Detecting seam boundary using pick sound

Details Detecting seam boundary using pick sound Detecting seam boundary using pick sound

1998-04-09

2000-10-17

Lillis, Eileen D.

Mining or in situ disintegration of hard material

Automatic control; signaling or indicating

Ore/rock interface determination during cutting

299 105, E21C 3524

Patent

active

061320056

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

THIS INVENTION relates to a method and apparatus for distinguishing a boundary between layers of compacted inert materials, such as bitumised surface of a roadway on a concrete substrate, or the boundary between a coal seam and surrounding rock in a mine. The invention is, however, broadly applicable to any apparatus which uses picks or similar mining bits to dislodge the required inert material, the picks comprising a body which is rotatably held at one end terminating at a hardened tip at the other end. Naturally the tips of the picks wear out during use, and they have to be replaced. This wear increases when the pick reaches the boundary as it is not designed to penetrate the material beyond the boundary.


STATE OF THE ART

Picks used on mining machines are usually cylindrical with cone-shaped front ends that scrape through the inert material to be mined. The particles or small rocks that are loosened by the picks fall down onto the base of a mining machine and are transported to the rear of the machine by a conveyor belt. A cacophony of sounds are generated during mining and which emanate from the material being mined, the picks, and the mining machine itself. Various attempts have been made to use changes in the amplitudes of these sounds to indicate that the picks are mining a different material as a result of crossing the boundary.
U.S. Pat. No. 4,143,552 proposes using the beam frequency of resonance of the picks, to indicate the nature of the material being mined. The patent suggests that by monitoring the amplitude of the beam resonant frequency and its harmonics one can detect movement of a cutting tool carrying the picks, into the unwanted rock surrounding a coal seam. Because of the wide range of noises generated during operation of a mining machine, the specification instructs the reader that the beam resonant frequencies should be detected by mounting a vibration transducer conducted along an arm carrying the cutting tool so that, in theory, the vibrations of the pick are transmitted through the structure of the mining machine to the transducer. As this is mounted to detect vibrations conducted along the arm, it is virtually unaffected by air-borne sounds generated by the mining process. These sounds emanate from many sources, such as the conveyor used to convey the material to the rear of the mining machine; the propulsion unit used to move the mining machine forwardly as mining progresses; the sound of fractured coal tumbling onto the conveyor section in front of the machine and, after passing through the machine, onto the conveying system behind it; the scraping sounds generated by the coal lumps as they are conveyed through the machine; the rotational drive fed to the cutting tool in which the picks are mounted; and the ripping sounds created by the dislodgment of the coal from the coalface by the action of the picks.
The teaching of the US patent is unfortunately theoretical, rather than practical, as it ignores the fact that the geometry and the relative movement of the portions of the machine through which the sounds pass, distort the amplitude of the beam resonant frequency and its harmonics so that it is varied by factors which have nothing to do with the nature of the material being cut by the pick.


OBJECT OF THE INVENTION

An object of this invention is to provide an improved apparatus and method for determining when a boundary between two layers of compacted material is encountered.


SUMMARY OF THE INVENTION

In accordance with one aspect of this invention a method of detecting when picks of a cutting head of a machine for breaking up a compacted layer stray beyond the boundary of the layers, comprises detecting in the vicinity of the head sets of predetermined air-borne sound frequencies, converting these sets of frequencies into electrical signals, filtering the electrical signals and applying correction factors to them in order to provide corrected signals corresponding to the respective amplitudes of a unique combination of frequencies making up ea

REFERENCES:
patent: 4143552 (1979-03-01), Godfrey
patent: 5090775 (1992-02-01), Berger
patent: 5121365 (1992-06-01), Leigh et al.
Mowrey, G.L. "Promising coal interface detection methods" Mining Engineering Magazine Jan. 1991, pp134-138.

Affiliated with

Also associated with

Rating

Detecting seam boundary using pick sound does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Detecting seam boundary using pick sound, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detecting seam boundary using pick sound will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-461342