Turbomolecular Pump Strut Constriction for Flow Resistance
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Solution Overview
Problem
Conventional vacuum pump holders with massive, constantly dimensioned struts in the intake area create flow obstacles, reducing pump efficiency due to excessive material and rigidity demands for supporting high shaft loads.
Innovation Solution
The holder's struts are tapered or constricted in the radially central area to reduce flow resistance while maintaining axial and torsional rigidity, with end areas made more massive to absorb greater loads, allowing for a more efficient vacuum pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the holder is designed to be massive with constant rectangular cross-section struts, then the radial and axial rigidity is sufficient to support high shaft loads, but the flow resistance increases and pump efficiency decreases
Solution Approach 1:
The strut cross-section is varied along its length: the central area has a reduced cross-section to minimize flow resistance, while the end regions (near the bearing support and housing connection) maintain larger cross-sections to ensure adequate load-bearing capacity. This local differentiation allows the structure to have different properties in different regions - slender in the flow-critical central area, massive in the load-critical end areas.
2Ease of manufacture
If the struts are made with constant cross-section, then the manufacturing is simple, but the flow resistance is excessive and material is wasted
Solution Approach 1:
The cross-sectional parameters of the struts are changed along their length. The central portion has a smaller cross-section than the end portions, creating a tapered or constricted geometry. This parameter variation optimizes the balance between flow resistance (reduced by the smaller central cross-section) and structural strength (maintained by the larger end cross-sections).
3Productivity
If the struts are constricted in the central area, then the flow resistance is reduced and efficiency increases, but the rigidity might be compromised
Solution Approach 1:
The rigidity is maintained by preserving larger cross-sections at the critical end regions of the struts, where the loads are highest and structural stability is most important. The central constriction is positioned in the region least critical for load-bearing, allowing flow resistance to be reduced without significantly compromising overall rigidity.
4Reliability
If the holder design prioritizes load-bearing capacity, then the bearing support is reliable, but the material usage increases and flow obstacles are created
Solution Approach 1:
The strut cross-sectional parameters are optimized along their length, with reduced dimensions in the central flow-critical area and maintained or increased dimensions at the load-critical end areas. This creates a non-uniform geometry that uses material only where structurally necessary, minimizing overall material consumption while maintaining bearing support reliability.
Data Source
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AI summary
The invention relates to a vacuum pump, in particular a turbomolecular pump, comprising a housing, a rotatably mounted shaft for at least one pumping stage, and a bearing support located in an intake region of the vacuum pump for supporting the shaft. The support comprises a central section accommodating the bearing and a plurality of struts extending at least substantially in a radial direction, which connect the central section to a housing ring connected to the housing. At least one of the struts has a constriction in a radially central region.