Foldable Hinge Swing Arm Joint to Prevent Pin Shear Fracture
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Solution Overview
Problem
The pin connecting the secondary swing arm and the main swing arm in foldable electronic devices experiences high shear stress, leading to fracture and interruption of damping force transmission, compromising the device's damping characteristic.
Innovation Solution
A foldable electronic device design featuring a first swing arm with an annular groove and a second swing arm with a boss that overlap in the axial direction of a pin, increasing the joint's sectional area and reducing shear stress, along with a pin-shaft connection using connection lugs and slide grooves to enhance structural strength and damping force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pin is used to connect the secondary swing arm and main swing arm, then the damping force can be transmitted between the two swing arms, but the pin experiences high shear stress and is prone to fracture
Solution Approach 1:
The connection function is segmented between the pin and the annular groove-boss structure. The pin handles axial loading and rotation, while the annular groove and boss handle shear stress and damping force transmission. This division of labor reduces the shear stress on the pin and prevents fracture.
Solution Approach 2:
The annular groove on the main swing arm and the boss on the secondary swing arm are merged to form a composite connection structure with the pin. This merging creates a multi-point contact system that distributes shear stress across multiple contact surfaces, significantly improving the pin's shear stress resistance while maintaining damping force transmission reliability.
2Device complexity
If the pin connects the swing arms, then the structure remains simple, but the sectional area of the joint is small leading to high shear stress
Solution Approach 1:
The connection structure transitions from a single-point pin connection to a multi-dimensional contact system. The annular groove provides radial contact surfaces, the boss provides axial contact surfaces, and the pin provides rotational contact. This dimensional expansion increases the joint's sectional area and load-bearing capacity without significantly increasing overall structural complexity.
3Ease of manufacture
If the pin is used for connection, then the manufacturing process is simple, but the pin is prone to fracture under large shear stress
Solution Approach 1:
The annular groove and boss structure is designed beforehand to cushion and distribute the shear stress before it reaches the pin. This pre-stress distribution mechanism protects the pin from excessive shear stress and prevents fracture, while the overall connection structure remains easy to manufacture using conventional machining processes.
Data Source
AI summary
Embodiments of this application provide a foldable electronic device, including a shaft cover, a device body, and a first swing arm; a second swing arm coupled to a damping component inside the shaft cover and distributed in parallel to the first swing arm; and a pin connecting the first swing arm and the second swing arm so that the second swing arm follows the first swing arm to rotate and transmits a damping force produced by the damping component to the first swing arm through the pin. In the electronic device according to the embodiments of this application, fitting between the annular groove and the boss increases a sectional area of a joint between the first swing arm and the second swing arm and reduces shear stress experienced by the pin, avoiding fracture of the pin under undesirably large shear stress, thereby improving reliability of the device.