Piezoelectric ceramic switching devices and systems and methods 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

This application is a division of application Ser. No. 685,109, filed 12/21/84, now bestportions capacitorusefullness usefulness with minaturized miniaturized circuit component improved. Further, because the circuit components with which 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 including in combination at least one piezoelectric ceramic bender-type switching device having a movable piezoceramic bender member comprised by at least two 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 thicknesses, said bender-type piezoelectric switching device further including at least one set of coacting electrical switch contacts opened and closed by the prepolarized movable bender member of the piezoelectric ceramic switching device, and clamping means securing a different non-poled portion of the piezoelectric ceramic plate elements adjacent to and mechanically supporting the selectively prepoled movable bender member portion in a cantilever manner for opening and closing the set of coacting electrical contacts, the different non-poled portions of the piezoelectric ceramic plate elements disposed under said clamping means remaining non-movable as being mechanically unstrained and electrically neutral, wherein the unpoled piezoelectric plate element portions extend beyond the clamped portion thereof in a direction opposite from the prepoled movable 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 and greater dependent upon power rating and usable as circuit components in an electrical circuit for controlling operation of the piezoelectric bender-type switching device or otherwise.

2. A piezoelectric ceramic switching device according to claim 1 wherein the piezoelectric ceramic plate elements disposed under said clamping means have the outer conductive surfaces thereof removed from the portion 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, and which further includes a conformal electrically insulating coating that extends over and covers the outer planar conductive surfaces and their 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.

3. A piezoelectric ceramic switching device according to claim 2 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 including any capacitors formed according to claim 2 1 in a desired circuit relationship.

4. A piezoelectric ceramic switching devices device according to claim 3 1 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 including any capacitors formed according to claim 2 in a desired circuit relationship.

5. A piezoelectric ceramic switching device according to either of claims 3 1 or 4 2 further including a relatively thin flexible stiffening member secured widthwise across the free movable end of the prepoled movable bender portion of the bender-type piezoelectric switching device.

6. A piezoelectric ceramic switching device according to claim 5 1 further including a relatively thin inflexible stiffening member secured widthwise across the free movable end of the prepoled movable bender portion of the a bimorph piezoelectric switching device.

7. A piezoelectric ceramic switching device according to claim 6 1 further including an extended length of a portion of the central conductive surface in the form of a conductive foil which is bent back over the top of the a stiffening member and secured thereto to form an exposed electrical contact electrically and physically connected to the central conductive surface for coacting with an opposed electrical contact to close or open an electrical circuit therethrough upon energization of the piezoelectric ceramic switching device.

8. A piezoelectric ceramic switching device according to claim 5 further including a relatively thin inflexible insulating stiffening member secured widthwise across the free movable end of the prepoled movable bender portion of the bender-type piezoelectric switching device and wherein an extended length of a portion of the central conductive surface in the form of a conductive foil is bent back over the top of the stiffening member and secured thereto to form an exposed electrical contact electrically and physically connected to the central conductive surface for coacting with an opposed electrical contact to close or open an electrical circuit therethrough upon energization of the piezoelectric ceramic switching device.

9. A piezoelectric ceramic switching device including in combination at least one piezoelectric ceramic bender-type switching device having a movable piezoceramic bender member comprised by at least two 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 thicknesses, said bender-type piezoelectric switching device further including at least one set of coacting electrical switch contacts opened and closed by the prepolarized movable bender member of the piezoelectric ceramic switching device, and clamping means securing a different non-poled portion of the piezoelectric ceramic plate elements adjacent to and mechanically supporting the selectively prepoled movable bender member portion in a cantilever manner for opening and closing the set of coacting electrical contacts, the different non-poled portions of the piezoelectric ceramic plate elements disposed under said clamping means remaining non-movable as being mechanically unstrained and electrically neutral, wherein the unpoled piezoelectric plate element portions extend beyond the clamped portion thereof in a direction opposite from the prepoled movable bender portion and carry switch energization circuit means which selectively applies a source of bender energization potential to the prepoled movable bender portion of each prepoled piezoelectric plate element 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 operation of the piezoelectric ceramic bender-type switching device.

10. A piezoelectric ceramic switching device as in claim 9 wherein said switch energization circuit means includes electrical circuit components comprising either active semiconductor devices or passive circuit elements or both fabricated either in discrete, hybrid or monolithic integrated circuit from physically formed on and/or supported by the unpoled piezoelectric plate element portions extending beyond the clamping means.

11. 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) the piezoceramic plate elements further including polarized and unpolarized portions when conducting the switching operation with at least one set of coacting electrical switch contacts being opened and closed by the polarized portions thereof,

(c) clamping means securing the piezoceramic plate elements together and mechanically supporting the unpolarized portions thereof in a cantilever manner for opening and closing the set of coacting the electrical contacts, and

(d) selectively operable electric excitation circuit means connected to the piezoelectric ceramic bender-type switching device for selectively and respectively actuating the polarized portions of 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 polarized portions of 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. 12. The piezoceramic switching means of claim 11 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. 13. The piezoceramic switching means of claim 11 wherein the electric excitation circuit means includes multiplier circuit means for increasing the value of direct current energization potential to a level suitable for actuating the piezoelectric ceramic bender-type switching device. 14. The piezoceramic switching means of claim 11 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. 15. A piezoelectric switching device comprising:

at least one 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 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 a movable end of a movable bender portion of said bender member;

means for clamping a non-bending portion of said bender member, said clamping means being adjacent to and mechanically supporting said bender portion in a cantilever manner for opening and closing said set of coacting electrical contacts;

said non-bending portion of said bender member which is disposed under said clamping means remaining non-movable and being electrically insulated from said conductive surfaces;

wherein said non-bending portion extends beyond said clamped portion thereof in a direction opposite from said bender portion to form a further piezoelectric plate element portion, said non-bending portion having conductive surfaces for forming capacitors which are usable as circuit components in an electrical circuit for controlling operation of said bender member, said capacitors having any desired capacitance value in the range of tenths of a microfarad and greater, said capacitance value being

dependent upon power rating. 16. The device of claim 15 wherein:

portions of said plate elements disposed under said clamping means do not have outer conductive surfaces;

said central and outer conductive surfaces are selectively formed following fabrication of said plate elements to desired size, with side edges of said conductive surfaces being recessed relative to side edges of said plate elements to thereby provide increased voltage stress withstandability around side edges of said bender member;

said bender member further including a conformal electrically insulating coating that extends over and covers said outer conductive surfaces and said side edges of said plate elements in said bender portion, and further extends over and covers said side edges of said plate elements and said central conductive surface sandwiched therebetween at least over said bender portion; and

said coating also extending down to and covering said portions of said plate elements exposed by the removal of said outer conductive surfaces thereon as well as edge portions of said outer conductive surfaces exposed by such removal. 17. The device of claim 16 further including electrical circuit components comprising either active semiconductor devices, passive circuit elements or both, fabricated either in discrete, hybrid or monolithic integrated circuit form, physically formed on and/or supported by said non-bending portion, and also including preformed conductive pathways selectively formed by appropriate fabrication of said conductive surfaces on said non-bending portion to interconnect said circuit components. 18. The device of claim 15 further including electrical circuit components comprising either active semiconductor devices, passive circuit elements or both, fabricated either in discrete, hybrid or monolithic integrated circuit form, physically formed on and/or supported by said non-bending portion, and also including preformed conductive pathways selectively formed by appropriate fabrication of said conductive surfaces on said non-bending

portion to interconnect said circuit components. 19. The device of claim 15 further including a relatively thin flexible stiffening member secured widthwise across said movable end of said movable bender portion. 20. The device of claim 16 further including a relatively thin inflexible stiffening member secured widthwise across said movable end of said movable bender portion. 21. The device of claim 15 further including an extended length of a portion of said central conductive surface in the form of a conductive foil which is bent back over the top of a stiffening member and secured thereto to form an exposed electrical contact electrically and physically connected to said central conductive surface for coacting with an opposed electrical contact to close or open an electrical circuit therethrough upon energization of the device. 22. The device of claim 19 wherein an extended length of a portion of said central conductive surface is provided in the form of a conductive foil, is bent back over the top of said stiffening member and is secured thereto to form an exposed electrical contact, said contact being electrically and physically connected to said central conductive surface for coacting with an opposed electrical contact to close or open an electrical circuit therethrough upon energization of the device. 23. A piezoelectric switching device comprising:

at least one 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 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 a movable end of a movable bender portion of said bender member; and

means for clamping a different non-bending portion of said bender member adjacent to and mechanically supporting said bender portion in a cantilever manner for opening and closing said set of coating electrical contacts;

said non-bending portion remaining non-movable and electrically insulated from said conductive surfaces, wherein said non-bending portion extends beyond said clamped portion thereof in a direction opposite from said bender portion and carries switch energization circuit means which selectively applies a source of bender energization potential to said bender portion, said source having a single selected polarity so that no depolarization of said piezoelectric plate elements occurs during successive operation of the switching device. 24. The device of claim 23 wherein said switch energization circuit means includes electrical circuit components including active semiconductor devices, passive circuit elements or both, fabricated either in discrete, hybrid or monolithic integrated circuit form, physically formed on and/or supported by said non-bending portion.