| 主权项 |
1. A drug delivery device comprising:
a compartment adapted to receive a cartridge in a loaded position, the cartridge comprising a body portion, a distal outlet portion and an axially displaceable piston with a proximal portion, an electronically controlled expelling assembly comprising an axially displaceable piston drive member adapted to engage the proximal piston portion of the cartridge, the piston drive member being moveable between a proximal loading position and a distal loaded position in engagement with the proximal piston portion, a proximity sensor system adapted to provide a varying output indicative of a varying distance between the piston drive member and the proximal piston portion, a first light source providing a light directed at least in part against the proximal piston portion of the cartridge, a light sensor coupled to the piston drive member and adapted to measure light from the first light source reflected from the proximal piston portion of the cartridge, whereby the first light source and the light sensor provide at least in part a proximity sensor system adapted to provide an output indicative of the distance between the proximal piston portion and the piston drive member a controller coupled to the proximity sensor system and the expelling assembly and configured to control the expelling assembly to move the piston drive member from the loading position to the loaded position and stop movement when the controller based on input from the proximity sensor system determines that the loaded position has just been reached, the controller further configured to: determine a first condition in which the piston drive member and the proximal piston portion of the cartridge are at a loading distance from each other corresponding to the loading position of the piston drive member and in which a low level of reflected light is directed to and measured by the light sensor, determine a second condition in which the piston drive member and the proximal piston portion of the cartridge are at an intermediate distance from each other corresponding to an intermediate position of the piston drive member and in which an intermediate level of reflected light is directed to and measured by the light sensor, determine a third condition in which the piston drive member and the proximal piston portion of the cartridge are in engagement with each other corresponding to the loaded position of the piston drive member and in which a low level of reflected light is directed to and measured by the light sensor, and control the expelling assembly to move the piston drive member from the loading position, through the intermediate position to the loaded position, and stop movement when the loaded position has been reached. |
