Razor Blade Unit Asymmetric Geometry for Bi-Directional Shaving
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Solution Overview
Problem
Existing razors, particularly those designed for bi-directional shaving, face challenges in achieving optimal shaving geometry that balances closeness, comfort, and safety, as the arrangement of blades and their interaction with the skin are not effectively optimized for both forward and backward strokes.
Innovation Solution
A blade unit design featuring a guard element and cap elements circumscribed by an arc, with blades positioned between these elements such that their cutting edges are above or below specific planes defined by the arc, allowing for bi-directional shaving even when the razor is moved unidirectionally, facilitated by a motor-driven oscillation mechanism that pivots the blade unit about a central axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If blades are arranged with cutting edges facing opposite directions for bi-directional shaving, then the razor can be used with back and forth movement, but the shaving geometry becomes difficult to optimize for both directions simultaneously
Solution Approach 1:
The patent applies asymmetry by positioning blades at different heights relative to the guard and cap surfaces. Specifically, at least one blade has its cutting edge positioned above the plane extending between the guard and cap surfaces, while other blades may be at or below this plane. This asymmetric arrangement allows each blade to be optimized for specific stroke directions while maintaining overall bi-directional functionality, resolving the contradiction between versatility and geometric optimization precision.
2Object-affected harmful factors
If the guard projects significantly above the shaving plane to protect skin, then skin protection is improved, but the cutting edges end up below planes extending between guard and cap surfaces, reducing cutting effectiveness
Solution Approach 1:
The patent resolves this contradiction by introducing vertical positioning as an additional dimension for blade arrangement. Instead of all blades being at the same level, the invention positions at least one blade above the plane extending between guard and cap surfaces. This multi-level arrangement allows the guard to project above the shaving plane for skin protection while specific blades extend above the guard-cop plane to maintain cutting effectiveness, effectively using vertical space to satisfy both requirements.
3Productivity
If unidirectional razor geometry is optimized for single direction shaving, then shaving performance in that direction is maximized, but the razor cannot effectively shave in the opposite direction
Solution Approach 1:
The patent applies universality by designing a blade arrangement that serves multiple functions and directions. The asymmetric positioning of blades, with at least one blade above the guard-cap plane and others at or below it, creates a universal configuration that effectively cuts hairs in both forward and backward strokes. This multi-functional design allows the same blade unit to optimize performance across different shaving directions, resolving the contradiction between performance maximization and directional versatility.
Data Source
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AI summary
A blade unit (110) for a razor including a guard element (35) , first and second cap elements (36,37) on opposite sides of the guard element, a plurality of blades (32) with cutting edges (33) disposed between the guard element and the first cap element and facing towards the guard element. At least one blade with a cutting edge is disposed between the guard element and the second cap element and faces towards the guard element. The first cap element, guard element and second cap element are circumscribed by an arc of a circle (46) . A first plane (47) extends between positions at which the circumscribing arc meets a first surface (35a) on the guard element and a surface on the first cap element. A second plane (48) extends between positions at which the circumscribing arc meets a second surface (35b) on the guard element and a surface (37b) on the second cap element. The cutting edge of at least one of the blades in the plurality of blades has a position that is above the first plane and at or below the circumscribing arc.