US2484950A

US2484950A - Bender type electromechanical device with dielectric operating element

Info

Publication number: US2484950A
Application number: US740461A
Authority: US
Inventors: Jaffe Hans
Original assignee: Brush Development Co
Current assignee: Brush Development Co
Priority date: 1947-04-09
Filing date: 1947-04-09
Publication date: 1949-10-18
Anticipated expiration: 1966-10-18

Description

Oct. 18, 1949. H. JAFFE 2,484,950

manna TYPE ELECTROMEGHANICAL DEVICE um! nmwc'rarc ornrwrme ELEMENT Filed April 9, 1947 2 Sheets-Sheet 1 mwzmm HANS JAWE Oct. 18, 19495 H. JAFFE 2,484,950

BENDER TYPE ELECTROMECHANICAL DEVICE WITH DIELECTRIC OPERATING ELEMENT Filed April 9, 1947 2 Sheets-Sheet 2 AC SIGNAL TERMINALS 47 I I FIG. 5

AC SIGNAL TERMINALS 57 FIG. 6

INVENTOR. HANS JAIF'FE A TORNEY 1 Pmnaaoa. 18, 19.49

ENTI OFFICE BENDEB TYPE ELECTROMECHANICAL DE VICE WITH DIELECTRIC OPERATING ELE- MENT Hans Jafle, Cleveland Heights, Ohio, assignor to The Brush Development Company, Cleveland, Ohio, a corporation of Ohio Application April 9, 1947, Serial No. 740,461

. 6 Claims.

This invention relates to electromechanical transducers of the general type known as benders, in which mechanical action results from the application of an electric held and vice versa. More particularly, it relates to improved bender type electromechanical devices which are highly stable with reference to temperature and humidity conditions.

Electromechanical transducers of the piezoelectric type are well known in the art. One such arrangement has comprised Rochelle salt as the operating element thereof and transducers of this type are widely used commercially. However, the properties of Rochelle salt are such that transducers comprising this material as an operating element do not provide entirely satisfactory operation under some operating conditions. For example, the temperature of such a unit must be maintained at all times below a rather low maximum value or otherwise the piezoelectric properties of the operating element are destroyed. Also, it is well known that such operating elements are somewhat fragile and, inasmuch as Rochelle salt is hygroscopic, it is necessary in trans ducers of the type under consideration to insure that the operating properties of the unit are not adversely affected by humidity conditions.

Electromechanical transducers of the bender type are also well known in the art, being described, for example, in U. S. Letters Patent Re'. 20,213, granted to C. B. Sawyer on December 22, 1936. Such bender elements, as heretofore used,

have generally comprised an operating element consisting of two layers of some piezoelectric material.

In the research work leading to the present invention, it was discovered that certain ceramic materials, having-some very desirable operating characteristics, could be utilized to provide an operating element generally analogous to that of a iezoelectric operating element. One such arrangement is described in full in my copending application, Serial No. 740,460, filed concurrent- 1y with the present invention and assigned to the same assignee as the present invention. This copending application discloses an arrangement using a ceramic dielectric material which is polarized to provide an action somewhat of the nature of that provided by the crystal which is frequently used in crystal transducers. The specific arrangement disclosed in the copending application for polarizing the material of the operating element comprises the application of a high unidirectional electrical field thereto. It would be desirable to provide a bender type of operating element for an electromechanical transducer which uses dielectric material as the operating element, and it is to this that the present invention is directed.

It is an object of the present invention to provide an improved electromechanical transducer of the type in which mechanical action results from the application of an electrostatic field, and vice versa.

It is a, further object of the invention to provide an improved electromechanical transducer which may be readily and inexpensively produced and which is rugged and relatively immune to the influences of extraneous conditions such as temperature and humidity effects.

In accordance with the invention there is provided a bender-type electromechanical device comprising an even number of superimposed layers of dielectric material. These layers comprise two groups of elements, one of which is to expand while the other group is to contract, and vice versa, to provide a bender type of electromechanical transducer element. There is also provided unidirectional electrical polarizing means for each of the layers. Also electrical terminal connections are provided for each of the layers, such that the charges which would be associated with the application of a voltage thereto are of the same sign in each of the layers of one of the two above-mentioned groups of elements as the charge in each layer of the group due to the polarizing means, while the charges in each of the layers of the other of thevtwo above-mentioned groups due to the applied voltage are of the opposite Sign to the charge in each layer of the last-mentioned group due to the polarizing means. By this arrangement the device can be used to convert bending movements'of'the transducer element into electrical energy, or vice versa.

For a better understanding of the present invention together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

- 3 Referring now to the drawings. Figure 1 is a broken-away isometric view of a phonograph pickup embodying a bender-type electromechanical device in accordance with the invention; Figures 2, 3 and 4 illustrate various circuit connections suitable for use with the transducer element of Figure 1; Figures 5 and 6, respectively, illusance with the invention embodied in a phonograph pickup of well known design. In this phonograph pickup, a needle chuck it is mounted on elastic bearings ll, l2 in a twopart molded housing, only one part I! oi which is shown for the sake of simplicity. Enclosed within the housing is an operating element comprising two plates or layers of dielectric material I4, l5 cemented together face-to-face, with an electrode l 8 between them and electrodes l1 and I8 on the outer faces. The material of which the elements I4 and I5 are comprised is one which normally does not have the property of a substantially linear relationship as a first order eifect between its electrical and mechanical actions but which can be, as described in full in the above-mentioned copending application, polarized by the application of a unidirectional electrical field to respond to the fundamental component of an alternating electrical field applied thereto in at least one mechanical mode. The operating element comprising the layers l4 and I5 of dielectric material is mounted within the housing between similar soft pads i9, 20 of rubber or like material engaging it at one end. The element is engaged at its other end by a fork-like extension 22 of the needle chuck ID. A thin sheet of rubber or like material 23 is disposed between the operating element and the needle chuck to act as a compliant coupling member and to provide insulation to prevent shortclrcuiting of the electrodes l1,- l8 by the needle chuck. The three electrodes are connected to pin-

like terminals

25, 26 and 27.

Neglecting for the moment the polarizing action, which is mentioned above, when lateral vibrations are applied to the needle 28, vibratory bending forces are applied by the chuck to the two-plate crystal assembly, setting up alternating compression and tension forces. Thus when the needle is moved in the direction indicated by the arrow A, the plate or layer It is subjected to compression forces and the plate or layer 15 is subjected to tension forces. Conversely, when the needle is deflected in direction 13, plate i 5 is subjected to compression forces, and plate i4 is subjected to tension forces. When, as will be subsequently described, the plates are suitably polarized, alternating potential difl'erences are developed at the

terminals

25, 26, 27 in response to the vibrations of the needle. Suitable circuit connections for the arrangements of Figure 1 are illustrated in Figures 2, 3 and 4, in which circuit elements which correspond to those of Figure l have identical reference numerals.

Referring now to Figure 2, an arrangement is shown in which the operating element supplies input signals for a vacuum-tube amplifier 30. Th center electrode iii of the operating element is connected through a condenser 56 to the input electrode of tube 30, theouter electrode i8 of the operating element being grounded. The other outer electrode i1 is connected to a unidirectional source 3| which is used to polarize the operating elements of the transducer of the invention. The negative terminal of the source 3| is g ou ded. If the alternating impedance of the source Ii is high, a by-pass condenser 32 may be shunted across it. A grid leak resistor 33 is provided for tube 30.

Coming now to a consideration of the operation of the arrangement of Figure 2,.it will be seen that, with the circuit connection shown, the two plates or layers l4 and I5 are connected in series with the battery 3i. Under these conditions, the charges resulting from the connection of the battery are illustrated by the plus and minus signs to the left of the operating element. For alternating currents, however, the two plates are connected in parallel with the input electrodes of tube 30 since the electrode I1 is effectively connected to the electrode [8 through the potential source 3! or through the by-pass condenser 12. When the plates are polarized as shown, if a potential were applied to the alternating current output terminal it would tend to develop charges in one of the plates which correspond in sign to the component of charge developed in the same plate .by the unidirectional polarizing source ll, while charges of reverse sign are simultaneously developed in the other plate. This relationship is illustrated by the plus and minus signs to the right in the operating element. Under these conditions, the induced charges due to a bending force are of the same sign as applied to the input circuit of the vacuum tube 30.

It will be seen, therefore, that the arrangement described comprises an even number (specifically two) of superimposed layers of dielectric material comprising two groups of elements, one group of which is to expand while the other group oi which is to contract, and vice versa, to provide a bender type of electromechanical transducer element. In the case under consideration there is only one layer (specifically layer I4 or- I5) in each of the two groups of elements mentioned.

.Also, it will be seen that the source 3| comprises a unidirectional electrical polarizing means for each of the layers mentioned. Furthermore, electrical terminal-circuit connections are provided for each of the layers such that the charges associated with a theoretical application of voltage thereto, are of the same sign in each of the layers of one of the two groups of elements as the charge in each such layer of the one group due to the polarizing means. Also, it will be seen that the charges in each of the layers of the other of the two groups of elements due to this theoretical application of voltage are of opposite sign from the charge in each such layer due to the polarizing means. It is therefore seen that the device is used to convert bending movements of the transducer element into electrical energy for application to the input circuit of tube 30.

In Figure 3 is illustrated an arrangement in which the two plates are polarized in parallel while being connected in series for alternating signals as applied to the input circuit of the tube 30. In Figure 3 the outer electrode I1 is connected directly to the grid of tube 30 while the outer electrode i8 is connected to ground. A unidirectional path between the outer electrode I1 and ground is provided by the grid leak resistor 33. The polarizing source 3! is connected between ground and the inner electrode l6 through a high resistance 35 and a switch 36. The plus and minus signs shown to the left in the flgure illustrate the components of charge due to the battery action. It will be noted that in this case the polarity of the upper plate is reversedwith reference to the polarity shown in Figure 2. However, for signal potentials the upper plate is also reversed as shown by the plus and minus signs to the right so that the voltages developed by a bending of the element are additive in the input circuit of vacuum tube 30. Here again it will be seen that the charges associated with theoretical application of voltage to the plates i'l, l8are of the same sign in the top layer as the charge due to the action of the polarizing means, while the charge associated with the theoretical voltage in the bottom layer is of opposite sign from the charge associated with the battery.

Still another way of utilizing the element of Fig. 1 is illustrated in Fig. 4. In this case the outer electrode I1 is connected to the grid of a tube 38, and the outer electrode I8 is connected to the grid of a tube 39. The two tubes have their output circuits connected together through a push-pull transformer 40. Unidirectional paths from the grids and outer electrodes to ground are provided by grid-leak resistors 4|, 42. The two outer electrodes are thus held at the same average unidirectional potential. The inner electrode I5 is connected through switch to the polarizing source 3|. In this case the plates are polarized in parallel but are effectively in series for signal voltages as in Fig. 3.

In Fig. 5 there is illustrated a bender element comprising four layers or

plates

42, 43, 44 and 45. In order to provide a bender element with four .3 plates, it is necessary for the plates 42 and to expand when the plates .44 and 45 contract,

p and vice versa. In order to provide this effect so that the unit can be operated either to convert a bending motion into an electrical output signal or an electrical input signal to a bending motion of the element, it is necessary to provide proper circuit connections. The principle which is to be followed in this case, also, is that the component of charge due to polarizing, of two layers on one 4 side of the center axis. should be of the same sign as the component of charge due to the theoretical application of a voltage to the A. C. terminals of the unit while the charges in the other two plates should be of opposite sign from those due to the theoretical application of voltage. In order to efiect this result, thecircuit connections of Fig. 5 are provided. Thus the positive terminal of the polarizing source 3| is connected by conductor 41 to the electrode between

plates

44 and 45 while the negative terminal of the source 5| is connected by a conductor 48 to the electrode between

plates

42 and 45. The outside electrodes of

plates

42 and 45 are connected together by a conductor 49. The alternating-signal terminals 50 and 5| of the unit are illustrated and terminal 50 is directly connected to the conductive element between the

plates

43 and 44 and to the outside electrodes. Terminal 5| is connected to the electrode between

plates

42 and 43 directly and, 66 through an isolating condenser 52, to the conductive electrode between

plates

44 and 45.

In considering the operation of the arrangement of Figure 5 it will be seen that the components of charge in the

plates

42 and 45 due 70 to the polarizing source 3| are as indicated by the polarity signs to the left. Also, the components of charge due to an applied signal voltage or to an induced signal voltage in the case of a bending of the element may be as illustrated 7 by the plus and minus signs on the right. Here again it is seen that the components of the two charges under consideration are of the same sign in

plates

42 and 43 and are of opposite sign in

plates

44 and 45. As stated above, this is the requirement for bender type of element in accordance with the invention. It will be seen. therefore, that the arrangement of Figure 5 comprises an even number (specifically four) of superimposed layers of dielectric material comprising two groups of elements (specifically

group

42, 42 and group 44, 45) one group of which is to expand while the other group is to contract, and vice versa, to provide a bender type of electromechanical transducer element. The terminal-circuit connections are such that the charges associated with an application of voltage to the A. C. signal terminals of the transducer elements are of the same sign in each of the

layers

42, 45 of one of the two groups as the charge in each said

layer

42 or 43 due to the polarizing means II, while the charges in each of the

layers

44, 45 of the other of the two groups of elements due to this application of voltage are of opposite sign from the charge in each

such layer

44 or 45 due to the charge therein resulting from the polarizing means. This relationship is clearly shown by the polarity signs of the figure.

A different circuit arrangement is illustrated in Figure 6 where circuit elements which correspond to those of Figure 5 have identical, reference numerals. In this case, the positive terminal of the polarizing source 3| is connected directly to the electrode common to

plates

44 and 45 and to, the electrode common to plates 42- and 45 through a resistor 54. The negative terminal of source II is connected to the outer electrode of plate 42, the electrode common to

plates

43 and 44, and the outer electrode of plate 45 through

resistors

55, 56 and 51 respectively. The resistors 54 to 51, inclusive, are isolating resistors for alternating currents. Terminal 5!) in this case is connected directly to the electrode common to

plates

42 and 43 and to the outer electrode of plate 45 while terminal 5| is connected directly to the outer electrode of plate 42 and to the electrode common to

plates

44 and 45.

In view of the description of the operation of the Figure 5 embodiment of the invention which has been given above, it is deemed entirely unnecessary to give a detailed description of the operation in Figure 6. It is sumcient to 'saythat the arrangement is such that, upon application of an alternating voltage to terminals 50, 5|, corresponding bending movements of the operating element including plates 42 to 45 are provided.

Conversely, a vibratory bending movement of the operating element comprising plates 42 to 45 results in the generation of an alternating voltage which is available at terminals 50, 5|. The arrangement of Figure 5 or the arrangement of Figure 6 may be used, for example, in a pickup device similar to that of Figure l.

i The arrangement of Figure 'l is generally similar to that of Figure 2 and corresponding elements have identical reference numerals while similar elements have identical reference numerals primed. The circuit arrangement of Figure 7 is identical to that of Figure 2 and the only difference in the arrangement is that the layers of actuating material having electrodes I5, l1, l8 are of circular shape in the of Figure '7. From the description which has been given in connection with Figure 2 and in connection with Figure 1 of the above-mentioned arrangement copending application, it will be seen that the arrangement of Figure 7 is such that in its operation one of the plates expands in all radial directions while the other plate contracts in all radial directions, and vice versa. Thus the arrangemet of Figure '7 effectively provides an actuating element of the diaphragm type wherein, upon application of the polarizing potential 32, an alternating voltage at the input circuit of tube is associated with cup shaped bending motions of the operating element.

Each of the embodiments, of the invention, as

will readily be understood by those skilled in the art, can be used either as a generator of a1temating voltages in response to bending motions of the actuating element or can be used to provide mechanical vibratory motion in response to an alternating current input thereto.

While the invention has been described with a certain degree of particularity, it is to be under stood that it has been by way of example and that changes can be made without departing from the spirit and scope of the invention.

I claim as my invention:

1. A bender-type electromechanical device comprising, an even number of superimposed layers of dielectric material comprising two groups of elements one group of which is to expand and the other group of which is to contract and vice versa to provide a bender-type of electromechanical transducer element, unidirectional electrical-polarizing means for each of said layers, and electrical terminal-circuit connections to each of said layers such that the charges associated with a theoretical application of voltage thereto are of the same sign in each of said layers of one of said two groups of elements as the charge in each such layer due to said polarizing means while the charges in each of said layers of the other of said two groups of elements due to said applied voltage are of opposite sign from the charge in each such layer due to said such polarizing means whereby said device can be used to convert bending movements of said such transducer element into electrical energy or vice versa.

2. A bender-type electromechanical device comprising, two layers of dielectric material effectively comprising two groups of elements one group of which is to expand while the other group is to contract and vice versa to provide a bender-type of electromechanical transducer element, unidirectional polarizing means for each of said layers, and electrical terminal-circuit connections to each of said layers such that the charge associated with a theoretical application of voltage thereto is of the same sign in one of said layers as the charge due to said polarizing means while the charge in the other of said layers due to said applied voltage is of opposite sign from the charge due to said polarizing means, whereby said device can be used to convert bending movements of said transducer element into electrical energy or vice versa.

3. A bender-type electromechanical device comprising an even number of relatively thin and elongated layers of dielectric material comprising two groups of elements one group of which is to expand while the other group is to contract and vice versa to provide a bender-type of electromechanical transducer element, unidirectional electrical-polarizing means for each of said layers, and electrical terminal circuit-connections to each of said layers such that the charges associated with a theoretical application of voltage thereto are of the same sign in each 01 said layers of one of said two groups of elements as the charge in each such layer due to said polarizing means while the charges in each of said layers of the other of said two groups of elements due to said applied voltage are of opposite sign from the charge in each such layer due to said such polarizing means, whereby said device can be used to convert bending movements or said such transducer element into electrical energy or vice versa.

4. A bender-type electromechanical device comprising an even number of relatively thin circular disks of dielectric material comprising two groups of elements one group of which is to expand radially while the other group is to contract radially and vice versa to provide a bendertype of electromechanical transducer element, unidirectional electrical-polarizing means for each of said disks, and electrical terminal-circuit connections to each of said disks such that the charges associated with a theoreticaI application of voltage thereto are of the same sign in each of said disks Of one of said two groups or elements as the charge in each such disk due to said polarizing means while the charges in each of said disks of the other of said two groups of elements due to said applied voltage are of opposite sign from the charge in each of said disks due to such polarizing means, whereby said device can be used to convert cup-like bending movements of said transducer element into electrical energy or vice versa.

5. A bender-type electromechanical device comprising, an even number of superimposed layers of dielectric material comprising two groups of elements one group or which is to expand while the other group is to contract and vice versa to provide a bender-type of electromechanical transducer element, unidirectional electrical-polarizing means for each of said layers, electrical terminal-circuit connections to each of said layers such that the charges associated with a theoretical application of voltage thereto are of the same sign in each of said layers of one of said two groups of said elements as the charge in each said layer due to said polarizing means while the charges in each of said layers in the other of said two groups of elements due to said applied voltage are of opposite sign from the charge in each such layer due to said polarizing means, means for mechanically vibrating said transducer element, and electrical output means coupled to said terminal circuit connections for deriving and utilizing a corresponding electrical output from said transducer element.

6. A bender-type electromechanical device comprising, an even number of superimposed layers of dielectric material comprising two groups of elements one group of which is to expand while the other group is to contract and vice versa to provide a bender-type of electromechanical transducer element, unidirectional electrical-polarizing means for each of said layers, electrical terminal-circuit connections to each of said layers such that the charges associated with a theo retical application of voltage thereto are of the same sign in each or said layers of one of said two groups of said elements as the charge in each,

said layer due to said polarizing means while the charges in each of said layers in the other 01 said two groups of elements due to said applied voltage are of opposite sign from the charge in each such layer due to said polarizing means, means for supplying alternating electrical energy to said electrical terminal-circuit connections, and means for deriving and utilizing a corre- 10 spending mechanical vibration from said traps- OTHER REFERENCES ducer element.

HANS JAFFE. E. W-ainer, Trans Electra Chemical Society, vol.

7 89, pgs. 331-356, 1946. REFERENCES CITED W. G. Cady, Piezoelectrlcity, pgs. 4, 198, 233- 235, 260, 261, 614, McGraw Hill, 1946.-

B. M. Wul 8: I. M. Goldman, C. R. Acad. Sci. URSS, vol. 46, pgs. 139, 154 (1945), vol. 49, pgs.

The following references are of record in the file of this patent:

UNITED STATES PATENTS 177-180, Library of Congress.

Nam m v 10 A. DeBretteville, Jr., Phys. Rev. 69; 687 (1946). 33 52 5 Mommiunnufi Jan. x P. R. Coursey and K. G. Brand, Nature. 157; 2,402,515 Wainer June 18. 1946 297%98 (1946)- 2,424,111 Navlas July 15, 1947