GB2197128A - Piezoelectric relay switching matrix - Google Patents

Description

1 GB2197128A 1

SPECIFICATION

Piezoelectric relay switching matrix The present invention relates to piezoelectric relays and more particularly to piezoelectric re lays arranged as a matrix switch.

Heretofore, matrix switches, particularly those adapted for telecommunication applica tions, have typically been implemented using 75 electromagnetic relays. Over the years, im provements in electromagnetic relay designs have resulted in increased efficiency and re duced physical size. Nevertheless, such relays have their drawbacks. They are relatively com- 80 plex and expensive to manufacture. Their op erating coils require a multitude of turns of very fine wire. The coil resistance, though low, nevertheless consumes significant power with the accompanying generation of heat.

When a plurality of electromagnetic relays are incorporated in a matrix switch configuration, power consumption and heat generation be comes substantial. This is particularly so if the relay actuated state is held by sustained coil energization. An alternative is to provide ela borate mechanisms for releasably holding the relays in their actuated states. Moreover, in large switching matrices the number of wiring interconnections between relays becomes very 95 large, rendering manufacture involved and ex pensive.

Recent improvements in piezoceramic ma terials have made piezoelectric relays an at tractive alternative to their electromagnetic counterparts. Piezoelectric relay drive elements may be batch fabricated from a number of different polycrystalline ceramic materials such as barium titanate, lead zirconate titanate, lead metaniobate and the like, which are precast and fired into a variety of desired shapes, such as recta ngula r-sha ped, thin plates. Piezo electric relays require very low actuating power, dissipate minimal power to hold an actuated state without outside assistance, and 110 draw no current while in their quiescent state.

Consequently, piezoelectric relays generate miniscule heat. They can be implemented in smaller physical sizes than comparably rated electromagnetic relays and require fewer, far simpler component parts. The electrical char acteristics of piezoelectric drive elements are basically capacitive in nature and thus, unlike electromagnetic relays, are immune to stray magnetic fields.

A principal object of the present invention is to provide an improved matrix switch. How ever the embodiments hereinafter described have also one or more of the following objec tives, namely:

to provide an improved matrix switch having particular application to the telecommunications field, to provide a matrix switch of the above elements, to provide a piezoelectric relay switching matrix utilizing an array of piezoelectric relays efficiently arranged in a compact matrix assembly, to provide a piezoelectric relay switching matrix of the above-character which is amenable to batch -fabrication utilizing printed circuit wiring techniques, to provide a piezoelectric relay switching matrix of the above-character, wherein printed circuit wiring of the matrix switch points is achieved without wiring cross-overs, to provide a piezoelectric relay switching matrix of the above-character, wherein a minimum number of switch terminals is required to provide a piezoelectric relay switching matrix of the above-character which is efficient in design, convenient to manufacture, compact in size and reliable in operation over a long lifetime.

Other objectives will in part be obvious and in part appear hereinafter.

As described herein, there is provided a pie- zoelectric relay switching matrix including a planar array of individually operable bimorph drive elements commonly, cantilever mounted within a housing. Mounted adjacent to the free end of each drive element is at least one movable contact poised in relation with at least one associated fixed contact mounted on a wall of the housing or a support member commonly mounting the drive elements. Electrical activation of selected drive elements pro- duces deflections thereof effective in bringing their movable contacts into or out of contacting engagement with the associated fixed contacts. Switching motion may be single throw or double throw. In the latter case, each drive element is adapted to selectively deflect in opposite directions to engage either one of a pair of associated fixed contacts. Each movable contact may be in the form of a shorting bar engageable with a pair of closely spaced fixed contacts. To wire the switching matrix, the row and column conductors thereof are applied to opposed surfaces of the fixed contact mounting members in printed circuit fashion with appropriate electrical connections made to the various relay contacts.

The multilevel, planar layout of these con ductor runs can be such as to eliminate wiring cross-overs, and thus resort to multilayer printing techniques avoided.

For a better understanding of the present invention, reference may be had to the follow ing detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view, partially in schema- tic form, of a piezoelectric relay switching matrix constructed in accordance with one embodiment of the present invention; Figure 2 is a side elevational view of the switching matrix of Fig. 1; character utilizing piezoelectric switch actuating 130 Figure 3 is a plan view, partially in schema- 2 GB2197128A 2 tic form, of a piezoelectric relay switching matrix constructed in accordance with an alternative embodiment of the invention; Figure 4 is a fragmentary side elevational 5 view of the switching matrix of Fig. 3; Figure 5 is a plan view, partially in schematic form, of a piezoelectric relay switching matrix constructed in accordance with another embodiment of the present invention; Figure 6 is a fragmentary side elevational view of the switching matrix of Fig. 5; and Figure 7 is a fragmentary perspective view of the movable contact end of a bimorph drive element applicable to the switching ma- trix embodiments of Figs. 3 and 5.

Like reference numerals refer to corresponding parts throughout the several views of the drawings.

In the embodiment of the invention seen in Figs. 1 and 2, a piezoelectric relay switching matrix, generally indicated at 20, includes a planar, unitary array 22 of individual bimorph drive elements 24. The drive element array is preferably of a configuration resembling a comb having a centrally located back or spine 26 with the individual drive elements extending in distributed, parallel relation, from both sides of the spine, in the tooth-like fashion. As seen in Fig. 2, drive element array 22 is fixedly mounted along its spine 26 atop a pedestal 28 supported within a housing 30. The individual bimorph drive elements 24 are thus seen to be cantilever mounted with their free ends uniformly spaced between an upper housing wall 32 and a lower housing wall 34. Each drive element is comprised of a pair of piezoceramic plates 36 and 38 bonded together in sandwich fashion with a common, intervening surface electrode 40. This inter- vening electrode may be common to all of the 105 drive elements 24. The exposed upper surface of plate 36 is coated with a conductive metal provide an electrode 42, while the exposed lower surface of plate 38 is similarly elec- troded, as indicated at 44. The plates are formed of a known piezoceramic material, such as lead zirconate titanate (PZT), while the surfaces electrodes are provided by deposited coatings of a suitable metal, such a nickel, silver and the like.

As illustrated diagrammatically in Fig. 2, an integrated circuit package 46 may be mounted atop spine 24 with separate output leads connected with the various electrodes 40, 42 and 44 of each of the drive elements 24. In response to selection signals, this integrated circuitry applies an activating voltage across one of the other of the piezoceramic plates 36, 38 of a selected one or selected plural drive ele- ments to produce deflections thereof either upwardly, as indicated by arrow 48a, or downwardly, as indicated by arrow 48b. The mechanisms operative in producing deflections of a cantilever mounted piezoceramic bimorph bender element, such as drive elements 24, are well understood in the art.

Still referring to Fig. 2, mounted adjacent the free end of each drive element is an opposed pair of movable contacts 50 and 52 electrically connected in common by an interconnecting stud 54. Mounted to the underside of housing top wall 32 in opposed, gapped relation to each upper movable contact 50 is a separate fixed contact 56, while a separate fixed contact 58 is mounted to the upper side of housing bottom wall 34 in opposed, gapped relation to each movable contact 52. Thus, upon upward deflection of a selected drive element 24, its movable contact 50 is engaged with the opposed one of the fixed contacts 56, and, upon downward deflection of a selected drive element, its movable contact 52 engages the opposed one of the fixed contacts 58. Contact engagement is sustained as long as the charged state of one of the piezoceramic plates 36, 38 is held. In their unactivated, quiescent state, the drive elements are situated as seen in Fig. 2 with movable contacts 50 and 52 in essentially uni- formly gapped relation with fixed contacts 56 and 58, respectively. It is thus seen that each drive element 24, together with its associated movable contacts 50, 52 and fixed contacts 56, 58, costitute a single pole, double throw piezoelectric relay.

Wiring the fixed and movable contacts of switching matrix 20 to create a 6x6 matrix utilizing eighteen double throw (upward and downward deflecting) drive elements 24 is il- lustrated in Fig. 1. Reference numerals Rl through R6 indicate what may be considered as six row conductors, and reference numerals Cl through C6 indicate six column conductors. As seen in Fig. 2, column conductors Cl, C2 and C3 are printed circuit conductor runs applied to the upper surface of the housing bottom wall 34 to the left of pedestal 26, while column conductors C4, C5 and C6 are printed circuit conductor runs applied to the upper surface of wall 34 tothe right of the pedestal. These column conductors are represented by dash-out lines in Fig. 1. Thus it is seen that column conductor Cl is connected, via flying leads 60 to the movable contacts 50 and 52 of the lower left three drive elements 24. Column conductor C2 is then connected via flying leads to the movable contacts of the intermediate three drive elements extending leftwardly from spine 26, and column conductor C3 is connected to the movable contacts of the upper left three drive elements. Column conductors C4, C5, and C6 are respectively connected to the movable contacts of the three upper right, the three middle right, and the three lower right drive elements 24, all as seen in Fig. 1.

Row conductors R2, R 4 and R6, shown in solid line, are provided as printed circuit conductor runs laid out in serpentine fashion on the upper or outer surface of housing upper 3 GB2197128A 3 wall 32. It will be appreciated that these row conductors could be printed on the inner surface of housing wall 32. Row conductors R1, R3 and R5, shown in dash line, are printed on the lower or outer surface of housing wall 34 in serpentine fashion. As illustrated, row conducto R1 is connected, via studs 59a extending through holes in housing wall 34, to the fixed contacts 58 associated with the first, sixth and seventh left and right drive elements 24, counting up from the bottom of Fig. 1. Row conductor R2 is connected via studs 59b penetrating housing wall 32 to the fixed contacts 56 also associated with the first, sixth and seventh opposed pairs of oppositely extending drive elements. Similarly, row conductors R3 and R4 are respectively connected to the fixed contacts 58 and 56 associated with the second, fifth and eight opposed pairs of drive elements 24, while row conductors R5 and R6 are respectively connected to the fixed contacts 58 and 56 associated with the third, fourth and ninth opposed pairs of drive elements. Housing wall 32 supports a first plurality of terminals 55 for making electrical contact with fixed contacts 56, while housing wall 34 supports a second plurality of terminals 57 for making electrical contact with fixed contacts 58. It will be appreciated that only one terminal 55 and one terminal 57 are visible in Fig. 2.

From the foregoing description, it is seen that any column conductor can be connected to any row conductor by appropriate activa- tion of a selected one of the drive elements. Thus, for example, if the lower right drive element 24 is activated to deflect downwardly, its relay contacts 52, 58 are engaged to connect column conductor C6 to row conductor R1. An input signal applied to column conductor C6 is thus outputted on row conductor R1, or vice versa. It will be appreciated that multiple drive elements may be activated to route an input signal applied to one row or column conductor out onto a selected plurality 110 of column or row conductors. By virtue of the serpentine layout of the row conductors, no cross-overs exist, and thus resort to dual layer conductor run printing is advantageously avoided.

The piezoelectric relay switching matrix embodiment in Figs. 3 and 4, generally indicated at 62, differs from the embodiment 20 of Figs. 1 and 2 basically from the standpoint that the movable contacts carried by the drive 120 elements 24 are not wired to the column conductors by flying leads 60 as described above. Instead, each drive element, as best seen in Fig. 4 carried separate, upper and lower movable contacts in the form of shorting bars 50a and 52a, respectively, which are not electrically interconnected. Each upper shorting bar 50a is engageable with an associated pair of closely spaced fixed contacts 56a and 56b to complate a circuit therebetween.

Similarly, each lower shorting bar 52a is engageable with an associated pair of fixed contacts 58a and 58b, completing a circuit therebetween. The pairs of fixed contacts 56a, 56b are mounted to the undersurface of housing top wall 32, while the pairs of fixed contacts 58a, 58b are mounted to the upper surface of housing bottom wall 34. It then remains to wire the column conductors into one fixed contact of selected pairs and the row conductors into the other fixed contact of selected pairs to create a relay switching matrix. It will be appreciated that housing walls 32 and 34 support terminals (not shown) similar to terminals 55, 57 (Fig. 2) for making electrical connection to the various fixed contacts.

Fig. 3 depicts in dashed outline the combshaped, planar, one-piece array 22 of eighteen drive elements 24 appropriate for a 6x6 switching matrix. The row and column conductor layout seen in Fig. 3, which may be printed on the undersurface of upper housing wall 32, includes the six column conductors C1 through C6, but only three row conduc- tors, for example, R1, R3 and R5. The same conductor layout is duplicated on the outer or lower surface of housing wall 34, except that the designated row conductors R2, R4 and R6 are involved instead of row conductors R1, R3 and R5. Thus, for example, row conductor R1, printed on housing wall 32, is routed about for convenient electrical connection with fixed contact 56a associated with (again counting from the bottom) the first left drive element 24, fixed contacts 56b of the third, fifth, sixth and eighth left drive elements, and fixed contact 56a of the ninth left drive element. Then, row conductor R2, printed on the lower side of housing wall 32 is connected to fixed con- tact 58a associated with the first left drive element, fixed contacts 58b of the third, fifth, sixth, and eighth left drive elements, and fixed contact 58a of the ninth left drive element. Row conductors R3 and R5 in the one layout, and row conductors R4 and R6 in the other layout are routed about in serpentine fashion for connection to the various fixed contacts illustrated in Fig. 3 without cross-overs.

As indicted above, the routing of column conductors C1-C6 is the same for the layouts printed on the two walls, except that for the one on wall 32 the column conductors C1-C6 are connected to selected ones of the fixed contact pairs 56a, 56b, while the column conductors C 1 -C6 of the layout on wall 34 are connected to selected ones of the fixed contact pairs 58a, 58b. While not shown, it will be understood the corresponding column conductors of the two layouts are connected in common externally of the switching matrix 62.

As seen in Fig. 3, column conductor C1 of the layout printed on wall 32 is connected to fixed contacts 56b associated with the first left and first right drive elements 24, and to fixed contact 56a of the second right drive 4 GB2197128A 4 element. In addition, column conductor C1 of the layout on wall 34 is connected to fixed contacts 58b of the first left and first right drive elements, and to fixed contact 58a of the second right drive element. Thus, for example, if the first right drive element is acti vated to deflect upwardly, as seen in Fig. 4, its shorting bar 50a bridges associated fixed contacts 56a, 56b to connect column conduc tor C1 to row conductor R3. On the other hand, if the first right drive element deflects downwardly to bridge associated contacts 58a, 58b via its shorting bar 52a, column conductor C1 is connected to row conductor R4. Similarly, it is seen that the first left drive 80 element can deflect upwardly to connect col umn conductor C1 to row R1 or downwardly to connect column condcutor C1 to row con cluctor R2. All of the other matrix switch points for connecting any column conductor to 85 any selected row conductor or conductors can be readily traced through in the illustration of Fig. 3.

In the embodiments thus far described, each piezoelectric relay operates to connect a single column conductor to a single row conductor.

In most telecommunication applications, such as telephony, both sides of a circuit must be switched concurrently. To this end, the switching matrix embodiment of Fig. 5 and 6, 95 generally indicated at 64, is a variant of the embodiment of Figs. 3 and 4 structured to connect any one column conductor pair of tip and ring conductors to any selected one row conductor pair of tip and ring conductors.

Thus, switching matrix 64, as seen in Fig. 5, includes a comb-shaped, planar array 22 of piezoelectric drive elements 24, shown in dash-dot outline and mounted in the manner shown in Fig. 2. As seen in Fig. 6, mounted at the free end of each drive element are a pair of upper, electrically isolated shorting bars 66a and 66b, and a pair of lower, electrical isolated shorting bars 68a and 68b. Mounted to the inner surface of housing wall 32 in opposed, gapped relation to each upper short ing bar 66a are a pair of closely spaced fixed contacts 70a and 70b, while a closely spaced pair of fixed contacts 72a and 72b are simi larly mounted in opposed, gapped relation to each shorting bar 66b. Fixed contact pairs 74a, 74b and 76a, 76b are mounted on the inner surface of housing wall 34 in opposed, gapped relation to shorting bars 68a and 68b, respectively, of each drive element 24. By vir tue of this construction, when a drive element deflects upwardly, its shorting bar 66a bridges fixed contact pair 70a, 70b and its shorting bar 66b bridges fixed contact pair 72a, 72b.

Similarly, when a drive element deflects clownwrdly, its shorting bars 68a and 68b re spectively bridge fixed contact pairs 74a, 74b and 76a, 76b. As will be seen in Fig. 5, the column conductor pairs are wired into one fixed contact of each of the pairs associated with selected drive elements, for example fixed contacts 70a and 72a, while the row conductor pairs are wired into the other fixed contacts 70b and 72b of the two fixed con- tact pairs associated with selected drive elements.

Referring to Fig. 5, the row and column conductor pair layout seen therein is printed on the opposed surfaces of housing wall 32 and includes the six row conductors pairs R1T, R 1 -R through R6-T, R6-R of a 6 x 6 switching matrix, but only three column conductor pairs, for example, C 1 -T, C 1 -R, WT, C3-R, and C5-T, C5-R. The identical conductor layout is duplicated on the opposed surfaces of the housing wall 34 to handle the other three column conductor pairs, C2-T, C2-R, C4- T, C4-R, and C6-T, C6-R. It will be assumed, for purposes of description, that the conductor runs shown in solid line in Fig. 5 are printed on the outer surface of housing wall 32 (Fig. 6), while the conductor runs shown in phantom or dash line are printed on the inner surface of this wall. This same convention may apply for the conductor layout printed on the opposed surfaces of housing wall 34. Again the conductor layout on each surface is executed in a manner as to avoid cross-overs. To this end, numerous situations call for conductive transistions from one wall surface to the opposite surface, which are effected by way of plated holes or vias 78. In some cases, these vias are executed at the sites of fixed contacts through the utilization of conductive studs 80, as seen in Fig. 6.

Considering Fig. 5, the column one tip conductor Cl-T runs on the inner surface of wall 32 to the fixed contact 72a associated with the eighth left drive element 24 and to fixed contact 72a of the eighth right drive element by way of conductor run 81 printed on the inner surface of wall 32, with transistions to the upper surface of wall 32 by way of vias 78 to connect into fixed contacts 72a of the second left and fifth left drive elements. These fixed contacts are connected in common with corresponding fixed contacts 72a of the second and fifth right drive elements via studs 80 and conductor runs 81. The column one ring conductor Cl-R runs over the inner surface of wall 32 to fixed contacts 70a of the second, fifth and eighth left drive elements and via conductor runs 81 to fixed contacts 70a of the second, fifth and eighth right drive ele- ments. It will be understood that the column two tip and ring conductors C2-T, C2-R are laid out on the opposed surfaces of housing wall 34 in identical fashion to feed fixed contacts 74a, and 76a of the same drive ele- ments.

Still referring to Fig. 5, the row one tip conductor R1-T runs on the inner surface of wall 32 to fixed contacts 72a of the ninth left and right drive elements 24, and via a stud 80 and jumper 82a printed on the upper surface GB2197128A 5 of wall 32 to fixed contact 72b of the eighth left drive element. The column one ring conductor R1-R similarly runs on the inner surface of wall 32 to fixed contacts 70a and the ninth left and right drive elements and via a stud 80 and jumper 82b printed on the upper surface of wall 32 to fixed contact 70b of the eighth left drive element. Again it will be understood that the row one tip and ring conductors R1-T and 131-13 are laid out on the surfaces of wall 34 to feed the corresponding fixed contacts 76a and 76b of the ninth left and right and eight left drive elements.

From the foregoing, it is seen that, for example, upward deflection of the eighth left 80 drive element causes its shorting bar 66a to bridge associated fixed contacts 70a, 70b and its shorting bar 66b to bridge associated fixed contacts 72a, 72b. As a result, the column one tip and ring conductors C1-T and C1-R are respectively connected to the row one tip and ring conductors 131-T and 131-13. On the other hand, downward deflection of the eighth left drive element connects the column two tip and ring conductors C2-T, C2-R to the row one tip and ring conductors Rl-T, 131-R. All of the other matrix switch points for connecting any column tip and ring conductor pair to any selected row tip and ring conductor pair can be readily traced through in the Fig. 5 sche matic. It is seen that in each case, a single drive element acts to connect a single column conductor pair to a single row conductor pair in concert. The row and column conductor printed circuit layouts are accomplished on 100 four readily available housing wall surfaces without resort to cross-overs on any one wall surface.

Fig. 7 illustrates a preferred free end confi guration for the drive element 24 when the movable contacts are in the form of shorting bars. In the case of the single pole piezocer amic relay configuration of switching matrix 62 in Figs. 3 and 4, the free end of each drive element 24 is bifurcated by virtue of a shallow slot 140 to provide a pair of relatively independently flexible fingers 142a and 142b.

Conductive pads 144a are deposited on the surfaces of these fingers adjacent their free ends and are integrally connected in common by a conductor run 144b routed around the closed end of slot 140. Contact buttons 146 are affixed to or plated on pads 144a so as to make electrical contact therewith. It is seen that surface electrode 42 terminates short of pads 144a and interconnecting run 144b. It will be appreciated that this shorting bar confi guration is duplicated on the undersurface of drive element 24 in opposed registry.

By virtue of this construction, fingers 142a and 142b are capable of flexing independently of each other to ensure good electrical contacting engagement with the opposed pair of fixed contacts, e.g. 56a and 56b in Fig. 4, despite minor variations in the relative heights 130 thereof and/or despite possibly slight twisting of the drive element incident with its deflection.

For the double pole piezoelectric relay confi- gurations of switching matrix 64 iin Figs. 5- and 6, the free end of each drive, element is provided with a centrally located deep slot 148 to create a pair of relatively findepen dently flexible switching poles 150a and 150b. Each pole is bifurcated via slots 140 in the manner shown in Fig. 7, and described above. The formation of the pads 144a, inter connecting run 144b, and contact buttons 146 is duplicated for each pole, as shown.

The advantages gained from have been alluded to above.

It will thus be seen that the objects set forth above, including those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in the limiting sense.

It is also recognised that whereas the invention is illustrated as embodied in a matrix switch having "normally-open" contacts which are selectively closable by activation of their piezoelectric drive elements, it could, if desired, be embodied in a matrix switch having "normally-closed" contacts selectively openable by activation of the drive elements.

this construction

Claims (28)

1. A piezoelectric switching matrix comprising, in combination:

a. an array of piezoelectric relays, each said relay including (1) an elongated drive element having opposed fixed and free ends, (2) at least one movable contact mounted adjacent said free end of said drive element, and (3) at least one fixed contact, b. First means cantilever mounting said drive elements adjacent said fixed ends thereof; c, second means mounting said fixed con- tact of each said relay in relation to said movable contact thereof; and d. pluralities of first and second conductors connection to said contacts of selected multiples of said relays, at least said first conduc- tors being deposited as printed circuit runs on said second means, any one of said first conductors being selectively connectable to any one of said second conductors by selective disposition of said drive element of a selected one of said relays with said fixed and movable contact thereof in engagement.

2. A switching matrix as defined in Claim 1 wherein said fixed contact of a relay is mounted in gapped relation with said movable contact, which is engageable with said fixed 6 contact by activation of said drive element of the relay.

3. A switching matrix as defined in Claim or 2 which further includes a housing enclos- ing said array of relays, said second means being constituted by a wall of said housing.

4. A switching matrix as defined in Claim 2, wherein each said relay includes first and second fixed contacts mounted by said sec- ond means on opposite sides of said movable contact in gapped relation therewith, said drive element of each said relay being selectively actuable to engage said movable contact thereof with either one of said first and see- ond fixed contacts.

5. A switching matrix as defined in Claim 4, which further includes a housing enclosing said array of relays, said second means mounting said first and second fixed contacts of each said relay being constituted by opposed walls of said housing.

6. A switching matrix as defined in Claim 5, wherein said first conductors are connected into said first and second fixed contacts of selected multiples of said relays, and said second conductors are connected into said movable contacts of selected multiples of said relays.

7. A switching matrix as defined in Claim 6, wherein said first conductors are laid out on surfaces of said opposed housing walls in a maner such as to avoid cross-overs.

8. A piezoelectric switching matrix comprising, in combination: 35 a. an array of piezoelectric relays, each said 100 relay including (1) an elongated drive element having opposed fixed and the free ends, (2) at least one movable contact mounted adjacent said free end of said drive element, and (3) at least one pair of first and second fixed contacts; b. first means cantilever mounting said drive elements adjacent said fixed ends thereof; c. second means mounting said pair of first and second fixed contacts of each said relay in spaced, side-by-side relation and in relation to said movable contact thereof; d. a plurality of first conductors connected to said first fixed contacts of selected mul tiples of said relays; and e. a plurality of second conductors con nected to said second fixed contacts of se- lected multiples of said relays, said first and second conductors being deposited on surfaces of said second means as printed circuit runs, any one of said first conductors being selectively connectable to any one of said second conductors by selective disposition of said drive element of a selected one of said relays with said movable contact thereon in shorting engagement with said first and second fixed contacts thereof.

9. The switching matrix defined in Claim 8 130 GB2197128A 6 wherein said first and second fixed contacts of a relay are mounted in gapped relationship with said movable contact thereof, which is movable into shorting engagement with the fixed contacts by activation of said drive element of the relay.

10. A switching matrix as defined in Claim 8 or 9, which further includes a housing enclosing said array of relays, said second means being constituted by a wall of said housing.

11. A switching matrix as defined in Claim 9, wherein each said relay includes first and second movable contacts mounted adjacent said free end of said drive element in electrically isolated relation, a first pair of said first and second fixed contacts mounted by said second means for shorting engagement by said first movable contact upon activation of said drive element, and a second pair of said first and second fixed contacts mounted by said second means for shorting engagement by said second movable contact upon activa tion of said drive element.

12. A switching matrix as defined in Claim 11, which further includes a housing enclosing said array of relays, said second means mounting said first and second pairs of fixed contacts constituted by at least one wall of said housing.

13. A switching matrix as defined in Claim 12, wherein said first and second pairs of fixed contacts are respectively mounted on opposed walls of said housing.

14. A switching matrix as defined in Claim 11, 12 or 13 wherein said first and second conductors are arranged as first and second conductor pairs, said first conductor pairs respectively connected to said first fixed contct of each of said first and second fixed contact pairs of selected multiples of said relays, and said second conductor pairs respectively connected to said second fixed contact of each of said first and second contact pairs of se- lected multiples of said relays, whereby any one of said first conductor pairs is connectable to any one of said second conductor pairs by activation of said drive element of a selected one of said relays.

15. A switching matrix as defined in Claim 9, wherein each said relay includes first, second, third and fourth movable contacts mounted adjacent said free end of said drive element in electrically isolated relation, and a first set of first and second pairs of said first and second fixed contacts and a second set of third and fourth pairs of said first and second fixed contacts, said first and second sets of fixed contact pairs mounted by said second means, whereby activation of said drive element in one direction brings said first and second movable contacts respectively into shorting engagement with said first and second fixed contacts of said first set of fixed contact pairs, and activation of said drive ele- 7 ment in an opposite direction brings said third and fourth movable contacts respectively into shorting engagement with said first and sec ond fixed contacts of said second set of fixed contact pairs.

16. A switching matrix as defined in Claim 15, wherein said first and second conductors are arranged as first and second conductor pairs, said first conductor pairs respectively connected to said first fixed contacts of each 75 of at least one of said first and second sets of said fixed contact pairs of selected mul tiples of said relays, and said second conduc tor pairs respectively connected to said sec ond fixed contact of at least one said first and 80 second sets of fixed contact pairs of selected multiples of said relays, whereby any,one of said first conductor pairs is connectable to any one of said second conductor pairs by activation of said drive element of a selected one of said relays.

17. A switching matrix as defined in Claim 16, which further includes a housing enclosing said array of relays, said housing including a first wall mounting said first and second fixed contact pairs of said first set and an opposed second wall mounting said third and fourth fixed contact pairs of said second set.

18. A switching matrix as defined in Claim 17, wherein said first and second conductor pairs are laid out as printed circuit runs on opposed surfaces of said first and second housing walls in a non-crossing manner with conductive transitions between opposed wall surfaces.

19. A piezoelectric switching matrix com prising, in combination:

a. an insulative substrate having a pedestal; b. an array of piezoelectric relays, each said relay including (1) an elongated drive element having op posed fixed and free ends; (2) mounting means including said pedestal by which said drive element is fixedly canti lever mounted adjacent its fixed end; (3) at least one movable contact mounted adjacent said free end of said drive element, and (4) at least one pair of first and second fixed contacts mounted on a surface of said substrate; c. first and second pluralities of terminals; d. a plurality of first conductors individually connected from terminals of said first plurality to said first fixed contacts of selected mul tiples of said relays; and e. a plurality of second conductors individu ally connected from terminals of said second plurality to said second fixed contacts of se lected multiples of said relays, said first and second conductors being deposed on at least one surface of said substrate as printed circuit runs; any one terminal of said first plurality being connectable to any one terminal of said secGB2197128A 7 ond plurality by selective disposition of said drive element of a selected one of said relays with said movable contact thereon in shorting engagement with said first and second fixed contacts thereof.

20. A switching matrix as defined in Claim 19, wherein said first and second terminal pluraities are mounted on said substrate.

21. A switching matrix as defined in Claim 20, having integrated circuitry for activating said drive element of a selected relay, and a third plurality of said terminals connected with said integrated circuitry by printed circuit runs laid out on at least one of said first and second substrate surfaces.

22. A switching matrix as defined in any of Claims 1-20, having integrated circuitry for activating said drive element of a selected relay.

23. A switching matrix as defined in Claim 21 or 22 having a housing enclosing said array of relays, wherein said integrated circuitry is mounted within the housing.

24. A switching matrix as defined in any preceding claim, wherein said drive elements of said array of relays are formed as a unitary structure of piezoceramic material.

25. A switching matrix as defined in Claim 20, wherein said unitary structure is of a comb-like configuration having a common spine from which said drive elements extend in parallel spaced relation, said spine being affixed to said drive element mounting means.

26. A switching matrix as defined in Claim 21, wherein said drive elements extend in opposite directions from opposed sides of said spine.

27. A switching matrix as defined in Claim 21 or 22 and Claim 25 or 26 wherein said integrated circuit is mounted on said spine.

28. A piezoelectric switching matrix substantially as hereinbefore described with reference to Figs. 1 and 2, Figs. 3 and 4 and optionally Fig. 7, or Figs. 5 and 6 and option- ally Fig. 7 of the accompanying drawings.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC I R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.