Variable-Pitch Screw Vacuum Pump for Backflow and Leakage Control
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Solution Overview
Problem
Existing screw-type vacuum pumps face challenges in achieving efficient gas conveyance and sealing, particularly in controlling the volume index without relying on exhaust port geometry, and suffer from backflow and leakage due to complex rotor designs.
Innovation Solution
The design incorporates a screw-type vacuum pump with a housing containing a first rotor with two helical lobes and a second rotor with three helical lobes, featuring variable pitch and wrap angles, along with oil injection for sealing and cooling, and blow-off valves for pressure relief, to enhance gas conveyance and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex rotor designs are used, then sealing performance may be improved, but backflow and leakage increase
Solution Approach 1:
The patent applies parameter changes by modifying the rotor geometry parameters, specifically using a variable pitch design where the pitch decreases linearly from 10% to 50% between suction and discharge end faces. The rotors also feature specific wrap angles (203°, 204°, 305°, or 306°) and length-to-diameter ratios ≥1.7. These parameter optimizations improve gas conveyance efficiency and sealing performance while reducing backflow and leakage, resolving the contradiction between sealing performance and harmful factors.
2Productivity
If variable pitch rotors are used, then gas conveyance efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The variable pitch design is implemented with specific controlled parameters: pitch decreases linearly by 10%-50% along the rotor length, with defined wrap angles and length-to-diameter ratios. While this improves gas conveyance efficiency, the manufacturing complexity increases. The patent balances this by providing specific design guidelines and parameter ranges that optimize performance while remaining manufacturable.
3Reliability
If oil injection is used, then sealing and cooling are improved, but device complexity increases
Solution Approach 1:
The patent uses oil as an intermediary substance that serves multiple functions: sealing between rotors and housing, cooling the rotors and pumped gas, and lubrication. The oil injection system, while adding device complexity, efficiently resolves sealing and cooling requirements, improving overall reliability. The oil acts as a mediator that simplifies the design compared to alternative sealing and cooling mechanisms.
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 configuration improves pump efficiency by reducing backflow and leakage, allowing for better control of the volume index and throughput without relying on exhaust port geometry, while maintaining high chamber volume and reducing manufacturing complexity.
Implementation Method 1
The oil may provide sealing of the first and second rotors against the housing and/or each other
Implementation Method 2
The oil may cool the rotors and/or a pumped gas
Implementation Method 3
the first and second rotors are configured to convey a gas along a longitudinal direction of the screw-type vacuum pump
Data Source
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AI summary
A screw-type vacuum pump (100) comprising: a housing (102) comprising a pumping chamber (126); a first rotor (104) having exactly two first helical lobes (300); and a second rotor (108) having exactly three second helical lobes (304); wherein the first helical lobes (300) and the second helical lobes (304) are enmeshed with one another in the pumping chamber (126) and the first and second rotors (104, 108) are configured to convey a gas along a longitudinal direction of the screw-type vacuum pump.