Bolt Tensioning Assembly for Accurate Axial Force Detection
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Solution Overview
Problem
The existing methods for detecting the tightening force of bolts suffer from accuracy issues due to insufficient circumferential length of the thread portion, leading to potential plastic deformation and increased axial force detection errors.
Innovation Solution
A tensioning device with a connection member, tensioning mechanism, and tension bearer that includes a tension rod, bearing, and axial force detection unit, where the connection member has a convex portion with a second male thread and a hollow portion with a second female thread, allowing for improved engagement and reduced friction torque, ensuring accurate axial force detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the tensioning device uses a female thread portion threadly engaged with the male thread portion of the bolt protruding from the upper surface of the nut, then the device can apply tension to detect the tightening force, but the insufficient circumferential length of the thread portion causes plastic deformation and increases axial force detection error
Solution Approach 1:
The invention transitions from threading engagement (circumferential direction) to bearing support (radial direction). The connection member's convex portion is supported by the bearing on the tension rod, providing stability through radial constraint rather than relying on circumferential thread engagement length. This dimensional shift resolves the contradiction by eliminating the need for long thread portions while maintaining measurement precision.
Solution Approach 2:
The bearing acts as an intermediary element between the connection member and the tension rod. It provides stable support for the convex portion of the connection member, enabling accurate force transmission without requiring extensive thread engagement. The bearing mediates the interaction, allowing precise axial force detection while avoiding plastic deformation issues.
2Reliability
If the bolt shaft has a small diameter and short extension length, then the bolt design remains compact, but the thread engagement length becomes insufficient leading to detection errors
Solution Approach 1:
The invention moves the engagement mechanism from the circumferential thread direction to the radial bearing support direction. This allows the bolt to maintain its compact small diameter and short extension length while achieving reliable force transmission through the bearing-supported connection member, which constrains the convex portion radially rather than requiring long circumferential thread engagement.
3Measurement precision
If the tensioning device applies tension through thread engagement, then the tightening force can be detected, but friction torque increases causing detection errors
Solution Approach 1:
The bearing serves as an intermediary that reduces friction torque in the system. By supporting the convex portion of the connection member through radial bearing contact rather than circumferential thread friction, the bearing enables accurate tightening force detection with minimal friction interference, directly resolving the measurement precision issue.
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 2(c)
AI summary
[Problem to be Solved] To improve an engagement between a tensioning device and a bolt-nut fastener while suppressing increase in the number of components. [Solution] A tensioning device 1 is configured to apply upward tension to a bolt-nut fastener including a bolt 10 insertedly fitted with a fastened member H, and a nut 14 to be fastened to a shaft 11 of the bolt 10, which protrudes from the fastened member. A first male thread portion 14a is formed on an outer circumferential surface of the nut 14. The tensioning device includes a connection member 2 having a first female thread portion 21a1 to be threadly engaged with the first male thread portion 14a, a tensioning mechanism 3 for tensioning the nut 14 via the connection member 2 in a state where the first male thread portion 14a is threadly engaged with the first female thread portion 21a1, and a tension bearer 4 which is disposed around an outer circumference of the connection member 2, and bears a reaction force applied from the fastened member H in tensioning performed by the tensioning mechanism 3.