Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: GRINDING TOOL FOR BUTTONS ON A ROCK DRILL BIT
BACKGROUND
The present disclosure relates to improvements in
apparatus for, grinding the hard metal inserts or working
tips of rock drill bits (percussive or rotary), tunnel
boring machine cutters (TBM) and raised bore machine
cutters (RBM) and more specifically, but not exclusively,
for grinding the cutting teeth or buttons of a rock drill
bit or cutter.
In drilling operations the cutting teeth (buttons) on the
drill bits or cutters become flattened (worn) after
continued use. Regular maintenance of the drill bit or
cutter by regrinding (sharpening) the buttons to restore
them to substantially their original profile enhances the
bit/cutter life, speeds up drilling and reduces drilling
costs. Regrinding should be undertaken when the wear of
the buttons is optimally one third to a maximum of one-
half the button diameter.
Manufacturers.have developed a range of different manual
and semi-automatic grinding machines including hand held
grinders, single arm and double arm grinding machines and
grinders designed specifically for mounting on drill
rigs, service vehicles or set up in the shop.
These types of machines utilize a grinding machine having
a spindle or rotor rotated at high speed. A grinding cup
or grinding pin, mounted on the end of the rotor or
spindle, grinds the button and typically the face of the
bit/cutter surrounding the base of the button to restore
the button to substantially its original profile for
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effective drilling. In addition to the rotation of the
grinding cup, these types of grinding machines may
include features where the grinding machine is mounted at
an angle to the longitudinal axis of the button and the
grinding machine is rotated to provide orbital motion
with the center of rotation lying in the center of the
grinding cup.. When grinding the buttons, the centering
aspects of the grinding machine tend to center the
grinding machine over the highest point on the button.
= Longstanding problems with these types of grinding
machines are vibration and noise due to high rotational
speeds, wear, the requirement for large compressors for
pneumatic systems and long grinding times per button, in
the larger sizes.
The grinding cups conventionally consist of a cylindrical
body having top and bottom surfaces. The bottom or
working surface consists of a diamond/metal matrix having
a centrally disposed recess having the desired profile
for the button to be ground. The rim around the recess
may be adapted, for example by bevelling, to remove steel
from the face of the bit around the base of the button.
Water and/or air, optionally with some form of cutting
oil, is provided to the grinding surface to flush and
= cool the surface of the button during grinding.
The grinding cups are provided in different sizes and
profiles to match the standard sizes and profiles of the
buttons on the drill bits or cutters. Typically the
button diameter varies from 6mm up to 26mm.
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Several different methods have been used to connect and
retain the grinding cups on to the grinding machine. The
grinding cups were conventionally held in the grinding
machine by inserting an upright hollow stem projecting
from the top surface of the grinding cup into a chuck for
detachable mounting. Special tools such as chuck
wrenches, nuts and collets are necessary to insert, hold
and to remove the grinding cup into and out of the chuck.
To eliminate the need for chuck wrenches etc. the use of
a shoulder drive on the grinding cups was developed. A
diametrically extending recess at the free end of a
hollow drive shaft of the grinding machine co-operates
with a shoulder or cam means on the adjacent top surface
of the grinding cup to provide the drive means. The stem
= of the grinding cup, in order to provide axially and
radial support, is inserted into the hollow drive shaft
and maybe held in place by one or more 0-rings either
located in a groove in the interior wall of the drive
shaft or on the stem of the grinding cup. See for example
Swedish Patent No. B 460,584 and U.S. Patent No.
5,527,206.
An alternative to the shoulder drive is shown, for
example, in Canadian Patent 2,136,998. The free end of
the stem of the grinding cup is machined to provide flat
drive surfaces on the stem that are inserted into a
corresponding drive part in the channel of the output
drive shaft into which the stem is inserted. The grinding
cup is retained in place by a spring biased sleeve which
forces balls mounted in the wall of the output drive
shaft into an annular groove on the stem of the grinding
cup.
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Other innovations are illustrated in U.S. Patent No.
5,639,273 and U.S. Patent No. 5,727,994. In these
patents, the upright stem has been replaced with a
centrally disposed hexagonal cavity provided in the top
surface of the grinding cup. The cavity is shaped and
sized to permit the output drive shaft of a grinding
machine to be inserted into the cavity. The end of the
output drive shaft has an end section having a
corresponding hexagonal cross section to fit into the
hexagonal cavity to provide the drive means. A second
section of the output drive shaft having a circular cross
section to fit into the cavity to provide axial and
radial support.
Some manufacturers, in order to provide grinding cups
that are compatible for use with other manufacturers'
grinding machines provide adapters that connect their
grinding cup to the output drive shaft of competitors'
grinding machines.
Regardless of the method of connecting the grinding cup
to the output drive shaft of the grinding machine, it is
important to optimize the operational stability of the
grinding cup. Lack of operational stability often results
in vibration and resonance during grinding. Vibration
and/or resonance also directly results in increased rates
of wear to all moving parts such as bearings, joints,
= etc. of the grinding apparatus and can potentially
interfere with settings within the operating control
circuits of the grinding apparatus. In addition, lack of
operational stability results in increased wear to all
key drive/contact surfaces of the output drive shaft
(rotor) and grinding cup which provide consistent, proper
alignment between grinding cup and or adapter and the
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rotor during operation. Operational instability and
associated vibration and/or resonance is a major
contributor to the deterioration of the preferred built-
in profile of the cavity in the grinding section of the
5 grinding cup. This directly results in deterioration in
the profile of the restored button. The net effect being
a substantial loss in the intended overall drilling
performance of the drill bit or cutter used.
These known drive systems provide means to axially and
radially suppOrt the grinding cup in the grinding machine
and separate drive means for transfer of torosional
forces to rotate the grinding cup.
SUMMARY OF THE INVENTION
Accordingly the present disclosure provides a grinding
cup for detachable connection to the output drive shaft
of a grinding machine for grinding buttons on drill bits
or cutters, said grinding cup having top and bottom
surfaces and consisting of a lower grinding section and
an upper body section co-axial with said grinding section
to form said grinding cup with a centrally disposed
recess formed in the bottom surface of the grinding
section having the desired profile for the button to be
ground; the improvement characterized by said body
section having a centrally disposed upright drive section
formed on the top surface of the grinding cup, said drive
section shaped and sized to both driveably engage within
a corresponding recess at end of the output drive shaft
of said grinding machine and provide axial and radial
support and retaining means for detachably connecting the
grinding cup to the output drive shaft of the grinding
machine wherein said drive section has a non-circular
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cross section and is tapered from the top surface of the
grinding cup to the free end of the drive section.
Another embodiment provides a series of grinding cups for
5 grinding working tips of rock drill bits, wherein said
working tips have a diameter of about 6mm to 26mm and a
desired profile, each of said grinding cups in said
series having a lower grinding section and an upper body
section connected to form a grinding cup having top and
10 bottom surfaces, a centrally disposed recess formed in
the bottom surface of said grinding cup having the
desired profile and diameter of the working tip,
combination drive means and support means provided on the
= upper body section of said grinding cup that cooperates
15 with the output drive shaft of a grinding machine,
wherein the combination drive means and support means
consists of an upright section centrally located on the
top surface of the grinding cup in the form of a
truncated elliptic cone sized to engage with a
20 corresponding elliptic conical recess at the free end of
the output drive shaft of the grinding machine, retaining
means provided in conjunction with the drive means for
detachable connection of the grinding cup to the output
drive shaft of the grinding machine during use.
Another embodiment of the present invention consists of a
holder device for detachable connection of a grinding cup
to a grinding machine, said grinding machine having a
pneumatically; hydraulically or electrically driven motor
30 which drives an output shaft. Suitably connected to the
output shaft by any conventional means is a holder device
of the present invention. The holder device may be an
integral extension of the output shaft or a separate
attachment. The holder device consists of a rotatable
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drive member having a free end adapted to extend axially
away from the the grinding machine. The drive member is
provided with a recess at its free end with a coaxial
passageway extending from the recess the length of the
drive member or part thereof and through which coolant
fluid may be directed to a grinding cup supported
thereon. The recess has a non-circular cross section and
is tapered inwardly from the free end of the drive
member.
Further features of the invention will be described or
will become apparent in the course of the following
detailed descTiption.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the disclosure may be more clearly
understood, embodiments will now be described in detail
by way of example, with reference to the accompanying
drawings, in which:
FIGURE 1 is perspective view from the right side of one
embodiment of a grinding apparatus having a grinding
machine carried for vertical and horizontal adjustment by
a support system, and means for holding the bit(s) to be
= ground.
FIGURE 2 is a perspective view from the left side of
another embodiment of a grinding apparatus suitable for
mobile applications and having a griding machine carried
for vertical and horizontal adjustment by a support
system and means for holding the bit(s)to be ground.
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FIGURE 3 is an enlarged view of a grinding machine of
FIGURE 1 having a spindle assembly including an ouput
drive shaft according to the present disclosure.
5 FIGURE 4 is an enlarged vertical cross section of the
spindle assembly of the grinding machine of Figure 2.
FIGURE 5 is a front plan view of part of one embodiment
of a grinding cup according to the present disclosure.
FIGURE 6 is a partial cross-section of the grinding cup
of FIGURE 5 along line 5-5.
FIGURE 7 is a. top plan view of the grinding cup of FIGURE
= 15 5.
FIGURE 8 is a front plan view of one embodiment of a
lower grinding section of the grinding cup of FIGURE 5.
20 FIGURE 9 is a perspective view of an embodiment of a
holder device in the form of a spindle for a grinding
machine of FIGURE 3 according to the present disclosure
with the grinding cup of FIGURE 5 attached to the
spindle.
FIGURE 10 is a perspective view of the spindle and
grinding cup of FIGURE 9 with the grinding cup detached
from the spindle.
30 FIGURE 11 is a front plan view of the spindle and
grinding cup Of FIGURE 9.
FIGURE 12 is a cross section of the spindle and grinding
cup of FIGURE 11 along line A-A.
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FIGURE 13 is a side by side view in cross-section of four
grinding cups in a series of grinding cups according to
the present disclosure, each of said grinding cups sized
to grind a different size of button.
DETAILED DESCRIPTION
With reference to the FIGURE 1 one embodiment of a
grinding apparatus is generally indicated at 1. The
grinding apparatus 1 includes a grinding machine 2, means
for holding one or more bits to be ground generally
indicated at 3 and a support system generally indicated
at 4. The grinding machine 2, means for holding the bits
3 and support system 4 are arranged to permit relative
movement between the grinding machine 2 and the bit to be
ground to permit alignment of the grinding machine 2 with
the longitudinal axis of the buttons on the bit. The
grinding apparatus 1 has a control system, part of which
is generally indicated at 5, having a programmable
operator control panel 6 capable of directly or
indirectly monitoring and adjusting one or more
operational parameters. The operational parameters may
include feed pressure, grinding cup RPM, grinding time
and other parameters as noted herein.
In the grinding apparatus 1 shown in Figure 1, the
grinding machine 2 is carried by support system 4 which
includes an arm or lever system 7 journaled on a stand 8
attached to the rear 9 of an open box 10. The bit holder
means 3 consists of a table 11 mounted within the box 10.
=
FIGURE 2 ilustrates a more compact grinding apparatus
optionally suitable for mobile applications. The grinding
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apparatus is generally indicated at 20. The grinding
apparatus 20 includes a grinding machine 22, means for
holding one or more bits to be ground generally indicated
at 23 and a support system generally indicated at 24. The
5 grinding machine 22, means for holding the bits 23 and
support system 24 are arranged to permit relative
movement been the grinding machine 22 and the bit to be
ground to permit alignment of the grinding machine 22
with the longitudinal axis of the buttons on the bit. The
10 grinding apparatus 20 has a control system, part of which
is generally indicated at 25, having a programmable
operator control panel 26 capable of directly or
indirectly monitoring and adjusting one or more
operational parameters. The operational parameters of
most interest are selected from the group consisting of
feed pressure, grinding cup RPM and grinding time.
In the embodiment of the grinding apparatus 20 shown the
grinding machine 22 is carried by support system 24 which
includes an arm or lever system 27 attached to the frame
28.
In FIGURES 3 & 4, an embodiment of a grinding machine
2,22 suitable for use with the grinding apparatus 1,20 of
either FIGURE 1 or 2. FIGURES 3 & 4 show the grinding
machine 2,22 attached to plates below a control box 5,24.
The grinding machine 2,22 is locked in place by levers
36. A water-cooled electric motor, generally indicated at
35, has an exterior housing defining a chamber in which
the rotor and stator are located. Within the wall of the
housing are located a series of longitudinal channels
for the cooling water. Ports permit water in and water
out respectively. A drive coupling at the bottom of
housing permits attachment of the spindle assembly 45.
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The drive coupling is inserted into the mating drive
coupling 50 on spindle assembly 45. The spindle assembly
45 has an output drive shaft 46 to which a grinding cup
can be connected. The spindle assembly 45 is attached to
the electric motor housing by bolts 47. Coolant water for
delivery to the grinding cup surface is provided though
connection 48. The electric motor 35 is preferably a
three-phase motor and power is connected through
connection 51 to connection box. A flexible splash cup 53
is placed around the output drive shaft 46 of spindle
assembly 45. The motor can be hydraulic, electric or the
like without departing from the substance of the present
invention. The dimensions of the casing are such that the
grinding machine may be handled manually if desired. For
the latter purpose, the casing is provided with handles
projecting diametrically oppositely outwardly from the
casing. Suitably connected to the output drive shaft 46
by any conventional means is a holder device 54. In the
illustrated embodiment in Figures 9-12, the holder device
54 is an integral extension of the shaft 46 which
constitutes a rotatable elongate drive member 55. The
shaft 46 and drive member 55 are provided with a coaxial
passageway 56 extending along the length or part thereof
and through which coolant/flushing fluid may be directed
to a grinding cup 60 supported thereon. The configuration
of the holder device is set out in FIGURES 9-12.
Figures 5-8 illustrate one embodiment of a grinding cup
60 for detachable connection to the output drive shaft of
a grinding machine for grinding buttons on drill bits or
cutters. The grinding cup 60 consists of a lower grinding
section generally indicated at 61 and an upper body
section 62 co-axial with said grinding section 61 to form
said grinding. cup 60. A centrally disposed recess 63 is
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formed in the bottom surface 64 of the grinding section
61 having the desired profile for the button to be
ground.
The bottom (grinding) surface 64 of the grinding section
61 is formed from a material capable of grinding the
tungsten carbide button bits. In the embodiment, the
grinding surface is formed from a metal and diamond
matrix. The peripheral edge 72 in the bottom surface 64
is beveled to facilitate the removal of steel from the
face of the bit around the base of the button during
grinding.
The body section 62 has a base 65 having a centrally
disposed upright drive section 66 formed on the top
surface 67 of the base 65. The drive section 66 is
shaped and sized to driveably engage within a
corresponding recess (see Figures 9 and 11) at end of the
output drive shaft of said grinding machine. Retaining
means, generally indicated at 68, for detachably
connecting the grinding cup to the output drive shaft of
the grinding machine are provided on the upright drive
section. In the embodiment illustrated the retaining
means 68 comrises an annular groove 69 in the outer
surface 70 of the upright drive section 66 sized and
shaped to retain an 0-ring (not shown).
The upright drive section 66 has a non-circular cross
section and is tapered from the top surface 67 of the
base 65 to the free end 71 of the drive section 66. In
the embodiment illustrated in Figures 5-6, the upright
drive section 66 has a truncated elliptical cone shape.
The peripheral edge of the bottom 79 of the drive section
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36 is the same as or smaller than the diameter of the top
surface 67 of base 65.
=
A passageway 73 is provided in the drive section 66. The
5 passageway 73 is co-axial with the up-right drive section
66 and communicates with one or more openings (not shown)
on the grinding surface 64 through which coolant/flushing
fluid may be directed to the surface of the button being
ground during grinding.
As shown in Figure 8, integral with and adjacent the top
surface 74 of the grinding section 61 are means 75 to
connect the grinding section 61 to the upper body section
62. The means 75 to connect the grinding section 61 to
15 the upper body section 62 can be formed integrally with
the grinding section 61 and machined to the desired
configuration or cast separately and attached to the top
surface 74 of the grinding section 61. In the embodiment
illustrated in Figure 7, the means 75 to connect the
20 grinding section 61 to the upper body section 62,
consists of a generally cylindrical stub 76 centrally
= located on the top surface 74 of the grinding section 61.
The stub 76 is intended to be inserted into a
corresponding cavity on the upper body section 62 in a
25 manner (1) that will prevent the grinding section 61 from
rotating or spinning free relative to the upper body
section 62 and (2) that will support axial, radial,
torsion and feed forces associated with the use of the
grinding cup. In the preferred embodiment illustrated the
= 30 stub 76 is press fit into the drive connection member and
the grinding section 61 TIG welded to the upper body
section 62. Alternatively a stub on the upper body
section 62 could fit into a corresponding cavity on the
lower grinding section. Some examples of other possible
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connection methods are taper fits, threaded connections,
adhesives, solder, friction welding and pins. The stub 76
= could have a non-circular cross-section. It may be
desireable tb have stub 76 be in the form of an
5 elliptical tapered cone.
The bottom surface 77 of base 65 on the upper body
section 62 has cavity 78 formed therein sized and shaped
to accommodate the cylindrical stub 76 centrally located
10 on the top surface 74 of the grinding section 61.
In the embodiment illustrated grinding cup 60 is one in
a series of grinding cups for grinding the working tips
or buttons of rock drill bits wherein the working tips
15 or buttons have a diameter of about 6mm to 26mm and a
desired profile. The base 65 of the upper body section 62
of each grinding cup 60 in the series may be a constant
height across the series of grinding cups 60a, 60b, 60c
and 60d as shown in FIGURE 13. Alternatively the base 65
20 may be a constant height thru a group in the series of
grinding cups and vary in height for the next group.
Referring to Figs. 1-4, a grinding machine 2,22 is
illustrated which includes a motor housing or casing
25 within which is suitably supported a rotary motor. The
motor can be hydraulic, electric or the like without
departing from the substance of the present invention.
The dimensions of the casing are such that the grinding
machine may be handled manually if desired.
For the
30 latter purpose, the casing is provided with handles
projecting diametrically oppositely outwardly from the
casing.
The motor drives an output drive shaft.
Suitably connected to the output drive shaft by any
conventional means is a holder device 54.
In the
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illustrated embodiment in Figures 9-12, the holder device
54 is an integral extension of the shaft 46 which
constitutes a rotatable elongate drive member 55. The
shaft 46 and drive member 55 are provided with a coaxial
5 passageway 56 extending along the length or part thereof
and through which coolant/flushing fluid may be directed
to a grinding cup 60 supported thereon, the grinding cup
being shown in Figs. 5-8 and described in detail above.
An end portion 57 of the elongate drive member 55,
10 extending from its free end 59, is provided with a non-
circular recess 106 adapted to accomodate a corresponding
sized and shaped upright drive section 66 on grinding cup
60. As shown in Figures 9-16, the exterior wall 70 of the
upright drive section 66 on grinding cup 60 is adapted to
15 driveably engage within recess 106 centrally disposed in
the free end 59 of elongate drive member 55. In the
embodiment illustrated the interior wall 107 of the
recess 106 in drive member 55 is machined to an
elliptical cross section and tapering inwardly from the
end 59 of the drive member 55. This design permits the
upright drive section 66 of grinding cup 60 to be
inserted easily within recess 106 without the necessity
of specific alignment of the drive member and grinding
cup. The grinding cup can simply be pushed on the drive
member 55. When positioned in recess 106, the drive
member 55 will rotate the grinding cup without slipping
when in use. During grinding, the feed pressure applied
to the grinding machine results in the grinding cup 60
being pressed securely within recess 106 providing a
rigid connection to reduce wobbling of the grinding cup
60 during grinding. Further the present disclosure
maximizes the contact surfaces between the upright drive
section 62 on grinding cup 60 and the interior wall 107
of recess 106 on drive member 55. This reduces the wear
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to all key drive/contact surfaces of the output drive
shaft (rotor) and grinding cup which provide consistent,
proper alignment between grinding cup and or adapter and
the rotor during operation.
Retaining means may be provided in recess 106 of drive
member 55 to detachably retain the grinding cup 60 so
that grinding cup 60 will not fly off during use but can
still be easily removed or changed after use. The
retaining means may include one or more annular grooves
in the interior wall of the recess 106 in drive member
55. 0-rings or expansion rings may be inserted into the
grooves.
In the embodiment illustrated, both the grinding cup 60
and drive member 55 are fabricated from stainless steel
to prevent corrosion and to facilitate clean up after
grinding.
Having illustrated and described a preferred embodiment
of the invention and certain possible modifications
thereto, it should be apparent to those of ordinary skill
in the art' that the invention permits of further
modification in arrangement and detail and is not
restricted to the specific semi-automatic grinding
apparatus illustrated. For example the design of the
upper body section of the grinding cup and the free end
of the output drive shaft can be reversed. In this
embodiment the free end of the output drive shaft has a
non-circular cross-section and is tapered. The tapered
end of the output drive shaft is sized and shaped to fit
within a corresponding recess in the top surface of the
upper body section of the grinding cup.
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The present disclosure utilizes drive means to provide
=
both axial and radially support and transfer torosional
forces. A non-circular tapered connection provides both
support and drive. The resistance of the connection to
5 slippage improves as the feed pressure increases,
resulting in a relative increase in support and drive
capacity as feed increases. However the grinding cup can
still be easily removed from the output drive shaft after
= grinding with no more than a light tap from the side.
It will be appreciated that the above description related
to the preferred embodiment by way of example only. Many
variations on the invention will be obvious to those
knowledgeable in the field, and such obvious variations
15 are within the scope of the invention as described and
claimed, whether or not expressly described.
=
