DOSE SETTING DEVICE

摘要

In a drug delivery device a dose to be apportioned from a cartridge is set by changing the relative position of co-operating dose setting elements (3, 5) and is injected by pressing a button (5) until this button abuts a stop (6). By operation of count up (7) or count down (8) buttons the dose is set and read into an electronic circuit (9) comprising a microprocessor and the dose setting movement of the dose setting elements relative to each other is performed by a motor (11) controlled by the circuit in accordance with the read in dose. The set dose is shown on a display (10). The motor (11) is further controlled to perform certain movements of the piston rod (3) so as retraction of this rod when a cartridge (1) is going to be changed an advancing of the piston rod to abutment with the piston (2) after the cartridge has been changed and further to advance this piston to expel air from the cartridge.