Electronic mine roof bolt tester
AssigneeConoco, Inc. (formerly Continental Oil Company)
InventorsStanley E. Hinshaw, Charles F. Cole, Jr.
Life of this patent
Estimating the term…
Abstract
The integrity of mine roofs and rock bolts is tested by determining the natural frequencies of the roof and bolt. The roof is struck at a plurality of locations and the resulting vibrations sensed with accelerometers. The output of each accelerometer is separated into a plurality of signals of different frequencies by a comb filter having selected band passes. The amplitude of the outputs of each of the band passes of the filter are used to determine the condition of the roof and bolt adjacent each accelerometer. The high amplitude signal resulting from the initial impact of the striking implement is electrically gated from the accelerometer output.
Claims9
A device for testing mine roof stability, comprising:
- means for exciting the mine roof to vibration at the natural occurring frequencies;
- transducer means sensing mine roof vibration to generate characteristic electrical signal output;
- gate means receiving input of said generated electrical signal output and providing a gate output signal for a predetermined duration;
- timing means responsive to said characteristic electrical signal output to turn on said gate means after a first predetermined duration;
- second timing means to turn off said gate means after a second predetermined duration;
- means for amplifying said gate output signal and providing an amplified output;
- filter means receiving said amplified output at a plurality of parallel inputs each to a respective one of plural frequency band filtering channels successively allotted within a predetermined total frequency range, each channel providing a band pass signal output;
- plural amplifier and indicator means each connected to a respective one of said channel signal outputs with each responsive to display indication when signals are detected within the respective designated frequency band.
A system for surveillance of mine roof stability, comprising:
- plural exciter means disposed at selected mine locations for exciting the mine roof to vibrations at the naturally occurring frequencies;
- plural acoustic detection means disposed adjacent respective ones of the plural exciter means;
- control means disposed at a selected location and effective to energize selected exciter means and to receive output from selected detection means;
- means for amplifying received outputs from selected detection means to provide a detection output;
- gate means receiving input of said detection output;
- timing means responsive to said detection output to turn on said gate means after a first predetermined duration;
- second timing means turning off said gate means after a second predetermined duration;
- filter means receiving said gate output at each of a plurality of inputs to provide plural filtered outputs of plural different frequency bands successively allotted within a predetermined frequency range;
- and
- plural amplifier and indicator means each connected to receive one of said filtered outputs and each responsive to display indication when sufficient signal is detected within the respective designated frequency band.
Dependencies are inferred from the claim text.