Plastic Blind Rivet with Segmented Legs and Locking Mechanism
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Solution Overview
Problem
Plastic blind rivets face challenges in achieving consistent expansion without breaking and maintaining desired strength, especially under varying humidity conditions, due to complex molding requirements and instability in fastening force.
Innovation Solution
A plastic blind rivet design featuring a hollow sleeve with constant-width slits and flexible legs that expand radially, stabilized by body locks and a mandrel lock, eliminating the need for multiple stages of latching grooves and projections, and using polyoxymethylene (POM) which does not require humidity supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If latching grooves and latching projections are formed in multiple stages in the axial direction on the mandrel and sleeve, then the expansion deformation can be maintained at the desired position, but the molding becomes complex and machining is no longer easy
Solution Approach 1:
The sleeve is divided into multiple leg portions by slits, allowing independent expansion control. The constant-width slits create uniform legs that can be controlled to expand at specific positions without requiring complex multi-stage latching structures, thus simplifying molding while maintaining expansion position control.
Solution Approach 2:
The patent changes the geometric parameters of the slits (constant width) and the leg portions (flexibility, intermediate position) to control expansion behavior. By optimizing these parameters, the sleeve expands at the desired position without needing complex latching grooves and projections.
2Manufacturing precision
If slits are formed with different widths in different portions along the longitudinal direction to achieve expansion at the desired position, then expansion control is improved, but molding becomes complex and machining is no longer easy
Solution Approach 1:
The patent applies local quality by forming legs with specific properties at specific locations. The leg portions at the intermediate position are designed to be flexible and expand outward, while other portions maintain structural integrity. This localized differentiation achieves expansion control without varying slit widths, keeping molding simple.
3Reliability
If plastic materials with good elongation (such as Nylon) are selected to prevent cracks, then crack resistance is improved, but the elongation performance during drying becomes poorer and continuous humidity supply is required, increasing cost and affecting fastening force stability
Solution Approach 1:
The patent changes the material parameter from humidity-sensitive plastics (Nylon) to humidity-insensitive plastics (polyoxymethylene/POM). This material substitution maintains crack resistance through proper structural design (leg portions with intermediate positions) while eliminating the need for continuous humidity supply, reducing cost and stabilizing fastening force.
4Strength
If the sleeve expands without breaking to achieve desired fastening strength, then fastening strength is improved, but it is not easy to achieve expansion deformation at the desired position without the sleeve breaking
Solution Approach 1:
The sleeve is segmented into multiple leg portions by slits, allowing controlled expansion at specific locations. The leg portions can flex and expand outward at the intermediate position without breaking the entire sleeve, achieving both desired expansion position control and sufficient fastening strength.
Solution Approach 2:
The patent introduces dynamic flexibility through the leg portions that can bend and expand outward. This dynamic capability allows the sleeve to adapt to the expansion force and achieve deformation at the desired position without brittle failure, maintaining 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 ensures stable expansion and increased fastening force without cracking, simplifying manufacturing and reducing environmental sensitivity, while maintaining consistent performance across different humidity levels.
Implementation Method 1
the legs can be flexed so as to expand outward in the radial direction at an intermediate position therein, by a pressing force acting from the head to the other end of the sleeve when a pulling-out force is applied
Implementation Method 2
body locks are formed for maintaining the expanded condition of the legs, at a position near the flange; in the shank, a mandrel lock is formed for maintaining the expanded condition of the legs
Data Source
AI summary
A plastic blind rivet includes a sleeve with a plurality of legs formed by a plurality of slits of constant width. A body lock is formed on the inside of the rivet sleeve, and a mandrel lock is formed in the shank of the mandrel. When the rivet is set, the body lock and mandrel lock are engaged so as to maintain the legs in an expanded condition. A stopper is formed in the mandrel shank and abutments formed in the sleeve body. During rivet setting, the stopper and abutments engage to limit further deformation of the sleeve legs.