Concave Razor Cutting Head with Sub-90 Degree Threading Edge
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Solution Overview
Problem
Existing cutting heads for electric razors face issues with hair threading due to flat or obtusely angled contact surfaces, leading to hair entanglement and skin irritation, and inefficient shaving performance as hairs often escape the threading slots before being cut.
Innovation Solution
A cutting head design featuring a concave contact surface with exposed comb tips and an outer radius less than 90° at the threading edge, combined with increasing web thickness towards the threading edge, ensures effective hair threading and prevents skin lift-off, while a convex contact surface facilitates shaving in problem zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat contact surface is used, then manufacturing is simple, but hair threading capability deteriorates
Solution Approach 1:
The contact surface is designed with a specific curvature radius (R1 for the concave portion and R2 for the convex portion) to create optimal threading geometry. The curved surfaces guide hairs into the slots more effectively than flat surfaces, improving threading capability while maintaining manufacturability through standardized rounding processes.
2Strength
If an obtusely angled contact surface is used, then structural strength increases, but hair threading behavior deteriorates
Solution Approach 1:
Different regions of the contact surface have different geometric properties: the concave portion (with radius R1) provides optimal threading angles for hair guidance, while the convex portion (with radius R2) provides structural support. This local differentiation allows each region to optimize for its specific function.
3Ease of manufacture
If slots taper towards the middle, then manufacturing is easier, but hair entanglement and pulling increases
Solution Approach 1:
The slot geometry incorporates rounded features with specific radii (R3 at the groove base and R4 at the slot opening) to eliminate sharp edges and corners. This rounding prevents hairs from catching and being pulled during the shaving process, reducing skin irritation while maintaining manufacturability through standard finishing processes.
4Ease of operation
If threading means are provided in front of the threading edge, then hair threading is improved, but hair escape from slots increases
Solution Approach 1:
The concave contact surface portion acts as a preliminary threading zone that guides hairs toward the slots before they reach the cutting edge. This pre-positioning ensures hairs are properly oriented and captured by the slots, preventing escape and improving cutting reliability.
5Object-affected harmful factors
If the outer radius at threading edge is large, then skin friendliness is improved, but hair threading efficiency decreases
Solution Approach 1:
The contact surface features two distinct radii: R1 for the concave portion that optimizes threading efficiency, and R2 for the convex portion that ensures skin friendliness. This dual-radius design allows each region to optimize for its specific function without compromising the other.
Data Source
AI summary
A cutting head for an electric razor is provided. The cutting head has at least one upper blade and a lower blade associated with the upper blade, which upper and lower blades are movably supported relative to one another and can be driven accordingly by a drive device. The upper blade has a contact surface for the skin to be shaved, which contact surface is formed by a plurality of webs that are each bounded by slots. The longitudinal extent of the webs runs substantially perpendicular to a threading edge bounding the contact surface. The contact surface is designed to be concave and rises towards the threading edge, where the threading edge has an outer radius and this outer radius encloses an angle of less than 90°.