Piezoelectric ceramic switching devices and systems and method of making the same

Abstract

Improved piezoelectric ceramic switching devices are described along with their method methods of fabrication. In addition to the devices themselves, novel electric circuits are described for the energization as well as the use of such devices as switching elements in electrical systems. Parts of both the energization circuits and/or utilization circuits employing the piezo ceramic switching device are physically mounted on and supported by non-polarized parts of the piezoelectric ceramic plate elements comprising the switching devices so that lightweight compact construction is achieved along with substantial reduction of stray inductance intercoupling.

Description

TECHNICAL FIELD

This invention relates to improved piezoelectric ceramic switching devices and to novel electrical systems for the energization, control and utilization of such devices.

More particularly, the invention relates to improved piezoelectric ceramic switching devices, their fabrication, and to novel electrical circuits for the energization as well as use of such improved devices as switching elements in electrical systems, some parts of which may be physically mounted on and supported by the improved piezoelectric ceramic switching devices themselves.

BACKGROUND PRIOR ART PROBLEM

In conventional electrical circuits, electrical relays and switches are employed at points in such circuits where it is desired either to initiate or interrupt (or both) electric current flow through the circuit. In the past, electromagnetic solenoid operated switches and relays have been employed to either close or open the contacts of a power switch or relay in response to a small control signal (low voltage, low current) which initiates either closure or opening of the bestportions capacitor circuits or utilization circuits or both which are physically mounted on and supported by non-prepoled portions of the piezoelectric ceramic plates which comprise the piezoceramic switching devices. By such fabrication, the size, weight and bulk of the switching devices is greatly reduced so that their compactness and usefullness usefulness with minaturized miniaturized circuit components is greatly improved. Further, because the circuit components with which the devices are used can be mounted right on a portion of the devices themselves, stray circuit inductance is greatly reduced thereby improving the circuit noise immunity characteristics during operation of the devices.

The piezoelectric ceramic switching devices fabricated in accordance with the invention are of greatly improved construction and operating characteristics than the comparable prior art devices of the same general nature. The improved piezoceramic switching devices consequently operate with greater stability, reliability and longevity in service over extended periods of operation requiring substantial numbers of switching operations.

INDUSTRIAL APPLICABILITY

Improved piezoelectric ceramic switching devices and systems having the features of construction made available by the invention are useful in a wide number of residential, commercial and heavy industrial electrical systems for use as switching devices in controlling current flow to widely different types of electrical loads having different power ratings. Because of their novel construction, the devices are of lighter weight, less bulk and lower cost than comparable electromagnetically operated switching devices currently being used and have much faster response times.

Having described several embodiments of new and improved piezoelectric ceramic switching devices and systems using the same and their methods of manufacture in accordance with the invention, it is believed obvious that other modifications and variations of the invention will be suggested to those skilled in the art in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

Claims

1. A piezoelectric ceramic switching device being operated as a normally-open three-position switch including in combination at least one piezoelectric ceramic bender-type switching device having movable contacts that is positioned between a pair of fixed contacts to close one of said fixed contacts upon selective energization of said bender-type switching device producing movement in the direction of said fixed contact contacts whereas the other of said fixed contacts is closed upon successive selective energization of said bender-type switching device causing movement in the opposite direction toward said other fixed contact contacts and with both of said fixed contacts being opened by return movement of said bender-type switching device to its original unenergized position when energization of said bender-type switching device is discontinued, said piezoelectric ceramic bender-type switching device having a piezoceramic bender member comprised by at least two planer planar selectively prepoled piezoelectric plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of at least one central conductive surface and having respective outer conductive surfaces that are insulated from each other and the central conductive surface by the respective intervening piezoelectric plate element thickness thicknesses, said piezoceramic bender member further including movable contacts which coact with the fixed contacts to open and close the electrical switch contacts of said piezoelectric ceramic switching device, clamping means securing a different non-poled portion of the piezoelectric ceramic plate elements adjacent to and mechanically supporting the selectively prepoled movable bender portion in a cantilever manner for opening and closing said coacting fixed contacts, the different non-poled portion of the piezoelectric ceramic plate elements disposed under said clamping means remaining non-movable as being mechanically unstrained and electrically neutral, and switch energization circuit means operatively associated with said piezoelectric ceramic bender-type switching device which selectively applies a source of bender energization potential to the prepoled moveable movable bender portion of each prepoled piezoelectric plate element in a successive manner and having the same polarity as the polarity of the prepoled electric field previously permanently induced in said prepoled movable bender portions so that no depolarization of the piezoelectric plate elements occurs during successive operations of the piezoelectric ceramic bender-type switching device.

2. A piezoelectric ceramic switching device according to claim 1 wherein the different portions of the piezoelectric ceramic plate elements disposed under said clamping means have the outer conductive surfaces thereof removed from the portions disposed under the clamping means and wherein said central and outer conductive surfaces are selectively formed following fabrication of the planar piezoelectric plate elements to desired size with the side edges of the conductive surfaces being recessed relative to the side edges of the piezoelectric ceramic plate elements to thereby provide increased voltage stress withstandability around the side edges of the piezoceramic bender member.

3. A piezoelectric ceramic switching device according to claim 1 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of the prepoled movable portion of the bender-type piezoelectric device.

4. A piezoelectric ceramic switching device according to claim 3 wherein the conformal electrically insulating protective coating comprises a polyimide siloxane copolymer.

5. A piezoelectric ceramic switching device according to either of claims 3 or 4 wherein the conformal electrically insulating coating extends over and covers the outer planar conductive surfaces and their the edges of the prepoled planar piezoelectric ceramic plate elements, and further extends over and covers the side edges of the piezoelectric plate elements and the central conductive surface sandwiched therebetween at least over the prepoled portions of the device.

6. A piezoelectric ceramic switching device according to claim 2 further including a conformal electrically insulating coating which extends over and covers the outer planar conductive surfaces and their the edges of the prepoled planar piezoelectric ceramic plate elements, and further extends over and covers the side edges of the piezoelectric plate elements and the central conductive surface sandwiched therebetween at least over the prepolarized portions of the device and wherein the conformal insulating coating covering the outer planar conductive surfaces of the prepoled portions of the piezoelectric plate elements also extends down to and covers the portions of the piezoelectric plate elements exposed by the removal of the outer conductive surfaces thereon as well as the edge portions of the outer conductive surfaces exposed by such removal.

7. A piezoelectric ceramic switching circuit employing a piezoelectric ceramic switching device according to claim 1 and further including respective switch energization circuit means connected in circuit relationship across respective ones of the prepolarized piezoelectric plate elements of the piezoelectric bender-type switching device for selectively closing or opening respective ones of sets of coacting electrical switch contacts for controlling electric current supplied to a load with opening and closing of the contacts, said switch energization circuit means comprising a source of bender energization potential, normally open low power rated user operated electric switch means, current limiting resistor means and diode rectifier circuit means poled to provide an electric energization potential having the same polarity as the polarity of the prepoling potential used to polarize the prepoled piezoelectric plate elements of the bender-type piezoelectric switching device, all connected in series circuit relation with a respective one of the prepoled piezoelectric plate elements of the bender-type piezoelectric switch upon closure of the normally open low power rated user's switch, whereby the respective prepolarized piezoelectric plate element of the bender-type piezoelectric switch selectively and respectively can be excited with a direct current excitation field which always has the same polarity as the prepoling electric field previously permanently induced in the respective piezoelectric plate element and no depolarization of the piezoelectric plate element occurs during successive operations of the piezoelectric bender-type switching device to close or open the load current controlling electric switch contacts.

7. The device of claim 76 wherein said non-bending portions of said bender member disposed under said clamping means have said outer conductive surfaces removed from the portion disposed under said clamping means, and wherein said central and outer conductive surfaces are selectively formed following fabrication of said plate elements to desired size, with said conductive surfaces being recessed from the side edges of said plate elements to thereby provide increased voltage stress

withstandability of said bender member. 78. The device of claim 76 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of said movable bender portion. 79. The device of claim 78 wherein said coating comprises a polyimide siloxane copolymer. 80. The device of either of claims 78 or 79 wherein said coating extends over and covers all of the outer surfaces of said movable bender portion. 81. The device of claim 77 further including a conformal electrically insulating coating which extends over all of the outer surfaces of said movable bender portion, including portions of said plate elements exposed where said outer conductive surfaces are recessed. 82. The device of claim 76 wherein

said switch energization circuit means are connected in circuit relationship across said selected plate element for selectively closing or opening said fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said fixed contact and said movable contact means,

said switch energization circuit means including a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of said user-operated switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender

member. 83. The device of claim 82 further including

normally-closed electric switch means connected in parallel circuit relationship across said plate element for electrically discharging said plate element, and

means interconnecting said normally-closed switch means with said normally-open switch means,

whereby upon closure of said normally-open switch means said normally-closed switch means is opened to allow energization of said plate element. 84. The device of claim 76 wherein

said switch energization circuit means are connected in circuit relationship across at least one of said plate elements for selectively closing or opening said fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said fixed contact and said movable contact means,

said switch energization circuit means comprising a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of said normally-open switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender member, and

snubber circuit means including a series-connected resistor and capacitor connected in parallel circuit relationship across said fixed contact and said movable contact means,

said snubber circuit means being formed by a passive resistor element mounted on said non-bending portion and being electrically interconnected with a capacitor formed by at least a part of one of said plate elements.

85. The device of claim 81 wherein

said switch energization circuit means are connected in circuit relationship across at least one of said plate elements for selectively closing or opening said fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said fixed contact and said movable contact means,

said switch energization circuit means comprising a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of the normally-open switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender member. 86. The device of claim 85 further including

normally-closed electric switch means connected in parallel circuit relationship across said plate element for electrically discharging said plate element, and

means interconnecting said normally-closed switch means with said normally-open switch means,

whereby upon closure of said normally-opened switch means said normally-closed switch means is opened to allow energization of said plate element. 87. The device of claim 86 further comprising snubber circuit means including a series-connected resistor and capacitor connected in parallel circuit relationship across said fixed contact and said movable contact means, said snubber circuit means being formed by a passive resistor element mounted on said non-bending portion and being electrically interconnected with a capacitor formed by at least a part of one of said plate elements. 88. The device of claim 82 wherein said diode rectifier circuit means also comprises multiplier circuit means for increasing the value of said energization potential to a level suitable for actuating said bender member. 89. The device of claim 87 wherein said diode rectifier circuit means also includes multiplier circuit means for increasing the value of said energization potential to a level suitable for actuating said bender

member. 90. The device of claim 82 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in a second selected plate element also acting as a capacitor, and

second electrical contact means connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said selected plate element, said bender portion closes said first and second electrical contact means momentarily, and a sufficient electric current pulse is discharged from said selected plate element into said gate to turn on said gated switch. 91. The device of claim 87 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in both of said plate elements acting also as capacitors, and

second electrical contact means separately connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said selected plate element, said bender portion closes said first and second electrical contact means momentarily, and a sufficient electric current pulse is discharged from said respective plate elements into said gates to turn on said gated

switches. 92. The device of claim 89 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in a second selected plate element acting also as a capacitor, and

second electrical contact means connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said second selected plate element, said bender portion closes said first and second contact means momentarily, and a sufficient electric current pulse is discharged from said plate element into said gate to turn on said gated switch. 93. The device of claim 76 wherein said central conductive surface includes two separate adjacent inner conductive metal foil elements, each separately secured to a respective one of said plate elements, with said plate elements being physically secured together by a thin adhesive layer disposed between said adjacent inner conductive elements. 94. The device of claim 93 wherein said adhesive layer is electrically insulating, and separate terminal tabs are provided to respective ones of said adjacent inner conductive elements. 95. The device of claim 93 wherein said thin adhesive layer is electrically conductive and said adjacent inner conductive elements share a common terminal tab. 96. The device of claim 83 wherein said non-bending portion of said bender member disposed under said clamping means has said outer conductive surfaces removed from said portion disposed under said clamping means. 97. The device of claim 96 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of said bender and wherein said coating includes a polyimide siloxane copolymer. 98. The device of claim 97 wherein said coating extends over and covers all of the outer surfaces of said movable bender portion, including portions of said plate elements exposed where said outer conductive surfaces are recessed. 99. The device of claim 98 further including third plate element portions extending beyond said clamped portion thereof in a direction opposite from said movable bender portion, and wherein said third plate element portions are located between said respective outer conductive surfaces and said central conductive surface, said third plate element portions forming capacitors having any desired capacitance value in the range of tenths of a microfarad dependent on power rating and being usable as circuit components in an electrical circuit for controlling operation of the device. 100. The device of claim 99 further including additional electrical circuit components including either active semiconductor devices or passive circuit elements, or both, fabricated either in discrete, hybrid or monolithic integrated circuit form, physically formed on and/or supported by said third plate element portions which extend beyond said clamping means, and also including preformed conductive pathways selectively formed by appropriate fabrication of said conductive surfaces on said third plate element portions to interconnect said active devices and/or passive circuit elements. 101. The device of claim 76 further including a relatively thin inflexible stiffening member secured widthwise across said movable end of said movable bender portion. 102. The device of any of claims 76, 81, 93, 97 or 101 wherein said plate element portions including said movable bender portion are initially polarized in place after assembly of the device.

8. A piezoelectric ceramic switching circuit according to claim 7 further including normally-closed electric switch means connected in parallel circuit relationship with a respective piezoelectric plate element for electrically discharging the same and means interconnecting the normally-closed electric switch means with the normally-open low power rated user operated electric switch means for energizing the respective piezoelectric plate element whereby upon closure of the normally-open user operated switch means the interconnected normally-closed electric switch means connected in parallel with the respective piezoelectric plate element to be energized automatically is opened to allow energization of the respective piezoelectric plate element.

9. A piezoelectric ceramic switching circuit employing a piezoelectric ceramic switching device according to claim 1 and further including respective switch energization circuit means connected in circuit relationship across respective ones of the prepolarized piezoelectric plate elements of the piezoelectric bender-type switching device for selectively closing or opening respective ones of sets of coacting electrical switch contacts for controlling electric current supplied to a load with opening and closing of the contacts, said switch energization circuit means comprising a source of bender energization potential, normally open low power rated user operated electric switch means, current limiting resistor means and diode rectifier circuit means poled to provide an electric energization potential having the same polarity as the polarity of the prepoling potential used to polarize the prepoled piezoelectric plate elements of the piezoelectric bender-type switching device, all connected in series circuit relation across a respective one of the prepoled piezoelectric plate elements of the bender-type switch upon closure of the normally open low power rated user's switch, whereby the respective prepolarized piezoelectric plate element of the bender-type piezoelectric switch selectively and respectively can be excited with a direct current excitation field which always has the same polarity as the prepoling electric field previously permanently induced in the respective piezoelectric plate element and no depolarization of the piezoelectric plate element occurs during successive operations of the piezoelectric bender-type device to close or open the load current controlling electric switch contacts, and snubber circuit means comprising a series connected resistor and capacitor connected in parallel circuit relationship across the load current controlling electrical switch contacts opened and closed by the bender-type piezoelectric switching device upon energization of a respective prepolarized piezoelectric plate element, and snubber circuit means being formed by a passive resistor element mounted on an unpolarized piezoelectric plate element portion of the bender-type piezoelectric switching device and electrically interconnected with a capacitor formed by at least a part of such unpolarized piezoelectric plate element portion.

10. A piezoelectric ceramic switching circuit employing a piezoelectric ceramic switching device according to claim 6 and further including respective switch energization circuit means connected in circuit relationship across respective ones of the prepolarized piezoelectric plate elements of the piezoelectric bender-type switching device for selectively closing or opening respective ones of sets of coacting electrical switch contacts for controlling electric current supplied to a load with opening and closing of the contacts, said switch energization circuit means comprising a source of bender energization potential, normally open low power rated user operated electric switch means, current limiting resistor means and diode rectifier circuit means poled to provide an electric energization potential having the same polarity as the polarity of the prepoling potential used to polarize the prepoled piezoelectric plate elements of the piezoelectric bender-type switching device, all connected in series circuit relation across a respective one of the prepoled piezoelectric plate elements of the bender switch upon closure of the normally open low power rated user's switch, whereby the respective prepolarized piezoelectric plate element of the bender-type piezoelectric switch selectively and respectively can be excited with a direct current excitation field which always has the same polarity as the prepoling electric field previously permanently induced in the respective piezoelectric plate element and no depolarization of the piezoelectric plate element occurs during successive operations of the piezoelectric bender device to close or open the load current controlling electric switch contacts.

11. A piezoelectric ceramic switching circuit according to claim 10 further including normally-closed electric switch means connected in parallel circuit relationship with a respective piezoelectric plate element for electrically discharging the same and means interconnecting the normally-closed electric switch means with the normally-open low power rated user operated electric switch means for energizing the respective piezoelectric plate element whereby upon closure of the normally-open user operated switch means the interconnected normally-closed electric switch means connected in parallel with the respective piezoelectric plate element to be energized automatically is opened to allow energization of the respective piezoelectric plate element.

12. A piezoelectric ceramic switching circuit according to claim 11 further including snubber circuit means comprising a series connected resistor and capacitor connected in parallel circuit relationship across the load current controlling electric switch contacts opened and closed by the bender-type piezoelectric switching device upon energization of a respective prepolarized piezoelectric plate element, said snubber circuit means being formed by a passive resistor element mounted on an unpolarized piezoelectric plate element portion of the bender-type piezoelectric switching device and electrically interconnected with a capacitor formed by at least a part of such unpolarized piezoelectric plate element portion.

13. A piezoelectric ceramic switching circuit according to claim 7 wherein said diode rectifier circuit means also comprises multiplier circuit means for increasing the value of the energization voltage to a level suitable for actuating the piezoelectric bender type switching device.

14. A piezoelectric ceramic switching circuit according to claim 12 wherein said diode rectifier circuit means also comprises multiplier circuit means for increasing the value of the energization voltage to a level suitable for actuating the piezoelectric bender-type switching device.

15. A piezoelectric ceramic switching circuit according to claim 7 wherein said sets of coacting electrical switch contacts each comprise a first electrical contact means electrically connected to and supplied with electric charge stored in a respective piezoelectric plate element also acting as a capacitor and second electrical contact means connected to and supplying gate current to a gated power semiconductor switch such as an SCR, triac or transistor whereby upon selective energization of the respective piezoelectric plate element, the prepoled movable bender portion of the switching device closes the first and second electrical contact means momentarily and a sufficient electric current pulse is discharged from the respective piezoelectric plate element into the gate of the gated power semiconductor switch to cause it to turn-on turn on.

16. A piezoelectric ceramic switching circuit according to claim 12 wherein said sets of coacting electrical switch contacts each comprise a first electrical contact means electrically connected to and supplied with electric charge stored in a respective piezoelectric plate element acting also as a capacitor and second electrical contact means connected to and supplying gate current to a gated power semiconductor switch such as an SCR, triac or transistor whereby upon selective energization of the respective piezoelectric plate element, the prepoled movable bender portion of the switching device closes the first and second electrical contact means momentarily and a sufficient electric current pulse is discharged from the respective piezoelectric plate element into the gate of the gated power semiconductor switch to cause it to turn-on turn on.

17. A piezoelectric ceramic switching circuit according to claim 14 wherein said sets of coacting electrical switch contacts each comprise a first electrical contact means electrically connected to and supplied with electric charge stored in a respective piezoelectric plate element acting also as a capacitor and second electrical contact means connected to and supplying gate current to a gated power semiconductor switch such as an SCR, triac or transistor whereby upon selective energization of the respective piezoelectric plate element, the prepoled movable bender portion of the switching device closes the first and second electrical contact means momentarily and a sufficient electric current pulse is discharged from the respective piezoelectric plate element into the gate of the gated power semiconductor switch to cause it to turn-on turn on.

18. A piezoelectric ceramic switching device according to claim 1 wherein the central conductive surface comprises two separate adjacent inner conductive metal foil elements each separately secured to a respective one of the planar piezoelectric plate elements with the planar piezoelectric plate elements being physically secured together by a thin adhesive layer disposed between the adjacent inner conductive surfaces of said foil elements.

19. A piezoelectric ceramic switching device according to claim 18 wherein the thin adhesive layer is electrically insulating and separate terminal tabs are provided to respective ones of the adjacent inner conductive surfaces.

20. A piezoelectric ceramic switching device according to claim 18 wherein the thin adhesive layer is electrically conductive and the inner adjacent conductive surfaces share a common terminal tab.

21. A piezoelectric ceramic switching device according to claim 8 wherein the different portion of the piezoelectric plate elements disposed under said clamping means have the outer conductive surfaces removed from the portion disposed under the clamping means.

22. A piezoelectric ceramic switching device according to claim 21 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of the prepoled bender member movable portion of the piezoelectric ceramic bender-type switching device and wherein the conformal electrically insulating protective coating comprises a polyimide siloxane copolymer.

23. A piezoelectric ceramic switching device according to claim 22 wherein the conformal electrically insulating coating extends over and covers the outer planar conductive surfaces and the side edges of the prepoled planar piezoelectric plate elements, and further extends over and covers the side edges of the piezoelectric plate elements and the central conductive surface sandwiched therebetween at least over the prepoled portions portion of the device and wherein the conformal insulating coating covering the outer planar conductive surfaces of the prepoled portions of the piezoelectric plate elements also extends down to and covers the portions of the piezoelectric plate elements exposed by the removal of the outer conductive surfaces thereon as well as the edge portions of the outer conductive surfaces exposed by such removal.

24. A piezoelectric ceramic switching device according to claim 23 wherein the device further includes unpoled piezoelectric plate element portions extending beyond the clamped portion thereof in a direction opposite from the prepoled movable bender portion and wherein the further unpoled piezoelectric plate element portions between the respective outer conductive surfaces and the central conductive surface form capacitors having any desired capacitance value in the range of tenths of a microfarad dependent on power rating and useable usable as circuit components in an electrical circuit for controlling operation of the piezoelectric bender-type switching device or otherwise.

25. A piezoelectric ceramic switching device according to claim 24 further including additional electrical circuit components comprising either active semiconductor devices or passive circuit elements or both fabricated either in discrete, hybrid or monolithic integrated circuit form physically formed on and/or supported by the unpoled piezoelectric plate element portions extending beyond the clamping means and also including preformed conductive pathways selectively formed by appropriate fabrication of the conductive surfaces on the unpoled piezoelectric plate element portions to interconnect the active devices and/or passive circuit elements.

26. A piezoelectric ceramic switching device according to claim 25 1 further including a relatively thin inflexible stiffening member secured widthwise across the free movable end of the prepoled movable bender portion of the bender-type piezoelectric switching device.

27. A piezoelectric ceramic switching device according to either of claims 1 6, 18, 22 or 26 wherein the set of coacting electrical switch contacts opened and closed by the movable bender member are fabricated from a copper-vanadium alloy.

28. A piezoelectric ceramic switching circuit according to either of claims 1, 6, 18, 22 or 26 wherein the bender-type piezoelectric drive member can be made to operate to either side of a center position normally assumed with the bender member in an unexcited condition whereby the bender member can coact with two different sets of make and break electrical contacts disposed on opposite sides of the bender member for selectively making or breaking at least two different and separate electrically conductive paths extending through the respective sets of contacts.

29. A piezoelectric ceramic switching circuit according to either of claim claims 1, 6, 18, 22 or 26 wherein the bender type piezoelectric drive member can coact with two different sets of moveable movable make and break electrical contacts disposed on opposite sides of the bender member for selectively making or breaking at least two different and separate electrically conductive paths extending through the respective sets of movable and fixed contacts, wherein each set of coacting movable and fixed contacts opened and closed by the movable bender member are fabricated from a copper-vanadium alloy.

30. A piezoelectric ceramic switching device according to either of claim claims 1, 6, 18, 22 or 26 wherein the piezoelectric plate element portions comprising the prepolarized movable bender member portion of the device are prepolarized in place after assemblage of the switching device into a complete structure.

31. A piezoelectric ceramic switching circuit according to claim 1 wherein the bender-type piezoelectric drive member can coact with two different sets of movable make and break electrical contacts desposed disposed on opposite sides of the bender member for selectively making or breaking at least two different and separate electrically conductive paths extending through the repective respective sets of movable and fixed contacts wherein each set of coacting movable and fixed contacts opened and closed by the movable bender member are fabricated from a copper-vanadium alloy, and wherein the piezoelectric plate element portions comprising the prepolarized movable bender member portion of the device are prepolarized in place after assemblage of the switching device into a complete structure.

32. A piezoelectric ceramic switching circuit according to claim 26 wherein the bender-type piezoelectric drive member can be made to operate to either side of a center position normally assumed with the bender member in an unexcited condition whereby the bender member can coact with two different sets of make and break electrical contacts disposed on opposite sides of the bender member for selectively making or breaking at least two different and separate electrically conductive paths extending through the respective sets of contacts, wherein the set of coacting electrical switch contacts opened and closed by the movable bender member are fabricated from a copper-vanadium alloy, and wherein the piezoelectric plate element portions comprising the prepolarized movable bender member portion of the device are prepolarized in place after assemblage of the switching device into a complete structure.

33. A piezoelectric ceramic switching circuit according to claim 1 wherein the selectively operable electric excitation circuit means comprises respective switch energization circuit means connected in circuit relationship across respective ones of the selectively prepolarized piezoelectric plate element of the piezoelectric ceramic bender-type switching device for selectively selectrively closing or opening respective ones of sets of coacting movable and fixed contacts for controlling electric current supplied to a load with opening and closing of the contacts, said switch energization circuit means comprising a source of bender energization potential, normally open low power rated user operated electric switch means, current limiting resistor means and diode rectifier circuit means poled to provide an electric energization potential having the same polarity as the polarity of the prepoling potential used to selectively polarize the prepoled piezoelectric plate elements of the piezoelectric bender-type switching device, all connected in series circuit relationship with a respective one of the selectively prepoled piezoelectric plate elements of the bender-type switch upon closure of the normally open low power rated user's switch whereby the respective prepolarized piezoelectric plate element of the bender-type piezoelectric switch selectively and respectively can be excited with a direct current excitation field to close or open the load current controlling electric switch contacts.

34. A piezoelectric ceramic switching circuit according to claim 33 further including normally-closed electric switch means connected in parallel circuit relationship with a respective piezoelectric plate element for electrically discharging the same and means interconnecting the normally-closed electric switch means with the normally-open low power rated user operated electric switch means for energizing the respective piezoelectric plate element whereby upon closure of the normally-open user operated switch means the interconnected normally-closed electric switch means connected in parallel with the respective piezoelectric plate element to be energized automatically is opened to allow energization of the respective piezoelectric plate element.

35. A piezoelectric ceramic switching circuit according to claim 34 further including snubber circuit means comprising a series connected resistor and capacitor connected in parallel circuit relationship across the load current controlling electrical switch contacts opened and closed by the bender-type piezoelectric switching device upon energization of a respective prepolarized piezoelectric plate element, said snubber circuit means being formed by a passive resistor element mounted on an unpolarized piezoelectric plate element portion of the bender-type piezoelectric switching device and electrically interconnected with a capacitor formed by at least a part of such unpolarized piezoelectric plate element portion.

36. A piezoelectric ceramic switching device according to claim 35 wherein said diode rectifier circuit means also comprises multiplier circuit means for increasing the value of the energization voltage to a level suitable for actuating the piezoelectric bimorph bender switching device.

37. A piezoelectric ceramic switching circuit according to claim 35 wherein said sets of coacting electrical switch contacts each comprise a first electrical contact means electrically connected to and supplied with electric charge stored in a respective piezoelectric plate element also acting as a capacitor and second electrical contact means connected to and supplying gate current to a gated power semiconductor switch such as an SCR, triac or transistor whereby upon selective energization of the respective piezoelectric plate element, the prepoled movable bender portion of the switching device closes the first and second electrical contact means momentarily and a sufficient electric current pulse is discharged from the respective piezoelectric plate element into the gate of the gated power semiconductor switch to caus cause it to turn-on turn on.

38. A piezoelectric ceramic switching circuit device according to claim 35 36 wherein said sets of coacting electrical switch contacts each comprise a first electrical contact means electrically connected to and supplied with electric charge stored in a respective piezoelectric plate element also acting as a capacitor and second electrical contact means connected to and supplying gate current to a gated power semiconductor switch such as an SCR, triac or transistor whereby upon selective energization of the respective piezoelectric plate element, the prepoled movable bender portion of the switching device closes the first and second electrical contact means momentarily and a sufficient electric current pulse is discharged from the respective piezoelectric plate element into the gate of the gated power semiconductor switch to cause it to turn-on turn on.

39. A piezoelectric ceramic switching device according to claim 36 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of the prepoled bender member movable portion of the piezoelectric ceramic bender-type switch device with the conformal electrically insulating protective coating comprising a polyimide siloxane copolymer, and wherein the conformal electrically insulating coating extends over the side edges of the prepoled planar piezoelectric plate elements, and further extends over and covers the side edges of the piezoelectric plate elements and the central conductive surface sandwiched therebetween at least over the prepoled portions portion of the device and wherein the conformal insulating coating covering the outer planar conductive surfaces of the prepoled portions of the piezoelectric plate elements also extends down to and covers the portions of the piezoelectric plate elements exposed by the removal of the outer conductive surfaces thereon as well as the edge portions of the outer conductive surfaces exposed by such removal.

40. A piezoelectric ceramic switching device including in combination at least one piezoelectric ceramic bender-type switching device having a piezoceramic bender member comprised by at least two planar prepoled piezoelectric plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of at least one central conductive surface and having respective outer conductive surfaces that are insulated from each other and the central conductive surface by the respective intervening piezoelectric plate element thicknesses, said bender-type piezoelectric switching device further including at least one set of coacting electrical switch contacts opened and closed by a prepolarized movable bender member of the piezoelectric ceramic switching device, and a conformal electrically insulating protective coating covering at least some of the outer surfaces of the prepoled bender member movable portion of the piezoelectric ceramic bender-type switching device, the conformal electrically insulating protective coating comprising a polyimide siloxane copolymer, and extending over and covering the outer planar conductive surfaces and the side edges of the prepoled planar piezoelectric plate elements, and further extending over and covering the side edges of the prepoled piezoelectric plate elements and the central conductive surface sandwiched therebetween at least over the prepoled portions of the bender member and also extending down to and covering the portions of the prepoled piezoelectric plate elements exposed by the removal of the outer conductive surfaces thereon as well as the edge portions of the outer conductive surfaces exposed by such removal.

41. Electrical switching apparatus comprising

(a) at least one piezoelectric ceramic bender-type switching device having a movable piezoceramic bender member, said bender member having at least two planar piezoceramic plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of at least one central conductive surface and having respective outer conductive surfaces that are insulated from each other and the central conductive surface by the respective intervening piezoceramic plate element thicknesses,

(b) said piezoelectric ceramic bender-type switching device further including at least one set of coacting electrical switch contacts opened and closed by the movable bender member of the piezoelectric ceramic switching device,

(c) clamping means securing the piezoceramic plate elements together and mechanically supporting the movable bender member in a cantilever manner for opening and closing said set of coacting electrical contacts, and

(d) selectively operable electric excitation circuit means connected to the piezoelectric ceramic bender-type switching device for selectively and respectively actuating each piezoceramic plate element thereof with a direct current energizing potential which is applied in the same direction employed to produce initial polarization in the respective plate elements,

(e) the electric excitation circuit means being connected in circuit relationship across the respective ones of the piezoceramic plate elements of the piezoelectric ceramic bender-type switching device for selectively closing or opening the set of coacting electrical switch contacts to control electric current being supplied through a load by the opening and closing of the switch contacts. 42. The piezoceramic switching means of claim 41 wherein the movable bender member includes coacting electrical switch contacts disposed on opposite sides to selectively make or break at least two separate electrically conductive paths extending through the respective sets of contacts. 43. The piezoceramic switching means of claim 41 wherein the electrical excitation circuit means includes multiplier circuit means for increasing the value of the direct current energizing potential to a level suitable for actuating the piezoelectric ceramic bender-type switching device. 44. The piezoceramic switching means of claim 41 which further includes circuit means to prevent excess arcing across the coacting electrical contacts when opened to interrupt the electrical

current being supplied through a load. 45. A switching device operable as a normally-open three-position switch comprising:

at least one movable piezoelectric bender member having two planar piezoelectric plate elements secured in sandwich fashion on opposite sides of at least one central conductive surface;

an outer conductive surface extending at least over a movable bender portion of said bender member and secured to each of said plate elements so that said outer conductive surfaces are insulated from each other and said central conductive surface by said plate elements, each said outer conductive surface having at least one movable contact means operatively secured thereto;

clamping means for clamping a non-bending portion of said bender member located adjacent to and mechanically supporting said bender portion in a cantilever manner;

said non-bending portion disposed under said clamping means remaining non-movable and being electrically isolated from said conductive surfaces;

a first fixed contact secured adjacent one planar side of said bender portion for contact with said movable contact means when one of said plate elements is energized, and a second fixed contact secured adjacent the other planar side of said bender portion for contact with said movable contact means when the other of said plate elements is energized; and

switch energization circuit means operatively associated with said bender member for selectively applying a direct current potential to a selected one of said plate elements on said bender portion, each successive energization of said respective plate elements having the same polarity so that no depolarization of said plate elements occurs during successive energizations of said plate elements;

whereby sufficient energization of one of said plate elements causes movement of said bender portion toward said first fixed contact for contacting said first fixed contact, and sufficient energization of said other plate element and sufficient deenergization of said first plate element causes movement of said bender portion toward said second fixed contact for contacting said second fixed contact, and upon deenergization of both of said plates, said bender member is positioned so that both of

said fixed contacts are open. 46. The device of claim 45 wherein said non-bending portions of said bender member disposed under said clamping means have said outer conductive surfaces removed from the portion disposed under said clamping means, and wherein said central and outer conductive surfaces are selectively formed following fabrication of said plate elements to desired size, with said conductive surfaces being recessed from the side edges of said plate elements to thereby provide increased voltage stress withstandability of said bender member.

47. The device of claim 45 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of said movable bender portion. 48. The device of claim 47 wherein said coating comprises a polyimide siloxane copolymer. 49. The device of either of claims 47 or 48 wherein said coating extends over and covers all of the outer surfaces of said movable bender portion. 50. The device of claim 46 further including a conformal electrically insulating coating which extends over all of the outer surfaces of said movable bender portion, including portions of said plate elements exposed where said outer conductive surfaces are recessed. 51. The device of claim 45 wherein

said switch energization circuit means are connected in circuit relationship across at least one of said plate elements for selectively closing or opening said first fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said first fixed contact and said movable contact means,

said switch energization circuit means including a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of said user-operated switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender

member. 52. The device of claim 51 further including

normally-closed electric switch means connected in parallel circuit relationship across said plate element for electrically discharging said plate element, and

means interconnecting said normally-closed switch means with said normally-open switch means,

whereby upon closure of said normally-open switch means said normally-closed switch means is opened to allow energization of said plate element. 53. The device of claim 45 wherein

said switch energization circuit means are connected in circuit relationship across at least one of said plate elements for selectively closing or opening said first fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said first fixed contact and said movable contact means,

said switch energization circuit means comprising a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of said normally-open switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender member, and

snubber circuit means including a series-connected resistor and capacitor connected in parallel circuit relationship across said first fixed contact and said movable contact means,

said snubber circuit means being formed by a passive resistor element mounted on said non-bending portion and being electrically interconnected with a capacitor formed by at least a part of one of said plate elements.

54. The device of claim 50 wherein

said switch energization circuit means are connected in circuit relationship across at least one of said plate elements for selectively closing or opening said first fixed contact and said movable contact means for controlling electric current supplied to a load with opening and closing of said first fixed contact and said movable contact means,

said switch energization circuit means comprising a source of bender energization potential, normally-open, low power rated, user-operated electric switch means, current limiting resistor means and diode rectifier circuit means oriented to provide a selected direct current electric energization potential, all connected in series circuit relation with said plate element upon closure of the normally-open switch,

whereby said plate element can be selectively excited with a direct current excitation field which always has the same polarity, and no depolarization of said plate element occurs during successive operations of said bender member. 55. The device of claim 54 further including

normally-closed electric switch means connected in parallel circuit relationship across said plate element for electrically discharging said plate element, and

means interconnecting said normally-closed switch means with said normally-open switch means,

whereby upon closure of said normally-opened switch means said normally-closed switch means is opened to allow energization of said plate element. 56. The device of claim 55 further comprising snubber circuit means including a series-connected resistor and capacitor connected in parallel circuit relationship across said first fixed contact and said movable contact means, said snubber circuit means being formed by a passive resistor element mounted of said non-bending portion and being electrically interconnected with a capacitor formed by at least a part of one of said plate elements. 57. The device of claim 51 wherein said diode rectifier circuit means also comprises multiplier circuit means for increasing the value of said energization potential to a level suitable for actuating said bender member. 58. The device of claim 56 wherein said diode rectifier circuit means also includes multiplier circuit means for increasing the value of the energization potential to a level suitable for actuating said bender

member. 59. The device of claim 51 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in a selected plate element also acting as a capacitor, and

second electrical contact means connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said plate element, said bender portion closes said first and second electrical contact means momentarily, and a sufficient electric current pulse is discharged from said plate element into said gate to turn on said gated switch. 60. The device of claim 56 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in both of said plate elements acting also as capacitors, and

second electrical contact means separately connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said plate elements, said bender portion closes said first and second electrical contact means momentarily, and a sufficient electric current pulse is discharged from said respective plate elements into said gates to turn on said gated switches.

61. The device of claim 58 further comprising

first electrical contact means electrically connected to and supplied with electric charge stored in a selected plate element acting also as a capacitor, and

second electrical contact means connected to and supplying gate current to a power semiconductor switch having a gate, such as an SCR, triac or transistor,

whereby upon selective energization of said plate element, said bender portion closes said first and second contact means momentarily, and a sufficient electric current pulse is discharged from said plate element into said gate to turn on said gated switch. 62. The device of claim 45 wherein said central conductive surface includes two separate adjacent inner conductive metal foil elements, each separately secured to a respective one of said plate elements, with said plate elements being physically secured together by a thin adhesive layer disposed between said adjacent inner conductive elements. 63. The device of claim 62 wherein said adhesive layer is electrically insulating, and separate terminal tabs are provided to respective ones of said adjacent inner conductive elements. 64. The device of claim 62 wherein said thin adhesive layer is electrically conductive and said adjacent inner conductive elements share a common terminal tab. 65. The device of claim 52 wherein said non-bending portion of said bender member disposed under said clamping means has said outer conductive surfaces removed from said portion disposed under said clamping means. 66. The device of claim 65 further including a conformal electrically insulating protective coating covering at least some of the outer surfaces of said bender member and wherein said coating includes a polyimide siloxane copolymer. 67. The device of claim 66 wherein said coating extends over and covers all of the outer surfaces of said movable bender portion, including portions of said plate elements exposed where said outer conductive surfaces are recessed. 68. The device of claim 67 further including third plate element portions extending beyond said clamped portion thereof in a direction opposite from said movable bender portion, and wherein said third plate element portions are located between said respective outer conductive surfaces and said central conductive surface, said third plate element portions forming capacitors having any desired capacitance value in the range of tenths of a microfarad dependent on power rating and being usable as circuit components in an electrical circuit for controlling operation of the device. 69. The device of claim 68 further including additional electrical circuit components including either active semiconductor devices or passive circuit elements, or both, fabricated either in discrete, hybrid or monolithic integrated circuit form, physically formed on and/or supported by said third plate element portions which extend beyond said clamping means, and also including preformed conductive pathways selectively formed by appropriate fabrication of said conductive surfaces on said third plate element portions to interconnect said active devices and/or passive circuit elements. 70. The device of claim 45 further including a relatively thin inflexible stiffening member secured widthwise across said movable end of said movable bender portion. 71. The device of any of claims 45, 50, 62, 66 or 70 wherein said bender member can be made to operate to either side of a center position normally assumed with said bender portion in an unexcited condition, whereby said bender portion can coact with two different sets of make and break electrical contacts disposed on opposite sides of said bender portion for selectively making or breaking at least two different and separate electrically conductive paths extending through said respective sets of contacts. 72. The device of any of claims 45, 50, 62, 66 or 70 wherein said plate element portions including said movable bender portion are initially polarized in place after assembly of the device. 73. The device of claim 45 wherein said bender member can coact with two different sets of movable make and break electrical contacts disposed on opposite sides of said bender portion for selectively making or breaking at least two different and separate electrically conductive paths extending through said respective sets of movable and fixed contacts, wherein each set of coacting movable and fixed contacts opened and closed by said bender portion are fabricated from a copper-vanadium alloy, and wherein said plate element portions comprising said movable bender portion are initially polarized in place after assembly of the device. 74. The device of claim 70 wherein said bender member can be made to operate to either side of a center position normally assumed with said bender portion in an unexcited condition, whereby said bender portion can coact with two different sets of make and break electrical contacts disposed on opposite sides of said bender portion for selectively making or breaking at least two different and separate electrically conductive paths extending through the respective sets of contacts, wherein said set of coacting electrical switch contacts opened and closed by said bender portion are fabricated from a copper-vanadium alloy, and wherein said plate element portions comprising said movable bender portion are initially polarized in place after assembly of the device. 75. A piezoelectric switching device comprising:

at least one bender member including at least two planar piezoelectric plate elements secured in sandwich fashion on opposite sides of at least one central conductive surface;

an outer conductive surface secured to each of said plate elements so that said outer conductive surfaces are insulated from each other and said central conductive surface by said plate elements;

said bender member further including at least one set of coacting electrical switch contacts opened and closed by said bender member; and

a conformal electrically insulating protective coating covering at least some of the outer surfaces of said bender member, said coating including a

polyimide siloxane copolymer. 76. A piezoelectric switching device comprising:

at least one movable piezoelectric bender member having two planar piezoelectric plate elements secured in sandwich fashion on opposite sides of at least one central conductive surface;

an outer conductive surface extending at least over a movable bender portion of said bender member and secured to each of said plate elements so that said outer conductive surfaces are insulated from each other and said central conductive surface by said plate elements, each said outer conductive surface having at least one movable contact means operatively secured thereto;

clamping means for clamping a non-bending portion of said bender member located adjacent to and mechanically supporting said bender portion in a cantilever manner;

said non-bending portion disposed under said clamping means remaining non-movable and being electrically isolated from said conductive surfaces;

a fixed contact secured adjacent said bender portion for contact with said movable contact means when a selected one of said plate elements is energized; and

switch energization circuit means operatively associated with said bender member for selectively applying a direct current potential to said selected plate element, each successive energization of said selected plate element having the same polarity so that no depolarization of said plate element occurs during successive energizations of said plate element;

whereby sufficient energization of said selected plate element causes movement of said bender portion toward said fixed contact for contacting said movable contact, and upon deenergization of said plate, said bender member is positioned so that said fixed contacts is open. PAR