Patent ID: 8357120

Claim:
An injection device comprising a helical torsion spring ( 12 ) operatively connected to a dose setting member ( 1 ), the dose setting member ( 1 ) being adapted to set a dose to be ejected from the injection device, and a rotatably mounted display member adapted to display the dose to be ejected from the injection device in accordance with a setting of the dose setting member ( 1 ), the rotatably mounted display member being rotatable over an angle corresponding to at least one revolution of the display member, and wherein the device further comprises a drive member for driving a non-rotating threaded piston rod, the drive member having a threaded surface for engaging the thread on the piston rod, the drive member being rotatable within the device but axially fixed and wherein a ratchet couples the dose setting member to the drive member so that the dose setting member is moveable in a first direction to set a dose, the first direction being against the bias of the torsion spring, and being moveable in a second direction with the bias of the spring in order to reset or reduce a set dose without rotating the drive member, and wherein the ratchet retains the dose setting member from rotating under influence of the spring and wherein upon release of a latch the spring drives the drive member to rotate, thereby axially advancing the piston rod, and wherein rotation of the drive member is accompanied by rotation of the dose display member which returns to a zero position upon completion of the ejection of the dose.