Foldable Hinge Cam Geometry for Thin Freestop Mechanisms
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Solution Overview
Problem
Existing folding display phones achieve the freestop characteristic by increasing the number and size of springs, which results in increased thickness and weight, making it difficult to maintain a thin body design.
Innovation Solution
A foldable electronic device with a shaft cap, body, swing arm, first cam component, second cam component, and elastomer, where the first and second cam components are coaxially arranged in the shaft cap, and an elastomer applies an elastic force to maintain contact between the cam components, allowing for a freestop characteristic without increasing the device's thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quantity and size of springs are increased to achieve the freestop characteristic, then the friction coefficient increases and the freestop characteristic is improved, but the overall thickness and weight of the device increase
Solution Approach 1:
The patent changes the geometric parameters of the cam components, specifically designing the cam surface with a locking section where the angle between the normal direction and the central shaft is ≤ arctan μ. This parameter optimization allows the mechanism to achieve self-locking and freestop characteristics without requiring additional springs or increasing spring size, thereby maintaining device weight and thickness.
2Reliability
If the quantity and size of springs are increased to achieve the freestop characteristic, then the friction coefficient increases and the freestop characteristic is improved, but the overall thickness of the device increases
Solution Approach 1:
The patent optimizes the cam surface geometry by controlling the angle α between the normal direction of the locking section and the central shaft to be ≤ arctan μ. This parameter change enables the mechanism to achieve self-locking capability with the existing spring configuration, eliminating the need to increase spring quantity or size, thus maintaining the device thickness.
3Reliability
If the cam surface is designed with a locking section having a specific angle relationship, then the freestop characteristic is achieved without increasing spring quantity, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies that the angle α between the normal direction of the locking section and the central shaft should be ≤ arctan μ, where μ is the friction coefficient. This parameter design leverages the inherent friction properties of the materials to achieve self-locking, converting a potentially complex geometric constraint into a simpler friction-based solution that is more tolerant to manufacturing variations.
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
The solution enables the implementation of the freestop characteristic while maintaining a thin body, improving user experience and extending the service life of the cam components by reducing contact stress.
Implementation Method 1
The damping force is provided by a friction force generated by surface design of the cam component and the pressure contact
Data Source
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AI summary
Embodiments of this application provide a foldable electronic device, including: a shaft cap, a body rotatable around a rotation shaft in the shaft cap, a first cam component, and a second cam component. The first cam component and the second cam component are arranged in the shaft cap along a direction of the rotation shaft to form pressure contact. The first cam component is connected to the body through a swing arm and is configured to be rotatable around a central shaft of the first cam component. The second cam component is configured to be slidable along a direction of the central shaft. A contact surface of the first cam component and the second cam component includes at least one cam surface that matches with each other. The cam surface includes a locking section, an angle between a normal direction of the locking section and the central shaft is less than or equal to an arctan function of µ, where µ is a friction coefficient between the first cam component and the second cam component, and a resultant force of a cam driving member in a rotation direction of the cam driving member is 0, so that the body is not automatically unfolded or folded, thereby implementing the freestop characteristic.