An electronic buzzer comprises an acoustic vibrator comprised of a circular metal plate having its entire periphery rigidly secured to a support, and a piezoelectric element adhered to one face of the metal plate. A driving circuit applies electric driving signals to the vibrator to vibrationally drive it at a 1/N multiple of its natural frequency, where N is an integer, so that the vibrator emits an audible buzzing sound. The metal plate is preferably mounted to undergo vibration in a natural vibration mode having only one nodal circle. The drive circuit includes an inductor connected in a closed loop with the vibrator, which functions as a capacitor, and the circuit applies signals at a selectively variable frequency to the closed loop to accordingly vary the inductance of the inductor to thereby vary the period of oscillation of the acoustic vibrator and the resultant frequency of the buzzing sound.
The present invention produces at least two sound signals such as warning signals or actuating signals by one sounder having a resonant frequency, wherein one of the sound signals is indicated by the resonant frequency of the sounder to enable a higher intensity sound to be produced.
A piezoelectric sounder quickly discharges water when such water enters and eliminates the influence of water or moisture thus intruded. A cylindrical case with a closed bottom is made of glass-fiber reinforced polyester resin, a metal vibrating plate with a piezoelectric ceramic disk mounted on it is fixed on a graded step formed inside the cylindrical case with a closed bottom using a silicon type adhesive, and a conductive layer and the disk-like metal vibrating plate are contacted with two connection terminals. On a circumference side of the case, at least one opening serves as a sound releasing hole and a water drain hole and silicon varnish is coated on at least the surface where the piezoelectric vibrator contacts the two terminals. This sounder has no sound hole at the bottom and even when water drops enter, water is discharged through the opening extended to the bottom of the case. Silicon varnish is coated on at least the surface of the piezoelectric vibrator with which the two connection terminals are in contact so water has no effect. The side of the metal vibrating plate where silicon varnish is coated may be water-tightly fixed on the graded step formed inside the cylindrical resin case using a silicon type adhesive, and the sound and water releasing hole opening on the circumference side of the case may extend from the graded step in the cylindrical resin case toward the bottom thereof.
An electrically actuated positioning element system utilizes a positioning element formed of piezo-electrical bodies each formed of a plurality of lamellae having electrodes. The lamellae have a length substantially greater than their thickness and upon application of an electrical voltage with a field direction which promotes a polarization of the material of the lamellae, the body is shortened. The two bodies are connected to one another at one end by a cross arm and at the other end the one body end is active and free to move relative to the other body end such that a resultant relative motion occurring between the two body ends may be utilized. Preferably a connection is provided for absorbing a lateral thrust of the bodies. The two piezo-electrical bodies are each electrically connected to one another for reverse-phase operation such that one contracts while the other is in a lengthened condition and vice versa.
The piezo-electric device (9) which connects a glass (8) to a movement (3) of the timepiece (1) is arranged in such a way as to deform in flexion in response to an exciting signal applied to its electrodes. The attachment zones (9a,9b) of this device (9) to this glass (8) and respectively to this movement (3) are distinct one from the other when the timepiece (1) is looked at in a direction perpendicular to the planes of the principal faces of the device (9). Thanks to this arrangement, the sound produced by the displacement of the glass (8) when the exciting signal is applied to the electrodes of the piezo-electric device (9) is more intense than in a known timepiece.
A warning module for use with a motor vehicle having multiple sensor inputs and multiple sensor outputs. The inputs are coupled to sensing circuits for monitoring a condition such as engine temperature. The outputs are coupled to one or more light bulbs or other visual indicators which are activated at a lamp flash frequency. A variable frequency oscillator activates an audible output device, preferably a piezoelectric buzzer. The light output levels are diminished for nighttime use. A plastic housing supports a piezo-electric transducer and reverberation plate and achieves a high sound output.
