Roots Rotor Curvature for Particle-Free Vacuum Pump Gaps
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Solution Overview
Problem
Particles accumulate between the convex and concave surfaces of Roots rotors in vacuum pumps, hindering their rotation and preventing accurate measurement of the gap between them, which is crucial for maintaining pump efficiency.
Innovation Solution
The Roots rotors are designed with involute side surfaces smoothly coupled by outer and inner smooth curved surfaces, featuring different radii of curvature, allowing for smooth rotation and accurate gap measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gap between Roots rotors is made as small as possible to improve pump efficiency, then pump efficiency is improved, but particles can be caught between the rotors and hinder rotation
Solution Approach 1:
The invention applies curvature to the rotor surfaces by replacing the conventional sharp-angled outer peripheral surface with a smooth curved surface that has a continuous radius of curvature. This curved surface prevents particles from being trapped in sharp corners while maintaining a sufficiently small gap between rotors for high pump efficiency. The smooth curvature allows particles to roll off rather than become lodged, resolving the contradiction between small gap requirements and particle accumulation prevention.
2Shape
If the outer peripheral surface of Roots rotors is composed of circular arc and involute curve combination, then the rotor shape is defined, but the feeler gauge cannot accurately measure the gap between rotors
Solution Approach 1:
The invention changes the geometric parameters of the rotor surface from a combination of circular arc and involute curve to a smooth curved surface with continuous radius of curvature. This parameter change enables the feeler gauge metal leaf to conform smoothly to the rotor surface, allowing accurate gap measurement. The continuous curvature eliminates the non-smooth connection points that previously prevented accurate measurement.
3Device complexity
If convex and concave surfaces of Roots rotors are in surface contact, then there is no place for particles to escape, but particles are strongly sandwiched and may hinder rotation
Solution Approach 1:
By applying smooth curved surfaces with continuous radius of curvature to the rotor surfaces, the invention eliminates sharp corners and crevices where particles could become trapped. The curved geometry ensures that particles have escape paths and cannot be strongly sandwiched between contact surfaces, preventing particle accumulation while maintaining the necessary contact configuration for rotor operation.
Data Source
Figure 1
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Figure 3
AI summary
Each of the first Roots rotor (8) and the second Roots rotor (9) has an involute side surface (31) having a shape of an involute curve, an arcuate convex surface (34) located radially outwardly of the involute side surface (31), an outer smooth curved surface (35) smoothly coupling the involute side surface (31) to the arcuate convex surface (34), an arcuate concave surface (36) located radially inwardly of the involute side surface (31), and an inner smooth curved surface (37) smoothly coupling the involute side surface (31) to the arcuate concave surface (36). A radius of curvature (R1) of the arcuate convex surface (34) is smaller than a radius of curvature (R2) of the arcuate concave surface (36).