Drive mechanism for an injection device

Abstract

Injection devices are known for the self administration of medicament by patients. The medicament is typically contained within a cartridge located within the injection device. It is a problem that injection devices should be small enough to fit into a jacket pocket or a hand bag without difficulty. Also, the injection device must be of a size that enables a piston or similar used to drive the Cartridge bung within the cartridge to be moved both to a maximum dispense position within the cartridge and to be fully withdrawn from the cartridge to allow for replacement of the cartridge. A drive mechanism for an injecting device is disclosed in which the drive mechanism comprises a displaceable dosing spindle 6, a dial dose means 8, a transmission means 10, and a cable means 12, a piston comprising a plurality of nested piston members 30, 32, 34, displacement of the transmission means 10 causing the cable means 12 to move at least one of one of the nested piston members to drive a cartridge bung 18.

Dependencies are inferred from the claim text.