Inner Cutter Blades with Variable Wedge Angles for Rotary Shavers
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Solution Overview
Problem
The existing inner cutter units for rotary shavers suffer from a cutting gap between the inner and outer units due to deformation under cutting forces, affecting shaving performance, and are not optimized for varying shaving conditions encountered by different cutter blades.
Innovation Solution
The inner cutter unit is designed with cutter blades having wedge angles tailored to specific shaving conditions, with central blades having larger wedge angles and higher bending resistance to minimize deformation and gap formation, while circumferential blades have smaller wedge angles for optimal cutting performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all cutter blades are given the same wedge angle for uniform manufacturing, then manufacturing precision is improved, but shaving performance deteriorates because different blades experience different shaving conditions
Solution Approach 1:
The patent applies local quality by giving different wedge angles to cutter blades based on their specific positions and functions. Central blades have larger wedge angles (70°-85°) for stability, while circumferential blades have smaller wedge angles (40°-50°) for cutting performance. This localized differentiation allows each blade to be optimized for its specific shaving conditions rather than using a uniform angle across all blades.
2Productivity
If circumferential cutter blades have sharp edges with small wedge angles for cutting performance, then shaving performance is improved, but gap formation worsens due to blade deformation under cutting forces
Solution Approach 1:
The patent differentiates blade design by location: circumferential blades have small wedge angles (40°-50°) optimized for cutting efficiency where tangential speed is highest, while central blades have large wedge angles (70°-85°) that resist deformation and prevent gap formation. This local optimization allows each region to be tuned for its specific functional requirements.
Solution Approach 2:
The patent changes the wedge angle parameter across different blade positions to balance cutting performance and stability. By varying this geometric parameter from small at the circumference to large at the center, the system achieves both efficient cutting and minimal deformation under operating conditions.
3Reliability
If central cutter blades have large wedge angles for stability, then gap formation is reduced, but cutting performance deteriorates due to reduced sharpness
Solution Approach 1:
The patent recognizes that central blades operate under different conditions than circumferential blades. Central blades have lower tangential speeds and experience different contact pressures, so they are optimized with large wedge angles (70°-85°) for stability. Circumferential blades have higher speeds and are optimized with small wedge angles (40°-50°) for cutting performance. Each location's blades are locally optimized for its specific operating conditions.
Data Source
AI summary
An inner cutter unit for a rotary shaver includes cutter blades arranged at different radii from a rotation axis of the unit. Depending on their respective positions within the unit, the respective cutter blades may be provided with different wedge angles and/or different bending resistance.