WO2003022025A1

WO2003022025A1 - Safety switchgear, especially for safely switching off industrial machinery

Info

Publication number: WO2003022025A1
Application number: PCT/EP2002/008607
Authority: WO
Inventors: Gerhard Ehrlich
Original assignee: Pilz Gmbh & Co.
Priority date: 2001-08-28
Filing date: 2002-08-02
Publication date: 2003-03-13
Also published as: DE10142737B4; DE10142737A1

Abstract

The invention relates to a safety switchgear, especially for safely switching off industrial machinery. The switchgear comprises a component support (12) on which at least one electronic component (14, 16, 18, 20) is disposed, and a metal screen that at least partially surrounds the electronic component (14, 16, 18, 20) to suppress interfering electromagnetic radiation. The screen comprises a ribbon cable (30, 32) with a plurality of parallel cores, said ribbon cable (30, 32) extending along at least one side of the electronic component (14, 16, 18, 20).

Description

Safety switchgear, especially for the safe shutdown of industrial machinery

The present invention relates to a safety switching device, in particular for safely switching off industrial machine systems.

Such safety switching devices are well known due to their use in industrial production environments. For example, such a safety switching device is described in DE 197 07 241 C2. The safety switching devices are primarily used to switch off industrial plants or industrial processes in a fail-safe manner depending on defined input signals. Input variables can be machine or process parameters. In addition, the input signals often come from protective grilles, covers, emergency stop switches, light barriers and the like. The essential task of the safety switching device is to evaluate the defined input signals and, depending on this, to shut down the machine or the process, which must be done with an extremely high degree of reliability. Otherwise, health and life, for example of operators, are at risk. The safety switching devices are therefore made intrinsically fail-safe with complex measures, and they require approval from the responsible supervisory authorities, such as the professional associations in Germany, before they are commissioned. These test the device's intrinsic failure safety based on relevant standards, such as the European standard EN 954-1. Safety switching devices in the sense of the present invention are therefore only devices which at least meet category 3 of the standard mentioned or a comparable safety standard. Within this group, however, the invention is not restricted to individual devices, so that, for example, fail-safe speed monitors or complex fail-safe controls are also covered by the term "safety switching device" chosen here.

Due to the required intrinsic failure safety, safety relays are still built to a large extent using "conventional" technology, especially using relays. Electronic components and in particular highly integrated electronic circuits (ICs) have only been used increasingly in the recent past. Compared to these "modern" components, the classic discrete components and in particular relays are very robust, especially against external, unknown electromagnetic interference radiation. Due to the desirable use of highly integrated circuit conditions on the one hand and the increasing number of interference sources, such as mobile radio devices, on the other hand, however, the sensitivity of the safety switching devices to interference radiation is increasing. The so-called electromagnetic compatibility (EMC) decreases. The consequence of this is that safety switching devices will have to be shielded from electromagnetic interference radiation in the future, not least to prevent undefined sources of error with regard to the functional safety of the devices. Methods for shielding electronic devices are known per se.

An effective method is to surround the entire device or at least the sensitive circuit components with metal housings. This creates a Faraday shear or a galvanic cage, which keeps external electromagnetic interference from the components arranged inside. Conversely, such a metal housing can also serve to shield radiating components to such an extent that the radiation cannot penetrate "outwards" unhindered.

One possibility is to manufacture the entire device housing of the safety switching devices from metal, but this is expensive. Cheap plastic housings unfortunately do not have a shielding effect. In addition, it is known to surround sensitive circuit components with separate metallic housings within the device housing. Depending on the frequencies to be shielded, metallic gratings can also be used instead of solid housings. Another option for shielding electronic components is to provide the walls of plastic housings with conductive lacquers. However, all known measures mean a considerable additional Effort that was so far not or only very rarely necessary with "conventional" technology. The additional effort is, of course, also reflected in the production costs, which partially nullifies the advantages that are inherent in the use of highly integrated circuits.

Against this background, it is an object of the present invention to provide a safety switching device of the type mentioned at the outset which, with little additional production outlay, has an effective shielding of the sensitive components against electromagnetic interference radiation. The effectiveness of the shielding must primarily depend on the safety requirements, i.e. measured against the requirements with regard to intrinsic failure safety.

This object is achieved by a safety switching device, with a component carrier on which at least one electronic component is arranged, and with a metallic shield which at least partially surrounds the electronic component for suppressing electromagnetic interference radiation, the shielding comprising a ribbon cable with a large number of includes parallel wires, and wherein the ribbon cable runs on at least one side of the electronic component.

The object is also achieved in very general terms in that at least one ribbon cable is used in a safety switching device to shield electronic components from electromagnetic interference radiation. Ribbon cables, sometimes also referred to as ribbon cables, are sufficiently known in the prior art as means for connecting electrical assemblies. For example, ribbon cables are widely used for the electrical connection of the individual assemblies within personal computer systems (PCs). The ribbon cables consist of a large number of wires that are insulated from each other and arranged parallel to each other, resulting in a wide, flat conductor bundle. Such ribbon cables are sold by numerous manufacturers and in various specific forms. Commercially available ribbon cables are, for example, the flat cable system 720, which is sold by Eberhard Köpf GmbH in 63920 Großheubach, Germany. Another well-known manufacturer is Amphenol, which sells commercially available cables under the type designations UL-Style 2651 or UL-Style 2697.

The basis of the present invention is the surprising finding that such commercially available ribbon cables can ensure adequate shielding of the electronic components of modern safety switching devices. This applies at least to ribbon cables of the aforementioned types and more generally to ribbon cables that have at least a grid dimension of up to 7 mm. Since the above-mentioned commercially available ribbon cables are mass-produced and can be obtained very inexpensively, an inexpensive, shielded safety switching device can be realized on the basis of the surprising finding by using the cables.

The use of ribbon cables for shielding electronic components in safety switching devices a number of advantages. On the one hand, ribbon cables are readily available as mass products and are extremely inexpensive. In addition, they can be shaped without difficulty, so that the shielding can be very easily adapted to the existing needs and the available space. As a result, subsequent screening at individual points in a larger circuit is also easily possible. In addition, ribbon cables are easy to assemble and can therefore be easily integrated into the production process even in large quantities. Last but not least, flat cables can be used to achieve very light shielding, whereas, for example, the use of known shielding plates noticeably increases the weight of the safety switching devices.

Overall, it has been shown that the use of ribbon cables for shielding the electronic components can significantly increase the functional reliability of safety switching devices without significantly increasing the production costs.

In one embodiment of the invention, the wires of the ribbon cable are electrically connected to a constant potential. This measure differs significantly from the usual use of ribbon cables, via which signals with changing potential are usually transmitted. Because the wires, preferably all the wires of the ribbon cable, are connected to a constant potential, the effectiveness of the shielding is improved. In a further embodiment, the constant potential is a ground potential.

This measure further improves the effectiveness of the shielding, since all incoming signals are "short-circuited" via the ribbon cable. Interference signals are thus derived against ground.

In a further embodiment, a first end of the wires is attached to the component carrier. The first end can be clamped or plugged in using plugs known per se. Such connections have the advantage that the ribbon cable can be easily released again. In addition, at least for some applications, it is preferred if the first end of the wires is soldered to the component carrier. This is because it is extremely cost-effective. Regardless of the type of attachment, the measure has the advantage that the ribbon cable is fixed in relation to the electronic components to be protected. This increases the robustness of the shielding and thereby the functional reliability of the safety switching device.

In a further embodiment, a second end of the wires is loose. This measure is particularly advantageous in combination with the measure mentioned above, since it fixes the shielding ribbon cable on the one hand, while the components to be protected remain easily accessible on the other hand. In the case of a repair measure, the loose second end can simply be folded aside so that the shielded components are accessible. Beyond that too perform any calibration work in the manufacture of the safety device very easily and therefore inexpensively.

In a further embodiment, the second end is completely isolated.

In principle, it is also possible to simply cut the ribbon cable used to length at the second end, so that the individual wires at the end of the ribbon cable are open. Depending on the arrangement of the ribbon cable within the safety switching device, there may be a risk of unwanted contacts, short circuits and the like. Such risks are eliminated by completely insulating the wires at the second end of the ribbon cable.

In a further embodiment, the safety switching device has a device housing with a housing wall, the housing wall holding the second end in a desired position.

This measure is particularly advantageous with regard to minimizing production costs, since the ribbon cable used for shielding is brought into the desired position when the component carrier is mounted in the device housing. Additional fixings or special assembly steps can therefore be reduced or even completely eliminated. The measure thus enables particularly cost-effective production.

In a further embodiment, the component carrier has a first and an opposite second side, the electronic component being arranged on the first side and wherein the second side has a flat metallization.

In this embodiment, the flat metallization, which can be, for example, a copper cladding of the component carrier known per se, contributes to the shielding of the electronic component. The measure enables a further reduction in production costs, since the corresponding side of the electronic component no longer has to be shielded in any other way.

In a further embodiment, the ribbon cable surrounds the electronic component on the first side of the component carrier.

This measure ties in with the previously mentioned design. Overall, this results in a very simple “housing” of the electronic component with shielding components, which is favorable in terms of production technology.

In a further embodiment, the wires of the ribbon cable are electrically conductively connected to the flat metallization.

This measure further increases the effectiveness of the shielding, since the wires of the ribbon cable form a closed Faraday 'cage together with the flat metallization.

In a further embodiment, the ribbon cable surrounds the component carrier from at least two sides. The ribbon cable preferably surrounds the component carrier at least on the first and second sides in the sense of the configurations described above. Figuratively speaking, the measure leads to the component carrier and with it the component to be shielded being "wrapped" by the ribbon cable. As a result of this measure, the previously described flat metallization can be dispensed with, which enables the production process to be optimized with regard to the production costs. In addition, the measure is particularly suitable for retrofitting effective and inexpensive shielding in a very simple manner even with existing safety switching devices.

In a further embodiment, the shield further includes at least one metallic wall, in the area of which the ribbon cable runs.

A metallic wall in this sense can be a sheet metal or a grid, which is used in a manner known per se for shielding the electronic component. This also includes a housing wall provided with conductive lacquer. In contrast to previous measures, however, single walls, possibly a single wall, are sufficient. It is therefore no longer necessary to install a complete metal housing. On the other hand, by using one or fewer metallic walls, the shielding can be optimized without giving up the basic advantages that result from the use of ribbon cables. Basically, the ribbon cable does not require an electrically conductive contact with the metallic wall, at least for simpler shields, although such a contact is advantageous for a particularly effective shielding. In a further embodiment, the shield contains at least two ribbon cables, which partially overlap.

This measure allows a "closure" of the shield to be created in a simple and therefore cost-effective manner without preventing access to the components to be protected. The overlapping cables can simply be folded aside for repair or calibration purposes. On the other hand, very effective shielding is achieved by the overlap.

In a further embodiment, the wires of the ribbon cable are cut to different lengths.

This measure enables a very flexible and individual adaptation of the shielding to the existing conditions. In addition, it is also possible in a simple manner to shield different areas of the component carrier in a targeted manner with only one ribbon cable. The variety of parts and consequently the production costs can be further reduced.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention.

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description. Show it: 1 shows a first embodiment of a safety switching device according to the invention in a cross-sectional view,

2 is a plan view of a ribbon cable used in the safety switching device according to FIG. 1,

Fig. 3 shows a second embodiment of a safety switching device according to the invention, and

FIG. 4 shows a flat cable from the safety switching device according to FIG. 3 in a top view.

In FIG. 1, a safety switching device according to the invention is designated in its entirety by reference number 10.

The safety switching device 10 contains a component carrier 12 on which a number of components are arranged in a manner known per se. A transistor 14, a resistor 16, an integrated circuit (IC) 18 and a capacitor 20 are shown here as examples. The transistor 14, the resistor 16 and the capacitor 20 are contacted in a manner known per se via bores 22 to the rear side 24 of the component carrier 12 and soldered there with soldering points 26. The IC 18 is contacted in known SMD technology on the front 28 of the component carrier 12.

The reference numbers 30 and 32 denote two ribbon cables, which correspond to the surprising finding Shielding of the components 14 to 20 can be used, in particular for shielding the IC 18.

The ribbon cables 30, 32, one of which is shown again in FIG. 2, have a first end 34 and a second end 36. These are commercially available ribbon cables with a multiplicity of cores 38 arranged parallel to one another and insulated from one another. The pitch of the The ribbon cable 30, 32 used here is 2.54 mm, but larger grid dimensions can also be used. Smaller grid dimensions increase the height of the shielding, so that there are no limits in this regard.

The first end 34 of the ribbon cable 30, 32 is stripped so that the wires 38 emerge from the cable jacket there. The second end 36 is provided with a separate insulation 40.

For use in the safety switching device 10, the two ribbon cables 30, 32 as well as the components 14, 16 and 20 are contacted through holes 22 on the rear side 24 of the component carrier. There they are soldered to a flat metallization 42 applied to the back 24. The metallization 42 has ground potential. Consequently, the individual cores of the ribbon cables 30, 32 are also at a constant ground potential.

The loose second ends 36 of the ribbon cables 30, 32 are folded from the right or from the left over the components 14 to 20 to be shielded and overlap in the central region of the component carrier 12. This creates an effective shielding at least with regard to electromagnetic interference radiation, which can impair the functionality of safety switching devices. On the other hand, it is very easy to repair the components 14 to 20 for repair purposes by folding the loose ends 36 of the two ribbon cables 30, 32 aside.

The safety switching device 10 is installed in a device housing 44 in a manner known per se. Here, the device housing 44 consists of two housing halves which are put together during assembly in the direction of arrow 45 and locked via a locking mechanism. A particularly inexpensive assembly of the shielding results for the present exemplary embodiment, since the housing dimensions are dimensioned such that the loose second ends 36 of the two ribbon cables 30, 32 are brought from a housing wall 46 of the housing 44 into the desired overlapping position and are held there ,

A further exemplary embodiment of a safety switching device according to the invention is designated in its entirety by reference number 60 in FIG. 3. Otherwise, the same reference numerals designate the same elements as before.

The safety switching device 60 differs from the safety switching device 10 primarily in the manner in which the ribbon cable, which is designated here by the reference number 62, is used for shielding. In the present case, the ribbon cable 62 surrounds the component carrier 12 both on the front and on the back. As a result, the components 14 to 20 to be shielded are surrounded on two sides, so that the flat metallization 42 of the component carrier 12 can be omitted. The wires 38 of the ribbon cable 62 are, as before, at a constant shield potential.

The ribbon cable 62, which is shown again in a more detailed illustration in FIG. 4, is provided at its second end 64 in a manner known per se with a commercially available ribbon cable plug 66. With this plug 66, the ribbon cable 62 is detachably attached to the underside of the component carrier 12. The counterpart of the plug 66 is soldered to the component carrier 12 in a manner known per se.

In contrast to the previous exemplary embodiment, the ribbon cable 62 is cut to different lengths at its first end 68. The wires 38 are stripped at the respective ends as before. The different positions of the first ends 68 enable the ribbon cable 62 to be fastened very flexibly to the component carrier 12, as is shown by way of example in FIG. 3. The ends of the ribbon cable 62 of different lengths are soldered to the front of the component carrier 12 at different locations. Overall, areas that are shielded in different ways can be produced in this way. These can also be used to shield the individual components 14 to 20 from one another.

Another difference between the exemplary embodiment in FIG. 3 and the previously illustrated exemplary embodiment is the additional use of a metallic wall 70, which is arranged laterally of the IC 18 and perpendicular to the component carrier 12. The upper free end of the metallic wall 70 ends in the area of the ribbon cable 62, and the two form together see a Faraday 'cage for the IC 18. A second wall (not shown here) is arranged in mirror image to the wall 70 on the other side of the IC 18.

The use of ribbon cables enables a very simple, inexpensive and yet effective shielding of electronic components in safety switching devices. The two exemplary embodiments shown are actually to be understood as examples. The special features shown separately here can also be combined with each other in order to achieve optimal shielding. Depending on the application, both "rigid" ribbon cables (with solid individual wires) or flexible ribbon cables (individual conductors made of stranded wire) can be used. The use of flexible ribbon cables is particularly advantageous for the arrangement according to FIG. 3, since these can be deformed more easily. On the other hand, ribbon cables with solid individual wires are easier to solder.

Claims

claims

1. Safety switching device, in particular for the safe shutdown of industrial machine systems, with a component carrier (12) on which at least one electronic component (14, 16, 18, 20) is arranged, and with a metallic shield that protects the electronic component (14, 16, 18, 20) for suppressing electromagnetic interference radiation at least partially, wherein the shield includes a ribbon cable (30, 32; 62) with a plurality of parallel cores (38), and wherein the ribbon cable (30, 32; 62) on at least one side of the electronic component (14, 16, 18, 20) runs.

2. Safety switching device according to claim 1, characterized in that the wires (38) of the ribbon cable (30, 32; 62) are electrically connected to a constant potential (42).

3. Safety switching device according to claim 2, characterized in that the constant potential (42) is a ground potential.

4. Safety switching device according to one of claims 1 to 3, characterized in that a first end (34; 68) of the wires (38) is fastened to the component carrier (12).

5. Safety switching device according to one of claims 1 to 4, characterized in that a second end (36) of the wires (38) is loose.

6. Safety switching device according to claim 5, characterized in that the second end (36) is completely isolated.

7. Safety switching device according to claim 5 or 6, characterized in that it has a device housing (44) with a housing wall (46), the housing wall (46) holding the second end (36) in a desired position.

8. Safety switching device according to one of claims 1 to 7, characterized in that the component carrier (12) has a first (28) and an opposite second side (24), the electronic component (14, 16, 18, 20) on the first side (28) is arranged and wherein the second side (24) has a flat metallization (42).

9. Safety switching device according to claim 8, characterized in that the ribbon cable (30, 32; 62) surrounds the electronic component (14, 16, 18, 20) on the first side (28) of the component carrier (12).

10. Safety switching device according to claim 8 or 9, characterized in that the wires (38) of the ribbon cable (30, 32) with the flat metallization (42) are electrically conductively connected.

11. Safety switching device according to one of claims 1 to 10, characterized in that the ribbon cable (62) surrounds the component carrier (12) from at least two sides.

12. Safety switching device according to one of claims 1 to 11, characterized in that the shield further includes at least one metallic wall (70), in the area of which the ribbon cable (62) runs.

13. Safety switching device according to one of claims 1 to 12, characterized in that the shield includes at least two ribbon cables (30, 32) which partially overlap.

14. Safety switching device according to one of claims 1 to 13, characterized in that the wires (38) of the ribbon cable (62) are cut to length differently.

15. Use of a ribbon cable (30, 32; 62) for shielding electronic components (14, 16, 18, 20) against electromagnetic interference radiation in a safety switching device (10; 60), in particular a safety switching device for safely switching off industrial machine systems.