FIELD: medicine.SUBSTANCE: invention relates to medical equipment, namely to a drive unit for a device for medication delivery, the device for medication delivery and to the application of a spring in the device for medication delivery. The drive unit for medication delivery, made with a possibility of returning into an initial position, contains a case, a plunger rod, a drive element, intended for the displacement of the plunger rod in the distal direction to the terminal position when a dose is supplied, and a stopper. The case has the proximal end and the distal end. The plunger rod is made with a possibility of rotation relative to the case and with a possibility of displacement in the axial direction relative to the case between the proximal initial position and the distal terminal position. The drive element is made with a possibility of being brought into action for being brought into interaction with the plunger rod in order to form the first blocking means, made with a possibility of unblocking. The first blocking means can be brought into action to block the movement of the plunger rod in the proximal direction relative to the drive element. The stopper is made with a possibility of being brought into action for its bringing into interaction with the plunger rod in order to form the second blocking means, made with a possibility of unblocking. The second blocking means can be brought into action to block the movement of the plunger rod in the proximal direction relative to the case. When the drive unit is in the drive mode, the first and the second blocking means are blocked in such a way that the first blocking means and the second blocking means prevent the movement of the plunger rod in the proximal direction from the terminal position into the initial position. To transfer the drive unit from the drive mode into the mode of return into the initial position the plunger rod can be turned relative to the drive element to unblock the first blocking means.
