Taking the (SWL screw jack) as an example, its structural form is mainly divided into two categories, namely Type 1 and Type 2. The characteristic of the Type 1 structure is that the screw in the middle of the jack will perform axial movement, that is, the screw will move up and down reciprocally. Through this kind of movement, the function of lifting or lowering is achieved. However, the Type 2 structure is different. In this structure, the screw does not move up and down reciprocally, but rotates instead. At this time, the nut on the screw will move up and down with the rotation of the screw, thereby performing the lifting function.
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