Shouldered Blind Rivet Shank to Prevent Bushing Seizure
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Solution Overview
Problem
The deformation of the bushing in blind fasteners can cause an internal swelling, leading to seizure between the grip zone and the shank of the pin, requiring excessive tightening force during installation.
Innovation Solution
A rivet design with a shank comprising two cylindrical portions connected by a shoulder, where the second portion has a smaller diameter than the first, creating a progressive transition and reducing the risk of seizure by providing a radial space between the internal swelling and the shank, facilitating easier tightening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bushing deformation zone is deformed to form an external bulge, then the rivet achieves proper installation configuration, but an internal swelling forms in the grip zone causing seizure between the bushing and pin shank
Solution Approach 1:
The pin shank is divided into two cylindrical portions with different diameters (first portion with larger diameter, second portion with smaller diameter), separated by a shoulder. This segmentation allows the second portion to fit within the internal swelling created during bushing deformation, preventing seizure while maintaining the external bulge for proper installation configuration.
Solution Approach 2:
Different portions of the pin shank are given different local qualities (diameters) to address different functional requirements. The first portion has a larger diameter for initial engagement, while the second portion has a smaller diameter specifically to accommodate the internal swelling and prevent seizure during tightening, thereby improving ease of operation.
2Ease of operation
If excessive tightening force is applied to overcome seizure, then the pin can be tightened in the bushing, but the bushing may rotate during installation
Solution Approach 1:
The segmented shank design with two portions of different diameters prevents seizure by allowing the second portion to fit within the internal swelling with radial clearance. This eliminates the need for excessive tightening force, thereby preventing bushing rotation and maintaining installation stability without compromising ease of operation.
3Strength
If the pin shank has a uniform diameter to maximize shear strength, then the structural strength is optimized, but the internal swelling causes seizure requiring excessive tightening force
Solution Approach 1:
The shank is segmented into two portions: the first portion with larger diameter contributes to shear strength, while the second portion with smaller diameter specifically addresses the seizure problem by fitting within the internal swelling. This segmentation allows the structure to maintain adequate shear strength while eliminating the need for excessive tightening force.
Solution Approach 2:
Different local qualities (diameters) are assigned to different portions of the shank to optimize both strength and ease of operation. The first portion maintains larger diameter for strength, while the second portion has reduced diameter locally to prevent seizure, achieving both objectives simultaneously.
Data Source
AI summary
A rivet may includea pin comprising: a threaded portion (36), a shank (38) and a head (40); anda bushing (32) comprising an essentially cylindrical body, said body comprising a deformation zone designed to form an external bulge (80); a collar (70) designed to receive the head of the pin; and a tapped portion (66) designed to engage with the threaded portion of the pin.The shank (38) of the pin comprises a first cylindrical portion (44) and a second cylindrical portion (46) connected by a shoulder (48), the first portion being adjacent to the head and having a first diameter, the second portion being adjacent to the threaded portion and having a second, smaller diameter.