The ordinary screw jack depending on the thread self-lockingaction support heavy item, the structure is simple, but the transmission efficiency is low, the return trip is slow.
普通螺旋千斤顶靠螺纹自锁作用支持重物,构造简单,但传动效率低,返程慢。
2
From falls screw jack's thread non-self-lockingaction, is loaded with the brake.