Detecting seam boundary using pick sound

• US 6,132,005 A
• Filed: 04/09/1998
• Issued: 10/17/2000
• Est. Priority Date: 11/14/1995
• Status: Expired due to Term

• Current Assignee: Tangential Technologies Pty
• Original Assignee: Tangential Technologies Pty
• Inventors: Marston, Brian, Mazlin, David John, Mazlin, John Gordon
• Primary Examiner(s): Lillis, Eileen D.
• Assistant Examiner(s): KRECK, JOHN J
• Application Number:
  US09/051,527
• Time in Patent Office: 922 Days
• Field of Search: 299/1.05, 299/1.1, 299/1.2
• US Class Current: 299/1.1
• CPC Class Codes: E21C 35/24 Remote control specially adapted for machines for slitting or completely freeing the mineral control in general G05
• CPC Class Codes: G01H 3/00 Measuring characteristics of vibrations by using a detector in a fluid G01H7/00, G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00

Abstract

A mining machine (4) has a vertically movable jib (6) mounted in front of it and carrying a drum shaped drilling head (12) at its forward end. The drilling head is provided with radially projecting picks which rip coal out of a coal seam (1) located between an underburden (3) and an overburden (2). A forwardly-facing directional microphone (16) is mounted on the forward end of the machine (4) between the lines M where it can monitor the resonant frequencies of the picks. Electrical circuitry mounted on the machine controls the position of the jib (6) in accordance with the relative amplitudes of a unique set of natural resonant frequencies produced by the picks during mining.

Claims

1. A method of detecting when picks of a cutting head of a machine for breaking up a compacted layer of material stray beyond the boundary of the layer, comprising:

detecting in the vicinity of the head sets of predetermined air-borne sound frequencies corresponding to resonant frequencies of the picks of the cutting head,

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 each of the different sets, wherein the correction factors are related to physical dimensions of the picks and the nature of the material being broken up, and

using the relative changes of the corrected signal amplitudes to control the position of the head so that the amplitudes of the frequencies of the sets are restored to a predetermined relationship.

2. A method as claimed in claim 1, in which the number of frequencies in a set lies between two and twelve.

3. A method as claimed in claim 2, in which three frequencies are used in a set and correspond to the natural resonant frequency of a pick when vibrating axially,

4. Apparatus for breaking up a compacted layer of material, comprising:

a head equipped with picks and rotatable to bring them into ripping engagement with the layer;

an arm supporting the head and moveable in order to bring it into engagement with different portions of the layer;

a vehicle supporting the arm and moveable to advance the head progressively in relation to the layer;

a unidirectional microphone mounted in a position of safety adjacent the front end-portion of the vehicle and directed to receive signals from the head for converting air-borne sound signals produced in the vicinity of the picks into corresponding electrical signals;

electrical circuitry for selectively amplifying predetermined sets of frequencies of the electrical signals, each set corresponding to a unique set of resonant frequencies of the pick, and for applying to the amplified sets of electrical signals respective correction factors which are related to physical dimensions of the picks and the nature of the material being broken up, and for computing from the amplitudes of the sets of corrected signals the position of the picks in relation to a boundary between the layer and an adjoining different material, the electrical circuitry including a set of bandpass filters which are individually located in respective parallel signal paths of which there are between two and twelve in number, and each bandpass filter supplying its output to a frequency discriminator circuit into which a correction factor is fed so that the output of the frequency discriminator circuit reflects one of the unique natural resonant frequencies of the pick; and

a controller connected to respond for changing the position of the head to confine the action of the picks to the thickness of the layer in response to the output of said electrical circuitry. radially and circumferentially.

5. Apparatus as claimed in claim 4, in which the combination of the microphone, electrical circuitry and controller is detachably mounted on the vehicle.