Transparent Crystal Peripheral Rim Ultrasonic Welding

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Solution Overview

Problem

The existing methods for securing a transparent plastic crystal to a portable object's case, such as a wristwatch, using ultrasonic welding are inadequate as they often damage the rigid transparent conductive electrodes due to mechanical and thermal stresses, and adhesive bonding is prone to aging and mechanical resistance issues.

Innovation Solution

A transparent plastic crystal with a peripheral rim extending along its perimeter, which provides surfaces for ultrasonic welding away from the conductive paths on the bottom surface, reducing mechanical and thermal stress on the electrodes and requiring less ultrasonic energy, thus protecting the conductive paths and improving weld quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If ultrasonic welding is performed on the crystal to secure it to the case, then the crystal is firmly attached with good mechanical resistance, but the rigid transparent conductive electrodes are damaged or detached due to mechanical and thermal stresses

Engineering Contradiction:

Improvemechanical resistance of crystal attachmentVSAvoidintegrity of conductive paths

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The crystal is divided into distinct functional zones: a bottom surface carrying the conductive paths and a peripheral rim for welding. This segmentation allows the welding operation to be isolated to the rim area, preventing stress transmission to the conductive paths on the bottom surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The peripheral rim is given different properties than the bottom surface - specifically, it provides a dedicated welding surface that is spatially separated from the conductive paths. This local differentiation allows ultrasonic welding to occur at the rim without affecting the integrity of the conductive paths on the bottom surface.

Inventive Principle:

Principle #3Local quality

2Reliability

If adhesive bonding is used to secure the crystal to the case, then the conductive paths are protected from welding stresses, but the adhesive ages over time causing sealing problems and mechanical resistance issues

Engineering Contradiction:

Improveintegrity of conductive pathsVSAvoidlong-term durability of attachment

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The chemical bonding mechanism of adhesives is replaced with ultrasonic welding, a mechanical/thermal process. This substitution eliminates the aging problems associated with adhesives while maintaining protection of conductive paths through proper welding surface location on the peripheral rim.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If ultrasonic welding is attempted on the crystal surface with conductive paths, then the crystal can be attached, but the transparent conductive material makes the welding operation awkward due to its hardness

Engineering Contradiction:

Improveattachment strength of crystalVSAvoidease of ultrasonic welding operation

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The welding function is extracted from the bottom surface area and relocated to the peripheral rim. This extraction allows welding to be performed on a surface free of conductive paths, eliminating the manufacturing difficulties caused by the hardness of transparent conductive materials.

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution effectively prevents damage to the conductive paths during ultrasonic welding, enhances weld quality, and provides better mechanical resistance compared to adhesive bonding, ensuring reliable sealing and durability of the portable object's case.

Implementation Method 1

an element known as a waveguide is arranged on the peripheral edge of the crystal. This waveguide concentrates the ultrasonic waves and causes localised heating which results in a weld by melting the crystal and the watch case

Methodology Applied

Scientific EffectUltrasonic welding: Ultrasonic Vibration

Implementation Method 2

This waveguide concentrates the ultrasonic waves and causes localised heating which results in a weld by melting the crystal and the watch case

Methodology Applied

Scientific EffectLocalised heating: Heating

Implementation Method 3

an element known as a waveguide is arranged on the peripheral edge of the crystal. This waveguide concentrates the ultrasonic waves and causes localised heating

Methodology Applied

Scientific EffectUltrasonic wave concentration: Ultrasonic Vibration

Data Source

PatentUS9149983B2Crystal used for closing the top of the case of a portable object and method of welding a crystal of this type

Publication Date: 2015.10.06 THE SWATCH GRP RES & DEVELONMENT LTD

AI summary

A crystal and an ultrasonic welding method for a crystal. The crystal is used to close a top of a case of a portable object, the crystal being made of a transparent plastic material and being secured to the case of the portable object by ultrasonic welding. The crystal includes a top surface and a bottom surface that carry one or more conductive paths made of a transparent conductive material, and a peripheral rim that extends along at least one portion of the perimeter of the crystal. The peripheral rim provides at least one surface for the ultrasonic welding of the crystal to the case of the portable object.