A drug delivery device , comprising: a housing , wherein said housing defines an opening and a chamber for a drug cartridge ; a movable door connected to said housing , having a range of movement between a fully open position and a closed position, wherein said door blocks access to said opening when said door is in said closed position; characterized in that : said door further comprises a transmission to couple between a motor of said device and said drug cartridge when said door is in said closed position; said device further comprises: a biasing element connected to said housing or said door , wherein said biasing element is positioned to interfere with the movement of said door by applying an opening force to open said door when said range of movement of said door is near said closed position, thus defining an exclusion zone; wherein said biasing element applies said opening force in the last 20-30 degrees of the rotation of said moveable door toward closure or when during the rotation of said movable door said door reaches the last 20-30% of said range of movement; and a locking mechanism between said door and said housing , said locking mechanism applies a locking force on said door greater and in an opposite direction to the force applied by said biasing element . a housing , wherein said housing defines an opening and a chamber for a drug cartridge ; a movable door connected to said housing , having a range of movement between a fully open position and a closed position, wherein said door blocks access to said opening when said door is in said closed position; characterized in that : said door further comprises a transmission to couple between a motor of said device and said drug cartridge when said door is in said closed position; said device further comprises: a biasing element connected to said housing or said door , wherein said biasing element is positioned to interfere with the movement of said door by applying an opening force to open said door when said range of movement of said door is near said closed position, thus defining an exclusion zone; wherein said biasing element applies said opening force in the last 20-30 degrees of the rotation of said moveable door toward closure or when during the rotation of said movable door said door reaches the last 20-30% of said range of movement; and a locking mechanism between said door and said housing , said locking mechanism applies a locking force on said door greater and in an opposite direction to the force applied by said biasing element . said door further comprises a transmission to couple between a motor of said device and said drug cartridge when said door is in said closed position; said device further comprises: a biasing element connected to said housing or said door , wherein said biasing element is positioned to interfere with the movement of said door by applying an opening force to open said door when said range of movement of said door is near said closed position, thus defining an exclusion zone; wherein said biasing element applies said opening force in the last 20-30 degrees of the rotation of said moveable door toward closure or when during the rotation of said movable door said door reaches the last 20-30% of said range of movement; and a locking mechanism between said door and said housing , said locking mechanism applies a locking force on said door greater and in an opposite direction to the force applied by said biasing element . <EOS>