The invention refers to an injection device comprising a housing (10) containing a cartridge (20) containing a medicament and a movable bung (21), wherein the housing (10) comprises an inner thread (17), a piston rod (30) for moving the bung (21) during dose dispensing, wherein the piston rod (30) comprises an outer thread (31) engaging the inner thread (17) of the housing (10) a bearing (33) at its end facing the bung (21), and a driver (40) coupled to the piston rod (30) for driving the piston rod (30) during dose dispensing. In the unused delivery state of the device, the bearing (33) abuts the bung (21). The invention further refers to an assembly method for such an injection device.本發明提及一種注射裝置，包含：一殼體(10)，容納一匣筒(20)，該匣筒(20)容納一藥物及一可移動的塞子(21)，其中殼體(10)包含一內螺紋(17)；一活塞桿(30)，用於在劑量分配期間移動塞子(21)，其中活塞桿(30)包含一接合殼體(10)之內螺紋(17)之外螺紋(31)，以及一軸承(33)，軸承(33)於末端面向塞子(21)；以及一驅動器(40)，耦接至活塞桿(30)，用於在劑量分配期間驅動活塞桿(30)。在裝置之未使用的輸送狀態下，軸承(33)鄰接塞子(21)。本發明更進一步提及這種注射裝置之組裝方法。
