Movable Contact Body for Switch with Convex Leaf-Spring and Through-Hole

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Solution Overview

Problem

Conventional movable contact bodies for switches face issues such as instability during transfer, limited durability, especially in small form factors like smartphone side surfaces, and variations in spring characteristics due to solder reflow, which affect positional accuracy and reliability.

Innovation Solution

The design incorporates a movable contact with an upwardly convex leaf-spring shape, a cover member, and a holding member with a contact through-hole, secured by multiple adhesive sheets and a flexible substrate, eliminating the need for solder reflow and enhancing positional accuracy and durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the movable contact is fixed only by a gluing tape, then the structure is simple, but the movable contact may fall off during transfer

Engineering Contradiction:

ImprovestructureVSAvoidstability during transfer

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The holding member is divided into a body portion and a protruding portion that extends into the movable contact. This segmentation allows the holding member to securely engage with the movable contact through the protruding portion while maintaining a simple overall structure, preventing the movable contact from falling off during transfer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protruding portion of the holding member is nested within or engages with the movable contact structure. This nesting arrangement provides secure fixation of the movable contact to the holding member without requiring complex external fixing mechanisms, thus maintaining structural simplicity while ensuring reliability.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If solder reflow is used to connect movable contact and fixed contact, then electrical connection is achieved, but spring characteristics vary

Engineering Contradiction:

Improveelectrical connectionVSAvoidspring characteristics

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The solder reflow process is completely removed from the manufacturing process. Instead of using solder to connect the movable contact with fixed contacts, the invention uses mechanical contact through the holding member structure, thereby eliminating the harmful thermal effects of solder reflow that cause variation in spring characteristics while still achieving reliable electrical connection.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The electrical connection is achieved through direct mechanical contact between the movable contact and fixed contacts rather than through soldering. The holding member provides structural support and positioning, allowing the movable contact to maintain electrical connection through controlled mechanical engagement, replacing the thermal-chemical soldering process with a purely mechanical system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If the switch size is reduced for small form factors, then the switch becomes compact, but durability decreases

Engineering Contradiction:

Improveswitch sizeVSAvoiddurability

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The holding member features a protruding portion with specific local geometry that concentrates structural strength at the critical engagement point with the movable contact. This local quality enhancement allows the switch to maintain high durability in a compact size, as the strengthened local region provides robust mechanical support without increasing overall switch volume.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The holding member is made of a resilient material that combines structural support with flexibility. This composite approach allows the holding member to maintain strong mechanical engagement with the movable contact while accommodating the reduced dimensions of small-form-factor switches, thereby preserving durability despite size reduction.

Inventive Principle:

Principle #40Composite materials

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 reduces the risk of defects during transfer, maintains durability even in smaller sizes, and prevents variations in spring characteristics, enabling cost-effective production of small, reliable switches with improved click sensation and longevity.

Implementation Method 1

a second adhesive sheet bonded to a surface of the holding member

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS11270855B2Movable contact body for switch, and switch

Publication Date: 2022.03.08 CITIZEN ELECTRONICS CO LTD

AI summary

The movable contact body for a switch includes at least one movable contact having an upwardly convex leaf-spring shape, a cover member disposed so as to cover an upper surface of the movable contact, and a holding member disposed so as to face a lower surface of the movable contact, the holding member having a contact through-hole through which a top portion of the movable contact can pass.