Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: MASS REDUCED GRINDING CUP
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 and the means for detachably connecting
the grinding cups to the grinding machine.
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 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. A beveled rim around the recess
removes 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
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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.
The grinding cups are conventionally manufactured
by first machining a blank. 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. 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.
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 may be 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 United States Patent 5,688,163. The free end
of the stem of the grinding cup is machined to provide flat
drive surfaces. The flat drive surfaces match the profile of
a corresponding drive part in the channel of the output drive
shaft into which the stem is inserted. The grinding cup is
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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.
Recent 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 optimize the operational stability and loads
forces within the chosen method of connection. Lack of
operational stability, and/or the presence of excessive
loads, often results in increased wear/damage, as well as
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 surfaces of
the output drive shaft (rotor) and grinding cup which provide
consistent, proper alignment between grinding cup and/or
adapter and rotor during operation. The mass of the grinding
cup, particularly in larger sizes, negatively impacts
operational stability, wear/damage in many areas within the
grinding apparatus including wear/damage within drive/contact
areas between rotor and/or adapter and grinding cup, due to
mass associated loads. The mass of the grinding cup and/or
adapter also greatly affects mass associated start-up forces
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such as increased torsion forces within the drive and/or
contact surfaces due to forces such as inertia. Wear/damage
has a negative impact on operational stability. Operationa-
instability and associated vibration and/or resonance are 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.
SUMMARY OF THE INVENTION
It is an object of the present invention to
optimize/reduce the mass of the grinding cup to reduce the negative
impact of mass associated forces on operational stability,
wear/damage and/or deformation of drive and/or contact surfaces, as
well as other potential associated wear/damage caused by vibration
and/or resonance.
It is a further object of the present invention to
minimize the negative impact of mass associated start-up loads such
as increased torsion forces within the drive and/or contact
surfaces due to forces such as inertia.
It is a further object of the present invention to
minimize the negative impact of mass associated forces on var_ous
material types used, thereby potentially allowing for the use of,
for example, elastomeric materials, in various contact/drive areas
in which the use of such materials may previously not have been
feasible.
It is a further object of the present invention to
minimize the deterioration of the preferred built-in profile
of the cavity in the grinding section by reducing vibratio=
and/or resonance.
It is a further object of the present invention to
provide methods to reduce the mass of the grinding cup to
optimize the wall thickness between the inner cavities,
passageways, etc. and the outer structure. This results in a;r
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outside form substantially linked to the inside form with
consideration given to the drive means selected and providing
areas required for product identification and necessary
structural strength and/or support.
5 It is a further object of the present invention to
increase the diameter of the passageway through the stem
and/or grinding cup to reduce mass of grinding cup and
optimize flow and hence volume of flushing medium/coolant
delivered to the grinding section under varying operational
conditions.
Accordingly, the present invention provides a
grinding cup having a lower grinding section and an upper
body section integrally connected to form a grinding cup
having top and bottom surfaces. The grinding section is
formed from a material capable of grinding the hard materials
such as tungsten carbide inserts of button bits etc. A
centrally disposed convex recess is formed in the bottom
surface having the desired profile for the button to be
ground. One or more passageways in the upper body section and
grinding section 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,
through outlet(s) on the bottom surface. Drive means are
provided on or in the upper body section that cooperate with
the output shaft of the grinding machine. Retaining means are
provided in conjunction with the drive means to releasably
secure the grinding cup to the output shaft of the grinding
machine during use. The drive means or upper body section or
grinding section or any combination thereof are adapted 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, and mass associated operational loads. Mass
associated operational loads include start-up loads such as
increased torsion loads caused by inertia. By reducing
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vibration and/or resonance, deterioration of the preferred
built-in profile of the cavity in the grinding section is
minimized.
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 perspective view of an embodiment of a
shoulder drive, mass reduced grinding cup according
to the present invention
Fig. 2 is a top plan view of the grinding cup of Fig. 1.
Fig. 3 is a cross section of the grinding cup of Fig. 2
along 3-3.
Fig. 4 is a bottom plan view of the grinding cup of Fig.
1-3.
Fig. 5 is a perspective view of another embodiment of a
grinding cup according to the invention for
grinding small button bits.
Fig. 6 is a top plan view of the grinding cup of Fig. 5.
Fig. 7 is a cross section of the grinding cup of Fig. 6
along 7-7.
Fig. 8 is a bottom plan view of the grinding cup of Fig.
5-7.
Fig. 9 is a perspective view of an embodiment of a hex
drive, mass reduced grinding cup according to the
present invention
Fig. 10 is a cross section of the grinding cup of Fig. 9
along 10-10.
Fig. 11 is a top plan view of the grinding cup of Fig. 9.
Fig. 12 is a bottom plan view of the grinding cup of Fig.
9.
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DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The grinding cups and/or adapters of the present
invention have a number of features directed to reducing the
mass of the grinding cup and/or adapter 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, and mass associated
operational loads and to increasing the diameter of the
passageway through the stem and grinding cup or adapter to
reduce mass of grinding cup and optimize volume of coolant
delivered to the grinding section. Mass associated
operational loads include start-up loads such as increased
torsion loads caused by inertia.
Referring to Figs. 1-4, one embodiment of a mass
reduced grinding cup according to the present invention is
generally indicated at 1. The grinding cup 1 is intended for
use with a grinding machine which incorporates a
diametrically extending recess at the free end of a hollow
drive shaft 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. The present invention
is not restricted to grinding cups of this type. As will be
explained, the present invention has application to all types
of grinding cups regardless of the means of driving the
grinding cup or attaching it to the grinding apparatus. In
the illustrated embodiment, the means of driving the grinding
cup would normally be an integral extension of the output
shaft of rotor of the grinding machine. The means of driving
the grinding cup could also consist of either a separate
attachment to the output shaft of the rotor or an adapter to
connect a grinding cup having one type of drive means to an
output drive shaft having a different type of drive means.
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For example the adapter could connect a shoulder drive
grinding cup to a different output drive shaft such as the
hex drive system as illustrated in U.S. Patent No. 5,639,273
or U.S. Patent No. 5,727,994 or the drive system illustrated
in Canadian Patent 2,136,998.
The grinding cup 1 consists of a lower grinding
section 2 and an upper body section 3 integrally connected to
form a grinding cup having top and bottom surfaces 4 and 5
respectively. The grinding section 2 is formed from a
material capable of grinding the tungsten carbide inserts o=
button bits etc.. In the preferred embodiment, the grinding
section is formed from a metal and diamond matrix. The
peripheral edge 6 in the bottom surface 5 is preferably
beveled to facilitate the removal of steel from the face o=
the bit around the base of the button during grinding. A
centrally disposed convex recess 7 is formed in the bottom
surface 5 having the desired profile for the button to be
ground.
Drive means 8 are provided on or in the upper body
section 3 that cooperate with the output shaft of the
grinding machine. As noted above, the drive means can be any
of the methods currently being used including chuck nut and
collet systems, shoulder drive systems, machined drive
surfaces on the free end of the stem or hex drive systems. In
Figs 1-4, the drive means 8 consists of a hollow vertical
upright stem 9 centrally located on the top surface 4 of the
grinding cup 1. Cam means or shoulder 10 is provided at the
base of the stem 9 and is sized to engage with a
diametrically extending recess at the free end of a hollo~
drive shaft of the grinding machine. The hollow stem 9 is
inserted into the hollow drive shaft of the grinding machine.
Retaining means 11 are provided in conjunction wit:~
the drive means 8 to releasably secure the grinding cup to
the output shaft of the grinding machine during use. In the
preferred embodiment illustrated in Figs. 1-4, the retaining
means 11 are one or more 0-rings 12 located in one or more
grooves 13 on the stem 9 of the grinding cup. Optionally the
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retaining means could also be achieved by the drive means or
a combination of both working independently or cooperatively.
The passageway 14 in stem 9 connects to a
corresponding passageway 15 in the body section 3 and
grinding section 2 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,
through one or more outlets 16. As shown in Fig. 4, the
outlets 16 in this embodiment consist of three slots 17,18,19
radially extending from the centre 20 of the convex recess 7.
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 15 adjacent to outlets 17-19 may be expanded to
facilitate optimized flow between passageway and outlets.
In the embodiment shown, the upper body section 3,
grinding section 2 and drive means 8 of the grinding cup 1
are adapted to reduce the mass of the grinding cup to reduce
negative impact on operational stability, drive/contact
surface area wear/damage and/or deformation, wear/damage
and/or deformation of elastomeric materials in drive and/or
contact areas, as well as other potential associated
wear/damage to the grinding apparatus caused by vibration
and/or resonance, and mass associated operational loads. Mass
associated operational loads include start-up loads such as
increased torsion loads caused by inertia. In addition,
minimizing the deterioration of the preferred built-in
profile of the cavity in the grinding section can be
accomplished by substantially reducing vibration and/or
resonance.
In the preferred embodiment illustrated, the top
surface 4 of the upper body section 3 has a diameter D about
the same as the diameter of the diametrically extending
recess at the free end of the hollow drive shaft of the
grinding machine. One way to reduce the mass of the grinding
cup consists of reducing the diameter of exterior surface 21
of the upper body section 3. In the grinding cup illustrated
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in Figs. 1-4, the diameter of the body section 3 is reduced
by tapering part or all the exterior surface 21 to form a
beveled portion 22. Alternatively the reduction of the
diameter of the exterior surface 21 can be radial or form a
5 reverse radius. The beveled portion 22 terminates in neck
portion 23 that connects to the grinding section 2. In the
embodiment illustrated in Figs. 1-4, neck portion 23 is
generally cylindrical with a diameter sufficient to provide
structural support for the grinding cup 1.
10 Another way to reduce the mass of the grinding cup
is to machine the outer surface 24 of the metal portion 25 of
grinding section 2 to the point of connection 26 with the
neck portion 23 in a profile preferably corresponding to the
mating surface 28 of metal portion 25 with the diamond matrix
27. The thickness T of the metal portion 25 of the grinding
section 2 in the area should be sufficient to provide
structural support for the diamond matrix 27.
To further reduce the mass of the grinding cup and
optimize volume of coolant delivered to the grinding section
2, the diameters of the passageways 14, 15 through the stem 9
and grinding cup 1 are increased as wide as possible without
negatively impacting the structural integrity of the
components.
The above noted methods to reduce the mass of the
grinding cup attempt to optimize the wall thickness between
the inner cavities, passageways, etc. and the outer
structure. This results in an outside form substantially
linked to the inside form with consideration 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. The present invention does not require in each case
all of the possible methods of reducing the mass of the
grinding cup to be employed. Either the drive means, upper
body section or grinding section may be adapted or any
combination thereof. Further the invention is applicable to
all types of grinding cups or adapters regardless of the
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means used to drive, connect and retain the grinding cup on
the grinding machine. Further the invention is applicable to
all types of grinding cups regardless of the means used to
drive, connect and retain the grinding cup on the grinding
machine. The invention is applicable regardless of whether
the grinding cup is of the type having an upright hollow step
for insertion into a chuck, has a shoulder drive as shown in
Figs. 1-4, is of the type illustrated in U.S. Patent No.
5,688,163 where the free end of the stem is machined to
provide the drive surfaces or is of the type illustrated in
U.S. Patent Nos. 5,639,237 and 5,727,994 or is provided with
an adapter that connects one type of grinding cup to an
output drive shaft having a different drive system or any
modifications or improvements thereon.
Cam means or shoulder 10 provided at the base of
the stem 9 is preferably substantially the same size as the
diametrically extending recess at the free end of a hollow
drive shaft of the grinding machine. This optimizes the
contact area between the drive shaft and the grinding cup.
Figs.5-8 illustrate the application of the present
invention with a grinding cup 30 intended to grind small
diameter buttons. As with the embodiment illustrated in Figs.
1-4, the grinding cup 30 is intended for use with a grinding
machine which incorporates a diametrically extending recess
at the free end of a hollow drive shaft 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.
The grinding cup 30 consists of a lower grinding section 31
and an upper body section 32 integrally connected to form a
grinding cup having top and bottom surfaces 33 and 34
respectively. The grinding section 31 is formed from a
material capable of grinding the tungsten carbide inserts of
button bits etc.. In the preferred embodiment, the grinding
section is formed from a metal and diamond matrix. The
peripheral edge 35 in the bottom surface 34 is preferably
beveled to facilitate the removal of steel from the face of
the bit around the base of the button during grinding. A
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centrally disposed convex recess 36 is formed in the bottom
surface 34 having the desired profile for the button to be
ground.
Drive means 37 are provided on the upper body
section 32 that cooperate with the output shaft of the
grinding machine. In Figs 5-8, the drive means 37 consists of
a hollow vertical upright stem 38 centrally located on the
top surface 33 of the grinding cup 30. Cam means or shoulder
39 is provided at the base of the stem 38 and is sized to
engage with a diametrically extending recess at the free end
of a hollow drive shaft of the grinding machine. The hollow
stem 38 is inserted into the hollow drive shaft of the
grinding machine. Retaining means 40 are provided in
conjunction with the drive means 37 to releasably secure the
grinding cup to the output shaft of the grinding machine
during use. In the preferred embodiment illustrated in Figs.
5-8, the retaining means 40 are one or more 0-rings 41
located in one or more grooves 42 on the stem 38 of the
grinding cup. Optionally the retaining means could also be
achieved by the drive means or a combination of both working
independently or cooperatively.
The passageway 43 in stem 38 connects to a
corresponding passageway 44 in the body section 32 and
grinding section 31 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,
through one or more outlets 45. In addition the diameter of
passageway 44 adjacent to outlet 45 may be expanded to
facilitate optimized flow between passageway and outlets.
The drive means 37 and upper body section 32 of the
grinding cup 30 are adapted to reduce the mass of the
grinding cup to reduce negative impact on operational
stability, drive/contact surface area wear/damage,
wear/damage and/or deformation of elastomeric materials in
drive and/or contact areas, as well as other potential
associated wear/damage to the grinding apparatus caused by
vibration and/or resonance, and mass associated operational
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loads. Mass associated operational loads include start-up
loads such as increased torsion loads caused by inertia.
In this embodiment, the top surface 33 of the upper
body section 32 has a diameter D* about the same as the
diameter of the diametrically extending recess at the free
end of the hollow drive shaft of the grinding machine. One
way to reduce the mass of the grinding cup consists of
reducing the diameter of exterior surface 47 of the upper
body section 32. In the grinding cup illustrated in Figs. 5-
8, the diameter of the body section 32 is reduced by tapering
part or all the exterior surface 47 to form a beveled portion
48. Alternatively the reduction of the diameter of the
exterior surface 47 can be radial or form a reverse radius.
The beveled portion 48 terminates in neck portion 49 that
connects to the grinding section 31. In the embodiment
illustrated in Figs. 5-8, neck portion 49 is generally
cylindrical with a diameter sufficient to provide structural
support for the grinding cup 30.
The grinding section 31, in the embodiment
illustrated in Figs. 5-8, has the same diameter as the neck
portion. Due to the size of the button intended to be ground,
the grinding section, as illustrated, may not have sufficient
diameter to have its exterior surface 50 machined in a
profile corresponding to the diamond matrix 51 as in Figs 1-
4.
To further reduce the mass of the grinding cup and
optimize volume of coolant delivered to the grinding section
31, the diameters of the passageways 43, 44 through the stem
38 and grinding cup 30 are increased as wide as possible
without negatively impacting the structural integrity of the
components. In addition, the diameter of passageway 44
adjacent to outlet 45 may be expanded to facilitate optimized
flow between passageway and outlets.
The above noted methods to reduce the mass of the
grinding cup optimize the wall thickness between the inner
cavities, passageways, etc. and the outer structure. This
results in an outside form substantially linked to the inside
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form with consideration given to the size of the grinding
cup, the drive means selected, areas required for product
identification and necessary structural strength and/or
support. The present invention does not require in each case
all of the possible methods to be employed. Either the drive
means and the upper body section or grinding section may be
adapted or any combination thereof. Where an adapter is used
to connect one type of grinding cup to an output drive shaft
having a different drive system the methods to reduce the
mass of the grinding cup can be used to reduce the mass of
the adapter, which methods are included within the present
invention.
Cam means or shoulder 39 provided at the base of
the stem 38 is preferably substantially the same size as the
diametrically extending recess at the free end of a hollow
drive shaft of the grinding machine. This optimizes the
contact area between the drive shaft and the grinding cup.
The principles of the present invention can be
applied to all types of grinding cups including those
illustrated in U.S. Patent Nos. 5,639,237 and 5,727,994. Figs
9-12 illustrate another embodiment of a grinding cup
according to the present invention intended for use with
grinders as illustrated in these two patents. The grinding
cup 60 consists of a lower grinding section 61 and an upper
body section 62. In the preferred embodiment the grinding
section 61 and body section 62 are integrally connected to
form a grinding cup having top and bottom surfaces 63 and 64
respectively. The grinding section 61 is formed from a
material capable of grinding the tungsten carbide button
bits. In the preferred embodiment, the grinding section is
formed from a metal and diamond matrix. The peripheral edge
65 in the bottom surface 64 is preferably beveled to
facilitate the removal of steel from the face of the bit
around the base of the button during grinding. A centrally
disposed convex recess 66 is formed in the bottom surface 64
having the desired profile for the button to be ground.
Drive means 67 are provided in the upper body
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section 62 that cooperate with the output shaft of the
grinding machine. In the embodiment illustrated in Figs. 9-
12, the body section 62 has a centrally disposed cavity 68
formed in the top surface 63 of the grinding cup. This cavity
5 68 is shaped and sized to permit the grinding cup 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 adapted to fit
within the corresponding sized centrally disposed cavity 68
10 in the top surface 63 of the grinding cup 60. The output
drive shaft is adapted to driveably engage within the top
portion 69 of cavity 68. In the preferred embodiment shown
the top portion 69 of cavity 68 in grinding cup 60 has a
hexagonal cross section. To provide support for the grinding
15 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 70 of cavity
68 in grinding cup 60. In the shown embodiment, both the free
end of the output drive shaft and the bottom portion 70 of
cavity 68 have a circular cross section slightly smaller in
diameter than the hexagonal drive section 69. 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 grinding cup 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. In addition, retaining means can be provided by a
combination of both retaining means acting concurrently,
cooperatively providing improved retention. For example in
the preferred embodiment shown in Fig. 10 a groove 84 is
provided in the wall 85 of cavity 68 into which an 0-ring 86
is placed. The 0-ring 86 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
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resonance. Additional 0-rings on the output drive shaft will
co-operate with the wall 85 of the bottom portion 70 of
cavity 68 and 0-ring 86 to retain the grinding cup in place
during use.
One or more passageways 71 connect cavity 68 with
the recess 66 in the grinding section 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, through outlets 72. As shown in Fig. 12, the
outlets 72 in this embodiment consist of three slots 73,74,75
radially extending from the centre 76 of the convex recess
66.
The drive means 67, upper body section 62 and
grinding section 61 of the grinding cup 60 are adapted to
reduce the mass of the grinding cup to reduce negative impact
on operational stability, drive/contact surface area
wear/damage and/or deformation, wear/damage and/or
deformation of elastomeric materials in drive and/or contact
areas, as well as other potential associated wear/damage to
the grinding apparatus caused by vibration and/or resonance,
and mass associated operational loads.
One way to reduce the mass of the grinding cup
consists of reducing the diameter of exterior surface 77 of
the upper body section 62. In the grinding cup illustrated in
Figs. 9-12, the diameter of the body section 62 is reduced by
tapering part or all the exterior surface 77 below the cavity
68 to form a beveled portion 78. Alternatively the reduction
of the diameter of the exterior surface 77 can be radial or
form a reverse radius. The beveled portion 78 terminates in
neck portion 79 that connects to the grinding section 61. In
the embodiment illustrated in Figs.9-12, neck portion 79 is
preferably cylindrical with a diameter sufficient to provide
structural support for the grinding cup 60.
Another way to reduce the mass of the grinding cup
is to machine the outer surface 80 of the metal portion 81 of
grinding section 61 to the point of connection 82 with the
neck portion 79 in a profile preferably corresponding to the
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mating surface 87 of the metal portion 81 with diamond matrix
83. The thickness of the metal portion 81 of the grinding
section 61 that has been machined should be sufficient to
provide structural support for the diamond matrix 83.
To further reduce the mass of the grinding cup and
optimize volume of coolant delivered to the grinding section
61, the diameter of the passageway 71 through the grinding
cup 60 is increased as wide as possible without negatively
impacting the structural integrity of the components.
All of the above noted methods are intended to
reduce the mass of the grinding cup optimize the wall
thickness between the inner cavities, passageways, etc. and
the outer structure. This results in an outside form
substantially linked to the inside form with consideration
given to the size of the grinding cup, drive means selected,
manufacturing costs, areas required for product
identification and necessary structural strength and/or
support.
To further reduce the mass of the grinding cup it
is possible to utilize lighter weight materials such as
elastomeric materials in the upper body section of the
grinding cup or to form part of the drive means or retaining
means.
As noted earlier, the principles of the present
invention can be applied to an adapter used to connect one
type of grinding cup to an output drive shaft having a
different drive system. In this case the methods to reduce
the mass of the grinding cup can be used to reduce the mass
of the adapter, which methods are included within the present
invention. The present invention does not require in each
case all of the possible methods to be employed. One or more
methods or any combination thereof can be utilized.
The grinding cups of the present invention can be
manufactured in general by the same process conventionally
used to make grinding cups: by first forming a blank for the
body section by machining, casting, forging etc. The blank is
then pressed into a mould preferably containing a hot
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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 or other suitable
method to a blank.
The blank for the grinding cup can be machined
either before or after it is pressed into the mould
containing the hot diamond/metal mixture. The preferred
procedure would be to the extent possible pre-machine the
blank before attaching the grinding matrix section. In any
event some form of post-furnace machining may be required for
clean up purposes. Clean up of the interior and exterior
surfaces post-furnace, to remove "flash" and other matrix
material which may have seeped out of the mold during
furnacing/pressing, is carried out by holding the grinding
cup 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.
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.
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.
