Drill Hole Guidance System

Abstract

An apparatus for directing the drilling of a bore hole through a mineral vein which includes a drilling apparatus which has means for changing its direction near the bit, a guidance system mounted near the bit which includes a radiation source, a radiation detector and electrical and mechanical apparatus operated in accordance with the detected signal and connected to the direction changing apparatus to cause the drill to bore a hole in a prescribed manner. The bore hole drill is capable of following precisely between the top and the bottom of a coal seam or at the prescribed distance from the top or the bottom of a coal seam.

Description

DISCUSSION OF THE PRIOR ART

A patent to R. Monaghan et al, U.S. Pat. No. 3,019,338, entitled "Thickness Detector for Coal Mining Machine" describes a system whereby a coal mining machine incorporates a top and a bottom radiation source and backscattering detector which are coupled to an alarm system. When the coal digging machine gets too close to the top of the coal seam or to the bottom of the coal seam, the alarm sounds, indicating to the machine operator that he must change direction of the digging apparatus.

The invention as described in this patent is not applicable to a system for controlling a drill which incorporates means for taking the information from the backscattering detector and operating on a drill so as to keep it within a prescribed distance from the top or the bottom of the coal seam.

BRIEF DESCRIPTION OF THE INVENTION

For many years pilot holes have been drilled from mine workings into virgin coal for the purpose of methane gas drainage; however the length of these holes has been limited by drift of the drill bit into the hanging wall or foot wall of the coal seam. The aforementioned limitation has severely handicapped the safety and economic benefits to be derived from pilot hole drilling.

The invention hereindescribed insures the drilling of a directional pilot hole deep into the virgin coal by providing a means for sensing the location of the drill bit with respect to one or both walls of the coal seam and includes additional means for automatically correcting the direction of the drilling apparatus in order to maintain a prescribed distance from the walls of the coal seam to the pilot hole being drilled.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A, 1B and 1C illustrate the drilling of a pilot hole utilizing the principles of this invention;

FIGS. 2A and 2B are graphic plots of the radiation versus received signal for various thicknesses of coal;

FIG. 3A is a cross-sectional view of the guidance apparatus used to direct the drill bit in accordance with the received signal;

FIG. 3B is a cross-sectional view illustrating one method for moving the center bearing so that the drill shaft will be deflected;

FIG. 3C is a top view of the apparatus shown in FIG. 3B;

FIG. 3D is a cross-sectional view of FIG. 3B taken through lines 3D--3D;

FIG. 4 is a block diagram showing the source and detecting apparatus used in the drawing illustrated in FIG. 1C;

FIG. 5 is a detecting apparatus used in the apparatus illustrated in FIGS. 1A and 1B; and

FIG. 6 is one method for accepting the information from the apparatus illustrated in FIGS. 4 and 5 and applying an output signal to a control system for operating the control system illustrated in FIG. 3B.

DETAILED DESCRIPTION OF THE DRAWINGS

Similar numbers will be used throughout the specification for similar elements wherever possible.

In order to provide an adequate drainage hole for methane gas in a coal mine, the pilot hole must have sufficient length to bleed a considerable portion of the coal seam. Furthermore, the pilot hole should be maintained a prescribed distance from the hanging wall rock in order to provide adequate drainage. If, for example, the hanging wall should dip as illustrated in FIG. 1B, then it becomes necessary for the drill to be directed downwardly so that the pilot hole will maintain a prescribed location with respect to the hanging wall rock. Without knowing where the hanging wall rock is with respect to the drill bit, it becomes virtually impossible to drill a pilot hole having any length, since in a short time the drill will have entered either the hanging wall rock or the foot wall rock above or below the coal seam, respectively.

Another advantage in having a precisely directed pilot hole is the eventual automation of the digging machine. If, for example, a coal digging machine can have some means for being directed along a prescribed path, such as a pilot hole, then the machine can be controlled in its digging operation without the continuous supervision of a human operator.

One advantage for automating the digging machine is to eliminate the hazards in a coal mine operation in the vicinity of the digging machine. Since most of the vibration is occurring in that region where the roof is still substantially unsupported by roof bolting operation, shoring, or any other method of protecting the roof from being dislodged, roof falls can occur at any time. These falls comprise one of the major sources of injury to mining personnel.

Referring to FIGS. 1A, 1B, and 3A a simplified version of a means for controlling the direction of the drilling operation is shown and comprises essentially a housing 10, a forward bearing 11, a rear bearing 12, and a center bearing 13. Stabilizing means in the form of cross-members 14 are attached between bearings 12 and 13, and 13 and 11. A drill rod 15 is journaled in each of the bearings 12, 13, and 11, respectively. Center bearing 13 is better illustrated by referring to drawings 3B, 3C, and 3D.

Referring specifically to 3B, bearing 13 has an upper thrust jack 20 and a lower thrust jack 21. Jacks 20 and 21 have attached thereto a first pair of gears 22 and 23, respectively, which are innerconnected (see FIG. 3D) by a second pair of gears 24 and 25. A shaft 26 is axially journaled in an upper bearing 27 and a lower bearing 28 and has attached thereto by any suitable means gears 24 and 25. A bilateral rack 30 is connected at one end to a control cylinder 31 through a shaft 32. The other end of rack 30 is connected through a shaft 33 to a support member 34. The remaining end of control cylinder 31 is pivotally attached to a support 35.

The operation of the mechanical portion of the drill direction control system described in FIGS. 3A-D is done in the following manner. An up or down command from the electronic circuitry (to be described) causes the control cylinder to move shaft 32 in the direction of support 34 or in the direction of support 35, depending upon the requirement. A movement in shaft 32 will cause a corresponding lateral movement of rack 30. Movement of rack 30 will cause a corresponding rotation of gears 24 and 25 through shaft 26 along with rotation of gear 23. Gear 22 will rotate by rotation of gear 24. Rotation of gears 23 and 22 will cause lengthening of thrust jack 21 and shortening of thrust jack 20 or vice versa, depending upon which direction the bilateral rack has moved. Movement of the thrust jacks 20 and 21 will cause bearing 33 to move up or down which will in turn cause a deflection in drill shaft 15. If, for example, the movement of bearing 13 is upwardly, the drill shaft will be bent in an upward arc between bearings 12 and 11, causing the drill adjacent bearing 11 to be deflected downwardly, thereby changing the direction of the drill assembly so that it will drill away from the hanging wall rock as illustrated in FIG. 1C.

DETECTION CIRCUITRY

The distance from the hanging wall rock, the foot wall rock, or both is determined by the detection apparatus illustrated in FIGS. 4 or 5. If, for example, it is desired to maintain the drilling apparatus a fixed distance from the hanging wall rock, for example, a detection apparatus such as that illustrated in FIG. 4 is utilized and comprises essentially a housing 40 which includes radiation shielding, a source 41 which may comprise, for example, Cesium 137, a gamma ray source or other suitable radiation source which has sufficient penetration to pass through the coal, create backscattering and be detected. One particularly useful probe is manufactured by the Dowty Electronics, Ltd., NCB Isleworth Type 707A coal sensing probe manufactured in England. In experiments conducted using the above probe, a five millicurie radium source was used as well as a five millicure Cesium 137 radiation source.

A detector device such as Harshaw Model NR-10 linear rate meter could be incorporated to detect the backscattering from the radiation source.

In actual experiments carried out, a curve was found as illustrated in FIGS. 2A and 2B. In viewing the curve it will be noted that a peak 43 was detected as the coal became thicker, whereupon the voltage detected by the detecting system 42 began to decrease. Thus, for a thickness T1 a voltage V1 was measured and for a thickness T2 a voltage V2 was measured.

The discovery of this curve afforded a simple means for determining if the drill bit was moving toward or away from the hanging wall rock as shown in FIG. 1C. For example, if the drill bit began to approach the hanging wall rock, the voltage would begin to increase. This increase in voltage would be transmitted from the detector 42 to a rate meter 44. Rate meter 44 is connected to relays 1 and 2 which in turn are connected to hydraulic solenoids S1 and S2. Solenoids S1 and S2 are coupled to a hydraulic control system 45. A hydraulic pipe 46 functions as an inlet for a source of oil and pipe 47 functions as an outlet. Pipe 48 is connected to control cylinder 31 on one side, and pipe 49 is connected to control cylinder 31 on the opposite side of pipe 48. A hydraulic piston 50 is mounted internal to cylinder 31 and moved back and forth, depending upon the position of hydraulic control system 45.

The system shown in FIGS. 4 and 6 illustrates the control circuitry and includes source 41 for generating radiation which is applied to a coal seam. Backscattering is received by a detector 42 and applied through wires to a rate meter 44. The output from rate meter 44 is applied to the inputs of a pair of relays 1 and 2. If the proper command is generated by rate meter 44, either relay 1 or relay 2 will operate, depending upon the magnitude of the voltage from rate meter 44. Each relay, 1 and 2, has its magnitude set by a control 60 or 61, respectively. If solenoid S1 is energized, it will move hydraulic control valve 45 to connect Section A with pipes 46 through 49. If relay 2 is energized, it will move Section B with pipes 46 through 49. Solenoids S1 or S2 will, of course, operate control cylinder 31 by applying hydraulic pressure to either pipe 48 or pipe 49 causing piston 50 to move and, as a consequence, shaft 32.

When a double source is used, such as that shown in FIG. 5, corresponding detectors 42A and 42B must be used. Such a use is illustrated in FIGS. 1A and 1B. The output from 42A is applied to rate meter 1, and the output from 42B is applied to rate meter 2. The output from both rate meters 1 and 2 is applied to a mixer 61.

The operation of the device in FIG. 5 can be understood by referring to FIGS. 1A, 1B, 2A and 2B. When both detectors are receiving the same signal, an equal voltage will be applied to rate meters 1 and 2. The output from mixer 61, therefore, will have no voltage.

As the drill moves toward the hanging wall rock the thickness T1 (see FIG. 2B) will diminish, causing an increase in voltage V1, and at the same time thickness T2 will increase, causing a corresponding decrease in voltage V2. The difference between V1 and V2 will result in a positive voltage being applied to relays 1 and 2. Conversely, if the drill is moved away from the hanging wall rock, the result in voltage will be negative. Relays 1 and 2 should then be adjusted for a differentiation in polarity rather than a differentiation as to magnitude. Thus, for example, relay 1 could be adjusted to be responsive to a negative voltage, and relay 2 could be adjusted to be responsive to a positive voltage. The output from the relays will then control solenoids S1 and S2 in a manner so that the control response 32 will properly move the drill to respond to the deviation of the drill from its set path.

Viewing the above, it is obvious that other substitutions and modifications can be made which are well within the skill of the art, and such modifications and changes are within the intent of this invention as claimed in the appended claims. One such modification is the mere substitution of air for hydraulic fluid as described in FIG. 6. Other modifications are the methods for deflection of the drill shaft 15 other than the particular mechanical configuration disclosed in the specification. Not mentioned but also obvious is the orientation of housing 10 with respect to the hanging wall. Systems such as pendulums and other obvious means can be incorporated to maintain the housing in an upright position so that the detectors will also be measuring the vertical distance to the hanging wall rock or the foot wall rock, respectively. One obvious method of maintaining orientation without the use of pendulums, etc., is to continue housing 10 back to the beginning of the bore hole. Sections can be added to not only the drill pipe but the housing 10 as drilling progresses.

Claims

What is claimed is:

1. In combination with a cylindrically shaped bore hole drilling apparatus having a longitudinal axis having means incorporated therein for arcuately deflecting said axis for changing the direction of said drilling apparatus thereby changing the axial direction of said bore hole; a guidance system, said guidance system having a radiation source means, a radiation backscattering receiving means; radiation counter means having an input and an output, said input connected to the output of said radiation backscattering receiving means and producing an output responsive to the received backscattered radiation, said output connected to said means for arcuately deflecting said axis for changing the direction of said drilling apparatus, whereby as said drilling apparatus deviates from a prescribed direction, said received backscattered radiation as received will indicate said deviation and supply a responsive signal from the output of said radiation counter means to said means for changing direction of said drilling apparatus to return said drilling apparatus to its prescribed direction.

2. A device as described in claim 1 wherein said drilling apparatus comprises a housing, a drill shaft axially mounted in said housing by end bearings, means for changing direction of said drill apparatus comprising a third bearing supporting said drill shaft, said third bearing mounted between said end bearings, an upper and lower threaded sleeve means attached between the upper and lower portion of said third bearing and said housing, a rack drive means, gear means co-operatively engaging said upper and lower threaded sleeve means and said rack drive means, and control means connected to said rack means and to the output of said receiving source, whereby a signal from said receiving source will cause a responsive movement of said rack means, rotating said gear means which results in said upper and lower threaded sleeves moving said third bearing up or down thereby changing the axial alignment of said drill shaft.

3. The combination as described in claim 1, further defined to include said source means adapted to focus radiation in opposite directions and wherein said receiving means includes first and second oppositely positioned detectors adapted to receive the backscattering from said radiation focussed in opposite directions; and shield means between said source means and said receivers.