| 摘要 |
Injection devices are known for the self administration of medicament by patients in which 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 a 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bung within the cartridge to be moved both to a maximum dispense position within the cartridge and to be fully withdrawn from the cartridge to allow for replacement of the cartridge.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 second piston ( 42 ) is successively moved in relation to a first end of a medicament cartridge ( 8 ) containing a medicament selectively to drive a bung ( 10 ) into the medicament cartridge ( 8 ), the drive mechanism comprising a means ( 36 ) defining a passageway ( 38 ), a first piston ( 40 ) and the second piston ( 42 ), in which the passageway ( 38 ) has a first end and a second end, the first piston ( 40 ) closing the first end of the passageway ( 38 ) and a first end of the second piston ( 42 ) closing the second end of the passageway ( 38 ) to define a chamber in the passageway ( 38 ), a non-compressible medium being contained within the chamber such that a first relative movement in a first direction at the first end of the passageway ( 38 ) results in a second relative movement in a direction opposite the first direction at the second end of the passageway ( 38 ). |
