Design of Short-Pipe Restrictor of Hydrostatic Thrust Bearings

High stiffness hydrostatic bearings are needed in order to achieve precise motions of the machine components of ultra-precision machine tools or other precision machines. Design procedure of restrictors of hydrostatic thrust bearings, making bearing stiffness maximize under given conditions, is considered in the paper. In particular, the paper focuses on design of short pipe restrictors that are used in the hydrostatic thrust bearings in many industrial applications. Derived mathematical model predicting load capacity and stiffness of the hydrostatic bearings with short pipe restrictors are verified by compared with experimental results. Based on the derived mathematical model, an optimum condition of a ratio between the diameter and length of the short pipe restrictor is then derived. Designed short pipe restrictors are used in a water hydrostatic thrust bearing. Then the experimental results show that the bearing stiffness significantly increased. It is noted that the optimum condition of the restrictors is represented by defined non-dimensional parameters.