Patent ID: 6340357
Filing Date: 2002-01-22
Classification: A61M,Y10S

Abstract:
A drug delivery device for dispensing set doses from a cartridge of the type containing medicine sufficient for a number of dosed injections and a piston which can be moved forward inside the cartridge to expel doses of medicine, said device comprising:a cartridge holder having open and closed positions, and into which a cartridge can be loaded when in an open position; a cartridge holder switch which generates a signal when said cartridge holder is moved from said open position to said closed position; an electrical motor; a piston rod coupled to said motor for movement responsive to activation of said motor; and an electronic circuit which receives said signal from said cartridge holder switch and activates said motor responsive to receiving said signal to move said piston rod in a first direction, towards the piston of a cartridge which has been loaded in said cartridge holder; and wherein said electronic circuit further includes a sensor to sense the power consumption of said motor and stops said motor, and thereby the movement of said piston rod in said first direction, upon detecting a predetermined increase in power consumption, indicating that the piston rod has encountered such a piston, whereby said circuit automatically sets a desired initial position of said piston rod whenever a new cartridge is loaded.