US3697790A - Transducers having piezoelectric struts - Google Patents
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- US3697790A US3697790A US94232A US3697790DA US3697790A US 3697790 A US3697790 A US 3697790A US 94232 A US94232 A US 94232A US 3697790D A US3697790D A US 3697790DA US 3697790 A US3697790 A US 3697790A
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Images
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R17/00—Piezoelectric transducers; Electrostrictive transducers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
- B06B1/0648—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element of rectangular shape
Definitions
- the frame is subjected to [56] References C'ted face shear stress by deflections of a generally saddle UNITED STATES PATENTS shaped diaphragm termed a diabow, inducing 1ongitudmal stresses 1n the piezoelectric strut.
- the strut 5 ygg has electrodes for connection with an electrical cir- 2,40 92 i etts m 2,421,586 6/1947 Tibbetts ..310/8.5 2,877,362 3/1959 Tibbetts ..310/8.9 33 Claims, 10 Drawing Figures PATENTEDBBHO I972 3597,790
- This invention relates generally to transducers for converting electrical energy to mechanical energ or mechanical energy to electrical energy, or both. More specifically, it relates to devices for efficiently using the piezoelectric properties of certain known substances.
- the piezoelectric properties of single crystals have long been known and have been widely used in electromechanical and electroacoustic transducers. Examples are described in U. S. Pat. No. 2,403,692 to George C. Tibbetts, dated July 9, 1946.
- Various vibrational modes either natural or essentially static may be employed. Each static mode has a corresponding piezoelectric coupling coefficient k related to the way in which energy is stored in the piezoelectric body.
- piezoceramics which are polycrystalline aggregates of ferroelectric materials, one example of which is a ceramic comprising barium titanate fired to vitrification, as described in U. S. Pat. No. 2,540,412 to Robert Adler, dated Feb. 6, 1951.
- Contemporary piezoceramics commonly are based on solid solutions of lead zirconate and lead titanate.
- a piezoceramic material is poled, that is, it has a remanent polarization imparted to it, by subjecting it to a high electric field at room or elevated temperatures.
- Piezoceramic materials are preferred over single crystal elements in many current applications, such as hearing aid transducers, phonograph pickups, underwater sound transducers, and so forth. The reasons for this preference include greater strength to withstand mechanical shock, thermal and environmental stability, high electromechanical coupling coefficients, ease of fabrication, versatility of the poling techniques and low cost of manufacture.
- the longitudinal piezoelectric coupling coefficient is that which applies to changes in dimension in the direction of poling when other changes in dimension are unconstrained.
- the transverse piezoelectric coupling coefficient is that which applies to changes in dimension perpendicular to the direction of poling, and is about half the value of the longitudinal coupling coefficient for a typical piezoceramic material. In each of these particular cases the electric signal field is parallel to the direction of poling.
- any practical electromechanical or electroacoustic transducer using a piezoelectric body it is necessary to provide mechanically vibratable means and electrical circuit means for coupling to the body. Both of these means present practical problems.
- the electrical circuit means must have an impedance adapted to that of the piezoelectric body.
- the mechanically vibratable means should also provide mechanical and environmental protection to the piezoelectric body.
- Electromechanical transducers employing piezoceramics for audio frequency applications have 0 which persists even when the relatively stronger piezoceramic materials are employed rather than single crystal materials.
- To overcome fragility it has been proposed to use trilaminates having metal substrates, in which reliance is placed on the strength of ceramics in compression. These methods in turn impose their own limitations including permissible directions of poling, usable coupling coefficients and electrical properties.
- This invention provides improvements in piezoelectric transducers that afford a combination of desirable properties in a unit of simple construction and low cost of fabrication. It permits the utilization of the preferred piezoceramics in simple one-piece shapes such as struts of rectangular cross section, which are easily fabricated and readily poled. Moreover, the other parts are also simple in structure and readily assembled to provide a small, compact, rugged and highly sensitive transducer.
- the invention comprises one or more piezoelectric struts having electric signal field directions either longitudinal or transverse with respect to their lengthwise axes, the struts extending along one or both diagonals of a quadrilateral.
- Means are provided to transform external stress into face shear stress in a plane parallel to this quadrilateral, and means are further provided to transform this face shear stress into longitudinal stress in the struts.
- energy may be transformed from the mechanical form to the electrical form, or from the electrical form to the mechanical form, or in both directions. That is, both the stress transforming means and the overall transduction are bilateral in operation.
- the preferred means for transforming the face shear stress into longitudinal stress in the struts comprises a peripheral frame, preferably in the general shape of the quadrilateral, the strut or struts being mounted within the outline of the frame in force-transmitting relation to the frame in the regions of the respective comers of the quadrilateral.
- the preferred means for transforming external stress into face shear stress comprises one or two diabows.
- diabow includes a diaphragm lying near a plane and so shaped that face shear stress applied to its periphery in that plane produces displacements of the diaphragm relative to its periphery that have relatively large components normal to the plane.
- the term also includes any other means, whether in the form of a diaphragm or not, that is capable of transforming such face shear stress into an external stress system. The reverse is also true, namely, that the diabow transforms deflections or forces normal to the plane of its periphery into forces delivered at its periphery that correspond approximately to a uniform face shear stress system in the plane.
- the stress within the strut produces, or is produced by, electric signal fields having directions oriented with respect to the strut.
- These signal field directions may be along any of the three dimensions of the strut, and may also be symmetrically oriented with respect to its midpoint. For example, they may be directed from the midpoint longitudinally toward the respective ends of a strut, and this particular configuration may provide important advantages including that of having the strut ends and the stress transforming means at a common ground potential, with the mid-point of the strut providing a signal electrode with respect to that ground potential.
- a substantial number of other possible configurations are also provided, as will be evident from the following description from which the various other advantages of the invention will become evident.
- FIG. 1 is an exploded view of an electroacoustic piezoelectric transducer or cell embodying a preferred form of this invention.
- FIG. 2 is a view in plan showing the transducer of FIG. 1 with the diabows and some electrical parts removed.
- FIG. 3 is an elevation in section taken on line 33 in FIG. 2 with all parts of FIG. 1 in place.
- FIG. 4 is a plan view in section of a hearing aid type microphone incorporating the transducer'of FIGS. 1 to 3.
- FIG. 5 is an end view of the microphone viewed from the left in FIG. 4.
- FIG. 6 is an elevation in section of an alternative form of transducer utilizing a different piezoelectic coupling coefficient preferred for loudspeaker type applications.
- FIGS. 7a and 7b are diagrams illustrating forces existing within an idealized transducer of the type embodying the invention.
- FIG. 8 is a diagram illustrating in exaggerated degree the flexure of the frame of the transducer associated with face shear deflection.
- FIG. 9 is a view illustrating a method of poling and fabricating one embodiment of the piezoelectric struts.
- FIG. 1 shows in exploded form the principal parts of an electroacoustic transducer or cell, designated generally at 12 (also shown in FIGS. 4 and 5).
- the cell comprises an enclosure having sides formed by a generally rectangular or square shaped frame 14 preferably fabricated from a material having a low thermal expansion coefficient and a relatively high elastic modulus, such as the nickel-iron alloy containing 36 percent nickel and commonly known as lnvar.
- a relatively high elastic modulus such as the nickel-iron alloy containing 36 percent nickel and commonly known as lnvar.
- rectangular is intended to include square as well as other shapes, as is commonly understood.
- the frame is gold plated to provide surfaces having good electrical contact with the struts as hereinafter more fully described.
- Diabows 16 and 18 in the form of generally saddleshaped metal diaphragms having peripheral flanges 20 and 22, respectively, are assembled with the flanges abutting the side edges of the frame. This forms a closure that protects the parts contained within it.
- the structure and configurations of the diabows are well known in the art.
- the saddle-shaped central re gions are preferably smoothly curved, and preferably each diabow is mirror symmetrical with respect to the other.
- the flanges each lie in a plane to which the central portions are joined by integral skirts 23 of varying height.
- the skirts 23 are of maximum height at two diagonally opposite corners and of minimum height at the other two diagonally opposite corners.
- Other suitable forms of diabows are described in the above-mentioned patent to Tibbetts.
- the diabows have the property that if forces with components normal to their principal surfaces are delivered thereto, such forces are transformed into forces delivered to the frame at their peripheries as face shear stresses, that is, stresses acting to draw two diagonally opposed comers of the frame toward one another while simultaneously forcing apart the other two diagonally opposed corners, and acting in the opposite direction to have the reverse effect.
- face shear stresses that is, stresses acting to draw two diagonally opposed comers of the frame toward one another while simultaneously forcing apart the other two diagonally opposed corners, and acting in the opposite direction to have the reverse effect.
- face shear stresses that is, stresses acting to draw two diagonally opposed comers of the frame toward one another while simultaneously forcing apart the other two diagonally opposed corners, and acting in the opposite direction to have the reverse effect.
- a pair of piezoelectric struts 24 and 26 extend diagonally across and within the frame 14. These struts are preferably fabricated from a piezoceramic material such as a lead zirconate-titanate polycrystalline body of a commercially available form, or the equivalent.
- the strut 24 has a pair of center or mid-point electrodes 28 (FIGS. 2 and 3) and two pairs of end electrodes 30 (FIG. 2) respectively located within rectangular apertures blanked in chamfers 32 formed in the frame.
- the strut 26 has a pair of center electrodes 34 and two pairs of end electrodes 36 respectively located within rectangular apertures blanked inchamfers 38 formed in the frame.
- a typical aperture in one of the chamfers is designated 40 in FIG. 3 and preferably provides a clearance vertically for the strut as viewed in FIG. 3.
- These electrodes are all preferably coatings having precious metal powder bases, glass bonded and fired on the strut material.
- the struts are electrically poled in the directions indicated by solid arrows 41 in FIG. 2.
- Each strut is poled in directions parallel to its lengthwise dimension.
- One strut is poled in one direction from its center electrode toward one of its end electrodes and in the opposite direction from its center electrode toward the other of its end electrodes, while the other strut is poled in one direction from one of its end electrodes toward its center electrode and in the opposite direction from the other of its end electrodes toward its center electrode.
- a suitable method of poling the struts is described below in connection with FIG. 9.
- the struts may be threaded through the apertures such as 40, or alternatively one end may be tipped through one aperture before insertion of the other end if the vertical clearance in the aperture is sufficient.
- a gold alloy curved leaf spring 42 (FIG. 3) which also seats each strut outwardly in its respective apertures with sufficient force to provide reliable electrical contact at each end of the strut between one of the electrodes 30 or 36 and the corresponding aperture.
- a suitable adhesive such as epoxy adhesive may be flowed into the five sets of joints to provide fillets 44 and 46. After curing of the adhesive, which may be done at temperatures such that depoling of the struts is negligible, the ends of the struts will, in general, slightly protrude outwardly of the aperture in the frame.
- Corner plates 48 fabricated from a high elastic modulus material, are then bonded to the outside of the frame chamfers by a similar adhesive.
- the purpose of the comer plates 48 is to increase the elastic stiffness of the joints between the struts and the frame.
- the adhesive in the butt joints between the struts and the corner plates, and between the corner plates and the outside chamfers of the frame, is partially confined because the lateral extensions of the joints are much greater than the film thickness of the adhesive.
- the partial confinement of the adhesive raises the effective elastic modulus of the adhesive to a considerably greater value than the Youngs elastic modulus of the adhesive. This in turn is nearly three times greater than the elastic modulus in shear, which is applicable to the adhesive within the apertures 40 during operation of the system as described below.
- FIGS. 1 to 3 When assembled, as described below, the structure of FIGS. 1 to 3 has very high resistance to mechanical breakage of the struts when the assembly is subjected to mechanical shock.
- the system Since the center electrodes are electrically connected together, and since the frame is a common contact to all the ends of the struts, the system possesses four essentially capacitive generators, each having the same voltage, polarity of voltage and capacitance, which are placed electrically in parallel by the nature of the construction. Because of the equality of the signal voltages, the electrostatic signal energies of the four capacitive generators are additive. In this embodiment, which is preferred for mechanical to electrical transduction as in microphones, an important advantage resides in this efficient provision of an electrical signal voltage at the center of the structure and relative to an equipotential periphery. When the directions of the face shear forces indicated by arrows 50 are reversed, the directions 52 of the signal polarizations are also reversed and thus point outwardly. That is, the operation of the system is essentially linear, and it can be used in linear electromechanical or electroacoustic devices such as microphones, phonograph pickups, and the like.
- each diabow by the nature of its configuration, possesses a negligible self-stiffness in excess of the flexural stiffness that it would have if formed as a flat plate.
- self-stiffness is meant the stiffness of the diabow in the case that motion of its periphery is unconstrained in any direction parallel to the plane of its flange. This fact explains in part why the above described embodiment has a high overall electromechanical coupling coefficient. Of equal importance is the fact that this coefficient is degraded very little by the frame as hereinafter more fully discussed.
- the electrical capacitance is low because of the relatively large spacing between the center electrodes and the frame, and the relatively small cross section of the struts.
- the pairs of electrodes 28, 30, 34 and 36 on opposite sides of the struts are pair-wise interconnected.
- the system is operative without such externally applied conductive means because of the relatively high capacitance between such electrode pairs.
- a transistor amplifier chip 54 is bonded to the strut 24 over an electrode 28, and one of the electrical connections of the chip is made at the face bonded to this chip.
- External leads 56, 58 and 60 are fabricated from film insulated wire similar to magnet wire, and pass through holes in the frame 14. The leads 56 and 60 are secured to the frame but electrically insulated therefrom, and the lead 58 is electrically contacted to the frame, as by spot welding, in order to make electrical connection with the electrodes 30 and 36 at the ends of the struts.
- lntemal wires 62 interconnect the chip 54 with the leads 56, 58 and 60.
- a vent may be made in the frame 14 to equalize the atmospheric pressure between the enclosed space 63 (FIG. 3) and the exterior of the cell. In certain cases it is practical to fabricate the cell without the vent, as a hermetically or substantially hermetically sealed case that provides protection of the transistor amplifier chip against adverse environmental conditions.
- a microphone embodiment incorporating the cell 12 of FIGS. 1 to 3 is shown in FlGS. 4 and 5.
- the cell is compliantly supported within a tubular metal casing 64 of generally rectangular cross-section, by eight elastomeric mounts 66.
- the mounts are L-shaped and are adhesively bonded to the cell 12 before insertion into the casing.
- the casing is closed at one end by an end plate 68 which carries an acoustic inlet tubulation 70 having an aperture 72 which also extends through the end plate.
- a U-shaped bulkhead 74 is mounted within the casing to provide support for the adjacent elastomeric mounts and to locate, by its major edges, a terminal plate 76.
- the leads 56, 58 and 60 are connected to soldered terminals 78 on the plate 76.
- the terminal plate has a thick film circuit on its inner face which is used in conjunction with the transistor amplifier contained within the cell 12.
- the space between the terminal plate 76 and the facing major surface of the bulkhead 74 is used to provide space for the thick film circuitry as well as for the leads S6, 58 and 60.
- the leads are disposed in such a way as to obtain maximum elastic compliance between the soldered terminals 78 and the entrance of the leads through the frame of the cell 12. By reason of this disposition of the leads, the elastic support of the'cell within the casing is provided mainly by the elastomeric mounts 66.
- the elastomeric mounts are aligned with the centers of the frame sides so that forces exerted on the frame by the mounts as a result of acceleration of the casing 64 in directions parallel to the plane of FIG. 4 are not electromechanically coupled to the signal electrodes of the transducer.
- the compliance of the mounts reduces such forces to a minimum, and likewise attenuates the acceleration of the cell 12 compared with that of casing 64 when the casing is accelerated normally to the plane of FIG. 4.
- the compliance of the mounts also prevents constraint on the motion of the frame in response to electroacoustic transduction.
- the entire structure is very resistant to mechanical shock and also has substantially no accelerometer sensitivity from the point of view of mechanical vibration, as discussed further below.
- the microphone embodied in FIGS. 4 and 5 can be rigidly bonded into the casing of devices such as hearing aids, and with the described structure the in situ mechanical shock resistance and accelerometer insensitivity characteristics will be excellent. The resulting saving of space and complexity in such devices will widen the applicability of transducers constructed in accordance with this disclosure.
- FIG. 7a is a schematic diagram that indicates the effect of a uniform face shear force per unit length N applied to a frame 14' idealized to have zero wall thickness and connected to struts 24' and 26' idealized to have zero width. Because of the symmetry of the structure, the total force applied along any side of the frame divides into two halves delivered at each end of the side. This is shown in FIG. 7b, which shows the force components delivered to the strut 24' at its lower end as viewed in FIG. 7a. By reason of the fact that the force components are proportional to the lengths of the corresponding sides of the frame, the total force resultant 79 is directed along and parallel to the axis 80 of the strut 24'.
- FIG. 8 is a schematic diagram showing a greatly exaggerated deformation of an idealized unchamfered frame 14" relative to the undeformed frame indicated by broken lines.
- the right angles in the neighborhoods of the frame comers persist under deformation of the frame, and therefore the frame is required to flex as it deforms.
- the flexure of the frame is partially constrained by the diabows. Energy is required to flex the frame, and this energy is least (zero) when the frame wall thickness is zero.
- each frame side also serves to transform the shear forces per unit length applied at its edges, to forces at the strut ends that cause the displacements of the strut ends and the corresponding flexure of the frame.
- a membrane force system exists in each of the frame sides in order to effect this transformation.
- This force system also results in the storage of elastic energy, which becomes smaller as the wall thickness of the frame becomes greater. Since both of these energies are subtracted from the total energy delivered to the frame-strut system to give the energy stored in the pair of struts, there exists an optimum for the wall thickness of the frame such that the electromechanical coupling coefiicient of the frame-strut system is maximum. The higher the elastic modulus of the frame material, the
- the frame In this restricted sense the behavior of the frame is analogous to that of a diabow, but at the same ti e it is obvious that the frame is distinguished from the diabow in many other respects. In combination with a diabow and a strut, the frame ranks in importance with the diabow itself. In combination with a strut, the frame is a novel element essential to the provision of a structure that is face shear responsive over a periphery.
- FIG. 3 illustrates some of the advantages that are obtained when the diabows are the only diaphragms of an electroacoustic transducer incorporating the cell of FIGS. 1 to 3.
- acoustic pressure differences act directly on the diabows l6 and 18 as described above, and acoustic volume displacements are produced solely by the deflections of the diabows.
- Dotted arrows 82 and 84 indicate the direction of the forces on the diabows l6 and 18, respectively, when the external pressure exceeds the pressure in the space 63.
- the diabows have low self-stiffness as discussed above, each is bonded to the frame. Under inertial forces the diabows develop membrane forces N of opposite sign which are connected together by the frame in such a way that the distortion of the frame is negligible. As a result, the total stiffness of the diabows with respect to inertial forces is even greater than the total stiffness with respect to acoustic pressures, and consequently the diabows deflect only moderately and substantially linearly when very large accelerations are applied by mechanical shock pulses.
- the embodiment of FIGS. 1 to 3 is preferred for transduction to the electrical form of energy. This is because the piezoelectric coupling coefficient of a piezoceramic is greatest when the direction of poling is in the direction of the tensile-compressive signal forces, and because the path length between the signal electrodes (in this case between the center and the end electrodes) is maximum. As a result, the opencircuit electrical signal voltage is relatively large for the embodiment of FIGS. 1 to 3. A corollary of this, however, is that the electrical capacitance of the transducer is minimized in the embodiment of FIGS. 1 to 3.
- the high open-circuit signal voltage can be used to advantage only if the impedance of the electrical load on the transducer is at least comparable with that of the transducer itself.
- a transducer using currently available piezoceramics and constructed according to FIGS. 1 to 3 typically has an electrical capacitance of only a few pico-farads. Therefore it is essential that an electronic amplifier be placed as close ly as possible to the set of center electrodes, and this is accomplished by mounting the transistor amplifier chip 54 directly on a center electrode 28 and causing the mounted face of the chip to be the high impedance electrical input terminal of the amplifier, as described above.
- Piezoceramic struts such as 24 and 26 may be fabricated conveniently from larger strips as illustrated in FIG. 9.
- a strip of piezoceramic material 92 carries electrodes 94 surrounding its outer edges, and a pair of central electrode strips 96, one on each major face.
- the electroded strip may be poled in the directions indicated by arrows 98 by conventional techniques adapted to the particular piezoceramic body. Such techniques are described, for example, in said patent to Adler.
- the strip may be mounted on a flat surface by means of a fairly low temperature hot melt adhesive.
- Struts such as 24 may then be produced by slicing the strip, as by diamond wheel slotting indicated by broken lines 99, and then removing and cleaning the struts in a solvent for the adhesive.
- Struts such as 26 can also be produced by reversing the polarity of the D. C. poling voltage and thus the directions of poling in the strip 92.
- FIGS. 1 to 5 Various modifications and variations may be made in the embodiment of FIGS. 1 to 5.
- the system is operable with only a single strut in combination with the frame.
- the system is operable with only a single diabow in combination with the frame and either one or two struts, although two diabows are preferred.
- FIG. 6 illustrates another variation characterized by a different direction of poling of the struts.
- the frame 14 is identical with that of FIGS. 1 to 3 but piezoceramic struts 100 and 102 are preferably employed.
- the strut 100 has electrodes 104 and 106 on its major surfaces and the strut 102 has electrodes 108 and 110 on its major surfaces.
- Each strut is poled in the direction of its thickness as indicated by solid arrows 112.
- the electrodes do not extend to the frame 14.
- the leaf spring 42 which may be identical to that of FIGS. 1 to 3, connects the electrodes 106 and 108.
- the two struts are placed electrically in parallel with a common connection 114 being made to the electrodes 104 and 110 and another connection 116 being made to the electrode 106.
- the directions of the signal polarizations for the directions of shear stress shown by the arrows 50 in FIG. 2 are indicated by dotted arrows 118 through the thickness of the struts.
- This embodiment in which the struts are electroded on major surfaces is preferred for electrical to mechanical transduction, even though the transverse piezoelectric coupling coefficient employed in the embodiment of FIG. 6 is only about one-half of the longitudinal piezoelectric coupling coefficient employed in the embodiment of FIGS. 1 to 3. This is because the electrical voltage required to produce a given mechanical displacement is much smaller for the embodiment of FIG. 6 than that for the embodiment of FIGS. 1 to 3.
- Struts fabricated from single crystal piezoelectric materials may also be employed in the embodiment of FIG. 6. Further, the embodiment of FIG. 6 may be modified to have electrodes on the side edges rather than the major surfaces of the struts, whether the struts are made of piezoceramic or single crystal piezoelectric material. In this case the central areas of the struts are not electroded to avoid the shorting of electrode pairs on one strut by the other strut. If a piezoceramic is used, the direction of poling is edgewise, that is, at right angles to the arrows 41 in FIG. 2 and in the same plane.
- Poling may be uniform through out the strut, or it may have opposite directions on each side of the non-electroded central area.
- the resulting four pairs of electrodes may be connected all in series, all in parallel, or in any suitable series-parallel combination, as desired.
- similar variations are applicable to the embodiment of FIG. 6 electroded on major surfaces of the struts if at least two electrode pairs are provided on each strut.
- a face shear responsive transducer having, in combination,
- an elastic peripheral frame generally in the form of a quadrilateral, supporting the strut near the ends thereof and substantially only at a diagonally opposite pair of corners of the quadrilateral,
- a transducer according to claim 1 having a pair of electrodes on the strut and spaced transversely of its lengthwise axis.
- An electroacoustic transducer having, in combination,
- each diabow having a substantially closed periphery
- An electroacoustic transducer in which the diabows are substantially mirror symmetrical with respect to one another to provide substantial cancellation of accelerometer sensitivity.
- a face shear responsive transducer having, in
- a strut of piezoceramic material poled in one direction between a mid region thereof and one end thereof along its lengthwise axis and in the opposite direction between the other end thereof and said mid region along said lengthwise axis
- an elastic peripheral frame generally in the form of a quadrilateral and supporting the strut substantially on a diagonal thereof, said frame transforming bilaterally between longitudinal stress in the strut and face shear stress acting at the frame in a plane substantially parallel to said quadrilateral, said frame being flexurally deformable cooperatively with longitudinal deformation of the strut, and said frame being compliant flexurally relative to the longitudinal compliance of said strut.
- a face shear responsive transducer having, in combination,
- a peripheral frame said frame being generally in the form of a quadrilateral and supporting a strut substantially on each diagonal thereof, said elastic means being adapted to transform bilaterally between longitudinal stress in the struts and face shear stress acting at the frame in a plane substantially parallel to said diagonals, said longitudinal stress being of opposite sense in the respective struts.
- struts are each formed of piezoceramic material, each strut being poled in one direction between a mid region thereof and one end thereof along its lengthwise axis and in the opposite direction between the other end thereof and said mid region along said lengthwise axis.
- a transducer according to claim 10 in which one strut is poled outwardly from the mid region thereof and the other strut is poled inwardly toward the mid region thereof, and in which said mid regions are connected together.
- a transducer according to claim 10 in which the frame is electrically conductive and electrically connected with the ends of the struts.
- a transducer between an external stress system and electrical terminals having, in combination,
- each strut substantially only near the ends thereof, the struts crossing one another, said frame transforming bilaterally between longitudinal stress in the struts and face shear stress acting at the frame in a plane substantially parallel to the lengthwise axis of each strut, said longitudinal stress being of opposite sense in the respective struts,
- a transducer in which the elastic means is a diabow having a substantially closed periphery, and in which the frame is attached to said periphery.
- each strut is poled in one direction between a mid re gion thereof and one end thereof along its lengthwise axis and in the opposite direction between the other end thereof and said mid region along said lengthwise axis.
- each strut has a pair of electrodes thereon spaced transversely of its lengthwise axis.
- each strut is poled in one direction between a mid region thereof and one end thereof along its lengthwise axis and in the oppositedirection between the other end thereof and said mid region along said lengthwise axis.
- a transducer according to claim 14 having a pair of electrodes on each strut and spaced transversely of its lengthwise axis.
- a transducer according to claim 14 having a second diabow having a substantially closed periphery, said frame being attached to the peripheries of both diabows.
- a transducer according to 'claim 26 in which each of the peripheries of the diabows is substantially rectangular.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Mechanical Engineering (AREA)
- Piezo-Electric Transducers For Audible Bands (AREA)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US9423270A | 1970-12-02 | 1970-12-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3697790A true US3697790A (en) | 1972-10-10 |
Family
ID=22243917
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US94232A Expired - Lifetime US3697790A (en) | 1970-12-02 | 1970-12-02 | Transducers having piezoelectric struts |
Country Status (11)
Country | Link |
---|---|
US (1) | US3697790A (xx) |
JP (1) | JPS5438490B1 (xx) |
AT (1) | AT310273B (xx) |
CA (1) | CA941953A (xx) |
CH (1) | CH571799A5 (xx) |
DE (1) | DE2158723C3 (xx) |
ES (1) | ES397051A1 (xx) |
FR (1) | FR2116473B1 (xx) |
GB (1) | GB1365085A (xx) |
IT (1) | IT945061B (xx) |
NL (1) | NL7112773A (xx) |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4044350A (en) * | 1974-08-22 | 1977-08-23 | Oleg Tretiakoff | Electromechanical transducer for relief display panel |
US4318023A (en) * | 1980-02-21 | 1982-03-02 | Physics International Company | Sagittally amplified piezoelectric actuator |
US4933591A (en) * | 1988-01-06 | 1990-06-12 | Ford Aerospace Corporation | Double saggital pull stroke amplifier |
US6715363B1 (en) * | 1998-02-20 | 2004-04-06 | Wilcoxon Research, Inc. | Method and apparatus for strain amplification for piezoelectric transducers |
US20050279566A1 (en) * | 2002-09-17 | 2005-12-22 | Anthony Hooley | Loudspeaker |
US20060050904A1 (en) * | 2002-12-20 | 2006-03-09 | Metheringham William J | Acoustic actuators |
CN1729715B (zh) * | 2002-12-20 | 2010-12-15 | 费奥尼克有限公司 | 声致动器 |
CN104012113A (zh) * | 2012-12-25 | 2014-08-27 | 京瓷株式会社 | 音响发生器、音响发生装置以及电子设备 |
US20150304781A1 (en) * | 2012-12-25 | 2015-10-22 | Kyocera Corporation | Acoustic generator, acoustic generation device, and electronic device |
US9380365B2 (en) * | 2012-12-17 | 2016-06-28 | Kyocera Corporation | Acoustic generator, acoustic generation device, and electronic device |
US20180139542A1 (en) * | 2015-04-29 | 2018-05-17 | Goertek Inc. | Piezoelectric speaker and method for forming the same |
US20210392439A1 (en) * | 2020-06-15 | 2021-12-16 | Lg Display Co., Ltd. | Sound apparatus |
US20220217472A1 (en) * | 2021-01-06 | 2022-07-07 | Lg Display Co., Ltd. | Sound generator, sound apparatus and apparatus comprising the same |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011046508A1 (en) * | 2009-10-16 | 2011-04-21 | Siemens Medical Instruments Pte Ltd | Elastomeric suspensions and integrated frame structures for electronic components |
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- 1971-09-17 NL NL7112773A patent/NL7112773A/xx not_active Application Discontinuation
- 1971-10-22 CA CA125,825A patent/CA941953A/en not_active Expired
- 1971-11-05 ES ES397051A patent/ES397051A1/es not_active Expired
- 1971-11-09 GB GB5186871A patent/GB1365085A/en not_active Expired
- 1971-11-20 IT IT54236/71A patent/IT945061B/it active
- 1971-11-26 DE DE2158723A patent/DE2158723C3/de not_active Expired
- 1971-12-01 CH CH1749371A patent/CH571799A5/xx not_active IP Right Cessation
- 1971-12-01 FR FR7143142A patent/FR2116473B1/fr not_active Expired
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- 1971-12-02 JP JP9681071A patent/JPS5438490B1/ja active Pending
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US4044350A (en) * | 1974-08-22 | 1977-08-23 | Oleg Tretiakoff | Electromechanical transducer for relief display panel |
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US6715363B1 (en) * | 1998-02-20 | 2004-04-06 | Wilcoxon Research, Inc. | Method and apparatus for strain amplification for piezoelectric transducers |
US20050279566A1 (en) * | 2002-09-17 | 2005-12-22 | Anthony Hooley | Loudspeaker |
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US20180139542A1 (en) * | 2015-04-29 | 2018-05-17 | Goertek Inc. | Piezoelectric speaker and method for forming the same |
US10284986B2 (en) * | 2015-04-29 | 2019-05-07 | Goertek Inc. | Piezoelectric speaker and method for forming the same |
US20210392439A1 (en) * | 2020-06-15 | 2021-12-16 | Lg Display Co., Ltd. | Sound apparatus |
US11800293B2 (en) * | 2020-06-15 | 2023-10-24 | Lg Display Co., Ltd. | Sound apparatus |
US20220217472A1 (en) * | 2021-01-06 | 2022-07-07 | Lg Display Co., Ltd. | Sound generator, sound apparatus and apparatus comprising the same |
Also Published As
Publication number | Publication date |
---|---|
DE2158723A1 (de) | 1972-06-15 |
AU3644171A (en) | 1973-06-21 |
DE2158723B2 (xx) | 1979-10-11 |
FR2116473B1 (xx) | 1975-08-29 |
IT945061B (it) | 1973-05-10 |
CA941953A (en) | 1974-02-12 |
JPS5438490B1 (xx) | 1979-11-21 |
CH571799A5 (xx) | 1976-01-15 |
FR2116473A1 (xx) | 1972-07-13 |
ES397051A1 (es) | 1975-03-01 |
GB1365085A (en) | 1974-08-29 |
DE2158723C3 (de) | 1980-07-03 |
AT310273B (de) | 1973-09-25 |
NL7112773A (xx) | 1972-06-06 |
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