U.S. patent number 3,841,434 [Application Number 05/328,306] was granted by the patent office on 1974-10-15 for noise attenuator.
This patent grant is currently assigned to Aero-Dyne. Invention is credited to Clifford Culpepper, Jr..
United States Patent |
3,841,434 |
Culpepper, Jr. |
October 15, 1974 |
NOISE ATTENUATOR
Abstract
Noise otherwise emanating from a duct system through which
airborne particulate matter is conveyed is attentuated by a device
in which an energy absorbing material is sealed within an
impervious film bag, so that decay in the noise attenuation
efficiency of the device otherwise occurring due to accretion of
particulate matter to the energy absorbing material is avoided.
Inventors: |
Culpepper, Jr.; Clifford
(Charlotte, NC) |
Assignee: |
Aero-Dyne (Charlotte,
NC)
|
Family
ID: |
23280432 |
Appl.
No.: |
05/328,306 |
Filed: |
January 31, 1973 |
Current U.S.
Class: |
181/224;
126/299D; 454/49 |
Current CPC
Class: |
F01N
1/24 (20130101); G10K 11/16 (20130101); F01N
2310/02 (20130101) |
Current International
Class: |
F01N
1/24 (20060101); G10K 11/00 (20060101); G10K
11/16 (20060101); F01n 003/06 () |
Field of
Search: |
;98/115R,115K,115LH
;23/277C ;181/35R,35C,36R,36B,36C,36D,42,50,71,35C,33G
;126/299R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wilkinson; Richard B.
Assistant Examiner: Gonzales; John F.
Attorney, Agent or Firm: Parrott, Bell, Seltzer, Park &
Gibson
Claims
That which is claimed is:
1. The combination, with a hood positioned adjacent a food
preparation area within a building and an air pollution control
system including an afterburner disposed outside the building and
in which particulate grease is burned and noise is generated and a
duct extending between the hood and the afterburner and through
which airborne particulate grease is conveyed from the food
preparation area, the duct including a vertically rising portion
and a horizontally directed portion forming an ell with the
vertically rising portion, of an arrangement for attenuating noise
otherwise transmitted from the afterburner to the hood and
comprising first and second noise attenuating devices each
comprising a grease impervious film bag, energy absorbing means
sealed within said bag for dissipating by mechanically compressive
absorption sonic energy impinging on said bag, said bag precluding
accretion of grease on said energy absorbing means and thereby
avoiding decay in the noise attenuation efficiency thereof, and
means for mounting said bag within said duct in exposure to sonic
energy being transmitted from the afterburner to the hood, said
mounting means disposing said first noise attenuation device
adjacent said ell for substantially direct, perpendicular
impingement of sonic energy thereon and mounting said second noise
attenuator device in predetermined spaced relation within the duct
from said first noise attenuator device.
Description
Duct systems are frequently employed for the entrainment and
conveyance of airborne particulate matter. Particularly in
instances where such systems are employed in connection with public
spaces, such as in a fast service restuarant having a ventilation
system for removing airborne liquid grease, difficulties have been
encountered in circumstances where noise generators are included in
the duct systems. Most notably, certain forms of disposal devices
and particularly afterburners have been known to have operating
conditions which give rise to objectionable noise levels. Where
such a noise generator is included in a duct system, the resulting
emanation of noise endangers the success of the restaurant and the
mental and physical well-being of employees working in the
restaurant.
Heretofore, attempts at suppressing or attenuating such noise have
included use of conventional silencers or suppressors. However,
such devices have had only limited success due to more or less
prompt failure of the devices. In particular, it has been
discovered that the particulate matter being conveyed through the
duct system "loads" or gathers on the silencer or suppression
device, causing decay in the noise attenuation efficiency
thereof.
Accordingly, it is an object of this invention to overcome the
deficiencies of prior arrangements by avoiding decay in the noise
attenuation efficiency of an arrangement which attenuates noise
otherwise emanating from a duct system. In realizing this object of
the present invention, noise is attenuated by mechanically
compressive absorption and dissipation of sonic energy while
"loading" or accretion of particulate matter on the energy
absorbing material is precluded by sealing the material in an
impervious film bag.
Some of the objects and advantages of the invention having been
stated, others will appear as the description proceeds, when taken
in connection with the accompanying drawings, in which
FIG. 1 is a perspective view, partially in section, of an
arrangement in accordance with this invention;
FIG. 2 is an enlarged elevation view, partially in section, through
a portion of the arrangement of FIG. 1 taken generally along the
line 2--2 in that figure; and
FIG. 3 is an enlarged perspective view of an attenuation device in
accordance with this invention.
While the description which follows will set forth the best mode
presently contemplated for the practice of this invention, it is
anticipated that there may be variations in specific details in
following the present invention. For that reason, the description
is to be taken as a broad teaching, and not as a restriction or
limitation on the scope of this invention.
FIG. 1 illustrates, somewhat schematically, a duct system in which
the present invention has been found to be of particular utility.
The duct system, as illustrated, includes a hood 10 disposed within
a building structure and generally overlying a cooking area (not
shown). Typically, such a hood 10 is installed in a fast service
restaurant adjacent a cooking apparatus which generates airborne
particulate matter, such as a charbroiler or frier from which
liquid grease is discharged into the ambient atmosphere.
The arrangement of FIG. 1 further includes a duct 11 operatively
communicating with the hood and passing from within the building
structure to a location outside the building structure. Operatively
associated with the duct 11 is a suitable means for inducing the
flow of air from the area within the building, into the hood 10 and
through the duct 11. Further, the arrangement includes means, such
as an after-burner generally indicated at 12, which functions as a
noise generator within the ventilation system, and which
operatively communicates with the airflow inducing means, the duct
11 and the hood 10.
In accordance with this invention, noise attenuation or suppression
devices generally indicated at 14 and 15 are positioned within the
duct 11 for attenuating noise otherwise emanating from the duct
system (FIGS. 1 and 2). Inasmuch as the devices 14, 15 are of
identical construction and assembly, the discussion which follows
will be limited to particular reference to device 14, with it being
understood that the construction of the device 15 is the same.
The noise attenuating device 14 comprises energy absorbing means
for dissipating by mechanically compressive absorption of sonic
energy which impinges on the device. Preferably, the energy
absorbing means is in the form of a body 16 of agglomerated fibers.
More specifically, the body 16 preferably is a glass fiber batt of
suitable dimensions for the overall dimensions of the device 14.
The fiber body 16 is sealed within an impervious film bag 18, in
order to preclude access of the airborne particulate matter to the
body 16 of fibers. While the impervious bag 18 thus protects the
device 14 against the decay of noise attenuating efficiency which
would occur with such accretion of particulate matter, it is to be
understood that the bag in no way significantly impedes impingement
of sonic energy or dissipation of such energy by mechanically
compressive absorption in the body 16 of fibers. Particularly in
applications intended for fast service restaurants where the
particulate matter conveyed through the duct 11 is liquid grease,
it is desirable for the material of the film bag 18 to be Tedlar
brand of polyvinylflouride, inasmuch as that material has a
particularly notable resistance to grease, oil and the like. Other
membrane materials may, however, be found to be satisfactory in
various specific applications and may include, by way of example,
neoprene, butyl rubber, Hypalon brand of chlorosulfonated
polyethylene, polyisobutylene rubber, vinylidene chloride or
polyvinylchloride.
The impervious film bag 18 and the body 16 of fibers sealed
therewithin are received within a mounting means 20 suitably
fabricated out of sheet metal. As so fabricated, one face 21 of the
sheet metal mounting means 20 is perforated, to assure exposure of
the bag to sonic energy present in the system including the duct
11.
As illustrated, it is preferred that a system incorporate first and
second devices 14, 15. Preferably, the devices are secured to
oppositely facing walls of a duct such as the duct 11, in
predetermined spaced apart relation correlated to the dimensions of
the devices taken longitudinally of the duct and the frequency of
the noise to be attenuated. By so mounting the devices 14, 15,
otherwise unacceptable restrictions of the flow path for the air
and conveyed particulate matter are avoided (FIG. 2) while the
desired efficiency of noise attenuation is maintained.
In the drawings and specification, there has been set forth a
preferred embodiment of the invention, and although specific terms
are employed, they are used in a generic and descriptive sense only
and not for purposes of limitation.
* * * * *