The present invention relates to a medicament delivery device, comprising a housing having a proximal end and a distal end； a hollow plunger rod being arranged within the housing； a telescopic dose drum being concentrically arranged between the housing and the plunger rod, the telescopic dose drum being bidirectional movable in relation to the housing and in relation to the plunger rod when setting a dose and delivering a dose； and plunger rod driving means for driving the hollow plunger rod towards the proximal end. The plunger rod driving means comprises: a hollow ratchet arm drum being movably arranged within the hollow plunger rod and being fixedly connected to the telescopic dose drum, wherein the hollow ratchet arm drum and the hollow plunger rod are releasably coupleable to each other； a dose activator having a longitudinal rod being movably arranged within the hollow ratchet arm drum, wherein the longitudinal rod and the hollow ratchet arm drum are releasably coupleable to each other； a dose setting knob being fixedly connected to the dose activator and being releasably coupleable to the hollow ratchet arm drum； and a resilient element arranged between the hollow ratchet arm drum and the dose activator biasing them in a direction decoupling the longitudinal rod of the dose activator from the hollow ratchet arm drum and coupling the dose setting knob with the hollow ratchet arm drum, such that during a dose setting, turning of the dose setting knob by a user forces the hollow ratchet arm drum and the telescopic dose drum to rotate together.本發明有關藥物輸送裝置，包括外殼，具有近側端及遠側端；中空柱塞桿，被配置在該外殼內；可伸縮的劑量圓筒，被同心地配置於該外殼與該柱塞桿之間，當設定一劑量及輸送一劑量時，該可伸縮的劑量圓筒係可關於該外殼及關於該柱塞桿雙向運動；及柱塞桿驅動機制，用於驅動該中空柱塞桿朝該近側端。該柱塞桿驅動機制包括：中空棘輪臂圓筒，可運動地配置在該中空柱塞桿內及固定地連接至該可伸縮的劑量圓筒，其中該中空棘輪臂圓筒及該中空柱塞桿係可釋放地耦接至彼此；劑量啟動器，具有可運動地配置在該中空棘輪臂圓筒內之縱長桿，其中該縱長桿及該中空棘輪臂圓筒係可釋放地耦接至彼此；劑量設定鈕，被固定地連接至該劑量啟動器，且係可釋放地耦接至該中空棘輪臂圓筒；及彈性元件，被配置於該中空棘輪臂圓筒及該劑量啟動器之間，使它們於一方向中偏向，而斷開該中空棘輪臂圓筒與該劑量啟動器之縱長桿的耦接，並使該劑量設定鈕與該中空棘輪臂圓筒耦接，使得在劑量設定期間，藉由使用者轉動該劑量設定鈕將強迫該中空棘輪臂圓筒及
