Shaving Cutting Unit Curved Aperture Wall Geometry
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Solution Overview
Problem
Existing shaving apparatuses face issues with hair snagging and pulling due to the shape of hair introduction openings, leading to discomfort and skin irritation.
Innovation Solution
The cutting unit features a second wall portion with a gradual transition from the lower side to the upper side of the external cutting member, forming a virtual circle with a radius of at least 30 micrometers, reducing the risk of hair snagging and allowing for a thicker external cutting member to prevent jamming, with edge portions that transition smoothly to minimize skin irritation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the hair introduction opening is made wide at the upper surface and narrow at the lower surface with opposed projecting edges, then the cutting performance is improved, but the risk of snagging and pulling of hairs increases
Solution Approach 1:
The patent applies curvature by defining the edge portion of the second wall portion to touch a virtual circle with a radius of at least 30 micrometers. This circular geometry creates a smooth, rounded transition instead of sharp edges, allowing hairs to pass through the aperture without snagging while maintaining effective cutting geometry.
Solution Approach 2:
The patent changes the geometric parameters of the aperture walls by specifying that the edge portion must touch a virtual circle of at least 30 micrometers radius, with tangents at successive contact points enclosing an angle of at least 150 degrees. This parameter specification transforms the wall geometry from sharp-edged to smoothly curved, eliminating the harmful snagging effect while preserving cutting performance.
2Ease of operation
If the external cutting member is made thinner to improve flexibility, then the ease of operation is improved, but the risk of jamming of hairs increases
Solution Approach 1:
By implementing curved edge portions with a minimum radius of 30 micrometers, the patent eliminates sharp corners that could catch and jam hairs. This curvature allows the external cutting member to maintain adequate thickness for structural integrity and hair passage while avoiding jamming issues.
Solution Approach 2:
The patent specifies geometric parameters including the virtual circle radius of at least 30 micrometers and the tangent angle of at least 150 degrees, which together define an optimal wall geometry that prevents hair jamming while allowing the cutting member to be sufficiently thin for flexibility and comfort during operation.
Data Source
Figure 1~2
Figure 3
Figure 4A~5B
AI summary
A shaving apparatus (1) provided with at least one cutting unit (3) comprising an external cutting member (4) and an internal cutting member (5) which is drivable relative to the external cutting member in at least one driving direction P. The internal cutting member comprises at least one cutting element (10) comprising a cutting edge (11) being movable along a cutting path (12) whilst being driven in the at least one driving direction. The external cutting member comprises at least one hair-entry aperture (8) which is bounded by at least a first and a second wall portion of the external cutting member, at least the first wall portion (13) comprising a cutting edge A for cooperation with the cutting edge of the internal cutting member. An edge portion of the second wall portion (44, 54) facing a plane comprising the cutting path, in a cross section taken substantially perpendicularly to the plane (22) comprising the cutting path, touches a virtual circle (58) with a radius of at least (30) micrometer at at least two contact points (59, 60) on the virtual circle, and wherein the tangents at two successive contact points where the edge portion touches the virtual circle, enclose an angle of at least 150 degrees.