Patent ID: 8915886

Claim:
An autoinjector for receiving in use a syringe containing a dose of medicament, said syringe ( 12 ) comprising a syringe body ( 14 ) of generally cylindrical form, a needle ( 18 ) at the forward end of the syringe body, and a piston ( 20 ) slideably mounted in said syringe body for expressing a dose, said autoinjector comprising: a housing ( 10 ) for receiving in use said syringe ( 12 ) for sliding movement between a retracted position and an extended, injection position in which said needle ( 18 ) projects from said housing; a drive mechanism ( 30 - 36 ) for being released from an energised condition to drive the syringe forwards to the injection position and to expel a dose; wherein said drive mechanism includes: a plunger ( 36 ) adapted to drive said piston ( 20 ) in use; an intermediate drive member ( 34 ); a first compression drive spring ( 30 ) disposed between said intermediate drive member and said housing or a part associated therewith to urge said intermediate drive member forwardly ( 34 ), and a second compression spring ( 32 ) acting between said intermediate drive member and said plunger to urge said plunger ( 36 ) forwardly, the intermediate drive member ( 34 ) having an internal cylindrical space for receiving the rear end of said second compression spring ( 32 ), whereby following release of said drive mechanism, as it expands the second spring is surrounded along at least a major portion of its length by at least one of the cylindrical space and the internal bore of the syringe body.