AU649497B2

AU649497B2 - Housing with radio frequency interference shielded cable entry

Info

Publication number: AU649497B2
Application number: AU88263/91A
Authority: AU
Inventors: Christian Haouy; Janos Kappel; Werner Rohrmann
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1990-12-05
Filing date: 1991-11-29
Publication date: 1994-05-26
Anticipated expiration: 2011-11-29
Also published as: AU8826391A; DE4038690A1

Description

649497 P/00/011 28/5/91 Repuliaon 3.2

AUSTRALIA

Patents Act 1990 @0 40 0 0

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT "HOUSING WITH RADIO FREQUENCY INTERFERENCE SHIELDED CA- B3LE ENTRY" Tli, following statomont is a full fCscripLiCon or tils invcntio 1 including the best methiod of performing it known to us:- 2 This invention relates to a housing with Radio Frequency Interference (RFI)-shielded cable entry for communications equipment, wherein a sheet-metal wall contains a slot-like opening along one long side of which is disposed a supporting plate which is provided with a flexible contact tube and between which and a pressure part provided on the other long side of the opening, the braids of cables passed through said opening can be clamped.

Such a housing is known. Normally, electronic circuits susceptible to interference are accommodated in such housings and connected to connecting leads or cables fed from the outside which are shielded by means of an earth metal braid against electromagnetic sweep radiation. In order to achieve a transition as uninterrupted as possible from 'the cable shielding to the shielded housing, the opening, constructed as a relatively long slot, for feeding the connecting leads is covered by means of a sealing element. It consists of two foam rubber cords resting closely next to one another which, in each case, are covered by a metal braid and are pressed by cable clamp-type supports against the connecting cables passed through between the cords. The supports constructed in the shape of a rail have slots which allow the supports to be shifted. When a connecting cable is installed, the appropriate fastening screws of the supports are loosened and the latter with the foam rubber cords are pushed apart, the connecting cable is passed through, the supports pushed back subsequently against each other until mutual contact of the cords is established whereafter the supports are screwed back to e °o the housing wall. With regard to the shielding effect, such an RFI-shielded cable entry, indeed, produces quite good results; however, it requires considerable input a. CC a for manufacture and mounting.

It is an object of the present invention to provide a simple cable entry with strain relief of the cables capable of being produced at low cost for housings which can be substantially sealed against penetration and emission of electromagnetic radiation.

According to the present invention there is provided a communications equipment housing having a radio frequency interference shielded cable entry including an oblong slot along a first long side of which is disposed a supporting pla e at an angle to the plane of the slot, and wherein a pressure part is disposed alkng the second long side of the slot, the pressure part including at least one pressure plate and being approximately parallel with the supporting part and located opposite thereto, wherein the pressure part has a transversely extending crimp and the support plate includes a complementary crimp, the transversely extending crimp and the complementary crimp forming a three-edge strain relief to grip the shielding of shielded cables passing through the cable entry, and wherein a flexible contact tube is retained in the complementary crimp, the contact tube having a cross section which protrudes beyond the complementary crimp when no force is applied to the contact tube, whereby the contact tube makes electrical contact with the shielding when the pressure part is applied so that the transversely extending crimp urges the shielded cables towards the complementary crimp.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: *a a o *oe a a Figure 1 shows a first embodiment of the invention of a housing with a RFI-shielded cable entry, part section in lateral view; Figure 2 shows a pressure plate of the cable entry of Figure 1, in lateral view; Figure 3 shows the pressure plate of Figure 2, in frontal view; Figure 4 shcws a second embodiment of the invention of a housing with RFI-shielded cable entry, part section in lateral view; Figure 5 shows a pressure plate of the cable entry in accordance with Figure 4, in frontal view; Figure 6 shows the pressure plate of Figure 5, in lateral view.

Referring to Figure 1, the RFI-shielded cable entry is designated by I. It is a component of a housing 2, eg. of a metal cabinet with a double bottom in the case of which the sheet-metal wall 3 of the bottom plate has a slot-type opening 4 for pulling through shielded cables 5. On each side of the opening 4, provision is made for a sheet-metal plate in upright position on the interior side of the housing 2. One 15 of these slheet-metal plates is used as the supporting plate 6 while the other one, arranged in parallel to it, constitutes the pressure plate 7. Both plates are bent at an angle and each of them has a short leg 8,8' used as fastening base, and a longer leg S9,9' used as guide walls for the cables. Two narrow hooks 10 bent toward the inside of the cable entry are provided on the free end of the longer leg 9 of pressure plate 7. These hooks always finish flush with the longitudinal sides of pressure plate 7.

On the one hand, the hooks 10 are used as fastening elements and, on the other hand, they constitute a lateral limitation for the cables 5 passing through. Although the width of the cable entry I between the hooks 10, in the case of the represented example, are dimensioned so that four cables 5 can be passed through next to one 25 another, it can be arbitrarily larger or smaller.

In the case of the pressure plate 7 in accordance with Figures I to 3, the longer

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S* leg 9 is arranged at an angle of about 750 relative to the short leg 8 spreading horizontally outwardly from the interior of the cable entry 1 and the approximately parallel leg 9' of the supporting plate 6 at an angle of about 1050 relative to the fastening level of the short leg 8, though the cable entry I can have also any other appropriate inclination toward the sheet-metal wall 3.

A strain relief for the cables 5, preferably located centrally, is arranged between the cable inlet on the bottom plate and the free end of the cable entry 1. It consists of a crimp 11 and a complementary crimp 12 of which crimp 11 extends transversely to the cable entry and, with an approximately triangular cross section, is forced into the pressure plate 7, while the complementary crimp 12, opposite from crimp 11, is impressed from the inside outwardly into the supporting plate 6. In this manner, three bending edges 13 are formed within the cable entry 1 around which the installed cables 5 are deflected and, by so doing, are kept mechanically in position and accordingly strain-relieved.

The linear section of the cables 5 passing through the cable entry 1, usually, is freed from the external cable sheathing down to the shielding braid 14 by what means the bending edges 13 form a three-point bearing where the earthed cable entry 1 electrically bonds the braid 14. In order to ensure an electrical contact resistance as low as possible between the braid 14 and cable entry, the supporting and pressure plates 6 and 7 are manufactured preferably from stainless steel. Moreover, a flexible contact tube 15, for example, consisting of a metal braid is embedded in the crimp 12 of supporting plate 6. The diameter of the contact tube 15, in slack condition, is larger than the space between the supporting and pressure plates 6, 7. For example, 15 the contact tube 15 is fastened in the supporting plate by means of cable ties (not il- Slustrated) which are pulled through adequate slots in the supporting plate 6. Of course, the contact tube 15 can be also a foam rubber cord covered by metal braid Sor a flexible plastic tube covered by it. Between crimp 11 and the short leg 8, the pressure plate 7 has a side cheek 16 on each side. It is bent rectangularly upward toward the inside. It prevents a lateral shifting of installed cables 5. Moreover, on the free end of the short leg 8, an obliquely bent holding lug 17 for engaging into an adequately narrow slot 18 of the sheet-metal wall 3 is arranged on the free end of short leg 8.

Supporting and pressure plates 6, 7 are stamped metal parts which can be easily 25 produced. They are ben so that their raw edges point outwards. Both sheet-metal plates can be produced as individual components. In this case, for example, the short S leg 8' of the supporting plate 6 has been fastened to the sheet-metal wall 3 by means of rivet or spot welding. In the case of metal cabinet with a double bottom, the longer leg 9' of the supporting plate 6, for practical reasons, can consist also of a section bent upward from the bottom plate which does not require further fastening. Here, the supporting plate 6 has been shaped like a rail of which the length extends nearly over the entire cabinet width and which interacts with pressure plates 7 arranged next to one another with almost no gaps between them. During assembly of entry I, the top end of the pressure plate 7, in the area of braid 14, is put against the cables 5 previously nulled throu-h the oncnin, 4 and hooked into the hooks 10 above the end of the fixed supporting plate 6 equipped with the contact tube 15. Subsequently, the bottom portion of the pressure plate 7 is pressed thus far against the shielding braid 14 until th'i holding lug 17 of the short leg 8 locks in position in slot 18 of the sheetmetal wall 3. By so doing, the convex portion of the crimp 11 presses the cables with braid 14 against the bending edges 13 of the supporting plate 6 and the transversely resting contact tube 15 into the supporting plate crimp 12 during which the contact tube next to the bending edges 13 establishes another electrical connection being under mechanical pressure between the braid 14 of the cables 5 and the cable entry 1.

The distance of the slot 18 to the opening 4 with the fed cables 5 and the hooks of the pressure plate 7 are adjusted to a specified cable diameter which, for example, amounts to 14 mm. However, the cable entry allows for feeding RFI-shielded cables of smaller diameters into the housing 2. For it, provision is made for another slot 18' arranged at a shorter distance to the opening 4 in the sheet-metal wall 3. The 15 second slot 18' makes possible shifting the bottom portion of the pressure plate 7 closer to the supporting plate 6, clamping of thinner cables in the entry, and fastening the pressure plate 7 in this position by locking it in position. This stop location is used Spreferably also in the case of the cable entry 1 remaining unused for the time being.

If required, fastening can be released by simply unlocking the lug. If the supporting plate 6 is a component of the bottom plate, the opening caused by the longer leg 9' is covered by means of a cover plate which leaves the openings 4 free for pulling through the cables 5 and contains the slots 18, 18' for locking in position the pressure plates 7.

6"10 In the case of the cable entry I represented in Figure 4 which is used preferably 25 for housing 2 with cables installed under the ceiling, the short leg 8' attached to the sheet-metal wall 3 of the supporting plate 6 has a U-shaped cross section of which the open side points to the cables 5. This arrangement permits hook-type mounting on the she,': metal wall 3 of the cabinet ceiling, in the case of which the portion of the shorter leg 8' attached to the long leg' of supporting plate 6 has a gap toward the sheet-metal wall 3. This portion of the leg 8' contains the slots 18, 18' for hooking in the hooks 10 of the pressure plate 7. In the case of the latter, provision is made for 2 narrow spring legs 19 pointing to the inner side of entry 1 being always flush with the longitudinal sides of pressure plate 7, replacing a leg projecting outwardly on the bottom end (Figure On the free end, the spring legs 19 always have a detent hook formed by reverse bending by means of which the pressure plate 7 is fastened in a detachable fashion to the supporting plate 6 (Figure 4 and If the supporting plate 6 is fixed to the sheet-metal wall 3, its long leg for practical reasons, is pressed against holding lugs 21 of the cabinet frame which gives additional support to the cable entry 1.

During assembly, the top end of the pressure plate 7 containing hooks 10, is hooked into the slots 18 or 18' of the supporting plate 6, in the course of which the shielding braids 14 of the cables 5, previously stripped and pulled through the opening 4 in the sheet-metal wall 3, come to rest between the hooks 10. After that, the bottom portion of the pressure plate 7 is swivelled in until the detent hooks 20 lock in position behind the supporting plate 6 and lock the pressure plate 7. The latter takes place in a manner that either the detent hooks 20 back-grip the lower edge of the supporting plate 6 or, as indicated in Figure 4, the spring legs 19 penetrate through adequate openings 22 in the supporting plate 6. As described initially, the shielding braids 4 of cables 5 are pressed against the contact tube 15 fastened by 15 means of cable ties 23 in the crimp 12 of the supporting plate 6 and clamped between the bending edges 13 of the three-point rest when the pressure plate 7 is swivelled in.

In order to keep lateral pressure away from the spring legs 19, an additional side cheek 16' each is arranged between the spring legs 19 and crimp 11 on the long sides of pressure plate 7.

If the cable entry 1 remains temporarily vacant or cables of smaller diameter have been passed through, the hooks 10 of pressure plate 7 are hooked into slots 18' which are away further from the longer leg 9' of supporting plate 6. Then, the pressure plate 7 is swivelled in until the detent hooks 20 of the spring leg 19 lock in behind a second lock-in step. The cross sectional view of this lock-in stop shows stepped 25 sheet-metal squares 24 which are assigned to each detent hook 20 and fixed to the exterior of supporting plate 6. Instead of individual sheet-metal squares 24, the second lock-in step can consist of a sheet-metal rail having the same length as the supporting plate. The latter applies, in particular, if the supporting plate is designed in the form of a rail. For production-technical reasons,.it is of advantage to produce the pressure plate 7 from two plain separate sections, for example, like a plate equipped with hooks 10, crimp 11 and side cheeks 16,16', and a sheet-metal strip which has the spring legs with detent hooks 20, and combine the two by means of spot welding.

Moreover, it is appropriate to mount an angular sheet-metal shielding protruding over the top to the outside of pressure plate 7, It seals electromagnetically the gap between the nressure n1ate 7 and the sheer-mreltn wnll 3

Claims

1. A communications equipment housing having a radio frequency interference shielded cable entry including an oblong slot along a first long side of which is disposed a supporting plate at an angle to the plane of the slot, and wherein a pressure part is disposed along the second long side of the slot, the pressure part including at least one pressure plate and being approximately parallel with the supporting part and located opposite thereto, wherein the pressure part has a transversely extending crimp and the support plate includes a complementary crimp, the transversely extending crimp and the complementary crimp forming a three-edge strain relief to grip the shielding of shielded cables passing through the cable entry, and wherein a flexible contact tube is retained in the complementary crimp, the contact tube having a cross section which protrudes beyond the complementary crimp when no force is applied to the contact tube, whereby the contact tube makes electrical contact with the shielding when the pressure part is applied so that the transversely extending crimp urges the shielded cables towards i' the complementary crimp. C

2. A housing with a cable entry as claimed in claim 1, wherein the transversely extending crimp and the complempntary crimp are V-shaped crimps and wherein the three-edge strain relief comprises inwardly pointing bending edges of the 20 V-shaped crimps of the supporting and pressure plates.

3. A housing as claimed in claim 1 or claim 2, wherein the pressure part °e includes latch means which can be latched in a first position or a second position relative to the support plate to accommodate different sized cables, the second o" position being located so that ve pressure part is closer to the support plate when O::l 25 the pressure part is latched in the second position than when the pressure part is latched in the first position. S" 4. A housing as claimed in claim 3, wherein the end of the pressure plate remote from the slot includes two hooks capable of engaging the corresponding end of the support plate, and wherein the end of the pressure part proximate to the slot includes a foot-plate substantiaiiy parallel with the plane of the slot, the latch means including a holding lug projecting from the foot-plate to engage in one of one or more recesses in the housing as the pressure part is pressed against the shielded cables. 9 V 8 A housing with a cable entry as claimed in claim 1, wherein at one end of the pressure plate, the pressure plate is fastened to a corresponding end of the supporting plate by means of two hooks hooked into slots of a leg of the supporting plate, and that at the other end of the presssure plate, the pressure plate is fastened to the supporting plate by means of two spring legs having detent hooks which grip the supporting plate.

6. A housing as claimed in any one of claims 1 to 5, wherein the ends of the pressure part transverse to the plane of the slot include inwardly extending flanges to retain the cables.

7. A housing with a cable entry as claimed in claim 1, wherein the supporting plate is in the form of a rail, and wherein two or more pressure plates are hooked to the supporting plate side by side nearly without a gap.

8. A housing as claimed in claim 1, wherein the housing includes a sheet S metal wall containing the cable entry, wherein the support plate is formed by stamping out the support plate from the wall, and wherein the opening formed in the wall by stamping out the support plate is partially closed by a cover plate, leaving the oblong slot open. S sees 9. A housing as claimed in claim 8, wherein the cover plate includes recesses for latching the pressure plate in position. co 20 10. A housing with a radio frequency interference-shielded cable entry, substantially as herein described with reference to Figures 1 to 6 of the accompanying drawings. DATED THIS TWENTYFOURTH DAY OF JANUARY 1994 ALCATEL N.V. ABSTRACT This invention relates to a housing with a radio frequency interference-shielded cable entry for communications equipment, of the type having a sheet-metal wall containing a slot-like opening along one long side of which is disposed a supporting plate which is provided with a flexible contact tube. According to this invention, be- hind the slot-like opening the housing wall contains two plates 7) each of which is provided with a transversely extending crimp (11, 12), and one of which, fitted with a contact tube is fixed while the other is fastened by being hooked and lockea in position. Bending edges (13) of the crimps (11, 12) form a three-point bearing between whose bearing points the braids (14) of cables are clamped. Figure 1. 04 4 as lt0 0 o 0** <4 *O 0 *0 0 0 04 4I