Piezoelectric acoustic device

Details Piezoelectric acoustic device Piezoelectric acoustic device

1999-03-02

2001-08-14

Harvey, Minsun Oh (Department: 2644)

Electrical audio signal processing systems and devices

Circuitry combined with specific type microphone or loudspeaker

With piezoelectric microphone

C381S190000, C381S173000

Reexamination Certificate

active

06275594

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a piezoelectric acoustic device, and more particularly to a piezoelectric acoustic device in the form of a piezoelectric speaker, a piezoelectric buzzer or the like which is used for an electronic equipment such as a portable telephone or the like.
In general, a piezoelectric acoustic device includes a casing made of an insulating resin material or the like and a piezoelectric vibrator received in the casing. In recent years, it is highly demanded to small-size an electronic equipment and provide it with multiple functions. For this purpose, it is required that the electronic equipment is provided on a surface thereof or an operation face section thereof with parts for multi-functioning. The parts include, for example, a liquid-crystal display element for a telephone receiver, various kinds of switches and the like. Arrangement of such additional parts on the operation face section of the electronic equipment or large-sizing of the parts requires to increase an area of the operation face section. However, an increase in area of the operation face section is contrary to small-sizing of the electronic equipment.
A piezoelectric acoustic device which has been conventionally used for such an electronic equipment is disclosed in, for example, Japanese Utility Model Publication No. 879/1984, Japanese Patent Application Laid-Open Publication No. 75578/1994, Japanese Patent Application Laid-Open Publication No. 28167/1995, U.S. Pat. No. 3,970,879, U.S. Pat. No. 4,122,365, U.S. Pat. No. 4,183,017 and the like. The piezoelectric acoustic device disclosed is generally constructed in the form of a piezoelectric buzzer or a piezoelectric speaker which includes a casing and a drum provided at a substantially central portion of a front side wall of the casing in a manner to communicate with the casing. Unfortunately, the conventional piezoelectric acoustic device fails to increase an area of an operation face section of an electronic equipment because the drum is arranged at the substantially central portion of the front side wall of the casing.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a piezoelectric acoustic device which is capable of permitting an increase in area or space of an operation face section of an electronic equipment required for arranging parts for the electronic equipment.
It is another object of the present invention to provide a piezoelectric acoustic device which is capable of attaining small-sizing of an electronic equipment.
It is a further object of the present invention to provide a piezoelectric acoustic device which is capable of minimizing intrusion of water and dust into a front air chamber through a drum.
It is still another object of the present invention to provide a piezoelectric acoustic device which is capable of eliminating arrangement of any waterproof or dust-proof cloth member at a sound discharge hole of a housing of an electronic equipment.
In accordance with the present invention, a piezoelectric acoustic device is provided. The piezoelectric acoustic device includes a piezoelectric vibrator including a metal vibrating plate and a piezoelectric ceramic element joined to the metal vibrating plate, a casing including a front side wall and a rear side wall arranged on both sides of the piezoelectric vibrator so as to define a space therebetween in which the piezoelectric vibrator is received, and a drum arranged on an outside of the front side wall so as to extend in a direction across the front side wall. The piezoelectric vibrator and front side wall are arranged so as to define a chamber therebetween and the drum is formed therein with a passage in a manner to communicate with the chamber. The drum is so arranged that a center thereof is deviated from a center of the front side wall toward an outer peripheral portion of the front side wall. Such construction, when the piezoelectric acoustic device of the present invention is mounted in a housing of an electronic equipment, permits a gap of a size substantially equal to a length of the drum or less to be formed between the housing and the piezoelectric acoustic device, so that parts such as a circuit board and the like may be arranged in the gap. This results in the electronic equipment being small-sized. In particular, the drum is arranged at a position deviated from the center of the front side wall of the casing toward the outer peripheral portion of the front side wall, so that an operation face section of the housing of the electronic equipment may be significantly increased in space or area in which electronic parts such as a display element, switches and the like are arranged.


REFERENCES:
patent: 3970879 (1976-07-01), Kumon
patent: 4122365 (1978-10-01), Stephens
patent: 4156800 (1979-05-01), Sear
patent: 4183017 (1980-01-01), Sims
patent: 5321761 (1994-06-01), Kitanishi
patent: 59-879 (1984-01-01), None
patent: 6-75578 (1994-03-01), None
patent: 7-281670 (1995-10-01), None

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