U.S. patent application number 09/741589 was filed with the patent office on 2001-08-16 for drilling system.
Invention is credited to Brady, William J..
Application Number | 20010013428 09/741589 |
Document ID | / |
Family ID | 27534942 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013428 |
Kind Code |
A1 |
Brady, William J. |
August 16, 2001 |
Drilling system
Abstract
The invention encompasses improvements in noise attenuation
systems for reducing the audible noise level generated during earth
boring operations using a hard surfaced rotary drill bit, and in
dual bore-cutting elements for performing sequential first and
second bore cutting to the design bore-gauge.
Inventors: |
Brady, William J.; (Creve
Coeur, MO) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT AND ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
US
|
Family ID: |
27534942 |
Appl. No.: |
09/741589 |
Filed: |
December 19, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09741589 |
Dec 19, 2000 |
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09543933 |
Apr 6, 2000 |
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09741589 |
Dec 19, 2000 |
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09260159 |
Mar 1, 1999 |
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6161635 |
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09260159 |
Mar 1, 1999 |
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09046382 |
Mar 23, 1998 |
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6092612 |
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09046382 |
Mar 23, 1998 |
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08689667 |
Aug 13, 1996 |
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5875858 |
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08689667 |
Aug 13, 1996 |
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08472913 |
Jun 7, 1995 |
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Current U.S.
Class: |
175/320 ;
175/210; 175/424 |
Current CPC
Class: |
C21D 6/04 20130101; Y10T
408/76 20150115; C21D 9/22 20130101; E21B 17/04 20130101; C23C
30/005 20130101; E21B 17/03 20130101; C21D 1/30 20130101; F16F
15/10 20130101; E21B 10/60 20130101; Y10S 173/02 20130101; E21B
21/14 20130101; E21B 17/1092 20130101; E21B 10/5735 20130101; Y10T
408/5586 20150115 |
Class at
Publication: |
175/320 ;
175/210; 175/424 |
International
Class: |
E21B 012/00 |
Claims
What is claimed is:
1. A rotary drilling system for cutting bores in earth formations,
comprising noise suppression means for significantly reducing the
audible decibel level of drilling generated noise.
2. The drilling system of claim 1, in which said noise suppression
system comprises first and second bore-cutting means constructed
and arranged to operate at different noise generating levels with a
significantly lower aggregate noise.
3. The drilling system of claim 2, in which the first bore-cutting
means comprises a rotary drill bit for drilling a pilot bore hole
smaller than the final bore size.
4. The drilling system of claim 2, in which the second bore-cutting
means comprises over-reamer insert means for cutting a pilot bore
hole to the final bore gauge specification therefor.
5. The drilling system of claim 4, in which said second
bore-cutting means comprises a drill bit coupler for connecting a
rotary drill bit on one end to a drive steel column on its other
end, and at least two over-reamer insert means carried on said
coupler adjacent to the one end thereof.
6. The drilling system of claim 3, in which the second bore-cutting
means comprises a drill bit coupler having one end for connecting
the rotary drill bit and a second end for connection to a drive
steel column, and said second bore cutting means including a pair
of over-reamer inserts mounted at the one end of the coupler
adjacent to the drill bit thereon.
7. The drilling system of claim 6, in which said over reamer insert
means comprise hard surfaced insert discs having outer bore gauge
cutting margins, and said insert discs being mounted on said
coupler at preselected negative rake and negative skew angles laid
back relative to an axial plane normal to the direction of
rotation.
8. The drilling system of claim 7, in which the negative rake angle
is about 15.degree., and the negative skew angle is about
7.degree..
9. The drilling system of claim 1, in which said noise suppression
system comprises annular means constructed and arranged for use in
association with a drive steel column during drilling
operations.
10. The drilling system of claim 9, in which the annular means
comprises a noise attenuating unit having a central bore to
accommodate part of the steel column.
11. The drilling system of claim 10, in which the noise attenuating
unit is a muffler device for placement in a bore hole
circumscribing location and including sound absorbing material.
12. The drilling system of claim 11, in which said muffler device
comprises an annular structural casing of C-shaped cross-section
and packed with sound absorbing material, and a cylindrical
perforating liner defining a central opening for the steel
column.
13. The drilling system of claim 10, in which said noise
attenuating unit comprises an annular resilient collar for
placement in circumscribing engagement with a portion of the drive
steel column.
14. The drilling system of claim 13, in which the steel column
includes a coupler having an enlarged central section and at least
one threaded end connector, and said annular resilient collar is
mounted against the central section and adapted for vibration
attenuating compression between the coupler and a connected steel
column member.
15. The drilling system of claim 14, in which the connected steel
column member has a coupler-receiving end with an outer cavity to
accommodate said resilient collar, and a threaded inner counterbore
for connection to the coupler threaded end.
16. The drilling system of claim 13, in which the steel column
includes a starter section for driving connection to a drilling
machine and at least one other section, coupler means for
connecting said sections, and in which the resilient collar is
strategically mounted in circumscribing relationship with one of
said sections for vibration attenuation thereof.
17. The drilling system of claim 16, in which said resilient collar
is contained within an outer shell having an open end, and means
for compressing the resilient collar within said shell and onto the
one steel column section for securing the noise suppression means
thereto.
18. In combination with a rotary drilling system comprising a
sectional steel column having a first member for connection with a
drilling machine and a second member for connecting a rotary drill
bit for cutting bores, the improvement comprising noise suppression
means associated with at least one of said first and second members
for significantly reducing the audible decibel level of drilling
generated noise.
19. The combination of claim 18, and including other bore-cutting
means associated with said second member adjacent to said drill bit
for reaming bores to the design bore-gauge specification
therefor.
20. In combination with a rotary drilling system comprising a
sectional steel column having a first member for connection with a
drilling machine and a second member for connecting a rotary drill
bit for cutting bores, the improvement comprising other
bore-cutting means associated with said second member adjacent to
said drill bit for reaming bores to the design bore-gauge dimension
therefor.
21. The combination of claim 20, and including noise suppression
means associated with at least one of said first and second members
for significantly reducing the audible decibel level of drilling
generated noise.
22. A rotary drilling system comprising a sectional steel column
having a first member for connection with a drilling machine and a
second member for connecting a rotary drill bit for initiating bore
drilling; comprising in combination: other bore-cutting means
associated with said second member adjacent to said drill bit for
the primary cutting of bores to the design bore-gauge specification
therefor, and noise suppression means associated with at least one
of said first and second members for significantly reducing the
audible decibel level of drilling generated noise.
23. A noise suppression system for a drill steel column having at
least one tubular drill steel member with an outer wall section,
comprising a vibration dampening unit having an annular resilient
body of substantial axial length sized to have a predetermined snug
fit at the outer wall section of the tubular member.
24. The noise suppression system of claim 23, in which said tubular
member is a starter section of the drill steel column to be
removably attached to the chuck of a drilling machine, and said
vibration dampening unit is applied to annularly circumscribe the
outer wall section of the tubular member adjacent to the chuck end
thereof.
25. The noise suppression system of claim 24, in which said annular
resilient body of said vibration dampening unit is constructed and
arranged to have a different wall thickness at one axial portion
thereof.
26. The noise suppression system of claim 23, including at least
two of said tubular members and the one of which is a coupling unit
having a coupling section of reduced annular cross-section adjacent
to a larger wall section thereof, and said annular resilient body
being applied to the coupling section in axial abutment with the
larger wall section thereof.
27. The noise suppression system of claim 26, in which the other of
said tubular members is constructed and arranged to be removably
attachable to the coupling section of the one tubular member and
exert an axial compressive force against the annular resilient body
of said vibration dampening unit.
28. The noise suppression system of claim 26, in which said one
tubular member is constructed and arranged for removably attaching
a drill bit to its coupling section with compressive force against
the annular resilient body of said vibration dampening unit
thereon.
Description
[0001] This application is a continuation-in-part of my co-pending
patent application Ser. No. 09/543,933 filed Apr. 6, 2000 for Heat
Management Drilling System and Method and my other co-pending
patent application Ser. No. 09/260,159 filed Mar. 1, 1999 for
Drilling System Drive Steel, which is a continuation-in-part of
patent application Ser. No. 09/046,382 filed Mar. 23, 1998 for
Rotary Drilling Systems (U.S. Pat. No. 6,092,612), which is a
continuation-in-part of patent application Ser. No. 08/689,667
filed Aug. 13, 1996 and entitled Low Volume Air-Water Drilling
Systems and Methods (U.S. Pat. No. 5,875,858 on Mar. 2, 1999, which
is a continuation-in-part of parent patent application Ser. No.
08/472,913 filed Jun. 7, 1995 (now abandoned).
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to rotary drilling systems,
and more specifically to improvements for drilling systems as used
in drilling and boring for roof bolting operations for tunnel
construction, mining and the like.
[0004] 2. Description of the Prior Art
[0005] In the fields of industrial, mining and construction tools,
polycrystalline diamond (PCD) is now in wide use in making cutting
tool inserts, sometimes called polycrystalline diamond compacts
(PDC). PCD materials are formed of fine diamond powder sintered by
intercrystalline bonding under high temperature/high pressure
diamond synthesis technology into predetermined layers or shapes;
and such PCD layers are usually permanently bonded to a substrate
of "precemented" tungsten carbide to form such PDC insert or
compact. The term "high density ceramic" (HDC) is sometimes used to
refer to a mining tool having a PCD insert. "Chemical vapor
deposition" (CVD) and "Thermally Stable Product" (TSP)
diamond-forms may be used for denser inserts and other super
abrasive hard surfacing and layering materials, such as layered
"nitride" compositions of titanium (TiN) and carbon
(C.sub.2N.sub.2)and all such "hard surface" materials well as
titanium carbide and other more conventional bit materials are
applicable to the present invention.
[0006] The principal types of drill bits used in rotary drilling
operations are roller bits and drag bits. In roller bits, rolled
cones are secured in sequences on the bit to form cutting teeth to
crush and break up rock and earth material by compressive and
percussive forces as the bit is rotated at the bottom of the bore
hole as in mining operations. In drag bits, PCD or like cutting
elements on the bit act to cut or shear the earth material. The
action of some flushing fluid medium, such as fluid drilling mud,
water or a compressed air/vacuum system, is important in all types
of drilling operations to cool the cutting elements and to flush or
transport cuttings away from the cutting site. It is important to
remove cuttings from the hole to prevent accumulations that may
plug water passages and otherwise interfere with the crushing or
cutting action of the bit; and the cooling action is particularly
important in the use of PCD/CVD/TSP cutters to prevent carbon
transformation of the diamond material.
[0007] Roof drill bits are one form of a rotary drag bit used in
roof bolting operations, which are overhead so the drilling
operation is upward through earth structures of extremely hard rock
or mineral (coal) deposits; and stratas of shale, loose (fractured)
rock and mud layers are frequently encountered.
[0008] My prior U.S. Pat. Nos. 5,180,022; 5,303,787 and 5,383,526
disclose substantial improvements in HCD roof drill bits using PCD
cutting elements constructed in a non-coring arrangement, and also
teach novel drilling methods that greatly accelerate the speed of
drilling action and substantially reduce bit breakage and
change-over downtime.
[0009] My prior U.S. Pat. No. 5,875,858 discloses a compressor and
air-water mixing system that greatly reduces the amount of water
required for effective hole flushing while substantially reducing
the amount of respirable dust. My prior U.S. Pat. No. 6,092,612
discloses rotary drilling systems including improvements in drive
steel columns and secondary bore reamers whereby to ensure delivery
of flushing fluid and effective bit and reamer cooling without
substantial pressure loss, and especially using the low volume air
mist system of my earlier work. My co-pending application Ser. No.
09/260,159 involved improvements in chuck adaptors for the
connection of the drive steel to the chuck of a drilling machine,
and my co-pending application Ser. No. 09/543,933 discloses heat
management techniques for strengthening PCD and like hard surfaced
disc compacts.
[0010] One continuing problem in the mining industry has been the
high volume of noise generated by the drill bit and drive steel
during drilling operations. Environmental regulations prescribe
that the noise level shall not exceed 80 DB (maximum) during a work
shift of 8 hours whereas the usual amount of noise generated is
frequently at or in excess of 100 DB thereby requiring shorter work
shifts. Another continuing concern is in the adaptation and
utilization of new technology to provide improved drilling systems,
apparatus and components.
SUMMARY OF THE INVENTION
[0011] The invention is embodied in improvements in rotary drilling
systems for drilling bores in earth formations using a hard
surfaced rotary drill bit, comprising a noise suppression system
associated with a drive steel column for significantly reducing the
audible decibel level of drilling generated noise, and dual
bore-cutting elements for providing first and second bore cutting
to the design bore-gauge specification therefor.
[0012] It is an object of the present invention to provide a rotary
drilling system that provides a drive steel coupling arrangement
for steel column members and a drill bit and having noise
suppression means. Another object is to provide a drive steel
column having dual bore drilling elements for starting a pilot bore
and completing the bore to design specifications. Still other
objectives of the invention include substantial noise and vibration
abatement at the bore hole and in the drive steel and improved
tandem bore-cutting features increasing penetration speed with
lower noise generation. Another major objective is to provide a
safe, strong drill steel that is dampened against vibration,
operates at a significantly lower decibel level, drills at a
straighter and faster penetration, and which is economically and
correctly fabricated. These and other objects and advantages will
become more apparent hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the accompanying drawings which form a part of this
specification and wherein like numerals refer to like parts
wherever they occur:
[0014] FIG. 1 is a side elevational view, partly broken away,
showing one form of a rotary drill bit useful in the present
invention;
[0015] FIG. 2 is a side elevational view, partly broken away,
illustrating another form of a rotary drill bit and a bit
coupler;
[0016] FIG. 3 is a side elevational view of the bit coupler as
rotated 45.degree. from FIG. 2;
[0017] FIG. 4 is a side elevational view of the bit coupler as
rotated 90.degree. from FIG. 3;
[0018] FIG. 5 is a top plan view of the bit coupler;
[0019] FIG. 6 is a diagrammatic view of an air-water drilling
system to which the invention pertains;
[0020] FIG. 7 is an exploded view of a drill steel column and
coupling system to which the invention pertains;
[0021] FIG. 8 is an enlarged elevational view of a drive steel
member of the drive steel column;
[0022] FIGS. 9-12 are views of a drive steel column and coupling
system from my U.S. Pat. No. 6,092,612 and co-pending application
Ser. No. 09/260,159;
[0023] FIG. 13 is a greatly enlarged cross-sectional view, partly
broken away and similar to FIG. 2, illustrating the dual drilling
system and one noise suppression system of the invention;
[0024] FIG. 14 is an elevational view of the dual drilling system
of FIG. 13 as rotated 90.degree. therefrom;
[0025] FIG. 15 is a top plan view of the bit coupler component of
FIG. 14 as taken along line 15-15 thereof;
[0026] FIG. 16 is an exploded elevational view, partially
fragmentary, illustrating one noise abatement device for a drill
steel coupler;
[0027] FIG. 17 is an exploded elevational view of another noise
abatement collar of the invention; and
[0028] FIG. 18 is an enlarged sectional view of the noise abatement
collar of FIG. 17.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention pertains generally to mining
operations that include roof drilling, longwall mining and
continuous mining, and specifically the invention pertains to
improvements providing noise abatement, vibration attenuation and
enhanced boring speed and accuracy.
[0030] FIG. 1 shows one embodiment of my earlier non-coring roof
drill bit as taught by U.S. Pat. Nos. 5,180,022; 5,303,787 and
5,383,526--the disclosures of which are incorporated by reference.
Briefly stated, this non-coring roof drill bit 10 is typically
seated on the end of a long rod drive steel 19 (119) of a drilling
machine 76, such as a New Fletcher double boom roof bolter (shown
in FIG. 6). The bit shank 16 and drive steel 19 have a
complementary sliding fit and are typically cross-pinned together
at bolt holes 17 or threadedly connected (see FIG. 7) for
co-rotational movement. The shank 16 has vertical flutes 18 formed
on opposite sides for channeling water or air flushing fluid used
for cooling and cleaning the cutter inserts 20 of the drill bit 10.
This drill bit embodiment is shown drilling bore B in roof top R,
and constitutes a long wearing drill bit that is especially
successful in drilling through extremely hard rock formations.
[0031] FIG. 2 shows one embodiment of my earlier coring roof drill
bit as taught by my U.S. Pat. No. 5,535,839--the disclosure of
which is incorporated by reference. This coring-type drill bit 110
is shown connected through a bit coupler or mounting adapter 112 to
a drive steel 119 and operates to drill bore B in the roof R as in
a mine or tunnel. The roof top formation in FIG. 2 illustrates
solid rock S, fractured rock or shale F and mud seams M. The drill
bit 110 has a mounting shank 116 that is secured to the drive
column of the drilling machine 76 (see FIG. 6). Although the drill
bit 110 could be connected directly to the drive steel 119 (as in
FIG. 1), the mounting adapter or coupler 112 of FIGS. 3-5 provides
an improved coupling arrangement. The shank portion 116 of the
drill bit in this embodiment is also provided with the usual
vertical flutes 118 recessed inwardly on opposite sides of the
shank and which serve to channel air/vacuum/liquid flushing fluid
for cooling the cutter inserts 120 and cleaning away debris from
the cutting area of the tool.
[0032] The bit coupler or mounting adapter 112 permits assembly and
disassembly for replacing the drill bit 110 on the drive steel 119
with a minimum of unproductive downtime. An important function of
the coupler 112 is to accommodate the flow of flushing fluid from
the drilling machine 76 through bore 119A of the drive steel and
bit flutes 118 to the cutter inserts 120. To that end the coupler
112 has a central body chamber 50 that connects a through port or
bore 52 to the drive steel chamber 119A. The distribution and the
vertical flow of flushing fluid upwardly through the coupler 112 is
enhanced by providing vertical water flumes or canals 55 openly
exposed to the shank water flutes 118.
[0033] Patent application Ser. No. 08/689,667 (U.S. Pat. No.
5,875,858) teaches low volume air-water drilling systems and
methods to provide efficient irrigation and drill bit cooling using
minimal amounts of water and improving mine safety conditions. A
preferred embodiment of such a drilling system is shown in FIG. 6
in which the drilling system 75 uses a double boom New Fletcher
roof bolter machine having two machine drives 76 operating vertical
long rod drive steel columns 119 to rotationally drive roof drill
bits 10, 110, 210 (FIG. 7) or 310 (FIG. 13). As will be readily
apparent, the drilling system 75 has a separate flushing fluid
handling network for each drilling column 119, although a common
air-water source may be employed for double boom machines as will
now be briefly summarized.
[0034] The system 75 is designed to provide an air-water mist as
the flushing fluid for use in roof drilling and other mining
operations where the fluid is non-recoverable. A compressor-pump 77
receives a flow of water at about 100-120 psi through inlet line 67
from a water source, and this flow of water coolant to the
compressor 77 preferably constitutes the water source for the
air-water mist of the system 75. The water flows through the
compressor to an adjustable water volume regulating valve 80 and
thence is delivered through one-way check valve 69 and an orifice
port 70 to the intake port 81 of an atomizing jet pump 82. The
orifice restrictor 70 is important to control the flow of water in
the internal manifold area 89 of the jet pump so the water does not
cut off the air intake and prevent admixing in this chamber.
[0035] The air compressor 77 compresses ambient air and delivers it
past check valve 71 to a compressed air receiver 73 and thence
through a check valve 73 to an adjustable air volume regulating
valve 84 providing a constant air output volume in the range of
12.0 to 22.0 cfm at a pressure of about 100 to 120 psi. Compressed
ambient air is then delivered at a constant flow rate through
another one-way check valve 85 and an orifice restrictor 74 to air
intake port 86 of the jet pump 82. Thus, both water and air are
delivered into the large mixing chamber 89 of the jet pump 82 at
about 120 psi through the respective orifice restrictors 70 and 74
thereby creating a turbulent admixture thereof.
[0036] The jet pump 82 typically operates on the principal of
entrained fluids. Thus, water flow through a restrictor chamber 87
to a venturi or nozzle 88 produces a high velocity water jet
discharge into and across the large manifold chamber 89, which
receives air flow from inlet port 86 substantially at right angles.
The high velocity water and air streams flowing into and through
the chamber 89 are entrained and the flow of pressurized ambient
air into the water stream converts the water particles to an
air-water mist, which is then pushed or carried forwardly into a
diffuser section 90 and out through discharge nozzle 91 connected
to a fluid line 92 extending to the drive steel column 119 of the
drilling machine 76.
[0037] It is of great importance when working with optimum low
volumes of air or air-water mist that there be no air loss or
leakage in the system that would create problems such as
insufficient air to flush cuttings from the drill hole B resulting
in plugged drill bits and build up of cuttings, slowed bit
penetration and premature bit wear. Thus, my prior application Ser.
No. 09/046,382 was directed to improvements in rotary drilling
systems having a "no-leak" drill steel coupling and reamer means
cooperatively constructed and arranged to deliver optimum drilling
fluid flow and remove bore-hole cuttings, as shown and now briefly
described with reference to FIGS. 7-12.
[0038] FIG. 7 shows a vertically oriented drill steel column and
reamer coupler system 221 in exploded view and includes a drive
steel starter member 226 (FIG. 8), a drive steel coupler member 227
(FIGS. 9, 10), an extension member 228 (FIG. 11, 12) and a reamer
bit seat or coupler member 223 (FIG. 7) to seat and couple drill
bit 210 to the column 221. In this embodiment the drive steel
column has a substantially circular outer wall 230 with opposed
longitudinal or axially disposed flats 231 to provide tool-engaging
surfaces for assembly and disassembly (FIGS. 10 and 12). A
principal feature of that invention was to facilitate such assembly
or disassembly while maintaining substantially air tight, sealed
joints between the column members during drilling operations, and
my drive steel coupling system was developed to employ combinations
of threaded ends and socket-type ends having multi-faced sides to
provide a non-rotational slip-fit connection. In a preferred
embodiment a hexagonal (hex) female end socket 232 on one drive
steel or coupler member receives a mating hex male end plug 233 of
the adjacent member.
[0039] My co-pending application Ser. No. 09/260,150 relates to the
chucking connection of the drive steel column 119, 221 or the like
with the drilling machine (76) in order to further the sealed
integrity of the fluid delivery system from the drilling machine to
the drilling bit (10, 110, 210). Thus, the improvement of that
invention relates to a fixed chuck shank adapter on the drive end
234 of the lower or first drive steel starter member 226 (FIGS. 7,
8) and which is constructed and arranged for driving connection in
the conventional chuck sealing grommet means (not shown) of the
drilling machine (76). Referring to FIGS. 7-12, the drive steel
starter member 226 has an elongated body 224 shown to be of
circular cross-section (230) with flats (231), and has an axial
through-bore 235 as the fluid passageway from end to end. The upper
second end 236 has an internally threaded female end socket 237. It
will be understood that the steel column members could have
hexagonal or other exterior shapes instead of circular outer walls
(230).
[0040] A typical drive steel column may require one or more middle
extension drive steel members so as to appropriately position the
drill bit (10, 210, 310) for drilling engagement with the roof.
FIGS. 9 and 10 show that the half-threaded/half hex connecting
system of my earlier disclosures uses a relatively short drive
steel coupler member 227 for mounting an extension member 228 on
the starter member 226. The coupler member 227 is constructed and
arranged with different coupler end means; an exteriorly threaded
male end plug 241 on one end and a slip fit hexagonal outer wall on
the other end. Both ends having a mating sealing engagement with
the ends of adjacent drive steel members, and the coupler 227
having an axial through-bore 246. FIGS. 11 and 12 show one form of
a middle extension member 228 joined in the column 221 by coupler
227; and a reamer/bit coupler 223 is connected to the drive steel
column and constructed to threadedly receive a drill bit 210. The
bit coupler 223 has a through-bore 252 for delivery of flushing
fluid to the drill bit, and my prior invention accommodated
extended drilling operations with the drill bit (210) by providing
reamer means 225 on the bit coupler (223) preferably arranged on
opposite outer sides thereof.
[0041] My prior inventions presented improvements in rotary drill
bits and in drilling systems for more efficient drilling of bore
holes and extended drill bit life. It will be seen that prior drill
bits have been designed to cut a bore hole to a specified diameter
gauge, and my prior bit coupler/reamer (223) is highly effective to
maintain such bore specification as the drill bit begins to wear
through continued use.
[0042] The present invention is directed to improvements in the
combined drilling system of a rotary drill bit (310) and a bit
coupler 323 having novel over-reamer means 325, and in the use of
noise abatement means during the drilling operation. Referring to
FIGS. 13-15, a dual drilling system embodying the invention
comprises a first bore cutter in the form of rotary drill bit 310
secured on a bit coupler 323 that permits assembly and disassembly
on a section (338) of drive steel column 319 and accommodates
passage of flushing fluids in a through-bore 355 to cool the
cutting elements. The coupler 323 is constructed and arranged with
a novel second bore cutter in the form of a ceramic reamer bit 325
for drilling the holes piloted by the first cutter drill bit 310 to
the prescribed design bore-gauge dimension. In the preferred
embodiment a pair of ceramic disc cutters 325 are mounted on
opposite sides of the bit adapter or coupler 323 at the top or
entry end 324 thereof. These second cutters 325 are typical of my
other diamond-faced drill bit inventions, and have a working cutter
element or insert supported on a tungsten carbide base or the like.
The outer gauge-cutting margins 326 of the second cutters project
outwardly of the coupler body and the disc cutting faces are set at
a negative rake angle of 15.degree. and a negative skew angle of
about 7.degree., or in the ranges taught in my U.S. Pat. No.
5,180,022 for instance. As shown best in FIG. 13, the first drill
bit 310 is constructed and arranged with ceramic cutter inserts 322
(as described with reference to the bits 10 and 210) and, in
operation, start and cut a pilot bore B1. The second cutters 325
follow immediately and cut or ream the bore B2 to its full design
gauge specification.
[0043] The dual bore-cutting system of drill bit 310 and the second
"over-reamer" cutter inserts 325 allows faster penetration into
rock and other structures and for drilling straighter holes due to
the small pilot bore (B1). My co-pending application Ser. No.
09/543,933 (incorporated by reference) teaches heat management
techniques for stress relief in the manufacture and assembly of
cutter discs, and provides a way of eliminating delamination and
chipping to thereby make the second over-reamer cutter practical
and cost effective. Further, the second bore-cutter arrangement
constitutes a primary cutting arrangement of two or more cutting
elements, as in combination with the pilot bit 310, "over-reamer"
as used here being distinguished from an under-reamer arrangement
for secondary cutting if necessary to maintain bore-gauge.
[0044] The dual bore-cutting system is relevant in the general area
of noise abatement, as to which this invention also pertains. The
full size or single bore cutting drill bit 10, 210 of my earlier
inventions along with other prior art drills, has been known to
generate excessive noise levels exceeding 100 decibels and ranging
up to 137 db depending on cutter blade material and sharpness,
drill speeds and pressure, type and hardness of materials being
cut, etc. This has resulted in government regulations mandating
that the noise level to which an operator is subjected shall not
exceed 80 db for an eight (8) hour period. A smaller first pilot
bit 310 of 1{fraction (1/32)}" for cutting bore B1 to a gauge of
13/8" to 11/2" bore size or a pilot bit 310 of 13/8" for cutting
bore B1 to a gauge of 15/8" to 3" will clearly generate a noise
level significantly lower than a single full sized bore bit with a
gauge of 11/2" to 3". In this respect, even a reduction of as
little as 2 db is considered to be a "significant" level noise
abatement change. Further, the additional noise level that will be
generated by the second cutters of the dual bit system will still
be lower than that of the single bore bit because of the easier or
reduced cutting forces required to "over-ream" and because
different noise harmonics will be generated.
[0045] Still referring to FIG. 13, and also to FIGS. 16-18, the
present invention contemplates at least three additional noise
abatement forms. FIG. 13 discloses a silencer or muffler device 300
for suppressing primary noise levels generated at the drilling
site; FIG. 16 shows a coupler noise dampener 301; and FIGS. 17 and
18 show a drill steel collar 302 for attenuating noise and
vibration of the drill steel. Variable test procedures with changes
in thrust pressure, rotational speed, fluid circulation and various
combinations of noise suppression units seem to establish that
primary noise sourcing occurs at the bore hole. Thus, a principal
embodiment for noise attenuation is the silencer device 300 of FIG.
13.
[0046] The silencer 300 comprises an annular drill steel
circumscribing means that acts to dampen or attenuate the audible
decibel level of drilling generated noise in the hole. This
silencer has an annular collar formed as a C-shaped metal outer
shell 304 packed with fiber glass 304A or like noise absorbing
material and closed on its inner annulus by a cylindrical liner
304B of metal or suitable plastic that is perforated (at 304C). The
top and bottom of the outer shell 304 have rubber caps or cushions
304D. The silencer 300 defines a central passageway through the
liner 304B in which the drill steel column will work to bore holes
B1, B2 into the roof structure R. The silencer will be pressed
against the roof-circumscribing the bore entry site by a suitable
hydraulically operated attachment arm (not shown) associated with
the drilling machine 76.
[0047] Referring to FIGS. 9 and 16, the noise dampening device 301
is constructed and arranged to attenuate noise and vibration
occurring at a coupler unit 327 between steel column members (326,
228). As described, this coupler (227, 327) may be constructed with
different end joining means; a threaded male plug 241, 341 on one
end and a hexagonal slip-fit outer wall 233, 333 on the other. The
enlarged central section 238,338 matches with the exterior
configuration of the steel column members (326) and the coupler has
a through-bore for flushing fluids. The noise dampener 301
comprises an annular collar 305 of rubber, neoprene or like
resilient material that is arranged to abut the central section at
the threaded male end 341. The drill steel member (326) may be
provided with a large bore 305A to accommodate the dampener 301
which is compressed by the threaded connection of the male end 341
to the threaded counterbore (237, 337) of the adjacent drive steel
member (226, 326). An annular O-ring 305B is provided at the
enlarged central section shoulder (243, 343) for abutment with the
mating section at that end 333.
[0048] Referring to FIGS. 17 and 18, the other dampener collar 302
is similar in construction and concept to that of FIG. 16. This
collar 302 has an annular outer metal jacket 306 with an inturned
keeper flange 306A at one end, and the other end 306E is threaded.
An inner resilient dampener sleeve 306B is molded into the outer
jacket 306 and has a central bore 306C sized to receive a drill
steel member therethrough. A compression locking cap 306D is
threadedly received into the end 306E. The collar 302 is preferably
applied to the starter drive steel member 226 adjacent to the chuck
end 234 where speed variations first occur in drilling
operations.
[0049] The noise and vibration dampening means of the present
invention result in significant reduction in audible decibel levels
generated during drilling.
[0050] It is now apparent that the objects and advantages of the
present invention have been met. Changes and modifications of the
disclosed forms of the invention will become apparent to those
skilled in the mining tool art, and the invention is only to be
limited by the scope of the appended claims.
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