Injection device

Injection device for injecting liquid medicine to a patient, comprising:

• a static structure comprising a first gear member,
• a dynamic structure comprising a medicine container, means for pushing liquid medicine out of said medicine container for its injection to a patient, and a second gear member engaged with the first gear member,
• a drive member for driving one of the first and second gear members so as to cause the dynamic structure to move relative to the static structure along a predetermined direction due to the engagement between the first and second gear members, and
• clutch means for maintaining engagement between the first and second gear members in normal condition of the injection device, and for allowing disengagement of the first and second gear members upon a shock received by the injection device along the predetermined direction,
• said clutch means comprising:
• means for allowing the other of the first and second gear members to move away from said one of the first and second gear members and thus disengage from said one of the first and second gear members, wherein the means for allowing the other of the first and second gear members to move away from said one of the first and second gear members comprise at least one flexible member through which the other of the first and second gear members is mounted in the injection device,
• a blocking member which, in a predetermined position, prevents the other of the first and second gear members from moving away from said one of the first and second gear members, and
• a return spring for maintaining the blocking member in the predetermined position, the force of said return spring being overcomeable by the other of the first and second gear members upon a shock received by the injection device along the predetermined direction and moving the other of the first and second gear members away from said one of the first and second gear members.