Vacuum Pump Bearing Cage Retainer for Safe Cage Ejection Control
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Solution Overview
Problem
Turbomolecular pumps often fail due to contamination causing axial displacement and ejection of the bearing cage, leading to potential catastrophic failures and contamination of instruments, with existing solutions failing to safely manage such failures.
Innovation Solution
A bearing cage retainer that limits longitudinal axial displacement of the outer race and engages the bearing cage only in a failure configuration, maintaining separation of rolling elements and allowing the cage to remain rotatable, thereby preventing complete ejection and enabling safe shutdown of the pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bearing cage is left unrestrained during operation, then the pump can operate smoothly during normal conditions, but the bearing cage may become axially displaced and ejected during operation due to contamination
Solution Approach 1:
The bearing cage retainer is pre-installed in the bearing assembly during manufacturing, positioned to be disengaged from the bearing cage during normal operation but ready to engage if axial displacement occurs. This preliminary positioning allows the pump to operate smoothly while having safety protection already in place.
Solution Approach 2:
The bearing cage retainer acts as an intermediary component between the bearing cage and the bearing assembly. It provides a safety mechanism that can engage with the bearing cage if axial displacement occurs, preventing ejection without interfering with normal operation when disengaged.
2Reliability
If a retainer is added to prevent bearing cage ejection, then catastrophic failures are prevented, but the device complexity increases
Solution Approach 1:
The bearing cage retainer is designed as a separate, extractable component that can be independently installed and removed. This extraction approach allows the safety function to be added without permanently complicating the basic bearing structure, and the retainer can be accessed separately during maintenance.
Solution Approach 2:
The bearing cage retainer is designed as a simple, inexpensive component that can be easily replaced if needed. Rather than making the entire bearing assembly more complex, a simple sacrificial safety component is added that provides protection at minimal cost and complexity.
3Reliability
If the retainer engages the bearing cage during normal operation, then the bearing cage is restrained, but the bearing cage rotation and pump operation are interfered with
Solution Approach 1:
The bearing cage retainer is designed with dynamic engagement characteristics - it remains disengaged during normal operation to allow free rotation of the bearing cage and smooth pump operation, but automatically engages if axial displacement occurs. The retainer's geometry allows it to transition from a non-intrusive state to a restraining state based on operating conditions.
Solution Approach 2:
The retainer is pre-positioned to provide anti-action only when needed - it is arranged to counteract axial displacement forces only if the bearing cage moves out of position, while leaving normal rotational operation unaffected. The preliminary positioning ensures protection is available without continuous interference.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A bearing cage retainer (11) for a rolling element rotor bearing in a vacuum pump. The bearing cage retainer being configured to have an operational arrangement in which, at the maximum longitudinal axial displacement limit of the outer race (5) in the direction of the retainer, the bearing cage retainer is disengaged from the bearing cage (7), and a failure configuration where the dislocation of the bearing cage by a longitudinal axial displacement of the bearing cage relative to the outer race in the direction of the retainer and in which the bearing cage retainer engages said bearing cage and the bearing cage maintains the separation of the rolling elements within the bearing.