The injection device comprises: - a static structure (2) comprising a first gear member (14), - a dynamic structure (3) comprising a medicine container (11), means (6, 7, 8, 12) for pushing liquid medicine out of said medicine container (11) for its injection to a patient, and a second gear member (13) engaged with the first gear member (14), - a drive member (4) for driving one (14) of the first and second gear members (13, 14) so as to cause the dynamic structure (3) to move relative to the static structure (2) along a predetermined direction (D) due to the engagement between the first and second gear members (13,14), and - clutch means (23, 25, 28) for maintaining engagement between the first and second gear members (13, 14) in normal condition of the injection device, and for allowing disengagement of the first and second gear members (13, 14) upon a shock received by the injection device along the predetermined direction (D).
