短语词组短語derrick head span block 吊杆頭跨繩滑車derrick head purchase block 上吊貨滑車derrick head cargo block 吊杆頭起貨滑車;吊杆頭起重滑車;上吊貨滑車derrick head shipment block 吊杆頭起貨滑車derrick k head cargo block 吊杆頭起貨滑車 返回 derrick head block