Battery Pack Cell Holder Rib Suppresses Rattling

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Solution Overview

Problem

Existing battery packs for electric power tools experience rattling of the cell holder within the case, leading to movement discrepancies and premature wear of terminals due to vibration and impact, which reduces the lifespan of the battery pack components.

Innovation Solution

Incorporating a dimensional difference interposition member molded integrally with the cell holder to bridge the dimensional gap between the cell holder and the case, generating a pressing force that stabilizes the cell holder during assembly and operation, thus reducing rattling and wear on terminals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a clearance is provided between the case and the cell holder for assembly purposes, then the cell holder can be easily assembled into the case, but the cell holder rattles during operation

Engineering Contradiction:
Improveease of assemblyVSAvoidstability of cell holder
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

A cushion member is introduced as an intermediary element between the case and the cell holder. This cushion member fills the clearance space that was previously problematic, providing both assembly ease and operational stability. The cushion member acts as a mediator that eliminates rattling while maintaining the necessary assembly clearance.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If the cell holder is loosely fitted in the case to facilitate assembly, then assembly is easier, but terminals wear out prematurely due to vibration and impact

Engineering Contradiction:
Improveease of assemblyVSAvoidterminal lifespan
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The cushion member is installed beforehand between the case and cell holder to provide cushioning against vibration and impact. This prior cushioning prevents the transmission of mechanical shocks to the terminals, thereby extending terminal lifespan while maintaining easy assembly through the initial clearance design.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If no clearance is provided between the case and cell holder, then rattling is suppressed, but assembly becomes difficult

Engineering Contradiction:
Improvestability of cell holderVSAvoidease of assembly
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The assembly clearance is segmented into two functional zones: an outer clearance that facilitates assembly, and an inner region filled by the cushion member that suppresses rattling. This segmentation allows the same space to serve dual purposes of easy assembly and vibration suppression.

Inventive Principle:
Principle #1Segmentation

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 suppresses rattling of the cell holder relative to the case, enhances contact stability, and extends the lifespan of terminals by maintaining precise alignment and reducing mechanical stress on components.

Implementation Method 1

a dimensional difference interposition member serving to bridge a dimensional difference between the cell holder and the inside of the case by generating a pressing force applied to the case when the cell holder is assembled

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP2787558B1Battery pack for electric power tool
Publication Date: 2017.12.06 MAKITA CORP
  • EP2787558B1 patent drawingFigure 1
  • EP2787558B1 patent drawingFigure 2
  • EP2787558B1 patent drawingFigure 3

AI summary

A front pressing rib (541) is formed integrally with the cell holder (50). The front pressing rib (541) bridges a dimensional difference between the inside of the case (11) to be assembled and the cell holder (50) by generating a pressing force on the front side. That is, the cell holder (50) is pressed rearward in the case (11) by a pressing force of the front pressing rib (541) that is applied to the inside of the case (11). The front pressing rib (541) serves to completely bridge the dimensional difference when the cell holder (50) is inserted into the case (11).