Piezoelectric acoustic speaker system

• US 3,978,353 A
• Filed: 05/06/1975
• Issued: 08/31/1976
• Est. Priority Date: 05/10/1974
• Status: Expired due to Term

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Kinoshita, Shouzo
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/574,983
• Time in Patent Office: 483 Days
• Field of Search: 310/8.2, 310/8.5, 310/8.6, 310/8, 310/9.4, 310/9.5, 310/9.6, 179/110 A, 179/111 R, 307/88 ET
• US Class Current: 310/317
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 17/005 using a piezoelectric polymer
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A Piezoelectric speaker system with a piezoelectric diaphragm supported in a cylindrical form and provided with a plurality of vibration regions, which is capable of controlling the directional characteristics by easy operation according to necessity or listener'"'"'s preference.

Claims

1. A piezoelectric acoustic speaker system comprising:

a cylindrical substructure assembly;

at least one piece of piezoelectric film and a holding means connected to adjacent film ends and engaged with said cylindrical substructure assembly to hold said film around the substructure assembly under a predetermined tension and in the form of cylindrical diaphragm;

pairs of electrodes, each having an electrode on the outside of said diaphragm and a further electrode on the inside of said diaphragm, and forming vibration regions of number corresponding to the number of electrode pairs, at least two said independently responsive electrode pairs being circumferentially offset on said cylindrical substructure;

input terminal means for receiving an acoustically reproduceable, alternating input signal;

alternating signal path means establishing a first connection of said input signal terminal means to the electrodes of said at least two electrode pairs for applying alternating input signals related in a first magnitude and phase relation to said two electrode pairs;

switch means interposed in said alternating signal path means and switchable to instead establish at least one differing second connection of said input signal terminal means and pair electrodes for applying alternating input signals related in a second and different relation to said electrode pairs, thereby differently directing sounds reproduced by said speaker system.

2. The speaker system of claim 1, in which said two pairs of electrodes are on opposite circumferential sides of said cylindrical substructure so as to provide diametrally oppositely facing and separately energizable semicircular sound radiators, said switch means including movable conductive element means shiftable for changing at least one of the phase and voltage of the alternating in put signal applied to said at least one of said electrode pairs thereby positively changing the directional response pattern of said speaker system at least in the diametral plane thereof.

3. The speaker system of claim 1, in which said cylindrical substructure assembly includes a cylindrical suspension member having a plurality of small openings therethrough, a pair of base plate members spaced axially by and connected by said suspension member, sound absorbing material packed in said cylindrical suspension member, resilient means between said cylindrical suspension member and at least radiating portions of said diaphragm, and means securing the diaphragm ends with respect to said base plate members for maintaining circumferential tension on said diaphragm.

4. The speaker system of claim 3, including a plurality of felt-like partition members disposed within said cylindrical suspension member and dividing the interior thereof into a plurality of small chambers, said sound absorbing material being in the chambers, wherein subdivision of the interior of said cylindrical member into such small chambers increases the resonant frequency of the speaker system and permits maintaining a desired sound absorption level with less sound absorbing material.

5. The speaker system of claim 3, in which said holding means includes a pair of platelike holders, one for each of a pair of circumferentially adjacent diaphragm ends, each said platelike holder having on one side thereof a pair of side-by-side extending, spaced conductive strips insulatively separated from each other, means conductively and fixedly connecting the radially inner electrode at one said diaphragm end in overlapped relation to one said conductive strip of said holder, and conductive means spanning said insulative separation and fixedly and conductively connecting the radially outer electrode at said one diaphragm end to the other conductive strip of said holder.

6. The speaker system of claim 5, in which said cylindrical substructure assembly includes a radially opening, axially extending slot disposed circumferentially between two pairs of electrodes on said film, said film being fitted circumferentially around said cylindrical substructure assembly with said platelike holders inserted in close circumferentially spaced relation in said slot for holding the circumferential edge of said diaphragm under tension while permitting application of an alternating input signal through such holder to the associated pair of electrodes on said diaphragm, said electrode pairs being substantially diametrally opposed to each other across said cylindrical substructure assembly and being substantially of half-circular cross section, said switch means being connected between the conductive members of said holders and said input terminal means and being actuable to switch the interconnection of said electrodes and input terminal means as to change the directional response characteristic of the speaker system.

7. The speaker system of claim 2, in which said movable means of said switch means comprises ganged first and second multithrow switch members connected respectively to said input terminal means, and respective first and second sets of alternatively selectable contacts for controlling application of said input signal to one said electrode pair, said alternatively selectable contacts including one portion selectable for energizing said electrode pairs in phase, a further portion selectable for energizing said electrode pairs in the opposite phase, and a third portion selectable for de-energizing said one electrode pair, the other said electrode pair being energized, without switching, from said input terminal means.

8. The speaker system of claim 2, in which said signal path means includes first means coupling said input terminal means across one said electrode pair, and second means coupling said input terminal means across said other electrode pair and including a movable switch contact connected to an electrode of said other pair and a plurality of contacts alternatively selectable by said movable contact, said alternatively selectable contacts including a first set fed with differing fractions of an alternating input signal appearing across said input terminal means and a second set also fed with differing fractions of such alternating input signal but in opposite phase.

9. The speaker system of claim 8, in which said signal path means includes a transformer with a primary winding connected to said input terminals, said first means being a first secondary winding of said transformer connected across said first mentioned electrode pair, said second means including a second secondary winding of said transformer and having a center tap commonly connected to one electrode each of said two electrode pairs as well as to the center one of said alternatively selectable contacts, said second primary winding including further taps connected to the first set of said alternatively selectable contacts and still further taps connected to said second set of alternatively selectable contacts, the induced voltage across said secondary winding being twice that across said first secondary winding, such that actuation of said movable switch contact serially through said set of alternatively selectable contacts steps said speaker system through a plurality of differing polar sound radiation patterns.

10. The speaker system of claim 2, in which said signal path means includes electronic valve means connected across a d.c. potential source, said signal input terminal means being connected across a control electrode of said electronic valve means and one side of said d.c. potential source, a first signal system connected to a first electrode pair and a second signal system connected to a second electrode pair, means connecting the input side of one signal system to one side of said electronic valve means for receiving input signals in a first phase, said switch mean comprising a switch actuable for alternatively connecting opposite sides of said electronic valve means to said second signal system such that actuation of said switch reverses the polarity of signals applied to said second signal system, and attenuation means in series with one said signal system, whereby to switch the directional characteristics of said speaker system.

11. A piezoelectric speaker system comprising a cylindrical substructure assembly;

one or more piezoelectric film with holding means connected to the both ends of the or each film;

said holding means being engaged with said cylindrical substructure assembly to hold the or each film around said substructure assembly while imparting a predetermined tension the the or each film, thereby to form a cylindrical diaphragm; and

a plurality of electrodes provided on each side of the diaphragm to form vibration regions of number corresponding to the number of said electrodes, input terminal means for receiving an input signal to be reproduced by said speaker system;

means interconnecting said input terminal means and electrodes and including switching means actuable for switching the interconnection of at least one said electrode with respect of said input terminal means as to at least one of input signal phase and amplitude and thereby permit the user to vary the directionality of sound produced by the speaker system.

12. A piezoelectric speaker system as set forth in claim 11, wherein the respective vibration regions are applied with signals of different phases.

13. A piezoelectric speaker system as set forth in claim 12, wherein the respective vibration regions are applied with signals of different levels.

14. A piezolelectric speaker system as set forth in claim 13, wherein the respective vibration regions are applied with signals of different phases and levels.