Pressure Balanced Vane Pump Offset Tip Design
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Solution Overview
Problem
Conventional vane pumps experience high adhesive wear stresses due to excessive radial pressure loads, leading to damage and reduced displacement capacity, which necessitates the use of expensive and brittle materials like Tungsten Carbide, complicating fabrication and increasing costs.
Innovation Solution
The design incorporates radially pressure-balanced vanes with an inverted 'L' shape, where the vane tip radius is offset from the leading edge, distributing pressure over a larger area and using ductile steels to reduce material costs and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vane design with vane tip radius at leading edge is used, then sealing contact is maintained, but excessive radial pressure load causes high adhesive wear stresses and damage
Solution Approach 1:
The vane tip radius is intentionally offset from the leading edge to create an asymmetric contact configuration. This offset positions the contact point away from the leading edge, distributing the radial pressure load over a longer arc length and reducing the peak adhesive wear stresses at the contact interface while maintaining adequate sealing contact.
Solution Approach 2:
The solution moves the contact point from a single point at the leading edge to a distributed contact zone along an offset arc. By changing the dimensional distribution of the contact area from a point contact to an arc-length distributed contact, the pressure load is spread out, reducing stress concentration.
2Strength
If hard brittle materials like Tungsten Carbide are used, then wear resistance is improved, but fabrication difficulty increases and cost increases
Solution Approach 1:
The invention changes the operational parameters by reducing the radial pressure load through the offset vane tip design. This parameter change in the pressure distribution allows the use of ductile materials with lower hardness (such as hardened steel) instead of extremely hard brittle materials like Tungsten Carbide, while still achieving adequate wear resistance through the reduced stress environment.
Solution Approach 2:
The invention enables the use of more affordable, easier-to-machine materials like hardened steel that can be readily replaced if worn, rather than relying on expensive, difficult-to-machine Tungsten Carbide. The design accepts that these softer materials will eventually wear but provides sufficient service life through the reduced adhesive wear stresses.
3Strength
If hard brittle materials are used, then wear resistance is improved, but material cost increases
Solution Approach 1:
The offset vane tip design changes the pressure distribution parameters to reduce adhesive wear stresses. This allows substitution of expensive hard brittle materials with cheaper ductile materials that have sufficient wear resistance under the reduced stress conditions, directly reducing material cost while maintaining functional performance.
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 reduces compressive stresses, allowing the use of ductile steels instead of hard materials, providing predictable failure modes, increased durability, and simplified fabrication while maintaining efficient sealing and fluid displacement.
Implementation Method 1
The offset centerline of the vane tip radius provides a positive vane contact with the inner surface of the cam block without over loading the contact point
Implementation Method 2
In the pump arc and the seal arc to maintain a seal between the vane tip and the cam inner surface discharge pressure is provided under the vanes. Above the vane one half of the vane is subject to discharge pressure
Data Source
AI summary
A radially pressure balanced vane pump includes a housing that defines an inlet port and a discharge port. A cam block disposed within the housing defines a continuous inner surface. A plurality of vanes are supported within rotor slots and rotated above a shaft. Each vane includes a vane tip having a radius with a centerline offset from the centerline of the vane. A pressure biasing the vane into contact with the cam block is distributed over the vane tip radius. Further, the vanes are biased into contact with the inner surface of the cam block by communication of discharge pressure under the vane. The vane tip radius along with the pressure balance between under vane and under vane discharge pressure provide for the use of low cost and easily fabricated ductile steels.