Key Rubber Fixation via Flexible Cable Reaction Force

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Solution Overview

Problem

In electronic devices like cellular phones, the key rubber can peel off from the printed board module due to the reaction force of a folded key flexible cable, especially when other members like a slide module come into contact with the folded portion, causing mechanical stress and potential detachment.

Innovation Solution

The implementation of a key rubber with a contact portion that interacts with the folded portion of the flexible cable and a locking portion pressed against the case by the reaction force, which includes a locking pawl that engages with a protrusion on the case to prevent peeling, eliminating the need for additional members to secure the key rubber.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the key flexible cable is folded and connected between printed boards, then electrical connection between boards is achieved, but the folded portion may come into contact with other members and press the key rubber, causing it to peel off

Engineering Contradiction:

Improveconnection reliabilityVSAvoidkey rubber attachment stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent introduces a pressing member as an intermediary component between the folded flexible cable and the key rubber. This pressing member receives the reaction force from the flexible cable and transmits it to press the key rubber against the printed board, preventing peeling while avoiding direct contact between the cable and key rubber that would cause damage

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The pressing member acts as a counterbalancing element that converts the harmful reaction force from the flexible cable into a useful pressing force. By positioning the pressing member on the opposite side of the key rubber relative to the flexible cable, the system transforms the potential peeling force into a stabilizing pressing force that secures the key rubber attachment

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Reliability

If a front case is used to hold the key rubber, then the key rubber is securely fixed, but the device thickness increases

Engineering Contradiction:

Improvekey rubber fixation reliabilityVSAvoiddevice thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent extracts the key rubber fixation function from the front case structure and relocates it to the printed board assembly. The key rubber is directly bonded to the printed board with the key module, eliminating the need for a separate front case to hold the key rubber, thereby reducing device thickness while maintaining secure fixation

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the key rubber attachment function with the printed board structure. By bonding the key rubber directly to the printed board and integrating the key module assembly, the design combines multiple functions (structural support, electrical connection, and key rubber fixation) into a single integrated assembly, eliminating the need for additional thickness-consuming components

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If adhesive force alone is used to attach the key rubber to the printed board, then the structure is simple, but the attachment may fail under mechanical stress from the flexible cable

Engineering Contradiction:

Improveattachment structure complexityVSAvoidkey rubber attachment reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements preliminary action by pre-positioning the pressing member to apply continuous pressing force on the key rubber before any peeling occurs. This constant pre-pressure counteracts the reaction force from the flexible cable, preventing the adhesive bond from failing under mechanical stress

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The pressing member serves as a cushioning element that absorbs and distributes the mechanical stress from the flexible cable before it can reach the adhesive bond. By providing this protective cushioning force, the system prevents stress concentration at the adhesive interface, thereby preventing bond failure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This configuration effectively prevents the key rubber from peeling off, reduces the thickness of the device, and minimizes noise and dimension tolerance issues, while ensuring secure attachment without relying solely on adhesion forces.

Implementation Method 1

the key rubber includes a contact portion that is in contact with the folded portion of the flexible cable and subjected to reaction force of the flexible cable

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS8811023B2Electronic device

Publication Date: 2014.08.19 FCNT LLC

AI summary

An electronic device includes a case including a fixing portion, a printed board fixed to the fixing portion, a key rubber provided with key tops and fixed to the printed board, and a flexible cable attached to the printed board and bent in a direction different from the surface of the fixing portion to which the printed board is fixed, wherein the key rubber includes a contact portion that is in contact with the folded portion of the flexible cable and subjected to reaction force of the flexible cable, and a locking portion pressed against the case by the reaction force.