US Patent 8491538 Injection device comprising several coupling mechanisms

An injection device including a drive unit, a delivery unit, a dosing unit, a trigger for triggering an injection, a first coupling mechanism between the drive unit and the delivery unit, and a second coupling mechanism between the dosing unit and the drive unit, wherein the drive unit is tensioned by a rotation of the dosing unit and when the drive unit is tensioned the first coupling mechanism is disengaged and the second coupling mechanism is engaged, and wherein when an injection is triggered first the first coupling mechanism is engaged and then the second coupling mechanism is disengaged. In some embodiments, the device may include a third coupling mechanism which only releases the delivery unit after the engagement and disengagement which follow a triggering.