U.S. patent number 3,642,093 [Application Number 05/010,778] was granted by the patent office on 1972-02-15 for sound attenuator with fluidic control.
This patent grant is currently assigned to Barber-Colman Company. Invention is credited to Albert W. Schach.
United States Patent |
3,642,093 |
Schach |
February 15, 1972 |
SOUND ATTENUATOR WITH FLUIDIC CONTROL
Abstract
A main flow of air passes through an inlet into a unit which
serves as a sound attenuator and which also acts as a fluidic
control whereby the air is divided to be discharged through two
outlets in unequal amounts or is discharged through only one
outlet. Areas of low pressure are created around the inlet by the
flow of air through the inlet and, by creating a pressure
differential between the areas, the flow of air is deflected toward
the outlet on the same side of the unit as the area of lowest
pressure. To create the differential, two baffles are spaced from
one another to form a channel for the main flow of air through the
unit and are each spaced from opposed walls of the unit to form
passages which empty into the areas of low pressure. A portion of
the main flow of air may flow back through the passages and into
the areas of low pressure. Dampers control the amount of flow
through each passage so that the pressure in one area is raided a
greater amount than the pressure in the other area thereby creating
the pressure differential which controls the direction of airflow.
To reduce the noise level in the unit and downstream thereof, each
baffle comprises a zigzag-shaped sheet of lead positioned to
reflect sound waves toward the other baffle and toward the inlet, a
padding of fiber glass surrounding the sheet to dampen the sound
waves, and a covering of perforated sheet metal to protect the
fiber glass from the eroding effect of the flow of air. With this
arrangement, the sound waves pass repeatedly back and forth within
the unit until they are substantially dissipated.
Inventors: |
Schach; Albert W. (Rockford,
IL) |
Assignee: |
Barber-Colman Company
(Rockford, IL)
|
Family
ID: |
21747378 |
Appl.
No.: |
05/010,778 |
Filed: |
February 12, 1970 |
Current U.S.
Class: |
181/239; 454/284;
454/333; 181/256 |
Current CPC
Class: |
F24F
13/24 (20130101); F24F 13/10 (20130101) |
Current International
Class: |
F24F
13/24 (20060101); F24F 13/00 (20060101); F24F
13/10 (20060101); F24f 013/06 (); F24f 013/10 ();
F01n 001/10 () |
Field of
Search: |
;181/50,56,42,60
;98/4R,4A,4B,4C,4D,41R,41AV |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
566,997 |
|
Sep 1957 |
|
IT |
|
364,340 |
|
Oct 1962 |
|
CH |
|
Primary Examiner: Ward, Jr.; Robert S.
Claims
I claim as my invention:
1. For use in an air distribution system, a unit comprising in
combination, a generally rectangular box having an end wall,
sidewalls, and opposed upper and lower walls, an inlet positioned
in said end wall for directing a main flow of fluid toward the
other end of said box and thus tending to create upper and lower
areas of low pressure in the end portion of said box above and
below said inlet, outlet means in the other end of said box, an
upper baffle connected to said upper wall and extending generally
from one sidewall to the other, and a lower baffle connected to
said lower wall and extending generally from one sidewall to the
other, said baffles being spaced apart to define between themselves
a central channel for the flow of fluid from said inlet toward said
outlet means, said upper baffle being spaced from said upper wall
to define an upper passage communicating between said upper
low-pressure area and the other end of said box, said lower baffle
being spaced from said lower wall to define a lower passage
communicating between said lower low-pressure area and the other
end of said box, a portion of said fluid at said other end being
drawn through said passages and into said low-pressure areas to
increase fluid pressure in said low-pressure areas to reduce the
turbulent flow of fluid into the box through the inlet and,
thereby, reduce noise normally produced by said turbulent flow.
2. The unit of claim 1 in which each said baffle comprises a body
formed of sound wave dampening material to dampen sound waves in
the fluid flowing through said box whereby the noise level of the
flow of fluid through said outlet means is kept low.
3. The unit of claim 2 in which each baffle further comprises a
zigzag-shaped sheet of sound-reflecting material embedded within
said sound wave dampening material, the sheets generally opposing
one another to reflect sound wave through said dampening material
and away from said outlet means.
4. The unit of claim 3 in which each said baffle further includes a
perforated casing of wear-resistant material around said dampening
material thus protecting such material from the eroding effects of
the flow of fluid past said baffles.
5. The unit of claim 1 further including supports extending through
said upper and lower passages to connect said upper and lower
baffles to said upper and lower walls respectively while spacing
said baffles from said walls, and said supports being made of
material which is a poor conductor of sound waves.
6. The unit of claim 2 in which said outlet means comprises upper
and lower outlets and further including a third baffle adjacent
said other end and between said outlets and being made of a
sound-dampening material.
7. The unit of claim 6 in which each of said three baffles includes
a zigzag-shaped sheet of sound-reflecting material embedded within
said sound-dampening material.
8. The unit of claim 1 in which said outlet means comprises upper
and lower outlets and further including means for selectively
controlling the flow of fluid through said passages whereby a
greater amount of fluid may be allowed to flow through one of said
passages to raise the pressure in the corresponding area of low
pressure to create a differential in pressure between the two areas
and thus deflect the main flow of fluid in the direction of the
area of lower pressure.
9. A fluidic control comprising a box having an inlet and a pair of
outlets for moving a flow of fluid through said box, and means in
said box for selectively apportioning the flow of fluid between
said outlets by creating selected pressure differentials in areas
adjacent the sides of the inlet so as to deflect a portion of the
flow toward the outlet on the same side of the box as the lower
low-pressure area and away from the outlet on the same side of the
box as the higher low-pressure area, said means including a baffle
positioned adjacent the flow of fluid, said baffle comprising sound
wave dampening material so that a large portion of the sound waves
in said flow of fluid is dampened as the flow of fluid passes said
baffle.
10. A fluidic control comprising, a box having an inlet for
directing a flow of fluid into said box and having a plurality of
outlets spaced from said inlet for conducting said flow out of said
box and means in said box for apportioning said flow and directing
the latter to said outlets, said means including two opposed
baffles spaced apart to define between themselves a central channel
for the flow, each said baffle comprising a zigzag-shaped sheet of
sound wave reflecting material, and sound wave dampening material
surrounding said sheet, said sheets being positioned to reflect
sound waves toward said inlet and toward one another so that sound
waves from the flow are passed through said sound wave dampening
material until dissipated to provide a quite flow of fluid beyond
said outlets.
11. The fluidic control of claim 10 in which said box has first and
second opposed sidewalls, a first support connecting one of said
baffles to said first wall while spacing said baffle from said
first wall, and a second support connecting the other said baffle
to said second wall while spacing said other baffle from said
second wall, said supports being made of material which is a
nonconductor of sound waves whereby sound waves are not transmitted
from said baffles to the walls of said box.
12. The fluidic control of claim 10 in which each said baffle
further includes a covering of wear resistant material to help
protect said dampening material from the eroding effects of the
flow of fluid.
13. For use in an air distribution system, a unit comprising in
combination, a box having two ends and first and second opposed
walls extending between said ends, an inlet positioned in said one
of said ends between said walls for directing a main flow of fluid
toward said other end and thus tending to create first and second
areas of low pressure in the end portion of said box adjacent said
inlet, a first outlet disposed in the other said end adjacent said
first wall, a second outlet disposed in said other end adjacent
said second wall, a first baffle connected to said first wall, a
second baffle connected to said second wall, said baffles being
spaced apart to define between themselves a main channel for the
flow of fluid from said inlet toward said outlets, said first
baffle being spaced from said first wall to define a first passage
beginning adjacent said first outlet and ending adjacent said first
area of low pressure for the flow of fluid around said first baffle
toward said first area of low pressure, said second baffle being
spaced from said second wall to define a second passage beginning
adjacent said second outlet and ending adjacent said second area of
low pressure for the flow of fluid around said second baffle toward
said second area of low pressure, said baffles having opposed
surfaces curved away from each other and toward the beginning of
said passages to help guide a portion of said flow of fluid into
said passages, and means for selectively controlling the flow of
fluid through said passages to allow a greater amount of flow
through one of said passages to raise the pressure in the
corresponding area of low pressure thereby creating a differential
in pressure between the two areas thus deflecting the main flow of
fluid in the direction of lower pressure.
14. The unit of claim 13 in which said controlling means comprises
dampers positioned adjacent said baffles and each mounted for
selective movement to block or partially block said passages.
baffles
15. The unit of claim 14 in which each said damper comprises a body
with a curved edge portion said edge portion being positioned to
guide fluid into a respective passage when said damper is
positioned to partially block said respective passage.
16. A fluidic control comprising in combination, a box having two
ends and opposed sidewalls extending between said ends, an inlet
positioned in one of said ends between said walls for directing a
main flow of fluid toward said other end and thus tending to create
first and second areas of low pressure in the end portion of said
box adjacent said inlet, a plurality of outlets disposed in the
other said end, means contained within said box for creating a
pressure differential between said areas whereby the flow of fluid
is deflected toward one of said outlets said means comprising two
opposed baffles spaced apart to define a central channel for the
flow of fluid from said inlet toward said outlets each said baffle
being spaced from a sidewall to create a passage having one end
adjacent and communicating with one of said areas of low pressure
and one end adjacent an outlet so that fluid may pass through each
passage and into the area of low pressure to raise the pressure in
that area, and control means for regulating the amount of fluid
passing through each passage so that more fluid is directed to a
selected one of said areas to create a pressure differential
between the areas to deflect the flow of fluid.
Description
BACKGROUND OF THE INVENTION
This invention relates to an air distribution system with a unit
which serves both as a sound attenuator and as a fluidic control
operable either to divide a main flow of fluid into a plurality of
flows as the fluid passes through the unit from an inlet to a
plurality of outlets or to direct the fluid to only a selected one
of the outlets. The unit dampens sounds generated upstream of the
unit as well as within the unit itself. More particularly as
regards the fluidic control, the main flow is deflected toward a
selected one of the outlets to direct the larger portion of the
fluid through the selected outlet, the amount of the flow going
through the selected outlet depending on the amount the flow that
is deflected toward the selected outlet. To deflect the flow, a
pressure differential is created between areas on opposite sides of
the flow as the latter enters the control unit, the flow being
deflected toward the area of lowest pressure and thus toward the
outlet corresponding to such area.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a unit which is
simpler and easier to make and is less expensive to manufacture
than similar control units heretofore available and which is a
self-contained unit.
One object is to provide a control unit that discharges flows of
fluid having lower noise levels than flows discharged by similar
control units heretofore available.
Another object is to provide a control unit which is operable to
self-induce a pressure differential between the areas and thus does
not require the introduction of a high or low-pressure force into
the unit from an outside source.
It is a more detailed object to take advantage of the natural laws
of fluid flow not only to induce areas of low pressure within the
unit but also to selectively raise the pressure in one area to
create the pressure differential.
The invention also resides in the novel provision of a plurality of
baffles with each baffle comprising a zigzag-shaped sheet of sound
wave reflecting material surrounded by sound wave dampening
material with the sheet being positioned to reflect the sound waves
through the dampening material and upstream of the flow to help
prevent the sound waves from being discharged through the
outlets.
Other objects and advantages of the invention will become apparent
from the following detailed description taken in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary, perspective view of a fluidic control unit
embodying the novel features of the present invention and with
parts broken away for clarity.
FIG. 2 is a cross section taken substantially along the line 2--2
in FIG. 1.
FIG. 3 is a fragmentary cross-sectional view of a second embodiment
of a damper for use with one of the baffles.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in the drawings for purposes of illustration, the
invention is embodied in a unit 10 (FIG. 1) placed between an
upstream fluid supply line 11 and a number, herein two, of
downstream fluid distribution lines 12, 13 to dampen noise and to
control the distribution with respect to the two distribution lines
of a pressurized gas, such as air, flowing into the unit from the
supply line, The air flows into the unit through an inlet 14 (FIG.
2) at one end of the unit (the left in FIG. 2) and is directed by
the inlet toward the other end of the unit in which an upper outlet
16 joins the unit to one distribution line 12 and a lower outlet 17
joins the unit to the other distribution line 13. Between the two
outlets, a flow divider 18 with a generally triangular cross
section extends generally horizontally across substantially the
entire width of the unit and, when no other forces are acting on
the flow of air, the divider splits the flow into two equal flows
which pass through the two outlets.
To divide the flow of air unevenly between the two outlets 16, 17
or to direct the entire flow to one outlet, force is applied to the
flow to deflect the latter toward one outlet or the other. Since
the outlets are oriented one above the other in this instance, such
a force acts to deflect the flow either upwardly or downwardly as
the flow passes through the unit 10. Herein, such a deflecting
force is created by establishing a pressure differential between an
area 20 above the flow as the latter enters the unit and an area 21
below the flow, the flow being deflected in the direction of the
area of the lowest pressure.
In accordance with one aspect of the present invention, advantage
is taken of the natural laws of fluid flow to use the flow of air
through the unit to create a selected, self-induced, pressure
differential between the upper and lower areas 20, 21 to deflect
the flow of air toward one or the other outlet 16, 17. For this
purpose, the unit 10 is shaped so that the areas 20 and 21 become
low pressure due to the air flowing through the inlet 14, and two
baffles 23 and 24 are positioned within the unit so that small
amounts of airflow into the areas to raise the pressure in the
areas. The amount of air directed to each area may be controlled so
that different amounts flow into the areas to create a pressure
differential between the areas. With this arrangement, the flow of
air may be divided unevenly between the outlets or directed
entirely through one outlet, and the unit utilizes the flow of air
to create the pressure differential and thus the deflecting force
to eliminate any need for an external deflecting force being
introduced into the unit.
Herein, the unit 10 is in the shape of generally rectangular box
formed with a flat end wall 25 (left end in FIG. 2), opposed top
and bottom walls 26 and 27 and sidewalls 28 and 29 (FIG. 1). The
walls may be made of sheet metal lined with sound dampening
material 29'. There is no end wall as such on the right end of the
box because the upper outlet 16 and lower outlet 17 extend from
sidewall to sidewall and are separated only by the flow divider 18.
From FIG. 1, it will be observed that the inlet 14 is centered in
the end wall 25 and extends into the interior of the box to divide
the left end of the box into the upper and lower areas 20 and 21.
The air passing from the supply line through the inlet and into the
box is pressurized, and the resulting flow of air past the inner
end of the inlet creates a low or negative pressure in the upper
and lower areas in a manner well known in the art of fluid
flow.
The baffles 23 and 24 are positioned to channel the flow of air
toward the outlet end of the box 10 while directing small amounts
of the air into the low-pressure areas 20 and 21 to raise the
pressures in those areas. For this purpose, the upper baffle 23 is
connected to and spaced from the upper wall 26 to form an upper
passage 30 with an inlet end 31 adjacent the upper outlet 16 and
with an outlet end 32 adjacent the upper area 20 while the other
baffle 24 is connected to and spaced from the lower wall 27 to form
a lower passage 33 with an inlet end 34 adjacent the lower outlet
17 and with an outlet end 35 adjacent the lower area 21. As shown
in FIG. 1, the baffles extend substantially from sidewall 28 to
sidewall 29 so that the passages do likewise.
Due to the Coanda Effect, some of the air flowing between the
baffles 23 and 24 will adhere to the outer surfaces of the baffles
and will follow around the baffles and through the passages 30 and
33 and into the upper and lower low pressure areas 20 and 21 thus
raising the pressure in these areas. The Coanda Effect generally is
the principle that, when fluid is expelled under pressure into a
chamber and contacts a surface therein, the fluid will adhere to
that surface and move along the surface.
So that a pressure differential is created between the upper and
lower low pressure areas 20 and 21, the amount of air that is
allowed to flow through each passage 30, 33 is controlled. For this
purpose, dampers 36 and 37 are positioned at the inlet ends 31 and
34 of the passages to regulate the airflow through the passages. As
shown in FIGS. 1 and 2, each damper may be a sheet of metal
extending from the sidewall 28 to the sidewall 29 and pivotally
mounted between the sidewalls to turn about a generally horizontal
and laterally extending axis at the center of the damper. Each
damper may be turned about its axis and set in any selected
position from horizontal to vertical. As shown in FIG. 2, the upper
damper 36 is vertically positioned and completely closes the upper
passage 30 while the lower damper is horizontally positioned and
thus allows the maximum airflow through the lower passage 33. When
the dampers are set as shown in FIG. 2, the greatest pressure
differential is created between the upper and lower areas with the
pressure in the upper area being the lowest since no air flows into
the upper area. When the dampers are positioned in the above
manner, the flow of air entering the box is deflected toward the
upper outlet 16 to such an extent that substantially no air flows
through the lower outlet 17. The flow of air can be divided
unevenly between the two outlets by opening the upper damper less
than the lower damper thus creating less of a pressure differential
between the areas to deflect the flow of air only somewhat toward
the upper outlet thus resulting in the larger portion of the flow
going through the upper outlet or by opening the lower damper less
than the upper damper to deflect the flow of air somewhat toward
the lower outlet. If both dampers are horizontal or vertical, the
pressures in the areas will be equal, and the flow will be evenly
divided between the two outlets. Thus, by selectively setting the
inclination of the dampers, the flow of air may be directed
entirely through the upper outlet or the lower outlet or be divided
in any proportions between the two outlets.
A modified damper 39, shown in FIG. 3, gives added assistance in
guiding the air through the passages 30 and 33. Each damper (only
one of which is shown in FIG. 3) is formed with a curved end
portion 40 which, when the damper blocks its respective passage,
overlaps its respective baffle 23, 25 and which, when the damper
does not completely block the passage, tends to guide air around
the end of the baffle and into the passage to aid the Coanda
Effect.
Noises produced upstream of the box 10 and turbulence caused by the
flow of air rushing into the box are objectionable if allowed to
reach the area where the air is to be used. In accordance with
another aspect of the invention, the baffles 23 and 24 are utilized
to dissipate the sound waves in the box and reduce the sound
traveling downstream with the air. For this purpose, the baffles 23
and 24 comprise cores 41 of sound wave reflecting material
surrounded by paddings 42 of sound wave dampening material.
Additionally, the flow divider 18 is formed by a core 43 of sound
wave reflecting material covered by a padding 44 of sound wave
dampening material and thus also serves as a baffle. With this
arrangement, the sound waves pass through the paddings 42 and 44
and bounce off the cores 41 and 43 to pass repeatedly through the
paddings until dampened and thus the noise levels in the
distribution lines 12 and 13 are very low.
Each baffle core 41 is shaped to reflect the sound waves either
toward the other baffle core or toward the inlet 14 so as to reduce
the possibility of the sound waves progressing through the box 10
to the outlets 16 and 17. As best shown in FIG. 2, each core is
formed with a zigzag surface comprised alternately of generally
vertically inclined faces which face the inlet and generally
horizontal faces which face the opposed baffle. Thus, sound waves
bounce off the vertical faces toward the inlet and off the
horizontal faces toward the other baffle. In either case the sound
waves pass repeatedly through the paddings 42 until dampened. The
core 43 of the flow divider 18 also is zigzag in shape but is bent
into a V so that the sound waves are reflected back toward the
inlet after passing through the padding 44. Lead is a satisfactory
sound wave reflecting material and may be used to make the
cores.
Paddings 42, 44 which are effective for the purpose usually are
made of a material which may be easily worn away or eroded by the
flow of air moving across the baffles 23 and 24 and the flow
divider 18. Such a material which possesses the requisite sound
wave dampening characteristics is fiber glass. To protect the
paddings from the eroding effect of the moving air, protective
coverings 46 encase each baffle and cover the flow divider. While
burlap or cheesecloth might be used for this purpose, perforated
sheet material is preferred, the perforations allowing the sound
waves to penetrate into the paddings.
Advantageously, the baffles 23 and 24 are connected to and spaced
from the upper and lower walls 26 and 27, respectively, so that
sound wave vibrations are not transmitted from the baffles to the
walls. For this purpose, each baffle is mounted on its wall by a
set of vibration dampening posts 47, in this instance four. Hard
rubber has been found to be a satisfactory material for the
posts.
Spacing of the baffles 23 and 24 from the walls 26 and 27 to permit
the flow of some air back into the areas 20 and 21 also has the
effect of reducing noise which would result from the otherwise low
pressure in these areas. Thus, the unit 10 may be used simply as a
sound attenuator without producing fluidic action. In such a case,
both dampers 36 and 37 are placed in the open position or are
eliminated completely and the air from the outlets 16 and 17 may
flow into a common conduit instead of the distribution lines 12 and
13 shown in the drawings.
It will be observed that the provision of the baffles 23 and 24
spaced from the upper and lower walls 26 and 27 of the box 10 to
create the passages 30 and 33 which are controlled by the dampers
36 and 37 is a particularly advantageous arrangement for
controlling the flow of air through the box. With this arrangement,
air may be diverted from the main flow and directed into one or the
other or both of the upper and lower low-pressure areas 20 and 21
to create a pressure differential between the areas thus exerting a
force on the flow of air into the box to deflect such flow toward
the outlet associated with the area of lowest pressure. Also of
particular advantage is the construction of the baffles 23 and 24
so that they prevent the passage of most of the sound waves into
the distribution lines. More particularly, the zigzag-shaped cores
41 repeatedly reflect the sound waves through the sound wave
dampening paddings 42.
* * * * *