U.S. patent application number 10/025089 was filed with the patent office on 2002-06-06 for grinding wheel.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Cesena, Robert T., Palmgren, Gary M., Preston, Jay B., Tselesin, Naum N..
Application Number | 20020068518 10/025089 |
Document ID | / |
Family ID | 22973791 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020068518 |
Kind Code |
A1 |
Cesena, Robert T. ; et
al. |
June 6, 2002 |
Grinding wheel
Abstract
A cylindrical, abrasive grinding wheel having a cylindrical
abrasive region with an abrasive surface at an outer circular band
thereof. The abrasive region includes layers of abrasive particles.
The layers of abrasive particles can be tilted with respect to an
axis of rotation of the grinding wheel or they can such that
grooving in the grinding wheel and a workpiece ground by the
grinding wheel can be reduced. Alternatively, the abrasive region
can be formed from a plurality of abrasive segments each having
layers of abrasive particles. The layers of abrasive particles can
be staggered in the direction of the axis of rotation from one
segment to another. This can also reduce grooving in the grinding
wheel and workpieces.
Inventors: |
Cesena, Robert T.;
(Richfield, MN) ; Tselesin, Naum N.; (Atlanta,
GA) ; Palmgren, Gary M.; (Lake Elmo, MN) ;
Preston, Jay B.; (Woodbury, MN) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
22973791 |
Appl. No.: |
10/025089 |
Filed: |
December 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10025089 |
Dec 18, 2001 |
|
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09256837 |
Feb 24, 1999 |
|
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|
09256837 |
Feb 24, 1999 |
|
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09019657 |
Feb 6, 1998 |
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Current U.S.
Class: |
451/541 |
Current CPC
Class: |
B24D 5/16 20130101; B24D
5/02 20130101; B24D 18/00 20130101; B24D 5/10 20130101; B24D 3/06
20130101; B24D 5/066 20130101 |
Class at
Publication: |
451/541 |
International
Class: |
B24B 005/00 |
Claims
What is claimed is:
1. An abrasive grinding wheel that can be rotated about an axis of
rotation, the abrasive grinding wheel comprising: a means for
defining an axis of rotation of the abrasive grinding wheel; a
substantially cylindrical region of abrasive material having a
circumferentially extending abrasive surface at a peripheral band
thereof and formed from a plurality of layers of abrasive
particles, each layer of abrasive particles extending along at
least a portion of the circumference of the abrasive surface and in
a radial direction of the substantially cylindrical region of
abrasive material from the abrasive surface toward the axis of
rotation; and wherein any circular path defined by an intersection
of a plane perpendicular to the axis of rotation of the abrasive
grinding wheel and a complete circumference of the abrasive surface
will intersect at least one of the plurality of layers of abrasive
particles.
2. The abrasive grinding wheel of claim 1 wherein the plurality of
layers of abrasive particles are substantially planar and parallel
to one another.
3. The abrasive grinding wheel of claim 1 including a first support
plate and a second support plate, and wherein the region of
abrasive material is sandwiched between the first support plate and
the second support plate.
4. The abrasive grinding wheel of claim 3 wherein the abrasive
material is bonded to the first and the second support plates with
an adhesive.
5. The abrasive grinding wheel of claim 3 wherein a plane
substantially parallel with the layers of abrasive particles forms
an angle of between 0 degrees and 180 degrees, exclusive, with the
axis of rotation of the abrasive grinding wheel.
6. The abrasive grinding wheel of claim 5 wherein the region of
abrasive material includes a first surface and a second surface
which is substantially parallel to the first surface, and wherein
both the first surface and the second surface are tilted at an
angle of between 0 degrees and 90 degrees, exclusive, with the axis
of rotation of the abrasive grinding wheel.
7. The abrasive grinding wheel of claim 1 wherein at least a first
layer of abrasive particles of the plurality of layers of abrasive
particles extends along the abrasive surface such that at least one
path defined by the intersection of a plane perpendicular to the
axis of rotation and the abrasive surface will intersect the first
layer of abrasive particles in at least three locations.
8. The abrasive grinding wheel of claim 1 further including: first
and second support plates forming outer axial surfaces of the
grinding wheel; and a plurality of discrete abrasive segments
circumferentially spaced between the first and second support
plates to form the region of abrasive material, each abrasive
segment having a plurality of layers of abrasive particles.
9. The abrasive grinding wheel of claim 8 wherein the abrasive
segments are bonded to the first and the second support plates with
an adhesive.
10. The abrasive grinding wheel of claim 8 wherein at least one of
the plurality of layers of abrasive particles in at least one of
the plurality of abrasive segments are offset in an axial direction
from at least one of the plurality of layers of abrasive particles
in at least one other of the plurality of abrasive segments.
11. The abrasive grinding wheel of claim 10 wherein the plurality
of layers of abrasive particles in each of the plurality of
abrasive segments is oriented to extend substantially perpendicular
to the axis of rotation of the abrasive grinding wheel.
12. The abrasive grinding wheel of claim 10 wherein at least one of
the plurality of layers of abrasive particles in each of the
plurality of abrasive segments is separated from an adjacent layer
of abrasive particles in a same segment by a separation distance
perpendicular to each layer of abrasive particles and further
wherein at least one separation distance in at least one of the
plurality of abrasive segments is different from at least one
separation distance in at least one other of the plurality of
abrasive segments.
13. The abrasive grinding wheel of claim 8 further including: at
least one opening provided in the abrasive surface; a first channel
positioned radially interior to the abrasive surface and in fluid
communication with the opening; a second channel opening to the
interior of the abrasive grinding wheel and located in a center
region thereof; and at least one radial channel extending from the
second channel of the abrasive grinding wheel to the first channel
and in fluid communication with both the first channel and the
second channel; so that a liquid lubricant provided under pressure
to first channel can pass through the radial channel, into the
circular channel and through the opening to lubricate the abrasive
surface of the grinding wheel during rotation of the grinding
wheel.
14. The abrasive grinding wheel of claim 8 wherein an abrasive
segment that extends over a circumferential portion of the abrasive
surface is made up of plural axial segments that are stacked
adjacent to one another in the axial direction of the grinding
wheel and supplied between the first and second support plates.
15. The abrasive grinding wheel of claim 8 wherein at least a first
abrasive particle layer of the plurality if abrasive particle
layers in at least one abrasive segment of the plurality of
abrasive segments intersects in at least two locations a path
defined by the intersection of a plane perpendicular to the axis of
rotation and the abrasive surface.
16. The abrasive grinding wheel of claim 1 wherein the abrasive
surface includes a grinding profile which is convex.
17. The abrasive grinding wheel of claim 1 wherein the abrasive
surface includes a grinding profile which is concave.
18. An abrasive grinding wheel for connection to a rotary tool so
that the abrasive grinding wheel can be rotated about an axis of
rotation, comprising: a means for defining an axis of rotation of
the abrasive grinding wheel; a substantially cylindrical abrasive
region having layers of abrasive particles, each layer of abrasive
particles extending along at least a portion of the circumference
of the abrasive surface and in at least a radial direction of the
substantially cylindrical region of abrasive material, and wherein
the plurality of layers of abrasive particles form an angle of
between 0 degrees and 180 degrees, exclusive, with the axis of
rotation of the abrasive grinding wheel.
19. The abrasive grinding wheel of claim 18 wherein the abrasive
region includes a first surface and a second surface, both the
first surface and the second surface being substantially parallel
to the plurality of layers of abrasive particles, both the first
and second surfaces further being tilted at an angle of between 0
degrees and 90 degrees, exclusive, with the axis of rotation of the
abrasive grinding wheel.
20. The abrasive grinding wheel of claim 19 including a first
support plate and a second support plate, and wherein the region of
abrasive material is sandwiched between the first support plate and
the second support plate.
21. The abrasive grinding wheel of claim 20 wherein the region of
abrasive material comprises a single laminated block.
22. An abrasive grinding wheel that can be rotated about an axis of
rotation, comprising: a means for defining an axis of rotation of
said abrasive grinding wheel; a first support plate; a second
support plate; and a substantially cylindrical region of abrasive
material sandwiched between the upper support plate and the lower
support plate and formed from a plurality of discrete abrasive
segments, each of the plurality of abrasive segments having a
plurality of layers of abrasive particles extending along at least
a portion of the circumference of an abrasive surface; wherein at
least one of the plurality of layers of abrasive particles in at
least one of the plurality of abrasive segments are offset in a
direction of the axis of rotation from at least one of the
plurality of layers of abrasive particles in at least one other of
the plurality of abrasive segments.
23. The abrasive grinding wheel of claim 22 wherein each of the
plurality of layers of abrasive particles in each of the plurality
of abrasive segments is oriented to extend substantially
perpendicular to the axis of rotation of the abrasive grinding
wheel.
24. The abrasive grinding wheel of claim 22 further including: at
least one opening provided in the abrasive surface of the grinding
wheel; a first channel positioned radially interior to the
plurality of abrasive segments and in fluid communication with the
opening; a second channel opening to the interior of the abrasive
grinding wheel and located in a center region thereof; and at least
one radial channel extending from the second channel of the
abrasive grinding wheel to the first channel and in fluid
communication with the first channel and the second channel; so
that a liquid lubricant provided under pressure to the first
channel can pass through the radial channel, into the second
channel and through the opening to lubricate the abrasive surface
during rotation of the grinding wheel.
25. The abrasive grinding wheel of claim 22 wherein an abrasive
segment that extends over a circumferential portion of the abrasive
surface is made up of plural axial segments that are stacked
adjacent to one another in the axial direction of the grinding
wheel and supplied between the first and second support plates.
26. A method of fabricating a grinding wheel for rotating about an
axis of rotation, comprising the steps of: providing a sheet of
abrasive material comprising a plurality of abrasive particle
layers; shaping the sheet of abrasive material into a substantially
cylindrical grinding wheel having a substantially cylindrical
abrasive region, wherein the layer of abrasive particles extends
along at least a portion of the circumference of the abrasive
surface and in a radial direction of the substantially cylindrical
region of abrasive material from the abrasive surface towards a
center of the grinding wheel; defining an axis of rotation for the
grinding wheel so that the layers of abrasive particles are at an
angle of between 0 degrees and 180 degrees, exclusive with the axis
of rotation.
27. The method of claim 26 wherein the step of providing the sheet
of abrasive material further comprises forming the sheet of
abrasive material by: interleaving a plurality of layers of
abrasive particles with a plurality of layers of bond material; and
sintering the plurality of layers of abrasive particles with the
plurality of layers of bond material to form the sheet of abrasive
material.
28. The method of claim 26 further including the step of fixedly
securing the sheet of abrasive material between a first support
plate and a second support plate by sintering the sheet of abrasive
material between the first support plate and the second support
plate.
29. The method of claim 26 further including the step of fixedly
securing the sheet of abrasive material between a first support
plate and a second support plate by adhesively bonding the sheet of
abrasive material to the first support plate and the second support
plate.
30. A method of fabricating an abrasive grinding wheel for rotating
about an axis of rotation, comprising the steps of: providing a
plurality of abrasive segments each having a plurality of layers of
abrasive particles forming an abrasive surface, the layers of
abrasive particles extending along at least a portion of the
circumference of the abrasive grinding wheel; circumferentially
spacing the plurality of abrasive segments between a first support
plate and a second support plate; fixedly securing the plurality of
abrasive segments between the first support plate and the second
support plate such that at least one of the plurality of layers of
abrasive particles in at least one of the plurality of abrasive
segments is staggered in the direction of the axis of rotation of
the grinding wheel from at least one of the plurality of layers of
abrasive particles in at least one other of the plurality of
abrasive segments.
31. The method of claim 30 wherein the step of fixedly securing the
plurality of abrasive segments between the first support plate and
the second support plate comprises bonding the plurality of
abrasive segments to the first and the second support plates with
an adhesive.
32. The method of claim 30 including wherein the step of providing
a plurality of abrasive segments includes forming the plurality of
abrasive segments by: forming at least a first sheet of abrasive
material having a plurality of layers of abrasive particles; and
cutting the plurality of abrasive segments from the first laminated
sheet.
33. The method of claim 32 wherein the step of forming at least a
first sheet of abrasive material includes: interleaving a plurality
of layers of abrasive particles with a plurality of layers of bond
material; sintering the plurality of layers of abrasive particles
with the plurality of layers of bond material to form the laminated
sheet.
34. A method of fabricating a grinding wheel comprising the steps
of: interleaving a plurality of layers of abrasive particles with a
plurality of layers of bond material; placing the plurality of
layers of abrasive particles and plurality of layers of bond
material between a first support plate and a second support plate;
spacing a plurality of spacers between the plurality of layers of
abrasive particles and plurality of layer of bond material and the
first support plate; spacing a plurality of spacers between the
plurality of layers of abrasive particles and plurality of layer of
bond material and the second support plate; and sintering the
plurality of layers of abrasive particles, the plurality of layers
of bond material, the spacers and the first and second support
plates under pressure to form the grinding wheel such that the
spacers cause the plurality of layers of abrasive particles
undulate in a wave-like pattern.
35. An abrasive grinding wheel comprising: a perimeter edge having
an abrasive surface; at least one opening provided in the abrasive
surface; a first channel positioned radially interior to the
abrasive surface and in fluid communication with the opening; a
second channel opening to the interior of the abrasive grinding
wheel and located in a center region thereof; and at least one
radial channel extending from the second channel of the abrasive
grinding wheel to the first channel and in fluid communication with
the first channel and the second channel; so that a liquid
lubricant provided under pressure to the first channel can pass
through the radial channel, into the second channel and through the
opening to lubricate the abrasive surface.
36. The abrasive grinding wheel of claim 35 further including a
first circular surface and a second circular surface opposed to the
first circular surface and wherein the second channel includes an
opening on the first circular surface to allow liquid lubricant to
be provided to the second channel via the opening.
37. The abrasive grinding wheel of claim 36 further including a
central bore wherein the second channel includes an opening to the
central bore to allow liquid lubricant to be provided to the second
channel via the opening.
38. An abrasive grinding wheel that can be rotated about an axis of
rotation, the abrasive grinding wheel comprising: a means for
defining an axis of rotation of the abrasive grinding wheel; a
substantially cylindrical region of metal bond abrasive material
having a circumferentially extending abrasive surface; and at least
one support plate; wherein the region of metal bond abrasive
material is bonded to the support plate with an adhesive.
39. The abrasive grinding wheel of claim 38 wherein the region of
abrasive material is formed from a plurality of discrete abrasive
segments which are circumferentially spaced at the periphery of the
grinding wheel to provide the circumferentially extending abrasive
surface.
40. The abrasive grinding wheel of claim 38 including a first and a
second support plate the first and second plates forming the outer
axial surface of the grinding wheel wherein the region of abrasive
material is interposed between the first support plate and the
second support plate and wherein the region of abrasive material is
bonded to the first and the second support plate by an
adhesive.
41. The abrasive grinding wheel of claim 38 wherein the adhesive is
a thermosetting adhesive.
42. The abrasive grinding wheel of claim 38 wherein the adhesive
has a shear strength of at least about 1000 psi.
43. The abrasive grinding wheel of claim 38 wherein the adhesive
has a shear strength of at least about 1500 psi.
44. The abrasive grinding wheel of claim 38 wherein the abrasive
particles are selected from the group consisting of diamond, cubic
boron nitride, boron suboxide, and combinations thereof.
45. The abrasive grinding wheel of claim 38 wherein the metal bond
abrasive material comprises a plurality of abrasive particles
randomly distributed in a metal bond material.
46. The abrasive grinding wheel of claim 38 wherein the metal bond
abrasive material comprises a plurality of abrasive particles which
are present in substantially planar, parallel layers.
47. The abrasive grinding wheel of claim 38 wherein the support
plate is made of steel, aluminum, brass, titanium, polymer, fiber
reinforced polymer, or a combination thereof.
48. An abrasive grinding wheel that can be rotated about an axis of
rotation, comprising: a means for defining an axis of rotation of
the abrasive grinding wheel; a first support plate; a second
support plate; a substantially cylindrical region of metal bond
abrasive material formed from a plurality of discrete abrasive
segments interposed between the first support plate and the second
support plate and bonded to the first and the second support plate
with an adhesive.
49. A method of making an abrasive grinding wheel for rotating
about an axis of rotation, comprising the steps of: (i) providing a
first support plate having an inner and an outer major surface;
(ii) providing a second support plate having an inner and an outer
major surface; (iii) providing a region of metal bond abrasive
having a first and a second major surface; (iv) circumferentially
spacing the region of metal bond abrasive between the inner major
surface of the first support plate and the inner major surface of
the second support plate, wherein a first layer of adhesive is
interposed between the inner major surface of the first support
plate and the first major surfaces of the metal bond abrasive
layer, and wherein a second layer of adhesive is interposed between
the inner major surface of the second support plate and the second
major surfaces of the metal bond abrasive layer; and (v) curing the
first and the second layers of adhesive to provide an abrasive
grinding wheel having a circumferentially extending abrasive
surface.
50. The method of claim 49 wherein the region of metal bond
abrasive material is formed from a plurality of discrete abrasive
segments which are circumferentially spaced at the periphery of the
support plates.
51. The method of claim 49 wherein the adhesive is a thermosetting
adhesive.
52. The method of claim 49 wherein the adhesive has a shear
strength of at least about 1000 psi.
53. The method of claim 49 wherein the adhesive has a shear
strength of at least about 1500 psi.
54. The method of claim 49 wherein the metal bond abrasive material
comprises a plurality of abrasive particles randomly distributed in
a metal bond material.
55. The method of claim 49 wherein the metal bond abrasive material
comprises a plurality of abrasive particles which are present in
substantially planar, parallel layers.
56. The method of claim 49 wherein the support plate is made of
steel, aluminum, brass, titanium, polymer, fiber reinforced
polymer, or a combination thereof.
Description
[0001] This application is a continuation-in-part of pending prior
application Ser. No. 09/019,657, filed on Feb. 6, 1998.
TECHNICAL FIELD
[0002] The present invention relates generally to abrasive or
superabrasive tools. In particular, the present invention relates
to a rotatable grinding wheel having an abrasive or superabrasive
surface.
BACKGROUND OF THE INVENTION
[0003] Certain types of workpieces (plastic and glass lenses,
stone, concrete, and ceramic, for example) can be advantageously
shaped using grinding tools, such as a wheel or disc, which have an
abrasive work surface, particularly a superabrasive work surface, a
superabrasive surface also being an abrasive surface but having a
higher abrasivity. The work surface of the grinding tool can be
made up of an abrasive band around the outer circumference of the
wheel or disk. The work surface usually includes particles of super
hard or abrasive material, such as diamond, cubic boron nitride, or
boron suboxide surrounded by a bond material and/or embedded in a
metal matrix. It is these abrasive particles that primarily act to
cut or grind a workpiece as it is brought into contact with a
rotating work surface of the grinding tool.
[0004] It is known to form cutting or grinding wheels comprising
segments of abrasive material. The abrasive segments can be formed
by mixing abrasive particles such as diamonds and metallic powder
and/or other filler or bond material in a mold and pressure molding
the mixture at an elevated temperature. Forming abrasive segments
in this way, however, can create areas having high concentrations
of hard or abrasive particles and areas having low concentrations
of abrasive particles in the segment. Further, the concentration of
abrasive particles at an abrasive surface affects grinding
characteristics of the wheel such as wheel wear rate and grinding
rate. As such, non-uniform or randomly varying concentrations of
abrasive particles can cause unstable cutting or grinding
performance. Also, forming abrasive segments in this way can be
relatively expensive because a relatively high number of abrasive
particles are used.
[0005] To reduce problems associated with non-uniform or randomly
varying concentrations of abrasive particles in abrasive surfaces,
it is known to form abrasive segments in which concentrations of
abrasive particles vary in an orderly manner. For example, abrasive
segments can be formed having substantially parallel, planar layers
of abrasive particles separated by regions of bond material.
Abrasive material having such layers of abrasive particles are
disclosed in, for example, U.S. Pat. No. 5,620,489, issued on Apr.
15, 1997 to Tselesin, entitled Method for Making Powder Preform and
Abrasive Articles Made Therefrom; U.S. Pat. No. 5,049,165, issued
Sep. 17, 1991 to Tselesin entitled Composite Material; and Japanese
Laid Open Patent Publication J.P. Hei. 3-161278 by Tanno Yoshiyuki,
published Jul. 11, 1991 for Diamond Saw Blade ("Yoshiyuki").
[0006] Yoshiyuki discloses a saw blade for cutting stone, concrete,
and/or fire resistant material. The saw blade is formed from
abrasive segments having planar layers of abrasive particles. The
layers of abrasive particles are aligned with a direction of
rotation of the saw blade such that the cut in a workpiece forms
grooves, as can be seen in FIG. 3 of Yoshiyuki. Such grooves are
formed because the areas of bond material between planes of
abrasive particles wear faster than the areas of the planes of
abrasive particles.
[0007] However, for some applications of a grinding tool, wear
grooves are undesirable or unacceptable. In some cases, it is
specifically desirable to be able to produce a smooth, rounded edge
on a workpiece. For example, a type of grinding wheel, known as a
pencil wheel, is generally used to grind the edges of panes of
glass to remove sharp edges of the glass and leave rounded edges
free of cracks that could cause the glass to break. The production
of grooves in the rounded edge would be undesirable.
[0008] In addition to the foregoing, an improvement over the
generally practiced methods of assembling grinding wheels is
desired. Typically, assembly of a grinding wheel includes either a
brazing or a sintering process in order to bond the abrasive
material to the support plate(s). These processes may be disfavored
for a number of reasons. For example, brazing an abrasive layer to
an aluminum support plate (a preferred material due to its light
weight) may be difficult to accomplish due to the presence of
aluminum oxide on the surface of the support plate which inhibits
wetting-out of the braze material. Sintering is generally
disfavored due to the long time period and high temperature
required. Furthermore, both sintering and brazing are incompatible
with non-metallic (e.g., polymeric) support plates. In view of
these disadvantages, an improved method of bonding the abrasive
layer to the support plate(s) in a grinding wheel is desired.
SUMMARY OF THE INVENTION
[0009] In accordance with the present invention, a grinding wheel
exhibits an abrasive surface having an ordered concentration of
abrasive particles to advantageously produce stable grinding
results. But also, the abrasive surface of the wheel is able to
produce a smooth edge on a workpiece. In some instances, the edge
produced on a workpiece may also be rounded.
[0010] The present invention includes a generally cylindrical
abrasive grinding wheel which is rotatable about an axis of
rotation. A substantially cylindrical region of abrasive material
having an abrasive surface on an outer peripheral surface thereof
is formed from a plurality of layers of abrasive particles. Each
layer of abrasive particles extends in at least a circumferential
direction and a radial direction of the cylindrical region of
abrasive material. By extending the layers in a radial direction,
as an edge of an abrasive particle layer is worn away by use of the
wheel, a fresh edge will advantageously be exposed. When a wheel
having a shaped or profiled edge is used, however, the edge may
have to be re-profiled as it is worn down.
[0011] One aspect of the invention is characterized by the layers
of abrasive particles being arranged on the abrasive surface such
that any circular path defined by an intersection of a plane
perpendicular to the axis of rotation of the grinding wheel and a
complete circumference of the abrasive surface will intersect at
least one of the plurality of layers of abrasive particles.
[0012] Another aspect of the invention can be characterized by the
layers of abrasive particles being tilted with respect to the axis
of rotation of the grinding wheel to form an angle of between 0
degrees and 180 degrees, exclusive, therewith. In this way, as the
grinding wheel is rotated through a 360 degree rotation, an exposed
edge of a single abrasive particle layer will sweep over an axial
distance wider than the width of the exposed edge of the abrasive
particle layer. If the layers of abrasive particles are tilted with
respect to the axis of rotation such that the width of the axial
distances over which each abrasive particle layer sweeps meet or
overlap, then grooving on the surface of a workpiece can be reduced
and preferably eliminated.
[0013] Yet another aspect of the invention can be characterized by
the grinding wheel being formed from a plurality of abrasive
segments each including layers of abrasive particles. The layers of
abrasive particles are staggered in an axial direction from one
segment to another. In this way, the exposed edges of the abrasive
particle layers will sweep across a greater portion of an axial
thickness of the abrasive surface. This can also reduce grooving on
a workpiece. In some embodiments, it may be feasible to reduce
grooving with segments whose abrasive particles are not in layers
but are randomly spaced.
[0014] Yet another aspect of the invention can be characterized by
the grinding wheel including a layer of metal bond abrasive which
is adhesively bonded to at least one support plate. As used herein
the term "adhesive" refers to a polymeric organic material capable
of holding solid materials together by means of surface attachment.
As used herein the term "metal bond abrasive" refers to an abrasive
material comprising a plurality of abrasive particles distributed
throughout a metal bond material. The abrasive particles may be
randomly distributed (i.e., non-uniform or randomly varying
concentrations) throughout the metal bond material or the
concentration of abrasive particles may vary in an orderly manner
(e.g., substantially parallel, planar layers of abrasive particles
separated by regions of metal bond material). The layer of metal
bond abrasive may comprise a single mass or more than one mass. In
a preferred embodiment, a plurality of discrete metal bond abrasive
segments are circumferrentially spaced between two support plates
and are adhesively bonded to the support plates by a structural
adhesive which is interposed between the abrasive segments and the
support plates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of an abrasive grinding wheel
having a tilted abrasive surface in accordance with the present
invention.
[0016] FIG. 2 is a cross-sectional view of the grinding wheel shown
in FIG. 1 taken along section line 2-2 of FIG. 1.
[0017] FIG. 3 is a front view of the grinding wheel shown in FIG. 1
illustrating layers of abrasive particles in an abrasive region
thereof.
[0018] FIG. 4 is a partial side view in cross section of an
abrasive grinding wheel grinding a workpiece illustrating how
layers of abrasive particles between bond regions on the abrasive
surface of the grinding wheel can cause grooving of the grinding
wheel and workpiece.
[0019] FIG. 5a is a partial front view of a sheet of abrasive
material which can be used to fabricate the grinding wheel shown in
FIG. 1 showing abrasive particles and abrasive particle layers
exaggerated for purposes of illustration.
[0020] FIG. 5b is a partial front view of the grinding wheel shown
in FIG. 1 showing abrasive particle layers exaggerated for purposes
of illustration and tilted with respect to an axis of rotation of
the grinding wheel.
[0021] FIG. 6 is a perspective view of a laminated block from which
the abrasive grinding wheel shown in FIG. 1 can be formed.
[0022] FIG. 7 is a top view of a laminated sheet from which an
abrasive region of the grinding wheel shown in FIG. 1 can be
formed.
[0023] FIG. 8 is an exploded front view of an example of a
laminated sheet such as that shown in FIG. 7.
[0024] FIG. 9 is a top view of a first embodiment of porous
material which can be used to fabricate the laminated sheet shown
in FIG. 7.
[0025] FIG. 10 is a top view of a second embodiment of porous
material which can be used to fabricate the laminated sheet shown
in FIG. 7.
[0026] FIG. 11 is a perspective view of a second embodiment of an
abrasive grinding wheel including abrasive segments having abrasive
particle layers in accordance with the present invention.
[0027] FIG. 12 is a cross-sectional view of the grinding wheel
shown in FIG. 11 taken along section line 12-12 of FIG. 11.
[0028] FIG. 13 is a cross-sectional view of the grinding wheel
shown in FIG. 12 taken along section line 13-13 of FIG. 12.
[0029] FIG. 14 is a cross-sectional view of the grinding wheel
shown in FIG. 12 taken along section line 14-14 of FIG. 12.
[0030] FIG. 15 is a top cross-sectional view, taken along the same
section line as FIG. 12, of another embodiment of a grinding wheel
in accordance with the present invention.
[0031] FIG. 16 is a cross-sectional view of the grinding wheel
shown in FIG. 15 taken along line 16-16 of FIG. 15.
[0032] FIG. 17 is a front view of the grinding wheel shown in FIG.
11 showing abrasive particles and abrasive particle layers
exaggerated for purposes of illustration.
[0033] FIG. 18 is a front view of a third embodiment of an abrasive
grinding wheel including stacked abrasive segments in accordance
with the present invention.
[0034] FIG. 19 is a cross-sectional view of the grinding wheel
shown in FIG. 18 taken along section line 19-19 of FIG. 18.
[0035] FIG. 20 is a front view of another embodiment of an abrasive
grinding wheel in accordance with the present invention having an
abrasive surface with the axial position of the abrasive particle
layers varying.
[0036] FIG. 21 is a perspective view of a spacer which can be used
to fabricate the grinding wheel shown in FIG. 20.
[0037] FIG. 22 is a front view of another embodiment of an abrasive
grinding wheel in accordance with the present invention having an
abrasive surface formed from abrasive segments.
[0038] FIG. 23 is a front view of another embodiment of an abrasive
grinding wheel in accordance with the present invention having an
abrasive layer which is adhesively bonded to the support
plates.
[0039] FIG. 24 is a front view of another embodiment of an abrasive
grinding wheel in accordance with the present invention having an
abrasive layer which formed from a plurality of abrasive segments
which are adhesively bonded to the support plates.
[0040] FIG. 25a is a front view of another embodiment of an
abrasive grinding wheel in accordance with the present invention
having an abrasive layer which formed from a plurality of abrasive
segments which are adhesively bonded to the support plates.
[0041] FIG. 25b is an assembly view of the embodiment of FIG.
25a.
DETAILED DESCRIPTION
[0042] FIG. 1 is a perspective view of cutting or grinding wheel 10
having an abrasive perimeter surface in accordance with the present
invention. Wheel 10 is substantially cylindrical in shape and
includes an abrasive region 12 preferably sandwiched between a
first support plate 14 and a second support plate 16. An outer
abrasive surface 18 of abrasive region 12 is a substantially
cylindrical band which extends about a portion of the
circumferential surface 24 of wheel 10. Wheel 10 includes a bore 20
in the center thereof which passes entirely though wheel 10. Bore
20 is to allow wheel 10 to be mounted to a rotatable shaft (not
shown) for rotating wheel 10 thereabout. Accordingly, a rotatable
shaft placed through bore 20 would extend along the axis of
rotation 23 of wheel 10. Alternatively, the axis of rotation can be
defined by longitudinally aligned shaft portions fixed within
plates 14 and 16. It is also contemplated to attach wheel 10 to a
rotatable shaft by attaching a substantially circular mounting
plate (not shown) having a central shaft (not shown) to wheel via
mounting holes 9. It is to be understood, however, that mounting
holes 9 are not necessary. By rotating wheel 10 on or by a
rotatable shaft, a workpiece can be held against the
circumferential surface 24 of wheel 10 to be abraded by abrasive
surface 18 so that the workpiece can be appropriately shaped,
ground, or cut.
[0043] Support plates 14 and 16 are substantially rigid and
preferably formed of steel, but could also be bronze, aluminum, or
any other suitably rigid material. Support plates 14 and 16 can be
formed from unsintered or sintered powder material. At least one of
these plates can comprise no abrasive particles or can comprise
some abrasive particles of lesser concentration and/or size than
abrasive region 12. Plates 14 and 16 have outer surfaces 14a and
16a respectively which are preferably perpendicular to the axis of
rotation 23 of disk 10. Plates 14 and 16 also have inner surfaces
14b and 16b respectively. As shown in FIG. 3, which is a front view
of wheel 10, inner surfaces 14b and 16b are preferably
substantially parallel with one another but tilted to form an angle
.theta. with a plane perpendicular to the axis of rotation 23. It
is to be understood, however, and as described more fully below,
that it is also within the ambit of the present invention to have
non-parallel layers of abrasive particles, or layers which may not
be parallel but that follow contours of any adjacent layer. It is
also contemplated that inner surfaces 14b and 16b can be
perpendicular to the axis of rotation 23 rather than tilted.
[0044] Abrasive region 12 is preferably substantially cylindrical
having an upper surface 31 and a lower surface 33 which are
substantially parallel with one another and also preferably tilted
at angle .theta. with a plane perpendicular to axis of rotation 23.
In this way, abrasive region 12 can be supported between support
plates 14 and 16 at angle .theta. to a plane perpendicular to axis
of rotation 23 of wheel 10. Because top surface 14a of plate 14 and
bottom surface 16a of plate 16 can be substantially perpendicular
to axis of rotation 23, surfaces 31 and 33 can be tilted at angle
.theta. with respect to surfaces 14a and 16a. It is to be
understood that support plates 14 and 16 are optional. To
facilitate rotation of a grinding wheel formed without support
plates 14 and 16, a rotatable shaft can be fixed directly to upper
and lower surfaces 31 and 33, respectively.
[0045] As shown in FIG. 2, which is a sectional view of wheel 10
taken along line 2-2 of FIG. 1, abrasive region 12 is annular,
extending radially inward from surface 24 towards the center of
wheel 10. In this way, as outer abrasive surface 18 is worn down by
use, additional abrasive surface is exposed, thus extending the
useful life of wheel 10. In the embodiment shown in FIG. 2,
abrasive region 12 extends through the entire radial distance
between circumferential surface 24 and bore 20. It is also
contemplated, however, that abrasive region 12 extend radially
through only of portion of the region between surface 24 and bore
20.
[0046] Abrasive region 12 contains particles of abrasive or hard
material including, but not limited to, superabrasives such as
diamond, cubic boron nitride, boron carbide, boron suboxide, and
other abrasive particles such as silicon carbide, tungsten carbide,
titatnium carbide, and chromium boride suspended in a matrix of
filler or bond material. As shown in FIG. 3, in accordance with the
present invention, the abrasive particles can be arranged in
substantially planar, parallel layers 26 in abrasive region 12 with
regions of bond material 28 between the layers 26 of abrasive
particles. Abrasive particle layers 26 can define a plane which
extends in a radial and circumferential direction in wheel 10. As
shown in FIG. 3, which is a front view of wheel 10, abrasive
surface 18 can be formed to cut across the layers 26 of abrasive
particles, represented by dashed lines. In this way, the edges of
abrasive particle layers 26 can be exposed at abrasive surface 18.
Also, the edges of the regions of bond material 28 are exposed at
surface 18.
[0047] Exposing the edges of layers 26 at surface 18 affects the
shape, wear profile, or surface morphology of surface 18 as tool 10
is used. It also affects the profile of a surface of a workpiece
which has been ground using tool 10. This is because the regions of
bond material 28 will wear more rapidly and cut a workpiece less
effectively than the abrasive particle layers 26. FIG. 4 is a side
view illustrating the wear profile a grinding wheel 310 and a
workpiece 308 that has been abraded thereby. Wheel 310 has abrasive
region 312 which can be sandwiched between support plates 314 and
316. Abrasive region 312 includes abrasive particle layers 326
separated by bond material regions 328. Edges of layers 326 are
aligned in a plane perpendicular to the axis of rotation 323 of
wheel 310, and each edge of layer 326 extends continuously around
the perimeter of wheel 310. As shown, grinding the edge of
workpiece 308 using wheel 310 can result in grooving in abrasive
region 312. The high spots of the grooves of abrasive region 312
occur at the edges of abrasive particle layers 326 and low spots
occur at the regions of bond material 328. As shown, this grooving
can be mirrored in the surface of workpiece 308 which is being
ground because the edges of the abrasive particle layers 326 will
remove workpiece material more rapidly than the surrounding regions
of bond material 328.
[0048] However, as noted in the Background section, it is generally
desirable to produce a smooth, surface on a workpiece surface. For
example, manufacturers of glass for automobiles and furniture use
pencil wheels to grind the edges of glass to be smooth and
relatively free of defects. Therefore, to reduce grooving or other
surface anomalies in a workpiece, as shown in FIG. 3, abrasive
particle layers 26 can be tilted at an angle .theta. to a plane
perpendicular to the axis of rotation 23. Angle .theta. is
preferably between 0 degrees and 180 degrees, exclusive. Abrasive
particle layers 26 are preferably tilted far enough such that any
path 32 defined by the intersection of a plane perpendicular to the
axis of rotation of wheel 10 and a complete circumference of
abrasive surface 18 will intersect or cut across at least one
abrasive particle layer 26. Thus, the entirety of a surface of a
workpiece ground by wheel 10 can be ground at substantially the
same rate and fewer grooves or other anomalies are formed due to a
region of the surface being ground only by bond material or,
alternatively, a disproportionately large amount of abrasive
particles.
[0049] The minimum angle .theta..sub.min at which abrasive region
12 should be tilted to a plane perpendicular to the axis of
rotation of wheel 10 so that any path 32 will cut across at least
one abrasive particle layer 26 depends upon the size of the
particles used in forming abrasive region 12, the diameter of wheel
10, and the thickness of the regions of bond material 28 between
the abrasive particle layers 26. FIGS. 5a and 5b show schematic
illustrations of partial views of an abrasive material of the type
from which wheel 10 can be formed. Two abrasive particles 34 and 36
are in adjacent abrasive particle layers 26a and 26b, respectively,
represented by dashed lines. FIG. 5a shows a schematic of
cylindrical abrasive region 12 before being tilted in wheel 10 to
illustrate a method for determining .theta..sub.min. Particles 34
and 36 are diametrically opposed to one another across a diameter
of the wheel 10. Thus, particles 34 and 36 are at a distance from
each other which would equal the diameter D of abrasive region 12.
Abrasive particle layers 26a and 26b are at a separation t between
each other. An abrasive particle has a diameter d. Thus, angle
.theta..sub.min is given by the equation:
.theta..sub.min=arctan(d+t/D)
[0050] For example, for a 4 inch diameter wheel (D=4 inches) having
separation between adjacent particle layers of 0.05 inches (t=0.05
inches) and abrasive particle diameter of 0.01 inches (d=0.01
inches), angle .theta..sub.min is approximately 0.86 degrees. FIG.
5b shows a schematic illustration of wheel 10 after cylindrical
abrasive region 12 has been tilted through angle .theta..sub.min
and sandwiched between support plates 14 and 16. While the above
equation gives the minimum tilt angle .theta..sub.min for abrasive
region 12 to generally insure that a path 32 will intersect an edge
of an abrasive particle layer, it is also within the ambit of the
present invention to tilt abrasive region 12 at an angle .theta.
greater than .theta..sub.min. It is also considered to tilt
abrasive region 12 at an angle less than that given by
.theta..sub.min, however, if such a tilt angle .theta. less than
.theta..sub.min were used, a path 32 defined by the intersection of
a plane perpendicular to the axis of rotation 23 and a
circumference of abrasive region 12 may not intersect with an edge
of an abrasive particle layer.
[0051] The above discussion regarding angle .theta..sub.min assumes
that the same diameter d of abrasive particles is used throughout
the abrasive region 12 and that the separation t between adjacent
abrasive particle layers is substantially the same throughout the
abrasive region 12. It is within the scope of the present
invention, however, to use different diameter abrasive particles
and different separations between adjacent layers of abrasive
particles. Nonetheless, the above equation for angle
.theta..sub.min is useable if the greatest separation between
adjacent abrasive particle layers is used for the separation t.
Further, the above equation for .theta..sub.min only applies if the
layers of abrasive particles in the abrasive region are
substantially planar and parallel to each other.
[0052] FIG. 6 shows one embodiment of a method of fabricating wheel
10 and FIGS. 7 and 8 show a laminated sheet 51 of abrasive material
having layers of abrasive particles therein. A method for
fabricating laminated sheet 51 of abrasive material is detailed
below. It is to be understood that sheet 51 can preferably be
formed as discussed below prior to carrying out the steps of
assembling wheel 10. As shown in FIG. 6, sheet 51 is stacked with
first outer plate 53 and second outer plate 55 to form rectangular
block 56. This block 56 can then be sintered under pressure.
Generally, this sintering step is performed at temperatures between
about 480.degree. C. and 1600.degree. C., at pressures as high as
100 to 550 kg/cm.sup.2, and with dwell times from about 5 minutes
to 1 hour. Block 56 can then be cut, as shown in phantom, by laser,
water jet, EDM (electrical discharge mechanism), plasma
electron-beam, scissors, blades, dies, or other known method, to
form wheel 10. Bore 20 can be cut, as shown in phantom, using the
same or other method either before or after cutting wheel 10 from
block 56. It should be understood that the shape of block 56 and/or
sheet 51 is not limited to the rectangular shape but can be any
shape including round, with or without an inside opening which can
also be any shape.
[0053] Depending upon the design, wheel 10 may have an axially thin
or thick abrasive region 12. Abrasive region 12 can then be mounted
on a core, such as a metallic or composite core. The core can be
integrated with abrasive region 12 by any available means that
includes but is not limited to mechanical locking and
tensioning/expansion, brazing, welding, adhering, sintering and
forging.
[0054] For extracting wheel 10 out of sheet 51, it is advantageous
to use cutting machines with a cutting media characterized by being
able to move in 3 to 5 degrees of freedom. For example, a laser or
a water jet having nozzles which can move in 5 degrees of
freedom.
[0055] First and second outer plates 53 and 55, respectively can be
formed from steel, aluminum, bronze, resin, or other substantially
rigid material by known methods. In forming plates 53 and 55, inner
surface 53a of first plate 53 is preferably angled at angle .theta.
to outer surface 53b thereof and inner surface 55a of second plate
55 is preferably angled at angle .theta. to outer surface 55b
thereof.
[0056] Alternately, an annular abrasive region can be cut from a
sheet of abrasive material prior to sintering first support plate
14 and second support plate 16 therewith. First support plate 14
and second support plate 16 can also be formed prior to sintering.
The annular abrasive region can then be layered with support plates
14 and 16 and sintered under pressure to form a grinding wheel in
accordance with the present invention.
[0057] A second alternate method for forming an abrasive wheel
having a tilted abrasive region in accordance with the present
invention includes forming a top plate and bottom plate each having
parallel inner and outer surfaces. Sheet 51 can then be sandwiched
and sintered between the top and bottom plates. A bore with which
to mount the abrasive wheel on a rotating shaft can then be formed
at an angle other than 90 degrees with the inner and outer surfaces
of the top and bottom plates. The wheel could optionally be dressed
while mounted.
[0058] A third alternate method for forming an abrasive wheel in
accordance with the present invention includes forming an abrasive
region from sheet 51 in which the layers of abrasive particles are
at an angle between 0 degrees and 180 degrees, exclusive, with
substantially parallel top and bottom surfaces of the abrasive
region. Such an abrasive region can be formed by cutting the
abrasive region from a sheet such as sheet 51 using cuts that are
at an angle between 0 degrees and 180 degrees with an upper or
lower face of sheet 51. The abrasive region can preferably be
sandwiched between upper and lower support plates each having
substantially parallel interior and exterior surfaces. Preferably,
a bore can be formed through the support plates and the abrasive
region substantially perpendicular to the top and bottom surfaces
of the abrasive region. In this way, a rotating shaft placed
through the bore results in the abrasive wheel having an abrasive
region with layers of abrasive particles that are at an angle
between 0 degrees and 180 degrees, exclusive, with respect to a
plane perpendicular to an axis of rotation of the abrasive
wheel.
[0059] After forming wheel 10 using any of the above described
methods, abrasive surface 18 can be dressed using known processes
to recess or curve in from the remainder of the outer perimeter 24
of wheel 10, as shown in FIG. 1. It is also contemplated to dress
wheel 10 to have other shapes of abrasive surface 18 as a specific
application may require. Examples include convex, concave, and more
complicated surfaces such as "ogee."
[0060] Another method of fabricating wheel 10 having a concave,
convex, or other abrasive surface 18 is by extracting various rings
or rims from sheet 51 having varying diameters and then stacking
the rings. For example to fabricate a wheel having a concave
abrasive surface, rings having varying outer diameters can be
extracted from sheet 51. The rings can then be stacked on a core so
that the resulting wheel has the desired concave shape.
[0061] A method of fabrication of sheet 51 having substantially
parallel layers of abrasive particles is fully disclosed in
co-pending U.S. patent application Ser. No. 08/882,434 filed on
Jun. 25, 1997, entitled "Superabrasive Cutting Surface", currently
assigned to the assignee of the present invention, and which is
hereby incorporated by reference in its entirety.
[0062] FIG. 7 is a top view of laminated sheet 51. In the
embodiment of FIG. 7, laminated sheet 51 is square with a front
edge 37 and a side edge 38. However, other shapes of laminated
sheet 51 are also within the scope of the present invention. Sheet
51 is made up of a plurality of thickness layers. Each thickness
layer preferably includes a layer of bond material and a layer of
abrasive particles. Each thickness layer of sheet 51 can also
include a layer of porous material and/or adhesive substrate.
[0063] FIG. 8 is an exploded front view of front edge 37 of sheet
51 showing the stack up of thickness layers which can be used in
the fabrication of sheet 51. For purposes of illustration in the
embodiment of FIG. 8, sheet 51 is made up of only three thickness
layers 40, 42, and 44. However, sheet 51 can be made up of a
different number of thickness layers and is preferably made up of
from 2 to 10,000 layers. Each thickness layer 40, 42, and 44
includes a bond material layer 50, 52, and 54, respectively; a
porous material layer 60, 62, and 64, respectively; and an abrasive
particle layer 70, 72, and 74, respectively, comprising abrasive
particles 90. Each thickness layer 40, 42, and 44 may also include
adhesive layers 80, 82, and 84, respectively, placed on one face of
the porous material layers 60, 62, and 64, respectively, and each
having at least one face which includes a pressure sensitive
adhesive. The adhesive face of the adhesive layers 80, 82, and 84
are positioned against the porous layers 60, 62, and 64,
respectively. In this way, when abrasive particles 90 of abrasive
particle layers 70, 72, and 74 are placed in the openings of the
porous layers 60, 62, and 64, respectively, the abrasive particles
90 adhere to the adhesive layers 80, 82, and 84 such that the
abrasive particles 90 are retained in the openings of the porous
layers 60, 62, and 64. It should be understood that the above
mentioned porous layers may be selected from, for example,
mesh-type materials (e.g., woven and non-woven mesh materials,
metallic and non-metallic mesh materials), vapor deposited
materials, powder or powder-fiber materials, and green compacts,
any of which include pores or openings distributed throughout the
material. It should also be understood that the order or placement
of the various layers may be different than shown.
[0064] The porous layer may be separated or removed from the
adhesive layer after the abrasive particles have been received by
the adhesive layer. The use of adhesive substrates to retain
abrasive particles to be used in a sintering process is disclosed
in U.S. Pat. No. 5,380,390 to Tselesin and U.S. Patent No.
5,620,489 to Tselesin and U.S. patent application Ser. No.
08/728,169, filed Oct. 9, 1996, each of which is hereby
incorporated by reference in its entirety.
[0065] Thickness layers 40, 42, and 44 are compressed together by
top punch 84 and bottom punch 85 to form sintered laminated sheet
51. As noted above, sintering processes suitable for the present
invention are known in the art and described in, for example, in
U.S. Pat. No. 5,620,489, to Tselesin, which has been incorporated
by reference in its entirety. Though FIG. 8 shows a single bond
material layer for each thickness layer 40, 42, and 44, it is also
contemplated to include 2 or more bond layers for each thickness
layer 40, 42, and 44.
[0066] In carrying out the above fabrication process, the bond
material making up bond material layers 50, 52 and 54 can be any
material sinterable with the abrasive particle layers 70, 72, and
74 and is preferably soft, easily deformable flexible material
(SEDF) the fabrication of which is known in the art and is
disclosed in U.S. Pat. No. 5,620,489, which has been incorporated
by reference in its entirety. Such SEDF can be formed by forming a
paste or slurry of bond material or powder such as tungsten carbide
particles or cobalt particles, and a binder composition including a
cement such as rubber cement and a thinner such as rubber cement
thinner. Abrasive particles can also be included in the paste or
slurry but need not be. A substrate is formed from the paste or
slurry and is solidified and cured at room temperature or with heat
to evaporate volatile components of the binder phase. The SEDF used
in the embodiment shown in FIG. 5 to form bond material layers 50,
52, and 54 can include methylethylketone:toluene, polyvinyl
butyral, polyethylene glycol, and dioctylphthalate as a binder and
a mixture of copper, iron, nickel, tin, chrome, boron, silicon,
tungsten carbide, titanium, cobalt, and phosphorus as a bond matrix
material. Certain of the solvents will dry off after application
while the remaining organics will burn off during sintering. An
Example of an exact composition of an SEDF that may be used with
the present invention is set out below in the Examples. Components
for the composition of such an SEDF are available at a number of
suppliers including: Sulzer Metco, Inc. of Troy, Mich.; All-Chemie,
Ltd. of Mount Pleasant, S.C.; Transmet Corp. of Columbus, Ohio;
Valimet, Inc., of Stockton, Calif.; CSM Industries of Cleveland,
Ohio; Engelhard Corp. of Seneca, S.C.; Kulite Tungsten Corp. of
East Rutherford, N.J.; Sinterloy, Inc. of Selon Mills, Ohio;
Scientific Alloys Corp. of Clifton, N.J.; Chemalloy Company, Inc.
of Bryn Mawr, Pa.; SCM Metal Products of Research Triangle Park,
N.C.; F. W. Winter & Co. Inc. of Camden, N.J,; GFS Chemicals
Inc. of Powell, Ohio; Aremco Products of Ossining, N.Y.; Eagle
Alloys Corp. of Cape Coral, Fla.; Fusion, Inc. of Cleveland, Ohio;
Goodfellow, Corp. of Berwyn, Pa.; Wall Colmonoy of Madison Hts,
Mich.; and Alloy Metals, Inc. of Troy, Mich. It should also be
noted that not every bond layer forming sheet 36 need be of the
same composition; it is contemplated that one or more bond material
layers could have different compositions.
[0067] The porous material can be virtually any material so long as
the material is substantially porous (about 30% to 99.5% porosity)
and preferably comprises a plurality of non-randomly spaced
openings. Suitable materials are organic or metallic non-woven, or
woven mesh materials, such as copper, bronze, zinc, steel, or
nickel wire mesh, or fiber meshes (e.g. carbon or graphite).
Particularly suitable for use with the present invention are
stainless steel wire meshes, expanded metallic materials, and low
melting temperature mesh-type organic materials. In the embodiment
shown in FIG. 8, a mesh is formed from a first set of parallel
wires crossed perpendicularly with a second set of parallel wires
to form porous layers 60, 62, and 64. The exact dimensions of a
stainless steel wire mesh which can be used with the present
invention is disclosed below in the Example.
[0068] As shown in FIG. 9, which is a top view of a single porous
layer 60 of sheet 51 having abrasive particles 90 placed therein, a
first set of parallel wires 61 can be placed parallel with front
edge 37 of sheet 51 and the second set of parallel wires 69 can be
placed parallel to side edge 38. However, as shown in FIG. 10 it is
also possible to angle the porous layer such that the sets of
parallel wires 61 and 69 are at an approximately 45 degree angle
with front edge 37 and side edge 38. It is also contemplated to
form sheet 51 having some layers using the configuration of FIG. 10
and some layers using the configuration of FIG. 9.
[0069] The abrasive particles 90 can be formed from any relatively
hard substance including superabrasive particles such as diamond,
cubic boron nitride, boron suboxide, boron carbide, silicon carbide
and/or mixtures thereof. Preferably diamonds of a diameter and
shape such that they fit into the holes of the porous material are
used as abrasive particles 90. It is also contemplated to use
abrasive particles that are slightly larger than the holes of the
porous material and/or particles that are small enough such that a
plurality of particles will fit into the holes of the porous
material.
[0070] The adhesive layers 80, 82, and 84 can be formed from a
material having a sufficiently tacky quality to hold abrasive
particles at least temporarily such as a flexible substrate having
a pressure sensitive adhesive thereon. Such substrates having
adhesives are well known in the art. The adhesive must be able to
hold the abrasive particles during preparation, and preferable
should burn off ash-free during the sintering step. An example of a
usable adhesive is a pressure sensitive adhesive commonly referred
to as Book Tape #895 available from Minnesota Mining and
Manufacturing Company (St. Paul, Minn.).
[0071] Another embodiment of the present invention is shown in
FIGS. 11-17. Like elements are labeled with like numbers throughout
FIGS. 11-17. FIG. 11 shows a grinding wheel 110 having a first
support plate 114, a second support plate 116 and an abrasive
region 112 sandwiched therebetween. Grinding wheel 110 is generally
cylindrical and has bore 120 passing through a top and bottom face
thereof. Like wheel 10, wheel 110, via bore 120, can be mounted on
a rotatable shaft (not shown) and rotated about axis of rotation
123. Abrasive region 112 has a substantially cylindrical abrasive
surface 118 extending around a perimeter surface 124 of wheel 110.
Unlike abrasive region 12 of wheel 10, upper surface 131 and lower
surface 133 of abrasive region 112 are illustrated as substantially
aligned with a plane which is substantially perpendicular to the
axis of rotation 123 of wheel 110.
[0072] Abrasive region 112 is made up of abrasive segments 113
which can have substantially planar, parallel layers 126 of
abrasive particles, represented in FIG. 11 by dashed lines.
However, it is also within the scope of the present invention to
have non-parallel layers or layers which may not be parallel but
that follow the contours of any adjacent layer. Abrasive segments
113 are circumferentially spaced about the perimeter of wheel 110
and are supported between first support plate 114 and second
support plate 116. With the provision of plural discrete abrasive
segments 113, gaps 119 can advantageously exist between adjacent
abrasive segments 113. As shown in FIG. 11, gaps 119 are
substantially rectangular and extend between upper and lower
surfaces 131 and 133, respectively, at an angle other than 90
degrees thereto. The segments 113 and gaps 119 should be arranges
so that before a workpiece looses contact with a first segment 113
during grinding it comes into contact with an adjacent segment 113.
This can advantageously reduce noise or "chatter" generated by
grinding a workpiece against wheel 110. It is also contemplated,
however, that gaps 119 extend between upper and lower surfaces 131
and 133, respectively, at substantially a 90 degree angle
thereto.
[0073] As shown in FIG. 12, which is a sectional view of wheel 110
taken along section line 12-12 of FIG. 1, wheel 110 has radial
distribution channels 117. As shown in FIGS. 13 and 14, which are
sectional views of wheel 110 taken along section lines 13-13 and
14-14, respectively, of FIG. 12, radial distribution channels 117
are formed from generally U-shaped troughs or channels 127 and 129
cut in support plates 114 and 116, respectively. Radial
distribution channels 117 preferably extend from a circular
distribution channel 121 near the center of wheel 110 radially
outward to a circumferential distribution channel 125. Circular
channel 121 is preferably formed in support plates 114 and 116 from
generally U-shaped troughs 127 and 129 to extend around an inside
circumferential edge 111 of wheel 110. Circumferential distribution
channel 125 passes radially behind or interior to abrasive segments
113. A lubricant, such as water, can be fed under pressure into
circular distribution channel 121 to pass through radial
distribution channels 117 and into circumferential distribution
channel 125. The lubricant is then forced through gaps 119 between
segments 113 to lubricate abrasive surface 118 during grinding.
Alternately, as shown in FIGS. 11 and 12, segments 113 can include
openings 130 which place the perimeter of wheel 110 in fluid
communication with distribution channel 125 and through which
lubricant can be delivered to the abrasive surface 118 during
grinding. Openings 130 can be of a variety of shapes including
circular, square, polygonal, or any other shape. Each opening 130
may taper throughout the thickness of segment 113. Wheel 110 can
include openings 130 either with or without gaps 119. Either with
or without openings 130, wheel 110 can be used with a center
waterfeed grinder. Use of a lubricant on grinding surface 118
during grinding can increase the useful life of wheel 110 and
improve workpiece finish. Although the embodiment shown in FIG. 12
includes 4 radial distribution channels 117, it is also within the
scope of the present invention to include fewer or greater than 4
channels 117.
[0074] Distribution channels 121, 117 and 125 are formed from
generally U-shaped troughs 127 and 129 machined or otherwise formed
in inside surfaces of plates 114 and 116, respectively. When plates
114 and 116 are mounted on top of one another, troughs 127 and 129
are aligned to form channels 121, 117 and 125.
[0075] As shown in FIG. 13, to feed a lubricant into circular
distribution channel 121, wheel 110 is mounted on spindle 190.
Spindle 190 includes flange 191, longitudinal distribution channel
193, and transverse distribution channel 192. Wheel 110 rests on
flange 191 so that transverse distribution channel 192 is aligned
with circular distribution channel 121 and is in fluid
communication therewith. Longitudinal distribution channel 193
intersects transverse distribution channel 192 and is in fluid
communication therewith. Longitudinal channel 193 opens at one end
of spindle 190 at coupling 194. Coupling 194 allows spindle 190 to
be connected to a water feed spout 195 such that spindle 190 can
rotate about axis of rotation 123 on spout 195, and longitudinal
channel 193 can be in sealed fluid communication with interior
channel 196 of spout 195. Such sealed connections are known in the
art. Spindle 190 can rotate with wheel 110 such that lubricant can
be fed through interior channel 196, through longitudinal channel
193, into transverse channel 192 and into circular distribution
channel 121. It is also contemplated that wheel 110 rotate with
respect to spindle 190. Spindle 190 can be formed of steel or other
rigid material and distribution channels 192 and 193 can be formed
therethrough by drilling or other known methods.
[0076] An alternate method of feeding liquid lubricant through
distribution channels in a grinding wheel in accordance with the
present inventions is shown in FIGS. 15 and 16. FIG. 15 is a top
sectional view, taken along the same section line as the sectional
view of grinding wheel 110 shown in FIG. 12, of a grinding wheel
410 in accordance with the present invention. Like grinding wheel
110, grinding wheel 410 includes abrasive segments 413 arranged
about a perimeter thereof, a circumferential distribution channel
425 extending radially behind or interior to abrasive segments 413,
and radial distribution channels 417 in fluid communication with
circumferential distribution channel 425. However, grinding wheel
410 includes circular distribution channel 421 which is open along
upper face 431 of wheel 410. As shown in FIG. 16, which is a
sectional view of wheel 410 take along section line 16-16 of FIG.
15, circular distribution channel 421 is in fluid communication
with radial distribution channels 417. As such, liquid lubricant
can be fed into circular distribution channel 421 via a stationary
spout 495 while wheel 410 is rotated by spindle or rotatable shaft
490 and be fed into distribution channels 417, through
circumferential distribution channel 425 and through gaps 419
and/or openings (not shown) in segments 413 to lubricate the
grinding surface of wheel 410. Wheel 410 can be fabricated in
substantially the same manner as wheel 110.
[0077] Returning attention now to wheel 110, as noted above,
abrasive region 112 can be formed from abrasive segments 113 having
layers 126 of abrasive particles. Preferably, layers 126 are
substantially planar and parallel, but need not be. Moreover, the
layers of abrasive particles 126 can be arranged to be in a plane
perpendicular to the axis of rotation. As shown in FIG. 17, which
is a partial front view of wheel 110 having abrasive particles 134
and abrasive particle layers 126a, 126b, and 126c exaggerated for
purposes of illustration, abrasive particle layers 126a, 126b, and
126c are shown in a plane substantially perpendicular to axis of
rotation 123. However, to ensure complete and smooth abrasion,
layers 126a, 126b, and 126c are offset in an axial direction
(direction of the axis of rotation 123) between segment one 113 to
another segment 113. That is, layers 126 are not circumferentially
aligned from one segment 113 to an adjacent segment 113. It is
within the ambit of the present invention, however, not to axially
shift abrasive particle layers 126 between adjacent segments, but
rather, for example, between every 2nd or 3rd segment. All that is
necessary is that abrasive particle layers 126 are axially shifted
in some segment or segments around the perimeter of wheel 110.
[0078] Because abrasive particle layers 126 are not
circumferentially aligned, neither are regions of bond material 128
between layers 126. Accordingly, as a workpiece is ground against
abrasive surface 118, the likelihood that a some portion or
portions of the surface of the workpiece being ground will contact
only bond material regions 128 or only abrasive particle layers 126
is reduced and can be minimized. This reduces the likelihood that
grooves or other surface anomalies will form on the surface of the
workpiece being ground and facilitates the formation of a smooth
surface on the workpiece.
[0079] An explanation of how circumferentially mis-aligning
abrasive particle segments 113 in wheel 110 can facilitate the
grinding of a smooth surface on a workpiece can be made with
reference to FIG. 17. FIG. 17 is a front schematic view,
exaggerated for purposes of illustration, of three segments 113a,
113b, and 113c having abrasive particle layers 126a, 126b, and
126c, respectively, and bond material regions 128a, 128b, and 128c,
respectively. In the schematic illustration of FIG. 17, the axial
height 169 of abrasive region 112 is approximately six times the
diameter 168 of abrasive particles (or thickness of the abrasive
particle layers) making up abrasive particle layers 126a, 126b, and
126c. The separation 167 between abrasive particle layers is shown
to be approximately two times diameter 168.
[0080] Segment 113a is formed and placed in wheel 110 such that one
of the two abrasive particle layers 126a provides a lower surface
133 of abrasive region 118. Bond material provides an upper surface
131 of abrasive region 118 and extends axially to abrasive particle
layer 126a closest to upper surface 131. Segment 113b is formed and
placed in wheel 110 such that one of the two abrasive particle
layers 126b is spaced a distance 179 from the lower surface 133 of
abrasive region 118. Distance 179 is preferably approximately equal
to the abrasive particle diameter 168. Bond material fills the
region between lower surface 133 and abrasive particle layer 126b
closest to lower surface 133. Bond material also fills the region
between upper surface 131 and abrasive particle layer 126b closest
to upper surface 131. Segment 113c is formed and placed in wheel
110 such that one of the two abrasive particle layers 126c defines
the upper surface 131 of abrasive region 118. Bond material fills
the region between lower surface 133 and abrasive particle layer
126c closest to lower surface 133. For ease of illustration, in the
embodiment shown in FIG. 17, segments 113a, 113b and 113c each
include only two abrasive particle layers 126a, 126b, and 126c,
respectively. However, it is within the ambit of the present
invention to include more than two abrasive particle layers per
segment. Further, the thickness of each abrasive particle layer
and/or and diameter of abrasive particles used can vary between
segments and within segments.
[0081] By staggering abrasive particle layers 126a, 126b and 126c
as shown in FIG. 17, any path 132 defined by the intersection of a
plane perpendicular to axis of rotation 123 and a full
circumference of abrasive region 118 will intersect an abrasive
particle layer 126 of at least one abrasive segment 113. This means
that substantially all of a surface of a workpiece in contact with
abrasive surface 118 as wheel 110 is being rotated will intersect
an abrasive particle layer 126a, 126b, or 126c. As noted above,
this facilitates forming a smooth edge or surface on a
workpiece.
[0082] The sequence of staggered abrasive particle layers need not
be as shown. It is only important that to accomplish smooth
abrasion of a workpiece surface, the axial distance of the abrasive
surface 118 should include at least a layer of abrasive particles
to cover the axial distance.
[0083] Due to manufacturing variations, precise control of the
thickness of abrasive particle layers 126 and bond material region
128, and alignment thereof, can be difficult. Accordingly,
formation of wheel 110 precisely as shown in FIG. 17 can be
difficult to achieve. As such, abrasive particle layers 126a, 126b,
and 126c can be formed thicker to better facilitate overlap thereof
between segments. Additionally, wheel 110 is preferably formed from
more than three segments and can be formed with as many segments as
can be accommodated around the perimeter of wheel 110. This creates
a greater number of abrasive edges of abrasive layers 126 for a
workpiece to pass across in a single rotation of wheel 110.
[0084] Segments 113 can be extracted, i.e. cut, from the laminated
sheet 51 as shown in phantom in FIG. 7. Laminated sheet 51 should
be at least partially sintered, and preferably fully sintered,
prior to any extraction. First and second support plates 114 and
116, respectively, are solid and can be formed from steel, resin,
or other substantially rigid material as known in the art. Troughs
127 and 129 can be machined, molded, or otherwise formed in plates
114 and 116, respectively, as known. Aperture 121 can be formed in
plate 114 by drilling or other known method. Segments 113 are then
stacked between plates 114 and 116 and brazed, or preferably,
sintered therewith under pressure. When segments 113 are stacked
with support plates 114 and 116, trough 127 in support plate 114 is
axially aligned with trough 129 in support plate 116 so as to form
channels 117 and 125, as shown in FIGS. 12, 13, and 14. Segments
113 can also be secured by adhesive, brazing, welding (including
laser welding) or other known means between plates 114 and 116. It
should be noted that if segments 113 are sintered with plates 114
and 116, this sintering process can be in addition to the sintering
process, detailed above, used to form sheet 51 from which segments
113 can be cut. Bore 120 can be formed by drilling or other known
process either before or after sintering plates 114 and 116 with
segments 113.
[0085] To form segments 113 having differing distances between
abrasive particle layers, such as segments 113a, 113b, and 113c
shown in FIG. 17, segments can be cut from different laminated
sheets having differing distances between layers 126. Also, in some
cases such as segments 113a and 113c, segments are substantially
the same as each other, but are inverted in wheel 110. Accordingly,
it is considered to form such segments from the same sheet and
inverting one or the other before final assembly the segments with
plates 114 and 116.
[0086] To form laminated sheets such as sheet 51 but having
differing distances between abrasive particle layers, greater or
fewer layers of bond material layers such as layers 50, 52, or 54
shown in FIG. 8, can be placed between abrasive particle layers
before sintering to form a sheet such as sheet 51. The number of
bond material layers required to produce a given distance between
abrasive particle layers can be determined empirically.
[0087] It is also within the ambit of the present invention to form
wheel 110 having abrasive segments, such as abrasive segments 113,
wherein the abrasive particle layers are at an angle between 0
degrees and 180 degrees with a plane perpendicular to the axis of
rotation of grinding wheel 110. What is important is that abrasive
surface 118, when rotated about axis of rotation 123, will sweep an
edge of an abrasive particle layer 116 across an axial distance
greater than the axial thickness of the edge at any given
point.
[0088] It is to be understood that the segmented design of wheel
110 can also be formed with abrasive segments such as segments 113,
having abrasive particles randomly distributed therein as discussed
in the Background of the Invention section. Though segments such as
segments 113 having randomly distributed particles would lack the
advantages of segments 113 having layers of abrasive particles, to
form a wheel such as wheel 110 using segments having randomly
distributed particles would still allow liquid lubricant to be
distributed to the grinding surface of the wheel during grinding
using a grinding wheel having channels such as channels 117, 121,
and 125.
[0089] FIG. 18 shows an alternate embodiment of the present
invention. Elements in FIG. 18 functionally similar to those of
FIGS. 1 and 2 are shown with like numerals incremented by 200. FIG.
18 shows wheel 210 having stacked abrasive segments 213a and 213b
between upper and lower support plates 214 and 216, respectively.
By stacking abrasive segments 213a and 213b, an axially thicker
abrasive wheel can be formed, However, so stacking segments 213a
and 213b can cause grooves 247 to form therebetween. To reduce the
chances of grooves 247 forming a raised lip in a workpiece,
segments 213a and 213b can be stacked, with narrow segments 213a
alternating positions with thicker segments 213b between
circumferentially adjacent segments. In this way grooves 247 are
staggered in an axial direction around the circumference of
abrasive surface 218. By axially staggering grooves 247, the
likelihood of the grooves contacting a workpiece for an entire
rotation of wheel 210 is reduced, thus reducing the chances of
forming a raised lip on a workpiece surface. Wheel 210 can be
fabricated in substantially the same manner as wheel 110.
[0090] FIG. 19 is a sectional view of wheel 210 taken along line
19-19 of FIG. 18. FIG. 19 shows one possible configuration for
vertically stacking abrasive segments 213a and 213b. As shown,
abrasive segments 213a and 213b are splined together. Splining
together abrasive segments 213a and 213b as shown has the advantage
of providing for a more secure attachment of segments 213a and 213b
to support plates 214 and 216. It is also contemplated that
abrasive segments 213a and 213b be splined together in any other
configuration. It is also contemplated that segments 213a and 213b
meet only at a butt-joint without any splines.
[0091] FIG. 20 is a front view of another embodiment of a grinding
wheel in accordance with the present invention. In the embodiment
of FIG. 20, wheel 510 includes an abrasive region 512 preferably
sandwiched between a first support plate 514 and a second support
plate 516, but need not be. Abrasive region 512 includes an outer
abrasive surface 518 which can be a substantially cylindrical band
that extends around the perimeter of abrasive grinding wheel 510.
Wheel 510 has an axis of rotation 523.
[0092] Like abrasive region 12 of wheel 10, abrasive region 512 is
made up hard or abrasive particle layers 526, represented by dashed
lines, surrounded by bond material regions 528. However, the
abrasive particle layers 526 are not substantially planer, rather,
they can be configured to have a sinusoidal-like exposed edge along
abrasive surface 518. In this way, abrasive surface 518, when
rotated about axis of rotation 523, will sweep an edge of an
abrasive particle layer 526 across an axial distance greater than
the axial thickness of the edge at any given point on the edge.
Also, at least one path defined by the intersection of a plane
perpendicular to the axis of rotation and the abrasive surface will
intersect at least one layer of abrasive particles in at least
three locations. Further, in the embodiment shown in FIG. 20, the
distance in the axial direction between two adjacent abrasive
particle layers can remain substantially constant around the
perimeter of wheel 510, but need not.
[0093] Additionally, the peaks of any first abrasive particle layer
edge can extend to a point axially level with or above the troughs
of an another abrasive particle layer edge adjacent to and above
the first abrasive particle layer edge. In this way, any path
defined by the intersection of a plane perpendicular to the axis of
rotation of wheel 510 an a complete circumference of abrasive
region 512 will intersect or cut across at least one abrasive
particle layer 526. It is also contemplated that abrasive particle
layers 526 have edges which form other configurations such as
sawtooth waves or irregular smooth waves.
[0094] To form wheel 510 having edges of abrasive particle layer
526 which undulate in a waveform as shown in FIG. 20, the layers
which comprise the abrasive region 512, that is bond layers 50-54,
hard or abrasive particle layers 70-74, and if desired, porous
material layers 60-64 and adhesive layers 80-84, are preferably
stacked and sintered in a single sintering step with support plates
514 and 516. Such a sintering process can be substantially the same
sintering process as that used to form laminated sheet 51, however,
support plates 514 and 516 would be stacked above and below,
respectively, the layers forming abrasive region 512. However,
support plates 514 and 516 do not need to have interior faces
angled with respect to a plane parallel to the axis of rotation 523
of wheel 10. Also, to create the undulations, spacers 597 are
preferably circumferentially spaced between the layers forming
abrasive region 512 and first support 514 and between the layers
forming abrasive region 512 and second support plate 516. The
position of spacers 597 that are adjacent to first support plate
514 can be circumferentially shifted from the position of spacers
597 that are adjacent to second support plate 516.
[0095] One embodiment of spacers 597 is shown in a perspective view
in FIG. 21. As shown, spacer 597 is preferably conical and wedge
shaped having a front face 597a and a tapering tail 597b. Only
front face 597a is visible in FIG. 20. Spacers 597 can be formed
from any substantially rigid material such as steel, aluminum, or
bronze. Because the layers of abrasive region 512 are each
flexible, each layer can be formed to smoothly pass over or under
spacers 597 such that when the layers of material forming the
abrasive region 512 are sandwiched with spacers 597 between support
plates 514 and 516, the sinusoidal-like undulations are formed in
the layers of material forming the abrasive region 512, including
the abrasive particle layers 526. It is also contemplated to form
spacers 597 in other configurations such as rectangular, prism
shaped, cylindrical, or semi-cylindrical. After sintering, wheel
510 can be mounted on a rotating shaft in substantially the same
manner as wheel 10.
[0096] FIG. 22 is a front view of still another embodiment of an
abrasive grinding wheel in accordance with the present invention.
In the embodiment of FIG. 22, wheel 610 includes an abrasive region
612 preferably sandwiched between a first support plate 614 and a
second support plate 616. Abrasive region 612 includes an outer
abrasive surface 618 which can be a substantially cylindrical band
that extends around the perimeter of abrasive grinding wheel 610.
Wheel 610 has an axis of rotation 623.
[0097] Like abrasive region 512 of wheel 510, abrasive region 612
is made up hard or abrasive particle layers 626, represented by
dashed lines, surrounded by bond material regions 628. Further, the
edges of abrasive particle layers 626 undulate in a sinusoidal-like
form like edges of abrasive particle layers 526 so that at least
one edge of an abrasive particle layer intersects in at least two
locations at least one path defined by the intersection of a plane
perpendicular to the axis of rotation and the abrasive surface.
However, abrasive region 612 is formed from abrasive segments 613
like abrasive segments 113 of wheel 110. Each segment 613 has
abrasive particle layers 626 which curve or undulate in a
sinusoidal-like form. Further, like wheel 510, the peaks of any
first abrasive particle layer edge will extend to a point axially
level with or above the troughs of an another abrasive particle
layer edge adjacent to and above the first abrasive particle layer
edge. Accordingly, like wheel 510, any path defined by the
intersection of a plane perpendicular to the axis of rotation of
wheel 510 an a complete circumference of abrasive region 512 will
intersect or cut across at least one abrasive particle layer 526.
It is also contemplated that abrasive particle layers 626 have
edges which form other configurations such as sawtooth waves or
irregular smooth waves.
[0098] Wheel 610 can be formed in substantially the same manner as
wheel 110 with the exception that when forming a laminated sheet
such as sheet 51 from which segments 613 are cut, spacers 697,
which can be substantially the same as spacers 597, are placed
between the layers forming the laminated sheet and top punch, such
as punch 84, and between the layers forming the laminated sheet and
a bottom punch, such as punch 85. Spacers 697 are circumferentially
spaced in a circular configuration like the spacers used to form
wheel 510. Also, spacers 697 adjacent to the top punch are
circumferentially shifted with respect to the spacers adjacent to
the bottom punch. The layers used to form the laminated sheet are
then sintered together with the spacers. Abrasive segments 613 can
then be cut from the resulting laminated sheet as shown in FIG.
7.
[0099] The present invention also provides abrasive grinding wheels
and a method for making abrasive grinding wheels in which the
abrasive layer is adhesively bonded to one or more support plates.
Various embodiments of adhesively bonded grinding wheels are shown
in FIGS. 23-25. Like elements are labeled with like numbers
throughout FIGS. 23-25.
[0100] Referring now to FIG. 23 a first embodiment of an adhesively
bonded abrasive grinding wheel is shown. Grinding wheel 710
includes first support plate 714 (having inner major surface 714a
and outer major surface 714b), second support plate 716 (having
inner major surface 716a and outer major surface 716b), metal bond
abrasive layer 712 (having first major surface 712a and second
major surface 712b), first adhesive layer 715, and second adhesive
layer 717. Metal bond abrasive layer 712 is a single (i.e.,
continuous) mass of metal bond abrasive and is interposed between
first adhesive layer 715 and second adhesive layer 717. First
adhesive layer 715 bonds the first major surface 712a of abrasive
layer 712 to the inner major surface 714a of first support plate
714. Likewise, second adhesive layer 717 bonds the second major
surface 712b of abrasive layer 712 to the inner major surface 716a
of second support plate 716. Grinding wheel 710 is generally
cylindrical and has bore 720 passing through a top and bottom face
thereof. Wheel 710, via bore 720, can be mounted on a rotatable
shaft (not shown) and rotated about axis of rotation 723. It is
also contemplated to attach wheel 710 to a rotatable shaft by
attaching a mounting plate (not shown) having a central shaft (not
shown) to the wheel using mounting holes 709. It is to be
understood, however, that mounting holes 709 are not necessary. By
rotating wheel 710 on or by a rotatable shaft, a workpiece can be
held against the abrasive surface 718 of wheel 710 so that the
workpiece can be shaped, ground, or cut. Metal bond abrasive layer
712 has a substantially cylindrical abrasive surface 718 extending
around a perimeter surface of wheel 710. Abrasive surface 718 may
have any desired grinding profile. In a preferred embodiment, the
grinding profile of abrasive surface 718 is concave which allows
grinding wheel 710 to impart a rounded edge to a workpiece. Metal
bond abrasive layer 712 may have ordered layers (e.g., planar
layers, sinusoidal layers) of abrasive particles as described
herein or the abrasive layer may have abrasive particles randomly
distributed throughout the metal bond material. In FIG. 23,
abrasive layer 712 is shown having abrasive particles 724 randomly
distributed throughout bond material 726. The abrasive particles
724 may be formed from any relatively hard substance including
superabrasive particles such as diamond, cubic boron nitride, boron
suboxide, boron carbide, silicon carbide and mixtures thereof.
[0101] Referring now to FIG. 24 a second embodiment of an
adhesively bonded grinding wheel of the present invention is shown.
Grinding wheel 810 includes first support plate 814 (having inner
major surface 814a and outer major surface 814b), second support
plate 816 (having inner major surface 816a and outer major surface
816b), metal bond abrasive layer 812, first adhesive layer 815, and
second adhesive layer 817. Like wheel 710, wheel 810 via bore 820
and optional mounting holes 809 can be mounted on a rotatable shaft
(not shown) and rotated about axis of rotation 823. Metal bond
abrasive layer 812 is made up of a plurality of discrete metal bond
abrasive segments 813 which are circumferentially spaced about the
perimeter of wheel 810. The abrasive segments 813 each have first
major surface 813a and second major surface 813b. The metal bond
abrasive segments 813 are interposed between first adhesive layer
815 and second adhesive layer 817. First adhesive layer 815 bonds
the first major surfaces 813a of metal bond abrasive segments 813
to the inner major surface 814a of first support plate 814.
Likewise, second adhesive layer 817 bonds the second major surfaces
813b of metal bond abrasive segments 813 to the inner major surface
816a of second support plate 816. Metal bond abrasive layer 812 may
have ordered layers (e.g., substantially planar, parallel layers,
or sinusoidal layers) of abrasive particles or randomly distributed
abrasive particles (see, for example, FIG. 23). It is also within
the scope of the present invention to include both abrasive
segments having ordered layers of abrasive particles and abrasive
segments having randomly distributed abrasive particles in the same
grinding wheel. In FIG. 24, the abrasive segments 813 are shown
having abrasive particles 824 distributed throughout the bond
material in substantially planar, parallel layers 828 (represented
with dashed lines in FIG. 24).
[0102] Referring now to FIGS. 25a and 25b, a third embodiment of an
adhesively bonded grinding wheel of the present invention is shown.
Grinding wheel 910 includes first support plate 914 (having inner
major surface 914a and outer major surface 914b), second support
plate 916 (having inner major surface 916a and outer major surface
916b), abrasive layer 912, first adhesive layer 915, and second
adhesive layer 917. Like wheel 710, wheel 910 via bore 920 and
optional mounting holes 909 can be mounted on a rotatable shaft
(not shown) and rotated about axis of rotation 923. As shown in
FIG. 25b, first support plate 914 includes axially extending
surface 930. Second support plate 916 has inner circular opening
922 which mates with first support plate 914 over axially extending
surface 930. Abrasive layer 912 is made up of a plurality of
discrete metal bond abrasive segments 913 which are
circumferentially spaced about the perimeter of grinding wheel 910.
The abrasive segments 913 each have a first major surface 913a and
a second major surface 913b. Metal bond abrasive segments 913 are
interposed between first adhesive layer 915 and the second adhesive
layer 917. First adhesive layer 915 bonds the first major surfaces
913a of metal bond abrasive segments 913 to inner major surface
914a of first support plate 914. Likewise, second adhesive layer
917 bonds the second major surfaces 913b of metal bond abrasive
segments 913 to inner major surface 916a of second support plate
916. Optionally, adhesive may be applied to axial surface 930 to
further bond the metal bond abrasive segments 913 to first support
plate 914. Metal bond abrasive segments 913 may have ordered layers
(e.g., substantially planar, parallel layers or sinusoidal layers)
of abrasive particles or randomly distributed abrasive particles.
It is also within the scope of the invention to include both
abrasive segments having ordered layers of abrasive particles and
abrasive segments having randomly distributed abrasive particles in
the same grinding wheel. In FIGS. 25a and 25b, abrasive layer 912
is shown having abrasive particles 924 randomly distributed
throughout bond material 926.
[0103] Suitable adhesives for bonding the abrasive layer to the
support plate(s) include those adhesives which have sufficient
strength to bond the abrasive layer to the support plate(s) under
typical use conditions for a grinding wheel. That is, the adhesive
must hold the abrasive layer against the forces generated during
the abrading operation. Primarily, this includes shear force(s)
generated by the rotation of the grinding wheel about its axis and
shear force(s) generated by contact between the abrasive layer and
the workpiece.
[0104] A preferred class of adhesives may be described as
structural adhesives in that they are capable of forming a bond
between two materials wherein the bond has high shear and peel
strength. Examples of the types of adhesives which may be suitable
include one-part thermosetting adhesives, two-part thermosetting
adhesives (e.g., two-part epoxies), acrylics, urethanes, pressure
sensitive adhesives, hot melt adhesives, moisture curing adhesives,
and the like. Such adhesives may be provided as liquids, solids,
powders, pastes, films, and may be thermally cured, dried, reactive
mixtures and the like. The adhesive may be applied over the entire
area of contact between the metal bond abrasive layer and the
support plate(s) or the adhesive may be applied to only a portion
of the contact area. It should be understood that the selection of
a suitable adhesive for bonding the metal bond abrasive layer to
the support plate(s) may be dependent upon factors such as the
diameter of the grinding wheel, the mass of the abrasive layer or
abrasive segments, the surface area of adhesive, the rotational
speed of the grinding wheel. For example, as the maximum rotational
speed of the grinding wheel is increased, the strength of the
adhesive bond must be increased to counteract the shear force(s)
(e.g., centripetal force) acting on the abrasive layer. Similarly,
as the bonding area between the abrasive layer and the support
plate is decreased, the strength of the adhesive bond must be
increased to counteract the increased unit force(s).
[0105] Similarly, it should be recognized that changes in the
diameter of the wheel require changes in the adhesive strength
necessary to hold the wheel together. By way of example, for a 6
inch (15.24 cm) grinding wheel with segments having a mass of 0.110
lbs (0.05 kg) and a bonding area of 2 square inches, an adhesive
shear strength of about 42 psi is required at about 3000 rpm and an
adhesive shear strength of about 168 psi is required at about 6000
rpm. Following the same as above, for a 10 inch (25.4 cm) grinding
wheel with segments having a mass of 0.110 lbs (0.05 kg) and a
bonding area of 2 square inches, an adhesive shear strength of
about 70 psi is required at about 3000 rpm and an adhesive shear
strength of about 279 psi is required at about 6000 rpm.
[0106] Typically, it is desirable to exceed, preferably
substantially exceed, the required adhesive shear strength. To this
end, preferred adhesives may be described as structural adhesives
in that they form high strength (e.g., high shear and peel
strength) and load bearing adhesive bonds. Suitable adhesives
typically provide a shear strength of at least about 6.89 MPa (1000
psi), preferably at least about 10.34 MPa (1500 psi), more
preferably at least about 13.79 MPa (2000 psi), and most preferably
at least about 27.58 MPa (4000 psi).
[0107] A particularly suitable class of adhesives is thermosetting
structural adhesives which are heat cured to provide a structural
bond. A commercially available thermosetting structural adhesive is
available under the trade designation "SCOTCH-WELD" and is
identified as Structural Adhesive Film AF-30 (commercially
available from Minnesota Mining and Manufacturing Company, St.
Paul, Minn.). Another suitable structural adhesive is an
acrylic-epoxy adhesive identified as Structural Bonding Tape 9244
(commercially available from Minnesota Mining and Manufacturing
Company, St. Paul, Minn.).
[0108] Support plates suitable for use in adhesively bonded
abrasive grinding wheels of the present invention may be made of
any suitable substantially rigid material. Preferably, the support
plates are made of metal, for example, steel, aluminum, brass, or
titanium. Most preferably, the support plates are made of aluminum
to reduce the overall weight of the grinding wheel. Support plates
made of polymeric materials and fiber reinforced polymeric
materials may also be used. It should be recognized that the
adhesives selected, while dependent on strength properties required
for this application, are also selected based on the surface
material being bonded. Adhesives used to bond abrasive bodies to
steel support plates may be different than those selected to bond
to aluminum support plates.
[0109] Bonding of the metal bond abrasive segments to the support
plate may be improved by surface treating the support plate(s)
and/or the metal bond abrasive layer prior to forming the adhesive
bond. Surface treating techniques include, for example, abrasive
surface conditioning (e.g., sandblasting), solvent cleaning, acid
or base treatment, and chemical priming. A suitable chemical primer
is commercially available under the trade designation "Primer
EC1660" (available from Minnesota Mining and Manufacturing Company,
St. Paul, Minn.). Bonding may also be improved by axially
compressing the grinding wheel assembly (e.g., using a platen
press) while curing the adhesive. In the case of thermosetting
adhesives, it may be desirable to heat the platen press in order to
cure the adhesive while under compression.
EXAMPLES
Example 1
[0110] The following procedure was used to form an abrasive wheel
in accordance with the present invention.
[0111] Two steel plates were machined such that the total
dimensions of the plates were 25.4 cm by 25.4 cm by 0.476 cm thick
(10 inches by 10 inches by {fraction (3/16)} inch thick) with a one
sided taper of 0.150 degrees. Between these two steel plates
(tapered side in and opposite), 34 alternating layers of metal tape
and patterned diamond abrasive cut to 25.4 cm (10 inch) nominal
squares were aligned.
[0112] The metal tape layers consisted of a 1:1 ratio of bronze to
cobalt, with the addition of a small amount of low temperature
braze, and a few organic binders to allow the tape to be
handleable. The composition of the slurry used to make the metal
tape layer was specifically as shown in the chart below, the values
representing percent by weight of the substance.
1 38.28 cobalt 38.28 bronze 2.38 nickel 0.195 chromium 0.195
phosphorous 17.74 1.5/1 MEK/toluene 1.387 polyvinyl butyral 0.527
polyethylene glycol having a molecular weight of about 200 0.877
dioctylphthalate 0.132 corn oil
[0113] These tapes were cast so that the area density was roughly
0.15 gram/cm.sup.2 (1 gram/inch.sup.2) when dry.
[0114] To form the diamond abrasive particle layers, a pressure
sensitive adhesive commercially available from Minnesota Mining and
Manufacturing Company (St. Paul, Minn.) under the trade designation
"SCOTCH" brand adhesive tape was placed on one side of an open mesh
screen having approximately 107 .mu.m openings, 165 openings per
square inch, and made from 0.48 mm diameter stainless wire. Diamond
abrasive particles of approximately 170/200 mesh were dropped onto
the screen openings in a 20.32 cm (8 inch) radial ring pattern so
that the diamonds adhered to the tape. This resulted in diamond
particles occupying the majority of the screen openings. Once the
radial pattern of diamonds was applied, small steel shot was used
to fill in all remaining exposed area.
[0115] The screens, filled with abrasive particles, and flexible
sheets of metal powder were stacked upon each other to form a
laminar composite. After layering the metal tape and abrasive
layers between the plates, the part was sintered as shown in the
following table:
2 Time Temp. Pressure (sec.) (.degree. C.) (kg/cm.sup.2) 0 20 0 550
420 100 730 420 100 950 550 100 1030 550 100 1210 590 100 1240 590
100 1980 890 100 2400 890 100 2410 895 250 2520 895 250 2860 895
350 500 20 350
[0116] Once the final part had cooled, the 25.4 cm by 25.4 cm plate
was machined to extract the diamond abrasive region in the form of
a round wheel. This wheel was then balanced, trued and dressed to
the final 20.32 cm (8 inch) diameter. Appropriate mounting holes
were also introduced.
[0117] Though the present invention has been described with
reference to preferred embodiments, those skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the invention.
Example 2
[0118] The following procedure was used to form an abrasive wheel
in accordance with the present invention.
[0119] Fifty-five alternating layers of metal tape and patterned
diamond abrasive cut into 5 inch nominal squares were stacked and
aligned. These layers were then cold compacted to produce a green
structure, ready of sintering.
[0120] The metal tape layers consisted of iron/copper diamond
setting powders, with the addition of a small amount of low
temperature braze, and a few organic binders to allow the tape to
be handleable. The composition of the slurry used to make the metal
tape layer was specifically as shown in the chart below, the values
representing percent by weight of the substance.
3 copper 33.7 iron 27.5 nickel 7.87 tin 3.41 chromium 2.43 boron
0.34 silica 0.44 tungsten carbide 9.38 cobalt 0.67 phosphorus 0.17
Methyl Ethyl Ketone 12.6 polyvinyl butyral 0.89 Santicizer
160.sup.1 0.62 .sup.1Santicizer 160 is commercially available from
Solutia Inc., St. Louis MO.
[0121] These tapes were cast so that the area density was on
average 0.65 gram/inch.sup.2 when dry.
[0122] To form the diamond abrasive particle layers, a pressure
sensitive adhesive commercially available from Minnesota Mining and
Manufacturing Company (St. Paul, Minn.) under the trade designation
"SCOTCH" brand adhesive tape designated as book Tape #845 was
placed on one side of an open mesh screen having approximately 107
.mu.m openings, 165 openings per square inch, and made from 0.48 mm
diameter stainless wire. Diamond abrasive particles of
approximately 200/230 mesh were dropped onto the screen such that
one diamond was in each opening of the 5 inch square layer. This
resulted in diamond particles occupying the majority of the screen
openings.
[0123] The screens, filled with abrasive particles, and flexible
sheets of metal powder were stacked upon each other to form a
laminar composite. After layering the metal tape and abrasive
layers between the plates, the part was sintered as shown in the
following table:
4 Time Temp. Pressure (sec.) (.degree. C.) (kg/cm.sup.2) 0 20 0 550
420 100 730 420 100 950 550 100 1130 550 100 1210 590 100 1240 590
100 1750 880 200 2110 880 200 2430 1007 200 2790 1007 200 2970 870
250 3330 850 400
[0124] Once the final part had cooled, the metal bond abrasive was
converted into arc shaped metal bond abrasive segments by means of
abrasive water jet cutting.
[0125] These metal bond abrasive segments were then bonded to two
aluminum support plates using a structural adhesive. The support
plates and segments were cleaned and treated to provide an adequate
surface for bonding. In the case of the aluminum support plates,
the bonding surfaces were cleaned with MEK, acid etched, and
primed. The acid etching of the aluminum support plates comprised
several steps. First, the support plates were dipped in an alkaline
wash for 10 minutes at 88.degree. C. The alkaline wash was made up
of approximately 9-11 ounces per gallon of Oakite 164 (commercially
available from Oakite Products, Inc., Berkeley Hgts., N.J.). After
a thorough rinse with water, they were acid etched for 10 minutes
at 71.degree. C. in a sulfuric acid mixture. After rinsing with
water, the support plates were allowed to air dry for 10 minutes on
a tilted rack and were then oven dried for an additional 10 minutes
at 71.degree. C.
[0126] The surface priming was performed by brushing a thin layer
of EC1660 primer (commercially available from Minnesota Mining and
Manufacturing Company, St. Paul, Minn.) onto the bonding surfaces.
The primer was allowed to dry in accordance with the manufacturer's
recommended conditions.
[0127] In the case of the metal bond abrasive segments, the bonding
surfaces were sandblasted, solvent washed with methyl-ethyl ketone,
and surface primed. The sandblasting process was performed using 80
grit aluminum oxide at approximately 60 psi pressure. The surface
priming was performed by brushing a thin layer of EC1660 primer
onto the bonding surfaces. The primer was allowed to dry in
accordance with the manufacturer's recommended conditions.
[0128] After the surface preparation was complete, a 10 mil layer
of a structural adhesive (commercially available from Minnesota
Mining and Manufacturing Company, St. Paul, Minn. under the trade
designation "AF30") was placed onto the first bonding surface of
the support plate. The arc-shaped metal bond abrasive segments were
then placed onto the adhesive surface creating a cylindrical region
of abrasive around the center of the support plate. The segments
were then covered with a second layer of structural adhesive of the
same type. A second aluminum support plate was then placed over the
second layer of structural adhesive thereby forming a grinding
wheel assembly (see, FIG. 25b).
[0129] The grinding wheel assembly was then placed into a heated
platen press to cure the thermosetting adhesive in order to form
bonds between the abrasive segments and the support plates. The
wheel assembly was then heated from 38.degree. C. to 177.degree. C.
at a rate of 5.6.degree. C./minute under a constant pressure of 689
KPa. After holding at 177.degree. C. for one hour, the grinding
wheel assembly was cooled to room temperature under the same
applied pressure.
[0130] The resulting abrasive grinding wheel was then balanced,
trued and dressed to the final 20.32 cm (8 inch) diameter.
[0131] Though the present invention has been described with
reference to preferred embodiments, those skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *