Abstract:
A passively guarded, fillable injection syringe includes an adapter for holding the proximal end of a hollow needle. An inverted plunger is slidingly mounted on the adapter to establish a medicament chamber that is in fluid communication with the needle. Also, a substantially cylindrical needle guard is positioned on the needle for reciprocal axial movement under the influence of a spring which biases the guard and adapter in opposite axial directions. A mechanism is provided such that plunger movements that are required in a typical fill and inject procedure also function to control the position of the guard relative to the needle. Initially, the guard is locked covering the needle tip. A plunger movement unlocks the guard and retracts the guard for syringe filling and injection. Depressing the plunger to complete the injection releases the guard for distal movement under the spring force into a needle protecting position.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains generally to syringes for medical use. More particularly, the present invention pertains to protective devices for injection syringes that are filled by the user prior to the administration of an injection. The present invention is particularly, but not exclusively, useful for passively covering and protecting the needle of an injection syringe after its use.  
       BACKGROUND OF THE INVENTION  
       [0002]     Recent research from the Centers for Disease Control and Prevention (CDC) shows that approximately 384,000 needle sticks or similar injuries occur among health care workers in U.S. hospitals each year. Unfortunately, each accidental needle stick has the potential to expose a health care worker to a life-threatening virus such as hepatitis or HIV. In addition to the needle sticks that occur in hospitals, accidental needle sticks can also occur in other health care settings. For example, needle stick injuries can occur at clinics or during home health care. In fact, some studies have estimated that over 600,000 needle sticks occur in the U.S. each year, and approximately 1,000 of these accidental needle sticks result in a life-threatening infection.  
         [0003]     For each accidental needle stick, health care providers are obligated to test and counsel the exposed worker. Further, follow-up testing for HIV must be conducted approximately six months after the exposure. It is to be appreciated that the costs associated with the testing, lab work, the worker&#39;s lost time, and the associated tracking and administrative costs, can be considerable.  
         [0004]     Accidental needle sticks can occur in several ways. For example, sudden movement by the patient can cause a health care worker to lose control of a syringe, resulting in injury. Attempts to manually recap a needle following an injection can also result in injury. Moreover, injuries often result when contaminated, unprotected needles are left unattended or disposed of improperly. In addition to accidental needle sticks, unnecessary exposure to bloodborne pathogens can result when a health care worker mistakenly reuses a contaminated needle on a patient.  
         [0005]     One particular type of syringe that is prone to needle stick injuries is the fillable injection syringe. In overview, these fillable injection syringes are designed to be filled with a medicament from a medicament vial by the same user that administers an injection. Heretofore, a typical procedure has involved removing a cap that covers the sharp needle tip of the fillable injection syringe. With the needle exposed, the needle tip is inserted into a vial containing medicament. This step generally occurs just prior to an injection. Next, the plunger is depressed to void the syringe chamber of air. With the syringe voided, the plunger is retracted to draw a specified quantity of medicament into the syringe chamber. Once the medicament has been loaded into the syringe, the needle is then inserted into a patient and the plunger is depressed to inject the medicament into the patient. After the injection, the needle is removed from the patient and often must be manually recapped to protect the contaminated needle. After recapping, it is often difficult to distinguish between used and unused syringes.  
         [0006]     In light of the above, it is an object of the present invention to provide a fillable medical syringe that passively covers and protects the needle of the syringe after first filling the syringe with medicament and then injecting the medicament into a patient. It is another object of the present invention to provide a fillable syringe which guards the needle prior to an injection procedure and uses the same guard to passively guard the needle after an injection procedure. It is still another object of the present invention to provide a passively guarded, fillable injection syringe in which the position of the needle guard is controlled and regulated by plunger movements that are required in a typical fill and inject procedure.  
         [0007]     It is yet another object of the present invention to provide a fillable injection syringe having an integral mechanism that prevents reuse of the syringe (after use and contamination) by disabling the plunger at the completion of an injection procedure. Yet another object of the present invention is to provide a protective device for a medical syringe that is easy to use, relatively simple to implement, and comparatively cost effective.  
       SUMMARY OF THE INVENTION  
       [0008]     A passively guarded, fillable injection syringe includes an elongated hollow needle that defines an axis and has a sharp, distal needle tip. The syringe also includes an adapter for holding the proximal end of the needle. With this cooperation of structure, the needle extends in a distal direction from the adapter. In addition, an inverted plunger is slidingly mounted on the adapter to establish a medicament chamber that is in fluid communication with the needle. For the present invention, a substantially cylindrical needle guard is positioned on the needle for reciprocal axial movement relative to the needle. Also, a spring is positioned between the guard and the adapter to bias the guard along the axis in a distal direction away from the adapter.  
         [0009]     As described in greater detail below, a mechanism is provided to selectively engage and disengage the plunger and guard during the course of an injection procedure. More specifically, the plunger movements that are required to fill the syringe and dispense a medicament from the syringe also function to control the position of the guard relative to the needle. In functional overview, prior to an injection procedure, the guard is locked in a distal position covering the tip of the needle and can only be unlocked by a movement of the plunger. Once unlocked, the guard can be retracted to expose the needle tip. This allows the needle tip to be inserted into a medicament vial to fill the syringe, and in addition, allows the exposed needle to be inserted into a patient for an injection. When the plunger is withdrawn proximally relative to the adapter, the plunger and guard engage and the guard moves proximally to expose the needle. On the other hand, when the plunger is depressed (i.e. moved distally), the plunger releases the guard. Once released, the guard is free to move distally under the influence of the spring. As a consequence of this interaction, after the plunger is depressed to complete an injection, the guard is released and allowed to translate distally, relative to the needle, to cover and protect the needle tip.  
         [0010]     In greater structural detail, the adapter includes a substantially cylindrical portion that is centered on the needle axis and has a proximal end and an open distal end. In addition, a standoff is formed at the proximal end of the adapter to attach the proximal end of the needle to the adapter. From the standoff, the needle passes distally through the cylindrical adapter and extends beyond the adapter&#39;s distal end to a distal needle tip. Also, the adapter is sized to allow the cylindrical guard to move axially along the needle and within the cylindrical portion of the adapter.  
         [0011]     In a typical embodiment of the present invention, the syringe includes an inverted plunger that has a substantially cylindrical portion which extends from a closed proximal end to an open distal end. Structurally, the cylindrical portion surrounds a medicament chamber and is slidingly mounted on the proximal end of the adapter. A seal is interposed between the proximal end of the adapter and the cylindrical portion of the plunger to establish fluid communication between the medicament chamber and the lumen of the needle. With this arrangement, the plunger can be retracted to draw fluid through the needle and into the chamber and the plunger can be depressed to expel fluid from the chamber and out of the needle&#39;s distal tip.  
         [0012]     As indicated above, a mechanism is provided to selectively engage and disengage the plunger and guard during the course of an injection procedure. Structurally, this mechanism includes a tang that is formed on the cylindrical portion of the plunger and an axially aligned slot that is formed in the guard. Specifically, the tang extends distally and inwardly toward the needle axis from the cylindrical portion of the plunger. An axially aligned slit formed in the adapter allows the tang to pass through the adapter and interact with the slot in the guard. In greater structural detail, the guard slot has a proximal end that is formed as an abutment and a distal end that is formed as a ramp. With this arrangement, the tang engages the abutment during a proximal movement of the plunger to engage the plunger with the guard. On the other hand, during a distal movement of the plunger, the ramp directs the tang out of the slot and disengages the guard and plunger.  
         [0013]     In another aspect of the invention, the syringe includes a mechanism to lock the guard in a distal position covering the tip of the needle prior to an injection procedure. Specifically, once locked by the mechanism, the guard can only be unlocked by a movement of the plunger. For this purpose, the cylindrical adapter is formed with a cam lever having a distal lever end and a cam surface. For the syringe, the cam lever is deflectable by the cylindrical portion of the plunger from a relaxed position to a biased position. In the relaxed position, the cam surface extends radially outward from the remaining cylindrical section of the adapter. On the other hand, in the biased position, the lever end extends radially inward from the remaining cylindrical section of the adapter. When the plunger is in a distal position, the cylindrical portion of the plunger contacts the cam surface and deflects the cam lever into the biased position. Functionally when the cam lever is in the biased position, the lever end engages the guard and prevents a proximal movement of the guard. When the plunger is retracted, the cam lever relaxes and unlocks the guard.  
         [0014]     In one particular embodiment of the invention, the syringe includes a substantially cylindrical shaped syringe body that is formed with open distal and proximal ends. A flange is formed at the distal end of the syringe body and extends radially inward relative to the cylindrical portion of the syringe body. At the proximal end, the syringe body is formed with a finger grip that extends radially outward form the cylindrical portion. For the syringe, the body is slidingly mounted on the adapter. Specifically, the syringe body is capable of an axial movement relative to the adapter from an operational position to a locking position. In the operational position, the syringe body does not interfere with relative movement between the guard and adapter. In the locking position, however, the flange at the distal end of the syringe body deflects the cam lever and holds the cam lever in the biased position (i.e. the position where the guard is locked). After an injection, the syringe body can be moved proximally relative to both the plunger and adapter and into the locking position. This then locks the guard into a needle tip covering position and prevents inadvertent reuse of the syringe.  
         [0015]     Another safety feature that can be incorporated into the syringe includes a recess that is formed in the syringe body at the body&#39;s proximal end. Specifically, this recess is sized and positioned to receive a grip flange that is formed at the proximal end of the plunger. After an injection, the plunger can be advanced until the grip flange is positioned in the recess. With the grip flange positioned in the recess, subsequent movement of the plunger relative to the syringe body is effectively prevented.  
         [0016]     In operation, the plunger is initially located in a distal position relative to the adapter with the tang extending into the slot. In this configuration, the cylindrical portion of the plunger holds the cam lever deflected inward into the biased position in which the guard is locked. Next, the plunger is withdrawn proximally. The effect of this proximal movement is threefold. First, initial proximal movement of the plunger allows the cam lever to relax and unlock the guard. Second, additional proximal movement engages the tang of the plunger with the proximal abutment in the slot, causing the guard to move proximally with the plunger. Third, proximal movement of the plunger draws air through the needle and into the medicament chamber.  
         [0017]     With the guard retracted, the next step is to insert the exposed distal tip of the needle into a medicament vial. At this point, the plunger can be depressed to expel air into the vial and void the medicament chamber. During plunger advancement, the ramp formed at the distal end of the slot directs the tang out of the slot and disengages the guard from the plunger. Thus, distal guard movement is only prevented by the contact between the guard and the vial at this point. Next, the plunger can be withdrawn to fill the chamber with medicament. During this plunger withdrawal, the tang reenters the slot and engages the proximal abutment. The result is that the plunger engages the guard and prevents distal advancement of the guard relative to the needle. Thus, when the needle is removed from the vial, the distal tip of the needle remains unguarded and exposed. The syringe is now ready for an injection.  
         [0018]     To inject a medicament into a patient, the distal tip of the needle is inserted into the patient and the plunger depressed. This distal advancement of the plunger releases the guard. Specifically, during plunger advancement, the ramp formed at the distal end of the slot directs the tang out of the slot and disengages the guard from the plunger. Once released, the guard is free to move distally under the influence of the spring. Thus, as the needle is withdrawn from the patient, the needle retracts proximally into the guard which remains in contact with the patient&#39;s skin. Once the syringe has been removed from the patient, the plunger and adapter can be advanced distally relative to the syringe body to lock the guard in place. This also places the grip flange of the plunger in the recess formed in the syringe body. Functionally, in this last configuration, the guard completely covers the hollow needle to protect the user from unwanted needle sticks and prevents inadvertent reuse of the syringe. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0020]      FIG. 1  is a perspective view of a passively guarded, fillable injection syringe, shown in its initial configuration;  
         [0021]      FIG. 2A  is a sectional view of the syringe as seen along line  2 - 2  in  FIG. 1 , shown in its initial configuration in which the guard is locked over the needle&#39;s distal tip;  
         [0022]      FIG. 2B  is a sectional view of the syringe as in  FIG. 2A , shown after a plunger movement has unlocked and distally retracted the guard;  
         [0023]      FIG. 2C  is a sectional view of the syringe as in  FIG. 2A , shown after the needle&#39;s distal tip has been inserted into an object (i.e. medicament vial or patient) and thereafter the plunger has been advanced proximally;  
         [0024]      FIG. 2D  is a sectional view of the syringe as in  FIG. 2A , shown after the needle has been withdrawn from a patient after an injection;  
         [0025]      FIG. 2E  is a sectional view of the syringe as in  FIG. 2A , shown after the plunger and adapter have been advanced distally relative to the syringe body to lock the guard in position and prevent inadvertent reuse of the syringe;  
         [0026]      FIG. 3A  is a top, front perspective view of an adapter for use in the syringe shown in  FIG. 1 ;  
         [0027]      FIG. 3B  is a bottom, rear perspective view of the adapter shown in  FIG. 3A ;  
         [0028]      FIG. 4  is a perspective view of a plunger for use in the syringe shown in  FIG. 1 ;  FIG. 5  is a perspective view of a seal for use in the syringe shown in  FIG. 1 ;  
         [0029]      FIG. 6A  is a top, front, perspective view of a guard for use in the syringe shown in  FIG. 1 ;  
         [0030]      FIG. 6B  is a bottom, rear perspective view of the guard shown in  FIG. 6A ; and  
         [0031]      FIG. 7  is a perspective view of a syringe body for use in the syringe shown in  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     Referring initially to  FIG. 1 , a passively guarded, fillable injection syringe is shown and generally designated  10 . As shown in  FIG. 1 , the syringe  10  includes a substantially cylindrical syringe body  12  that is centered on a needle axis  14  and formed with a finger grip  16  at its proximal end.  FIG. 1  further shows that the syringe  10  includes an adapter  18  that is sized to fit within the syringe body  12  and includes a cylindrical portion that is also centered on the needle axis  14 . For the syringe  10 , a substantially cylindrical needle guard  20  is provided that is positioned co-axially with both the syringe body  12  and adapter  18 , and is sized to fit within the adapter  18 . For the embodiment shown, the guard  20  is formed with a slight taper characterized by a decreasing outside diameter in a distal direction. It can be further seen that the syringe  10  includes a plunger  22  that is formed with a grip flange  24  at its proximal end.  
         [0033]     As best seen in  FIG. 2A , the passively guarded, fillable injection syringe  10  includes a straight, elongated hollow needle  26  that has a sharp, distal needle tip  28 .  FIG. 2A  also shows that the adapter  18  includes a substantially cylindrical portion that is centered on the needle axis  14  and has a proximal end  30  and an open distal end  32 . A standoff  34  is formed at the proximal end  30  of the adapter  18  to attach the proximal end of the needle  26  to the adapter  18 . As shown in  FIG. 2A , from the standoff  34 , the needle  26  passes distally through the cylindrical adapter  18  and extends beyond the adapter&#39;s open distal end  32  to the distal needle tip  28 . As best seen in  FIG. 2A , the adapter  18  is sized to allow the cylindrical guard  20  to move axially along the needle  26  and within the cylindrical portion of the adapter  18 .  
         [0034]     Cross-referencing  FIGS. 2A and 4 , it can be seen that the inverted plunger  22  has a substantially cylindrical portion  36  which extends from a closed proximal end  38  to an open distal end  40 . Structurally, the cylindrical portion  36  surrounds a medicament chamber  42  and is slidingly mounted on the proximal end  30  of the adapter  18 .  FIGS. 2A and 4  further show that the plunger  22  is formed with a tang  44  that extends distally and inwardly (i.e. toward the needle axis  14 ) from the cylindrical portion  36  of the plunger  22 .  
         [0035]     Cross-referencing  FIGS. 2A and 5 , it can be seen that the syringe  10  includes an elastomeric seal  46  that is attached onto the proximal end  30  (best seen in  FIG. 2A ) of the adapter  18 . As shown, the seal  46  has a generally fusiform shape or spindle-like shape and is formed with a through-hole  48 . When the open distal end  40  of the plunger  22  is slid over the proximal end  30  of the adapter  18 , the seal  46  compresses between the adapter  18  and the cylindrical portion  36  of the plunger  22  to establish sealed fluid communication between the medicament chamber  42  and the lumen of the needle  26 . With this arrangement, the plunger  22  can be retracted to draw fluid through the needle  26  and into the chamber  42  and, in addition, the plunger  22  can be depressed to expel fluid from the chamber  42  and out of the needle&#39;s distal tip  28 .  
         [0036]     The structure of the guard  20  can be best appreciated with initial reference to  FIGS. 2A and 6A . As shown there, the guard  20  extends from an open proximal end  50  to an open distal end  52  and is formed with an axially aligned slot  54  for interaction with the tang  44 . Specifically, as shown in  FIGS. 2A and 3A , an axially aligned slit  56  formed in the adapter  18  allows the tang  44  to pass through the adapter  18  and interact with the slot  54  in the guard  20 . As best seen with cross-reference to  FIGS. 2A and 6A , the guard slot  54  has a proximal end that is formed as an abutment  58  and a distal end that is formed as a ramp  60 . With this arrangement, the tang  44  engages the abutment  58  during a proximal movement of the plunger  22  to engage the plunger  22  with the guard  20 . On the other hand, during a distal movement of the plunger  22 , the ramp  60  directs the tang  44  out of the slot  54  and disengages the guard  20  and plunger  22 . As seen in  FIGS. 2A and 6B , the guard  20  is also formed with a living hinge  62  that extends radially outward when in a relaxed, undeflected state.  FIG. 6A  further shows that the guard  20  is formed with two alignment guides  64   a,b  which each extend radially outward from the cylindrical portion of the guard  20 . These alignment guides  64   a,b  travel within a pair of corresponding slots  66  (see  FIG. 3A ) in the adapter  18  and maintain the guide  20  azimuthally aligned within the adapter  18 .  
         [0037]     By cross-referencing  FIG. 2A  with  FIG. 3B , it can be seen that the syringe  10  includes a mechanism to lock the guard  20  in a distal position covering the needle tip  28  prior to an injection procedure. Specifically, once locked by the mechanism, the guard  20  can only be unlocked by a movement of the plunger  22 . Specifically, as shown, the cylindrical adapter  18  is formed with a cam lever  68  having a distal lever end  70  and a cam surface  72 . Comparing  FIG. 2A  with  FIG. 2B , it can be seen that the cam lever  68  is deflectable by the cylindrical portion  36  of the plunger  22  from a relaxed position ( FIG. 2B ) to a biased position ( FIG. 2A ). In the relaxed position ( FIG. 2B ), the cam surface  72  extends radially outward from the remaining cylindrical section of the adapter  18 . On the other hand, as shown in  FIG. 2A , in the biased (i.e. deflected) position, the lever end  70  extends radially inward from the remaining cylindrical section of the adapter  18 . When the plunger  22  is in the distal position shown in  FIG. 2A , the cylindrical portion  36  of the plunger  22  contacts the cam surface  72  and deflects the cam lever  68  into the biased position. Functionally, as shown in  FIG. 2A , when the cam lever  68  is in the biased position, the lever end  70  engages the hinge  62  of the guard  20  and prevents a proximal movement of the guard  20  relative to the needle  26 . When the plunger  22  is retracted as shown in  FIG. 2B , the cam lever  68  relaxes into its undeflected, outward position (as shown in  FIG. 3B ) and allows the guard  20  to move distally relative to the needle  26 .  
         [0038]      FIG. 2A -shows that the distal end of the cylindrical syringe body  12  is formed with a flange  74  that extends radially inward relative to the cylindrical portion of the syringe body  12 . In addition, as shown in  FIG. 2A , the adapter  18  is formed with a raised distal tab  76  and a raised proximal tab  78  that is formed with a ramp. As shown, the proximal tab  78  is axially spaced from the distal tab  76  to create a gap between the tabs  76 ,  78 . Typically, as shown in  FIGS. 3A and 3B , four sets of tabs  76 ,  78  are uniformly distributed about the circumference of the adapter  18 . Functionally, the tabs  76 ,  78  releasably hold the flange  74  of the syringe body  12  in the gap when the syringe body  12  is in an operational position and releases the flange  74  for proximal movement relative to the adapter  18  into a locking position. In the operational position, as shown in  FIG. 2A , the syringe body  12  does not interfere with relative movement between the guard  20  and adapter  18 . In the locking position, as shown in  FIG. 2E , the flange  74  deflects the cam lever  68  and holds the cam lever  68  in a position where the guard  20  is locked. After an injection, the syringe body  12  can be moved proximally relative to both the plunger  22  and the adapter  18  and into the locking position shown in  FIG. 2E . This then locks the guard  20  into position covering the needle tip  28  and prevents inadvertent reuse of the syringe  10 .  
         [0039]     Cross referencing  FIG. 2E  with  FIG. 7 , it can be seen that the finger grip  16  of the syringe body  12  is formed with a recess  80  at the body&#39;s proximal end. Specifically, as best seen in  FIG. 2E , the recess  80  is sized and positioned to receive the grip flange  24  that is formed at the proximal end  38  of the plunger  22 . Functionally, the plunger  22  can be advanced distally after an injection until the grip flange  24  is positioned in the recess  80 . With the grip flange  24  positioned in the recess  80 , subsequent movement of the plunger  22  relative to the syringe body  12  is effectively prevented.  
       Operation  
       [0040]     The syringe  10  is typically delivered to the end user configured as shown in  FIG. 2A . Specifically, as  FIG. 2A  shows, the plunger  22  is initially located in a distal position relative to the adapter  18  with the tang  44  extending into the slot  54  to prevent distal movement of the guard  20 . In this configuration, it can be seen that the cylindrical portion  36  of the plunger  22  holds the cam lever  68  deflected inward to lock the guard  20  and prevent proximal movement of the guard  20 . As illustrated by  FIG. 2B , use of the syringe  10  begins by withdrawing the plunger  22  proximally.  FIG. 2B  shows this proximal movement of the plunger  22  has several effects. For one, initial proximal movement of the plunger  22  allows the cam lever  68  to relax outwardly from the needle  26  and unlock the guard  20  for proximal movement relative to the needle  26 . Additional proximal movement of the plunger  22  engages the tang  44  with the proximal abutment  58 , causing the guard  20  to move proximally with the plunger  22 . Also, proximal movement of the plunger  22  draws air through the needle  26  and into the medicament chamber  42 .  
         [0041]     Once the guard  20  has been retracted as shown in  FIG. 2B , the next step is to insert the exposed distal needle tip  28  into a medicament vial (illustrated by surface  82  in  FIG. 2C ). At this point, the plunger  22  can be depressed as shown in  FIG. 2C  to expel air into the vial and void the medicament chamber  42 . Comparing  FIG. 2B  with  FIG. 2C , it can be seen that during advancement of the plunger  22 , the ramp  60  formed at the distal end of the slot  54  directs the tang  44  out of the slot  54  and disengages the guard  20  from the plunger  22 . Thus, as illustrated by  FIG. 2C , after depressing the plunger  22 , distal movement of the guard  20  is only prevented by the contact between the guard  20  and the surface  82 . Next, the plunger  22  can be withdrawn to fill the chamber  42  with medicament (note  FIG. 2B  is representative of the configuration of the syringe  10  after the chamber  42  is filled with medicament). From  FIG. 2B , it can be seen that during withdrawal of the plunger  22 , the tang  44  reenters the slot  54  and engages the proximal abutment  58 . The result is that the plunger  22  engages the guard  20  and prevents distal advancement of the guard  20  relative to the needle  26 . As illustrated by  FIG. 2B , when the needle  26  is removed from the vial, the distal tip  28  of the needle  26  remains unguarded and exposed. The syringe  10  is now ready for an injection.  
         [0042]     As illustrated by  FIG. 2C , to inject a medicament into a patient, the distal tip  28  of the needle  26  is inserted into the patient (represented by surface  82 ) and the plunger  22  depressed. As shown in  FIG. 2C , the distal advancement of the plunger  22  releases the guard  20 . Specifically, during advancement of the plunger  22 , the ramp  60  directs the tang  44  out of the slot  54  and disengages the guard  20  from the plunger  22 . Once released, the guard  20  is free to move distally under the influence of a coil spring  84  that is interposed between the guard  20  and adapter  18 . Thus, as the needle  26  is withdrawn from the patient, the needle  26  retracts proximally into the guard  20  which remains in contact with the patient&#39;s skin (represented by surface  82 ).  FIG. 2D  shows the syringe  10  after the needle  26  has been withdrawn from the patient and the needle  26  has passively retracted into the guard  20 . Comparing  FIG. 2C  with  FIG. 2D , it can be seen that the hinge  62  deflects to advance distally past the cam lever  68 .  
         [0043]     Comparing  FIG. 2D  with  FIG. 2E , it can be seen that once the syringe  10  has been removed from the patient ( FIG. 2D ), the plunger  22  and adapter  18  can be advanced distally relative to the syringe body  12  to lock the guard  20  in place ( FIG. 2E ).  FIG. 2E  also shows that this places the grip flange  24  of the plunger  22  in the recess  80  formed in the syringe body  12 . Functionally, once the syringe  10  is in the configuration shown in  FIG. 2E , the plunger  22  is disabled and the guard  20  completely covers the hollow needle  26  to protect the user from unwanted needle sticks and prevents inadvertent reuse of the syringe  10 .  
         [0044]     While the particular devices and methods as herein shown and disclosed in detail are fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.