US2242757A - Piezoelectric device - Google Patents

Description

May 20, 1941. F. F. ROMANOW 2,242,757

PIEZOELECTRIC DEVICE Filed Feb. 11, 1939 2 Sheets-Sheet 1 FIG! FIG. 7

INVENTORT By FFROMANOW A TTOR/VEV 7 1941- F. F. ROMANOW 2,242,757

PIEZOELECTRIC DEVICE Filed Feb. 11, 1939 2 Sheets-Sheet 2 FIG. 8

INVENTOR y FE ROMANOW A TTORNFY Patented May 20, 1941 PIEZOELEC'IIIIC DEVICE Frank I. Bomanow, Berkley Heights, N. 1., assign- Incorpor e ortonell'l clephone Iaboratorl New York. N. 1.. a corporation es, olNewljork Application February -11, 1939, Serial No. 255,826 1; Claims. (01.. 110-110) This invention relates to piezoelectric devices and more particularly to acoustic devices of the type disclosed in the application Serial No. 255,817, filed February 11, 1939, of Thomas J. Pope, and comprising a diaphragm and a piezoelectric element in energy transferring relation with the diaphragm.

One object of this invention is to obtain a uniform response and a high response level for piezoelectric acoustic devices.

Another object of this invention is to distribute the load upon the crystal eiement in piezoelectric devices.

A further object of this invention is to obtain a relatively simple mode of vibration of composite piezoelectric elements. I

Still another object of this invention is to improve the character of vibration of the diaphragm in a piezoelectric acoustic device.

In one illustrative embodiment of this invention, a telephone receiver comprisesadiaphragm and piezoelectric means for actuating the diaphragm.

In accordance with one feature of this invention, the actuating means comprises a pair of spaced, similar, composite elements. Each piezoelectric element may include a pair of rectangular, for example, square, crystal platesor slabs secured together in face-to-face relation and so oriented that diagonally opposite corners of the element deflect in the same direction in response to electrostatic stresses. One pair of diagonally opposite corners of one composite element is connected to the diaphragm.

In accordance with another feature of this in- I vention, the two composite piezoelectric elements are oriented so that the axes of similar deflection of one are at an angle to the corresponding axis of the other. v

In one specific embodiment, these axes of one element are at right angles to the corresponding axis of the other, and two diagonally opposite corners of one element are connected to two corners of the-other. The other two corners of one element are connected to the diaphrasm- The other two corners of the other element may be unrestrained or may be fixed against displacement.

In another specific embodiment, the two composite elements have their axes of similar deflection at substantially 45 degrees to one another. Two diagonally opposite corners of each element arefixed and the other corners are connected to the diaphragm, the orientation being such that the corners connected to the diaphragm deflect in the same directions in response to electrostatic stresses. 1

The invention and the foregoing and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawings wherein:

Fig. l is a perspective view of a telephone receiver illustrative of one embodiment of this invention, a portion of the casing being broken away to show the internal structure;

Fig. 2 is a viewin' section along line 2-2 of Fig. 1;

Fig. 3 is a fragmentary view in section of one of the composite piezoelectric elements, showing the construction thereof; v

Fig. 4 is a atic exploded view of one 'of the composite piezoelectric elements, showing the characteristic axes thereof;

Fig. 5 is a diagrammatic view illustrating the relative directions of deflection of the corners of the two composite piezoelectric elements;

Fig. 8 is a perspective view of a telephone receiver illustrative of another embodiment of this invention, a portion of the casing .being broken away to show the internal structure; Fig. 9 is a view in section along line 9-8 of Fig. 'l; and Fig. 10 is a diagrammatic view illustrating relatively the direction of deflection, of the corners of the composite piezoelectric elements in the receiver shown in Figs. '7 and 8.

Referring now to the drawings, the,telephone receiver shown in Figs. 1 and 2 comprises a casing ll, for example, of molded insulating mate--.

rial, and a centrally apertured cap or ear-piece l9 threaded to the casing ii. The casing is provided with an internal shoulder H on which there is seated amannular spacer ll.

1 Seated in turn upon the spacer I8 and held thereagainst by the cap or ear-piece I6 is adiaphragm having a flexible, flat supporting portion I9, a bodily vlbratile central portion and an 9 intermediate annular portion 29, L-shaped in sec- .tion. The bodily vibratile portion includes a cenconcavo-ccnvex section 2i, anda pair of frusto- conlcal sections 22 and 29. The diaphragm may be formed in a single piece and electric elements'fla and 24b. Each of these elepreferably is of a lightweight metal such as duralumin.

Mounted within the casing I5 is a pair of rectangular, for example, square, composite piezo- The two plates or slabs are secured together in faceto-face relation as by a suitable cement.

' be cut from a mother crystal, as described in the aforementioned application of Thomas J. Pope,

so that the sides thereof are'parallel to the Y and Z axes and the faces are normal to the X or electrical axis, as illustrated in Fig. 4. When a potential is impressed between the electrodes on opposite faces of such a crystal plate or slab, the plate or slab will tend to expand along one diagonal, for example, along the diagonal AC in Fig. 4,-and to contract along the other diagonal, for example, along BB in Fig. 4. The two crystal plates or slabs are oriented so that corresponding axes of expansion and contraction thereof are at right angles to one another. For example, as shown in Fig. 4, they may be related so that .the Y and Z axes of one are at right angles to the corresponding axis of the other, whereby when the crystal 24 tends to expand along AC and to contract along BD, the crystal 24 will tendto contract along BD, which is in line with AC, and to expand along A'C, which is in line with BB. Consequently, because the two plates or slabs 24 and 24 are secured together in face-to-face relation, the diagonal forces will result in deflection of the corners of the composite element, substantially normal to the faces thereof. Thus, if the polarity of the impressed potential is suchas to produce diagonal stresses of the direction shown in Fig. 4, as illustrated on the composite element 24b in Fig. 5 two, diagonally opposite corners (BC' and AD) will deflect upwardly and the other two diagonally opposite corners (AB' and CD) .will deflect downwardly.

If the two plates or slabs 24 have their Y and Z axes related as shown in Fig. 4, the indicated directions of expansion and contraction will obtain if the potentials applied are such that corresponding surfaces of the two plates or slabs are at the same polarity. In this case, the upper surface of the slab 24* is opposite in polarity to the lower face of the slab 24 and electrically insulated therefrom by a suitable medium.

.It will be understoodthatthe relative directions of expansion and contraction indicated in Fig. 4'may be obtained if the Y and Z axes of each plate or slabare parallel to thoseof the other and the potentials applied are such that corresponding surfaces of the two faces are opposite in polarity. In this case, the upper face of the slab 24 is at the same polarity as the lower face of the slab 24 and hence, need not be insulated therefrom. For this case, the conductors 28 may be connected together and the conductors 21 also connected together as noted heretofore.

As illustrated by the arrows in Fig. 5, the two composite elements 24a and 24b are oriented so that for the potentialat any particular instant aligned corners of the two deflect in opposite directions. The desired orientation, it will be understood may be obtained by proper correlation of .the polarity of the potentials applied to the electrodes of the plates or slabs and by proper orientation'of the axes of contraction and ex-' pansion of the two crystals. That is to say, the

- two composite elements may have their diagonals in the relation indicated by the letters in Fig. 5 and potentials of'like polarity applied to corresponding surfaces. Alternatively, the two elements may have their corresponding diagonals in alignment in which case the potentials applied to corresponding surfaces thereof would be opposite in polarity.

It will be understood, of course, that in Figs. 4 and 5 the arrows indicate the direction of stresses and deflection for potentials of one p0.- larity. When the polarity of potential is reversed, the direction of stresses and deflection also will be reversed. Hence, if the potential applied is variable, for example, corresponding to speech andmusic frequencies, the corners of the composite elements will vibrate at corresponding frequencies, the amplitude of deflection being proportional to the magnitude of the potential.

As shown in Figs. 1 and 2, two diagonally opposite corners of the composite element 24b are connected to diametrically opposite points on the annular portion 20 of the diaphragm, as by balsa wood blocks 28 cemented thereto. The other two corners of the composite element 241) are connected to the juxtaposed corners of the composite element 24a, as by balsa wood blocks 29 eemented thereto, only one of which is shown in each of Figs. 1 and 2. Hence, the composite element 24a provides a load upon the composite element 24b which, it has been found, results in an increase in the response at low frequencies. This in turn enables the attainment of a high average response level throughout a wide range of frequencies.

The composite element 24a may (be unrestrained except for its connection to the element 241), as illustrated in Figs. 1 and 2, or, as shown in Fig. 7, it may be fixed along one diagonal as by a rigid bracket or bridge member 30 carried by the ring member l8 and afiixed, as :by cementing, to the .element 24a. In Fig. 7, the construction of the other parts and the orientation of the composite elements is the same as in the construction shown in Figs. 1 and 2.

If desired, the upper crystal element 24a in Fig. 1 may be utilized also to apply driving forces to the diaphragm. Thus, the two free corners of this element in Fig. 1 may be connected to points on the diaphragm adjacent the blocks 2| through a direction reversing mechanism, such as a lever. so that the forces applied thereby to the diaphragm are directionally inphase with those applied by the element 24b through the blocks 28. Such construction is illustratedin Fig. 6 wherein 40 is a lever having a fulcrum H, the ends of the lever being connected to the portion 20 of the diaphragm and the element 24 by balsa wood blocks 42.

In the embodiment of this invention illustrated.

-is aflixed along one diagonal thereof to the bracket or bridge member 30. The composite element 24b also is aflixed along one diagonal thereof to a second bracket or bridge member ll carried by the ring spacer IS. The two elements 24a and 24b have their corresponding diagonals at substantially 45 degrees to one another and are oriented so that, as indicated in Fig. 10, all the unfixed corners of the two elements deflect in the same direction in response to electrostatic forces. These corners are connected to equally spaced points on the annular intermediate portion 20 of the diaphragm by the balsa. wood blocks 28. The diaphragm; therefore, has spaced equal forces applied thereto so that the rigid control portion 2|, 22, 23 vibrates bodily analogous to a piston. Although the invention has been described with particular reference to telephone receivers, it will beapparent that it is applicable as well to transmitters. It will be understood, of course, that although several specific embodiments of this invention have been shown and described, various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An acoustic device comprising a diaphragm,

and means for actuating said diaphragm including a pair of similar rectangular piezoelectric elements spaced from one another in face-to-face relation, each of said elements including a pair of crystal plates secured together in faceto-face and contraction, and said elements being oriented so that the axes of similar deflection of one are at an angle to the corresponding axis of the other.

2. A piezoelectric device comprising a vibratory I relation and having diagonal axes of expansion member, a rectangular piezoelectric element having diagonalaxes of deflection, means connecting two diagonally opposite corners of said element to said vibratory ,member, a second rectangular piezoelectric element spaced from said first element and having diagonal axes of deflection, and v means connecting two diagonally opposite corners of said second element to the other two corners of said first element, said elements being oriented so that each two corners thereof connected by said second means tend to deflect in opposite directions in response to electrostatic stresses in said elements.

3. A piezoelectric device in accordance with claim 2 wherein said first piezoelectric element is supported solely by said vibratory member.

4. A piezoelectric device in accordance with claim 2 wherein said second piezoelectric element is supported solelyby said first piezoelectric element.

5. A piezoelectric device in accordance with claim 2 wherein said first piezoelectric element is supported solely by said vibratory member and said second element is supported solely by said first element.

6. A piezoelectric device. in accordance with claim 2 comprising means'fixing the other two corners of said second piezoelectric element against movement.

7. A piezoelectric device in accordance with claim 2 comprising a bridge member secured to said second piezoelectric element along the diagonal extending between the other two corners thereof, and means supporting said bridge member.

8. An arcuate device comprising a pair of superposed piezoelectric elements of similar rectangular configuration, said elements having diagonal axes of similar deflection and their corresponding axes of similar deflection at an angle one pair of diametrically opposite points of one.

of said plates, and means connecting the other diagonally opposite points of said one plate in v fixed relation to one pair of diagonally opposite points of the other of said plates.

10. An acoustic device comprising a pair of substantially square piezoelectric elements arranged one above the other and having diagonal axes of deflection and their corresponding axes of deflection. at equal angles to "one another, means fixing one pair of diagonally opposite comers of one of said plates, means fixing the corresponding pair of diagonally opposite corners of the other of said plates, and a vibratory member connected to the other comers of both of said plates.

11. A telephone receiver comprising a diaphragm, and means for actuating said diaphragm comprising a pair of substantially square piezoa second rigid member fixedly supporting the corresponding pair of diagonally opposite comers of the other of said plates, and means connecting the other corners of both of said plates to said diaphragm. v

12. A piezoelectric device comprising a rectangular composite piezoelectric element including a pair of crystal slabs the faces of which are parallel to the Y and Z axes thereof,'said slabs being secured together in face-to-face relation and oriented so that the axes, of deflection of said element are along the diagonals thereof, a second rectangular composite piezoelectric element similar to said first element, in face-to-face relation therewith and spaced therefrom, said elements being oriented so that each of the diagonals of one is at right angles to the corresponding diagonal of the other whereby, in response to electrostatic stresses in said elements, juxtaposed corners of the two tend to deflect in opposite directions, vibrating means connected to two diagonally opposite corners of one of said elements, and means connecting the other two corners of said one element to the corners of the other element in juxtaposition thereto.

13. A piezoelectric device comprising a pair of composite rectangular piezoelectric plates having corresponding diagonal axes of similar deflection, said plates being mounted in face-toface relation and spaced from one another with corresponding axes thereof at equal angles to each other, a vibratory member, and means connecting two diagonally opposite corners of each to one another, a diaphragm, means connecting slid P181585 to said V b a y ember.

two diagonally opposite extremities of one of said elements tosaid diaphragm, and means FRANK I". ROMANOW.

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