Needle insertion mechanism for an injection device with an improved impact resistance

A needle insertion mechanism for an injection device, comprising:

• a housing;
• a needle holder holding an insertion needle, the needle holder linearly guided by the housing and movable along a longitudinal axis of the needle;
• a slider linearly guided by the housing and transversely moveable with respect to the longitudinal axis of the needle from a first slider position to a second slider position,
• wherein in the first slider position, the slider is operatively coupled to the needle holder thereby retaining the needle holder in a needle retracted position against a bias of a spring force acting on the needle holder,
• wherein in the second slider position, the slider is decoupled from the needle holder and the needle holder is moved into a needle insertion position by the spring force;
• and
• a gear rack arranged between the slider and the housing, wherein the gear rack blocks a movement of the slider from the first slider position to the second slider position and is moveable by an active drive for unblocking the movement of the slider, and wherein the active drive subsequently moves the slider to the second slider position,
• wherein the active drive comprises a rotatable cam shaft in a bearing engagement with said housing, and the rotatable cam shaft comprises a blocking member forming a motion-link system between the cam shaft and the slider.