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Патент USA US2404391

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July 23, 1946.
Filed Feb. 19, 1942
4 Sheets-Sheet 1
80 90 I00
+10 -
+60 -
July 23, 1946.
Filed Feb. 19, 1942'
4 Sheets-Sheet 2
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July 23, 1946;
2,404,391‘ -
Filed Feb. 19, 1942
4 Sheets-Sheet 3
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July 23, 1946.
Filed Feb. 19, 1942
4 Sheets-Sheet 4
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FREQUENCY //v x/Locrcus
BY “3
Patented July 23, 1946
2,404,391 ’
Warren P. Mason, West Orange,
.,_‘assig'nor to 7
Laboratories,’ Incorporated, I
New York, N. Y., a corporation of NewiYork
Application February 19, 1942,1'SerialjNo. 431,558
6 Claims.
(01. 177-386)",
This invention relates to multiunit radiating
and receiving devices and to high power com
pressional wave radiating devices. In the here
become an appreciable factor causing further
heating, with consequent deterioration and ulti
inafter-described preferred embodiments, illus
trative of the principles thereof, it relates par
ticularly to radiating and receiving devices em
ploying a large number of piezoelectric crystals
.The prismatic characteristics of the devices of
the present invention are, of course, similarto
those of the devices ‘of my'copending application
which are capable of radiating high power com
pressional energy waves and to compressional
wave energy radiators and receivers which have
1, 1941, serial No. 381,236.
“prismatic” properties.
By way of de?nition, in the present speci?ca
tion, a prismatic device, for other than light en
mate destruction of the crystals.
> -,
entitled "Pipe antennas and prisms,” ?led March
Principal objects of the invention are to pro
vide high power compressional wave piezoelectric
radiators, prismatic compressional wave radiators
and receivers of a novel type and wide band radi
ating and receiving composite compressional wave
ergy waves should be understood to be a device
which in transmitting a wave comprising energy 16 . Another important object is to reduce the dele
of numerous frequencies within a particular fre
terious effects of cavitation in the use of piezo—
quency spectrum, Will spread the frequency spec
electric crystals and’other electromechanical vi
trum by imparting a change in direction, differ
brating devices employed‘ in'_ compressional wave
ing for each frequency, to the several frequencies
of the spectrum or which in receiving energy will 20 A-further object is to provide suitable imped-.
respond to the several frequencies of the spectrum
ance matching media and power distributing
only when they approach the device at particu
mediabetwe'en the array of crystals of. a multi- '
lar respective angles, differing for each frequency.
crystal, piezoelectric radiator and sea water.
This application is also directed to the discov
Other and further objects will become apparent
ery that if a piezoelectric crystal be immersed 25 during the ,course'of the following description
in a ?uid of relatively great viscosity thepower
and from the-appended claims.
' ‘e
limiting phenomena known as “cavitation” will
The character and features of'the invention
not become troublesome until substantially high
will be more readily understood from the follow
er power levels have been reached than for crys
tals immersed in ?uids of relatively low viscosity.
“Cavitation” comprises the formation of .bub
bles on the surface of the crystal and is accom
panied by a substantial increase in the dissipa
tion of power at the surface of the crystal. When
the point at which cavitation occurs has been
reached, further increases of input power result
ing description of particular illustrative embodi
ments, taken. in conjunction ‘with the. accom
panyingdrawings, in which:
Fig. 1A illustrates in electrical schematic and
diagrammatic form aniarray of piezoelectric crys
tals in-jcombination with a multisection electric
Wave ?lter;'.
~ .Fig, 1B shows in simpli?ed electrical schematic
in increased dissipation, deterioration, and the
form the equivalent electrical circuit of a plu-V
ultimate destruction of the crystal, with relative
rality of piezoelectric crystals employed as a com
ly small increase in power output. Cavitation is
pressional-wave energy radiator ,or receiver;
therefore de?nitely a serious limitation in the 40
Figs. 2 and 3 show the outstanding mechanical
operation of high power crystal radiators. For
featuresof an illustrative embodiment of a multi
crystal piezoelectric compressional wave high
other types of vibrating radiators also, such as
magnetostrictive or electromagnetic vibrators
power radiator of the invention;
cavitation will seriously impair the efficiency with
Figs. 4 and? illustrate the vertical and-hori
which compressional wave energy may be radi
ated and the use of a highly viscous liquid to in
crease the power level at which cavitation takes
place is extremely advantageous.
As pointed out in my copending application
Serial No, 413,429, ?led October 3, 1941, entitled
zontal directive characteristics of ‘the device of '
Figs. 2 and 3;
Figs. 6 and 7 are top and side cross-sectional
views of an. assembly of ?ve units providing a
broad band compressional Wave piezoelectric re
ceiver or radiator of the invention;
“Compressional wave radiators and receivers,”
the heating of Rochelle salt crystals from any
- Figs. 8 and.9 are electrical schematic diagrams
employed in explaining the character and use of '
cause to a temperature of 40° C. or higher is most
the deviceillustra'ted in Figs. 6 and '7;
objectionable since this reduces the leakage re
Fig. 10 illustrates the composite transmission
sistance of the crystals to such a low value asto 55 characteristics of .ther?ve units of Figs. 6 and 7;
particular frequency within the pass-band of
Fig. 11 illustrates the change in the velocity
of sound with temperature for sea water and for
distilled water; and
Fig. 12 illustrates the prismatic directive char
the ?lter sections the arrangement illustrated in
Fig. 1A will respond with maximum e?‘iciency
only if the energy approaches from a particular
angle which is dependent upon the phase shift
per section of the wave ?lter at that frequency.
The arrangement of; Fig. IA, therefore, nor
mally has “prismatic” properties as de?ned above.
Relay switches 28 are provided to operate on
voltage placed on conductor 30 and to disconnect
the ungrounded conductors of the crystal groups
from their respective ?lter sections and to con
acteristics of a piezoelectric radiating or receiv
ing array of the invention, such as is illustrated
in Figs. 2. and 3.
In more detail in Fig. 1A a plurality of groups
of four piezoelectric crystals in each group, name
ly, groups la, 2a, 3a, etc., are shown associated:
with a multisection band-pass electrical. wave
?lter comprising shunt arms [5,. IT, I29, etc., and
nect them to a common conductor 3| so that
series arms l6, I8, 20, etc. Successive groups of
all crystal units may be operated in phase at all
the crystals are connected‘ electrically‘ in shunt
frequencies in the event that prismatic charac
with successive shunt arms of the ?lter respec
teristics are not desired. Radiation will then
tively, as shown in Fig. 1A. The‘ right“ end‘ of ‘the
be broadside or normal to the longitudinal axis
?lter is terminated in a resistive impedance 26
of the array for all frequencies.
which is appropriately related to the impedance
Figs. 2 and 3 show the salient mechanical de
of the adjacent ?lter section over the transmit
ting band of the latter as will be described here 20 sign features of a device, the electrical sche
matic of; which can be that shown inv Fig. IA.
inafter. If the arrangement. is- to. be used. as. a
To. permit the. radiation of greater power, and
radiator, electrical energy comprising frequen
to. increase.- the vertical directivity characteristics
cies within the pass-band 0f the ?lter is: intro
of the device, each of the crystal groups la,
duced. through the terminals 32 at.- the left end
of- the ?lter.
When used as a receiver the com
25 20., 3a,. etc. of Fig. 1A is. further expanded by
pressional wave energy is converted by the crys
tals into‘ electrical energy which mayv be drawn
adding eight similar groups of four- crystals: each,
connected electrically in parallel with the. origi
nal group so that the. complete radiator‘ of‘ Figs. 2
and 3 comprises fourteen vertical rows of crys
ably aligned with a distance between centers" 30 tal groups, each row comprising‘ nine groupsv and
each group comprising four crystals, i‘. e-., thirty
which is less than half the wavelength of. the
six. crystals per row and ?ve hundred and four
highest frequency to be. radiated or received. This
crystals for the complete. radiator. The nine
is necessary in order that a single. direction of
groups of each row, for example, groups In to Ii,
transmission or reception will obtain for. each
frequency. Aswave-length. is the quotient‘ of 35 inclusive, or Me to Mr‘, inclusive, as shown in
Fig.v 2, can conveniently have common electrodes
velocity of propagation divided by the; frequency
from terminals 32.
The crystal groups Ia, 2a,. 3a, etc. are prefer
the nature of the propagating medium must be
taken into consideration. Fig; 11 shows the; vari
ation of sound velocity with temperaturefor sea
water, curve 59, and distilled water, curve 58, 4.0
In general, the directivity of such a device for
both radiation and reception. in any particular
plane will vary with the dimension. of‘ the de
('55 of Fig. 2) running the entire length ofv the
Five electrodes. are, of course, required, one
between each pair of adjacent crystals‘ and one
on the outer surface of the two outside crystals
of each group. The electrodes 55‘ can be of
metal’ foil and are cemented or otherwise at
tached to the adjacent crystal surfaces.
The groups of crystals of each row are in turn
lengths of the lowest. frequency employed is de
cemented‘ to their respective mounting strips 45,
a thin insulating spacer being interposed be
tween the crystal g-roups- and the metal mounting
pl'ate to afford high insulation resistance. Ce
~ The phase shift of an electrical wave. ?lter sec
ramic spacers of‘ low dielectric constant and a
vice. parallel to that plane. For sharp directivity
a dimension in the order of at least ?ve wave
tion of the type.- employed‘ in the ?lter illustrated 50 cement also of‘ low dielectric constant and un
usually strong adhesive properties have been
in Fig. 1A is well known in the art. For exam
found most suitable for this purpose», since lower
ple, see. the text-book‘ “Transmission Networks
values of’ capacity to ground as well as higher
and Wave Filters,” by T. E. Shea, published by
breakdown voltages. are thus. obtained. These
D. Van Nostrand Company, Inc., New York, 1929,
pages 215 and 216, Figs. 106 and 107. It varies 55 features are ofv especial importance for devices
which are to radiate high power. The crystal
from. ~11 at the lower cut-o? to +1r at. the upper
groups are equally spaced along the‘ mounting
cut-off, passing through zero at the mid-fre
strip with a small interval between groups to
quency of its transmission band. Thus any de
afford appropriate directi'vity in the vertical‘ plane
sired phase shift, between the above-stated limits,
as described hereinafter. The mounting strips
per- ?lter section can. he obtained. by selecting the
frequency in the pass-band corresponding to the
45 are screwed to. a mounting plate 42, which is
assembled‘, as shown. in Fig. 3, to clamp the edges
desired phase. shift. ()f course, for eachparticu
of a composition rubber cover 461 tightly against
lar phase shift per section. the array of‘ crystal
a casing 52 by means of bolts 48 and nuts 50.
groups will transmit or receive. energy at a par
ticular angle since each crystal group differs: in 65 The composition rubber cover is preferably of a
material recently developed by one or more of
phase from adjacent groups by the phase shift
the large rubber manufacturers to have substan
of one. ?lter section.
If; two. or more different frequencies, within
tially the same velocity’ of’ propagation of com
pressional. wave energy as sea water and thus to
the pass-band of the ?lter sections, are intro
duced into the device of Fig. 1A, each frequency 70 increase the efficiency of‘ energy‘ transfer to or
from the water.
willbe transmitted in a particular direction, dif
ferent for each frequency, respectively, since the
A.‘ multisection ?lter, such as is illustrated in
phase shift per ?lter section will be different for
the schematic diagram of Fig. 1A, is mounted in
each. frequency.
a case 54 attached to mounting plate 42 by brack_
Conversely, for the. reception of‘ energy of a
ets 56. As the successive rows of crystals are
it would, it-is felt, render. the drawing. obscure.
directly shunted across successive Shunt arms of
the ?lter the effective electrical, impedanceof
Alsorelay switching devices 28 of Fig. 1A are not
shownv in Figs. 2 and 3 butythe necessary ar-g
the rows of crystals and the distributed capacity
in the wiring thereto should be taken into‘ cone
sideration in the ?lter design as an integral part
of its associated ?lter arm impedance. The use
of 45 degree Y-cut crystals again is very advan
tageous in this connection, since the capacity of
such crystals varies very little with temperature
changes and will not, therefore, appreciably im
rangements including appropriate wiring,v can, of.
course, readily be inserted in accordance withithe _
diagram of Fig. LA by one skilled in the art.
‘In; addition to affording increased radiation the,
inclusion of nine crystal groups‘ in each‘ row
broadens the radiation or response pattern of the
device of Figs. 2 and 3 in the plane of the row.
Since the. device will, normally employ its pris
pair the ?lter’s characteristics with temperature
changes normally encountered in submarine sig
naling. As a practical matter the provision of
small trimming capacities whereby the resonance
matic properties in the horizontal plane, the
broadening just mentioned will occur in the ver
ticalplane, Forsubmarine detection work thisis
of the arms may be exactly adjusted after ?nal 15 desirable as it will compensate for the roll of the
assembly will be found advantageous.
vessel upon which, the radiator or; receiveris car.-.
ried. "Typical response or radiation patterns at
Gaskets 58 of rubber or oil-proofed felt or the
like are placed between the mounting strips 45
several frequencies over a range of vertical and 1
of adjacent rows and the space between the rub
horizontal angles are. shown in Figs. 4 and 5, re
ber cap and the crystals is ?lled with castor oil 20 spectively.~ In Fig‘. 4 the solid‘line curve 64 is the;
or some other highly viscous ?uid, such as olive
response at the lower edge of the ?lter pass,
oil or linseed oil, which will eliminate cavitation
band, i. ,e., 18 kilocycles, while the dash curve 66.
at the power level to be employed and will serve
is the response at the upper edge of the pass-band,v
to e?iciently transmit compressional wave en
i. e.,‘24 kilocycles. In Fig, 5 curves 68,- ‘I0 and",
ergy. The viscous ?uid should be of such charac 25 are for'frequencies of 178.4, 20.6 and 23.6-kilo-q.
ter that it can be dried conveniently to exclude
cycles, respectively. The model thus formedis
moisture from the crystal surfaces.
?ve wave-lengths long in the horizontal and
The mounting strips 45 include a backing block
three wave~lengths long in the vertical plane at
of metal 44 for each group of crystals. The crys
the lowest operating frequency of v18 kilocycles. . _
tal groups are mechanically one-quarter wave
length high and the backing blocks are likewise
mechanically one-quarter wave-length high, the
For high power submarine radiators, the use of
45 degree Yp-cut Rochelle salt‘ piezoelectric, crys
tals,=or some out of Rochelle salt crystal approx,
difference in height between the crystals and the
imating the 45 degree Y-cut, o?'ers substantial
backing blocks arising from the difference in the
advantages‘ as, describedin my above-mentioned
velocity of propagation of compressional wave 35 copending application Serial No. 4135429.
energy in the two materials. This type of mount
mentioned abovehthe practicable maximum power
ing is discussed in detail in my above-mentioned
output limit for crystal radiators is a point below
copending application Serial No. 413,429 and its
that at which, cavitation begins to, take place.
purpose is to produce a node of motion at the
For. a crystalvsubmerged in anlordinary liquid, _
mounting strip 45 so that energy from the‘ crystal 40 such as kerosene, for example, it'has been. dis,-:
groups in one row will not be transmitted'to
covered-that cavitation will beginueto. occur-at
groups of adjacent rows or to the mounting plate
acoustic pressures of .85 to .90 atmosphere. , ~ When
42 and casing 52. If transmitted to adjacent
submerged in-a highly viscous liquid, such as cas
rows it can impair or destroy the desired direc~
tor oil for examiple,'it has been discovered that
tive effects by introducing energy of other than
cavitation Will not begin until an acoustic pres
the desired phase and if transmitted to the 45 sure in V excess of ?ve atmospheresv has been
mounting plate and case it can result in substan
reached. The adsorbed water of the crystal sur-.
tial dissipation and in the radiation or reception
faces should, :of course, be carefullyremoved and
of energy from the sides or rear of the device,
the castor, oil _,or other highly viscous medium
thus again impairing the efficiency and the direc
should be carefully dried as explained in my
tive properties of the device. For a well bal 50
anced assembly in which the backing blocks and
crystals are accurately proportioned the fourteen
mounting strips 55 can be replaced by a single
mounting plate and the backing blocks 44 for
above-mentioned copending application Serial
No. 413,429.
‘Since the powerisproportional to thesquare
of the, acoustic pressure, the output power capac
each row can be replaced by a single bar running 55 ity of the crystal which can be realized Without
destruction of the crystal is increased in the or
the length of the row, thus eliminating gaskets
der of twenty-?ve times by immersing'it in a
58 and reducing the amount of milling work re
highly viscous liquid.
quired on the backing blocks.
The greatly increased power which maybe radi
Casing 52 should provide adequate clearance
between backing blocks 44 and the ?lter case 54 60 ated with crystals immersed. in a highly viscous
liquid probably results from the sluggishness of
as well as the casing 52 itself so that substanthe‘ liquid, which ?ows so slowly that no cavities '
tially no energy will be lost or radiated in unde
form during the short intervals in which nega
sired directions from the sides or the-rear of the
tive pressure exists.
assembly. In exceptional cases the casing 52 may
The increased power capacity of the individual
be evacuated to prevent the transmission of com 65
crystal thus realized may be employed to advan
pressional wave energy across it. Aspointed out
tage in constructing compressional wave radiators,
in my above-mentioned copending application,
which will transmit in the order of twenty-?ve
the reception of energy through the sides or rear
times the power of prior art radiators of like
of a directional receiving device is particularly
undesirable in submarine detecting systems for 70 physicakdimensions: or it may be employed to
obtain a given power radiation with a greatly
use on naval craft since the propeller noise from
reduced number of crystals and a much smaller
the craft itself will then be very likely to mask
over-all radiator structure than is required'with
the relatively weak sound waves from a distant
submarine. Wiring between the crystals and?l
ter, etc., is not shown in Figs. 2 and. 3 as ' 75
lprior’art devices.
. It is important. that the cap. enclosing-the crysrl.
tals provide a su?i‘cient volume and a cross-sec“
tionali area of the viscous: fluid- within' it-parall'el
the end or terminating unit, depending upon the
power distribution desired; The principles in—
volved are, of course, those discussed in- my above
to the radiating surfaces of- the crystals. The
cross~sectional area should expand substantially
as the distance‘ from the radiating surfaces is in
mentioned copen‘d-ing‘ application on Radiating
systems, Serial No. 407,457‘, coupled with the well—
known principle‘ that the power which a load of
a given impedance will absorb is a function of the
impedance of the circuit from which the power
creased, so as to “spread” thepower to an extent‘
such that the acoustic pressure-transmitted? to the
water‘ in contact with the cap is somewhat less
than- an atmosphere. If e?ective- spreading ofthe
poweris- not realized, cavitation in the- water with
consequent loss of‘ power will‘ take place adjacent
the outer surface‘ of the cap and the efficiency of
is to‘ be drawn.
For the illustrative- model radiator mentioned
above, a pass-band of’ 181 to 24 kilocycles was
chosen as representative‘ of’ a frequency range
the radiator can be seriously impaired. This re
often employed in the art. The actual “cut-o?En
quirement of spreading the» power is more readily
frequencies were 17685 cycles and 24033 cycles,
satis?ed for radiators of the type- described in my
respectively, so that the phase shift at 18 kilo
copending' application Serial No. 407,457, ?led
cycles was correct for-a direction of —-90°’ and at
August‘ 19, 1941-’, entitled “Radiating systems” in
24 kilocycl‘es'it was for a direction of +90“; Each.
row of nine groups of four crystals each, was
which, to reduce “minor-lobe" radiation (i. e.,
found to have substantially a static capacitance.
radiation at angles other than that of maximum
radiation)’ the more central‘ units of a multicrys 20 of 451 ,u/lf, a motional capacitance of, 29.8 p44)‘, an
tal radiator are driven with greater power than
equivalent" inductance of 1.922 henries, a distrib
the peripheral or end crystals. However, in any
uted capacitance, mainly in the wiring, of 39 mlf
typev of‘ radiator the cap may readily be propor
and a radiation resistance When the device was
tionedl to! afford an adequate spreading of the
operating, in sea water of 115,000 ohms. Fig. 1B
power and reduction of pressure to avoid cavita
shows,_ in electrical schematic‘ form,‘ the equiva
tion at the cap’s outer surface with the water or
lent electrical circuit‘ of. a. row of crystals as de
other medium into which it is to radiate energy.
scribed above,_ condenser 38' representing the
In the structure of Figs. 2. and 3’ the spacings be
static and distributed capacitances, condenser 3.4
tween crystal groups and between the rows of
representing the motional capacitance, induct
crystal groups provide in e?ect an immediate ex 30 ance 36 representing, the equivalent inductance.
.pansion of the cross-sectional area through which
and resistance 40 representing the effective load
into which the device is radiating. The imped
the‘ energy is to be transmitted in the viscous
?uid; "
radiators~ of the above type in which the suc
cessive groups of radiating elements are con
nected at corresponding points of successive sec
tions of a wave ?lter, respectively, in order to ob
tain- the particular desired distribution of the
radiated power between the successive groups of
radiating elements the impedance of the succes
si-ve ?I-t'er sections can‘ be adjusted. For the‘ pur
poses ‘of- this speci?cation this process is desig
nated as tapering the-?lter impedance and a ?lter
so- adj-‘u'sted is designated as a tapered ?lter. For
ance across the input terminals is substantially
115,000 ohms. as. stated above whenradiating. into.
The crystals. are adjustedto be reso
sea. water.
nant at the. mid-frequency of the. range.- of fre
quencies. to. be used when. the device is operating.
into the load. impedance under. which it is to be
operated. In. the model radiator the crystals.
were found. to. be resonant at. the mid-frequency.
(21 kilocycles). oi the range. used with the device
operating in seawater if they were. designed for
resonance at 24=.kilocycles. in air
For a. particular. phase angle a between the
example, in the radiator illustrated in Figs; 1A, - * radiation from successive. rows. of crystals (or
1B‘, 2 and‘ 3-’, if it is desired to- drive each of the
other. radiating units) the: angular direction of
fourteen groups of" crystals by substantially equal
radiation may» be‘ determined from the. formula‘;
amounts of power, it is necessary to compensate.
for the attenuation in the ?lter structure and the
absorption of power‘ by the successive radiating 50.
groups as power is transmitted from the input
where w. is21n times thefrequency; d is the separa
terminals 32 toward the terminating resistance 26.
tion between: the center of‘ successive radiating.
The diminution of energy is, of course, principal
units (3 cm. for: the. illustrative model, radiator of
ly- a function of the dissipation of the ?lter sec
ti'ons and» the absorption oi‘ power by the succes 5.5. Figs. 1 to 3, inclusive). ;. 12‘ is, the. velocity of,
compressional-wave energy in the medium
si've crystal groups in- the sequence. In a‘ par
through which: the radiation is. to be effected; and:
ticular model it was found satisfactory to- increase
the impedance of each section» by approximately
0 is, of course, the angle, at which radiationtakes.
place. The angle-frequency relationsv for radia
?ve- percent of the impedance of the preceding
?lter section to provide substantially equal power 60; tion- in- sea water (12:1.5 x10?" cm. persecond) are:
shown in the full-line curve 601 of Fig.._12; The
probable; extreme variations in directivity result
ing from variation of the velocity of propagation‘,
was 6000 ohms and‘ the impedances of the suc
with change. in temperature. are; indicated by the
cessive sections were 6320 ohms, 67110 ohms, 7100
ohms, ‘7600 ohms, 8140 ohms, 8770 ohms, 9480 6.5 dash-line curve.- Eli» and.‘ the dash-dot linecurye 62‘
radiation from all fourteen rows of crystals.
this instance the impedance of the ?rst section
ohms,v 10,320 ohms‘, 11,350 ohms, 12,600 ohms,
1a,.130: ohms, and 16,100 ohms, respectively.
Of course, if a distribution of power in which
the more central units are to be driven with more
power than the- peripheral. units is desired, for
instance, to obtain smaller minor-lobe radiation,
the impedance of the successive sections should
increase more rapidly than above from the input
for the lowest andhighest probabletemperatures
of sea water, respectively.
A: minimum velocity
of 1~.45~><- 105' cm. per second and: a, maximum ve
locity of 1155x1105’ cm. per' second. appear. reason"
3 able limiting values: for sea water.
For the radiation cit-reception of: a band? of ire-1
quencies with substantially uniform‘. e?ici'en'cy;. it
is' desirable to‘ correlate. the". mechanical‘. and. elecl-v
trical components: of‘ the radiating or‘ receiving:
end to the central unit and then either remain
substantially the same or even- decrease again to 755i. system so as to: comprise an electric-mechanical‘
quencies to be radiated or received.
phere.“ (It is ‘assumed that thedevice is to
employed submerged in sea water.) A lining 103
band-pass wave ?lter passing the bandof fre
' '
of felt or other compressional-Wave damping [ma
For ?lters employing sharply resonant complex
terial is preferably ‘ provided to prevent energy
reactive elements such as piezoelectric crystals or
magnetostrictive vibrators it has always been a 5 from ,reaching‘case 89 and impairing the direc
tive characteristicsof the device. Auxiliary in‘:
ductances I00, I02, I04, etc.,‘for use with the
vibrating crystal groups‘may be mounted in the
ing the use of an inductance in serieswith a
bottom of the case 89. The wiring is not shown;
crystal to permit broadening the pass-band of the
?lter are discussed in my Patent 1,921,035, issued 10 to avoid confusing the drawingunnecessarily.
problem to provide extremely wide pass-bands.
This problem and a partial solution of it, includ
August 8, 1933. However, a maximum band width
in the order of 28 per cent of the mid-band fre
quency is the greatest that can be conveniently
, The action of each of the ?ve‘units, can be
ceivers, it is necessary to subdivide the wide range
into a number of bands such that the width of
each band, i. e., the difference between its lowest
20 tromechanical impedance transformation involved
explained in connection, with Figs. 8 and (9 as
follows: The equivalent'circuit in electrical-schee
matic diagram form of any one'of the five, groups
realized with substantially non-dissipative ?lter
structures of the prior art employing Rochelle 15 of crystals and its associated steelbackingfmem-f
her is ‘shown in Fig. 8.
salt piezoelectric crystals or similar electro
In Fig.8 capacity m, is‘ the ‘combined static
mechanical resonant devices. Consequently, to
and distributed capacities of'the radiatorhand-hitss
cover a very wide range of frequencies with
wiring, the transformer H6 represents'the-elece
Rochelle salt piezoelectric crystal radiators or re;
and highest frequencies, does not exceed approxi
mately 28 per cent of its mid-frequency and then
to construct a like number of crystal radiators de
signed as ?lters to pass the selected bands, re
spectively, the ?lters being arranged in accord
ance with Well-known wave-?lter design theory
in the couplingbetween, the ‘electrical and me;
chanical portions of the radiator, capacity-"H8
is the motional capacity. (or mechanical complif
ance) of the crystal, and inductance I220 repre
25 sents ‘theequivalentinductance (mass)*-‘of-‘_the
crystal. If the length and width of th’e'radiating
surface of a crystal group are each substantially.
one-half wave-lengthier greaterv the effective raj
diation ,resistance'of the medium'to the radiatorv
Such an arrangement'is illustrated in Figs.’ 30 (castor oil'or the like) will bejvery closely equal
to be operated in parallel.
to’ po‘ the radiation resistancewof'water." ‘If an
electrical coil is nowadded in series withQthe',
crystal input the combination ‘can be. designed;
has been divided into ?ve bands as indicated in
in accordance with classical ‘?lter 'desig‘nytheory
Fig. 10 and a group of crystals designed’ for op
eration over the particular frequency band‘ has‘ '5 as an electromechanical band-pass wave {?lterv
having a pass-‘band which is asfbroad as-QBA
been provided for each of the ?ve bandsfas shown
per cent of its‘mid-band frequency, provided 45°,
in Figs. 6 and 7. The group of crystals Bll'com
6 to 10, inclusive, where a Wide range of fre-v
quencies (viz. 10 to 50 kilocycles, approximately)
prises the radiator for the lowest band and vthe
groups 82, 84, 86 and 88 are the radiators for
lar crystals of the proper dimensions are ern-‘
the four successively higher bands, respectively. “'0' ployed. The'following' table gives’ by way. of
illustration, design data 'for‘ the group of ‘five
The crystal groups are each one-quarter ‘wave
units of Figs. 6 and [7' and" having- pass-‘bands
length of their respective mid-band frequencies
as indicated in Fig. 10:,
‘ ‘
1 ->
in height and are provided with steel backing
Crystal dimensions
p I .
in em;
. d V‘
-' *
No. of
crystals I
cg? M. H
Length Width T111282"
5. 4
,2. 5
0. 936
14 to is _____ -.
_ 2.62
2. 5
27.45 to 35.3---
_ 1.5
38.5110 49.4...- . 1. 392
blocks 90, 92, 94, 96, v98, respectively, each backing block also being one-quarter wave-length of
ing member,
,10 to 12.8.- _-.
' '
steelgoaic‘ke , '
‘10,6 _ ~
7.57 ' a4 '
3.3285 ;
. Fig. 9represents.the piezoelectric crystalgroup
of Fig. 8 with a‘ series inductance I22 asvabo've ,
described and a terminal load resistance l24.rep-‘
the mid-band frequency of its associated group
, resenting the impedance of the liquid load:v on.»
of crystals. As previously describedLSuch an ar
rangement induces a node at the mounting plate 60 the vibrating crystal group. The ?lter'units thus
formed: will have an impedance slightly less than
and thus tends to eliminate the interaction of .
9000 ohms, and when connected with theirin
any vibrating crystal group upon the others and
the loss of energy to the case.
The compartment containing the radiating
puts electrically in parallel,‘ the ?ve unitslpro-q
. .l vide substantially uniform radiation or reception.
5" of compressional-wave energy over the extremely
wide range of frequencies from 10 to 50 kilo
cycles, inclusive. Prismatic properties may of
course be imparted to each group of vibrating
be radiated, the liquid above-mentioned should,
in addition to the other properties mentioned, be n crystals by the straight-forward application of the
highly viscous to reduce di?iculties from cavita i 0 principles described in detail above in conneo-y
groups should be ?lled with a liquid which has
been thoroughly dried of water and which has
an appropriate impedance. If high power is to
tion and a sui?cient increase in radiating area
between the crystal groups and the diaphragm
I I0 should obtain to reduce the acoustic pressure
transmitted to the sea water on the outside of
diaphragm H0 so as not to exceed one atmos
tion with Figs. 1A, 2 and 3 inclusive ofrthe ac-r
companying drawings.
The above arrangements are preferred illustra
_ tive embodiments of the principles of the inven
" tion. Numerous other arrangements Within the
spirit and scope of the invention will readily oc-.
our to those skilled in the art. For example.
quency within the pass-band of the ?lter im
pinges upon said plurality of vibrating units and
while the above illustrative embodiments employ
is converted by them into electrical energy the
electrical energy to be withdrawn from said ?lter
will be dependent upon the angular direction at
which the compressional-wave energy approaches
the vibrating units, the electrical energy for a
groups of piezoelectric vibrators it is obvious that
magnetostrictive, electromagnetic or other vibrat
ing members could be substituted therefor and
the prismatic properties, the increased power ra
diation and the like improved performance char
particular frequency within the pass-band being
acteristics, can be realized. The scope of the
maximum for a particular angle of approach and
10 decreasing to substantially zero as the angle of
invention is de?ned in the following claims.
What is claimed is:
approach becomes substantially different from the
1. In a compressional-wave system a directive
said particular angle.
radiator and. receiver of. compressional-wave en
3. The arrangement of claim 2 the successive
ergy comprising the combination of a plurality
sections of the wave ?lter being identical as to
of substantially identical piezoelectric crystal vi 15 the band of frequencies transmitted by each and
brators mounted with a corresponding vibrating
as to phase characteristics but of differing im
surface of each vibrator aligned in a common
pedance whereby the power distribution to sue
plane and spaced less than one-half wave-length
cessive vibrating units is adjusted to produce a
apart, a multisection electrical band-pass Wave
predetermined desired effect upon the directive
?lter having a plurality of sections, the driving
electrodes of successive crystal vibrators of said
plurality of vibrators being electrically connected
characteristics of the assembly.
4. A prismatic compressional wave radiator
and receiver comprising a plurality of electro
across a corresponding impedance branch of suc
mechanical vibrating units aligned at intervals
cessive sections of said multisection electrical
wave ?lter respectively whereby said crystal vi-.
brators can be driven with any of a large number
of phase relations between successive vibrators
by selecting a frequency within. the pass-band of
trical transmission device the sections thereof
said ?lter for which a section of the ?lter has
the desired phase shift and the angular direction 30
of effective radiation of compressional-wave en-.
ergy by the array of crystal vibrators can thus
be determined and controlled at will and where
by the effective angle of reception of compres
sional wave energy by the array of crystals is
made dependent upon the frequency of the en
ergy impinging upon the array, being different,
for each frequency within a particular predeter
mined band of frequencies.
which are small with respect to the wave-length
of the energy to be transmitted and received, said
units being ef?ciently operative within a pre
determined frequency region, a multisection elec
being substantially identical and freely passing
said predetermined frequency region but impart
ing a different phase shift to each frequency
thereof, the number of sections at least equalling
the number of vibrating units less one,- succes
sive vibrating units being electricallyrconnected
at corresponding points of successive sections of
said transmission device whereby each frequency
within said predetermined region will be trans
mitted or received with greatest amplitude in a
particular predetermined direction, the direction
2. In a compressional-wave energy system a 40 being different for each frequency.
plurality of electromechanical vibrating units in
alignment, the center-to-center spacing between
successive units being less than one-half wave
length of the highest frequency to be employed
in the system, an electrical wave ?lter passing
a band of frequencies within the useful frequency
range of the system, said wave ?lter having a
plurality of ?lter sections all transmitting the
frequency region of interest and being substan
tially identical as to pass-band and phase char
acteristics and being equal in number at least
to the number of vibrating units less one, the
successive vibrating units being connected across
a particular impedance arm of the successive ?l
ter sections, respectively, whereby when electri
cal energy having a frequency within the pass
band is transmitted longitudinally through said
?lter, successive vibrating units will be driven
transmission device differing progressively where
by a particular effective distribution of the total
energy throughout the plurality of vibrating units
is achieved and the directional properties of the
assembly are modi?ed in a predetermined desired
6. In a multifrequency compressional wave
transmission system the combination of a plu
rality of electromechanical vibratory units, a plu
rality of sections of an electrical transmission
medium connected in series relation and freely
55 transmitting all frequencies of said system but
imparting a different phase to each frequency
thereof the number of said sections being at least
equal to the number of vibrating units less one
and means for connecting successive vibrating
with a phase relation which is dependent upon
units at corresponding points of successive sec~
the frequency selected and the direction of ra-. BO tions of said transmission medium whereby the
diation of compressional-wave energy by said
directive properties of said combination will dif
plurality of vibrating units will likewise be dependent upon the frequency selected or when
compressional-wave energy of a particular fre
5. The radiator and receiver of claim 4, the
impedances of successive sections of the electrical
fer for each frequency of the system.
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