Piezoelectric electronic switch
First Claim
1. In a push button switch of the type comprising a piezoelectric element having opposite faces with one face bonded to a flexible support pate to form a laminate, electrodes coupled with the opposite faces of said piezoelectric element, an electronic switching circuit responsive to a predetermined voltage having a first polarity to switch its conductive state, a push button for flexing said laminate and thereby generating a voltage between said electrodes having said first polarity and having a magnitude at least as great as that of said predetermined voltage, said electrodes being electrically coupled with said circuit for switching its conductive state when said laminate is flexed by said push button, said support plate and said piezoelectric element having different temperature coefficients of expansion whereby said laminate is flexed by a predetermined rate of temperature increase to generate a voltage between said electrodes having a magnitude at least as great as that of said predetermined voltage, the improvement comprising:
- said push button being coupled with said laminate for flexing it in a direction opposite the direction the laminate is flexed due to increasing temperature, whereby the voltage produced by flexion of the laminate due to increasing temperature has a polarity opposite that of said first polarity.
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Accused Products
Abstract
An electronic switch is disclosed using a piezoelectric push button transducer and an electronic switching circuit. The push button piezoelectric transducer is connected with the switching circuit with a polarity to provide a switching voltage in response to actuation of the push button switch by finger pressure. The connection is such that the polarity of the voltage generated as a result of differential thermal expansion of the piezoelectric transducer is opposite that produced by finger pressure on the push button switch and does not produce false switching from fast temperature rise. In order to protect against false switching due to high temperature soak of the electronic switch, a thermistor is provided in the electronic switching circuit.
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Citations
15 Claims
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1. In a push button switch of the type comprising a piezoelectric element having opposite faces with one face bonded to a flexible support pate to form a laminate, electrodes coupled with the opposite faces of said piezoelectric element, an electronic switching circuit responsive to a predetermined voltage having a first polarity to switch its conductive state, a push button for flexing said laminate and thereby generating a voltage between said electrodes having said first polarity and having a magnitude at least as great as that of said predetermined voltage, said electrodes being electrically coupled with said circuit for switching its conductive state when said laminate is flexed by said push button, said support plate and said piezoelectric element having different temperature coefficients of expansion whereby said laminate is flexed by a predetermined rate of temperature increase to generate a voltage between said electrodes having a magnitude at least as great as that of said predetermined voltage, the improvement comprising:
said push button being coupled with said laminate for flexing it in a direction opposite the direction the laminate is flexed due to increasing temperature, whereby the voltage produced by flexion of the laminate due to increasing temperature has a polarity opposite that of said first polarity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- 12. A push button switch comprising a piezoelectric element having opposite faces with one face bonded to a flexible support plate to form a laminate, electrodes coupled with the opposite faces of said piezoelectric element, a push button for flexing said laminate and thereby generating a voltage between said electrodes, and an electronic switching circuit, said electrodes being electrically coupled with said circuit for switching its conductive state when said laminate is flexed by said push button, said support plate and said piezoelectric element having different temperature coefficients of expansion whereby said laminate may be flexed by increasing temperature and generate a voltage between said electrodes, said push button being coupled with said laminate for flexing it in a direction opposite the direction the laminate flexes due to increasing temperature, said switching circuit comprising a switch having an input circuit and an output circuit and a thermistor in said input circuit for inhibiting switching of said switch in response to an elevation in temperature.
Specification