Rock Bolt End Coupling Recessed Torque Transfer
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Solution Overview
Problem
Conventional rock bolt systems face difficulties in rotating and tensioning bolts when the bolt end is recessed in a bore, especially in environments where no tail protrudes from the rock face, making it hard to mix resin or grout and apply tension effectively.
Innovation Solution
An end coupling with a lead portion and a tail portion, where the lead portion has a slim design to fit within the bore without enlarging it, and a mechanism for torque transfer, such as a polymeric plug or stop element, allows for rotation and tensioning of the rock bolt shaft, even when the tail is recessed, by enabling torque transfer and axial movement of the coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the bolt end is recessed in the bore to achieve a clean rock face appearance, then the aesthetic appearance is improved, but the accessibility for rotation and tensioning operations deteriorates
Solution Approach 1:
The coupling device is segmented into a lead portion that fits within the bore and a tail portion that extends outward. This segmentation allows the functional elements (threaded engagement for rotation) to be positioned within the bore while the operational interface (tail portion for tensioning) remains accessible outside the bore, resolving the contradiction between aesthetic appearance and operational accessibility.
2Ease of manufacture
If the lead portion is made slim to fit within the existing bore without enlargement, then the installation complexity is reduced, but the structural strength may be compromised
Solution Approach 1:
The coupling device exhibits local quality variations: the lead portion has a slim profile to fit within the existing bore, while the tail portion has a larger diameter to provide structural strength for tensioning operations. This localized differentiation of dimensions allows the device to satisfy both installation constraints and structural requirements simultaneously.
3Ease of operation
If the coupling extends beyond the shaft end to provide operational access, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The coupling device is designed as a multi-functional component that simultaneously provides threaded engagement with the shaft, structural strength through its extended tail portion, and operational interface for tensioning devices. This integration of multiple functions into a single device reduces overall system complexity compared to using separate components for each function.
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
Enables efficient rotation and tensioning of rock bolts with minimal protrusion from the rock face, facilitating effective grout or resin mixing and bolt activation, while allowing for attachments to be securely fastened, enhancing rock support and ease of operation in mining and tunnelling applications.
Implementation Method 1
a first thread extending along at least part of the first portion of the passage and being arranged to threadingly engage the external thread on the shaft
Implementation Method 2
the coupling is able to impart torque up to a threshold level under rotation of the coupling in this first direction as the plug acts as a stop and prevents any further relative rotation between coupling and shaft
Data Source
AI summary
An end coupling for a shaft of a rock bolt comprises a body having a lead portion with a leading end, and a tail portion with a trailing end. The tail portion is arranged to be connected to a drive to impart rotation to the coupling about its axis. The body defines a passage extending between the leading and trailing ends and a first portion of the passage extends from the leading end and has a first diameter. A second portion of the passage is disposed adjacent the first portion and has a second diameter that is larger than said first diameter. A first thread extends along at least part of the first portion of the passage and is arranged to engage an external thread on the rock bolt shaft. A rock bolt assembly incorporating the end coupling is also disclosed.