driving a bung of the medicament cartridge a drive mechanism including a motor for providing an output drive to the piston rod for delivering the medicament and control means for controlling operation of the device the device is additionally provided with a bung sensor for sensing when the piston rod is in contact with the bung and the control means is operative for advancing the drive of the piston rod towards the bung application_number US 201013145835 A description in fig1 a medicament delivery device 1 comprises a case 2 having a display 3 for displaying functional information relating to the operation of the medicament delivery device including the set dose number of doses remaining in the medicament cartridge user interface buttons 4 5 and 6 are provided to allow the user to operate the injector including priming setting a dose opening a medicament cartridge holder and door 7 and activating the dispensing of the set dose a threaded needle attachment 8 is provided to which a needle can be attached for dose delivery and subsequently removed and discarded a cover not shown may be provided to fit over the lower portion of the case 2 to assist in protect the device from the ingress of particles and fluid fig2 shows the medicament delivery device 1 with the cartridge holder and door 7 in an open position for receiving a replacement medicament cartridge 9 fig3 shows the cartridge holder and door 7 in more detail with the cartridge 9 seated therein the holder 7 is pivotally fixed to the case 2 by an attachment 11 so that the holder 7 can move between an open position see fig2 and a closed position see fig1 an arm.