Patent ID: 7717877

Claim:
An injection device comprising: a housing having a proximate end and a distal end, the distal end having an opening therein; a shield slideably coupled to the housing and having a shield base and aperture positioned at said distal end thereof; a cartridge barrel within the housing, the cartridge barrel having proximate and distal ends; a needle cannula fixed to the distal end of the cartridge barrel, or attachment means for fixing a needle cannula to the distal end, said needle cannula being disposed within said shield prior to activation of said device; a stopper within the cartridge barrel; a driver coupled to the stopper; a spring coupled between the housing and the driver; an automatic driver trigger for retaining the driver fixed to the housing and in which state the spring is in a compressed state, the trigger being actuable by displacing said shield towards said proximal end of housing, thereby permitting passage of said needle cannula through said aperture, said actuated trigger automatically releasing the driver from the housing thereby allowing the spring to urge the driver through the housing and with it the stopper through the cartridge barrel; and a release mechanism for releasing the spring from the driver at some point on its travel through the housing, whereupon the spring engages the shield base and automatically urges the shield away from the housing so as to cover the needle cannula.