Blind Bolt Sleeve Expansion for Stable Fastening Across Plate Thicknesses
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Solution Overview
Problem
Conventional blind bolts and rivets face challenges in maintaining consistent fastening loads across varying plate thicknesses, leading to unstable fastening states and insufficient mounting strength, especially when thick and thin plates are fastened with the same axial force.
Innovation Solution
A blind bolt design comprising a bolt, an outer nut, a valve sleeve, and an inner nut, where the valve sleeve is pressed between the outer nut and the nut head portion of the inner nut to form a diameter-expanded portion, ensuring consistent crimping force regardless of plate thickness, achieved through a cylindrical valve sleeve with specific tapered and cylindrical portions and outer peripheral grooves for adaptive deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional blind bolt or rivet is used to fasten members, then the fastening operation can be performed from one side only, but the fastening load becomes unstable and inconsistent when plate thickness varies
Solution Approach 1:
The blind bolt is divided into multiple functional segments: a rivet body with sleeve and rivet head, a separate mandrel with head and shaft, and a breakable portion. This segmentation allows the rivet body to provide stable one-sided fastening while the mandrel shaft transmits controlled breaking force through the breakable portion, ensuring consistent fastening load regardless of plate thickness variations.
Solution Approach 2:
The mandrel shaft incorporates a breakable portion with specific dimensional parameters (reduced diameter or wall thickness) that change the mechanical properties at that location. This parameter change ensures the mandrel breaks at a predetermined load, providing consistent fastening force independent of the total plate thickness being fastened.
2Strength
If the mandrel shaft is made stronger to withstand higher fastening loads, then the fastening strength increases, but the mandrel cannot break at the intended thin portion
Solution Approach 1:
The mandrel shaft exhibits local quality differentiation: the main shaft portion is made strong to withstand high fastening loads, while a specific breakable portion has reduced strength through decreased diameter or wall thickness. This local quality change allows the mandrel to both support high loads and break controllably at the intended location.
Solution Approach 2:
The mandrel is pre-designed with a breakable portion during manufacturing, creating a predetermined weak point before assembly. This preliminary action ensures that when fastening occurs, the mandrel will break at the intended location under controlled conditions, providing reliable fastening load without requiring complex breaking mechanisms.
3Productivity
If a special fastening tool is used to pull the mandrel shaft strongly to break it, then the fastening operation can be completed, but the equipment complexity and cost increase
Solution Approach 1:
The mandrel shaft is designed to break automatically under the fastening load itself, without requiring a separate breaking mechanism or special fastening tool. The breakable portion self-activates when the predetermined load is reached, simplifying the fastening tool requirements while maintaining productive fastening operation completion.
Solution Approach 2:
The potential harmful effect of mandrel shaft breakage is converted into a beneficial automatic breaking mechanism. By intentionally designing a weak point, the mandrel's structural failure becomes a controlled feature that ensures consistent fastening load and simplifies the fastening process, eliminating the need for complex breaking tools.
4Adaptability or versatility
If the sleeve is expanded to fasten thick plates, then the fastening capability for thick plates is achieved, but the fastening load becomes excessive for thin plates
Solution Approach 1:
The fastening system transitions from a static expansion mechanism to a dynamic controlled-breaking mechanism. The mandrel shaft dynamically adjusts the fastening process by breaking at a predetermined load, preventing excessive force on thin plates while still enabling sleeve expansion for thick plates. This dynamic element adapts the fastening load to different plate thicknesses.
Solution Approach 2:
The breakable portion of the mandrel shaft acts as a predetermined cushioning element that limits the maximum fastening load before it can become excessive. This prior cushioning prevents damage to thin plates by breaking the mandrel before the sleeve expansion generates harmful excessive forces, while still allowing sufficient expansion for thick plate fastening.
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 enables consistent and strong fastening loads across different plate thicknesses, enhancing the range of applications by maintaining a stable crimping force, even when fastening thin or thick plates, thereby addressing the limitations of existing technologies.
Implementation Method 1
when the blind bolt is inserted into the member to be mounted and the mounting hole of the mounting member and the bolt is rotated, the valve sleeve is axially compressed and expanded in diameter between the outer nut and the stepped portion of the nut head portion of the inner nut
Data Source
AI summary
A blind bolt with a bolt head, a shaft portion on which a male screw is formed, and a bolt. An outer nut having a polygonal outer surface, and an outer nut hole penetrating in the axial direction. A cylindrical valve sleeve formed with a sleeve hole and an inner nut having a cylindrical portion. A nut head portion formed at one end of the cylindrical portion, and an inner nut hole having a female screw formed in a part inside. A plurality of outer peripheral grooves, extending in the outer peripheral direction are formed on the outer circumference of the valve sleeve. The cylindrical portion of the inner nut being inserted into the sleeve hole of the valve sleeve, the tip portion of the cylindrical portion inserted into the outer nut hole of the outer nut to prevent the inner nut from rotating with respect to the outer nut.