U.S. patent application number 14/453755 was filed with the patent office on 2015-02-12 for brush assembly for an electric motor.
This patent application is currently assigned to Black & Decker Inc.. The applicant listed for this patent is Black & Decker Inc.. Invention is credited to Colin M. Crosby, Barak N. Gohn, Daniel F. Heck, Stephen P. Osborne, Ryan F. Schroeder, William D. Spencer.
Application Number | 20150042189 14/453755 |
Document ID | / |
Family ID | 51292873 |
Filed Date | 2015-02-12 |
United States Patent
Application |
20150042189 |
Kind Code |
A1 |
Osborne; Stephen P. ; et
al. |
February 12, 2015 |
BRUSH ASSEMBLY FOR AN ELECTRIC MOTOR
Abstract
An electric motor includes a stator, an armature rotatably
received within the stator and having an armature shaft on which a
commutator is mounted, and a brush assembly defining a first
surface facing the stator and a second surface opposite the first
surface. The brush assembly includes a brush card mount disposed
around the commutator, brushes in sliding contact with the
commutator to supply electric current to the commutator, and
thermally-conductive brush holders. Each brush holder a base
portion disposed substantially along a same plane as a surface of
the brush card mount to form the first surface of the brush
assembly, and a main portion protruding from the second surface of
the brush assembly to house a respective brush. The base portions
of the brush holders are exposed on the first surface of the brush
assembly to transfer heat generated by the brushes through the
first surface of the brush assembly.
Inventors: |
Osborne; Stephen P.;
(Pikesville, MD) ; Heck; Daniel F.; (Baltimore,
MD) ; Crosby; Colin M.; (Baltimore, MD) ;
Schroeder; Ryan F.; (Hampstead, MD) ; Gohn; Barak
N.; (Shrewsbury, MD) ; Spencer; William D.;
(Ellicott City, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Black & Decker Inc. |
Newark |
DE |
US |
|
|
Assignee: |
Black & Decker Inc.
Newark
DE
|
Family ID: |
51292873 |
Appl. No.: |
14/453755 |
Filed: |
August 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61864264 |
Aug 9, 2013 |
|
|
|
61932932 |
Jan 29, 2014 |
|
|
|
Current U.S.
Class: |
310/63 ;
310/239 |
Current CPC
Class: |
H02K 3/38 20130101; H02K
3/527 20130101; H01R 39/385 20130101; H02K 7/145 20130101; H02K
5/18 20130101; H02K 13/00 20130101; H01R 39/381 20130101; H02K 9/04
20130101; H02K 7/085 20130101; H02K 13/10 20130101; H02K 9/28
20130101; H02K 9/06 20130101; H02K 5/148 20130101 |
Class at
Publication: |
310/63 ;
310/239 |
International
Class: |
H02K 13/10 20060101
H02K013/10; H02K 9/06 20060101 H02K009/06 |
Claims
1. An electric motor comprising: a stator; an armature rotatably
received within the stator, the armature having an armature shaft
on which a commutator is mounted; and a brush assembly defining a
first surface facing the stator and a second surface opposite the
first surface, the brush assembly comprising: a brush card mount
disposed around the commutator; a plurality of brushes in sliding
contact with the commutator to supply electric current to the
commutator; and a plurality of thermally-conductive brush holders
each having a base portion disposed substantially along a same
plane as a surface of the brush card mount to form the first
surface of the brush assembly, and a main portion protruding from
the second surface of the brush assembly to house a respective
brush; wherein the base portions of the brush holders are exposed
on the first surface of the brush assembly to transfer heat
generated by the brushes through the first surface of the brush
assembly.
2. The electric motor of claim 1, further comprising a fan
rotatably attached to the armature and disposed between the brush
assembly and the stator.
3. The electric motor of claim 2, wherein the first surface of the
brush assembly is disposed in close proximity to the fan.
4. The electric motor of claim 3, wherein rotation of the fan
causes air to flow from the second surface of the brush assembly,
through the brush assembly and around the commutator, towards the
fan.
5. The electric motor of claim 4, wherein the first surface of the
brush assembly forms a baffle for the fan to redirect airflow
generated by the fan in a centrifugal direction.
6. The electric motor of claim 1, wherein the brush card mount
includes a plurality of openings and the main portions of the brush
holders protrude from the base portions through the plurality of
openings.
7. The electric motor of claim 6, wherein the plurality of brush
holders are received from the first surface of the brush assembly
through the openings of the brush card mount and are affixed to the
brush card mount on the second surface of the brush assembly.
8. The electric motor of claim 7, wherein the brush card mount
includes recessed surfaces around the plurality of openings on the
first surface of the brush assembly and the base portions of the
brush holders are partially disposed within the respective recessed
surfaces.
9. The electric motor of claim 7, wherein the base portion is
provided as a separate piece from the main portion.
10. The electric motor of claim 1, wherein the brush card mount
includes a plurality of openings and the plurality of brush holders
are slidingly received within the plurality of openings from the
periphery of the brush card mount in a radial direction.
11. The electric motor of claim 10, wherein the brush card mount
comprises separate planar pieces separated by the plurality of
openings, and the base portions of the brush holders are slidingly
received within the openings and supported by the separate planar
pieces of the brush card mount.
12. The electric motor of claim 10, wherein each brush holder
includes grooves on both sides thereon and the planar pieces
comprise side guides on both sides thereon arranged to mate with
the grooves of the brush holder as the brush holder is received
inside the opening of the brush card mount.
13. The electric motor of claim 1, wherein the plurality of brush
holders comprises four brush holders disposed equidistantly around
a periphery of the brush card mount.
14. The electric motor of claim 1, wherein the plurality of brush
holders occupy at least 40% of a total area of the first surface of
the brush assembly.
15. The electric motor of claim 1, wherein the brush card mount
comprises: a planar portion disposed around the commutator; a
bridge portion disposed at an end of the commutator and extending
from the planer portion via a plurality of legs; and at least one
metal routing disposed on or within the bridge portion to
electrically couple the plurality of brushes.
16. A power tool comprising: a housing; and an electric motor
including a stator; an armature rotatably received within the
stator, the armature having an armature shaft on which a commutator
is mounted; and a brush assembly defining a first surface facing
the stator and a second surface opposite the first surface, the
brush assembly comprising: a brush card mount disposed around the
commutator; a plurality of brushes in sliding contact with the
commutator to supply electric current to the commutator; and a
plurality of thermally-conductive brush holders each having a base
portion disposed substantially along a same plane as a surface of
the brush card mount to form the first surface of the brush
assembly, and a main portion protruding from the second surface of
the brush assembly to house a respective brush; wherein the base
portions of the brush holders are exposed on the first surface of
the brush assembly to transfer heat generated by the brushes
through the first surface of the brush assembly.
17. The power tool of claim 16, further comprising a fan rotatably
attached to the armature and disposed between the brush assembly
and the stator.
18. The power tool of claim 16, wherein the brush card mount
includes a plurality of openings and the main portions of the brush
holders protrude from the base portions through the plurality of
openings.
19. The power tool of claim 16, wherein the brush card mount
includes a plurality of openings and the plurality of brush holders
are slidingly received within the plurality of openings from the
periphery of the brush card mount in a radial direction.
20. The power tool of claim 16, wherein the plurality of brush
holders occupy at least 40% of a total area of the first surface of
the brush assembly.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This utility application claims the benefit of U.S.
Provisional Application No. 61/864,264 filed Aug. 9, 2013, and U.S.
Provisional Application No. 61/932,932 filed Jan. 29, 2014,
contents of both of which are incorporated herein by reference in
their entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to a brush assembly for
electric motors, and more particularly to a brush assembly for
motors used in electric power tools.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] Known portable power tools typically have an electric motor
received within a tool housing. One common type of electric motor
used in power tools has a rotor, a stator, and brushes. The rotor
includes a rotor shaft, laminations mounted on the rotor shaft,
armature windings wound in slots in the lamination stack, and a
commutator mounted on the rotor shaft and electrically connected to
the armature windings. The stator may have field windings wound in
laminations, or may have permanent magnets. The brushes are mounted
in brush housings, often known as brush boxes or brush holders, in
sliding electrical contact with the commutator. Electric current is
supplied from a power source through the brushes to the commutator,
and from the commutator to the armature windings.
[0005] The brushes and brush holders are typically part of a brush
assembly(ies). The brush holders and brushes are disposed
diametrically opposite to each other with the commutator disposed
therebetween. The brush assembly(ies) includes springs that urge
the brushes against the commutator. Exemplary brush assemblies may
utilize two or four brushes around the commutator.
[0006] Generally, in brush assemblies, transmission of electric
current across the sliding interface between the brushes and the
motor commutator generates a considerable amount of heat. This heat
is often associated with the material used in the brushes. Such
materials have relatively higher electrical resistance in order to
enhance desirable brush properties such as low friction coefficient
and high durability. The heat is also generated from the electrical
arcing that occurs when electrical switching occurs as the
commutator and brushes rotate with respect to each other. It is
desirable for this heat to be transferred away from the brushes and
dissipated, for example by impinging air flow.
[0007] Conventional brush holder designs often include a brush card
mount that is made of a plastic material and the brush holders
mounted on a top surface of the brush card mount. The plastic brush
card mount separates the brush holders and the brushes from the
rest of the motor, where a cooling fan is usually disposed to cool
the motor stator and armature. This results in a high thermal
coefficient between the brushes and the cooling air, which
correspondingly results in high temperatures. Some conventional
designs utilize larger brushes or larger air flow paths to increase
the surface area of the brushes or brush holders in the path of the
airflow, but such designs result in larger and more expensive
motors.
[0008] What is needed is a brush assembly design that enables more
efficient heat transfer from the brushes and brush holders.
SUMMARY
[0009] According to an embodiment of the invention, an electric
motor is provided including: a stator, an armature rotatably
received within the stator and having an armature shaft on which a
commutator is mounted, and a brush assembly. In an embodiment, the
brush assembly defines a first surface facing the stator and a
second surface opposite the first surface. In an embodiment, the
brush assembly includes a brush card mount disposed around the
commutator, brushes in sliding contact with the commutator to
supply electric current to the commutator, and thermally-conductive
brush holders. In an embodiment, each of the brush holders includes
a base portion disposed substantially along a same plane as a
surface of the brush card mount to form the first surface of the
brush assembly, and a main portion protruding from the second
surface of the brush assembly to house a respective brush. In an
embodiment, the base portions of the brush holders are exposed on
the first surface of the brush assembly to transfer heat generated
by the brushes through the first surface of the brush assembly.
[0010] According to an embodiment, a fan is rotatably attached to
the armature and disposed between the brush assembly and the
stator. In an embodiment, the first surface of the brush assembly
is disposed in close proximity to the fan. In an embodiment,
rotation of the fan causes air to flow from the second surface of
the brush assembly, through the brush assembly and around the
commutator, towards the fan. In an embodiment, the first surface of
the brush assembly forms a baffle for the fan to redirect airflow
generated by the fan in a centrifugal direction.
[0011] In an embodiment, the brush card mount includes a plurality
of openings and the main portions of the brush holders protrude
from the base portions through the plurality of openings. In an
embodiment, the brush holders are received from the first surface
of the brush assembly through the openings of the brush card mount
and are affixed to the brush card mount on the second surface of
the brush assembly. In an embodiment, the brush card mount includes
recessed surfaces around the openings on the first surface of the
brush assembly and the base portions of the brush holders are
partially disposed within the respective recessed surfaces. In an
embodiment, the base portion is provided as a separate piece from
the main portion.
[0012] In an embodiment, the brush card mount includes a plurality
of openings and the brush holders are slidingly received within the
openings from the periphery of the brush card mount in a radial
direction. In an embodiment, the brush card mount includes separate
planar pieces separated by the openings, and the base portions of
the brush holders are slidingly received within the openings and
supported by the separate planar pieces of the brush card mount. In
an embodiment, each brush holder includes grooves on both sides
thereon and the planar pieces include side guides on both sides
thereon arranged to mate with the grooves of the brush holder as
the brush holder is received inside the opening of the brush card
mount.
[0013] In an embodiment, there are four brush holders disposed
equidistantly around a periphery of the brush card mount. In an
embodiment, the brush holders occupy at least 40% of a total area
of the first surface of the brush assembly.
[0014] In an embodiment, the brush card mount includes a planar
portion disposed around the commutator, a bridge portion disposed
at an end of the commutator and extending from the planer portion
via two or more legs, and at least one metal routing(s) disposed on
or within the bridge portion to electrically couple the
brushes.
[0015] According to an embodiment of the invention, a power tool is
provided, comprising a housing and an electric motor disposed in
the housing. According to an embodiment, the motor includes a
stator, an armature rotatably received within the stator and having
an armature shaft on which a commutator is mounted, and a brush
assembly. In an embodiment, the brush assembly defines a first
surface facing the stator and a second surface opposite the first
surface. In an embodiment, the brush assembly includes a brush card
mount disposed around the commutator, brushes in sliding contact
with the commutator to supply electric current to the commutator,
and thermally-conductive brush holders. In an embodiment, each of
the brush holders includes a base portion disposed substantially
along a same plane as a surface of the brush card mount to form the
first surface of the brush assembly, and a main portion protruding
from the second surface of the brush assembly to house a respective
brush. In an embodiment, the base portions of the brush holders are
exposed on the first surface of the brush assembly to transfer heat
generated by the brushes through the first surface of the brush
assembly.
[0016] The above-described embodiments substantially improve heat
transfer from the brushes and brush holders by providing metallic
heat sinks on the first surface of the brush assembly on the path
of air flow from the motor fan. This arrangement thus improves heat
transfer from the brushes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1A and 1B depict perspective side views of a four-pole
brush assembly (also referred to herein as brush card) 100,
according to an embodiment;
[0018] FIGS. 2 and 3 respectively depict top and bottom views of
the four-pole brush card 100, according to an embodiment;
[0019] FIG. 4 depicts a perspective expanded view of brush card
100, according to an embodiment;
[0020] FIG. 5 depicts a zoomed-in view of the bridge portion 112
showing the channels 124a and 124b and the vertical drop 128 within
the channel 124b, according to an embodiment;
[0021] FIG. 6A depicts a rear perspective view of the brush card
mount 102 prior to the bearing 136 being inserted and heat-staked,
according to an embodiment;
[0022] FIG. 6B depicts a rear perspective view of the brush card
mount 102 after the bearing 136 is inserted into the bearing pocket
126 and heat-staked, according to an embodiment;
[0023] FIG. 7A depicts a front perspective view of a four-pole
brush card 200, according to an alternative embodiment;
[0024] FIG. 7B depicts a rear perspective view of the brush card
mount 202 of the brush card 200, according to an embodiment;
[0025] FIG. 7C depicts a perspective view of the brush card mount
202, according to an embodiment;
[0026] FIG. 8 depicts a rear perspective view of a conventional
brush assembly 300 including a brush card mount 302, brush holders
304, and brushes 306, according to an embodiment;
[0027] FIGS. 9A-9C depict various expanded and assembled views of a
brush holder 104 and a brush card mount 102, according to an
embodiment;
[0028] FIG. 10 depicts a zoomed-in perspective view of the top
surface of the brush card 100 showing the upwardly-projecting legs
158 crimped over the top surface of the brush card mount 102 within
recessed pockets 172, according to an embodiment;
[0029] FIGS. 11A through 11D depict various views of the brush
holder 104, including the base piece 150 and the main piece 160
crimped together, according to an embodiment;
[0030] FIG. 12 provides a rear perspective view of the brush card
100 and a cut-off portion of a motor fan 502, according to an
embodiment;
[0031] FIG. 13A depicts a perspective view of a brush card 400
having a modified (extruded) brush holder 404 design, according to
an alternative embodiment;
[0032] FIG. 13B depicts a perspective view of the brush card 400
without the brush holders 404, according to an embodiment;
[0033] FIGS. 14A and 14B depict perspective and cross-sectional
views of the brush holder 404, according to an embodiment;
[0034] FIG. 15 depicts a partial cross-sectional view of a power
tool 500 including a motor assembly 510 having a brush assembly
100, a stator 512, a rotor 514, and a fan 502, according to an
embodiment;
[0035] FIGS. 16A-16C depict various perspective and side views of
the fan 502, according to an embodiment;
[0036] FIG. 17 depicts a zoomed-in view of the fan 502 inside the
tool housing 508, according to an embodiment;
[0037] FIG. 18 depicts a cross-sectional view of a tool housing 508
including the brush card 100, without the motor 510 and the fan
502, according to an embodiment;
[0038] FIG. 19 depicts the fan 502 mounted on a fully wound and
molded rotor 514, according to an embodiment;
[0039] FIG. 20 depicts a perspective view of the same fan 502 and
rotor 514 without the windings 552, according to an embodiment;
[0040] FIGS. 21A-21C depict perspective views of a rotor end
insulator 560, according to an embodiment;
[0041] FIG. 22 depicts a spring 110 used in the brush card 100,
according to an embodiment;
[0042] FIG. 23 depicts a partial perspective view of the brush card
100 with the spring 110 inserted on the post 108 and engaging the
brush 106, according to an embodiment;
[0043] FIG. 24 depicts a rear view of the brush card 100 showing
the first leg 604 of the spring 110 inside the pocket 614,
according to an embodiment; and
[0044] FIG. 25 depicts a brush 106 inside the brush holder 104,
according to an embodiment.
DETAILED DESCRIPTION
[0045] Reference will now be made in detail to various aspects and
embodiments of the invention, examples of which are illustrated in
the accompanying drawings.
Four-Pole Brush Card with Bridge Connector
[0046] A first aspect of the invention is discussed herein. FIGS.
1A and 1B depict perspective side views of a four-pole brush
assembly (also referred to herein as brush card) 100, according to
an embodiment of the invention. FIGS. 2 and 3 respectively depict
top and bottom views of the four-pole brush card 100, according to
an embodiment. In this embodiment, brush card 100 includes a brush
card mount 102 and four brush holders 104. The brush card mount 102
has a substantially circular circumference and the four brush
holders 104 are arranged equidistantly on four sides of the brush
card mount 102. Each brush holder 104 accommodates a brush 106
therein. The brushes 106 housed in brush holders 104 facing each
other are electrically connected to one another, as discussed
below. Both ends of each brush holder 104 are open to allow radial
movement of the brush 106 towards and away from a center of the
brush card 100. The brush card mount 102 includes upright posts 108
in close proximity to the brush holders 104. Each post 108 is
arranged to hold a wound portion of a spring 110. Each spring 110
includes an extended arm that engages a back surface of brush 106
inside the brush holder 104 to bias the brush 106 towards the
center of the brush card 100.
[0047] According to an embodiment, brush card mount 102 includes a
planar portion, to which brush holders 104 are secured. A middle
section of the planar portion includes an opening that receives a
motor commutator (not shown). The brush card mount 102 also
includes a bridge portion 112 arranged above the commutator opening
(and the commutator) and connected to the planar portion via four
bridge legs 114a, 114b, 116a, and 116b. Bridge legs 114a, 114b,
116a, and 116b extend longitudinally (i.e., in the direction of the
motor, at a substantially right angle with respect to the plane of
the brush card mount 102) from the planar portion to the bridge
portion 112. Radially formed between bridge legs 114a, 114b, 116a,
and 116b are gaps that allow for the radial movement of brushes
106.
[0048] According to an embodiment, bridge leg 114a and 114b form
walls that extend radially from the bridge portion 112 to (or near)
outer edges of the brush card mount 102. In an embodiment, the
bridge legs 116a and 116b similarly extend towards (or near) outer
edges of the brush card mount 102. This arrangement strengthens
support for the bridge portion 112. In addition, bridge leg 114a
mechanically supports and electrically isolates two terminals 118a
and 118b provided on both sides of its outward-extending wall.
Terminals 118a and 118b are connected to metal routings 120a and
120b, which extend over the bridge portion 112 to bridge leg 114b.
Metal routings 120a and 120b connect the brushes 106 facing each
other to one of the terminals 118a and 118b. Specifically, ends of
metal routings 120a and 120b are connected via wires 122 to either
corresponding brush holders 104 or brushes 106 via wires 120. In an
embodiment, metal routings 120a, 120b are routed around a shaft
bearing pocket 126, which holds a shaft bearing 136, as discussed
below in detail. In an embodiment, metal routing 120a crosses over
routing 120b to allow for opposite brushes 106/brush holders 104 to
be connected to the same terminal 118a or 118b.
[0049] FIG. 4 depicts a perspective expanded view of brush card
100, according to an embodiment. In this figure, brush card mount
102 is depicted separately from the rest of the brush card 100
components. In an embodiment, bridge portion 112 of the brush card
mount 102 includes channels 124a, 124b that accommodate metal
routings 120a, 120b. Each of the channels 124a, 124b in this
embodiment extends from leg 114a to leg 114b, around shaft bearing
pocket 126. Metal routings 120a, 120b include vertically-extending
teethed ends 132a, 132b on both ends, arranged to get pushed into
slots 134 of bridge legs 114a, 114b during the assembly process. It
is noted that other means such as an adhesive or molding mean be
used to secure the metal routings 120a, 120b to the bridge portion
112. Terminals 118a and 118b integrally extend from the routings
120a and 120b above the teethed ends 132a and 132b on the two sides
of leg 114a. Channel 124b includes a recessed portion 128 that
penetrates into bridge portion 112 between the shaft bearing pocket
126 and the bridge leg 114b. In an embodiment, recessed portion 128
is substantially vertical. The channel 124b extends out through the
bridge portion 112 from the end of the recessed portion 128 along a
lower plane. The recessed portion 128 intersects a portion of
channel 124a.
[0050] Metal routing 120b includes a penetrating portion 130 that
is received inside the recessed portion 128 of channel 124b. In an
embodiment, the penetrating portion 130 is substantially vertical.
This allows routing 120a to cross over metal routing 120b as it
extends through channel 124a to bridge leg 114b. This arrangement
creates a gap between the metal routings 120a and 120b that, in an
embodiment, is 1-3 mm. This gap is sufficient to prevent an
electrical shortage.
[0051] FIG. 5 depicts a zoomed-in view of the bridge portion 112
showing the channels 124a and 124b and the recessed portion 128
within the channel 124b, in an embodiment.
Shaft Bearing Retention
[0052] Another aspect of the invention is discussed herein with
reference to FIGS. 6A-7C.
[0053] According to an embodiment, as shown in FIG. 1A through FIG.
3 and FIGS. 6A and 6B, motor shaft bearing 136 is secured inside
the shaft bearing pocket 126 via heat staking. FIG. 6A depicts a
rear perspective view of the brush card mount 102 prior to the
bearing 136 being inserted and heat-staked. As shown in this
figure, the brush card mount 102 includes a plastic ring 138 around
the back side of the pocket 126. In an embodiment, plastic ring 138
slightly projects from a rear surface of the bridge portion 112.
FIG. 6B depicts a rear perspective view of the brush card mount 102
after the bearing 136 is inserted into the bearing pocket 126 and
heat-staked. In this embodiment, after the shaft bearing 136 is
inserted into the pocket 126, the plastic ring 138 is heated to
deform around the circumference of the rear surface of the shaft
bearing 136. The plastic ring 138 in this manner folds inwardly to
contain the bearing 136. This secures the bearing 136 inside the
pocket 126. According to an embodiment, the remaining components of
the brush card 100 are assembled on the brush card mount 102 after
the heat-staking is completed. Once brush card 100 is fully
assembled, the bearing 136 is press-fitted onto the motor shaft
(not shown) during motor assembly.
[0054] FIG. 7A depicts a front perspective view of a four-pole
brush card 200, according to an alternative embodiment of the
invention. FIG. 7B depicts a rear perspective view of the brush
card mount 202 of the brush card 200, according to an embodiment.
FIG. 7C depicts a perspective view of the brush card mount 202,
according to an embodiment. As shown in these figures, the top of
the bridge portion 212 does not include an opening as in the
previous embodiment. In other words, pocket 226 of the brush card
mount 202 is not open-ended. Instead, pocket 226 encloses the top
end of the shaft bearing 236. Metal routings 220a, 220b extend in
parallel over the bridge portion 212. The pocket 226 includes one
or more pins 228 inserted through two through-holes that extend
into the pocket 226 within the bridge portion 212. The
through-holes are positioned to place a portion of the pins 226
inside the pocket 226, as shown in FIG. 7B. The shaft bearing 236
includes a groove 238 formed on its outer surface. The groove 238
has the same width as the pins 226. As the shaft bearing 236 is
forced inside the pocket 226, it slides past the pins 228 until the
pins 228 are locked inside the groove 238. In an alternative
embodiment, the shaft bearing 236 is first placed inside the pocket
226 and the pins 228 are then inserted through the grooves 238. The
pins 228 securely hold the shaft bearing 236 inside the pocket
226.
[0055] In an alternative embodiment, instead of using two pins 226
as shown herein, any retention mechanism, e.g., an E-clip, a
C-clip, a single piece U-shaped retainer, a split ring, etc., may
be used to retain the shaft bearing 236.
Bottom-Mount Brush Holder
[0056] Another aspect of the invention is discussed herein with
reference to FIGS. 8-14B. FIG. 8 depicts a rear perspective view of
a conventional brush assembly 300 including a brush card mount 302,
brush holders 304, and brushes 306. Brush holders 304 are mounted
on a top surface of the brush card mount 302. Brush holders 304
include legs 308 that penetrate through openings, or around the
edges of the brush card mount 302 and crimp on the rear side of the
brush card mount 302. Brush holders 304 may be provided as single
piece or multi-piece units.
[0057] In four-pole motor platforms, particularly in the context of
power tool designs, the brush card 300 is arranged around a motor
commutator, with the rear surface of the brush card 300 facing the
motor stator and fan. The top surface of the brush card 300 (i.e.,
where the brush holders 304 are located) is arranged and at end of
the power tool in the proximity of air inlets. Brush holders 304
generate a substantial amount of heat resulting from the electrical
current passing through the brushes 306. As the fan spins, air is
sucked through the air inlets. Air flows around the brush holders
304, through the opening in the brush card 300 and around the outer
circumference of the brush card 300, into the fan. While the air
flow cools the brush holders 304 to some degree, the cooling effect
of the air flow in this conventional design is not sufficient in
many power tool designs, in particular in high power applications.
What is needed is a more effective cooling mechanism for the brush
assembly.
[0058] According to an embodiment of the invention, as shown in
FIGS. 9A-9C, a new brush holder/brush card design is provided. In
an embodiment, brush card mount 102 includes four openings 140 for
receiving the brush holders 104 through its rear surface. This
results in brush holders 104 occupying a large portion of the
surface area of the rear surface of the brush card 100 adjacent the
motor fan. Thus, in an embodiment, brush holders 104 act as heat
sinks to transfer heat away from the brush card 100. This design
significantly improves heat transfer as compared to the
conventional design discussed above.
[0059] According to an embodiment, each opening 140 of the brush
card mount 102, as viewed from the rear surface of the brush holder
104, is defined by two recessed surfaces 142 of the brush card
mount 102 on its sides and a boundary portion 144 of the brush card
mount 102 on its radial end. The recessed surfaces 142 each include
two slots 146.
[0060] As shown in the expanded view of FIG. 9A, the brush holders
104 (only one of which is shown herein) each include a base piece
150 and a main piece 160, according to an embodiment. The base
piece 150 in this embodiment includes a flat portion 152 and two
side portions 156. Flat portion 152 includes two rectangular slots
154. Side portions 156 each include two upwardly-projecting legs
158.
[0061] The main piece 160, in an embodiment, includes a
brush-holder portion 162 that is shaped to contain two side
surfaces and a top surface of the brush 106. Extending from side
ends the brush-holder portion 162 are two flat portions 166 that
extend parallel with the rear surface of the brush card mount 102.
The flat portions 166 each include two slots 168 that correspond to
and receive upwardly-projecting legs 158 of the base piece 150. In
addition, the brush-holder portion 162 includes two downward
protrusions 164 that correspond to and are received inside
rectangular slots 154 of the base piece 150. The side surfaces of
the brush-holder portion 162, in an embodiment, include openings
170 that is open-ended on a distal end of the brush holder 104 and
extends radially to accommodate the back and forth movement of the
spring 110 and the wires 122.
[0062] FIGS. 9B and 9C depict steps of assembling the brush holder
104 into the brush card mount 102, according to an embodiment of
the invention. As shown in FIG. 9B, the main piece 160 of the brush
holder 104 is inserted into the opening 140 of the brush card mount
102. The top surfaces of the flat portions 166 mate with the
recessed surfaces 142 of the bush card 102 around the opening 140.
The brush holder portion 162 penetrates through the opening 140 and
projects above the top surface of the brush card mount 102. Slots
168 of the main piece 160 in this position are aligned with slots
146 of the recessed surfaces 142.
[0063] Next, as shown in FIG. 9C, upwardly-projecting legs 158 of
the base piece 150 are inserted through the aligned slots 168 of
the main piece 160 and slots 146 of the recessed surfaces 142.
Downward protrusions 164 are received inside the rectangular slots
154 as the base piece 150 comes in contact with the main piece 160.
Side portions 156 of the base piece 150 mate with the back surfaces
of the flat portions 166 of the main piece 160. Once this step is
complete, the upwardly-projecting legs 158 are crimped as discussed
below. The flat portion 152 of the base piece 150, together with
the brush holder portion 162, form a rectangular box for holding
the brush 106.
[0064] FIG. 10 depicts a zoomed-in perspective view of the top
surface of the brush card 100 showing the upwardly-projecting legs
158 crimped over the top surface of the brush card mount 102 within
recessed pockets 172. Recessed pockets 172 each include two slanted
surfaces (see FIG. 4) between the slots 146. Crimped portions of
the upwardly-projecting legs 158 rest on these slanted surfaces
once they are crimped.
[0065] It is noted with reference to FIG. 10 that the top surface
of the boundary portion 144 of the brush card mount 102 is recessed
to accommodate insertion of the brush 106 inside the brush holder
104 once the brush holder 104 assembly is complete. It is further
noted that openings 170 of the brush holder 104 are arranged to
accommodate the back and forth movement of the spring 110 and the
wires 122 along with the brush 106.
[0066] FIGS. 11A through 11D depict various views of the brush
holder 104, including the base piece 150 and the main piece 160
crimped together. The brush card mount 102 is not shown in these
figures. However, as discussed above, in the fully-assembled brush
card 100, areas of the brush card mount 102 between recessed
surfaces 142 and recessed pockets 172 are sandwiched between the
crimp portions of the upwardly-projected legs 158 and the top
surfaces of the flat portions 166 of the brush holders 104.
[0067] The brush holder design of the invention discussed herein
provides several advantages. The two-piece assembly of the brush
holders into the brush card mount is relatively easy. Furthermore,
since the brush holders are inserted through a rear surface of the
brush card mount, the metallic base pieces 150 of the brush holders
104 are exposed in close proximity to the motor fan. The brush
holders 104 thus act as heat sink to transfer heat away from the
brush holders 104 and brushes 106. This arrangement substantially
improved overall heat transfer from the brush card 100.
[0068] FIG. 12 provides a rear perspective view of the brush card
100 and a cut-off portion of a motor fan 502, according to an
embodiment of the invention. As shown herein, in an embodiment, the
brush holders 104 occupy at least 40% of the total surface area of
the rear surface of the brush card 100. Preferably, the brush
holders 104 take up at least 45% of the total area of the surface
area of the rear surface of the brush card 100. More preferably,
the brush holders 104 take up at least 50% of the total area of the
surface area of the rear surface of the brush card 100.
Furthermore, in an embodiment of the invention as discussed in
detail below, the rear surface of the brush card 100 (including the
brush card mount 102 and brush holders 104) acts as a baffle for
the fan 502. As the motor fan 502, including the motor blades 504,
spins, air is sucked through air vents disposed across the top
surface of the brush card 100, through and around the brush card
100, into the fan 605. The air is then expelled radially between
the fan 502 and the brush card 100 through air outlets disposed in
alignment with the fan 502. The generated air flow thus makes
substantial contact with the rear surface of the brush holders 104,
which act as heat sinks for the respective brush holders 104 and
brushes 106, allowing them to cool down. This design substantially
improves heat control over the conventional design of FIG. 8
discussed above.
Brush Holder with Extruded Heat Sink
[0069] An alternative brush holder design is discussed herein with
reference to FIGS. 13A-14B, according to an embodiment of the
invention. FIG. 13A depicts a perspective view of a brush card 400,
according to this embodiment. The brush card 400 includes a brush
card mount 402 and brush holders 404. As in the previous
embodiment, brush card mount 402 has a substantially circular
periphery and the four brush holders 404 are arranged equidistantly
around the periphery of the brush card mount 402. The brush holders
404 facing each other are electrically connected to one another.
Each brush holder 404 houses a brush 406 therein. Both ends of each
brush holder 404 are open to allow radial movement of the bush
towards a center of the brush card 400. The brush card mount 402
includes posts 408 in close proximity to the brush holders 404. The
posts 408 accommodate springs 410, each of which includes an
extended arm that engages a back portion of a corresponding brush
406 to bias the brush 406 towards the center of the brush card 400.
Metal routings 420a, 420b are disposed on (over or within) bridge
portion 412 to connect brushes 406 that are arranged opposite each
other. As in the previously-described embodiments, metal routings
420a, 420b cross over each other within bridge portion 412.
Terminals 418a, 418b are disposed at the ends of the metal routings
420a, 420b. Wires 422 are also coupled between brushes 406 and the
metal routings 420a, 420b.
[0070] FIG. 13B depicts a perspective view of the brush card 400
without the brush holders 404. According to an embodiment,
similarly to the previous embodiments, bridge portion 412 includes
channels 424a, 424b formed therein for placement of metal routings
420a, 420b. Unlike the previous embodiment shown in FIGS. 9A-12, a
planar portion of the brush card mount 402 includes four separate
planar pieces 411 connected together via legs 414 of bridge portion
412. In other words, unlike the previous embodiment where boundary
portions 144 of the brush card mount 102 define openings 140 for
receiving the brush holder 104, the planar pieces 411 in this
embodiment are not connected to one another along the main plane of
the brush card mount 400. Instead, planar openings 416 between the
planar pieces 414 receive the brush holders 404 in a radial
direction. Planar pieces 411 include side guides 415 arranged to be
received in corresponding grooves of the brush holders 404, as
discussed below.
[0071] In an alternative embodiment, planar openings 416 may be
open-ended on the outer end for receiving the brush holders 404,
but close ended on the inner end to mechanically join the planar
pieces 411 to one another. In yet another embodiment, planar
openings 416 may be open-ended on the inner end for receiving the
brush holders 404, but close ended on the outer end to mechanically
join the planar pieces 411 to one another. Placing a ring on either
the inner or outer circumferences of the planar pieces 411 to
connect the planar pieces 411 together provides mechanical support
for the brush card 400 and enhances the moldability of the planar
pieces 411 during the manufacturing process.
[0072] FIGS. 14A and 14B depict perspective and cross-sectional
views of the brush holder 404, according to an embodiment. Brush
holder 404 in this embodiment includes a main body 450 and a base
portion 452 formed together integrally as one piece. The main body
450 includes openings 470 for facilitating the back and forth
movement of the springs 410 and the wires 422. The main body 450
includes side projections 454, which together with ends of the base
portion 454 form grooves 462. Grooves 462 receive side guides 415
of the brush card mount 402 as the brush holders 404 slides into
planar openings 416. In an embodiment, the grooves 462 are
press-fitted onto the guides 415. In an alternative embodiment, an
adhesive is used to secure the guides 415 inside the grooves
462.
[0073] According to an embodiment, once the brush holders 404 are
fitted between the planar pieces 411, a lower surface of the base
portion 452 acts as a heat sink to carry heat away from the brush
card 400, including the brush holder 404 and the brushes 406,
similarly to the previous embodiment. Additionally, in an
embodiment, the brush holder 404 includes projections 456, 458
projecting from the main body 450. In an exemplary embodiment shown
herein, four side projections 456 and two top projections 458 are
provided. Projections 456 and 458 increase the total surface area
of the brush holder 404, thereby improving heat transfer away from
the brush holder 404.
[0074] It must be noted that while projections 456, 458 shown in
FIGS. 14A and 14B are used with a single-piece brush holder design,
the same projections may be incorporated into the two-piece design
of FIGS. 9A-12 to improve heat transfer.
Motor Fan Assembly
[0075] Another aspect of the invention is discussed herein with
reference to FIGS. 15-17. FIG. 15 depicts a partial cross-sectional
view of a power tool 500, according to an embodiment. In this
embodiment, one half of the power tool housing 508 is shown for
illustration purposes, though it is understood that the second half
of the power tool housing includes more or less the same or similar
features. The power tool 100 in this embodiment includes the brush
card 100, including the brush card mount 102 and the brush holders
104, disposed at one end of the housing. Motor 510 in this
embodiment includes a motor stator (i.e., can) 512, a rotor 514,
and a commutator 516 rotatatably coupled to the rotor 514. The
commutator 516, only a portion of which is visible in this figure,
is disposed inside the brush card 100 between the four brushes 106.
The fan 502 is also rotatably attached to the rotor 514. The
operation of the motor 510 and its components is beyond the scope
of this disclosure and is not discussed in further detail, but
reference is made to U.S. Pat. No. 7,126,242 issued Oct. 24, 2006,
which is incorporated by reference in its entirety, as an example
of an electric motor.
[0076] FIGS. 16A-16C depict various perspective and side views of
the fan 502, according to an embodiment. FIG. 17 depicts a
zoomed-in view of the fan 502 inside the tool housing 508. As shown
in these figures, fan 502 includes a plurality of blades 504
arranged between a first inner ring 520 and a second outer ring
522. The inner ring 520 is arranged to mate with the rotor 514,
while the second ring 522 is disposed in the proximity of the brush
card 100, as shown in FIG. 15. Each fan blade 504 includes an inner
edge 524 that extends from a first end 520a of the inner ring 520
towards the rear surface of the brush card 100. In an embodiment,
the inner edge 524 is inclined towards the armature 516 and the
rotor 514 (i.e., at an angle to the longitudinal axis of the motor
510), though the inner edge 524 may be parallel to the tool housing
in an alternative embodiment. Each fan blade 504 also includes an
outer edge 526 that extends from the outer ring 522 towards the
stator 512 substantially in parallel with the longitudinal axis of
the motor 510. A first side edge 528 extends from a second end 520b
of the inner ring 520 to the end of the outer edge 526. The first
side edge 528, in an embodiment, is arranged at an angle away from
the stator 512 in the direction of the end of the outer edge 526. A
second side edge 530 extends from the outer ring 522 to the end of
the inner edge 524, substantially parallel to the rear surface of
the brush card 100. In an alternative embodiment, however, the
second side edge 530 may be inclined slightly towards the brush
card 100 as it meets the inner edge 524.
[0077] Since the inner edge 524 of the blades covers less air that
the outer edge 526 of the blades as the fan 502 spins, inner edge
524 generates lower air velocity near the center of the fan. In
order to generate equal air velocity throughout the fan 502, it is
desirable for the inner edge 524 to be longer than the outer edge
526. The embodiment of the invention discussed above ensures that
the length inner edge 524 of each blade 504 is greater than the
length of the outer edge 526. According to a further embodiment of
the invention, the outer surface of the inner ring 522 includes a
slanted surface 532 that is arranged at an angle away from the
brush card 100 in the direction of the outer edge 526. In an
embodiment, this slanted surface 532 may be arranged at at least a
45 degree angle with respect to the rear surface of the brush card
100. This arrangement helps reduce the length of the outer edge 526
of each blade 504 even further for more effective air flow
generation.
[0078] FIG. 18 depicts a cross-sectional view of a tool housing 508
including the brush card 100, without the motor 510 and the fan
502. According to an embodiment of the invention, air inlets 542
and 544 are provided in the rear and center portion of the power
tool housing 508. As the fan 502 rotates, it generates an air flow
from front inlets 542 through the motor 510, in particular in the
area between the stator 512 and the rotor 514, in an axial
direction to cool the motor 510. The air is then redirected in a
radial direction out of the power tool 500 through air vents 540
disposed in the tool housing 508 adjacent the fan 502. Similarly,
the fan generates an air flow from rear inlets 544 through the
brush card 100, particularly around the brush holders 104, and
through the area between brush holders 104 and the commutator 516,
in an axial direction to cool the brush card 100. This air is also
redirected in a radial direction out of the power tool 500 through
the same air vents 540. The rear surface of the brush card 100
(i.e., brush card mount 102 together with the brush holders 104)
forms a baffle to contain the air flow inside the fan 502 and out
of the vents 540. Similarly, the end surface 513 of the stator 512
facing the fan 502 forms a second baffle for the fan 502. These
baffles ensure that the air is property redirected through the
vents 540.
[0079] The angled surface of the first side edge 528 creates a gap
between the stator 512 end surface baffle and the fan 502.
Similarly, the angled surface of the outer ring 522 creates a gap
between the brush card 100 baffle and the fan 502. These gaps may
adversely affect air flow through the fan 502. In order to prevent
such an adverse affect, according to an embodiment of the
invention, two ribs 534 and 536 corresponding to the slanted
surface 532 of the outer ring 522 and the first side edge 528,
respectively, are provided in the tool housing 508. In an
embodiment, the first rib 534 includes a sloped surface disposed in
close proximity to and in parallel with the slanted surface 532 of
the outer ring 522. Similarly, the second rib 536 includes a sloped
surface in close proximity to and in parallel with the first side
edge 528 of the fan 501. Both ribs 534 and 536 also include
surfaces that are in contact with the rear surface of the brush
card 100 (including a portion of the brush holders 104 and the
brush card mount 102) and the end surface 513 of the stator 512,
respectively. The ribs 534 and 536 are both ring-shaped and extend
around the two housing halves to fully close the gaps between the
housing 508 and the fan 502 created by the angled surfaces of the
outer ring 522 and the first side edge 528. In this embodiment, a
combination of the rear surface of the brush card 100 (including
the brush card mount 102 and the brush holders 104), and the sloped
surface of the first rib 534, forms the first baffle for the fan
502. Similarly, a combination of the end surface 513 of the stator
512 and the sloped surface of the second rib 536 forms the second
baffle for the fan 502. Additionally, in an embodiment, the ribs
534 and 536 provide alignment features for placement of the brush
card 100 and the stator 512 within the power tool housing 508.
Rotor End Insulator
[0080] Another aspect of the invention is disclosed herein with
reference to FIGS. 19-21C, and with continued reference to FIGS.
16A-16C.
[0081] FIG. 19 depicts the fan 502 mounted on a fully wound and
molded rotor 514. In this figure, the rotor 514 includes a
lamination stack 550, windings 552, and end insulators 560. End
insulators 560 are disposed at the ends of the lamination stack 550
prior to the lamination stack 550 being wound. End insulators 560
provide insulation between the rotor windings and the rotor
lamination stack 550 and protect the wires from being cut during
the winding process. FIG. 20 depicts a perspective view of the same
fan 502 and rotor 514 without the windings 552.
[0082] According to an embodiment of the invention, in order to
property attach the fan 502 to the rotor 514, the fan 502 is
provided with a plurality of tongues 580, as shown in FIGS. 16A,
16C, 19 and 20. Tongues 580 in an embodiment project in the
direction of the rotor 514 from the inner ring 520 of the fan 502.
In an embodiment, tongues 580 may be 2-6 mm in length. In an
embodiment, tongues 580 may be disposed equidistantly around the
periphery of the inner ring 510. The number of tongues 580 may
correspond to the number of slots in the lamination stack 550,
although a lesser number of tongues 580 may be provided. According
to an embodiment of the invention, end insulator 560 facing the fan
502 is provided with a plurality of notches 562 arranged to receive
the tongues 580 of the fan 502, as discussed below in detail.
[0083] FIGS. 21A-21C depict perspective views of a rotor end
insulator 560, according to an embodiment of the invention. End
insulator 560 is pre-molded to include a base portion 564 shaped to
match a cross-sectional profile of the lamination stack 550. The
base portion 564 includes radially-extending slots 566 formed
between teeth 558 of the base portion 564. The slots 566 and teeth
568 respectively correspond to the slots and teeth of the
lamination stack 550. At the periphery of the base portion 564, the
teeth 568 extend outwardly along the circumference of the base
portion 564 to partially close the outer end of the slots 566. The
slots 566 of the base portion 564 have walls 570 projecting
perpendicularly to the base portion 564 (in the longitudinal
direction of the motor) on one side. The walls 570 are arranged to
form-fittingly protrude into the slots of the lamination stack 550
to insulate the lamination stack teeth. The walls 570 may be, for
example, 4 to 12 mm in depth.
[0084] The base portion 564 includes a through-hole 572 at its
center portion for accommodating the rotor shaft. On the side of
the base portion 564 opposite where the walls 570 are arranged, is
an annular ring 574 fitted over the rotor shaft.
[0085] In an embodiment, two end insulators 560 are form-fittingly
mounted on the ends of the lamination stack 550. In an embodiment,
there may be a gap of, for example, 2 to 10 mm between the ends of
the inner walls 570 of the two end insulators 560 within the
lamination stack 550 slots. As the coils are wound into the
lamination stack slots over the end insulators 560, the thickness
of the walls 570 ensures that no contact is made between the coil
and the lamination stack 560. Furthermore, the outer surface of the
base portion 564 has a slanted profile near the outer ends of the
teeth 568 that forces the coils to be packed tightly into the
lamination stack slots.
[0086] According to an embodiment of the invention, as mentioned
above, notches 562 are arranged at the outer ends of the teeth 568
on the periphery of the end insulator 560 to receive the tongues
580 of the fan 502. The notches 562 extend longitudinally through
the entire length of the teeth 568. This arrangement allows the
tongues 580 of the fan 502 to make direct contact with the end of
the lamination stack 550. This embodiment reduces the tolerances
associated with the motor over a comparable design in which the fan
502 is mounted on the end insulator 560. Specifically, since the
tongues 580 are mounted directly on the lamination stack 550,
calculating the total tolerances for the fan 502 needs only take
into account the tolerance levels of the fan 502 and the lamination
stack 550, and not the tolerance levels of the end insulator 560,
which is made of plastic and has a relatively large tolerance. It
is noted that tongues 580 may be secured within the notches 562
form-fittingly, or via heat-taking, welding, adhesive-bonding,
etc.
[0087] According to an embodiment of the invention, with reference
to FIGS. 16A-16C, 19 and 20, the fan 502 may be further provided
with one or more additional tongues 582 arranged on opposite ends
of the inner ring 520. In an embodiment, tongues 582 are longer
than tongues 580 and are arranged to be received between two
adjacent teeth of the lamination stack 550. Long tongues 582 are
provided to ensure that tongues 580 are placed inside the notches
562, and not between the adjacent teeth of the lamination stack
550, during assembly.
Spring Assembly
[0088] Another aspect of the invention is discussed herein with
reference to FIGS. 22-24. FIG. 22 depicts a spring 110, according
to an embodiment. Spring 110 includes a wound portion 602, a first
leg 604, and a second leg 606 that is longer than the first leg 604
and includes a hook 608 at its distal end.
[0089] FIG. 23 depicts a partial perspective view of the brush card
100, according to an embodiment. In this embodiment, the wound
portion 602 of the spring 110 is arranged around the post 108 of
the brush card mount 102. The hook 608 of the second leg 606
engages the back of the brush 106. The first leg 604 of the spring
110 engages a pocket 614 of the brush card mount 102. In an
embodiment, pockets 614 for each spring 110 are formed within end
portions of the bridge legs 116a, 116b on both sides (e.g., close
to the periphery of the brush card mount 102). The position of the
first leg 604 within the pocket 614 allows the torsion spring 110
to be loaded as it engages the back of the brush 106.
[0090] During the assembly process, in one embodiment, the first
leg 604 is placed within the pocket 614 as the wound portion 602 is
pushed down the post 108. The second leg 606, which at this point
rests on top of the brush holder 104, is then pulled to engage the
back of the brush 106 (or an end portion 620 of the brush holder
104). The problem with this assembly process, however, is that it
is difficult to engage and move the second leg 606 after the wound
portion 602 has been pushed down the post 108. This process is time
consuming and burdensome.
[0091] According to an embodiment of the invention, in order to
ease the assembly process of the springs 110, the end of the bridge
legs 116a, 116b are each provided with an arcuate surface 612, as
shown in FIG. 23. Arcuate surface 612 is located above the pockets
614. A sloped surface 610 is provided extending from the top of the
bridge leg 116a or 116b to the top of the arcuate surface 612.
During the assembly process, after the wound portion 602 is placed
on the post 108 but before it is pushed down, the hook 608 of the
second leg 606 of the spring 110 is placed within a recess 622 of
the end portion 620 of the brush holder 104. The first leg 604 at
this point is placed on the sloped surface 610 or the arcuate
surface 612. As the round portion 602 of the spring 110 is pushed
down, the hook 608 remains within the recess 622. Meanwhile, the
end of the first leg 604 slides down the sloped surface 610 over
the arcuate surface 612, and along the arcuate surface 612 until it
snaps into the pocket 614. As the first leg 604 moves down the
arcuate surface 612 it loads the torsion spring 110, so the spring
110 will be loaded even after the first leg 604 snaps into the
pocket 614.
[0092] FIG. 24 depicts a rear view of the brush card 100 showing
the first leg 604 of the spring 110 inside the pocket 614,
according to an embodiment. As seen herein, the pockets 614 for
adjacent springs 110 are located under the arcuate surface 612,
forming a mushroom-shaped cross-sectional profile. The arcuate
surface 612 may be shaped as a half-circle above the pockets 614,
although a cam surface may be utilized to optimize the movement of
the first leg 604 into the pocket 614.
Brush Design
[0093] Another aspect of the invention is described herein with
reference to FIG. 25. In this figure, brush 106 is shown inside the
brush holder 104. As discussed above, the hook 608 of the spring
110 engages the recess 622 of the end portion 620 of the brush
holder during the assembly process. Once the motor is fully
assembled and the commutator is placed inside the brush card 100,
the hook 608 and the second leg 606 are pulled down to engage the
rear surface of the brush 106.
[0094] According to an embodiment of the invention, in order to
ease the above-described step, the rear surface of the brush 106
includes two humped surfaces 624 and 626 and a groove 628
therebetween. The rear surface of the brush 106 is designed and
arranged such that, after the motor is assembled and the commutator
is placed inside the brush card 100, a portion of the humped
surface 624 is aligned with a lower end of the recess 622.
Specifically, the recess 622 includes a slanted lower end 622a
which, as viewed from the side, ends in alignment with (or slightly
above) the humped surface 624. Using this arrangement, instead of
having to pull the hook 608 out of the recess 622 and push it down
inside the groove 628, the second leg 606 of the spring 110 is
simply pushed down. As the second leg 606 is pushed down, the hook
608 (or the second leg 606) slides down the slanted lower end 622
of the recess, onto and over the humped surface 624, and into the
groove 628. This design substantially eases the assembly
process.
[0095] In this embodiment, each the humped surfaces 624 may be
semi-circular shaped, although a cam surface may be utilized to
optimize the movement of the hook 608 over the humped surface 624.
It is also noted that two humped surfaces are shown in this
embodiment to ease the assembly process, but the brush 106 may
include a single humped surface above the groove 628.
[0096] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
scope of the invention.
* * * * *