Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-31
2001-07-10
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S317000, C310S328000, C310S348000, C310S353000, C310S367000
Reexamination Certificate
active
06259188
ABSTRACT:
ORIGIN OF INVENTION
The invention disclosed herein was jointly conceived and made by employees of the United States Government and employees of Projects Unlimited, Inc. under a Space Act Agreement No. MOA#400.
BACKGROUND
The present invention relates to personal communication devices, and more particularly, to a vibrational and/or acoustic transducer for use with personal communication devices.
Vibrating alarms for use with personal communication devices are well known in the art. Many of these alarms comprise conventional motors having an eccentric weight attached to the rotor shaft. Accordingly, when the motor is activated, the rotation of the rotor shaft and corresponding rotation of the eccentric weight causes vibration within the personal communication device that is detected by the holder of the device. Typically, such vibrating alarms are not capable of also producing an acoustic alert signal; or if the vibrating alarm is capable of producing an acoustic alert signal, the design of the combination vibrating/acoustic alarm is complicated—rendering it not feasible for inexpensive mass production.
Accordingly, a need exists for a combination vibrating and acoustical alarm mechanism that has a relatively uncomplicated design, is relatively inexpensive to produce, that is substantially durable and is suited (relatively light-weight and small) to be incorporated into a hand-held communication device.
SUMMARY
One aspect of the present invention is to provide an alert apparatus for a personal communication device that includes: a mechanically prestressed piezoelectric wafer positioned within the personal communication device and an alternating voltage input line coupled at two points of the wafer where polarity is recognized. Preferably the alert apparatus also includes a variable frequency device coupled to the alternating voltage input line, operative to switch the alternating voltage on the alternating voltage input line at least between an alternating voltage having a first frequency and an alternating voltage having a second frequency. The first frequency is preferably sufficiently high so as to cause the wafer to vibrate at a resulting frequency that produces a sound perceptible by a human ear, and the second frequency is preferably sufficiently low so as to cause the wafer to vibrate at a resulting frequency that produces a vibration readily felt by a holder of the personal communication device.
It is another aspect of the present invention to provide a personal communication device (such as a wireless telephone or pager) that includes: a housing; a receiver component, mounted within the housing, for receiving messages transmitted to the communications device; a processor, mounted within the housing, operatively coupled to the receiver component for processing messages received by the receiver component; and an alarm apparatus operatively coupled to the processor; where the alarm includes: a mechanically prestressed piezoelectric wafer positioned within the personal communication device and an alternating voltage input line coupled at two points of the wafer where polarity is recognized. Preferably the alarm also includes a variable frequency device coupled to the alternating voltage input line, operative to switch the alternating voltage on the alternating voltage input line at least between an alternating voltage having a first frequency and an alternating voltage having a second frequency. The first frequency is preferably sufficiently high so as to cause the wafer to vibrate at a resulting frequency that produces a sound perceptible by a human ear, and the second frequency is preferably sufficiently low so as to cause the wafer to vibrate at a resulting frequency that produces a vibration readily felt by a holder of the personal communication device. Usually, the frequency of the high frequency supply is approximately 1200 to 20,000 Hz and the frequency of the low frequency supply is less than approximately 300 Hz.
It is also preferred that the personal communication device includes a voltage amplifier operatively coupled to the alternating voltage input line to amplify the alternating voltage input to the wafer, producing an amplified, alternating voltage signal, where the amplified, alternating voltage signal is approximately 20 Volts to approximately 120 Volts. However, with some applications of the present invention, the voltage amplifier may amplify the signal up to approximately 300 Volts.
It is also preferred that the wafer be clamped to the housing of the personal communication device at one or both ends of the wafer or that the wafer be held within a guide mounted within the housing, where the wafer is not attached to the guide or to the housing. Alternatively, the wafer may be clamped to a sounding board, which is in-turn fixed to the housing of the personal communication device.
In an alternate embodiment of the invention, the transducer includes an additional weight or tuning mass attached to the wafer. The additional tuning mass, when combined with the mass of the wafer and the spring constant of the wafer, permits the resonant vibrational frequency of the system to be more definitely tuned to a desired frequency. In another alternate embodiment of the invention, the transducer includes a speaker assembly that provides better impedance matching to the air. This allows a voice frequency range to be produced by the device. Thus the device not only produces an acoustic alert, but may also produce acoustic sounds having a voice range frequency capability.
Accordingly, it is an object of the present invention to provide a combination vibrating and acoustical alarm mechanism that has a relatively uncomplicated design, is relatively inexpensive to produce, is substantially durable and is suited (relatively light-weight and small) to be incorporated into a hand-held communication device. These and other objects and advantages of the present invention will be apparent from the following description, the appended claims and the attached drawings.
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International Search Report of PCT/US99/19911 mailed Mar. 21, 2000.
Balein Rizza
Daugherty Robert H.
Denhardt Gerald A.
Fox Robert L.
Hellbaum Richard F.
Dougherty Thomas M.
Projects Unlimited, Inc.
Thompson Hine LLP
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