U.S. patent application number 09/933292 was filed with the patent office on 2003-02-27 for blower noise reducing device and a blower having same.
This patent application is currently assigned to Xerox Corporation. Invention is credited to Wargo, John A..
Application Number | 20030039541 09/933292 |
Document ID | / |
Family ID | 25463699 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030039541 |
Kind Code |
A1 |
Wargo, John A. |
February 27, 2003 |
Blower noise reducing device and a blower having same
Abstract
A blower noise reducing device for use in a blower having a
blower housing defining a volute, a discharge opening through the
blower housing, and a discharge nozzle connected over the discharge
opening. The blower noise reducing device comprises a moving air
deflecting member having a generally triangular cross-section, a
first end representing a base of the generally triangular
cross-section, a second end representing an apex of the generally
triangular cross-section, a first side for mounting against a wall
of the discharge nozzle (at a connecting point between the
discharge opening and the discharge nozzle), and a second and
opposite side for protruding into the discharge opening and
discharge nozzle when the first side is mounted against the wall of
the discharge nozzle, thereby reducing noise causing
characteristics of air being moved by deflecting such moving air in
a predetermined manner.
Inventors: |
Wargo, John A.; (Farmington,
NY) |
Correspondence
Address: |
Patent Documentation Center
Xerox Corporation
100 Clinton Ave. S.
Xerox Square 20th Floor
Rochester
NY
14644
US
|
Assignee: |
Xerox Corporation
|
Family ID: |
25463699 |
Appl. No.: |
09/933292 |
Filed: |
August 20, 2001 |
Current U.S.
Class: |
415/119 ;
415/206; 415/211.1 |
Current CPC
Class: |
F04D 29/422 20130101;
F04D 29/661 20130101 |
Class at
Publication: |
415/119 ;
415/206; 415/211.1 |
International
Class: |
F04D 029/66 |
Claims
What is claimed is:
1. A blower noise reducing device for use in a blower having a
blower housing defining a volute, a discharge opening through the
blower housing, and a discharge nozzle connected over the discharge
opening, the blower noise reducing device comprising a moving air
deflecting member having: a. a generally triangular cross-section;
b. a first end representing a base of said generally triangular
cross-section; c. a second end representing an apex of said
generally triangular cross-section; d. a first side for mounting
against a wall of the discharge nozzle (at a connecting point
between the discharge opening and the discharge nozzle); and e. a
second and opposite side, said second and opposite protruding into
the discharge opening and discharge nozzle when said first side is
mounted against the wall of the discharge nozzle for reducing noise
causing characteristics of air being moved by the blower by
deflecting such moving air in a predetermined manner.
2. The blower noise reducing device of claim 1, wherein said moving
air deflecting member includes a heel portion at said first
end.
3. The blower noise reducing device of claim 1 wherein said first
end representing said base of said generally triangular
cross-section has an external surface for projecting into the
volute.
4. The blower noise reducing device of claim 1, wherein as mounted
within the discharge nozzle, said moving air deflecting member
comprises a reverse-aerofoil relative to air being discharged
through the discharge nozzle.
5. The blower noise reducing device of claim 1, wherein said moving
air deflecting member is made of a non-metallic material.
6. The blower noise reducing device of claim 1, wherein said moving
air deflecting member is made of a metallic material.
7. The blower noise reducing device of claim 2, wherein said heel
portion has a first surface aligned with said base of said
triangular cross-section.,
8. The blower noise reducing device of claim 2, wherein said heel
portion has a second surface for attaching to a wall of the
volute.
9. An air blower comprising: (a) a housing having walls defining an
intake region for incoming air, a discharge region including a
discharge opening for discharging air from said housing, and an air
path for controllably directing air entering said intake region
towards said discharge region; (b) an air moving assembly including
a rotatable impeller assembly mounted within said housing for
drawing air into said air path through said intake region, and for
accelerating air within said air path towards said discharge
region; (c) a discharge nozzle, mounted over said discharge
opening, for directing air being discharged away from said housing;
and (d) a blower noise reducing device comprising a moving air
deflecting member having: (i) a generally triangular cross-section;
(ii) a first end representing a base of said generally triangular
cross-section; (iii) a second end representing an apex of said
generally triangular cross-section; (iv) a first side for mounting
against a wall of the discharge nozzle (at a connecting point
between the discharge opening and the discharge nozzle); and (v) a
second and opposite side, said second and opposite protruding into
the discharge opening and discharge nozzle when said first side is
mounted against the wall of the discharge nozzle for reducing noise
causing characteristics of air by deflecting such moving air in a
predetermined manner.
10. The air blower of claim 9, wherein said moving air deflecting
member includes a heel portion at said first end.
11. The air blower of claim 9 wherein said first end representing
said base of said generally triangular cross-section has an
external surface for projecting into the volute.
12. The air blower of claim 9, wherein as mounted within the
discharge nozzle, said moving air deflecting member comprises a
reverse-aerofoil relative to air being discharged through the
discharge nozzle.
13. The air blower of claim 9, wherein said moving air deflecting
member is made of a non-metallic material.
14. The air blower of claim 9, wherein said moving air deflecting
member is made of a metallic material.
15. The air blower of claim 9, wherein said discharge nozzle is
attached tangentially to said blower housing.
16. The air blower of claim 9, wherein said air moving assembly
includes drive means for rotating said impeller assembly.
17. The air blower of claim 9, wherein a volume of said air path
increases from said intake region to said discharge region.
18. The air blower of claim 10, wherein said heel portion has a
first surface aligned with said base of said triangular
cross-section.,
19. The air blower of claim 10, wherein said heel portion has a
second surface for attaching to a wall of the volute.
20. An air blower comprising: (a) a housing having a housing wall
defining an air path, and an air discharge opening; (b) a discharge
nozzle, mounted over said discharge opening for directing air being
discharged away from said housing; (c) a pinch point formed between
said housing wall and said discharge nozzle at said discharge
opening; (d) an air moving assembly including a rotatable impeller
assembly mounted within said housing for drawing air into said air
path; and (e) a blower noise reducing device on said pinch point
for minimizing air stagnation at said pinch point, said blower
noise reducing device including a first surface for protruding into
said air path, and a second surface for protruding into said
discharge nozzle for minimizing air stagnation within said air path
and within said discharge nozzle.
Description
RELATED APPLICATION
[0001] This application is related to U.S. application Ser. No.
______ (Applicants' Docket No. D/A0860Q) entitled "Office Machine
Including a Blower Having A Blower Noise Reducing Device" filed on
the same date herewith, and having at least one common
inventor.
BACKGROUND OF THE INVENTION
[0002] This invention relates to blowers using an impeller assembly
to draw in and centrifugally accelerate a air for controlled
discharge through a projecting discharge conduit thereof.
[0003] Power blowers, for example those having a tangentially
located discharge conduit, are widely used by homeowners, and
professionally as stand alone devices, or within a machine or
controlled environment for conditioning a air such as air within
such environment. Some such power blowers are hand-holdable, gas
powered units used for example in landscape and maintenance
industries.
[0004] In either case, each such power blower includes a powered
drive motor including a drive shaft, and a rotatable impeller
assembly coupled to the drive shaft. In such blowers having a
tangentially located discharge conduit, the impeller assembly
typically has a laterally extending rotational axis, and draws air
inwardly as it rotates. Each such blower typically also has an
impeller assembly housing including a forwardly and tangentially
projecting discharge conduit that can be conveniently oriented for
directing air discharge during use.
[0005] In one exemplary construction, the impeller assembly has an
unbladed core volume and radially projecting blades having upstream
ends at the core volume and downstream ends located radially
outwardly therefrom. Operation or rotation of the impeller assembly
causes air to be drawn into the core volume, picked up by the
blades, centrifugally accelerated in a volute, and diverted at a
point of separation from the downstream ends of the blades at high
volume into the discharge conduit for directed discharge as
described above.
[0006] A significant problem with such powered blowers is that they
generate a significant amount of noise during operation. Powered
blower designers are therefore constantly seeking ways to further
attenuate the noise generated at different locations throughout the
powered blower assembly so as to make it more environmentally
compatible and acceptable.
[0007] One source or location of noise from such powered blowers
has been identified as being at a branching location or juncture
where the accelerated flow in the volute divides into a first
volume (a) being directed tangentially through the projecting
discharge conduit, and a second volume (b) that remains in the
volute for recirculation. It has been found that somewhere between
these divided flow paths and volumes, some of the air volume is
abruptly halted. Such abrupt halting tends to generate significant
noise as the impeller assembly blades travel past this location and
shear such halted air volume.
[0008] Experimental measurements and calculations therefrom have
indicated that such noise in significant part can be attributed to
the frequency of the blades passing through the stagnated air at
the juncture point. In such experiments, the blade passage
frequency is the number of times that an actual blade passes by the
juncture or pinch point. As an equation, the blade Passage
Frequency=(# of blades) (Rev/Min)(Min/60 Sec)=(6)
(2850R/Min)(Min/60 Sec)=285 Pulse/Sec. Tabulation and examination
of 1/3 Octive data from the experiment clearly showed that the pure
tone fell in an octive band which is relatively close to the 285
Pulse/Sec calculation. This therefore showed that the blade passage
frequency was the source of the noise.
SUMMARY OF THE INVENTION
[0009] The invention is directed to a blower noise reducing device
for use in a blower having a blower housing defining a volute, a
discharge opening through the blower housing, and a discharge
nozzle connected over the discharge opening. The blower noise
reducing device comprises a moving air deflecting member having a
generally triangular cross-section, a first end representing a base
of the generally triangular cross-section, a second end
representing an apex of the generally triangular cross-section, a
first side for mounting against a wall of the discharge nozzle (at
a connecting point between the discharge opening and the discharge
nozzle), and a second and opposite side for protruding into the
discharge opening and discharge nozzle when the first side is
mounted against the wall of the discharge nozzle, thereby reducing
noise causing characteristics of air being moved by deflecting such
moving air in a predetermined manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a fragmentary, perspective view of an exemplary
blower of the present invention including a noise reducing device
in accordance with the present invention;
[0011] FIG. 2 is an enlarged, perspective view of the blower in
FIG. 1 with part of the housing thereon removed to show the noise
reducing device of the present invention;
[0012] FIG. 3 is a schematic of a conventional blower without the
noise reducing device of the present invention;
[0013] FIG. 4 is a schematic of the blower of FIG. 2 including the
noise reducing device of the present invention;
[0014] FIGS. 5 and 6 are detailed illustrations of the noise
reducing device of the present invention; and
[0015] FIG. 7 is a table of noise level measurements from a typical
blower without (column 2), and with various models of the noise
reducing device of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] While the present invention will be described in connection
with a preferred embodiment thereof, it will be understood that it
is not intended to limit the invention to that embodiment. On the
contrary, it is intended to cover all alternatives, modifications,
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims.
[0017] Referring first to FIGS. 1-2 and 4, a blower in accordance
with the present invention, for example, a hand-holdable blower is
shown generally as 10. As shown, the blower 10 includes a housing
12 having walls 13, 14 defining an intake region 47, an internal
air path or volute 24 through which air moves, and a discharge
region 48 including a discharge opening 25. The blower 10 also
includes an air moving assembly in the form of a bladed impeller
assembly 16, which rotates around a laterally extending axis 18 to
draw air axially inwardly, as indicated by the arrow 20, through a
grill 22 within the intake region 47. The impeller assembly 16 then
directs the incoming air radially and outwardly into the volute 24.
Within the volute 24, the air is centrifugally accelerated by the
impeller assembly blades 36, towards the discharge region 48, and
ultimately communicated to and through the discharge opening 25
into a discharge conduit 26. The impeller assembly 16 for example
can be rotated by any suitable power device such as a gas or
electric powered motor 28 which is regulated by controls 30, which
in the case of a hand-holdable blower, can be located on a handle
32.
[0018] The precise air flow pattern into and through the blower
housing 12 can be seen for example in FIGS. 3 (prior art) and 4. In
each case, the motor 28 drives the impeller assembly 16 in the
direction of the arrow 34. The impeller assembly 16 has radially
projecting blades 36 which are spaced uniformly around the axis 18
of the impeller assembly 16. Relative to air movement, each blade
has an upstream end 38 and a radially outwardly spaced downstream
end 40. Between the axis 18 and the upstream ends 38 of the blades
36, a core volume 42 exists that does not have any air accelerating
blades therewithin.
[0019] The blades 36 when being rotated, centrifugally propel air
against a radially and inwardly facing surface 44 of the volute 24.
As such, a low pressure region is thereby developed in the core
volume 42, as a result of which intake air is drawn axially and
laterally through the air intake grill 22 and into the core volume
42. Initially, the air flows axially, then the impeller assembly 16
abruptly changes its direction is so that it then flows in the
radial direction as described above. The radial flow again abruptly
changes direction upon encountering the radially and inwardly
facing surface 44 of volute 24, after which such air then moves in
a curved path, through the volute 24, in the direction of the arrow
34.
[0020] The volute 24 may be designed such that it progressively
increases in volume from the intake region 47 towards the discharge
region 48. As illustrated, within the volute 24, the air is moved
from the intake region 47, and is accelerated and expanded, in the
progressively increasing volume of the volute 24, until some of it,
after branching at a juncture or pinch point 50, is discharged
through the discharge opening 25 into the discharge conduit 26. The
rest of it, after branching at a juncture or pinch point 50,
continues to move through the volute 24.
[0021] Typically, a blower 10, 11 has a number of areas at which
noise generation is significant when moving air as above through
the volute 24. For example, as shown in FIG. 3 (prior art), an area
of significant noise generation is located at the branching
juncture or pinch point 50 where the air accelerated by the
impeller assembly 16 branches so that some of it is discharged
through the discharge opening 25 and into the discharge conduit 26,
and the rest re-enters the volute 24 at the intake region 47.
[0022] As illustrated, the juncture or pinch point 50 is located at
an intersection of a first generally flat surface 52 of the walls
13, 14 of blower housing 12, and a second generally flat surface 54
of the wall 27 of the discharge conduit 26. Because the discharge
nozzle 26 is arranged for tangential flow of accelerated air out of
the volute 24, the juncture or pinch point 50 as shown in FIG. 3 is
ordinarily at a V-shaped apex 56 defined by the flat surface 52 of
the blower housing 12 and that 54 of the nozzle wall 27, meeting
and being connected in an impervious manner.
[0023] It has been found that at the juncture or pinch point 50
between the surfaces 52, 54 there is ordinarily a stagnation point
58 within the volute 24, and a stagnation point 59 within the
discharge nozzle 26 (FIG. 3), where some of the air being
accelerated and branched between the continued volute 24 and the
discharge conduit 26, abruptly stops and is stagnated. Such
stagnated air within the volute 24 is then sheared by the radially
outwardly spaced downstream end 40 of each of the rotating blades
36 as it is rotated passed the juncture or pinch point 50. The
shearing has been found to cause and produce a significant amount
of noise, for example, see TABLE 1 and FIG. 7, column 2 in each
case.
[0024] Referring now to FIGS. 4-6, it has been found that the
shearing noise caused at the juncture or pinch point between the
flat surface of a volute and a flat surface of a discharge conduit
in a blower (for example juncture or pinch point 50) can be
significantly reduced by a blower noise reducing device 60. As
shown, the blower noise reducing device 60 can be formed as a part
of the housing 12 or discharge conduit 26. It can also be an insert
that is attached to either or both the housing 12 or conduit 26,
and over what would ordinarily be the apex 56 at the juncture or
pinch point, for example juncture or pinch point 50. As further
illustrated, the noise reducing device 60 comprises a moving air
deflecting member 62 that has a generally triangular cross-section
64, a first end 66 representing a base 67 of the generally
triangular cross-section, a second end 68 representing an apex
portion 70 of the generally triangular cross-section 64, a first
side 72 for mounting against a wall of the discharge nozzle 26 (at
the connecting point and hence at the juncture or pinch point 50
between the discharge opening 25 and the discharge nozzle 26) and a
second and opposite side 74. The second and opposite side 74 as
shown is shaped for protruding into the discharge opening 25 and
into the discharge nozzle 26 when the first side 72 is formed or
mounted against the wall 27 of the discharge nozzle 26. It has been
found that the noise reducing device 60 as shaped, and when formed
or mounted as described, significantly alters the noise causing
characteristics (for example stagnation) of some of the air being
moved within the volute 24, ass well as within the discharge nozzle
26. The noise reducing device 60 does so by aerodynamically
deflecting such moving air in a predetermined manner as shown in
FIG. 4.
[0025] As further shown, the moving air deflecting member 62
includes a heel-like or heel portion 76 located at the first end 66
for projecting into the volute 24, particularly into the intake
region 47 of the volute for modifying the inside profile of the
volute, and hence the flow pattern of the air being moved, at the
discharge opening 25, in other words at the intake region 47. The
heel portion 76 has a first surface 77 aligned with the base 67 of
the triangular cross-section 64, and a second surface 78 for
attaching to, or that is connected to, the inside of the walls 13,
14 of the volute 24. The second surface 78 of the heel portion 76
comprise the part thereof projecting into the volute 24. The
projection of the heel portion 76 into the volute 24 of course is
such as not to interfere with free movement or rotation of the
distal ends 40 of the rotating blades 36 of the blower impeller
assembly 16. The projection or protrusion of the second surface 78
of the heel portion 76 into the volute 24 changes or alters the
profile of the blower volute tongue or intake region 47. The
projection or protozoon of the second side 74 into the discharge
nozzle 26 also changes or alters the profile of the discharge
nozzle 26 near the juncture 50.
[0026] These changes or alterations have been found to minimize air
stagnation, and hence air shear at or near the juncture 50. The
result is a significant reduction in the overall noise level, as
well as in the blade passage noise level. As shown in FIG. 7, in
one experiment, such noise for example was reduced significantly
from 78.1 dB to 71 dB in the 500 Octive bandwidth.
[0027] In the case where the air deflecting member 62 or noise
reducing device 60 is an insert, the heel portion 76 may include
provisions or features 80 for allowing or enabling it to be
attached to the walls 13, 14 and 27 of the volute 24 and nozzle 26,
respectively.
[0028] As mounted, that portion of the noise reducing device 60 or
the moving air deflecting member 62 that lies within the discharge
nozzle 26, comprises a reverse-aerofoil in shape, relative to air
being discharged by the blower through the nozzle 26. As a
consequence, the discharge nozzle 26 becomes more aerodynamic and
efficient and thus also contributing to the reduction in overall
noise level.
[0029] When the noise reducing device 60 is an insert, it need not
be made of the same material as the walls 13, 14 of the blower
housing. In fact, it can be made of a suitable non-metallic
material such as rubber, plastic, or wood, or out of a suitable
metallic material, provide any such material is an air impervious
material so as to suitably deflect moving air. The insert as such
can then be installed or retro-fitted into even off-the-shelf
blowers for reducing blower noise, and without affecting
performance of the blower. Where the attaching or mounting
provision is for example an adhesive, or merely a friction fitting
slot over the V-shaped apex 56 of the blower housing, the insert or
moving air deflecting member 62 can therefore be easily added or
retro-fitted to an existing standard blower with no tooling costs
to the blower supplier.
[0030] Without the present invention, the typical conventional
approach for noise reducing blower noise would be to add a muffler
system which is more costly and would complicate the overall air
system. The benefits from use of the noise reducing device 60 of
the present invention therefore include the reduced noise level
itself, and the avoidance or replacement of such muffler
systems.
[0031] Table 1, and FIG. 7 illustrate the effectiveness of the
present invention by showing experimental measurements of blower
noise at various Octive Bands (column 1) for a typical blower
without the present invention (column 2), and for reductions due to
use of trial models of the device of the present invention to
modify the tonge/pinch point of the particular blower.
[0032] In this experiment, the blade passage frequently is the
number of times that an actual blade passes by the pinch point. As
an equation:
Blade Passage Frequency=(# of blades) (Rev/Min)(Min/60 Sec)=(6)
(2850R/Min)(Min/60 Sec)=285 Pulse/Sec.
[0033] A look at the 1/3 Octive data clearly shows that the pure
tone falls in the 312 octive band which is relatively close to the
285 Pulse/Sec calculation. This therefore shows that the blade
passage frequency is the source of the noise.
1TABLE 1 1/3 Blower Blower Blower Blower Blower Reduc- Octive
Without With With With With tion Bands invention Mod. 1 Mod. 4 Mod.
11 Mod. 12 dB 160 63 db 63 63 64 63 0 200 73.4 72.1 71 71 69 -4.4
250 73.1 72 71 69 69 -4.1 315 82.2 79 78 77 77 -5.2 400 78.2 75 74
74 73 -5.2 500 78.1 76 74.1 74 71 -7.1
[0034] As can be seen, there has been provided a blower noise
reducing device for use in a blower having a blower housing
defining a volute, a discharge opening through the blower housing,
and a discharge nozzle connected over the discharge opening. The
blower noise reducing device comprises a moving air deflecting
member having a generally triangular cross-section, a first end
representing a base of the generally triangular cross-section, a
second end representing an apex of the generally triangular
cross-section, a first side for mounting against a wall of the
discharge nozzle (at a connecting point between the discharge
opening and the discharge nozzle), and a second and opposite side
for protruding into the discharge opening and discharge nozzle when
the first side is mounted against the wall of the discharge nozzle,
thereby reducing noise causing characteristics of air being moved
by deflecting such moving air in a predetermined manner.
* * * * *