Self-Piercing Rivet Element for Punch-Free Slug Removal
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Solution Overview
Problem
Existing self-piercing rivet elements are not suitable for attaching to metal components, particularly sheet metal parts, due to issues with reshaping and strength, and require a follow-up punch for slug removal, which is problematic for nut elements.
Innovation Solution
A self-piercing rivet element with a hollow rivet section that has a larger diameter at the transition to the body part and a closed peripheral wall, featuring a tapering design with a circular opening at the free end, allowing for easy slug removal through the thread cylinder without a follow-up punch, and can be used for both nut and bolt elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spike-shaped rivet section with segmented structure is used for self-piercing attachment, then the attachment quality to fiber composite materials is improved, but the strength and fatigue characteristics become questionable when used with metal components
Solution Approach 1:
The rivet section is divided into multiple segments that can move apart during dilation, allowing the rivet to expand within the pre-formed hole while maintaining structural integrity. This segmented structure enables the rivet to adapt to the hole geometry and distribute stresses more effectively, improving both attachment quality and strength.
Solution Approach 2:
The invention changes the geometric parameters of the rivet section, specifically introducing a tapering design with controlled angles and specific diameter relationships. The rivet section has a larger diameter at the transition to the body part and tapers toward the free end, with specific angle ranges (20°-100°, preferably 30°-60°) that optimize both the piercing process and the final attachment strength.
2Device complexity
If a self-piercing rivet element is used to attach to sheet metal parts, then the attachment process is simplified, but the sheet metal undergoes considerable reshaping and displacement which is problematic
Solution Approach 1:
The rivet section is designed to create a pre-formed hole through the sheet metal before final dilation occurs. This preliminary piercing action separates the hole creation from the expansion process, allowing the metal to be punched through with minimal lateral displacement, and then the rivet segments expand within the established hole geometry.
Solution Approach 2:
The rivet section has different geometric properties at different locations: a larger diameter at the transition to the body part for structural strength, a tapered section with specific angles for controlled metal displacement during piercing, and a smaller diameter at the free end for clean hole formation. This local variation in geometry optimizes the attachment process while minimizing overall sheet metal deformation.
3Ease of operation
If a follow-up punch is used to remove the piercing slug, then the slug can be removed from the nut element region, but the process becomes more complex and the thread cylinder could be damaged
Solution Approach 1:
The invention extracts the slug removal function from the attachment process by designing the rivet section with a diameter at the transition region that is larger than the outer diameter of the thread cylinder. This size difference creates a clearance path that allows the slug to be automatically ejected through the thread cylinder after piercing, eliminating the need for separate slug removal operations and avoiding thread cylinder damage.
4Ease of operation
If the rivet section diameter at the transition to the body part is larger than the thread cylinder outer diameter, then the slug can be removed easily without a follow-up punch, but the rivet section structure becomes more complex
Solution Approach 1:
The invention uses specific parameter relationships to simplify the overall structure: the rivet section diameter at the transition is larger than the thread cylinder outer diameter, creating a clearance path for slug ejection. The tapering design with controlled angles (20°-100°) and the segmented structure work together to enable automatic slug removal while maintaining manufacturing feasibility and structural efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-quality attachment to sheet metal parts without the need for a follow-up punch, ensuring the slug can be removed easily and reinforcing the connection between components, enhancing the strength and stiffness of the assembly.
Implementation Method 1
the rivet section is formed at least regionally to be dilated by means of a die button
Implementation Method 2
tapers in the direction of the central longitudinal axis away from the body part
Data Source
AI summary
A self-piercing rivet element is provided with a body part having a thread cylinder and with a hollow rivet section to be pressed into an as yet unpierced component. In this arrangement, the rivet section is designed to be at least regionally dilatable by means of a die button and tapers in the direction of the central longitudinal axis and away from the body part. The hollow rivet section has, in the region of the transition to the body part, a diameter, which is larger than the outer diameter of the thread cylinder. Furthermore, the rivet section has a closed peripheral wall and an opening at its free end which corresponds at least substantially in diameter to the core diameter of the thread cylinder. Furthermore a component assembly, a method for the manufacture of the component assembly and the die button are claimed.