close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3059574

код для вставки
Oct. 23, 1962
B. E. CURRAN ETAL
3,059,564
LOW NOISE AIR DISTRIBUTOR
Filed Oct. 30, 1959
'
2 Sheets-Sheet 1
IN VEN TORS
BERNARD E. CURRAN
GLENN E. KAUTZ
BY THEODORE w. MARSHALL
up’? AgoRNEY
Oct. 23,.’ 1962'
B. E. CURRAN ETAL
3,059,564
LOW NOISE AIR DISTRIBUTOR
Filed Oct. 50, 1959
2 Sheets-Sheet 2
O
4.
5
76
8o
3o
75
300
600
I200
2400
4800
SOUND FREQUENCY, CYCLES PER SECOND
cozEmw .5980
54
6O
7
8
75
I50
300
600
I200
2400
4800
SOUND FREQUENCY, CYCLES PER SECOND
9O
.o>z_mw.z_ JUQM
38 0
75
I50
300
600
I200
2
SOUND FREQUENCY, CYCLES PER SECOND
(~38
wBGT
4R0
Y/4 ?gN OAND
B
AwDER
%
L
M
EMRNN8 m
"H
.EO
WWTMEY
AW
.R ZA
E.K0 ICU. N
L
United States Patent 0 rice
3,059,564
1
1.
Patented Oct. 23, 1962
2
showing the present invention in its simplest embodiment;
3,059,564
LOW NOISE AIR DISTRIBUTOR
Bernard E. Curran and Glenn E. Kautz, Sewickley, and
Theodore W. Marshall, Conway, Pa., assignors to
H. H. Robertson Company, Pittsburgh, Pa., a corpora
tion of Pennsylvania
Filed Oct. 30, 1959, Ser. No. 849,940’
2 Claims. (CI. 98—38)
FIGURE 2 is a cross-section illustration of a ventila
tion distributor adapted to practice the present invention;
FIGURE 3 is a cross-section illustration of a preferred
embodiment of a ventiiation mixing box for blending
and discharging separate streams of ventilation air into
a room;
FIGURE 4 is a cross-section illustration of the ventila
tion mixing box taken along the line 4—4 of FIGURE 3;
The present invention relates to air distributing means 10
FIGURES 5, 6 and 7 are graphical representations of
having a low noise level.
various relationships between sound intensity and sound
In the ventilation art, air is supplied through duct work
frequency which illustrates certain properties of the pres
into rooms of buildings for distribution. Noises accom
ent invention;
pany the release of air in the individual rooms. These
FIGURE 8 is a view of an enlarged scale illustrating
noises include sounds of a wide frequency spectrum includ 15 the structure of a preferred permeable obstruction; and
ing low frequency sounds and high frequency sounds. ,
FIGURE 9 is a cross-sectional view, on an enlarged
Noises in the audible sound range from about 15 cycles
scale, illustrating the connection between a pressure sensing
per second to about 20,000 cycles per second become ob
conduit and a filter shown in FIGURE 4.
jectionable to the occupants of the rooms. Noises arise
Referring to FIGURE 1 there is illustrated a duct 10
in ventilation systems from a variety of sources including 20 through which gases, indicated by the arrow A, are ?ow
ing for discharge into an enlarged chamber such as room
fan noises, mechanical vibrations, duct resonance, air
turbulence, direction changes in the air ?ow, duct oscilla
tions, air velocity effects, and the like. All of these noises
as indicated by the arrow B.
Associated with the flow
of gases at A is a noise phenomenon including sounds
‘blend together into a spectrum of sounds which are pre
ranging through the entire spectrum of frequencies in~
sented at the air distribution point. It is a commonplace 25 cluded in the audible sound range.
'
practice to cover the surfaces of air discharge apparatus
A permeable obstruction vII extends across the duct
with ?brous materials capablev of absorbing a portion of
the energ of relatively high frequency sound waves.
While sound absorbing coatings are effective in lower
It? in the path of the ?owing gases A. The permeable
obstruction 11 has a multiplicity of gas passageways ex
tending therethrough, each gas passageway having a cross
ing the intensity of the relatively high frequency sounds, 30 section which is negligible in contrast to that of the duct
the coatings are ineffective in reducing the intensity of
the relatively low frequency sounds.
‘
'
.
According to the present invention ventilating gases
are passed initially through a permeable obstruction hav
ing a multiplicity of gas passageways therethrough. Each
gas passageway has a cross-section which is negligible
in contrast to that of the duct in vwhich ‘the ventilating
gases are ?owing. The cumulative.cross-sectional area of
said gas passageways is between about 50 and about 75
percent of the cross-section ofpthe duct in which the gases
1t). Suitable materials for the permeable obstruction 11
include a perforated plate of solid material such as metal
or plastic, a filamentary screen such as wire mesh or plastic
?lament mesh, a batt of coarse fibrous materials such as
straw, coconut ?ber, steel wool, or similar filamentary
material. The cumulative cross—sectional area of all of
the said gas passageways should be from about 50V to
about 75 percent of the cross-section of the duct It‘.
In traversing the permeable obstruction II, the gases
A experience a measurable pressure drop, preferably slight.
The spectrum of sounds which are airborne by the ?owing
gas stream experiences a pecular frequency shift. The
relatively low frequency sounds are in part converted to
are ?owing. The function of the permeable obstruction is
to convert the energy of the relatively low frequency
sounds into energy having a relatively higher frequency.
relatively high frequency sounds. The relatively high
In the higher frequency form, the sound energy can be
absorbed by the conventional sound absorbing linings.
45 frequency sound waves are virtually unaffected by the
When the ventilating gases, having passed through the
passage of the gases through the permeable obstruction
permeable obstruction, subsequently impinge against a
1i. Downstream from the permeable obstruction 11 the
conventional sound absorbing lining, sound energy is ab
gases impinge against a duct lining 12 having sound ab
sorbed from the relatively high frequency sounds which
sorbing properties. The airborne sounds of relatively high
were originally present as well as from the relatively 50 frequency impinge against the sound absorbing lining 12.
high frequency sounds resulting from conversion of the ‘ The residual relatively low frequency sounds are virtually
relatively low frequency sounds originally present. As
unaffected by the sound absorbing lining 12. Thus the
a result, the over-all noise intensity presented in. the region
noise spectrum associated with the discharging gases B
of the gas distributor can be maintained at an acceptable
has a lower intensity of relatively low frequency sounds
level in the audible sound range to minimize the discom 55 and of relatively high frequency sounds than the noise
fort of the room occupants.
spectrum associated with the ?owing gases at A.
The principal object of this invention is to'provide a
In the absence of the permeable obstruction 1-1, the
method and apparatus for minimizing the level of audible
sound absorbing lining 12 would serve to absorb sound
noise accompanying discharge of ventilating gases into a
energy originally, present as relatively ‘high frequency
sounds which are airborne by the ?owing gases ‘at A.
A further'object of this invention is to provide a method
In the absence of the sound absorbing lining 12, the
and apparatus for converting a portion of. the energy of
permeable obstruction 11 would serve merely to convert
the relatively low frequency sounds associated with a
some of the sound energy of the relatively low frequency
flowing stream of ventilating gas into relatively‘high fre
sounds to ‘sound energy in the form of relatively high
quency forms of sound energy and thereafter absorbing 65 frequency sounds which would pass unabsorbed into the
a portion of the relatively high frequency sound energy
enlarged chamber at B. Thus it is the sequential com
associated with the gas stream in its altered condition.
bination of the permeable obstruction 11 and the sound
These and other objects and advantages of the present
absorbing lining 12 which forms the improvement of the
invention will become apparent from the following de
present invention.
tailed description by reference to the accompanying draw 70 Where the cumulative cross-sectional area of the gas
ings in which:
'
1
I
;
~
7
passageways in the permeable obstructions is less than
FIGURE 1 is a schematic illustration in cross-section
about 50 percent of the cross-section of the duct in
room.
‘
_
~
.
3,059,564
3
which the obstruction is placed, there is excessive pres
sure drop in the gases ?owing through the obstruction.
For example, a sponge which possesses a highly devel
oped independent pore structure will present few gas
passageways extending through a section of the material.
4
44.
Pressure taps for this regulation include a conduit
45 positioned downstream from the vane 44 and a con
duit 46 positioned upstream from the vane 44. The
precise control mechanism forms no part of the present
tion of the duct, the desired optimum reduction in noise
invention.
According to the present invention, a permeable ob
struction 47, as hereinbefore described, is positioned
horizontally across the cross-section of the chimney 38
level is not attained.
between the vanes 43 and 44.
charge into a room as indicated by the arrows D. A
permeable obstruction 16 extends across the duct 15 as
previously described. The duct 15 communicates with a
mixing chamber 17 having a grid outlet 18. Mounted
within the chamber 17 is a ba?le 19 positioned in direct
line between the grid opening 18 and the duct 15. The
walls of the chamber 17 as well as the baffle 19 are
32 are lined with a sound absorbing lining 48 for the
hereinbefore described purpose of ‘absorbing sound energy
Where the cumulative cross-sectional area of the gas
passageways exceeds about 75 percent of the cross-sec
The permeable obstruction 47 performs the same func
Referring to FIGURE 2, there is illustrated a preferred 10
tion in the mixing box chimneys 38 as hereinbefore de
mixing and discharge outlet unit in which the discharging
scribed, i.e., a portion of the sound energy appearing
gases pass through a tortuous path prior to discharge
as relatively low frequency sound is converted to sound
into a room whereby greater absorption of the sound
energy in the form of relatively high frequency sounds.
energy of the relatively ‘high frequency sounds is as
The exposed surfaces on the interior of the mixing box
sured. A duct 15 conveys ventilating gases C for dis
covered with a lining 20 of sound absorbing material such
as bat-ts of glass Wool or mineral wool. By providing
the ba?ie 19 in the direct line of flow between the duct
15 and the grid opening 18, the discharging gases after
passage through the permeable obstruction 16 are re
quired to follow a tortuous path prior to discharge. The
of the relatively high frequency sounds. The sound
absorbing lining 48 may comprise any acoustical insula:
tion mate-rial such as glass wool, mineral wool and the
like.
In the mixing box 32 illustrated in FIGURES 3, 4 and
9, the permeable obstruction 47 performs an additional
‘function. It will be noted by reference particularly to
FIGURES 4 and 9 that the downstream pressure tap con
duit 45 is positioned between the top and bottom of the
permeable obstruction 47.‘ The permeable obstruction 47
serves to minimize the turbulence of the gases in the
region ‘between the two vanes 43 and 44 whereby reliable
static pressure indications are obtainable through the
downstream pressure tap conduit 45. In the absence of
As before, the permeable obstruction 16 is positioned
some ‘form of grid between the two rotatable vanes 43
in the line of gas ?ow upstream from the sound absorb
and 44, the well recognized wall effects of moving gases
ing linings. The intensity level of airborne noises asso
tend to interfere with accurate pressure indication,
cited with the gases discharged at D is lower than the
through the downstream pressure tap conduit 45 and
intensity level of the airborne noises in the ?owing gases
reduce the efficiency of static pressure control within
C both in the relatively high frequency ranges and in
the chimney 38. The permeable obstruction 47 may be
the relatively low frequency ranges.
at the level of the downstream pressure tap conduit 45
The present invention ?nds particular utility in mix
or may be positioned vertically above the conduit 45,
ing and distribution boxes for dual duct air conditioning
systems of the type disclosed in co-pending application 40 i.e., downstream with respect thereto.
A convenient means for supporting the permeable ob
S.N. 755,048 (now abandoned) by Bernard B. Curran,
struction ‘47 is illustrated in FIGURES 3 and 4 where
?led August 14, 1958. A typicalidual duct air condi
a number of thin wire pins 49 extend across the chimney
tioning mixer box and discharge unit is illustrated in
38 above and below the pad of permeable obstruction
cross-section in FIGURE 3. A conduit 30 is provided
47. The bottom pins 49‘ are bent against the wall 39‘ at
to deliver warm air from a central source to a mixing
one end for a permanent installation. The top pins 49
box 32. A conduit 31 is provided to deliver cool air
probability of impingement against the sound absorbing
lining 20 thereby is enhanced.
from a central source to the mixing box 32. The mix
ing box 32 is a generally rectangular structure having vertical sidewalls 33 and a horizontal top wall 34 in
may be equipped with quickly removable fastening clips
50 to permit extraction of pins 49‘ in the event it is de
sired to replace the pad of permeable obstruction 47.
A preferred material for the permeable obstructions of
cluding a grid opening 35. The air supply ducts 30 and 50
31 preferably are mounted below the level ?ooring 36.
Within the mixing box 32 is a horizontal baffle plate
37 serving as a de?ector to direct the passage of air
around its edges as indicated by the arrows E. Within
the mixing box 32, control chimneys 38 are connected
to each of the air ducts 30‘ and 31. Each control
chimney 38 has vertical sidewalls 39 and a rectangular
cross-section. Bearings 40 in the sidewalls 39 support
horizontal shafts 41 and 42. A ?at vane 43 is mounted
to the shafts 41 within the chimneys 38. A ?at vane 44 60
is mounted on the shafts 42 within the chimneys 38. The
this invention is coarse coconut ?bers coated with a ?lm
of natural rubber or synthetic rubber.
Such materials,
commercially available under the name- “Tulatex,” can be
formed into batts which are effective as the permeable
obstructions.
A portion 51 of this material is illustrated
in FIGURE 8 on an enlarged scale. This material has
a plurality of interlaced coated ?bers 52 which de?ne gas
passage-ways 53.
SOUND COMPARISONS
Equal loudness contours have been plotted in FIG
vanes 43 are employed to regulate the ?ow of gases exit~
URES 5, 6 and 7 as curves I and II.
ing from the chimney 38 in response to thermostatic
frequently are characterized for reference and comparison
by the intensity of the sound at frequencies of 1000 cycles
control elements (not shown) which position the shafts
Noise intensities
41. The vanes 44 serve to regulate the flow of gas
into the chimneys 38 in order to maintain a constant static
pressure in the region between the vanes 44 and 43.
The regulation of the vanes 44 can be accomplished
direct-1y in response to the gas pressure within the ducts
3G and 31 respectively as disclosed in the aforemen 70
per second.
The relative “loudness” of a noise is a com
tioned too-pending application S.-N. 755,048. This regula
40 decibel at 1000 cycles per second are considered as
posite of the relative “loudness” of its constituentsounds.
Equal loudness curves indicate the sound intensity at all
frequencies required to create equivalent “loudness” im
pressions.
In general noise levels having an intensity below about
tion can be accomplished by a pressure regulator device
quiet; noise levels having an intensity above about 60
Which operates by sensing the static pressures existing
decibel at 1000 cycles per second are considered as loud.
Curve I of FIGURES 5, 6‘ and 7 is an equal loudness
between (1) a ‘?rst control point located above the vane
44 and (2) a second control point located below the vane 75 contour having a value of 60 decibel at about 1000 cycles
3,059,564
5
per second. Noise levels above curve I can be considered
as loud. Curve II of FIGURES 5, 6 and 7 is an equal
loudness contour having a value of 40‘ decibel at about
1000 cycles per second. Noise levels below curve II can
be considered as quiet. Noise levels between curve I and
6
ducing the noise level of the relatively low frequency
sounds.
According to the provisions of the patent statutes, we
have explained the principle, preferred construction and
mode of operation of our invention and have illustrated
and described what we now consider to represent its best
will be considered as “loud” by some persons and con~
embodiment. However, we desire to have it understood
sidered as “quiet” by other persons.
that within the scope of the appended claims, the inven
To develop the comparative information for FIGURES
tion may be practiced otherwise than as speci?cally illus
5, 6 and 7, air conditioning apparatus as shown in FIG 10 trated and described.
URES 3 and 4 was employed. Sound intensities were re
We claim:
corded at a variety of sound frequency bands under vari
1. In a dual duct air conditioning system which includes
ous conditions. The curve F in FIGURE 5 is a loud
separate ducts in a building for supplying separate streams
ness contour obtained from a mechanical fan which was
of separately conditioned air to selected zones within the
curve 11 are in general of moderate sound intensity and
employed to impel conditioned air through the cool air 15 said building, the improvement comprising air discharge
cells 31. It will be observed that the curve F is entirely
means within said zones including open ended discharge
above the curve I in the low and intermediate frequency
chimneys extending from each of said ducts, mixer box
bands. Thus the noise of the fan is considered as loud.
means surrounding said chimneys and being internally
As already discussed, fan noises are only one compo
lined with sound absorbing means comprising ?brous
nent of the noise level resulting at an air conditioning out 20 coatings, a grid opening in said mixer box means for
let. The actual noise level will vary according to the
discharging air therefrom, ?rst valve means and second
velocity of air flow, the quantity of air ?ow, and other
valve means downstream therefrom in each said chimney,
parameters. FIGURE 6- illustrates noise levels resulting
and a permeable obstruction within each of said chimneys
at air flows of 2001 cubic feet per minute of conditioned
between said ?rst valve means and said second valve
air at 11/2 inches (water) pressure. FIGURE 7 illus 25 means, said permeable obstruction having a multiplicity
trates noise levels resulting at air flows of 300 cubic feet
of gas passageways therethrough, each of said gas passage
ways having a cross-section which is negligible in con
per minute of conditioned air at 4 inches (water) pressure.
trast to the cross-section of said chimney, the cumulative
Curve X of FIGURES 6 and 7 was obtained by using
only the air discharge chimneys 38 of FIGURES 3 and 4,
cross-sectional area of said gas passageways being be
without the permeable obstruction 47 and without the 30 tween 50 and 75 percent of the cross-section of said
sound-absorbing linings 48. It will be observed that the
curves X represent noise levels which are characterized
as loud, i.e., above the curve I at frequencies of about
1000‘ cycles per second.
chimneys, said ?rst valve means being adapted to regulate
the flow of ‘conditioned air through said chimney to main
tain a substantially constant static pressure downstream
therefrom, separate pressure sensing conduits associated
The curves Y of FIGURES 6 and 7 represent noise 35 with said ?rst valve means positioned one upstream and
one downstream with respect to said ?rst valve means,
levels measured by using the air discharge chimneys 38
of FIGURES 3 and 4 in conjunction with the sound-ab
sorbing linings 48‘ of matted glass-?bers; no permeable
said one downstream sensing conduit communicating with
said chimney between said ?rst valve means and the down
stream extremity of said permeable obstruction.
obstruction 47 was included in the structure while data
2. Discharge means for releasing ventilating air from
for the curves Y was obtained. It will be observed from 40
a duct into an enlarged zone including a permeable ob
the curves Y that the addition of sound absorbing sur
struction in said duct comprising a pad of ?brous material
faces in an air discharge system serves to reduce the noise
providing a multiplicity of gas passageways therethrough,
level at substantially all frequencies, although the relative
ly high frequencies are reduced more than relatively low 45 said pad of ?brous material comprising coconut ?bers
coated with a rubbery substance, each of said gas passage
frequencies. This latter feature is not clearly brought out
ways having a cross-section which is negligible in con
in FIGURES 6 and 7 although it will be observed that
trast to the cross-section of said duct, the cumulative
the departure between curves X and Y exhibits a tendency
cross-sectional area of said gas passageways being be
to increase with frequency.
The curves Z of FIGURES 6 and 7 represent the noise 50 tween about 50 and about 75 percent of the cross-section
of said duct, a chamber including an inlet port and an
level recorded when the permeable obstruction 47 was
outlet port, said inlet port being in communicating rela
placed in the air discharge chimneys 38 of FIGURES 3
tion with the said duct downstream of said permeable
and 4 in combination with sound absorbing linings 48.
obstruction, and sound absorbing means in sound absorb
The speci?c material was a batt of “Tulatex” which is
randomly arranged coconut ?bers, individually coated 55 ing relation with the gases discharged through said ob
struction and said duct, said sound absorbing means being
with a ?lm of synthetic rubbery material such as neoprene.
downstream from said obstruction and comprising ?brous
The chimneys 38 were nine inches wide by three inches
coatings on the exposed surfaces of said chamber against
thick, i.e., 27 square inches in cross-section. The “Tula
which the said gases impinge.
tex” batts were about %-inch thick.
It will be observed that the curves Z represent the noise 60
level reduction achieved by the combination of the pres
ent invention.
In FIGURE 6, the curve Z is entirely beneath the equal
loudness contour curve II indicating that the noise level is
characterized as quiet. In FIGURE 6, the curve Z is 65
signi?cantly lowered to a level which is closer to curve II
than to curve I. Further in FIGURE 7 the substantial re
duction of intensity in the relatively low frequency sounds
should be noted. ‘The contrast in FIGURE 7 between
curves Y and Z in the relatively low frequency ranges 70
illustrates the effectiveness of the present invention in re
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,001,916
2,644,389
2,750,865
2,896,849
2,948,210
Mazer _______________ __ May 21, 1935
Dauphinee ____________ __ July 7, 1953
Argentieri ____________ .. July 28, 1959
Conlan ______________ __ Aug. 9, 1960
17,441
Great Britain __________ __ July 31, 1911
Tutt ________________ __ June 19, 1956
FOREIGN PATENTS
Документ
Категория
Без категории
Просмотров
0
Размер файла
677 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа