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Internal structure of the screw jack Nov 07, 2018

The screw jack, also known as the mechanical jack, is driven by a manpower through a screw pair, and a screw or nut sleeve is used as a jacking member. The ordinary screw jack supports the weight by the thread self-locking function, and the structure is simple, but the transmission efficiency is low and the return stroke is slow. The thread of the self-propelled screw jack has no self-locking action and is equipped with a brake. When the brake is released, the weight can be quickly lowered by itself and the return time can be shortened, but the structure of the jack is complicated. The screw jack can support heavy objects for a long time, and the maximum lifting capacity has reached 100 tons, which is widely used. After the horizontal screw is mounted on the lower part, the weight can be traversed at a small distance.

Principle of use:

The mechanical jack is one of the types of manual lifting tools. Its compact structure makes reasonable use of the rocking of the rocker to rotate the pinion. It is operated by a pair of conical gears to drive the screw to rotate and push the lifting sleeve so that the weight rises or decline.


1. Before use, it is necessary to check whether the jack is normal, whether the components are flexible, add lubricating oil, and correctly estimate the weight of the heavy object. Use a jack of appropriate tonnage and avoid overloading.

2. Adjust the method of supporting the teeth on the rocker. Firstly, turn the rocker directly in the clockwise direction by hand to 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 weight will rise. When the red warning line appears on the lifting sleeve, the handle should be stopped immediately. If you need to lower the teeth in the opposite direction, the weight will start to fall.


1. Always keep the surface of the machine clean, check the internal structure regularly, make the pinion in the rocker flexible and reliable, and lift the lifting sleeve freely.

2. The friction surface between the lifting sleeve and the housing must be oiled at any time. Other oil filling holes should be lubricated regularly.

3. In order to consider the safety in use, avoid overloading, work with illness, it is not appropriate to use multiple units to avoid danger.