Patent ID: 8840591

Claim:
A drive mechanism for a medication delivery device, comprising, in combination, a. a housing having a proximal end and a distal end; b. a rotation member axially fixed with respect to the housing, but rotatable with respect to the housing, and not accessible to a user of the drive mechanism, the rotation member is connected to a dose member that moves axially relative to both the housing and the rotation member during dose setting and a dose delivery; c. a drive member releasably coupled to the rotation member through two or more cooperating teeth, where the teeth are spaced a distance apart proportional to a settable dose and the drive member is movably fixed to the rotation member only during dose delivery; d. a stop member position within the housing that is fixed axially and rotationally relative to the housing, the rotation member, and the drive member, where the stop member is releasably coupled to the drive member and prevents rotational movement of the drive member with respect to both the housing and the rotational member during dose setting; e. a piston rod engaged through threads or teeth to the drive member such that movement of the drive member only causes the piston rod to be displaced in a distal direction with respect to the housing for delivering the dose; and f. a resilient member axially fixed to prevent movement relative to the housing, where the resilient member provides a force that prevents decoupling of the drive member and stop member during dose setting.