The screw jack, also called the mechanical jack, is driven by a manpower through a screw pair, and a screw or nut sleeve can be used as a jacking member. The normal screw jack supports the weight by the thread self-locking function, and the framework is simple, but the transmission performance is usually low and the come back stroke is sluggish. The thread of the self-propelled screw jack has no self-locking action and is equipped with 
a brake. When the brake is normally released, the weight can be quickly lowered by itself and the return period can be shortened, but the structure of the jack is complicated. The screw jack can support heavy objects for a long period, and the utmost lifting capacity has reached 100 tons, which is widely used. Following the horizontal screw is usually mounted on the low part, the weight can be traversed at a little distance.
Principle of use:
The mechanical jack is one of the types of manual lifting tools. Its compact structure makes reasonable usage of the rocking of the rocker to rotate the pinion. It really is operated by a pair of conical gears to drive the screw to rotate and press the lifting sleeve so that the pounds rises or decline.
Instructions:
1. Before use, it’s important to check if the jack is regular, whether the components are flexible, add lubricating oil, and properly estimate the pounds of the large object. Use a jack of suitable tonnage and prevent overloading.
2. Adjust the technique of supporting the teeth on the rocker. Speed reducer Firstly, turn the rocker straight in the clockwise path by hand to help make the lifting sleeve quickly ascend the top weight.
3. Insert the handle into the rocker hole, move the handle up and down, and the excess weight will rise. When the red warning line shows up on the lifting sleeve, the handle should be stopped instantly. If you need to lower one’s teeth in the opposite direction, the excess weight will start to fall.
Precautions:
1. Always keep the top of machine clean, check the internal structure frequently, make the pinion in the rocker flexible and reliable, and lift the lifting sleeve freely.
2. The friction surface between your lifting sleeve and the housing must be oiled at any time. Other oil filling holes ought to be lubricated regularly.
3. In order to consider the security in use, avoid overloading, use illness, it is not appropriate to make use of multiple units to avoid danger.