U.S. patent application number 12/817461 was filed with the patent office on 2011-02-17 for apertured abrasive disk assembly with improved flow dynamics.
Invention is credited to Stephen J. Benner, Darryl W. Peters.
Application Number | 20110039485 12/817461 |
Document ID | / |
Family ID | 43357061 |
Filed Date | 2011-02-17 |
United States Patent
Application |
20110039485 |
Kind Code |
A1 |
Benner; Stephen J. ; et
al. |
February 17, 2011 |
Apertured Abrasive Disk Assembly With Improved Flow Dynamics
Abstract
The evacuation properties of an abrasive disk are improved by
forming its apertures to exhibit a configuration that will direct
process fluids onto or away from a workpiece (or contact) interface
through capillary action, surface tension/affinity, and/or boundary
layer pump actions. The capillary action is accomplished by
modifying the geometries of the apertures to form capillary tubes,
where the orientation and lift angle of the capillary tubes is
controlled to improve the flow of relatively thin layers of
liquids. The surface tension/affinity between a liquid material and
the abrasive disk is controlled by modifying the through-hole
apertures to exhibit a serrated inner surface, which will decrease
the attraction between the material of the abrasive disk and the
process liquid. A plurality of apertured disks may be stacked, and
their respective apertures properly arranged on each surface, to
create a Tesla pump such that the kinetic energy associated with
rotation of the disk assembly will preferentially bias both the
vertical and tangential flow of liquids between the working surface
and the disk assembly.
Inventors: |
Benner; Stephen J.;
(Lansdale, PA) ; Peters; Darryl W.;
(Stewartsville, NJ) |
Correspondence
Address: |
Wendy W. Koba, Esq.
PO Box 556
Springtown
PA
18081
US
|
Family ID: |
43357061 |
Appl. No.: |
12/817461 |
Filed: |
June 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61218473 |
Jun 19, 2009 |
|
|
|
Current U.S.
Class: |
451/548 |
Current CPC
Class: |
B24D 7/10 20130101; B24B
55/06 20130101 |
Class at
Publication: |
451/548 |
International
Class: |
B24B 27/00 20060101
B24B027/00 |
Claims
1. An abrasive disk assembly comprising: a substrate having a top
surface and a bottom surface, at least the bottom surface having a
coating of an abrasive composition; and a plurality of apertures
formed through the thickness of the substrate wherein the plurality
of apertures are configured to bias the flow of process fluids
therethrough.
2. An abrasive disk assembly as defined in claim I wherein the
plurality of apertures are configured as capillary tubes to bias
the flow of liquids therethrough.
3. An abrasive disk assembly as defined in claim 2 wherein the
plurality of capillary tube apertures comprise essentially
identical dimensions and orientation.
4. An abrasive disk assembly as defined in claim 2 wherein at least
a first group of the capillary tube apertures are oriented to
direct fluid away from a surface being worked and a second group of
the capillary tube apertures are oriented to direct fluid toward a
surface being worked.
5. An abrasive disk assembly as defined in claim 2 wherein the
plurality of capillary tube apertures comprise a teardrop-shaped
configuration.
6. An abrasive disk assembly as defined in claim 5 wherein each
teardrop-shaped aperture is defined by an internal angle .phi. that
is defined by the relation 2(90.degree.-.alpha.), where .alpha. is
defined as the wetting angle of the fluid passing through the
aperture.
7. An abrasive disk assembly as defined in claim 2 wherein the
plurality of capillary tube apertures comprise apertures of varying
dimension.
8. An abrasive disk assembly as defined in claim 2 wherein the
plurality of capillary tube apertures are disposed at a
predetermined angle with respect to the thickness of the
substrate.
9. An abrasive disk assembly as defined in claim 1 wherein the
plurality of apertures comprise a serrated interior wall to reduce
the affinity between the material forming the substrate and the
liquid passing therethrough.
10. An abrasive disk assembly as defined in claim 1 wherein the
assembly further comprises a plurality of apertured disks aligned
with the substrate in a stacked configuration so as to create
boundary layers therebetween, wherein upon rotation of the abrasive
disk assembly the combination of the apertures and boundary layers
create laminar flow of liquids between the assembly and a worked
surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/218,473, filed Jun. 19, 2009, which is herein
incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to an abrasive disk assembly
and, more particularly, to an abrasive disk assembly including
through-hole apertures of a form that create flow of liquid
materials between the abrasive disk and the surface being worked,
with the configuration of the individual apertures and their
arrangement designed to bias the flow of material either away from
(i.e., exhaust) or onto (i.e., dispensed) the surface being worked
(or a combination of both).
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. Additionally, the
mechanical abrasion process generates significant heat as a
by-product of the frictional forces and plastic deformation of the
workpiece; it is advantageous to control this heat with lubricants
and/or coolants. Abrasive grinders come in many forms, stationary
or portable, where an exemplary form of the prior art comprises a
portable body that is adapted to be held by a user, the grinder
including a motor that drives an abrasive disk assembly or backing
plate, which in turn carries an abrasive disk for grinding the
surface of a workpiece. In a "vacuum" type grinder, a shroud in the
vicinity of the backing plate and abrasive disk defines a chamber
through which air and entrained particles are drawn to an outlet,
"powered" by a separate vacuum source, leading to an accumulation
point. The abrasive disk and backing plate are provided with holes
that, when aligned, form an air passage to allow the flow of air
and entrained particles which were drawn by suction to the shroud.
At times, liquids are dispensed onto the surface of the article
being abraded for cooling and/or to assist in the removal of the
surface material and provide a mechanism for transporting the
abraded particles away from the workpiece.
[0004] In some abrasive tool configurations, dust is collected in a
complex collection system through a hose connected to the abrasive
tool. Dust collection systems, however, are not always available
for the abrasive tool operator and cannot be used to contain
processing liquids that may be need to be extracted from the
surface of a work piece.
SUMMARY OF THE INVENTION
[0005] The needs remaining in the prior art are addressed by the
present invention, which relates to an abrasive disk assembly
utilized in grinding/polishing/planarizing applications and, more
particularly, to an abrasive disk assembly including through-hole
apertures of a form that create a flow of gaseous and/or liquid
materials between an apertured abrasive disk and the surface being
worked, with the configuration of the individual apertures and
their arrangement designed to bias the flow of liquids either away
from (exhaust) or onto (dispense) the surface being worked (or a
combination of both).
[0006] In accordance with the present invention, the evacuation
properties of an abrasive disk are improved by forming the
apertures to exhibit a configuration that will draw process fluids
upward through capillary action, surface tension/affinity, and/or
boundary layer pump actions. The capillary action of one embodiment
of the inventive disk is accomplished by modifying the geometries
of the through-hole apertures to form capillary tubes, where the
orientation, lift angle and capacity/volume of the capillary tube
apertures is controlled to improve the flow (based on the
requirements of the process) of relatively thin layers of liquids,
to larger volumes of air or coolants; the capillary "tubes" (or
spaces) may vary in geometry across the surface of the abrasive
disk and can, in fact, include a first set of capillary tubes
oriented to bias the flow of liquids toward a working surface and a
second set of capillary tubes oppositely oriented to bias the flow
of liquids away from a working surface. The surface
tension/affinity between a liquid material and the abrasive disk
can also be controlled in accordance with the present invention by
further modifying the through-hole apertures to exhibit a serrated
inner surface, which will decrease the attraction between the
material of the abrasive disk and the process liquid. Additionally,
a plurality of apertured disks may be stacked, and their respective
apertures properly arranged on each surface, to create a Tesla
(boundary layer) pump such that the kinetic energy associated with
rotation of the disk assembly will preferentially bias both the
vertical and tangential flow of liquids between the working surface
and the disk assembly, controlling the flows and self-powering the
input/dispense and exhaust functions.
[0007] In one embodiment of the present invention, an abrasive disk
with improved capillary action is provided by including a plurality
of teardrop-shaped apertures across the surface of the abrasive
disk, where the wetting angle of the involved materials (i.e.,
abrasive disk and process fluid) is controlled to provide the
desired capillary action. The apertures thus form a plurality of
capillary tubes; the tubes themselves may be disposed at an angle
with respect to the top and bottom major surfaces of the abrasive
disk. The specific geometry, of the teardrops can also be modified
as a function of placement across the disk (i.e., radial
differential) to adjust for differences in fluid movement at the
periphery of the disk when compared to the central area of the
disk. The orientations of different groupings of the apertures may
also be controlled so that a first set of apertures draw liquid
away from the working surface, and a second set of apertures direct
liquid toward the working surface.
[0008] In an alternative embodiment, the abrasive disk apertures
may also be formed to exhibit serrated sidewalls that function to
break the surface tension between the process fluid and the
material forming the apertured disk itself, thus improving the flow
of liquid through the apertures.
[0009] In yet another embodiment of the present invention, a
plurality of apertured disks are stacked such that a combination of
their apertures form flow paths (input and/or exhaust) that take
advantage of the rotational velocity of the stack in the form of a
Tesla pump, regulating and controlling the flow volumes associated
with the cooling/lubricating (input) and abrading (removal/exhaust)
process.
[0010] Various other aspects and embodiments 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
[0011] Referring now to the drawings, where like numerals represent
like parts in several views:
[0012] FIG. 1 is a top view of an exemplary apertured abrasive disk
formed in accordance with the present invention to encourage
capillary flow through the apertures;
[0013] FIG. 2 is a top view of an exemplary teardrop-shaped
aperture as included in the apertured conditioning disk of FIG.
1;
[0014] FIG. 3 is a cut-away side view of the teardrop-shaped
aperture of FIG. 2;
[0015] FIG. 4 is a cut-away side view of an angularly-disposed,
teardrop-shaped aperture for use in the abrasive disk of the
present invention;
[0016] FIG. 5 is a top view of an exemplary abrasive disk including
capillary action-based apertures having different geometries,
formed in accordance with the present invention;
[0017] FIG. 6 is a top view of yet another embodiment of a
capillary action-based embodiment of the present invention, with
the orientation of the apertures controlled to provide paths for
both dispensing liquids to and exhausting liquids from a workpiece
surface;
[0018] FIG. 7 is a top view of an alternative aperture geometry for
use in the apertured abrasive disk of the present invention, in
this case comprising a serrated geometry, used to break the surface
tension between the material of the abrasive disk and the
composition of the liquid;
[0019] FIG. 8 is a cut-away side view of the serrated aperture of
FIG. 7;
[0020] FIG. 9 is an isometric view of the serrated aperture of FIG.
7; and
[0021] FIG. 10 is a cut-away side view of an exemplary Tesla pump
configuration of an apertured abrasive disk assembly formed in
accordance with the present invention.
DETAILED DESCRIPTION
[0022] In accordance with the present invention, is has been
discovered that fluid movement in association with an abrading
process can be improved by configuring an abrasive disk assembly to
include apertures in the disk that bias the flow of liquids between
the disk assembly and working surface. In particular, a plurality
of three-dimensional (vertical and horizontal) apertures are formed
through the thickness of an abrasive disk to improve flow dynamics
in at least one of several ways: (1) configuring the apertures as
capillary tubes (e.g., teardrop shape, triangular, diamond, or the
like); (2) configuring the apertures to break the surface tension
between the disk and the flowing liquid (e.g., serrated apertures,
reverse sloped/chamfered walls, etc.); or (3) configuring the disk
assembly as a stack of apertured disks to create fluid movement
upon rotation (e.g., Tesla pump) and extend the flow toward the
periphery.
[0023] By properly designing the apertures of an abrasive disk, for
example in a teardrop geometry, it is possible to take advantage of
capillary action along a sidewall of the apertures within the
abrasive disk to draw the process fluids up and away from a surface
being abraded (i.e., an embodiment for exhausting the fluid flow
away from the interface between the abrasive disk and the work
surface). In essence, each aperture becomes a capillary tube,
drawing process fluids up and away from the surface being abraded.
Alternatively, the capillary-based apertures may be oriented to
encourage the movement of the fluid toward the surface being worked
(i.e., an embodiment to bias the flow of liquids toward the
interface between the abrasive disk and the work surface), an
embodiment useful in dispensing process fluids/coolant onto the
work surface.
[0024] FIG. 1 is a top view of an exemplary abrasive disk 10 with
improved capillary action formed in accordance with the present
invention. In this particular embodiment, abrasive disk 10 is
formed to include a plurality of through-hole apertures 12 of a
teardrop-shaped geometry that allows for capillary action to take
place as shown. While the "teardrop" shape is shown in FIG. 1 and
various other drawings, it is to be understood that other
geometries, as mentioned above, may also be used. FIG. 2 is an
enlarged top view of an exemplary teardrop-shaped abrasive disk
aperture 12 and FIG. 3 is an isometric view of an exemplary
aperture 12, showing its capillary tube structure. Apertures 12 are
understood to be formed through the entire thickness of abrasive
disk 10, between its top surface 14 and bottom surface 16. The
location of top surface 14 is shown in both FIGS. 1 and 3, with the
location of bottom surface 16 indicated in FIG. 3.
[0025] Capillary action is associated with the movement of liquids
within thin tubes (or porous material) in an "up-hill" manner
contrary to the force of gravity. Capillary action is based on the
wetting angle .alpha. of the materials involved, in this case, the
chemistry of the particular process fluids and the composition of
the abrasive disk. For example, when drawing water into a plastic
capillary tube (with a surface tension of about 70 mN/m at room
temperature), a wetting angle .alpha. of 80.degree. has been found
sufficient. For purposes the present invention, an internal angle
.phi. of aperture 12 of less than 2*(90.degree.-.alpha.) will
provide the desired capillary action. FIG. 2 illustrates this
internal angle .phi.. Presuming a contact angle .phi. of
80.degree., an internal angle .phi. of 20.degree. or less for
aperture 12 is preferred.
[0026] As best shown in FIG. 3, capillary action will draw the
process fluids up a sidewall 18 of aperture 12 in the area of
internal angle .phi., taking advantage of the surface tension
between the fluid and the abrasive disk to initiate/leverage the
forces for liquid removal. The capillary action creates an affinity
between the process fluids and the material forming the abrasive
disk, enhanced by aperture geometry, drawing the fluid up into the
capillary tube and away from the surface (when employed in a n
embodiment where the desired action is to draw the processing
fluids and entrained wastes away from the interface). Further
improvements in capillary action can be achieved by angling the
capillary-tube apertures 12 in the manner shown in FIG. 4. In
particular, FIG. 4 illustrates an exemplary aperture 12 that has
been formed to exhibit an angle .gamma. with respect to bottom
surface 16 of disk 12.
[0027] By configuring the apertures of the abrasive disk so as to
bias the operation of the disk to encourage evacuation of process
fluids and wastes, the arrangement of the present invention is able
to remove desired amounts from extremely thin layers of liquid
(e.g., thickness on the order of 10 .mu.m), up to large interfacial
or air/fluid volumes. Prior abrasive processes have not necessarily
been able to take full advantage of the available surface tension
for removing such thin layers of material. These apertures can also
be designed whereby they are "activated" with adjustments to liquid
properties (e.g., surfactants or non-reactive liquids with high or
low surface tensions can be added to increase or decrease the
contact angle).
[0028] As mentioned above, the capillary action-based apertures in
the inventive abrasive disk may comprise different geometries
across the surface of the disk. In particular, the capillary
action-based apertures around the outer periphery of the abrasive
disk may have a different configuration than the capillary
action-based apertures in the central area of the abrasive disk to
adjust for rotationally-induced flow dynamics.
[0029] FIG. 5 is a top view of an exemplary abrasive disk 20
including capillary action-based apertures having different
geometries in terms of their internal angle (based upon, for
example, differences in desired wetting angle as a function of
aperture distribution across the disk). Referring to FIG. 5, a
first group of apertures 22, formed around the periphery area 24 of
disk 20, is configured to exhibit a relatively large internal angle
.phi..sub.outer while a second of group of apertures 26, formed in
the central region of disk 20, is configured to exhibit a
relatively small internal angle .phi..sub.inner. The dimensions of
the capillary-based apertures may also be modified and multiple
other groups of apertures may be included, with each having a
specifically-tailored geometry based on, for example, their radial
displacement across the surface of the abrasive disk.
[0030] The apertured abrasive disk of the present invention, as
noted above, may be used to either effectively dispense liquids
onto a surface being worked, or draw liquid away from the surface.
It is further possible to configure and arrange capillary
action-based apertures that perform both operations (i.e., dispense
and exhaust) across the surface of a single disk. FIG. 6 is a top
view of one exemplary configuration of this embodiment, with a
first plurality of apertures 30 disposed to have the teardrop
internal angle .phi. disposed on the "left-hand" termination of
apertures 30. A second plurality of apertures 32, of similar
dimension, are disposed to have their teardrop internal angle
disposed on the "right-hand" termination of apertures 32. Upon use,
when the disk is rotating in one direction (for example,
clockwise), apertures 30 will function to draw liquid upwards and
away from a surface being worked (not shown). Alternatively, when
the disk is rotating in the opposite direction (for example,
counterclockwise), apertures 32 will function to quickly and
efficiently dispense liquids onto the surface being worked. As with
the arrangement discussed above in FIG. 5, the apertures themselves
do not all have to be the same size. Moreover, various ones (or
all) of the apertures may further include a serrated interior
surface to break the affinity between the disk and the liquid being
moved.
[0031] Using apertures of differing geometries will enable balanced
evacuation to take place across the surface of the abrasive disk.
Additionally, the use of capillary action-based apertures helps to
maintain the directional bias during operational conditions such as
slow rotational speed of the abrasive disk, low effluent flow, and
the like. Moreover, as described above, the capillary action-based
apertures may be configured to provide embodiments to either draw
liquid away from the working surface or dispense liquid onto the
working surface, as desired.
[0032] Another technique for improving flow through an apertured
disk, as mentioned above, is the use of serrated apertures. FIG. 7
is a top view of an exemplary serrated aperture 50, having
corrugated periphery 52 that functions to break the surface tension
between the material forming the abrasive disk itself and the
liquid flowing through the aperture. FIG. 8 is a cut-away side view
of serrated aperture 50, particularly illustrating a set of
sidewall fins 54 created by the serrated structure. FIG. 9 is an
isometric view of aperture 50. The serrated geometry reduces the
liquid/solid surface energy and, as a result, reduces the
attraction between the two sufficient to enable the complete
transfer of liquid therebetween.
[0033] As mentioned above, the flow of liquids through an abrasive
disk assembly may also be improved by using a plurality of stacked
disks, with the apertures aligned to assist in the vertical and
tangential movement of fluids. FIG. 10 is a cut-away side view of
an exemplary disk assembly 60 illustrating this embodiment, which
includes an apertured abrasive disk 62 positioned at the "bottom"
of the stack and used to perform the abrading action. Abrasive disk
62 includes a plurality of apertures 64, as shown. Also included in
disk assembly 60 is a set of backing disks 66, 68 and 70, with
apertures 67 formed in disk 66 and apertures 69 formed in disk 68
70. The apertures are shown as being aligned, thus allowing for the
free flow of liquids through the stack away from (or on to) the
surface being worked. By virtue of having a gap "g" in the spacing
between adjacent disks, a plurality of channels (i.e., boundaries)
are formed create a laminar flow situation, efficiently moving
liquids away from the worked surface.
[0034] This structure is considered as a Tesla pump arrangement
where, as the abrasive disk assembly is rotated, the kinetic energy
associated with rotation and surface tension of the liquid causes
the liquid to be drawn upward and into the channels, extracting the
liquid away from the surface being abraded. The Tesla pump
configuration is particularly useful in applications where the disk
is rotating at relatively low speeds and an efficient method of
removing/dispensing liquid material is desired.
[0035] 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, as well as their application to
other abrasive tool forms (e.g., cup, periphery, shaped, polishing
pads, brushes, and the like) 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.
* * * * *