A power pack assembly for a medicament delivery device, the power pack comprising a plunger rod (64) extending along a longitudinal axis (L) and having a proximal and an opposite distal ends, an actuator (90) provided with a holding element (96) and configured to interact with a corresponding holding element on the plunger rod (64), a first force element (68) arranged to exert a force on the plunger rod； an actuator sleeve mechanism (119) arranged to releasibly lock said holding element (96) in engagement with the corresponding holding element of said plunger rod (64) such as to hold said first force element (68) in a tensioned state. The invention is characterised in that said actuator sleeve mechanism (119) comprises an actuator cap (134) configured to hold said holding element (96) in engagement with the corresponding holding element of said plunger rod (64) and an actuator sleeve (120) interconnected with said actuator cap (134) such that in relation to the actuator (90), said actuator cap (134) is moved a shorter distance than the actuator sleeve (120) when said actuator sleeve is distally displaced in relation to the distal housing part.藥物輸送裝置用的動力包組合體，該動力包包含柱塞桿(64)，沿著縱軸(L)延伸且具有近側端及相反之遠側端；致動器(90)，設有固持元件(96)，且被建構來與該柱塞桿(64)上的對應固持元件互相作用；第一力量元件(68)，被配置來在該柱塞桿上施加力量；致動器套筒機構(119)，被配置成可釋放地鎖定與該柱塞桿(64)之對應固持元件嚙合的固持元件(96)，以便將該第一力量元件(68)固持於拉緊狀態中。本發明之特徵為該致動器套筒機構(119)包含致動器套蓋(134)，其被建構來固持與該柱塞桿(64)之對應固持元件嚙合的固持元件(96)，且致動器套筒(120)與該致動器套蓋(134)互連，使得關於該致動器(90)，當該致動器套筒係關於該遠側外殼零件朝遠側地位移時，該致動器套蓋(134)被運動一段比該致動器套筒(120)較短的距離。
