Zebra Connector Compression for Watch Crystal Sealing

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Solution Overview

Problem

The existing methods for manufacturing electronic watches with digital displays face challenges in achieving reliable electrical connections and watertight sealing between the crystal and the printed circuit board, particularly during the ultrasonic welding process, where the bearing surface melts and is consumed, affecting the crystal's fixation and connection reliability.

Innovation Solution

The method involves ultrasonic welding of the watch crystal to the caseband using a sonotrode, where the zebra connector is prestressed and compressed, ensuring a reliable electrical connection and watertight sealing by allowing the crystal to lower towards the printed circuit board, compressing the zebra connector for optimal contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ultrasonic welding is used to secure the crystal to the caseband, then the sealing and fixation reliability is improved, but the bearing surface melts and is consumed, affecting the crystal level and electrical connection reliability

Engineering Contradiction:

Improvesealing reliabilityVSAvoidcrystal level precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The zebra connector is pre-compressed between the display device and the printed circuit board before ultrasonic welding occurs. This preliminary compression ensures that when the bearing surface melts and is consumed during welding, the connector maintains optimal contact pressure for reliable electrical connection, compensating for the anticipated level change.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the state of the zebra connector from uncompressed to compressed by positioning it between the display device and the printed circuit board. This parameter change (compression state) ensures that the connector can withstand the level changes caused by bearing surface consumption during ultrasonic welding while maintaining reliable electrical connection.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the crystal is fixed at a higher level, then the electrical connection distance is reduced, but the compression on the zebra connector is insufficient for reliable connection

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoiddistance between crystal and printed circuit board

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The invention changes the compression parameter of the zebra connector by positioning it between the display device and the printed circuit board. This compression transforms the connector to a conductive state, ensuring reliable electrical connection even when the distance between the crystal and printed circuit board is reduced.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the bearing surface is made larger to support the crystal, then the sealing area is improved, but the material consumption during welding increases

Engineering Contradiction:

Improvesealing reliabilityVSAvoidbearing surface material consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The invention converts the harmful effect of bearing surface material consumption during ultrasonic welding into a beneficial effect. The melting and consumption of the bearing surface creates a recess that automatically compresses the zebra connector, transforming material loss into a mechanism for ensuring reliable electrical connection.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach simultaneously secures the crystal to the watch case in a durable and watertight manner while ensuring a reliable electrical connection between the digital display device and the printed circuit board, enhancing the watch's operational reliability and water resistance.

Implementation Method 1

ultrasonic welding of the watch crystal (4) to the caseband (2) using a sonotrode (36)

Methodology Applied

Scientific EffectUltrasonic welding: Ultrasonic Vibration

Implementation Method 2

the zebra connector (30) will ensure the electrical connection with an optimum compression rate between the printed circuit board (26) and a digital display device (12) fixed under the glass (4)

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentEP2666061B1Watch comprising a zebra connector for electrical connection between a digital display device and a printed circuit board and method of assembling such a watch

Publication Date: 2020.06.03 ETA SA MFG HORLOGERE SUISSE

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AI summary

The watch has a middle (2) and a glass (4) for defining a watch case (1). A digital display device i.e. LCD (12), is fixed to an inner face (10) of the glass. A printed circuit card (26) is placed in the case under the device, where case is remote from the device. The device is electrically linked to the card by a zebra type electric connector i.e. elastomer connector (30). The glass is mounted on a staff and the middle, where height of the staff with respect to the card is provided such that the connector is compressed between the device and card when the glass is connected on the staff. An independent claim is also included for a method for providing ultrasound welding for a glass of a watch.