Blind Rivet Nut Geometry for Automated Offset-Tolerant Setting
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Solution Overview
Problem
Existing blind rivet nuts face challenges in achieving perfect alignment between the axis of the rivet nut and the hole, which complicates automated setting and requires precise tolerance adjustments, limiting their use in industrial environments.
Innovation Solution
A blind rivet nut design with a specific ratio of foot end diameter to external wall diameter and a 23-degree foot end angle, combined with internal chamfers and a polygonal shank, allows for fully automated setting without the need for precise alignment, using a robot-driven setting method that accommodates up to 1.5 mm offset between the rivet nut and hole axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If close tolerance between hole diameter and blind rivet nut body diameter is used to ensure perfect assembly and anti-rotation, then assembly quality is improved, but manufacturing difficulty increases due to industrial environment constraints
Solution Approach 1:
The blind rivet nut body is given an asymmetric polygonal cross-section instead of a circular one. This asymmetric shape provides inherent anti-rotation capability and ensures perfect assembly without requiring close tolerance control between hole and rivet nut diameters, thus improving manufacturing ease while maintaining assembly quality
Solution Approach 2:
The polygonal shank is designed with a specific cross-section that预先 (pre) establishes the anti-rotation function and alignment capability before the setting process begins. This preliminary geometric configuration eliminates the need for precise tolerance adjustments during manufacturing
2Ease of operation
If chamfer is added to facilitate blind rivet nut insertion, then insertion ease is improved, but automation capability remains insufficient for fully-automated setting
Solution Approach 1:
The polygonal shank cross-section provides asymmetric geometry that guides the rivet nut into correct alignment during automated insertion. The flat sides and corners of the polygonal shape engage with corresponding features in the hole, enabling fully-automated setting without requiring additional chamfers or alignment features
Solution Approach 2:
The polygonal shank design replaces traditional chamfer-based alignment with curved-like engagement surfaces that guide the rivet nut into proper position during automated insertion, facilitating fully-automated setting while maintaining insertion ease
3Manufacturing precision
If precise alignment between rivet nut axis and hole axis is required, then assembly quality is maintained, but productivity decreases due to complex alignment procedures
Solution Approach 1:
The polygonal shank cross-section provides inherent alignment capability that eliminates the need for precise manual or machine alignment procedures. The asymmetric geometry self-aligns during insertion, maintaining assembly quality while dramatically reducing manufacturing time for fully-automated production
Solution Approach 2:
The polygonal shank design enables the blind rivet nut to self-align and self-center during the automated insertion process. The geometric features of the polygonal cross-section automatically guide the rivet nut into correct position without requiring external alignment devices or procedures, thus improving productivity while maintaining assembly quality
Data Source
AI summary
The present invention relates to a blind rivet nut allowing an easy automated setting comprising a head forming a flange, a shank comprising a head end, a foot end and a cylindrical bore extending along a longitudinal axis (X) from the head end to the foot end, the bore having a first bore segment near the foot end and a second bore segment near the head end, the wall surrounding the second bore segment forming a deformable region of the shank and having an external wall diameter, the foot end having a foot end diameter, wherein the foot end of the shank comprises a tapered chamfer making a foot end angle of 21 to 25 degrees with the longitudinal axis (X), and wherein the ratio of the foot end diameter to the external wall diameter is between 0.65 and 0.82.