Railcar Junction Box Gasket with Segmented Width for Thermal Stress Relief

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Solution Overview

Problem

Existing gaskets for electrical junction boxes in railcars face challenges in maintaining water-tightness, stability, and preventing deformation due to heat expansion, leading to potential water intrusion and structural issues.

Innovation Solution

A gasket design featuring alternating small and large width portions with projections, ensuring equal clearances and uniform deformation, which stabilizes the repulsive force and prevents the gasket from falling off, while accommodating heat expansion without excessive pressure on the box main body or cover.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gasket is fitted in the groove without any gap to prevent unstable contact and falling off, then the water-tightness is improved and the gasket stability is improved, but the pressure applied to the box main body or cover by heat expansion increases causing deformation

Engineering Contradiction:

Improvewater-tightnessVSAvoidpressure from heat expansion

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The gasket is divided into multiple segments along its circumference, with each segment having a独立的 compression mechanism. This segmentation allows each segment to independently accommodate thermal expansion while collectively maintaining the water-tight seal around the entire junction box opening.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gasket incorporates dynamic elements that allow it to adapt its compression force based on temperature conditions. The segmented structure enables the gasket to dynamically adjust to thermal expansion of the box main body or cover without transferring excessive stress to the mating surfaces.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the gasket is made larger to ensure full contact with the groove, then the water-tightness is improved, but the pressure from heat expansion on the box main body or cover increases

Engineering Contradiction:

Improvewater-tightnessVSAvoidstructural integrity of box main body or cover

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the gasket have different properties - the segments provide localized compression zones that maintain seal pressure without uniformly distributing stress across the entire structure, thereby protecting the box main body and cover from excessive thermal stress.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If the gasket is attached to the cover to prevent falling off, then the stability is improved, but the complexity of the assembly process increases

Engineering Contradiction:

Improvegasket stabilityVSAvoidassembly process

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The gasket segments are integrated with the cover through attachment mechanisms that combine the gasket and cover into a single assembly unit. This merging ensures the gasket cannot fall off during installation while maintaining relatively simple manufacturing and assembly processes.

Inventive Principle:

Principle #5Merging (Combining)

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 gasket effectively secures water-tightness between the box main body and cover, prevents water intrusion, and reduces the risk of cracking due to heat expansion, ensuring reliable operation under varying temperature conditions.

Implementation Method 1

when the electrical junction box is placed under a high-temperature circumstance during the operation of the railcar or the like, the gasket made of rubber expands by heat

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

an elastic member having a through hole through which the electric cable penetrates

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS9583925B2Gasket for electrical junction box of railcar and electrical junction box of railcar

Publication Date: 2017.02.28 KAWASAKI RAILCAR MFG CO LTD

AI summary

A gasket for an electrical junction box of a railcar is fitted in a groove portion formed on a contact surface of a side wall portion or a contact surface of a cover in the electrical junction box including: a box main body having the side wall portion defining an opening communicating with an outer space; and the cover closing the opening. Further, the gasket for the electrical junction box of the railcar includes: small width portions, a width of each of the small width portions being smaller than a width of the groove portion; and large width portions each having projections projecting toward both respective sides of the small width portion in a width direction and having a larger width than the width of the small width portions. The small width portions and the large width portions are alternately provided.