KR20020031308A - A protection device for protecting a pcb electrical connector from electromagnetic interference - Google Patents

Abstract

PURPOSE: A protection device is provided to protect an electrical connector including a main body made of a plastic material having a front surface cooperating with the removable plug, from electromagnetic interference. CONSTITUTION: A connector(3) includes a main body made of a plastic material having a connection surface contacting a PCB(2) and a front surface cooperating with the removable plug; and a plurality of contacts(31) each of which have an end shaped as a spike protruded from the connection surface of the main body of the connector. The spike is accommodated into a through hole formed at the PCB so as to electrically connect contacts to conductor tracks of the PCB. A protection device comprises a first shield element extended toward a side surface of the connector opposed to the connection surface and toward a rear surface of the connector, in such a manner that the first shield element contacts the conductor track of the PCB; and a second shield element mounted at the PCB opposed to the plane contacting the connector and extended toward the connection surface. The second shield element forms a potential cage by contacting the conductor track connected to the ground track of the PCB and by being electrically connected to the first shield element.

Description

Protection device to protect the PC electrical connector from electromagnetic interference {A PROTECTION DEVICE FOR PROTECTING A PCB ELECTRICAL CONNECTOR FROM ELECTROMAGNETIC INTERFERENCE}

The present invention relates to a protective device for protecting a PCB electrical connector from electromagnetic interference comprising a body portion made of a plastic material having a front side and a connecting side in contact with a printed circuit board which functions to cooperate with a removable plug.

In particular, the device of the present invention is generally used for interconnecting control or power supply cables and printed circuits, for example electronic cards carried by mounted shelf modules, which are the driving force units of rail vehicles. Known types of connectors, such as standard F48 or E48 type connectors, can be used to protect against electromagnetic interference.

Particularly in the prior art, in accordance with the standard DIN 41612 / IEC 603-2 or using DIN F48 or E48 type connectors, electrons from electromagnetic radiation using removable plugs shielded by conductive cladding of the "Zamak" type It is known that it is possible to protect the card. Unfortunately, this method has the disadvantage that the plug overall size increases significantly. This requires a reduction in the number of possible contacts in the plug for the card at the same pitch. In addition, such shielding plugs are more expensive to manufacture than conventional plugs made of plastic, increasing the additional limitations in particular in terms of vibrational response. Another drawback of shielded plugs is that sometimes the magnetic protection disappears when the plug is removed, especially if the plug needs to be plugged for testing or maintaining any electronic card. This method increases device costs by permanently connecting shielded plugs to ensure that the electronic card is magnetically protected.

Accordingly, it is an object of the present invention to ameliorate the various disadvantages of the prior art described above.

Accordingly, the present invention relates to a protective device for protecting an electrical connector from electromagnetic interference comprising a body made of a plastic material having a front face which functions to cooperate with a removable plug.

The connector includes a body portion made of plastic material having a connecting side contacting the printed circuit board and a front surface functioning to cooperate with the removable plug, and a plurality of contacts each having one end in the form of spikes protruding from the connecting side. Spikes are inserted into the through-holes in the substrate to electrically connect the contacts to one or more conductor tracks of the printed circuit, and extend toward the side of the connector opposite the connection side and subsequently to the rear side of the connector for printing. A first shielding element in contact with the ground conductor track of the circuit board, and a second shielding element mounted on a side of the printed circuit board opposite the side in contact with the connector and extending toward the connecting side, the second shielding element The element contacts the conductor track connected to the ground track of the printed circuit to transfer it to the first shielding element. It is ever connected to form a potential cage.

The first shielding element comprises a metal element that is generally continuous and extends to an adjacent portion of the printed circuit board toward the rear face of the connector, the spike of which the edge of the metal element adjacent the printed circuit board is inserted into the plated through hole in the printed circuit board. The hole is in contact with the ground track of the printed circuit.

In certain embodiments, the protective device of the present invention may include one or more of the following properties taken upon isolation or any technically possible combination.

The first shielding element consists of a metal angle bracket having a branch extending opposite the side of the connector opposite the connecting surface and a branch extending toward the rear surface of the connector.

The connector includes a plurality of top rows of contacts having a rearmost portion extending away from the printed circuit board such that spike-shaped contact ends penetrate into the plated through holes in the substrate and extending perpendicularly to the printed circuit board at the rear surface of the connector. A row of contacts, wherein the top row of contacts connects the spikes of the top row of contacts to the ground conductor tracks to form a first shielding element.

The first shielding element is formed by a metal sheet that cooperates with the upper row of contacts,

The metal sheet extends toward the side of the connector opposite the connecting surface and has a curved end in contact with the upper row of contacts.

The second shielding element is constituted by a metal sheet connected to the ground track which is in contact with the track disposed on the surface of the substrate and to which the spike of the first shielding element is connected.

The printed circuit board is designed to install a shelf module with a plurality of electronic cards arranged side by side, the metal sheet being a face element to form electrical contacts and shielding elements of the connector carried by adjacent electronic cards held in the shelf module. It has an elastic tongue which protrudes laterally from the side.

The face element is mounted on the connector and has fixing means for mounting the printed circuit on the shelf module.

The face element supports the metal element of the first shield element.

The connector complies with DIN standard F48.

The face element includes an electrical conductor body that surrounds all four sides of the connector, and includes an upper wall adjacent the side wall of the connector opposite the connecting surface and a lower wall adjacent the printed circuit board, wherein the walls include first and Each second shielding element is formed.

The first shielding element is formed by a top wall and by a metal angle bracket mounted against the top wall, each bracket extending toward the rear face of the connector so that electrical continuity is present between each bracket and the top wall. It has a branch fixed to it.

The first shielding element is formed by a top sheet and by a metal sheet mounted against the top wall and cooperating with the top row of contacts, the metal sheet having a curved end in contact with the top row of contacts.

The second shielding element is formed by a bottom wall disposed on the surface of the printed circuit board and in contact with the conductor track connected to the ground track to which the spike of the first shielding element is connected.

The printed circuit board is designed to install a shelf module with a plurality of electronic cards arranged side by side, the face element such that the bottom wall forms an electrical contact with the shield element of the connector carried by an adjacent electronic card held in the shelf module. It has an elastic tongue which protrudes laterally from the side.

The face element 4 is a "zamark" casting and the connector conforms to DIN standard E48 type.

The objects, features and advantages of the present invention will be better understood from the other embodiments of the present invention, given with reference to the accompanying drawings and with the description of the following embodiments and non-limiting examples.

1 is a perspective view of the front side of a shelf module for supporting a plurality of electronic cards, each comprising a printed circuit board with a DIN F 48 type connector equipped with a first embodiment of the protective equipment of the present invention;

FIG. 2 is a detailed perspective view of a three quarter rear view of the connector of the printed circuit board of FIG. 1; FIG.

3 is symmetric to FIG. 2 with respect to the plane of the printed circuit board.

4 is a side detail view of two electronic cards shown in FIG. 1 mounted adjacently.

5 is a rear perspective view of another embodiment of the protective equipment of FIG.

FIG. 6 is a view similar to FIG. 4, showing another embodiment of FIG.

Figure 7 is a perspective view of a shelf module for supporting a plurality of electronic cards each including a printed circuit board with a DIN E 48 type connector equipped with another embodiment of the protective equipment of the present invention.

FIG. 8 is a detailed perspective view of a three quarter rear view of the connector of the printed circuit board of FIG.

9 is symmetrical to FIG. 8 with respect to the plane of the printed circuit board.

FIG. 10 is a side detail view of the two electronic cards shown in FIG. 7 mounted adjacently. FIG.

Figure 11 is a rear perspective view of another embodiment of the protective equipment of Figure 8;

FIG. 12 is a view similar to FIG. 10, showing another embodiment of FIG.

<Explanation of symbols for the main parts of the drawings>

1: electronic card

2: Connector

4: face element

6: first shielding element

7: second shielding element

8: metal sheet

9: tongue

10: shelf module

11: fixing screw

12: metal element

31: contact

1 shows a shelf module 10 of the type described in Applicant's French application No. 99 10 097, which supports a plurality of electronic cards 1 installed in a railroad vehicle. The shelf module 10 includes a frame 20 provided with a metal wall to which a guide rail 21 is fixed. The guide rail makes it possible to insert the electronic card 1 via the front face of the frame 20. Each electronic card 1 comprises a printed circuit board 2 having a connector 2 and a face element 4 surrounding the connector 3 so that the front edge blocks the front face of the frame 20. . The printed circuit board 2 supports electronic components (not shown) and their rear ends support a second connector (not shown) which is automatically connected to the link cable at the end of the insertion stroke. The electronic card is inserted into the guide rail 21.

As shown in FIG. 1, the face element 4 has a set screw 41 which holds the electronic card 1 fixed in the frame 20. The face element 4 also has a front face provided with a stud 42 used in cooperation with the guide orifice in the plug to guide the plug (not shown) when inserted into the connector. The face element 4 is preferably a “zamark” casting to be an electrical conductor. Conductivity may be improved by surface treatment including nickel precipitation. In addition, in other embodiments suitable for environments that are not very rigorous, the face element 4 is made of cast plastic material and nickel plated metal.

As shown in Figs. 1 to 4, the connector 3 comprises a body part made of plastic material according to the DIN 41612 / IEC 603-2 standard of F48, and three mutually parallel rows of sixteen connecting pins 31. It has a front surface with. The pins 31 are fitted in the body mold of the connector, each of the pins having a rear portion with a bend inside the body mold, and the ends of the pins 31 protruding from the connecting side 3c of the connector 3. ). The connecting side 3c has a single layer for receiving the printed circuit board 2 on the connector 3 without increasing the overall width of the connector.

The connector 3 is held via the connector surface 3c to the printed circuit board 2 such that the spike 31a penetrates the plated through hole in the printed circuit and slightly protrudes from the other side of the printed circuit. The spike 31a is soldered on the printed circuit to form an electrical contact between the conductor track (not shown) and the pins 31.

The face element 4 has a channel section body that surrounds three sides of the connector 3 which are not supported against the printed circuit board 2. The front face of the face element 4 is mounted slightly flat from the front edge of the connector 3.

The central portion 4a of the body portion of the face element 4 is parallel to the printed circuit board 2 and faces, on the outer side, adjacent to the side face 3a of the connector opposite the connector side face 3c, one branch being A first shield consisting of a metal angle bracket 6a extending parallel to the printed circuit board and the other branch 6b extending along the rear face 3b of the connector 3 perpendicular to the printed circuit board 2. Support element 6. A branch 6a parallel to the printed circuit extends from the front edge of the face element 4 to the rear edge of the connector 3, so that the electrical continuity is maintained between the bracket 6 and the face element 4. Is in direct contact with (4). Branches 6b extending along rear face 3b of connector 3 are continuous, and the edges of branch 6b adjacent to substrate 2 are plated through in a printed circuit board connected to the ground conductor tracks. It has a spike 61 inserted through the hole. As shown in Fig. 4, the branching portion 6a parallel to the printed circuit is generally continuous and is conveniently formed by cutting and folding to form a contact with the shielding element of an adjacent card disposed in the shelf module 10. And an elastic tongue 9 projecting from one side of the face element 4.

As shown in Figs. 3 and 4, the surface of the printed circuit board opposite the surface in contact with the connector 3 is composed of a second shielding element 7 consisting of a metal sheet extending facing the connecting side 3c of the connector. Covered with) The metal sheet 7 is in contact with the conductor track (not shown) which abuts the surface of the integrated circuit board at this point and connects to the ground conductor track to which the spike 61 of the first shielding sheet 6 is connected. To provide electrical continuity between the first shielding element 6 and the second shielding element 7.

The metal sheet 7 forming the second shielding element projects the spike 31a of the pin 31 so as to cover the front part of the connecting side 3c of the connector 3 up to the front face of the face element 4. It has a fitted shape extending along the area and has a stepped portion that matches the tomographic portion formed by the junction where the front edge of the substrate 2 meets the connector 3.

The shielded metal sheet 7 is printed circuit board by two fastening screws 11 which are screwed to the face element 4 and which are in contact with the connector 3 and the printed circuit board 2 and the metal sheet 7. It remains in contact with (2).

The resulting protective equipment forms a potential cage surrounding the rear, connecting and opposing surfaces of the connector to protect electronic components carried by the printed circuit board from electromagnetic interference through the front surface of the connector. In addition, because the face elements surrounding the front face of the connector are made of conductive material and electrically connected to the shielding elements of the connector, a set of electronic cards positioned to touch each other can enter through the front face of the shelf module. A potential blocking that limits the amount of interference is formed to protect all electromagnetic components carried by the electronic card.

5 and 6 show another embodiment of a protection device for protecting the electronic connector described with reference to FIGS. In this other embodiment, the ground conductor track of the printed board and the first shielding element are implemented differently while the other elements remain the same as described above. As shown in Fig. 5, the central portion 4a of the channel-section body of the face element (same as the face element of Figs. 1-4) is generally continuous and has a side face of the connector 3 opposite the contact side 3c. The shielding metal sheet 8 which extends facing 3a is supported. The metal sheet 8 is in contact with the curved end in conformity with the shape of the rear end of the face element 4 and the upper row of pins 31 of the connector 3, ie the furthest from the printed circuit board 2. It is provided with the tab 8a which enters a part. The upper row of pins 31 of the connector extends from the front face of the connector 3 to the adjacent portion of the rear face of the connector 3 in parallel with the board 2, and then forms the spikes 31a. The end of the extends perpendicularly to the printed circuit board 2 at the rear face of the connector 3 so as to penetrate through the plated through hole in the substrate 2 and contact the ground conductor track of the printed circuit.

The shielding metal sheet 8 has an elastic tongue 9 protruding from one side of the face element 4 to form a contact with the shielding element of an adjacent card disposed in the shelf module, as shown in FIG. 6.

The printed circuit board is shown in FIGS. 1 to 4 and has the same second shielding element 7 as the element disposed in contact with the conductor track connected to the ground conductor track to which the end spike 31a in the upper row of fins 31 is connected. ).

In this other embodiment, the top row of pins is used to implement the first shielding element in accordance with the metal sheet supported by the top of the face element. The shield at the rear of the connector is then implemented by a mesh formed by a series of pins extending perpendicular to the printed circuit board and connected to the ground circuit. This alternative embodiment is possible when the top row of pins is made useful for shielding, i.e., the number of pins needed to transfer information through the connector is less than the number of pins on the connector. This variant provides a simple advantage implemented by a very small number of holes and conductor tracks on the printed circuit board. The greater the number of pins used for shielding and the more densely arranged the pins together, the higher the performance at high protection frequencies from electromagnetic interference produced by this variant embodiment. Of course, in another variant embodiment (not shown) of the protection device of the present invention, it is possible to use a smaller number of pins for shielding to have more efficient pins for information transmission.

7 to 10 show a second embodiment of the protective device of the present invention. The connector 3 used on the front side of the electronic card 1 conforms to the standard DIN E 48.

Similar to the connector of the first embodiment described above, the DIN E 48 standard connector 3 is made of plastic material and has a body portion having a front face with three mutually parallel rows of sixteen pins 31. Only the spacing between the pins 31 is wider than the spacing between the DIN F 48 standard connectors.

The connector 3 contacts the printed circuit board 2 via the connecting side 3c. The end spike 31a of the pin 31 penetrates through a plated through hole (not shown) to provide electrical contact between the pin 31a and the conductor track (not shown) on the printed circuit board 2. To be soldered.

A face element 4 having a generally rectangular body part is mounted around the electronic card 1 constituted by the connector 3 and the printed circuit board 2. The body part of the face element 4 has a fitted opening that makes it possible to insert the face element 4 into a position above the assembly comprising the connector 3 and the substrate 2. As a result, the front face of the face element 4 becomes flat with the front edge of the connector. The face element 4 is made by casting an electrical conductor material, such as “zamark,” and functions to cooperate with the guide orifice in a plug (not shown) which guides the plug when inserted into the connector 3. It has a front face with two studs 42. In addition, the front face of the face element 4 is provided with two fixing screws 41 for holding the electronic card 1 fixedly on the frame 20, and aligned with the printed circuit board 2 in a square direction. A protruding guide edge strip 43.

The body portion of the face element 4 has a top wall 4a adjacent to the side 3a of the connector 3, and is a metal angle bracket 12 mounted against the top wall 4a constituting the first shielding element. It extends parallel to the printed circuit board 2 which cooperates with. Each bracket 12 is a rear of the face element 4 while maintaining electrical contact with the bottom face of the top wall 4a by two screws such that electrical continuity exists between each bracket 12 and the face element 4. It has a continuous branch 12a extending parallel to the printed circuit board 2 over the portion. In addition, each bracket 12 extends along the rear surface 3b of the connector 3 and includes a continuous branch 12b extending vertically adjacent to the printed circuit board 2, the substrate 2. It has an edge adjacent to the printed circuit board 2 with the spike 12c inserted through the plated through hole in the) and connected to the ground conductor track.

As shown in FIGS. 9-10, the body portion of the face element 4 extends facing the connecting side 3c of the connector 3 to contact the printed circuit board 2 and constitute a second shielding element. Bottom wall 4b. The lower wall 4b adjacent to the printed circuit board 2 extends along the area where the spike 31a of the pin 31 protrudes, touches the surface of the printed circuit board 2, and the spike of the shielding sheet 12 It has a fitted back shape that contacts the conductor track (not shown) connected to the connected ground conductor track and covers the front portion of the printed circuit board 2.

The printed circuit board 2 is kept in contact with the lower wall 4b by two fixing screws 11 screwed to the connector 3 via the printed circuit board 2. The outer side of the bottom wall 4b is a metal strip provided with an elastic tongue 9 protruding laterally from the side of the face element 4 to form a contact with the shield element of the adjacent card, as shown in FIG. 10. It has a groove to accommodate.

Such an embodiment having an assembly formed by a face element assembled to an electronic card that takes a limited amount of space to the side provides a good protection against electronic components carried by the printed circuit board from electromagnetic interference passing through the front face of the connector. Enable provision.

11 to 12 show a variant of the second embodiment of the protective device described with reference to FIGS. 7 to 10. The ground conductor tracks of the first shield element and the printed circuit are implemented differently. The other elements remain the same as those described with reference to Figures 7-10. As shown in Fig. 11, the body portion of the face element 4 (same as the element described in the second embodiment) is a continuous metal sheet 13 mounted against the top wall 4a constituting the first shielding element. ) And an upper wall 4a cooperating. The metal sheet 13 extends parallel to the printed circuit board over the rear part of the face element 4 and at the junction to the top row of pins 31 of the connector 3, ie the furthest from the printed circuit board 2. It has a curved end with an entry tab 13a. The upper row of pins 31 extends from the front face of the connector 3 to the adjacent portion of the back face of the connector 3 parallel to the board and then perpendicular to the printed circuit board 2 at the back face of the connector 3. Is extended. As a result, an end portion of the pin 31 forming the spike 31a penetrates the plated through hole in the printed circuit board 2 and contacts the ground conductor track of the printed circuit.

The metal sheet 13 is held in contact with the lower surface of the upper wall 4a by two screws such that electrical continuity exists between the metal sheet 13 and the face element 4 made of an electrically conductive material.

The second shielding element 4b of this variant embodiment is exactly the same as described with reference to FIGS. 7 to 10 and is in contact with the conductor track of the printed circuit board 2 connected to the ground conductor track of the circuit. End spikes 31a in the upper row of pins 31 are connected to the ground track.

This variant embodiment, similar to the variant embodiments of FIGS. 5 and 6, allows the use of the upper row of pins associated with the metal sheet supported by the top of the face element that implements the first shielding element of the connector.

According to the present invention there is provided a protective device for protecting an electrical connector from electromagnetic interference comprising a body made of a plastic material having a front face which functions to cooperate with a removable plug.

Claims (17)

The connector 3 has a body portion made of a plastic material having a connecting side 3c in contact with the printed circuit board 2 and a front side functioning to cooperate with the removable plug, and spikes protruding from the connecting side 3c. A plurality of contacts 31 each having one end in the form of 31a, wherein the spike 31a is in the substrate 2 to electrically connect the contacts to one or more conductor tracks of the printed circuit. A protective device for protecting an electrical connector for a printed circuit board (2) from electromagnetic interference inserted into a through hole, A first shielding element extending toward the side 3a of the connector facing the connecting side 3c and subsequently toward the rear face 3b of the connector, in contact with the ground conductor track of the printed circuit board 2, A second shielding element mounted on a face of the printed circuit board 2 opposite the face in contact with the connector 3 and extending toward the connecting side, And the second shielding element is in electrical contact with the first shielding element in contact with a conductor track connected to the ground track of a printed circuit to form a potential cage. 2. The printing device according to claim 1, wherein the first shielding element is substantially continuous and comprises metal elements 6b, 12b extending to an adjacent portion of the printed circuit board 2 towards the rear face 3b of the connector 3. The edges of the metal elements 6b, 12b adjacent to the circuit board 2 have spikes 61, 12c into which the plated through holes in the printed circuit board 2 are inserted, so that the holes are connected with the ground track of the printed circuit. Protective device for protecting an electrical connector, characterized in that the contact. The connector according to claim 2, wherein the first shielding element extends toward the rear face 3b of the connector 3 and the branch 6a extending opposite the side face 3a of the connector opposite the connecting face 3c. A protective device for protecting an electrical connector, characterized by consisting of a metal angle bracket (6) having a branching portion (6b). The connector (3) according to claim 1, wherein the connector (3) is a column furthest from the printed circuit board (2) so that the ends of the contact portions 31 in the form of spikes (31a) penetrate into the plated through holes in the substrate (2). A plurality of contact rows, including a top row of contacts having a rear portion extending perpendicular to the printed circuit board 2 at the rear surface 3b of the backplane 3b, wherein the top row of the contacts 31 is a ground conductor track. Protective device for protecting the electrical connector, characterized in that it is used to connect the spikes (31a) of the contacts (31) in the upper row to the first shielding element. The method according to claim 4, wherein the first shielding element is formed by a metal sheet (8) that cooperates with the top row of contacts (31), The metal sheet 8 is characterized in that it has a curved end 8a extending toward the side 3a of the connector 3 opposite the connecting surface 3c and in contact with the upper row of contacts 31. Protective device to protect the connector. 6. The second shielding element according to claim 1, wherein the second shielding element is in contact with a track disposed on the surface of the substrate 2 and connected to a ground track to which the spikes 61, 31a of the first shielding element are connected. A protective device for protecting an electrical connector, characterized by comprising a metal sheet (7). 7. The method of claim 6, wherein the printed circuit board 2 is designed to install a shelf module 10 having a plurality of electronic cards 1 arranged side by side, Resilient tongues 9 projecting laterally from the face element 4 such that a metal sheet 7 forms an electrical contact with the shielding element of the connector 3 carried by an adjacent electronic card held in the shelf module 10. A protective device for protecting an electrical connector, comprising: a. 8. A surface element (4) according to any one of the preceding claims, wherein a face element (4) is mounted on the connector (3) and has fastening means (41) for mounting a printed circuit on the shelf module (10). A protective device for protecting an electrical connector, characterized in that. 9. Protective device as claimed in claim 8, characterized in that the face element (4) supports the metal element (6, 8) of the first shielding element. 10. A protective device according to any one of the preceding claims, wherein the connector complies with DIN standard F48 type. 8. The side wall 3a of the connector 3 according to claim 7, wherein the face element 4 comprises an electrical conductor body part surrounding all four sides of the connector 3. A protective device for protecting the electrical connector, comprising an upper wall 4a adjacent to and a lower wall 4b adjacent to the printed circuit board 2, said walls forming first and second shielding elements, respectively. . 12. The first shielding element according to any one of the claims 2 to 11, wherein the first shielding element is formed by a top angle 4a and by a metal angle bracket 12 mounted against the top wall 4a. Is characterized by having a branch 12b extending towards the rear face 3a of the connector 3 and fixed to the top wall 4a so that electrical continuity exists between each bracket 12 and the top wall 4a. Protective device to protect electrical connector. The method according to claim 4, wherein the first shielding element is mounted by means of an upper wall 4a and against an upper wall 4a by means of a metal sheet cooperating with the upper row of contacts 31. Formed, the metal sheet (13) having a curved end (13a) in contact with the upper row of contacts (31). The conductor according to any one of claims 11 to 13, wherein the second shielding element is arranged on the surface of the printed circuit board 2 and connected to a ground track to which the spikes 61, 31a of the first shielding element are connected. Protective device for protecting an electrical connector, characterized in that it is formed by a bottom wall (4b) in contact with the track. 15. The shelf module (10) according to claim 14, wherein the printed circuit board (2) is designed to install a shelf module (10) having a plurality of electronic cards (1) arranged side by side, and a lower wall (4b) is provided for the shelf module (10). Electrical connector, characterized in that it has an elastic tongue 19 protruding laterally from the face element 4 to form electrical contact with the shield element of the connector 3 carried by the adjacent electronic card 1 retained therein. Protective device to protect the. 14. Protective device according to one of the claims 8 to 13, characterized in that the face element (4) is a "zamark" casting. The protective device as claimed in claim 11, wherein the connector (3) complies with DIN standard E48 type.