Friction Bolt Retainer Mechanism for Component Ejection Prevention
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Solution Overview
Problem
Friction rock bolts face safety risks and equipment damage due to potential ejection of bolt components under load, with existing solutions relying on resin or cement anchoring methods that are costly, cumbersome, or prone to failure under tensile and shear forces.
Innovation Solution
A friction bolt assembly with a retainer mechanism that distributes loading forces axially, using a nut and flange configuration to prevent ejection of broken components by sharing tensile loads between the bar and tube, and employing a retainer mechanism that functions independently of the rock strata to retain fractured parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If friction rock bolts are used to stabilise rock strata, then installation speed and cost are improved, but safety risks increase due to potential ejection of broken components under load
Solution Approach 1:
The retainer mechanism is pre-installed within the tube before the bolt is inserted into the bore. This preliminary arrangement ensures that if the bolt breaks under load, the broken components are automatically contained by the retainer mechanism, preventing ejection and eliminating the need for post-failure intervention. The retainer acts as a pre-positioned safety barrier that counteracts the harmful ejection effect before it can occur.
Solution Approach 2:
The retainer mechanism serves as a protective barrier positioned beforehand within the tube to cushion and contain broken bolt components. This pre-positioned protective structure absorbs and contains the energy of potential component ejection, preventing harmful effects to workers and equipment while maintaining the simplicity and speed of friction bolt installation.
2Object-affected harmful factors
If resin or cement anchoring is used to prevent component ejection, then safety is improved, but installation complexity and cost increase
Solution Approach 1:
The retainer mechanism is designed as a self-contained component that automatically contains broken bolt parts without requiring external resin or cement materials. The mechanical structure of the retainer itself provides the containment function, eliminating the need for additional anchoring materials and simplifying the installation process to only require inserting the complete assembly into the bore.
Solution Approach 2:
The retainer mechanism is integrated with the tube as a single assembly, combining the containment function with the existing structural component. This merging eliminates the need for separate resin or cement anchoring systems, reducing installation complexity while maintaining effective prevention of component ejection.
3Force
If the tube is placed in axial tension during use, then anchoring force is improved, but the tube becomes susceptible to fracturing and ejection
Solution Approach 1:
The anchoring function is extracted from the tube and transferred to the retainer mechanism. The tube is relieved of tensile loading by having the retainer mechanism bear the anchoring forces through frictional engagement with the bore wall. This separation of functions allows the tube to maintain its structural integrity while still achieving effective anchoring through the retainer.
Solution Approach 2:
The retainer mechanism acts as an intermediary between the bolt assembly and the bore wall, mediating the anchoring forces. Instead of the tube directly bearing tensile loads against the bore wall, the retainer mechanism provides the frictional engagement, protecting the tube from tensile stress while maintaining anchoring effectiveness.
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 solution effectively reduces the risk of component ejection and maintains stability against rock strata fracture or collapse by distributing loads and preventing axial elongation of the bar, thereby enhancing safety and reducing the likelihood of equipment damage.
Implementation Method 1
the tube is already a friction fit within the bore prior to expansion of the bolt which maximises frictional engagement of the rock bolt with the bore wall
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
A friction bolt assembly to frictionally engage a bore formed in rock strata. The assembly comprises an elongate tube and an expander mechanism acted on by an anchor mechanism via an elongate bar or cable. A retainer mechanism is mounted to act between the bar or cable and the tube to prevent ejection of the bar or cable from the assembly should the bar or cable break.