The screw jack, also referred to as 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 pounds by the thread self-locking function, and the framework is simple, but the transmission effectiveness can be low and the come back stroke is gradual. The thread of the self-propelled screw jack does not have any self-locking action and has a brake. When the brake is released, the weight could be quickly lowered by itself and the return time can be shortened, however the framework of the jack is complicated. The screw jack can support heavy items for a long period, and the utmost lifting capacity has reached 100 tons, which is trusted. Following the horizontal screw can be mounted on the low part, the weight can be traversed at a small distance.
Principle useful:
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 set of conical gears to drive the screw to rotate and force the lifting sleeve to ensure that the pounds rises or decline.
Instructions:
1. Before use, it is necessary to check if the jack is normal, whether the components are flexible, add lubricating oil, and correctly estimate the excess weight of the large object. Make use of a jack of suitable tonnage and avoid overloading.
2. Adjust the method of supporting one’s teeth on the rocker. First of all, turn the rocker straight 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 deal with along, and the pounds will rise. When the red warning line appears on the lifting sleeve, the handle should be stopped immediately. If you need to lower one’s teeth in the contrary direction, the fat will start to fall.
Precautions:
1. Generally keep the top of machine clean, verify the internal structure regularly, make the pinion in the rocker flexible and dependable, and 
lift the lifting sleeve freely.
2. The friction surface between your lifting sleeve and the casing must be oiled at any time. Other oil filling holes ought to be lubricated regularly.
3. In order to consider the safety in use, avoid Conveyor Chains overloading, work with illness, it is not appropriate to use multiple units to avoid danger.