Cable Rock Bolt Expander Mechanism for Immediate Anchoring
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Solution Overview
Problem
Cable rock bolts in underground mining are cumbersome and time-consuming to install, providing limited support until cement grout cures, and their length cannot be customized to match drilled bores, requiring separate operations for fitting and tensioning after grout curing.
Innovation Solution
An expander mechanism for cable bolts that can be connected on-site, allowing for customizable lengths and immediate installation with a rock plate and tensioning, even in grout-filled bores, using a non-cylindrical design to facilitate grout flow and axial movement of gripper elements for secure anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cable rock bolts are installed with cement grout to secure the cable within the bore, then the cable is anchored in the bore, but the installation process becomes time-consuming and the cable provides no wall reinforcement until the grout cures (up to 2 days)
Solution Approach 1:
The anchoring function is segmented into two independent mechanisms: mechanical expansion anchoring (providing immediate support) and cement grout bonding (providing long-term reinforcement). The expander mechanism with conical wedge and radially expandable elements provides instantaneous mechanical anchoring, while the grout provides subsequent chemical bonding, eliminating the waiting period for support.
Solution Approach 2:
The mechanical expander mechanism is activated before the grout cures to provide immediate anchoring and wall reinforcement. The cable is tensioned and the expander elements are forced into engagement with the bore wall in advance, so that support is provided during the grout curing period rather than waiting for it.
2Adaptability or versatility
If cable rock bolts are used to provide flexible installation with customizable lengths, then the cable can be fed into bore from directions not aligned with the bore, but the cable cannot be rotated to generate axial movement for mechanical expansion anchoring
Solution Approach 1:
The rotation-based expansion mechanism (suitable for rigid solid bars) is replaced with a linear axial movement-based expansion mechanism suitable for flexible cables. The conical wedge converts axial cable movement into radial expansion of the elements, eliminating the need for cable rotation while maintaining mechanical expansion anchoring functionality.
Solution Approach 2:
The expansion mechanism changes from rotational parameter (for solid bars) to axial linear parameter (for flexible cables). The conical wedge geometry transforms the axial movement parameter into radial expansion, adapting the expansion mechanism to the flexibility characteristics of cable rock bolts.
3Ease of manufacture
If a wedge arrangement is used to attach the mechanical anchor to the cable, then the anchor can be fitted to the flexible cable, but the biasing load applied to the expander elements is low and only sufficient to maintain position during installation
Solution Approach 1:
The expander mechanism transitions from a static low-load biased position (during installation) to a dynamically high-load engaged position (during tensioning). The spring bias maintains element position during installation, but when the cable is tensioned, the elements are forced axially to expand radially and engage the bore wall with high frictional strength, exceeding the spring bias force.
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
This solution significantly reduces installation time and costs by enabling a single-stage process with immediate support, customizable lengths, and eliminates the need for post-curing operations, enhancing structural support as the cable bonds with the rock upon grout curing.
Implementation Method 1
a coil spring can be provided which acts between the housing and the expander elements to bias the elements into initial engagement with the wedge
Implementation Method 2
the elements can move axially relative to and over the wedge to expand... the elements are forced into frictional engagement with the bore wall
Data Source
Figure 1
Figure 2~5
Figure 3~4
AI summary
An expander mechanism 10 and a cable bolt, in which the expander mechanism includes gripper elements 13 which define a central bore 14 into which a cable end 15 can be inserted. A housing 16 houses the elements 13 and the housing 16 and the elements 13 cooperate slidingly along facing inclined surfaces 17, 18 so that relative movement increases or decreases the diameter of the central bore 14. A plurality of expander elements 25 cooperate slidingly against an outside surface 26 of the housing 16, so that movement of the housing 16 relative to the expander elements 25 can shift the expander elements 25 radially outwardly. The housing 16 has front and rear ends 21, 31 and an opening 32 formed in the rear end 31 to allow insertion of the cable 1 1 to enter the central bore 14 of the gripper elements 13. A biasing arrangement 34 acts between the housing 16 and the expander elements 25 to bias the expander elements 25 in a direction relative to the housing 16. A cable bolt including an expansion mechanism 10 is also provided.