The present invention relates to a medical delivery device comprising a housing (10) a medicament container (16) arranged to be placed in said housing a stopper (18) movable within said container a medicament dispensing means attachable to said housing and to said container through which medicament can be expelled characterized in that the device further comprises a power unit (22) comprising a cover (24), a volute spring (26) arranged within said cover, and a pressure member (28) having a pressure pad (30) in contact with the stopper, a guide rod (34) extending into the volute spring and an annular ledge (32) in contact with the edges of the volute spring activation means (36) mechanically connected to the cover and to the housing and a spring locking means mechanically connected to said activation means, wherein said spring locking means (39) comprises a deformable ring-shaped member having (40) an inner diameter somewhat larger than the annular ledge, such that said ring-shaped member presents an oval shape when it is in contact with the annular ledge for locking the volute spring in a tensioned state.La présente invention porte sur un dispositif médical dadministration comprenant un boîtier (10) un contenant de médicament (16) conçu pour être placé dans ledit boîtier une butée (18) mobile à lintérieur dudit contenant un moyen de délivrance de médicament pouvant être lié audit boîtier et audit contenant au moyen duquel on peut expulser le médicament caractérisé en ce que le dispositif comprend en outre une unité dalimentation (22) comprenant un capot (24), un ressort en spirale conique (26) agencé à lintérieur dudit capot et un élément de pression (28) comportant un tampon de pression (30) en contact avec la butée, une tige de guidage (34) sétendant à lintérieur du ressort en spirale conique et un rebord annulaire (32) en contact avec les rebords du ressort en spirale conique un moyen dactivation (36) mécaniquement relié au capot et au boîtier et un moyen d
