Blind Rivet Nut Geometry for Automated Hole Alignment
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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, making fully automated setting difficult due to close tolerance requirements and inadequate chamfering for insertion.
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 or cylindrical shank, allows for easy alignment and automated setting without precise hole-finding devices, enabling an offset up to 1.5mm between the rivet nut and hole axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If close tolerance is maintained between hole diameter and blind rivet nut body diameter to ensure perfect assembly and anti-rotation, then assembly quality is improved, but manufacturing difficulty increases due to difficulty in ensuring close tolerance in industrial environment
Solution Approach 1:
The patent changes the geometric parameters of the blind rivet nut by introducing a specific ratio relationship between the first diameter (at foot end) and second diameter (at head end), where the ratio is between 0.65 and 0.82. This parameter change allows the rivet nut to accommodate tolerance variations while maintaining assembly quality, resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The patent applies asymmetry by creating a blind rivet nut with non-uniform diameter along its length - the foot end has a smaller diameter (first diameter) than the head end (second diameter). This asymmetric design with specific ratio between diameters enables the rivet nut to self-align and tolerate misalignment, reducing manufacturing difficulty while maintaining assembly quality
2Ease of operation
If chamfer is provided at the end of blind rivet nut body to facilitate insertion, then insertion ease is improved, but automation capability remains insufficient for fully-automated setting
Solution Approach 1:
The patent specifies a particular ratio range (0.65-0.82) between the foot end diameter and head end diameter, combined with a specific foot end angle between 15-30 degrees. These optimized parameters enable the chamfered foot end to effectively guide automated setting tools while maintaining ease of insertion, achieving both insertion ease and automation capability
Solution Approach 2:
The chamfer at the foot end is prepared in advance during manufacturing, creating a preliminary guiding feature that facilitates both manual insertion and automated setting. This preliminary action of providing the chamfer enables the rivet nut to self-align and be easily set by automated equipment
3Ease of operation
If offset between center of hole and axis of rivet is allowed to improve insertion ease, then insertion capability is improved, but alignment precision deteriorates
Solution Approach 1:
The asymmetric diameter design with smaller foot end diameter and larger head end diameter creates a tapered profile that naturally guides the rivet nut into the hole even with offset. The specific ratio between diameters (0.65-0.82) ensures that the rivet nut can accommodate misalignment while maintaining proper assembly, resolving the contradiction between insertion capability and alignment precision
Data Source
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AI summary
The present invention relates to a blind rivet nut, a blind rivet nut arrangement and a setting method. More particularly, the present invention relates to a blind rivet nut allowing an easy automated setting comprising a head (12) forming a flange, a shank (14) comprising a head end (16), a foot end (18) and a cylindrical bore (20) extending along a longitudinal axis (X) from the head end (16) to the foot end (18), the bore having a first bore segment near the foot end (18) and a second bore segment near the head end (16), the wall surrounding the second bore segment forming a deformable region of the shank and having an external wall diameter (D1), the foot end (18) having a foot end diameter (D2), wherein the foot end (18) of the shank comprises a tapered chamfer (22) making a foot end angle (A) of 21 to 25 degrees with the longitudinal axis (X), and wherein the ratio of the foot end diameter (D2) to the external wall diameter (D1) is between 0.65 and 0.82.