1. A dose setting mechanism for a drug delivery device, preferably a re-installable drug delivery device, the mechanism comprising: a dose setting element (3), a drive element (4) for moving the piston rod in the distal direction during the dose delivery process, wherein the drive element (4) comprises a proximal drive element (4 ") and a distal drive element (4 '), a first clutch for coupling to disconnect the proximal drive element (4") and the dist an alalum driving element (4 '), spring means (7) for displacing the proximal actuating element (4 ") and the distal driving element (4') in the connected state during dose setting and dispensing, and engagement means (3a, 4a), associated with the proximal drive element (4 ”) and the dose setting element (3), characterized in that the engagement means (3a, 4a) comprise hooks (4a) provided on the fingers protruding from the proximal end of the proximal drive element (4”), and corresponding inwardly extending flange (3a) on the proxim at the far end of the dose setting element (3), so that the proximal drive element (4 ”) entrains the dose setting element (3) in the distal direction during dose delivery, but allows relative axial movement of the proximal drive element (4”) with respect to to the element (3) setting the dose in the proximal direction. 2. The dose setting mechanism according to claim 1, characterized in that the mechanism is a resettable mechanism, further comprising a dose button for transmitting force1. Механизм установки дозы для устройства доставки лекарственного вещества, предпочтительно повторно устанавливаемого устройства доставки лекарственного вещества, при этом механизм содержит:элемент (3) установки дозы,приводной элемент (4) для перемещения стержня поршня в дистальном направлении в процессе выдачи дозы, при этом приводной элемент (4) содержит проксимальный приводной элемент (4”) и дистальный приводной элемент (4'),первую муфту сцепления для соединения с возможностью разъединения проксимального
