US2346655A

US2346655A - Electrodynamic vibrator

Info

Publication number: US2346655A
Application number: US389209A
Authority: US
Inventors: Benioff Hugo
Original assignee: Submarine Signal Co
Current assignee: Submarine Signal Co
Priority date: 1941-04-18
Filing date: 1941-04-18
Publication date: 1944-04-18
Anticipated expiration: 1961-04-18

Description

18, 11944. H BENIOFF 2,346,655

ELECTRODYNAMIC VIBRATOR I I Filed April 18, 1941 5 Sheets-Sheet 1 1 INVENITOR BY HUGO BENIOFF plillws, 19. H BENIOFF 2,345,655

ELECTRODYNAMIC VIBRATOR I Filed April 18, 1941 3 Sheets-Sheet 2 INVENTOR HUGO ESENIQFF ATTORNEY April 18, 1944- H. BENIQFF ELECTRODYNAMIC VIBRATOR 3 Sheets-Sheet 3 Filed April 18, 1941 Patented Apr. 18, 1944 I 2,346,655 ELnc'rRonYNAMro vmnATon Hugo Benio', La Canada, Calif., assigner to Sub marine Signal Company, Boston, Mass., a corporation of Maine Application Api-u 1s, 1941, serial No. 389,209

(ci. 11i-sse) Claims.

The present invention relates to the art of sound transmission and reception by the use of compressional waves and more particularly relates to this art as applied to propagating media heavier than air, and in particular to the art of submarine signaling in frequency ranges in and' above the limit of audibility of the human ear for the production of .directive sound ywaves and the reception of sound waves by directive receivers.

In the present invention for the reception of directive waves and Athe propagation of sound beams a plurality of similar vibrators mounted on a radiating element and operative in substantially the same manner yfrom an electric source may be usedffor the creation of the sound'v waves. Each. vibrator in the present invention is lset into vibration by means' of the reaction between an alternating current flowing in a coil fastened to the vibrator and a. 'constant magnetic ield. These driving coils are mounted each at one end of the vibrators and the group thus forms a system for properly converting the electric energy to acoustic energy as will be more fully explained below.

In the present invention the electrical driving means is positioned at the very end of the vibrating system where the greatest amplitude of motion of the vibrator is obtained. The driving element comprises a coil` rigidly mounted at one end of the vibrator in such a manner as not to interfere with the propagation of the mechanical or acoustic wave in the tube upon which the'coil is mounted.

Further merits and advantages of the present invention will be more readily understood from the description given in the specification below and taken in connection with the drawings showing an embodiment of the invention in which Fig. 1 shows a central section through the device; Fig. 2 shows a section on the line 2-2 of Fig. 1; Fig. 3 shows a section on the line 3-3 of Fig. l; Fig. 4 shows enlarged portion of a section of Fig. 1 with a slight modification inthe construction of the magnetic' circuit; and Fig. 5'shows a section on the line 5-5 of Fig. 1.

In the drawings there is provided a casing I on the forward end of which may be mounted a diaphragm 2 which may be round or hexagonal as indicated in Fig. 3. The central section 3 of this diaphragm is made of a plate preferably integrally f formedwith the flange edges 4 and joined to it by means of the continuous web running all the `way around the central heavy plate` 3. "The web 5, as indicated in Fig. 2, is in a hexagonal form,

but other forms may be used, depending upon the construction of the drivingk units 6, the purpose 4being tonest the units 6 together in such a fashion as to cover substantially the whole central section 3 of the diaphragm. 1

The unit 6 comprises a heavy base element 1 of hexagonal or other desirable form for nesting the units together, which base element 'I narrows and tapers upward with sloping sides 8 to a symmetrically located mechanically vibratable tube 9 which is preferably formed integral with the base member 1. The unit 6 as a whole is mounted to the plate 3 preferably by means of al centrally located machine screw I0 passing through the base 1 and threading into the plate.3, clamping the-unit E direct to the plate. It is essential that this joint be rigid and tight and preferably the joining faces are cemented together by means of cement indicated at II. The tube 9, which may be slotted longitudinally, should have a diameter' approximately one-half that of the base member 1. A solid rod or bar with some mass atits free end may be used in place of the tube 9 but in general the tube is preferable. The tube diameter should preferably in all cases be less than one-half wave length of the wave propagated in the material of the u nit and it may be smaller than this. Essentially the unit 6 and the section of the plate 3 immediately below it, to which the unit is fastened, form longitudinally of-the tube a one-half wave length system at the desired fre- 'quency of vibration with the'node near the base element I and in this manner the vibration at the free end of the tube 9 may be made large compared with the amplitude of vibration in the plate 3. The free end of the tube 9- is provided with a. coil I2 which may be independently formed on a non-conducting form such as glass, Lucite, or some such material, and rigidly cemented at the end of the tube 9. The coil I2 is short in length, generally not longer than approximately one-half the tube diameter. This coil is immersed in airgap I3 which is supplied with magnetic ux by means of the magnetic circuit comprising the shell I4 which is composed of an upper plate-like member I5 with downwardly extending arms I6 and I6' by which the magnetic field unit is fastened to a soit iron plate member I1 by -means of the screws I8. lThe plate member I1 has its pole faces vI9 narrowed to increase the ux concentra#- tion. The plate member I1 and.its pole pieces I9 are preferably made of soft iron so as to offer a low reluctance path for the magnetic ux, while the member lvwith its downwardly extending arms I6 ,and I6? maybe made of Alnico or some similar metal that provides a very powerful pervided with numerous airgaps I3.

22 around the central. core 20 might be iilled by means .of a direct current magnetizing coil 23. In this case, of course, it is preferable to make the central core 20 and the plate |5701 the same material and in one-piece and this, of course, would preferably be soft magnetic iron. The direct current magnetizing system may be supported by the plate I'I resting upon a shoulder 24 on the wal1 25 oi. the casing I.

In the operation ofthe system, which may be 'used either as a transmitter or a receiver of sound waves, alternating current of the ldesired frequency is impressed upon the coil I2 and direct current in the magnetizing field unless a permanent magnet is used. The units 6 will vi brate substantially independently at the driving frequency with equal amplitudes, thus providing a uniform vibration of the whole plate 3. The device described is resonant at a frequency in which a. node is produced in the tubes 9 near the base 1. The units 8 are made similar and all are similarly mounted so that the nodes in each unit form approximately a plane parallel to the plane of the plate 3. By making the surface dimension of the plate 3 many times lthe wave length in the medium, the plate will produce a directive beam as a transmitter, and as a receiver will respond to waves approaching only from a corresponding sector generally normal tothe plate surface. l

Having now described my invention, I claim:

1. A device for producing or receiving compressional waves comprising, in combination, a casing having a radiating plate, a plurality of electrodynamically driven resonant vibrator units each comprising `a solid metallic base element having a` large mass comparative to the rest of the resonant unit, each such base element being rigidly mounted within said casing on said radiating plate, said units each having a comparatively thin tube 'extending from the base and having at its free end a driving coil, said tube comprising theelastic element of the vibrator and said base element being substantially inelastic in thev operation of the vibrator, the combined elements forming with the radiating plate a half wave length resonant vibrating system means providing a magnetic eld in which each of said coils is positioned whereby said device may be lised for sound transmission and sound recep ion. 2. A device for producing or receiving compressional waves comprising, in combination, a casing having a radiating plate, a plurality of electrodynamically driven resonant vibrator units each comprising a solid metallic base element havinga large mass 4comparative to the rest of y the resonant unit, each such base element being rigidly mounted withinl said casing'on said radlating plate, said baseelements being nested together in approximately abutting positions, said base elements having comparatively thin tubes extending upwards and integrally formed therewith, each having at their free ends a driving coil, said tube comprising the elastic element of the vibrator and said base element being substantially inelastic in the operation of the vibrator,-

the combined elements forming with the radiating plate a half wave length resonant vibrating system and means providing magnetic ilelds for each of said driving coils. n

3. A device ior producing or receiving compressional waves comprising, in combination, a casing having a radiating plate joined'thereto in a thin web extending entirely around the plate,

. a plurality of electromagnetically driven resonant vibrator units each comprising a solid metallic base element having a large mass comparative to the rest of the resonant unit, such units being nested together covering the entire plate and rigidly held thereto, said vibrators each having extending from the 'side opposite said plate a comparatively small but elongated thin driving tube, the end of said driving tube having currentconducting means and means immersing said current-conducting means in a magnetic neld the vibrators with the tube and base elements, together with the plate, forming a resonant, half wave length, vibrating system.

4. A device for producing or receiving compressional'waves comprising, in combination, a casing hav-ing a radiating plate joined thereto in a thin/ web extending entirely around the plate, a plurality of electromagnetically driven resonant vibrator units each comprising a. solid metallic base element having a large mass comparative to the rest of the resonant unit, such `units being nested together and covering the entire plate and rigidly held thereto, said vibrators each having extending from the side opposite said plate a comparatively small but elongated thin driving tube, the end of said driving tube having current-conducting means and means immersing said currentconducting means in a magnetic iield, said current-conducting means being short in length compared to the length' of said tube and the vibrators with the tube and base elements, together with the plate, forming` a resonant, half wave length, vibrating system.

5. A device for producing or receiving compressional waves comprising, in combination, a casing having a radiating diaphragm, a great number of electrodynamically driven vibrators rigidly mounted and nested closely together on said radiating plate within said casing, said vibrators comprising a small tube member-and a large end mass member having a base substantially llarger thanl the cross-sectional tube area. a driving coil short in length compared to the length of the tube mounted at the end of the tube and meanssupplying an electromagnetic field in which said driving coil is positioned the vibrators with the tube and base elements, together with vibrating system.

.HUGO BENIOFF.