Retractable Pin Watch Strap Mechanism for Scratch-Free Attachment
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Solution Overview
Problem
Conventional watch strap fastening systems are difficult to use for changing straps, often requiring special tools and can scratch the watch case, and existing solutions are either rigid or prone to accidental disengagement.
Innovation Solution
A system with retractable pins controlled by independent movable levers, actuated by a slider, and a locking mechanism that allows easy attachment and detachment of the strap, using a spring for deployment and automatic unlocking when inserted between the watch lugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional spring-loaded pins are used for attaching the bracelet, then the structure is simple, but the pins scratch the internal face of the lugs during insertion and require special tools for uncoupling
Solution Approach 1:
The pin is pre-loaded in a retracted position within the tubular body before the attachment operation begins. The user manually positions the pin against the lug hole, ensuring proper alignment before activation. This preliminary positioning prevents the pin from scratching the lug surface during insertion, as the pin only extends forward after correct placement is achieved.
Solution Approach 2:
The pin transitions from a static extended position to a dynamic retracted position during the attachment process. The pin is held retracted by a locking mechanism (such as a detent or cam lock) that releases only when properly positioned. This dynamic control allows the pin to remain retracted during handling and alignment, eliminating scratching, while extending only when needed for secure attachment.
2Ease of operation
If the pins are pushed outwards by a spring for easy attachment, then the attachment process is simplified, but the pins cannot be independently controlled and may scratch the lugs
Solution Approach 1:
The attachment system is segmented into two independent pin mechanisms, each capable of being controlled separately. Instead of a single spring pushing both pins simultaneously, each pin has its own activation mechanism (such as individual buttons, levers, or release buttons) that allows independent extension and retraction. This segmentation enables precise control over each pin's position, allowing one pin to be secured while the other remains retracted if needed.
3Reliability
If a locking mechanism is added to prevent accidental disengagement, then the stability is improved, but the device complexity increases
Solution Approach 1:
The locking mechanism is designed to engage automatically when the pin is inserted into the lug hole. As the pin extends forward, its end surface or a associated locking element naturally contacts a corresponding feature on the lug, creating a self-locking condition that prevents accidental disengagement. No additional active locking components or complex mechanisms are required—the attachment geometry itself provides the locking function.
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
Enables quick and easy exchange of straps without scratching the watch case, with independent pin activation and stable deployment, simplifying the process and preventing accidental disengagement.
Implementation Method 1
a spring pushing the pins into their deployed position
Implementation Method 2
an elastic means is placed between the pins to hold them in the deployed position. Preferably, this elastic means is a spring.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The system (1) for attaching a variable element, such as a bracelet, to a fixed object, such as a watch case, comprises at least two retractable pins (4, 4'), two independent rotating levers (6, 6'), the movement of the levers (6, 6') displacing the pins (4, 4') into a deployed position allowing the variable element to be attached to the fixed object, or into a retracted position allowing the variable element to be detached from the fixed element. The rotation of the levers (6, 6') is caused by the movement of a slider (10), and the system further comprises a locking mechanism (12, 12') for holding the levers in a position corresponding to a retracted position of the pins (4, 4').