U.S. patent application number 12/002013 was filed with the patent office on 2008-07-03 for abrasive configuration for fluid dynamic removal of abraded material and the like.
This patent application is currently assigned to TBW Industries, Inc.. Invention is credited to Stephen J. Benner.
Application Number | 20080160883 12/002013 |
Document ID | / |
Family ID | 39536907 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080160883 |
Kind Code |
A1 |
Benner; Stephen J. |
July 3, 2008 |
Abrasive configuration for fluid dynamic removal of abraded
material and the like
Abstract
An abrasive tool utilized to remove material from a workpiece is
formed to comprise fluid-dynamically-designed features (apertures,
airfoils) configured to efficiently remove abraded material and
waste from the surface of the workpiece. An abrasive component
(and/or backing plate) is formed to include
fluid-dynamically-designed features that create an air flow
stream/pressure differential which draws the created debris
(variously referred to as "swarf", meaning in general any material
removed by an abrading tool) away from the grinding surface.
Inventors: |
Benner; Stephen J.;
(Landsdale, PA) |
Correspondence
Address: |
Wendy W. Koba
PO Box 556
Springtown
PA
18081
US
|
Assignee: |
TBW Industries, Inc.
|
Family ID: |
39536907 |
Appl. No.: |
12/002013 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60875094 |
Dec 15, 2006 |
|
|
|
Current U.S.
Class: |
451/73 ;
451/259 |
Current CPC
Class: |
B24B 55/06 20130101;
B24D 7/00 20130101 |
Class at
Publication: |
451/73 ;
451/259 |
International
Class: |
B24B 7/00 20060101
B24B007/00 |
Claims
1. An abrasive tool incorporating fluid-dynamically-designed
features to improve removal of waste material from a workpiece, the
abrasive tool comprising: a substrate having a working surface and
a backing surface, wherein at least the working surface has a
coating of an abrasive composition; and a plurality of features
formed on or through the substrate, wherein the plurality of
features are configured to create a pressure differential between
the working surface and the backing surface of the substrate during
the abrading process.
2. An abrasive tool as defined in claim 1 wherein the substrate
comprises a circular disk and the plurality of features comprises a
plurality of blower vanes attached to the substrate working surface
and disposed downwardly therefrom, the plurality of blower vanes
for channeling waste material directed to the periphery of the
circular disk substrate as the abrasive tool is rotated.
3. An abrasive tool as defined in claim 1 wherein the plurality of
features comprise a plurality of apertures formed through the
thickness of the substrate.
4. An abrasive tool as defined in claim 3 wherein at least some of
the plurality of apertures are formed to comprise a working surface
diameter, which is less than an associated backing surface
diameter, creating a pressure differential upon use of the abrasive
tool.
5. An abrasive tool as defined in claim 4 wherein a sidewall of the
least some of the plurality of apertures is formed to include a
curved surface.
6. An abrasive tool as defined in claim 3 where at least one of the
plurality of apertures is tilted with respect to the thickness of
the substrate, the tilted apertures creating a pressure
differential when the abrasive tool is used.
7. An abrasive tool as defined in claim 1 wherein the substrate
comprises a linear belt.
8. An abrasive tool as defined in claim 1 wherein the substrate
comprises a drum component.
9. An abrasive tool as defined in claim 8 wherein the substrate
includes a plurality of apertures formed therethrough and a
plurality of airfoils disposed on an inner perimeter thereof to
create the desired pressure differential upon rotation of the
drum.
10. An abrasive tool as defined in claim 1 wherein the substrate
comprises a wheel component.
11. An abrasive tool as defined in claim 10 wherein the substrate
includes a plurality of apertures formed therethrough and a
plurality of airfoils disposed on an inner perimeter thereof to
create the desired pressure differential upon rotation of the
wheel.
12. An abrasive system including an abrasive component having a
working surface and a backing surface, at least the working surface
having a coating of an abrasive composition; a plurality of
apertures formed through the thickness of the abrasive component;
and an impeller coupled to the abrasive component for imparting
motion to the abrasive component, the impeller including a
plurality of spaced-apart impeller blades coupled to the backing
surface of the abrasive component, wherein the plurality of
apertures and/or the plurality of spaced-apart impeller blades are
configured to create a pressure differential between the working
surface and the backing surface of the abrasive component upon
movement of said abrasive disk.
13. An abrasive system as defined in claim 12 wherein the impeller
blades are configured to exhibit an airfoil geometry for creating
the pressure differential between the abrasive component working
and backing surfaces upon movement.
14. An abrasive system as defined in claim 12 wherein the impeller
blades are configured to exhibit an airfoil geometry for removing
heat from the abrasive component during use.
15. An abrasive system as defined in claim 12 wherein the impeller
blades are configured to exhibit a pinwheel-like structure for
creating the pressure differential between the abrasive component
working and backing surfaces upon movement.
16. An abrasive system as defined in claim 12 wherein the impeller
blades are configured to exhibit a pinwheel-like structure for
removing heat from the abrasive component during use.
17. An abrasive system as defined in claim 12 where at least one of
the plurality of apertures is formed to comprise a working surface
diameter less than an associated backing surface diameter, creating
a pressure differential upon movement of the abrasive disk.
18. An abrasive system as defined in claim 12 wherein a sidewall of
at least one of the plurality of apertures is formed to include at
least one curved surface.
19. An abrasive system as defined in claim 12 where at least some
of the plurality of apertures are tilted with respect to the
thickness of the abrasive component, the tilt creating a pressure
differential when said abrasive component is moved.
20. An abrasive tool incorporating fluid-dynamically-designed
features to contain waste material from a workpiece, the abrasive
tool comprising: a substrate having a working surface and a backing
surface, wherein at least the working surface has a coating of an
abrasive composition; a plurality of features formed on or through
the substrate, wherein the plurality of features are configured to
create a pressure differential between the working surface and the
backing surface of the substrate during the abrading process so as
to draw waste material away from the workpiece; and a containment
channel coupled to the substrate to contain the removed waste
material in an isolated manner such that re-entry of the waste
material onto the workpiece is prevented.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/875,094, filed Dec. 15, 2006.
TECHNICAL FIELD
[0002] The present invention relates to an abrasive utilized to
remove material from a workpiece and, more particularly, to an
abrasive including fluid-dynamically-designed features to
efficiently use the mechanical energy of the equipment to remove
(or direct) abraded material, heat, coolants and waste from the
surface of the workpiece.
BACKGROUND OF THE INVENTION
[0003] When performing any type of grinding or polishing operation,
a large amount of abraded material is generally created and needs
to be captured and removed from the work area. Abrasive grinders of
the prior art generally comprise a portable body that is adapted to
be held by a user, the grinder including a motor that drives a
backing plate which in turn carries an abrasive component for
grinding the surface of a workpiece. The abrasive component may
take the form of a disk, belt, drum, wheel or any other
configuration suitable for a given grinding/polishing
operation.
[0004] In a "vacuum" type grinder, a shroud in the vicinity of the
backing plate and abrasive component defines a chamber through
which air and entrained particles flow to an outlet leading to an
accumulation point. The abrasive and backing plate are provided
with holes that, when aligned, form an air passage to allow the
flow of air and entrained particles which are drawn by suction
applied to the shroud.
[0005] One problem with these vacuum-based prior art systems is the
large abrasive area in relation to the small, peripheral vacuum
area, and indirect path flows, which result in an increase in the
temperature of the workpiece and the instability of the process.
The generation of heat is particularly problematic in
chemical-mechanical planarization (CMP) abrasive disks, where the
chemistry at the workpiece surface will be affected by local
temperature changes. Abrasive tools having a large abrasive area
coupled with a high concentration of fine abrasives also typically
become loaded with workpiece debris or swarf, limiting the speed of
the abrading process, smearing debris on the workpiece, and
creating additional `workpiece heating`.
[0006] Additionally, the vacuum effectiveness cannot be reliably
controlled since the vacuum must be sufficient over the surface
area of the entire abrasive so as to entrain swarf created at any
point on the abrasive (e.g., if grinding on a bevel, only the
cross-sectional area being cut is in contact with the
abrasive).
[0007] Conventional porous abrasive tools, having pores positioned
throughout the entirety of the abrasive structure, are well-known
in the art. Conventional porous metal composite grinding wheels are
commonly formed by sintering a loosely-packed metal composite, or
by adding hollow glass and ceramic spheres to the composite.
However, it has been found to be difficult to control the size and
shape of the porosity in such abrasives and, if hollow spheres are
used, it is difficult to prevent crushing the spheres during
manufacture or use. While these porous abrasive tools are capable
of trapping removed debris, they do not have any type of channel or
pathway for clearing the debris from the tool itself. Therefore,
additional mechanisms are required to move the abraded material
away from the interface between the workpiece and the abrasive or
the same clogging, smearing and overheating can occur.
[0008] The removal and containment of debris from various types of
grinding/polishing operations may also raise various health and/or
environmental issues. For example, the removal of asbestos, paint,
silica, fiber composites and the like needs to be carefully
controlled in a manner that minimizes the creation of any airborne
contaminants that may be inhaled, released into the environment or
become re-incorporated into the workpiece.
[0009] Accordingly, there is a need for an abrasive configuration
that efficiently moves materials (i.e., coolant, air) to, and
removes materials (i.e., heat, swarf) from, a workpiece during an
abrading process.
SUMMARY OF THE INVENTION
[0010] The needs remaining in the prior art are addressed by the
present invention, which relates to an abrasive utilized to remove
material from a workpiece and, more particularly, to an abrasive
including fluid-dynamically-designed features that are configured
to efficiently remove abraded material and waste from the surface
of the workpiece. The direction of flow through the features may
also be reversed in accordance with the present invention (i.e.,
toward the workpiece) to provide the introduction of cleaning
fluids, coolants, process chemicals and the like.
[0011] In accordance with the present invention, an abrasive
component (and/or backing plate) is formed to include
fluid-dynamically-designed features which create an air flow
stream/pressure differential that draws surface materials
(including coolants or other process consumables) and the created
debris (variously referred to as "swarf", meaning in general any
material removed by an abrading tool) away from the grinding
surface. Advantageously, the inclusion of such features within the
abrasive component eliminates the need for a separate, external
vacuum source to pull the debris away from the workpiece. Various
other features formed within the abrasive may be specifically
designed to introduce materials onto the workpiece surface. The
abrasive component itself may take the form of a disk, belt, drum,
wheel or any other suitable design. The fluid-dynamically-designed
features include elements such as apertures, air foils, blower
vanes and the like.
[0012] It is an advantage of the fluid-dynamic design of the
inventive fluid-dynamic abrasive that the created flow properties
are used to control environmental properties such as the velocity,
pressure, density (including abrasive particle density), chemistry,
cleanliness and temperature at the workpiece surface. The included
features function individually to remove localized debris, while
the entirety functions globally to manage the environmental
conditions across the workpiece and abrasive tool surface. By
removing the by-products of the abrasive process (mechanical,
chemical, heat, etc.) before they can interact with the workpiece
(or the abrasive), the chance of workpiece contamination (or
abrasive clogging/blockage) is significantly reduced. Also as
mentioned above, a conventional grinding process creates heat at
the workpiece area. The ability to lower the temperature via the
inventive fluid-dynamic abrasive prevents overheating of the
material.
[0013] The apertures and associated pressure differential
associated with the fluid-dynamic abrasive also allow for a more
uniform flow over the contact area and localized control of the
workpiece/abrasive interface (balancing waste entrainment and
abrasive contact area). The use of a large number of apertures
allows the abrasive to function in the manner of a serrated cutting
tool, creating swarf of minimal chip size, while maximizing
`cutting tool` clearance. In particular, the aperture dimensions
and configuration are designed to result in a predictable flow
pattern at a finite granularity/resolution in conjunction with
macroscopic or collected vortices to: move debris from the surface
in a preferred direction (e.g., flow from the edge of a
disk/drum/wheel to the center, from the center to the edge, a
radial flow around a disk, a lifting flow above an abrasive belt,
etc.). A backing plate may be configured to include a plurality of
containment channels to balance exhaust and/or coolant flow from
the center of an abrasive element to its outer periphery.
[0014] Advantageously, the unique configuration of the subject
abrasive components, which incorporates various principles of fluid
dynamics, has provided the following features: the overall process
is "cleaner" than prior art arrangements since the constant
movement (rotational or translational) of the abrasive itself
creates the `pull` to remove the debris from the surface without
allowing re-entry or "clogging" of the work area or abrasive
surface (as opposed to the use of prior art external vacuum system
that may allow re-entry of contaminants); the overall process is
"cooler" since the same increased air flow also functions to remove
heat as it is created; the overall process is "uniform" in terms of
providing the same abrading function and balanced cooling across
the entire face of the workpiece (regardless of the degree of
contact between the workpiece and the abrasive) in a manner such
that the waste or by-products are not permitted to interact with,
damage or taint the freshly-exposed surfaces; the overall process
is more economical than prior art systems requiring utilization and
maintenance of a separate vacuum source; and the overall process
provides a higher quality result, since any potential contaminants
are immediately and continuously removed from the work area,
significantly reducing any potential environmental, health or
workproduct contamination concerns.
[0015] Other and further advantages and features of the present
invention will become apparent during the course of the following
discussion and by reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Referring now to the drawings,
[0017] FIG. 1 illustrates a prior art tool including an abrasive
disk and vacuum system for removing debris from the work area;
[0018] FIG. 2 is a side view of a prior art conditioning head for a
chemical mechanical planarization (CMP) system, illustrating the
apertured abrasive disk included within the conditioning head;
[0019] FIG. 3 is an exploded view of a portion of the arrangement
in FIG. 2, illustrating in particular the impeller and apertured
abrasive disk components of the conditioning head;
[0020] FIG. 4 is a top view of one exemplary
fluid-dynamically-designed abrasive disk formed in accordance with
the present invention;
[0021] FIG. 5 illustrates an alternative embodiment of the present
invention where the geometry of the apertures within the abrasive
disk are themselves configured to provide the fluid dynamic
improvements in debris removal;
[0022] FIG. 6 shows yet another embodiment of the present
invention, where the disk apertures are tilted to create the
desired pressure differential and directional force component;
[0023] FIG. 7 illustrates another fluid-dynamic-based abrasive disk
design of the present invention;
[0024] FIG. 8 contains an illustration of yet another
fluid-dynamic-based abrasive disk configuration formed in
accordance with the present invention;
[0025] FIG. 9 contains an isometric perspective view of an
exemplary fluid-dynamically-designed impeller (backing plate) for
use with an abrasive disk in accordance with the present
invention;
[0026] FIG. 10 illustrates an alternative
fluid-dynamically-designed impeller configuration;
[0027] FIG. 11 illustrates an exemplary fluid-dynamically-designed
abrasive belt formed in accordance with the present invention;
[0028] FIG. 12 illustrates an exemplary fluid-dynamically-designed
abrasive drum formed in accordance with the present invention;
and
[0029] FIG. 13 illustrates an exemplary fluid-dynamically-designed
abrasive wheel formed in accordance with the present invention.
DETAILED DESCRIPTION
[0030] The fluid-dynamic based abrasive component of the present
invention is intended to find use in a variety of applications,
where any specific application mentioned in the following
discussion is intended to merely provide a full illustration of the
various features of the inventive abrasive component. Indeed,
abrasives are used in grinding/polishing many different surfaces
(metals, glass, ceramic and the like) in a variety of heavy-duty
industrial and/or commercial applications. In industrial
applications, abrasives are typically driven at speeds in the range
of 1750-3200 rpm. The generated swarf will follow the path of
abrasive grit impact. Other applications may utilize a higher speed
abrasive or a lower speed abrasive. For example, a lower speed
abrasive is typically used in semiconductor industry applications
when polishing/treating the surface of semiconductor wafers and in
particular conditioning the polishing pads used to perform the
polishing operations. Regardless of the application, the
configuration of the subject abrasive is not considered to be
dependent upon its field of use. Rather, the fluid dynamic
properties of the abrasive are designed specifically for the
operating speeds, fluid properties (viscosity, volume, containment,
lift, flow direction, pressures, etc.) and the like.
[0031] Prior to describing the details of the inventive abrasive,
an overview of a conventional prior art abrasive disk will be
described in order to provide a sufficient knowledge base for
gaining the best understanding of the features of the present
invention.
[0032] FIG. 1 is a cut-away side view of an exemplary prior art
sanding head 1 that requires the use of a separate, stand-alone
vacuum system (not shown) for removing debris from the surface of
the workpiece being sanded. Sanding head 1 includes a shaft 2
rotatably mounted in a casing 3 and mechanically connectible to a
drive motor of an electric drill (not shown). Shaft 2 is also
connected at one end to a backing plate 4. Backing plate 4 has in
its center, as is known, a hollow cylindrical element 5 which is
closed at its lower end by an end wall 6. An abrasive disk 7 is
attached to shaft 2 in a manner that allows abrasive disk 7 to
rotate and perform the sanding operation. The application of a
vacuum to a vacuum port 8 then allows for the sanding debris to be
drawn up around the periphery of abrasive disk 7, through an inner
chamber 9 of sanding head 1, then through vacuum port 8 and into a
collection unit (not shown). In particular, the debris generated by
abrasive disk 7 is projected by centrifugal force towards the
periphery of disk 7. As shown by the arrows in FIG. 1, the vacuumed
debris along the periphery is then drawn upward into inner chamber
9 and through port 8 to the separate vacuum system.
[0033] One problem with this arrangement, however, is that the
removal of debris relies on the separate vacuum system capturing
all of the material that has moved to the periphery of the disk.
Clearly, some of the debris will always remain in a central portion
of the abrasive disk. Also, as mentioned above, this approach is
also problematic in situations where less than full face abrasive
contact is maintained (i.e., edge grinding) and the vacuum flow is
formed only at the periphery of the disk.
[0034] While the prior art arrangement of FIG. 1 shows a
conventional sanding head as used for many diverse applications,
there are also specialized applications as mentioned above that
require the use of an abrasive for operations such as fine
polishing of glass, planarizing of semiconductor wafers and, even
more particularly, re-conditioning the polishing pad surface of the
material used to planarize semiconductor wafers. As is well-known
in the art, chemical mechanical planarization (CMP) systems use an
abrasive disk to remove collected debris and planarizing fluids
from the surface of a polishing pad (referred to as a
"conditioning" process). FIG. 2 is a cut-away side view of an
exemplary prior art CMP conditioning head 20, and FIG. 3 contains
an exploded view of certain of the pertinent elements within
conditioning head 20. U.S. Pat. No. 6,508,697, issued on Jan. 21,
2003 to the assignee of this application contains a complete
description of such a conditioning arrangement and is herein
incorporated by reference.
[0035] For the purposes of understanding the benefits of the
fluid-dynamic abrasive of the present invention, the aspects of
conditioning head 20 related to its abrasive disk will be briefly
described. Referring to both FIGS. 2 and 3, prior art conditioning
head 20 comprises an outer housing 22 including an inlet port 24
for dispensing conditioning/cleaning agents onto a polishing pad 26
and a vacuum outlet port 28. An abrasive conditioning disk 30 is
disposed at the bottom of conditioning head 20 and functions to
rotate against the surface of polishing pad 26, sufficiently
abrading the surface to remove any embedded particulates. As fully
described in the above-referenced patent, abrasive conditioning
disk 30 includes a plurality of apertures 32 formed across the
entire surface. The exploded view of FIG. 3 best illustrates the
placement and size of apertures 32. In this particular embodiment,
an impeller 34 is disposed between abrasive disk 30 and outer
housing 22, where impeller 34 is used to provide the rotational
motion to abrasive disk 30.
[0036] The application of a vacuum force through port 28, as shown
by the arrows in FIG. 2, allows for the dislodged debris and other
effluent materials to be pulled off of polishing pad 26, through
apertures 32 of abrasive disk 30 and along blades 36 of impeller 34
into vacuum port 28. Impeller blades 36 function to sectionalize
the vacuum. This improves the localized pressure and corresponding
removal of the effluent and, in some embodiments, may also include
apertures for either dispensing conditioning materials or
evacuating debris (or both). While the use of an apertured abrasive
disk has been successful in improving the removal of effluent from
the pad's surface, improvements in flow efficiency, containment,
and partial-contact cleaning ability (i.e., just beyond the edge of
the pad 12 where the vacuum force will be broken) are
desirable.
[0037] By incorporating fluid dynamic considerations into the
configuration of an apertured abrasive component (e.g., disk, belt,
drum, wheel or the like), the various embodiments of the present
invention, as described below, will create an extremely localized
pressure differential (i.e., a pressure differential in the region
of the aperture, also referred to variously as a "venturi") that
assists or replaces the vacuum removal operation, balance flow
across the radial direction and direct flow toward the periphery,
thereby improving the performance of the abrasive. Indeed, the
fluid-dynamic design is useful in any abrasive application, from
industrial heavy-duty abrasive tasks to the highly-specialized pad
conditioning of polishing pads in the semiconductor industry.
[0038] FIG. 4 is a top view of one exemplary
fluid-dynamically-designed abrasive disk 100 formed in accordance
with the present invention. Similar to prior art abrasive disk 20
described above, fluid-dynamic abrasive disk 100 includes a
plurality of apertures 110 formed therethrough to allow for the
abrading debris to be drawn away from the workpiece surface (not
shown). In accordance with the fluid dynamic principles of the
present invention, a plurality of blower vanes 120 are disposed
around the outer periphery of disk 100, as shown in FIG. 4. Between
each pair of adjacent blower vanes, a vacuum outlet channel 130 is
formed. Accordingly, when abrasive disk 100 is rotated (illustrated
by the arrows labeled "R" in FIG. 4) the presence of blower vanes
120 creates a pressure differential across the surface of abrasive
disk 100. That is, the pressure in the central area of disk 100 is
greater than the pressure around the periphery of disk 100, forcing
the evacuated debris into vacuum outlet channels 130. In this
particular embodiment, the configuration of apertures 110 remains
similar to those of prior art designs. More generally, it is
conceivable that such a fluid dynamic abrasive disk of this
embodiment of the present invention may utilize fewer apertures (or
apertures of varying size--smaller toward the center to balance
flow and abrasive particle engagement as a function of revolution),
relying on the pressure differential created by blower vanes 120 to
move the debris from the workpiece surface into channels 130.
[0039] It is to be understood that a variety of different factors
are involved in determining the pressure differential created by
the fluid-dynamic abrasive of the present invention. Some of the
factors include, but are not limited to, the
rotational/translational speed of the abrasive, the size, shape,
and number of blower vanes/airfoils, the distribution of blower
vanes/airfoils on the abrasive, the size and number of outlet
channels, and the like. Any or all of these factors (and others)
may be considered when implementing the inventive fluid-dynamic
abrasive for a particular purpose. Further, the abrasive of the
present invention may be formed to include only a surface layer of
abrasive material or a distributed volume of abrasive throughout a
cast or sintered abrasive material. In these arrangements using
only a surface abrasive layer, the fluid-dynamic-based attributes
are formed as part of the `substrate` or backing plate upon which
the abrasive layer is affixed.
[0040] As shown in FIG. 4 and more particularly described in
association with the remaining figures, the fluid-dynamic-based
abrasive of the present invention functions to increase the amount
of waste material removed from the workpiece surface, and provides
the additional benefit of also removing heat from the work area. By
specifically incorporating fluid dynamic principles into the
configuration of the apertured abrasive, various types of directed
flow may be created. That is, the abrasive apertures may be
configured to direct the flow upward away from the work area
(lift), between the abrasive and workpiece (flush), or from the
center to edge of the disk/drum/wheel, or vice versa (radial). The
apertures may also be configured to improve the evacuation of
abraded material from the center portion of the abrasive, relative
to prior art arrangements, thus improving the cleanliness of the
abraded workpiece surface, as well as the abrasive itself and
aiding in the collection/containment from otherwise uncontrolled
waste dispersion.
[0041] FIG. 5 illustrates an alternative disk embodiment of the
present invention where the geometry of the apertures within the
abrasive disk is specifically configured to provide the
improvements in debris removal. In the cut-away side view of FIG.
5, an exemplary fluid-dynamic abrasive disk 200 is shown as
including a plurality of apertures 210. In accordance with this
embodiment of the present invention each aperture 210 tapers
outwardly from a first diameter D1 along bottom surface 230 of
abrasive disk 200 to a second, larger diameter D2 along top surface
240 of abrasive disk 200. In accordance with the present invention,
the tapered apertures (increasing from D1 to D2) create an inverse
pressure gradient as disk 200 is rotated (again, the magnitude of
the gradient being a function of factors such as taper design, disk
rotation speed, etc.). This pressure gradient, illustrated by the
references +P and -P in FIG. 5, is created locally at each aperture
210, thus providing instantaneous and offsetting forces for
particle entrainment.
[0042] The various, localized venturi will force the removed debris
from the central portion of the workpiece being abraded (not shown)
upward, through and outward toward the periphery of the abrasive
disk and thereafter into the waste stream. By utilizing the
inventive fluid-dynamically-configured apertures, the process of
removing debris is significantly accelerated when compared to
standard prior art structures; indeed, the aggregate airflow can be
sufficient to eliminate the need for an external vacuum source.
Since the pressure differential is localized, the removal forces
and effectiveness are not affected by the workpiece size or
abrasive contact area. For example, in the field of CMP pad
conditioning, the use of the localized venturi complement
separately applied flows and will allow for a sufficient vacuum to
be maintained as the abrasive moves outward over the edge of the
polishing pad (a situation which, in the past, would cause the
applied vacuum force to "break" and allow the debris to remain in
the peripheral region of the pad). By localizing the pressure
differential at the point where abrasion is occurring and
containing it within a backing plate, the swarf can therefore be
directed in a more predictable manner. The localized aspect of the
created flow is also useful from a mechanical point of view, in
terms of allowing for localized introduction of coolants, removal
of heat, and the ability to control the stream direction for both
introduced and removed elements.
[0043] Instead of creating apertures of tapered geometry, the
plurality of apertures themselves may be tilted to create a similar
pressure differential, as shown in the embodiment of FIG. 6. In
this case, a fluid-dynamically-configured abrasive disk 300
includes a plurality of apertures 310. Each aperture 310 has
essentially the same diameter D, as illustrated along bottom
surface 320 and top surface 330 of abrasive disk 300. However, the
apertures are shown as tilted to a predetermined angle .theta.,
where the angled arrangement will create the desired pressure
differential or impart a predetermined directional force vector at
a predetermined radial position.
[0044] The scope of the present invention is intended to cover any
fluid-dynamically configured arrangement of features within an
abrasive component. FIGS. 7 and 8 illustrate two more exemplary
arrangements, also shown in the form of an abrasive disk. FIG. 7
illustrates a fluid-dynamic abrasive disk 400 where each aperture
410 is formed to comprise a first diameter d1 through a certain
predetermined thickness of disk 400, and thereafter taper outward,
as shown by opening 420, to a final diameter d2. The resultant
structure exhibits a funnel-like configuration. Again, the
difference in diameter from d1 to d2 will provide the pressure
differential sufficient to force the debris upward and away from
the workpiece surface (venturi action). The apertures need not
comprise linear sidewalls, as shown by the embodiment of FIG. 8,
where a fluid-dynamic abrasive disk 500 includes apertures 510
having a curved or `airfoil`-shaped sidewall(s) 520. As described
above, the rotation of abrasive disk 500 will draw the material
from the workpiece surface and into a collection system (not
shown).
[0045] In arrangements that utilize an impeller (or backing plate)
in conjunction with an abrasive disk, the impeller blades
themselves may be configured to improve the flow of debris from the
workpiece surface to the waste system. It is possible to design
both the abrasive disk and impeller to exhibit fluid dynamic
attributes or, alternatively, so design one or the other component.
Indeed, by incorporating fluid-dynamic features into the impeller
design, additional advantages may be obtained. For example, the
movement of air will function to cool the surface of the workpiece
being abraded (thus preventing overheating). Moreover, the
application of cleaning materials (in conjunction with the abrading
process) will be considerably more uniform across the workpiece
surface by virtue of the specific impeller configuration.
Additionally, the impeller can be designed to contain the removed
waste material or alternatively pump `coolant` back into the
workpiece for additional process benefits. In particular, the
impeller can be formed to include a plurality of channels for
directing the flow of waste material in a manner such that the
material is sectionalized (e.g., into regions defined by the
impeller blades) into isolated regions to reduce the possibility of
re-entry into either the abrasive or the workpiece.
[0046] FIG. 9 contains an isometric perspective view of an
exemplary fluid-dynamic impeller 600 formed to include a plurality
of impeller blades 610. In accordance with the present invention,
each blade 610 is specifically designed to exhibit an airfoil-like
structure (i.e., curvedly tapering inward from the outer periphery
620 of impeller plate 630 toward the central region 640 of impeller
plate 630). The curvature of blades 610 in the manner shown will
improve the pressure balance and flow of debris from a workpiece
surface toward an associated outlet port. An alternative impeller
configuration is shown in FIG. 10, where a two-dimensional
modification of the blade profile (compared to the prior art blade
shown in FIG. 3) will provide fluid-dynamically-based improvement
in the movement of debris material from the workpiece surface. In
this arrangement, an impeller 700 comprises a set of impeller
blades 710 disposed in a type of "pinwheel" configuration such that
as the impeller is rotated, the created pressure differential will
force the debris to the periphery of the system.
[0047] While the embodiments of the present invention discussed
thus far have illustrated the formation of a fluid-dynamic abrasive
disk, it is to be understood that the abrasive may also take the
form of a belt, drum, wheel, or any other abrasive configuration
suitable for a specific purpose. FIG. 11 illustrates an exemplary
fluid-dynamically-designed abrasive belt grinder 800, including a
belt 810 that moves in a linear direction with respect to the
workpiece being abraded, this translational movement indicated by
arrow L in FIG. 11. A plurality of apertures 820 are formed in belt
810 that create a pressure differential between bottom surface 830
and top surface 840 of belt 810, directing the swarf upward and
away from a workpiece (a lifting force). Thereafter, the swarf is
drawn through apertures 845 in a vacuum plenum 850 and ultimately
directed into a containment vessel (not shown). Importantly, the
fluid-dynamically-designed arrangement of FIG. 11 will draw
substantially all of the swarf/debris from the workpiece. As
mentioned above, there are many situations where the workpiece
being abraded includes a hazardous material that will be introduced
into the exhaust flow. The ability to provide an efficient and
complete containment of this material in accordance with the fluid
dynamic aspects of the inventive abrasive greatly diminishes the
potential for contamination of the environment, inhalation by a
worker, and/or re-incorporation of the material into the
workpiece.
[0048] FIG. 12 illustrates an exemplary abrasive drum embodiment of
the present invention. As shown, a drum 900 is formed to include at
least an outer surface 910 of abrasive material (alternatively, the
abrasive grit may be disposed through the thickness t of the drum),
with a plurality of apertures 920 formed therethrough. The number
and configuration of the apertures is considered to be a matter of
design choice. In accordance with the present invention, a
plurality of airfoils 930 are disposed on an inner surface 940 in
the manner shown in FIG. 12. As drum 900 rotates (shown by arrow r
in FIG. 12), the presence of the airfoils will pull any swarf
created by the abrading process through apertures 920 and toward
the center 950 of drum 900. A central vacuum attachment (not shown)
may then be used to remove the entrained swarf.
[0049] Yet another embodiment of the present invention is shown in
FIG. 13, in this case in the form of an abrasive wheel 1000, having
an abrasive outer surface 1100. Abrasive wheel 1000 is shown as
having a thickness T, with a plurality of apertures 1200 formed
through the thickness thereof. A plurality of airfoils 1300 are
disposed around the inner periphery 1400 of wheel 1000. As wheel
1000 rotates, the combination of apertures 1200 and airfoils 1300
will draw the swarf towards the center of wheel 1000. In this
particular embodiment, a containment shroud 1500 is included and
disposed around the central portion of wheel 1000 to collect the
swarf.
[0050] Having thus described various embodiments of the present
invention, it is to be appreciated that there are many other
variations, alterations, modifications and improvements of the
specifically-described embodiments that may be made by those
skilled in the art. Such variations, alterations, modifications and
improvements are intended to be part of this disclosure and thus
also intended to be part of this invention. Accordingly, the
foregoing description and drawings are by way of the example only,
and the scope of this invention is rather defined by the claims
appended hereto.
* * * * *