Spiral jacks have the characteristics of simple construction and excellent lifting ability. Both the top cover with anti slip function and the thickened base showcase the designer's exquisite ideas. In fact, the internal structure of the screw jack is also not complex, and each component has a clear division of labor. They cooperate with each other to achieve the effect of force transmission. The component that plays an important role in force transmission is undoubtedly its worm gear transmission device.

The worm gear transmission device is located at the bottom of the screw jack. Among them, the worm gear is equipped with deep groove ball bearings and thrust ball bearings, while the worm gear is equipped with powder metallurgy sleeves and thrust ball bearings. Such settings can not only improve the rotation accuracy of the jack gear, but also enhance the rigidity of the bearing device, and effectively reduce the vibration caused by force transmission when the jack lifts heavy objects.

Worm gear transmission is similar to spiral transmission and belongs to multi tooth meshing transmission. Because of this characteristic, the transmission process is very smooth and the noise generated is minimal. When the lead angle of the worm is less than the equivalent friction angle between the meshing teeth, the jack has self-locking ability and can achieve reverse self-locking, that is, only the worm can drive the worm wheel to operate, and the worm wheel cannot drive the worm to move. Just like the self-locking worm mechanism used in jacks, its reverse self-locking property can provide safety protection.

When the screw jack is subjected to external force applied by the handle or handwheel, the force will gradually be transmitted to the large and small gears as well as the worm gear. At this time, the worm gear will bear radial and axial forces, and the entire transmission system, including the lifting sleeve, will smoothly make upward or downward movements with the heavy object, thereby achieving the purpose of lifting the heavy object.