Grommet Recesses Reduce Insertion Force

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Solution Overview

Problem

Existing grommets require high insertion force and lack effective methods to reduce friction during insertion through panel holes while maintaining secure retention, with lubricants being messy or incompatible and geometric designs increasing material and cost.

Innovation Solution

A grommet with recesses centered about a circle perpendicular to the axis, featuring arcuate sidewalls and endwalls that expand during insertion to reduce friction and then contract for secure retention, allowing for lower insertion force and higher pull-out force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a lubricant is applied to the exterior surface of the grommet to reduce friction during insertion, then the insertion force is decreased, but the lubricant may be messy or incompatible with insulation on wires passing through the grommet

Engineering Contradiction:

Improveinsertion forceVSAvoidcontamination and incompatibility

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The harmful lubricant substance is completely removed from the system. Instead of applying lubricant to reduce friction, the invention extracts the need for lubrication by redesigning the grommet geometry itself - using a tapered configuration that naturally reduces insertion force without introducing any contaminating substances.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The chemical mechanism of lubrication is replaced with a mechanical solution. The tapered geometry of the grommet creates a mechanical advantage during insertion, reducing friction and insertion force through its shape rather than through chemical lubrication, thereby eliminating contamination risks.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Force

If thick ribs are placed on the outside surface of the grommet to create localized points of contact and reduce friction during insertion, then the insertion force is decreased, but material and cost increase

Engineering Contradiction:

Improveinsertion forceVSAvoidmaterial and cost

Core Design Contradiction:

ForceVSQuantity of substance

Solution Approach 1:

Instead of adding thick ribs that increase material throughout the grommet structure, the invention applies local quality by creating a tapered configuration concentrated at the insertion end. This localized geometric modification reduces friction where needed during insertion without adding material to the entire grommet body.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Rather than adding material (thick ribs) to reduce friction, the invention inverts the approach by removing material or creating a tapered void that reduces insertion force. The inverted cone shape creates reduced contact area and friction during insertion without requiring additional material investment.

Inventive Principle:

Principle #13The other way round (Inversion)

3Force

If relief grooves are placed on the internal surface of the grommet to decrease insertion force, then the insertion force is reduced, but the grooves contract during insertion minimizing their benefit

Engineering Contradiction:

Improveinsertion forceVSAvoidinsertion force reduction effectiveness

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

Instead of using internal relief grooves that contract and fail to provide benefit, the invention inverts the approach by placing the friction-reducing geometry on the external surface. The external tapered configuration maintains its friction-reducing properties throughout insertion without the contraction problem that plagues internal grooves.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The tapered configuration is pre-formed on the grommet exterior before insertion begins. This preliminary geometric preparation ensures that the friction-reducing shape is already in place and maintains its effectiveness throughout the insertion process, unlike internal grooves that contract and lose their benefit during insertion.

Inventive Principle:

Principle #10Preliminary action

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 grommet design significantly reduces insertion force while maintaining a secure pull-out force, ensuring effective sealing and retention without adding material or cost, and is compatible with various panel geometries.

Implementation Method 1

each recess expands to a second width greater than the first width when the funnel-shaped section passes through the hole during insertion of the grommet into the hole. Each recess returns to the first width when the panel is received within the retention groove

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP2662243B1Grommet

Publication Date: 2014.11.26 DELPHI TECHNOLOGIES INC

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AI summary

A grommet (22) extends along an axis (A) for insertion into a hole (44) of a panel (24). The grommet (22) includes a hollow funnel-shaped section (32) inclined to the axis (A) such that a portion of said funnel-shaped section (32) is compressed radially inward during insertion of the grommet (22) into said hole (44), the funnel-shaped section (32) terminates at a circular ridgeline (40). The grommet (22) also includes a retention groove (48) adjacent to the ridgeline (40) for receiving the panel (20) upon complete insertion of the grommet (22) into the hole (44). An array of recesses (62) is included on an inside surface (56) of the grommet (22). The recesses (62) are arranged to expand when the funnel-shaped section (32) passes through the hole (44) during insertion of the grommet (22) into the hole (44).