Power Tool Cord Protector Labyrinth Friction Design

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Solution Overview

Problem

Heavier portable power tools often experience cord separation due to impulse loads or jerks, particularly when dropped or maneuvered, leading to connection failures.

Innovation Solution

A power tool design featuring a cord set load protector with a labyrinthine internal structure and radially extending bosses within the housing, combined with a crimp-on device and cord clamp system, which absorbs forces and distributes stress along the power cord to prevent separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a power cord is directly connected to the motor without protection, then the device complexity is reduced, but the reliability deteriorates due to cord separation from impulse loads

Engineering Contradiction:
Improvecord connection reliabilityVSAvoidcord protection structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The cord protector is nested within the housing structure, with the labyrinthine internal features integrated into the housing wall itself. The cord protector passage is formed as an internal cavity within the housing, allowing the protection mechanism to be embedded rather than added as a separate external component.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The labyrinthine structure creates localized friction zones at specific positions along the cord protector passage. The first and second bosses are positioned at different locations within the housing to create distributed friction points that engage with the cord protector at different stages of cord movement.

Inventive Principle:
Principle #3Local quality

2Reliability

If a labyrinthine structure with multiple bosses is added to the housing, then the cord protection capability is improved, but the manufacturing complexity increases

Engineering Contradiction:
Improvecord separation resistanceVSAvoidhousing manufacturing difficulty
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The cord protector passage and the labyrinthine friction features are merged into a single integrated housing structure. The first and second bosses are formed as integral parts of the housing wall, eliminating the need for separate manufacturing steps for these protection features.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If the first boss extends farther radially inward than the second boss, then the frictional force distribution is optimized, but the manufacturing precision requirements increase

Engineering Contradiction:
Improvefrictional force distributionVSAvoidboss extension dimension tolerance
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The first and second bosses are designed with asymmetric extension distances from the housing interior surface. The first boss extends farther radially inward than the second boss, creating an intentional asymmetric friction force distribution that optimizes cord protection while providing built-in alignment features.

Inventive Principle:
Principle #4Asymmetry

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

The solution effectively absorbs and distributes applied forces, reducing the likelihood of cord separation and enhancing the durability and flexibility of the power cord connections.

Implementation Method 1

a frictional force occurs between the cord protector and the cord jacket in response to a load being applied to the power cord

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP2581175B1Cord protector for power tools
Publication Date: 2015.05.27 BLACK & DECKER CORP
  • EP2581175B1 patent drawingFigure 1
  • EP2581175B1 patent drawingFigure 2~4
  • EP2581175B1 patent drawingFigure 5~7

AI summary

A power tool having a housing, a motor disposed in the housing, a power cord connected to the motor, and a cord protector operably engaging the power cord. The housing includes a labyrinth that engages the cord protector providing an additional frictional force on the power cord.