Abstract:
An injection device includes a multi-use drive assembly  10  and a single use disposable syringe assembly  12  releasably connected thereto. The syringe assembly includes a syringe  18  and a shield  26  mounted for telescopic movement. The drive assembly  10  is operable to extend the syringe  18  relative to the shield  26  and then to express a dose. Continued forward drive movement extends the shield  26  to re-cover the syringe needle  22  and then ejects the spent syringe assembly  12  in a safe (shrouded) condition.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to injection devices and, in particular, but not exclusively, to autoinjection devices. 
     2. Description of the Related Art 
     Many autoinjection devices are single use, disposable devices. With the growing awareness of the environmental impact of such devices once used, there is a desire to make part of such devices reuseable and to reduce the proportion of the device that is single use and disposable. Furthermore, it is desirable to design the disposable, single use, part of the device so that it is readily adapted for recycling. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, in one aspect, this invention provides a syringe assembly comprising:
         a syringe having a body and a needle, and   a shield slideably mounted around said syringe for telescopic movement between a retracted position in which the syringe needle is exposed in use and an extended position in which the needle is at least partially shrouded by said shield,   wherein said syringe body has a feature thereon which cooperates with an associated feature on the shield to control relative movement thereof.       

     Advantageously said syringe body and said feature are of moulded plastics material. Preferably said cooperating features limit the extent of telescopic movement of the syringe and the shield, and further may be operable releasably to latch said shield in a forward position relative to the syringe. 
     The cooperating features may typically comprise a projection on one of the syringe or shield, cooperating with a control slot on the other thereof. The slot may be provided at one end region with a latch recess for releasably retaining said projection, and the wall of the slot, at least in the region of said latch recess, is preferably resiliently deformable to allow said projection to snap out of said recess to allow said shield to move rearwardly relative to the syringe. There may be a locking member engageable adjacent or near said slot for inhibiting resilient movement of said latch recess to prevent release of said projection, and the locking member may be engageable by being longitudinally slideable into a locking slot provided alongside said control slot. The locking member may carry at its forward end a cap for closing the forward end of said shield, when applied to the forward end of said shield, and with the locking member slid longitudinally into said locking slot. Where as is common the syringe includes a boot covering said needle prior to use, the cap conveniently includes means for engaging said boot when said cap is applied to said shield, such that removal of said cap removes said boot. 
     Where said syringe assembly is adapted to be releasably coupled in use to the drive assembly of an autoinjection device in which the drive assembly includes a drive for expelling a dose from the syringe, a trigger for releasing said drive, and a safety arrangement for preventing inadvertent actuation of said drive, said locking member is preferably arranged to release said safety arrangement and/or unlock said safety arrangement for subsequent release, when said locking member is removed from said shield. 
     A number of different configurations are possible, but the syringe may typically be carried inside said shield by direct sliding engagement therebetween. 
     In order to reduce the number of parts and amount of material that is required to be disposed of in a multi-use autoinjector arrangement, of the type in which a syringe assembly as described is adapted to be releasably coupled in use to the drive assembly of the autoinjector device, the syringe assembly is preferably coupled to said drive assembly in use by interengagement of a portion of said shield with said drive assembly, so that the shield acts as both shield and container, thereby obviating the need for a separate container so that just the syringe and the shield are disposed of post use. The shield may include one or more features for snap engagement in use with an associated one or more features on said drive assembly. To automate ejection the syringe and shield after use, said drive may be adapted to uncouple said shield from said drive assembly on approaching or reaching the forwardmost extent of movement. 
     The invention extends to an autoinjection device including a removable syringe as set out above. 
     In order to provide simple, safe and reliable operation, and thereby a device whose use is intuitive yet inherently safe, the inventors have designed an autoinjection device in which a number of locks keep the device in a safe condition prior to use, but are all released by removal of a single element. 
     Accordingly, in another aspect of this invention provides an autoinjection device comprising:
         a syringe having a needle which prior to injection carries a boot;   a shield movable relative to said syringe between an extended position in which the needle is at least partially shrouded and a retracted position in which the needle is exposed;   a drive assembly for expelling a dose from the syringe;   a trigger for actuating said drive assembly;   a safety arrangement for preventing inadvertent actuation of said drive assembly, and   a boot remover applied to the forward end of said autoinjector and adapted to engage said boot, said boot remover being arranged to prevent movement of said syringe relative to said shield in at least one direction, and to prevent release of said safety arrangement until said boot remover is removed from the front end of the device.       

     Conventional autoinjector devices are either single use disposable items or, where multi-use, require the user to open the device to remove and insert the syringe or cartridge. This latter carries the risk of exposure to potential needle stick injury and also requires manual dexterity of the user. The inventors have therefore designed an autoinjector where on completion of the injection, the syringe assembly is automatically released from the autoinjector body. 
     Accordingly, in another aspect, this invention provides an autoinjection device comprising:
         a drive assembly and a syringe assembly adapted to be coupled and uncoupled in use, the syringe assembly including a shield and a syringe movable with respect to said shield and having a needle, the drive assembly including a drive and a trigger for actuating said drive to drive a plunger forwardly to move the syringe forwardly relative to the shield and to expel a dose from the syringe, characterised in that the syringe assembly is coupled to said drive assembly by one or more engagement elements on said shield engaging one or more directly or indirectly cooperating elements on said drive assembly, and in that said plunger or a part associated therewith disengages said features as it approaches or reaches its forward position, to release the syringe assembly.       

     The action of releasing the syringe assembly also provides an important confirmation to the user that injection is complete. 
     In a number of applications, it may be desirable to resist or obstruct movement of a syringe plunger in the separation direction, for example to prevent re-use or to hold the syringe on the plunger whilst a shield is deployed post-injection. 
     Accordingly, in another aspect, this invention provides an injection device comprising:
         a syringe having a body and a plunger having a portion extending within the body of said syringe and adapted to expel a dose, including means to impart significantly greater resistance to separating movement of the plunger and the syringe, than in the opposite direction.       

     As set out above, there is a growing desire to reduce the amount of material that has to be disposed of post-injection. 
     Accordingly, in yet another aspect, this invention provides an autoinjection device comprising:
         a reusable drive assembly releasably coupled to a disposable syringe assembly, the syringe assembly comprising a shield and a syringe, the syringe having a needle, the syringe being telescopically movable within said shield, between a retracted position in which the need is at least partially shielded, and an extended position in which the needle is exposed, the drive assembly comprising a drive and a trigger for actuating said drive arrangement to expel a dose from the syringe, characterised in that the syringe assembly is releasably coupled to the drive assembly by engagement of a coupling portion on the shield with a coupling portion in the drive assembly.       

     Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description or claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be performed in various ways and, by way of example only, an embodiment thereof will now be described with reference to the following drawings, in which: 
         FIG. 1  is a general view of an embodiment of autoinjection device, showing the reuseable drive assembly and the disposable syringe assembly prior to coupling; 
         FIG. 2  is a general view of the components making up the syringe assembly; 
         FIGS. 3( a ) to ( c )  are detailed views showing the coupling engagement between the syringe assembly and the drive assembly; 
         FIG. 4  is a longitudinal cross-section view through the drive assembly, with the safety catch locked; 
         FIG. 5  is a detailed view on the mechanism associated with the plunger for releasing the syringe assembly from the drive assembly at the end of the forward stroke of movement of the plunger; 
         FIGS. 6( a ) and ( b )  are longitudinal section views through a forward part of the drive assembly showing operation of the release mechanism; 
         FIGS. 7( a ) and ( b )  are a view of the syringe assembly coupled to the drive assembly prior to removal of the boot remover, and a detailed view on the syringe latch respectively; 
         FIGS. 8( a ) and ( b )  are views similar to  FIGS. 5( a ) and ( b )  but after removal of the boot remover; 
         FIG. 9  is a detailed view on the syringe latch showing resilient flexing thereof to release the shield latch pip on the syringe; 
         FIGS. 10( a ) and ( b )  are views similar to  FIGS. 6( a ) and ( b )  but following release of the plunger to drive the syringe forwardly to expose its needle; 
         FIGS. 11( a ) and ( b )  are longitudinal section views through the syringe assembly showing the release mechanism that re-extends the shield over the syringe to shield the needle on completion of the injection and release of the syringe assembly, and 
         FIGS. 12( a ) and ( b )  are longitudinal sections through the forward end of the syringe assembly showing operation of the one way gripper arrangement between the syringe plunger and the syringe body  20 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , the illustrated embodiment of autoinjection device comprises a drive assembly  10  releasably coupled to a syringe assembly  12  by a pair of coupling tongues  14  on the syringe assembly designed to snap fit into locking recesses  16  on the drive assembly, as to be described below in relation to  FIGS. 3( a ) to ( c ) . The drive assembly is designed to be reusable whereas the syringe assembly is a single use disposable item. In order to reduce the environmental impact, the syringe assembly is made of just three components as illustrated in  FIG. 2 , all of which, with the exception of the syringe needle, are moulded from recyclable plastics material. 
     As seen in  FIG. 2 , the syringe assembly comprises a moulded plastic syringe  18  having a cylindrical body  20  from the forward end of which extends a needle  22  and provided at its rear end with a radially projecting shield latch pip  24 . The needle shield  26  is of open ended shell form with the coupling tongues  14  extending rearwardly therefrom. The coupling tongues  14  have coupling ramps  28  which effect a snap fit coupling as to be described below and are capable of resilient flexing movement. At the rear end of the needle shield  26  (and viewable on enlarged scale in  FIG. 3( a ) ) is a control slot  30  designed slideably to receive the shield latch pip  24 . At its rear end, the control slot  30  has a latch recess  32  in which the shield latch pip  24  can be releasably latched. A locking slot  34  runs in a keyway  36  extending along the length of the needle shield  26  with the keyway  36  being cut away at its rear end to leave a resilient finger  37  defining one edge of the slot  30  and allowing resilient flexing to release the latch recess  32  when the locking slot  34  is empty. 
     A boot remover  38  carries at its forward end a cap  40  from the rear of which extends a cylindrical boot remover portion  42 , having internal barbs or other suitable grip elements (not shown) to engage a boot  43  which covers the needle  22  prior to use. Extending rearwardly from the cap  40  is a boot remover finger  46  designed to be a slideable fit in the locking slot  34 . When the boot remover  38  is fitted to the front end of the shield (as seen for example in  FIGS. 1 and 3 ( a )) the boot remover finger  46  extends alongside the slot  30  to protrude rearwardly from the edge of the needle shield  26  to lock a safety catch arrangement as to be described below. 
     Referring now to  FIGS. 3( a ) to ( c ) , the syringe assembly is coupled to the drive assembly by offering up the tongues  14  to the locking recesses  16  and pushing the syringe assembly rearwardly to effect a snap fit. The main body portion  48  of the drive assembly  10  has a tooth  50  extending rearwardly and inwardly from each locking recess  16  and designed so that when the coupling tongues  14  pass through the recesses  16 , the ramps  28  snap fit behind the teeth  50  to lock the syringe assembly  12  against forward movement. 
     Referring now to  FIG. 4 , the drive assembly  10  includes a trigger sleeve  52  slideably mounted around the outside of the main body  48 . A plunger  54  is slideably mounted within the main body  48  and urged forwardly by a main drive spring  56 . The plunger has at its rear end a split arrowhead locking latch  57  or similar which holds the plunger in a rearward position in the main body with the drive spring energised. A trigger cap  58  is slideably mounted on the rear end of the main body  48  and movable forwardly from a rest position to squeeze together the split arrowhead to release the locking latch  57  and to release the plunger  54  for forward movement. At the forward end of the main body  48  there is a flexible safety catch  60  which, when in the ‘safe’ position shown in  FIG. 4 , prevents forward movement of the trigger sleeve  52  to the firing position. The safety catch  60  is held in its ‘safe’ position in  FIG. 4  by the rearward end of the boot remover finger  46 . Upon forward withdrawal of the boot remover finger  46 , this constraint is removed thereby unlocking the safety catch so that it can be cammed or pushed manually down as the trigger sleeve  52  is moved to a forward position in which it moves the trigger cap  58  to release the plunger. As evident from  FIG. 4 , upon forward movement, the plunger  54  will engage at its forward end the syringe bung  62 . 
     Referring now more particularly to  FIGS. 5 and 6 ( a ) and ( b ), a release collar  64  is slideably mounted towards the rear end of the plunger and biased forwardly by an ejection spring  66  acting between a flange  68  integral with the plunger and the rear end of the release collar  64 . The release collar  64  has at its forward end opposed part-conical release surfaces  70  designed to urge the coupling tongues  14  inwards to release the coupling ramps  28  to uncouple the syringe assembly  12  from the drive assembly  10  at the end of an injection. As seen in  FIG. 6( a ) , as the plunger approaches its forwardmost position, the release collar  64  squeezes the coupling tongues  14  inwards and then pushes the shield  26  forwardly relative to the drive assembly as seen in  FIG. 6( b ) . 
     In use, the drive assembly is loaded if necessary by pushing the plunger  54  back into the main body so that the plunger is latched in its rearward position and the trigger sleeve is locked in a rearward position by the safety catch  60 . A fresh syringe assembly  12  with its boot remover  38  closing the forward end and with the syringe latched in its rearward position relative to the shield  26  is offered up to the drive assembly  10  and snap fitted into position with the tongues  14  locked into the locking recesses  16 . In this configuration, the boot remover  38  fulfils several different functions. It closes off the front end of the shield; the boot remover finger  46  prevents resilient flexing movement of the resilient finger  37  and thus prevents unlatching and forward movement of the syringe relative to the shield; the boot remover finger  46  also prevents release of the safety catch  60 , as seen in  FIGS. 7( a ) and ( b ) . 
     Removal of the boot remover removes the boot  43  from the syringe needle  22  and unlocks the resilient finger  37  so that the syringe is ready for forward movement. Finally, the safety catch  60  is unlocked. The assembled autoinjector is then offered up to the injection site with the front end of the shield placed against the skin. The safety catch  60  is released and the trigger sleeve  52  moved forwardly to release the plunger. Upon initial release of the plunger, it acts via the piston bung  62  and the liquid charge in the syringe which acts initially as a solid to move the syringe  18  bodily forward so that the shield latch pip  24  springs out of the latch recess  32  and moves down the control slot  30  to the position shown in  FIGS. 10( a ) and ( b )  with its needle  22  extended. The syringe is then prevented from further movement by the pip reaching the forward end of the slot and so the plunger now moves the bung  62  forwardly to express the dose. 
     As shown in  FIGS. 11( a ) and ( b ) , as the plunger  54  reaches its forward end, the release collar  64  squeezes the ends of the coupling tongues  14  together to uncouple the shield  26  from the main body of the drive assembly. At this point the shield  26  does not yet move forwardly relative to the syringe because the injection device is still pressing against the skin. On release of that pressure, the needle shield  26  moves forwardly under the influence of the ejection spring  66  until the shield latch pip  24  snaps back into the latch recess  33 . 
     During this movement, it is important that the syringe does not move forwardly with the shield. For this purpose, as shown in  FIGS. 12( a ) and ( b )  there is a one-way clutch arrangement provided between the plunger and the syringe body  20 . The plunger has an annular groove  70  with a ramped or frusto conical base  72 , which receives a ‘O’ ring  74 . When the plunger is moving towards or into the bore  76  of the syringe the ‘O’ ring  74  is urged towards the deeper part of the groove  70  thus providing little or no resistance to movement, as shown in  FIG. 12( a ) . However, movement of the plunger in the opposite sense drives the ‘O’ ring into engagement with the syringe body  20  thus tending to resist rearward movement, as shown in  FIG. 12( b ) . The resistance to rearward movement of the plunger is designed to be sufficient to hold the syringe against forward movement to ensure proper extension and latching of the needle shield, but to be overcome when it is required to slide the uncoupled syringe assembly off the extended plunger. 
     The boot remover  38  is reapplied to the shield with the boot remover finger  46  sliding along the slot  34  to block resilient movement of the resilient finger  37 . The syringe assembly  10  is now safe for disposal. Apart from the needle which will typically be of metal material, the remainder of the syringe assembly may be made principally or wholly of recyclable plastics material such as thermoplastic material.