Abstract:
An injection device including a barrel, a hollow plunger having a portion structured and arranged to move within the barrel, a needle unit, and a safety system that one of automatically causes the needle unit to retract into the plunger when the plunger reaches a substantially fully depressed position and utilizes a frangible or breakable seal arranged within the plunger. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The instant application is a US non-provisional application based on U.S. provisional application No. 61/167,741, filed Apr. 8, 2009, the disclosure of which is hereby expressly incorporated by reference hereto in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to syringes, e.g., hypodermic syringes, such are utilized for injection of medicament into the body tissues of human and animal patients. More specifically, this invention relates to a hypodermic syringe having a plunger, piston and needle support structure or needle unit that permits retraction of the needle support and its needle into the plunger of the syringe to prevent the possibility of inadvertent needle pricks and which incorporates a frangible plunger seal that may be broken away to prevent subsequent use or re-use of the syringe. 
     This invention also relates to single-use syringes which automatically retracts the needle into the syringe when the plunger is substantially fully depressed which is more easily and/or less costly to produce. 
     This invention also relates to syringes which can be used only once, i.e., single-use syringes, and/or to syringes which utilize a built-in safety system which cannot be easily overridden by a user thereof. 
     2. Discussion of Background Information 
     In hospitals, nursing home facilities and the like, injection of medicament into the body tissues of patients is done on a daily basis. Typical hypodermic syringes are provided with a barrel having a needle that is fixed or removably attached at one end thereof. A plunger typically having an elastomeric piston is movable within the barrel to load the barrel with liquid medicament by suction as the plunger and piston are moved within the barrel in a direction away from the needle. After the needle has penetrated the body tissues of the patient, as the direction of movement of the plunger and piston are reversed and the piston is forced toward the needle, medicament contained within the barrel will be injected through the needle into the body tissues. 
     After hypodermic syringes have been used in this manner, those syringes that are disposable present a significant problem to users, e.g., hospital or nursing home staff, because the possibility of inadvertent needle pricks subject personnel to the possibility of cross-contamination by, among other things, virile or bacterial contaminants that might be present on the needle after its use. In an effort to avoid the possibility of inadvertent needle pricks special waste containers are often provided at hospital facilities into which the used disposable hypodermic syringes are placed. These containers and the syringes contained therein are then disposed of in a specifically organized manner to insure against the possibility of inadvertent infectious contamination of nursing personnel. Further, refuse handlers and other persons who might inadvertently come into contact with the used hypodermic syringes are also subject to the same hazards. Often times the needles themselves are bent over so as to minimize the possibility of inadvertent needle pricks and to preclude the possibility of subsequent use of disposable hypodermic syringes. 
     In certain situations, medicaments are injected into patients and not quickly thereafter discarded properly. Instead, the used syringe is placed in a temporary position. After the procedure has ended, the syringe can be manually recovered for disposal. However, between the time of use and the time of disposal, there is the possibility that inadvertent needle pricks will occur. Accordingly, it is desirable to provide a suitable way protecting personnel, e.g., nursing personnel, paramedics and other persons, from the hazards of inadvertent needle pricks as they go about their daily tasks. 
     It is therefore desirable to provide a syringe that includes a system for rendering the needle thereof to a protected, completely encapsulated condition such that it is less likely to cause, after use, an inadvertent needle prick during its handling or during its disposal. It is also desirable to provide a syringe having the capability of causing the automatic retraction of the needle to a position inside the plunger of the syringe and maintaining the needle in its retracted position so that the needle of the syringe is always enclosed after its use, thus precluding the possibility that the needle might cause an accidental needle prick as the syringe is subsequently handled. It is also desirable to provide a syringe of the disposable type that is provided with facility for rendering it completely inoperative such that it can not be subsequently used. Additionally, it is desirable to provide for a syringe which also has minimal dead-space so that it can be ideally used for injecting very expensive medicaments with minimal waste. Finally, it is desirable to provide for a syringe which also has a system for selectively locking the plunger in a substantially fully depressed position so that the syringe can have dual, multiple, and/or parallel safety systems, i.e., one system can include causing the needle unit to retract into the plunger and another system can include locking the plunger in a substantially fully depressed position. 
     SUMMARY OF THE INVENTION 
     According to one non-limiting aspect of the invention there is provided an injection device comprising a barrel, a hollow plunger having a portion structured and arranged to move within the barrel, a needle unit, and a safety system that one of automatically causes the needle unit to retract into the plunger when the plunger reaches a substantially fully depressed position and utilizes a frangible or breakable seal arranged within the plunger. 
     The injection device may be a single-use syringe. The barrel may comprise a cylindrically shaped internal space structured and arranged to receive therein a medicine. The barrel may further comprise a proximal opening within which the needle unit is at least one of press fit and in sealing engagement therewith. The plunger may comprise a piston arranged at a proximal area of the plunger and an actuating end arranged in front of the piston. The plunger may further comprise at least one of the piston being an elastomer or rubber piston, a hollow space sized and configured to receive therein the needle unit in its entirety, and a locking member adapted to lock with a locking member arranged on the barrel. The barrel, the plunger, and a hub portion of the needle unit may each comprise a synthetic resin material. The needle unit may comprise a generally cylindrical hub and a hollow needle projecting from the hub. The needle may comprise at least one of metal and stainless steel. The barrel may comprise at least one releasable retaining member which releasably retains the needle unit in an initial position. The barrel may comprise plural releasable retaining members which each releasably retain the needle unit in an initial position. The barrel may comprise at least one deflectable retaining member which releasably retains the needle unit in an initial position. The barrel may comprise plural deflectable retaining members which each releasably retain the needle unit in an initial position. 
     The device may further comprise a locking arrangement that is structured and arranged to lock a distal end portion of the plunger to the barrel. The device may further comprise a locking arrangement selectively locking a portion of the plunger to the barrel upon the plunger reaching a substantially fully depressed position. The device may further comprise a biasing member, wherein, when the plunger is moved to a full injection position, the needle unit is automatically caused to retract into the plunger via the spring. The device may further comprise a spring arranged within the barrel, wherein, when the plunger is moved to a full injection position, the needle unit is automatically caused to retract into the plunger via the spring. The device may further comprise a system providing an indication to the user that further forward movement of the plunger will cause the needle unit to automatically retract into the plunger. The device may further comprise a system providing an indication to the user that at least one of the plunger has reached a full injection position and the further forward movement of the plunger will cause the needle unit to automatically retract into the plunger. 
     According to one non-limiting aspect of the invention there is provided a syringe comprising a barrel, a plunger having a portion structured and arranged to move within the barrel, a needle unit, and a safety system that one of automatically causes the needle unit to retract into the plunger when the plunger reaches a substantially fully depressed position and utilizes a frangible or breakable seal arranged within the plunger. 
     The syringe may further comprise a system providing an indication to the user that the plunger has reached a full injection position and the further forward movement of the plunger will cause the needle unit to automatically retract into the plunger. 
     According to one non-limiting aspect of the invention there is provided a single-use syringe comprising a barrel, a hollow plunger having a portion structured and arranged to move within the barrel, a needle unit, and a safety system that one of automatically causes the needle unit to retract into the plunger when the plunger reaches a substantially fully depressed position and utilizes a frangible or breakable seal arranged within the plunger. 
     The syringe may further comprise a system providing an indication to the user that the plunger has reached a full injection position and the further forward movement of the plunger will cause the needle unit to automatically retract into the plunger. 
     According to one non-limiting aspect of the invention there is provided a method of using the injection device described above, wherein the method comprises moving the plunger away from the needle unit so as to cause a desired amount of medicine to enter into the barrel and moving the plunger towards the needle unit so as to cause medicine to exit the barrel through the needle. The method may further comprise locking the plunger to the barrel to prevent re-use of the syringe. 
     Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
         FIG. 1  shows a side cross-section view of a first non-limiting embodiment of the device according to the invention. The needle is not shown in cross-section.  FIG. 1  shows the device with a safety cap installed thereon. The device is in an initial prior-use and/or packaged configuration; 
         FIG. 2  shows the device of  FIG. 1  after the safety cap is removed and in a ready-to-use position; 
         FIG. 3  shows the device of  FIG. 2  with the plunger retracted as would occur when medicine is caused to be suctioned into the syringe via the needle; 
         FIG. 4  shows the device with the plunger fully depressed as would occur during injection. In this position, the leading end of the plunger has moved deflectable retaining members out of locking engagement with the needle hub. Moreover, a rear end of the needle hub has caused an inner seal, i.e., a frangible plunger seal, to come out of sealing engagement with the needle hub; 
         FIG. 5  shows the device after the needle unit is caused to automatically retract into the plunger under the biasing force of a spring. The configuration shown in  FIG. 5  occurs automatically when the plunger reaches the position shown in  FIG. 4 ; 
         FIG. 5   a  shows a rear end view of the device of  FIG. 5 ; 
         FIG. 6  shows an enlarged partial view of the device of  FIG. 4  just before the plunger reaches the fully depressed position; 
         FIG. 7  shows an enlarged partial view of the device of  FIG. 4  just as the plunger reaches the fully depressed position thereby causing deflection of the retaining members and breaking of the frangible plunger seal caused by movement of the plunger against a rear end of the needle hub; 
         FIG. 8  shows a side cross-section view of the plunger used on the first non-limiting embodiment shown in  FIG. 1  and with the plunger piston and inner seal removed; 
         FIG. 9  shows a side view of the plunger of  FIG. 8  with the plunger piston installed thereon; 
         FIG. 10  shows a side cross-section view of the plunger piston used on the plunger shown in  FIG. 9 ; 
         FIG. 11  shows a side view of the plunger piston shown in  FIG. 10 ; 
         FIG. 12  shows a side view of the inner seal used on the plunger shown in  FIG. 1 ; 
         FIG. 13  shows a front end view of the inner seal shown in  FIG. 12 ; 
         FIG. 14  shows a side cross-section view of the inner seal shown in  FIG. 12 ; 
         FIG. 15  shows a side cross-section view of the device shown in  FIG. 1  with the plunger removed; 
         FIG. 16  shows a side cross-section view of the syringe body used in the device shown in  FIG. 1 ; 
         FIG. 17  shows a rear end view of the syringe body shown in  FIG. 16 ; 
         FIG. 18  shows a rear end view of another embodiment of the syringe body; 
         FIG. 19  shows a rear end view of still another embodiment of the syringe body; 
         FIG. 20  shows a side view of the needle unit used in the device shown in  FIG. 1 ; 
         FIG. 21  shows a side cross-section view of the needle unit shown in  FIG. 20 ; 
         FIG. 22  shows a rear end view of the needle unit shown in  FIG. 20 ; 
         FIG. 23  shows a side cross-section view of the spring used in the device shown in  FIG. 1 ; 
         FIG. 24  shows a rear end view of the spring shown in  FIG. 23 ; 
         FIG. 25  shows a side cross-section view of the needle sealing guide member used in the device shown in  FIG. 1 ; 
         FIG. 26  shows a side view of the needle sealing guide member shown in  FIG. 25 ; 
         FIG. 27  shows an enlarged partial view of another embodiment of a plunger which can be used on a device of the type shown in  FIG. 1 . The plunger is similar to that used in  FIG. 1  except that the inner seal is axially retained within the plunger via a separately formed ring; 
         FIG. 28  shows an enlarged partial view of a modified version of the device of  FIGS. 1 and 6 . In this embodiment, the device of  FIGS. 1 and 6  is modified to include a puncturable sealing washer to provided sealing between the needle and the syringe body; 
         FIG. 29  shows an enlarged partial view of another modified version of the device of  FIGS. 1 and 6 . In this embodiment, the device of  FIGS. 1 and 6  is modified to eliminate the needle sealing guide and to instead include a puncturable sealing washer to provided sealing between the needle and the syringe body; 
         FIG. 30  shows a side cross-section view of the device shown in  FIG. 29  with the needle unit and spring removed; 
         FIG. 31  shows a cross-section view through the section (indicated by arrows) shown in  FIG. 30 ; 
         FIG. 32  shows an enlarged partial view of another modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 1  is modified to replace the integrally formed deflectable retaining members with a separately formed ring which is axially retained in the syringe body and which has the deflectable retaining members; 
         FIG. 33  shows an enlarged partial view of another modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 1  is modified to include a locking system to prevent re-use of the device as well as an optional vent opening. The locking system locks the plunger to the syringe body when the plunger is fully or nearly fully depressed; 
         FIGS. 34 and 35  each show an enlarged partial view of another embodiment of a plunger which can be used on a device of the type shown in  FIG. 1 . The plunger is similar to that used in  FIG. 1  except that the inner seal is axially retained within the plunger via a recess and frangible projection system. In  FIG. 35 , the inner seal is axially retained within the plunger. In  FIG. 34 , the inner seal has been moved back sufficiently to cause the inner seal to break the frangible projection of the plunger; 
         FIG. 36  shows an enlarged partial view of another embodiment of a plunger which can be used on a device of the type shown in  FIG. 1 . The plunger is similar to that used in  FIG. 1  except that the inner seal is axially retained within the plunger via a recess and frangible projection system. In  FIG. 36 , the frangible projection of the plunger has annular v-shaped recesses which weaken the projection so that it breaks (via shearing forces) in a predictable manner; and 
         FIG. 37  shows an enlarged partial view of another non-limiting embodiment of a device. The device is similar to that of  FIG. 1 , except that it utilizes a sealing member that utilizes a sealing member which can extend into the opening of the needle which prevents medication from passing into the needle when it is inserted into the distal end of the needle. The device also utilizes plural locking members which lock to the needle unit when the plunger is moved to the fully depressed position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and first to  FIGS. 1-17  and  20 - 26  which shows a first embodiment of an injection device  1 . In embodiments, the device is a retractable hypodermic syringe. The syringe includes a generally elongate cylindrical barrel  10  having a transverse flange  11  arranged at a distal end of the barrel  10 . The barrel  10  includes a main generally cylindrical section  12 . A proximal end of the barrel  10  includes a reduced diameter section  13 . A safety cap  60  is removably disposed on a proximal end of the syringe body  10 . 
     A needle support  30  has a hub portion  31  that is substantially axially retained within a proximal area of the body  10  (see  FIG. 3 ) and includes a rear end surface which can contact an inner seal  25  of a plunger  20  as will be described in detail below. The needle support  30  also has a main needle portion  32  that has a rear end fixed within a needle hub  31  and a proximal end that is pointed or a puncturing end which extends out past the proximal end of the syringe body  10 . A sealing guide member  50  provides sealing between the needle  32  and the syringe body  10 , also allows the needle  32  to slide into the syringe  1  as will be described below. A spring  40  is arranged within the section  13  and the syringe body  10 , and in the configuration shown in  FIG. 2 , is fully or nearly fully compresses. The spring  40  biases the needle unit  30  towards a distal end of the syringe  1 . 
     Substantially arranged within the barrel  10  of the syringe is movably disposed a plunger  20 . The plunger  20 , like the syringe body  10 , includes an end flange  21  which is typically engaged by the thumb of the user while the transverse flange  11  is engaged by the fingers of the user in order to enable the plunger  20  to be forced into the barrel  10  for the purpose of expelling the medicament from the barrel  10  through the needle  32 . The plunger  20  additionally includes a generally cylindrical space  22  which is sized to receive therein the needle unit  30  (see  FIG. 5 ). A piston  23  (see  FIG. 9 ) is arranged on a proximal end of the plunger  10 . The plunger  20  also utilizes a proximal engaging end  24  which is sized and configured to engage with deflectable retaining members  15  (see  FIGS. 6 and 7 ) when the plunger  20  is fully depressed. An inner seal or sealing member  25  is arranged within the plunger  20 . As is apparent from  FIGS. 6 and 7 , the seal  25  has frangible circumferential projections which are sized and configured to break and/or shear off when the plunger  20  is depressed to the point where the seal  25  contacts the hub  31 . Before the projections of the seal  25  break, they provide sealing between the seal  25  and the plunger  20 . This sealing ensures that no medication passes into the plunger space  22  until the seal  25  is broken. 
     As is apparent from  FIGS. 6 and 7 , to unsure that the needle unit  30  is prevented from moving forwards when the plunger  20  is fully depressed, a plurality of stop projections or ribs  14  are arranged within the section  13  of the syringe body  10 . 
     The operation of the device shown  FIGS. 1-7  will now be described. Once the user obtains the device  1  shown in  FIG. 1 , he or she can then remove the safety cap  60 . The device  1  so shown in  FIG. 2  can now be used for, e.g., injection. This can occur when the user injects the needle  32  into a medication container and withdraws the plunger  20  as shown in  FIG. 3 . This causes medication fluid to fill the space in the body  10  between the plunger piston  23  and seal  25  and the sealing member  50 . As this point, the user can move the plunger  20  forwards slightly to remove any air in the syringe  1 . The needle  32  can then be injected into, e.g., tissue. Then, the user will depress the plunger  20  to cause the medication to pass out of the needle  32 . Once fully or nearly fully depressed, the proximal end  24  of the plunger  20  contacts the deflectable retaining members  15  (see  FIGS. 6 and 7 ) and causes them to deflect out of locking and/or retaining engagement with the hub  31 . Since engagement between the deflectable retaining members  15  and the hub  31  is the only mechanism which presents the spring  40  from moving the needle unit  30  backwards, once this engagement is removed, the needle unit  30  will be forced backwards by the spring  40 . Also, once fully or nearly fully depressed, the seal  25  of the plunger  20  contacts the rear surface of the hub  31  (see  FIGS. 6 and 7 ). Since the ribs  14  prevent any forward movement of the hub  31 , contact between the seal  25  and the hub  31  causes the frangible sealing projections of the seal  25  to shear or break. At this point, the spring  40  automatically expands axially and pushes the needle unit  30  and seal  25  into the space  28  disposed inside the plunger  20  as shown in  FIG. 5 . This action withdraws the needle  32  into the syringe and renders the device  1  unusable. The device  1  of  FIG. 5  can then be safely disposed of without the user having to worry about being accidently pricked by the needle  32 , which is safely disposed inside the plunger  20 . 
     In embodiments, the engagement between the deflectable retaining members  15  and the hub  31  is removed or disengages prior to the sealing engagement between the seal  25  and the plunger  20 . In other embodiments, the engagement between the deflectable retaining members  15  and the hub  31  is removed or disengages just prior to the sealing engagement between the seal  25  and the plunger  20 . In embodiments, the engagement between the deflectable retaining members  15  and the hub  31  is not removed or disengaged until after the frangible sealing engagement between the seal  25  and the plunger  20  is broken. In embodiments, the engagement between the deflectable retaining members  15  and the hub  31  is not removed or disengaged until just after the frangible sealing engagement between the seal  25  and the plunger  20  is broken. In embodiments, the force required to unlock or remove the engagement between the deflectable retaining members  15  and the hub  31  is less than that required to break the sealing engagement between the seal  25  and the plunger  20 . In embodiments, the force required to unlock or remove the engagement between the deflectable retaining members  15  and the hub  31  is greater than that required to break the sealing engagement between the seal  25  and the plunger  20 . In embodiments, the force required to unlock or remove the engagement between the deflectable retaining members  15  and the hub  31  is substantially equal to that required to break the sealing engagement between the seal  25  and the plunger  20 . In embodiments, a noise is produced (providing an auditory signal to the user) when the engagement between the deflectable retaining members  15  and the hub  31  is removed. In embodiments, a noise is produced (providing an auditory signal to the user) when the sealing engagement between the seal  25  and the plunger  20  is broken. In embodiments, a visual indication is produced (providing a visual signal to the user) when the engagement between the deflectable retaining members  15  and the hub  31  is removed. In embodiments, a visual indication is produced (providing a visual signal to the user) when the sealing engagement between the seal  25  and the plunger  20  is broken. Such visual indicators can be facilitated by making the plunger  20  and body  10  substantially transparent and/or translucent. 
       FIGS. 8 and 9  show views of the plunger  20  used on the first non-limiting embodiment shown in  FIG. 1 . The plunger  20 , in embodiments, is a one-piece integrally formed member to which is axially secured a piston  23  and an inner seal  25 . The plunger  20  includes a distal flange  21 , a main cylindrical section  22 , a generally cylindrical proximal end  24 , one or more inner generally circumferential tapered recesses  26 , a generally cylindrical recess  27  sized and configured to receive therein and axially retain the piston  23 , and a generally cylindrical space  28 . 
       FIGS. 8 and 9  show views of the piston  23  used on the plunger of  FIGS. 8 and 9 . The piston  23 , in embodiments, is a one-piece integrally formed member to which is axially secured within the recess  27  of the plunger  20 . In embodiments, it can be substantially similar at pistons conventionally used in syringes which include plural external circumferential sealing projections. 
       FIGS. 12-14  show views of the inner seal  25  used on the plunger of  FIGS. 8 and 9 . The seal  25 , in embodiments, is a one-piece integrally formed member to which is axially secured to an inner portion of the plunger  20 . In embodiments, the seal  25  includes a distal or rear surface  25   a , one or more tapered external circumferential projections  25   b , and a proximal surface  25   c . The one or more tapered external circumferential projections  25   b  each extend into one of the recesses  26  of the plunger  20 . The tapered external circumferential projections  25   b  are designed to be frangible and sized and configured to shear upon experiencing a predetermined force applied to the surface  25   c . The shape, i.e., rearward orientation, of the tapered external circumferential projections  25   b  is such that a force applied to the surface  25   c  will cause the projections  25   b  to grip recesses  26  by a greater amount and such that a force applied to the surface  25   a  will cause the projections  25   b  to grip recesses  26  by a lesser amount. In embodiments, a force applied to the surface  25   a  will cause the projections  25   b  to start to move out of engagement with the recesses  26  by a significant amount without breaking. 
       FIGS. 15-17  show how the syringe body  10  used on the device of  FIG. 1  receives therein the seal guide  50 , the needle member  30  and the spring  40  before receiving therein the plunger  20  of  FIGS. 8 and 9 . The body  10 , in embodiments, is a one-piece integrally formed member. The body  10  includes a distal flange  11 , a main cylindrical section  12 , a generally cylindrical proximal end  13 , one or more inner radially oriented spaced-apart ribs  14 , plural deflectable retaining members  15  which are equally spaced-apart and which are sized and configured to engage with the circumferential recess  33  of the needle unit  30  (see  FIG. 20 ), and a generally cylindrical opening  17  sized and configured to receive therein (in a sealing and/or press-fit manner) the generally cylindrical surface  50   a  of the sealing guide  50  (see  FIG. 26 ). In embodiments, two oppositely arranged deflectable retaining members  15  are utilized. In embodiments, three equally spaced deflectable retaining members  15  are utilized. In embodiments, between four and eight equally spaced deflectable retaining members  15  are utilized.  FIG. 18  shows an optional embodiment wherein section  13 ′ utilizes four equally spaced deflectable retaining members  15 ′ and four ribs  14 ′ which have the same orientation.  FIG. 19  shows an optional embodiment wherein section  13 ″ utilizes four equally spaced delectable retaining members  15 ″ and four ribs  14 ″ which are offset with respect to one another. These systems/configurations can be utilized on any of the herein disclosed device embodiments. 
       FIGS. 20-22  show views of the needle unit  30  used on the device  1  of  FIG. 1 . The needle unit  30 , in embodiments, can be a one-piece integrally formed member. The needle unit  30 , in embodiments, utilizes a one-piece needle hub  31  and a one-piece needle  32  that has a distal end secured (e.g., press-fit) within an opening the hub  31 . The needle hub  31 , in embodiments, also utilizes a tapered section  36  and a circumferential groove or recess  33  which can receive therein the free ends of the deflectable gripping members  15  (see  FIG. 6 ). In embodiments, the needle  32  has a main lumen  34  and a puncturing end  35 . In embodiments, the needle  32  can be substantially similar at pistons conventionally used in syringes which include plural external circumferential sealing projections. 
       FIGS. 23 and 24  show views of the spring  40  used on the embodiment of  FIG. 1 .  FIG. 23  shows the spring  40  in an expanded or relaxed position. In the position shown in  FIG. 1 , the spring  40  is fully or nearly fully compressed. Expansion of the spring  40  causes the needle unit  30  to retract fully into the plunger  20  (see  FIG. 5 ). 
       FIGS. 25 and 26  show views of the sealing guide  50  used on the embodiment of  FIG. 1 . The seal  50  has a generally cylindrical section  50   a , a tapered section  50   b , and a generally cylindrical opening  50   c . The generally cylindrical section  50   a  is sized and configured to sealingly and frictionally engage with opening  17  in the body  10 . The tapered section  50   b  is sized and configured to sealingly and frictionally engage with a corresponding tapered surface of the body  10 . The generally cylindrical opening  50   c  is sized and configured to sealingly engage with the needle  32 . The seal  50 , in embodiments, can be a one-piece integrally formed member. 
       FIG. 27  shows an enlarged partial view of another embodiment of a plunger  20 ′ which can be used on a device of the type shown in  FIG. 1 . The plunger  20 ′ is similar to that used in  FIG. 1  except that the inner seal  25 ′ is axially retained within the plunger  20 ′ via a separately formed ring  29 ′. The ring  29 ′ is seated in a circumferential recess formed in the seal  25 ′. In embodiments, a distal circumferential shoulder is sized and configured to break when the plunger  20 ′ is fully depressed. In embodiments, a ring  29 ′ is a frangible ring and is sized and configured to break when the plunger  20 ′ is fully depressed. As with the previous embodiments, the plunger  20 ′ includes a proximal engaging end  24 ′ and a piston  23 ′. This system/configuration can be utilized on any of the herein disclosed device embodiments. 
       FIG. 28  shows an enlarged partial view of a modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 1  is modified to include a puncturable sealing washer  70  to provided sealing between the needle  32 ′ and the guide  50  and/or syringe body  10 ′″. The needle unit  30 ′ is also modified to include a generally cylindrical section  37 ′. As with the previous embodiments, the device utilizes ribs  14 ′″ and deflectable retaining members  15 ′″. This system/configuration can be utilized on any of the herein disclosed device embodiments. 
       FIGS. 29-31  show views of another modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 28  is modified to remove the ribs and the guide seal and instead sealing is provided between the opening  17   IV  of the syringe body  10   IV  and the needle  32 ′. As with the previous embodiments, the device utilizes deflectable retaining members  15   IV . This system/configuration can be utilized on any of the herein disclosed device embodiments. 
       FIG. 32  shows an enlarged partial view of another modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 1  is modified to replace the integrally formed deflectable retaining members with a separately formed ring  16   V  which is axially retained in the syringe body  10   V  via a projection and recess securing arrangement. The ring  16   V  is a one-piece member that has the deflectable retaining members  15   V . This system/configuration can be utilized on any of the herein disclosed device embodiments. 
       FIG. 33  shows an enlarged partial view of another modified version of the device of  FIG. 1 . In this embodiment, the device of  FIG. 1  is modified to include a locking system to prevent re-use of the device as well as an optional vent opening. The locking system has the form of one or more projections LP and one or more recesses LR adapted to receive therein the locking projection LP. The locking system locks the plunger  120  to the syringe body  110  when the plunger  120  is fully or nearly fully depressed. Other configurations can also be utilized such as arranging the locking projections LP on the syringe body  110  and the locking recesses LR on the plunger  120 . The projection LP can be, in embodiments, continuous or intermittent and the recess LR can be a circumferential recess. The device can also be modified to utilize an optional vent opening VO in the plunger  120 . The locking system prevents re-use of the device. The systems shown in  FIG. 33  can be utilized on any of the herein disclosed device embodiments. 
       FIGS. 34 and 35  each show an enlarged partial view of another embodiment of a plunger which can be used on a device of the type shown in  FIG. 1 . The plunger is similar to that used in  FIG. 1  except that the inner seal  125 ′ is axially retained within the plunger body  122 ′ via a recess and frangible projection FP. In  FIG. 35 , the inner seal  125 ′ is axially retained within the plunger. In  FIG. 34 , the inner seal  125 ′ has been moved back sufficiently under the action of a force F to cause the inner seal  125 ′ to break the frangible projection FP of the plunger. The systems shown in  FIGS. 34 and 35  can be utilized on any of the herein disclosed device embodiments. 
       FIG. 36  shows an enlarged partial view of another embodiment of a plunger which can be used on a device of the type shown in  FIG. 1 . The plunger is similar to that used in  FIG. 1  except that the inner seal  125 ″ is axially retained within the plunger body  122 ″ via a recess and a selectively weakened frangible projection FP′. In  FIG. 36 , the frangible projection FP′ of the plunger has annular v-shaped recesses which weaken the projection FP′ so that it breaks (via shearing forces) in a predictable manner. The system shown in  FIG. 36  can be utilized on any of the herein disclosed device embodiments. 
       FIG. 37  shows an enlarged partial view of another non-limiting embodiment of a device. The device is similar to that of  FIG. 1 , except that it utilizes a sealing member  25 ″ that utilizes a sealing member SM which can extend into the distal opening of the needle  32 ″ so as to prevent medication from passing into the needle  32 ″ when it is inserted into the distal end of the needle  32 ″. The device also utilizes plural locking members LM which lock to a circumferential engaging projection EP of the needle unit  31 ″ when the plunger is moved to the fully depressed position (indicated by arrow). Once locked to each other, the seal  25 ″ and needle unit  30 ″ retract into the plunger as a unit. The system shown in  FIG. 37  can be utilized on any of the herein disclosed device embodiments. 
     The devices described herein can also utilize one or more features disclosed in prior art documents expressly incorporated by reference in pending U.S. patent application Ser. No. 11/616,196 (Publication No. 2008/0154212). This application and the documents expressly incorporated therein is hereby expressly incorporated by reference in the instant application. Furthermore, one or more of the various parts of the device can preferably be made as one-piece structures by e.g., injection molding, when doing so reduces costs of manufacture. Non-limiting materials for most of the parts include synthetic resins such as those approved for syringes, blood collection devices, or other medical devices. Furthermore, the invention also contemplates that any or all disclosed features of one embodiment may be used on other disclosed embodiments, to the extent such modifications function for their intended purpose. 
     It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.