Note: Descriptions are shown in the official language in which they were submitted.
CA 02363352 2008-06-09
TITLE: GRINDING MEMBER FOR BUTTONS ON A ROCK DRILL BIT
BACKGROUND OF THE INVENTION
The present invention relates to improvements in devices
for use as grinding cups for grinding the hard metal inserts or
working tips of 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 tungsten carbide
cutting teeth or buttons of a 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.
Different manual and semi-automatic grinding machines are
known for grinding button bits/cutters (see for example U.S. Patent
No. 5,193,312; 5,070,654). In a conventional type of machine a
grinding cup having the desired profile is rotated at high speed,
typically from about 15,000 to 25,000 RPM, to grind the carbide
button and the face of the bit/cutter surrounding the base of the
button to restore the button to substantially its original profile
for effective drilling.
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 convex
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
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the drill bits or cutters. Typically the button diameter varies from
6mm up to 26mm.
Several different methods are 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 of tools. 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. The stem of the grinding
cup 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 that 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.
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 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.
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
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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 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 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.
The grinding cups are conventionally manufactured by
first forming a blank for the body section by machining, casting,
forging etc. It is necessary to machine different blanks for each
size of button to be ground and for the different methods of
attaching the grinding cup to the grinding machine. This results in
higher costs of manufacture and a large inventory of parts for
manufacture of the grinding cups over the full range of sizes, shapes
and methods of connection. The blank is then pressed into a mould
containing a hot diamond/metal mixture. The bottom surface of the
blank is heated and bonds to the diamond/metal matrix. Several means
of heating and bonding the diamond/metal matrix to the blank are
known. Alternatively the diamond/metal matrix can be formed into the
grinding section and then bonded either by a shrink fit and/or with
adhesives or solder to a blank.
SUMMARY OF THE INVENTION
It is an object of the present invention to standardize
components regardless of the size of the button to be ground or
method of connection to reduce manufacturing costs.
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It is a further object of the present invention to
provide a standardized grinding means for each size and shape of
button to be ground that it can be custom connected to different or
re-useable drive means.
It is an object of the present invention to reduce
negative impact on operational stability, drive/contact surface
wear/damage, wear/damage and/or deformation of elastomeric materials
in the drive and/or contact areas, as well as other potential
associated wear/damage to the grinding apparatus caused by vibration
and/or resonance
It is a further object of the present invention to
improve operational stability by optimizing/harmonizing the forces
transferred between the rotor and grinding cup or grinding cup and
adapter or adapter and rotor during operation including torsion
(rotational) forces, axial (feed) forces and radial (varying side
load) forces.
Accordingly the present invention provides a grinding member
for connection to a drive connection member to form a grinding cup
for grinding the hard metal inserts or working tips of drill bits
(percussive or rotary), tunnel boring machine cutters (TBM) and
raised bore machine cutters (RBM) to restore them to substantially
their original profile. The grinding member has:
(a) a grinding section having top and bottom surfaces, a
centrally disposed convex recess formed in the bottom
surface of said grinding section having the desired profile
to be ground;
(b) a support section adjacent the top surface of said grinding
section; and
(c) means to connect the grinding member to the drive connection
member wherein the grinding member can be disconnected from
the drive connection member when it becomes worn.
In a preferred embodiment the means to connect the grinding member to
the drive connection member drive consists of a longitudinally
extending stub adapted to fit in a corresponding recess on said drive
connection member.
In another aspect the present invention provides a drive
connection member having a first section adapted for connection to
the grinding member and a second section adapted to detachably
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connect to the output drive shaft of a grinding machine. The second
section consists of a drive section and a support section and
preferably has engagement surfaces sized and shaped to substantially
match contact areas on the output drive shaft of the grinding machine
or any adapter connecting said drive connection member to the output
drive shaft of a grinding machine.
Further features of the invention will be described or
will become apparent in the course of the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more clearly
understood, the preferred embodiment thereof will now be described in
detail by way of example, with reference to the accompanying
drawings, in which:
Fig. 1 is a side elevation, partly in section, of an embodiment
of a grinding member and a drive connection member
utilizing a shoulder drive that when connected form a
grinding cup according to the present invention;
Fig. 2 is a side elevation, partly in section, of an embodiment
of a grinding member and a drive connection member
utilizing a hex drive that when connected form a grinding
cup according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention is illustrated in Fig. 1 in
conjunction with grinding cups utilizing a shoulder drive but is also
applicable to other types of drive means on grinding cups.
Referring to Fig. 1, one embodiment of a grinding cup
according to the present invention is generally indicated at 1. The
grinding cup 1 is for use with a grinding machine of the type which
incorporates a diametrically extending slot at the free end of the
output drive shaft of the grinding machine that co-operates with a
shoulder or cam means on the adjacent top surface of the grinding cup
such as described in U.S. Patent No. 5,527,206.
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The grinding cup 1 is formed of two distinct components:
a grinding member 2 and drive connection member 3. The grinding member
2 has a grinding section 4 formed from a material capable of grinding
the tungsten carbide inserts of button bits. In the preferred
embodiment, the grinding section 4 is formed from a metal and diamond
matrix. The peripheral edge 5 in the bottom surface 6 of the grinding
section 4 is preferably beveled to facilitate the removal of steel
from the face of the bit around the base of the button during
grinding. Other means for removal of steel from the face of the bit
around the base of the button either during or before or after
grinding are known including the use a separate tool for this purpose,
use of wear splines or broach marks around the periphery or varying
the angle of the peripheral edge. A centrally disposed convex recess 7
is formed in the bottom surface 6 having the desired size and profile
for the button to be ground.
Preferably integral with and adjacent the top surface 8 of
the grinding section 4 is a support section 9 whose bottom surface 10
is bound to the top surface 8 of the grinding section 4. Several means
of heating and bonding the diamond/metal matrix of the grinding
section 4 to support section 9 are known. The support section 9
consists of a metal portion 11, machined, forged or cast. The metal
portion 11 for the support section 9 can be machined either before or
after it is attached to diamond/metal grinding section 4. The
preferred procedure would be to the extent possible pre-machine the
support section 9 before attaching the grinding section 4. In any
event some form of post-furnace machining may be required for clean up
purposes. Clean up of the exterior surfaces post-furnace is carried
out by holding the grinding section 4 in the chuck of a lathe and then
skimming the relevant surfaces wherever needed. At this time it is
also possible to remove additional material wherever suitable. Post-
furnace machining is used to remove "flash" and other matrix material
which may have seeped out of the mold during furnacing/pressing. The
thickness T of the metal portion 11 of the support section 9 should be
sufficient to provide structural support for the grinding section 4.
Means 13 to connect the grinding member 2 to the drive
connection member 3 are provided on the top edge 14 of the support
section 9. The means 13 to connect the grinding member 2 to the drive
connection member 3 can be formed integrally with the support section
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9 and machined to the desired configuration or cast separately and
attached to the support section9. In the embodiment illustrated in
Fig. 1, the diameter of the support section 9 relative to the size of
the grinding section 4 is optimized to reduce the mass of the grinding
member 2 by machining the peripheral surface 15 to its top edge 14 in
a profile generally corresponding to the profile of the top surface 8
of the grinding section 4.
In the embodiment illustrated in Fig. 1, the means 13 to
connect the grinding member 2 to the drive connection member 3,
consists of a generally cylindrical section 16 whose bottom edge 17 is
attached and/or with the top edge 14 of support section 9. A
cylindrical stub 18 is centrally located on the top edge 19 of the
cylindrical section 16. The stub 18 is intended to be inserted into a
corresponding cavity on the drive connection member 3 in a manner (1)
that will prevent the grinding member 2 from rotating or spinning free
relative to the drive connection member 3; (2) that will support
axial, radial, torsion and feed forces associated with the use of the
grinding cup and (3) permit removal of a grinding member 2 with worn
grinding section 2 and replacement with a new grinding member to
permit re-use of the drive connection member. In the preferred
embodiment illustrated the stub 18 is press fit into the drive
connection member. Other possible connection methods are taper fits,
threaded connections and pins.
A passageway 20 through the grinding member 2 connects to
one or more outlets 21 in the grinding section 4 to permit a coolant,
preferably water, optionally mixed with cutting oil or a water/air
mist, to be provided to the surface of the button during grinding. The
coolant prevents excessive heat generation during grinding and flushes
the surface of the button of material removed during grinding. In
addition, the diameter of the passageway 20 through the support
section 9 and means 13 may be expanded to reduce the mass of the
grinding section.
In the present invention the grinding member 2 for any
particular size and shape of convex recess 7 is the same regardless of
the method of connecting the grinding cup to the output drive shaft of
a grinding machine. Standardizing the components will reduce
manufacturing costs and the amount of inventory required.
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The drive connection member 3 in the embodiment
illustrated in Fig. 1 has a first section 22 adapted for connection to
the grinding member 2 and a second section 23 adapted to detachably
connect to the output drive shaft of a grinding machine. The first
section 22, in the embodiment illustrated the outer wall 24 of first
section 22, generally cylindrical in the embodiment shown although
other shapes are possible, defines a recess 25 adapted to receive the
stub 18 of the grinding member 2. The stub 18 is adapted to fit within
recess 25 so that the grinding member 2 carinot rotate or spin relative
to the drive connection member 3. The bottom 26 of the outer wall 24
is sized and shaped to fit against the top edge 19 of the cylindrical
section 16 of means 13 on the grinding member 2. While the stub 18 and
recess 25 are illustrated as circular in cross section other shapes
are possible such as elliptical, oval, square, rectangular, hexagonal
etc.
The second section 23 of the drive connection member is
integral with the top 27 of the outer wall 24 of the first section.
The configuration of the second section 23 will vary depending on the
drive system on the grinding machine to which the grinding cup is
intended to be attached. Regardless of the drive system being
utilized, in general the second section 23 will have a drive section
and a support section. In Fig. 1 has previously indicated the drive
system to which the drive connection member 3 is intended to co-
operate is a shoulder drive system. In the illustrated embodiment the
drive section, generally indicated at 28, cam means or shoulder 29
provided at the top 27 of the outer wall 24 of the first section 22.
The cam or shoulder 29 is sized to engage with a diametrically
extending slot at the free end of the output drive shaft of a grinding
machine. The cam 29 has an upper surface 30, parallel side walls 31
and end walls 32. The support section, generally indicated at 33,
consists of a hollow vertical upright stem 34 centrally located on the
upper surface 30 of the cam 29. The hollow stem 34 is intended to be
inserted into a corresponding axial recess in the output shaft of the
grinding machine. Retaining means 35 are provided in conjunction with
the upright stem 34 to releasably secure the grinding cup to the
output shaft of the grinding machine during use. In the preferred
embodiment illustrated in Fig. 1, the retaining means 35 are one or
more 0-rings 36 located in one or more grooves 37 on the stem 34.
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Optionally the retaining means could also be located on the output
drive shaft or a combination on both the grinding cup and the drive
shaft working independently or cooperatively.
In the embodiment shown, the drive section 27 is adapted
to optimize contact between the engagement surfaces (upper surface 30
and side walls 31 of cam 29) on the drive connection member 3 and the
corresponding engagement surfaces on the output drive shaft of the
grinding machine to reduce vibration to reduce rotor wear, as well as
other potential associated wear to the grinding apparatus caused by
vibration and/or resonance and to improve operational stability by
optimizing and harmonizing the forces transferred between the rotor
and grinding cup during operation including torsion (rotational)
forces, axial (feed) forces and radial (varying side load) forces and
to reduce negative impact on operational stability, drive/contact
surface wear/damage, wear/damage and/or deformation of elastomeric
materials in the drive and/or contact areas.
In the embodiment shown, cam means or shoulder 29 is sized
and shaped so that the engagement surfaces on said cam or shoulder are
optimized to and match with the corresponding engagement surfaces of
slot on the output shaft of the grinding machine. In addition the cam
or shoulder 29 is preferably substantially the substantially the same
length, width and depth as the diametrically extending slot at the
free end of the output drive shaft of the grinding machine. This
optimizes the contact area between the walls of slot on the drive
shaft and the upper surface 30 and side walls 32 of the cam 29
resulting in reduced vibration and rotor wear, as well as other
potential associated wear to the grinding apparatus caused by
vibration and/or resonance. Reduced vibration also improves
operational stability, drive/contact surface wear/damage, wear/damage
and/or deformation of elastomeric materials in the drive and/or
contact areas by optimizing and harmonizing the forces transferred
between the rotor and grinding cup during operation including torsion
(rotational) forces, axial (feed) forces and radial (varying side
load) forces. In addition, substantially reducing vibration and/or
resonance, minimizes the deterioration of the preferred built-in
profile of the cavity in the grinding section.
To optimize and harmonize the various loads such as
torsion loads and resulting operational loads such as radial and axial
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loads over a range of various sizes and profiles of grinding cups, the
cam or shoulder may be sized differently in relation to the
diametrically extending slot at the free end of the output drive shaft
or adaptor if one is being used.
The above noted methods to optimize the contact area
between the drive shaft and the grinding cup and standardize
components, wherever practical, regardless of the size of the button
to be ground will reduce manufacturing costs. In addition, this
results in less vibration to reduce rotor wear, as well as other
potential associated wear to the grinding apparatus caused by
vibration and/or resonance and reduces negative impact on operational
stability, drive/contact surface wear/damage, wear/damage and/or
deformation of elastomeric materials in the drive and/or contact areas
by optimizing and harmonizing the forces transferred between the rotor
and grinding cup during operation including torsion (rotational)
forces, axial (feed) forces and radial (varying side load) forces. In
addition, deterioration of the preferred built-in profile of the
cavity in the grinding section is minimized. Consideration is given to
the size of the grinding cup, the drive means selected, manufacturing
costs, areas required for product identification and necessary
structural strength and/or support in implementation of the present
invention.
Alternative manufacturing methods in order to achieve
further standardization, simplify manufacturing, reduce costs and
minimize inventory are within the scope of the present invention.
Alternative materials and processes can be used that are currently
incompatible with any one or more parts or the manufacturing process.
For example, brass is not normally compatible with many forms of
sintering, etc., due to the fact that it cannot take the heat
necessary to produce a good bond within the diamond matrix of the
grinding section. Making a separate drive connection member out of
brass and attaching the grinding member, post furnace, would make
this possible. Heat treating the drive connection member may not
feasible when done on a finished grinding cup, but on a re-useable
one, it may be both operationally beneficial and cost efficient for
the customer.
Since a standardized drive connection member according
to the present invention, can be mass produced, the advantage of
CA 02363352 2001-11-21
higher precision, reduced cost, etc. are possible by the category of
machining equipment available to make this component. Further by
making a standardized drive connection member with greater precision
could result in better dynamic balance, etc. due to factors such as
less runout, etc..
Fig. 2 illustrates a grinding cup 300 formed from two
components a grinding member and drive connection member for
connection to grinding machine utilizing a hex drive system as
illustrated in U.S. Patent 5,727,994. The grinding member 2 is the
same as described above in connection with Fig. 1. The drive
connection member generally indicated at 303 in the embodiment
illustrated in Fig. 2 has a first section 322 adapted for connection
to the grinding member 2 and a second section 323 adapted to
detachably connect to the output drive shaft of a grinding machine.
The first section 322, in the embodiment illustrated the outer wall
324 of first section 322 defines a recess 325 adapted to receive the
stub 18 of the grinding member 2. The stub 18 is adapted to fit within
recess 325 so that the grinding member 2 cannot rotate or spin
relative to the drive connection member 303. The bottom 326 of the
outer wall 324 is sized and shaped to fit against the top edge 19 of
the cylindrical section 16 of means 13 on the grinding member 2.
The second section 323 of the drive connection member 303
is integral with the top 327 of the outer wall 324 of the first
section. The configuration of the second section 323 will vary
depending on the drive system on the grinding machine to which the
grinding cup is intended to be attached. Regardless of the drive
system being utilized, in general the second section 323 will have a
drive section and a support section. In Fig. 2 as previously
indicated the drive system to which the drive connection member 303
is intended to co-operate is a hex drive system. In the illustrated
embodiment the drive section, generally indicated at 328, is intended
to cooperate with the output shaft of the grinding machine. In the
embodiment illustrated in Fig.2, the second section 323 has a outer
wall 304 defining a centrally disposed cavity 315 open at the top 305
of the outer wall 304. This cavity 315 is shaped and sized to permit
the drive connection member 303 to be detachably connected to the
output drive shaft of the grinding machine and rotated during the
grinding operation. The end portion of the output drive shaft is
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adapted to fit within the corresponding sized centrally disposed
cavity 315. The output drive shaft is adapted to driveably engage
within cavity 315. In the preferred embodiment shown the top portion
316 of cavity 315 in second section 323 is adapted to define drive
section 328. In the embodiment shown, dive section 328 is machined
with a hexagonal cross section corresponding to the shape of the
corresponding drive section on the output shaft of the grinding
machine. The drive section 328 can be formed other than by machining.
To provide support for the grinding cup and minimize vibration
generated axial side load on the grinding cup, the free end of the
output drive shaft is adapted to fit snugly within the bottom portion
317 of cavity 315 in the second section 323 of the drive connection
member 303. In the embodiment illustrated, both the free end of the
output drive shaft and the bottom portion 317 of cavity 315 would
have a circular cross section slightly smaller in diameter than the
hexagonal drive section 328. Other arrangements are possible, for
example the support section of the cavity can be above the drive
section located at the bottom of the cavity or the drive section can
be located intermediate two support sections.
Retaining means are provided on either the output drive
shaft or in the cavity 315 or a combination of both to detachably
retain the grinding cup so that grinding cup will not fly off during
use but can still be easily removed or changed after use. For example
in the preferred embodiment shown in Fig. 2 a groove 318 is provided
in the wall 319 of cavity 315 into which an 0-ring 320 is placed. The
0-ring 320 will co-operate with the exterior surface of the output
drive shaft to assist in retaining the grinding cup in place during
use and reducing vibration and resonance. Additional 0-rings on the
output drive shaft will co-operate with the wall 319 of the bottom
portion 317 of cavity 315 and 0-ring 320 to retain the grinding cup
in place during use. These grooves and 0-rings are points of
engagement which work to optimize the transfer of loads between the
adapter and the output drive shaft.
In the embodiment shown, the drive connection member 303
is adapted to optimize the engagement or drive surfaces on the drive
section 328 of the grinding cup with the corresponding contact
surfaces on the output drive shaft to reduce vibration to thereby
reduce rotor wear, as well as other potential associated wear to the
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grinding apparatus caused by vibration and/or resonance and to
improve operational stability by optimizing and harmonizing the
forces transferred between the rotor and grinding cup during
operation including torsion (rotational) forces, axial (feed) forces
and radial (varying side load) forces. Reduced vibration also
improves operational stability, drive/contact surface wear/damage,
wear/damage and/or deformation of elastomeric materials in the drive
and/or contact areas by optimizing and harmonizing the forces
transferred between the rotor and grinding cup during operation
including torsion (rotational) forces, axial (feed) forces and radial
(varying side load) forces. In addition, substantially reducing
vibration and/or resonance, minimizes the deterioration of the
preferred built-in profile of the cavity in the grinding section.
To further reduce vibration and improve operational
stability, drive/contact surface wear/damage, wear/damage and/or
deformation of elastomeric materials in the drive and/or contact
areas by optimizing and harmonizing the forces transferred between
the rotor and grinding cup during operation including torsion
(rotational) forces, axial (feed) forces and radial (varying side
load) forces, it is possible to utilize lighter weight materials such
as elastomeric materials in the grinding member or drive connection
member or to form part of the drive means or retaining means.
The grinding cups of the present invention are intended to
reduce manufacturing costs by standardizing components and reducing
inventory on hand. However they also may have a number of features
directed to (1) optimizing the drive surface on the drive means to
prevent uneven wear and further reduce vibration to optimize the drive
and/or contact surfaces on the drive means of a grinding cup relative
to the corresponding drive and/or contact surfaces of the grinding
apparatus rotor/adapter to prevent uneven wear and reduce vibration
(2) reduce negative impact on wear/damage and/or deformation of
elastomeric materials in drive and/or contact areas (3) improving
operational stability by optimizing/harmonizing the forces transferred
between the rotor and grinding cup during operation including torsion
(rotational) forces, axial (feed) forces and radial (varying side
load) forces (4) minimizing operator exposure to sharp and/or
protruding features when the grinding cup and rotor have engaged (5)
substantially streamline/harmonize all contact surfaces including the
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combined outside geometry at the transition point between grinding
cups and rotor/adapter and (6) reducing the mass of the grinding cups
by reducing the outside and inside profile of the grinding cup and/or
using lighter weight materials.
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.
For example the grinding cup may include an adapter to connect the
grinding cup of one drive system to the output drive shaft of a
different drive system.
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 are within the scope of the invention as
described and claimed, whether or not expressly described.
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