WormScrew Jack:

Economical: Compact design,easy operation, convenient maintenance. 
Lowspeed, low frequency:Be suitable for heavy load, low speed, lowservice frequency.
Self-lock: Trapezoid screwhas self-lock function, it can hold up load without braking devicewhen screw stops traveling. 
Brakingdevice equipped for self-lock will be of malfunction accidentallywhen large jolt & impact load