Blind Rivet Mandrel Head Asymmetric Elliptical Cross-Section
Solution Overview
Problem
Existing blind rivets face issues where the broken mandrel portion often drops off the rivet body, leading to noise and potential damage, and the solutions proposed in prior patents compromise the fastening strength by weakening the sleeve's expanded portion.
Innovation Solution
A blind rivet design featuring a mandrel head with a unique elliptical cross-sectional shape that maintains constant circumferential length, ensuring the sleeve's thickness and strength during expansion, thereby preventing the mandrel from dropping and maintaining high fastening strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mandrel head has a shape with a nearly round horizontal cross-section in the root portion and an oval-shaped horizontal cross-section in the tip portion, then the broken mandrel portion is kept from dropping off the rivet body, but the sleeve end is expanded and deformed again which weakens the strength of the expanded and deformed sleeve portion
Solution Approach 1:
The mandrel head is designed with asymmetric cross-sectional shapes: a nearly round horizontal cross-section in the root portion and an oval-shaped horizontal cross-section in the tip portion. This asymmetry allows the root portion to prevent mandrel dropping while the tip portion controls sleeve deformation to maintain fastening strength.
Solution Approach 2:
Different portions of the mandrel head are given different geometric properties: the root portion has a round cross-section for preventing mandrel dropping, while the tip portion has an oval cross-section that deforms the sleeve in a controlled manner to maintain fastening strength without excessive deformation.
2Reliability
If the sleeve end is expanded and deformed multiple times by the mandrel head shape changes, then the mandrel portion is kept from dropping off, but the fastening strength of the blind rivet is reduced
Solution Approach 1:
The mandrel head employs asymmetric cross-sectional geometry with a round root portion for stability and an oval tip portion for controlled deformation, preventing excessive sleeve deformation that would weaken fastening strength.
Solution Approach 2:
The mandrel head cross-sectional parameters are carefully controlled: the round portion maintains constant thickness to preserve strength, while the oval portion creates minimal additional deformation to maintain fastening strength.
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
The design effectively keeps the broken mandrel portion attached to the rivet body while maintaining high fastening strength by ensuring the sleeve's expanded portion remains strong and consistent, preventing noise and damage.
Implementation Method 1
A portion of the sleeve (for example, the portion at the end near the mandrel head) expands outward radially and is deformed
Implementation Method 2
the mandrel shaft extending from the flange on the attached component side is forcibly drawn out by the operation of the fastening tool until it breaks off
Implementation Method 3
Because the mandrel portion is not connected to the rivet body, gravity often causes it to drop off the rivet body
Data Source
AI summary
A head is formed so that the maximum diameter portion as viewed from the front is arranged in a different position axially with respect to the maximum diameter portion as viewed from the side. The horizontal cross-section of the head is such that a first ellipse is formed in the maximum diameter portion, and a second ellipse is formed in the maximum diameter portion with the long axis perpendicular to the long axis of the first ellipse. The horizontal cross-sectional shape of the head is gradually changed in the axial direction so as to continue from the first ellipse to the second ellipse. Each one of the horizontal cross-sections has the same circumferential length at different axial positions on the head.