US Patent 7125395 Device for controlled delivery of an injectable liquid

A device for the controlled delivery of an injectable liquid from a liquid container, wherein a flexible force transferring means transfers the drive force of a drive wheel onto a piston which can be slid axially in the device, a preferably permanently acting restoring force of a spiral spring is applied to the drive wheel in order to advance the piston and expel the liquid, and a locking means locks the drive wheel against rotation and releases the drive wheel to expel the liquid. In one embodiment, the amount of liquid expelled can be indicated by audible clicks and, in one embodiment, the drive wheel moves only incrementally when the locking mechanism releases the drive wheel.