Why can't hydraulic jacks be permanently pivoted?

Under the same specifications, hydraulic jacks and hydraulic jacks of the same tonnage are used to hoist the same hanging objects, and it is more labor-saving to apply hydraulic jacks. However, hydraulic jacks can often fulcrum and hang objects, but hydraulic jacks cannot be fulcrum for a long time. Why?

 

When the hydraulic jack is used to hoist the objects, the operator continuously pushes the remote rod, and continuously pulls the hydraulic oil out of the fuel tank of the car and embeds it in the hydraulic cylinder, so that the gas pressure in the hydraulic cylinder is expanded, and the large hydraulic cylinder is promoted to rise. Finally lift the object.

 

When the hydraulic jack is used to lift the object at the permanent fulcrum, the large hydraulic cylinder subjected to the force of the lifting object continuously presses downward, and now the user no longer presses the remote lever once, the hydraulic oil in the hydraulic cylinder will only receive The working pressure released by the large hydraulic cylinder downwards, the hydraulic oil will be continuously put on the hydraulic cylinder. In addition, the hydraulic oil in the hydraulic cylinder is reduced, and the large hydraulic cylinder will also be relatively reduced.

 

Hydraulic jacks can fulcrum and hang objects for more than ten minutes or ten minutes. Therefore, when using hydraulic jacks to hoist objects, they should try to work immediately, or place a solid fulcrum column under the hanging objects.