Plastic Watch Case Bayonet Crystal Mounting
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Solution Overview
Problem
Watch cases made of plastic or electroformed materials face challenges in securely attaching removable components like crystals or backs, as they deform under stress, leading to detachment issues, and adding metal stiffening parts is often not feasible due to size constraints.
Innovation Solution
A bayonet-mounted crystal with a rotation stop mechanism that uses angled lugs and clearances to secure the crystal in place, eliminating the need for additional metal parts, and incorporating a bezel that clips onto the caseband to prevent rotation, ensuring secure attachment without deformation or breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a plastic or electroformed middle part is used, then the watch case can be made lighter and more cost-effective, but the middle part creeps under stress and cannot securely hold removable components
Solution Approach 1:
The solution divides the holding mechanism into two functional segments: the plastic middle part provides lightweight structure, while a separate rotation stop mechanism (clicker) provides the necessary locking strength. This segmentation allows each component to optimize its material properties without compromise.
Solution Approach 2:
The rotation stop mechanism acts as an intermediary element between the removable component and the plastic middle part. It transfers and distributes the holding stress, preventing the plastic material from bearing the full load that would cause creeping.
2Strength
If a metal stiffening part is added to prevent creeping, then the holding strength improves, but the device size increases and small caseband sections cannot accommodate it
Solution Approach 1:
The rotation stop mechanism introduces a dynamic locking system that engages only when needed (when the removable component is attached). The spring-loaded clicker provides variable resistance, offering strong holding force in the locked position while occupying minimal space during normal operation.
Solution Approach 2:
The solution changes the mechanical parameters of the holding system by using elastic deformation of the spring-loaded clicker to provide holding force. This allows high holding strength to be achieved through material elasticity rather than through increased structural dimensions.
3Ease of operation
If a bayonet mounting system is used, then removable components can be easily attached and detached, but the plastic middle part deforms under the mounting stress
Solution Approach 1:
The spring-loaded rotation stop mechanism provides beforehand cushioning by absorbing the mounting stress through elastic deformation. The spring element anticipates and cushions the impact of bayonet mounting, preventing stress transmission to the plastic middle part.
Solution Approach 2:
The invention extracts the stress-bearing function from the plastic middle part and places it in the rotation stop mechanism. This separation allows the bayonet mounting system to operate independently without compromising the structural integrity of the plastic case.
Data Source
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AI summary
A watch case (1) comprising a case (2) made of plastic or electroformed material and a removable crystal (3). Said crystal (3) or respectively said case (2) has a plurality of angled lugs (4), each insertable frontally into a recess (5) of said case (2) or of said crystal (3), in a first angular position, towards a first recessed position when the distance between said case (2) and said crystal (3) is minimal, said case (2) and said crystal (3) being pivotable relative to each other, in said first recessed position, up to a second angular position where a portion of each said lug (4) is fixed frontally behind a retaining surface of said case (2) or respectively of said crystal (3), and said case (1) has a rotation-stopping means (6) angularly securing said case (2) and said crystal (3) in said second angular position.