Holweck Pump Stage Radial End Face Design
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Solution Overview
Problem
The pumping speed of vacuum pumps, particularly turbomolecular vacuum pumps, is limited by inlet conductance issues due to gas molecules being desorbed back towards upstream stages, reducing efficiency.
Innovation Solution
The Holweck pump stage design features radially aligned end faces with obtuse angles less than 300°, increasing the inlet surface area by up to 20% and reducing desorption, thereby enhancing inlet conductance and pumping speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Holweck thread design with end faces in the inlet plane is used, then the structure is simple and easy to manufacture, but gas molecules are desorbed back toward upstream stages reducing inlet conductance and pumping speed
Solution Approach 1:
The end faces of the Holweck thread webs are designed with different orientations: radially aligned end faces at the inlet end to improve conductance, and conventional end faces at other locations. This local differentiation optimizes gas molecule conveyance at the critical inlet region while maintaining structural integrity elsewhere.
Solution Approach 2:
The end faces of the Holweck thread webs are oriented radially aligned instead of lying in the inlet plane, changing the spatial dimension of the surface orientation. This dimensional change increases the effective inlet surface area and directs gas molecules more effectively into the pumping stage.
2Productivity
If the inlet surface area is increased to improve inlet conductance, then pumping speed increases, but the Holweck thread structure becomes more complex
Solution Approach 1:
The orientation angle of the end faces relative to the radial direction is optimized to provide sufficient inlet surface area. By adjusting this geometric parameter, the invention achieves improved inlet conductance while controlling structural complexity.
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 increases pumping speed by more than 5% for nitrogen and 2% for helium, improving overall vacuum pump efficiency.
Implementation Method 1
generates a molecular flow by rotating a Holweck rotor relative to a stationary Holweck stator
Implementation Method 2
gas molecules to be pumped impinge on these end faces and are highly likely to be desorbed back toward an upstream turbomolecular pump stage
Data Source
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AI summary
The present invention relates to a vacuum pump, in particular a turbomolecular vacuum pump, with a pump inlet, a pump outlet, and at least one Holweck pump stage, which has a Holweck stator sleeve with an inner and an outer surface and an inlet end facing the pump inlet opposite to the pumping direction. A Holweck thread with several spirally circumferential webs is formed on the inner and/or outer surface of the Holweck stator sleeve, each web having a first thread flank facing the inlet end and a second thread flank facing away from the inlet end. At the inlet end of the at least one Holweck pump stage, the webs each have a radially oriented end face that forms an obtuse first angle with the second thread flank, which is less than 300°.