US Patent 7195613 Injection device

Injection devices are known for the self administration of medicament by patients, in which 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 the like 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bung within the cartridge to be moved both to a maximum dispense position within the cartridge and to be fully withdrawn from the cartridge to allow for replacement of the cartridge.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 injection device is disclosed in which a piston 42 comprises a first piston part 44 guided for linear movement to selectively drive a bung 18 and a second piston part 46 connected for pivoting movement with respect to the first piston part 44.