A motorized drug delivery device configured to administer at least one pre-set dose of a medicament contained within a medicament container. The delivery device comprising a user activation system (13), a motor (22), a gear train (15) operatively coupled to the user activation system and the motor, and a piston plunger system (200) operatively coupled to the gear train. The piston plunger system comprises a piston plunger (50) and at least one plunger extension (42； 44) for extending a length of the piston plunger. The piston plunger system is configured to act on a stopper contained within the medicament container to deliver at least one pre-set dose of medicament. The user activation system comprises a mechanical automatic reset activation system for automatically resetting the drug delivery device after administration of the pre-set dose.機動化的藥物輸送裝置被建構來給予裝盛在藥物容器內之藥物的至少一預先設定劑量。該輸送裝置包含使用者啟動系統(13)；馬達(22)；齒輪系(15)，操作地耦接至該使用者啟動系統(13)及該馬達(22)；與活塞柱塞系統(200)，操作地耦接至該齒輪系。該活塞柱塞系統包含活塞柱塞(50)及至少一柱塞延伸件(42；44)，用於延伸該活塞柱塞之長度。該活塞柱塞系統被建構來作用在該藥物容器內所含有的塞子上，以輸送藥物之至少一預先設定劑量。該使用者啟動系統包含機械式自動重置啟動系統，其在該預先設定劑量的投藥之後自動地重置該藥物輸送裝置。
