Panel Fastener Boss Geometry for Cam Shaft Retention
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Solution Overview
Problem
Existing panel fasteners, particularly those with curved lip bosses, are prone to spreading or bulging when subjected to engagement forces, leading to malfunction due to the cam shaft riding on the curved surface, especially under misalignment or large pulling forces, which can cause the cam shaft to dislodge from the boss.
Innovation Solution
A panel fastener design featuring a boss with an inwardly indented, circular recess and a bearing surface oriented coaxially with the cam shaft, which counteracts cocking or pulling forces by biting into the cam shaft, preventing the sidewalls from spreading by forming a seat or groove, thus maintaining axial alignment and preventing bulging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a curved lip boss is used in the panel fastener, then the fastener can be manufactured with simple geometry, but the casing becomes susceptible to spreading and bulging under engagement forces
Solution Approach 1:
The patent applies curvature by replacing the traditional curved lip boss with a boss featuring a curved recess that receives the cam shaft. This curved recess geometry provides mechanical engagement surfaces that prevent casing spreading while maintaining manufacturability through standard forming processes.
Solution Approach 2:
The patent applies local quality by creating specific geometric features (curved recess with bearing surface) in localized areas of the boss where engagement forces are applied. This allows the boss to have different functional zones: a curved recess for cam shaft engagement and bearing surfaces for force distribution, while the rest of the casing maintains its original simple geometry.
2Ease of operation
If the cam shaft rides on the curved surface of the lip, then the fastener operation is simplified, but the cam shaft may dislodge from the boss under misalignment or large pulling forces
Solution Approach 1:
The curved recess in the boss provides a guided path for the cam shaft, allowing smooth movement during operation while the curved geometry naturally retains the cam shaft through geometric constraint rather than relying solely on friction or alignment.
Solution Approach 2:
The curved recess acts as an intermediary structure between the cam shaft and the boss body. It provides a controlled engagement interface that guides cam shaft movement while preventing dislodgement, mediating between the need for smooth operation and secure retention.
3Device complexity
If the boss has a curved lip structure, then the fastener assembly is simpler, but the engagement forces cause the casing walls to spread significantly
Solution Approach 1:
The curved recess geometry provides mechanical advantage by creating bearing surfaces that distribute engagement forces. The curved shape allows the cam shaft to engage at optimal angles, reducing lateral spreading forces on the casing walls while maintaining structural simplicity.
Solution Approach 2:
The patent introduces localized geometric features (curved recess with bearing surface) specifically where forces are applied, allowing the boss to have enhanced load-bearing capacity in critical areas while maintaining overall structural simplicity and manufacturing ease.
Data Source
AI summary
A panel fastener (20) is disclosed having a hook and cam assembly (21). The fastener has a metallic casing 23 comprised of two sidewalls (24) formed with a boss (27′) inwardly indented from the main sidewall portion through which a cam shaft (28) is journaled. The boss (27′) is formed as a circular or annular recess or depression having an inwardly extending boss sidewall 51 extending inwardly from the sidewalls (24) and extending to an end portion or end wall (52) having a cylindrical terminal end or bearing surface (53). The bearing surface is located along a cylinder substantially coaxially aligned with the cam shaft and substantially normal to the plane (55) of the outer surface of the adjacent portion of the casing sidewall.