Razor Cartridge Virtual Pivot Axis Asymmetry
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Solution Overview
Problem
Conventional shaving razors with pivot axes parallel to the blade face limitations in maintaining a flat cartridge-to-skin angle, leading to nicks, cuts, and suboptimal shaving efficacy due to restricted pivoting mechanisms and physical constraints.
Innovation Solution
A shaving razor design featuring a pivoting mechanism that allows the cartridge to rotate about a virtual pivot axis located forward of the cartridge midpoint and into the skin, defined by specific boundary conditions on the X and Y axes, enabling a flat cartridge-to-skin angle and improved pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pivot axis is positioned in the center of the cartridge extending parallel to the cutting edges, then the cartridge can pivot to follow skin contours, but the blades are compressed into the skin increasing the risk of nicks and cuts
Solution Approach 1:
The patent positions the pivot axis asymmetrically forward of the cartridge center, specifically beneath the guard member rather than at the center. This asymmetric positioning creates a guard-heavy cartridge where the guard extends further forward than the cap, allowing the cartridge to pivot while maintaining a more favorable cartridge-to-skin angle and reducing blade compression into the skin.
Solution Approach 2:
The patent introduces a new dimensional parameter by positioning the pivot axis not only forward of center but also at a specific distance below the cutting plane (into the skin). This three-dimensional positioning (forward distance and depth below cutting plane) creates a virtual pivot axis that optimizes both conformance and safety.
2Object-affected harmful factors
If a forward pivot axis is positioned beneath the guard to reduce nicks and cuts, then the blades are free to rotate away from the skin, but the guard heavy cartridge impacts the contact with the skin and pressure distribution
Solution Approach 1:
The patent optimizes specific parameters of the forward pivot axis positioning: (1) the forward distance from the cartridge center, and (2) the depth below the cutting plane. By carefully selecting these parameters, the design achieves a balance where the guard is heavy enough to prevent nicks and cuts but not so heavy as to compromise cartridge-to-skin contact and pressure distribution.
3Adaptability or versatility
If shell bearings are used to produce a virtual pivot axis, then pivoting movement is enabled, but the bearings can rattle and bind leading to poor functionality and low quality feel
Solution Approach 1:
The patent removes the shell bearing component entirely from the pivoting mechanism. Instead of using a physical bearing to enable rotation, the design relies on the geometric configuration of the pivot axis position and the natural pivoting capability of the cartridge structure, eliminating the source of rattling and binding while maintaining reliable pivoting functionality.
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 2C~5D
AI summary
A razor blade assembly having a razor cartridge connected to a handle via a pivoting mechanism. The razor cartridge rotates about a virtual pivot axis produced by the pivoting mechanism. The virtual pivot axis is positioned in a virtual pivot axis region located forward of the cartridge midpoint toward the front edge of the cartridge and into the skin.