Semi-hollow Self-Piercing Rivet for Thin Sheet Metal Joints
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Solution Overview
Problem
Classic semi-tubular punch rivets are not suitable for producing joints in thin sheet metal connections due to their length and spreading behavior, and existing adaptations, such as filling the central shank bore with hydrostatic substances, are not reliable for varying sheet metal thicknesses and materials.
Innovation Solution
A semi-tubular punch rivet with a reduced overall length and shank bore depth, featuring a cylindrical outer surface that extends beyond the shank bore depth, and a radially inwardly inclined chamfer, which controls the radial expansion of the rivet shank to ensure reliable attachment of thin sheets without material damage, and is made of steel or steel alloys for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If classic semi-tubular punch rivets with long shank bores are used, then the rivet can penetrate through thicker materials, but the rivet shank spreads excessively during the joining process
Solution Approach 1:
The patent changes the geometric parameters of the rivet shank by reducing the shank bore depth relative to the total rivet length (TB/LN ≤ 0.5) and providing a cylindrical outer surface section. This parameter change fundamentally alters the spreading behavior during joining, enabling reliable thin sheet metal connections without excessive radial expansion.
2Duration of action of moving object
If the central shank bore is filled with hydrostatic substances to influence expansion, then the expansion process begins earlier, but the adaptation to different sheet metal thicknesses and materials is unreliable
Solution Approach 1:
The patent extracts the hydrostatic substance filling from the shank bore, leaving it empty instead. This extraction eliminates the need for material adaptation while the geometric design (reduced TB/LN ratio and cylindrical surface) provides consistent expansion control across different sheet metal thicknesses and materials.
3Shape
If the shank cavity length is increased to achieve sufficient expansion, then the rivet can spread properly, but the punching of the top sheet is affected
Solution Approach 1:
The patent optimizes the shank cavity depth parameter (TB) to be no more than 50% of the total rivet length (LN), creating an optimal balance where sufficient expansion occurs without interfering with the punching process. This parameter optimization enables both proper expansion and clean punching simultaneously.
4Shape
If the conical shape of the shank cavity is used, then radial expansion is supported, but the thinner areas spread far outwards reaching the rivet head diameter
Solution Approach 1:
The patent applies local quality by providing a cylindrical outer surface section with constant diameter in the lower portion of the rivet shank. This localized cylindrical geometry controls the expansion pattern, preventing excessive radial spreading in thinner areas while maintaining structural integrity, unlike the conical shape that causes uncontrolled outward expansion.
Data Source
Figure 1
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Figure 3A
AI summary
The invention relates to a semi-tubular self-piercing rivet (1) having a rivet head (10) and a rivet shaft (30), the shaft bore (32) of which satisfies the following relationship in relation to the length of the semi-tubular self-piercing rivet: (formula I), the total length of the self-piercing rivet LN being ≤ 4 mm. The invention further relates to a corresponding self-piercing rivet joint, to a method for producing the self-piercing rivet, and a to method for producing the self-piercing rivet joint.