Shouldered Blind Rivet Sleeve to Prevent Screw Seizing
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Solution Overview
Problem
The deformation of the sleeve in blind rivets, which forms an external bulb, can lead to an internal bulge in the clamping area, causing seizing between the tightening zone and the shaft of the screw, requiring excessive screwing force during installation.
Innovation Solution
The assembly features a screw with a shoulder forming a gradual transition between two diameters, a maximum clamping capacity, and a gripping element, along with a sleeve that forms an external bulb with a deformation zone, allowing for a radial space between the internal bulge and the shaft to prevent seizing during screwing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sleeve is deformed to form an external bulb, then the fastening capability is improved, but an internal bulge forms in the clamping area causing seizing between the tightening zone and screw shank
Solution Approach 1:
The screw shank is divided into two portions with different diameters: a first portion with a larger diameter that engages the clamping zone, and a second portion with a smaller diameter that passes through the deformation zone. This segmentation allows the screw to navigate the internal bulge without seizing while maintaining fastening capability.
Solution Approach 2:
Different portions of the screw shank have different local diameters optimized for different zones: the first portion has a larger diameter for optimal clamping engagement, while the second portion has a smaller diameter to clear the internal bulge formed during deformation. This local quality variation resolves the contradiction between fastening strength and ease of operation.
2Ease of operation
If excessive screwing force is applied to overcome the internal bulge, then the screw can be inserted, but rotational drive issues occur and installation becomes difficult
Solution Approach 1:
By segmenting the screw shank into two diameter portions, the second portion with smaller diameter acts as a pilot that clears the internal bulge path, allowing the gripping element to rotate the screw without binding. This maintains rotational drive reliability while enabling easy insertion.
Solution Approach 2:
The second portion of the screw shank with smaller diameter acts as an intermediary element that clears the deformation zone path, allowing the gripping element to transmit rotational force without interference from the internal bulge, thus maintaining rotational drive reliability.
3Strength
If the screw shank has a uniform diameter optimized for clamping, then clamping capacity is maximized, but the screw cannot pass through the deformed sleeve without seizing
Solution Approach 1:
The screw shank is segmented into a first portion with larger diameter for optimal clamping capacity and a second portion with smaller diameter for easy passage through the deformed sleeve. This segmentation allows both maximum clamping capacity and easy installation.
Solution Approach 2:
Different local diameters are applied to different portions of the screw shank: the first portion has larger diameter for maximum clamping engagement, while the second portion has smaller diameter optimized for passage through the deformation zone, resolving the contradiction between clamping capacity and installation ease.
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
Facilitates easier screwing into the socket after the formation of the external bulb, reducing the need for higher screwing forces and minimizing the risk of rotational drive issues, while maintaining adequate clamping capacity and shear resistance.
Implementation Method 1
a deformation zone, adjacent to the clamping zone and suitable for receiving the shank of the screw, and a threaded portion adjacent to the deformation zone
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a fitting rivet comprising: – a screw comprising a threaded portion (36), a sleeve (38) and a head (40); and - a bushing (32) comprising an essentially cylindrical body, said body comprising a deformation zone designed to form an external bulge (80); a collar (70) designed to receive the head of the screw; and a tapped portion (66) designed to engage with the threaded portion of the screw. The sleeve (38) of the screw comprises a first cylindrical portion (44) and a second cylindrical portion (46) that are connected by a shoulder (48), the first portion being adjacent to the head and having a first diameter, the second portion being adjacent to the threaded portion and having a second, smaller diameter.