US3307055A

US3307055A - Electromechanical device

Info

Publication number: US3307055A
Application number: US511180A
Authority: US
Inventors: Hugo W Schafft
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1963-11-19
Filing date: 1965-12-02
Publication date: 1967-02-28
Anticipated expiration: 1984-02-28

Description

Feb. 28, 1967 H. w. SCHAFFT 3,307,055

ELECTROMECHANI CAL- DEVI CE Original Filed Nov. 19, 1963 2 Sheets-Sheet 1 flilli- I! Feb. 28, 1967 Original Filed Nov. 19, 1963 H. W. SCHAFFT ELEGTROMECHANT'LICAL DEVICE 2 Sheets-Sheet 2 f 74 sounce ZZZ AM P.

' REVERB AME INVENTOR.

Jags

United States Patent O 3,307,055 ELECTROMECHANICAL DEVICE Hugo W. Schaift, Des Plaines, Ill., assignor to Motorola, Inc., Franklin Park, Ill., a corporation of Illinois Original application Nov. 19, 1963, Ser. No. 324,638, now

Patent No. 3,281,724. Divided and this application Dec. 2, 1965, Ser. No. 511,180

9 Claims. (Cl. 3108.6)

This invention relates to devices for producing delayed decaying electrical signals, and more particularly to a reverberation device which may be used in connection with sound reproduction apparatus for electrically simulating the acoustic conditions of a large room.

This application is a division of application Serial No. 324,638, filed November 19, 1963, now Patent No. 3,281,- 724, and assigned to the assignee of this application.

Certain musical performances, such as a symphony orchestra concert, are generally given in a large hall wherein the music will reach the ear of the listener via a direct path and via several other reflecting paths that are caused by sound waves bouncing off the walls, ceiling, and other reflecting surfaces of the hall. Numerous reflections will therefore reach the ear of the listener in a successive order, the amplitude thereof decreasing exponentially. Because commercially available recordings or broadcasts often contain no reverberation, when such sound is reproduced in living room or automobile of a listener, the smallness of the enclosure will generally preclude the occurrence of any detectable reverberation.

It is, therefore, often desirable, in sound reproduction systems which are used in rooms that are smaller than the rooms in which the sound being reproduced is normally heard, to utilize a reverberation device. Such a device will produce delayed, decaying electrical signals to simulate the acoustical characteristics of a large room, auditorium, or concert hall with a sound source located therein at some distance from a listener. The concert hall effect thus attained achieves a subjective enlargement of the room or enclosure in which the listener is located.

Numerous ways have been proposed to produce delayed decaying electrical signals. One of those ways is to change the electrical signals to mechanical vibrations to be transmitted along a vibration transmitting path which delays the trans-mission and produces echoes or re fiections, which are then re-converted into electrical signals for the desired reverberation effect. Devices providing suflicient delay within a reasonable range of frequencies, and providing suflicient reflections such that their separate arrival times are indistinguishable by ear, have been relatively complex and expensive. Furthermore, such devices are often excessively large and are sometimes very sensitive to vibrations from outside sources. This latter defect can be especially annoying in automobiles.

Accordingly, it is an object of this invention to provide an improved reverberation device closely simulating the acoustical characteristics of the concert hall.

Another object of the invention is to provide a compact reverberation device which is low in cost and simple of construction.

A further object of the invention is to provide an improved high efliciency transducer device for a reverberation unit, and a mounting for such device wherein all but torsional vibrations are damped.

A feature of the invention is the provision, in a device for producing delayed decaying electrical signals, of a pair of vibration transmitting members, each having one end connected to a transducer device and the other end suspended. A link couples vibrations between the two members at a point intermediate their ends to provide a primary vibrational path between the transducers, and a 3,307,055 Patented Feb. 28, 1967 plurality of secondary paths of different lengths for reflected vibrations.

Another feature of the invention is the provision, in a device as described, of structure for suspending the ends of the vibration transmitting members to reflect vibrations therein in different phase relationships.

Another feature of the invention is the provision of a transducer device including a pair of adjacent levers and an energy converting element for displacing a first end of each of the levers according to an electrical signal, and for producing an electrical signal according to displacement of those ends. The levers are disposed so that the second ends move in opposite directions to produce torsional movement upon displacement of the first ends, and such that displacement of the second ends in opposite directions due to torsional movement causes displacement of the first ends.

In the drawings:

FIG. 1 is a top plan view of a accordance with the invention;

FIG. 2 is a perspective view of a portion at the upper end of the device shown in FIG. 1;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a perspective view of the transducer device of the invention;

FIG. 4a is a perspective view of an alternative construction for the transducer device of FIG. 4;

FIG. 5 is a schematic showing of the transducer device of FIG. 4;

FIG. 6 is a perspective view of the transducers and connection for the right hand spring shown in FIG. 1:

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 1;

FIG. 8 is a perspective view of the mounting block for the transducer shown in FIG. 4; and

FIG. 9 is a block diagram of a circuit in which a device constructed in accordance with the invention may be incorporated.

A reverberation unit constructed in accordance with the invention comprises two identical torsional transducers, two helical springs of equal length, a coupling link between the ends of the springs, and a housing for carrying these elements. One of the transducers operates as a driving element while the other operates as a receiving element. One side of the first spring is connected to the driver transducer while its opposite end is suspended in such a way as to rotate freely. One end of the second spring is connected to the receiver transducer while its other end is connected rigidly to a mass. A coupling link intermediate the ends of the springs transmits torsional vibrations therebetween.

The driving and receiving transducers are substantially identical. The transducers incorporate a ceramic bender or bimorph and a lever system which converts the bending motion of the bimorph into a force couple. When this force couple acts upon the helical spring in the reverberation unit, it produces a torsional motion therein. The reverse is also true so that identical lever systems are used for both input and output. The lever system comprises a pair of levers which are fulcrumed intermediate their ends, and these fulcrums are fixed in relation to the center of the bimorph by a joining web. Each of the ends of the bimorph engages a respective one of the ends of each of the levers for displacing the same according to electrical signals applied to the bimorph, or in the case of the receiver transducer, for .being displaced according to its drive motion to produce an electrical signal in the bimorph. The ends of the levers opposite the bimorph move in opposite directions in response to bending of the device constructed in bimorph or in response to vibration of the spring to which they are attached.

One means of attaching the levers to the springs is by a stainless steel extension of generally U-shaped configuration. The free sides of the U-shaped extension are attached to respective ends of the levers, and the joining portion of the extension is connected to drive the spring. An alternative connection includes a nylon pin extending between the two levers, the center of which is joined to the spring. The transducer is mounted in a universal mounting which is not susceptible to torsional vibrations but which is free to move and damp out all other modes of vibration. Further damping is provided by a mounting plate upon which the elements of the reverberation device are suspended, which mounting is attached to a housing which may also be damped when mounted.

Referring now to FIG. 1, a reverberation unit constructed in accordance with the invention is shown. The unit is carried on a mounting plate 11 which in turn is attached in a housing 12 by means of rubber dampers 13 fixed to projections 14 of plate 11. A pair of

transducers

16 and 17 are mounted on one end of the plate. The details of the transducers and their mounting will be described subsequently.

Transducers

16 and 17 are nearly identical and may serve as either the input transducer or the output transducer for the reverberation unit. In FIG. 1, transducer 16 is the input or driving transducer whereas transducer 17 is the pick-up or receiving transducer.

A pair of helical delay springs 20 and 21 are coupled at one end to

transducers

16 and 17 respectively. As will be explained subsequently, transducer 16 imparts a torsional vibration to spring 20 which is transmitted to spring 21 and received by transducer 17. Both springs 20 and 21 are identical except that they are wound in opposite directions. This is because any helix, when expanded or retracted, will produce a torsional motion, and hence springs 20 and 21 are susceptible to producing a torsional motion by a strong shock from outside of the reverberation unit. Because the springs are oppositely wound, however, the effect of such outside vibrations is virtually cancelled out. The number of turns in each spring is the same.

Referring now to FIGS. 1 and 2 the reflective means for suspending the springs at the ends opposite the transducers may be seen. Spring 20 is provided with a hook 22, and a length of string 23 (preferably of Dacron or some other similar durable material) is knotted to the hook 22 such as by a girth hitch. A lead terminal 24 is mounted in an upwardly extending flanged end 25 of plate 11, and string 23 is drawn through a slot 26 in terminal 24 to the position shown in FIG. 2. The two sides of notch 27 in the end of terminal 24 are then deformed over the end of string 23 to secure the string in the terminal, as shown in FIG. 1. The free end of string 23 may be cut off. The result of such a suspension is effectively equivalent to an open circuit and will reflect substantially all vibrations exactly in phase.

The hook 28 of spring, 21 is secured in a notch 29 in an upwardly extending flange portion 30 of plate 11. Accordingly, this end of spring 21 is rigidly secured to the mass of the plate and is effectively equivalent to a short circuit. At this end of spring 21, substantially all the vibrations will be reflected with a phase reversal, that is, 180 out of phase with the incident vibrations.

A link 33 is used to couple vibrations between

springs

20 and 21 at respective points intermediate the midpoint and the suspended end of the spring. The link includes a pair of

clip portions

34 and 35 which clip over the top part of a coil of

springs

21 and 20 respectively. The

clips

34 and 35 extend downwardly from opposite ends and opposite sides of a rigid and flexible cross bar 36. Because

clips

34 and 35 are on opposite sides of cross bar 36, the coils of

springs

21 and 20 to which they are clipped are at different distances from the transducers. distribute the standing wave pattern for even frequency This helps.

response, and also breaks up the path lengths of travel for reflected signals for even reverberation.

Placement of link 33 affects the distribution of standing wave patterns in the system. Of course the further away from the transducers the link is placed, the longer will be the delay time. The reverberation time is also affected by the link placement. It is desirable to keep the high frequency reverberation time as long as possible in relation to the low because there are so many more losses at the higher frequencies than at the lower frequencies that if this were not done an unnatural sound could result. The closer toward the suspended ends of the springs the link is placed, the more the high frequency reverberation time is emphasized. Thu the placement of the link involves a compromise of several factors including the delay time, the high and low frequency reverberation times, and the optimum distribution of standing wave patterns for even frequency response.

A reverberation unit should provide a delayed signal of decaying amplitude. The ideal delay line would consist of a vibration transmitting member such as a spring having a resonant frequency at the lowest possible number of cycles. Accordingly, the harmonics at which the particular spring is resonant will extend through the entire range of frequencies desired to be conveyed. Most of the fre quencies desired to be conveyed will thereby fall at one of the harmonic peaks of the spring to be transmitted thereby at peak efficiency. The length of such a vibration transmitting member would be selected according to the delay time desired.

A difliculty with a device of the above type is the fact that the reflections of the vibrations occurring at each end of the spring will be spaced sufficiently that the arrival time of echos will be audible to the listener. In other words, a repetitious reproduction of the input signal will occur at a diminishing amplitude. To convert such a device into an acceptable reverberation unit, suflicient reflective paths would have to be added to cause the reflections to occur at a rate that would make them indistinguishable. Such a modification can be extremely complex and may result in excessive size of the unit.

The reverberation device constructed in accordance with the invention utilizes a construction wherein the characteristics of a very low resonant frequency spring are achieved by utilizing two springs of a higher resonant frequency. Spring 20 is a one-quarter wavelength resonator because of the freely suspended mounting, while spring 21 is a one-half wavelength resonator because of its grounded or fixed end mounting. Harmonics will occur at odd intervals in spring 20 and even intervals in spring 21 such that when combined, the harmonic peaks fall directly in between each other and maintain that relationship. The result is an even distribution of resonant harmonic peaks at which energy may be transferred, with reinforcement or cancellation occurring due to the even distribution of peaks. Furthermore, because of the even distribution of resonant peaks, the minimum energy transfer level is also raised. By placing coupling link 33 intermediate the ends of the springs, reflecting paths are created between the link and the suspended ends to provide additional resonant combinations which further fill in the gaps between the harmonic peaks. This further raises the minimum energy transfer level at all frequencies. The various combinations of resonant frequencies and harmonies available thus provide an even response curve for the reverberation unit.

The foregoing device also provides sufficient reflective paths of different lengths for vibrations so that the arrival of reflected vibrations is not distinguishable by ear. When an AC. voltage in the audio frequency range is placed on driver transducer 16, the electrical energy is converted into torsional vibration in the first helical spring 20. The mechanical impedance of the driver transducer is selected to be several times lower than the characteristic impedance of the spring 20. As the vibrational wave starts to propagate along the first spring it can travel along several paths. One path, the primary path, leads from spring 20 to coupling link 33 back along spring 22 to transducer 17. There the wave will arrive with a delay time which depends upon the delay characteristic of the spring and its length. The impedance of transducer 17 is selected to be many times lower than the characteristic impedance of coil spring 21. Accordingly, only a small fraction of the vibrational energy is converted back into electrical energy while the largest percentage is reflected. The reflected wave will again travel along several paths of which one leads along the spring 21 through coupling link 33 back along spring 20 to the transducer 16. Here again because of the mismatch condition of the impedances, most of the vibrational wave will'be reflected. The vibrational wave will continue to commute between driver and receiver until its energy is fully dissipated by the inherent losses of the system. The time it takes for these reflected vibrations to decay to a given level is the reverberation time.

The construction of the reverberation unit provides a number of other possible paths for vibrational transmission. Because coupling link 33 represents a transmission irregularity, it reflects a certain amount of the vibrational energy. At the freely suspended end of spring 20, full reflection of the wave with no phase reversal takes place while at the grounded end of spring 21, full reflection with a phase reversal occurs. Because of the various places in the spring system at which reflections occur, the multitude of standing wave patterns previously discussed are set up. Together with the initial delay time and the numerous echos produced by the spring system and its various paths, the output of the reverberation unit is a delayed signal of decaying amplitude closely resembling the conditions of a concert hall.

Various relationships exist between the dimensions and properties of the system components. The fundamental resonance frequency of the spring depends upon the number of turns of wire, diameter of the wire, the diameter of the coil, the density of the material of which the spring is made, and the modulus of elasticity of the spring. Of all the foregoing parameters, varying the diameter of the coil seems to be the most effective way of altering the fundamental frequency of a spring. It will probably be desirable in the system to damp out all vibrations below 200 cycles and above 5,000 cycles. This range has been found satisfactory for a proper acoustical effect, although other circumstances may dictate that a difference range of frequencies be used. The delay time, of course, will be determined by the length of the transmission spring between input and output transducers, and the reverberation time will be affected by the Q of the spring. It has been found that tension on the springs does not affect any measurable parameter, however, it was noticed that a springy sound becomes apparent with increased tension on the spring. The diameter of the spring, and the diameter of the wire, inversely affect the upper cut off frequency. More turns, and a lower cut off frequency of the spring, increases the delay. An increase in wire diameter and an increase in the modulus of elasticity increases the reverberation time. The mass of coupling link 33 inversely affects the high frequency response as does the compliance of the coupling link and of the wire of the spring.

It will be apparent that the foregoing described con struction results in a considerably improved reverberation device. Because both springs are identical, the device is simplified. .Furthermore, only one input and one output transducer is necessary and a short physical length for a given reverberation time is possible. Reinforcements and cancellations are generally avoided because of the planned placement of the harmonic peaks of resonance for a smooth response curve throughout the frequency range.

Referring now to FIG. 4, the construction of the transducer may be seen in more detail. Both

transducers

16 and 17 are constructed alike and are driven by a ceramic bender or bimorph 41. The impedance of the respective benders may be selected to properly match the impedance of the driving and driven electrical circuits. The benders drive a lever system that converts the bending motion of the ceramic bender into a force couple. When this force couple acts upon opposite points on the circumference of the spring it produces a torsional motion. On the other hand, when a force couple is exerted on the ends of the lever system by torsional motion of the spring, the ceramic bender is bent to produce an electrical signal.

The lever system includes a pair of

lever arms

42 and 43 which are bent longitudinally for rigidity. The

arms

42, 43 are joined by an integral web 44, and the ceramic bender 41 passes through an opening in web 44 and through openings in the

respective lever arms

42 and 43. Thus, the ceramic bender engages one end of each of

levers

42 and 43, which levers in turn are fulcrumed at the juncture with the integral web 44. Since the ceramic bender extends through an opening in web 44, its center is fixed in relation to the fulcrums of

respective levers

42 and 43. Epoxy cement is used to secure the bender to the

levers

42 and 43 and to web 44, and also serves to insulate the bender from the metal levers and web. Wires 48 connect each side of the benders 44 to terminals on terminal board 63, so that input and output signals are conducted to and from the respective benders.

In FIG. 5 the lever system is shown schematic-ally for clarity, wherein portion A represents the long portion of lever 42 and portion B the long portion of lever 43. Portion C represents the short portion of lever 42 which is engaged by bender 41, while portion D represents the short portion of lever 43 which is engaged by bender 41. Member E represents the connecting web 44, and portions F and G represent the junctures between web 44 and levers 42 and 43 respectively. Member H represents the bender or bimorph 41. It may be seen that as member H bends to the X position, the leverage at the ends exerts a force couple at the fulcrums represented by points F and G. This twists member E with the ends of members A and B moving in opposite directions as designated X to set up a force couple. When member H bends to the Y position, similar action causes displacement of the ends of A and B as designated Y. Conversely, it may be seen that a force couple applied to the ends of members A and B will cause opposite displacement thereof to displace points C and D in the same direction with respect to the center of member E. Accordingly, this will bend member H and produce an electrical signal therein. At the ends of

levers

42 and 43 is a stainless steel U-shaped connecting member 46 (FIG. 4). The center portion of U-shaped member 46 is curved slightly to prevent twisting, and the spring 20 is rigidly cemented therein. The sides of U-shaped member 46 are respectively connected to the ends of

levers

42 and 43 by cementing projections in openings in the levers. The result is a resilient extension of the levers which offers maximum stiffness to the force couple being transmitted to or from spring 20, but which offers minimum resistance or stiffness to outside vibrations for damping the same.

A damping rubber cylinder 45 is placed between the two

levers

42 and 43 in order to introduce maximum damping to flexural vibrations of the lever arms while having a negligible affect on the torsional motion thereof.

FIG. 4a shows an alternative coupling between

levers

42, 43 and spring 20. A nylon bearing 51 extends between the

levers

42 and 43 and spring 20 is hooked about bearing 51 in a groove about the circumference thereof. In either the case of FIG. 4 or the case of FIG. 4a the compliance of the lever arms, together with the combined masses of the bearing 51 or member 46 and the hook of the spring are adjusted to resonate at a frequency near the upper cut off frequency of the entire system. This supplements the response curve of the system, which normally declines at this point, to provide a sharper response cut off at the upper cut off frequency.

The

transducer units

16 and 17 are mounted in univers-al joints to present high damping to all vibrations except the torsional mode set up by the transducers themselves. This mounting is shown in FIGS. 6 through 8. The integral stamping of

levers

42 and 43 and connecting web 44 is provided with a pair of mounting

ears

53 and 54. These ears are cemented into

notches

55 and 55, respectively, of a lead block 57, and are flexible so that the lever system may pivot in a horizontal plane with respect to the block. Lead is used for the block because its elasticity is negligible and therefore cannot transmit any vibration, isolating cross talk between the input and output transducers. Each of blocks 57 are pivot-ally mounted on a horizontal pin 58 by means of a damping rubber insert 59. The mass of the block together with the damping rubber insert is a low pass filter which provides the low frequency cut off of the transducer. The resistive component of the rubber introduces loss below the cut off frequency. Because mounting

ears

53 and 54 are flexible, and because the blocks 57 are pivotal, the transducer is provided with a high loss universal hinge which allows the transducer to move freely in two planes and at the same time introduces sufficient loss to damp out low frequency flexural waves in the springs. This is very significant in damping out vibrations caused by outside sources.

The transducers are mounted on plate 11 as follows. Pin 58 is mounted in a U-shaped'flange 61 formed out of a mounting plate 62 secured to support plate 11. An insulating board 63 is mounted between plate 62 and plate 11 and may carry the terminals for the electrical connections to the respective ceramic bimorphs 41. The outer housing may be mounted by means of springs or damping pads, etc., to further reduce the effect of outside vibrations and to protect the system.

Referring to FIG. 9 a simplified schematic diagram of a circuit is shown in which a reverberation unit of the type described may be used. A source of audio frequency signals 71 is coupled through a preamplifier '72, through an amplifier '73, and from there to a speaker 74,

' where they are audibly reproduced. Some of the output of amplifier 73 is fed through a further amplifier '75 for driving a reverberation unit 76 of the type described. Output signals from the reverberation unit 76 are then fed back to the amplifier 73 so that they may be reproduced by speaker 74. By including signals of delayed decaying amplitude in the reproduced sound, a concert hall effect is created. This results from adding to the sound reaching the listeners ears, reflected and delayed sound waves which would normally be present in a large auditorium or concert hall.

From the foregoing description it may be seen that the invention provides an improved device for producing delayed decaying electrical signals which is low in cost and simple of construction. The device produces sufiicient reflections to render them indistinguishable by ear and is insensitive to outside vibration. The transducer which drives the device is an efficient unit which produces torsional vibrations for driving the springs in the reverberation device, and the identical receiver transducer which converts torsional vibrations of the springs into electrical signals is similarly efficient.

I claim:

1. A transducer device adapted to transform between electrical signals and a vibrating body operating in the torsional mode, including in combination, a pair' of spaced levers each with first and second ends and each having a fulcrum intermediate said ends thereof, said first ends each adapted to be joined to the vibrating body and to move about said respective fulcrums associated therewith in opposite directions relative to each other, and a bimorph joined to said second ends of said levers and .adapted to be coupled to an electrical circuit for trans- :forming in a bending mode between electrical signals and mechanical motion. Y

2. The transducer of claim 1 wherein said bimorph has an intermediate region fixed with respect to said fulcrums of said levers, said bimorph transforming between electrical signals and mechanical motion in opposite directions about said region.

3. A transducer device adapted to transform between electrical signals and a vibrating body operating in the torsional mode, including in combination, first and second levers each having first and second adjoining arm portions forming a bell crank like structure and including a fulcrum at the juncture of said arm portions, means positioning said fulcrums relative to one another, said second arm portions each adapted to be joined to the vibrating body and to move about said fulcrum associated therewith in opposite directions relative to each other, a bimorph connected to the first arm portion of said first lever on one side of said fulcrum associated therewith and to the like arm portion ofsaid second lever on the side of said fulcrum associated therewith opposite from said one side, said bimorph having a center fixed with respect to said fulcrum, and means for electrical connection to said bimorph, said bimorph being responsive to an electrical signal to bend thereby applying a force couple to each of said first arm portions of said levers lo move said second arm portions thereof about said fulcrums in opposite directions relative to each other, and said himorph further being responsive to displacement of said second arm portions with respect to said fulcrums associated therewith to produce electrical signals.

4. A transducer device for producing torsional motion from electrical signals and electrical signals from torsional motion including in combination, a pair of elongated levers disposed adjacent one another, each of said levers having a first end and a second end and a fulcrum intermediate the same and fixed in relation to the fulcrum of the other of said levers, means at said first ends of said levers and responsive to electrical signals applied thereto to displace said first ends, said means further being responsive to displacement of said first ends to produce electrical signals, said levers being disposed such that the second ends thereof move in opposite directions to produce torsional movement upon displacement of said first ends, and such that displacement of said second ends in opposite directions due to torsional movement causes displacement of said first ends to cause said means to produce electrical signals.

5. The transducer device of claim 4 wherein said means at said first ends of said levers includes a bimorph having a point intermediate the ends thereof fixed in relation to the fulcrums of said levers.

6. A transducer device for producing torsional motion from electrical signals and electrical signals from torsional motion, including in combination, a pair of elongated levers disposed adjacent one another, each of said levers having a first end and a second end and a fulcrum intermediate the same, 'an integral web portion connecting said fulcrums such that they are fixed in relation to each other, an elongated bimorph with the respective ends thereof engaging said first ends of said levers, said bimorph extending through an opening in said web portion and'having a point intermediate-its ends fixedly engaging said web portion, said bimorph being responsive to electrical signals applied thereto to bend and displace said first ends of said levers in relation to said web portion and hence to the fulcrums of said levers, said bimorph further being responsive to displacement of said first ends with respect to said web portion and the fulcrums of said levers to produce electrical signals, said levers being disposed such that the second ends thereof move in opposite directions to produce torsional movement upon displacement of said first ends, and such that displacement of said second ends in opposite directions due to torsional movement causes displacement of said first ends.

7. The transducer device of claim 6 further including a U-shaped link having a pair of free sides fixed to respective ones of said levers at the first ends thereof and having a center portion and means thereon for coupling said center portion to a vibration transmitting member.

8. The transducer device of claim 6 further including a ridged bearing member extending between said first ends of said first and second levers to be angularly displaced thereby, and means intermediate the ends of said bearing member for coupling to a vibration transmitting member.

9. The transducer device of claim 6 further including a lead mounting block and means pivotally mounting the same, and flexible ears extending from said Web portion between said levers, said ears being mounted in said lead block such that said levers and integral Web portion are pivotal with respect to said lead block about an axis 15 transverse to the pivotal axis of said lead blocks, said mounting thereby providing universal motion for said transducer device to damp all but torsional vibrations therein.

References Cited by the Examiner UNITED STATES PATENTS 2,513,326 7/1950 Bauer 179-10041 2,565,586 8/1951 Bauer 3108.6 2,671,178 3/1954 Tomcik 3l08.5

MILTON O. HIRSHFIELD, Primary Examiner. A. J. ROSSI, .T. D. MILLER, Assistant Examiners.

Claims

1. A TRANSDUCER DEVICE ADAPTED TO TRANSFORM BETWEEN ELECTRICAL SIGNALS AND A VIBRATING BODY OPERATING IN THE TORSIONAL MODE, INCLUDING IN COMBINATION, A PAIR OF SPACED LEVERS EACH WITH FIRST AND SECOND ENDS AND EACH HAVING A FULCRUM INTERMEDIATE SAID ENDS THEREOF, SAID FIRST ENDS EACH ADAPTED TO BE JOINED TO THE VIBRATING BODY AND TO MOVE ABOUT SAID RESPECTIVE FULCRUMS ASSOCIATED THEREWITH IN OPPOSITE DIRECTIONS RELATIVE TO EACH OTHER, AND A BIMORPH JOINED TO SAID SECOND ENDS OF SAID LEVERS AND ADAPTED TO BE COUPLED TO AN ELECTRICAL CIRCUIT FOR TRANSFORMING IN A BENDING MODE BETWEEN ELECTRICAL SIGNALS AND MECHANICAL MOTION.