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Патент USA US2405225

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Aug» 6, 1946-
2,405,225 l
Filed 001'.. 14, 1942
2 Sheets-Sheet 1
F/G. 3
` Aug, L6, 1946.
Filed oct. 14, 1942 '
2 Sheets-sheet 2
25 -
Y so_
FREQUENCY /N k/LocycLEs PER seco/vo
Patented Aug. 6, 1946
Warren P. Mason, West Orange, N. J., assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application October 14, 1942, Serial No. 462,042
6 Claims. ' (Cl. 177-386)
This invention relates to submarine signaling Y
systems and more particularly to submarine sig
nal projectors.
An object of this invention is to radiate or pro
signalling device or apparatus embodying the in
It comprises a frame or support IB
having an enlarged, hollow, substantially cylin
drical portion II, and a bail or carrier portion
I2 whereby the device may be submerged or sus
pended at the end of rope or cable I3 in a body
of water. A signal wave projector or radiator
Another object of the invention is to convert
I4 is supported from the portion I I by a pair of
electrical signals into sonic or supersonic sig
metallic tubes or pipes I5 through Which elec
nals in Water with substantially constant effici
10 trical connections may be made between com
ency over a broad band of frequencies.
ponents in the hollow portion II and the pro
In accordance with the invention, the radiator
ject signal waves of a wide range of frequencies
into and under Water.
or projector comprises piezoelectric crystal
means, for example, electrically connected units
or blocks of Rochelle salt crystals which may be
of the ‘l5-degree Y-cut type. The resonant fre
quency of the crystal means is preferably well
beyond the upper limiting frequency of the fre
quency band of interest.
Resistance means is
The projector is constructed of a plurality of
piezoelectric crystal units or blocks I6. Each of
these runits may comprise four Llô-degree Y-cut
Rochelle salt crystals or plates Il, I8, I9, ZIJ,
each of which may be 1.6 centimeter longy 1.0
centimeter .wide and .4 centimeter thick. When
connected together they constitute a block or
connected in series with the crystal means and
is chosen of such impedance as to be substan 20 unit 1.6 cm. >< 1.6 cm., with a width in the ra
diation direction of 1.0 centimeter. The crystal
tially equal to the reactive impedance of the
plates are coated on their faces With platinum
crystal means at a relatively low frequency
rhodium about .00017 inch in thickness. The in
whereby, at the higher frequencies of interest,
nermost faces 2|, 22 and the two outermost faces
the current into the crystal means will be con
trolled by the resistance and be substantially in 25 23,24 are connected together with a copper wire
25 to constitute one terminal of the unit; the
dependent of frequency.
intermediately located other two pairs of crys
A more complete understanding of the inven
tal faces are connected together by a second
tion will be derived from the detailed descrip
copper wire 26. The crystal units, which, in a
tion that follows, taken in conjunction with the
30 specific embodiment were twenty-five in num
appended drawings, wherein:
ber, are fastened to and between thin ceramic
. Fig. 1 shows a front elevational view of ap
plates or discs 21, 28. 'I‘he latter may be of the
paratus embodying the invention;
order of .1 centimeter thick. The crystal units
Fig. 2 shows a side elevational view of the ap
ceramic plates assembly is enclosed by a rectan
paratus of Fig. 1;
Fig. 3 shows a front View of the piezoelectric 35 gular frame 29 the open ends of which are closed
by a pair of phosphor-bronze diaphragms 3B, 3l
crystal means, projector or radiator included in
of the order of .003 inch in thickness, soldered
the apparatus of Fig. 1, partly broken away and
at their marginal portions to the frame 29 and
partly in section to show details of structure,
and Fig. 3A an enlarged elevational view of one
fastened on their inner surfaces to the ceramic
of the component crystal blocks of that means 40 plates 21, 28.
The procedure in assembling the projector
showing the electrical wiring connections be
may be as follows. "I_'he crystal blocks I6 are
tween the individual crystal plates;
connected in parallel by suitable wiring and ar
, Fig. 4 shows a sectional view of the crystal
ranged symmetrically, as shown, between the
means of Figs. 1 and 3 taken along the line 4-4
45 ceramic plates 2l, 28 to which they may be glued
or cemented. The diaphragm 30 is soldered to
Figs. 5, 6 and 7 show equivalent electrical cir
the frame 29 and the crystal units-ceramic plates
cuits or analogues of the piezoelectric crystals in
assembly fastened thereto by cementing the
the projector of Figs. l and 3 under different con
ceramic plate 2l to the inner surface of di
Fig. 8 shows curves illustrating the calculated 50 aphragm 3|). By having the frame 29 of suf
íicient size, a small clearance may be provided
elìciency of conversion with respect to frequency,
between the crystal units for their wiring which
of the arrangement of this invention; and
terminates at the two leads 32, 33, brought out
Fig. 9 shows curves evidencing the> response
of Fig. 1;
of the frame through the glass seals 34 in the
frequency characteristic determined from exper
‘unental tests of an actual embodiment of the 55 tubes I5; and for dry Rochelle salt 35 to keep
Figs. 1 to 3, 3A and 4 illustrate a submarine
the humidity low. The second diaphragm 3l is
cemented to the ceramic plate 28, and, after the
assembly is thoroughly dried out, the diaphragm
With these values, the element constants be
3l is soldered to the frame 29. To facilitate the
latter soldering operation, a narrow slot 36 may
be milled into the frame 29. This carries little
heat to the main frame and affords protection CTI
against overheating of the crystal units. As a
further precaution against excessive heating »of
the crystal units, the assembly may be placed in
farads '
a pan of water during the final soldering operaf`
tion. The cement used is preferably one that has'
a very rubbery consistency when dry, and may be
of the type known commercially a's Vulcalock. '
The portion Il encloses a transformer 31fand
a pair of electrical resistances 38, 39,7the latter
being connected in series with the parallel-con~ 15
nected crystal units and theV secondary winding _' .
-The‘transformer <I> transforms from mechanical
impedance units (expressed as a ratio of force
‘ in dynes to velocity in centimeters per second) to
of the transformer, the portion I I otherwise being
oil-filled as shown by the dashed horizontal lines
designated 5l). The primary winding of the
electrical impedance units.
transformer 3'1 is connected through the conduc
When th'e crystal lis used to drive water' and the
tors 4D of the cable 4i Witha, source (not shown)
of electric waves to be converted by the projector
radiating surface is 1a half wave-length or greater,
the mechanical end of the equivalentlci-r'cuit'will
into signal waves in the water. This electric wave
be terminated by the radiationìresistancef *Y
source may be in a suitable vessel on the'surface
of the Water, or at a shore station. The pro 25
jector is intended to radiate ‘signal Waves over a
broad band of frequencies, for example, Y from
about 10 kilocycles per second Vup to'about 60
kilocycles per second, with substantially constant ’
eñiciency. The resonant frequency of the crystal 30
means should be substantially higher than'the
upper, limiting frequency of the band of interest.
In general, Ythetelec’trical impedance as meas
ured fromr the electrical terminals of the crystal
is of interest. For such’ a case, the: mechanical
The resistances 38,239 are’ ch'osen so as to present
elements can beV taken .through the electrome
a resistive impedance substantially equal to the
chanicaltransformer,'the resulting yelements as
reactive impedance of the crystal units at a very 35 `shown`inFig56 being >
‘ r
*low frequency in the frequency band of interest,
whereby at the zhigher frequencies of interestthe
current .into theradiator will be controlled by
the .resistance:-and will be `independent .of the
frequency. A-further` understandingef thisV as
pect Aof the invention will be derived from th‘e fol
y farads
The -equivalent electrical ' circuit or , analogue of
al1 ofthe crystals in parallel is yshown inFig.` 5,
which can be derived from the `equivalent circuit 45
of the `crystal given inthe inventor’s paper, “Dy-v
hms. y
In the specific embodiment Vconstructed’infac-l
cordance with the invention, one hundred crystals
Review, volume 55, (1939) ,pages 775 to‘789.' The
were included. With dimensions ly=l.'0“centi-I
element values for a-single crystal of `the-45-de-- 50 meter, Zw=l'.6 centimeters, and 11s-:.4 centimeter,
gree Y-cut type, radiating on both- sides, eX
the constants for twenty-ñvegparallel connected
pressed in c. g. s. relectrostatic'Y units, ïbecome.
blocks of four'crystals .each become
namic measurement of the elastic, electric fand Y
piezoelectric constantsofRochelle salt,” Physical
The distributed capacity resulting“fromY thé
' presence'of’ the diaphragms 30,; 3| ’ is vkept l'ow’by?
the inclusion of the' ceramic plates "21, 28 between,`
the crystals and diaphragms.` In 'the> particular
structure, ,the _'added, capacitance, was about" ¿5_0v
K=1'0.0=dielectric lconstant of ¿l5-degree` Y-cut
Rochelle salt.
S22f=9~26><10r12=inverse of Young’s modulus
along the length.
p=1.775=density of Rochellesalt.
Cs5=3ß04><1010=shear elastic constant.
Zy=length of crystal along direction of vibration
Zwzwidth of crystal in centimeters.
binatio'n isj over 100- ‘,kilocycles per second; Hence,
up to about 50 kilocycles per second, the vmass.,
circuit may be represented by Fig. 7., lThere>-`
lr=thickness of crystal in centimeters.
reactance may be neglected and the equivalent.V
fz5=6.33><1O4=piezoelectric constant of Rochellel ì
vin centimeters.
The resonant frequency for this crystal com'-î
sistances 38, 39 are included .in series.V with 'the
crystal Vmeans, ,andV withV the secondary winding
of the transformer 31. If the -résistances 'are
chosen' to have a resistive'impedance equal tothe
reactive impedance of the crystalat a relatively
low frequency, at the higher frequencies of _inÍ-f'
terest the current into the radiator will be' con
trolled by the resistance and Vwill be independentl
of the frequency. The impedance presented by
the radiator will be primarily the capacitive re
actance ofthe shunt condenser and, hence, sub
octave. The Vdivergence of curves D and Eis a
measure of the variation in the conversion efli
ciency of the projector with frequency. It will
be observed that between l0 and 60 kilocycles per
second, the variation is of the order of only two
stantially all of the input current ilows through
such condenser, whereby the voltage thereacross
is inversely proportional to the frequency. ÀThe
- Although this vinvention has been disclosed with
current into the radiation resistance is controlled
reference to a speciñc embodiment, it Will be
primarily by the series capacitance since this
understood that it is not limited thereto but is
presents a much larger impedance than the re 10 of a scope evidenced by the appended claims.
sistive impedance. Consequently, the current
What is claimed is:
into the radiation resistance will be independent
1. .A submarine signal projector for signal ra
of frequency.
diation over a broad band of frequencies with
substantially constant conversion eiiiciency, com
In using the described device to produce a
definite pressure, account should be taken of the 15 prising a plurality of 45-degree Y-cut Rochelle
salt crystals connected in parallel, and electrical
fact that the radiating surface becomes more
resistance meansnconnected in series with Vsaid
directive the higher theV frequencyV because the
crystals and having a resistive impedance sub
radiator becomes a larger number of wave-lengths
stantially equal to the reactive impedance of
at the higher frequencies. It can be shown that
the increased directivity results in an increase in 20 the crystals at a relatively low frequency in the
pressure equal to 6 decibels per octave for all fre
2. Submarine signaling means comprising a
quencies of interest.
plurality of Llä-degree Y-cut Rochelle salt cry
With the equivalent circuit of Fig. 7, the eni
stals connected in parallel, and electrical re
ciency of conversion from electrical to mechani
cal energy can be readily calculated. 'I'he series 25 sistance means connected in series with said
crystals and of a resistive impedance substan
resistance (RA) added by the resistances 38, 39
tially equal to the reactive impedance of the
was taken as 80,000 ohms. In the particular case,
crystals at a relatively low frequency in the band
the transformer 31 transformed from 115 ohms to
of frequencies below the resonant frequency of
75,000 ohms but its loss was less than .5 decibel
from 5 to 100 kilocycles per second. From a 30 the crystals.
3. Submarine signaling means comprising a
75,000-ohm source (Rs) the current in into the
plurality of Ll5-degree Y-cut crystals for translat
radiation impedance is given by
ing electric energy into signal waves in water
over a band of frequencies the upper limiting
frequency of which is substantially lower than
the resonant frequency of the crystals, and elec
The current into the radiation resistance (Ra)
trical resistance means in series with said cry
stals and of a resistive impedance substantially
if connected to the sending resistance Rs by a
equal to the reactive impedance of the crystals
perfect transformer would be,
40 at a relatively low frequency in said band.
4. A device for converting electrical energy
into acoustic energy for radiation to a water
Hence the efliciency of conversion is given by the
medium with substantially constant eñiciency
over a wide band of frequencies, comprising a
With the values RA=80,000 ohms, Rs=75,000 50 housing adapted for submersion in the water
ohms, RR=21,000 ohms, Co=942><10-12 farads,
medium, including a frame and a pair of dia
C1=29.’1><10-l2 farads, the calculated eiliciency of
phragms affixed to and extending across the
conversion is shown by the dotted curve A of Fig.
open portions of said frame so as to provide
8. This represents the efñciency of conversion
an enclosed space therebetween, a pair of thin
from electrical to total acoustic energy. When 55 electrically insulating plates each respectively
using the device to measure pressure, only the
aiiixed to and contacting substantially the en
energy on one side is useful so that for radiation
tire inner surface of a diiferent one of said
diaphragms, a plurality of piezoelectric crystal
from one side the conversion efliciency is three
decibels lower as shown by the solid curve B of
units connected electrically in parallel with each
60 other and supplied with electrical energy of said
Fig. 8.
Fig. 9 shows an experimentally obtained re
band of frequencies, each of said units compris
sponse-frequency characteristic of the device de
ing a plurality of electrically-connected Rochelle
scribed hereinabove. The input to the projector
salt crystals, said plurality of crystal units being
was ten watts, the pick-up microphone being
fastened to and arranged between said insulat
located two feet distant in the water from the 05 ing plates within said space so that the array
projector and the microphone amplifier having
thereof, collectively, contacts substantially the
a gain of 80 decibels. The dotted curve C repre
entire inner surfaces of the insulating plates,
thereby applying the mechanical vibrations pro
sents the composite response 0f the projector,
microphone and recording system associated
duced in them in response to the supplied elec
therewith. After correction for the system and 70 trical energy through said insulating plates uni
the microphone response as a function of fre
formly over the entire area of each of said dia
phragms, the outer surfaces of both of said
quency, the solid curve D was obtained as the
projector response-frequency characteristic. The
diaphragms contacting directly with and radiat
dot-dash line E represents a characteristic in
which the response varies by six decibels per
ing acoustic energy to said medium when said
housing is submerged therein.
»'SQThe device of claim 4,»ín lwhich each Rochelle
salt ’crystal in each of said crystal units is
45idegree Y cut and said crystal units are sep
arated fromv each other and said frame by dry
Rochelle salt crystals to -maintain the humidity 5
10W Within said enclosed space.
6. The device of claim 4 in which each Rochelle
'ral'ity of rows’each n’comprising- the’sjanie? nuniber
of '1,1’I1îts,v extending between diiîerent' portions
of the two insulating plates, the asserrilolyl being
onercrystal wide in the radiation> direction, so
that all _the individual crystals‘vilorate in uni
son in response to the supplied electrical energy
to provide uniform'vibration of al1 parts of each
salt crystal in each crystal unit is 454degree
diaphragm through the insulating plates.
Y cut, said crystal units being assembled sym
metrically Within said enclosed space in a plu» l0
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