Switch, especially relay

A switch has at least two switching elements and a drive member for moving at least one of the switching elements relative to the other switching element for opening and closing the switch. The at least one switching element is fixedly connected to the drive member and the drive member is a solid-state energy converter.

BACKGROUND OF THE INVENTION 
The present invention relates to a switch, especially a relay, with at 
least two switching elements. One of them is movable by a drive member 
relative to the other switching element for opening and closing the 
switch. 
In known relays, the switching element are contact springs which are 
connected to one another by a slide. The slide is brought into its initial 
position by the contact springs whereby in the initial position the slide 
rest at the drive member which is the armature of a solenoid. When the 
relay is supplied with current, the armature is moved so that an opener of 
the relay opens and/or a closing element is closed. As soon as the relay 
opens, the slide, in general, is returned by the spring bias of the 
contact spring or by an additional spring into the initial position. The 
armature itself is biased by a spring force so that when the relay opens 
it is returned into the initial position. When fusing of the contact 
pieces connected to the contact springs occurs, the slide remains in its 
moved position while the armature is returned by the spring force into the 
initial position. Such a relay is constructively complicated and expensive 
because a plurality of contact springs and optionally additionally a 
return spring must be provided. This requires a large constructive size of 
the relay and results in considerable movable masses and thus increased 
switching times. 
It is therefore an object of the present invention to embody a switch of 
the aforementioned kind such that it is comprised only of a few 
components, requires only a minimal constructive size and has minimal 
switching times. 
SUMMARY OF THE INVENTION 
The switch of the present invention is primarily characterized by the 
following features: 
at least two switching elements; 
a drive member for moving at least one of the switching elements relative 
to another one of the switching elements for opening and closing the 
switch: 
wherein the at least one switching element is fixedly connected to the 
drive member and wherein the drive member is a solid-state converter. 
The control voltage is supplied to the monitoring unit. 
In the inventive switch one of the switching elements is connected fixedly 
to the drive member which is in the form of a solid-state energy 
converter. Due to the fixed connection of switching element and drive 
member, the drive member remains in the displaced or moved position when 
fusion of the switching element occurs so that, in a simple manner and 
without additional sensors, this state of the switch can be detected and 
evaluated. Since the drive member is embodied as a solid-state energy 
converter, very short switching times are provided. Furthermore, the 
masses to be moved are very small which is also advantageous with respect 
to the switching times. Due to the fixed connection of the switching 
element and drive member, it is, in principle, sufficient to provide two 
switching elements in order to monitor the proper operation of the switch.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will now be described in detail with the aid of 
several specific embodiments utilizing FIGS. 1 through 
FIG. 1 shows a switch 1 which in the shown embodiment is a relay. The 
switch 1 can, for example, be also embodied as a high-speed circuit 
breaker, a low voltage release, a residual current operated device etc. In 
the following, the switch 1 in the form of a relay is to be disclosed in 
detail. 
The switch 1 comprises as switching elements two contact springs 2, 3 which 
are supported within the switch housing 4. The ends of the contact springs 
2, 3 extending from the switch housing 4 provide connectors (terminals) 
via which current can be supplied. The two contact springs 2, 3 may be 
provided with a contact piece 5, 6 respectively. The longer one of the 
contact springs 2 is fixedly connected to the energy converter 7. The 
energy converter 7 is comprised of a ferroelectric piezo ceramic material, 
for example a foil comprised of lead zirconate titanate or polyvinylidene 
fluoride, or of a magnetostrictive rare earth metal, for example, 
Terfenol-D. When the energy converter 7 is moved in a manner to be 
described in the following, the contact spring 2 is bent resiliently such 
that its contact piece 5 comes into contact with the contact piece 6 of 
the contact spring 3. In the schematic representation according to FIG. 1, 
the force F resulting from bending of the energy converter 7 as well as 
the corresponding displacement travel s are represented symbolically by an 
arrow. 
Should the contact pieces or points 5, 6 become fused together, the energy 
converter 7, because of its rigid connection to the contact spring 2, 
remains in the displaced position. Thus, the electric terminal behavior, 
especially the electric impedance, will change. The switch 1 is connected 
to evaluation circuit 8 and a control circuit 9. The evaluation circuit 8 
detects the electrical terminal behavior of the energy converter 7 and 
emits a corresponding signal to monitoring unit 10. When the contact 
points 5, 6 are not fused to one another, the monitoring unit 10 will 
receive a corresponding signal. It will then send, in turn, a 
corresponding signal to the control circuit 9 which can again trigger the 
switch 1. When the contact points 5, 6 are fused together, this is 
detected by the evaluation circuit 8 and a respective locking signal is 
supplied to the monitoring unit 10. The latter, in turn, supplies a 
corresponding signal to the control circuit 9 so that it will no longer 
trigger the switch 1. 
In the embodiment according to FIG. 2, the energy converter 7 is in the 
form of a piezo element. The monitoring unit 10 supplies a control signal 
to the switch 11 of the control circuit 9. It is represented by a dashed 
line. Downstream of the switch 11 a boost converter 12 is provided which 
is represented by a dash-dotted line. It converts a low voltage, for 
example, 24 V into high voltage, for example, 400 V required for operating 
the piezo element 7. The boost converter 12, for example, has a resistor 
13, an inductor 14, and a diode 15. These components are serially 
connected to one another and to the switch 11. The voltage supplied to the 
piezo element 7 is monitored by the input voltage monitor 16. When voltage 
for operating the piezo element 17 is too low, a switch T.sub.1 is 
switched by the output voltage monitor 16 with high frequencies, for 
example, between 20 and 40 kHz until the required voltage is present at 
the piezo element 7. Then the switch T.sub.1 is opened again. When the 
voltage at the piezo element 7 drops below the preset limit, this is 
detected by the output voltage monitor device 16, and the switch T.sub.1 
is again operated in the aforedescribed manner. The switch T.sub.1 is 
connected parallel to the piezo element 7 (and serially connected to the 
diode 15) and is a component of the boost converter 12, as is the output 
voltage monitor 16. 
When the switch 11 of the control circuit 9 is opened by the monitoring 
unit 10 with the aid of a corresponding signal, no input voltage is 
provided. This is detected by an input voltage monitor 17 of the boost 
converter 12 to which is connected a switch T.sub.2. It is switched in 
parallel to the piezo element 7 and in series to the resistor 18 of the 
boost converter 12. When no input voltage is present, the switch T.sub.2 
is closed by the input voltage monitor 17. Accordingly, the charge of the 
piezo element 7 can be discharged quickly via the resistor 18 and the 
closed switch T.sub.2. When the piezo element 7 is discharged, the switch 
T.sub.2 is opened by the input voltage monitor 17. 
The output voltage monitor 16 and the input voltage monitor 17 are 
preferably combined in an IC component. 
The evaluation circuit 8 comprises an oscillator 19 which generates 
alternating current. The alternating current is detected by 
current-voltage measuring unit 20 which is connected by a capacitor 21 to 
the piezo element 7. The piezo element 7 and the capacitor 21 provide a 
load for the oscillator 19. 
When the piezo element 7 is excited, its impedance and thus also the 
voltage, respectively, current change. This is detected by the measuring 
unit 20 which sends corresponding signals to the evaluation and decision 
unit 22. The unit 22 compares the transmitted valued with a preset nominal 
value. It corresponds to a state in which the contact points 5, 6 (FIG. 1) 
of the switch 1 are not fused to one another. The two measuring units 20 
and 22 are advantageously combined in an IC component of the evaluation 
circuit 8. 
When the piezo element 7 is exited, it expands and deflects the contact 
spring 2 (FIG. 1) to such an extent until its contact point contacts the 
contact point 6 of the contact spring 3. During proper operation of the 
switch 1, the contact spring 2 will return when the piezo element is no 
longer actuated into the position represented in FIG. 1 in which the two 
contact points 5, 6 are spaced from one another. However, when the contact 
points 5, 6, due to fusing remain attached to one another, the piezo 
element 7 remains in the moved position because it is fixedly connected to 
the contact spring 2. This results in the measuring unit 20 receiving and 
measuring a voltage and current value which deviates from the nominal 
value. The measuring unit 20 thus supplies corresponding signals to the 
evaluation and decision unit 22 which compares these transmitted signals 
with a nominal value and, upon detection of deviations, sends a 
corresponding control signal to the monitoring unit 10. The monitoring 
unit 10 in conjunction with the control circuit 9 then ensures that the 
switch 1 can not be activated (triggered) again, as has been explained in 
connection with FIG. 1. 
In addition to the aforedescribed contact fusion, any allowable or 
prohibited state, for example, breakage of the piezo element or breakage 
of the slide 26 (FIG. 5) can be compared and evaluated based on the 
combination of input and output values in monitoring unit 10. 
Since the contact spring 2 of the switch is directly and rigidly connected 
to the energy converter 7, the deflection of the energy converter 7 is 
directly detected by the aforedescribed circuitry, for example, that of 
the piezo element in the embodiment according to FIG. 2. With the 
disclosed embodiment an electronic error detection is provided without 
requiring additional sensors. When a piezo element is used as the energy 
converter, energy can be regained by using the generating effect and the 
charge provided within the piezo element in the respective contracted 
phase of the piezo element and can be supplied to the system as a whole. 
Thus, the electromechanical efficiency of the system as a whole can be 
increased. The switch 1 in the form of a relay has, because of its 
disclosed construction, only a minimal constructive size and also only 
minimal masses that must be moved. Accordingly, such a relay has 
substantially shorter switching times than conventional relays which 
operate with a slide and indirect coupling to the armature of the relay. 
Especially, in the disclosed relay 1 an opener is no longer needed; such 
an opener in conventional relays is a necessity in order to monitor the 
proper operation of the relay. In the inventive relay 1 the number of 
required contact springs is thus lower. In the simplest case, as 
represented in FIG. 1, the relay has only one single closing element with 
the two contact springs 2, 3. Relays for safety application of a 
conventional design with force-guided contacts require in the simplest 
embodiment, in addition to such a closing element, an opener. 
In addition to its use as a relay, the switch, for example, can also be 
used as a residual current operated device and residual voltage operated 
device, a power switch, or as a protective motor switch. By changing the 
electrical terminal behavior, as, for example, the converter resonance or 
attenuation during load, monitoring of the state of the energy converter 7 
is possible. Especially, it is also possible to perform an evaluation 
during static operation. The disclosed device for this reason is 
especially suitable as a relay drive in safety-relevant devices. 
In the embodiment according to FIG. 3 the energy converter 7 is embodied in 
the form of a piezoelectric bending element which can be in the form of a 
two, three or multi-layer converter. In the shown embodiment, two 
electrically separated layers are provided which are fixedly connected to 
one another. When the switch 11 is triggered, one layer of the bending 
converter 7 will contract whereby, because of the fixed connection to the 
second piezo layer, the second layer is also bent. Thus, in the second 
piezo layer a charge separation occurs, i.e., a voltage impulse will 
result which is detected and evaluated by the evaluating circuit 8. This 
evaluating circuit 8 comprises two comparators 23, 24 to which the bending 
converter 7 is respectively connected. Within the comparators 23, 24 the 
reference voltage U.sub.ref1, respectively, U.sub.ref2 is compared to the 
voltage impulses generated within the second piezo layer of the bending 
converter 7. The two comparators 23, 24 supply a corresponding output 
signal U.sub.ref1 and U.sub.ref2 that is supplied to the monitoring unit 
10. The monitoring unit 10, as has been disclosed in detail in connection 
with FIGS. 1 and 2, will send corresponding signals to the control circuit 
9 which is embodied identical to the aforedisclosed embodiments. 
In principle, a two, three or multi-layer converter can also be employed 
and evaluated in the manner disclosed in connection with FIG. 2. 
When the contact pieces 5, 6 (FIG. 1) of the switch 1 fuse together, this 
is detected with the aid of comparing the reference voltage with the 
voltage values provided by the bending converter 7 within the comparators 
23, 24. Corresponding output signals will be supplied to the monitoring 
unit 10, which in the manner disclosed in connection with FIG. 1 and 2, 
will send corresponding signals to the control circuit 9. In this manner, 
a reliable error detection is also ensured whereby the control circuit 9 
ensures that for fused contact pieces 5, 6 the switch 1 with the bending 
converter 7 cannot be triggered. 
The embodiment according to FIG. 4 differs from the previously disclosed 
embodiments only in that a monitoring device 10 to which is connected the 
control circuit 9 is not provided. The voltage output signals U.sub.out1 
and U.sub.out2 of the cooperators 23, 24 of the evaluation circuit 8 in 
this case are, for example, supplied to a display which, when the contact 
pieces 5, 6 are fused, will illuminate and thus visually indicate an error 
at the switch 1. In addition or instead of the visual indicator, it is, 
for example, also possible to use an acoustic signal. In other aspects the 
embodiment according to FIG. 4 operates identical to the embodiment of 
FIG. 3. 
FIG. 5 shows in longitudinal section a switch 1 embodied as a relay. This 
switch 1 has a piezoelectric bending converter 7 with two piezo layers 7a 
and 7b which are electrically separated from one another. The bending 
converter 7 is fastened to the bottom 25 of the switch housing 4. At the 
upper end the bending converter 7 is fixedly connected to the slide 26 
which is, in turn, fixedly connected to the contact spring 2. The slide 
26, for example, can be placed onto the upper end of the bending converter 
7 and can be secured by clamping. It is also possible to connect the slide 
26 in a non-detachable manner to the bending converter 7, for example, by 
using an adhesive. 
In the shown embodiment the two contact springs 2 and 3 provide an opener, 
i.e., the contact pieces 5 and 6 of the contact springs 2, 3 abut one 
another. The relay 1 is provided at the opposite side, below the plane of 
the drawing, with a corresponding closing element whose two contact 
springs have contact pieces which in the non-excited state of the relay 
are spaced apart. One of the contact springs of this closing element is 
also connected to the slide 26 and thus fixedly connected to the bending 
converter 7. 
When the relay 1 is actuated, the bending converter 7 is bent to the right 
in the representation of FIG. 5. The slide 26 fixedly connected thereto is 
correspondingly moved to the right and entrains the contact spring 2. The 
respective contact spring of the non-represented closing element of the 
relay 1 is also entrained. The contact piece 5 of the contact spring 2 
lifts thus the contact piece 6 of the contact spring 3 so that the opener 
opens the relay. Correspondingly, on the other side of the relay the 
contact pieces of the contact springs of the closing element are brought 
into contact. 
In the shown embodiment the piezo layer 7b (to the right in the drawing 
FIG. 5) is connected to the evaluating circuit 8 (FIGS. 1 through 4) which 
evaluates the impedance change or the occurring voltage impulses of this 
piezo layer 7a in the aforedescribed manner. When the relay 1 is no longer 
actuated, i.e., the bending converter 7 is no longer supplied with 
current, it is returned into the initial position shown in FIG. 5. With 
the aid of the slide 26 it entrains the contact spring 2 until the contact 
piece abuts the contact piece of the contact spring 3. At the opposite 
side of the relay the two contact pieces of the contact springs are 
disengaged. 
Advantageously, the contact spring 2 of the opener can be resiliently 
biased in the open direction (FIG. 5). Thus, it assists in bending the 
bending converter 7 into the non-represented actuated position. Upon 
closing the contacts 5, 6 of the non-represented closing element, the 
required contact pressure is determined to a minimal amount by the force 
of the bending converter 7, and primarily by the bias of the contact 
spring 2 so that the required contact pressure can be reliably achieved. 
The bias of the contact spring 2 is selected such that even for extended 
use of the relay and respective wear of the contact pieces 5, 6 a 
sufficient contact pressure is ensured. 
In the same manner, the contact spring 2 of the non-represented closing 
element can be biased in the actuating direction in a manner similar to 
the aforedescribed one. For relays with multiple contacts, a combination 
of the bias of the contact springs can ensure a force situation that 
assists the movement of the piezoelectric converter and generates the 
required contact forces. 
The piezo layer 7b which is advantageously strip-shaped, forms an 
activating piezo layer while the oppositely arranged piezo layer 7a is a 
sensory piezo layer. The bending converter 7 and the contact springs 2, 3 
can be mounted easily within the relay housing 4. The slide 26 can also 
simply be fastened to the bending converter 7 and the corresponding 
contact springs of the opener and the closing element of the relay. A 
contact spring 3 for the opener, respectively, the closing element of the 
relay 1 is without connection to the slide 26. It is comprised of 
electrically non-conducting material, preferably plastic. In order to 
provide for a simple fastening to the contact springs, the slide 26 is 
provided with respective snap-on openings for the contact springs. 
FIGS. 6 through 9 show a further switch 1 in the form of a relay. In FIGS. 
6 and 7, the two sides of the relay are represented which include the 
contact springs 2, 3. The contact springs 2, 3 according to FIG. 6 form a 
closing element while the contact springs 2, 3 according to FIG. 7 provide 
an opener. The contact pieces 5, 6 of the contact springs 2, 3 (FIG. 6) 
forming the closing element have in the initial position a spacing 
therebetween. The contact pieces 5, 6 of the contact springs 2, 3 forming 
the opener are contacting one another in the initial position. The two 
sets of contacts are separated from one another by a wall 27 of the relay 
housing 4, respectively, its contact socket. The lower ends of the contact 
springs 2, 3 are fastened at the bottom 25 of the contact socket in a 
manner known per se. The contact springs 2, 3 project upwardly past the 
wall 27. 
In the relay housing 4 the piezoelectric converter 7 is fastened. The 
bending converter 7 is represented in strip shape and is comprised of a 
single, double, triple or multi layer converter that is fastened with its 
lower end within the bottom 25. The upper end of the bending converter 7 
projects past the wall 27. The slide 26, which is embodied plate-shaped in 
the shown embodiment, is fixedly connected to the upper end of the bending 
converter 7. Furthermore, the contact spring 2 of the closing element 
(FIG. 6) as well as the contact spring 3 of the opener (FIG. 7) are 
fastened to the slide 26. The two other contact springs of the closing 
element and of the opener are not connected to the slide 26 which is 
arranged at a small distance above the wall 27. Since the slide 26 is 
fixedly connected to the piezoelectric bending converter 7, the contact 
spring that is respectively connected to the slide can be resiliently 
biased. 
When the bending converter 7 is deformed under a current load, the slide 26 
in FIG. 6 moves to the right, respectively, to the left in FIG. 7. Thus, 
the contact pieces 5, 6 of the closing element (FIG. 6) contact one 
another, while the contact pieces 5, 6 of the opener (FIG. 7) are moved 
away from one another. Since the contact springs 2 of the closing element 
and of the opener are advantageously resiliently biased, the slide 26 is 
moved assisted by the spring bias and the respective contacts 5, 6 are 
closed or opened. Especially during closing of the contacts 5, 6 (FIG. 6), 
the required contact pressure is provided only to a small amount by the 
force of the bending converter 7, but is primarily provided by the bias of 
the contact spring 2. 
It is also possible to provide a resistance measuring element 28 (FIG. 10) 
onto the piezoelectric ceramic layer that is not actively used with the 
aid of serigraphy in order to use it as a sensor. Due to the mechanical 
connection of the two piezo layers 7a, 7b the sensor layer 29 is then also 
bent. With the stretching of the resistant measuring path 28 which 
extends, for example, in the shape of a meander, the bending action can be 
detected similar to the function of a wire strain gauge. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.