Torque-Limiting Nut Structure for Tool-Free Break-Off Bolt Installation
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Solution Overview
Problem
The installation of break-off bolts in connectors often requires a specific torque wrench, which may not be available on-site, making the process inconvenient and inefficient.
Innovation Solution
A torque-limiting nut with a thread section and a head section separated by a predetermined breaking area, where the thread section has an internal thread and the head section includes an abutment shoulder extending radially inward, allowing the nut to be connected rigidly to the bolt for rotational installation without a torque wrench, breaking at a predetermined torque to ensure secure installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque wrench is used to install the break-off bolt, then the predetermined torque can be ensured, but the installation requires specialized tools that are often not available on-site
Solution Approach 1:
The torque-limiting nut is designed to automatically limit the installation torque through its own structural features (breaking area and abutment shoulder) without requiring external torque-wrenching tools. The nut itself performs the torque control function by breaking at a predetermined torque value, making the system self-regulating and eliminating the need for specialized measurement tools during installation
Solution Approach 2:
The nut's material properties and geometric parameters (breaking area dimensions, abutment shoulder position) are specifically designed to achieve torque limitation at a predetermined value. By changing the material strength and geometric parameters of the breaking area, the torque limit can be adjusted to match installation requirements without needing external tools
2Stability of the object's composition
If the head section is rigidly connected to the thread section, then the rotational position is kept stationary for proper torque transfer, but the head section becomes difficult to remove after breaking
Solution Approach 1:
The nut is divided into two functional segments: the head section (providing rotational stability and torque transfer) and the thread section (providing threaded engagement). These segments are rigidly connected during installation to ensure stable torque transfer, but can be easily separated after the breaking area fails, allowing the head section to be removed without additional tools
Solution Approach 2:
The abutment shoulder acts as an intermediary element between the head section and the break-off bolt. It provides the necessary rotational stability during torque application while its geometric design (extending radially inward) facilitates easy removal of the head section after breaking by providing a clear separation interface
3Ease of operation
If the thread section tapers out towards the distal end, then the installation is simplified, but the structural strength may be reduced
Solution Approach 1:
The thread section employs different geometric characteristics at different locations: it tapers towards the distal end to facilitate easy installation and removal, while maintaining sufficient strength in the critical engagement regions. The local geometry is optimized to provide the right balance between installability and structural integrity at each specific location along the thread section
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a torque-limiting nut (1) for a break-off bolt (24), especially for an electric connector (38), the torque-limiting nut (1) comprising a thread section (2) and a head section (4) which are separated by a predetermined breaking area (6), wherein the thread section (2) comprises an internal thread (8) and the head section (4) comprises at least one abutment shoulder (10) extending further towards the radial inward direction than the internal thread (8), the at least one abutment shoulder (10) being arranged adjoining to the predetermined breaking area (6). Therefore, the break-off bolt (24) may easily be installed in the connector (38) without the necessity of specialised tools, such as a torque wrench.