Mine Roof Support Crib Preloading Mechanism
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Solution Overview
Problem
Existing mine cribs lack a method for preloading that does not create imbalance or unsafe conditions, relying on wedges driven between the crib and roof for securing.
Innovation Solution
Incorporating a preloading assembly with a jack mechanism within the crib, allowing for the separation of crib planks to apply a load vertically, thereby preloading the crib without causing imbalance or unsafe conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wedges are driven between the crib and roof to secure the crib, then the crib is secured in place, but imbalance and unsafe conditions may occur
Solution Approach 1:
The preloading assembly is divided into multiple jack mechanisms distributed around the crib perimeter. Each jack mechanism independently applies force to separate crib members, distributing the loading process across multiple points rather than relying on single-point wedge insertion. This segmentation ensures balanced force application and eliminates the imbalance risks associated with traditional wedge methods.
Solution Approach 2:
The jack mechanisms are positioned and ready within the crib structure before loading begins. The system performs preliminary positioning of all jack mechanisms and then applies preload forces in a controlled sequence. This preliminary preparation ensures that all components are in place and can apply force simultaneously or in a predetermined sequence, preventing the unsafe conditions that arise from sequential wedge insertion.
2Reliability
If a preloading assembly with jack mechanism is used within the crib, then consistent load is applied to roof and floor, but device complexity increases
Solution Approach 1:
The jack mechanisms serve multiple functions: they act as both the preloading device and structural components integrated into the crib framework. The same jack mechanisms that apply preload forces also serve as positioning elements and load distribution points. This multi-functionality reduces the need for separate dedicated preloading equipment, thereby limiting the increase in overall device complexity while achieving consistent loading.
Solution Approach 2:
The preloading assembly is designed to be self-contained within the crib structure, with jack mechanisms that utilize the crib's own members as reaction points. The system loads itself by using its integrated components to apply and distribute forces without requiring external preloading equipment. This self-service approach minimizes additional complexity by making the crib structure serve its own preloading needs.
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 preloading assembly effectively secures the crib by applying a consistent load to both the mine roof and floor, enhancing stability and reducing the need for wedges, while allowing for adjustments due to shrinkage.
Implementation Method 1
a jack mechanism between crib members adapted to drive the said crib members apart in order to preload the crib
Implementation Method 2
threaded rods extending through the plates and each rod having an adjustment nut located between the plates used to jack the plates apart
Data Source
AI summary
A mine crib from interlocking planks has pair of jack planks on opposite slides of the crib comprising an upper plank 19, lower plank 20 equipped with plates 23 and 24 having screw holes 34, 35 and threaded rod pass through holes 36, 37 and 38 so that threaded rods 39, 40 and 41 may slide through the holes and passing to corresponding cavities 42, 43 and 44 in plank 19. Each rod has a nut 45 and washer 46 so that the nut may be used with an appropriate tool so that as the nuts wound upward along the threaded rods then the jack plank sections 19 and 20 may be jacked apart and be used to preload the crib.