Cable Bushing Grommet Structure for Watertight Sealing Under Cable Bending

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Solution Overview

Problem

Existing grommets for sealing cables in cable bushings are prone to water ingress due to asymmetrical compression from excessive cable bending and require precise orientation and installation to ensure watertightness, making them difficult to assemble correctly and prone to human errors.

Innovation Solution

A grommet design with an inner and outer sealing portion connected only at one end, featuring a chamfer for easier cable insertion and a flange for defined positioning, along with ribs for enhanced sealing and stability, ensures effective sealing regardless of cable bending and simplifies the installation process by preventing incorrect cable insertion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the cable is pushed through the grommet, then the cable is sealed in the grommet body, but material around the opening is pulled into the camera and may cause leakage

Engineering Contradiction:
ImprovewatertightnessVSAvoidassembly process
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The grommet is divided into two separate sealing portions (inner and outer) that are connected only at one end, allowing independent sealing actions at the cable opening and grommet body interface without interfering with each other

Inventive Principle:
Principle #1Segmentation

2Adaptability or versatility

If the cable is bent excessively to lead it to a connection, then the cable can reach the connection point, but asymmetrical compression of the grommet occurs leading to water ingress

Engineering Contradiction:
Improvecable routing flexibilityVSAvoidwatertightness
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

By separating the inner sealing portion from the outer sealing portion, the grommet allows the cable to bend and move independently without transmitting asymmetric forces to the sealing surfaces, maintaining watertightness despite cable routing requirements

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The decoupled structure changes the mechanical parameters of the sealing portions, allowing them to maintain constant compression and sealing pressure regardless of cable position or bending, ensuring consistent watertightness

Inventive Principle:
Principle #35Parameter changes

3Reliability

If the grommet requires precise orientation for correct cable insertion, then sealing function is maintained, but assembly errors increase and installation becomes difficult

Engineering Contradiction:
Improvesealing functionVSAvoidinstallation ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The grommet features an asymmetric design with the inner and outer sealing portions connected only at one end, creating a unique insertion orientation that is visually and physically distinct, making correct installation intuitive and preventing incorrect assembly

Inventive Principle:
Principle #4Asymmetry

Data Source

PatentEP4293844A1Grommet for sealing a cable in a cable bushing
Publication Date: 2023.12.20 ROBERT BOSCH GMBH
  • EP4293844A1 patent drawingFigure 1
  • EP4293844A1 patent drawingFigure 2
  • EP4293844A1 patent drawingFigure 3a~3b

AI summary

The invention relates to a grommet (1) for sealing a cable (2) in a cable bushing (4), a grommet assembly (1, 2, 4) for a camera, a camera including the grommet assembly (1, 2, 4), and a method for mounting the grommet (1) in the cable bushing (4). The grommet (1) for sealing a cable (2) in a cable bushing (4) comprises a grommet body (1A) having an inner sealing portion (1b) for sealing the cable (2) in the grommet body (1A) and an outer sealing portion (1c) for sealing the grommet body (1A) in the cable bushing (4), wherein the inner sealing portion (1b) and the outer sealing portion (1c) are connected at a first outer axial end (1A1) of the grommet body (1A), and a cavity (1f) is disposed between the inner sealing portion (1b) and the outer sealing portion (1c).