Note: Descriptions are shown in the official language in which they were submitted.
sa kground of the_lnvention
1. Field of the invention
The invention relates generally to drilling rnachine guidance
systems and, more particularly, bu-t no-t by way of lirnitation, it
5 relates to an improve(l yuidance systerrl Eor use in horizontal
drilling appara-tus of the type used in mining opera-tions.
2. Descrip-tlon of the Prior Art
There are numerous prior art guidance systems for use with
drilling apparatus, both horizontal drilling machines and vertical
10 or well drilling apparatus. U.S. Patent No. 3,362,750 to
J. Carnegie, dated January 9, 1968, discloses a mining apparatus
having programmed cutting direction and attitude controls, and
this teaching utilizes a comparator for sensing a departure of
the cutting machine from its programmed direction thereafter to
15 correct the deviations. The system utilizes a plurality of
pendulums and related comparator circuitry for sensing program
deviations. U.S. Patent No. 3,326,008 to P. Baron et al, dated
June 20, 1967, relates to an electrical gopher which is utilized
to bore horizontal cable holes. This device utilizes a plurality
20 of synchro motors to maintain its guidance direction. Still other
forms of circuitry are utilized in the prior art, especially that
art which is related to position keeping within vertical boreholes
and well drilling apparatus; however, none of the prior art
approaches are similar to the present circuit apparatus nor
25 do they offer the attendant functions and advantages for opera-
tion of a push drill remotely guided through a mineral stratum.
Summary of the Invention
The present invention contemplates a remote control system
for a push drill of the type used for drilling relatively long
30 distances through a mineral stratum. In a more limited aspeck,
the invention consists of an instrument package which is integrally
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.
connected into the push driLl string for contro] coMmunication
back to an operator positior,. ~he sys-tem utllizes accel~rometer
sensing to determine pitch and roll of the drill instr~nent ~Jhile
gamma ray coun-t is utilized to determine vertical positionin~ of
the push drill relative -to overlying and underlyiny rock forrna~
tions, e.g., shale forrnations adjacent coal seams. Control sig-
nals are then processed in the instrument package for trans-
mission back along a control cable to ~hè operator position,
whereupon output indication enables the operator to hydraulically
control the push drill to accomplish attitude correction during
progression through the mineral stratum.
Therefore, it is an object of the present invention to pro-
vide remote control apparatus for guiding a mining push drill
from an operating position that may be a great distance there-
from.
It is also an object of the present invention to provide an
electronic guidance system for a push drill that is remotely
guided by an operator using electrical signal indications re-
turned to the mineral stratum face by a long electrical cable
extending from the hydraulically controlled push drill.
It is yet another object of the invention to provide a
- system for guidance of a push drill through a coal seam utilizing
the natural~radioactivity of the surrounding shale deposits or
strata.
Finally, it is an object of the invention to provide an
I improved remote control instrument package for integral inclusion
- into the push drill string of operative elements.
Other objects and advantages of the invention will be evi-
dent from the following detailed description when read in con-
junction with the accompanying drawings which illustrate the
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~.3;~ 3
invention.
Brief Des ption of the ~rawings
FIG. l is a plan view in side ~levation of the push drill
assembly as it extends from an operatinc~ positiorl;
FIG. 2 is a block diagram illustrating the operative associa-
tion of elements;
FIG. 3 is a schematic diagram of the operator control unit
and interconnections; and
FIG. 4 is a schematic diagram of the instrum~nt package of
the present invention~
Detailed Description of the Preferred Embodiment
FIG. 1 illustrates a push drill assembly 10, as constructed
in accordance with the present invention to include control instru-
ments, as interconnected via control line 12 to an operating posi-
tion 14. The push drill unit lO includes a retraction hold unit
16, as rigidly connected via drill stem 18 to a hold unit 20 which,
again, is connected by drill stem 18 into a drill assembly 22 having
a forward output shaft 24 and drill head 26. The push drill assem-
~ bly 10 is the `p~rticular subject matter o~ U. S. Patent
20 ~ No. 3,888,319 in the name of Bourne et al. as issued on June 10,
1975, and particulars of that structure are fully brought out in
that disclosure.
The push drill assembly lO is a self-propelling drill unit
capable of directional drilling control under proper instrumen-
tation. The drill unit 22 includes a roll control unit 28, drill
motor 30 and deflection unit 32, and the control ins~rumentation
package may be carried as indicated by instruments 34. The push
drill assembly lO is connected back to the opera~ing position 14
by means of hydraulic hoses 36 and 38, and an electrical cable
40. Hydraulic hose 36 provides drive pressure to drill motor 30
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while hydraulic hose 38, actually three hoses in num~er, provide
control actuation to the hold and deflection units.
As shown in FIG. 2, the operating position 14 includes a
battery pack and charging circuit 44 connected through an
operator control unit 46 and remote cable 40 -to instruments 34.
The battery pack and charging circuit 44 is a conventional form
of circuit as energized by ~-C source 42 to utilize full wave
rectifiers and respective rechargeable alkaline cells, to
provide continual power supply output. A power output of
positive 18 volts, common and negative 18 volts is supplied
via three conductors to the operator control unit 46. The A-C
power source 42, is used to charge the battery pack at the
surface of a mine, but it is not used during guidance operations.
Referring to FIG. 3, the operator control unit 46 receives
15 power supplied at a connector 48 via leads 50, 52 and common lead
54, the power leads also being connected directly through an
eight pin connector 56 for connection to push drill supply cable
40, as will be described. The negative 18 volt lead 52 is connec-
ted to ZERO ADJUST potentiometers 58 and 60, pitch and roll respec-
tively, which return via respective resistors 62 and 64 to the
I positive 18 volt lead 50. The center tap of PITCH potentio-
meter 58 is connected via a conductor 66 through connector 56
and cable 40, and the center tap of ROLL potentiometer 60 is
connected via conductor 68 to connector 56. Operator indication
25 of RATE, PITCH and ROLL appears on meters 70,72 and 74, respec-
tively. Meter 70, 15ma D-C, connects through a gain potentiometer
76 and lead 78 to connector 56; in like manner, meters 72 and 74
(each 10ma-0-lOma) connect through gain potentiometers 80 and
82 and respective leads 84 and 86 for connection at connector 56.
.3 ~d ~
Output from connector 56 is then by drill contxol ca~le 40
to the instrumen-~ unl-t 34 within dri,ll unit 22, as shown in F-LJ~
4. The control cable 40 may be on the order of 1000 to 20U0
feet in length~ Connec-tor input from drl,ll control cable 40 is
5 applied at receptacle 88, as like conductors bear the same desig~
nators as were input at connector 56 (FIG. 3). The po~"er leads
50, 52 and 54 are applied directly to a 12 volt regulator 90, a
standard form of regulator circuit, which provides regulated volt-
age output, i.e., positive 12 volts at a terminal g2 and negative
12 volts at terminal 94. Common connection of 12 volt regulator
90 is indicated as ground in the circuit of FIG. 4.
Positive 12 volt output and common connection from 12 volt
regulator 90 are also provided on respective leads 96 and 98
to a high voltage power supply 100 for energization, i.e., 120û
volts, via shielded lead 102 to a BICRON (trade mark of the
Bicron Corporation) counter tube 104, a scintillation detector.
The high voltage power supply 100 is a 100:1 step-up DC-DC trans-
former type, Model K-15, as is commercially available from Venus
Scientific of Farmingdale, New York. The sICRON counter tube 104
is a commercially available gamma ray counter tube, Model 2M2P
that is available from the Bicron Corporation of Newbury, Ohio.
Gamma co~mt output in the 2 volt range is then present on a lead
106 through a coupling capacitor 108 and resistor 110 to one
input of an integrated circuit pre-amplifier 112, IC Type 715393.
Output from amplifier 112 is taken at junction 114 via lead 116,
and control feedback from junctlon 114 through resistor-capacitor
network 118 is applied to the input 120. A diode 115 provides
for removal of any negative voltage spikes.
The gamma count output on lead 116 is then applied to a
threshold limiting circuit 122, an integrated circuit dual NOR
B
'h~
gate, Type CM 4001. Input on lead 116 to NO~ yate 124 is
latched to conditio~ by NOR gate 126 with output present at
junction 128 only when exceeding the bias present ~t junction
129. The output signal is then applied th.rough resistor 130
to an inpu~ 132 of an inteyrator 134, an integrated circuit
operational amplifier, Type MC 17410 Integration of output at
junction 136 is effected by feedback through a capacitor-
resistor timing network 138 to input 132. The integrated
output signal is applied on lead 140 to a resistor network
consisting of resistor 142 in series with a calihration poten-
tiometer 144 and a common connected resistor 146.
Potentiometer 144 provides a gamma count calibration adjust-
ment as signal is applied to an input 148 of a VA converter 150,
a D-C amplifier, as biased by a voltage divider consisting of
resistors 152, 154 and 156 to provide reference input at input
158. The converter 150 is once again the integrated circuit
Type MC 1741 with output provided at a junction 160 and feedback
through resistor-capacitance network 162 to the input 148. Out-
put in the form of current indication from junction 160 is then
present on lead 78 for return to receptacle 88 and control cable
40 to gain potentiometer 76 and RATE meter 70 of the operator
control unlt 46 (See FIG. 3~. Thus, meter 70 will read the
instantaneous rate of gamma count as sensed by BICRON counter
tube 104.
The BICRON counter tube 104 is preferably mounted and shielded
to view upward or downward from the instrument unit 34, depend-
ing upon initial installation and the paxticular type of drilling
surveillance. It is now established that gamma radiation pro-
duced by the radioactive decay or uranium, thorium, potassium-40,
as is naturally present in shale rock, is attenuated by coal in a
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lo~arithmic manner with a h~ t~:ickness val.ue o~ apprc)~imate:L~
7 inches. Also, shale formations are nearl.y alwa~s present abo~e
and below coal seams or strata ~nd these stra-ta will contain the
necessary radioactive elements. Thus, sensing of this natural
radioactivity provides a means for enabliny a rneter inaication
that will allow the drill operator to hydraulically change the
push drill's position relative to adjacent strata for guidance
through the minera]. stratum.
The pitch of the push drill assembly 10 is sensed by an
accelerometer 164 with output signal provided through a dropping
resistor 166 to input 168 of a VA converter amplifier 170 ~DC
amplifier), Type MC 1741. Reference input is applied via lead
.66 from ZERO ADJUST potentiometer 58 in the operator control
unit 46 (FIG. 3) as applied to amplifier input 172. Control feed-
15- back is applied from the output via resistor-capacitor network ,
174 to the input 168~ and amplifier out~ut is applied on lead
84 through receptacle 88 and the control cable 40 for representa-
tion on pitch meter 72 at control unit 46. The accelerometer
164 is a static displacement form known as the Columbia Type SA
107 as made available by Columbia Research Laboratories. The
accelerometer 164 provides a steady D-C ou'put proportional to
angle such that an adjusted meter 72 range of 0-5 volts will be
indicative of pitch change from 0 to 90. Accelerometer 164
may be suitably mounted in instrument unit 34 to sense the longi-
tudinal angular deviation.
The roll sensing is carried in like manner as a similar type
of accelerometer 176 provides input to identical circuitry at
amplifier input 178 of a D-C amplifier 180 (also Type MC 1741).
A reference input 182 is connected to lead 68, control cable 40
and control unit ~ERO ADJUST potentiometer 60 (FIG. 3), and output
~ J~
on lead 86 is similarly conducted ba~ throuyh control cable
40 and gain control 82 for indic~-tion at the Roll meter 74 at
the control unit. (Roll accelerometer 176 is rnounted to sense
transverse angular deviation~.
In opexation, after proper ZER~ ~DI-lUS~ of the pitch and
roll meters and rate meter 70 relative to the push drill assem-
bly 10 with zero attitude and indication, the guidance system is
ready to function. The operator will also have access to the
hydraulic control mechanism at the operating position 14 so that,
as he observes the operator control unit 46, he is able to actuate
hydraulic controls for any of drill motor 30, deflection unit
32, roll control unit 28 or the hold assemblies to properly
direct the drill head 26 through the mineral stratum. As pre-
vlously stated, the BICRON counter tube 104 (FI~. ~) is preferably
shielded for isolation to a selected directivity, e.g., perpen-
dicular to the overlying shale stratum, so that variations in
reading of the rate meter 70 at operating position 14 enable
the operator ~o maintain a long hole course within the drilling
stratum of interest.
The foregoing discloses a new and useful guidance system
for controlling the position and attitude of a push drill through
a mineral stratum. The device employs a unique combination of
accelerometer sensing to determine pitch and roll of the drill
instrument while also sensing the natural gamma ray racliation
emanating from shale stratum above, below, banded within or
adjacent to the particular mineral stratum. The guidance system
has the unique capability of offering very accurate control indi-
cation while being packaged in a highly reliable yet relatively
small package, an instrumentation package that is quite easily
installed within the structure of the push drill assembly. It
3~ 7~
is also contemplated and a resul-~ of the logical course that
indications of pitch, roll and gamma incidence or rate, as re-
ceived at the remote operatiny position, wlll also be conditioned
for input to computer apparcltus whereupon detailed stratum analysis
can be carried out with subsequent printout of three-dimensional
or other mapping information. Further, it is conternplated that
two uni-directional BICRON counter tubes may be utilized in 180
displacement to enable a Rate reading in each of opposite direc-
tions from the push drill assembly thereby to enable still further
data compilation.
Changes may be made in the combination and arrangement of
elements as heretofore set forth in the specification and shown
in the drawings; it being understood that changes may be made in
the embodiments disclosed without departing from the spirit and
scope of the invention as defined in the following claims.
What is claimed is:
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