Shell-Retained Nut and Washer Assembly for Tight Clearances
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Solution Overview
Problem
Existing fasteners with collars and stepped washers are costly to manufacture and reduce the bearing surface, making it challenging to achieve proper clamp load and assembly in areas with restricted clearances.
Innovation Solution
A fastener system comprising a standard nut, a washer with a uniform inner diameter, and a shell with a bent section that axially retains the nut and washer, allowing the nut to freely rotate while maintaining concentricity and preventing inadvertent disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a collar is added to the nut and a stepped washer is used, then the fastener can be assembled in restricted clearances, but the manufacturing cost increases
Solution Approach 1:
The patent combines the collar and stepped washer functions into a single shell component. The shell includes an upper portion that acts as the collar and a lower portion that provides the stepped washer function, eliminating the need for separate collar and stepped washer components and reducing manufacturing cost.
Solution Approach 2:
The shell is divided into functional segments: an upper portion defining part of the top surface that retains the nut (collar function), a lower portion extending from the lower wall that contacts the washer (stepped washer function), and a middle portion connecting them. This segmentation allows each part to perform its specific function while being manufactured as a single integrated component.
2Adaptability or versatility
If a collar is added to the nut and a stepped washer is used, then the fastener can be assembled in restricted clearances, but the bearing surface area is reduced
Solution Approach 1:
The shell merges the collar and stepped washer into one component, where the lower portion provides a broad bearing surface that contacts the washer. This integrated design maintains adequate bearing surface area while achieving the clearance benefits of the collar-washer combination.
Solution Approach 2:
The shell's lower portion extends radially outward to provide sufficient bearing surface area in the radial dimension, compensating for any vertical space constraints imposed by the upper portion's collar function. This dimensional compensation ensures adequate bearing surface is available.
3Adaptability or versatility
If a collar is added to the nut and a stepped washer is used, then the fastener can be assembled in restricted clearances, but the assembly complexity increases
Solution Approach 1:
The patent combines the collar and stepped washer into a single shell component that is installed as one piece. This integration simplifies the assembly process by reducing the number of components that need to be individually positioned and assembled, while still providing the clearance benefits of the traditional collar-washer arrangement.
Data Source
AI summary
A fastener comprising a nut, a washer, and a shell that axially retains the nut and the washer together. In one embodiment, the shell axially retains the nut and the washer together, and has a lower wall axially retaining the washer to the nut in a first direction, and a s-shaped section retaining the nut to the washer in a second direction. In another embodiment, the shell has a bent section and a lower wall extending axially away from the bent section. The lower wall of the bent section retains the washer to the shell. In yet another embodiment, the shell comprises a base wall including a first bend, a first skirt depending away from the first bend, a second bend extending away from the second bend, a third bend extending away from the second bend, and a second skirt depending away from the third bend.