Cage-like Rotor Stages for Turbo Molecular Pump Speed
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Solution Overview
Problem
Conventional turbo molecular pumps face challenges in achieving high pumping speed while maintaining a compact design, particularly for mass spectrometers, as they require large sizes and high costs to achieve low pressures, which limits their application in systems with minimal gas loads.
Innovation Solution
The introduction of novel cage-like rotor stages, which complement traditional rotor stages, allowing for increased pumping speed by extending rotor blade portions both radially and paraxially, thereby increasing the active pumping cross-section area and reducing the overall pump dimensions without compromising pumping power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large rotor diameter is used to increase pumping speed, then pumping speed is improved, but pump size and system cost increase
Solution Approach 1:
The patent extends rotor blades in the axial direction (adding a third dimension) rather than only increasing radial diameter. This creates a cage-like structure where blades protrude into the vacuum chamber, effectively increasing the pumping cross-section area without increasing the pump's radial footprint, thus resolving the contradiction between pumping speed and pump size.
2Speed
If rotor blade material strength is increased to withstand higher centrifugal forces, then rotational speed is improved, but blade material optimization is already at limit
Solution Approach 1:
By extending blades axially rather than increasing radial diameter, the patent increases the effective pumping area without proportionally increasing the centrifugal forces on the material. The axial extension adds pumping capacity while the radial dimensions (and thus centrifugal stress) remain constrained by material limits.
Solution Approach 2:
The patent employs composite construction with radial blades providing structural strength to withstand centrifugal forces, while axial blade extensions provide additional pumping surface area. This composite approach allows the structure to achieve higher pumping speed without requiring the entire blade structure to withstand maximum centrifugal stress.
3Volume of moving object
If pump size is reduced for compact design, then system size is improved, but pumping speed decreases
Solution Approach 1:
The cage-like rotor design with axially extending blades allows the pump to maintain a compact radial footprint while achieving high pumping speed through increased axial blade length. The pumping cross-section area is effectively increased by utilizing the axial dimension, decoupling pump size from pumping speed.
Solution Approach 2:
The patent creates a dynamic cage-like structure where multiple blade portions (radial and axial) work协同 to pump gas molecules. The rotating cage configuration allows gas molecules to be captured and transported more efficiently, achieving high pumping speed in a compact volume through dynamic molecular interaction rather than static large surface area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances pumping speed by up to three times compared to conventional pumps of equal diameter, enabling the achievement of low pressures below 10−11 Torr while reducing the size and weight of the pump, making it suitable for compact mass spectrometers.
Implementation Method 1
Gas molecules, hit by the underside of the angled blades, move with momentum in the direction of the higher pressure exhaust section
Implementation Method 2
The rotational speed is limited by the strength of the blade material which has to withstand the centrifugal forces and which is heated to temperatures generated by the overall gas load to be pumped
Implementation Method 3
Surface friction is used to move molecules along the channel
Data Source
AI summary
The invention relates to turbo molecular pumps enabling high pumping speed. The disclosure suggests using one or more cage-like rotor stages to optimize pumping speed on vacuum systems with low gas flows and low ultimate pressures. This allows for a smaller motor as well as smaller overall form factor and makes it well suited, in particular, for compact mass spectrometers and desk-top mass spectrometers.