Dry Shaver Lower Blade Assembly with Adaptive Spring Pretension

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Solution Overview

Problem

Existing dry shaver lower blade assemblies are complex, with a large number of functional parts that increase friction, drive power requirements, and reduce shaving comfort due to skin irritation and the complexity of implementing skin protection and hair pulling mechanisms.

Innovation Solution

A lower blade assembly with only two functional parts, where the first and second lower blades alternate their functions with movement direction, reducing the number of components and incorporating adaptive spring pretension to provide skin protection and hair separation, thereby simplifying assembly and production while maintaining shaving effectiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a lower blade with a sharpened cutting edge is used to cut hair effectively, then shaving performance is improved, but skin irritations increase when skin sections protrude into the cutting plane

Engineering Contradiction:
Improveshaving performanceVSAvoidskin irritation
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The leading lower blade performs a preliminary action by pushing back skin sections before they can enter the cutting plane, preventing skin irritation before it occurs. This preliminary protective action is taken in the movement direction ahead of the cutting edge.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The lower blade is segmented into two distinct functional parts: a leading blade with a rounded-off edge for skin protection and pushing back, and a trailing blade with a sharpened cutting edge for hair cutting. This segmentation allows each part to specialize in its function without compromise.

Inventive Principle:
Principle #1Segmentation

2Object-affected harmful factors

If protector elements or pulling elements are added upstream of the lower blade to protect skin and pull hair, then skin protection and shaving quality are improved, but the number of functional parts increases significantly

Engineering Contradiction:
Improveskin protectionVSAvoidnumber of functional parts
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The protective function and cutting function are merged into a single lower blade component by integrating a leading protective edge and a trailing cutting edge into one piece. This eliminates the need for separate protector elements and pulling elements, reducing the total number of functional parts while maintaining all necessary functions.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The lower blade is designed as a multi-functional element that simultaneously performs skin protection (via the leading rounded edge), hair pulling (via the leading edge in movement direction), and hair cutting (via the trailing sharpened edge). This universal design consolidates multiple functions into one component.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Productivity

If multiple functional parts are arranged in the lower blade assembly to provide skin protection and hair pulling functions, then shaving quality is improved, but friction increases and drive power requirements increase

Engineering Contradiction:
Improveshaving qualityVSAvoiddrive power
Core Design Contradiction:
ProductivityVSUse of energy by moving object

Solution Approach 1:

By merging the protective function and cutting function into a single lower blade component, the total surface area in contact with the upper blade is reduced, thereby decreasing friction and the drive power required to operate the shaver.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The multi-functional lower blade performs multiple tasks (skin protection, hair pulling, hair cutting) with a single component, eliminating the need for multiple separate parts that would each contribute to friction and energy consumption.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Ease of manufacture

If the lower blade assembly is simplified to reduce the number of components, then assembly complexity and production costs are reduced, but skin protection and hair pulling functions may be compromised

Engineering Contradiction:
Improveassembly complexityVSAvoidskin protection
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The lower blade is designed as a universal component that integrates skin protection (rounded leading edge), hair pulling, and hair cutting functions into one piece, ensuring that simplification does not compromise protective or functional performance.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

Different regions of the lower blade have different local qualities: the leading edge has a rounded-off profile for skin protection and pushing back, while the trailing edge has a sharpened cutting edge for hair cutting. This local differentiation ensures each function is optimized without requiring separate components.

Inventive Principle:
Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design reduces assembly complexity and production costs while enhancing shaving comfort and performance by adapting the lower blades' functions to movement direction, ensuring effective hair cutting and skin protection with fewer components.

Implementation Method 1

At least one spring element is provided for supporting the at least one lower blade with respect to the upper blade in a pretensioned manner in the movement direction

Methodology Applied
Scientific EffectSpring pretension: Spring

Data Source

PatentEP2448725B1Lower blade assembly for dry shaver
Publication Date: 2016.08.24 BRAUN GMBH
  • EP2448725B1 patent drawingFigure 1~2
  • EP2448725B1 patent drawingFigure 3
  • EP2448725B1 patent drawingFigure 4

AI summary

The invention relates to a lower blade assembly for a dry shaver as well as to a dry shaver, which has an upper blade (5) equipped with openings and a motor for driving the upper blade and the lower blade assembly so as to oscillate with respect to one another, wherein the lower blade assembly has at least a first (10, 20; 30, 40) and a second (20, 10; 40, 30) lower blade, wherein the one blade (20, 10; 40, 30), which trails a blade that is leading (10, 20; 30, 40) in the movement direction, is provided for separating a hair protruding into the opening of the upper blade.