An electronic alarm wrist watch comprises a piezoelectric oscillator which vibrates the watch dial, crystal, or parts of the bezel such as the crystal mounting ring to produce an audible sound at predetermined times. The piezoelectric oscillator is energized by a low or high voltage power oscillator.
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.
A piezoelectric audio transducer adapted to produce a sound output when a vibrator which is formed by bonding a piezoelectric element to a metallic diaphragm is electrified, wherein the audio transducer is formed by securely supporting the outer periphery of the vibrator on an acoustic casing, and a fixing part to be fixed to a mounting body is provided on the audio transducer and is connected to the casing with an elastic body interposed therebetween so as to thereby enable the casing which is fixed to the mounting body to vibrate integrally with the vibrator when said vibrator is vibrated.
A correction switching device for a wrist watch provided with an electronic buzzer, comprising a stem having at least three stable positions, and a setting mechanism and an electronic buzzer switch which are operated by said stem such that said setting mechanism is set in a time setting position when said winding stem is in one of said three stable positions and in an alarm setting position when said stem is in one of the other stable positions, and said electronic buzzer switch is set in the "off" position when said stem is at least in one of the stable positions other than that for time setting and in the "on" position when said stem is in the other stable positions.
A watch with an electronic buzzer which comprises a double-constructed back cover including an inner back cover on which a piezoelectric element is mounted to produce a mechanical buzz sound when a voltage is applied thereto and an outer back cover provided with a plurality of small holes for enhancing transmission of the buzz. A driving circuit for actuating or energizing the piezoelectric element is disposed in the watch case releasably from the back cover and the piezoelectric element. This construction enables the watch to be made small in size and assures the watertightness of the watch.
