Spiral jacks rely on the interaction force between machines to complete lifting. Compared with hydraulic jacks, spiral jacks have a more stable structure and a larger lifting tonnage. However, spiral jacks have a disadvantage, which is slow return.

First of all, let's understand how the screw jack is reset. The screw jack rotates the small gear under the action of the lever to drive the large gear to rotate, and then drives the screw to rotate through the large gear to raise the top support in a spiral transmission manner.

On the return journey, the screw jack does not have a return valve and cannot press the top support back to its initial position under the weight of heavy objects. Therefore, it still needs to rotate the lever one by one to lower the top support around the screw. The process is relatively slow, but compared with hydraulic jacks, it is more stable and safe.

During the return process of a screw jack, gravity has no effect, so it needs to be manually operated almost the entire time, which is also one of the main differences between it and a hydraulic jack.