U.S. patent application number 11/828270 was filed with the patent office on 2008-01-24 for discontinuous abrasive particle releasing surfaces.
This patent application is currently assigned to Sierra Madre Marketing Group. Invention is credited to Bola Ajere, Fred Miekka.
Application Number | 20080020678 11/828270 |
Document ID | / |
Family ID | 38972025 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080020678 |
Kind Code |
A1 |
Miekka; Fred ; et
al. |
January 24, 2008 |
Discontinuous Abrasive Particle Releasing Surfaces
Abstract
Discontinuous abrasive particle releasing surfaces are disclosed
that may be employed in low speed wet grinding, sanding, and
polishing operations. The discontinuous abrasive surfaces of the
present invention may consist of abrasive containing protrusions
attached to rigid or flexible surfaces or alternatively may be
comprised of closed cell foam compositions impregnated with
abrasive materials such as aluminum oxide. The voids present in the
discontinuous abrasive surfaces of the present invention serve to
hold water and remove debris. The resulting discontinuous abrasive
particle releasing surfaces are long lasting and may be made low in
cost.
Inventors: |
Miekka; Fred; (Arcadia,
CA) ; Ajere; Bola; (Arcadia, CA) |
Correspondence
Address: |
DENIS KHOO
9729 CAMINO REAL
ARCADIA
CA
91007
US
|
Assignee: |
Sierra Madre Marketing
Group
Arcadia
CA
|
Family ID: |
38972025 |
Appl. No.: |
11/828270 |
Filed: |
July 25, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11503058 |
Aug 14, 2006 |
|
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11828270 |
Jul 25, 2007 |
|
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60764110 |
Feb 1, 2006 |
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60818571 |
Jul 5, 2006 |
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Current U.S.
Class: |
451/28 ; 451/532;
451/540 |
Current CPC
Class: |
B24D 15/045 20130101;
B24D 15/02 20130101 |
Class at
Publication: |
451/028 ;
451/532; 451/540 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1. An abrasive article for wet application comprising: a backing
having at least one major surface; a material matrix attached to
said major surface, forming a discontinuous surface topography on
said major surface; and a plurality of abrasive particles embedded
within said material matrix, wherein said material matrix is
wearable by said abrasive particles.
2. The abrasive article for wet application of claim 1 wherein said
plurality of abrasive particles is dispersed in a substantially
uniform manner throughout said material matrix.
3. The abrasive article for wet application of claim 1 wherein said
discontinuous surface topography is comprised of a plurality of
protrusions.
4. The abrasive article for wet application of claim 1 wherein said
discontinuous surface topography is comprised of a plurality of
cavities.
5. The abrasive article for wet application of claim 1 wherein said
material matrix wearing away causes said plurality of abrasive
particles to release in free form, whereby said plurality of
abrasive particles released in free form facilitate in wearing down
said material matrix.
6. The abrasive article for wet application of claim 5 wherein said
plurality of abrasive particles released in free form, wear away
said material matrix, forming a wet abrasive paste, whereby said
wet abrasive paste keeps said plurality of abrasive particles
active on the working surface.
7. The abrasive article for wet application of claim 1 wherein said
backing is rigid.
8. The abrasive article for wet application of claim 1 wherein said
backing is flexible.
9. The abrasive article for wet application of claim 8 wherein said
flexible backing is fabric.
10. The abrasive article for wet application of claim 8 wherein
said flexible backing is a glove.
11. The abrasive article of wet application of claim 1 wherein said
plurality of abrasive particles comprise of material selected from
the group consisting of aluminum oxide, silicon carbide, alumina
zirconia, diamond, ceria, cubic boron nitride, garnet, ground
glass, quartz, and combinations thereof.
12. An abrasive article for wet application comprising: a rigid
polymeric closed cell foam substrate having at least one major
surface, said at least one major surface having a discontinuous
surface topography; a plurality of abrasive particles dispersed
within said rigid polymeric closed cell foam, wherein said rigid
polymeric closed cell foam is wearable at said major surface by
said plurality of abrasive particles.
13. The abrasive article for wet application of claim 12 further
comprising means for softening said major surface upon exposure to
water, whereby a cushion is formed for said plurality of abrasive
particles.
14. The abrasive article for wet application of claim 12 wherein
said rigid polymeric closed cell foam contains a hydrophilic
additive, whereby said hydrophilic additive facilitates in
softening of said major surface upon exposure to water.
15. The abrasive article for wet application of claim 14 wherein
said hydrophilic additive is chemically bound to polymers within
said rigid polymeric closed cell foam.
16. The abrasive article for wet application of claim 12 wherein
said rigid polymeric closed cell foam comprises of a condensation
polymer.
17. The abrasive article of claim 16, wherein said condensation
polymer has a reduced molecular weight formed by polymerization
using an excess of at least one reactant, whereby said reduced
molecular weight condensation polymer facilitates in softening of
said major surface upon exposure to water.
18. The abrasive article of claim 17 wherein said excess reactant
is hydrophilic.
19. The abrasive article for wet application of claim 12 wherein
said major surface wears away, revealing a renewed surface having a
discontinuous surface topography.
20. The abrasive article for wet application of claim 19 wherein
said rigid polymeric closed cell foam contains a water soluble
material, whereby said water soluble material facilitates in
wearing away of said major surface upon exposure to water.
21. The abrasive article for wet application of claim 19 wherein
said rigid polymeric closed cell foam wearing away causes said
plurality of abrasive particles to release in free form, whereby
said plurality of abrasive particles released in free form
facilitates in wearing away of said major surface.
22. The abrasive article for wet application of claim 21 wherein
said plurality of abrasive particles released in free form, wear
away said rigid polymeric closed cell foam, forming a wet abrasive
paste, whereby said wet abrasive paste keeps said plurality of
abrasive particles active on the working surface.
23. The abrasive article for wet application of claim 12 wherein
said plurality of abrasive particles when released in free form
create additional voids in said major surface and said plurality of
abrasive particles, after release, abrade said major surface,
whereby said plurality of abrasive particles released in free form
facilitate in wearing away of said major surface.
24. The abrasive article for wet application of claim 12 wherein
said discontinuous surface topography is comprised of a plurality
of voids.
25. The abrasive article for wet application of claim 12 wherein
said plurality of abrasive particles are dispersed in a
substantially uniform manner throughout said rigid polymeric closed
cell foam.
26. The abrasive article for wet application of claim 12 wherein
said rigid polymeric closed cell foam forms the article in its
entirety, whereby no separate backing or handle is required.
27. The abrasive article of wet application of claim 12 wherein
said plurality of abrasive particles comprise of material selected
from the group consisting of aluminum oxide, silicon carbide,
alumina zirconia, diamond, ceria, cubic boron nitride, garnet,
ground glass, quartz, and combinations thereof.
28. An abrasive article for wet application comprising: a matrix
material with a plurality of hollow microspheres embedded
throughout having at least one major surface, said at least one
major surface having discontinuous surface topography; and a
plurality of abrasive particles dispersed within said matrix
material, wherein said matrix material is wearable at said major
surface by said plurality of abrasive particles.
29. The abrasive article for wet application of claim 28 wherein
further comprising means for softening said major surface upon
exposure to water, whereby forming a cushion for said plurality of
abrasive particles.
30. The abrasive article for wet application of claim 28 wherein
said plurality of hollow microspheres are comprised of one or more
polymers.
31. The abrasive article of wet application of claim 28 wherein
said plurality of abrasive particles comprise of material selected
from the group consisting of aluminum oxide, silicon carbide,
alumina zirconia, diamond, ceria, cubic boron nitride, garnet,
ground glass, quartz, and combinations thereof.
32. A method of abrading an object comprising the steps of: wetting
said object; sliding a major surface of an abrasive article over
said object, wherein said abrasive article is comprised of a
material matrix with a plurality of abrasive particles dispersed
throughout and said major surface has a discontinuous surface
topography; softening said major surface upon exposure to water;
wearing away of said abrasive article at said major surface; and
releasing said plurality of abrasive particles in free form.
33. The method of abrading an object as defined in claim 32 further
comprising the step of embedding said plurality of abrasive
particles released in free form into the softened major
surface.
34. The method of abrading an object as defined in claim 32 further
comprising the step of producing a renewed surface also having a
discontinuous surface topology
35. The method of abrading an object as defined in claim 32 further
comprising the step of exposing and releasing deeper plurality of
abrasive particles when said abrasive article wears away at said
major surface.
36. The method of abrading an object as defined in claim 32 further
comprising the step of abrading said major surface by said
plurality of abrasive particles released in free form.
Description
[0001] This is a Continuation-in-Part of application Ser. No.
11/503,058 filed Aug. 3, 2006, which claimed priority to
provisional application No. 60/764,110 filed on Feb. 1, 2006 and
provisional application No. 60/818,571 filed on Jul. 5, 2006.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to abrasive materials and surfaces.
More particularly this invention relates to discontinuous abrasive
surfaces employing discrete areas containing abrasive particles
that are continuously released in free form during wet low speed
sanding, grinding, and polishing operations. The discontinuous
abrasive surfaces of the present invention may consist of abrasive
containing protrusions attached to rigid or flexible surfaces, a
raised portion and a cavity portion, or alternatively may be
comprised of closed cell foam compositions impregnated with
abrasive materials such as aluminum oxide. The voids present in the
discontinuous abrasive surfaces of the present invention serve to
hold water and remove debris.
[0004] 2. Description of the Related Art
[0005] There are numerous methods that may be employed to sand
surfaces. One of the more common methods employs sand paper. Sand
paper is a thin sheet material usually made of paper that has an
abrasive material securely bonded onto one side. Despite its name,
the abrasive is rarely if ever sand. Commonly used abrasives such
as aluminum oxide and silicon carbide are significantly harder than
sand and are therefore more effective. This may be especially true
when sanding hard materials such as glass or steel.
[0006] Sand paper may be used by hand. This process is often
referred to as hand sanding. The process of hand sanding involves
using manual labor to repeatedly slide the sand paper back and
forth and/or in a circular motion over the surface until smooth.
Numerous textures of abrasives are available. Often sanding starts
out with a relatively course grade of sand paper of about 80 grit
followed by finer grades of several hundred grit to finish the
job.
[0007] One drawback often associated with sand paper is the
production of dust. Sanding surfaces often produces dust that clogs
the sand paper and may create an inhalation hazard as well. This is
especially true for sanding hazardous materials such as lead paint.
One way to alleviate this problem is by using wet or dry Emery
cloth. Wet or dry Emery cloth is an abrasive coated cloth having a
wide variety of grades. It is designed for use with water thereby
reducing clogging effects and significantly or even completely
eliminating the production of air bourn dust.
[0008] Another drawback with using sand paper is the tendency for
the abrasive to become dull and fall off from the sand paper
backing surface.
[0009] Sanding by hand using sand paper is not always practical
owing to the amount of labor required. This is especially true for
large jobs that may take a long time resulting in fatigue.
[0010] In order to alleviate the worker fatigue issue in hand
sanding operations, numerous power sanding techniques and/or
equipment have been developed. Drum sanding, belt sanding, disc
sanding, and orbital sanding are commonplace. These standard power
sanding tools often employ some form of sand paper and therefore
often suffer from many of the previously mentioned drawbacks. In
particular is the need to change the sanding surface at regular
intervals.
[0011] Numerous modifications to ordinary sand paper have been made
in order to improve the overall process. For example, sand paper
having a lowered surface density of abrasive particles is
available. This particular sand paper is made by 3M Corporation of
ST. Paul Minn. and is designed for use in sanding relatively soft
materials that quickly gum up ordinary sand paper. Significant
improvements in sand paper life may be realized by reducing the
tendency of particulate matter to clog the needed spaces between
adjacent abrasive particles.
[0012] Another improvement that may be made to ordinary sand paper
involves the use of flexible and conformable foam backing. Such
backing materials allow the sand paper to conform to surface
contours thereby more rapidly smoothing contoured surfaces.
Individual pieces of sand paper may be applied to foam pads or
conversely, foam pads having previously attached sand paper may be
employed. For example, Finishing Buddies (Mona Lisa Products 10770
Moss Ridge Road Houston, Tex., 77043) is a complete sanding tool
kit consisting of a steel wool pad, oval sanding disc, and coarse,
medium, and fine sanding pads. The oval pad is relatively rigid,
and the three other sanding pads have a softer foam backing that
has a greater degree of flexibility. This sanding kit is designed
for slow hand sanding and finishing operations.
[0013] There are numerous flexible sanding surfaces, components,
and articles comprised of abrasive materials fixedly attached to
flexible foam backings. Of particular interest is a sanding system
employing a relatively thin rigid foam backing disclosed in U.S.
Pat. No. 6,923,840 and assigned to 3M Innovative Properties
Company, St. Paul Minn. (US). U.S. Pat. No. 6,923,840 discloses a
flexible abrasive product comprised of an open cell foam backing, a
foraminous barrier coating, and a shaped foraminous abrasive
coating. The top abrasive coating is discontinuous and allows for
holding lubricants such as water as well as spaces for removal of
debris.
[0014] U.S. Pat. No. 6,949,128 also assigned to 3M, discloses a
method for making a foam backed abrasive article having embossed
raised areas.
[0015] U.S. Pat. No. 3,401,490 discloses a method for forming an
abrasive article having a resiliently yielding open cell meltable
base which is passed under a heated roll to melt the surface to a
desired depth followed by application of abrasive particles to the
melted surface. The result is a flexible foam based abrasive
article capable of following irregular, uneven, or sunken
surfaces.
[0016] U.S. Pat. No. 6,997,794 by James Matthew Pontieri discloses
a disposable sanding device fabricated as a continuous rope like
article adapted for selective segmentation. This device may employ
a foam central portion along with an abrasive outer portion. In
particular the flexible cylindrical geometry illustrated in several
embodiments of the invention lends itself to the hand sanding of
difficult to reach contours and may prove especially useful in
woodworking applications.
[0017] There are numerous flexible foam based cleansing and
scouring pads having added abrasive materials. An example of this
can be found in U.S. Pat. No. 3,377,151. U.S. Pat. No. 3,377,151
discloses a method for making flexible resilient cleansing and
scouring pads having an abrasive surface. A thermoplastic foam web
material is hot laminated to abrasive web material. In addition,
one or more cleansing materials may be added.
[0018] U.S. Pat. No. 3,619,843 discloses sponges having dry
impregnated materials. In this invention, impregnated sponges are
prepared by a process that deposits particulate material on one
surface of the sponge and subsequently pierces the sponge with
spikes to form crevices followed by drawing particulate material
into the crevices. The result is a modified sponge suitable for
surgical and sanitizing applications.
[0019] Also of interest are flexible open cell foam scouring and
cleaning pads having numerous protrusions. These pads are disclosed
in U.S. Pat. No. 4,055,029 by Heinz Kalbow, Lichgasse. The flexible
pad has numerous protrusions on the working surface having an
abrasive layer. U.S. Pat. No. 4,111,666 also by Heinz Kalbow
discloses a method of manufacturing flexible abrasive cleaning pads
along with improvements in tear resistance.
[0020] U.S. Pat. No. 4,421,526 discloses polyurethane foam cleaning
pads composed of a densified flexible sponge like polyurethane foam
material impregnated with various cleansing additives. Excessive
mixing of the freshly blended polymers inhibits foam formation long
enough to add the cleansing ingredients. The resulting pads have
added strength due to collapsed, ruptured, and distorted cells
along with fibers that result from the specific mixing process
employed. The result is an unusually strong dense flexible cleaning
pad capable of absorbing substantial amounts of water that releases
additives along with absorbed water on gentle squeezing.
[0021] U.S. Pat. No. 4,594,362 discloses a dry type textile
cleaning article comprised of a friable hydrophilic polyurethane
foam with incorporated abrasive particles as well as other
additives. The abrasive particles are chemically bonded to the foam
using silane coupling agents thereby reducing their tendency to
separate from the mass and subsequently damage cloth material.
[0022] While the above described examples of foam based abrasive
articles provide a wide variety of uses, there exists a need in the
art for lightweight semi-rigid or rigid closed cell foam abrasive
articles suitable for hand and/or low speed wet sanding, and/or wet
grinding, and/or wet polishing operations.
[0023] Many of the above described examples outline the use of foam
with abrasive materials in order to achieve certain advantageous
and desirable properties. Still others outline some of the more
simple methods and materials commonly employed in sanding,
grinding, and polishing operations. While generally effective for
sanding, grinding, and polishing, there exists a need in the
industry for further improvements in low speed wet sanding,
grinding, and polishing operations. For example, lapping is a
process that uses special equipment to grind surfaces to a high
degree of flatness. Unfortunately, this equipment tends to be
expensive and bulky. In addition, producing a good flat grind may
require certain acquired skills to master. This results in
difficulties for small shops and individuals in the hobby field in
grinding surfaces flat.
[0024] Another example where further improvements in low speed wet
sanding, grinding, and polishing operations may be realized is in
the area of sanding cloths. Flexible abrasive cloth materials such
as emery rapidly become dull and shed abrasive particles. Because
of this, sanding operations often require several pieces of emery
cloth to complete. While making discrete zones of attached adhesive
may serve to reduce the tendency of debris to build up in the
sanding surface, the issue of rapid dulling and shedding of surface
abrasive particles still remains a major issue to be resolved.
[0025] Finally, flexible abrasive surfaces employing foam have
certain added benefits that may be realized in numerous
applications. Many of the earlier patents referenced in this
application fall under this class of abrasive surfaces.
[0026] Despite numerous advancements in the field of abrasives
there is a need for discontinuous abrasive particle releasing
surfaces for wet sanding, grinding, and polishing operations.
[0027] It is an object of this invention to provide wet low speed
sanding, grinding and polishing surfaces.
[0028] It is a further object of this invention to provide numerous
grades of wet sanding, grinding, and polishing surfaces.
[0029] It is a further object of this invention to provide wet
sanding, grinding, and polishing surfaces resistant to excess build
up of debris
[0030] It is a further object of this invention to provide wet
sanding, grinding, and polishing surfaces in both rigid and
flexible forms.
[0031] It is a further object of this invention to provide wet
sanding, grinding, and polishing surfaces that are low in cost.
[0032] It is a further object of this invention to provide simple
methods for producing wet sanding, grinding, and polishing
surfaces.
[0033] Finally it is an object of this invention to provide wet
sanding, grinding, and polishing surfaces that may be used for
extended periods of time without wearing out.
SUMMARY OF THE INVENTION
[0034] The present invention is for discontinuous abrasive surfaces
employing discrete areas containing abrasive particles that are
continuously released in free form during wet low speed sanding,
grinding, and polishing operations. The discontinuous abrasive
surfaces of the present invention may consist of abrasive
containing protrusions attached to rigid or flexible surfaces, a
raised portion and a cavity portion, or alternatively may be
comprised of closed cell foam compositions impregnated with
abrasive materials such as aluminum oxide. The closed cell foam
compositions of the present invention may soften with water to
provide a cushioning layer for abrasive particles at the working
surface. The voids present in the discontinuous abrasive surfaces
serve to hold water and remove debris.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] A more complete appreciation of the invention and many of
the advantages thereof will be readily obtained as the same becomes
better understood by reference to the detailed description when
considered in connection with the accompanying drawings,
wherein:
[0036] FIG. 1 shows a lapping surface suitable for grinding
surfaces flat.
[0037] FIG. 2 shows a blank grinding block having an adhesive zone
for mounting disposable lapping surfaces.
[0038] FIG. 3 shows a lapping block consisting of a lapping surface
adhered to the top of a flat surfaced block.
[0039] FIG. 4 shows a cross sectional view of numerous surface
protrusions embedded with hard abrasive particles.
[0040] FIG. 5 shows a cross sectional view of numerous flat topped
surface protrusions embedded with hard abrasive particles.
[0041] FIG. 6 shows a sectional view of a low speed sanding disc
for a rotary tool.
[0042] FIG. 7 shows a hand held abrasive foam sanding block of the
present invention.
[0043] FIG. 8 shows a hand held abrasive article made entirely out
of the foam based abrasive of the present invention.
[0044] FIG. 9 shows a sectional view of a low speed wet abrasive
foam disc for use with a rotary tool.
[0045] FIG. 10 shows an abrasive fabric employing polymeric resin
protrusions of the present invention embedded with coarse aluminum
oxide.
[0046] FIG. 11 shows an abrasive loaded polymeric resin protrusion
having a top surface portion containing a pattern of grooves and
ridges.
[0047] FIG. 12 shows an abrasive fabric glove having numerous
abrasive protrusions attached to working surfaces in accordance
with the present invention.
[0048] FIG. 13 shows a sectional view of a low speed wet sanding
disc for a rotary tool having a plurality of layers of surface
protrusions comprised of hard abrasive particles dispersed within a
softer material matrix.
[0049] FIG. 14 shows a sectional view of cloth material for low
speed wet sanding having a plurality of layers of surface
protrusions comprised of abrasive particles dispersed within a
softer material matrix.
[0050] FIG. 15 shows a lapping surface of the present suitable for
grinding surfaces flat having numerous cavities for holding water,
and removal of debris.
[0051] FIG. 16 shows a sectional view of an abrasive material for
wet application comprised of hard abrasive particles embedded
within a softer polymeric matrix material along with added hollow
micro-spheres.
[0052] FIG. 17 shows a sectional view of abrasive foam material
having a softened top surface resulting from exposure to water.
[0053] FIG. 18 shows a sectional view of abrasive foam material
having added water soluble particles that facilitates wear on
exposure to water.
[0054] FIG. 19 shows a foam abrasive article that may be used to
wet sand automotive surfaces.
[0055] FIG. 20 shows an abrasive pad for wet scouring applications
having 400 grit silicon carbide abrasive particles along with
hollow polymeric micro-spheres embedded in a water softening
polymeric matrix.
DETAILED DESCRIPTION OF THE INVENTION
[0056] FIG. 1 shows a lapping surface suitable for grinding
surfaces flat. Lapping surface 2 is comprised of numerous
protrusions 4 extending upward from rigid backing laminate 6.
Protrusions 4 may take the form of numerous shapes including
polygons such as squares and hexagons, spheres, such as those shown
in FIG. 4, and/or modified spheres such as those shown in FIG. 5.
Furthermore, the top surfaces of protrusions 4 may have added
grooves as shown in FIG. 9. It should be noted that protrusions 4
are separated from each other and therefore may be considered to be
discontinuous providing lapping surface 2 with a discontinuous
surface topography. The spaces formed between individual
protrusions 4 provide means for holding water and for the rapid
removal of debris. Protrusions 4 may be comprised of a relatively
soft matrix material such as a polymer impregnated with abrasive
particles possessing a degree of hardness significantly greater
than that of the matrix material itself. The result is an abrasive
particle releasing surface for low speed wet lapping operations
providing good abrasive properties. It should be noted that it may
be desirable to control the hardness of the protrusions themselves.
Opposite first major surface 2 of rigid backing laminate 6 is a
second major surface (not shown) this second major surface may have
mounting hardware and/or materials such as pressure sensitive
adhesives to facilitate mounting to a more rigid flat substrate
surface.
[0057] Polymeric resin based materials such as epoxy may be cast in
a suitable mold. For example, a laminate construction may be
assembled having numerous protruding spherically shaped particles.
The laminate may then be treated with a suitable release coating
and used to make a silicone rubber mold. Once the mold is cured,
the laminate may then be removed. The now vacant mold may then be
used to cast a lapping surface. Abrasive powder may be first
sprinkled evenly in the numerous voids in the mold that are to
become protrusions. Abrasive loaded polymeric resin such as epoxy
may then be added on top of the already existing free abrasive
particles residing within the individual discrete protrusion
cavities within the mold. If desired, further addition of abrasive
particles to the epoxy resin in the mold may then be carried out
followed by allowing the above described composition to set into a
hard mass.
[0058] West system 105 epoxy resin (West Systems Inc. PO Box 665
Bay City, Mich. 48707 USA) has been used for producing working
prototypes employing aluminum oxide abrasive. It should be noted
that aluminum oxide is a dense material and therefore tends toward
settling to the bottom of the mold. Other dense abrasive materials
include silicon carbide, zirconia, diamond, ceria, cubic boron
nitride, garnet, ground glass, quartz, and combinations thereof.
Since the bottom of the mold represents the tops of the protrusions
in the final part, this method of manufacture may be employed to
keep numerous abrasive particles on the outer exposed surfaces of
the protrusions themselves. This particular configuration may help
to facilitate the initial release of abrasive particles. This
technique may be employed to improve the initial release of
abrasive particles on first time use. Once the process of abrasive
particle release starts, it becomes self sustaining.
[0059] Alternatively, it may be desirable to have the abrasive
particles dispersed uniformly throughout the material matrix. A
high loading density of abrasive particles within the uncured resin
may help to keep abrasive particles more uniform throughout the mix
by forming a paste. Rapid cure times and high resin viscosity may
also contribute to the abrasive particles being dispersed in a
substantially uniform manner throughout the material matrix.
[0060] When abrasive particles are uniformly distributed within the
material matrix, the new surface may not have suitable initial
abrasive properties owing to a glaze over the abrasive particles.
In order to provide initial aggressive abrasive properties this
glaze may be removed by sanding, sand blasting, cutting, or
grinding.
[0061] During use, abrasive particles embedded within the material
matrix become dislodged and contribute to the overall process of
wearing down lapping surface 2. These abrasive particles may fall
away from the working surface relatively quickly or remain on the
working surface continuously grinding away at lapping surface 2.
The grinding away of lapping surface 2 may help to facilitate the
exposure and subsequent release of more abrasive particles from the
material matrix. Additionally, the released abrasive particles may
grind away at the substrate surface (not shown) that is lapped.
This may result in the formation of a paste at the working surface
during wet lapping. This paste may contain abrasive particles in
free form and finely divided particles from both lapping surface 2
and the substrate surface (not shown). Paste formation may help to
keep the abrasive particles active on the working surface and
depends on numerous factors. These factors include surface
topography, rate of lapping, and the amount of water used in the
process. Depending on the process used, it may be desirable to
enhance or retard the formation of abrasive paste at the working
surface.
[0062] FIG. 2 shows a blank grinding block having an adhesive zone
for mounting disposable lapping surfaces. Block 8 is shown having
adhesive pattern 10 on top surface 12. Top surface 12 of block 8 is
flat and rigid and therefore helps to maintain flatness of the
final assembly. Top surface 12 of block 8 becomes a rigid backing
when lapping surface 2 of FIG. 1 is attached to form lapping block
14 shown in FIG. 3.
[0063] FIG. 3 shows a lapping block abrasive article. Lapping block
14 consists of top exposed abrasive particle lapping surface
portion 20 (lapping surface 2 of FIG. 1) attached to top flat
surface portion 18 of base block portion 16. Exposed abrasive
particle releasing lapping surface portion 20 is shown to be larger
in area than side surface portion 16 and therefore may be
considered a first major surface of lapping block 14. Lapping block
14 has a second major surface (not shown) oppositely facing first
major surface 20. Lapping block 14 is shown having side surface
portion 16 and top flat surface portion 18. Also shown is
disposable lapping pad 20 attached to top surface 18 of block
16.
[0064] Lapping block 14 is suitable for lapping small articles
flat. The article may be glued to a holder and lapped in a circular
motion by hand, or alternatively lapped at a relatively slow rate
by machine. Some articles may also be held directly by hand and
subsequently lapped flat. In many instances water in pure form or
with special additives may be employed in the process. Generally
speaking the lapping surfaces of this invention will retain water
in the voids between surface protrusions. Employing water as a
lubricant may also help to flush debris from the area being used.
When finished, the lapping surface may be cleaned of residual
debris with running water. When the lapping surface portion 20 of
lapping block 14 becomes worn out, it can be replaced at a
reasonable cost. Removable attachment means such as pressure
sensitive adhesives may be employed to achieve this end.
[0065] FIG. 4 shows a cross sectional view of numerous surface
protrusions shown in discontinuous arrangement comprised of
abrasive particles dispersed within a softer material matrix such
as epoxy resin. Laminate backing portion 22 is shown along with
attached protrusions 24. Attached protrusions 24 are shown having
abrasive particles 25 embedded into softer material matrix portion
27.
[0066] FIG. 5 shows a cross sectional view of numerous protrusions
having a flat top surface geometry shown in discontinuous
arrangement comprised of abrasive particles dispersed within a
softer material matrix such as epoxy resin. Laminate backing
portion 26 is shown along with attached protrusions 28. Attached
protrusions 28 are shown having abrasive particles 29 embedded into
softer material matrix portion 31.
[0067] FIG. 6 shows a sectional view of a low speed sanding disc
for a rotary tool. Abrasive particle releasing disc 33 is shown
having abrasive releasing first major top surface portion 37 along
with rigid backing portion 35 and central hole 39 for mounting to a
shaft (not shown). Top abrasive releasing surface portion 37 is
comprised of numerous protrusions 41 fixedly attached to rigid
backing portion 35. Protrusions 41 are comprised of hard abrasive
particles dispersed within a softer material matrix. Protrusions 41
are shown in greater detail in FIGS. 4 and 5. Bottom surface
portion 47 of rigid backing portion 35 may be regarded as a second
major surface portion.
[0068] Abrasive particle releasing disc 33 is suitable for wet
rotary sanding operations. A shaft may be attached using central
hole 39 and a threaded screw. The shaft may be subsequently fitted
into the chuck of a low speed rotary tool such as a drill. A
relatively low speed of about 50 to 500 RPM may be employed to wet
sand numerous surfaces. It should be noted that high RPM conditions
of 1000 or more may result in excess loss of water employed in wet
sanding operations.
[0069] FIG. 7 shows a hand held abrasive foam sanding block of the
present invention for wet low speed sanding, grinding, and
polishing operations. Abrasive foam block 30 is shown having side
portion 32 along with exposed abrasive particle releasing surface
portion 34. Side portion 32 has a thin skin over the surface as a
result of the molding process used to prepare abrasive foam block
30. Exposed abrasive particle releasing surface portion 34 is shown
having closed foam cells 36 that have been severed by a sharp knife
(not shown) and are therefore exposed. Exposed closed foam cells 36
are made of a rigid material such as polyurethane in order to
maintain a rigid geometry during use and form a discontinuous
surface for holding water and removing debris during wet sanding,
grinding, and polishing operations. The closed cell foam material
of exposed abrasive particle releasing surface portion 34 is shown
to be larger in area than side surface portion 32 and therefore may
be considered a first major surface of abrasive foam block 30. A
second major surface (not shown) is on the opposite side from
exposed particle releasing surface portion 34 of abrasive foam
block 30. Surface portion 34 provided by exposed closed foam cells
36 may be considered a major surface having a discontinuous surface
topography. A plurality of abrasive particles dispersed within
abrasive foam block 30 are released from particle releasing surface
portion 34 during use. Abrasive particles released from surface
portion 34 during use may facilitate the further wearing away of
surface portion 34 thereby releasing more abrasive particles.
[0070] FIG. 8 shows a hand held abrasive article made entirely out
of the discontinuous rigid closed cell foam based abrasive material
of FIG. 7. Hand held abrasive article 38 is shown having bottom
portion 40 along with handle portion 42. Also shown are handle
mounts 44 used to attach handle portion 42 to bottom portion 40. It
should be noted that hand held abrasive article 38 may be one
continuous piece consisting of abrasive foam material that has been
formed in a single operation in a suitable mold (not shown). It
should also be noted that hand held abrasive article may be adhered
to a handle of different material composition and shape. Exposed
discontinuous hard abrasive particle releasing surface 49 of hand
held abrasive article 38 forms a first major surface and may be
used for wet sanding, grinding, and polishing operations. Second
major surface 51 is shown opposite of first major surface 49.
Second major surface 43 serves as the attachment surface for handle
42 using handle mounts 44.
[0071] The abrasive foam compositions of the present invention are
intended for low speed wet mechanical as well as wet hand sanding,
grinding, and polishing operations. In general, no reinforcement is
needed and the compositions may be adjusted to attain desirable
levels of rigidity, strength, and rate of wear. Various
compositions may be used with different foam densities. The foam
materials used in the present invention may be formed from numerous
polymeric materials, however special attention will now be paid to
polyurethane pour foam compositions.
[0072] Polyurethane pour foam comprises a class of two component
reactive foaming agents that when combined react with each other to
polymerize and produce gaseous products during the polymerization
process. The result is polyurethane foam. The polyurethane pour
foam compositions employed in the present invention are rigid
closed cell foams. The above described rigid polyurethane pour foam
compositions may be comprised of a first component isocyanate
containing prepolymer resin and a second component reactive
prepolymer resin containing numerous hydroxyl groups. The
isocyanate containing prepolymer resin may contain the higher
oligomers of methyl diisocyanate along with other reactive
diisocyanates such as 4,4-diphenylmethane diisocyanate. The second
component hydroxyl group prepolymer resin may contain reactive
oligomers having poly hydroxy functionality such as hydroxy
terminated polyglycol ethers. Rigid closed cell polyurethane pour
foam materials are commercially available in various foam
densities. Foam density may be considered to be the overall density
of the fully cured foam. Foam density is often given in units of
pounds per cubic foot. A low density 2 pound foam refers to a foam
having a cured density of 2 pounds per cubic foot. Such foam
materials are often employed where lightweight properties are
desirable. It should be noted that ordinary water has a density of
about 62 pounds per cubic foot and therefore a 2 pound foam would
be 1/30 the density of water.
[0073] Generally speaking, the lower the density of the foam, the
more rapid will be the wear rate of the abrasive foam composition.
Furthermore, the addition of excess abrasive materials to the
polymeric foam compositions of the present invention may result in
rapid wear degradation of the foam and associated rapid release of
abrasive particles. These abrasive particles may then find their
way into crevices thereby enhancing sanding, grinding and polishing
operations. In order to achieve this end, the abrasive materials
may each have a percent composition in the mix that has the above
described unique desirable properties. Discussed below are several
examples of the abrasive loaded polyurethane closed cell foam
compositions of the present invention.
[0074] It may be desirable to modify the hardness of the exposed
abrasive surface during wet operations. When a surface is wet
sanded with sand paper, the sand paper starts out having a high
degree of abrasive properties. This may be due to the abrasive
particles themselves having a high degree of exposure on the paper
surface. During sanding, these abrasive particles become dull.
Additionally, the spaces between abrasive particles tend to fill
with debris. After a relatively short timeframe the sand paper may
loose enough abrasive qualities to render it no longer useful. At
this point the sand paper is discarded and replaced with a new
piece to continue with the sanding operation. Because the sand
paper becomes less abrasive during use a fresh piece of sand paper
of the same grit will start sanding more aggressively than the last
used piece.
[0075] The abrasive foam compositions of the present invention may
differ substantially from sand paper. In particular, the grit used
in the foam composition behaves finer than if it were used to make
sand paper. For example, a foam sanding block of the present
invention having embedded within the foam material matrix a 220
grit silicon carbide abrasive may behave in a similar manner to
fresh sand paper of 400 grit or finer. Because of this, it is
important to bear in mind that the abrasive particle size used may
be sufficient to produce surface scratches. One way of alleviating
this issue is to render the working surface of the abrasive foam
somewhat soft and pliable on exposure to water. The depth of this
zone of softness need not be very deep so long as it provides a
cushion effect for the abrasive particles when they become exposed
and subsequently released.
[0076] With rigid closed cell polyurethane foam systems, this may
be accomplished by using a slight excess of one component. For
example, if a slight excess of the hydroxyl functional polyol
component is used, the molecular weight will be significantly
reduced and the resulting polymeric foam rendered somewhat
hydrophilic. The mixture need not be modified very much from the
ideal mixture quoted by the manufacturer. An excess of 10% of
either component will drastically affect molecular weight. This has
to do with the inherent properties of condensation polymers. In
order for a two component reactive condensation polymer to achieve
a high molecular weight, exact proportions need to be combined and
subsequently allowed to react to completion. If the mixture is off
by even a small amount, the reaction stops as soon as the first
reactant runs out. The result is limited molecular weight with the
polymeric chains terminated by the excess reactant. If the excess
reactant has hydrophilic properties (polyol reactant) then the
resultant polymer may exhibit increased hydrophilic properties.
Additionally, one or more reactive hydrophilic polyol additives may
be employed that chemically bond to polymers to modify the mix.
[0077] Under certain circumstances, polyurethane foam compositions
containing abrasive materials like silicon carbide may be produced
having a controlled limited molecular weight combined with
hydrophilic properties. Such compositions may be prepared by using
a slight excess of the polyol reactant that may be on the order of
a few percent to about 10 percent by weight of the mix.
[0078] Foam abrasive surfaces of articles made in this way may
soften on exposure to water rendering them somewhat compressible.
This compressibility may be used to provide a cushion effect to
abrasive particles released from the working surface during use.
This cushion effect may help to prevent deep surface scratches that
may otherwise be produced by rubbing abrasive particles between two
hard surfaces. It is important to bear in mind that the abrasive
foam compositions of the present invention have abrasive properties
resembling sand paper of a much finer grit than what was employed
in the mix. This effect may be quite substantial. The actual grit
size may be over twice as coarse as the rating of the sanding
surface. For example, an abrasive foam sanding surface of the
present invention having an abrasive particle size of 200 grit may
have similar abrasive properties to fresh sand paper having an
abrasive particle size of 400 grit or finer.
EXAMPLE 1
[0079] 5.0 grams of foam A (2 pound per cubic foot density pour
foam type rigid closed cell) polyurethane foam pre-polymer from
Plastic Depot (2900 San Fernando Blvd Burbank, Calif. 91054) were
placed into a small plastic cup. To this were added 5.0 grams of 70
grit aluminum oxide abrasive. The mixture was then stirred with a
wooden popsicle stick until uniform. In a separate plastic cup were
placed 5.0 grams of foam B polyurethane pre-polymer from the same
source as the foam A. To this were added 5.0 grams of 70 grit
aluminum oxide abrasive and the mixture stirred until uniform. Then
two mixtures were then combined and stirred until uniform. The
resultant mixture was then poured into a small polyethylene
container and allowed to foam and subsequently cure. The cured foam
composition was then allowed to sit overnight to stabilize. The
foam abrasive composition was then removed from the polyethylene
container. A small section of the outside portion was cut off with
a sharp knife to expose the foam cells underneath the outside skin.
A small amount of water was placed on this exposed surface. This
wet exposed surface was then used to sand the paint off of a soda
can. Removal of the thin paint layer occurred within a few seconds
leaving a scratched surface behind. It should be noted that the
aluminum surface underneath the paint did not bind up as often
happens with sand paper but rather tended to disperse in the water
and accumulate in the exposed voids of the foam.
EXAMPLE 2
[0080] The experiment of example 1 was repeated with increasing
concentrations of 70 grit aluminum oxide abrasive. At a
concentration of 70% by weight, the foam composition became
exceedingly weak and readily broke off when wet sanding rough
surfaces. The resulting particles formed a mixture of broken off
foam and free aluminum oxide abrasive. This particular mixture was
exceedingly efficient at sanding rough and irregular surfaces.
EXAMPLE 3
[0081] The experiment of example 2 was then repeated with 100 grit
aluminum oxide abrasive. It was found that a concentration of
aluminum oxide of 66% was required to attain similar results.
EXAMPLE 4
[0082] The experiment of example 3 was repeated with finely divided
aluminum oxide polishing powder. It was found that a concentration
of this finely divided aluminum oxide of about 50% by weight was
required to disrupt the polyurethane foam to a level sufficient to
cause its break up during use. The resulting use of this
composition produced good polishing properties to rough wet
surfaces.
EXAMPLE 5
[0083] 5.0 grams of foam A polyurethane foam pre-polymer from
Plastic Depot (2900 San Fernando Blvd Burbank, Calif. 91054) were
placed into a small plastic cup. To this were added 8.0 grams of
finely divided ferric oxide abrasive. The mixture was then stirred
with a wooden popsicle stick until uniform. In a separate plastic
cup were placed 5.0 grams of foam B polyurethane pre-polymer from
the same source as the foam A. To this were added 8.0 grams of
finely divided ferric oxide abrasive and the mixture stirred until
uniform. The two mixtures were then combined and stirred until
uniform. The resultant mixture was then poured into a small
polyethylene container and allowed to foam and subsequently cure.
The cured foam composition was then allowed to sit overnight to
stabilize. The foam abrasive composition was then removed from the
polyethylene container. A small section of the outside portion was
cut off with a sharp knife to expose the foam cells underneath the
outside skin. A small amount of water was placed on this exposed
surface. This wet exposed surface was then used to polish rough
sanded automotive paint. Polishing was quick with noticeable
results occurring within a few seconds leaving a polished surface
behind. It should be noted that the resulting debris tended to
disperse in the water and accumulate in the exposed voids of the
foam.
[0084] FIG. 9 shows a sectional view of a low speed wet abrasive
foam disc for use with a rotary tool. Abrasive particle releasing
foam disc 53 is shown having abrasive releasing first major top
surface portion 55 along with rigid backing portion 57 and central
hole 59 for mounting to a shaft (not shown). Top abrasive releasing
surface portion 55 is comprised of numerous abrasive particles
embedded into closed cell foam attached to rigid backing portion
57. Bottom surface portion 61 of rigid backing portion 57 may be
regarded as a second major surface portion.
[0085] Abrasive particle releasing disc 53 is suitable for wet
rotary sanding operations. A shaft may be attached using central
hole 59 and a threaded screw. The shaft may be subsequently fitted
into the chuck of a low speed rotary tool such as a drill. A
relatively low speed of about 50 to 500 RPM may be employed to wet
sand numerous surfaces. It should be noted that high RPM conditions
of 1000 or more may result in excess loss of water employed in wet
sanding operations.
[0086] FIG. 10 shows an abrasive fabric 46. Abrasive fabric 46 is
comprised of a flexible water absorbent fabric such as cloth
backing layer 48 along with attached abrasive loaded polymeric
resin protrusions 50. Abrasive fabric 46 is shown as a
discontinuous surface that releases hard abrasive particles during
low speed wet sanding, grinding, and polishing operations. The
separation of individual abrasive loaded polymeric resin
protrusions 50 between each other forms a discontinuous surface.
Also shown is material matrix portion 52 in the form of a polymer
resin such as epoxy embedded with coarse aluminum oxide abrasive 54
having a hardness significantly greater than polymer matrix portion
52. Abrasive fabric 46 may be used for machine driven sanding
surfaces such as belts and discs as well as hand sanding
applications.
[0087] It should be noted that the protrusions themselves provide
points of high pressure that facilitate wet sanding and grinding
operations. It should also be noted that water absorbent flexible
fabric 48 employed allows individual abrasive loaded polymeric
resin protrusions to follow surface contours during wet sanding
operations in addition to absorbing and releasing excess water
during these same operations. This may be used to significantly
control the moisture of surfaces during wet sanding operations.
Individual protrusions 54 may have grooves like those shown in FIG.
11.
[0088] FIG. 11 shows an abrasive loaded polymeric resin protrusion
56 having a top surface portion 58 containing a pattern of grooves
60. Grooves 60 provide means for holding water and for the
subsequent removal of debris in wet low speed sanding, grinding,
and polishing operations. Furthermore, ridges 62 resulting from
grooves 60 in top surface portion 58 provide for increased pressure
at the start of wet sanding operations. This added pressure helps
to facilitate the process of dislodging abrasive particles 62 and
assures a good start to the wet sanding process. Once ridges 64
wear, abrasive particles 62 will continue to be released during
use.
[0089] The above described abrasive loaded polymeric resin
protrusions of FIG. 11 were prepared in the following manner. A
mold pre-form was made in the following manner. Pre-form may be
defined in this context to be "The original part from which a
casting is made for the purpose of producing a mold." A
4''.times.6'' piece of flat glass was thoroughly cleaned and dried.
To this surface were attached Vitreous Glass Mosaic Tiles
(Landscape L83/8''-1/6LB from Mosaic Mercantile). The tiles were
evenly spaced in eleven rows of seven having their widest side
facing down against the glass surface. Two part five minute epoxy
resin was then used to firmly attach the tiles to the glass
surface. It should be noted that the tiles themselves were 0.4''
square at the bottom tapered evenly to 0.325'' square at the top,
and had an overall thickness of 0.15''. The top surface had three
ridges as shown in FIG. 9. Once hard, the epoxy was allowed to
further cure overnight. A thin layer of vegetable oil was applied
to the entire tile coated glass surface and the glass placed smooth
side down in a 5''.times.7'' polyethylene flat bottom container.
One hundred and fifty grams of two part silicone RTV rubber molding
compound (PD-1000-A) from Plastic Depot 2907 San Fernando BLVD
Burbank, Calif. 91504 Tel# 818-843-3030) were mixed thoroughly in
accordance with the enclosed instructions and carefully poured over
the mold pre-form in the polyethylene container. The silicone
rubber was allowed to cure at room temperature for twenty four
hours. The mold was then removed from the polyethylene container
and peeled off from its pre-form. The silicone mold was then
thoroughly washed with a strong detergent to remove residual
vegetable oil and subsequently allowed to dry.
[0090] Fifteen grams of West systems 105 epoxy resin were mixed
with 3.0 grams of West systems 205 fast curing catalyst. The
mixture was stirred thoroughly followed by the addition of 36 grams
of 70 grit coarse aluminum oxide abrasive. The mixture was then
stirred until completely uniform. Immediately after mixing the
resultant abrasive paste was placed into the voids in the silicone
mold. A flat edge was then dragged against the mold surface to
level the resin mixture in the voids. The resin was allowed to cure
for twenty four hours. Once cured, the abrasive protrusions were
removed from the mold and inspected for quality. The best sixty
samples were then ground flat on their largest side and attached to
the front surface of a cotton glove using West systems 105 epoxy
resin and 205 hardener. Unfortunately, the glove tended to absorb
the low viscosity resin. The abrasive protrusions were then removed
and wiped clean with a paper towel. The glove with the still wet
adhesive was then stuffed with paper towels to prevent the resin
from gluing the glove shut. The resin was allowed to harden
somewhat. The paper towels in the glove were then removed and the
resin on the glove allowed to thoroughly cure. Five minute epoxy
was then applied to the widest side of each abrasive protrusion and
the protrusions glued to the glove at the positions corresponding
to the previously cured spots of resin on the glove. This approach
worked exceptionally well with the resultant glove having sixty
abrasive protrusions firmly attached to the required areas for hand
sanding operations.
[0091] The above described glove was then tested against numerous
surfaces including automotive paint on plastic, automotive paint on
metal, aluminum, painted aluminum, and glass. This testing was
carried out with and without water. The dry sanding produced
numerous coarse scratches in the above mentioned surfaces while the
wet sanding was more rapid and complete with more uniform finer
sanding. It should be noted that this particular sanding glove
rapidly wet sanded all of the above described surfaces by hand in a
matter of seconds.
[0092] FIG. 12 shows an abrasive fabric glove having numerous
discrete abrasive protrusions attached to major working surfaces in
accordance with the present invention. Sanding glove 62 is shown
having abrasive loaded polymeric resin protrusions 64 that are
discontinuous from each other and attached to glove 66 with epoxy
resin 68. Also shown are ridges 70 on protrusions 64. Ridges 70 on
protrusions 64 provide points of high pressure and help to hold
water during the first use. Protrusions 64 consist of polymeric
resin portion 72 along with abrasive particle portion 74 thereby
forming a mixture of hard abrasive particles dispersed within a
softer epoxy resin material matrix.
[0093] FIG. 13 shows a sectional view of a low speed wet sanding
disc for a rotary tool having a plurality of layers of surface
protrusions comprised of hard abrasive particles dispersed within a
softer material matrix. Abrasive particle releasing disc 76 is
shown having abrasive releasing first major top surface portion 78
along with rigid backing portion 80 and central hole 82 for
mounting to a shaft (not shown). Top abrasive releasing surface
portion 78 is comprised of numerous protrusions 82 fixedly attached
to rigid backing portion 80 forming a first layer 84. A second
layer 86 of protrusions 88 are also shown. Protrusions 88 forming
second layer 86 are shown fixedly attached to protrusions 82 of
first layer 84. Protrusions 82 and 88 are comprised of hard
abrasive particles dispersed within a softer material matrix.
Protrusions 82 and 88 are shown in greater detail in FIGS. 4 and 5.
Bottom surface portion 90 of rigid backing portion 80 may be
regarded as a second major surface portion.
[0094] FIG. 14 shows a sectional view of fabric material for low
speed wet sanding and grinding having a plurality of layers of
surface protrusions comprised of abrasive particles dispersed
within a softer material matrix. Abrasive particle releasing fabric
92 is shown having abrasive releasing first major top surface
portion 94 along with flexible water absorbent fabric portion 96.
Top abrasive releasing surface portion 94 is comprised of numerous
protrusions 98 fixedly attached to flexible water absorbent fabric
portion 96 forming a first layer 100. A second layer 102 of
protrusions 104 are also shown. Protrusions 104 forming second
layer 102 are shown fixedly attached to protrusions 98 of first
layer 100. Protrusions 98 and 104 are comprised of hard abrasive
particles dispersed within a softer material matrix. Protrusions 98
and 104 are shown in greater detail in FIGS. 4 and 5. Bottom
surface portion 106 of flexible water absorbent fabric portion 96
may be regarded as a second major surface portion.
[0095] The above descriptions of FIGS. 13 and 14 outline a
plurality of layers. These may be formed by forming a first layer
of abrasive containing protrusions followed by adhesion of a second
layer on top of the first layer using a suitable adhesive material
such as epoxy.
[0096] FIG. 15 shows a lapping surface of the present suitable for
grinding surfaces flat having numerous cavities for holding water,
and removal of debris. FIG. 15 shows a lapping block 108 consisting
of top exposed abrasive particle lapping top surface portion 112 of
lapping block 108. Exposed abrasive particle releasing lapping
surface portion 112 is shown to be larger in area than side surface
portion 110 and therefore may be considered a first major surface
of lapping block 108. Lapping block 108 has a second major surface
(not shown) oppositely facing first major surface 112. Lapping
block 108 is shown having side surface portion 110 and top flat
abrasive particle releasing surface portion 112.
[0097] Lapping block 108 is suitable for lapping small articles
flat. As with lapping block 14 of FIG. 3, the article may be glued
to a holder and lapped in a circular motion by hand, or
alternatively lapped at a relatively slow rate by machine. Some
articles may also be held directly by hand and subsequently lapped
flat. In many instances water in pure form or with special
additives may be employed in the process. Generally speaking the
lapping surfaces of this invention will retain water in surface
cavities 114 of top surface portion 112 of lapping block 108.
Employing water as a lubricant may also help to flush debris from
the area being used. When finished, the lapping surface may be
cleaned of residual debris with running water.
[0098] Abrasive particle releasing lapping surface 112 of lapping
block 108 is shown having a relatively large percentage of the
particle releasing surface 112 flat with a relatively small
percentage of lapping surface 112 comprised of cavities. Particle
releasing lapping surface 112 of lapping block 108 has a
discontinuous surface topography due to the presence of surface
cavities 114.
[0099] FIG. 16 shows a sectional view of an abrasive material for
wet application comprised of hard abrasive particles embedded
within a softer polymeric matrix material along with added hollow
micro-spheres. Abrasive material 116 is shown in cross sectional
view. Abrasive material 116 is shown having abrasive particles 118
embedded within polymeric matrix material 120. Abrasive particles
may comprise a material selected from the group consisting of
aluminum oxide, silicon carbide, zirconia, diamond, ceria, cubic
boron nitride, garnet, ground glass, quartz, and combinations
thereof. Also shown are hollow micro-spheres 122. Major surface 124
is shown having numerous cavities 126. Cavities 126 are also shown.
Cavities 126 may result from wearing open hollow micro-spheres 122
during use. Alternatively, cavities 126 may be formed during
manufacture by cutting or wearing of the surface prior to use.
Cavities 126 are shown providing discontinuous surface topography
to major surface 124.
[0100] Numerous materials including polyurethane and epoxy resins
may be used for polymer matrix material 116. Of particular interest
is the use of polyurethane condensation polymers having both rapid
wear and hydrophilic properties. Polyurethane condensation polymers
may be prepared having a slight excess of polyol reactant thereby
providing reduced molecular weight as well as hydrophilic
properties. Alternatively, one or more reactive hydrophilic polyol
additives may be employed.
[0101] FIG. 17 shows a sectional view of abrasive foam material
having a softened top surface resulting from exposure to water.
Abrasive foam material 128 is shown having abrasive particles 130
distributed uniformly throughout softer polymer matrix portion 132.
Abrasive particles 130 may comprise a material selected from the
group consisting of aluminum oxide, silicon carbide, zirconia,
diamond, ceria, cubic boron nitride, garnet, ground glass, quarts,
and combinations thereof. Also shown are foam voids 134. Also shown
is top major surface portion 136. Top major surface portion 136 is
shown having a discontinuous surface topography resulting from the
presence of numerous exposed foam voids 138. Top major surface
portion 136 is shown having expanded outer layer portion 140.
Expanded outer layer portion 140 results from the interaction of
water with top major surface portion 136. Expanded outer layer
portion 140 is shown having a limited thickness owing to the closed
cell nature of abrasive foam material 128. Expanded outer layer
portion 140 becomes the working surface during use. Expanded outer
layer portion 140 may have unique cushion properties to abrasive
particles released from the working surface during use.
[0102] Several formulations were used for making high foam density
abrasive articles employing 8 pound per cubic foot density rigid
closed cell polyurethane two component pour foam. The 8 pound per
cubic foot rigid closed cell polyurethane pour foam used was from
Silpack INC 470 East Bonita AVE., Pomona, Calif. 91767. Their
telephone number is (909) 625-0056. The product name is 8# rigid
foam SP-328-8. This product comes in two components. Component A
and component B. They are formulated to combine into equal volumes.
Component A has a density of 8.5 pounds per gallon. Component B has
a density of 7.5 pounds per gallon. Blending these foam components
into equal parts by weight results in an excess of component B (the
poly hydroxyl functional component). This results in a final foam
having significantly reduced molecular weight along with enhanced
hydrophilic properties. When prepared in this manner, blended with
abrasive materials, cured into a hard mass, and cut open. The
resulting exposed abrasive surface will soften on exposure to water
and cushion abrasive particles released during use.
[0103] The following formulations were used to make large hand
sanders.
[0104] 100 grams of SP-328-8 A from Silpack were placed into a
polypropylene plastic bowl. To this were added 183 grams of 220
grit silicon carbide abrasive from Lortone. A wooden tongue
depressor was used to blend the abrasive and resin. 183 more grams
of 220 grit silicon carbide were added to completely cover the
surface of the mix. 100 grams of resin SP-328-8 B from Silpack were
then carefully poured on top of the abrasive. This top layer of
abrasive prevents the resins from mixing until vigorously stirred
to break the layer. This provides some extra time to mix and pour
before the foam starts to set. The contents of the plastic bowl
were then rapidly blended together by mixing with the original
tongue depressor. After about 45 seconds of mixing, the contents of
the bowl were then poured into a silicone rubber mold to cast the
part. After a few hours of room temperature cure, the part was
removed from the mold. The working surface had a large excess of
foam protruding outward. This foam was trimmed off with a saw to
expose the active working abrasive surface. The experiment was
repeated using 320 grit and 400 grit silicon carbide abrasive. The
amount of abrasive for the finer grit values was reduced slightly.
The following formulations were used. For the 320 grit sanding
tool, 100 grams of resin A, 170 grams of 320 grit silicon carbide
abrasive, another 170 grams of silicon carbide abrasive and 100
grams of resin B. For the 400 grit sanding tool, 100 grams of resin
A, 160 grams of 400 grit silicon carbide abrasive, another 160
grams of 400 grit silicon carbide abrasive and 100 grams of resin
B.
[0105] The three resulting tools were allowed to cure for an
additional 48 hours. The exposed working surface of each tool was
sprayed with water and allowed to stand for several minutes. The
wet working surface softened to a limited depth. The wet surfaces
of the tools were then used to sand down numerous painted metal
surfaces. The 220 grit hand sanding tool behaved like new 400 grit
wet sand paper. The 320 grit hand sanding tool behaved like new 600
grit wet sand paper. The 400 grit hand sanding tool behaved like
new 800 grit wet sand paper.
[0106] The above described tools were used for a significant period
of time (about half an hour). During this timeframe the sanding
remained consistent. Although there were abrasive particles
released from the working surface of the tool, they were cushioned
by the thin soft outer tool layer. No deep scratches were observed
in the painted metal surfaces that had been sanded in this
manner.
[0107] During use, abrasive particles were released from the
working surface of the tool. These abrasive particles sanded down
the paint while at the same time renewing the abrasive surface by
sanding down the foam of the tool. This clearly indicates that this
particular rigid polymeric closed cell foam composition is wearable
at the major surface by the plurality of the abrasive particles
released. This debris formed an abrasive paste with the wet
surface. Some of this abrasive paste found its way into the surface
irregularities of the tools thereby keeping abrasive particles
active on the working surface. It should be noted that the abrasive
particles released in free form facilitated in wearing away the
major working surface of these tools. Additionally it should be
noted that the release of abrasive particles from the major working
surfaces of these tools creates additional voids. These additional
voids further facilitated to wear away major working surfaces of
these tools. The abrasive particles released in free form helped to
further abrade the major working surfaces of these tools. Once the
sanding operation was complete, the tools were rinsed off with
water and allowed to dry.
[0108] FIG. 18 shows a sectional view of abrasive foam material
having added water soluble particles that facilitates wear on
exposure to water. Abrasive foam material 142 is shown having
abrasive particles 144 distributed uniformly throughout softer
polymer matrix portion 146. Also shown are foam voids 150. Also
shown is top major surface portion 152. Top major surface portion
152 is shown having a discontinuous surface topography resulting
from the presence of numerous exposed foam voids 154. Also shown
are water soluble particles 148. Water soluble particles 148 are
shown distributed throughout softer polymer matrix portion 146.
During use water soluble particles 148 become exposed to water and
dissolve away thereby creating voids and helping to facilitate the
break up of polymer matrix portion 146.
[0109] Numerous materials may be used for water soluble particles
148. Included in this list are sugar (both powdered and granular),
dextrin, non-ionic, anionic, and cationic water soluble surfactants
(surfactant materials may provide further benefit as well). It
should be noted that compounds containing hydroxyl groups may
interact with the isocyanate components of polyurethane resin
systems.
[0110] FIG. 19 shows a foam abrasive article that may be used to
wet sand automotive surfaces. Foam abrasive article 156 is shown
comprising a main portion 158 and a major surface working portion
160. Also shown is side groove 162. Side groove 162 provides an
ergonomic fit to the hand for easier use. Foam abrasive article 156
may be composed of the rigid abrasive containing polymeric closed
cell foam composition of FIG. 17 and may have added water soluble
particles added as well to facilitate wearing away of major surface
working portion 160. Foam abrasive article 156 is shown formed
entirely from the foam abrasive material itself with no separate
backing or handle required.
[0111] FIG. 20 shows an abrasive pad for wet scouring applications
having 400 grit silicon carbide abrasive particles along with
hollow polymeric micro-spheres embedded in a water softening
polymeric matrix. Abrasive article wet scouring pad 164 is shown
comprised of flexible cloth backing 166 along with major abrasive
surface portion 168. Grooves 170 are shown in major surface portion
168 and help to provide flexibility as well as providing a
discontinuous surface topography. Major abrasive surface portion
168 is made from the material shown in FIG. 16 and therefore has a
discontinuous surface topography resulting from the presence of a
plurality of cavities representing surface voids.
[0112] The above described abrasive scouring pad 164 was produced
in the following manner. 17 grams of 341-A polyurethane resin from
Plastic Depot (2907 San Fernando Blvd. Burbank, Calif. 91504.
Telephone number (818) 843-3030) were mixed with 17 grams of 341-B
polyurethane resin until uniform. To this mixture were rapidly
added 63 grams of 400 grit silicon carbide along with 3 grams of
West System 407 low density fairing filler. West systems INC. P.O.
box 665. Bay City Mich. 48707 USA. Telephone number (866) 937-8797.
The mixture was rapidly mixed until uniform and spread out onto a
piece of 8''.times.10'' denim cloth before the urethane resin
mixture became too viscous to handle. The spread out area was then
allowed to cure for one hour. Once cured, the rigid construction
was rendered flexible by bending to form numerous cracks and
grooves into the major abrasive surface portion of the abrasive
article.
[0113] This scouring pad was then cut into 2''.times.2'' pieces.
One of these pieces was used to scour dirty dishes. This pad slowly
wore out over a period of 60 days. After this timeframe, the pad
was discarded.
[0114] Although the present invention has been described in detail
with respect to certain embodiments and examples, variations and
modifications exist which are within the scope of the present
invention as defined in the following claims.
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