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 ordinary screw jack supports the fat by the thread self-locking function, and the structure is simple, however the transmission effectiveness can be low and the come back stroke is slow. The thread of the self-propelled screw jack does not have any self-locking action and is equipped with a brake. When the brake is definitely released, the weight can be quickly lowered by itself and the return time can be shortened, but the framework of the jack is complicated. The screw jack can support heavy items for a long time, and the utmost lifting capacity has reached 100 tons, which is widely used. After the horizontal screw is usually mounted on the low part, the weight can be traversed at a little distance.
Principle useful:
The mechanical jack is one of the types of manual lifting tools. Its compact structure makes reasonable utilization of the rocking of the rocker to rotate the pinion. It is operated by a pair of conical gears to operate a vehicle the screw to rotate and press the lifting sleeve so that the excess weight rises or decline.
Instructions:
1. Before use, it is necessary to check if the jack is normal, whether the elements are flexible, add lubricating oil, and correctly estimate the weight of the heavy object. Use a jack of appropriate tonnage and prevent overloading.
2. Adjust the method of supporting the teeth on the rocker. 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 in to the rocker hole, move the handle along, and the weight will rise. When the red Conveyor Chain warning line appears on the lifting sleeve, the handle ought to be stopped instantly. If you need to lower the teeth in the opposite direction, the fat will start to fall.
Precautions:
1. Constantly keep the top of machine clean, check the internal structure regularly, make the pinion in the rocker versatile and reliable, and lift the lifting sleeve openly.
2. The friction surface between your lifting sleeve and the casing must be oiled anytime. Other oil filling holes should be lubricated regularly.
3. In order to consider the safety in use, avoid overloading, work with illness, it isn’t appropriate to make use of multiple units in order to avoid danger.