U.S. patent application number 11/193908 was filed with the patent office on 2007-02-01 for reduced noise diffuser for a motor-fan assembly.
Invention is credited to David B. Finkenbinder, James P. Shawcross.
Application Number | 20070025848 11/193908 |
Document ID | / |
Family ID | 37694480 |
Filed Date | 2007-02-01 |
United States Patent
Application |
20070025848 |
Kind Code |
A1 |
Shawcross; James P. ; et
al. |
February 1, 2007 |
Reduced noise diffuser for a motor-fan assembly
Abstract
An air diffuser for a motor-fan unit having reduced blade
passage frequencies, and reduced noise generation, includes a
baffle plate, external vanes, internal vanes, diffuser ports, and a
central opening. The baffle plate of the diffuser is made integral
with the internal and external vanes, such that any leaking,
rattling, or pure tone noise that may be generated from air
movement over the surface of the diffuser are prevented or reduced.
Additionally, the number of internal and external vanes provided by
the diffuser is that equal to a prime number, thus resulting in a
reduction of harmonic and pure tone noise generated during the
operation of the motor-fan unit.
Inventors: |
Shawcross; James P.;
(Hudson, OH) ; Finkenbinder; David B.; (Ravenna,
OH) |
Correspondence
Address: |
RENNER, KENNER, GREIVE, BOBAK, TAYLOR & WEBER
FIRST NATIONAL TOWER FOURTH FLOOR
106 S. MAIN STREET
AKRON
OH
44308
US
|
Family ID: |
37694480 |
Appl. No.: |
11/193908 |
Filed: |
July 29, 2005 |
Current U.S.
Class: |
415/208.2 |
Current CPC
Class: |
F05D 2250/52 20130101;
F04D 29/444 20130101 |
Class at
Publication: |
415/208.2 |
International
Class: |
F04D 29/44 20060101
F04D029/44 |
Claims
1. A diffuser interposed between a shrouded fan assembly and a
motor assembly having a shaft that rotates a fan carried within
said shrouded fan assembly, the diffuser comprising: a baffle plate
having a motor side and a fan side, said baffle plate having an
opening therethrough; and a plurality of vanes extending from said
motor side, each said vane having an external portion which
radially extends from said baffle plate, wherein adjacent vanes
have a port therebetween, said plurality of vanes directing airflow
generated by the fan from said fan side through said ports to said
motor side.
2. The diffuser according to claim 1, wherein each said vane has an
internal portion contiguous with said external portion, said
internal portions extending toward said opening.
3. The diffuser according to claim 2, wherein said vanes are
curvilinear and spaced apart from each other.
4. The diffuser according to claim 2, wherein said internal
portions terminate prior to reaching said opening so as to
collectively form a collection chamber for the airflow.
5. The diffuser according to claim 1, wherein each said vane has a
plate edge at said motor side and ring edge opposite said plate
edge.
6. The diffuser according to claim 5, further comprising: a vane
support ring connected to at least some of said vanes.
7. The diffuser according to claim 6, wherein said vane support
ring is connected to at least some of said ring edges, said vane
support ring having an inner edge with a diameter at least equal to
or larger than said baffle plate's diameter.
8. The diffuser according to claim 1, wherein each said vane
comprises a radial turning vane.
9. The diffuser according to claim 1, wherein said baffle plate is
annular.
10. The diffuser according to claim 1, wherein said plurality of
vanes total a number equal to a prime number.
11. The diffuser according to claim 1, further comprising: at least
one brush cap connected to said motor side of said baffle
plate.
12. A motor-fan assembly comprising: a field winding; an armature
having a shaft, said armature rotatably mounted within said field
winding; a fan attached to said shaft; and a diffuser interposed
between said fan and said field winding, said diffuser comprising:
a baffle plate having a motor side and a fan side; said baffle
plate having an opening therethrough; a plurality of vanes
extending from said motor side; each said vane having an external
portion which radially extends from said baffle plate wherein
adjacent vanes have a port therebetween; and said plurality of
vanes directing airflow generated by the fan from said fan side
through said ports to said motor side.
13. The motor assembly according to claim 12, wherein each said
vane has an internal portion contiguous with said external portion,
said internal portion extending toward said opening.
14. The motor assembly according to claim 13, wherein said vanes
are curvilinear and spaced apart from each other.
15. The motor assembly according to claim 13, wherein said internal
portions terminate prior to reaching said opening so as to
collectively form a collection chamber for the airflow.
16. The motor assembly according to claim 12, wherein each said
vane has a plate edge at said motor side and ring edge opposite
said plate edge.
17. The motor assembly according to claim 16, further comprising: a
vane support ring connected to at least some of said vanes.
18. The motor assembly according to claim 17, wherein said vane
support ring is connected to at least some of said ring edges, said
vane support ring having an inner edge with a diameter at least
equal to or larger than said baffle plate's diameter.
19. The motor assembly according to claim 12, wherein each said
vane comprises a radial turning vane.
20. The motor assembly according to claim 19, wherein said
plurality of radial turning vanes total a number equal to a prime
number.
21. The motor assembly according to claim 12, wherein said baffle
plate is annular.
22. The motor assembly according to claim 12, wherein said
plurality of vanes total a number equal to a prime number.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to diffusers used in
association with various motor-fan systems. More particularly, the
present invention relates to an air diffuser that reduces vane
passage frequencies, and associated noise, which is generated from
air movement over the surface of the diffuser. Specifically, the
present invention is directed to a noise reducing diffuser that
operatively secures the brushes of an electric motor. More
specifically, the present invention relates to a noise reducing
diffuser that is interchangeable with existing diffusers installed
in various motor-fan units.
BACKGROUND OF THE INVENTION
[0002] Electric motors are well known in the art and have been put
to use in a variety of applications, including the handling of air.
In this circumstance, an electric motor is coupled to a fan,
creating a motor-fan unit, which produces an airflow as needed.
When providing air movement, the motor-fan unit may supply cooling
air to the motor, so as to maintain the motor's operating
temperature at an optimal level, allowing the motor's operating
life to be extended. The motor-fan unit may also be used to
generate working air for vacuum type devices.
[0003] To achieve this effect, the fan is mounted on a motor driven
shaft, which draws air into a fan shroud. The fan shroud compresses
or pressurizes the incoming air, which is resultantly released into
the motor housing via one or more ports in a diffuser plate,
causing the air to be directed toward the motor windings. As a
result, the heat from the motor is drawn into the airflow and
exhausted from the motor housing, thus enhancing the motor's
operating life.
[0004] Many diffusers used with motor-fan units, incorporate radial
turning vanes with a separately attached baffle plate to move the
pressurized air from the fan shroud to the motor assembly. However,
the baffle plates of these diffusers are not made integral with the
turning vanes. This results in a baffle plate that does not form a
complete seal with the attached turning vanes. Because of this
inadequate or compromised seal, the diffuser generates leaking,
rattling, and pure tone noises as the motor-fan unit draws air
through the diffuser. In addition, blade passage frequencies are
also created as air is passed over the diffuser's vanes. As such,
many motor-fan units are uncomfortably noisy to many users.
Further, the use of such motor-fan units may be limited to those
applications where such noise can be tolerated.
[0005] In addition to the diffuser portion of the motor-fan unit,
the motor itself comprises field windings that surround an armature
that is centrally located on a shaft, which is rotatably mounted on
suitable bearings. A commutator is also mounted on the shaft and
placed in electrical contact with a power supply by a pair of
opposed brushes contacting the commutator. Typically, these brushes
and/or armature are completely or partially closed off from the
cooling air provided by the fan unit. As such, the motor's
efficiency and operating life are reduced due to the heat generated
by the motor.
[0006] Therefore, there is a need for a diffuser for a motor-fan
unit with radial turning vanes that has an integrated baffle plate
to provide reduced noise during the motor-fan unit's operation.
Additionally, there is a need for a reduced noise diffuser that
allows cooling air to pass to the brushes and/or armature of the
motor while supporting the brushes of the motor. Further, there is
a need for an interchangeable diffuser with reduced vane passage
frequencies, and reduced noise generation that can be used in
association with existing motor-fan assemblies, while providing
suitable cooling for the motor's armature and/or brushes.
DISCLOSURE OF INVENTION
[0007] In light of the foregoing, it is a first aspect of the
present invention to provide a reduced noise diffuser for a
motor-fan assembly.
[0008] It is another aspect of the present invention to provide a
diffuser interposed between a shrouded fan assembly and a motor
assembly having a shaft that rotates a fan carried within the
shrouded fan assembly, the diffuser comprising a baffle plate
having a motor side and a fan side, the baffle plate having an
opening therethrough; and a plurality of vanes extending from the
motor side, each vane having an external portion which radially
extends from the baffle plate, wherein adjacent vanes have a port
therebetween, the plurality of vanes directing air flow generated
by the fan from the fan side through the ports to the motor
side.
[0009] It is yet another aspect of the present invention to provide
a motor-fan assembly comprising a field winding; an armature having
a shaft, the armature rotatably mounted within the field winding; a
fan attached to the shaft; and a diffuser interposed between the
fan and the field winding, the diffuser comprising a baffle plate
having a motor side and a fan side; the baffle plate having an
opening therethrough; a plurality of vanes extending from the motor
side; each vane having an external portion which radially extends
from the baffle plate wherein adjacent vanes have a port
therebetween; and the plurality of vanes directing airflow
generated by the fan from the fan side through the ports to the
motor side.
DESCRIPTION OF THE DRAWINGS
[0010] These and other features and advantages of the present
invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0011] FIG. 1 is a partially sectioned front elevational view of a
motor-fan unit according to the present invention showing the
details of a motor assembly, an end plate assembly, a diffuser
assembly, and a fan assembly;
[0012] FIG. 2 is an exploded perspective top view of the motor-fan
unit according to the present invention depicting details of the
motor assembly, the end plate assembly, the diffuser assembly, and
the fan assembly;
[0013] FIG. 3 is an exploded perspective bottom view of the
motor-fan unit according to the present invention depicting details
of the motor assembly, the end plate assembly, the diffuser
assembly, and the fan assembly;
[0014] FIG. 4 is a plan view of the end plate assembly depicting
details of a motor-side of the end plate;
[0015] FIG. 5 is an elevational view of the end plate assembly
depicting further details of the end plate assembly, including a
brush retainer assembly and motor brackets;
[0016] FIG. 6 is a partially sectioned side elevational view of the
end plate assembly depicting details of a commutator receiver;
[0017] FIG. 7 is a perspective view of the end plate assembly
depicting further details of the motor-side thereof, including the
location of brush retainers adjacent the commutator receiver;
[0018] FIG. 8 is an enlarged partially sectioned side elevational
view as seen along line 8-8 in FIG. 4, depicting details of the
brush retainer according to the present invention;
[0019] FIG. 9 is a plan view of the end plate according to the
present invention depicting details of the diffuser side of the end
plate assembly;
[0020] FIG. 10 is a perspective view of a fan side of the diffuser
assembly according to the present invention;
[0021] FIG. 11 is a plan view of the diffuser assembly including a
baffle plate, a plurality of external vanes, and a plurality of
diffuser ports;
[0022] FIG. 12 is a perspective view of a motor side of the
diffuser assembly according to the present invention;
[0023] FIG. 13 is a perspective view of a diffuser assembly
according to the present invention depicting brush cap assemblies
extending from the surface of the diffuser assembly;
[0024] FIG. 14 is a plan view of a diffuser assembly according to
the present invention showing the pair of brush cap assemblies
located adjacent a central opening of the diffuser;
[0025] FIG. 15 is a front sectional view along line 15-15 in FIG.
14 of the diffuser assembly according to the present invention
depicting the brush cap assemblies extending axially inward to
protrude beyond the radial channel members located on the
diffuser;
[0026] FIG. 16 is a side sectional view along line 16-16 in FIG. 14
of the diffuser assembly according to the present invention
depicting details of the brush cap assemblies, including a channel
formed within each cap assembly to direct air toward the brushes in
the motor-fan unit;
[0027] FIG. 17 is a perspective view of the diffuser according to
the present invention enlarged to show details of an alternative
brush cap assembly having snap-lock projections located thereon to
effect attachment of the end cap assembly to the diffuser assembly;
and
[0028] FIG. 18 is an enlarged perspective view of an end plate and
diffuser according to the present invention having an alternative
brush cap assemblies with snap lock projections that engage
surfaces on the commutator receiver of the end plate to couple the
end plate to the diffuser.
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] A motor-fan unit, indicated generally by the numeral 10 in
the accompanying FIGS. 1-3, generally includes a motor assembly 12
and a fan assembly 14. The motor assembly 12 comprises a lamination
stack 16, an armature 18, field windings 19, a commutator 20, and
brushes 22 (best seen in FIG. 7). A shaft 24 with a mounted
armature 18 is supported by suitable bearings 26, such that the
shaft 24 rotates when the motor assembly is energized. The
commutator 20 allows the shaft 24 to rotate while allowing the
armature 18 to remain electrically connected with a power supply
(not shown) via the brushes 22.
[0030] As shown in FIG. 1, the motor assembly 12 is configured with
the commutator 20 proximate the fan assembly 14. The fan assembly
14 of the motor-fan unit 10, comprises a fan 28 coupled to an end
30 of the shaft 24 that is proximate the commutator 20, via a nut
32. However, any other type of suitable system for connecting the
fan 28 to the shaft 24 may be utilized. Covering the outside of the
fan assembly 14 is a shroud 34. The shroud 34 has a cover portion
38 which has a centrally positioned intake port 36 that is
coaxially located with axis A of shaft 24. The intake port 36
allows the fan assembly 14 to draw air into the shroud 34 where it
is pressurized or compressed and radially exhausted. The air may
then be directed through the motor assembly.
[0031] The motor assembly 12 is provided with an end plate assembly
which is generally indicated by the numeral 42 shown in FIGS. 1-9.
The end plate assembly 42, shown clearly in FIGS. 2 and 3,
generally includes a planar plate portion 44, which may be annular
as shown, and a motor bracket portion 46 that extends from the
plate portion 44 toward the motor 16. The motor bracket portion 46,
shown more clearly in FIGS. 4 and 5, is adapted to allow the motor
assembly 12 to be rigidly mounted or fixated to the end plate
assembly 42. Continuing with FIGS. 3 and 4, the end plate assembly
42 defines a central opening 47, which receives the end of the
motor's shaft 24 that is proximate the commutator 20. The end plate
assembly 42 may be provided with a commutator receiver, generally
indicated by the numeral 48 that receives the commutator 20 and
provides suitable clearance for the free rotation of the commutator
20. The commutator receiver 48 shown clearly in FIGS. 5 and 6 may
bulge axially outwardly of planar plate portion 44 to define a well
50, in which at least a portion of the commutator 20 resides. The
well 50 may also retain a bearing 26 which is used to support the
shaft 24, thereby allowing the shaft 24 to freely rotate. In
addition, the commutator receiver 48 may include a plurality of
stepped concentric recesses 52, 54, 56 that accommodate the profile
of both the commutator 20 and the bearing 26. This arrangement
allows the commutator 20 to be placed close to the fan assembly 14,
such that the commutator 20 can receive cooling air prior to the
air's passage over the motor's armature 18. As a result, the
commutator 20 is more efficiently cooled, and the performance of
the motor is enhanced. Returning to FIGS. 2 and 3, it is shown that
in order to secure the motor assembly 12 to the end plate 42, a
fastening plate 58 is used. The fastening plate 58 has tabs 60 with
holes therethrough for receiving fasteners that are secured into a
receiver 61 carried by each motor bracket portion 46.
[0032] Because the brushes 22 make electrical contact with the
commutator 20 during the operation of the motor-fan unit 10, a pair
of brush retainers generally indicated by the 5 numeral 62 are
provided by the end plate assembly 42. The structure of each brush
retainer 62 is largely identical to the other, with one brush
retainer 62 being a mirror image of the other. Therefore, the
following discussion will describe only a single brush retainer 62.
As shown in FIGS. 4-8, and more clearly seen in FIGS. 6-8, the
brush retainer 62 may be in the form of a channel-like member
having three contiguous walls or members 64, 66, and 68 that define
an open end 70, such that the three contiguous walls or members 64,
66, 68 serve to cradle the brush 22. It is also contemplated that
the brush retainer 62 protrudes toward the motor assembly 12 to
facilitate the manufacture thereof.
[0033] As shown in FIG. 9, the brush retainers 62 each contain an
open mouth 72, which is contiguous with the open end 70, and which
opens toward the fan assembly 14. A projection in a mold cavity may
be used to create the open mouth 72 of the brush retainer 62 during
fabrication. Thus, by using the open mouth 72, mold design is
greatly simplified, and the use of sacrificial molding or
subsequent machining to create tubular brush retainers as used in
the art is obviated. Further, the formation of an open,
resilient-type brush retainer 62 allows for interference fitting of
the brush 22 within the brush retainer 62. As a result of this
interference fit, the use of retaining clips, which are commonly
used when attaching the brush 22 to a motor housing, are
eliminated. The brush retainer 62, may be formed as a single piece
or may contain spaced portions to suitably support the brush 22. As
an alternative to the channel-like brush retainer 62 shown in the
Figs., it is also contemplated that the brush retainer 62 may
include an L-shaped member or may incorporate one or more posts to
locate the position of the brush 22.
[0034] Continuing with the brush retainer 62 as shown in FIGS. 7
and 8, the brush retainer 62 includes a wall or member 64 that
extends axially outward from the plate portion 44 toward the motor
assembly 12, a wall or member 66 that extends outwardly from and
generally at a right angle to the wall or member 64, and a wall or
member 68 extending axially toward the plate portion 44 from the
wall or member 66. The wall or member 66 is axially spaced from the
end plate 42 to define a suitable vertical clearance 74 for the
brush 22, while the wall or members 68 and 64 serve to define a
horizontal clearance 76. As previously discussed, the wall or
members 64, 66, and 68 may be spaced such that clearances 74 and 76
create an interference fit between the brush 22 and the brush
retainer 62. It should also be appreciated that the wall or member
68 may not make a complete connection with the plate portion 44.
Thus, a gap or notch 78 is created between the plate portion 44 and
the wall or member 68 along one side of the brush retainer 62, as
shown. A support member 80, such as a post, may extend axially from
the plate portion 36 to support the cantilevered members 66 and 68.
The support member 80 is placed adjacent the brush retainer 62 near
an edge 82 of the brush retainer 62 that is closest to the
commutator receiver 48. At this location, the support member 80 may
further aid the brush retainer 62 in maintaining the position of
the brush 22.
[0035] To ensure contact between the brush 22 and the commutator 20
of the motor 16, the brush 22 is biased into engagement with the
commutator 20, as shown in FIG. 7. The biasing action is performed
by a spring 84 mounted on a spring holder 86 that is provided by
the end plate assembly 42. Although a spring is typically used,
other systems for biasing the brushes are contemplated.
Specifically, the spring 84 includes a coil 88, a leg 90, and a leg
92 which are employed to bias the brush 22 toward the commutator
20. The coil 88 is press fit over the spring holder 86, and the leg
90 is fixed in place with a suitable clip, such as spring retainer
projection 94 that is formed on the plate portion 44.
[0036] While spring retainer projection 94 may comprise a wall, an
L-shaped projection may be used as shown in FIG. 7. Thus, the
torsional force generated by the spring 84 holds leg 90 against
spring retaining projection 94, thus preventing leg 90 from moving
axially beyond spring retaining projection 94. Leg 92 of the spring
84 is positioned so that it contacts the rear of the brush 22, and
causes the brush 22 to be urged toward the commutator 20. Since the
brush 22 may be inserted after the assembly of the motor assembly
12, it may be necessary to preload the spring 84 to temporarily
hold it in place. To assist in the preloading of the spring 84, a
spring retaining projection 96 may be provided on the surface of
the end plate assembly 42 or the brush retainer 62. The spring
retaining projection 96 is located so that when the leg 92 of the
spring 84 is compressed, a torsional force is created within the
spring 60 sufficient to hold leg 92 against the spring retaining
projection 96. Specifically, in the embodiment shown in FIG. 7, an
L-shaped spring retaining projection 96 extends axially inward from
member 66 of the brush retainer 62, thereby defining a spring
recess 98 in which an end 100 of leg 92 may be inserted to allow
the spring 84 to assume a preloaded condition as shown in FIG. 4.
Prior to placing the brush 22 within the brush retainer 62, leg 92
is compressed so that it clears the brush retainer 62 and any
extending portion of the brush 22. Once the brush is inserted
within the brush retainer 62, the leg 92 is placed in contact with
the rear of brush 22 to urge the brush 22 toward the commutator
20.
[0037] As shown in FIG. 9, the brush retainers 62 define an open
mouth 72 within the end plate assembly 42, which open toward the
fan assembly 14 and extend into a portion of the commutator
receiver 48. The opening of the mouth 72, allows cooling air from
the fan assembly 14 to flow past the brushes 22, and motor 16 as
will be described more completely below. To allow air to pass over
the armature 18, or other parts of the motor assembly 12, the end
plate assembly 42 provides a pair of cavities 104. These cavities
104 may be at least partially sealed from the mouth 72, to prevent
particulates generated from the brushes 22 from being carried
downstream into the other areas of the motor assembly 12. To
further limit the passage of particulates into the motor assembly
12, dividers 106 and 108 extend from the plate assembly 42. To
further limit particulates from entering the motor assembly 12, a
bead of sealant may be provided, which extends adjacent cavities
104, and between the cavities 104 and each mouth 72 of the brush
retainer 62. As shown, the dividers 106, 108 generally cordon off a
sector surrounding each of the mouths 72, such that the plate
portion 44 is separated into distinct regions.
[0038] Air drawn into the shroud 34 by the fan assembly 14, is
directed to the motor 16 by a diffuser assembly that is designated
generally by the numeral 120. The diffuser assembly 120 is
interposed between the fan 28 and the end plate assembly 42 and is
configured to be interchangeable with existing diffuser assemblies
that are part of other motor-fan units 10. That is, the diffuser
assembly 120 of the present invention is designed to cooperate with
end plate assemblies 42 of varying motor-fan units 10 so that the
brushes 22 of such unit 10 are sufficiently supported. As shown in
FIGS. 10-16, the diffuser assembly 120 includes a baffle plate 122
which provides a fan side 123 which is opposite a motor side 124.
The fan side 123 is positioned adjacent the fan assembly 14 when
the motor-fan unit 10 is assembled. Likewise, the motor side 124 is
positioned adjacent the end plate assembly 42 and the motor
assembly 12 when the unit 10 is assembled. The baffle plate 122
includes an outer edge 125 which joins the fan side 123 to the
motor side 124 and the plate also provides a central opening 126
extending therethrough. The central opening 126 receives and seats
the commutator receiver 48 to allow contact between the commutator
20 and the brushes 22. Extending from the motor side 124 are a
plurality of curvilinear vanes designated generally by the numeral
128. The vanes 128 are spaced apart and each vane has a plate edge
129 connected to the motor side and a ring edge 130 opposite the
plate edge. The curvilinear vanes 128 are disposed about the outer
periphery of the motor side 124. In particular, each vane 128
provides an external portion 131 that extends radially outwardly
from the outer edge 125 on the motor side 124 and an internal
portion 132 that extends from the motor side 124. The adjacent
vanes 124 form a port 134 therebetween. A vane support ring 135
connects the external portions of the curvilinear vanes to one
another and, in particular, joins the respective ring edges 130 of
each vane 128. The ring 135 has an inner diameter edge 136 and an
outer diameter edge 137. It will be appreciated that the inner edge
136 has a diameter equal to or somewhat greater than the diameter
of the outer edge 125. The internal portions 132 of the curvilinear
vanes 128 collectively form a collection chamber designated
generally by the numeral 138. The construction of the baffle plate
122 is ideally suited for a molded construction, but it will be
appreciated that other materials could be used in formation
thereof. Accordingly, the curvilinear vanes 128 are integral with
the baffle plate 122 and the vane support ring 135 to provide a
sturdy and easily manufactured construction.
[0039] The curvilinear vanes 128 may comprise radial turning vanes,
wherein the number of vanes is equal to that of a prime number. It
is believed that by having such an arrangement, the diffuser
assembly 120 is able to reduce the harmonic interaction between the
fan 14 and the diffuser at certain revolutions-per-minute multiples
as the fan assembly 14 rotates. In general, many harmonics may be
generated by air passing by over the surface of the diffuser vanes.
For example, in arrangements where a diffuser utilizes a number of
vanes not equal to a prime number, generated harmonics may occur at
multiples of the smallest mathematical factor for the number of
vanes present. In contrast, a diffuser having a number of vanes
equal to that of a prime number only has two factors (i.e. the
number 1 and the prime number itself). As such, the use of the
diffuser 128 with a number of vanes equal to that of a prime number
eliminates the factor harmonics that would otherwise be created by
a diffuser with a number of vanes not equal to a prime number.
[0040] When the unit 10 is assembled and the motor assembly 12
rotates the fan assembly 14, air is drawn in through the shroud
intake 34 and into the fan assembly 14. The fan assembly 14
exhausts the air radially such that it swirls around within the
interior of the shroud and is redirected by the baffle plate 122
and, in particular, the curvilinear vanes 128. The air is guided
through the ports 134 and swirls about the collection chamber 138
so that the air is forced radially inwardly toward the central
opening 126 where it is then redirected so as to flow through the
cavities 104 and other regions of the end plate assembly 42.
Accordingly, the air drawn in through the shroud intake 136 is
directed through the motor assembly 12 as needed for the end
application.
[0041] Specifically, the vanes 128 may comprise radial turning
vanes and/or may be equal in number to that of a prime number. For
example, the number of turning vanes 128 may total 23, 29, or 37,
although any other suitable prime number of turning vanes 128 may
be utilized. By having such an arrangement, the diffuser assembly
120 is able to reduce the harmonic interaction between the fan 14
and the diffuser 120 at certain rpm multiples as the motor-fan unit
10 is in operation. More specifically, as high velocity air departs
from a vane the resulting airflow also includes a vortex component
that shears against other nearby vanes resulting in noise. The
generated noise has its largest magnitude at frequencies equal to
the multiples of the fan revolutions per minute (rpm) and the
number of diffuser vanes. Thus, by altering the number of vanes 128
and/or the rpm of the fan 28 of the motor-fan unit 10, the noise
frequencies with higher magnitudes may be shifted to different
frequencies, thus minimizing the noise that would otherwise occur.
As such, the noise generated by air passing through the diffuser
120 is thereby reduced.
[0042] Additionally as shown in FIGS. 12-16, the diffuser assembly
120 contains one or more brush cap assemblies 139. The brush cap
assemblies 139 may be made integral with the baffle plate 122
during manufacturing of the diffuser 120, or may be connected to
the baffle plate 122 using known techniques, including but not
limited to thermal welding, adhesives, or screw-type connection.
The brush cap assemblies 139 are configured to coact with the brush
retainer 62 to trap the brushes 22 therebetween. In general, the
brush cap assemblies 139 provide a surface that substantially
closes the open mouth 72 of the brush retainer 62 located on the
end plate assembly 42. To contact the brushes 22, or otherwise
penetrate the opening of the mouth 72, the brush caps 139, taking
on the form of a projection, may extend axially toward the motor
assembly 12, beyond the vanes 128 to a desired extent. In one
arrangement, the brush cap assembly 139 will not extend such that
its contact with the brushes 22 would interfere with the proper
assembly of the motor-fan unit 10. The brush cap assembly 139
generally conforms to the contours of the mouth 72 of the brush
retainer 62, and may be toleranced to provide a clearance that
would allow dust or particulates from the brushes 22 to escape
through open end 70 of the brush retainers 62. By providing such
clearance, dust build-up on the brushes 22 is reduced, and the
airflow generated by the motor-fan unit 10 is able to pass over and
cool the brush 22, thereby extending the life of the brush 22 and
the motor 16. Further, the air escaping the brush retainer 62, at
the radial interior extreme of the brush retainer 62 at the open
end 70 facing the commutator 20, flows over the commutator 20,
keeping it cooled.
[0043] As shown in FIGS. 12-18, the brush cap assemblies 139 have a
generally rectangular shape to conform to the rectangular opening
of the open mouths 72 of the end plate assembly 42. To channel air
from the fan assembly 14 toward the brushes 22, the brush cap
assemblies 139 may be provided with channels 140. The channels 140
are formed between upstanding members 142 and 144 that are
positioned on the motor side 124 of the diffuser 120. Members 142,
144 are generally located adjacent the diffuser central opening 126
and may radially project to an extent into the opening. To
accommodate the extension of the brush cap members 142,144 into the
region of the commutator receiver 48, recess window 146 may be
formed on the commutator receiver 48, as shown clearly in FIG. 7.
Advantageously, an interference or friction fit between the members
142,144 and the commutator receiver 48 may be used in coupling the
end plate assembly 42 and the diffuser assembly 120 together.
[0044] Upstanding members 142 and 144 are of a suitable height to
the internal curvilinear vanes 128 to allow for proper attachment
of the diffuser assembly 120 to the end plate assembly 42. Further,
upstanding members 142,144 may extend sufficiently beyond the
height of the vanes 128 to an extent, such that they extend into
the open mouths 72 defined by brush retainers 62. As a result the
diffuser 120 is capable of attachment to the end plate assembly 42.
Upstanding member 142 may have a raised edge 148 sized to fill the
gap or notch 78 between the plate portion 44 and member 68 of the
brush retainer 62. In this way, the brush cap assembly 139 encloses
the brushes 22 when the end plate 42 and diffuser 120 are coupled
to one another. Adjacent the raised edge 148, upstanding member 142
may be provided with a landing 150, which has the same height as
upstanding member 144, thereby forming a recessed area that lies
adjacent to the brush 22 when the diffuser assembly 120 and end
plate assembly 42 are joined. The channel 140, opens toward the
motor assembly 12 between the landing 150 and upstanding member
144. This arrangement, allows air generated by the fan assembly 14
to be distributed across the exposed surface 152 of the brush 22
that lies adjacent the brush cap assemblies 139 shown in FIG. 7.
The air directed through the channels 140 allows heat from the
brushes 22 to be carried away, thus improving operation of the
motor 16.
[0045] An alternative embodiment of the brush cap assemblies 139
are shown in FIGS. 17 and 18, which may be used in coupling the
diffuser 120 to the end plate assembly 42. To supplement the
interference or friction fit between brush cap assembly 139 and the
walls of open mouth 70 or surfaces of commutator receiver 48, the
brush cap assembly 139 may be provided with a projecting surface,
generally indicated by the numeral 154, that performs a snap-lock
function in connection with an attachment surface 156 provided by
the recess window 146 of the end plate assembly 42. It will be
appreciated that projecting surface 154 may be one of a number of
configurations commonly used in the art to perform a snap-lock
function, including but not limited to a flexible tab, a rounded
surface, or a tapered leading surface 158 and stop surface 160
combination as shown in FIG. 17.
[0046] As shown in FIGS. 17 and 18, brush cap assemblies 139 may
have triangular projections 162 extending radially inward from each
member 142,144. The tapered surface 158 of projection 162 slopes
outwardly from a member 142 or 144 toward diffuser 80. A stop
surface 160 extends inwardly from the tapered surface 158 and is
located vertically on members 142,144 to provide a clearance at 164
for the receipt of a portion of the commutator receiver 40. When
attaching the diffuser 120 to the end plate 42, the tapered surface
158 causes gradual deflection of members 142,144 and/or the members
64,66,68 of the commutator receiver 40. Once the brush cap
assemblies 139 are fully inserted within the open mouths 72 of the
brush retainers 62, the stop surface 160 engages the attachment
surface 156, such that end plate assembly 42 and diffuser 120 are
coupled together.
[0047] It will, therefore, be appreciated that one advantage of one
or more embodiments of the present invention is that the noise and
vane passage frequencies associated with air movement over the
diffuser's vanes are reduced. Still another advantage of the
present invention is that the diffuser plate is configured, such
that, the diffuser is capable of replacing a previously installed
diffuser of an existing motor-fan unit. Yet another advantages of
the present invention is that the diffuser is able to support the
brushes of the motor-fan unit without additional adjustment to the
diffuser.
[0048] Although the present invention has been described in
considerable detail with reference to certain embodiments, other
embodiments are possible. Therefore, the spirit and scope of the
appended claims should not be limited to the description of the
embodiments contained herein.
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