US2045404A - Piezoelectric vibrator device - Google Patents

Description

June 23, 1936. E. c. NICHOLIDES 2,045,404

' PIEZOELECTRIC VIBRATOR DEVICE Filed May 24, 1933 2 Sheets-Sheet l ATTO R N EY INVENTOR g c I mum S M Yvwlu June 23, 1936. E. c. NICHOLIDES I PTEZOELECTRIC VIBRATOR DEVICE Filed May 24, 1933 2 Sheets-Sheet 2 INVENTOR BY 8 "c .rfmam S MFML,

ATTO R N EY Patented June 23, 1936 I n UNITED STATES PATENT OFFICE 2,045,404 PIEZOELECTKIO VIBRATOR DEVICE Emmanuel Christ Nicholides. New York, N. Y., assignor, by mesne assignments, to Sonotone Corporation, New York, N. Y., a corporation of New York Application May 24, 1933, Serial No. 672,561

7 23 Claims. (01. 179-107) This invention relates to piezo-electric vibrator crystal, or similar piezo-electric substance, medevices and it has among its objects improvement chanically united to each other along a common of the energy transmission and increase of the junction face, with electrode sheets'attached to low frequency vibration output of the same. the faces for applying thereto electric fields tend- Special objects of the present invention are ing to impart to the two adjacent plates oppopiezo-electric sound apparatus, and particularly- .sitely directed deformations, restraining one hearing-aid bone vibrator devices with improved plate by the other, and producing a resulting vibratory power transmission and increased low bending motion of the unit larger-than the mofrequency output. tion that would be imparted to said crystal plates The foregoing and other objects of my invenin unrestrained condition. 10 tion will be best understood from the following The other type of vibrator unit known as description of exemplifications thereof, reference bender consists of two fiat crystal 45-X-cut, being had to the accompanying drawings, wherebars (cut from a Rochelle salt crystal plate perin pendicular to the electrical X-axis under an Fig. 1 is a vertical cross sectional view through angle of 45 against the optical axis Z) mechan- 15 a bone vibrator unit; ically united to each other along a common Fig. 2 is a horizontal sectional view along line junction face, with electrode sheets applied to the 2-2 of Fig. 1; faces for impressing upon the crystal bars elec- Fig. 3 is a vertical sectional-view of a modified trio fields tending to impart longitudinal expanform of bone vibrator; sion to one bar while imparting longitudinal con- 20 Fig. 4 is a vertical sectional view of Fig. 3 along traction to the adjacent other bar and thus muline 5- tually restraining their longitudinal movements Fig. 5 is a horizontal sectional view of the bone and causing the united bars to bend in a direcvibrator of Figs. 3 and 4 along line 5-5 of Fig. 3; tion perpendicular to the faces with a greater :5 Fig. 6 is a view of the-bone vibrator device as motion than could be obtained by the unrecarried on the head of a person; strained independent longitudinal motions of the v Fig. 7 is a circuit diagram of a bone-conduction two bars. hearing-aid device utilizing the bone vibrator; Such twisters and benders reverse their defor- Fig. 8 is a vertical sectional view of a telephone mations on reversal of the electric field applied receiver embodying the invention; to the individual crystal layers. By applying 30 Fig. 9 is a. horizontal sectional view through the soundfrequency electrical oscillations to the coup g connection between the vibrator and the .electrode sheets on the'faces of said crystals, diaphraghm of the telephone receiver of Fig. 8 alternating electric fields are impressed on the along line 9-9; two crystal bars, imparting to the two-layer Fig. 10 is an elevational view partially in sec.- crystal unit a vibratory bending movement of a tion illustrating a spectacle frame with a bone frequency corresponding to the impressed oscilvibrator unit in accordance with the invention, lations. r

the front cover of .the vibrator chamber being Such twisters and benders may be constructed removed; either as two-layer units described above, or as Figs. 11, 12 and 13 are elevational views parfou.r-, sixor multiple-layer'units in which case, 40

tially in section of loud speakers embodying modithe adjacent faces of individual two-layer units fications of the invention; and are united to each other to act as a single unit Fig. 14 is a detailed view of the vibrator unit with a multiple of the power of a two-layer unit. of Fig. 13 as seen from the left side of Fig. 13. As used broadly herein, the terms twister" and In my copending application on piezo-electric bender? apply to two-layer units as well as to 45 devices, Serial 'No. 672,560, filed concurrently larger multiple-layer units.

with the present application, I have described im- Heretofore, loudspeaker diaphragms, record provements in soundproducing devices driven by cutters and similar acoustic instruments have Diem-electric Vibrator units, and P ly been driven with such vibrator crystal units by f Rochelle crystal vibrator units. Vibrator units clamping one end portion of such unit to a heavy 50 m y uniting rys l pl es or strips of highly mass to definitely-locate one end of the unit in piezo-electric crystal substances, such as Rochelle space, and coupling the load to which the vibrasalt crystals, have been chiefly used in this field; tions are to be imparted to a vibrating end por- One type of vibrator unit, known as twister tion of the crystal unit having the largest ampliconsists of two flat Xcut plates of Rochelle salt tude, and thusutilizing the vibratory motion of 55 the unit for imparting vibratory energy to the coupled load.

While it is relatively easy to impart to a vibratory load high frequency vibrations of several thousand cycles by means of a piezo-electric vibrating unit, the amount of 'low frequency vibratory energy that can be imparted with such vibrating unit greatly decreases with the decrease of the frequency and very little of such. energy can be transmitted at frequencies of several hundred cycles per second important for speech and music reproduction, and in hearing-aid devices. Since Rochelle salt crystals have a much greater piezo-electric efiect than other available piezoelectric substances, Rochelle salt vibrator units are able to deliver more vibratory power at low frequencies than vibrator units made of the other crystal materials. But even with Rochelle salt crystal vibrators as heretofore known, the amount of low frequency vibration energy that can be imparted to an acoustic load is relatively small, thus making difficult practical sound produeing devices of good quality.

This difliculty is particularly great in caseof bone vibrators for bone-conducton hearing-aids which must be made very small in order to permit their inconspicuous wear on the head of the user, thus restricting the size of the crystal to small dimensions making impossible transfer of large vibratory power.

I have found that the difficulties of producing sufiicient low frequency vibrations and transferring the same with a small crystal vibrating unit to an acoustic load can be overcome by a special construction and mounting of the crystal vibrating unit and utilization of the. reactive forces produced by the vibrator unit during its vibration.

In accordance with the invention, I mount the crystal unit on a relatively light support of little weight and small inertia and utilize the reactive forces producedin the support by intensive vibration of the crystal vibrator unit for imparting corresponding vibrations to the acoustic load that is driven by the crystal unit.

A simple small-size bone vibrator for a boneconduction hearing-aid device made in accordance with my invention is shown in Fig. 1 of the drawings. The vibrator unit is in the form of a bender bar 20, made by uniting to each other two 45-X-cut Rochelle salt crystal bars 2|, 22 as explained in my copending application identified above. To the outer faces of the bar 20 are secured electrode sheets 23, 24 and an intermediate electrode sheet 25 is provided at the junc tion of the two crystal surfaces, these electrode sheets being of thin metal and being intimately united with the faces of the crystal strips to consume only little of the potential drop available for producing an electric field through the crystal bars. Because of the requirement that the vibrator be inconspicuous, very small crystals are used in the vibrator unit, the size of the individual crystals being about 1 x x of aninch.

At its lower end the flat portion of the crystal unit bar 20 is clamped against a clamping member 26 comprising two metallic clamping blocks 21 and 28 secured to a mass of rigid insulating material such as Bakelite. A clamping cavity 29 is formed between the two metallic clamping members 21, 28 into which the lower flat end of the vibrator bar 20 is fitted, a clamping bar 30 held pressed to the blocks 21, 28- by means of free vibration thereof.

screws 3| holding the vibrator bar in place. To prevent nonuniform pressure at the clamping surfaces,. layers 32 of yieldable material are interposed between the clamping members and the clamped portions of the crystal faces. Electrode sheets 33 on the outer surfaces of the crystal bars and the intermediate electrode sheet 34 are connected to the blocks 21 and 28, respectively, through the contact strips 35 and the contact strip 36, respectively. Electrical oscillations are I supplied to the electrode sheets 33, 34 by means of plug pins 31 inserted into perforations 38 extending from the bottom side ,of the contact blocks 21 and 28, the plug pins being connected to a conductor cord 39 leading to a source of electric sound-frequency oscillations, such as the output of an audio amplifier of a hearing-aid or radio broadcasting receiver.

To the upper free end of the vibrating crystal bar 20 is attached a weight 40, of lead, for'instance, having an interior cavity providing a portion fitting tightly and attached to the end of the crystal bar and an additional projecting skirtlike portion for accommodating additional weight without clamping additional crystal surface, a free space 4| being provided above the upper end surface of the crystal bar. 4

The clamping member 26 has an upwardly extending projecting wall 45 having a slightly elevated contact portion 46 which may be applied to the bone structure of the head for transferring vibratory power thereto. To the front side of the clamping block 30 is secured, as by screws, the lower end of a flat gripping member 41 connected to the end of a head band 48 by means of which the vibrator unit with its mounting may be held on the head of a person having impaired outer hearing organs, and pressed against the bone structure, such as the mastoid one.

With the vibrator held against the bone struccontact member 46 extending therefrom vigorous vibrations to the bone structure engaged by it. This reactive coupling of the vibrator with the bone structure secures efl'icient transmission of the vibratory energy produced by the vibrator unit to the bone structure of the head without the necessity of coupling buttons or other special coupling-connections to the vibratory portion of the bar and without in any way restraining the The mounting of the crystal unit is thus simplified and more eflicient transfer of energy secure With the reactive coupling it is easy to provide a coupling connection between the clamping member and the bone structure of the head at which a good impedance match is secured between the vibrator unit and the head structure, thus enabling an increase of the amount of low frequency vibrations transmitted to the bone structure without the difficulties of getting direct matched coupling with the vibratory portion of the crystal unit.

" son and against disturbances The increased amount of low frequency vibratory energy secured by the additional weight 48 attached to the vibratory portion of the crystal is thus increased by the reactive coupling of the crystal bar to the bone structure and the resulting vibrations of the free bar.

While the vibrator unit shown in Figs. 1 and 2 is very convenient for observing and studying the reaction-type bender unit, I prefer to enclose it completely in a casing for practical use as a hearing-aid bone vibrator. This is greatly facilitated by the fact that are required between the vibratory portion of the vibrator unit and the bone structure. Such bone vibrator is shown in Figs. 3 to 5 in which the vibrating bender crystal bar 28 is clamped in the interior of a small casing 5| "to the metallic clamping blocks 21 and 28, imbedded in and rigidly held by the interior of the casing wall 52 which has on its rear side an elevated portion 53 constituting the contact surface engaging the bone structure of the head of the user.

The vibrating portion of the crystal vibrator unit 28 is weighted at the top, and its lower end is clamped in the same way as in the arrangement shown in Fig. 1, and the connection to its electrode sheets is made. by plug pins and cord likewise in the same way. The rear side of the casing has an opening 8| through which the crystal unit is inserted into the casing and properly clamped therein. The casing opening is closed by a sheet cover 62 which hasattached thereto a second sheet member 63 of the same size having formed in its lower portion a channel 64 for engaging the fiat end of a gripping member 66 connected to a head band 61 by means of which the unit is supported on the head and held pressed with its contact surface 53 against the bone structure, such as the mastoid bone, as shown in Fig. 6. The two cover sheets 82 and 53 are suitably secured to the casing, for instance, by screws 68 and completely enclose the vibrator unit so that the vibrator is protected against contact with the body of the perfrom the exterior. By making the junction between the cover and the casing sufficiently tight, entrance of moisture into the interior casing may be positively prevented and its operativeness under all operating conditions maintained. Sufficient space is provided in the chamber for permitting free vibration of l the vibrating unit under the forces induced therein by the applied electric fields.

Through the reactive coupling of the vibrating unit with the head structure, which is exactly'like that explained in connection with Fig. 1, it will transfer a large amount of vibratory energy to the bone structure of the user without requiring any coupling between the vibratory portion of the crystal unit and the head. Enough low frequency will be produced, and transferred from the vibrator to the head because of the additional load attached-to the vibrating crystal bar section and due to the good impedance match between the crystal vibrator and the bone structure.

To actuate the vibrator unit, it may be supplied with electric sound-frequency oscillations either from the output circuit of an amplifier of a radio or phonograph instrument, or Home special sound transmitting apparatus as shown in Fig. '7. The apparatus comprises a transmitting microphone 18 connected through a cord II in the input circuit of an amplifying device no coupling connections additional weight is about 2 grams, and the total vibrator units with the casing weighs only about 16 grams. The completely assembled bone vibrator as shown in Figs. 3 to 5 is about 1%" long,

about. /1" wide, and about thick, being small and inconspicuous when worn on the head of a person, Many persons of impaired hearing do not mind carrying the hearing-aid on a lorgnette handle for instance, against the mastoid bone.

The produced oscillations are l as long as the weight of the hearing-aid is small.

The vibrator made according to the invention, as

shown in Figs. 3 to 5, is particularly light and suitable for use with a lorgnette handle by inserting a fiat strip mounted on its upper end into the channel 84 provided for carrying it with t the head band.

In Figs. 8 and 9 my invention is shown applied to a telephone receiver. It comprises a diaphragm 8| in thefcrm of a circular thin metal sheet held at its edges which are clamped between the shoulder 83 of an enclosing casing and the annular projecting portion 84 of the cover 85. The center of diaphragm 8| is connected to a coupling clamp 88 which embraces and clamps firmly the center portion of a crystal unit 89 like bender 28 shownin Figs. 1 to 5, but smaller in size. Thecrystal between two washers 82 unit 89 is preferably made of'Rochelle salt crystal strips and provided with electrode sheets and electrical connections therefrom to a lead 98 in a way similar to the bender shown in Figs. 1 to 5. Instead of clamping the crystal unit at one end, it is clamped in the center so that the two oppositely projecting bar portions extending from the clamp vibrate in synchronism between positions at which they approach thediaphragm 8| and positions at which they move away therefrom. The clamp 88, shown in detail in Fig. 9, comprises a pair of clamping members 9| embracing the flat crystal faces and clamped thereto by screws 82, resilient layers 93 on the clamped portions, of the crystals serving to equalize the clamping pressure. One of the clamping members is connected by a coupling rod 84 to the center of the diaphragm 8| and is connected thereto by clamping members 95 so that the two vibrator bars of the crystal unit 89 project on the opposite sides of the clamp 88 and are carried by the center of the diaphragm 8|, being free to vibrate like two individual benders Weights 98 are attached to the ends of the two vibrating bars like to the bender 28 of Fig. l. Upon energization of the crystal unit by connecting its leads 88 to a source of vibratory electric sound-frequency oscillations, a vibratory bending movement will be imparted to the two projecting bender members extending from the clamp 88, the vibrating units swinging in syn- .chronism back and forward and transferring the clamp 88 with the diaphragm 8| like the coupling connection between the bender clamp and the bone structure in the bone vibrator of Fig. 1.

An efiicient and simple telephone receiver is thus obtain-ed which gives a sound output having enough low as well as high frequency sound oscillations to permit good reproduction of speech and music.

In Fig. is shown a piezo-electric crystal unit -bridge wall I06 extending between the frame portions I01 which rest on the nasal bone of the wearer of the spectacle, the clamp I05 being constructed like the receiver clamp 88. Bending vibrations are imparted to the two projecting weighted bender portions by supplying to their electrode sheets sound-frequencyoscillations through a cord I08 mounted in the spectacle frame. These vibrations arereactively transmitted through the coupling'member I05 and the lower bridge wall I06 to the contact portions I01 engaging the nasal bone. The vibratory energy of the pair of benders within the bridge chamber is thus transferred through the reaction forces acting on the coupling member to the bone structure of the spectacle wearer in a way similar to the action of the double bender in the telephone of Fig. 8.

Fig. 11 shows a cone speaker driven by reactive coupling with a double bender in accordance with my invention. The speaker cone IIO has its front end supported on a. bracket I II which is attached to a casing II 2 having a relatively heavy support II3. Attached to the center of the cone IIO on the side facing the interior of easing I I2 is a clamp member I I4 similar to the clamp 88 of the telephone vibrator, but of suit- I able larger size, clamping the center portion of a relatively long bender unit I I5 having weights I I6 attached to its opposite vibrating ends. Additional flexible support is supplied to the junction of the cone center and to the bender coupled thereto by a flexible sheet H8.

Electrical sound-frequency oscillations supplied to the electrode sheets of the bender unit I I5 through cord II I impart a synchronous vibration of the two bender halves and the reactive forces exercised thereby on the clamp II4 cause transfer of vibratory energy to the cone IIO imparting thereto a vibratory movement producing a large volume of sound rich in low frequencies.

In Fig. 12 there is shown another modification of the invention in which a somewhat smaller cone I has attached to its center portion a clamp IZI holding a double bender vibrator unit I22 like that of the structure of Fig. 11 and a light casing I23 enclosing the vibrator unit and its additional weight members I24. the weight of the vibrator unit being sufiiciently small not to place an excessive strain on the cone. By impressing sound-frequency oscillations on the electrode sheets of the bender unit I22 through a suitably connected cord I 25, the two weighted bender portions of the crystal unit I22 are set 4 by said vibratory chanical vibrations to a a layer of piezo-electric crystal substance, elecinto a synchronous vibration and the reactive forces exercised by the vibratory motion reacts through the coupling clamp I2I on the cone, imparting to it vibratory energy rich. in low frequencies.

In the modification of the invention shown in Figs. 13 and 14, a cone loud speaker constructed similar to the speaker shown in Fig. 12 is actuated by the reactive forces of a pair of twister units I 30, referred to hereinbefore, and made in the way disclosed in my copending application on Piezo-electric devices, Ser. No. 672,560, filed concurrently herewith. Each twister unit I comprises two rectangular crystal plates I3I and I32 cut from a Rochelle salt crystal perpendicular to the, electric axis and united to each other, and with interior and exterior electrode sheets I33, I34 connected to produce bending of the diametrically opposite corners in opposite directions when in unclamped condition. Two adjacent edges I35, I36 of each crystal unit are clamped to a. cross-shaped rigid supporting member I38 by means of clamping plates I39, insulating yieldable layers I40 of fibre being interposed at the clamping surfaces. The center part I4I of supporting member I38 is attached to the center of a cone I 42 to transmit reactive vibratory forces impressed by the vibrating action of the twister units I30 upon the supporting member I38 on the cone I42 and impart corresponding vibrations thereto. The unclamped corner of each twister unit has attached thereto a weight I43, and the entire vibrator unit is enclosed in a casing I44. The small weight of the crystal makes further support of the vibration imparting structure unnecessary. By impressing through leads from a source of electric soundfrequency oscillations going through cord I45 to the insulated electrode sheets I33 and I34, respectively, oscillations on the two twister units I30, vibratory motion is imparted thereto and the reactive forces developed by the crystal unit act through the central I 42 impressing thereon vibrations producing sound rich in low frequencies.

The principles underlying the invention may be utilized in many other ways that will suggest themselves to those skilled in the art, and it is accordingly desired that the appended claims be given a broad construction commensurate with the invention.

I claim:

member I 4| on the cone 1. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator compriselectrode means for impressing electric oscillations on the piezo-electric substance of said member to produce a vibratory motion of said vibrator, and coupling means supporting said vibrator in a floating condition and coupling said vibrator to a load to cause transfer of vibratory energy produced motion to said load.

2. In a piezo-electric device for imparting meload, a vibrator including trode means for impressing electric oscillations across said crystal layer inducing therein alternating forces tendingto impart opposite longitudinal deformations to said layer, means restraining said crystal layer against longitudinal deformation and imparting under the action of said forces a vibratory bending motion .to said vibrator, and coupling means supporting said vibrator in a floating condition and coupling said vibrator to a load to cause transfer of vibratory energy produced by said vibratory .motion to said load.

3. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric substance for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling -one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a sufficient floating mass exerting reaction forces for imparting vibratory energy to said load.

4. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric substance for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a suflicient floating mass of the order or larger than one-half of the mass of the vibrator exerting reaction forces for imparting vibratory energy to said load.

- 5. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations onthe piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a suflicient floating mass exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting vibratory energy to said load.

6. In a piezo-electric device for imparting mechanical vibrations to a vibratory load, a vibrator comprising a member of piezo-electric crystal substance, electrode means for impressing electric oscillations across said crystal member inducing therein alternating forces producing a vibratory motion between two sections of said vibrator, and coupling means supporting said vibrator and holding one of said sections mechanically restrained and coupled to said load, the other section of said vibrator being supported in a freely vibrating floating condition for producing during vibration reactive forces transmitting vibratory energy to said load.

7. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part, of said vibrator having a suficient floating mass of the order or larger than one-half of the mass of the vibrator exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting vibratory energy to said load, said floating part of the vibrator includinga body of substantial mass of greater specific weight than said piezoelectric substance.

3, In a, piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric member for producing a vibrachanical vibrations to a load, a vibrator compristory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a sufficient floating mass exerting reaction forces 5 for imparting vibratory energy to said load, said floating part of the vibrator including a body of. substantial mass of greater specific weight than said piezo-electric substance.

9. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric member for producing a vibratory motion between two parts of said vibrator, sup- 15 porting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a suflicient floating mass exerting reaction forces for imparting vibratory energy to said load, and 20 a casing extending from the coupled part of the vibrator and enclosing the floating part of the vibrator.

10. In a piezo-electric device for imparting me- 25 ing a member of piezo-electric substance, electrode means impressing electric oscillations on the piezo-electric member for producing a vibratory motion between two parts of said vibrator, supporting means for coupling one part of said 30 vibrator to a load and supporting in a floating condition the other part of said vibrator having a suflicient floating mass of the order or larger than one-half of the mass of the vibrator exerting reaction forces for imparting vibratory energy 35 to said load, and a casing extending from the coupled part of the vibrator and enclosing the float ing part of the vibrator.

' dition the other part of said vibrator having a sufflcient floating mass exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting vibratory energy to said 5 load, and a casing extending from the coupled part of the vibrator and enclosing the floating part of the vibrator.

12. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator compris ing a member of piezo-electric substance, electrode means impressing electric ocillations on the piezo-electric member for producing a vibratory motion between two parts of said vibrator, supporting means for coupling one part of said vi- 60 brator to a load and supporting in a floating condition the other part of said vibrator having a sumcient floating mass exerting reaction forces for imparting vibratory energy to said load, said floating part of the vibrator including a body of. substantial mass of greater specific weight than said piezo-electric substance, and a casing extending from the coupled part' of the vibrator and enclosing the coating part of the vibrator.

13. In a piezo-electric acoustic device for im- 70 parting mechanical vibrations to an acoustic load,

a vibrator comprising a member of piezo-electric Rochelle salt crystal substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing a 75 vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a'load and supporting in a floating condition the other part of said vibrator having a suificient floating mass exerting reaction forces for imparting vibratory energy to said load.

14. In a piezo-electric acoustic device for imparting mechanical vibrations to an acoustic load, a vibrator comprising a member of piezo-electric Rochelle salt crystal substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to a load and supporting in a floating condition the other part of said vibrator having a sufficient floating mass exerting reaction forces for imparting vibratory energy to said load, said floating part of the vibrator including a body of substantial mass of greater specific weight than said crystal.

15. In a piezo-electric hearing-inducing bonevibrator device, a vibrator of a size suitable for inconspicuous wear on a person comprising a member of piezo-electric substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to hearing-inducing bone structure and supporting in a floating condition the other part of said vibrator having a mass exerting reaction forces for imparting hearing-inducing energy to bone structure of a person.

16. In a piezo-electric hearing-inducing bonevibrator device, a vibrator of a size suitable for inconspicuous wear on a person comprising a member of piezo-electric substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to hearing-inducing bone structure'and supporting in a floating condition the other part of said vibrator having a mass of the order of one-half of the mass of the vibrator or darger exerting reaction forces for imparting hearing-inducing energy to bone structure of a person.

17. In a piezo-electric hearing-inducing bonevibrator device, a vibrator of a size suitable for inconspicuous wear on a person comprising a member or piezo-electric substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing a vibratory motion between two parts of said vibrator, and supporting means for coupling one part of said vibrator to hearing-inducing bone structure and supporting in a floating condition the other part of said vibrator having a mass of the order of one-half of the mass of the vibrator or larger exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting hearing-inducing energy to bone structure of a person.

18. In a piezo-electric hearing-inducing bonevibrator device, a vibrator of a size suitable for inconspicuous wear on a' person comprising a member of piezo-electric substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member for producing avibratory motion between two parts of said vibrator, and supporting m ns t r c up one part of said vibrator to hearing-inducing bone structure and supporting in a floating condition the other part of said vibrator having a mass exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting hearing-inducing energy to bone structure of a person, said floating part of the vibrator including a body of substantial mass of greater specific weight than said piezo-electric substance.

19. In a piezo-eiectric hearing-inducing bonevibrator device, a vibrator of a size suitable for inconspicuous wear on a person comprising a member of piezo-electric substance, electrode means impressing sound-frequency electric oscillations on said piezo-electric member forproducing a vibratory motion between two parts of said vibrator, supporting means for coupling one part of said vibrator to hearing-inducing bone structure and supporting in a floating condition the other part of said vibrator having a mass of the order of one-half of the mass of the vi-. brator or larger exerting reaction forces perpendicular to the longitudinal direction of the vibrator for imparting hearing-inducing energy to bone structure of a person, and a casing extending from the coupled part of the vibrator and enclosing the floating part of the vibrator.

20. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric crystal substance, electrode means for impressing electric oscillations on the piezo-electric substance of said member producing a vibratory motion of said vibrator, coupling means supporting said vibrator in a floating condition and coupling a portion of said vibrator to a load for imparting vibratory energy produced by said motion to said load, and a body of substantial mass of greater specific weight than said crystal attached to the floating part of said vibrator.

21. In a piezo-electric device for imparting mechanical vibrations to a load, a vibrator comprising a member of piezo-electric crystal substance, electrode means for impressing electric oscillations on said crystal member producing a vibratory motion thereof, coupling means supporting said vibrator in a floating condition and coupling a portion of said vibrator to a load for imparting vibratory energy produced by said motionto said load, the floating part 01' said vibrator including a body .of substantial mass of greater specific weight than said crystal casing extending from said coupling means and enclosing the floating part of said vibrator.

22. In a piezo-electric energy translating device, a vibratory structure comprising a member of piezo-electric substance, electrode means associated with said piezo-electric substance for translating electric energy oscillations applied to said substance into mechanical vibrations of said vibratory structure and vice versa, and means coupling a part of said vibratory structure to an external vibratory body and supporting another part of said vibratory structure having a substantial mass subjected to the action of said electrode means in a freely floating position for transmitting by the inertia reaction of said floating vibratory structure vibratory energy between said vibratory structure and said vibratory body, the floating mass of said vibratory structure being of the order or larger-than one-half of the total mass of said vibratory structure.

23. In a piezo-electric energy translating device, a vibratory structure comprising a member of piezo-electric substance, electrode means associated with said piezo-electric Substance for translating electric energy oscillations applied to said substance into mechanical vibrations of said vibratory structure and vice versa, and

means coupling a part of said vibratory structure to an external vibratory body and supporting another part of said vibrator having-a mass subjected to the action of said electrode means in a freely floating position for translating by the inertia reaction of said floating vibratory structure vibratory energy between said vibrator and said vibratory body, the floating mass of said vibratory structure including a body of greater specific weight than said piezo-electric substance being of the order or larger than one-half of the total mass of said vibratory structure.

EMMANUEL CHRIST NICHOLIDES.

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