The present invention relates to a handheld injection device comprising a housing (10), a piston rod (130) located within the housing (10), a drive member (100) and a power reservoir (110) for driving the drive member (100). The drive member (100) is permanently coupled to the piston rod (130), with the drive member (100) being axially movable between a dose setting position, in which the drive member (100) is rotationally constrained to the housing (10), and a dose dispensing position, in which the drive member (100) is rotationally de-coupled from the housing (10). The power reservoir (110) comprises a reverse wound flat spiral spring having a first end attached to a first spool (120) and a second end attached to a second spool, which is axially and rotationally constrained to drive member (100).本發明是有關於一種手提注射裝置:包含一殼體(10)、一設置在殼體(10)之內的活塞桿(130)、一驅動構件(100)以及一用於驅動驅動構件(100)之動力儲存器(110)。驅動構件(100)係永久耦接至活塞桿(130),其中驅動構件(100)係可在一劑量設定位置與一劑量分配位置之間軸向移動,於劑量設定位置中,驅動構件(100)係旋轉受限於殼體(10),而於劑量分配位置中,驅動構件(100)係與殼體(10)旋轉地耦合。動力儲存器(110)包含一反向纏繞的平的螺旋形彈簧,其具有一裝設至一第一捲軸(120)之第一端與一裝設至一第二捲軸之第二端,其係軸向地且旋轉地受限於驅動構件(100)。I、II‧‧‧主軸11‧‧‧主要殼體12‧‧‧近端蓋13‧‧‧匣筒固持器20‧‧‧調撥把手30‧‧‧分配按鈕80‧‧‧劑量指示器90‧‧‧滑動計量器106‧‧‧近端齒部/花鍵介面110‧‧‧送進彈簧
