U.S. patent number 3,922,572 [Application Number 05/496,498] was granted by the patent office on 1975-11-25 for electroacoustical transducer.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Rufus L. Cook, James H. Elkins.
United States Patent |
3,922,572 |
Cook , et al. |
November 25, 1975 |
Electroacoustical transducer
Abstract
A reversible electroacoustical transducer, having a circular
configuration enerated about a longitudinal axis, is disclosed as
incorporating a backing plate disposed normal to said longitudinal
axis. A first plastic washer is disposed around said longitudinal
axis and spatially disposed from said backing plate. A trio of
piezoelectric ceramic energy converter rings, having similar
outside diameters and different inside diameters, is spatially
disposed around and along said longitudinal axis. Another plastic
washer is disposed around said longitudinal axis and spatially
disposed from said trio of piezoelectric ceramic energy converter
rings. And, with the exception of the aforesaid backing plate, all
of the aforesaid elements are encapsulated and potted in a
polyurethane material, the latter of which is bonded to said
backing plate.
Inventors: |
Cook; Rufus L. (Panama City,
FL), Elkins; James H. (Lynn Haven, FL) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
23972907 |
Appl.
No.: |
05/496,498 |
Filed: |
August 12, 1974 |
Current U.S.
Class: |
310/334; 310/337;
367/157; 367/165 |
Current CPC
Class: |
B06B
1/0607 (20130101) |
Current International
Class: |
B06B
1/06 (20060101); H01L 041/04 () |
Field of
Search: |
;310/8.2,8.3,8.9,9.1,9.4,9.5,9.6 ;340/10 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3144090 |
August 1964 |
Mazzagatti et al. |
3243768 |
March 1966 |
Roshon, Jr. et al. |
3277436 |
October 1966 |
Fitzgerald et al. |
3353150 |
November 1967 |
Jacox |
|
Primary Examiner: Budd; Mark O.
Attorney, Agent or Firm: Sciascia; Richard S. Doty; Don D.
David; Harvey A.
Government Interests
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or
for the Government of the United States of America for Governmental
purposes without the payment of any royalties thereon or therefor.
Claims
What is claimed is:
1. An electroacoustical transducer, comprising in combination:
a substantially rigid backing plate means, having at least one hole
therethrough;
first washer means, having a predetermined inside diameter and a
predetermined outside diameter, spatially disposed from said
substantially rigid backing plate means;
a first ring-shaped piezoelectric means, having a first inside
diameter and a first outside diameter, spatially disposed from said
first washer means, for producing a first acoustical energy in
proportional response to electrical energy supplied thereto and
vice versa;
a second ring-shaped piezoelectric means, having a second inside
diameter that is different from the first inside diameter of said
first ring-shaped piezoelectric means and a scond outside diameter
that is similar to the first outside diameter of said first
ring-shaped piezoelectric means, for producing a second acoustical
energy in proportional response to electrical energy supplied
thereto and vice versa;
a third ring-shaped piezoelectric means, having a third inside
diameter that is different from the first and second inside
diameters of said first and second ring-shaped piezoelectric means
and a third outside diameter that is similar to the first and
second outside diameters of said first and second ring-shaped
piezoelectric means, for producing a third acoustical energy in
proportional response to electrical energy supplied thereto and
vice versa;
a second washer means having a predetermined inside diameter and a
predetermined outside diameter, spatially disposed from said third
ring-shaped piezoelectric means;
electrical conductor means connected to said first, second, and
third ring-shaped piezoelectric means and effectively passing
through said at least one hole in said substantially rigid backing
plate means for effecting the electrical connection thereof in a
predetermined electrical circuit arrangement;
a plurality of polyurethane spacer means having inside diameters
greater than the largest of the inside diameters of said first,
second, and third ring-shaped piezoelectric means and outside
diameters smaller than the outside diameters thereof respectively
disposed between adjacent ones of said first, second and third
ring-shaped piezoelectric means and the aforesaid first and second
washer means; and
acoustically clear means connected to each of the aforesaid means
for effecting the holding thereof in the aforesaid spatial
dispositions, respectively, for the containment thereof as an
encapsulated unit of predetermined external geometrical
configuration.
2. The device of claim 1, wherein said substantially rigid backing
plate is a circular metallic backing plate having a plurality of
holes therethrough.
3. The device of claim 1, wherein said substantially rigid backing
plate is a circular aluminum backing plate having a plurality of
holes therethrough.
4. The device of claim 1, wherein said first washer means has an
inside diameter that is similar to the inside diameter of said
first ring-shaped piezoelectric means and an outside diameter that
is greater than the outside diameter thereof.
5. The device of claim 1, wherein said second ring-shaped
piezoelectric means has an inside diameter that is greater than the
inside diameter of said first ring-shaped piezoelectric means and
has an outside diameter that is similar to the outside diameter
thereof.
6. The device of claim 1, wherein said first ring-shaped
piezoelectric means has an inside diameter of 3.000 inches and an
outside diameter of 3.100 inches.
7. The device of claim 1, wherein said second ring-shaped
piezoelectric means has an inside diameter of 2.900 inches and an
outside diameter of 3.100 inches.
8. The device of claim 1, wherein said third ring-shaped
piezoelectric means has an inside diameter of 2.950 inches and an
outside diameter of 3.100 inches.
9. The device of claim 1, wherein the spaces between said first,
second, and third spatially disposed ring-shaped piezoelectric
means are each 0.032 inches.
10. The device of claim 1, wherein said third ring-shaped
piezoelectric means has an inside diameter that is smaller than the
inside diameter of said second ring-shaped piezoelectric means and
larger than the inside diameter of said first ring-shaped
piezoelectric means and an outside diameter that is similar to the
outside diameter of said first and second ring-shaped piezoelectric
means.
11. The device of claim 1, wherein each of said first, second, and
third ring-shaped piezoelectric means comprises a lead
zirconate-lead titanate ceramic ring and a pair of silver
electrodes connected to opposite side surfaces thereof.
12. The device of claim 1, wherein said second washer means has an
inside diameter that is similar to the inside diameter of said
third ring-shaped piezoelectric means and an outside diameter that
is greater than the outside diameter thereof.
13. The device of claim 1, wherein said acoustically clear means
connected to each of the aforesaid means for effecting the holding
thereof in the aforesaid spatial dispositions comprises a
substantially resilient polyurethane material.
14. The device of claim 1, wherein said electrical conductor means
comprises:
a pair of electrodes connected to opposite surface sides of each of
said first, second, and third ring-shaped piezoelectric means;
and
a pair of electric wires respectively connected to each of the
similar side electrodes of the pair of electrodes connected to
opposite surface sides of each of said first, second, and third
ring-shaped piezoelectric means for effecting the connection of
said first, second, and third ring-shaped piezoelectric means in
predetermined electrical circuit arrangement.
15. The device of claim 14, wherein said predetermined electrical
circuit arrangement is in electrical parallel.
16. The device of claim 14, wherein said predetermined electrical
circuit arrangement is in electrical series.
17. The device of claim 14, wherein said predetermined electrical
circuit arrangement is such that said first, second, and third
ring-shaped piezoelectric means are connected in electrically
independent arrangement.
18. The device of claim 1, wherein said acoustically clear means
connected to each of the aforesaid means for effecting the holding
thereof in the aforesaid spatial disposition is further disposed in
such manner as to encapsulate said first washer means, said first,
second, and third ring-shaped piezoelectric means, said second
washer means, and is connected to said substantially rigid backing
plate means in such manner to be securely attached thereto as
effectively an extension thereof.
19. The invention of claim 18, further characterized by a
substantially rigid forwarding plate disposed in abutment with that
external surface portion of the aforesaid acoustically clear
encapsulating means that is adjacent to said second washer means;
and means connected between said substantially rigid backing and
forwarding plate means for holding said encapsulated first washer
means, first, second, and third ring-shaped piezoelectric means,
and said second washer means therebetween.
20. The invention of claim 19, wherein said means connected between
said substantially rigid backing and forwarding plate means
comprises at least one threaded bolt and a nut screwed on the end
thereof.
21. The invention of claim 19, wherein said means connected between
said substantially rigid backing and forwarding plate means
comprises:
an end threaded bolt extending through said substantially rigid
backing plate means, said encapsulated first washer, first, second,
and third ring-shaped piezoelectric means, second washer means, and
said substantially rigid forwarding plate means; and
a nut tightly screwed on the threaded end of said bolt.
22. The invention of claim 20, further characterized by:
a first compartment connected to the rear end of said substantially
rigid backing plate means adapted for housing a predetermined
electronic utilization apparatus that is electrically connected to
the aforesaid electrical conductor means; and
a second compartment, having a substantially streamlined nose
configuration, connected to the front of said substantially rigid
forwarding plate means.
Description
FIELD OF THE INVENTION
The present invention, in general, relates to energy converters
and, in particular, is a reversible electroacoustical transducer
for converting electrical energy into acoustical energy
proportional thereto and vice versa. In even greater particularity,
the subject invention is an electroacoustical transducer having
doughnut-like or other acoustical radiation and response patterns
which are substantially uniform in configuration about an axis
normal thereto.
BACKGROUND OF THE INVENTION
Heretofore, numerous electroacoustical transducers of various and
sundry geometrical configurations and incorporating one or more
reversible piezoelectric elements have been used for projecting
acoustical energy in resonse to electrical energy excitation and
vice versa for many different purposes, especially in conjunction
with sonars. Accordingly, the electroacoustical transducer art is
so crowded that it would be impractical, if not impossible, to
described each one in sufficient detail for the purpose of setting
a predicate for the instant invention. Suffice to say, then, that
it is well known to employ piezoelectric ceramic elements, either
individually or in concert, as a generator and/or receiver of
acoustical or sonic energy within many different types of
environmental mediums, and especially in water, sea water, and the
like. Moreover, for many practical purposes, the electroacoustical
transducers of the prior art are quite satisfactory, although, to
date, they have not reached the stage of development where they are
perfect, even for some particular operational circumstance. Thus,
for example, in many instances the total structures thereof are
such that they may be cumbersome and unwieldy at times, the
resolution and fidelity thereof leaves something to be desired, the
bandwidths are too narrow because their frequency response curves
are not substantially flat (or are at least not flat enough for
some given purpose) and the functional power levels are too low for
optimum operation.
Because the present invention overcomes some of the disadvantages
of the prior art, it advances the state of the art to some degree,
thereby providing an improvement which is quite desireable at the
present time. Therefore, without further belaboring the prior art
-- inasmuch and much of it is obviously already known to the
artisans working in the research frontiers thereof -- the subject
invention will now be discussed briefly from the structural and
operational standpoints.
SUMMARY OF THE INVENTION
As suggested above, the present invention overcomes some of the
disadvantages of the prior art electroacoustical transducers. This
is so, because of the uniquely structured combination of elements
incorporated therein, with each thereof precisely dimensioned
(relatively speaking), so as to perform with optimum interaction
with its co-acting elements. Furthermore, the structure thereof has
been so simplified that otherwise spurious vibrations and adverse
electrical and acoustical effectations are reduced to an extent
ostensively unobtainable to this time. As a matter of fact, for its
intended purpose, the essence of the invention is so simple that
the structural and operational significance thereof is difficult to
comprehend unless one has access to the calibration and test
results thereof, the latter of which will be discussed in greater
detail subsequently.
Although other structure is or may be involved, the crux of the
invention appears to lie in three accurately dimensioned painted,
energy converter rings of similar outside diameters and different
inside diameters, and which may be of substantially identical
thickness that are geometrically held in predetermined optimum
spaced relationships with each other between a pair of
non-piezoelectric rings of different inside diameters and outside
diameters that are larger than the outside diameters of the
aforesaid energy converter rings by a unitary acoustically clear
support member having a durometer of thirty-five to forty. Such
simple but unique structure, of course, causes the desired
objectives of invention to be effected.
It is, therefore, an object of this invention to provide an
improved electroacoustical transducer.
Another object of this invention is to provide a relatively small,
high power, broadband, reversible electroacoustical transducer that
will function with improved operational resolution, fidelity, and
efficiency within numerous environmental mediums, including water,
sea water, and the like.
Still another object of this invention is to provide an easily
handled electroacoustical transducer that will operate over the
frequency range of seven to 15 kilohertz.
A further object of this invention is to provide a totally
polyurethane encapsulated electroacoustical transducer.
A further object of this invention is to provide a broadband
electroacoustical transducer that, for many practical purposes, is
more distortion-free than those of the prior art.
Another object of this invention is to provide a transducer that
will lend itself to the transmission of linear frequency modulated
signals.
Another object of this invention is to provide a transducer that
will simulate ocean vessel noises.
Still another object of this invention is to provide a transducer
that minimizes the effects of constructive and destructive
interference of sonar signals.
A further object of the present invention is to provide an improved
transducer having radiation and response patterns which are useful
for many underwater purposes and in many underwater
applications.
Another object of this invention is to provide an improved method
of constructing an electroacoustical transducer.
Still another object of this invention is to provide an improved
method and means for broadcasting acoustical energy having a
substantially disc-like, doughnut-like, or other radiation patterns
and for receiving and responding to a similar acoustical energy
pattern.
Another object of this invention is to provide an electroacoustical
transducer that is easily and economically manufactured, stored,
operated, maintained, and transported.
Other objects and many of the attendant advantages will be readily
appreciated as the subject invention becomes better understood by
reference to the following detail description, when considered in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an elevational view, predominantly in cross-section but
with parts broken away, of a preferred embodiment of the
electroacoustical transducer constituting the invention;
FIG. 2 is an elevational cross-sectional view (with parts broken
away) of another preferred embodiment of the electroacoustical
transducer constituting the invention;
FIG. 3 is an elevational view, partially in cross-section, which
illustrates a representative transducer construction mold for
potting the preferred embodiments of the invention depicted in
FIGS. 1 and 2;
FIG. 4 is an exemplary perspective view of the invention which
shows that the preferred embodiments thereof may be round in
configuration, as viewed from the top thereof;
FIG. 5 is an elevational view, partially in cross-section, of the
subject transducer combined with other utilization apparatus in a
projectile-like housing in such manner that it will transmit and
receive acoustical energy in one doughnut-like or disc-like pattern
that is normal to the longitudinal axis thereof;
FIG. 6 is an elevational view, partially in cross-section, of the
subject transducer combined with other utilization apparatus in a
projectile-like housing in such manner that it will transmit and
receive acoustical energy in sidewardly and forwardly
directions;
FIG. 7 is a schematic diagram of the electrical equivalents of the
piezoelectric energy converter elements of the subject invention
combined with the electrical equivalents of the cable, tuner,
transformer and signal generator elements which are designed to
provide optimum operation therewith;
FIGS. 8 and 9 are graphical representations of the radiation and
reception patterns which emanate radially -- that is, perpendicular
from the longitudinal axis of -- from and to the electroacoustical
transducer constituting this invention, respectively, regardless of
the preferred embodiment in which it is used;
FIG. 10 graphically illustrates the frequency response curve of the
subject transducer during the transmitting mode of operation
thereof; and
FIG. 11 graphically illustrates the frequency response curve of the
transducer constituting this invention during the receiving mode of
operation thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown the subject transducer 21
as having a base or backing plate 22, preferably made of aluminum
or some other metal but, of course, may be made of any
non-resilient or resilient material required to optimize transducer
operations during any given circumstances. In addition, backing
plate 22 may be integrally or otherwise conventionally connected to
a rearwardly extending body 23, which may have one or more bracing
walls 24 incorporating holes 25 and 26 to allow the passage of
electrical conductors or other apparatus therethrough.
For reasons which will be explained later -- but which are probably
obvious from FIG. 1 of the drawing -- base plate 22 has a forwardly
extending wall 27 containing a plurality of grooves 28 and 29 cut
in the inside surface thereof.
Perhaps at this time, it would be noteworthy that, when viewed from
the top or bottom, transducer 21 is round in configuration (as
indicated in FIG. 4); however, it should be understood that any
other suitable configuration may be the design therefor, if so
desired.
Base plate 22 includes a plurality of internally threaded holes 31
and 32 in which externally threaded insulated electrical lugs 33
and 34 are screwed, so as to allow electricity conduction through
said base plate 22, while maintaining sealed compartments 35 and 36
on both sides thereof. Base plate 22 and wall 24 also have holes 37
and 38 respectively extending through the center thereof, through
which a bolt 39 extends along the longitudinal axis of the entire
transducer, for reasons which will be more fully explained
subsequently.
At this time, it would appear to be worthy of note that, for
convenience sake, it will be assumed that the physical attitude of
the transducer shown in the drawing is such that the top thereof
(or front or forward position thereof) is located at the top of the
drawing and the bottom thereof (or rear or rearward portion
thereof) is located at the bottom of the drawing. Hence, the
aforementioned longitudinal axis of the subject transducer may be
seen to run up and down, although in actual practice, the invention
may be used in whatever physical disposition or attitude as is
necessary for any given operational situation.
Setting on base plate 22 but extending upward therefrom is a
plurality of cured polyurethane blocks or posts 40, the length of
which is approximately 0.5 inch, and setting on the top of said
plurality of blocks or posts 40 is an acoustically clear
acryonitrile-butadine-styrene (ABS) washer 41 of 3.30 inches
outside diameter and 3.00 inches inside diameter. And setting on
the top surface of washer 41 is a plurality of cured polyurethane
spacers 42 having a length of 0.032, upon which a first lead
zirconate-lead titanate piezoelectric ceramic ring 43 -- polarized
through its thickness dimension -- is disposed.
The specific dimensions of piezoelectric ring 43 of this preferred
embodiment are important. The outside diameter thereof is 3.100
inches and the inside diameter thereof is 2.900 inches, thereby
giving it a wall thickness of 0.100 inch. the thickness thereof (as
measured along the transducer longitudinal axis direction) is 0.272
inch. Of course, ring 43 is preferably cut in the convention
ceramic cutting manner, in order to have such accurate dimensions;
nevertheless, other dimension refining procedures may be employed,
if so desired.
Electroacoustical energy converter ring 43 has a pair of silver
electrodes 44 and 46 respectively attached to the opposite sides
thereof for the conventional purpose of effecting the electrical
energization thereof when supplied with appropriate electrical
current.
Sitting on the upper surface of electrode 46 of piezoelectric ring
43 is a second plurality of cured polyurethane spacers 47 having a
length of 0.032, like spacers 42, and sitting on said spacers 47 is
a second lead zirconate-lead titanate piezoelectric ceramic ring 48
that is, likewise, polarized through its thickness dimension.
The specific dimensions of piezoelectric ring 48 are, like those of
the aforementioned ring 43, of considerable importance. The outside
diameter thereof is 3.100 inches, and the inside diameter thereof
is 2.700 inches, thereby giving it a wall thickness of 0.200 inch.
The thickness thereof which is measured along the longitudinal axis
of the transducer is 0.272 inch.
Electroacoustical energy converter ring 48 also has a pair of
silver electrodes 49 and 51 respectively attached to the opposite
sides thereof for timely effecting the electrical excitation
thereof.
Sitting on the top surface of electrode 51 of ring 48 is a third
plurality of cured polyurethane spacers 52 having a length of
0.032, and sitting on said spacers 47 is a third lead
zirconate-lead titanate piezoelectric ceramic ring 53 that is also
polarized through its thickness dimension.
Like those of rings 43 and 48, the specific dimensions of
piezoelectric ring 53 are of considerable importance. The outside
diameter thereof is 3.100 inches, and the inside diameter thereof
is 2.800 inches, thereby making it have a wall thickness of 0.150
inch. The longitudinal thickness thereof -- as measured along the
longitudinal axis of the transducer -- is 0.272 inch.
Electroacoustical energy converter ring 53 also has a pair of
silver electrodes 54 and 55 respectively attached to the opposite
sides thereof for effecting the electrical excitation thereof when
electrical current is supplied thereto.
Still a fourth plurality of cured polyurethane spacers 57 sit on
the top surface of electrode 54 of ring 53, and they each have a
length of 0.032; and another acoustically clear
acryonitrile-butadine-styrene (ABS) washer 58 sits on top of said
spacers 57. Washer 58 has an outside diameter of 3.300 and an
inside diameter of 2.800 inches.
From the foregoing, it may be seen that the spatial distance
between the piezoelectric rings is 0.032 inch. Encapsulating all of
the aforesaid elements located above the upper surface of backing
plate 22 is an acoustically clear polyurethane housing 61 and
potting 62 material. How such housing and potting structure is
constructed in combination with their associated is very simple and
will be discussed more fully below. Suffice to say at this time,
that they form outside wall 63 and upper wall 64, as well as occupy
the space of compartment 35, including grooves 28 and 29. Of
course, the occupying of grooves 28 and 29 effects a joint between
potting 62 and the aforementioned extending body wall 27, the
rigidity or resiliency of which is contingent upon the resiliency
of potting material 62.
Although difficult to show and reference pictorially, a primer coat
of paint -- preferably of Hysol P-10 -- coats the external surface
of all of the aforementioned transducer elements above the upper
surface of backing plate 22; hence, it acts as a buffer between the
outside surfaces thereof and the inside surfaces of the housing and
potting material. For the sake of simplicity of disclosure, said
paint is hereby referenced as primer paint 65.
Mounted on the forward or upper end of transducer 21 is another
aluminum or other matal plate 66 containing a center hole 67
through which the aforementioned bolt 38 extends. A nut 68 screwed
tightly on bolt 38 very effectively holds transducer 21 in place
between forward and backing plates 66 and 22. Of course, forward
plate 66 may be integrally or otherwise connected to any other
compatible apparatus 67 (not shown in detail in FIG. 1) required to
be associated therewith, if operational circumstances so
warrant.
Without intending to limit the scope of the subject invention, the
preferred embodiment shows electroacoustical energy converter rings
43, 48, and 53 connected in electrical parallel by means of
electrical conductors 71 and 72 connected between the various
electrodes thereof and lugs 33 and 34, respectively. The other
electrical leads 73 and 74 are or may be connected between said
lugs 33 and 34 and any suitable utilization apparatus, such as, for
example, sonar systems, or the like. Nevertheless, it should be
understood that said electroacoustical energy converter rings may
be connected in series, independently, in parallel, or any
combination thereof, if so doing would optimize the operation of
the subject transducer during any given operational
circumstances.
Transducer 81, the preferred embodiment of the electroacoustical
transducer of FIG. 2, is very similar to that of FIG. 1, except
that it contains no mounting bolt extending therethrough, nor does
it contain a forward plate at the top thereof. Hence, to simplify
the discussion thereof, it should suffice to say that it contains a
backing plate 82, washers 83 and 84, energy converter rings 85, 86,
and 87, spacers 88, 89, 90, and 91, as well as acoustically clear
housing 92 and potting 93. Also, obviously missing are posts
similar to posts 39 of FIG. 1.
The energy converter rings thereof are, likewise, shown to be
connected in parallel by electrical conductors 94 and 95 which
extend down through a hole 95 in backing plate 82. Of course,
backing plate 82 may be integrally or otherwise attached to another
object or body 96. Although forward wall 97 of polyurethane housing
92 is depicted as being flat, it may be round, streamlined, or have
any other geometrical configuration, as long as it is acoustically
clear.
All of the elements of the embodiment of FIG. 2 are preferably
identical to similar ones of FIG. 1, as far as dimensions
materials, configurations, and construction procedures are
concerned.
FIG. 3 of the drawing is merely intended to show that either
transducer 21 or 81 may be constructed by setting up all of the
aforesaid elements thereof, respectively, in a mold 101 and then
pouring heated liquid polyurethane material into the top thereof --
as schematically indicated by reference numeral 102 -- until it is
filled to level 103, after which it is cooled or left to harden and
become the aforementioned housings and pottings.
In the case of the embodiment of FIG. 2, part of said polyurethane
material must be poured first and left to harden before assemblying
the elements located above backing plate 82, with the remainder of
the pouring thereof accomplished thereafter.
FIG. 4 has been included in the drawing to disclose the general
external appearance of the embodiment of the invention shown in
FIG. 1, but without bolt 38 or backing plate 22. Hence, reference
numerals are used therein which are the same as used in FIG. 1 for
similar parts. It is believed that the structure of FIG. 4 is
self-evident as it is shown; however, if further illucidation is
necessary, the reading of the discussion pertinent to FIG. 1
thereon should suffice to explain its structure quite
adequately.
Referring now to FIG. 5, it is shown therein that transducer 21 of
FIG. 1 may be incorporated in a substantially streamlined
projectile shaped body 110 which may contain various and sundry
electronic utilization apparatus 111 and other apparatus 112
disposed, as desired, in rearward and forward compartments 113 and
114, respectively. Of course, the structures of compartments 113
and 114 may be of any particular designs as would optimize their
being combined with electroacoustical transducer 21.
FIG. 6, like FIG. 5, shows another representative configuration in
which the embodiment of FIGS. 1 and 2 may be incorported, as long
as it is modified to extend forward polyurethane wall to have a
forward extension 121 with rounded or streamlined nose 122, and a
suitable nut 123 and passageway 124 included within extension 121
in such manner that bolt 39 may be screwed into it from the rear
for the purpose of securely connecting transducer 21 to a rear
compartment 125. Of course, as may readily be seen, rear
compartment 125 is designed to contain such electronic utilization
apparatus as would be suitable for being combined with transducer
21 or 81.
Obviously, it would be well within the purview of one skilled in
the art to design and construct the bodies, compartments, and the
like, of the devices of FIGS. 5 and 6 in such manner as to effect
the optimization thereof for any given purpose or ambient
environmental medium. Accordingly, further discussion of specific
structures thereof is deemed to be unnecessary.
THEORY OF OPERATION
The theory of the operation of the embodiments of the
electroacoustical transducers illustrated in FIGS. 1 and 2 will now
be discussed briefly in conjunction with FIG. 7.
If, for instance, an electrical signal of known voltage and
frequency, E.sub.1, is generated by any suitable generator 131 and
supplied to the input primary winding of transformer 132, a
voltage, E.sub.2, occurs which, in turn, is supplied via
transmission cable 133 -- represented by inductor 134, resistor
135, and capacitor 136 -- to the electroacoustical piezoelectric
elements I, II, and III. Because the total capacitive reactance of
the piezoelectric elements is much greater than that of the
transmission cable, when properly tuned, cable 133 serves primarily
as a transmission line, and the attenuation of the electrical
signal (E.sub.2) between transformer 132 and piezoelectric elements
I, II, and III would be, for all practical purposes, negligible. Of
course, the total capacitance of transmission line 133 and
piezoelectric elements I, II, and III combined is effected by the
proper adjustment of a variable inductance 137 connected in
parallel with the secondary winding of transformer 132, to
effectively compensate for the reactance inherently existing in
elements I, II, and III, and discussed below.
The circuit parameters to be considered from the operational
standpoint of the piezoelectric elements are Ra.sub.1, Ra.sub.2,
and Ra.sub.3, which represent the radiation resistance encountered
by ceramic elements I, II, and III, respectively; R.sub.1, R.sub.2,
and R.sub.3, which represent the internal motional resistance
within piezoelectric elements I, II and III, respectively; L.sub.1,
L.sub.2, and L.sub.3 which represent the effective inductance or
masses of piezoelectric elements I, II, and III, respectively;
C.sub.1, C.sub.2, and C.sub.3, which represent the effective
capacitance or stiffness of the piezoelectric elements I, II, and
III, respectively; C.sub.T1, C.sub.T2, and C.sub.T3, which
represent the total dielectric capacitance of piezoelectric
elements, I, II, and III, respectively; and the mass loading of the
polyurethane potting material on said piezoelectric elements I, II,
and III, respectively.
It is well known that when the inductive reactance X.sub.L and the
capacitive reactance X.sub.C of any given material -- in this case,
involving the aforementioned R, L, and C terms -- are equal, a
fundamental resonance frequency may be observed therein. However,
since in this particular instance the piezoelectric elements are
encapsulated in a potting material, such potting material produces
a mass loading effect or an additional inductance which must be
taken into consideration. In other words, such potting materials's
effective inductance causes the fundamental resonance of each
piezoelectric ceramic element to shift in a downward direction. For
example, piezoelectric element 43 of FIG. 1, having a wall
thickness of 0.100 inch, has its resonant frequency shifted down
4.88 KHz; piezoelectric element 48, having a wall thickness of
0.200 inch has its resonant frequency shifted down 0.32 KHz; and
piezoelectric element 53, having a wall thickness of 0.150 inch,
has its resonant frequency shifted down 2.63 KHz.
Hence, in view of the aforementioned dimensions, materials,
parameters, and resonant frequency downshifts, it may readily be
seen that a considerable number of factors have been taken into
consideration in the construction of the electroacoustical
transducer constituting this invention, in order to make it as
perfect as possible for its intended use. Of course, such
considerations also made it a relatively simple but unique device
which obviously advances the state of the electroacoustical
transducer art to some degree.
MODE OF OPERATION
The subject invention will operate equally well in a transmitting
mode of operation -- wherein it broadcasts acoustical energy in
proportion to the electrical energy supplied thereto -- and a
receiving mode of operation -- wherein it generates electrical
energy in proportion to the acoustical energy received thereby.
Therefore, if, for example, it is in the transmitting mode, it will
broadcast an acoustical radiation pattern similar to that shown in
FIG. 8; and if it is in the receiving mode, it will be responsive
to the acoustical pattern illustrated in FIG. 9, with said two
patterns being portrayed as if they were viewed from an extension
of the longitudinal axis of the entire transducer. Obviously said
two patterns are quite circular in shape for acoustical patterns
and, hence, the structure which produces and is affected thereby
constitutes an improvement, indeed.
Furthermore, as depicted in FIGS. 10 and 11, respectively, the
transmitting and receiving frequency response curves of the subject
calibrated invention are, relatively speaking, quite flat, indeed.
Thus, they, too, are indicative of the improved performance
obtainable from the subject invention within the broadband
frequency range of seven to fifteen kilohertz.
In any event, the subject transducer has been tested and found to
be very efficient and have a high fidelity in underwater acoustical
communication, things which have been desired for a long time.
While the transducer embodiment of FIG. 1 and the installation
thereof in FIG. 5 tend to broadcast and receive doughnut shaped
acoustical patterns similar to those shown in FIGS. 8 and 9, the
transducer embodiment of FIG. 2 and, say, a slightly modified
version thereof shown in FIG. 6 tend to broadcast and receive
semi-doughnut shaped acoustical patterns, with an elongated forward
projection thereof corresponding to some extent to elongation of
the forward polyurethane wall of the transducer. Thus, it may
readily be seen that a variety of acoustical radiation and response
patterns are possible, depending on the design of the forward end
of the subject transducer. Obviously, it would be well within the
purview of the artisan having the benefit of the teachings
presented herewith to design the nose of the subject transducer to
vary the forward acoustical pattern as desired.
METHOD OF CONSTRUCTION
Because the resulting transducer constituting this invention may be
exceedingly simple in its final form, the method of construction of
it may not be readily apparent. Hence, it is outlined as follows
for the exemplary embodiment of FIG. 1:
1. Place backing plate 22 with lugs 33 and 34 in mold (like mold
103 of FIG. 3).
2. Arrange polyurethane posts 39 in upright position on upper
surface of base plate 22.
3. Set washer 41 on posts 39.
4. Set spacers 42 on washer 39.
5. Set piezoelectric ring 43 on spacers 42.
6. Set additional rings and spacers like in step 5.
7. Set washer 58 on spacers 57.
8. Connect electrical leads between electrodes and lugs.
9. Insert bolt 38.
10. Pour molten polyurethane potting material into the mold in such
manner as to fill all space not occupied by the aforesaid elements
and let set.
11. Insert forward plate 65.
12. Tighten nut 68 on bolt 38.
The above procedure may be modified so that the posts and spacers
are of different materials from the polyurethane material used, or
it may be modified to eliminate the posts entirely, so as to effect
an embodiment similar to that shown in FIG. 2. However, it should
be understood that, in either case, the posts, spacers, and potting
material may be of the same -- that is, any appropriate --
material, which, in effect, makes said posts, spacers, potting
material, and wall integral with each other or not in the final
product, as preferred.
Obviously, other embodiments and modifications of the subject
invention will readily come to the mind of one skilled in the art
having the benefit of the teachings presented in the foregoing
description and the drawings. It is, therefore, to be understood
that this invention is not to be limited thereto and that said
modifications and embodiments are intended to be included within
the scope of the appended claims.
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