Abstract This invention relates to improvements of a piezoelectric acoustic device used for a warning buzzer, general buzzer, etc. The conventional piezoelectric acoustic device generates relatively small sound volume, and has disadvantages not sufficiently used practically. This invention contemplates to eliminate this disadvantage, and has a feature that a composite plate for generating a sound is supported in a casing having an opening provided in the direction of thickness, i.e. direction of sound propagation, of the composite plate, and a reflecting plate for reflecting the sound is provided at the rear surface side. Another feature of the present invention is that the above reflecting plate is formed in horn shape to further amplify the generated sound. This invention thus provides an acoustic device for generating large volume with compact structure and less power of consumption.
In a piezoelectric acoustic device including a planar piezoelectric element mounted in a housing, means for electrically energizing said element to cause mechanical vibration thereof to produce sound waves propagating in opposite directions substantially perpendicular to the plane of said piezoelectric element toward opposite ends of said housing, the housing having a first opening in one end thereof for passing sound waves propagating in one of said directions, the improvement comprising: a. a second opening in the other end of said housing for passing sound waves propagating in the other of said directions, and b. reflector means spaced from said housing for reflecting the sound waves passing through said second opening to cause them to progagate outside of said housing in said one direction and reinforce the sound waves passing through said first opening.
Claim 2
Dependent Claim
134 words
In a piezoelectric acoustic device including a planar piezoelectric element mounted in a housing, means for electrically energizing said element to cause mechanical vibration thereof to produce sound waves propagating in opposite directions substantially perpendicular to the plane of said piezoelectric element toward opposite ends of said housing, the housing having a first opening in one end thereof for passing sound waves propagating in one of said directions, the improvement comprising: a. a second opening in the other end of said housing for passing sound waves propagating in the other of said directions, and b. reflector means spaced from said housing for reflecting the sound waves passing through said second opening to cause them to progagate outside of said housing in said one direction and reinforce the sound waves passing through said first opening.
Claim 3
Dependent Claim
43 words
The improvement as defined in claim 1 wherein said reflector means is a flat reflector plate mounted on said housing and spaced therefrom opposite said second opening, the plane of said plate being substantially parallel to the plane of said planar piezoelectric element.
Claim 4
Dependent Claim
27 words
The improvement as defined in claim 2 wherein said flat reflector plate has flanges fixed to opposite edges thereof, said flanges being divergent in said one direction.
Claim 5
Dependent Claim
28 words
The improvement as defined in claim 2 wherein said reflector plate is circular and has a horn-shaped flange fixed to the periphery and diverging in said one direction.