Hinge Open Core Routing for Flexible Circuit Reliability
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Solution Overview
Problem
Traditional head-mounted wearable devices face challenges in their physical configuration, particularly in providing a low-profile, small volume technique for establishing a wired connection between the left and right temples, which often results in early breakage and additional bulk due to abrupt bends and excess material requirements.
Innovation Solution
A hinge with an open core design that allows a flexible printed circuit to twist, maintaining a consistent distance between bends and reducing strain on conductors, enabling a smaller hinge and improved reliability of the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wired connection is established between left and right temples using traditional methods, then data exchange is enabled, but the device experiences early breakage and additional bulk due to abrupt bends and excess material
Solution Approach 1:
The flexible printed circuit board is configured with a curved path that follows the contour of the hinge assembly, replacing abrupt bends with gradual curves. This curvature distribution reduces stress concentration at sharp corners, thereby improving connection reliability and resistance to breakage during hinge rotation
Solution Approach 2:
The wired connection is routed through the third dimension by passing through the hinge assembly rather than along the surface. This three-dimensional routing eliminates the need for excess material and reduces the overall bulk of the connection structure while maintaining data exchange functionality
2Reliability
If excess material is used to prevent breakage, then connection reliability improves, but device volume and bulk increase
Solution Approach 1:
The flexible printed circuit board uses controlled bend radius parameters and material flexibility characteristics to achieve reliable connections without excess material. By optimizing the bend radius and material properties, the design maintains connection reliability while minimizing hinge volume and eliminating unnecessary bulk
3Ease of manufacture
If abrupt bends are used in the wired connection, then installation is simplified, but early breakage occurs reducing service life
Solution Approach 1:
The wired connection employs gradual curved bends instead of abrupt angles, distributing mechanical stress along the circuit path. This curvature design prevents early breakage and extends service life while maintaining manufacturability through standard flexible circuit board fabrication techniques
Data Source
AI summary
A head-mounted wearable device utilizes electronics placed in one or more of a left temple or a right temple. The temples are joined to a front frame using hinges. The hinges provide passageways, slots, or other openings to permit passage of a flexible printed circuit (FPC) within an open core of the hinge. The FPC allows communication between the left temple and the right temple. During motion of the hinge, the FPC may twist such that the ends within the hinge are rotated relative to one another while remaining substantially parallel to one another. The overall length of the FPC passing through the hinge remains substantially unchanged between the hinge being open or closed. The FPC remains protected within the hinge and is minimally displaced, preventing the introduction of a crease in the FPC at a hinge line.