Roof control system
Roof control system for underground strata is described, comprising: (a) an elongated bolt adapted for insertion into a hole bored in underground strata; (b) anchor means for securely anchoring the bolt in the hole at a location where a significant length of the bolt remains between the opening of the borehole and the anchor means; (c) tension means for placing said significant length of said bolt in tension by rotating the bolt at a predetermined torque, the torque means including a plate mounted on the bolt and located adjacent to the outer surface of the strata, and a nut means on the end of the bolt for engaging the plate; (d) tension/torque adjustment means for selectively adjusting friction between adjacent surfaces which rub against each other when the bolt is rotated, whereby the tension/torque ratio of the bolt is selected to match the desired level for a particular type of underground strata, the tension/torque adjustment means including an array of friction reducing washers with different contact surface areas, for location between the nut means and plate. A method of mine control for underground strata is also described using this roof bolt.
- Assignee:
- Jennmar Corp., Pittsburgh, PA (United States)
- Patent Number(s):
- US 5232311; A
- Application Number:
- PPN: US 7-703162
- OSTI ID:
- 6371003
- Resource Relation:
- Patent File Date: 20 May 1991
- Country of Publication:
- United States
- Language:
- English
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