Split-Structure Grommet Assembly for Low-Stress Sealing
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Solution Overview
Problem
Conventional grommets face challenges in maintaining the assembly of a base member and grommet body due to excessive mold loads, especially when the base member is larger and more complex, leading to potential deterioration of the flexible grommet body.
Innovation Solution
A grommet design featuring a hard resin base member with an annular flange and a soft resin grommet body, where the grommet body is assembled to the base member with elastic deformation, and a holding mechanism ensures the assembly is maintained by elastic contact and hooks, reducing mold-induced stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the base member and grommet body are integrally molded, then manufacturing efficiency is improved, but the mold load becomes excessive causing deterioration of the flexible grommet body
Solution Approach 1:
The grommet is divided into two separate parts: a hard base member and a flexible grommet body. This segmentation allows each part to be molded independently with appropriate mold designs, reducing the overall mold load while maintaining manufacturing efficiency. The base member can be molded with complex features without compromising the grommet body quality.
2Reliability
If the base member size is increased to accommodate wiring member passage, then wiring protection is improved, but the base member shape becomes more complex increasing mold load
Solution Approach 1:
By separating the base member from the grommet body, the complex base member can be designed to accommodate wiring passage and protection requirements without the mold load concerns. The simplified grommet body can be molded separately with lower complexity requirements.
3Strength
If the base member and grommet body are assembled separately, then mold load is reduced, but assembly completion position cannot be maintained
Solution Approach 1:
A holding mechanism acts as an intermediary between the base member and grommet body to maintain the assembly completion position. This mechanism ensures that the separately molded parts remain properly positioned after assembly, solving the stability issue while allowing independent molding.
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 design effectively maintains the assembly of the base member and grommet body while minimizing mold-induced stress, ensuring reliable protection against liquid ingress and secure attachment to the insertion object.
Implementation Method 1
an annular grommet body coaxially assembled to the base member, and disposed in the one space at an attachment completion position with respect to a peripheral edge portion of the through hole of the insertion object... made of an elastically deformable synthetic resin material softer than the base member to be coaxially brought into tight contact with the outer peripheral edge portion of the flange at an assembly completion position with respect to the base member, and coaxially brought into tight contact with the peripheral edge portion at the attachment completion position
Data Source
AI summary
A hard resin base member of a grommet includes an annular flange. An elastically deformable soft resin grommet body includes an annular body. An annular lip is brought into tight contact with a first annular wall surface of the flange on an outer peripheral edge portion side at an assembly completion position. A first annular portion is coaxially disposed to face an outer peripheral edge portion of the annular body on an outer peripheral edge portion side of the flange with a gap therebetween. A second annular portion connects the outer peripheral edge portion of the annular body to an outer peripheral edge portion of the first annular portion. The first annular portion is hooked to the outer peripheral edge portion of the flange from a second annular wall surface side on a back side of the first annular wall surface over an entire circumference.