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Патент USA US2405186

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Aug. 6, 1946.
H, BENIOFF
2,405,186
PIEZOELEC'I‘RIG VIBRATOR
‘Filed Oct. 8, 1941
INVENTOR
Patented Aug. 6, 1946
FFEC
UNITED STATES PATENT
2,405,186
PIEZOELECTBIC VIBRATOR
Hugo Benio?", La. Canada, Calif., assignor to
Submarine Signal Company, Boston, Mass, a
corporation of Maine
Application October s, 1941, Serial No. 414,132
11 Claims.
1
The present invention relates to a piezoelectric
vibrator of the general type described and
claimed in my copending applications Serial Nos.
386,583, filed April 3, 1941, and 344,363, ?led July
8, 1940. In each of these applications there is dis- )
closed a vibrating unit in which the piezoelectric
(or 177-386)
2
carry. Due to the fact that the damping losses
of the sound or mechanical wave in metal is very
slight and that by proper choice of the mass ele
ments in the system the amplitudes e?ective upon
the crystals may be accurately chosen, it is pos
sible to design the longitudinal vibratory members
crystals are secured to channels or recesses in the
in such a manner that all the crystals operate
side walls of the vibrating unit, the unit itself
forming a vibrating element in which the end acts
synchronously for transmission and reception
as a acoustic radiating face. Where the unit is
attached to a diaphragm, the diaphragm forms a
without exceeding in any way the power which
the crystal is capable of handling.
In the piezoelectric harmonic vibrator of the
present design it has been possible by these ex
pedients to obtain from the impressed electrical
energy to the sound energy transmitted to the
ploying piezoelectric crystals is that the crystals
are limited in their power-handling capacity and 15 water an overall efficiency of approximately 90%
at frequencies well within the supersonic range.
while these factors are not detrimental when the
The so-called harmonic vibrator of the present
devices are acting as receivers, however, they may
invention may be nested together for projecting a
seriously interfere with the utility of piezoelectric
beam of compressional wave energy and for di
crystals in their use for transmitting increased
acoustic power.
20 rectively receiving compressional wave energy in
the Water or other medium. The harmonic vi
In the present invention a plurality of vibrators
part of the section of the unit. One of the limita—
tions encountered in the operation of devices em
brator may, however, also be used as a linear
are used in which the individual vibrating units
structure in which one or more long vibratory ele
have a plurality of nodes and loops corresponding
ments may be used independently or together.
in e?ect to a vibratory system of two or more
wave lengths. In these units the crystals are 25 These long vibratory structures may have a length
of twelve or more wave lengths and may be used
mounted in recesses at the sides of the units and
under various circumstances for directive or par
are cut and mounted such that the polarities of
tially directive transmission and reception.
successive crystals provide expansion and con
Various further objects and advantages of the
traction nodes in the corresponding crystals al
present invention will be understood from the de
ternately longitudinally along the vibratory struc
scription given in the speci?cation below in con
ture. This action is reciprocal inasmuch as the
nection with the illustrations in the drawing
expansion and contraction along the vibratory
showing an embodiment of the invention in which
structure generate potentials across the crystal
Fig. 1 is a sectional view of the invention taken
electrodes which cooperate together in the electri
longitudinally through the vibrating elements on
cal circuit. Various speci?c means may be em
the line l—l of Fig. 2; Fig. 2 is a sectional view
ployed to accomplish this result. In one case the
taken on the line 2——2 of Fig. 1; Fig. 3 shows a
crystals may be arranged so that the potentials
modi?cation of the form of oscillator used in Fig.
generated by alternate crystals under contraction
1 in which the vibrator units are double the length
and expansion produce the same potential on all
the exposed electrodes of the vibrator and simi- ., shown in Fig. 1; Fig. 4 shows a fragmentary sec
tion taken on the line ii—4 of Fig. 3; Fig. 5 shows
larly the same but opposite potential on all the
an end view of one of the vibrating units; Fig. 6
unexposed or grounded electrodes of the vibrator,
shows a detail of an insulating support in per
each group being opposite in potential to the other
spective; Fig. ‘7 shows the same detail in eleva
group at any instant. In another arrangement
tion; Figs. 8 and 9 show circuit connections for
the crystals may have a parallel series connec
the crystal elements of the vibrator; Fig. 10 shows
tion, in which case successive crystals have their
one of the oscillating units in a longitudinal view
external electrodes alternately poled. In the lat
partly in section; and Fig. 11 shows a horizontal
ter case the impedance will be four times the im
section taken on the view of Fig. 10.
pedance of the ?rst case and will under certain
In the arrangement indicated in Figs. 1 and 2
conditions not be as preferable as the ?rst-men 50
there are provided a number of longitudinal vi
tioned arrangement.
By the use of either of these arrangements the
brators I, l, I, etc., which are mounted on a dia
phragm or plate 2 which is exposed to the com
driving forces may be applied at many points
pressional Wave or sound-propagating medium
along the vibrator, thus substantially reducing the
power which each individual crystal needs to 55 which may be air, water or other medium, the il
2,405,188
4
lustration in Figs. 1 and 3
2 being more particularly
adaptable for a liquid medium.
In the arrangement shown in Fig. 1 a few
further details of construction should further
As indicated
more clearly in Fig. 2 the vibrators I, l, I, etc.,
be noted. The thin web 3 extending around the
may be nested together oVer substantially the
plate 2 begins directly on the line of the end
whole surface of the plate 2, thus applying the 5 vibrating units and the small shoulders ‘I’ at the
vibrations of the longitudinal vibrators | simul
ends are each one-half the width of the shoul
taneously over the Whole area of the plate. The
plate 2 is provided with a thin peripheral ?ange 3
supporting the plate 2 to the casing, ?ange or
wall 4. The wall or ?ange 4 may be joined in any 10
ders 7 between successive vibrating units. Fur
ther, the distance between the lower edge A of
the crystal nearest the plate 2 and the external
surface of the plate is equal to one-half of the
suitable manner to the supporting casing 5 which, » distance between successive crystal edges, as,
in turn, is supported by a plate 6 for mounting to
for instance, B, B’, and, further, that the dis
any desired structure.
tance between the top of the vibrating unit 0
As indicated in Figs. 1 and 2 the longitudinal
and the top edge of the crystal unit C’ is equal
units I are positioned between shoulders ‘I, ‘I, 1, 15 to the distance between the edge A and the ex
projecting slightly from the rear of the plate 2.
ternal water surface’ ofthe’ plate 2. The vibrat
These shoulders act to’ locate accurately the
ing unit by these means is made of a type which
might be called a true harmonic vibrator inas
much as the external water surface and the in
vibrating units and to space them slightly apart
from each other.
The Vibrating units are each
cemented to the plate 2 and also bolted and 20 ternal boundary of the vibrating unit with the air
screwed down by means of the screw 8 which is
medium have substantially the ‘same amplitude
located in the longitudinal hole 9 and extends
as the maximum amplitude between the points
through the base of the vibrator into the plate 2.
13 and B’ neglecting, of course, the slight dif
Each screw head is provided with a suitable ?ange
so that the vibrator is securely held in place.
Referring to Fig.
||, [2 and I3 are of
erably Rochelle-salt
similar piezoelectric
l, the crystal elements I0,
the piezoelectric type, pref
crystals or crystals having
action. These crystals are
ference that occurs because of energy radiation
25 or radiation resistance which, at the high fre
‘quencies here considered, hardly affects in any
way the uniformity of the vibrating element.
By making larger recesses for the crystals and
consequently increasing the metal masses in the
so cut that compression on the upper and lower 30 sections between crystals as compared to the
end surfaces produces electrical potentials across
\inass of metal where the crystals are placed, the
the crystal electrodes the inner ones l4 |5, |6_
vibrating element becomes loaded and this load
and I‘! of which are grounded to the metal of the
.ing may be so proportioned that maximum per
longitudinal vibrating bar or element |. The
outer electrodes |8,~ I9, 20 and 2|, on the other
hand, may all have the same potential when
missible vibrational amplitude is obtained. In
using units such as just described for projecting
sound beams is subaqueous media, it is essential
.to maintain the working of the crystal units well
excited oppositely or they may be so faced that
the potential of the group of the pair l8 and »
I9 is opposite to that of the pair 20 and 2| as
within their operating capacity,‘ since heating
of the crystal elements soon brings about a loss
illustrated by the circuit arrangement of Figs. 40 of ef?ciency and, in fact, considerable danger
8 and 9. The electrodes of the exposed surfaces
from possibility of destruction or burning up of
the crystals. This is particularly true. with the
of the crystals, that is, the outer electrodes, are
use of Rochelle-salt crystals.
connected by means of a conductive ribbon 22
In the arrangements indicated in Figs. 1 and
which may be an extension of the electrodes to
the bus wire 23. The ribbon 22 extends around
2 the vibrating units are of the type which may
the sides of the crystals through a channel 24
be called a whole wave-length vibrator. In this
which is cut out of the metal of the vibrating
case the lower set of units and the upper set of
unit. This channel 24 joins the vertical‘chan
units are always 180 degrees out of phase with
nel 25 in which the bus wire 23 is positioned.
each other, one set contracting while the other
The bus wire 23 is supported away from the chan- ' set isexpanding. In this arrangement all the
nel by an insulating bridge which is shown in
acoustic radiation is produced by the external
Figs. 6 and 7 and in section in Fig. 10. This
surface of the plate 2 in contact with the liquid
insulating bridge or support for the wire 23 com
propagating medium. The other free ends of
prises an insulating piece 26 made of a suitable
the vibrating unit are sealed off from the liquid
product, such as that known by the trade name
medium by means of the casing 5 and the cover
“Bakelite,” and which has a cross section in the
form of a rather ?at C, the bus wire 23 passing
through the end elements of the C and support
ing the wire away from the sides and base of the
channel. The internal electrodes l4, Hi, It and
I1 are grounded to the metal of the vibrating
unit by leading the conducting ribbon which may
plate 33.
of the vibrating unit in the same manner. In
' the arrangement indicated in Fig. 3 the plate 40
has its external surface in contact with the ra
diating medium. On the plate 40 is nested a
group of vibrators in a fashion similar to that
indicated in Figs. 1 and 2. The plate 40 is
form a part of the inner electrode over a chan
nel 21 similar to the channel 24 and joining
the end 28 of this conducting ribbon to a ter
minal connection 29 positioned in the vertical
channel 30 corresponding to the channel 25 but
~ bounded by a supporting thin ?ange 4| which
merges into a heavy peripheral supporting mem
ber 42 formed as a shell about the vibrating units
on the opposite side of the vibrating unit, as in
dicated clearly in Fig. 10.
Each external elec
trode is connected to a vertical bus wire 23 and
all of these, in the construction shown in ‘Fig. 1,
are joined and electrically connected to the bus
bar 30' which is supported at either end to in
sulating brackets or supports 3| and 32 attached
to the inside of the casing.
.
.7.
Where longer units are to be used as,
for instance, in the arrangement indicated in
Figs. 3 and 4, it is desirable to support both ends
((3
and radiating member. This shell 42 extends
backwards into the wall 43 which has formed
with it an outwardly. extending ?ange 44. At
tached to the other end of the vibrating units 46,
in which the piezoelectric crystals 45 are placed
similarly as H in Fig. 1, is a plate v4‘! which has
the same thickness and is of the same general
construction as the plate 49. The plate 40 is
2,405,186
5
6.
electrodes 13 and ‘M are negative, and that this
condition in the next half cycle of the oscillator
65’ is reversed. _ This arrangement, however, will
permit one group to operate under a contraction
node while the next group is operating under an
and thickness as the ?ange 4i, and this ?ange
expansion node, and vice versa. Where eight
50 merges into a supporting peripheral member
crystals are used, two alternate pairs will have
5| which extends backwards into the shell 52
the external electrodes connected to one termi
meeting the outwardly extending ?ange ‘44 in
nal of the oscillator and the two other pairs will
the section 53 at the end of the shell 52. The
?anges 53 and 44 come in face-to-face contact 16 have the external electrodes connected to the
other terminal of the oscillator.
with each other and are bolted together to sup
In the arrangement indicated in Fig. 9 the
port the vibrators at a point midway between
crystals are all excited in a similar fashion. In
their ends. A cover or casing 55 may be placed
this case the oscillator'B5 has one terminal con
on ithe back end of the unit Where it is desired
nected to the external electrodes of each crystal
that the unit shall radiate only from the for
iii, 82, 83 and 34 while the internal electrodes are
ward end as, for instance, the plate member 49.
all grounded, the ground being the other terminal
To provide electrical connections for the elec
of the oscillator 85. Since in the arrangement
trodes the plate member 4? is perforated at
of Fig. 9 the potentials will all be simultaneous
spaced intervals with holes 56 to which the ver
ly impressed in the same phase on all the exter—
tically extending bus wires 5'! connecting the ex
nal electrodes, the same result may be accom
ternal electrodes are projected. These bus wires
plished of operating the crystals with expansion
51 are electrically connected to a cross bus wire
and contracting nodes in successive crystals along
‘58 to which all of the vertically extending bus
the vibrator by orienting the crystals 8| and 82
wires 51 are joined. The insulating supporting
opposite from that of 83 and 84. In other words,
member 59 is of the same type as described in
the crystal 8| will be so oriented as regards 83
Figs. 6 and 7, and supports the electrical con
that when the external electrodes of 81 and 83
nections free from the metal of the vibrating
are positive, the crystal 8| will be under an ex
units.
pansion node and 83 under a contraction node,
In the assembly of the system the units 46 are
cemented to the radiating plate members 40 and 30 or vice versa, and when the potentials change,
the reverse effect will obtain. The orientation
boltedin place by means of screws 60 which may
is simply accomplished by using as the external
be properly adjusted through the hollow channel
electrodes alternately opposite crystal faces of
6! in each unit. At the top of the vibrating unit
the crystal, or, in other words, simply reversing
there is provided near diagonal corners two
threaded taps 62 and 63 and the screws 64 and ; the crystal.
The arrangement of the circuit of Fig. 9 may
65 screwed into these holes through the plate
at times be preferable to that of Fig. 8 since it
41. The unit should also be cemented in these
will be evident from the circuit that the arrange
joints to the plate 41 as well as in the joint to
ment of Fig. 8 has four times the impedance of
the plate 4!). In order to establish the units as
that of Fig. 9.
balanced harmonic vibrators the distance from
Having now described my invention, I claim:
the outer surface of the back plate 41 to the
1. A piezoelectric oscillator for the production
edge of the nearest crystal is half the distance
and reception of compressional Waves compris
between successive crystals and is equal to the
ing a radiating plate having mounted thereon a
distance between the water surface and the end
plurality of longitudinal vibrating elements sub~
of the nearest crystal.
stantially covering said radiating plate. said lon
The vibrating unit, when operating as a har
gitudinal vibrating elements each having mount
monic vibrator, has the crystals positioned suc
ed in recesses in the sides thereof a plurality of
cessively along the vibrator operating in oppo
piezoelectric crystals. said elements together with
site phases so that when one crysta1 is experi
encing an expansion node, the crystal next in line F the crystals and the radiating plate forming a
harmonic vibrator in which successive crystals
is experiencing a contracting node. In order
along the vibrator at any instant of operation
that the crystals should cooperate in this ar
are vibrating in opposite phase and all crystals
Arangernent they must be correctly poled. This
nearest the plate, for piston operation of the
may be accomplished either by the arrangement
indicated in Fig. 8 or that indicated in Fig. 9. i plate, are vibrating in the same instantaneous
phase. and electrodes attached to said piezoelec
In the arrangement of Fig. 8, which may be ap
tric crystals providing the desired instantaneous
plied to the vibratory unit of Fig. 1, in which
polarity to the crystals according to its instan
there are two pairs of crystals in line, the one
taneous phase of vibration.
pair of crystals 6!’ and 62’ may have their ex
2. A piezoelectric oscillator for the production
ternal electrodes 53’ and 64’ energized from one
and reception of compressional waves comprising
terminal 66 of the oscillating source 55’, the in
a longitudinal vibrating element having mounted
ner electrodes 61 and 68 being connected to
in the sides thereof a plurality of piezoelectric
ground which is the vibratory body itself. The
crystals, said element together with said crystals
inner electrodes 69 and. 10 of the other pair of
forming a harmonic vibrator in which successive
crystals ‘H and 12 are likewise grounded to the
crystals along the vibrator at any instant of op
vibratory unit ‘while the external electrodes 13
eration are vibrating in opposite phase, and elec
and 14 are connected to the other terminal 16
trodes attached to said piezoelectric crystals pro
of the oscillator 65'. In e?ect this may be called
viding the desired instantaneous polarity to the
a series parallel connection with the crystals BI’
crystals according to its instantaneous phase of
and. 62’ being connected in parallel as wel1 also
vibration.
as the crystals ‘H and ‘l2,v the two pairs being
3. A piezoelectric oscillator for the production‘
connected in series with the oscillating source.
and reception of compressional waves comprising
In this arrangement in Fig. 8 it will be noted
a radiating plate having mounted in rows there
that when the potentials on. the electrodes 63'
and 64’ are positive that the potentials on the ' on a. plurality of longitudinal vibrating elements,
provided with separating ribs 48 andsimilarly
the plate 41 is provided with the same kind of
separating ribs ‘49. The plate 41 is also sup
ported by the flange 50 of the same construction
2,405,186
'
r
7
said plate having on the inner side thereof a‘
8
tive bus elements positioned in channels at'the'
plurality of small projecting ribs spacing said
sides of'said longitudinal vibrating elements con
rows of vibrators from each other, said longitudi
nal vibrating elements having mounted in recesses
nectingrto said external electrodes.
,
7. A piezoelectric oscillator for the production
in the sides thereof a plurality of piezoelectric (Ill and reception of compressional waves compris
crystals, said elements together with said crys
ing a radiating plate'having mounted thereon a
tals and the radiating plate forming a harmonic
plurality of longitudinal vibrating elements sub
vibrator in which successive crystals along the
vibrator at any instant of operation are vibrat
ing in opposite phase, and electrodes attached to
said piezoelectric crystals providing the desired
instantaneous polarity to the crystals according
to its instantaneous phase of vibration.
‘ g
4. A piezoelectric oscillator for the production
and reception of compressional waves compris
ing a radiating plate having mounted thereon a
plurality of longitudinal vibrating elements sub
stantially covering said radiating plate, said 1on
gitudinal vibrating elements each having ‘mount:
ed in recesses in the sides thereof a plurality of
piezoelectric crystals, said elements together with
the crystals and the radiating plate forming a
harmonic vibrator in which successive crystals
along the'vibrator at any instant of operation are‘
vibrating in opposite phase, electrodes attached
to said piezoelectric crystals providing the de
sired instantaneous polarity to the crystals-ac
cording to its instantaneous phase of vibration,
and‘ a non~radiating plate element to which the
ed in recesses in the sides thereof a plurality of 20 other ‘ends of said longitudinal vibrating ele
piezoelectric crystals, said elements together with
ments are attached, said plate element being of
the crystals ‘and the radiating plate forming a
the same thickness as said radiating plate and '
harmonic vibrator in which successive crystals
means for supporting the same in a plane mid
stantially covering said radiating plate, said lon
gitudinal vibrating elements each having mount
along the vibrator at any instant of operation are
way between the ends of the vibrator.
'
vibrating in opposite phase, and electrodes at
8.‘ A‘piezoelectric oscillator for. the production
tached to said piezoelectric crystals providing the
and reception of compressional waves comprising
desired instantaneous polarity to the crystals ac
a radiating plate having mounted thereon a plu
cording to its instantaneous phase of vibration,
rality of longitudinal vibrating elements substan
the spacing between the radiating surface of said
tially covering said radiating plate,’ said longi
radiating plate and the end of the nearest crys 30 tudinal vibrating elements each having mounted
tal being equal to one-half the distance along the
in recesses in the sidesthereof a plurality of
longitudinal vibrating element between successive
piezoelectric‘crystals, said elements together with
crystals.
the crystals and the radiating plate forming a
5. A piezoelectric oscillator for the production
harmonic vibrator in which successive crystals
and reception of compressional Waves compris
along the vibrator at any instant of operation
ing a radiating plate having mounted thereon a
are vibrating in opposite phase, electrodes at
plurality of longitudinal vibrating elements sub
tached to said piezoelectric crystals providing
stantially covering said radiating plate, said Ion“
the desired instantaneous polarity to the crystals
gitudinal vibrating elements each having vmount
according to its instantaneous phase of vibration,
ed in recesses in the sides thereof a plurality of 40 and a non-radiating plate element to which the
piezoelectric crystals, said elements together with
the crystals and the radiating plate forming a
harmonic vibrator in which successive crystals
along the vibrator at any instant of operation are
vibrating in opposite phase, and electrodes at
tached to said piezoelectric crystals providing the
desired instantaneous polarity to the crystals ac
cording to its instantaneous phase of vibration,
the spacing between the radiating surface of said
radiating plate and the end of the nearest crys- '
other ends of said longitudinal vibrating ele
ments are attached, said plate element being of
the same thickness as said radiating plate and
means for supporting said plate.
9. A piezoelectric oscillator for the production
and reception of compressional waves compris
ing a radiating plate having mounted thereon a
plurality of longitudinal vibrating elements sub
stantially covering said radiating plate, said lon
gitudinal vibrating elements each having mount
tal being equal to one half the distance along
ed in recesses in the sides thereof a plurality of
the longitudinal vibrating element between suc
cessive crystals and the distance between the end
piezoelectric crystals, said elements together with
the crystals and the radiating plate forming a ,
of any vibrating element and the nearest crystal
harmonic vibrator in which successive crystals
is also equal to one-half the distance between suc 55 along the vibrator at any instant of operation‘
cessive crystals along the longitudinal vibrating
are vibrating in opposite phase, electrodes at
element.
tached to said piezoelectric crystals providing the
6. A piezoelectric oscillator for the production
desired instantaneous polarity to the crystals ac
and reception of compressional waves comprising
cording to its instantaneous phase of vibration,
a radiating plate having mounted thereon a plu 60 a non-radiating plate element to which the other
rality of longitudinal vibrating elements sub
ends of said longitudinal vibrating elements are
stantially covering said radiating plate, said lon
attached, said plate element being of the same
gitudinal vibrating elements each having mount
thickness as said radiating plate, means for sup
ed in recesses in the sides thereof a plurality of
porting said plate, and a cover spaced away from
piezoelectric, crystals, said elements together with 65 and. covering said plate element and separating
the crystals and the radiating plate forming a
said plate element from the compressional wave
harmonic vibrator in which successive crystals
propagating medium.
along the vibrator at any instant of operation
10. A piezoelectric oscillator for the production
are vibrating in opposite phase, electrodes at
and reception of compressional waves comprising
tached to said piezoelectric crystals providing
a radiating plate having mounted thereon a plu
the desired instantaneous polarity to the crystals
rality of longitudinal vibrating elements sub
according to its instantaneous phase of vibra
stantially covering said radiating plate, said 1on
tion, the external electrodes having conductive
gitudinal vibrating elements having mounted in
elements extending in channels to the sides of
recesses formed in two opposite sides only of said
said longitudinal vibrating elements and conduc
vibrator piezoelectric crystals, said .elements to
2,405,186
9
10
gether with said crystals and said radiating plate
forming a harmonic vibrator in which successive
ing face at one end, said longitudinal vibrating
element having uniformly spaced recesses
crystals along the vibrator at any instant of op
formed in the sides thereof, piezoelectric crystals
'
"
eration are vibrating in opposite phase, elec
mounted in said recesses and having electrodes
trodes attached to said piezoelectric crystals, one CI on opposite faces thereof, one of which substan
group of said electrodes being in face-to-face
tially abuts the inner longitudinal wall of said
contact with said longitudinal vibrating element
recess and the other being external thereto, said
and making electrical contact therewith, the
longitudinal vibrating element together with the
other external electrodes of said crystals having
crystals forming a harmonic vibrator in which
means connecting the same to a bus conductor, 10 successive crystals along the vibrator at any in
said bus conductor being mounted in a channel
stant of operation are vibrating in opposite
in the side of said longitudinal vibrating element
phase, and electrodes attached to said piezo
adjacent the side in which said crystals are
electric crystals providing the desired instan
mounted.
taneous polarity to the crystals according to its
11. A piezoelectric oscillator for the production
instantaneous phase of vibration.
and reception of compressional waves comprising
a longitudinal vibrating element having a radiat
HUGO‘ BENIOFF.
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