Powerpack sub-assembly

A powerpack sub-assembly for a medicament delivery device, the powerpack sub-assembly extending along an axis in an axial direction from a proximal end to a distal end, the powerpack sub-assembly comprising:

• a housing extending from the distal end of the powerpack sub-assembly;
• a flexible arm connected to the housing and extending proximally;
• a lock ring slidable in the axial direction relative to the housing;
• an activation ring slidable in the axial direction relative to the housing and relative to the lock ring, where the lock ring is arranged closer to the distal end of the powerpack sub-assembly than the activation ring;
• a connection mechanism to connect the activation ring to the lock ring during use, the connection mechanism comprising a connector on the activation ring and a corresponding connector on the lock ring;
• a spring engaged with a distal end of the activation ring such that the spring biases the activation ring in a proximal direction;
• and
• a lock mechanism that locks the powerpack sub-assembly after use, where the lock mechanism comprising a distally-facing surface on the lock ring that engages a corresponding proximally-facing surface on a proximal end of the flexible arm.