Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1981-01-15
1983-01-11
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
179110A, 310326, 310345, H01L 4108
Patent
active
043684009
DESCRIPTION:
BRIEF SUMMARY
DETAILED DESCRIPTION OF THE INVENTION
This invention is related to ultrasonic transducer. Conventionally, there are available many kinds of transducers used at ultrasonic range, most of which are composed of joined two (2) pieces of ceramic plates, or consist of sandwiched one plate and they are inferior to our newly invented transducers by 6 dB in receiving sensitivity.
Particularly, our newly invented transducers show better performance than the conventional units of the type of bimorph remarkably at a range of center frequency, saying, 20 KHz to 38 KHz.
Hereunder, we explain the contents of our invention with reference to the accompanying drawings. We had many tests related to the center frequency and we take here 25 KHz as the center frequency and describe it.
The most essential part of the transducer embodying the present invention is the vibrating assembly which includes the vibrator proper consisting of a piezoelectric ceramic element bonded concentrically to a resonant plate for the purpose of the present disclosure is conveniently metal aluminum in material, since it can most easily be given form in processing, and is circular-shaped with a radiator positioning seat at the center. Selection of other material than metal aluminum depends on given conditions in designing, that is, permanent elasticity steel like semi-melt aluminum oxide or Nispan may be employed when further stability in temperature characteristic is desired.
DESCRIPTION OF THE DRAWINGS
The invention will be better understood from the following description taken in connection with the accompanying drawings in which:
FIGS. 1 and 2 illustrate overall merit of the vibrator proper in relation to ratios of diameter and thickness of the resonant plate to those of the ceramic element;
FIGS. 3a, 3b and 3c are vertical sectional views of radiators where:
FIG. 4 illustrates electrical characteristics of radiators, curves a, b and c corresponding to those in FIG. 3;
FIGS. 5a, 5b and 5c are views of baseplate where: baseplate embodying the invention;
FIG. 6 is a longitudinal section view of the holding member together with the metal grill and the baseplate embodying the invention;
FIG. 7 illustrates pattern directivity according to the invention (curve 72) in comparison with a conventional one (curve 71);
FIGS. 8a and 8b are longitudinal sectional views of the typical housing shapes embodying the invention illustrating a taper thereto;
FIGS. 9a and 9b are partially sectional views of the soleplate embodying the invention illustrating variation in its application depending on diametral requirements of the housing;
FIGS. 10a and 10b are, respectively, an exploded pictorial view and a sectional elevated view of the transducer embodying the invention.
With regard to the diametral ratio of the resonant plate to the ceramic element, FIG. 1 should be referred to, where on the X-abcissa is the ratio R.phi.=.phi.2/.phi.1, .phi.1 being the diameter of ceramic element and .phi.2 that of resonant plate, and on the Y-abcissa is the overall merit of the transducer from the view points of both manufacturing process and electroacoustic performance. Where R.phi.<1, i.e. diameter of resonant plate (.phi.2) being less than that of ceramic element (.phi.1), the latter needs to be manufactured dimensionally large if lower resonant frequencies are desired of the resonant plate. This apparently is against the current trend for smaller sized electronic parts, and decreases its overall merit on account of loss in marketability.
On the other hand, where R.phi.>2, i.e. the diameter or resonant plate (.phi.2) being greater than twice that of ceramic element (.phi.1), acoustic characteristic of the transducer is materially detracted since a dimensionally large resonant plate to be excited overloads the exciting ceramic element. Therefore, the diametral ratio of the resonant plate to the ceramic element, where 1<R.phi.>2, is suitable for embodying the present invention.
With regard to the thickness ratio of the resonant plate to the ceramic element, FIG. 2 sh
REFERENCES:
patent: 3675053 (1972-07-01), Mifune et al.
patent: 3749854 (1973-07-01), Mifune et al.
patent: 4052627 (1977-10-01), Hayakawa et al.
patent: 4283649 (1981-08-01), Heinouchi
Akiyama Masanori
Kinoshita Osamu
Taniguchi Yoshiharu
Budd Mark O.
Burt Pamela S.
Shortley John L.
Weiner Irving M.
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