VACUUM PUMP WITH BACK-UP BEARING ASSEMBLY

摘要

A vacuum pump has a back-up bearing assembly (15a, b) for allowing its rotor (14) to spin down safely without damaging the pump if the primary system (16a, b) becomes disabled. The drive shaft (10) of the rotor (14) is tubular and contains the back-up bearing assembly (15a, b) in its hollow interior (13). Back-up bearings (15a, b) are mounted onto a tubular center shaft (12) which is coaxial with and inside the drive shaft (10). An axial position sensor (25) is nested inside the center shaft (12) and light emitted from its light emitter is reflected by a reflective target inside the drive shaft (10) to detect the relative axial position of the drive shaft (10) with respect to the center shaft (12). A polymer sleeve (17) is attached to the end of the drive shaft (10) as a thermal compensator, which restricts the axial movement of the drive shaft.