US3320578A

US3320578A - Electroacoustic transducers for submarine echo sounding

Info

Publication number: US3320578A
Application number: US463257A
Authority: US
Inventors: Ahrens Erhard; Feher Karl
Original assignee: ELAC Electroacustic GmbH
Current assignee: ELAC Electroacustic GmbH
Priority date: 1964-06-15
Filing date: 1965-06-11
Publication date: 1967-05-16
Anticipated expiration: 1984-05-16
Also published as: DE1441496B2; GB1115524A; DE1441496A1

Description

y 1967 E. AHRENS ETAL ELECTROACOUSTIC TRANSDUCERS FOR SUBMARINE ECHO SOUNDING 4 Sheets-Sheet 1 Filed June 11, 1965 FlG.l

It'll. I

v C x 1 FIG.2

y 16, 1967. E, AHRENS QETAL 3,320,578

UBMARTNE ECHO SOUNDING Filed June 11, 1 965 4 Sheets-Sheet 2 Fl G. 3 24,

y 16, 1967 E. AHRENS ETAL ELFICTROACOUSTIC TRANSDUCERS FOR SUBMARTNB ECHO SOUNDING Filed June 11, 1965 4 Sheets-Sheet 3 FIG. I?

FIG44 Hul O May 16, 1967 E. AHRENS ETAL 3,320,578

Y ELECT OOOOOOO IC TRANSDUCERS FOR SUBM AAAA NR ECHO S0 TTTTTT 1 G Filed June 11, 1965 FIG-5 FIG..6

IFIG.|| FlG.l2

4 Sheets-Sheet for determining the depth of the net.

3,320,578 ELECTROACOUSTIC TRANSDUCERS FOR SUBMARINE ECHO SOUNDING Erhard Ahrens and Karl Fcher,-bth of Kiel, Germany,

assignors to Electroacustic G-esellschaft mit beschrankter Haftung, Kiel, Germany, a corporation of Germany Filed June 11, 1965, Ser. No. 463,257 Claims priority, application Germany, June 15, 1964,

E 27,220 28 Claims. (Cl. 340-8) Our invention relates to electroacoustic transducers for submarine echo sounding (sonar).

When working with echo sounding devices to determine the presence of certain objects in bodies of water, the particular objects may be situated at relatively large depths. This happens, for example, in searching for sunken wrecks, when tracking schools of fish with a dragnet, or when applying sonar techniques for exploratory purposes such as offshore drilling for oil. When soundings are taken from the surface of the body of water, the resolution of the recorded reflections is very slight. Thus, even with a transducer characteristic having an opening angle as small as approximately 10, which can only be achieved with great effort, there results a reflection from an area of 100 meters diameter at a depth of 600 meters.

It is possible, for example, to improve the resolution by using net-supported sonar probes, inasmuch as the net itself can be dragged behind a ship at a depth of 500-600 meters, this net carrying an oscillator for tracking a swarm of fish in the vicinity of the net opening or It is possible also to increase the resolution by taking soundings from an unmanned container dragged by a suitable drag line, the components of the sounding equipment, such as the recorder, transmitter, receiver, and at least a transducer, being mounted in'this container. This permits sounding from a considerably shorter distance, for example only 100 meters from the sea bottom which may have a depth of 600 meters. With a beam opening angle of 10 an area of 17 m. diameter can thus be resolved. By changing the depth of the transducer-carrying container, the sonically impinged area and consequently the resolution of details in the recording can be varied within wide limits. For example, by first producing survey pictures with the aid of recordings at which the transducer or container is located at a larger height above the sea bottom, any particular localities of interest can then be recorded with greater resolution by lowering the transducer'and performing the sounding from a smaller distance above sea bottom.

When carrying out operations of the above type, the problem of high pressure is encountered. At a depth of 500 meters, for example, the pressure may be in the order of 50 atmospheres. As a result, considerable dif- United States Patent ficulties are encountered in the construction of a transducer which is required to operate effectively at high hydrostatic pressures while at the same time being required, in spite of these high pressures, to fulfill a number of further requirements in such a way that the fulfilling of certain requirements in no way conflicts with the fulfilling of other requirements.

In addition to encountering problems of this latter type in an individual electroacoustic transducer, particular problems arise when a plurality of transducers are assembled into a group. Extreme difficulty is encountered in arranging the forwardly directed outer surfaces of the diaphragms of such transducers close enough to each other to provide sharply concentrated primary radiations with minimum secondary radiations. This is particularly true of electroacoustic transducers where the oscillatory diaphragms are connected by an elastic means to the transducer housings for oscillatory movement relative thereto. Where such elastic connections between the diaphragms and housings are not used, it has been possible to provide an arrangement where the radiation receiving or emitting surfaces of the diaphragms are situated quite close to each other, but these structures do not have a high efiiciency, because they unavoidably short-circuit the projecting portions of the exterior forwardly directed diaphragm surfaces, so that these short-circuited surface portions cannot effectively transmit or receive radiations. This undesirable effect increases where the forwardly directed surface areas of the various diaphragms of such an assembly are of approximately the same area, as the central effective area, inasmuch as the size of the area increases as the square of the radius thereof. Therefore, the outer surface portions adjacent the periphery of the diaphragms are ineffective for radiation purposes while the actually effective central portions of the radiating areas are not situated as close to each other as appears from the exterior of the structure, so that in spite of the fact that the several transducers of the group are structurally situated quite close to each other, the same disadvantages are encoun- I tered in connection with radiations as with the structures where the diaphragms are connected by an elastic means to the housings for oscillatory movement relative thereto.

Moreover, with structures of the above type the transmitted frequency band is undesirably narrow inasmuch as this factor is determined by the relation between the emitting (or receiving) area F to the actual mechanical or physical area F of the active transducer element. As a result of the short-circuiting of the peripheral portions of the adjoining diaphragms of a group, as referred to above, where there is only an apparently large emitting or receiving area, a large part of otherwise effective emitting or receiving area. is excluded, so that with structures of this type the effective emitting area is only approximately as great as the physical area of the active transducer element, and thus F reF To provide for shielding against undesirable radiations, it has been known to arrange outside of the emitting area of the diaphragm a porous and/o1" air-containing body. Such bodies, however, neither have any desirable resistance to pressure nor permit the transducer to be covered by a coating which is resistant to pressure and which protects against corrosion, so that structures of this type do not lend themselves to efiicient operation at relatively great depths in the bodies of water.

It is accordingly a primary object of our invention to provide individual and groups of transducers which will avoid or greatly minimize the above-mentioned drawbacks and will instead permit highly efficient operation at great depths in bodies of water.

Thus, it is an object of our invention to provide a transducer which, with respect to etliciency, coupling factor, frequency band, radiation concentration, and impedance, fulfills all of the desired requirements while at the same time having a perfect seal of the interior of the transducer with respect to the exterior thereof and providing great resistance to constant jarring of the transducers in such a way that it is possible to fulfill all of these requirements and achieve a sufiiciently concentrated radiation beam of a plurality of transducers which can be arranged in a group without Wasting too much energy on secondary radiations of the characteristic.

Another, more specific, object of our invention is to provide an electroacoustic transducer capable of sending or receiving radiations in liquid and suited for operation at great depths while being capable of being arranged in compact groups with the diaphragms of the several transducers respectively driven by active elements thereof.

The objects of our invention further include the provision of transducers capable of being arranged in groups with the outer peripheral edges of the forwardly directed as great hydrodynamic pressures, while also being quite insensitive to explosions, as is required when taking seismographic measurements.

In addition, it is an object of our present invention to provide transducers which have a high efficiency as well as large coupling factors and which can transmit through wide frequency bands as well as being capable of being arranged in groups where the individual transducers can have their forwardly directed emitting (or receiving) surfaces of their diaphragms arranged quite close to each other without any interfering intermediate spaces therebetween, so that it is possible to achieve a highly concentrated beam of primary radiations with a small degree of secondary radiations.

Furthermore, the objects of our present invention include the possibility of applying the principles of the invention to many different types of transducer structures, such as, for example, transducers where the diaphragm is carried by the active driving element of the transducer as well as transducers where the diaphragm is connected to the transducer housing by way of one or more elastic connections. In the latter type of structure the transducers of the present invention will have the elastic connecting means arranged next to a shielding chamber which shields out interfering radiations.

In particular, the objects of our invention include the provision of electroacoustic transducers where substantially the entire, forwardly directed, outer physical surface area of the diaphragm can effectively transmit or receive radiations, so that F F and thus a large band width and a high efficiency can be achieved.

The objects of our invention also include a transducer structure where, even though a plurality of transducers are situated quite close to each other, nevertheless the walls of the transducer housings can be made quite thick so that they will have a large mass, thus increasing the ef: ficiency inasmuch as transducer housings of large mass will remain relatively stationary.

In addition, the objects of our invention include the provision of transducers which can be enveloped in a pressure-resistant and corrosion-resistant coating without in any way detracting from the efficiency of the operation of the transducer or group of transducers.

In addition, the objects of our invention include the provision of transducers having structures which enable them either to be constructed as complete individual transducers each having their own housing, with the housings arranged next to each other when the transducers are collected in a group, or a structure where each transducer does not have its own individual housing and instead a plurality of fully operative transducers are arranged in a common housing.

Primarily, according to our present invention, the transducer includes a plurality of components arranged along a longitudinal central axis of the transducer and cooperating together to provide a completely operative transducer. These components include a diaphragm which has a forwardly directed outer surface capable of sending and receiving radiations. In accordance with the present invention, this forwardly directed diaphragm surface will project onto a plane normal to the longitudinal central axis an area which is at least substantially coextensive with the largest area projected onto this plane by any other component of the transducer. The diaphragm of the transducer of the present invention has, to the rear of its forwardly directed surface, additional surface area with which a second component of the transducer cooperates to define a shielding chamber capable of shielding out interfering radiations of the rear peripheral surfaces of the diaphragm, and this shielding chamber is highly resistant to pressure.

The invention is illustrated by way of example in the accompanying drawings which form part of the application, and in which:

FIG. 1 is a longitudinal sectional elevation of an embodiment of an electroacoustic transducer according to the invention, the section of FIG. 1 being taken in a plane which includes the longitudinal central axis of the transducer;

FIG. 2 is a longitudinal sectional elevation fragmentarily illustrating how a pair of transducers can be arranged to form a group or part of a group of transducers;

FIG. 3 is a fragmentary sectional elevation illustrating another embodiment of a transducer;

FIG. 4 is a fragmentary schematic plan view of transducers of the invention combined in a group;

FIGS. 5-12 are sectional elevations of different configurations of part of a transducer of the present invention;

, FIG. 13 is a fragmentary sectional elevation of another group of transducers of the present invention;

FIGS. 14 and 15 are fragmentary sections of two other transducers of the present invention;

1 FIG. 16 shows another embodiment of a group of transducers of our invention; and

FIG. 17 is'a longitudinal sectional elevation, schematically illustrating still another embodiment of a transducer according to our invention.

Referring now to FIG. 1, the illustrated transducer according to our invention is made up of a plurality of coactive components all of which are arranged along a longitudinal central axis of the transducer. The components include an active driving or driven oscillator element 1 opertaively connected with a diaphragm composed of

parts

2 and 2a which are connected to each other to form a piston-like oscillatory diaphragm. The transducer further includes a housing part 4 and an elastic means 3 connecting the

diaphragm

2, 2a to the housing part 4 for oscillatory movement relative thereto in response to the drive from the active element 1. A counterweight '13 is afiixed to that side of the active transducer element 1 which is directed away from the

diaphragm

2, 2a. The counterweight 13 is affixed to an insulating plate 57 which is in turn affixed to the active transducer element 1. Moreover, the counterweight 13 is connected through the elastic elements 14 with a rigid.

part 15 which is affixed to the housing. The elastic means 3 as well as the elastic elements 14 are capable of resiliently yielding during operation of the transducer. At its exterior surface, the part 15 is formed with recesses 25a for receiving a layer of cement by which the part 15 is affixed to the housing part 4. i

The counterweight 13 together with the junction for the electrical conductors are closed off from the exterior 'by a pressure-resistant and water-tight cap 18 which also forms a part of the housing, and this housingpart or cap 18 also serves to guide the cable of the transducer to the exterior thereof. This cap or housing part 18 is connected with the housing part 4 by way of a resilient compressible seal 16 in the form of an elastic member extending between and cemented to the

housing parts

4 and 18. The entire transducer is enveloped and closed off from the exterior in a gap-free manner by means of a corrosion-resistant rubber or plastic covering or layer 11 which is incapable of reacting with water, and it will be noted that the elastic sealing structure 16 is formed by a pair of inwardly directed flanges of the plastic coating 11, these flanges directly engaging and being bonded to each other as well as to the surfaces of the

housing parts

4 and 18 which are directed toward each other in the manner illustrated in FIG. 1. These flanges are not only sealed against each other but also against the annular housing surfaces of the

parts

4 and 18, respectively, which are directed toward each other, and it is the material of the plastic or rubber coating 11 which is elastic and yieldably compressible so as to form the elastic sealing structure 16 shown in FIG. 1. The cable 20, which extends outwardly beyond the housing part 18 to the exterior, is

surrounded, in the opening of the housing part 18 through which the cable 20 extends, by a tension-relieving spring ring '21. The conductors 22 are electrically connected with the active transducer element 1 by way of the soldering assembly 23 to which the conductors are soldered so as to be supported thereby, and the structure 23 is connected to the counterweight 13 while the conductors are electrically connected with the active'element 1.

The active transducer element 1 can take the form of any known driving or driven transducer element operating according to any well established principle, such as, for example, electrostrictive, magnetostrictive, or piezoelectric principles. The element 1 can take any of a number of different geometric configurations such as, for example, cubic, tubular, and/ or multi-layer configurations, and with this latter construction the different layers would be parallel to each other and to the

diaphragm

2, 2a, as well as perpendicular thereto. The transducer element 1 serves to convert electrical energy into acoustic energy or to convert acoustic energy into electrical energy. The acoustic energy is emitted from the radiation surface 8 of the

membrane

2, 2a, this surface 8 being an outer forwardly directed surface of the diaphragm. The outer forwardly directed surface 8 of the

diaphragm

2, 2a is adapted to send or receive the radiations. The diaphragm is coupled to the active transducer element 1 by way of the insulating plate 57'. By suitably arranging the transducer, particularly with respect to the polarity thereof, it is ossible to eliminate one or both of the insulating plates 57 and 57'. The coupling can, for example, take the form of cementing. The recesses 25 formed in those rear surfaces of the

diaphragm elements

2 and 2a which are directed downwardly, as viewed in FIG. 1, are adapted to receive layers of cement for fixing the components to each other. The elastic means 3, which connects the

diaphragm

2, 2a to the housing 4for oscillatory movement relative thereto, has a structure which enables it to' withstand a high hydrostatic pressure, but at the same time in such a way that'no appreciable energy is transmitted from the

diaphragm

2, 2a to the housing 4 through the elastic means 3.

As may be seen from FIG. 1, according to one of the more important features of the present invention, the outer, forwardly directed surface 8 of the diaphragm, which is adapted to send or receive the radiations, when projected onto a plane normal to the longitudinal central axis along which all of thetransducer elements are arranged, has an area which is'at least substantially coextensive with the largest area projected onto this plane by any other component. Thus, ,in the illustrated example the largest area will be projected onto this plane by the housing part 4 which, it will be noted has an outer periph ery only slightly greater than the outer periphery of the surface 8, so that this surface 8 does indeed cover an area which, if not as large as the largest area projected onto a plane normal to the-longitudinal central axis by any component, is at least almost as large as the largest area, and it is in this way that some of the outstanding results of the present invention are achieved, as will be apparent from the description which follows.

According to another important feature of our invention, there is provided with the transducer of the invention a pressure-resistant, shielding chamber situated to the rear of the outer forwardly directed surface 8 of the diaphragm.

In the embodiment of FIG. 1, this radiation shielding chamber takes the form of a relatively narrow annular gap 5 which coaxially surrounds the

diaphragm

2, 2a. This gap or chamber 5 is defined on the one hand by the additional surface area 7 of the diaphragm, this latter area being in addition to the outer forwardly directed surface 8 thereof, and the inner surface 6 of the housing part 4. In this way the rearwardly situated surface area 7 of the diaphragm, located at the peripheral edge thereof, is shielded by an air cushion which prevents formation of an acoustic short circuit as well as preventing any interfering radiations. In contrast to known constructions, of the type referred to above, the radiation-shielding chamber 5 is capable of satisfactorily fulfilling its intended function even at high hydrostatic pressures.

A further highly advantageous feature resides in extending the annular gap 5 on the one hand inwardly all the way up to the elastic means 3 and on the other hand outwardly all the way up to the emitting or receiving, forwardly directed, outer surface 8 of the diaphragm. With this construction it is possible to have the advantage of situating the entire transducer within a corrosionresistant plastic or rubber coating 11 which envelops the transducer on all sides thereof so that the transducer is completely closed off from the exterior by the protective coating 11, and in spite of this construction the movement v of the diaphragm itself is not obstructed in any way.

A further feature of the construction shown in FIG. 1 resides in covering-the outer end 10 of the gap 5, situated at the outer peripheral edge of the forwardly directed diaphragm surface 8, by means of an elastic material 9. It is to be noted that the gap 5 has a thickness which gradually increases from its end 10 toward the elastic connecting means 3, so that the thickness of the gap 5 is at a minimum at its outer open end 10, and in this way it is possible to provide a pressure-resistant elastic closure of the gap without obstructing movement of the

diaphragm

2, 2a even when the transducer is provided with the protective coating 11. Thus, it is notessential to maintain the gap 5 throughout as small as its size at the elastically covered end 10,'and instead it is of advantage to provide the gap 5 with different, or even alternating, thicknesses between its ends. It has been found to be of advantage to provide an elastic covering 9 which is of an angular cross section so as to extend over and engage the corner at the end of the transducer where the forwardly directed emitting or receiving surface 8 of the diaphragm is situated. way there is provided an'extrcmely compact and at the same time stable closure for the outer end of the annular gap 5.

In the embodiment illustrated in FIG. 1, the annular gap 5 is formed by extending the side wall of the housing part 4 all the way up to the forwardly directed surface 8 of the

diaphragm

2, 2a, beyond the elastic means 3, and the outer diaphragm element 2 is seated upon-and fixed to the diaphragm carried 2a so that it is between the housing -part 4 which extendsforwardly beyond the elastic means 3 and the forward part 2 of the diaphragm that the annular gap 5 is for the most part formed. It is thus possible with this construction to construct the carrier element 2a of the diaphragm in such a way that it therewith, thereis provided a gap 5 which is defined by 7 very smoothly and cleanly machined surfaces 6 and 7, and as a result the width of the gap can be maintained at a very small size. Furthermore, it is possible in this way to make a diaphragm quite rigid and at the same time In this rearwardly toward the interior of the housing.

very light. The diaphragm can be made, at its part 2, of a material which is lighter than the material used for the housing. A further way of saving weight, while retaining rigidity, is to provide a structure, as shown, where the side surface of the diaphragm part 2 forms part of a cone which extends inwardly toward the longitudinal central axis of the transducer. Also, it is in this way easier, in the interest of achieving a high efficiency, to make the entire housing 4 as heavy as possible, in comparison with the diaphragm part 2.

FIG. 2 illustrates, in section, how individual transducers constructed as shown in FIG. 1, and of course each completely operable as a separate unit, can be combined together to form a group of transducers. It is to be noted that the outer peripheral edges a of the

diaphragms

2, 2a, shown in FIG. 2, extend outwardly beyond the elastic connecting means 3, the housing interiors 4a, and the greatest part of the thickness of the outer walls of the

housings

4, 18 so that these peripheral edges of adjoining transducer diaphragms are quite close to each other, and it is, of course, in this way that the radiation-shielding chambers 5 are formed between the membrane part 2 and the housing part 4, respectively.

Further features of our invention reside in defining part of the radiation-shielding chamber 5 by theelastic means 3 itself, so that in this way the complete freedom of movement of the elastic means is retained, and also,

in accordance with our invention, the radiation-shielding chamber 5 is separated from the interior 4a of the housing by means of the elastic connecting means 3. As is also shown in the embodiments hereinafter described, there are many different possibilities according to which transducers may be constructed in accordance with the invention, with the radiation-shielding chambers taking widely different forms and arrangements, as is also true of the elastic connecting means of the invention.

Preferably, the elastic connecting means 3 is arranged in such a way that it is situated in the immediate vicinity of, or directly at, the inner diaphragm surface 12 of the diaphragm part let, this inner surface 12 being directed In this way, the requirements with respect to pressure-resistance as well as those of providing sufficient yieldability of the elastic means are both capable of being fulfilled. The pressure-resistance is enhanced by providing a structure where the pressure forces acting between the diaphragm and the housing are absorbed not only by the elastic means 3 but also (FIG. 1) by the elastic connecting structure,14, between the counterweight 13 and the part which is fixed to the housing, as described above. The transmission of forces takes place from the diaphragm through the active transducer element 1, the counterweight 13 and the elastic connecting structure 14 to the part 15, which is afiixed to the housing. The part 15 is atfixed to the housing part 4, by being cemented thereto, for example. In this way the counterweight 13 can be made of a heavier material than that used for the housing part 4 or the diaphragm, so that the transducer is not only pressure resistant but also is capable of operating in a wide band. A maximum reduction in the load on the elastic connecting means 3 is achievedv if, instead of an elastic connection 14, a rigid connection between the counterweight and the housing is provided. With such a construction, it will indeed be possible to provide a larger band width, but also a lower efficiency would re sult, so that according to the particular purposes for which the transducer of the invention is designed, the choice will be made between an elastic connection 14 for interconnecting the counterweight 13 with the housing part 15, or a rigid connection between the parts 13 and 15.

A further possibility for rendering the transducer resistant to high pressure while at the same time providing an elastic connection 3, or 3 and 14, which is as soft as possible, so that in this way the smallest possible loss of energy to the housing 4 is achieved, resides in designing the pressure resistance of the elastic connecting means 3, or 3 and 14, with a narrow tolerance at the range where the maximum operating depth is to be expected, and providing a protecting means which, when the maximum permissible stressing of the elastic means is exceeded, will protect against damaging the transducer because of the narrow tolerance of the stressing range of the elastic connecting means. For example, this protective means can be provided by choosing the width of the radiation-shielding gap 5 in such a way that at its narrowest part it is only so wide that when the diaphragm is loaded to such an extent that the opposed side surfaces of the shielding gap engage each other, the elastic connecting means 3, or 3 and 14, between the diaphragm and the housing has not yet reached its yield point. However, the annular shielding gap or chamber must be selected at a size great enough so that during normal operations free oscillatory motion of the diaphragm is not prevented.

The construction according to this feature can, for eX- ample, be carried out in such a way that behind the diaphragm part 2, the housing is provided with an annular stop shoulder 55 which is directed toward a cooperating annular stop shoulder 56 of the diaphragm part 2. The shoulder 55 of the housing is situated in the path of inward movement of the shoulder 56 of the diaphragm part 2, and the distance between the

annular shoulders

55 and 56 is selected so as to be great enough during normal operation to provide for unrestricted free oscillatory movement of the diaphragm. On the other hand, the distance between the stop shoulders 55 and 56 is selected to be small enough so that when an excessive pressure on the diaphragm, which would otherwise result in overloading the elastic connecting means 3 and 14, is encountered, the stop shoulder 56 engages the stop shoulder 55 to prevent damaging of the elastic connecting means.

The safety of the transducer, against being damaged at the highest permissible pressures, is further enhanced by providing for the compressible sealing means 16 also a limiting stop shoulder arrangement which will limit the extent to which the sealing means 16 can be compressed by the displacement of the

housing parts

4 and 18 toward each other. For this purpose the housing part 4 is'provided with a stop shoulder 17 directed toward an annular surface 17a of the housing part 18, so that these

surfaces

17 and 17a directly engage each other after the sealing structure 16 has been compressed to a predetermined extent.

As pointed out above, the elastic sealing structure is situated between the

housing parts

4 and 18 and is formed from the protective coating 11. In addition, it is possible to further protect the elastic seal 16 by way of an outer relatively wide elastic band 19 which surrounds and engages the coating 11 and extends across the latter at its portions which extend inwardly to form the seal 16. The

surfaces

17 and 17a define between themselves the narrow gap 52, and the gap 53 between the housing part 15 and the housing part 18 isof the same thickness as the gap 52, so that at average pressures the sealing structure 16 will be compressed, placing the

surfaces

17 and 17a in engagement with each other and thus placing the inner housing part 15 directly in engagement with the housing part or cover 18, so that the cement connection between the inner housing part 15 and the housing part 14, as well as the elastic sealing structure 16, is not stressed by the hydrostatic pressure acting between'the diaphragm' and the housing this is brought about by an additional annular body 24, which serves to complete the housing and extend into the annular groove which would be present without the body 24. It is the inner surface of this body 24, which forms a part of the housing, which defines the outer limit of the annular gap 5. With this construction there is, on the one hand, sufficient space for machining the surfaces which determine the size of the gap 5, and, on the other hand, it is possible to maintain for this gap an extremely small size. The body 24 can, for example, be made up of a number of elements which are of arcuate configuration and which are arranged together so as to form a complete ring. Thus, with this construction it is possible to insert the individual elements of the ring 24 radially into the position indicated in FIG. 3. For the purpose of making the diaphragm 2 quite rigid while at the same time as light as possible, it is preferably composed of a light metal and tapers towards its center, as indicated in FIG. 3.

In FIG. 1 the

diaphragm

2, 2a was composed of a pair of elements afiixed to each other and serving to complete the formation of the gap 5, while in FIG. 3 it is the body 24 which serves as the element for completing the housing part 4 and forming the gap 5. The invention, however, can also be realized in the form of a combination of these features (FIG. 15) inasmuch as the known diaphragm 2b shown in FIG. 15 as well as the known housing 4b illustrated therein, are both completed by additional ele ments 49 and 50, respectively, which are afiixed respectively to the diaphragm element 2b and housing element 4b, and which have the configuration shown in FIG. 15 so as to form the gap 5. In this way, with the process of manufacture indicated in FIG. 15, it is possible to make a transducer according to our invention from a known, conventional transducer construction. Thus, with this particular embodiment the structure shown below the dotted line 48 in FIG. 15 is readily available in the form of a complete transducer which is conventional, and this conventional transducer structure can be modified to have the structure of the present invention by completing the transducer structure in the manner shown in FIG. 15 and described above, so that in this way manufacturing procedures which are conventional and which have been widely used up to the present time can be maintained for the most part without any change.

Of particular advantage is the feature of the transducer of the invention according to which the peripheral edge of the diaphragm, at its outer, forwardly directed surface is at least approximately coextensive with the outer periphcry of the housing at its top end. In this way the emitting or receiving surface 8 is of the same size as, or approximately of the same size, as the largest cross-sectional area of the transducer housing situated behind the forwardly directed diaphragm surface, or of the element such as the element 24 which completes the housing so as to form the gap 5. This construction is of particular significance when a plurality of transducers are arranged in a group since with this construction it is possible to provide a group of transducers where the individual transducers of the group are arranged next to each other without any interfering intermediate chambers therebetween.

Where a plurality of oscillators are arranged in a group, the problem of mounting and holidng the plurality of oscillators is of considerable significance. The

mounting must be constructed in such a way that the emitting or receiving surfaces of the group-of oscillators have no dead spaces resulting from the structure of the mounting which supports the plurality of transducers. For this purpose, there is provided in one example of the structure of our invention, in the exterior surface of the side wall portions of the transducer housings, depressions 26, indicated in FIG. 1. These depressions of several housings are situated in a common plane with adjoining depressions of adjoining housings communicating with each other so as to form passages for receiving the connecting means for interconnecting the several housings to each other. Thus, there is shown in FIG. 4 an example of a suitable structure for interconnecting a plurality of transducers. The transducers 27 shown in FIG. 4 are of square cross section, so that they can be placed next to each other without any gaps therebetween. The dotted lines 28 indicate the outer peripheral edges of the forwardly directed, outer emitting (or receiving) surfaces of the diaphragms, and it is apparent that in each transducer the area of its forwardly directed outer surface 8 fills almost the entire cross section of the transducer. The transducers 27 are individually inserted into a mounting plate 29 which has the configuration of a double H. Thus, as may be seen from FIG. 4, the mounting plate 29 has the configuration of a double H where the two Hs have a common leg joining the pair of Hs to each other. As a result, the individual transducers can he slipped along the legs of the mounting plate 29 with these legs slidably received in the grooves 26, and of course the outer legs 30 of the mounting plate will be situated at the exterior of the assembly. After the plurality of transducers have been assembled together on the legs of the plate 29, a pair of transverse end bars 31 are fixed to the free ends of the legs of the plate 29, as by being bolted thereto, so that in this way, it is possible to mount the plurality of transducers quite close to each other in a group occupying the smallest possible amount of space. Of course, the structure of the invention is not limited to transducers having square diaphragms, inasmuch as transducers having rectangular or hexagonal, as well as circular, diaphragms can also be used.

The individual transducers can also be grouped to gether compactly in another way. For example, a mounting plate is formed with openings spaced from each other by distances suitable for the individual transducers, and the transducers are interested into these openings from the front of the mounting plate, and are affixed to the mounting plate at their rear portions, for example at the rear,housing oncover parts 18. The transducer may be affixed, for example, by adhesive or bolts. One possibility resides also in making the mounting plate 29a (FIG. 16) so thick that the openings or bores 40 formed for the individual transducers have a sufficient depth to constitute in and of themselves the interior portions of the transducers, so that these bores 40 can receive in their interiors the components of the several transducers in order to replace the individual housings of the plurality of transducers. Therefore, in the embodiment of FIG. 16, there is but a single wall 29a formed with the plurality of openings 40 which respectively receive the plurality of transducers, none of which include their own housings, inasmuch as all of the transducers have in this embodiment a common housing 29a. With this construction the radiation-shielding chambers of adjoin: ing transducers communicate with each other so that each radiation-shielding chamber 5a is defined by the rearwardly directed surfaces 7a and 7b at the peripheries of the diaphragms of at least a pair of adjoining transducers. A coating 11a, which is common to all of the diaphragms, seals, together with the elastic covering elements 9a, the radiation-shielding chambers 54.

Further embodiments of our invention are illustrated by way of example in the figures hereinafter referred to. In these embodiments, the diaphragms are indicated by the reference character 2, the elastic connection means by the reference character 3, and the transducer housing parts by the reference character 4. The elastic covering for the annular gap is indicated by the reference characters 9 or 9a, while the plastic or rubber covering for the entire assembly is not illustrated. The structures for defining the outer limits of the radiation shielding chamber, as well as for forming the elastic connection between the diaphragm and the housing and for forming the 1 1 shielding chamber itself, can take the widest variety of forms.

In FIGS. 5 and 11, an annular body 32 of rectangular cross section extends forwardly from and forms part of the side wall of the

housing part

4,50 as to determine the outer limits of the shielding chamber 5. This ring 32 can be made of a strong high quality material and thus can be manufactured-with a relatively small thickness. Furthermore, this structure has the advantage of being capable of being mounted around the diaphragm 2 as a single one-piece body, so that dividing of the ring 32 up into a plurality of elements is not required. In FIG. 11, the ring or body 32 can in many cases be dispensed with if the elastic connection 40 is situated at the outer periphery of thediaphragm 2. However, the ring 32 of FIG. 11 will serve to completely eliminate residual radiations which will eventually be present. In the embodiment of FIG. 6, therannular body 33, which completes the housing part 4, has a tapered cross section so that it is of a small thickness at its outer free edge situated substantially at the same plane as the forwardly directed outer surface of the diaphragm 2. Also, stepped cross sectional areas for the ring may be provided, as is shown by the ring 34 in FIG. 7. Such a stepped construction is also shown for the ring 35 in FIG. 8, the ring 36in FIG. 9, and also the ring 37 inFIG. 10. It will be noted, however, that in the case of the ring 37 of FIG. 10, the dimension of the ring in a direction parallel to the forwardly directed outer surface of the diaphragm is greater than its dimension in a direction parallel to the longitudinal central axis of the transducer. In the case where a plurality of transducers are combined into a group, it is possible to have a common body perform the functions of the individual rings 32-37 shown in FIGS. 5-10, respectively. In addition, it is not essential that the pressure-resistant exterior closure of the radiation sealing chamber be made of an elastic covering material 9 or 9a, as indicated in FIGS. 5-7. Instead, an additional elastic connection 38 (FIG. 8) or 39 (FIG. 9) can be provided between the diaphragm 2 and the housing 4, that is, between the diaphragm 2 and the

rings

35 and 36 of the embodiments of FIGS. 8 and 9, so as to close off the outer end of the shielding gap with this further elastic connectingstructure. In this case, it is of advantage in the embodiment of FIG. 8 to pre-stress the elastic connecting means 38 when the annular body 35 is mounted in the position indicated in FIG. 8, so that during oscillatory movement of the diaphragm the elastic means 38 cannot become separated from the annular body 35. Of course, it is also possible, if desired, to fasten the elastic means 38 to the body 35 by soldering, welding, cementing, or

the like.

Also, the elastic connecting means which connects the diaphragm to the housing can take many different forms and arrangements. In the embodiment of FIGS. 1 and 3 as well as FIGS. 5-10 and 13-16, the elastic means 3 is situated in a plane normal to .the longitudinal central axis of the transducer and is bendable in a direction transverse to this plane. However, it is not essential that the elastic means be flat and extend along a straight line, since the elastic means can be curved or can have an angular cross section, as is indicated by the elastic means 3 of FIG. 7. Also, it is apparent that the location of the connection between the elastic means 3 and the diaphragm can be varied widely. The elastic connection structures 40 and 41 of FIGS. 11 and 12, respectively, are so formed and arranged that they are situated substantially in a cylinder whose axis includes the longitudinal central axis of the transducer, and these elastic structures are designed to yield in the directions in which they extend, that is, in a direction parallel to the longitudinal central axis of the transducer. Thus, it will be seen that in the embodiments of FIGS. 11 and 12 the elastic means 40 and 41, respectively, are in effect extensions of the side walls of the housing part 4. The elastic means 41 shown in FIG. 12 can either be situated in the illustrated position .where it forms an extension of the exterior surface of the side wall of part 4, or it can be arranged closer to the longitudinal central axis of the transducer, where the inner surface of the elastic means 41 forms an extension of the inner surface of the side wall of the housing part 4. .In the latter construction, the diaphragm 2 of course extends radially outwardly beyond the elastic means 41. For example, the elastic means 40 of FIG. 11,

I or the elastic means 41 of FIG. 12, can be situated at any desired location within the

chambers

42 and 43 while maintainingthe illustrated magnitude of the diaphragm.

One special embodiment of a transducer according to the present invention does not include any elastic connecting means 3 between the diaphragm and the hon-sing. In this case, it is the elastic covering structure 9 which takes over the role of the elastic means, the elastic covering 9 operating together with the plastic or rubber envelope 11, in this case, to perform the function of the elastic connecting means between the diaphragm and the housing, a-s well as to provide a pressure-resistant seal of the interior of the transducer from the exterior thereof. A' construction of this type is illustrated in FIG. 17 in a longitudinal sectional elevation. Referring to FIG.

17, it will be seen that the radiation-shielding chamber 5 has at the right side of FIG. 17 a cross-sectional configuration somewhat different from its configuration illustrated at the left side of FIG. 17, so that FIG. 17 illustrates how it is even possible according to the present invention to provide a radiation-shielding chamber which need not be of uniform cross section circumferentially with respect to the longitudinal central axis of the transducer, although, of course, the transducer may be provided with a uniform cross section of the chamber 5, either conforming to the cross section shown at the right side of FIG. 17 or with that shown on the left side of FIG. 17. In this embodiment, it is to be noted that the transducer housing formed by the

parts

4, 24a, and 18 has a tapered configuration making it possible to arrange the transducer on a curved surface such as a cylindrical surface. Inother words, where the supporting plate which carries a plurality of transducers is curved so as to extend along a cylinder, for example, if the housings of the transducers have the tapered configuration illustrated in FIG. 17, they can be arranged in close proximity to each other in side-by-side relation with a minimum of spacing therebetween, even though the plate, whose legs are received in the grooves 26 as described above, is not fiat but instead extends along a cylinder or other suitable curve. Thus, even under these conditions, the transducers can be arranged in very close proximity to each other. Thus the emitting or receiving surfaces of the diaphragm can under these conditions also have a minimum of space therebetween. The parts which are illustrated in FIG. 17 and which correspond to those of FIGS. 1 and 3, for example, are designated by the same reference characters. Thus, the housing part 4 supports the member 24a, which forms part of the housing and which defines the outer limit of the annular shielding chamber 5. As indicated above, there is no elastic connecting means integral with the housing, for example, and instead the elastic connecting means is formed bythe yieldable sealing structure 9a, which closes the outer end of the chamber 5, this yieldable sealing structure being itself covered by the plastic or rubber envelope 11 which also participates in the elastic mounting of diaphragm 2 with respect to the

housing

4, 24a, 18. -It will be noted that with this construction the envelope 11 has between the housing parts 4 and -18 inwardly directed flanges forming the elastic means 16. Also FIG. 17 shows the cable 20 extending through the tubular cable outlet of the cap or housing part 18 where the tension-relieving spring ring 21 is provided, and FIG. 17 also fragmentarily illustrates the electrical conductors 22. Furthermore, the active element 1 connected to the diaphragm 2 is illustrated, and of course this important element is in turn connected to the'counterweight 13 which is connected by the elastic means 14 to the housing part 4.

In the particular embodiment shown in FIG. 17 it is possible for the transducer housing part 4 to have at its lower portion, in the region of the mounting groove 26, a circular cross section while, for example, the diaphragm 2 as well as the housing part 24a situated directly behind the diaphragm have a hexagonal cross section. Therefore, with such a construction the housing part 24a not only participates in theformation of the radiation-shielding chamber 5, but in addition it serves to provide a transition between the different cross sectional configurations of the diaphragm 2 and the housing 4.

Furthermore, FIGS. 5-16 demonsetrate that the pressure-resistant radiation-shielding chamber need not be limited to the particular configuration illustrated. in FIGS. 1-3. In the first place, the annular gap 5 of FIGS. 1-3, can extend along and form part of acone or a sphere, as well as a cylinder. Also, the annular gap can have one or more sharp angles in its cross sectional configuration as well as different widths in its cross sectional configuration. Moreover, the radiation-shielding chamber need not necessarily be separated from the interior of thehousing, as is demonstrated by FIGS. -12, where the sound or radiation shielding chamber includes the portion 42 (FIGS. 10 and 11) and 43 (FIG. 12). In the embodiment of FIG. 12, the entire radiation shielding chamber 43 communicates with the housing interior 44. In fact,

this radiation-shielding chamber-43d FIG. 12 is formed from the wall of the housing itself, taking the form of a groove which is cut into the side wall of'the housing. FIGS. 10 and 11, however, demonstrate that the radiation-shielding chamber can include two or more chamber portions which do not communicate with each other. Thus, it will be seen that in FIGS. 10 and 11 the radiation-shielding chamber.

portions

5 and 42 do not in fact communicate with each other.

In the special embodiment which is illustrated-in FIG. 14, the outer peripheral edge of the diaphragm 2 extends all the way up to the exterior side surface of the transducer and in fact forms part of the exterior side surface of the transducer. Thus, the exterior side surface of the diaphragm 2 of FIG. 14 is situated in a longitudinal extension of the exterior side surface of the body 51 which completes the side wall of the housing part 4 and which contributes to the formation of the radiation-shielding gap 5. Thus, in this embodiment the radiation-shielding gap 5 has an outer end which is situated at the side wall of the transducer and which communicates with the exterior side surface of the transducer. In the embodiment of FIG. 13, the radiation-shielding chambers 45 also open onto the exterior surfaces of the transducers, but in the illustrated arrangement of a group of transducers the adjoining chambers 45 communicate with each other so that one transducer in effect forms the outer limit for the radiation-shielding chamber of an adjoining transducer. However, the entire group of transducers is surrounded by the wall 46, which, of course, limits the outer portions of the radiation-shieldingchambers of the outer transducers of the group.

A tongue-and-groove mounting structure 47 is provided for the plurality of transducers in the embodiment of FIG.

Thus, after the plurality of transducers are assembled so that. their grooves, similar to the grooves 26, communicate with each other, the elongated bars or legs 47 of the mounting structure are inserted into these grooves to form a mounting as illustrated in FIG. 13. The diaphragms of the individual transducers can be arranged so that each will be free to move independently of the remaining diaphragms, although, it is also possible to provide an arrangement where the diaphragms are capable of being interconnected for common movement. Such an interconnection between a plurality of diaphragms can be provided through a structure which may be quite similar to a tongue-and-groove arrangement as shown at 47 in FIG. 13.

The invention, of course, is not limited to the particular embodiments described above and shown in the drawings. Many variations are possible without departing from the invention, and the transducers canbe used for many different purposes invaddition to those referred to above. Thus, the transducers of the invention can be used in the same way as hereinbefore described at regions of relatively low static pressure, as, for example, in water of low depth. By reason of the particular construction hereinbefore described and shown in the drawing, the transducers of the invention are mechanically particularly robust and stable, so that the largest possible emitting or receiving area for the radiations is provided within a given physical space.

Although in all the embodiments described above the annular shielding chamber 5 is simply disclosed as being filled with a gas, such as air, it is also possible to provide within the shielding gap 5, a porous material which fills the gap 5 and which has gas-filled cells, for example, while being relatively soft and elastic so that there is no substantial resistance-to displacement of the diaphragm resulting from the porous filling material situated in the gap 5 with such a construction.

It is apparent that in the aforedescribed structure of the invention, the emitting areas formed by the forwardly directed outer surfaces of the diaphragms ofa group of transducers, because they can be effectively arranged so close to each other, make it possible to provide an output of a beam of sharply concentrated primary radiations without detracting essentially therefrom with secondary radiations.

We claim:

1. Electroacoustic transducer for transmitting and receiving sonic waves in water, suitable for high water pressure and for arrangement in transducer groups, comprising a housing having a front wall forming the frontal side thereof and a thick side wall having an inside surface in said housing, a piston-type oscillatory diaphragm structure joined with said housing by pressure tight means and forming the front wall thereof, said pressure tight means comprising elastic means in interconnecting said diaphragm structure and housing to support said diaphragm structure for oscillatory movement relative to said housing, an oscillator member disposed in said housing be hind said diaphragm structure and mechanically con nected therewith, said diaphragm structure having a rear surface in said housing and a front face covering substantially the entire frontal side of said housing and extending to substantially the outer limits of the side wall of said housing, said diaphragm structure and said housing forming a sound-shielding and pressure-tight interspace behind said diaphragm front face and near and around the perimeter of said diaphragm structure between part of the rear surface of said diaphragm structure and part of the inside surface of the side wall of said housing and extending substantially to the front face of said diaphragm structure.

2. An electroacoustic transducer as recited in claim 1, wherein said elastic means defines part of said interference-shielding interspace.

3. A transducer as recited in claim 1, wherein said interspace has an outer substantially annular end opening into the front wall of said housing, and further comprising resilient sealing means pressure sealing said interspace at its outer end at said front wall of said housing.

4. A transducer as recited in claim 3, and wherein said resilient sealing means is a separate plastic covering material through which sound can freely pass and which completely envelops the transducer and which is situated over and covers said outer end of said interspace.

5. A transducer as recited in claim 3, wherein said resilient sealing means forms a connection between said diaphragm and another component of said transducer for supporting said diaphragm for oscillatory movement.

6. A transducer as recited in claim 3-, and wherein said resilient sealing means is of angular cross section and is situated at the exterior of the transducer at the peripheral edge of the front wall of said housing.

7. An electroacoustic transducer for transmitting and receiving sonic waves in water, suitable for high water pressure and for arrangement in transducer groups, comprising a housing having a front wall forming a frontal side thereof and a thick side wall, said thick side wall having an outside surface forming the cross sectional area of said housing in the vicinity of said front wall, a plurality of coactive components in said housing arranged along a predetermined longitudinal central axis of the transducer, said components including a dia phragm joined with said housing by pressure-tight means and having an outer forwardly directed surface adapted to send and receive radiations, said pressure tight means comprising elastic means interconnecting said diaphragm and housing to support said diaphragm for oscillatory movement relative to said'housing, said surface of said diaphragm having an area in a plane normal to said axis substantially equal to the cross sectional area of said housing' in the vicinity of said front wall, said diaphragm having a peripheral edge defining the outer limit of said forwardly directed outer surface thereof and said diaphragm having in the region of said peripheral edge thereof additional surface area situated to the rear of said forwardly directed diaphragm surface, one of said components forming part of the side wall of said housing and being situated adjacent but spaced from said additional surface area of said diaphragm decreasing in thickness to a small fraction of the thickness of the remainder of said side wall of said housing as it approaches the front wall of said housing and extending to form a peripheral edge of said front wall of said housing and defining with said additional surface area of said diaphragm a pressure-resistant chamber for shielding out interfering radiations of said additional surface area of said diaphragm, said chamber extending substantially to the peripheral edge of the front wall of said housing formed by said one of said components forming part of said side wall of said housing.

8. A transducer as recited in claim 7, wherein said elastic means forms a wall which has a surface defining part of said chamber, said chamber opening into the front wall of said housing, and further comprising resilient sealing means pressure sealing said chamber at its opening at said front wall of said housing.

9. A transducer as recited in claim 8, wherein said wall seperates a hollow interior of said housing from said chamber.

10. An electroacoustic transducer as recited in claim 7, wherein said elastic means is situated behind said forwardly directed surface of said diaphragm, said chamber opening into the front wall of said housing, and further comprising resilient sealing means pressure sealing said chamber at its opening at said front wall of said housing.

11. A transducer as recited in claim 10, wherein said diaphragm has an inner rearwardly directed surface, said elastic means being situated in the region of said inner rearwardly directed surface of said diaphragm.

12. A transducer as recited in claim 7, wherein said chamber has the configuration of a narrow annular gap surrounding said axis, said chamber opening into the front wall of said housing, and further comprising resilient sealing means pressure sealing said chamber at its opening at said front wall of said housing.

13. A transducer as recited in claim 12, wherein said gap extends from said elastic means, on the one hand, outwardly to said forwardly directed surface of said diaphragm, on the other hand.

14. A transducer as recited in claim 12, wherein said component comprises a housing portion separate from and connected tothe remainder of said housing and defining an outer limiting surface of said gap, said portion of said housing-being separable from and separately connected thereto in order to facilitate the manufacture of the surfaces which-define said gap.

15. A transducer as recited in claim 7, said resilient sealing means extends along and forms part of a cylinder whose axis coincides with said longitudinal central axis.

16. A transducer as recited in claim 7, wherein said housing portion extends forwardly beyond said elastic means and surrounds said diaphragm, said forwardly extending portion of said housing having an inner funnel-shaped surface directed toward and spaced from said additional surface area of said diaphragm to define therewith said shielding chamber, said forwardly extending portion of said housing terminating substantially at the same plane as said outer peripheral edge of said forwardly directed surface of said diaphragm.

17. A transducer as recited in claim 16, wherein a carrier is connected by said elastic means to said housing, said diaphragm being cemented to said carrier.

18. A transducer as recited in claim 17, wherein said diaphragm has a surface directed toward said carrier formed with recesses for receiving cement which fixes said diaphragm to said carrier.

19. An electroacoustic transducer assembly comprising a plurality of electroacoustic transducers arranged in a group and each comprising a housing having a front wall forming the frontal side thereof and a thick side wall, said thick side wall having an outside surface forming the cross sectional area of said housing in the vicinity of said front wall, a plurality of components in said housing arranged along a predetermined longitudinal central axis and cooperating together to form an operative transducer, said components of each transducer including a diaphragm joined with said housing by pressure tight means and having an outer forwardly directed surface adapted to send and receive radiations, said pressure tight means comprising elastic means interconnecting said diaphragm and housing to support,said diaphragm for oscillatory movement relative to said housing, said diaphragm having an outer peripheral edge defining the outer limit of said surface, said surface when projected onto a plane normal to said axis having an area which is at least sub stantially coextensive with the largest, said group of transducers being arranged with all of said forwardly directed outer surfaces thereof situated adjacent each other so that said peripheral edges of said forwardly directed surfaces are close to each other providing a minimum of space between said diaphragms of the transducers which form said" group of transducers, and each transducer having additional surface area in the region of said peripheral edge of its forwardly directed outer surface, a second one of the components of each transducer forming part of the side wall of said housing and defining with said additional surface area thereof a shielding chamber for shielding interfering radiations from said additional surface area of each diaphragm decreasing in thickness to a small fraction of the thickness of the remainder of said side wall of said housing as it approaches the front wall of said housing and extending to form a peripheral edge of said front wall of said housing, said chamber extending substantial-ly to the peripheral edge of the front wall of said housing formed by said one of said components forming part of said side wall of said housing.

20. A transducer assembly -as recited in claim 19, wherein said. components of each transducer includes a transducer housing formed at'an exterior portion with a depression, and said depressions'of all of said housings cooperating to form predetermined passages, and connecting means extending into said passages formed by said depressions for interconnecting said housings of said plurality of transducers to each other with a minimum of space therebetween so as to maintain the space between.

the housings of the group of transducers at a minimum.

21. A transducer assembly as recited in claim 19, further comprising an envelope which covers and is common to the group of transducers.

22. A transducer assembly as recited in claim 19, further comprising a curved base plate which carries the entire group of transducers.

23. An electroacoustic transducer, comprising a plurality of coactive components arranged along a predetermined longitudinal central axis of the transducer and having an outer side surface, said components including a diaphragm having an outer forwardly directed surface adapted to send and receive radiations, and said surface of said diaphragm when projected onto a plane normal to said axis having in said plane an area which is at least substantially coextensive with the largest area projected onto said plane by any other one of said components, said diaphragm having a peripheral edge defining the outer limit of said forwardly directed outer surface thereof and said diaphragm having in the region of said peripheral edge thereof additional surface area situated to the rear of said forwardly directed diaphragm surface, and at least a second one of said components being situated adjacent but spaced from the additional surface area of said diaphragm and defining with said additional surface are-a a pressure-resistant chamber for shielding out interfering radiations of the additional surface area of said diaphragm, said chamber having the configuration of a narrow annular gap surrounding said axis and having an annular outer open end opening onto the outer side surface of said components.

24. An electroacoustic transducer, comprising a plurality of coactive components arranged along a predetermined longitudinal central axis of the transducer, said components including a diaphragm having an outer forwardly directed surface adapted to send and receive radiations, and said surface of said diaphragm when projected onto a plane normal to said axis having in said plane an area which is at least substantially coextensive with the largest area projected onto said plane by any other one of said components, said diaphragm having a peripheral edge defining the outer limit of said forwardly directed outer surface thereof and said diaphragm having in the region of said peripheral edge thereof additional surf-ace area situated to the rear of said forwardly directed diaphragm surface, and at least a second one of said components being situated adjacent but spaced from the additional surface area of said diaphragm and defining with said additional surface area a pressure-resistant chamber for shielding out interfering radiations of the additional surface area of said diaphragm, said chamber having the configuration of a narrow annular gap surrounding said axis and having outer and inner ends, the outer end of said annular gap being situated nearer to the forwardly directed surface of said diaphragm than the inner end of said gap and said gap having a non-uniform width between the ends thereof but having its minimum width at its outer end and resilient sealing means pressure sealing said gap at its outer end at the outer forwardly directed surface of said diaphragm.

25. An electroacoustic transducer, comprising a plurality of coactive components arranged along a predetermined longitudinal central axis of the transducer, said components including a housing, a diaphragm having an outer forwardly directed surface adapted to send and receive radiations, and said surface of said diaphragm when projected onto a plane normal to said axis having in said plane an area which is at least substantially coextensive with the largest area projected onto said plane by any other one of said components, said diaphragm having a peripheral edge defining the outer limit of said forwardly directed outer surface thereof and said diaphragm having in the region of said peripheral edge thereof additional surface area situated to the rear of said forwardly directed diaphragm surface elastic means connecting said diaphragm to said housing for oscillatory movement relative thereto, said elastic means being adapted to yield in a narrow range situated in the region of the maximum pressure resistance of which said elastic means is capable, protective means for protecting said elastic means against failure in the region of said maxi mum pressure to which said elastic means can besubjected before failing, and said housing being situated adjacent but spaced from the additional surface area of said diaphragm and defining with said additional surface area a pressure-resistant chamber for shielding out interfering radiations of the additional surface area of said diaphragm, said chamber having the configuration of a narrow annular gap having a predetermined minimum width and the portions of said diaphragm and housing which determine said minimum width of said gapforming said protective means and engaging each other before the flow limit of said elastic means is reached when the latter is subjected to pressure.

26. An electroacoustic transducer, comprising a plurality of coactive components arranged along a predetermined -longitudinal central axis of the transducer, said components including a housing, a diaphragm having an outer forwardly directed surface adapted to send and receive radiations, and said surface of said diaphragm when projected onto a plane normal to said axis having in said plane an area which is at least substantially coextensive with the largest area projected onto said plane by any other one of said components, said diaphragm having a peripheral edge defining the outer limit of said forwardly directed outer surface thereof and said diaphragm having in the region of said peripheral edge thereof additional surface area situated to the rear of said forwardly directed diaphragm surface elastic means connecting said diaphragm to said housing for oscillatory movement relative thereto, said elastic means being adapted to yield in a narrow range situated in the region of the maximum pressure resistance of which said elastic means is capable, protective means for protecting said elastic means against failure in the region of said maximum pressure to which said elastic means can be subjected before failing, and said housing being situated adjacent but spaced from the additional surface area of said diaphragm and defining with said additional surface area a pressure-resistant chamber for shielding out interfering radiations of the additional surface area of said diaphragm, said housing comprising a pair of housing parts separate from but located closely adjacent to each other, and said protective means being formed by a compressible seal situated between and engaging said housing parts and stop surfaces res ectively forming portions of said housing parts and engaging each other to limit the extent to which said seal can be compressed as well as to limit the extent of stressing of said elastic means, said elastic means being operatively connected with one of said housing parts so that said one housing part will compress said seal when the maximum possible stressing of said elastic means, before failure thereof, is approached.

27. An electroacoustic transducer assembly comprising a plurality of electroacoustic transducers arranged in a group and each comprising a housing having a front wall forming the frontal side thereof and a thick side wall, a plurality of components in said housing arranged along a predetermined longitudinal central axis and co operating together to form an operative transducer, said components of each transducer including a diaphragm joined with said housing by pressure tight means and having an outer forwardly directed surface adapted to send and receive radiations, said pressure tight means comprising elastic means interconnecting said diaphragm and housing to support said diaphragm for oscillatory movement relative to said housing, said diaphragm having an outer peripheral edge defining the outer limit of said surface, said surface when projected onto a plane normal to said axis having an area which is at least substantially coextensive wtih the largest area projected onto being arranged with all of said forwardly directed outer surfaces thereof situated adjacent each other so that said peripheral edges of said forwardly directed surfaces are close to each other providing a minimum of space between said diaphragms of the transducers which form said group of transducers, and each transducer having additional surface area in the region of said peripheral edge of its forwardly directed outer surface, a second one of the components of each transducer forming part of the side wall of said housing and defining with said additional surface area thereof a shielding chamber for shielding transferring radiations from said additional surface area of each diaphragm, said chamber extending substantially to the outer surface of said'diaphragm, each transducer limiting the shielding chamber of its adjoining transducers, and limiting means surrounding the entire group of transducers for limiting the sound-shielding chambers of the transducers situated along the exterior of the group of transducers.

28. An electroacoustic transducer assembly comprising a plurality of electroacoustic transducers arranged in a group and each comprising a housing having a front wall forming the frontal side thereof and a thick side wall, a plurality of components in said housing arranged along a predetermined longitudinal central axis and cooperating together to form an operative transducer, said components of each transducer including a diaphragm joined with said housing by pressure tight means and having an outer forwardly directed surface adapted to send and receive radiations, said pressure tight means comprising elastic means interconnecting said diaphragm and housing to support said diaphragm for oscillatory movement relative to said housing, said diaphragm having an outer periphereal edge defining the outer limit of said surface, said surface when projected onto a plane normal to said axis having an area which is at least substantially co extensive with the largest area projected onto said plane by said housing, said group of transducers being arranged with all of said forwardly directed outer surfaces thereof situated adjacent each other so that said peripheral edges of said forwardly directed surfaces are close to each other providing a minimum of space between said diaphragms of the transducers which form said group of transducers, and each transducer having additional surface area in the region of said peripheral edge of its forwardly directed outer surface, a second one of the components of each transducer forming part of the side wall of said housing and defining with said additional surface area thereof a shielding chamber for shielding transferring radiations from said additional surface area of each diaphragm, said chamber extending substantially to the outer surface of said diaphragm, the shielding chambers of adjoining transducers communicating with each other to form common shielding chambers defined in part by the additional surface are-as of said diaphragms.

References Cited by the Examiner UNITED STATES PATENTS RODNEY D. BENNETT, Plimary Examiner.

CHESTER L. JUSTUS, Examiner. G. M. FISHER, B. L. RIBANDO, Assistant Examiners.

Claims

1. ELECTROACOUSTIC TRANSDUCER FOR TRANSMITTING AND RECEIVING SONIC WAVES IN WATER, SUITABLE FOR HIGH WATER PRESSURE AND FOR ARRANGEMENT IN TRANSDUCER GROUPS, COMPRISING A HOUSING HAVING A FRONT WALL FORMING THE FRONTAL SIDE THEREOF AND A THICK SIDE WALL HAVING AN INSIDE SURFACE IN SAID HOUSING, A PISTON-TYPE OSCILLATORY DIAPHRAGM STRUCTURE JOINED WITH SAID HOUSING BY PRESSURE TIGHT MEANS AND FORMING THE FRONT WALL THEREOF, SAID PRESSURE TIGHT MEANS COMPRISING ELASTIC MEANS IN INTERCONNECTING SAID DIAPHRAGM STRUCTURE AND HOUSING TO SUPPORT SAID DIAPHRAGM STRUCTURE FOR OSCILLATORY MOVEMENT RELATIVE TO SAID HOUSING, AN OSCILLATOR MEMBER DISPOSED IN SAID HOUSING BEHIND SAID DIAPHRAGM STRUCTURE AND MECHANICALLY CONNECTED THEREWITH, SAID DIAPHRAGM STRUCTURE HAVING A REAR SURFACE IN SAID HOUSING AND A FRONT FACE COVERING SUBSTANTIALLY THE ENTIRE FRONTAL SIDE OF SAID HOUSING AND EXTENDING TO SUBSTANTIALLY THE OUTER LIMITS OF THE SIDE WALL OF SAID HOUSING, SAID DIAPHRAGM STRUCTURE AND SAID HOUSING FORMING A SOUND-SHIELDING AND PRESSURE-TIGHT INTERSPACE BEHIND SAID DIAPHRAGM FRONT FACE AND NEAR AND AROUND THE PERIMETER OF SAID DIAPHRAGM STRUCTURE BETWEEN PART OF THE REAR SURFACE OF SAID DIAPHRAGM STRUCTURE AND PART OF THE INSIDE SURFACE OF THE SIDE WALL OF SAID HOUSING AND EXTENDING SUBSTANTIALLY TO THE FRONT FACE OF SAID DIAPHRAGM STRUCTURE.