Injection device

Abstract

An injection device comprising an outer housing inside which is located a medicament-holding barrel with a needle at one end thereof, at least part of the needle being moveable in and out of the outer housing, a plunger moveable within the barrel, an inner housing intermediate the outer housing and the barrel and plunger and an energy source in communication with said inner housing. The inner housing is moveable by the energy source between a first position in which the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing; a second position in which the plunger is movable axially into said barrel so as to expel medicament through the needle; and a third position in which the plunger and barrel are able to retract in order to retract the needle into the outer housing.

1 . An injection device comprising an outer housing inside which is located
 a barrel for holding a volume of a medicament;   a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;   a plunger, axially moveable within the barrel;   an inner housing intermediate the outer housing and the barrel and plunger; and   an energy source in communication with said inner housing,
 Characterized in that the inner housing is moveable by the energy source between three positions, namely
 a first position in which the inner housing has one or more readially flexible tags which are in communication with the barrel such that, in use, the plunger and the barrel are movable axially so as to move at least part of said needle out of the outer housing; 
 a second position in which the inner housing has one or more radially flexible tags which are in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and 
 a third position in which said one or more radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing. 
 
   
   
   
       2 . An injection device as claimed in  claim 1  further comprising a spring housing intermediate the outer housing and the inner housing. 
   
   
       3 . An injection device as claimed in  claim 1  wherein one or more of said tags is located at the end of a resiliently flexible leg. 
   
   
       4 . An injection device as claimed in  claim 1 , wherein one or more of said tags are situated at the rear end of the inner housing and are moveable radially into and out of communication with the plunger. 
   
   
       5 . An injection device as claimed in  claim 2 , wherein said tags are biased radially inwardly into communication with said plunger, preferably by communication with said spring housing. 
   
   
       6 . An injection device as claimed in  claim 1 , wherein said tags are stored in their relaxed condition, before initiating an injection. 
   
   
       7 . An injection device as claimed in  claim 2 , wherein each rear tag is moveable out of communication with the plunger when aligned with a corresponding recess in the spring housing. 
   
   
       8 . An injection device as claimed in  claim 1 , wherein each rear tag is substantially T-shaped. 
   
   
       9 . An injection device as claimed in  claim 1 , wherein one or more of said tags are situated at the forward end of the inner housing and are moveable radially into and out of communication with the barrel, wherein said forward tags are biased radially inwardly into communication with said barrel, preferably by communication with said spring housing, wherein said forward tags are stored in their relaxed condition, before initiating an injection, wherein each forward tag is moveable out of communication with the barrel when aligned with a corresponding recess in the outer housing, and wherein each forward tag is substantially L-shaped. 
   
   
       10 . An injection device as claimed in  claim 1 , further including means for allowing the inner housing to move axially only forward with respect to the outer housing, wherein said means is an arrangement of serrations, barbs, ratchet teeth or the like intermediate the housings. 
   
   
       11 . An injection device as claimed in  claim 1 , further comprising guide means for guiding, in use, the relative axial movement of the spring and outer housings, the guide means preferably comprising one or more protrusions on said spring housing which, in use, cooperate with corresponding recesses on an interior surface of said outer housing. 
   
   
       12 . An injection device as claimed in  claim 1 , wherein said needle is biased to be normally wholly inside said housing by means of a spring intermediate the barrel and the outer and/or spring housing. 
   
   
       13 . An injection device as claimed in  claim 1 , further including a removable needle cover which protects the needle during storage before use, wherein said needle cover includes means for pulling a protective rubber sheath or the like from said needle when said needle cover is removed from the device, and wherein said pulling means includes a floating rivet intermediate the needle cover and the protective rubber sheath or the like, whereby twisting forces applied to said needle cover are substantially prevented from being transmitted to said rubber sheath or the like. 
   
   
       14 . An injection device as claimed in  claim 13 , wherein the presence of said needle cover on said device serves as a safety lock, substantially preventing relative forward movement of said outer housing. 
   
   
       15 . An injection device as claimed in  claim 1 , further comprising a viewing window in said barrel aligned with a viewing window in said outer housing such that said medicament can be viewed by a user prior to an injection taking place. 
   
   
       16 . An injection device as claimed in  claim 15  wherein, in use during an injection, said inner housing moves intermediate said viewing window in the outer housing and said barrel so as to obscure the window in the barrel from the user's view. 
   
   
       17 . An injection device as claimed in  claim 1 , further comprising means for emitting an audible and/or physical indication to a user that the injection is complete. 
   
   
       18 . An injection device comprising an outer housing inside which is located
 a barrel for holding a volume of a medicament;   a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;   a plunger, axially moveable within the barrel;   an inner housing intermediate the outer housing and the barrel and plunger; and   an energy source in communication with said inner housing,   characterized in that the inner housing is moveable by the energy source between two positions, namely   a first position in which the inner housing has one or more radially flexible tags which are in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and   a second position in which said one or more radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.   
   
   
       19 . An injection device comprising an outer housing adapted to receive:
 a barrel for holding a volume of a medicament;   a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing; and   a plunger, axially moveable within the barrel,   wherein the injection device further comprises:
 an inner housing intermediate the outer housing and the barrel and plunger; and 
 an energy source in communication with said inner housing, 
 characterized in that the inner housing is moveable by the energy source between three positions, namely 
 a first position in which the inner housing has one or more radially flexible tags in communication the barrel such that, in use, the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing; 
 a second position in which the inner housing has one or more radially flexible tags in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and 
 a third position in which the said radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing. 
   
   
   
       20 . An injection device as claimed in  claim 19  further comprising a spring housing intermediate the outer housing and the spring housing.