Advanced piezoceramic power switching devices employing protective gastight enclosure and method of manufacture

Abstract

This application described a number of novel advanced piezoelectric ceramic power switching devices which are mounted within protective gastight enclosures that are either evacuated to a high degree of vacuum or filled with an inert gas protective atmosphere. The devices thus constructed are capable of operating over a range of load voltages extending from about 100 volts to 5000 volts or more with corresponding currents of from a few amperes to hundreds of amperes and wherein it is possible to provide a number of such structures in a single common protective gastight enclosure. For certain circuit applications the devices thus constructed have unpoled portions on which are mounted either passive circuit components such as resistors, capacitors and the like or active semiconductor devices all interconnected in circuit relationship with each other and the switching devices by using printed circuit or integrated circuit fabrication techniques. In these devices, stray circuit impedances whether capacitive, inductive or resistive in nature can be reduced to an absolute minimum by appropriate designs. Such complementary circuit components and active semiconductor devices can be, if desired, mounted within the common protective enclosures in close proximity to the piezoceramic switching devices to which they are connected, or alternatively may be mounted exteriorly of the protective enclosures.

Description

This application is a division of application Ser. No. 685,108, filed 12/21/84 with,preceedingpreceeding 15B18characteristics of a vacuum or protective gas atmosphere in which the device are mounted. Because of these characteristics and the protective atmosphere provided by the gastight enclosure, plural switching devices can be mounted in a single common enclosure and the need for conformal coatings or encapaulation encapsulation of the prepolarized portion of the piezoceramic plate elements is obviated. Further, it is possible to employ contact materials such as copper-vanadium alloys having low melting points for establishment of stable arcs to reduce di/dt at current chop (current extinction) during switching and high voltage withstandability. This is made possible since the protective atmosphere in which the contacts are used provides higher voltage withstandability upon contact opening and at current extinction and maintain while maintaining the contacts is a non-oxidizing atmosphere such as a vacuum to protect the low melting point contacts and prevent changes in their contact resistance. Because of the higher dielectric strength and other characteristics noted above which are achieved while operating in a vacuum or protective gas atmosphere, voltage withstandability of at least 2000 volts per mil are is obtainable with such devices. Further, repeatability timing of bender charging, contact closing, bender discharging, contact opening and reverse bender assist, as needed, is optimized.

INDUSTRIAL APPLICABILITY

The invention makes available a family of novel advance advanced piezoelectric ceramic power switching devices which are mounted within protective gastight enclosures that can be either evacuated to a high degree of vacuum of the order of .Badd.10-10 to 10-6 Torrs Torr or filled with an inert protective gas atmosphere such as nitrogen, argon, SF₆ or the like. The switching devices thus fabricated can be used over a wide power range for both industrial, commercial and residential applications.

Having described several embodiments of advanced piezoceramic power switching structures employing protective gastight enclosures and constructed 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 controlled atmosphere bender-type piezoelectric ceramic electrical switching device comprising a gastight protective enclosure secure secured to a base member for supporting the enclosure and sealing closed the interior of the enclosure in a gastight manner, at least one bender-type piezoelectric ceramic switching device having a bender member formed by two juxtaposed selectively prepolarized piezoelectric ceramic planar plate elements secured together sandwich fashion with each plate element having at least inner and outer conductive surfaces formed on the planar surfaces thereof together with respective terminal means for selective application of energizing electric operating potentials to the prepolarized portions of the respective plate elements, said bender-type piezoelectric ceramic switching device being physically supported on said base member within said enclosure by clamping means secured on opposite sides of the bender member at non-prepolarized portions of the respective plate elements and physically supporting the bender member cantilever fashion with only the prepolarized portions thereof being freely movable whereas the non-prepolarized portions of said piezoelectric ceramic plate elements clamped under said clamping means remain both electrically neutral and physically unstrained, first electric switch contact means within said gastight enclosure moved by the free movable end of said bender member, second electric switch contact means physically mounted within said gastight enclosure and selectively engageable by the first electric switch contact means upon the selective application of an energizing electric operating potential to a respective one of the piezoelectric plate elements for causing the bender member to bend and close the first and second electric switch contact means to allow electric current flow therethrough, and respective electrically conductive lead means connected to a respective one of said first and second electric switch contact means and extending to respective terminal means supported by said base member outside said protective gastight enclosure for selectively supplying electric load current to a load outside said enclosure via said first and second electric switch contact means, wherein the non-prepolarized piezoelectric ceramic planar plate element portions extend beyond the clamping means in a direction away from the prepolarized movable member portions, and wherein the device further includes electric circuit components in the form of passive circuit elements and/or active semiconductor devices supported by said non-prepolarized portions of said piezoelectric ceramic plate elements and electrically connected in circuit relationship with said switching device.

2. A controlled atmosphere bender-type piezoelectric ceramic electrical switching device comprising a gastight protective enclosure secured to a base member for supporting the enclosure and sealing closed the interior of the enclosure in a gastight manner, at least one bender-type piezoelectric ceramic switching device having a bender member formed by two juxtaposed selectively prepolarized piezoelectric ceramic planar plate elements secured together sandwich fashion with each plate element having at least inner and outer conductive surfaces formed on the planar surfaces thereof together with respective terminal means for selective application of energizing electric operating potentials to the prepolarized portions of the respective plate elements, said bender-type piezoelectric ceramic switching device being physically supported on said base member within said enclosure by clamping means secured on opposite sides of the bender member at non-prepolarized portions of the respective plate elements and physically supporting the bender member cantilever fashion with only the prepolarized portions thereof being freely movable whereas the non-prepolarized portions of said piezoelectric ceramic plate elements clamped under said clamping means remain both electrically neutral and physically unstrained, first electric switch contact means within said gastight enclosure moved by the freely movable end of said bender member, second electric switch contact means physically mounted within said gastight enclosure and selectively engageable by the first electric switch contact means upon the selective application of an energizing electric operating potential to a respective one of the piezoelectric plate elements for causing the bender member to bend and close the first and second electric switch contact means to allow electric current flow therethrough, and respective electrically conductive lead means connected to a respective one of said first and second electric switch contact means and extending to respective terminal means supported by said base member outside said protective gastight enclosure for selectively supplying electric load current to a load outside said enclosure via said first and second electric switch contact means, wherein the non-prepolarized piezoelectric ceramic planar plate element portions extend beyond the clamping means in a direction away from the prepolarized movable bender portions and carry switch energization circuit means which selectively applies a source of bender energization potential to the prepolarized movable bender portion of each plate element having the same polarity as the polarity of the prepoled electric field previously permanently induced in said prepolarized movable bender portions so that no depolarization of the plate elements occurs during successive operation of the piezoelectric ceramic bender-type switching device.

3. A controlled atmosphere bender-type piezoelectric ceramic electrical switching device as in claim 2 wherein said switch energization circuits circuit means includes electric circuit components in the form of passive circuit elements and/or active semiconductor devices.

4. A controlled atmosphere bender-type piezoelectric ceramic electrical switching device as in claim 2 wherein there are a plurality of bender-type piezoelectric ceramic switching devices physically mounted within a single common gastight protective enclosure with each such device being separately actuable for controlling load current flow therethrough.

5. A controlled atmosphere bender-type piezoelectric ceramic electrical switching structure comprising

(a) a gastight protective enclosure secured to a base member for supporting the enclosure and sealing closed the interior of the enclosure in a gastight manner,

(b) at least one bender-type piezoelectric ceramic switching device having a bender member formed by two juxtaposed piezoelectric ceramic planar plate elements secured together sandwich fashion with at least a selected plate element having inner and outer conductive surfaces formed on the planar surfaces thereof, together with terminal means for application of energizing electric operating potentials to the selected plate element,

(c) means connected to the terminal means for providing energizing electric operating potentials having a single selected polarity,

(d) the bender-type piezoelectric ceramic switching device being physically supported on the base member within the enclosure by clamping means secured on opposite sides of the bender member and physically supporting the bender member cantilever fashion with one end thereof being freely movable,

(e) first electric switch contact means within the gastight enclosure moved by the freely movable end of the bender member,

(f) second electric switch contact means within the gastight enclosure and selectively engageable by the first electric switch contact means upon the selective application of the energizing electric operating potential to the selective plate element for causing the bender member to bend and close the first and second electric switch contact means to allow electric current to flow therethrough, and

(g) respective electrically conductive lead means connected to the first and second electric switch contact means and extending to respective terminal means supported by the base member outside the protective gastight enclosure for selectively supplying electric load current to a load outside the enclosure via the first and second electric switch contact means.

6. The switching structure of claim 5 wherein there are a plurality of bender-type piezoelectric ceramic switching devices physically mounted within a single common gastight protective enclosure, with each such device being actuable for controlling electric load current flow therethrough. 7. The switching structure of claim 6 wherein each bender-type piezoelectric ceramic switching device mounted within the common protective enclosure includes its own coacting first and second electric switch contact means and operates independently of the other switching devices mounted within the common protective enclosure. 8. The switching structure of claim 6 wherein the bender-type piezoelectric ceramic switching devices mounted within the common protective enclosure can be made to coact interdependently with selected other switching devices mounted within the same common protective enclosure. 9. The switching structure of claim 5 wherein the gas-tight protective enclosure is permanently evacuated and maintains the bender-type piezoelectric ceramic device in a high degree of vacuum throughout is operating life. 10. The switching structure of claim 5 wherein the gas-tight protective enclosure is filled with an inert or high dielectric gas atmosphere. 11. The switching structure of claim 5 wherein the piezoelectric ceramic planar plate elements have unpoled portions which extend beyond the clamping means so as to remain electrically neutral and physically unstrained. 12. The switching structure of claim 11 wherein the device further includes circuit components in the form of passive circuit elements and/or active semiconductor devices physically supported by the unpoled portions of the piezoelectric ceramic plate elements and are electrically connected in circuit relationship with the switching device. 13. The switching structure of claim 12 wherein the unpoled portions of the piezoelectric ceramic plate elements and any electric circuit components supported thereby are physically located within the gastight protective

enclosure. 14. The switching structure of claim 11 wherein there are a plurality of bender-type piezoelectric ceramic switching devices physically mounted within a single common gastight protective enclosure with each such device being separately actuable for controlling load current flow therethrough. 15. The switching structure of claim 11 wherein there are a plurality of bender-type piezoelectric ceramic switching devices physically mounted within a single common gastight protective enclosure and wherein at least one of the bender-type piezoelectric ceramic switching devices can be made to coact interdependently with selected other bender-type piezoelectric ceramic switching devices mounted within the same common protective enclosure. 16. The switching structure of claim 11 wherein the unpoled portions of the piezoelectric ceramic plate elements and any electric circuit components supported thereby are physically located within the gastight protective enclosure. 17. The switching structure of claim 11 wherein the gastight protective enclosure is permanently evacuated and maintains the bender-type piezoelectric ceramic device in a high degree of vacuum throughout its operating life. 18. The switching structure of claim 11 wherein the gastight protective enclosure is filled with an inert or high dielectric gas atmosphere. 19. A controlled atmosphere bender-type piezoelectric ceramic switching structure comprising

(a) a gastight protective enclosure secured to a base member for supporting the enclosure and sealing closed the interior of the enclosure in a gastight manner,

(b) at least one bender-type piezoelectric ceramic switching device having a bender member formed by two juxtaposed piezoelectric ceramic planar plate elements secured together sandwich fashion with each plate element having inner and outer conductive surfaces formed on the planar surfaces thereof, together with respective terminal means for application of energizing electric operating potentials to the respective plate elements,

(c) means connected to the terminal menas for providing energizing electric operating potentials to each of the plate elements, the energizing operation potential applied to each plate having a single selected polarity,

(d) the bender-type piezoelectric ceramic switching device being physically supported on the base member within the enclosure by clamping means secured on opposite sides of the bender member and physically supporting the bender member cantilever fashion with a movable end,

(e) respective first electric switch contact means on the outer surfaces of each of the plate elements, the first switch contact means being within the gastight enclosure and moved by the movable end of the bender member,

(f) second electric switch contact means opposite the respective first switch contact means on each of the plate elements, the second switch contact means being within the gastight enclosure and selectively engageable by the opposing first electric switch contact means upon the selective application of an energizing electric operating potential to one of the piezoelectric plate elements for causing the bender member to bend and close the selected first and second electric switch contact means to allow electric current to flow therethrough, and

(g) respective electrically conductive lead means connected to respective ones of the first and second electric switch contact means and extending to respective load terminal means supported by the base member outside the protective gastight enclosure for selectively supplying load current from a power source to a load outside the enclosure via the first and second

electric switch contact means. 20. The switching structure of claim 19 wherein there are a plurality of bender-type piezoelectric ceramic switching devices physically mounted within a single common gastight protective enclosure with each such device being actuable for controlling electric current flow therethrough. 21. The switching structure of claim 20 wherein each bender-type piezoelectric ceramic switching device mounted within the common protective enclosure includes its own coacting first and second electric switch contact means and operates independently of the other switching devices mounted within the common enclosure. 22. The switching structure of claim 20 wherein the bender-type piezoelectric ceramic switching devices mounted within the common protective enclosure can be made to coact interdependently with selected other switching devices mounted within the same common protective enclosure. 23. The switching structure of claim 19 wherein the gastight protective enclosure is permanently evacuated and maintains the piezoelectric ceramic switching device in a high degree of vacuum throughout its operating life. 24. The switching structure of claim 19 wherein the gastight protective enclosure is filled with an inert or high dielectric gas

atmosphere. 25. Electrical switching apparatus comprising:

a gastight protective enclosure secured to a base member for supporting the enclosure,

means for sealing the interior of the enclosure in a gastight manner,

at least one piezoelectric bender member having

a bender portion formed by two juxtaposed piezoelectric planar plate elements secured together sandwich fashion, the bender portion having inner and outer conductive surfaces formed on the planar surfaces of the plate elements, and

a non-bending portion adjacent the bender portion, the non-bending portion being electrically isolated from the conductive surfaces,

first terminal means operatively connected to the conductive surfaces for applying electric potentials to the respective plate elements in the bender portion,

means for clamping the bender member within the enclosure by securing the non-bending portion so that the bender member is physically supported cantilever fashion with the bender portion being movable, the non-bending portion being clamped by the clamping means,

first electric switch contact means within the gastight enclosure mechanically connected to the movable end of the bender portion,

second electric switch contact means physically mounted within the gastight enclosure and selectively engageable by the first electric switch contact menas upon the selective application of an electric potential to a respective one of the piezoelectric plate elements for causing the bender member to bend and close the first and second electric switch contact means to allow electric current flow therethrough,

respective electrically conductive lead means connected to the first and second electric switch contact means and extending to respective second terminal means supported by the base member outside the protective gastight enclosure for selectively supplying electric load current to a load outside the enclosure via the first and second electric switch contact means, and

electric circuit components in the form of passive circuit elements and/or active semiconductor devices supported to said non-bending portion of the bender member and electrically connected in circuit relationship with the

first terminal means. 26. Electrically switching apparatus comprising

a gastight protective enclosure secured to a base member for supporting the enclosure,

means for sealing the interior of the enclosure in a gastight manner,

at least one piezoelectric bender member having

a bender portion formed by two juxtaposed piezoelectric planar plate elements secured together sandwich fashion, the bender portion having inner and outer conductive surfaces formed on the planar surfaces of each plate element, and

a non-bending portion adjacent the bender portion, the non-bending portion being electrically isolated from the conductive surfaces,

first terminal means operatively connected to the conductive surfaces for applying electric potentials to the respective plate elements in the bender portion,

means for clamping the bender member within the enclosure by securing the non-bending portion so that the bender member is physically supported cantilever fashion with the bender portion being movable,

first electric switch contact means within the gastight enclosure mechanically connected to the movable end of the bender portion,

second electric switch contact means physically mounted within the gastight enclosure and selectively engageable by the first electric switch contact means upon the selective application of an electric operating potential to a respective one of the piezoelectric plate elements for causing the bender member to bend and close the first and second electric switch contact means to allow electric current flow therethrough,

respective electrically conductive lead means connected to the first and second electric switch contact means and extending to respective second terminal means supported by the base member outside the protective gastight enclosure for selectively supplying electric load current to a load outside the enclosure via the first and second electric switch contact means, and

switch energization circuit means on the non-bending portion for applying bender energization potential to a selected plate element in the bender portion, the bender energization potential having a selected direct current polarity so that no depolarization of the plate elements occurs during successive operations of the bender member. 27. The apparatus of claim 26 wherein the switch energization circuit means comprises electric circuit components in the form of passive circuit elements and/or active semiconductor devices. 28. The apparatus of claim 26 comprising a plurality of bender members physically mounted within a single common gastight protective enclosure, with each bender member being separately actuable for controlling load current flow therethrough.