| 摘要 |
A hydrostatic bearing assembly is provided for a carriage and guide rail combination in wich the carriage (12) straddles and is guided by the guide rail (18). The guide rail (18) presents two outwardly facing parallel faces (24, 26) which cooperate with a pair of inwardly directed spaced apart hydrostatic pads (28, 38) which, in use, are spaced by a working clearance from the parallel faces (24, 26) of the guide rail (18). One of the parallel faces (26) is machined to a high level of precision alignment and flatness, and the hydrostatic pad (28) cooperating therewith is fixed relative to the carriage, but is adapted to exert gap control via a servo system so as to control the motion of the carriage (12) along the rail (18). The second pad (38) is movably mounted on the carriage (12) and cooperates with the other face (24) of the rail (18) only to apply a force thereto, i.e. without any gap control. Consequently, the motion of the assembly along the rail (18) is dictated by the flatness and alignment of the precision machine surface (26) of the rail (18). There is also shown a method of guiding a housing, such as the carriage (12), relative to a fixed structure (such as a bed (10)) by means of the rail (18) by applying hydrostatic fluid under pressure to the rear of the movable pad (38) of the hydrostatic assembly so as to force the latter towards the guide rail (18) whilst providing hydrostatic fluid and pressure through fluid flow restrictor means to pockets in the fixed brackets (28) and floating brackets (38). |
