US2450412A - Device for transmitting and receiving compressional energy - Google Patents

Description

0st. 5, 1948. H. BENIOFF 2,459,412

DEVICE FOR TRANSMITTING AND RECEIVING CQMPRESSIONAL ENERGY I 4 Sheets-Sheet 1 Filed Nov. 20, 1942 INVENTOR BY ps0 BENIOFF ATTORNEY Oct- 5, 1948. H. BENIOFF 2,450,412

DEVICE FOR TRANSMITTING AND RECEIVING CONPRESSIQNAL ENERGY Filed Nov. 20, 1942 4 Sheets-Sheet 2 D F v W 5 a 3 :5 w .0 N6 O 5 W 3 H 4 Sheets-Sheet 3 Get- 5, 1948. H. BENIOFF 2,450,412

DEVICE FOR TRANSMIT NG AND RECEIVING COMPRES L ENERGY INVENTOR Hucao BENIQFF ATTORNEY Oct 5, 1948. H. BENIOFF DEVICE FOR TRANSMITTING AND RECEIVING COMPRESSIONAL ENERGY Filed Nov. 20, 1942 4 Sheets-Sheet 4 4 an m II, i v

49/ W lNX-ENTOR 15 4 Huge BENIOFF' I BY 8,11%! We? ATTORNEY Patented a. s, 1948 DEVICE FOR TRANSMITTING AND RECEIV- ING COMPRESSIONAL ENERGY na, CallL, assignor, by

Hugo Benioff,- Pasade mesne assignments, to

Submarine Signal Company, Boston, Mesa, a corporation of Delaware Application November 20, 1942, Serial No. 466,535 I 8 Claims.

1 The present invention relates to improvements in subaqueous apparatus and finds its chief merits and advantages over the prior art in improvements and construction providing an improved electroacoustic transducer capable of being used under great hydrostatic pressure.

Further merits of the present invention are found in means of acoustically coupling the vibration-transducing means with the water medium. In the present invention the radiating member comprises a plurality of similar longitudinally vibrating passive resonant elements closely spaced one from the other in a symmetrical pattern and joined in a flange embracing a plane in which the nodal points for all the resonant elements lie.

The resulting structure is such that the radiation takes place from the outer surface of the longitudinal resonant elements in such a fashion that the amplitude of each element may be independently controlled by the generating means producing the longitudinal resonant vibrations.

A still further object of the present invention is to provide an electroacoustic transducer capable of withstanding not only normally high hydrostatic pressures, but also excessively high impulse pressure such as-may be caused by explosions and the like in the medium in the vicinity of thedevice,

A further advantage in the construction of the present invention is that the entire operating unit comprising the radiating element and the transiating element are all supported by the single nodal plane mounting and that the supporting case carries projecting members in opposed relation to the radiating units at many points so that if an excessive shock is received, as, for instance, by the discharge of the bomb, the radiating memher will seat itself against these supporting elements and prevent damage to the translating units.

Further advantages and merits of the present invention will be more fully explained and understood in connection with the drawings showing an embodiment of the same in which Fig. 1 shows a plan view of an embodiment of the invention; Fig. 2 shows a section taken on the line 2-2 of Fig. 1; Fig. 3 shows a detailed exploded view of the translating unit of Fig. 2 in section; Fig. 4 shows a section taken on the line 4-4 of Fig. 3; Fig. 5 shows a detail section taken on the line 55 of Fig. 2; Fig. 6 shows a modification of the embodiment of Figs. 1, 2 and 5 using a piezoelectric translating element; Fig. '7 shows a modification of a detail of the present invention; Figs. 8 and 8a show further modifications of a detail of 2 v the invention; Figs. 9, 10 and 11 show further modifications of details of the invention; and Fig, 12 is a section taken on Fig. 11 but extending over a than that shown in Fig. 11. I y

In the arrangement shown in the figures described there is provided a casing l of durable metal as, for instance, steel or other suitable material which is covered by an insulating coating greater fragment Hill of cork or the like which extends from the edge of the active diaphragm surface all over the back of the casing. The cover plate 2 has aportion serving as a compressional waveradiating element. The cover plate includes a peripheral flange 3 in which the cover is bolted to the casing by means of a group of rim bolts 4. The cover 2 has projecting from both faces a plurality of projecting blocks 5, 5 which are indicated in Fig. 1 as squares but which may, forms, as, for instance, hexagonal, octagonal, circular or the like. Similarly shaped blocks 6, 6, 6,

etc project from the cover within the casing aligned with the blocks 5. These projecting blocks 5 and 6 may be made integral withthe cover itself or they may be attached to it by suitable bolts or in other known manners. The blocks 5 and 6 form with the supporting flange 3 onehalf wave length resonant. elements and may therefore be used 'as a resonant coupling element with the water to provide eilicient acoustic coupling between the translating element and the water. These may be called passive vibrators as they are coupling units between the medium and the active vibrating elements. If the projecting blocks 5 and B are substantially of the same con struction, then the unit provides at both faces substantially the same vibrational amplitude,

while if one is longer than the other, the end face of the longer unit will have the greater amplitude. For a 20 kilocycle projector these blocks, if made of steel, may have surface dimensions approximately one and one-half inches each way. These dimensions may, of course, be varied but as a whole the size of the blocks may be larger than the adjoining surface of the driving element. A magnetostrictive unit'l is attached, as indicated in Fig. 2, to the end face of the blocks 6 preferably by means of a machine screw 8 passing through the base III of the magnetostrictive element 1 and being screwed into the face of the block 6.

The active magnetostrictive element is made of nickel or some suitable metal and comprises the base section Ill of substantial mass and rigidity which may be circular in section. The

the line l2-l2 of of course, be in other magnetostrictive element 1 has formed on the base ill a section having a conical surface II which is integral at its end with a cylindrical element l2. The thin cylindrical element l2 supports at its end a cylindrical mass member l3, the support being at the center of percussion of the cylinder i3 which is at a point more than a half wave out on the section l3, as indicated in Fig. 3. The magnetostrictive element l, in effect,

therefore, comprises a short cylindrical member to which is joined at each end mass members whose ratio is chosen according to the amplitude transformation desired. Since it is attached to the passive vibrator at an antinodepthis permits a freedom of choice of mass ratios with their corresponding transformation ratios not possible in other structures. The cylindrical members are hollowed to receive the magnetic polarizing member M which may be a magnet of "Alnico" or some such similar material capable of retaining a large permanent magnetizing effect. The permanent magnet it may be a solid cylindrical element fitting concentrically within the cylinders l2 and i3 and supported in a holder i5 which is recessed in its front face at E6 to receive by forced fit the end of the magnet M1. The holder it is retained in the support i! by means of the machine screw I8 in the recess i9 and this supporting member, in turn,- is seated in the recess 2! of the plate 2% and is-held to the plate by the screws 22 which pass through the flange 23 of the member ll into the plate 203.

The magnetostrictive element F has an energizing coil 26 which may also serve to carry a polarizing current and which is wound on a split form after the form has been placed over the magnetostrictive member. The coil 25 may have any desirable impedance in accordance with a choice of suitable electrical constants and this coil is located in a recess in the form 25 directly adjacent to the cylindrical stem if. The coil form 25 fits around the cylinder is but is spaced away from it so that vibration of the magnetostrictive element does not bring it into contact with the coil form in any way. The coil form 25 is also supported from the plate 2% by means of the screws it which pass through the plate 20 and thread into the end faces of the coil forms 25. The plate 23 which holds the polarizing magnet i4 and the coil form 25 of each of the magnetostrictive units 7 is supported around its periphery by a group of rods 21, which rods are threaded into the plate 3. The coils 24 may be connected together in any desired series or seriesparallel arrangement and are energized through the cables '28 and 29 which pass through the stufflng gland 30 mounted on a projecting flange 3| projecting from the rear of the casing.

When the magnetostrictive element is rigidly fastened to the block 6 by means of the conicalheaded screw 8 in the conical cavity 32 at the center of the base of the magnetostrictive member, the magnetostrictive element becomes a standing wave member at the operating resonant frequency at which the oscillator or projector is designed to operate. The desired ratio of transformation is established by properly proportioning the masses of the base Id of the magnetostrictive unit and the end cylinder l3. The radiating or cover member 2 with the projecting blocks 5 and 3 on opposite sides of it are also established as one-half wave length element with the central flange 3 embracing the node of this element as a Vibrator. This central flange 3 may be made heavy enough to withstand the end surfaces opposed to the corners of each of the blocks 5. As indicated in Fig. 5, the base I0 of the magnetostrictive units being circular, provides sufficient opening over the corners on the face of the block 6 so that the rods 34 have willcient room to extend upwards from the base 33. The clearance between the face of the rods 34 and that of the block 6 may be just a little more than the normal working maximum amplitude of motion for the block 6 so that when an explosion or excessive vibration occurs, an added support will be furnished to the cover 2 at a great number of points over its whole area and thereby help the unit to withstand considerably more pressure than that normally needed to be withstood for the depth of submergence.

The blocks 5 and B on either side of the cover may be arranged, as indicated in Fig. 1, to cover substantially the whole surface. The grooves 35 between adjacent blocks 5 may be made any desired width. Where the blocks are made separately and attached to the diaphragm, the units can be placed as close as desired providing the sidewise expansion. of the blocks does not interfere with the longitudinal vibrations.

The grooves between the radiating elements are shown small compared to the dimensions of the elements. Under conditions where the driving elements operate better with relatively larger amplitudes, the grooves may be made larger.

In the arrangement shown in Fig. 6, the cover unit 66 is similar to that described in Figs. 1 to 5 and is mounted in a casing I which has studs 34' projecting from the rear thereof. The cover unit 36 is provided with projecting blocks 4| and 42, the latter carrying piezoelectric vibratory elements 63 such as Rochelle-salt, quartz, etc., with electrodes 44, 44, 44, attached to the side faces of the crystals. These crystals may be cemented directly or in grooves 45 on the end faces of the block 42, adjacent crystals being separated and spaced by projecting ribs 46 forming the sides of the grooves. The crystals are mounted in groups or individually on the end faces of the block and may have their electrode connections brought out to a terminal 49 on the insulating plate 43 supported by the rods 21 from the cover 40. The plate 48 has perforations 50 to permit the plate to fit over the studs. These crystals 43 have substantially the same frequency when vibrating as half wave length vibrators as the resonant structure formed by opposing blocks 4! and 42 and the central portion of the cover 40.

The crystals may be mounted within the casing in an air or gas medium or they may be mounted on the outside face of the casing, in which case the casing should preferably be covered over or immersed in an oil medium. For this purpose a housing may be placed over the front of the easing and this maintained filled with castor oil or other suitable acoustic medium in which the crystals will not be harmed.

In Fig. 7 a further modification of the arrangement of the magnetostrictive unit illustrated in 51, corresponding member 54 merging into a magnetostrictive unit 52 to the block. The mag:

netostrictive element is polarized by means of the permanent magnet 58 which is cylindrical inform and has at its lower end a head 59 forming a pole piece, which fits into the conical cavity 51 of the magnetostrictive element. The magnet 58 also at its top end has a flat pole piece 88 which may be fitted over the end of the magnet. The flat surface of the magnet is positioned over the end of the magnetostrictive member 55 and completes the magnetic paththrough the magnetostrictive cylindrical portion. The energizing of the magnetostrictive element is supplied by the coil 6! which may be wound on a form 62 supported directly by the plate 83 corresponding 28 of Fig. 2. The magnets and their pole pieces may also similarly be supported by the plate 63 so that both these units are simultaneouslyremovable when the plate 83 is removed. The use of the straight cylindrical magnetostrictive element 55 permits a non-split coil form to be used and the coil to be wound before it isput over the magnetostrictive unit.

In the use of the unit of the type shown in Fig. '7 for mounting on the back of the blocks of the oscillator, the distribution of the mass with a heavy mass 53 at the base of the unit is such as to bring the node, when the unit is used as a half wave length element, in the vicinity of the base and permit, relative to the radiating surface amplitudes, large amplitudes of the magnetostric- 'tive member, particularly near its free end.

The apparatus described in the present specification has particular utility in the production of a beam of supersonic compressional waves. In this connection the energy applied to each unit in the structure may be such as to obtain the desired beam pattern both in relation to the angular opening of the beam and the control of secondary lobes around the central main beam. By properly choosing and increasing the energy of the central blocks over those around the periphery, secondary lobes may be substantially reduced. This is easily obtained either by properly proportioning the desired amounts of energy to each unit. The device in any of the forms described may be used in deep water, as, for instance, on a tripod mounting and will withstand, because of the heavy central flange, a substantial water pressure and yet provide free piston action because of the location of the mounting flange with respect to the radiating surface.

Due .to the reaction of the thick central flange the central blocks or vibrating units for the same length have a higher natural frequency than those blocks at the edges so that these blocks nearer the center for the same tuning are slightly longer than those at the edges.

In the arrangements described in Figs. 1 to 6 the translating elements or the vibrating units were positioned within the casing protected from the water medium. In the arrangement of Fig. 8 the translating elements may also be placed .on the radiating side of the radiating unit and acoustically coupled with the sound-propagatwindings or supplying otherwise the,

mg medium by means of some suitable liquid,

plastic or other sound-conductive material. In

the arrangement shown in Fig. 8 the diaphragm element 1| is within a dome 14 having liquid, which dome is formed by the shell 15 of a ma: terial to permit passage of compressional vibrations with little interference or attenuation. The

diaphragm carries a plurality of longitudinal vibrating elements 12 on both its faces. 0n the ends of the vibrating elements in contact with the propagating medium are grooves in which are mounted a group of piezoelectric vibrators 13, 13. 13, 13. This construction may be similar to that shown in Fig. 6 with the exception that the units 13, 13, 13, 13, etc., are mounted on the front of the casing within the liquid-filled dome which to the plate men't it should also be noted that the space may be of rubber or some similar synthetic composition as far as its acoustic. properties are concerned. The passive vibrating elements 12 within the casing away from contact with the propagating medium may carry magnetostrictive unit; 81 or other active vibratory elements. 1

In the arrangement of Fig. 8 the longitudinal vibrator, made up of the whole vibrating element including both blocks 12 on both sides of the cover itself and the vibrating unit 13, combine .to form together one wave length or an integral number of half wave length-s added to this at the frequency at which the supersonic waves are to be propagated and received. The blocks 12 and with the cover portion in between form a one-half wave length element, and the unit 13 forms the other half-wave length element. In this arrange- 10' within the casing 18 is filled with a medium having a comparatively low radiation resistance such as air. While in the description of Fig. 8 the vibra-ting units'13 are described as piezoelectric elements, which may be Rochelle-salt crystals or any other type of piezoelectric vibrating elements. nevertheless, electrodynamic of the moving coil type, electromagnetic of the variable reluctance type, or magnetostri-ction vibrating units, as illustrated in Fig. 8a where the magnetostrictive hollow cylindrlcally shaped units 13' are mounted on the blocks 12, may also be used in place of the elements 13 as described in connection other figures of the specification. In Fig. 8a a permanent magnet I4 may serve to provide the constant flux excitation by its poles adjacent the inner walls of the magnetostrictive cylindrical elemenw.

thickness is used on which are mounted members to form resonant structures vibrating at right angles to the cover plate. In Fig. 9 the blocks on one side of the plate are 81 8|, and on the other side of the plate 82, 82. These blocks are held to the cover plate respectively by screws 83, 83 and 84, 84 positioned centrally in the blocks. In Fig. 10 the resonant structure is formed by longitudinal elements 85, 85 and 8B, 86 which may be made heavier at their free end surfaces, if desired, thereby loading the elements in accordance with the design of the structure as chosen. In both Figures 9 and 10 the top holes in the elements 8| and 85 may be filled at their ends by plugs 81, 81' to form a continuous surface of that portion of the elements exposed to the acoustic propagating medium.

In both Figs. 9 respectively have and 10the elements 82 and 86 attached at their ends the half .wave length transducing elements 81 and 88 reare' shown as spectively which in these figures with the magnetostrictive elements similar to the element 1 of Fig. 2.

In Figs. 11 and 12 the magnetostrictive unit 1 is shown attached by screws 9| to a comparatively thin diaphragm 90. Here the unit 1 with the diaphragm portion adjoining it may make up a half wave length element. The units 1 are preferably nested together on the diaphragm as shown in Fig. 12, but a single element may alone be used in a transmitter or receiver. The construction of the unit 1 of Fig. 11 is otherwise similar to that illustrated in Fig. 2 and the same numerals have been applied to similar parts.

Having now described my invention, I claim:

1. A device for transmitting and receiving compressional energy comprising a casing having a radiating member at one side thereof with the external surface in acoustic relationship with the sound-propagating medium and the interior surface shielded therefrom, said radiating member comprising a heavy plate with elements aligned and projecting at right angles to the surface of the plate and forming longitudinal resonant vibratable elements in which the plate contains the nodal plane, and a second resonant vibrator for translating acoustic energy into electrical energy, or vice versa, attached at one end of said. first resonant vibratable element, said second resonant vibrating element comprising a longitudinal resonant magnetostrictive shell attached at the end of said first vibrating element, a plate member supported from said radiating member, a permanent magnet positioned within said magnetostrictive shell and an energizing coil surrounding said shell and means suspended by said plate supporting both said permanent magnet and said coil.

2. In a device for transmitting and receiving compressional waves, a longitudinal resonant vibrating element, means supporting the same in :ts nodal plane, said support embracing a conziderable thickness on either side of the nodal lane, a magnetostrictive resonant element havng substantially the same resonance frequency upported at one end of said longitudinal resonant lement, said magnetostrictive resonant element omprising a hollow longitudinal vibrating memler terminating at each end in a mass element, me mass member of which is attached to said irst longitudinal resonant element, a permanent nagnet providing a longitudinal magnetization of ;a-id magnetostrictive vibrator and a coil providlng variable current at the resonant frequency positioned to energize or receive energy from said magnetostrictive vibrator.

3. In a device for transmitting and receiving compressional waves, a longitudinal resonant vibrating element, means supporting the same in its nodal plane, said support extending for a, considerable section to either side of the nodal plane, a magnetostrictive resonant element having substantially the same resonant frequency supported at one end of said longitudinal resonant element, said magnetostrictive resonant element comprising a hollow longitudinal vibrating member terminatin at each end in a mass element, one mass member of which is attached to said first longitudinal resonant element, a permanent magnet supported within said hollow vibrator'and providing pole faces near opposite ends thereof, a coil form supported externally of said vibrator and having a coil positioned between the mass ends of the vibrator and a plate member for supporting both permanent magnet element and said coil form independently of said magnetostrictive vibrator.

4. In a device for transmitting and receiving compressional waves, a longitudinal resonant vibrating element, means supporting the same in its nodal plane, said support extending for a considerable section to either side of the nodal plane, a magnetostrictive resonant element having substantially the same resonant frequency supported at one end of said longitudinal resonant element, said magnetostrictive resonant element comprising a hollow longitudinal vibrator with mass elements at both ends thereof, the whole forming a unit resonant structure with the section joining the mass ends providing the compliance for the unit resonant structure, one of said mass elements bein joined to said longitudinal resonant vibrating element and the other mass element being joined to the compliance member of the magnetostrictive resonant element at a point of the center of percussion whereby transverse vibrations in the magnetostrictive resonant element are avoided or reduced.

5. A device for transmittin and receiving oompressional energy comprising a casing having a radiating member at one side thereof with the external surface in acoustic relationship with the sound-propagating medium and the interior surface shielded therefrom, said radiating member comprising a heavy plate with elements aligned and projecting at right angles to the surface of the plate and forming longitudinal resonant elements in which the plate contains the nodal plane, and a resonant vibrator for translating acoustic energy into electrical energy, or vice versa, attached at one end of said first resonant element, and means projecting from the-rear wall of the casing within the same to a point closely adjacent the end of the longitudinal vibrators whereby when excessive amplitude is reached, the longitudinal vibrators will come to rest against the members projecting from the rear wall of the casing.

6. In a compressional wave transmitting and receiving device, a longitudinal vibrating element having a nodal flange and supported by the same, a magnetostrictive vibrating unit mounted at one end thereof and itself forming a, resonant vibrator, said magnetostrictive vibrating unit comprising two mass elements joined by a compliance member forming a shell with the mass members at each end thereof, means attaching one mass member at the end face of said first longitudinal vibrator, the other mass member having the form of a ring element joined at its center of percussion to the compliance member.

7. In a compressional wave transmitting and receiving device, a longitudinal vibrating element having a nodal flange and supported by the same, a magnetostrictive vibrating unit mounted at one end thereof and itself forming a resonant vibrator, said magnetostrictive vibrating unit comprising two mass elements joined by a compliance member forming a shell with the mass members at each end thereof, means attaching one mass member at the end face of said first longitudinal vibrator and substantially covering the entire area thereof, the other mass member having the form of a ring element joined at its center of percussion to the compliance member, a permanent polarizing magnet supported and extending within the hollow shell and having pole races opposed to said magnetostrictive member in said mass sections, a supporting member in which said permanent magnet is recessed, a plate independently supported of said vibrating members and means held in a perforation in said plate for supporting said supporting member.

8. In a device for transmitting and receiving compressional waves, a longitudinal resonant vibrating element, means supporting the same in its nodal plane, said support embracing a considerable thickness on either side of the nodal plane, a magnetostrictive resonant element having substantially the same resonance frequency supportno ed at one end of said longitudinal resonant element, said magnetostrictive resonant element comprising a hollow longitudinal vibrating member terminating at each end in a mass element, one mass member of which is attached to said first longitudinal resonant element, polarizing means providing a longitudinal magnetization of said magnetostrictive vibrator and a coil providing variable current at the resonant frequency positioned to energize or receive energy from said magnetostrictive vibrator.

HUGO BENIOFF.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PATENTS Number Name Date 2,017,695 Hahnemann Oct. 15, 1935 2,063,950 Steinberger Dec. 15, 1936 2,170,206 Mason Aug, 22, 1939 FOREIGN PATENTS Number Country Date 25,406 Netherlands Oct. 16, 1931 298,382 Great Britain Oct. 11, 1928 832,891 France Oct. 4, 1938 OTHER REFERENCES AnElectromagnetic Sound Generator, Eta, an article by St. Clair, Review of Scientific Instruments, vol. 12, May 1941, pp. 250-256 (p., 251 of interest).

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