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Патент USA US2404784

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July 30, 1946.
L. e; 'BOSTWICK
2,404,784
’
‘ACOUSTIC DEVICE
Filed June 7,‘ 1940
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3 Sheets-Sheet 2
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INVENTOR
L.G. BOSTW/CK
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MA-MhéM'
A 7'7'ORNEY
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July 30, 1946.
L_ G, BosTwlcK
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2,404,784
ACOUSTIC, DEVICE
Filed June '7, 19,40
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3 Sheets-Sheet 3
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INVENT'OIR
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2,464,784
Patented July 30, 1946
UNITED STATES PATENT OFFICE
2,404,784
ACOUSTIC DEVICE
Lee G. Bostwick, Chatham, N. 3., assignor to Bell
Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application June 7, 1940, Serial No. 339,261
10 Claims.
1
This invention relates to electroacoustic trans
(Cl. 177-386)
2
end; a ring-shaped permanent magnet l3 secured
to ?ange I2 and a plate pole I4 attached to the
magnet I3. Members I 2', I3 and I4 may be se
cured together by welding or in any other suit
able rmanner. The diaphragm I5, of bronze or
other suitable material, has a ?ange I6 which is
clamped between rings I7 and“ I8 secured to plate
ducers suitable for underwater operation and
more particularly to submarine sound receivers
and transmitters.
One object of this invention is to provide an
electroacoustic transducer adapted for under
water operation and having abroad and uniform
pole I4 by fastening means such as screws I9.
frequency range.
A depending ?ange portion 20 of the diaphragm
Another object of this invention is to provide
a submarine type sound translating device, hav 10 supports the moving coil 2| in the annular air
gap 22 between members I I and Ill. A ring 23'
ing an electromechanical system, that is both e?i
of ?exible material, e. g. rubber or they like, or
cient and capable of withstanding high under
metal, is secured to the diaphragm I5 interme
water pressures.
diate its center and ?ange I6. The outer’ portion
One feature of this invention resides in a sub
marine sound translating device having a vi 15 of ring 23 may be secured to a ring 25, as by ce
menting. The ring 25', which may be of brass orv
brating system of low effective mass and stiffness.
other non-magnetic material, may be fastened to
In accordance with another feature of this in
plate pole I4 by means of screws 26. When the
vention, the translating device has a resonant
receiver is secured to the hull or skin 24 of the"
frequency low enough to be critically damped by
mechanical motional resistance and by simple 20 vessel, as by bolts ‘I0, the ring 23 is ?rmly clamped
between the hull and’ring 25.
damping means employing air or other gaseous
That portion of diaphragm I5 lying between
material.
the ring 23 and the ?ange It may contain a plu
A further feature of this invention involves the
rality of ori?ces 2'! which maybe provided with
use of a thin diaphragm and means for balancing
the static and low frequency pressures on oppo 25 ?anges 28. Acoustic resistance material, such as
felt or silk fabric 29, may be secured over the
site sides thereof.
ori?ces 21. The ?anges 28 may extend inwardly
An additional feature of this invention resides
as shown or outwardly, if desired. These flanges
in a thin domed diaphragm of a diameter suffi
28 are to stiffen the diaphragm around the ori?ces
cient to cooperate with an ef?cient magnetic sys
tem, but having only a restricted portion of its 30 2i‘ and may be dispensed with where such stiffen
ing is not necessary. The ori?ces, ?anges and re
area subjected to water pressure, whereby the
sistance material have been shown somewhat ex
water impedance is maintained at a desired value.
aggerated as to size in the interest of clarity of
Other and further objects and features of this
illustration.
,
invention will appear more clearly and, fully from
the following description of illustrative embodi 35 On the concave side of the diaphragm I5 and
secured to center pole‘ II is a member 30 which
ments thereof taken in connection with the ap
may be of brass or other non-magnetic material.
The outer surface of member 80 conforms to the
Fig. 1 is a sectional View of a receiver illustrat
inner surface of the diaphragm and is spaced
ing one embodiment of the invention;
Fig. 2 is a section taken on lines 2—2 of Fig, 1; 40 slightly therefrom‘. Member 30 serves as a stop
to prevent inward collapse of the diaphragm due
Fig. 3 is a view partially in section of a receiver
to extreme pressure or sudden surges caused by
like that of Fig. 1 including means for equalizing
waves, underwater explosions, etc. This member
the pressures on opposite sides of the receiver
pended drawings in which:
diaphragm;
Fig. 4 is an enlarged fractional view of the dia
phragm showing details thereof;
Fig. 5 is a section on line 5—5 of Fig, 4‘; and
Figs. 6 to 11, inclusive, show respectively three
modi?cations of a portion of the acoustic ele
ments of the device.
Referring now to the drawings, the receiver
designated generally by reference character It
comprises an annular magnetic structure and a
domed diaphragm. The magnetic structure com
prises a center pole H having a ?ange I2 at one
30 also is dimensioned to control the volume of
45 the chamber 3| behind the diaphragm in accord
ance with desired acoustic characteristics. A
plurality of ori?ces 32 in member 3!] connect the
chamber 31 to a passage 33 in the center‘pole I I.
Other means than the ori?ces 32 may be em
played to afford communication between chamber
3| and passage 33. For example, a plurality of
radial slots 'Ili may be formed in the bottom of
member 33, before it is secured to- pole-piece II
as shown in Figs. 6 and 7; member 30 may be
spaced slightly from pole-piece I I and supported
3
4
on a plurality of studs or pins 12 as shown in
Figs. 10 and 11 or by a notched or discontinuous
?ange ‘(I as shown in Figs. 8 and 9; or some suit
able combination of the foregoing expedients may
be used.
on the other hand, are su?iciently attenuated to
Portions of the ?exible ring 23, ring member
25, plate pole l4 and diaphragm I5, de?ne an
prevent their equalization, allowing actuation of
the diaphragm in response thereto.
The chambers 34, 3|, 4| and the various pas
sages interconnecting said chambers may be ?lled
with a suitable ?uid, preferably gaseous mate
rial, such as air or nitrogen.
annular chamber 34 on the convex side of the dia
When the diaphragm l5 vibrates, the ?uid in
phragm. The chambers 3| and 34 may be con
chambers 3| and 34 is forced back and forth
nected through the acoustic resistance material 10 through the acoustic resistance means 29. By
29 covering ori?ces 21.
employing air or a gas as the ?uid, mechanical
The stiffness of ?ange it of the diaphragm may
damping which is independent of temperature is
be reduced by means of a plurality of overlapping
thus afforded. The chambers 3| and 34 and the
arcuate slots 36, as may be seen in the detail
acoustic resistance material 29 are proportioned
views of Figs. 2, 4 and 5. If it is desired to pre 15 to give the required damping effect at low fre
vent leakage through slots 36, a thin membrane
quencies near resonance. Venting of the dia
31 of suitable material, such as a cellulose plastic
phragm through the ori?ces 21 reduces chamber
may be secured, as by cementing, to ?ange I6
stiffness and permits a low resonant frequency.
over said slots. This membrane 31 may be placed
In a device of this type the diaphragm should
on the under or back side of ?ange 16 as shown
be big enough so that a suitable magnetic system
is Fig. 5 or on the top or front side of said ?ange,
may be associated therewith; but not so large
if desired. In place of membrane 31 a plurality
that the mechanical impedance of the water too
of strips of plastic material may be employed one
greatly exceeds that of the vibrating system,
for each slot 36. If leakage through slots 36 is
which would result in ine?icient conversion.
indicated by the design requirements of the de 25 With the type of instrument disclosed, having a
vice, they may be left open, or only partially cov
low resonant frequency, the velocity
ered as the situation demands.
Connections may be made to coil 2| by suitable
$2
means, such as ?exible conductors 5B, which may
of the vibrating system at high frequencies will be
be brought out through the clamping rings l1 and 30
determined by the mass reactances KB. of the
I8. These conductors may be connected to leads
water and X of the vibrating system as a whole,
51, which may be brought out through the ring
respectively. Thus,
25, being sealed in to prevent leakage from the
chamber 34.
A ring or washer 35 of rubber or other suitable 35
E=m
(1)
material may be secured to center pole H and
where
plate pole 14, to close the inner end of the air-gap
f=the force produced by the sound effective at
22.
the diaphragm,
The diaphragm may be protected from damage
The force I‘ for a given sound water pressure is
by submerged objects and the like, by means of a
grid or screen 89.
The member 60 may be se
proportional to the diaphragm area or the square
cured to the hull of the vessel by any suitable
of its radius r; the reactance Xe is proportional
means, such as screws or bolts 6! .
to the cube of the diaphragm radius. Thus,
The ori?ces 62
in the screen are made large enough so that they
have no appreciable acoustic eifect on receiver *
operation.
In the sectional view, Fig. 2, which shows the
For a given value of X there is an optimum
value of r to obtain maximum velocity. Differen
convex surface of the diaphragm IS, the resilient
tiating Equation 2 with respect to r gives
ring 23 has been omitted in order that details
therebehind may be more clearly shown. The
region of attachment of this ring to the dia
phragm is shown by dot-dash lines on the dome
portion of the diaphragm.
Referring to Fig. 3, the passage 33 of the re
ceiver i0 is connected by a tube 40 to a chamber 65
41. The chamber 4| may comprise a bellows 42
of bronze or the like, secured in a housing 43
Since
by a cover 44. The bottom portion of housing 43
XR=K2T3
may be connected to the water outside of the ves
sel by means of a pipe 45 suitably secured to the 60
hull at ori?ce 46 as by ?ange 41.
The water mass then should be twice the mass
The water pressure outside of the vessel is
of the vibrating system to obtain maximum veloc
transmitted to receiver chamber 3| and hence to
ity. This desirable relationship can be realized
the back of the diaphragm l5 via ori?ce 46, pipe
with a light and e?icient vibrating system by re
45, interior of housing 43, bellows 42, chamber 4 I, 85 stricting the area of the diaphragm exposed to
tube 40, passage 33, ori?ces 32 to chamber 3|.
the water.
Since the front of the diaphragm i5 is also sub
The foregoing speci?c description has, for con
jected to the Water pressure, the foregoing means
venience, been restricted to a submarine sound
provides for equalization of pressure on the op
receiver. However, a transducer such as is con
posite sides thereof. The impedances of the 70 templated by this invention may also be em
tubes, pipes, chambers, etc., comprising the
ployed as a submarine sound transmitter. When
equalizing system, are such that it acts as a low
used as a sound transmitter or radiator, the
pass ?lter. The static pressure and low frequency
damping resistance at the diaphragm ori?ces 27
should be made low, the diameter of said ori?ces
pressures, such as are caused by waves, etc., are
thus equalized. Pressures at sound frequencies, 75 large, and the volume of the chamber of the con
52,404,784
5
6
cave side of the diaphragm large as compared
dome, and acoustic resistance means on said dia
phragm and interconnecting the chambers.
with a receiver. These changes will result in a
lower resonance frequency above which the Ve
locity of the diaphragm will Vary inversely with
frequency and closely compensate for the quad
ratic increase with frequency in the radiation or
, 6. A submarine sound receiver comprising a
is
loading resistance of the water. Substantially
uniform acoustic output will then result.
Although speci?c embodiments of this inven
tion have been shown and described, it will be 10
structure including ‘magnetic means having pole
pieces de?ning an annular air-gap, a diaphragm
of- non-magnetic material and having a thin, con
vex portion, a resilient peripheral‘ ?ange, and a
depending ?ange, a sound current coil mounted
on said depending ?ange, said peripheral ?ange
secured to a pole-piece to position the coil in the
air-gap, said diaphragm and structure de?ning a
chamber, and a ring of resilient material secured
at its inner edge to the convex side of the dia
understood that modi?cations may be made
therein without departing from the scope and
spirit thereof as de?ned by the appended claims.
What is claimed is:
phragm intermediate the center and the periph
1. A submarine sound receiver comprising a 15 eral ?ange and having its outer portion secured
structure including magnet means, a domed dia
to said structure, a portion each of said ring,
phragm attached to said structure, an electrical
diaphragm and structure de?ning a second cham
current conductor secured to the diaphragm and
ber, said portion of the diaphragm having acous
located in the ?eld of said magnet means, stop
tically resistant ori?ces connecting the two cham
means secured to said structure and spaced from 20 bers.
the inner surface of the diaphragm to de?ne
7. A submarine sound receiver comprising a
structure including magnetic means having a
therewith a chamber, ?exible means secured to
the outer surface of the diaphragm to restrict the
center pole, and a plate pole spaced therefrom to
area thereof subjected to exterior pressure, said
?exible means, diaphragm and structure de?ning
a second chamber, and acoustic resistance means,
associated with the diaphragm and connecting
the two chambers.
de?ne an annular air-gap, a diaphragm of non
magnetic material having. a thin, central dome
portion and a resilient supporting ?ange secured '
to said plate pole, a sound current coil secured
to the diaphragm and positioned in the air-gap,
2. An acoustic transducer comprising a struc
a stop member secured to the center pole and
ture including means for producing a magnetic 30 having its outer surface conforming to the inner
?eld, a domed diaphragm secured to said struc
surface of the diaphragm dome and spaced slight
ture and de?ning therewith an acoustic chamber,
ly therefrom to de?ne a chamber, a resilient ring
an electrical current conductor attached to the
attached to the structure and secured to the ex
diaphragm and positioned in said ?eld and re
terior surface of the diaphragm dome interme
silient means secured to said structure and dia
diate its center and edge to restrict the area
phragm for restricting the area of the diaphragm
thereof in contact with water pressure, a portion ,
subjected to sound pressure, a portion of the re
each of the resilient ring, the diaphragm and the
silient means and the diaphragm de?ning with
structure de?ning a second chamber, and acoustic ‘
resistance means associated with ori?ces in said
said structure a second acoustic chamber, said
diaphragm having acoustic resistance ori?ces
diaphragm, and connecting said chambers.
therein connecting the two acoustic chambers.
8. A submarine sound receiver comprising a
3. An acoustic device for operation in a sound
magnet structure including a pole-piece, an out
transmitting medium more dense than air, com
wardly convex diaphragm of thin non-magnetic
prising a structure including magnetic ?eld pro
material having an electrical current conductor
ducing means, a non-magnetic diaphragm having
secured thereto in cooperative relation to said '
a stiff, convex central portion and a resilient outer 45 pole-piece, resilient means secured to said dia
portion connected to said structure, a sound cur
phragm and associated with said structure to con
rent coil secured to the diaphragm in cooperative
?ne a restricted portion of said diaphragm to ex
relation with the magnetic field producing means,
ternal pressure and to de?ne with said diaphragm
means for restricting the area of the diaphragm
and structure a chamber on one side of said dia
subjected to the pressure of the sound transmit 50 phragm, a chamber on the other side of the dia
ting medium, acoustic impedance chambers on
phragm, and acoustic resistance means connect
opposite sides of the diaphragm, said restricting
ing said chambers together through said dia
phragm.
'
means cooperating with a portion of the dia
phragm to de?ne one of said impedance cham
9. A submarine sound receiver comprising a
bers, and acoustic resistance means secured to 55 structure including magnetic means having a cen
the diaphragm and connecting the impedance
ter pole, and a plate pole spaced therefrom to de
chambers.
4. An acoustic device for underwater operation
comprising a structure, an outwardly convex,
?ne an annular air-gap, a diaphragm of thin non
magnetic metal having a central, outwardly con
vex dome portion and a resilient supporting
domed diaphragm cooperating with said structure 60 flange portion secured to said plate pole, a sound
current coil secured to the diaphragm and posi
to de?ne a chamber, means in front of said dia
phragm for restricting water pressure to a por
tioned in the air-gap, an outwardly convex stop
tion thereof, said means cooperating with the
member secured to said center pole, spaced from
structure and diaphragm to de?ne another cham
the dome portion of the diaphragm and de?ning
ber, and means de?ning restricted passages be 65 therewith a chamber, a ring of rubber-like ma
tween said chambers.
terial secured to said structure and to the convex
5. -.A submarine sound translating device com
side of the diaphragm, intermediate the center
prising a structure, an outwardly convex, domed
and the supporting ?ange thereof, to limit a por
diaphragm resiliently attached to said structure
tion only of the diaphragm dome to external pres
and de?ning with said structure a chamber, a 70 sure, a portion each of the ring, the structure and
resilient ring secured to the convex surface of the
the diaphragm de?ning a second chamber, behind diaphragm dome and to the structure for con
said ring and outside of the diaphragm, the por
?ning water pressure to a restricted portion of
tion of the diaphragm between the ring and ?ange
the diaphragm, a second chamber behind said
containing perforations through which said
resilient means and outside of the diaphragm 75 chambers are interconnected, and acoustic re
2,404,784
8
sistance material secured to the diaphragm over
diaphragm dome and to the structure for con
said perforations.
?ning water pressure to a restricted portion of
the diaphragm, a second chamber behind said
?exible means and outside of the diaphragm
dome, and means including acoustic resistance
10. A submarine sound translating device com_
prising a structure, an outwardly convex, domed
diaphragm resiliently attached to said structure
and de?ning with said structure a chamber, ?ex
ible means secured to the convex surface of the
interconnecting said chambers.
LEE G. BOSTiWICK.
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