U.S. patent application number 13/497621 was filed with the patent office on 2012-10-11 for rotary buffing pad.
Invention is credited to Scott R. Culler, Gregory A. Koehnle, Brant A. Moegenburg, Schoen A. Schuknecht, Edward J. Woo.
Application Number | 20120258652 13/497621 |
Document ID | / |
Family ID | 43558369 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120258652 |
Kind Code |
A1 |
Koehnle; Gregory A. ; et
al. |
October 11, 2012 |
ROTARY BUFFING PAD
Abstract
Provided is a flat-faced buffing pad that includes a plurality
of apertures of variable size. The apertures are generally larger
in the areas toward the center of the pad, while being generally
smaller in the areas toward the periphery of the pad. Some
embodiments further include apertures disposed along one or more
concentric circular rings located along the front surface and
generally symmetrical about the rotation axis. These configurations
of apertures provide both superior cut performance and superior
finish. Moreover, these configurations minimize several undesirable
aspects in a polishing operation, such as slinging of the polishing
compound, vibration, wobbling, and drag felt by the operator as the
rotary pad slides across the surface to be polished.
Inventors: |
Koehnle; Gregory A.;
(Oakdale, MN) ; Culler; Scott R.; (Burnsville,
MN) ; Moegenburg; Brant A.; (Baldwin, WI) ;
Schuknecht; Schoen A.; (Hudson, WI) ; Woo; Edward
J.; (Woodbury, MN) |
Family ID: |
43558369 |
Appl. No.: |
13/497621 |
Filed: |
November 9, 2010 |
PCT Filed: |
November 9, 2010 |
PCT NO: |
PCT/US10/55905 |
371 Date: |
March 22, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61260498 |
Nov 12, 2009 |
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Current U.S.
Class: |
451/526 |
Current CPC
Class: |
B24B 37/26 20130101 |
Class at
Publication: |
451/526 |
International
Class: |
B24D 13/14 20060101
B24D013/14 |
Claims
1. A rotary buffing pad comprising: a substrate comprising an
open-celled polymeric foam that has a compression deflection value
when compressed to 25 percent of original volume ranging from 2000
to 7000 Pascals and having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising: an inner region adjacent to and
surrounding the rotation axis; an outer region surrounding the
inner region; a plurality of first apertures having a first average
size located within the inner region and extending from the front
surface toward the back surface; and a plurality of second
apertures having a second average size located within the outer
region and extending from the front surface toward the back
surface, wherein the first average size is larger than the second
average size.
2. A rotary buffing pad comprising: a substrate comprising an
open-celled polymeric foam that has a compression deflection value
when compressed to 25 percent of original volume ranging from 2000
to 7000 Pascals and having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising: an inner region adjacent to and
surrounding the rotation axis; an outer region surrounding the
inner region; a plurality of first apertures having a first
aperture density located within the inner region and extending from
the front surface toward the back surface; and a plurality of
second apertures having a second aperture density located within
the outer region and extending from the front surface toward the
back surface, wherein the first aperture density is larger than the
second aperture density.
3. The buffing pad of claim 2, wherein the first aperture density
ranges from 1.5 to 5.0 per square centimeter and the second
aperture density ranges from 0.8 to 1.5 per square centimeter.
4. The buffing pad of claim 1, wherein the plurality of second
apertures include a first subset of second apertures arranged
according to a series of replicated polygonal groupings that are
spaced apart from each another.
5. The buffing pad of claim 4, wherein the polygonal groupings are
hexagonal groupings.
6. The buffing pad of claim 1, wherein the plurality of first
apertures have a first average depth and the plurality of second
apertures have a second average depth that is less than the first
average depth.
7. The buffing pad of claim 1, wherein the plurality of first
apertures have a first average diameter and the plurality of second
apertures have a second average diameter that is less than the
first average diameter.
8. The buffing pad of claim 1, wherein the plurality of first
apertures occupy a first average volume and the plurality of second
apertures occupy a second average volume that is less than the
first average volume.
9. (canceled)
10. The buffing pad of claim 1, wherein the inner region has a
diameter ranging from 20 to 40 percent of the diameter of the
substrate.
11. The buffing pad of claim 1, wherein the inner region occupies
an area ranging from 4 to 16 percent of the total area of the front
surface.
12. (canceled)
13. The buffing pad of claim 1, further comprising a backing layer
extending along at least a portion of the back surface and having a
flexural modulus that is greater than that of the substrate.
14. The buffing pad of claim 13, wherein the backing layer
comprises a fibrous material to facilitate coupling to a power tool
having a hook face attachment surface.
15. The buffing pad of claim 1, wherein the plurality of first
apertures include all of the apertures present within the inner
region.
16. The buffing pad of claim 15, wherein the plurality of second
apertures include all of the apertures present within the outer
region.
17. The buffing pad of claim 1, wherein the outer region further
comprises at least one annular region and wherein the plurality of
second apertures further comprises a second subset of second
apertures located in the at least one annular region, the second
subset extending from the front surface toward the back surface and
being disposed along at least one circular ring, each circular ring
being coplanar with the front surface and generally symmetrical
about the rotation axis.
18. The buffing pad of claim 17, wherein the second subset of
second apertures have a certain diameter and a certain spacing
between neighboring apertures and the ratio between the certain
diameter to the certain spacing is at least 0.2.
19. The buffing pad of claim 18, wherein the ratio between the
certain diameter to the certain spacing is at least 0.3.
20. The buffing pad of claim 19, wherein the ratio between the
certain diameter to the certain spacing is at least 0.35.
21. The buffing pad of claim 17, further wherein the at least one
annular region comprises two or more annular regions and the at
least one circular ring comprises two or more circular rings that
are located within the respective annular regions and concentric
with each other.
22. A rotary buffing pad comprising: a substrate comprising an
open-celled polymeric foam that has a compression deflection value
when compressed to 25 percent of original volume ranging from 2000
to 7000 Pascals and having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising: an inner region adjacent to and
surrounding the rotation axis; an outer region surrounding the
inner region; and a plurality of apertures extending from the front
surface toward the back surface, wherein the apertures have a
distribution of sizes and the apertures having relatively large
size are predominantly located in the inner region relative to the
outer region.
Description
FIELD OF THE INVENTION
[0001] Buffing pads are provided for polishing the surface of a
workpiece. More particularly, patterned rotary buffing pads are
provided for polishing the surface of a workpiece.
BACKGROUND
[0002] The visual appearance of painted surfaces, for example,
exterior painted automotive and marine surfaces is an important
aesthetic property. Original equipment manufacturer and aftermarket
industries have devoted many resources to the development and
application of paint systems that provide aesthetic properties such
as, for example, low haze and good distinctness of image. It is
commonplace for vehicle and boat manufacturers to use a base coat
and clear coat paint system. The base coat provides the desired
color, while the clear coat, which is applied over the base coat,
provides a transparent scratch and chip-resistant protective coat.
Such paint systems, however, have the tendency to magnify defects
(for example, scratches, haze, and dust nibs) in either the base
coat or the clear coat. One common method for imparting, or
restoring, a high quality appearance to the paint system uses a
multi-step process.
[0003] First, the defects are abraded using a coated abrasive
product with a fine abrasive particle size, for example, sandpaper,
or a structured abrasive article. This step provides rapid removal
of the defects, but typically leaves scuff, or "swirl" marks, and
sometimes scratches, that need to be removed. Next, the swirl marks
are removed by buffing using a buffing composition. The buffing
composition is typically an aqueous or petroleum based medium
containing abrasive particles of smaller size than the abrasive
particles used in the coated abrasive article. However, depending
of the paint system, the buffing step may result in a surface with
a hazy appearance. The hazy appearance is removed by a finishing
step in which the hazy portion of the paint system is buffed with a
finishing composition. The finishing composition is typically an
aqueous or petroleum based medium containing abrasive particles of
smaller size than the abrasive particles used in the buffing
composition. Finally, residue from the buffing and/or finishing
compositions is removed, for example, with a soft cloth, thereby
producing an aesthetically appealing finish substantially free of
surface residue.
[0004] Buffing pads used in the above polishing steps are generally
compressible to allow even pressure to be applied across the
buffing surfaces. Such pads are often made from either wool or a
polymeric foam. While the polishing steps may be a manual process,
it can be facilitated by attaching the buffing pad to an electric
or air-driven pneumatic power tool. As used herein, "polishing
steps" include any of the steps used in restoring or improving a
surface, including compounding, buffing, and finishing steps.
[0005] The performance of a buffing pad may be appraised on a
number of factors. First, the buffing pad provides a certain level
of cut performance (or "cut"), defined as the rate at which the
moving pad removes surface defects. Cut performance should be
adequately high to allow polishing to be completed within a
reasonable amount of time. Second, the buffing pad provides a
certain level of finish. The finish provided by a buffing operation
is defined by the smoothness of the resulting surface and can be
quantified by measuring "haze". Haze decreases with increasing
smoothness, and thus should be as low as possible. Third, the
rotary buffing pad can be appraised on user experience. Here, it is
desirable for a rotary buffing pad to engage the surface to be
polished in a controlled manner to reduce the incidence of jerking
or other unpredictable motions (known as "chatter") of the power
tool during the polishing process. This assists the operator in
maintaining a high degree of control over the orientation of the
pad and helps avoid inadvertent gouging of the workpiece.
SUMMARY
[0006] In buffing applications, it is often a challenge to achieve
both good cut and fine finish simultaneously. Modifications to the
buffing pad or abrasive compound that enhance cutting performance
often lead to a coarser finish. Conversely, modifications which
lead to a finer finish often also tend to reduce the rate of
abrasion and thereby degrade cut performance. The apparent inverse
relationship between cut performance and finish has been a source
of frustration to many of skill in the art.
[0007] Herein are provided rotary buffing pads which overcome the
dilemma faced by one desiring to achieve both superior cut
performance and a fine finish. This combination of advantages is
provided by using a flat-faced buffing pad that includes a
plurality of apertures of variable size. The apertures are
generally larger in the areas toward the center of the pad, while
being generally smaller in the areas toward the periphery of the
pad. This synergistic arrangement of large and small apertures
provides both superior cut performance and a superior finish.
[0008] This configuration further provides other unexpected
advantages over conventional foam buffing pads. First, the center
apertures advantageously capture excess abrasive composition
thereby reducing the amount of liquid sling during the buffing
process and therefore reducing both waste and clean up time after
the operation is completed. Second, the amount of vibration, or
"chatter", felt by the operator during the buffing process is
maintained at low levels. Reduced vibration in turn leads to
reduced fatigue and enhanced operator comfort. Third, locating the
larger apertures toward the center of the pad improves operator
control by reducing the drag resistance due to the center of the
pad and also preventing the pad from wobbling during the buffing
process. Since wobbling can cause the buffing pad to jump or jerk
across the surface, this configuration improves operator control
and reduces the risk of damaging the surface being polished.
[0009] In one aspect, a rotary buffing pad is provided, comprising
a substrate having a front surface, back surface, and a rotation
axis perpendicular to the front and back surfaces, the substrate
further comprising an inner region adjacent to and surrounding the
rotation axis, an outer region surrounding the inner region, a
plurality of first apertures having a first average size located
within the inner region and extending from the front surface toward
the back surface; and a plurality of second apertures having a
second average size located within the outer region and extending
from the front surface toward the back surface, wherein the first
average size is larger than the second average size.
[0010] In another aspect, a rotary buffing pad is provided
comprising a substrate having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising an inner region adjacent to and
surrounding the rotation axis, an outer region surrounding the
inner region, a plurality of first apertures having a first
aperture density located within the inner region and extending from
the front surface toward the back surface, and a plurality of
second apertures having a second aperture density located within
the outer region and extending from the front surface toward the
back surface, wherein the first aperture density is larger than the
second aperture density.
[0011] In still another aspect, a rotary buffing pad is provided
comprising a substrate having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising an inner region adjacent to and
surrounding the rotation axis, an outer region surrounding the
inner region, a plurality of first apertures having a first average
size located within the inner region and extending from the front
surface toward the back surface, a plurality of second apertures
having a second average size located within the outer region and
extending from the front surface toward the back surface, wherein
the first average size is larger than the second average size, and
wherein the outer region further comprises at least one annular
region and wherein the plurality of second apertures further
comprises a second subset of second apertures located in the at
least one annular region, the second subset extending from the
front surface toward the back surface and being disposed along at
least one circular ring, each circular ring being coplanar with the
front surface and generally symmetrical about the rotation
axis.
[0012] In yet another aspect, a rotary buffing pad is provided
comprising a substrate having a front surface, back surface, and a
rotation axis perpendicular to the front and back surfaces, the
substrate further comprising an inner region adjacent to and
surrounding the rotation axis, an outer region surrounding the
inner region, and a plurality of apertures extending from the front
surface toward the back surface, wherein the apertures have a
distribution of sizes and the apertures having relatively large
size are predominantly located in the inner region relative to the
outer region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a front view of a buffing pad according to one
exemplary embodiment of the invention;
[0014] FIG. 2 is an elevational cross-sectional view of the buffing
pad along the line 2-2 in FIG. 1;
[0015] FIG. 3 is a perspective view of the buffing pad in FIGS.
1-2, looking at the back surface;
[0016] FIG. 4 is a magnified fragmentary front view of the buffing
pad shown in the rectangular inset 4 of FIG. 1; and
[0017] FIG. 5 is a front view of a buffing pad according to an
alternative embodiment of the invention.
DEFINTIONS
[0018] As used herein: [0019] "Aperture" refers to an opening in an
article which may or may not penetrate through the article; [0020]
"Aperture spacing" refers to the center-to-center distance between
two neighboring apertures; [0021] "Compressible" refers to a
material that reduces in volume upon application of pressure;
[0022] "Diameter" refers to the largest lateral dimension; and
[0023] "Aperture density" refers to the total population of
apertures located within a given region divided by the total
surface area of that region.
DETAILED DESCRIPTION
[0024] The following description is directed to buffing pads useful
for removing defects from a surface and polishing the surface to a
fine finish. These buffing pads are especially useful in the
automotive and marine applications, where there is a need to polish
a painted exterior surface to produce a glossy, aesthetic
appearance. However, the buffing pads are not limited to these
applications. For example, they may be useful on any other painted
surfaces or even non-painted surfaces, and are not limited to
polishing operations on any particular type of article. For
example, workpiece surfaces may include marbled, varnished,
composite, or gel coated surfaces.
[0025] Moreover, buffing pads are not limited to a specific method
of use. Any of a wide variety of abrasive polishes and compounds,
both in liquid and solid form, may be advantageously used with
these buffing pads to achieve a desirable surface finish. Various
power tools may be used to generate the relative motion between the
buffing pad and the surface to be polished. Moreover, the
application of these pads is not restricted to any particular stage
of a workflow used to polish an article. For example, they may be
used as a first step, intermediate step, or last step of a
multi-step polishing method. Alternatively, these buffing pads may
be used in a single-step polishing method.
[0026] An exemplary buffing pad according to one embodiment is
illustrated in FIGS. 1-4 and designated by the numeral 100. As
shown in front view by FIG. 1, the buffing pad 100 has a substrate
102 with a front surface 104. The front surface 104 is generally
flat and has a circular shape in plan view. While not shown here,
the front surface 104 may also assume non-circular shapes. As
shown, the substrate 102 further includes a side surface 106 and a
back surface 108. Optionally and as shown, a backing layer 110,
denoted by the dashed lines, extends across nearly all of the back
surface 108. In one exemplary embodiment, the buffing pad 100 has
an overall diameter of about 8.0 inches (20.3 centimeters (cm)) and
a thickness of about 1.5 inches (3.8 cm). In this description, the
"front" is defined as the side that contacts the workpiece and the
"back" is the opposite surface.
[0027] When used in a buffing operation, the buffing pad 100
rotates about a rotation axis 112, shown in FIGS. 1 and 2. The
rotation axis 112 is perpendicular to the front surface 104 and
passes through the center of the buffing pad 100. In the embodiment
shown, the substrate 102 is symmetrically disposed about the
rotation axis 112 to help minimize wobbling of the buffing pad 100
during operation.
[0028] In some embodiments, the substrate 102 is made from a
compressible material, such as a polymeric foam. Exemplary
substrates having this property include open-celled polyurethane
foams. Open-celled foams are advantageous in that they can be made
soft and compliant and do not significantly expand in the side
directions when compressed from the top and bottom directions.
Open-celled foams may also allow limited permeability to the
buffing polish or compound material. Such permeability may
advantageously improve overall retention of the polish or compound
material on the pad 100 during a polishing operation. Other
commercial foams are also possible, such as those disclosed in
issued U.S. Pat. No. 4,962,562 (Englund, et al.). In exemplary
embodiments, the stiffness of the substrate 102, as measured by the
pressure required to produce a compression to 25% of original
volume (or 25% Compression Load Deflection), ranges from 0.3 to 1
pound per square inch (2.1 to 6.9 kiloPascals (kPa)).
[0029] The optional backing layer 110 preferably has a flexural
modulus greater than that of the substrate 102 and augments the
stiffness along the back side of the buffing pad 100. As increasing
the stiffness of the backing layer 110 generally increases the rate
of cut, the flexural modulus can be tailored to provide the rate of
cut desired for the application. The backing layer 110 can be
coupled to the back surface 108 of the substrate 102 by physical
means such as thermal lamination. Alternatively, the backing layer
110 may be adhesively bonded to the substrate 102.
[0030] Optionally, the backing layer 110 may include a fibrous
material, such as a scrim or non-woven material. Advantageously,
the fibrous material can facilitate coupling the buffing pad 100 to
a power tool. In some embodiments, for example, the backing layer
100 includes one-half of a hook and loop attachment system, the
other half being disposed on a plate affixed to the power tool.
Such an attachment system secures the buffing pad 100 to the power
tool while allowing convenient attachment and removal of pads
between operations.
[0031] As particularly shown in FIG. 1, the substrate 102 includes
two mutually exclusive regions, an inner region 114 and an outer
region 116. The inner region 114, defined as the portion of the
substrate 102 located within the hexagonal dashed loop A', is both
adjacent to and surrounding the rotation axis 112. In some
embodiments, the inner region 114 is symmetrically disposed about
the axis 112. While the inner region 114 depicted in FIG. 1 happens
to have a hexagonal shape, other shapes (for example, a square,
circle, or octagon) are also possible. Preferably, the inner region
114 has a diameter ranging from 20 to 40 percent of the overall
diameter of the substrate 102. The outer region 116 is defined as
the portion of the substrate 102 located outside of the dashed loop
A'. The outer region 116 surrounds the inner region 114 and is both
contiguous and concentric with the inner region 114.
[0032] It is noted here that both the inner and outer regions
114,116 are solid three dimensional shapes. Therefore, these
regions 114,116 are defined not only by the visible areas of the
front surface 104 shown in FIG. 1 but also those portions of the
substrate 102 located directly thereunder (i.e. beneath the plane
of the page in perpendicular view). That is, the regions 114 and
116 include the front surface 104 of the substrate 102 and also
have the depth or thickness of the substrate 102.
[0033] A plurality of first apertures 120 and a plurality of second
apertures 122 extend from the front surface 104 toward the back
surface 108 at different locations along the inner and outer
regions 114,116 of substrate 102.
[0034] The plurality of first apertures 120 include all of the
apertures present within the inner region 114. Optionally and as
shown, the first apertures 120 have a generally uniform size and
shape and are distributed evenly across the inner region 114 in a
close packed (e.g. square, hexagonal) arrangement such that there
is a constant spacing between neighboring apertures 120. As an
alternative, the apertures 120 may be uniformly spread across the
front surface 104 but randomized with irregular spacing between
neighboring apertures 120. As another alternative, the apertures
120 may have an overall distribution that is non-uniform across the
inner region 114.
[0035] Optionally and as shown in this embodiment, the plurality of
second apertures 122 includes first and second subsets 123,124 of
apertures. The first and second subsets 123,124 of apertures
include all of the apertures present within the outer region 116,
and are distinguishable from each other based on having different
arrangements across the front surface 104 and different size/shape
characteristics. Although both subsets 123,124 of apertures are
shown, the outer region 116 may include only the first subset 123
or only the second subset 124.
[0036] As shown in FIG. 1, the first subset 123 of the second
apertures 122 are arranged in a series of discrete and replicated
polygonal groupings (or clusters) that are spaced apart from each
another. In this particular example, each grouping is hexagonal in
shape and consists of seven apertures each having the same size and
shape and being equidistant from its closest neighboring
aperture(s). The hexagonal groupings shown here are exemplary,
however, and other polygonal or even circular groupings can also be
used. As another alternative, the first subset 123 can be evenly
distributed across the outer region 116 in a configuration similar
to that of the first apertures 120. Although not shown here, the
first subset 123 can include all of the apertures present within
the outer region 114.
[0037] Optionally and as shown in FIG. 1, the second subset 124 of
the second apertures 122 are disposed along three generally
circular rings 140 located within the outer region 116. FIG. 4 is a
magnified view of the rectangular inset shown in FIG. 1 and shows
the outermost ring 140 in more detail. As shown, the second subset
124 of apertures are located in an annular region 118 within in the
outer region 116. The annular region 118 is defined herein as the
portion of the outer region 116 bounded between the circular dashed
lines B'-B' and B''-B'', shown in fragmentary view in FIG. 4. While
not shown in their entirety, the lines B'-B' and B''-B'' are
imaginary concentric circles located on the front surface 104 and
symmetrically disposed about the rotation axis 112. Like the inner
and outer regions 114,116, the annular region 118 is a
three-dimensional shape that includes not only the portions of the
front surface 104 located between the lines B'-B' and B''-B'', but
also portions of the substrate 102 located directly thereunder
(i.e. beneath the plane of the page in perpendicular view).
Although exactly three rings 140 are shown in FIG. 1, more or fewer
than three rings are also possible. Optionally but not shown here,
the second subset 124 can include all of the apertures present
within the outer region 114.
[0038] In the embodiment shown, the second subset 124 of apertures
have a generally uniform aperture diameter. In other words, the
diameters of the apertures 124 are not only generally uniform along
each individual ring 140 but also generally uniform across all
three of the rings 140. Further, neighboring apertures 124 display
a certain spacing (as measured between the centers of the
apertures) which is generally uniform across the rings 140.
Preferably, the ratio between the certain diameter to the certain
spacing is at least 0.2. More preferably, the ratio between the
certain diameter to the certain spacing is at least 0.3. Most
preferably, the ratio between the certain diameter to the certain
spacing is at least 0.35. As shown in FIG. 1, the three rings 140
are coplanar with the front surface 104, concentric with each other
and symmetrically disposed about the rotation axis 112. Optionally,
the three rings 140 are evenly spaced apart from each other in
radial directions, although this need not be the case.
[0039] FIG. 2 shows the apertures 120,123,124 in cross-section, the
cross-section being taken along cutting plane 3-3 in FIG. 1. As can
be seen in FIG. 2, the apertures 120,122 within the substrate 102
have a distribution of sizes, where the plurality of first
apertures 120 within the inner region 114 have an average size
larger than that of the plurality of second apertures 122 within
the outer region 116. In other words, the apertures 120,122 of
relatively large average size are predominantly located in the
inner region 114 relative to the outer region 116.
[0040] The "size" of a given aperture, as used herein, can refer to
any dimension of the aperture. For example, the size may represent
the diameter, perimeter, inner surface area, or depth of the
aperture, volume occupied by the aperture, or combinations thereof.
In FIG. 2, for example, both the average diameter and average depth
of the plurality of first apertures 120 is larger than those of the
plurality of second apertures 122. Likewise in this embodiment, the
average volume occupied by the plurality of first apertures 120
within the inner region 114 is larger than the average volume
occupied by the plurality of second apertures 122 within the outer
region 116.
[0041] In exemplary embodiments, the plurality of first apertures
120 have an average depth ranging from 8 to 12 mm, an average
diameter ranging from 2 to 4 mm, and average occupied volume
ranging from 25 to 150 cubic mm. In other embodiments, the first
subset 123 of apertures have an average depth ranging from 3.5 to
7.5 mm, an average diameter ranging from 3 to 5 mm, and average
occupied volume ranging from 25 to 147 cubic mm. In still other
embodiments, the second subset 124 of apertures have an average
depth ranging from 9 to 13 mm, an average diameter ranging from 0.5
to 1.5 mm, and average occupied volume ranging from 1.6 to 25 cubic
mm.
[0042] In addition to differences in dimensions, the aperture
density (in apertures per unit area) of the plurality of first
apertures 120 over the front side of the inner region 114 is
greater than that of the plurality of second apertures 122 over the
front side of the outer region 116. In some embodiments, the
plurality of first apertures 120 have a aperture density ranging
from 1.5 to 5.0 per square centimeter, while the plurality of
second apertures 122 have a aperture density ranging from 0.8 to
1.5 per square centimeter over their respective areas.
[0043] The apertures 120,123,124, as shown in FIGS. 1 and 2, are
generally cylindrical in cross-sectional shape. Optionally, some of
the apertures 120,123,124 are non-cylindrical. For example, one or
more of the apertures 120,123,124 may have rounded bottoms, tapered
walls, or even reverse tapered walls where the lateral dimension
increases with increasing depth. In some embodiments, the apertures
120,123,124 have an elongated shape in plan view (i.e. as viewed
normal to the front surface 104). Such elongated apertures may be
oriented in either the radial direction, the tangential direction,
or at some intermediate angle between the two.
[0044] Preferably, the buffing pad 100 uses apertures with a
length-to-width aspect ratio, measured in plan view, that does not
exceed 2:1. Use of discrete apertures with a relatively small
aspect ratio is advantageous because such apertures are resistant
to undue expansion during a polishing operation. Expansion of an
aperture can allow compounding or polishing material to accumulate
and become trapped in the pad. Agglomerations of abrasive material,
if sufficiently large, can scratch the workpiece and degrade haze
performance. It was additionally observed that expansion of an
elongated aperture can even cause the sidewalls of the aperture to
contact the workpiece, again causing undesirable scratches.
[0045] As shown in FIGS. 1, 2, and 4, the plurality of first
apertures 120 and the first and second subsets 123,124 of apertures
each has a uniform aperture size within its respective group.
However, this need not be the case. For example, any of the
apertures 120,123,124 could display a significant variability in
size, either by choice or as a result of manufacturing tolerances.
It is further contemplated that this variability may even result in
overlap between the size ranges of the apertures 120,123, the
apertures 123,124, or even the apertures 120,124 (as long as the
average size of the apertures 120 is larger than the average size
of the apertures 122).
[0046] Similarly, aperture density need not be uniform along the
front sides of regions 114,116. As a result, the plurality of first
apertures 120 may have an overall aperture density greater than
that of the plurality of second apertures 122 even when the former
apertures have a local aperture density within a certain area of
the inner region 114 less than that of the latter apertures within
some other area of the outer region 116. As such, there may well be
significant overlap between number densities observed on a local
level between the plurality of first apertures 120 and the
plurality of second apertures 122.
[0047] While the apertures 120,123,124 extend from the front
surface 104 into the substrate 102 in a generally perpendicular
fashion as shown in FIG. 2, they may also extend into the substrate
102 at an acute angle to the perpendicular direction if so
desired.
[0048] The described configuration of the apertures 120,123,124
along the substrate 102 of the buffing pad 100 has been shown to
provide a number of unexpected advantages in a polishing operation.
First, the apertures 120, by virtue of their larger average size
relative to the apertures 123,124, significantly reduce drag
resistance as the center of the rotating pad passes over the
surface being polished. Second, the generally larger apertures 120
also reduce the degree of buckling of the pad 100 that occurs as a
result of uneven friction between the front surface 104 and the
surface being polished. As a result, significantly less jerking and
jumping of the rotary pad occurs during operation. The alleviation
of jerking and jumping in turn improves operator control and
reduces strain and fatigue experienced by the operator.
[0049] Further advantages are provided by the concentric circular
rings 140 located along the outer region 116. By partitioning the
front surface 104 of the pad 100 into four distinct sections, the
rings 140 of apertures 124 help isolate localized deformation of
the pad 100 that occur during a buffing operation within its
particular section. This advantageously prevents propagation of
deformation across the entire front surface 104 and again results
in a more manageable and predictable buffing operation.
[0050] Use of apertures of larger sizes in areas near the center of
the pad 100 also provides superior performance compared with
conventional buffing pads. Particularly, these pads 100 provide
both increased cut rate and finer finish responses compared with
conventional pads in which the average size of the apertures is
generally uniform across the front surface. This is also an
unexpected advantage, because superior cut and finer finish are
often inversely related and it is generally difficult to realize
both qualities simultaneously. A buffing pad which provides both a
superior cut and finer finish allows a polishing job to be
completed more efficiently and with less opportunity for operator
error.
[0051] The apertures 120,123,124 in the substrate 102 may be
provided using any number of manufacturing methods known to the
skilled artisan. In some embodiments, the apertures 120,123,124 are
formed by providing a suitable substrate 102, then applying a
post-processing method to form the apertures. Examples of such
post-processing methods include thermal embossing methods such as
those described in U.S. Patent Publication No. 2007/0254567
(McLain) or water jet cutting as described in issued U.S. Pat. No.
5,527,215 (Rubino et al.) and U.S. Patent Publication No.
2007/0204420 (Hornby et al.). Alternatively, conventional methods
such as engraving, mechanical boring, or cutting are also
possible.
[0052] In one preferred method of making the pad 100, a laser is
used vaporize the foam to produce the apertures 120,123,124. Laser
cutting leaves behind a minimum amount of debris, and provides the
flexibility for an operator to make nearly any configuration of
apertures desired. Generally, the desired shape can be programmed
into a computer aided drafting (CAD) system that interfaces with
software that controls the position and intensity of the laser. The
methods are advantageous because they are robust, versatile, and
cost effective.
[0053] Alternatively, the apertures 120,123,124 may be provided in
situ without need for a post-processing step. For example, the
apertures 120,123,124 can be formed by casting and curing of the
foam in a suitably shaped mold.
[0054] FIG. 5 shows a buffing pad 200 according to another
embodiment of the invention. Like buffing pad 100, the buffing pad
200 has a substrate 202 with a flat, circular front surface 204
extending across the substrate 202. The buffing pad 200 further
includes apertures 220,223,224 in a pattern having characteristics
similar to the respective apertures 120,123,124 of the buffing pad
100. In an exemplary embodiment, the buffing pad 200 has a diameter
of about 3.25 inches (8.26 cm) and a thickness of about 0.88 inches
(2.2 cm). Other aspects of the buffing pad 200 are analogous to
those already described for pad 100 and shall not be repeated.
EXAMPLES
Comparative A.
[0055] A loop backed planar, open cell, polyurethane foam buffing
pad, 31/4-inches diameter by 1-inch depth (8.26 by 2.54 cm), was
obtained under the trade designation "VP FG 3570-ID, Anthrazit",
from Woodbridge FoamPartner Company, Chattanooga, Tenn. The foam
had an average density of 31.4 kilograms per cubic meter
(kg/m.sup.3) and 40% Compression Load Deflection (CLD) of 8.47
kiloPascals (kPa).
Comparative B.
[0056] The face side of the foam buffing pad described in
Comparative A, was formed into a convoluted pattern as described in
U.S. Pat. No. 4,962,562 (Englund et al.), the disclosure of which
is incorporated herein by reference. Convoluted square array
dimensions were 1.14 projections per square inch (0.18 projections
per square cm), with a peak-to-valley height of 0.16 inches (0.04
cm) and peak-to-peak distance of 0.88 inches (0.35 cm).
Comparative C.
[0057] The front side of the foam buffing pad described in
Comparative A was formed into a hexagonal channel array using an
Eagle CO.sub.2 Laser, Model No. 500, from LMI Technologies, Royal
Oak, Mich., according to the conditions listed in Table 1. The
pattern was similar to a commercially available foam buffing pad,
type "Hex-Logic", from Chemical Guys, Hawthorne, Calif.
TABLE-US-00001 TABLE 1 Hexagonal Channels Dimensions Width (mm) 3
Depth (mm) 2.5 Hexagon Dimension 10 (mm) Laser Settings Power (%)
10 Average Beam 0.0014 Diameter (mm) Mark Speed 445 (cm/second) No.
of Beam Sweeps 2
Example 1
[0058] The buffing pad substrate used in Comparative A was provided
and then a series of apertures were subsequently cut into the
exposed face of the planar foam sheet to provide the aperture
pattern shown in FIG. 5. The pattern cut into the face of the foam
includes the first apertures and both the first and second subsets
of the second apertures (hexagonal groupings and rings). This was
accomplished using the Eagle CO.sub.2 Laser operating according to
the conditions listed in Table 2.
TABLE-US-00002 TABLE 2 Second apertures First subset (hexagonal
Second subset First apertures groupings) (rings) Dimensions
Diameter (mm) 3 2 1 Depth (mm) 10 5.5 11 No. of Apertures 7 6
.times. 7 11 per radial inch (4.3 per radial cm) Laser Settings
Power (%) 15 10 10 Beam Diameter (mm) 1.97 1.97 1.97 Mark Speed
(cm/second) 508 635 635 No. of Beam Sweeps 3 1 2
Comparative D.
[0059] A loop backed planar, open cell, polyurethane foam
compounding pad, 8-inch diameter by 1-inch depth (20.3 by 2.54 cm),
having an average density of 28.7 kilograms per cubic meter
(kg/m.sup.3) and 25% CLD of 6.52 kiloPascals (kPa), obtained from
Pinta Foamtec, Inc., Minneapolis, Minn.
Comparative E.
[0060] The front side of the foam buffing pad Comparative D was
formed into a convoluted pattern as described in Comparative B,
wherein the peak-to-valley height was increased to 0.44 inches
(0.17 cm).
Comparative F.
[0061] The front side of the foam buffing pad Comparative D was
formed into a hexagonal channel array, as described in Comparative
C.
Example 2
[0062] The complete aperture pattern as shown in FIGS. 1-2 was
formed into the front side of foam buffing pad of Comparative D
according to the method described in Example 1. As in Example 1,
the first apertures and both first and second subsets of the second
apertures (hexagonal grouping and rings) were laser cut into the
face of the foam.
Comparative G.
[0063] A foam buffing pad was made as described in Example 2,
except only the second subset of the second apertures (rings) were
laser cut into the face of the foam.
Comparative H.
[0064] A foam buffing pad was made as described in Example 2,
except only the first subset of second apertures were laser cut
into the face of the foam.
Example 3
[0065] A foam buffing pad was made as described in Example 2,
except only the first apertures and first subset of second
apertures (hexagonal groupings) were laser cut into the face of the
foam.
Cut Test 1.
[0066] The foam buffing pad of Example 1 and Comparatives A-C, were
attached to a 31/4-inch (8.26 cm) diameter foam backup pad
available from 3M Company, St. Paul, Minn., under the trade
designation "3M Finesse-It Backup Pad, Part No. 84226". The backup
pad was then attached to an air driven pneumatic buffer, available
under the trade designation "Dyna Buffer #57240" from Dynabrade
USA, Clarence, N.Y., with a down weight of 5 pounds (2.27 kg), and
air pressure of 94 pounds per square inch (psi) (648.1 kiloPascals
(kPa)) at the face).
[0067] A pre-weighed 18 by 24-inch (45.7 by 61.0 cm) painted metal
test panel, type "APR 40577" obtained from ACT laboratories,
Hillsdale, Mich., was used as the test substrate. The test panel
had the following coatings: E-Coat ED6060; Primer 764204; Basecoat
542AB921 BLACK; Clearcoat RK8148". The panel was cleaned and dried
using a 50% by weight aqueous solution of isopropanol and a soft
lint-free cloth. The panel was then fixed horizontally in place and
10 grams of buffing compound, type "Finesse-it Purple Polish, Part
No. 51056", obtained from 3M Company, was applied to the center of
the panel. The entire panel uniformly buffed for 2 minutes, using
lateral motion and without applying substantial downward
hand-force, after which the panel was cleaned and dried as
described above. The buffing process was repeated 8 times.
[0068] Upon completion the panel was again wiped clean and dried as
described above, after which the panel was reweighed. Cut was
calculated as the difference between the initial and final weight
of the panel. Higher cut values are better.
Cut Test 2.
[0069] The foam buffing pads of Example 2 and Comparatives D-I,
were attached to an 8-inch (20.3 cm) diameter foam backup pad
available from 3M Company, St. Paul, Minn., under the trade
designation "3M Finesse-It Backup Pad, Part No. 5717", using an
adapter type "5710", also from 3M Company. The backup pad was then
attached to an electric buffer, available under the trade
designation "DeWALT DW849" from DeWALT Industrial Tool Company,
Baltimore, Md., with a down weight of 5 pounds (2.27 kg).
[0070] A pre-weighed 45.7 centimeter.times.61.0 centimeter (18
inch.times.24 inch) painted metal test panel, type "APR 51534(H)"
obtained from ACT laboratories, was cleaned and dried according to
the method described in Cut Test 1. The test panel had the
following coatings: E-Coat ED6060; Primer 765224EH; Basecoat
270AB921 BLACK; Clearcoat RK8148". 10 grams of rubbing compound,
type "Perfect-it Rubbing Compound, Part no. 6085", obtained from 3M
Company, was applied to the test panel and manually buffed for 1
minute at 1,400 revolutions per minute (rpm). The panel was cleaned
and dried as described above and the buffing process repeated four
more times, using successively less amounts of rubbing compound of
8, 6, 5 and 4 gram, respectively. After the fifth buffing step the
test panel was cleaned, dried and reweighed, and the cut in grams
determined. Each Example and Comparative was run in duplicate. As
before, higher cut values are better.
Haze Measurement.
[0071] Haze was measured using a haze gloss meter, Catalog no.
"AG-4601" from Byk-Gardener USA, Columbia, Md. Measurements were
made before and after Cut Test 1, at the approximate center of each
of the four quadrants of the test panel (that is, resulting in four
measurements), at a 20 degree measurement angle. Lower haze values
are better.
[0072] Comparative Samples A-C and Example 1 were subjected to Cut
Test 1 and Haze Measurement. Results are listed in Table 3. Tests
on Comparatives A and B, and Example 1, were run in triplicate.
TABLE-US-00003 TABLE 3 Sample Cut (grams)/Std. Dev. Haze/Std. Dev.
Test Panel Before Buffing Not Applicable 15.3 .+-. 1.9 Comparative
A 0.83 .+-. 0.34 30.4 .+-. 1.1 Comparative B 1.46 .+-. 0.01 23.2
.+-. 2.32 Comparative C 1.33 25.0 .+-. 2.0 Example 1 1.55 .+-. 0.04
19.05 .+-. 0.05
[0073] Comparatives D-F and Examples 2-3 was subjected to Cut Test
2, in duplicate. Results are listed in Table 4.
TABLE-US-00004 TABLE 4 Sample Average Cut (grams) Example 2 2.58
Comparative D 2.11 Comparative E 2.13 Comparative F 2.26
Comparative G 2.35 Comparative H 2.32 Example 3 2.37
[0074] All of the patents and patent applications mentioned above
are hereby expressly incorporated by reference. The embodiments
described above are illustrative of the present invention and other
constructions are also possible. Accordingly, the present invention
should not be deemed limited to the embodiments described in detail
above and shown in the accompanying drawings, but instead only by a
fair scope of the claims that follow along with their
equivalents.
* * * * *