US2408404A - Compressional wave transmitting and receiving apparatus - Google Patents

Description

06%. 1, 33. BATCHELDER 2,408,404

COMPRESSIONAL WAVE TRANSMITTING AND RECEIVING APPARATUS Original Filed May 19, 1933 Patented Oct. 1, 1946 CDMPRESSIONAL WAVE TRANSMITTING AND: RECEIVING APPARATUS Laurence Batcheld'er, Cambridge, Mass, assignor,

by mesne assignments, to Submarine Signal Company, Boston, Mass, a corporation "of De'l'aware Original application May 19., 671,870.. Divided and this. 13, '1'9'34',v Serial No. 715,349;

ber 19,1938.

1933, .Serial. No. application Marchv Renewed Septem- Claims. (Cl. 177-386) The present application is a division of my copending application filed May '19, 1933, Serial No. 671,870, Patent Number 2,380,931.

The present invention relates to apparatus for producing compressional waves and is applicable for the production of such waves in air, water or in other media.

In the present invention the compressional waves produced are more particularly in the range of so-called supersonic frequencies, that is, frequencies which are beyond the audibility of the human ear, although to some extent the present invention is also applicable to the production of high-frequency compressional or sound waves which are situated in the upper part of the audibility range of the human ear and just beyond it.

Due to the fact that metals possess great elasticity and that the wave lengths of high frequency compressional waves are very short in metals, it is difilcult to assume that the masses involved in compressional-wave apparatus of this type move as masses alone without partaking in the vibration of the vibrating elements.

In the prior art devices have been used in which a radiating surface or area was very large as compared with the wave lengthof the sound to be propagated in the propagating medium and the radiating surface was vibrated at a plurality of points in order to produce aplane wave or a directed beam of sound or compressional Waves. Such devices have been usefully employed both in so-called piezo-electric oscillators and in oscillators of the magnetic type.

In supersonic oscillators of the piezo-electric' type a mosaic of piezo-electric crystals are mounted between steel plates. The thickness of the plates together with that of the crystals are such as to establish a tuning in a direction perpendicular to the plate surface and, each crystal, in fact, vibrates that part of the plate where it. is attached. An examination of this type of. oscillator indicates that the whole plate does not move with the same amplitude and that between the places Where the crystals are applied the vibrational energy is sometimes quite small.

In other types of oscillators the same characteristics are found and while it is possible to pro-- time some vibration over an entire plate, it has been found a fact that the vibration is more particularly produced opposite the places where the vibrational energy is applied. This gives evidence of the fact that in high frequencies there is diiiiculty in making a plate act as a diaphragm and the tendency is for it simply to act as a transmitting medium.

In devices employing other than piers-electric means, for instance; in oscillators of "the :magnetosh'ictive type, itis possible to use resonant tubes or rods for driving a sound diaphragm over its surface inthe same phase. The dilficu lty', however, of making the whole diaphragm or plate to which the rod'sare attached vibrate isalso present here, and is is usually-observed that the vibration occurs more pa-rticularly' at the points where the rods 0r tubes, producing the compressional wave energy, are attached.

I have "also observed that it is quite impossible to predict just how such-"plates or diaphragms will vibrate and just what load either radiating or mass load should be considered as belonging to eac'h operating unit. In fact, itsappears that rods ortubes similarlyattached which beforehand had the same resonant frequencies may well after attaching have other resonant frequencies. Tl-us fact alone makes it difficult tonbtain a uniform resonance of all the operating and seriously handicaps and limits the available power output, since some units are operating on resonance whileother-un-its are off the resonant point. condition also distorts the soundbeam-sinceitis-apt to destroy the. uniform 'phasevi'bration of the entire vibrating surface.

In the present system which I have devised I have avoided may -ofthese diificulties by con-- structing-each unit as an independently operating unit and establishing the same resonance point for each so that they can all operatewith the same amplitude in the same phase at the same frequency; In order" to produce a fixed beam of compressional waves it isonly necessary in the'present system to have a s-ufliciently large number or independently operating units positioned or'nested close together vibrating the same phase in order to produce a plane wave whose width in the propagating medium will-be many times the wave len-gth of the sound or c0mpressi'onal wave produced;

When it-is desired to produce a directive beamof sounder compressional waves whose direction can be controlled or varied, this may be done-by vibrating lines or groups-hf individually spent-- ing units with proper phase-differences, it being preferable under such conditions to have them-'- dividuallyoperatingunits-relatively point sources so that each point in the medium may have the right vibrational phase.

Figure I shows a fragmentary section through the oscillator showing the rows. of oscillating ele ments; Figure 2 shows a sectional view oi the modification shown in Figure 1 taken on the line 2-2 of Figure 1; Figure 3 shows a perspective of a detail'fof the same modification; Figure-i 4 shows afurther modification on the same type ofview as indicated in Figure section along the line 5-5 of Figure 4; and Fig-" ure 6 shows a fragmentary perspective of a de-.

tail of the same modification.

In the present application which is a division of the applicant's copending case, as stated above, the structure more particularly described and claimed is one in which a group of long flat plates make up the radiating unit. These may be assembled together very closely with the center lines of the units substantially a half wave length apart or even less or they ma what wider in construction, depending upon the particular method in which it is desired to.op-

erate the units. Where the units are wider than ahalf wave length, each tobecome directive and therefore such a construction should not be used unless it is desired to'transmit a beam in a direction normal to the surface, of. the radiating units. Regardless of which type may beiemployed, the-principles set forth in the presentconstruction apply to the operation of the elements as long fiat plates operated by strips that are resonant with the plates longitudinally in the direction of the width of the strips.

The invention is illustrated in Figures 1, 2 and 3. In Fig. 1 the magnetostrictive element comprises an elongated strip I which has a radiating unit H made integral with the end thereof. The, radiating unit II is elongated, as indicated in Fig. 3, and may be constructed with inclined shoulders 12. The magnetostrictive strip I0 may be provided with slots I3 as indicated by the dotted lines in Fig. 2. The lower end of the strip I0 is held between similar magnetizable plates I4 and I made up of C-shapedlaminations and thus when assembled are recessed to contain the coil I6 which, as indicated in Fig. 3, is elongated and surroundsthe strip I0. At the lower end of the plate there is provided a plurality of flat head screws I1 which pass from one plate into the opposite plate and thereby clamp rigidly the end of the magnetostrictive strip 10. This furnishes a clamping mass for the magnetostrictive strip 10 which vibrates in its vertical dimension as shown in Fig. 1, and has a resonance of vibration normal to the efiective radiating plane of the unit H.

The plates I4 poles I8 shaped to conform to the inclined surface 13 underneath the top of the radiating element I I. In this manner the complete magnetic path for the coil 16 is through the strip 10 about the surrounding plates I4 and I5 and returning through the small air gap at the sides and underneath of the radiating plate I I.

The units indicated in Fig. 1 are in themselves independent and may preferably .be made of considerable length many times the wave length of the compressional wave which it is desired to generate in the sound-propagating: medium. Each of these units maybe arranged to form-- parallel successive rows and a greatnumberof the units maybe used so that the horizontal di mension of the device may be many times-the wave length of the sound produced in the propagating medium. In such an arrangement each unit will be vertically disposed and if they are independently eXGitQQ desired phase difierupon the distance of the units ences'depending 2; Figure 5 shows a y be made someindividual unit tends and I5 have upper projecting from each other and the wave length of the sound to be generated, a beam effect will be obtained. In the modification shown in Fig. 1 the units themselves may be mounted in a large base 5 plate 90 to which they are held by means of the screws 9|. The units may individually be made watertight by providing the plates 14 and 15 and also the radiating end II with a proper groove 92 in which the gasket 93 might be placed to prevent water from entering into and around the coil. This watertight gasket can also serve to center and space the radiating unit 1I so that no sideways motion will be present. A row of screws 94 is provided at the end of each unit so that the units may be firmly clamped both at the top and along the sides.

In the unit shown in Figs. 1, 2 and 3 a s'olid'structure is illustrated.

In Figs.' l, 5 and 6 part of the structure is laminated. In this modification the end-radiating element I00 and the strip IOI may be built up of a series of laminations which are held tight at the top by a bolt I05 passing completely through the whole group of laminations or this element in itself may be of a solid structure. The lower end of the strip IUI is clamped between clamping plates I02 and I03 which are firmly screwed together by means of the screws I04.

The coil I00 corresponding to the coil I6 of Fig. l is encased by a cover built up of laminations I01 which are held together by means of the stay rods I08, I08, etc. The laminations I0'I are built up in groups between which are the supporting members I09, I09, etc., through which the rods I08 also pass making a substantially rigid structure and uniting the laminations together in plates equivalent to the side plates I4 and I5 of Fig. 1. The members I09 extend downward below the laminations and rest in corners in the clamping blocks I02 and I03 to which they are held by means of the screws H0. The end radiating element I00 may be covered by means of a rubber cover III which may be cemented to it and also cemented to the casing H3 at the shoulder II l. As will be seen in Fig. 4, the oscillator is built up of a number of parallel units in which the radiating elements run substantiallyparallel. It should be noted that in this modification as well as in the structure shown in Figs. 1, 2 and 3 that the individual units are long as compared with the wave length of the wave transmitted in the propagating medium, and the length of the unit itself may be of a difierent order of magnitude than the wave length of the transmitting wave.

It should also be noted that the effective radiating length of the whole oscillator may also be many times the wave length of the wave transmitted, in which case a considerable number of I individual units will go to make up the entire oscillator.

In Fig. 6 is shown a perspective view of the modifications shown in Figs. 4 and 5. In this view the structure at the end of the oscillator is more clearly indicated. It will be noted that the corner which fits at the end of the last laminated group is composed of two pieces I I5 and I I6 which are themselves unjoined, being held to the laminated structure by means of the stay rods I08 as explained above.

Having now described my invention, I claim:

1. Means for producing a beam of compressional waves comprising a plurality of parallel elongated plates having magnetostrictive strips 7 attached to the same, means including said magnetostrictive strips for vibrating said plates at the desired frequency, means clamping said strips at the ends opposite the plates, said strip being tuned to resonance for the desired frequency of vibrations transverse to the long dimension of the strip.

2. Means for" producing a beam of compressional waves comprising a plurality of parallel elongated radiators having magnetostrictive stripsatt'ached to the same, means including an energizing coil and said magnetostrictive strips for vibrating said plates at the desired frequency, a plurality of elongatedplates positioned parallel to said strips and having projecting elements at the ends thereof, said plates being composed of magnetic material and serving "as the return magnetic path for the flux passing through the magnetostrictive strips to. provide. clamping surface at the lower ends of said stripsfeach of said strips being tuned to resonance for said desired vibrations normal to said radiators.

3. Means for producing a beam of compressional wave comprising a plurality of parallel elongated radiators having magnetostrictive strips attached to and vibrating the same, an elongated coil surrounding each of said strips, a plurality of elongated plates of magnetic material positioned parallel to said strips and having portions projecting therefrom near the ends towards said strips, said projecting portions serving to provide clamping surfaces and said plates serving as the return magnetic path, means cooperating with said plates for clamping the lower ends of said strips thereto, each strip being tuned to resonance for vibrations normal to the radiators and each coil adapted to be independently connected to a separate supply source.

4. Means for producing a beam of compressional Waves comprising a plurality of parallel elongated magnetostrictive strips having radiating means on a corresponding long edge of each,

- and being tuned to resonance for vibration normal to the radiating means, elongated coils each surrounding one of said strips, a plurality of elongated plates of magnetic material having portions projecting at the ends thereof and completing a return magnetic path for said coils enclosed by the plates and said projecting portions, means clamping the strips between plates at one set of projecting portions and means holding said plates together in parallel relation.

5. Means for producing a beam of compressional waves comprising a plurality of parallel magnetostrictive strips elongated in one dimension and resonant to the frequency desired to be produced in the width dimension, said strips having radiating means fixed on a corresponding edge of each, and being tuned to resonance for vibrations normal to the radiating means, an elongated coil surrounding each of said strips, a plurality of elongated plates of magnetic material having a recessed portion shaped to conform on one side to the contour of said coil and fur nishing a return magnetic path for the flux generated by said coil and passing through said strips, means including said plates for clamping the strips between said plates at the ends thereof and means holding together said plates in parallel relation.

6. Means for producing a beam of c0mpressional waves comprising a plurality of wave radiators associated together in a unitary device, each radiator having a vibrating unit having a T- shaped section, a coil surrounding the stem thereof, means of magnetic material clamping the lower end of the stem of the T, means of magnetic material including said clamping means for completing the magnetic circuit from the end of the stem to the cross piece of the T, and a -soft rubber diaphragm covering the radiating surface of the unitary device.

7. Means for producing a beam of compressional waves comprising a plurality of 'wave radiators associated together in a unitary device, each radiator having a vibrating unit having a T'- shaped section, a coil surrounding the stem thereof, means clamping the lower end of the-stem of the T, said means including means of magnetic material external of the coil for completing-the magnetic circuit to' the top cross piece of the T and means between the ends of the cross piece-cf the T and the magnetic means tocomplete closure of the coil and position the T-s'haped piece.

8. Means for producing a beam of compressional waves comprising a plurality of parallel elongated plates, said plates being arranged side by side with their surfaces forming a continued plane surface, strips of magnetostrictive material attached to and supporting said plates, electromagnetic means surrounding each of said strips for energizing the same, each of said plates being free to vibrate as a single piston element.

9. Means for producing compressional waves of high frequency comprising a rectangular elongated plate, a strip of magnetostrictive material supporting said plate substantially along the middle of the same, an elongated coil positioned about said strip, a plurality of side elements of magnetic material, said elements being provided with extending flanges extending over the top and bottom of said coil and furnishing at the bottom end a clamping surface for the bottom of said magnetostrictive strip and means clamping said plates and strips together at the bottom end thereof.

10. Means for producing compressional waves of high frequency comprising a rectangular elongated radiator, magnetostrictive means for driving said radiator, means forming an enclosed casing about said magnetostrictive means, said means providing a surface extending in the same plane as said radiator and means carried between said radiator and said casing for producing a watertight joint between the same.

11. Means for producing compressional waves of high frequency comprising an elongated rectangular radiator having one side flat and the opposite side tapered to form a V-shaped section, means forming a groove at the side of said radiator, means for driving said radiator simultaneously over its whole length, magnetic mean forming a casing about said driving means, said means being provided with a groove opposite said groove in said radiator and means extending between said grooves for providing a water-tight joint Within said casing.

12. In a means for producing a beam of compressional waves, a radiating element having a T-shaped section formed of a plurality of T- shaped laminated strips having means binding said strips into said T-shaped section, coil means for impressing magnetic flux through the stem of said T-shaped element, a plurality of substantially C-shaped lamination of magnetic material encasing said coil means and positioned to form pole elements for a magnetic circuit, the top and bottom horizontal portions of the 0 being positioned at the lower part of the stem and at the cross bar portion of the T strips and means for holding said laminations in position adjacent said strips.

13. In a means for producing a beam of compressional waves, an elongated radiating surface having magnetostrictive strip means formed as a part thereof running substantially the length of said surface, a plurality of C-shaped magnetic pole elements positioned at the sides of said strip, a coil surrounding said strip, the top and bottom portions of the C projecting over the coil and means for holding said pole elements in position against said strip at the lower end.

14.In a means for producing a beam of compressional waves, an elongated radiating element having magnetostrictive strip means extending substantially the length thereof and positioned symmetrical to the section of the radiator, coil means surrounding said magnetostrictive strip and providing electromagnetic flux for the same, means for clamping said strip at the bottom ineluding means of magnetic material providing a magnetic flux path having a pole face adjacent the radiating element at the top of the strip.

15. Means for producing a beam of compressional waves comprising a group of parallelly arranged elongated radiators, strips of magnetostrictive material each supporting one of said radiators, means separating said radiators one from the other providing surfaces opposed to one another, said means also having a surfacev in the extension of the same plane as the radiators themselves and means supported between said radiators and said separating means for maintaining the surfaces of said separating means and said radiators that are opposed to one another free from contact with each other.

LAURENCE BATCHELDER.

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