The invention relates to a multiple switching device for a plurality of electrically operated devices like electric motors or the like. Such electric motors may be arranged in actuators of valves, blow-out preventers (BOP), chokes or the like used in oil and natural gas production processes.

Such actuators are known e.g. from WO 01 86371 , WO 04 020785, DE 203 1 1 032 or WO 08 125136. Each of the known actuators is normally provided with a plurality of electric motors, especially for redundancy reasons, and each of said electric motors is capable of shifting the actuator in question alone.

Each electric motor has associated therewith a motor control. Such a motor control is comparatively expensive and it necessitates the use of additional components.

It is the object of the present invention to provide a multiple switching device in the case of which less components are necessary and the cost is reduced accordingly, without impairing in any way the functionality or the reliability of the overall system.

According to the present invention, this object is achieved by the features of claim 1.

The multiple switching device according to the present invention comprises a switch housing in which a plurality of contact elements, which are arranged in contact element groups, are displaceable in an axial direction, in particular in the axial direction of the switch housing. Each contact element of a group is adapted to be separately brought into electric contact with a feed contact when displaced in axial direction. Each contact element group has associated therewith a respective output contact element for each electric motor for supplying power to the same. This means that, by an axial displacement of the respective contact element group, one of the contact elements of this group is adapted to be brought into contact with the feed contact element. Furthermore, this contact element has associated therewith an output contact element, which will then supply power to the electric motor in question, one and the same electric motor being supplied with power, according to requirements, by a plurality of contact element groups via respective output contact elements. This means, for example, that three such output contact elements are associated with three electric connections of only one electric motor for effecting suitable rotation of the motor, whereas an additional output contact element provides e.g. a holding voltage or the like for the electric motor in question. In this way, all the connections of a respective electric motor are supplied with power from different output contact elements, each contact element group providing one output contact element. The respective contact elements of a contact element group can then be used for different electric motors, so that a plurality of electric motors can be accessed by only one multiple switching device according to the present invention. The multiple switching device can thus also access, by means of only one motor control, a plurality of electric motors which are associated with different actuators or with the same actuators.

The multiple switching device is used as follows: by selecting specific contact elements of various contact element groups, e.g. an BOP is first displaced to a specific position by supplying power to the associated electric motor. Subsequently, additional contact elements of the respective contact element groups are selected, which are associated with a different electric motor of some other actuator so as to displace the latter in an appropriate manner.

The other contact elements of each contact element group can then be used analogously for accessing additional electric motors of other actuators. Successive resetting of the actuators e.g. to a starting position or a closing position is effected in a corresponding manner.

In order to accomplish a compact structural design, each contact element can be substantially annular in shape and contact elements of a contact element group can be arranged successively in an axial direction.

In order to allow respective contact element groups to be prepared easily and to be varied, if necessary, each contact element group can be implemented as an insert module. This insert module is inserted in the respective switch housing or removed therefrom.

In order to allow easy displacement of the respective contact element groups or insert modules in common, the contact elements and contact element groups, respectively, can be arranged in a contact piston which is displaceable in an axial direction. This contact piston is displaceably supported in the switch housing and the respective contact element groups can be adapted to be inserted in the contact piston and to be releasably secured in position therein.

Normally, actuators of the type in question are nowadays operated electrically in oil and natural gas production processes. To allow this also for the contact piston, said contact piston can be displaceable by means of a step motor. Such a step motor is a synchronous motor in the case of which a rotor can be rotated by a specific angular step or a multiple of such an angular step by means of a controlled, stepwise rotating electromagnetic field produced by stator coils. The normal number of angular steps per rotation ranges from 20 to 200, whereby not only a high rotational accuracy of the step motor but also an axial dis- placeability of the contact piston are accomplished.

In order to movably interconnect the step motor and the contact piston in a simple manner, the step motor can be rotatably connected to a threaded spindle, which is associated with the contact piston for displacement in an axial direction.

For simplifying the connection between the contact piston and the threaded spindle, the contact piston can be provided with a threaded component which is in threaded engagement with the threaded spindle. This has the effect that each rotation of the threaded spindle results in a corresponding axial displacement of the contact piston, said contact piston being supported in the switch housing such that it is axially displaceable therein but secured against rotation relative thereto. In order to allow the contact piston to be displaced to a sufficient extent, the threaded spindle can be displaceably supported especially in a central bore of the contact piston.

In order to make the contact piston easily accessible, if necessary, for the purpose of maintenance, the step motor can be releasably secured to the outer surface of the switch housing and/or the switch housing can include in a housing wall a bearing bore in which the threaded spindle is supported and through which it extends. This mode of arrangement of the step motor allows said step motor to be replaced, if necessary, by a more powerful or a less powerful motor, according to requirements. The threaded spindle simply extends through the housing wall, and in the housing interior it is in threaded engagement with the respective threaded component of the contact piston. Essentially the whole interior of the switch housing can be used for displacing the contact piston therein. In order to be able to arrange the respective insert modules in the contact piston in a simple manner, the contact piston can comprise a plurality of insert bores for inserting therein a respective insert module, said insert bores being arranged especially in the shape of a ring and having each formed therein an insert opening. The insert openings are preferably arranged on one side of the contact piston so that, when the respective insert modules have been finished, they can all be inserted from this side.

In order to be able to easily contact the various contact elements by the feed contact element, each insert bore can be provided with a through hole located opposite the insert opening and used for displaceably passing therethrough a feed contact element.

When the contact piston is displaced, the respective feed contact element will be displaced analogously in the through hole and come into contact with the selected contact element of the respective contact element group.

In order to be able to establish a good and reliable contact with the respective contact element, the feed contact element can be provided with a contact bar having a contact end portion, said contact end portion being especially adapted to be attached by screwing-on. The use of such a contact bar provides a certain degree of inherent rigidity, so that the feed contact element can be passed more easily through respective openings in this area.

Furthermore, the feed contact element including the contact bar and the contact end portion is implemented such that e.g. 400 amperes or even more than that can easily be transmitted per contact. In order to be able to easily supply voltage to the contact bar from outside, the feed contact element can be provided with a substantially L-shaped end contact, which is adapted to be connected to the contact bar and which extends with an L-leg through the switch housing to the outside. This L-leg extends substantially radially, whereas an additional L-leg, which adjoins the first one, can extend in an axial direction so that a respective supply line can easily be connected thereto.

For connecting the output contact element, it may prove to be advantageous when each contact element is connected to an output contact element, especially in a releasable manner, said output contact element extending then through the associated insert opening of the contact piston to the outside. The output contact elements of the contact elements of a contact element group may also be part of the insert module. In this way, the insert module is fully prefabricated making use of contact elements and output contact elements and is then inserted in the respective insert bore of the contact piston, where it is secured in position.

Sufficient stability of the output contact elements will especially be obtained, when said output contact elements are rod-shaped and when they have one connection end releasably secured to the contact element.

Various possibilities are imaginable for accomplishing such a releasable fastening, one possibility being that the contact element can be provided with a screw-in bore for screwing in the connection end of the output contact element. In this case, no additional measures for connecting the contact element and the output contact element will be necessary. Instead, the two components are directly fixed to one another.

In order to easily secure the connection end at its screw-in position, the screw-in bore can be open at both ends thereof, and a counter-bearing element for the connection end can be screwed into the screw-in bore through an opening located opposite the connection end. Such a counter-bearing element is e.g. a set screw or the like.

Since each of the contact elements is connected to an output contact element, it can be considered advantageous when the output contact element extends from the contact element associated therewith through openings of the other contact elements arranged between said associated contact element and the insert opening. Such an opening may e.g. be implemented as an opening slot, which is radially open to the outside and through which the output contact element extends in an electrically insulated manner. In this way, the outer dimensions of the contact element group correspond substantially to the outer dimensions of the respective contact element, so that the output contact elements do not project radially outwards beyond the contact elements.

For electrically insulating the output contact element in this connection, the output contact element can be electrically insulated with respect to contact elements which do not belong thereto, said insulation being especially provided by a coating on the outer surface of said output contact element. One example for such a coating on the outer surface is a coating with polytetrafluoroethylene (PTFE). Such a material also has a very low coefficient of friction and a high specific resistance.

In order to easily avoid also an electric contact between the various contact elements, the contact elements of a contact element group can be electrically insulated with respect to the switch housing and/or with respect to one another and/or they may be arranged in spaced relationship with one another in an axial direction.

The ring shape of the contact elements can be used especially for the feed contact element. For example, when the contact piston is being displaced, the respective feed contact element associated with a contact element group can be displaceable through ring openings of the contact elements of said contact element group, and an electric connection with the respective selected contact element can be established within the ring opening by the contact end portion of said feed contact element.

Since the way in which the ring opening or the inner surface thereof contacts the respective contact end portion may perhaps not suffice to transmit also comparatively high currents, a contact spring element can be supported in the ring opening. The contact end portion is pushed into said contact spring element and is contacted thereby to a sufficient extent for allowing also a transmission of high currents.

According to a preferred embodiment, the contact spring element may be implemented as a lamellar contact spring element or a lamellar contact spring insert. Such a lamellar contact spring element extends, at least partially, along the circumference of the respective ring opening.

A simple possibility of avoiding a contact outside the contact end portion, when the feed contact element is being displaced, is to be seen in implementing the contact end portion such that it has a diameter which is larger than that of the rest of the feed contact element. This has the effect that only the contact end portion comes into contact with the respective contact spring elements in the ring openings of selected contact elements. It has already been pointed out at the beginning that, with respect to the operation of respective actuators and the like, redundancy is important in systems used for oil and natural gas production. In order to achieve this also in the multiple switching device according to the present invention, the step motor can be of redundant design. An example for such a redundant design is the arrangement of two independent step motors, which mutually replace each other if one of them should fail.

In this connection, it is also possible to provide the step motor as such with a redundant design comprising e.g. two or more suitable rotors which are associated with a stator.

In order to be able to determine the respective rotary position of the threaded spindle and the resultant axial position of the contact piston, the step motor and the threaded spindle, respectively, can have associated therewith a position sensor. It is also possible to associate a position sensor with each feed contact element so as to determine the relative position between the feed contact element and at least one contact element. On the basis of this determination of the relative position, it is then possible to determine the other relative positions which the feed contact element occupies with respect to additional contact elements by determining the rotations of the threaded spindle or of the step motor in a suitable manner.

A suitable position sensor can have the structural design described in the following. A measuring circuit can be connected to the first or the last contact element of the respective contact element group and to the contact end portion of the feed contact element, and this measuring circuit can supplied with power from a galvanically separated transmitter. The information on the first position can be transmitted e.g. by an optical coupler to the associated control electronics. In order to increase the position accuracy in this connection still further, it can be detected on the basis of a first measurement whether the contact is closed, i.e. whether the contact end portion is electrically connected to the respective contact element. Subsequently, the contact end portion and the contact piston can be moved on until the contact opens, or, if no contact existed previously, until the contact is closed. The positions in question are stored, whereupon the contact piston is moved to the respective other contact position, i.e. the contact will be closed or opened. Also these positions are detected and an average value is calculated. Together with a respective central position of the first contact position, this average value is then used for calculating the instantaneous position.

It has already been pointed out that the insert modules are releasably secured in position in the respective contact piston. A simple possibility of providing such a releasable fastening can be seen in that the insert modules are secured in position especially by means of screw-in elements which are adapted to be screwed-in in a radial direction. These screw-in elements can again be implemented as set screws or the like. They are preferably screwed in radially inwards from outside in the direction of the insert modules, and they contact said insert modules from outside or they may also contact two neighbouring insert modules so as to fix them relative to one another.

In order to easily prevent a possible rotary displacement of the contact piston, when said contact piston is being displaced in an axial direction, the switch housing may be provided with a guide slot which extends in an axial direction and which is engaged by a guide element projecting substantially radially from the contact piston. Displacement in an axial direction is then effected by moving the guide element along the guide slot, while said guide element is fixed by said guide slot in the circumferential direction of the contact piston.

It has already been pointed out that all the contact elements of a contact element group can be used for connections of an electric motor. It is, however, also possible to use one or a plurality of contact elements of a contact element group for other purposes, e.g. as a loop- through contact element or as an insulating contact element. A loop-through contact element is e.g. not used for providing a direct voltage supply for an electric motor, but for transmitting e.g. data so as to control a respective unit of an actuator or the like. Data transmission can take place in both directions. In addition, said loop-through contact element can be used for connection to a respective feed contact element of an additional multiple switching device. An insulating contact element can e.g. be used for the purpose of grounding or the like.

According to an alternative embodiment, the contact bars may be detachably connected to a corresponding fastening device of the feed contact element. Such a detachable connection may, for example, be realized by screwing or the like. Instead of the arrangement of contact springs within corresponding ring openings, it is also possible that such contact of the respective output contact elements or associated contact elements is realized by a contact spring portion elastically, radially, and externally protruding from a contact end portion of the contact bar.

It is also possible that, in particular, the contact piston is directly fastened at a mounting wall plate or the like in a releasable manner. Such a mounting wall plate can be arranged stationery with respect to the multiple switching devices and electrical driven devices.

In the following, advantageous embodiments of the present invention will be explained in more detail on the basis of the figures comprised in the drawings, in which:

Fig. 1 shows a perspective top view of an embodiment of a multiple switching

device according to the present invention;

Fig. 2 shows a longitudinal section through the multiple switching device according to Fig. 1 ;

Fig. 3 shows an enlarged representation of a detail "X" of Fig. 2;

Fig. 4 shows a longitudinal section, analogously to Fig. 2, at a different position of a contact piston;

Fig. 5 shows a section along line V-V of Fig. 4;

Fig. 6 shows a schematic diagram for an embodiment of the position sensor:

Fig. 7 shows a flowchart for determining the instantaneous position;

Fig. 8 shows a longitudinal section through a further embodiment of a multiple

switching device analogous to Fig. 4, and Fig. 9 shows an enlarged representation of detail "X" of Fig. 8.

Fig. 1 shows a perspective top view of an embodiment of a multiple switching device 1. The multiple switching device 1 has a step motor 32 at one end thereof. This step motor 32 is releasably secured to a housing wall 36 of a switch housing 2, cf. also Fig. 2. The step motor 32 rotates a threaded spindle 33 which extends through a bearing bore 37 into the interior of the switch housing 2. The switch housing 2 is substantially cylindrical, and a contact piston 31 is supported therein such that it is displaceable in an axial direction 16. In Fig. 1 , the contact piston 31 is arranged in its position of maximum extension, cf. also Fig. 2.

The switch housing end facing the step motor 32 has arranged thereon a number of feed contact elements 17 to 21 in the circumferential direction 63, cf. also Fig. 5, said feed contact elements being equally spaced in said circumferential direction. L-legs 62 extending from the feed contact elements are visible, said L-legs extending substantially parallel to the axial direction 16.

A plurality of output contact elements 22 to 29 project from the contact piston 31 , said output contact elements being adapted to be connected to additional electric connection means so as to supply a plurality of electric motors used in actuators of, for example, valves, BOPs, chokes or the like, in oil and natural gas production processes, said actuators being not shown.

The respective output contact elements are combined so as to form groups 3 to 7, cf. also Fig. 5, such a group corresponding to a respective contact element group. One output contact element 22 to 29 of each contact element group is e.g. associated with an electric motor of a specific actuator.

Fig. 2 shows a longitudinal section through the multiple switching device 1 according to Fig. 1.

The respective step motor 32 is releasably attached to the housing wall 36 from outside, e.g. by means of screw fastening. The step motor has the threaded spindle 33 rotatably connected thereto. The latter is in threaded engagement with a threaded component 34, said threaded component 34 being releasably connected to the contact piston 31. The threaded component 34 is provided with a female thread which is in engagement with the male thread of the threaded spindle 33. The threaded spindle 33 extends through the bearing bore 37 of the housing wall 36 into the interior of the switch housing 2.

When the contact piston 31 occupies the position according to Fig. 2, it is located at its position of maximum extension from the switch housing 2, the contact piston 31 being supported such that is displaceable in the switch housing 2 in an axial direction 16.

In Fig. 4 the contact piston 31 is shown at its position of maximum retraction.

The contact piston 31 is provided with a central bore 35, which is adapted to receive the threaded spindle 33 therein in a contactless fashion, cf. Fig. 4.

The bearing bore 37 is used for passing the threaded spindle 33 therethrough and for supporting the latter, and its contour is substantially complementary to that of the threaded component 34, cf. also Fig. 4, said threaded component 34 being arranged at least partially within the bearing bore 37 at the position of maximum retraction.

The respective feed contact elements 17 to 21 are arranged concentrically around the threaded spindle 33, cf. also Fig. 5, one of said feed contact elements being shown in a side view in Fig. 2. Such a feed contact element 17 is provided with contact bar 41 which extends parallel to the threaded spindle 33 in an axial direction 16. At the contact bar end facing the step motor 32, said contact bar 41 is connected to an L-shaped end contact element 43, cf. also Fig. 4, which is defined by a radially extending L-leg 44 and by the L-leg 62 which extends in an axial direction 16. The L-leg 62 serves to connect thereto a suitable supply line for supplying voltage/current.

In the case of the embodiment of the multiple switching device 1 shown here, a total of five feed contact elements 17 to 21 is provided.

Each of the feed contact elements 17 to 21 has associated therewith an insert module 30, cf. also Fig. 4. Such an insert module 30 comprises a plurality of annular contact elements 8 to 15. These contact elements are arranged side by side in an axial direction 16 in spaced relationship with one another. Each of the contact elements 8 to 15 has a respective ring opening 51 for passing therethrough the contact end portion 42 of the contact bar 41.

In the representation according to Fig. 2, the contact end portion 42 is arranged in the contact element 8, i.e. in the ring opening 51 thereof. The contact end portion 42 can be screwed onto a respective free end of the contact bar 41 , cf. also Fig. 3.

Each of the contact elements 8 to 15 is connected to an output contact element 22 to 29, the connection of the contact elements 8 to 15 with the respective output contact element being visible in Fig. 2.

The other output contact elements of the other contact elements 9 to 14 can be seen e.g. in Fig. 5 or in Fig. 1. These output contact elements are arranged such that they are spaced in the circumferential direction of the insert module 30. The respective output contact element of contact element 8 extends through openings 49 of the other contact elements 9 to 15, cf. in particular Fig. 2. Analogously, the output contact element of the most adjacent contact element 9 extends through the contact elements 10 to 15 arranged between said contact element 9 and a respective insert opening 38 of an insert bore 39 for the insert module 30. For this purpose, the respective contact elements 9 to 15 are provided with the openings 49 which may be open to the outside or closed in the radial direction. For the purpose of electric insulation, each of the respective output contact elements 22 to 29 is provided with a coating 50 on the outer surface thereof, said coating 50 consisting e.g. of polytetrafluoro- ethylene, i.e. said output contact elements have a coating with a high specific resistance value on the outer surface thereof. In this way, an electric contact between the respective output contact element and contact elements which do not belong thereto will be prevented.

Each of the output contact elements 22 to 29 is, at its end associated with the contact element belonging thereto, releasably connected to the latter.

More detailed explanations are provided in Fig. 3 on the basis of detail "X" of Fig. 2.

Quite generally, it should here be pointed out that respective identical components are provided with identical reference numerals, and that some of these identical components are described in more detail only in connection with one figure. In Fig. 3, a connection end 45 of the output contact element 26 is screwed into a screw-in bore 46 provided in the associated contact element 8. For this purpose, the connection end 45 is provided with a male thread and the screw-in bore 46 is provided with a female thread. For reliably fixing the connection end 45 in the screw-in bore 46, a counter-bearing element 48, in the form of a set screw or the like, is screwed in through an opening 47 of the screw- in bore 46 located opposite the connection end 45. This counter-bearing element 48 is screwed in up to a point where it abuts on the connection end 45.

Furthermore, it can be seen in Fig. 3 that the contact end portion 42 is screwed onto a free end of the respective feed contact element 17, i.e. on the contact bar 41 thereof. The contact end portion 42 has a diameter 53 which is larger than a complementary diameter 54 of the contact bar 41. In Fig. 3, the contact end portion 42 is substantially fully inserted into a ring opening 51 of the contact element 8. An electric contact is thus established between the feed contact element and the contact element, the further transmission of voltage or current taking place via the respective output contact element 26.

The ring opening 51 has arranged therein a contact spring element in the form of a lamellar contact spring element 52. The latter extends within the ring opening 51 at least partially along the circumferential direction. This contact spring element 52 establishes an electric contact between the contact end portion 42 and the associated contact element 8.

When the respective output contact element is axially displaced, it is displaced, cf. also Fig. 4, in the direction of the neighbouring contact elements 9 to 15, and, at its other extreme position according to Fig. 4, it is arranged in the last contact element 15 in the ring opening 51 thereof. Also this ring opening has arranged therein a respective contact spring element 52. For positioning the contact spring element 52, the ring openings 51 are provided with an inner area having a slightly enlarged diameter, which is delimited by edges having a smaller diameter at both ends of the ring opening 51. The respective contact lamellae of the spring element project into the ring opening 51 at least to such an extent that a reliable contact with the contact end portion 42 will be guaranteed when the latter is positioned in the associated ring opening. Fig. 4 shows a representation analogously to Fig. 2, the contact piston 31 occupying in this case its position of maximum retraction in the switch housing 2. This can be seen e.g. from the fact that, on the one hand, the threaded component 34 is arranged in the bearing bore 37 and that, on the other hand, the contact piston 31 abuts on the housing wall 36 from inside.

At this position, the contact end portion 42 is arranged in the contact element 15 which is arranged closest to the respective insert opening 38 of the associated insert module 30, cf. also Fig. 5.

The various insert modules 30, cf. Fig. 5, are fixed in position by a plurality of screw-in elements 57, said screw-in elements 57 being adapted to be screwed into the contact piston 31 in a substantially radial direction 56, cf. again Fig. 5. Some of the screw-in elements 57 radially engage the insert modules 30 from outside, others engage between two neighbouring insert modules.

For guiding the contact piston 31 in an axial direction 16 and for simultaneously preventing a rotational movement, the switch housing 2 is provided with a guide slot 58 extending in an axial direction 16. A guide element 59, which radially projects from the contact piston 31 , engages this guide slot 58.

Respective free ends of the output contact elements 22 to 29 can be connected to connection lines which then extend to the respective electric motors (not shown). One of the output contact elements of a respective contact element group is associated with a respective connection of an electric motor, so that, in the example shown, cf. also Fig. 5, a maximum of five output contact elements is provided for an electric motor. By a suitable displacement of the contact piston 31 , a respective contact element 8 to 15 is electrically contacted in each of the contact element groups 3 to 7, and an electric motor is supplied via the associated output contact element 22 to 29 of each contact element group. When the contact piston 31 is subsequently moved to a different position, five other output contact elements are brought into connection with the associated feed contact elements 7 to 21 , and a different electric motor is supplied via the associated output contact elements. It is also possible that, in each of the contact element groups or at least in the case of a few of them, specific contact elements are not connected directly to an electric motor, but to an additional multiple switching device, cf. e.g. the loop-through contact element 60 according to Fig. 2. When each of the contact element groups 3 to 7 comprises such a loop-through contact element 60, the multiple switching device 1 will be able to supply a further multiple switching device 1 having also five feed contact elements 17 to 21. In addition, it is also possible that a respective contact element of a contact element group is an insulating contact element 61 , which is used e.g. for the purpose of grounding. Furthermore, there is the possibility of transmitting data to subsequent units through a contact element of one or of a plurality of contact element groups.

It should here be pointed out once more that the number of insert modules 30, the number of contact elements provided in each insert module, and analogously the number of output contact elements can be varied, and that also insert modules 30 comprising different numbers of contact elements and output contact elements can be used for a multiple switching device 1 .

Fig. 5 shows a section along line V-V according to Fig. 4. Especially, the screw-in elements 57 used for fixing the insert modules 30 can be seen in said Fig. 5.

Each of the insert modules 30 is provided with eight output contact elements 22 to 29 and eight contact elements 8 to 15. Each of the contact elements is connected to a respective output contact element, cf. also Fig. 3.

The individual contact elements 8 to 15 of a contact element group 3 to 7 are electrically insulated from one another and arranged in spaced relationship with one another, especially in an axial direction 16, cf. Fig. 2 and 4. The contact piston 31 is provided with an insert bore 39 for each of the various insert modules, said insert bore extending in an axial direction 16. At the end of the insert bore 39 located opposite a respective insert opening 38, a spacer disk can be arranged, which is also annular in shape and which includes a ring opening for passing the respective contact bar 41 therethrough. In linear alignment with the various ring openings 51 , the contact piston 31 is provided with a respective through hole 40, cf. also Fig. 3, through which the contact bar 41 extends into the contact piston 31 . Also the various feed contact elements 17 to 21 can be provided with a suitable coating 50 on the outer surface thereof for insulating the elements with respect to the contact piston 31 as well as with respect to the switch housing 2.

In order to be able to precisely determine the position of the various feed contact elements 17 to 21 relative to the contact elements 8 to 15 of an associated contact element group 3 to 7, the feed contact element has assigned thereto a position sensor 55. This position sensor is shown, in principle, in Fig. 6.

It can be seen that a contact end portion 42 of a contact bar 41 is in contact with a contact spring element 52 in the ring opening 51 of a contact element 8. In order to be able to detect the position of the contact end portion 42 relative to the contact element 8, the contact element 8 as well as the contact end portion 42, i.e. the contact bar 41 , are arranged in a measuring circuit. This measuring circuit has power supplied thereto from a galvanically separated transmitter 64 e.g. in the form of an electromagnetic coupling of two coils. The information on a respective position is transmitted e.g. via an optical coupler 65 to a control electronics. This control electronics is only shown schematically in Fig. 6, cf. reference numeral 66. Normally, contacting and position recognition in the case of only one contact element of a respective contact element group will suffice. This contact element may e.g. be the first contact element or some other contact element of the contact element group in question.

In order to increase the position accuracy, various detected positions are averaged, cf. Fig. 7 in this respect.

To this end, the respective contact piston 31 is e.g. moved to a position at which a contact, cf. also Fig. 6, between the contact end portion 42 and the contact element 8 is closed in the measuring circuit. When the contact is closed, the contact piston 31 is moved on until the contact is open or separated, and this position is measured. Subsequently, the contact piston 31 is displaced until the contact is closed again. Also this position is stored.

The two detected positions are averaged, whereupon the difference between the average value and the centre of the first contact is calculated and this value is set as instantaneous position. Position detection is carried out in an analogous manner, if the contact is initially closed. Also in this case, the position in question is stored and the contact piston is then moved to a position at which the contact is open. After storage of this position, the two positions are again averaged and the difference between this average value and the centre of the first contact is calculated, the calculated value being then set as instantaneous position.

Figures 8 and 9 show representations analogue to figures 3 or 4 for a further embodiment of the multiple switching device according to the invention. For the particular description of figure 8, it is referred to the previous figures. Subsequently, only some deviations to the described embodiment are further explained.

According to figure 8, the contact piston 31 is detachably fastened on a mounting wall plate 69. This plate is arranged particularly stationery with respect to electrical means, which are actuated according to the multiple switching device. The entire mounting means according to figure 8 comprises plate 69 and a bottom plate essentially extending perpendicular to the plate.

According to figure 8, the contact bar 41 is connected with the feet contact element 17 by screwing, wherein a nut is arranged at a lower end of a corresponding L-web 44, in which the contact rod can be screwed in with one end.

At the opposite end, the contact rod 41 comprises its contact end section 42. This contact end section, see the embodiment according to figure 8, comprises a radially, elastically, and externally protruding contact spring section 68. Accordingly, the corresponding contact spring elements 52, see figure 3, in each of the different contact elements 8 to 15 are no longer necessary. The contact spring section may be realized by a leaf spring with raised lamellas. The contact spring section is fastened between two retaining sleeves on the contact end section 42 of the contact bar 41.

According to the present invention, the multiple switching device is used for supplying a plurality of electric motors of, for example, actuators by means of only one motor control. In the embodiment shown, eight electric motors having each five connections can be supplied, cf. the five feed contact elements 17 to 21 as well as the eight output contact elements 22 to 29 associated with each feed contact element. An output contact element of each contact element group is associated with a connection of an electric motor, and a total of five connections of said electric motor can be supplied by respective output contact elements of each contact element group. Three output connections may e.g. be connected to respective windings of the electric motor, whereas the two other output contact elements generate e.g. a holding torque of the electric motor or provide a DC emergency supply. Obviously, also other electrical devices with corresponding electrical terminals are switchable by the multiple switching device according to the invention.

Quite generally, it should here also be pointed out that the multiple switching device according to the present invention is able to transmit e.g. up to 400 amperes or even more than that per contact, i.e. per contact element, so that, making use of all the output contact elements, 8 x 5 x 400 amperes can be transmitted for controlling the electric motors in question.

The specified amperage per contact is, however, only an example; higher currents, e.g. 600 amperes or more per contact, are imaginable as well.

It goes without saying that it is also possible to make the multiple switching device smaller in the case of low amperages, or to reduce or increase the number of possible contacts, cf. the eight contact elements used for the insert module in the present embodiment and the arrangement of five insert modules. Also insert modules having different numbers of contact elements can be used in one and the same multiple switching device.