Lug-Free Watch Case Strap Mount With Snap-Fit Locking

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Solution Overview

Problem

Existing watch strap attachment devices are complex, requiring multiple parts, specialized tools, and manual assembly, making them costly and time-consuming to manufacture and use.

Innovation Solution

A wearable object with a case featuring longitudinal cavities and a single-piece mounting interface that uses elastic snap-fit mechanisms for easy assembly and disassembly, allowing automated manufacturing and user-friendly strap interchangeability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional attachment devices with lugs and transverse bars are used, then the strap can be securely attached to the watch case, but the device complexity increases and manufacturing becomes time-consuming and expensive

Engineering Contradiction:
Improvestrap attachment securityVSAvoidattachment device structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the attachment device into a single integrated component that combines the mounting interface, locking mechanism, and securing elements into one piece. This eliminates the need for separate lugs, transverse bars, and multiple intercalated parts, thereby reducing device complexity while maintaining secure strap attachment.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The single-piece mounting interface performs multiple functions simultaneously: it attaches the strap to the case, provides locking mechanisms in both axial and transverse directions, and enables easy removal. This multi-functionality replaces what previously required multiple specialized components.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If traditional attachment devices with multiple parts are used, then the strap can be securely attached, but the manufacturing time and cost increase

Engineering Contradiction:
Improvestrap attachment securityVSAvoidmanufacturing speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

By combining all attachment components into a single molded piece, the patent eliminates multiple assembly steps. The single-piece construction can be directly injection-molded or otherwise manufactured as one unit, significantly reducing manufacturing time and enabling automation without manual re-attaching operations.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The locking mechanisms and securing features are pre-integrated into the single-piece mounting interface during its primary manufacturing process. This preliminary incorporation of all necessary attachment features eliminates the need for subsequent assembly operations, thereby increasing productivity.

Inventive Principle:
Principle #10Preliminary action

3Reliability

If lugs are added to the watch case for strap attachment, then the strap can be securely attached, but the case manufacturing automation is prevented and manual operations are required

Engineering Contradiction:
Improvestrap attachment securityVSAvoidcase manufacturing automation
Core Design Contradiction:
ReliabilityVSExtent of automation

Solution Approach 1:

The patent extracts the attachment device from the case structure itself, creating a separate single-piece mounting interface that attaches to the case without requiring integrated lugs or protruding elements. This allows the case to be manufactured as a simple, smooth surface suitable for complete automation, while the attachment function is provided by the separate mounting component.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the attachment function from the case body, creating a separate mounting interface component. This segmentation allows the case to be manufactured using fully automated processes without complex lug features, while the attachment functionality is provided by the independently manufactured mounting piece that connects to the simplified case structure.

Inventive Principle:
Principle #1Segmentation

4Reliability

If traditional attachment devices are used, then the strap can be attached, but strap interchangeability requires specialized tools and professional assistance

Engineering Contradiction:
Improvestrap attachment securityVSAvoidstrap interchangeability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent incorporates elastic interlocking means that provide a dynamic, reversible locking mechanism. The elastic elements allow the mounting interface to be easily inserted into and removed from the longitudinal cavity by simple axial movement, enabling users to interchange straps without specialized tools while maintaining secure attachment during normal use.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The single-piece mounting interface with its integrated locking and release mechanisms enables users to perform strap interchange themselves without requiring professional assistance. The design includes user-friendly features such as accessible release elements and simple insertion/removal actions that can be performed by the end user.

Inventive Principle:
Principle #25Self-service

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

Facilitates easy and cost-effective production of symmetrical cases with interchangeable straps, reducing manufacturing costs and enabling users to change straps without professional assistance.

Implementation Method 1

the elastic interlocking means are formed by at least one elastic clip cooperating with at least one housing provided in the longitudinal cavity

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4202571B1Portable object comprising a middle without attachment lugs and a removable strap
Publication Date: 2026.01.28 ETA SA MFG HORLOGERE SUISSE
  • EP4202571B1 patent drawingFigure 1~2
  • EP4202571B1 patent drawingFigure 3~4
  • EP4202571B1 patent drawingFigure 5

AI summary

One aspect of the invention relates to a wearable object (1) comprising a case (20) having a case (21) without a fixing lug and having two longitudinal cavities (110) extending along a longitudinal direction (XX), a strap (30) having two ends (31), each end (31) of the strap (30) cooperating with a mounting interface (200) configured to cooperate removably with a longitudinal cavity (110) of said case (21) to allow the mounting of the strap (30), characterized in that the mounting interface (200) is monobloc and comprises: means (210) for receiving and securing one end (31) of the strap (30); elastic interlocking means (220) for axially locking the mounting interface (200) in said longitudinal cavity (110) along the longitudinal direction (XX);means (230) for locking the mounting interface (200) in said longitudinal cavity (110) in a direction transverse to the longitudinal direction (XX).;