Multi-stage cylinder has to be moved upper stage and lower stage at the same time when going up or down. If lower stage moves first then upper stage moves afterwards, passenger can be felt shaking or shocking when lower stage completely up. Which leads passengers feel uncomfortable and anxiety when riding. However, both upper and lower stage moves simultaneously oil pressure and oil flow are steady. Therefore, speed of elevator is gradually up and down. That makes passenger feels comfortable.
By above reasons, multi-stage cylinder is used at sensitive place and Donam Engineering has been providing multi-stage cylinder with own developed technology since April, 2008.