Injection device

Abstract

An injection device comprising a housing in which can be mounted a syringe comprising a barrel for holding a volume of medicament, a needle at one end of, the barrel and a plunger axially-moveable in the barrel to a forwardmost position, the injection device further comprising a syringe support means for supporting the barrel at an axial location at or forward of the forwardmost position of the plunger and having a reaction surface for the syringe, whereby in use said reaction surface provides an axial compressive force on said barrel when a forward axial force is applied to the plunger.

1 . An injection device comprising a housing in which can be mounted a syringe comprising 
 a barrel for holding a volume of medicament,    a needle at one end of the barrel and    a plunger axially-moveable in the barrel to a forwardmost position, the injection device further comprising a syringe support means for supporting the barrel at an axial location at or forward of the forwardmost position of the plunger and having a reaction surface for the syringe, whereby in use said reaction surface provides an axial compressive force on said barrel when a forward axial force is applied to the plunger.    
   
   
       2 . Injection device as claimed in  claim 1  wherein, in use, said reaction surface provides an axial compressive force to the front shoulder of the syringe barrel.  
   
   
       3 . Injection device as claimed in  claim 1  wherein, in use, said reaction surface provides an axial compressive force to the front cone of the syringe barrel.  
   
   
       4 . Injection device as claimed in  claim 1  wherein said syringe support means includes one or more inwardly-directed protrusions forming said reaction surface.  
   
   
       5 . Injection device as claimed in  claim 4  wherein said inwardly-directed protrusions are on the end of one or more radially-flexible fingers.  
   
   
       6 . Injection device as claimed in  claim 5  wherein said inwardly-directed protrusions comprise an inwardly-directed enlarged head on the or each radially-flexible finger.  
   
   
       7 . Injection device as claimed in  claim 5  further comprising a spring retainer, preferably made from steel, for urging the or each radially-flexible finger inwardly.  
   
   
       8 . Injection device as claimed in  claim 4  wherein the internal diameter between said inwardly-directed protrusions is smaller than the exterior diameter of the syringe barrel.  
   
   
       9 . Injection device as claimed in  claim 8  wherein, when the device is fully assembled ready for use, said inwardly-directed protrusions are axially located between a needle cover and the front shoulder of the syringe barrel.  
   
   
       10 . Injection device as claimed in  claim 1  wherein said syringe support means is generally cylindrical and of a diameter less than the diameter of the finger flange of the syringe barrel so that the syringe support means is suitably sized to closely surround the barrel of the syringe, in use.  
   
   
       11 . Injection device as claimed in  claim 1  wherein said syringe support means is capable of supporting said syringe barrel, at a specific axial location with respect thereto.  
   
   
       12 . Injection device as claimed in  claim 1  wherein said syringe support means includes one or more viewing windows, to permit a user to view the barrel of a syringe supported therein.  
   
   
       13 . Injection device as claimed in  claim 1  wherein said syringe support means further comprises one or more alignment tags at the front end thereof.  
   
   
       14 . Injection device as claimed in  claim 13  further comprising a front housing having a bore therethrough, the interior surface of the bore being provided with one or more longitudinal slots, positioned so that said alignment tags can locate therein, when said front housing and syringe support means are assembled together.  
   
   
       15 . Injection device as claimed in  claim 14  wherein the or each longitudinal slot comprises a rear section having a forwardly-increasing depth and a forward section having substantially constant depth.  
   
   
       16 . Injection device as claimed in  claim 15  wherein a boundary between the rear and forward sections is defined by a step.  
   
   
       17 . Injection device as claimed in  claim 16  further comprising an end cap having internal protrusions therein which protrude into the longitudinal slots in the bore of the front housing, when said end cap and said front housing are assembled together, so that a space is defined between said internal protrusions in the end cap and said step in the front housing.  
   
   
       18 . Injection device as claimed in  claim 17  wherein the alignment tags of the syringe support means locate into said defined space to determine the axial location of the syringe support means with respect to said front housing.  
   
   
       19 . Injection device as claimed in  claim 14  wherein said syringe support means includes a radially-extending flange, of greater diameter than the interior diameter of said front housing.  
   
   
       20 . Injection device as claimed in  claim 17  wherein, when assembled together, said end cap, front housing and syringe support substantially prevent damage to or movement of a needle cover on the needle of a syringe mounted in the device.  
   
   
       21 . Injection device as claimed in  claim 1  wherein the finger flange of the syringe barrel does not contact the syringe support means during delivery of the medicament.  
   
   
       22 . Injection device as claimed in  claim 5 , wherein said radially-flexible fingers can flex sufficiently outwardly to allow a needle cover or the like of larger diameter than the internal diameter between said radially-flexible fingers to pass thereby during assembly of a syringe into said injection device.  
   
   
       23 . Injection device as claimed in  claim 22  when dependent on  claim 18  wherein said axial location of the syringe support means with respect to the front housing is such that said radially-flexible fingers are not confined within said front housing and are free to flex radially, when the front housing and syringe support means are assembled together and before assembly of a rear part-assembly of the device thereto.  
   
   
       24 . Injection device as claimed in  claim 22  wherein, when the device is fully assembled ready for use, said, inwardly-directed protrusions closely abut the needle cover to reduce the risk of said needle cover becoming loose or detached from the needle.  
   
   
       25 . An injection device as claimed in any of the preceding claims, in which is mounted a syringe comprising 
 a barrel for holding a volume of medicament,    a needle at one end of the barrel and    a plunger axially-moveable in the barrel to a forwardmost position.    
   
   
       26 . A method of assembling an injection device comprising the steps of: 
 providing a first part-assembly comprising a front housing and a closely fitting end cap;    providing a second part-assembly comprising a rear part of the injection device;    providing a syringe comprising a barrel for holding a volume of medicament, a needle at one end of the barrel and a plunger axially-moveable in the barrel;    providing a syringe support means;    inserting the syringe axially into the rear end of the syringe support means until said syringe support means supports the syringe at a predetermined axial location;    inserting the front end of said syringe and syringe support means into said first part-assembly;    assembling said first part-assembly and second part-assembly together.    
   
   
       27 . A method of assembling an injection device comprising the steps of: 
 providing a first part-assembly comprising a syringe support means, a front housing and a closely fitting end cap;    providing a second part-assembly comprising a rear part of the injection device;    providing a syringe comprising a barrel for holding a volume of medicament, a needle at one end of the barrel and a plunger axially-moveable in the barrel;    inserting the syringe axially into the rear end of the first part-assembly until said syringe support means supports the syringe at a predetermined axial location;    assembling said first part-assembly and second part-assembly together.