Needle insertion mechanism for an injection or infusion device

A needle insertion mechanism for an injection device comprising:

• a needle holder holding a needle, the needle holder adapted to be advanced from a needle retracted position to a needle inserted position under a needle insertion bias;
• a slider adapted to be moved from a first position retaining the needle holder in the retracted position, towards a second position allowing movement of the needle holder to the inserted position;
• an intermediate member operatively arranged between the needle holder and the slider, the intermediate member configured to be moveable from a blocked position securing the needle holder in the retracted position to a release position releasing the needle holder for movement along a needle axis into the inserted position,
• wherein:
• a biased gearing between the intermediate member and the needle holder is configured for biasing the intermediate member towards the release position, and
• a lock between the intermediate member and the slider is configured for locking the intermediate member in the blocked position against the bias of the biased gearing, and
• movement of the slider towards the second position unlocks the lock and the biased gearing moves the intermediate member into the release position thereby releasing the needle holder.