U.S. patent application number 11/846207 was filed with the patent office on 2008-03-06 for method for achieving grain orientation.
This patent application is currently assigned to ENERGY CONVERSION SYSTEMS HOLDINGS, LLC. Invention is credited to Candace Stephenson Barefoot, George Dane Goodson, Shepard Lynn Hockaday, Timothy Glenn King, Ray John Matthews, John David Reece, Jr., Jeffrey Shaw Smith, Pimol Ballard Vonkchalee.
Application Number | 20080054708 11/846207 |
Document ID | / |
Family ID | 39030835 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080054708 |
Kind Code |
A1 |
Hockaday; Shepard Lynn ; et
al. |
March 6, 2008 |
METHOD FOR ACHIEVING GRAIN ORIENTATION
Abstract
Systems and methods for electrical component, e.g., brush,
manufacture are provided that control grain orientation. The
systems and methods utilize hot pressing techniques to enhance the
properties and functionalities of the electrical
components/brushes. An intermediate work product characterized by a
grain orientation is initially formed through a conventional
pressing technique. The conventionally-pressed intermediates are
positioned within a cavity/die with the grain orientation in a
predetermined orientation relative to the hot press force to be
applied thereto. The hot pressed final product exhibits superior
resistivity, strength and apparent density/durability. Surface
features may be formed on the face(s) of the final work product
during the hot pressing step that cannot be achieved in
conventional processing techniques. Advantageous articles of
manufacture, e.g., brushes and brush assemblies, are also
disclosed.
Inventors: |
Hockaday; Shepard Lynn;
(Benson, NC) ; Barefoot; Candace Stephenson;
(Dunn, NC) ; Goodson; George Dane; (Dunn, NC)
; King; Timothy Glenn; (Coats, NC) ; Matthews; Ray
John; (Willow Spring, NC) ; Reece, Jr.; John
David; (Erwin, NC) ; Smith; Jeffrey Shaw;
(Dunn, NC) ; Vonkchalee; Pimol Ballard; (Apex,
NC) |
Correspondence
Address: |
MCCARTER & ENGLISH , LLP STAMFORD OFFICE
FINANCIAL CENTRE , SUITE 304A, 695 EAST MAIN STREET
STAMFORD
CT
06901-2138
US
|
Assignee: |
ENERGY CONVERSION SYSTEMS HOLDINGS,
LLC
Dunn
NC
|
Family ID: |
39030835 |
Appl. No.: |
11/846207 |
Filed: |
August 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11515467 |
Sep 1, 2006 |
|
|
|
11846207 |
|
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Current U.S.
Class: |
300/21 ;
29/527.1; 419/11 |
Current CPC
Class: |
B22F 2998/10 20130101;
H01R 39/24 20130101; B22F 2998/00 20130101; B22F 7/02 20130101;
H01R 43/12 20130101; B22F 3/14 20130101; B22F 2003/145 20130101;
Y10T 29/49119 20150115; B22F 2998/00 20130101; B22F 2998/10
20130101; Y10T 29/4998 20150115; C22C 32/0052 20130101; B22F 3/02
20130101; B22F 3/14 20130101; B22F 2207/11 20130101; Y10T 29/49009
20150115 |
Class at
Publication: |
300/21 ;
29/527.1; 419/11 |
International
Class: |
A46D 3/00 20060101
A46D003/00; B22F 3/14 20060101 B22F003/14; B23P 17/00 20060101
B23P017/00 |
Claims
1. A method for fabricating a work piece, comprising: a. providing
a powder mixture; b. pressing the powder mixture to form an
intermediate work product characterized by a grain orientation that
is perpendicular to an axis defined by force application during
said pressing; c. orienting the intermediate work product in a
cavity with the grain orientation in a predetermined alignment
relative to a force axis to be applied to the cavity; and d. hot
pressing the intermediate work product to form a final work
product.
2. A method according to claim 1, wherein the powder mixture
includes at least one of carbon and copper.
3. A method according to claim 1, wherein the intermediate work
product is characterized by a specific resistivity, break strength
and apparent density.
4. A method according to claim 3, wherein the final work product is
characterized by (i) a specific resistivity that is less than the
specific resistivity of the intermediate work product; (ii) a break
strength that is greater than the break strength of the
intermediate work product; and (iii) an apparent density that is
greater than the apparent density of the intermediate work
product.
5. A method according to claim 1, wherein the intermediate work
product is oriented in the hot pressed cavity such that the grain
orientation is independent of the force axis.
6. A method according to claim 5, wherein the intermediate work
product is oriented in the cavity such that the grain orientation
defines a circumferential or axial grain orientation after hot
pressing.
7. A method according to claim 1, wherein the intermediate work
product is oriented in the cavity such that the grain orientation
defines a tangential grain orientation after hot pressing.
8. A method according to claim 1, further comprising positioning an
ancillary component to be joined to the intermediate work product
during hot pressing.
9. A method according to claim 8, wherein the ancillary component
is a lead wire.
10. A method according to claim 1, further comprising positioning a
plurality of intermediate work products in the cavity in
side-by-side relation prior to hot pressing.
11. A method according to claim 10, wherein the final work product
is a multi-layer brush assembly.
12. A method according to claim 1, wherein the cavity is adapted to
form at least one surface feature on a face of the final work
product during hot pressing.
13. A method according to claim 12, wherein the at least one
surface feature is formed on an end face of the final work product
and is non-planar.
14. A final work product fabricated according to the method of
claim 1.
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present disclosure is directed to systems and methods
for brush manufacture and, more particularly, to systems and
methods that control grain orientation in components, assemblies
and other articles of manufacture. Exemplary systems and methods
disclosed herein utilize hot pressing techniques to enhance the
properties and/or functionalities of brushes and other electrical
components.
[0003] 2. Background Art
[0004] In the field of motor design, a brush is provided to
interact with, i.e., contact, a rotating commutator. Brushes are
typically fabricated from carbon and/or copper-containing powder
mixtures and brush design is generally recognized as being critical
to the operation and durability of the motor assembly. A
conventional method for manufacturing a graphite brush is disclosed
in Japanese Laid-Open Patent Publication No. 90-51345. The brush is
manufactured from a mixture of powders including an aluminum
abrasive, molybdenum disulfide and tungsten disulfide, each powder
consisting of particles having diameters of less than 50 .mu.m. The
powders are combined in a solution of adhesives, pulverized and
prepared with powders having a diameter 100 .mu.m. The total
mixture is then compressed at a pressure of 0.25 tons/cm.sup.2 and
fired at a temperature of 700.degree. C.
[0005] U.S. Pat. No. 5,447,681 to Seung et al. discloses a method
for manufacturing a metal graphite brush that includes the steps of
preparing natural graphite powders, wet-mixing the graphite powders
with adhesives, pulverizing the mixed powders to diameters of less
than 200 .mu.m, press-molding the powders under a pressure of 2-3
ton/cm.sup.2 and heating at a temperature 700.degree. C. A lead
wire is then attached to the press-molded component.
[0006] Despite efforts to date, techniques for fabrication of
brushes imposes significant limitations on the design, geometry,
structural features and properties/performance. Moreover, brushes
and brush assemblies fabricated according to conventional
processing techniques/methodologies are characterized by durability
issues based, at least in part, on density limitations associated
with conventional fabrication techniques. These and other
shortcomings and limitations are overcome by the techniques,
methods and articles of manufacture disclosed herein.
SUMMARY
[0007] The present disclosure is directed to systems and methods
for manufacture of electrical components, e.g., brush manufacture,
and, more particularly, to systems and methods that enable and/or
support advantageous control of grain orientation in manufacture of
such components, e.g., brush manufacture. Exemplary systems and
methods disclosed herein utilize hot pressing techniques to enhance
the properties and/or functionalities of brushes and other
electrical components, e.g., carbon and/or copper-containing
components. The disclosed techniques and methodologies have wide
ranging applications, including the manufacture and/or fabrication
of pressed-to-size brushes that are anisotropic, i.e., brushes that
have differing physical properties based on the direction of
measurement.
[0008] According to exemplary embodiments of the present
disclosure, a powder mixture is initially pressed in a conventional
manner to form an intermediate work product. The conventional
pressing step establishes a grain orientation within the
intermediate work product that is perpendicular to the direction of
the compression forces applied thereto during the conventional
pressing process. Thereafter, the conventionally-pressed
intermediate work product is further processed by a hot pressing
technique, wherein the initial grain orientation of the
intermediate work product is maintained while compression forces
are applied in the hot pressing step. Through the hot pressing
step, the density of the work piece is further increased, thereby
enhancing the durability thereof, e.g., when employed as a brush or
other electric component. Superior functional properties, such as
specific resistivity and strength, are also imparted to the work
piece through the disclosed hot pressing technique.
[0009] Thus, an advantageous fabrication technique is disclosed
wherein a powder mixture is provided and processed to form a work
piece having desirable physical and/or functional properties. The
contents and percentage composition of the powder mixture are not
significant to the disclosed fabrication technique. Indeed, the
disclosed fabrication technique may be applied to any
mixture/blend, e.g., conventional carbon and/or copper-containing
powder mixtures. Thus, as is known in the art, different
mixtures/blends are routinely employed to fabricate brushes having
desired physical properties and functional characteristics, any of
which may be employed according to the disclosed fabrication
technique. Alternative powder mixtures may also be employed.
[0010] The powder mixture is initially subjected to a conventional
pressing technique to form an intermediate work product. The
conventional pressing step establishes a grain orientation within
the intermediate work product such that grains are substantially
perpendicular to the force vectors applied to the powder mixture.
According to conventional fabrication techniques, the conventional
pressing technique is generally followed by finishing steps, e.g.,
finish grinding and the like. However, according to the
advantageous fabrication technique of the present disclosure, the
conventionally-pressed intermediate work product is subjected to a
hot pressing step wherein the grains of the intermediate work
product are maintained regardless of the force vectors associated
with the hot pressing process.
[0011] Through the hot pressing step, the properties of the
intermediate work product are enhanced. In addition, the hot
pressing step may be used (i) to impart advantageous surface
features to the work piece that are not achievable in conventional
pressing techniques, (ii) to capture ancillary members/components,
e.g., a lead wire/flex member, in ways not possible with
conventional pressing techniques, and/or (iii) to form advantageous
multi-layer brush assemblies. Indeed, the disclosed fabrication
techniques and methods may be employed to form press-to-fit brush
members that are not achievable using conventional compression
molding techniques.
[0012] In addition to the advantageous fabrication techniques
disclosed herein, the present disclosure is directed to
advantageous electrical components, e.g., brushes and brush
assemblies, that are formed, in whole or in part based on the
disclosed fabrication techniques. Thus, the present disclosure
provides brushes and brush assemblies that define a first axis,
wherein the internal grains of the brush/brush assembly are
substantially aligned with the first axis and wherein molded
surface features are formed on at least one face that is traversed
by such first axis. In a further exemplary embodiment of the
present disclosure, a brush assembly is provided that is
characterized by a plurality of distinct conventionally-pressed
layers, wherein the layers are bonded to each other and wherein the
grains of the individual layers can be controlled independent of
each other. In exemplary embodiments of the disclosed multi-layer
brush assembly, a plurality of distinct intermediate work pieces
(e.g., three) are formed by conventional pressing techniques and
then introduced to a die for simultaneous hot pressing, thereby
forming the desired multi-layer brush assembly. Multi-layer brush
assemblies have particular applicability in washing machine
applications, as is well known to persons skilled in the art.
[0013] Additional features, functions and advantages of the
disclosed fabrication techniques/methods and the articles of
manufacture formed thereby will be apparent from the detailed
description which follows, particularly when read in conjunction
with the appended figures.
BRIEF DESCRIPTION OF THE FIGURE(S)
[0014] To assist those of ordinary skill in the art in making and
using the disclosed fabrication techniques and articles of
manufacture, reference is made to the accompanying figures,
wherein:
[0015] FIG. 1 is a schematic depiction of a conventional pressing
step according to the present disclosure;
[0016] FIGS. 2A-2C are schematic diagrams showing an exemplary hot
pressing technique for use in hot pressing an intermediate work
piece according to the present disclosure;
[0017] FIG. 3 is a schematic illustration of three work pieces
(brushes) that are distinguished by the orientation of the grains
as they would be defined relative to a commutator;
[0018] FIG. 4 is a plan view of an exemplary brush with flex
fabricated according to the advantageous method of the present
disclosure;
[0019] FIG. 5 is a flow chart illustrating an exemplary fabrication
technique according to the present disclosure;
[0020] FIG. 6 is a depiction of three individual conventionally
pressed components in a side-by-side arrangement; and
[0021] FIGS. 7A and 7B are depictions of a multi-layered brush
assemblies formed according to the present disclosure.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0022] Systems and methods for manufacture of electrical
components, e.g., brushes, and advantageous electrical components,
e.g., brushes/brush assemblies, are provided herein. The disclosed
systems, methods and articles of manufacture advantageously control
grain orientation in the manufacturing process such that
advantageous physical and functional properties are imparted
thereto. The disclosed systems and methods utilize hot pressing
techniques to provide enhanced properties and/or functionalities to
brushes and other electrical components, e.g., carbon and/or
copper-containing systems, and find wide ranging applications,
including the manufacture and/or fabrication of pressed-to-size
brushes.
[0023] According to exemplary embodiments of the present
disclosure, a powder mixture is initially pressed in a conventional
manner to form an intermediate work product. With reference to FIG.
1, a conventional pressing step is schematically depicted. A
substantially axial compression force, as represented by opposed
arrows F.sub.1 and F.sub.2, is applied to a powder mixture 10 that
is contained within a cavity or die (not pictured). As
schematically depicted in FIG. 1, application of the compression
force causes grains within the mixture to align in a substantially
perpendicular orientation. Grain alignment is schematically
depicted by a series of stacked planar regions 12a, 12b, etc. As is
known in the art, conventional pressing of powder mixtures, e.g.,
carbon and/or copper-containing powder mixtures used in the
fabrication of brushes/brush assemblies, necessarily establishes a
grain orientation that is perpendicular to the force vectors
applied thereto. Moreover, as is also known in the art, due to
limitations associated with conventional pressing equipment,
surface features can only be applied to or formed on the work piece
during conventional pressing techniques on the top or bottom
surface thereof. Attempts to apply/form surface features on side
walls of the work piece are generally limited and/or foreclosed by
the nature of the conventional pressing operation.
[0024] The operating conditions for the conventional pressing step
may vary according to various process parameters, e.g., powder
mixture, equipment capabilities, target geometry, and the like. The
degree to which work piece density may be increased through
conventional pressing techniques is generally restricted due to
various processing limitations, e.g., the potential for cracked
dies and/or parts sticking to tooling if the press tonnages are
increased beyond certain limits.
[0025] According to the present disclosure, the intermediate work
product formed through conventional pressing is further processed
in an advantageous hot pressing step to enhance the properties
thereof and, if desired, to provide beneficial surface features,
combine ancillary components (e.g., a lead wire/flex), and/or form
advantageous multi-layer articles, e.g., a multi-layer brush
assembly. The intermediate work piece is thus positioned in a
cavity/die that is adapted for hot pressing, as described herein.
With reference to FIGS. 2A-2C, the interaction between an exemplary
intermediate workpiece and an exemplary cavity/die in a hot
pressing step is schematically depicted. Individual cavities/dies
may be sized/configured so as to receive insets that provide
desired geometric properties, surface features and/or accommodate
positioning of ancillary component(s) that are to be joined to
and/or captured by the work piece, e.g., a lead wire/flex.
[0026] Of note, the intermediate work piece may be introduced to
the hot pressing cavity/die such that the grains formed in the
previously completed, conventional pressing step are substantially
aligned with the axis of the die, i.e., parallel to the force
vector associated with the hot pressing step, or are substantially
perpendicular to the force vector associated with the hot pressing
step. In circumstances where the grains are positioned parallel to
the hot pressing force vector, there are two degrees of freedom.
Thus, with reference to FIGS. 2A-2C, intermediate work piece 20 is
introduced to a hot pressing cavity/die 22 that includes a surface
treatment geometry 24 formed on a lower face thereof. As clearly
seen in FIG. 2A, the grains of the intermediate work piece 20 are
advantageously aligned with force vectors F.sub.3 and F.sub.4
within die/cavity 22 (see force vectors in FIG. 2B). A hot pressing
force is applied to intermediate work piece 20 (as shown in FIG.
2B), typically at an elevated hot pressing temperature, for a hot
pressing treatment period sufficient to achieve the desired
effect(s) on the intermediate work piece 20. A final work product
30 is formed with an advantageous surface effect 32 formed on the
face that was in contact with surface treatment geometry 24. In the
exemplary embodiment of FIGS. 2A-2C, the surface effect 32 takes
the form of an arcuate, ridged surface, although the present
disclosure is not limited to such exemplary surface effect, as will
be readily apparent to persons skilled in the art. Indeed, surface
effects may be achieved on the top, bottom and/or side surfaces of
the intermediate work piece (and ancillary components may be
introduced to the intermediate work piece, e.g., a lead wire)
during the hot pressing step disclosed herein.
[0027] With reference to FIG. 3, three exemplary brushes are
schematically depicted to illustrate potential grain orientations.
In the left-most view, the grains are aligned having a
circumferential grain orientation, i.e., a "G.C." orientation. In
the middle view, the grains are aligned with an axial grain
orientation, i.e., a "G.A." orientation. Finally, the right-most
view illustrates an exemplary brush assembly wherein the grains
form/define a tangential grain orientation, i.e., a "G.T."
orientation.
[0028] As with the conventional pressing step discussed above, the
processing parameters associated with the hot press step may be
varied without departing from the spirit or scope of the present
disclosure. Processing conditions will depend on such variables as
the composition of the intermediate work piece, the desired
geometric properties of such work piece at the conclusion of the
hot pressing step, and the desired physical/functional properties
thereof.
[0029] With further reference to FIG. 3, it is noted that surface
properties may be advantageously established through the disclosed
hot pressing technique on the top and/or bottom faces of the G.C.
and G.A. brushes that could not be effectively achieved with
conventional pressing techniques. While it is possible to machine
surface features onto the end faces of a work piece after
conventional pressing, it is not possible to form detailed and/or
non-planar surface features on the faces of the work piece that are
perpendicular to the grain orientation. Moreover, the advantageous
fabrication techniques of the present disclosure facilitate the
formation of detailed and/or non-planar surface features in the hot
pressing step, thereby greatly enhancing the effectiveness,
flexibility and utility of electrical component fabrication, e.g.,
brush fabrication.
[0030] With reference to FIG. 4, an exemplary brush 40 is depicted
that includes an intricate and non-planar surface geometry 42 on a
face that is perpendicular to the grain orientation thereof. Such
non-planar surface geometry 42--which may be termed a
"press-to-fit" geometry--is advantageously defined during the hot
pressing step by forcing the intermediate work piece (with grains
aligned with the force vector) into a mold having the desired
geometry. In addition, a lead wire/flex 44 is advantageously
introduced to and captured by brush 40 in an orientation that is
perpendicular to the grain orientation of the brush 40. As with
non-planar surface geometry 42, introduction of a lead wire 44 in a
perpendicular orientation as shown in FIG. 4 cannot be achieved
with conventional pressing techniques.
[0031] With reference to FIG. 5, an exemplary flow chart for the
disclosed fabrication technique is provided. As shown therein, the
process generally involves: [0032] 1. Providing a powder mixture
having desired blend characteristics, e.g., a carbon and/or
copper-based powder mixture; [0033] 2. Conventionally pressing the
powder mixture to form an intermediate work product; and [0034] 3.
Hot pressing the intermediate work product to form a final work
product.
[0035] Operating conditions associated with the hot pressing step
will vary depending on a host of factors, e.g., the powder
constituents and relative percentages thereof, size and geometry of
the intermediate work product, etc. Generally, the hot pressing
step is conducted at temperatures that range from about 125.degree.
to 1000.degree. F., at pressures that range from about 4000 to
50,000 psi, and for processing times sufficient to achieve the
desired work product design/functionality.
[0036] Through the hot pressing step, the density of the work piece
is further increased relative to the density achieved by way of a
conventional pressing step, thereby enhancing the durability of the
work piece, e.g., when employed as a brush/brush assembly. Superior
functional properties such as specific resistivity/lower resistance
and strength are also imparted to the work piece through the
disclosed hot pressing technique. The final work piece may also
demonstrate increased oxidation resistance, longer life and, as
noted previously, may feature complicated/advantageous
shapes/surface features. Exemplary advantageous results achieved
through the fabrication process of the present disclosure are set
forth in TABLE 1 herein below. The "control" results are reflected
at the left for each physical property, and the results according
to the present disclosure are set forth at the right.
[0037] As shown above, the disclosed fabrication method that
involves hot pressing a conventionally-pressed intermediate work
product yields a work piece with superior properties, with testing
showed excellent improvements in all relevant properties. The
disclosed fabrication method yielded products with reduced
resistance, greater strength, and higher density (which translates
to enhanced durability). The superior properties imparted through
the disclosed fabrication technique are effective across a variety
of powder mixtures, and the contents and percentage composition of
the such powder mixtures, e.g., carbon and/or copper-containing
mixtures, are not significant to the superior results achieved
thereby. Indeed, the disclosed fabrication technique may be applied
to any carbon and/or copper-containing powder mixture/blend.
[0038] With reference to FIGS. 6 and 7A, the advantageous utility
of the disclosed fabrication technique in forming a multi-layer
brush assembly is illustrated. In FIG. 6, three distinct
conventionally-pressed intermediate work products 50, 52, 54 are
shown in a side-by-side position. Each of the intermediate work
products is characterized by a grain orientation that is
independent of the potential line of contact with an adjacent work
product. Indeed, one or more of the elements that are positioned in
a side-by-side relationship may be devoid of grain orientations. By
positioning the intermediate work pieces in a cavity/die for hot
pressing, as disclosed herein, a multi-layered brush assembly 60 as
shown in FIG. 7A is fabricated. An adhesive material may be placed
between adjacent intermediate work products, if desired.
[0039] Of note, in exemplary embodiments of the present disclosure,
one or more of the layers need not take the form of a pressed work
product. For example, as shown in FIG. 7B, outer layers 72, 76 may
surround an intermediate layer 74 that takes the form of a tape,
powder and/or wafer of a completely different material, to form an
advantageous multi-layer assembly 70. The multi-layer brush
assemblies of FIGS. 7A and 7B benefit from the attributes of the
individual intermediate work products and are particularly useful
in high intensity applications, e.g., washing machine motors or the
like.
[0040] Thus, the present disclosure provides advantageous systems
and methods for fabrication of carbon-based members, e.g., brushes,
and advantageous articles of manufacture fabricated thereby.
Although the disclosed systems, methods and articles of manufacture
have been described with reference to exemplary embodiments
thereof, the present disclosure is not limited by such exemplary
embodiments. Rather, the disclosed systems, methods and articles of
manufacture are susceptible to modifications, enhancements and/or
variations without departing from the spirit or scope of the
present disclosure. Such modifications, enhancements and/or
variations are expressly encompassed within the scope of the
present invention.
* * * * *