WO1999014826A1 - Device for shielding connection between an enclosing case and a shielded cable - Google Patents

Abstract

The invention concerns a device for a shielding connection (10) between a protective enclosure case (12) of a high voltage apparatus (14) and a shielded cable (20) comprising at least two conductors (22, 24) and a tubular shielding braid (26) enclosing said conductors. The device comprises a rotating ferrule (20) including one first cylindrical end (34) and a second end (36) with a rotating ring-shaped rib (38) with a shoulder (40) facing the direction opposite to the first end (34),said rib (38) external diameter being larger than said opening (28), a clamp collar (46) maintaining said braid (26) and said ferrule (32), and an arc-shaped elastic retaining ring (54) extending over an angle with a centre of at least 200 DEG , said collar (46) being designed to co-operate with stop means (62) integral with said second ferrule (30) end (36). The invention is applicable to shielding connection between a discharge lamp and a high voltage generator.

Description

Shield connection device between a housing and a shielded cable

The invention relates to a shielding connection device between a protective and shielding box of a high-voltage device and a shielded cable comprising at least two conductors and a tubular shielding braid surrounding said conductors.

More specifically, the object of the invention is to ensure the electrical continuity of the shielding between the protective and shielding box of a high-voltage device such as a discharge lamp and the protective and shielding box of 'a high voltage generator. Discharge lamps need a high voltage supply of the order of 20 to 25 kV to ensure their operation, especially when they are re-ignited. Without specific protection, the cable supplying these discharge lamps generates electromagnetic interference which can disturb the electronic equipment of an automobile, such as radio, air conditioning, on-board computer, etc. It is understood that, to use discharge lamps within in an automobile, electromagnetic protection must be carried out on the high-voltage supply cable of the discharge lamp.

The purpose of the shielding connector according to the invention is to ensure the shielding continuity between a shielded cable and each of the protective and shielding boxes which surrounds an electrical appliance to which the conductors contained in the shielded cable are connected, in order to prevent the emission of electromagnetic interference from the shielded cable. The shielding efficiency can be measured using the transfer impedance of the assembly formed by the shielding and the housing. The transfer impedance defines in a given frequency the contact resistance between the shielding and the case for this frequency range. Connection techniques with 360 ° electrical continuity offer the best transfer impedance. Solutions have already been proposed in order to carry out the shielding connection between a protective and shielding box and a shielded cable, but the devices proposed comprise a fixed structure which is not easily removable. In the case of discharge lamps, it may be necessary to change the bulb, the base of which is electrically connected to the shielded cable conductors, so that there is a need for a shielding connection device which can be of easy assembly and disassembly and which easily adapts to different protective and shielding boxes. In addition, in the case of discharge lamps, the receptacle comprising all the elements forming a headlamp, such as a headlamp for a motor vehicle, is of very limited size, so that the shielding connection between the protective housing and shielding of the discharge lamp and the protective and shielding box of the high voltage generator must be able to fit into a very limited space. Thus, it is understood that it is desirable that the shielding connection device has a reduced bulk, can be easily disassembled and makes a shielding connection as efficient as possible.

To achieve this aim, an object of the invention is to provide a shielding connection device which has the abovementioned advantages and which ensures optimum shielding continuity despite a succession of assemblies and disassembly of the shielding connection device.

To achieve this object, the shielding connection device according to the invention is characterized in that said protection and shielding box comprises a circular opening and in that said device forms a removable rotating shielding fitting comprising:

a ferrule of revolution comprising a first cylindrical end and a second end having an annular rib of revolution with a shoulder turned in the opposite direction from said first end and which has a flat surface and orthogonal to the axis of revolution of said ferrule forming a contact surface intended to come against an annular zone of the external surface of said protection and shielding box which surrounds said opening, the external diameter of said rib being greater than the diameter of said opening, - a clamping ring maintaining a section of one end of said braid in bearing contact over substantially the entire periphery of the first end of said ferrule, and

an elastic retaining ring in the form of an arc of a circle extending over an angle at the center of at least 200 °, said ring having an internal contour and an outer contour included in two different planes, said outer contour being intended to be applied against the internal face of said housing and said internal contour being intended to cooperate with stop means integral with said second end of the ferrule. It is understood that, thanks to the invention, the electrical continuity of the braid constituting the cable shielding is ensured by the ferrule. This is profiled to receive the braid on its first end, the contact being made thanks to the clamping ring. The second end of the ferrule is profiled to be in contact with the protection and shielding box of the high-voltage device over an angle of 360 °, thanks to the cooperation between the elastic retaining ring and the annular rib of ferrule revolution.

This 360 ° contact makes it possible to obtain, in addition to a satisfactory transfer impedance, a removable rotary contact. Other characteristics and advantages of the present invention will appear more clearly on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the figures in which:

- Figure 1 is a longitudinal sectional view showing a shielding connection device according to the present invention for providing a shielded connection from a high voltage supply to a high voltage device such as a discharge lamp;

- Figure 2 is an enlarged view of detail II of Figure 1;

- Figure 3 shows a ferrule in side view; - Figure 4 is a view in the direction IV-IV of Figure 2 for viewing the elastic retaining ring from its front face;

- Figures 5A and 5B are cross-sectional views in the direction V-V of Figure 4 for two different forms of retaining ring; and - Figure 6 is a view similar to that of Figure 2 in the case where a protective element is used to make a bent shield connection.

In Figure 1, there is shown a shielding connection device 100 between a first protective and shielding box 12 of a device to high voltage 14 such as a discharge lamp (the electrical connection being made to a connector of the discharge lamp) and a second protection and shielding box 16 containing a high voltage supply 18. The high voltage apparatus 14 and the high-voltage power supply 18 are connected to each other by a screened cable 20 comprising two conductors 22 and 24 as well as a tubular shielding braid 26 surrounding said conductors. To allow the shielding connection between the shielding braid 26 and the two boxes 12 and 16, these two boxes include a circular opening 28 and the screen connection device 100 further comprises:

a first and a second ferrule of revolution 30, 32, each of them comprising a first cylindrical end 34 and a second end 36 having an annular rib of revolution 38 with a shoulder 40 turned in the opposite direction from said first end 34, said shoulder having a flat surface and orthogonal to the axis of revolution X of said ferrule 30 or 32 so as to form a contact surface 42, the contact surface 42 of said first ferrule 30 being intended to come against said annular zone 44 of the external surface of the protective and shielding box 12 of said high-voltage device 14 which surrounds said opening 28 and the contact surface 42 of said second ferrule 32 being intended to come against an annular zone 44 of the external surface of the second box of protection and shielding 16 which surrounds said opening 28, the outside diameter of said rib 38 being greater laughing at the diameter of said opening 28, - a first and a second clamping rings 46, 48, said first clamping ring 46 now a section of the first end 50 of said braid 26 in contact with contact over substantially the entire periphery of the first end 34 of the first ferrule 30 and said second clamping ring 48 maintaining a section of the second end 52 of said braid 26 in bearing contact over substantially the entire periphery of the first end 34 of the second ferrule 32, and

- a first and a second retaining rings 54, 56 elastic in the form of an arc of a circle extending over a central angle of at least 200 °, said rings 54, 56 having an internal contour 58 and an external contour 60 included in two different planes, said external contour 60 of the first ring 54 being intended to be applied against the internal face of said protection and shielding box 12 of said high-voltage device 14, said internal contour 58 of the first ring 54 being intended to cooperate with stop means 62 integral with said second end 36 of the first ferrule 30, said external contour 60 of the second ring 56 being intended to be applied against the internal face of said second protective and shielding housing 16 and said internal contour 58 of second ring 56 being intended to cooperate with stop means 62 integral with said second end 36 of the second ferrule 32.

Reference will be made to FIG. 2 in order to better visualize how the shielding connection takes place between the braid 26 and the protective and shielding box 12, using a shielding connection device 10. It is understood that the ferrule 30 serves intermediate piece allowing, thanks to a suitable shape, to carry out the shielding continuity between the braid 26 and the housing 12. At the first end 34 of the ferrule 30, there is a tight contact between the first end 50 of the braid 26 and the entire periphery of the first cylindrical end 34 of the ferrule 30. This 360 ° contact is ensured by virtue of the annular tightening ring 46 which is shaped to allow this support contact of the braid over substantially the entire periphery of the first end 34 of the ferrule 30.

Such a clamping ring 46 can be similar to the connection collar described in French patent 2,671,435 of the applicant. The shielding continues also at the second end 36 of the ferrule 30 which is shaped to allow 360 ° contact with the wall of the housing 12. For this, the second end 36 of the ferrule of revolution 30 comprises an annular rib of revolution 38 having a shoulder 40 facing the free edge of the second end 36 of the ferrule 30. This shoulder 40 has an annular contact surface 42, plane and orthogonal to the axis of revolution of the ferrule 30 .

So that this contact surface 42 can bear against the annular zone 44 of the outer surface of the housing 12 which surrounds the opening 28, it is provided that the annular rib 38 has a diameter outside greater than the diameter of the opening 28. In addition, provision is made for the cylindrical surface of annular revolution 43 which is longitudinal and contiguous to the radial contact surface 42 at the level of the shoulder 40 to enter the opening 28 of the housing 12 and therefore has a diameter at most equal to the diameter of the opening 28.

In order to force the contact surface 42 to remain in abutment against the annular zone 44, an elastic retaining ring 54 is removably mounted on the second end 36 of the ferrule 30, this elastic retaining ring 54 being shaped so that its external contour 60 rests on the internal face of the housing 12 and so that its internal contour 58 is retained against abutment means integral with the second end 36 of the ferrule 30.

Preferably, these abutment means consist of an annular abutment rib 62, of revolution and adjacent to the free edge of the second end 36 of the ferrule 30.

From the previous description of the shielding connection device 10, it is understood that it has a symmetry of revolution allowing both a 360 ° contact ensuring a correct transfer impedance between the braid 26 and the boxes 12 and 16 and the possibility of carrying out a 360 ° rotation between the ferrule 30 and the opening 28.

It is expected that, preferably, the shielded cable 20 is located inside a protective sheath 64, preferably flexible, surrounding the braid 26 at least up to the clamping ring 46. This protective sheath 64 is preferably made of a flexible material such as elastomer and is intended to mechanically protect the braid 26 in order to avoid any alteration of the shielding continuity provided between the two boxes 12 and 16 by this braid 26.

Reference will be made to FIG. 3 which illustrates a ferrule 30 which is metallic and is produced for example in a Cu-Zn alloy which can be coated with a metallic layer minimizing the electrical resistance of contact with the housing 12 or 16, preferably a nickel layer with a thickness between 2 and 5 μm. According to an exemplary embodiment of the ferrule 30, it has a length of 9.6 mm, its first cylindrical end 34 has a diameter of 9.8 mm and a bead 66 is disposed over the entire periphery of the first end 34 at the free edge in order to prevent sliding of the clamping ring and separation between the first end 50 of the braid 26 and the ferrule 30.

The internal diameter of the ferrule is for example of the order of 8.2 mm. At the second end 36 of the ferrule 30, there is the annular rib of revolution 38 having a crenellated profile and the shoulder 40 delimiting the side of the annular rib of revolution 38 facing the free edge of the second end 36 of the ferrule 30. This shoulder 40 comprises the contact surface 42 and the cylindrical surface of revolution 43. Preferably, the diameter of the surface 43 is equal to the diameter of the circular opening 28 of the housing 12, for example of the '' order of 10 mm. The free edge of the second end 36 of the ferrule 30 comprises a second annular rib of revolution 62 having a cross section in the form of a slot. The change in diameter between this rib 62 and the cylindrical annular peripheral surface 68 of the second end 36 of the ferrule 30, which is contiguous with this second rib 62, forms an abutment shoulder 70 intended to retain the internal contour 58 of the elastic retaining ring 54.

On the ferrule of Figure 3, it is provided that the outside diameter of the second rib 62 is equal to the outside diameter of the surface 43 (10 mm) so that there is a shoulder 72 between the surface 68 and the surface 43 .

The change in diameter at the shoulders 70 and 72, that is to say the difference in diameter between the surfaces 43 and 68, is for example of the order of 1 mm.

To allow a tight fit during assembly of the elastic retaining ring 54, it is provided that, preferably, the distance separating the annular rib 38 from the abutment means constituted by the rib 62 is substantially equal to the sum of the thickness of the wall of the annular zone 44 of the protection and shielding box 12 around the opening 28 and the distance separating the planes comprising respectively the inner contour 58 and the outer contour 60 of the retaining ring 54.

According to an exemplary embodiment, the wall of the housing 12 has a thickness of 0.3 mm equal to the thickness of the ring formed by the surface 43 and the width of the peripheral surface 68 is equal to the distance separating the planes respectively comprising the inner contour 58 and the outer contour 60 of the retaining ring 54, for example 1.3 mm.

Reference will now be made to FIGS. 4, 5A and 5B in order to illustrate the shape of the elastic retaining rings 54 and 56. In front view (FIG. 4), the elastic retaining ring 54 is not closed but s' extends over an angle at the center of at least 200 °, preferably at least 270 ° and even more preferably between 290 and 320 °.

The outer contour has an arc shape. For good elasticity of the elastic retaining ring 54, the internal contour comprises three sections of circular arc 74 between which recesses 76 are formed. It is also conceivable that the internal contour 58 is strictly in the form of a circular arc provided that the material in which the elastic retaining ring 54 is made is sufficiently flexible. This elastic retaining ring 54 can be made of plastic, metal or any other material sufficiently elastic to allow the elastic retaining ring 54 to be removed and put back easily between the rib 62 and the wall of the housing 12 Preferably, the ring 54 is made of XC 75 steel on which two coatings are made: a ZnlOZB coating (yellow bichromate zinc) and a finishing coating for resistance to salt spray for 400 hours before the appearance of red rust.

As can be seen in the sections shown in Figures 5A and 5B, in side view the elastic retaining ring 54 may have profiles having different shapes. In FIG. 5A, the elastic retaining ring 54 has a profile in the form of a truncated cone and in FIG. 5B the elastic retaining ring has a convex profile in the form of a meniscus. It is expected that, preferably, the elastic retaining rings 54 and 56 are identical and have a constant thickness of material. When mounting the two housings 12 and 16 in the receptacle of the headlight of an automobile, the space is very small and it may be necessary to form an elbow at the connection between the screened cable and at least one of the two boxes 12 and 16. In order to generally protect the connection 10 between the screened cable and the box and to keep the screened cable in a particular configuration near the box to which it is connected, a protective element 78 shown in FIG. 6 can be used in the particular case of the formation of a right angle bend of the shielded cable 20 at the outlet of the box 12. This protective element 78 is preferably overmolded outside the housing 12 and extends at least from the annular rib 38 of the ferrule 30 to the free edge of the first end 34 of the ferrule 30 by surrounding a section of the ferrule 30, the clamping ring 46 and a section of the first end 50 of the braid 26. In this case which is not illustrated, the protective element 78 constitutes a substantially cylindrical sleeve protecting the device connection throughout the area of the ferrule which is located outside the housing 12. It should be noted that this protective element 78 does not prevent disassembly of the connection device, in removing the elastic retaining ring 54 as will be described below.

When a protective element 78 is used at the same time as a sheath 64, if the space to be respected is small, the sheath 64 can then be shorter. In the case of a right protection element 78, the sheath can stop before the first end 34 of the ferrule 30 and in the case of a bent protection element 78 (Figure 6), the sheath can stop before the elbow while remaining in contact with the protective element 78 over a length sufficient to ensure the seal between these two elements.

In the situation illustrated in FIG. 6, the protective element 78 further extends around a section 80 of the shielded cable 20 which is adjacent to the first end 34 of the ferrule 30, this section 80 forming an angle α not zero with the axis of revolution X of the ferrule 30.

In the particular case of FIG. 6, the section 80 is rectilinear in a direction Y forming an angle α of 90 ° with the axis X which is the axis of revolution of the ferrule 30. Thus, in the case of the figure 6, the molded protection element 78 forms an L-shaped sleeve, in particular at the level of its hollow part surrounding the connection device 10 and the section 80. Preferably, the molded protection element 78 has a thickness more or less constant of the order of at least 1 mm and can be made of any plastic that can be overmolded. If we refer again to FIG. 1, the length L corresponding to the length of the shielded cable 20 separating the two boxes 12 and 16 is of the order of 150 to 300 mm. In order to guarantee an acceptable transfer impedance, it may be necessary to add a second shielding braid on the first shielding braid 26, especially when the length L is too great and in particular when L is greater than 250 mm.

We will now describe the process to be used to connect the shield between the shield protection box 12 of a high-voltage device and a shielded cable 20. In the case of the shield connection device 10 of FIG. 2, it is first necessary to insert the first cylindrical end 34 of the ferrule 30 between the end 50 of the braid 26 and the two conductors 22 and 24 which pass through the ferrule 30. We then place the clamping ring 46 around of the first end 50 of the braid 26 and of the first cylindrical end 34 of the ferrule 30. The contact is made between the first cylindrical end 34 of the ferrule 30 and the end of the braid 20 by tightening the clamping ring 46 in order to make a 360 ° contact.

It is then possible to optionally place the sheath 64 around the braid 26 and, optionally, on a section of the ring 46. It then suffices to insert the second end 36 of the ferrule 30 into the circular opening 28 of the housing 12 until the annular rib of revolution 38 comes into contact with the exterior surface of the wall of the housing 12. In order to fix the assembly and maintain 360 ° contact between the housing 12 and the ferrule 30, the elastic retaining ring 54 is placed between the rib 62 and the internal wall of the housing 12.

It is therefore understood that it is possible, simply by removing the elastic retaining ring 54, to open the shielding connection between the shielded cable 20 and the housing 12, if one wishes for example to change the defective discharge lamp and connect the screened cable 20 to another screen protection box of a new discharge lamp.

An essential characteristic of the invention is that the shielding connection device makes it possible to rotate the shielding connection through 360 ° by rotating the ferrule 30 in the opening 28 of the housing. Thus, in the case where the shielding connection device comprises a protection L-shaped 78, the section 80 of the shielded cable 20 can be oriented radially around the opening 28 in the most suitable desired direction within the projector so that this connection device according to the invention takes the least amount of place possible.

Alternatively, the protective element 78 may consist of two complementary parts or shells in the form of half-rings which surround the shielded cable 20 and which are fixed to one another by means of complementary fixing means.

Claims

1. Shielding connection device (10) between a protective and shielding box (12) of a high-voltage device (14) and a shielded cable (20) comprising at least two conductors (22,24) and a tubular shielding braid (26) surrounding said conductors, characterized in that said protective and shielding box (12) comprises a circular opening (28) and in that said device forms a removable rotating shielding connection comprising: a ferrule (30) of revolution comprising a first cylindrical end (34) and a second end (36) having an annular rib of revolution (38) with a shoulder (40) turned in the opposite direction from said first end (34) and which has a flat surface and orthogonal to the axis of revolution of said ferrule so as to form a contact surface (42) intended to come against an annular zone (44) of the external surface of said protective and shielding housing (12 ) which surrounds said opening (28), the outside diameter of said rib (38) being greater than the diameter of said opening (28), a clamping ring (46) maintaining a section of one end (50) of said braid (26) in bearing contact over substantially the entire periphery of the first end (34) of said ferrule (32), and - an elastic retaining ring (54) in the form of an arc of a circle extending over a central angle of at least 200 °, said ring (46) having an internal contour (58) and an external contour (60) included in two different planes, said external contour (60) being intended to be applied against the internal face of said housing (12) and said internal contour (58) being intended to cooperate with stop means (62) integral with said second end (36) of the ferrule (30). 2. Device according to claim 1, characterized in that it further comprises a flexible protective sheath (64) surrounding said braid (26) at least up to said clamping ring (46). 3. Device according to any one of the preceding claims, characterized in that it further comprises at least one protective element (78) molded outside of said housing (12) and extending at least from the annular rib (38) of the ferrule (30) to the free edge of the first end (34) of the ferrule by surrounding a section of said ferrule (30), said ring (46) and said end (50) of said braid (26). 4. Device according to claim 3, characterized in that said protective element (78) further extends around a section (80) of the braid (26) which is adjacent to the first end (34) of said ferrule (30), said section (80) forming a non-zero angle (α) with the axis of revolution (X) of said ferrule (30). 5. Device according to any one of the preceding claims, characterized in that said retaining ring (54) has a domed profile in the form of a meniscus. 6. Device according to any one of the preceding claims, characterized in that said retaining ring (54) has a profile in the form of a truncated cone. 7. Device according to any one of the preceding claims, characterized in that said high-voltage device (14) is a discharge lamp. 8. Device according to any one of the preceding claims, characterized in that the distance separating said annular rib (38) from said abutment means (62) is substantially equal to the sum of the thickness of the wall of said annular zone ( 44) of the protective and shielding box (12) around said opening (28) and the distance separating the planes respectively comprising the inner contour (58) and the outer contour (60) of said retaining ring (54). 9. Device according to any one of the preceding claims, characterized in that said abutment means consist of an abutment rib (62) which is annular, of revolution and adjacent to the free edge of the second end (36) of said ferrule (30). 10. Device (100) according to any one of the preceding claims, characterized in that it also provides the shielding connection between said shielded cable (20) and a second protective and shielding box (16) for a power supply. high voltage (18), said second housing (16) comprising a circular opening (28) and in that said device (100) comprises: - first and second ferrules of revolution (30, 32), each of them comprising a first cylindrical end (34) and a second end (36) having an annular rib of revolution (38) with a shoulder (40) turned in the opposite direction from said first end (34), said shoulder having a flat surface and orthogonal to the axis of revolution (X) of said ferrule (30 or 32) so as to form a contact surface (42), the contact surface (42) of said first ferrule (30) being intended to come against said annular zone (44) of the external surface of the protective and shielding casing (12) of said high-voltage device (14) which surrounds said opening (28) and the contact surface (42) of said second ferrule (32) being intended to come against an annular zone (44) of the external surface of the second protection and shielding casing (16) which surrounds said opening (28 ), the outer diameter of said rib (38) being greater than the diameter of said opening (28), - a first and a second clamping rings (46, 48), said first clamping ring (46) maintaining a section of the first end (50) of said braid (26) in bearing contact over substantially the entire periphery of the first end (34) of the first ferrule (30) and said second clamping ring (48) maintaining a section of the second end (52) of said braid (26) in bearing contact over substantially the entire periphery of the first end (34) of the second ferrule (32), and - a first and a second elastic retaining rings (54, 56) in the form of a circular arc extending over a central angle of at least 200 °, said rings (54, 56) having an internal contour (58 ) and an outer contour (60) included in two different planes, said outer contour (60) of the first ring (54) being intended to be applied against the internal face of said protective and shielding box (12) of said high-voltage device (14), said inner contour (58) of the first ring (54) being intended to cooperate with stop means (62) integral with said second end (36) of the first ferrule (30), said outer contour (60) of the second ring (56) being intended to be applied against the internal face of said second protection and shielding box (16) and said inner contour (58) of the second ring (56) being intended to cooperate with stop means (62) integral with said second end (36) of the second ferrule (32).