Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-12-12
2004-06-15
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S334000
Reexamination Certificate
active
06750595
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electroacoustic transducer and a packaging method for the transducer. More particularly, the present invention relates to an underwater wide-band electroacoustic transducer and a packaging method for the transducer.
2. Description of Related Art
Typical active electroacoustic transducer has a tonpilz shape design.
FIG. 1
is a schematic diagram showing the side view of a conventional tonpilz-shaped electroacoustic transducer. As shown in
FIG. 1
, the tonpilz-shaped transducer
100
consists of a plurality of identical dimension piezoelectric ceramic units
102
. The piezoelectric ceramic units are chained together using prestress bolt (not shown).
FIG. 2
is a graph showing the frequency response of the transducer in FIG.
1
. As shown in
FIG. 2
, a tonpilz-shaped transducer comprising of a series of identical dimension piezoelectric ceramic units can have a single resonance frequency only. Hence, an assembly of identical dimension piezoelectric ceramic units
102
only works in a neighborhood close to the resonance frequency. In other words, the transducer has a narrow frequency bandwidth.
To improve the operating frequency of the tonpilz-shaped transducer
100
, a matching layer
104
is often added to the front end of the transmitting surface.
FIG. 3
is a schematic diagram showing the side view of a conventional tonpilz-shaped transducer having a matching layer thereon. The matching layer
104
at the front end of the transmitting surface serves to increase operating bandwidth.
FIG. 4
is a graph showing the frequency response of the transducer shown in FIG.
3
. As shown in
FIG. 4
, the frequency response has a few peaks. However, material for fabricating the matching layer
104
is difficult to find and the manufacturing process is generally complicated.
In general, a tonpilz-shaped transducer is a package assembled together using compressed rubber pieces. Hence, a relatively large compressive force is often required during the assembling process. However, the ceramic unit is usually formed by powder sintering method and thus has moderate strength only. The exertion of too much pressure may cause unnecessary damages to the piezoelectric ceramic units. Moreover, even an electroacoustic transducer design that incorporates a matching layer still fells short of the target of having an operating frequency bandwidth over several octaves.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide an underwater wide-band electroacoustic transducer and a packaging method for the transducer. The transducer includes several groups of piezoelectric ceramic units each having a different resonance frequency whose distance of separation is finely adjusted for maximum bandwidth. Moreover, injection-molding method replaces direct compression of rubber during component assembly.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an underwater wide-band electroacoustic transducer. The electroacoustic transducer includes several groups of piezoelectric ceramic units and an acoustic plastic. Each group of piezoelectric ceramic units has a different dimension and separates from a neighboring group by a different distance. Each group of piezoelectric ceramic units contributes a frequency response curve so that together they constitute a frequency response curve with a wide bandwidth. The acoustic plastic is used as an injection-molding compound for joining various piezoelectric ceramic units together into a package.
This invention also provides a method of assembling an underwater wideband electroacoustic transducer. The underwater wide-band electroacoustic transducer comprises of several groups of piezoelectric ceramic units and acoustic window material. To produce the underwater wide-band electroacoustic transducer, groups of piezoelectric ceramic units each having a different dimension are assembled with each ceramic unit separated from each other by different distances. The frequency response of each ceramic unit groups are banded together to produce a package having a wide-band frequency response. The acoustic window material is injected to join the ceramic unit groups together into a package. Thus, groups of ceramic units each having a different dimension and distance of separation from their neighboring groups are assembled into a package having a wide-band frequency response.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 3182284 (1965-05-01), Green
patent: 3833825 (1974-09-01), Haan
patent: 3922572 (1975-11-01), Cook et al.
patent: 4025805 (1977-05-01), Coltman et al.
patent: 4439847 (1984-03-01), Massa
Dunn Sheng-Dong
Jih Jeng-Yow
Yeh Chi-Zen
Aguirrechea J.
Chung-Shan Institute of Science and Technology
Dougherty Thomas M.
J. C. Patents
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