment, the seal  74  is formed as an integral and unitary part of the plunger  66  so that the seal as provided by use of an O ring is obviated, and the seal is accomplished by forming the ring as an integral part of the plunger  66 .  
         [0070]      FIG. 13  is a cross-sectional view of the syringe  1  of this invention in an operable pre-injection state. Operation of the assembled syringe is discussed below. The syringe  1  has a barrel  6  and the plunger  66  mounted therein. The interchangeable needle  14  is contained within the needle assembly  8 , which is fixed to barrel  6  by ultrasonic welding means or other permanent attaching means.  
         [0071]     The interchangeable needle  14  has the needle head  12  that is releasably fixed to the needle hub  2 . The needle hub  2  is generally cylindrical in shape and positioned within and engaged by the deformable base  4 . The hub  2  has a top  46  which is preferably concave and diametrically cylindrical. The top of enlarged needle hub  2  can be flat in some embodiments. Below the top  46  on needle hub  2  is a diametrically wider area or flange illustrated by  48  in  FIG. 13 , which is slightly wider than top  46 . In some embodiments there are a plurality of diametrically wider areas or gradually extending flanges illustrated as areas  315  and  317  in  FIG. 41  and areas  415  and  417  in  FIG. 50 . The back of needle hub  2  is defined by a plurality of decreasing diameter steps. The steps closest to top  46  defines contacting portion  50  for contacting the energy storage means  10 . By appropriately positioning the needle hub  2  within deformable base  4  for a substantially mating engagement, the arrangement of top  46  and flange  48  of needle hub  2  can be substantially mated and held within deformable base  4  so that a liquid tight seal between needle hub  2  and deformable base  4  is created.  
         [0072]     The needle assembly  8  has contained therein the energy storage means, illustrated as spring  10  at the top of a passageway  15 , which is in contact with contacting portion  50  of the needle hub  2 . The deformable base  4  is positioned between the base shelf  3  on the barrel  6  and one end of the needle assembly  8  wherein the supports  21  of the base  4  contact the wall of the needle assembly  8 .  
         [0073]     Further referencing  FIG. 13 , the plunger  66  has a hollow  82  therein and has the boot  72  covering an end thereof which is fluid impermeable for forced movement of a fluid in the barrel  6  during ordinary injection. A portion of the boot  72  is illustrated as having been torn by needle hub  2  in  FIG. 22 , with the boot web  79  laying to the side in the hollow of plunger  66 .  
         [0074]     Preferably, the plunger  66  has an enlarged thumb push  84  which, upon completion of a compression stroke, is substantially locked within recess  42  in the syringe body  6  by a mating head portion  94  of barrel  6  (shown in  FIG. 24A ).  
         [0075]      FIG. 14  shows a side view of the needle guard  27 , with a needle assembly closing member  90  tethered at the end thereof. The closing member  90  is attached or tethered by a breakable tab  92  which can be of plastic construction and which is broken to remove the closing member  90 . As illustrated, the closing member  90  is preferably a plug which is attached by the tab  92  to the needle guard  27  at an angle wherein the tab  92  connects to the closing member  90  away from the end of the closing member  90  which can be inserted or plugged into the opening of the needle assembly  8  left after needle retraction. As discussed above, the closing member  90  of this invention can be of various types, such as a cap or a plug as shown, as long as the opening left by needle retraction can be closed. Preferably the opening is closed off so that a liquid tight seal is obtained. The angular attachment of the closing member  90  preferred herein and illustrated in  FIG. 14  allows a person completing needle retraction to handle just the needle guard  27  to insert the closing member  90  into the needle assembly  8  where the needle  14  was positioned prior to retraction. Quite advantageously, this can be accomplished with the user&#39;s hands always position behind the opening in the needle assembly  8  left as a result of needle retraction.  
         [0076]      FIG. 14A  is an enlarged view of the encircled area of  FIG. 14  showing slot  25  and bead  57 , used in conjunction with recess  29  (shown in  FIG. 2A ) for releasably fixing the needle head with its needle into the guard.  
         [0077]      FIG. 15  shows the needle guard  27  placed on the needle head  12 , with the needle assembly closing member  90  tethered at the tip of needle guard  27 . The guard is placed into its position by snapping bead  57  shown in drawing  14 A into recess  29  on fin  23  shown in drawing  2 A. Fins  23  on needle head  12  as seen in  FIG. 2  mate with slots  25  in guard  27  as shown in  FIG. 14  and releasably fix the guard  27  to the needle head  12  and prevent rotation of the needle head  12  in the needle guard  27 . As depicted in  FIG. 15 , the needle head  12  has been inserted into the open end of the passageway  15  of the needle assembly  8 . Female mating threads  20  on the needle head  12  (as shown in  FIG. 2 ) are guided by the passageway  15  into the male threads  22  on the needle hub  2  (as seen in  FIG. 6 ). The needle guard  27  with needle head  12  and its needle  14  releasably fixed therein has been twisted until the needle head  12  is substantially fixed to the needle hub  2  and a liquid tight seal is formed between the two parts, thus completing the assembly process. The circular groove  64  on the needle assembly  8  (shown in  FIGS. 10 and 10 A) serves as an indicator that the needle head  12  is in the proper position when the guard edge  65  (shown in  FIG. 10A ) on the needle guard  27  is over the center of the groove  64 .  
         [0078]     It will be apparent to those in the art that there exists other possible sequences of assembly other than those described that can be used to produce the completed assembly as shown in  FIG. 15 , producing the same syringe ready for operation.  
         [0079]      FIGS. 16 through 24  show the sequence of operation of the interchangeable needle safety syringe  1  and will now be described with reference to  FIG. 13  and  FIGS. 16 through 24 . As can be seen,  FIG. 13  is a cross-sectional view of safety syringe  1 . For normal syringe operating forces, the safety syringe  1  operates as any conventional syringe. For use, the syringe  1  is filled from an ampule in a normal manner, as standard procedure dictates. Once filled, the injection cycle is accomplished, again according to standard practice. At completion of the injection cycle, the plunger boot  72  is just mating with the base  4 , as shown in  FIG. 16 , and all fluids, which can be, are expended from syringe  1 . Before the syringe is released, or discarded, by the user, the needle retraction cycle should be accomplished.  
         [0080]     At the beginning of the needle retraction cycle, the syringe  1  is usually held between the index finger and the middle finger at the support flange  40 , with the thumb resting on thumb push  84 , presumably the same as the syringe was held at completion of the injection cycle. The plunger  66  is just mated with the base  4  at the boot  72 , as shown in  FIG. 16 .  
         [0081]     With reference to  FIG. 17 , force is applied between the finger support flange  40  and the thumb push  84 . This force is transmitted along the plunger  66  to the deformable base  4  and the supports  21 . As the force increases sufficiently, the supports  21  be in to flex and close towards one another as shown in  FIG. 17 , forcing the flange  19  to ride up on the interior wall of the needle assembly  8  thus allowing further forward movement of the base  4  and needle hub  2  with the interchangeable needle  14  contained therein.  
         [0082]     As shown in  FIG. 18  the continued application of force applied at the plunger  66  continues to cause the supports  21  to ride up on the interior wall of the needle assembly  8 , and as the deformable base  4  moves further, energy storage means  10  is further compressed. The deformable base  4  moves forward until a hub block  54 , on needle hub  2  which is in translation with the base  4 , comes into contact with the top of the passageway  15 , preventing further movement of hub  2 . This allows the plunger  66  to force the base  4  to deform and pass around the now stationary needle hub  2 .  
         [0083]     With reference now to  FIG. 19  as the deformable base  4  moves further toward the end of the barrel  6 , the needle hub  2  begins to protrude from the base  4  and come into contact with and stretch the web  76  of the boot  72  on the plunger  66 . Continued force causes further translation of the base  4  and the needle hub  2  to tear web  76  of the boot  72 , positioning the needle hub  2  just inside hollow  82  of the plunger  66  while the flange  48  on the needle hub  2  remains embedded within deformable base  4 , as shown in  FIG. 19 . As the base  4  moves forward in the barrel  6  and transverses the barrel shelf  44  which effectively increases the inter-diameter of barrel  6 , holding forces on the needle hub  2  as a result of circumferential compression of the base  4  in the narrower part of barrel  6  is diminished, facilitating release of the needle hub  2  from the base  4 .  
         [0084]     With reference to  FIG. 20 , continued translation of the deformable base  4  causes the flange  48  to eventually lose contact with the deformable base  4 , creating a trigger-like release of the needle hub  2 . Upon this trigger-type action, energy stored within the energy storage means  10  is released and imparted to the needle hub  2  to project the needle hub  2  and the replaceable needle  14  into the hollow  82  of the plunger  66 , as illustrated in  FIG. 21 .  
         [0085]     Referring now to  FIG. 22 , it is seen that the needle hub  2 , at its top  46 , contacts a capturing means  68  which elastically flexes to permit the needle hub  2  to pass through the constriction formed by the capturing means  68  and the interwall of the barrel  6 . This is further illustrated in  FIG. 23  where the needle hub  2  with replaceable needle  14  is shown having passed the capturing means  68  and captured within the hollow  82  of the plunger  66  where in the head of the needle hub  2  has moved back past the capturing means  68 . At this point, it should be noted that the plunger  66  has been substantially locked within recess  42  of the barrel  6 , by a mating head portion  94  engaging a portion of the plunger  66  near a thumb push  84 , as shown in  FIG. 24A . A liquid tight seal between a plunger seal  79  and a guard ring  86  is created.  
         [0086]     To finish the operational sequence, the closing member  90 , tethered to the end of the needle guard  27 , can be inserted into opening  22  of the needle assembly  8 , as shown in  FIGS. 23 and 24 . The closing member  90  is forced into position by pressing the front of the syringe against a heavy, solid object. Once the closing member  90  is lodged into position, the closing member  90  can be separated from the needle guard  27  with a twisting action, leaving syringe  1  as shown in  FIG. 24 . This closure process can therefore be advantageously accomplished with a user&#39;s hands always remaining behind the opening left by the retracted replaceable needle. As a result of accomplishing the needle retraction cycle, syringe  1  is left as shown in  FIG. 24 .  
         [0087]     The syringe operates on a “Force/Balance” principal as depicted in the graph of  FIG. 25 . In the graph normal operation is represented by regions I and II. In these regions limited positive and negative forces are applied between the plunger  66  and the body  6 , shown in  FIG. 15 , for normal operating functions of filling the syringe and for injections. Positive forces are defined as forces which move the plunger  66  into the syringe body  6 , while negative forces are defined as forces which pull the plunger  66  from the syringe body  6 .  
         [0088]     Typical “filling” and “injection” cycles are depicted in regions I and II, respectively. As long as the positive force applied between the plunger  66  and body  6  of syringe  1  is below threshold  39 , the base  4  balances the operating force and remains in its assembled position, as shown in  FIG. 15 . But, for positive forces applied to the syringe above threshold  39 , the base  4  becomes unbalanced and begins to move in the direction of needle assembly  8 . Once force above threshold  39  is applied and maintained, operation of the syringe moves into region III, where the needle is retracted into the plunger of the syringe. In  FIG. 25 , the item numbers “ 83 ”, “ 85 ”, and “ 87 ,” in region III of the graph respectively refer to where in a typical device the base  4  first begins to move, the needle hub  2  is released and the plunger  66  becomes substantially locked into the body  6 .  
         [0089]     At least four alternative embodiments are envisioned for the syringe invention defined herein.  FIGS. 26 through 32  define alternate embodiment 1 as syringe  101 ,  FIGS. 33 through 39  describe alternate embodiment 2 as syringe  201 ,  FIGS. 40 through 48  describe alternate embodiment 3 as syringe  301 , and  FIGS. 49 through 56 A describe alternate embodiment 4 as syringe  401 . Each of the embodiments is substantially similar in operation to syringe  1 , and as such differences between alternate embodiments and syringe  1  will be defined.  
         [0090]      FIGS. 26 through 32  show sectional views of an alternative embodiment of the replaceable needle head and needle, cooperating with an assembly of a needle hub, base, barrel, needle assembly, and spring, where no supports are utilized. With reference to  FIGS. 26 through 32 , components of syringe  101  that are different from syringe  1  taught herein are needle assembly  109 , needle hub  113 , base  111 , and body  105 . With reference to the figures,  FIG. 26  is an isolated sectional view of the needle assembly  109  of this invention showing locking slots  148  at the entrance of and recessed into the side wall of a passageway  123 , which extend part way through the passageway  123 .  FIG. 26A  is a cross sectional view of the needle assembly  109  along line  26 A- 26 A of  FIG. 26  showing a front view of the needle assembly  109 .  FIG. 27  of the drawings is an isolated view of the needle hub  113  showing locking bars  156  which extend radially out from the sidewall of the needle hub  113 .  FIG. 27A  is a cross sectional view of the needle hub  113  along line  27 A- 27 A showing a front view of locking bars  156 .  FIG. 28  is an isolated sectional view illustrating the base  111 , wherein flexible supports have been eliminated. Assembly of syringe  101  is accomplished in similar manner to syringe  1 . First, as shown in  FIG. 29 , the needle hub  113  is inserted into and matingly held in the base  111 . The base  111  and the needle hub  113  are next inserted into the front of the body  105 , until the base  111  comes into contact with the barrel shelf  102  as shown in  FIG. 31 . Placing the base  111  into body  105  circumferentially compresses the base onto the needle hub  113 , prevents movement of the needle hub  113  in the base  111 , and insures that a liquid tight seal between the needle hub  113  and the base  111 , and the base  111  and the body  105  is obtained.  
         [0091]     With reference to  FIG. 31 , a spring  121  is placed over the needle hub  113 . The needle assembly  109  is next guided onto the needle hub  113  such that the outwardly radially extending locking bars  156  on the sides of the needle hub  113  are mating with and engaged into locking slots  148  in the passageway  123  on the needle assembly  109 . The needle assembly  109  is next pushed into the open end of body  105 , which compresses spring  121 , until the sidewall of the needle assembly  109  bottoms out on the barrel shelf  114 . The needle assembly  109  is then permanently fixed to body  105  by heat staking techniques at position  181  as shown in  FIG. 31 , or other suitable permanent fixing means. With the needle assembly positioned into the body  105  as shown in  FIG. 32 , a hub block  125  (as shown in  FIG. 27 ) just contacts the bottom of locking slots  148  in the passageway  123  (as shown in  FIG. 26 ), thus restricting further movement of the needle hub  113  into the passageway. In the opposite direction the needle hub  113  is restrained from movement by mating engagement with the base  111 , which is blocked by the barrel shelf  102 . With reference to  FIG. 32 , the next step of the assembly process is accomplished by placing the boot  143  and a plunger seal  104  on plunger  107 , and inserting the plunger  107  into body  105  as illustrated in  FIG. 32 . Before insertion of the plunger  107  into body  105 , it is common manufacturing practice to lubricate the interior wall of body  105 . Silicon is usually the lubricant of choice for this application. Assembly is completed by placing the needle head  126  which is held in a needle guard  112  (in identical manner to syringe  1 ) into the open end of the needle assembly  109  and twisting the needle head  126  onto the needle hub  113 , which completes the assembly process. Rotation of needle hub  113  is prevented by interlocking bars  156  within slots  148 , as depicted in  FIG. 31 . Operation of syringe  101  is substantially the same as for syringe  1 , with one exception in that needle hub  113  is fixed in passageway  123  and initial forward movement of the needle hub  113  during the needle retraction cycle is prevented.  
         [0092]     With reference to  FIGS. 33 through 39 , an alternative embodiment of a syringe  201  having a replaceable needle is shown. With reference to the figures,  FIG. 33  is an isolated sectional view of a needle assembly  209  of this invention showing locking slots  248  at the entrance of and recessed into the side wall of a passageway  223 , which extend part way through the passageway  223 .  FIG. 33A  is a cross sectional view of the needle assembly  209  along line  33 A- 33 A of  FIG. 33  showing a front view of the needle assembly  209 .  FIG. 34  of the drawings is an isolated view of a needle hub  213  showing locking bars  256  which extend radially out from the sidewall of the needle hub  213 .  FIG. 34A  is a cross sectional view of the is needle hub  213  along line  34 A- 34 A showing a front view further illustrating locking bars  256 .  FIG. 35  is an isolated sectional view illustrating a base  211 , wherein flexible supports have been eliminated and a taper  256  along the length of the base  211  is illustrated. Assembly of syringe  201  is accomplished in similar manner to syringe  1  and syringe  101 .  
         [0093]     Referring to  FIGS. 36, 37  and  38 , the needle hub  213  is first inserted into and matingly held in the base  211 . The base  211  and the needle hub  213  are next inserted into the front of body  205 , until the base  211  comes into contact with the barrel shelf  202 .  
         [0094]     Placing the base  211  into body  205  circumferentially compresses the base  211  onto hub  213 , prevents movement of the hub  213  in the base  211 , and insures that a liquid tight seal between the hub  213  and the base  211  and the base  211  and the body  205  is obtained. A spring  221  is placed over the needle hub  213 . The needle assembly  209  is next guided onto the needle hub  213  such that the outwardly extending locking bars  256  on the sides of the needle hub  213  (seen in  FIG. 34 ) are mating with and engaged into locking slots  248  in passageway  223  on the needle assembly  209  (as seen in  FIG. 33 ). The needle assembly  209  is next pushed into the open end of body  205 , which compresses spring  221 , until the top edge of the body  205  bottoms out on the needle assembly shelf  214 . The needle assembly  209  is then permanently fixed to body  205  by ultrasonic welding techniques at position  281  as shown in  FIG. 38 , or other suitable permanent fixing means. With reference to  FIG. 39  the needle assembly  209  positioned into the body  205 , a hub block  225  just contacts the bottom of locking slots  248  in the passageway  223  (as shown in  FIG. 33 ) thus restricting further movement of the needle hub  213  into the passageway. In the opposite direction hub  213  is restrained from movement by mating engagement with the base  211 , which is blocked by a barrel shelf  202 . The next step of the assembly process is accomplished by placing a boot  243  and a plunger seal  204  on the plunger  207 , and inserting the plunger  207  into body  205  as illustrated in  FIG. 39 . It is common manufacturing practice to lubricate the interior wall of the body  205 , usually with silicon, before insertion of plunger  207  into body  205 . Assembly is completed by placing needle head  226  and needle  203  which is held in a needle guard  212  (in identical manner to syringe  1 ) into the open end of the needle assembly  209  and twisting needle head  226  onto the needle hub  213 , which completes the assembly process. Rotation of the needle hub  213  is prevented by interlocking bars  256  and slots  248 , as depicted in  FIGS. 33 and 34 . Operation of syringe  201  is substantially the same as for syringe  1 , with two exceptions. First, needle hub  213  is fixed into passageway  223  and initial forward movement of needle hub  213  during the needle retraction cycle is prevented, and secondly, as base  211  moves forward during the retraction cycle, mating tapers between the two parts spread, providing space at the body for the base to more easily deform around needle hub  213 .  
         [0095]     With reference to  FIGS. 40 through 48 , components of syringe  301  that are different from syringe  1  taught herein is a replaceable nose and needle cooperating with a body  305 .  
         [0096]     With reference to the figures,  FIG. 40  is an isolated sectional view of a needle assembly  309  of this embodiment of the invention showing the base retainer slots  362 , positioned at various points on the exterior sidewall of the needle assembly  309 , and threads  360 , also positioned on the exterior sidewall of the needle assembly  309 .  FIG. 40A  is a cross sectional view of the needle assembly  309  along line  40 A- 40 A of  FIG. 40  showing a front view of the needle assembly  309 .  FIG. 41  of the drawings is an isolated view of a needle head  326  showing diametrically larger areas  315  and  317  than top  310 , and a spring contact  325 , as described for syringe  1 .  FIG. 42  is an isolated sectional view of a base  311  illustrating the mating cavity for needle head  326  and flexible supports  331 , with support flange  332 . Also, illustrated are the base retainer catches  364  positioned on the back side of support flange  332 .  FIG. 42A  is a cross sectional view of the base  311  along line  42 A- 42 A showing an end view of the base  311 .  FIG. 43  is an isolated view of needle  303 , while  FIG. 44  is an illustration of spring  321 .  FIG. 45  is a partial isolated sectional view of body  305  showing a taper  314  and mating threads  364 . Assembly of syringe  301  is accomplished in similar manner to syringe  1 .  
         [0097]     Referring to  FIGS. 46, 47   47 A, and  48 , the needle head  326 , with the needle  303  mounted therein, is first inserted into the base mating cavity and held therein by the base  311  as indicated in  FIG. 46 . The spring  321  is placed over needle  303 , until contact with a spring contact  325  is made. The sub-assembly consisting of a base  311 , spring  321 , and needle head  326  is next inserted into the back of the needle assembly  309 , by guiding the needle  303  into and through a passageway  323  of the needle assembly  309  as shown in  FIG. 47 . The needle assembly  309  is next rotated relative to the base  311  to match the base retainer slots  362  on the needle assembly  309  with retainer catches  364  on the base  311  (as shown in  FIGS. 47 and 47 A). When the two parts are in alignment, the base  311  is forced into the needle assembly  309 , partially compressing spring  321  and placing a shaft  316  of needle head  326  into passageway  323 . Insertion of the subassembly into the needle assembly  309  is continued until base retainer catches  364  are latched into the base retainer slots  362 , as illustrated in  FIG. 47A . Once base retainer catches  364  are positioned into slots  362 , position of base  311 , and therefore needle head  326 , is restrained in both directions. In the one direction movement is restrained by the base catch, while movement of the base  311  and the needle head  326  in the opposite direction is restrained by the flange  332  against the opposite side of the base retainer slot  362  and the force of the spring  321  on the needle head  326  at a spring contact  325 . Placing the base  311  into the needle assembly  309  also circumferentially compresses the base  311  between the needle head  326  and the body  305  which insures that a liquid tight seal between needle head  326  and the base  311 , and the base  311  and the body  305  is established. The needle guard  312  is next placed on the sub-assembly, and the resulting completed assembly illustrated in  FIG. 47  represents the replaceable needle embodiment of syringe  301 . The replaceable needle  303  can then be attached to, or removed from, the body  305  by inserting the base  311  end of the assembly into the open end of the body  305  and threading the assembly into position with the needle guard  312 , until top  366  of body  305  (as shown in  FIG. 45 ) mates with flat area  368  on the needle assembly  309  (shown in  FIG. 40 ). In this position, a taper  314  on body  305  substantially mates with a taper  358  on the needle assembly  309  as shown in  FIG. 48  to form a liquid tight seal between the two parts. To remove the needle assembly from the body  305 , the process described above is reversed. Operation of syringe  301  is substantially the same as for syringe  1 .  
         [0098]     With reference to  FIGS. 49 through 56 A, an alternative embodiment syringe  401  having a replaceable nose and needle cooperating with a body  405  is shown. With reference to the figures,  FIG. 54  is an isolated sectional view of a needle assembly  409  of this embodiment of the invention showing base retainer slots  462 , positioned at various points on the exterior sidewall of the needle assembly  409 , and threads  460 , also positioned on the exterior sidewall of the needle assembly  409 .  FIG. 49A  is a cross sectional view of the needle assembly  409  along line  49 A- 49 A of  FIG. 49  showing a front view of the needle assembly  409 .  FIG. 50  of the drawings is an isolated view of a needle head  426  showing diametrically larger areas  415  and  417  than top  410 , and a spring contact  425 , as described for syringe  1 .  FIG. 51  is an isolated sectional view of base  411  illustrating the mating cavity for the needle head  426  and flexible supports  431 , with a support flange  432 . Also, illustrated are base retainer catches  464  positioned on the back side of the support flange  432 . At the front of base  411  is molded a sacrificial seal  470  used to seal the needle assembly  409  with body  405 .  FIG. 51A  is a cross sectional view of the base  411  along line  51 A- 51 A showing an end view of the base  411 , further illustrating a seal  470 .  FIG. 52  is an isolated view of the needle  403 .  FIG. 53  is a partial isolated sectional view of body  405  showing receiving surface  414  for the needle assembly  409 , mating threads  464 , and shelf  402 . Assembly of the syringe  401  is accomplished in similar manner to syringe  1  and syringe  301 . Referring to  FIGS. 54, 55 ,  55 A,  56 , and  56 A, the needle head  426 , with the needle  403  mounted therein, is first inserted into the base  411  mating cavity and held therein by the base  411  as indicated in  FIG. 54 . The spring  421  is placed over the needle hub  426 , until contact with a spring contact  425  is made. The sub-assembly consisting of base  411 , spring  421 , and needle head  426  in  FIG. 54  is next inserted into the back of the needle assembly  409  as shown in  FIG. 55 , by guiding needle  403  into and through passageway  423  of the needle assembly  409 . The needle assembly  409  is next rotated relative to base  411  to match base retainer slots  462  on the needle assembly with retainer catches  464  on the base. When the two parts are in alignment, base  411  is forced into the needle assembly  409 , substantially compressing the spring  421  and placing shaft  416  of the needle head  426  into the passageway  423 .  
         [0099]     Insertion of the subassembly into the needle assembly  409  is continued until base retainer catches  464  are latched into the base retainer slots  462 , as illustrated in  FIG. 55   a . With the base  411  locked into the needle assembly  409 , a sacrificial seal  470  is positioned at the back edge of the needle assembly  409 . Once the base retainer catches  464  are positioned into slots  462 , position of the base  411 , and therefore the needle head  426 , is restrained in both directions. In the one direction movement is restrained by the base catch  464 , while movement of the base  411  and the needle head  426  in the opposite direction is restrained by the flange  432  against the opposite side of the base retainer slot  462  and the force of spring  421  acting on the needle head at the spring contact  425 .  
         [0100]     Placing the base  411  into the needle assembly  409  also circumferentially compresses the base between needle head  426  and body  405  which insures that a liquid tight seal between needle head  426  and the base  411 , and the base  411  and the body  405  is established. The needle guard  412  is next placed on the sub-assembly, and the resulting completed assembly illustrated in  FIG. 55  represents the replaceable needle embodiment of syringe  401 . The replaceable needle  403  can then be attached to, or removed from, the body  405  by inserting the base end of the assembly into the open end of the body  405  and threading the assembly into position with a guard  412 , until top  466  of body  405  (as shown in  FIG. 53 ) mates with flat area  468  on the needle assembly  409  as shown in  FIG. 49 . In this position, the sacrificial seal  470  is compressed between the body  405  at shelf  402  and needle assembly  409  as shown in  FIG. 56A  to form a liquid tight seal between the two parts. To remove the needle assembly  409  from the body  405 , the process described above is reversed. Operation of syringe  401  is substantially the same as for syringe  1 .  
         [0101]      FIGS. 57 and 58  show an elevational view of the syringe  1  before and after needle retraction wherein an indicia has been revealed. During the needle retraction cycle revelation and amplification of an indicia or label such as biohazard label  512 , as shown in  FIG. 58 . Before the needle retraction cycle, the base  4  is under biohazard label  512  as seen in  FIG. 57  where in the label is not readable. It is preferred that biohazard label  512  be printed in black, or any other appropriate color, and base  4  also be the same or substantially similar color so that biohazard label  512  is unnoticeable to the user. It is also preferred that the boot  72  be of a different, contrasting color. After the needle retraction cycle, the base  4  is no longer left under the biohazard label, and the boot  72  is under the label as shown is  FIG. 58 . Since the plunger boot  72  is any appropriate highly contrasting color relative to the base  4  and the biohazard label  512 , such as orange when the other two are black, the biohazard label  512  is significantly revealed and amplified and becomes very noticeable to the user or other people, as shown in  FIG. 58 .  
         [0102]     It is thus seen that this invention with the illustrative alternative embodiments provides a novel syringe apparatus which has a needle that interchangeable and is operable by a single hand and which upon completion of injection captures the utilized interchangeable needle and renders such harmless within the plunger of the syringe. Further, such used syringe is rendered liquid tight to prevent possible leakage of contaminated fluids and such used syringe is automatically marked as a biohazard. As various other advantages and features will become apparent to those of skill in the art from a reading of the foregoing description which is exemplary in nature, such modification and variations are embodied within the scope of this invention.