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United States Patent 3,832,580
Yamamuro ,   et al. August 27, 1974

HIGH MOLECULAR WEIGHT, THIN FILM PIEZOELECTRIC TRANSDUCERS

Abstract

A transducer for converting electrical energy into mechanical or acoustic energy or vice versa using a converting means made of a thin film of high molecular weight polymer piezo-electric organic compound having orientated molecules and having electrodes bonded or deposited onto both surfaces thereof. When an electric current is applied to the electrodes, the thin film is extended or contracted in a direction different from the direction of orientation of the molecules. when the angle between these two directions is 45.degree., the extent of the extension or contraction of the thin film is at a maximum and the best converting efficiency can be obtained.


Inventors: Yamamuro; Isao (Tokyo, JA), Tamura; Masahiko (Tokyo, JA)
Assignee: Pioneer Electronic Corporation (Tokyo, JA)
Appl. No.: 05/321,072
Filed: January 4, 1973


Current U.S. Class: 310/328 ; 252/62.9R; 310/334; 310/337; 310/800; 369/144; 381/190
Current International Class: H04R 23/00 (20060101); H04R 17/00 (20060101); H04r 017/00 ()
Field of Search: 310/8,8.2,8.3,8.5,8.6,9.1,9.4,9.6,8.1,8.7 340/10 179/11A,1.41P,1.1B 317/144 252/62.9

References Cited

U.S. Patent Documents
2487962 November 1949 Arndt, Jr.
2549872 April 1951 Willard
2565159 August 1951 Williams
2640889 June 1953 Cherry, Jr.
2714642 August 1955 Kinsley
2778881 January 1957 Fryklund
2802147 August 1957 Crownover
2836738 May 1958 Crownover
2900536 August 1959 Palo
3007013 October 1961 Paull et al.
3115588 December 1963 Hueter

Other References

Chemical Abstract, Vol. 67, 1967, section 73959n "Radiation-induced Solid State Polymerization". .
Review of the Electrical Properties of Wood and Cellulose, by R. T. Lin, Forest Products Journal, Vol. 17, No. 7, July 1967..

Primary Examiner: Miller; J. D.
Assistant Examiner: Budd; Mark O.
Attorney, Agent or Firm: Sughrue, Rothwell, Mion, Zinn & Macpeak

Parent Case Text



CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of co-pending application Ser. No. 793,943, filed Jan. 27, 1969, entitled TRANSDUCER, now abandoned.
Claims



What is claimed is:

1. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle of approximately 45.degree. to said first direction when an electric current is supplied to said electrode means.

2. A transducer comprising:

a. a cylindrical converting means for converting electrical energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of high molecular weight polymer piezoelectric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, said converting means being separated into first and second portions by a center insulating portion,

b. a thin vibrator film secured at said center portion to said converting means,

c. electrode means disposed on both surfaces of said converting means, and

d. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means, said converting means being fixed by said fixing means at the outer ends of said first and second portions.

3. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a pair of rectangular thin film plane vibrators that are fixed at one end and are bonded at the other end in substantially perpendicular relation to each other, and a needle is secured to said bonded ends,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.

4. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a thin film plane vibrator having a V-shaped configuration with its ends fixed, and a vibrating means comprising a conical thin vibrating plate is attached at its apex to the apex of said V-shaped vibrator,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.

5. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a thin film plane vibrator fixed under tension such that said vibrator can only expand when it is stressed,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.

6. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a thin film tubular vibrator fixed at two opposite ends thereof, and a resilient element is in engagment with one face of said vibrator along the entire unsupported length thereof between said opposite ends to support it under tension such that the vibrator expands and contracts concentrically,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.

7. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a thin plane film fixed at opposite ends supported on one face along its center portions under tension by a resilient element,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.

8. A transducer comprising:

a. converting means for converting electric energy into mechanical energy or vice versa which is a thin film of from 10-200 microns of a high molecular weight polymer piezo electric material with a molecular weight of 5,000 to 500,000 having its molecules oriented in a first direction, which comprises a thin film in the configuration of a regular polygonal cylinder supported at the corners of said polygon under tension by equidistinctly spaced resilient elements,

b. electrode means disposed on both surfaces of said converting means, and

c. fixing means for fixing said converting means so that it will be stressed in a second direction at an angle to said first direction when an electric current is supplied to said electrode means.
Description



BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to transducers for converting electric energy into mechanical or acoustic energy or vice versa, and more particularly to an electroacoustic or electromechanical transducer or pickup using a natural or synthetic high polymer piezo-electric vibrator.

2. Description of the Prior Art

The conventional piezo-electric electroacoustic transducer such as piezo-electric speaker employs a vibrator such as Bimorph which is made by bonding together two piezo-electric materials such as Rochelle salt crystals, piezo-electric ceramics so that when one expands the other contracts. This vibrator is fixed at one end to a fixed surface and is engaged at the other end through a transmitting lever with a vibrating plate to drive it. Since it has a lever mechanism, the mass of its vibrating system cannot be small so that its efficiency is low and it is affected by the resonance of the lever. Further, the center of the vibrator moves arcuately when it vibrates so that the vibrator is subject to strain. Also, the mechanical quality Q of such piezo-electric substances is high so that it is very difficult to obtain a broad band frequency characteristic.

SUMMARY OF THE INVENTION

This invention eliminates these disadvantages of conventional piezo-electric transducers, and provides a novel and improved transducer for converting electric energy into mechanical or acoustic energy or vice versa using a natural or synthetic high molecular weight polymer piezo-electric substance. For natural substance, collagen as a main component of an animal tendon, silk fiber as a main component of a raw silk, and wood cellulose may be used. For synthetic substances, poly-.gamma.-methyl L gluatamate, poly-.gamma.-benzyl L glutamate, etc. which have large orientation of molecules and large crystallinity may be employed.

Because of the flexibility and the film forming characteristics of the high molecular weight polymer piezo-electric materials used in this invention, these high molecular weight polymer piezo-electric materials can be employed in this invention in the form of a thin film. For example, thin films of a thickness ranging from about 10 to about 200 microns prepared from high molecular weight polymeric piezo-electric materials having a molecular weight ranging from about 5000 to 500,000 can be employed.

According to one aspect of this invention there is provided a transducer comprising means for converting electric energy into mechanical or acoustic energy such as a square thin plane vibrator made of high molecular weight polymer piezo-electric substance. Means are provided for applying the electric energy to the vibrator such as two sheets of electrodes bonded or deposited onto both sides of the vibrator. A source of electric energy, conductor means for connecting the energy to the electrodes, and means for fixing the vibrator in a predetermined direction that is at an angle to the direction of an orientation of molecules in the vibrator, such as at 45.degree., are employed. Two corner ends of said vibrator are fixed directly to the stators and the other two corner ends are secured through resilient means such as springs to the stators. The vibrator is fixed at both ends to the stators which are themselves spaced shorter than the diagonal length of the vibrator. Thus, since the transducing element is a vibrating plate, its structure may be much simpler than the conventional microphone speaker. Strong mechanical rigidity is provided, in addition to lower production costs. Further, the overall transducer may be thinner.

According to another aspect of this invention there is provided a transducer comprising means for converting mechanical energy into an electric energy such as a rectangular thin plane vibrator made of high molecular weight polymer piezo-electric substance. Means for picking up the mechanical energy and for transmitting it into the vibrator, such as a needle, is secured to the center portion of the vibrator. Means for conducting electric energy produced at the vibrator, such as four sheets of electrodes bonded or deposited onto the front and back surfaces of both sides of the vibrator, are employed. The vibrator is fixed in a predetermined direction which is at an angle to the direction of orientation of its molecules, such as at 45.degree. . The vibrator is fixedly secured at both ends to the stators. The converting means may be two rectangular thin plane vibrators attached perpendicularly to each other at one end with the needle being secured to the crossing point of the vibrators and angularly spaced by 45.degree. from both vibrators, or the vibrators may be in the form of two rectangular thin plane members, perpendicularly crossed, and bonded at their central portions to each other, with the needle secured to the crossing point of the vibrators. Thus, since both ends of the vibrators are fixed to the stators, age deformation thereof is extremely small and its operation is very stable. Furthermore, since two sets of electrodes are provided on one piezo-electric vibrator, it may be manufactured less expensively and readily and the two vibrators may have the same characteristics.

According to a still further aspect of this invention, there is provided a transducer such as a V-shaped thin plane vibrator made of high molecular weight polymer piezo-electric substance, a vibrating means such as a conical thin vibrating plate having an apex attached to the vibrator, means for applying the electric energy to the vibrator such as two sheets of electrodes bonded or deposited onto both sides of the vibrator, means for fixing the vibrator in a predetermined direction at an angle to the direction of the orientation of molecules in the vibrator such as at 45.degree. with a frame. Both ends of the vibrator are fixed to the frame and said vibrating plate is secured to the frame. Thus, since the vibrator is attached directly to the vibrating plate without any transmitting lever, the overall transducer such as speaker may be very thin. Further, inasmuch as the vibrating plate moves linearly, it moves accurately and reciprocally, thereby preventing the generation of strains. Due to its simple structure it may be manufactured less expensively. Moreover, since the vibrator is made of flexible piezo-electric substance, its mechanical quality Q is low, thereby providing broad band frequency characteristics.

According to still another aspect of this invention there is provided a transducer such as a rectangular vibrator made of high molecular weight polymer piezo-electric substance, means for conducting energy such as a terminal, means for fixing the vibrator in a predetermined direction at an angle to the direction of orientation of molecules in the vibrator such as at 45.degree. with a supporting wall for the vibrator at both ends thereof. The vibrators including electrodes bonded or deposited onto both sides thereof and terminals are connected to the electrodes. Thus, since the acoustic energy is obtained merely by applying an alternate signal voltage to the vibrator, the transducer may be a very simple structure and be made less expensively. Further, since the acoustic impedance of some high polymer piezo-electric substance is similar to that of water, it provides great advantages when it is used in underwater acoustic equipment such as a transmitter and receiver of sonar.

According to still another aspect of this invention, there is provided a transducer such as two rectangular vibrators made of a high molecular weight polymer piezo-electric substance, means for applying the electric energy to the vibrator such as two electrodes bonded or deposited onto the upper and lower sides of central portion of the vibrators and two electrodes bonded or deposited onto the rear surface of the vibrator correspondingly to the electrodes. A vibrating means such as a central portion of the vibrator is employed and means for fixing the vibrator in a predetermined direction at an angle to the direction of orientation of molecules in the vibrator such as at 45.degree.. The converting means may be two cylindrical vibrators made of high molecular weight polymer piezo-electric substance with the vibrating means comprising a circular vibrating plate secured to the central portion within said cylindrical vibrator. The fixing means are supporting walls with both ends of said cylindrical vibrator being secured thereto. The cylindrical vibrator includes a plurality of small holes thereon or is sealed and a vibrating valve is provided thereon, and a horn is provided at one opening end of cylindrical vibrator. Thus, the vibrating plate accurately reciprocates and the transducer has extremely small strain. Further, it provides not only a simple structure with less expensive production but the mechanical quality Q is low similar to that previously described.

According to still another aspect of this invention there is provided a transducer as defined in the previous embodiment wherein said converting means are a plurality of vibrating plates of high molecular weight polymer piezo-electric substance and are supported by a plurality of supporting means at the respective ends, with each plate having a curvature. Electrodes are bonded or deposited onto each side of each vibrating plate which has an orientation of molecules in a direction different from the direction parallel to that of parallel supporting means. The supporting means are stators disposed on the lengthwise base for supporting said vibrating plate at each end.

According to still another aspect of this invention, there is provided a transducer such as a tubular vibrating element disposed around the periphery of means for imparting a resiliency and tension to the vibrating element such as a tubular resilient element disposed around the periphery of the base so as to press the resilient elements to a predetermined degree. The vibrating element is made of high molecular weight polymer piezo-electric substance having an orientation of molecules in a direction different from the longitudinal axis of the base, a cylindrical base, means for imparting a resiliency and tension to said vibrating element, and means for transmitting or receiving acoustic energy such as an upper and lower acoustic transmitter or receiver attached to the upper or lower end of the base, respectively, with electrodes being bonded or deposited onto both sides of the vibrating element.

According to still another aspect of this invention there is provided a transducer as defined in the previous embodiment wherein said resilient element is partially provided on the base below the vibrating element or is partially provided radially from the periphery of the base with the vibrating element being a regular polygonal cylinder supported by the partial resilient element around the base.

Thus, in addition to the advantages previously described, when used for the overall speaker the vibrating plate vibrates to expand and contract, with the division of the vibration produced in the conventional conical speaker being avoided. This invention provides a transducer for converting an electric energy into a mechanical or acoustic energy in which the vibrator is made of high molecular weight polymer piezo-electric substance. The transducer electrodes are bonded or deposited onto both sides of the vibrator. In the transducer, the direction of orientation of molecules is different from the fixed direction of the vibrator.

Thus, the present invention provides a simple but strong transducer which is readily and less expensively manufactured, is extremely thin as a whole, has small age deformation, operates very stably, the odd order of high harmonic wave strain is cancelled, it operates very accurately without any strain, and has low mechanical quality Q for broad frequency characteristics. The transducer eliminates the division of the vibration when used for a speaker.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a transducer in accordance with this invention;

FIG. 2 is a plan view of a transducer element with a distorted state designated by a broken line;

FIG. 3 is a view of the transducer according to this invention showing a principle thereof;

FIG. 4 is a sectional view of a transducer element shown in FIG. 3 taken as indicated by the line 4--4 therein showing a manner of vibration thereof;

FIG. 5 is a view showing a relationship between the direction of orientation of molecules and a stressed direction in the element;

FIG. 6 is a graph showing the variations of an apparent piezo-electric modulus of the element;

FIG. 7 is a side view of the second embodiment of this invention showing schematically a transducer element or vibrator;

FIG. 8 is a plan view of the vibrator shown in FIG. 7;

FIG. 9 is a schematic side view of the third embodiment of this invention for a 45--45 system;

FIG. 10 is a schematic view of the fourth embodiment of this invention for another 45--45 system;

FIG. 11 is a schematic side view of a piezo-electric speaker for the purpose of explanation of its principle;

FIG. 12 is a sectional view of a piezo-electric speaker showing a fifth embodiment of this invention;

FIG. 13 is a bottom plan view of the speaker shown in FIG. 12;

FIG. 14 is a view similar to FIG. 12 but illustrating the manner of vibration of the speaker;

FIG. 15 is a schematic plan view of sixth embodiment of this invention showing an explanatory electroacoustic transducer;

FIG. 16 is a side view of the transducer shown in FIG. 15;

FIG. 17 is a graph showing the relationship of waves between an input electric signal applied to the transducer in accordance with this invention and its acoustic output produced thereby;

FIG. 18 is a schematic view of a seventh embodiment of this invention showing an electroacoustic transducer in which a central strap electrode is interleaved between two rectangular high molecular weight polymer piezo-electric materials;

FIG. 19 is a view similar to FIG. 18 but showing the transducer in which the electrode is interleaved between two cylindrical materials secured fixedly, respectively;

FIG. 20 is a sectional view of the transducer in which a horn is mounted between the cylindrical vibrators shown in FIG. 19;

FIG. 21 is a perspective view of a plane transducer according to this invention;

FIG. 22 is a view similar to FIG. 21 but with a plurality of these transducers disposed integrally with each other;

FIG. 23 and FIG. 24 are elevational and plan views respectively of a cylindrical transducer in accordance with this invention;

FIG. 25 is a perspective view of an alternate form of a plane transducer; and

FIG. 26 is a perspective view of a modification of a cylindrical transducer .

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, particularly to FIG. 1, which shows an electroacoustic transducer in accordance with this invention, reference numeral 1 designates a square, thin plate made of a high molecular weight polymer piezo-electric material, and electrodes 2 are bonded or deposited onto both sides of the thin plate 1 and are connected to a source 3 of an alternating current.

Referring now to FIG. 2, which shows a transducer element or vibrator with a distorted state designated by a broken line, the thin plate 1 has an orientation of molecules in the direction designated by an arrow A, angularly spaced from a diagonal line through the square element by the amount of 45.degree.. When an alternating voltage is applied from the source 3 to both electrodes 2, bonded onto both sides of the thin plate 1 of piezo-electric material, a slip phenomenon occurs in the square plate 1 to distort it to a diamond shape 1' as illustrated by a broken line in FIG. 2.

Referring now to FIG. 3, which shows one of the transducers in accordance with this invention, reference numerals 4, 4 and 5, 5 designate stators for fixing the thin plate 1, suitable resilient means 6,6 being interposed between the stators 5,5 and the plate. When an alternating voltage is applied, similarly as described above, to the thin plate 1, the latter distorts as described in relation to FIG. 2. If the orientation of molecules in the thin plate exists in the direction designated by an arrow A similarly spaced from the diagonal line in FIG. 2, the thin plate extends in the direction of the diagonal line extending between the stators 4,4 to which the plate is directly secured at both corners, when the plate deforms similarly as described previously in relation to FIG. 2, so that the plate vibrates as illustrated by the broken lines in FIG. 4. If the distance between the stators 4 and 4 is set to less than the minimum of the length of the diagonal line of the thin plate along the stators 4,4 secured therebetween the the plate 1 contracts, most bidirectional vibration of the thin plate may be obtained as designated by the broken lines in FIG. 4. If an acoustic vibration is applied to the thin plate 1 so that the alternating voltage generated in the plate by a piezo-electric effect is removed by the electrodes 2,2 this is clearly an acoustic-to-electric transducer. Further, the periphery of the thin plate 1 may be secured, at other than the points of the stators 4,4.

Referring now to FIGS. 5 and 6, which show relationship between the orientation of molecules and a strained direction in the plate, and a graph of the variations of an apparent piezo-electric modulus of the plate, respectively, if .theta. is the angle between the orientation of molecules and the direction of the stress applied or produced as designated in FIG. 5, the apparent piezo-electric modulus d changes proportionally to sine 2.theta., which is known per se, that is to say:

d = A sine 2.theta.

where the symbol A represents a proportional constant equivalent to the component d.sub.14 of the piezo-electric tensor. Accordingly, if the thin plate is stressed in the direction of .pi./4 or 45.degree., angularly spaced from the orientation of molecules, the efficiency of conversion may be the best. If desired, other angular spacings may be used with somewhat lower efficiency of conversion. Also, the thin plate of piezo-electric material may be of other than a square shape within the scope of this invention.

Thus, a transducer, reversible between an electric and acoustic signal, may be obtained when the square thin plate made of high molecular weight polymer piezo-electric material is bent along one pair of diagonals thereof so that both corner ends of the plate along the diagonal line are secured to the stators. Due to the transducing element being a vibrating plate its structure may be much simpler than the conventional microphone, speaker, etc., strong mechanical rigidity being provided, and less expensive production is achieved. Further, the overall thickness of the transducer may be reduced to 5 mm resulting in an extremely thin acoustic equipment.

Referring now to FIGS. 7 and 8, which show another embodiment of a transducer according to this invention used for a pickup cartridge for music performance, electrodes 12, 13, 14, 15 are attached to the front and back surface of both sides of vibrator 11. To the center portion 11' a vibrating projection such as a needle 16 is attached. The vibrator 11 is fixed at both ends to stators 17,17. When the needle 16 moves in the direction as designated by an arrow A in FIG. 8, vibrator 11a disposed at the left of the needle 16 (FIG. 8) contracts and vibrator 11b located at the right of the needle 16 expands, and vice versa. The orientation of molecules is set relative to the direction of the stress so that when the stress is applied in the direction A as above, the piezo-electricity is produced at the electrodes provided on the vibrator 11 similarly to that described in relation to FIGS. 5 and 6.

When the needle 16 moves in the direction as designated by an arrow A in FIG. 8 so that a stress is applied to the vibrators 11a, 11b, plus and minus electricities are, for example, generated at the electrodes 12 and 13, respectively, whereupon minus and plus are produced at the electrodes 14 and 15, respectively. If these two vibrators 11a, 11b are connected in parallel or series with each other, the output current or voltage is varied to increase or decrease.

Referring now to FIG. 9, which shows a still further embodiment of a transducer according to this invention as applied to a 45--45 system which is known per se, vibrators 21a and 21b are attached perpendicularly to each other. Electrodes 22, 23, 24, 25 are attached similarly to the above embodiment on both sides of the vibrators, and needle 26 is attached at the cross point of the vibrators. The vibrators 21a, 21b are also fixed at the ends other than the cross point to stators 27,27. When the needle 26 is projected at the cross point as 45.degree. spaced angularly from both vibrators, this may detect stereo signals for the 45--45 system.

Referring now to FIG. 10, which shows still another embodiment of a transducer in accordance with this invention used for a 45--45 system, vibrators 31a, 31b and 31c, 31d similar to that shown in FIGS. 7 and 8 are perpendicularly crossed to be bonded at their central portions to each other so that the vibrators 31a, 31c correspond to that shown at 11a in FIG. 8 and the vibrators 31b, 31d to that shown at 11b. If the area between the vibrators 31b and 31c is termed as quadrant I, that between 31a and 31c as quadrant II, that between 31a and 31d as quadrant III and that between 31b and 31d as quadrant IV as designated in FIG. 10, the vibrators 31a, 31d extend and those 31b, 31c contract when the crossing point P of the junction of the vibrators moves, for example, toward the quadrant I. Here, the respective ends other than the point P are fixed to stators 37, respectively. The respective relationships of the movement of the vibrators are shown in the following Table I:

TABLE I ______________________________________ Vibrators Quadrant 31a 31b 31c 31d ______________________________________ I extend extend contract contract II contract extend extend contract III contract contract extend extend IV extend contract contract extend ______________________________________

It is clearly understood from Table I that the vibrators 31a and 31c counteract to expand or contract against the vibrators 31b and 31d. Consequently, this may detect stereo signals for the 45--45 system similarly to that with respect to the device in FIG. 9 with the advantages of the transducer shown in FIGS. 7 and 8.

From the above, in transducers according to this invention, since both ends of the vibrators are fixed to the stators, age deformation thereof is extremely small and its operation is quite stable. Further, inasmuch as two sets of electrodes are provided on one vibrator of piezo-electric material, it may be manufactured less expensively and readily and the vibrators may be provided to have the same characteristics as each other. The equiamplitude opposite polarity of piezo-electric energies are produced at the vibrators 11a and 11b or 31a and 31b or 31c and 31d. Accordingly, if these are connected electrically in series with each other for industrial use, large advantages may be effected such that the odd order of harmonic wave strain is cancelled as proved by the known Fourier expansion from the novel transducer of this invention.

This transducer is not restricted to cartridge pickups used for musical performances, but it may be used as a reversible transducer from mechanical to electric to mechanical conversion within the principle and scope of this invention.

Referring now to FIG. 11, which shows a piezo-electric speaker for the purpose of illustrating its principle, a vibrator 41, known per se as a Bimorph in which two piezo-electric materials such as Rochelle salt crystals, piezo-electric ceramics are bonded together, is shown in FIG. 11 so that when one expands the other contracts. This vibrator is fixed at one end to a fixed surface 47 and is engaged at the other end through a transmitting lever 48 with a vibrating plate 49 to drive it.

Referring now to FIGS. 12 to 14, which show a piezo-electric speaker as still another embodiment of this invention, reference numeral 50 designates a frame, and a conical thin vibrating plate 59 having an apex 59a is attached to a vibrator as will be described. A rectangular thin vibrator 51 is made of high molecular weight polymer piezo-electric substance which is V-shaped and is attached at both ends to the frame 50. This vibrator 51 has electrode surfaces deposited or bonded to both sides thereof. Numeral 58 designates a terminal for supplying a signal voltage to the electrodes.

Referring particularly to FIG. 13, the vibrator 51 has the orientation of molecules in a direction that is at an angle .theta. from the line designated by A--A' in FIG. 13, preferably 45.degree.. When an alternating voltage is applied to electrodes provided on both sides of the vibrator 51, it slips in a plane so that it expands or contracts along the line designated by A--A' (FIG. 13). Consequently, as shown in FIG. 14 illustrated by broken lines, the vibrator 51 vibrates in response to the alternate voltage applied through the terminal 58 to the electrodes in a reciprocal manner.

If the vibrator 51 is secured in a plane between the frame 50 other than the V-shape as described previously or in other words if the angle .alpha. in FIG. 12 is zero, the vibrator may expand but cannot contract so that it responds to merely a half cycle of the alternating voltage applied to the electrodes. Accordingly, in order to obtain a desired acoustic output a suitable mechanical bias such as an angle designated in FIG. 12 should be previously provided on the vibrator 51 so it will vibrate in a sufficient amplitude.

In this embodiment, the relationship described in relation to FIG. 5 and 6 is also pertinent. The vibrator 51 is not restricted to two sheets as shown in the drawings, multiple radial vibrators may be provided within the principle and scope of this invention, but the vibrators are preferably attached symmetrically to each other in a manner obvious to those skilled in the art.

From the above embodiment in accordance with this invention, since the vibrator is attached directly to the vibrating plate without any transmitting lever, the speaker may be very thinly formed which is particularly appropriate to compact acoustic equipment such as portable radios, earphones, etc., and to accurate equipment because the acting point for driving the vibrating plate by the vibrator does not move arcuately as illustrated by the broken line in FIG. 11, but moves in a linear path so that the vibrating plate reciprocates accurately thereby preventing the production of strains thereon. Due to its simple structure it may be manufactured less expensively and is susceptible to mass production. Further, as the vibrator is made of flexible piezo-electric substance, its mechanical quality Q is low so that it provides broad band frequency characteristics.

This transducer is not to be limited to a speaker application, but it may be used for a transducer for acoustic to electric or electric to acoustic conversion such as microphones or the like as is obvious to those skilled in the art.

Referring now to FIGS. 15 and 16, which show an electroacoustic transducer as still another embodiment of this invention for a supersonic usage such as a pulse generator, transmitter and receiver of sonar, thin rectangular vibrator 61 is made of high molecular weight polymer piezo-electric substance. Numeral 60 shows a supporting wall for the vibrator 61 at both ends thereof in its extending and contracting direction, and 68 illustrates a terminal for supplying an electric signal voltage on the electrode surfaces deposited or bonded on both sides of the vibrator 61.

In FIG. 15, the vibrator 61 has the direction of orientation of molecules as designated by an angle .theta. angularly spaced from the line illustrated by A--A', preferably 45.degree.. If an alternating voltage or pulse voltage is applied to the electrodes provided on both sides of the vibrator, it may slip in a plane so that it expands or contracts along the line shown by A--A'. However, since the vibrator 61 is fixed at both ends to the supporting walls 60 without any slack, it expands but does not contract. Therefore, as shown in FIG. 17, when an input illustrated at A is applied as an alternating voltage to the electrodes through the terminal 68, the output designated at B as a half cycle corresponding to the extension of the vibrator is provided by means of the vibration of the vibrator 61.

In this embodiment a similar relationship described with respect to FIGS. 5 and 6 may be also pertinent.

From the above embodiment according to this invention, inasmuch as an acoustic pulse signal output may be obtained merely by applying an alternate signal voltage to the vibrator 61 as a transducer, the vibrator 61 is not only a simple structure but allows less expensive production because in the manufacturing process the vibrator 61 is not pressed or bent due to its plane structure. Furthermore, since the acoustic impedance of poly-.gamma. -methyl L glutamate is similar to that of water, it provides a great advantage when it is used for an underwater acoustic equipment such as transmitter and receiver of a sonar.

This transducer may not be restricted to this usage for converting an electric signal into an acoustic signal, but it may be used for converting an acoustic signal into an electric signal within the principle and scope of this invention.

Referring now to FIG. 18, which shows an electroacoustic transducer in which a central strap electrode is interleaved between two rectangular high molecular weight polymer piezo-electric materials, reference numeral 71 designates a vibrator made of high polymer piezo-electric substance, numerals 72, 74 illustrate electrode surfaces deposited or bonded onto upper and lower sides of central surface portion 76 of the vibrator, and numerals 73, 75 show back surface electrodes disposed at the rear surface of the vibrator corresponding to the electrodes 72, 74. The central portion 76 of the vibrator acts as an insulator for separating the electrodes 72 and 74, and the electrodes 73 and 75. The electrodes 72,73 and vibrator 71 interleaved therebetween constitute upper vibrator 71a and the electrodes 74,75 and vibrator 71 interleaved therebetween constitute lower vibrator 71b.

Here, the vibrator 71 has a suitable orientation of molecules as designated by an angle .theta. angularly spaced from the line shown by A--A', preferably 45.degree.. If an alternate voltage is applied to the electrodes 72,73, the upper vibrator 71a slips in a plane so that it expands or contracts along the line shown by A--A'. If an alternate voltage which is 180.degree. out of phase from the above alternate voltage applied to the upper electrodes 74, 75 so that when the upper vibrator 71a expands the lower vibrator 71b contracts, the central portion 76 moves reciprocally up and down in response to the alternating voltage applied to the electrodes.

Referring now to FIG. 19, which shows an electroacoustic transducer in which the electrode is interleaved between two cylindrical materials and fixedly secured thereto. Reference numeral 87 designates a supporting wall for fixing upper and lower cylindrical vibrators 81a, 81b at the upper and lower ends, numeral 89 illustrates a circular vibrating plate which is secured to a central portion 86 within the cylindrical vibrator 81. As described previously the upper and lower opening ends of the cylindrical vibrators 81a, 81b are fixed to the supporting walls 87 and the circular vibrating plate 89 is bonded to the central portion 86 within the cylinder. If the vibrators have the orientation of molecules similarly to those shown in FIG. 18, the upper and lower vibrators move reciprocally up and down when alternating voltages are applied thereto, 180.degree. out of phase with each other so that when either side of said vibrators expands the other vibrator contracts similarly to those shown in FIG. 18. Thus, the central circular vibrating plate 89 vibrates in response to the alternating signal voltage applied thereto. Though the upper and lower cylindrical vibrators 81a, 81b are fixed to the supporting wall 87, in order that the air within the cylinder is not sealed or conversely, in order that a suitable damping action is applied to the vibrating plate 89, air holes may be provided thereon. Further, where the vibration produced by the vibrating plate 89 is not utilized directly for an acoustic output, the sound generated when the air within the sealed cylinder passes through small holes bored may be used, and if a vibrating valve is provided at the hole, a peculiar flute may be obtained.

Referring now to FIG. 20, which shows a transducer in which a horn is mounted on the supporting wall of the cylindrical vibrators, reference numeral 91 designates the vibrator having upper and lower cylindrical vibrators 91a and 91b, numeral 97 a supporting wall, numeral 99 the vibrating plate secured to the inner portion of vibrator 91, and numeral 98 a horn which is provided at the opening end of the cylindrical vibrator 91a, and serves to provide a speaker.

In this embodiment, a similar relationship described in relation to FIGS. 5 and 6 may also be pertinent.

Though this is described as a cylindrical vibrator, the invention should not be restricted to this cylindrical shape. Any shape in response to the requirement for vibrating the vibrating plate may be selected within the principle and scope of this invention. Further, if the central portion is removed and the upper and lower vibrators are connected by another insulating substance, to which the vibrating plate is fixed, a material that is difficult directly to bond to the high molecular weight polymer such as poly-.gamma.-methyl L glutamate may be used for the vibrating plate.

From the above embodiment according to this invention, the vibrating plate moves accurately reciprocally and the transducer has extremely small strain. It provides not only a simple structure but is less expensive in production, in particular, mass production. Further, since the vibrator is made of flexible piezo-electric substance, its mechanical quality Q is very low and broad band frequency characteristic is obtained.

Referring now to FIG. 21, which shows a plane transducer as still another embodiment of this invention, reference numeral 101 designates a base plate made of a stiff substance such as a rigid body, numeral 102 illustrates a vibrating plate made of high molecular weight polymer piezo-electric substance having electrodes bonded or deposited onto both sides thereof, numeral 103 designates a resilient element such as made of spongy synthetic resin or liquid for imparting a suitable resiliency and tension to the vibrating plate 102 and numeral 104 indicates a stator for supporting the vibrating plate 102. The vibrating plate 102 preferably has the direction of orientation of molecules angularly spaced by 45.degree. (or 30.degree. or 69.degree.) from the direction parallel to that of parallel stators 104, 104. When an alternating voltage is applied to the electrodes provided onto both sides of the vibrating plate 102, it slips in a plane so that it expands or contracts in a direction perpendicular to the parallel direction of the stators 104, i.e., in the direction as designated by line A--A' (FIG. 21). It thereby vibrates in the direction normal to the plane of the vibrating plate 102 with the resiliency of the resilient element 103. In this case if an appropriate curvature is not provided on the vibrating plate 102 supported between the stators 104, 104, the plate cannot contract but may merely expand resulting in vibrating only on the half cycle of the alternating voltage applied.

Referring now to FIG. 22, which is similar to FIG. 1 but a plurality of plates are integrally disposed in parallel relation as still another embodiment of this invention, the same elements are designated by the same reference numbers as those shown in FIG. 21. The base plate 101 extends lengthwise as predetermined, and a plurality of parallel stators 104 are secured thereon, then vibrating plates 102 and resilient elements 103 are disposed therebetween so that the area of the vibrating plate may be readily expanded. A multistereo acoustic effect may be obtained by independently applying various signal voltages to the respective vibrating plates.

Referring now to FIGS. 23 and 24, which show a cylindrical transducer as still another embodiment of this invention having similar principles to that shown in FIG. 21, a resilient element 113 is provided around the periphery of a cylindrical base body 111 so that a vibrating plate 112 is attached to the outer surface of the resilient elements 113 so as to suitably press the element. Acoustic transmitters or receivers 115 are attached on the upper and lower surface of the cylindrical base body 111. The vibrating plate 112 has electrodes bonded or deposited onto both sides thereof. When an alternating voltage is applied to the electrodes, the vibrating plate 112 expands or contracts due to its plane slippage so that the tubular vibrating plate 112 moves or vibrates to expand and contract outward and inward, respectively. By using this arrangement, there may thus be provided a nondirectional electroacoustic transducer in a plane.

Referring now to FIG. 25, which shows an alternative form of a plane transducer as still another embodiment of this invention, a resilient element 123 is supported on a base plate 121. Stators 124 are similarly provided to those shown in FIG. 21. A vibrating plate 122 in the form of a high molecular weight piezo-electric compound thin film having electrodes on both sides thereof is supported by the stators 124 and also by the resilient element 123 at its center portion so that the movement imparted to the plate is suitably damped by the resilient element 123.

Referring now to FIG. 26, which shows a modification of a cylindrical transducer as still another embodiment of this invention, a resilient element 133 is partially provided radially of the periphery of a base body 131 and a vibrating plate 132 is attached as regular polygonal cylinder through the partial resilient elements 133 around the base body 131 so that the elements 133 are equidistantly spaced therearound. The respective vibrating faces vibrate or move parallel or reciprocally outward and inward so that a pecular directional characteristic may be obtained such that the acoustic energy is directed toward each radially outwardly perpendicular direction, that is to each vibrating plane.

From the aforementioned embodiments, a reversible transducer for converting electric energy into acoustic energy or vice versa incorporated with solid base plate or body (or cylindrical base body), resilient element and vibrating plate with high molecular weight polymer piezo-electric substance is provided. Since the converting element as a vibrating plate is itself a very simple structure, the ultimate products have large mechanical strength and are less expensively manufactured. When this transducer is used for the overall speaker, the vibrating plate vibrates to expand and contract thereby with no occurrence of the division of the vibration produced by conventional conical speakers.

It will be understood that various changes in the details, materials and arrangements of parts which have been described herein and illustrated in order to explain the nature of this invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the following claims.

It will further be understood that the "Abstract of the Disclosure" set forth above is intended to provide a non-legal technical statement of the contents of the disclosure in compliance with the Rules of Practice of the United States Patent Office, and is not intended to limit the scope of the invention described and claimed therein.

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