Abstract
This research studies a new concept of sealed pad hydrostatic bearing. The goal of this development is to remove or reduce the cost issues associated with complex circulatory systems of traditional hydrostatic bearings. Based on the concept of mechanical seal, a sealing bearing element is added to the opening of a pressurized fluid pocket in contact with a guideway to prevent or at least significantly reduce fluid leaking. The hydrostatic pressure in the pocket still takes most of the load. Thus, this new sealed pad hydrostatic bearing is a combination of a traditional hydrostatic bearing with lightly loaded sliding contact bearing. The key issues of this new bearing concept are positioning/motion precision and sealing ability. These issues are studied experimentally by building and testing several prototype bearing devices with different sealing bearing materials. Test results show that several polished bearing guideway material pairs can achieve a positioning precision between 1-5μm under the condition of contacting pressure on the solid sealing bearing element up to 0.4-2.0 MPa. It is believed that this precision can be further improved by refining the prototypes and test setups. The friction coefficient was measured to be comparable to that of a regular sliding contact bearing. At these solid contact pressure levels, fluid pressure inside the pocket can be from 10% to 80% of the contacting pressure on the solid sealing bearing element, depending on allowed fluid leakage rate.