短语词组短语derrick head span block 吊杆头跨绳滑车derrick head purchase block 上吊货滑车derrick head cargo block 吊杆头起货滑车;吊杆头起重滑车;上吊货滑车derrick head shipment block 吊杆头起货滑车derrick k head cargo block 吊杆头起货滑车 返回 derrick head block