GB2266198A - Clipping cables to a bus-bar in a patch panel - Google Patents

Description

SHIELDED CABLE CONNECTORS This invention relates to connectors for shielded cables, in particular for shielded data communications cables.

In the installation of equipment used in the cabling of data communications equipment it is often necessary to connect large numbers of cable shields to a common earth. Furthermore, the cables must be restrained to prevent undesirable movement. In a typical application, 48 cable shields will be connected to a common point with 48 jack connectors. This can be time consuming and labour intensive, but is often made more difficult by the sheer volume of connections involved and the variety of wire types and connection techniques which may be involved. The matter is complicated by the fragility of the shield of the shielded cables. Often the shield is an expanded metalised foil. For example, metalised mylar. This type of shield is easily crushed which may damage its shielding properties.

We have identified the need for a connection arrangment which simplifies the process of connection and reduces the time involved to complete installation. We have also identified the need for a connection or arrangement which reduces the risk of damage to the cable shields.

The invention, in its various aspects, aims to meet these needs.

The invention is defined in the claims, to which reference should be made.

Preferred and advantageous featuree of the invention are set out in dependent claims.

Embodiments of the invention will now be described, by way of example, and with reference to the accompanying drawings in which: Figure 1 is a rear view of a patch panel suitable for connecting shielded cables to socket outlets; Figure 2 is a plan of the patch panel of Figure 1; Figure 3 is a plan of a busbar mounted on the patch panel of Figures 1 and 2; Figure 4 is a rear view of the patch panel of Figure 3; Figure 5 is a rear perspective view, partially in phantom, of the patch panel, assembled for use; Figure 5a is an enlarged view of a cable clip showing how a cable is engaged; Figure 5b is an enlarged view of a cable engaged in a cable clip; Figure 6 is a front perspective view, partially exploded of the patch panel; Figure 7 is a perspective view of a second embodiment of the busbar showing how shielded cables are retained;; Figure 8 is a perspective view of a clip embodying the invention.

The patch panel 10 of Figures 1, 2, 5 and 6 comprises a front wall 12 and a bottom wall 14. The bottom wall is provided with a plurality of holes 16 for attachment of one or more busbars 17 (Figures 5 and 6) and a plurality of slots 18 for securing cabling neatly to the bottom wall with, for example, plastic ties 19 (Figure 5).

The front wall has a plurality of holes 20 for attachment of cable retainers 21, as shown in Figure 6, and a series of eight rectangular apertures 22. The patch panel could be used for cabling unshielded cable but is particularly suited to shielded cables. Typically a cable from a data communications outlet will comprise four wire pairs 24 (Figure 7) around which is wrapped an aluminium foil or braided shield 26. This shield provides protection from external inteference such as noise which can corrupt data transmitted on the wires. An outer plastics or rubber sheath 28 extends along the length of the cable. At the patch panel, a number of cables 29, up to 48, (see Figure 5), are terminated and connected to outlet sockets for connection to communications devices, for example computer terminals or telephones.The sockets 23 (Figures 5, 6) are housed in the apertures 22 in the front of the patch panel and may be typically of the type sold by Mod-Tap Limited under the trade mark EUROMOD and described in our co-pending patent application PCT/US91/08100. These socket connectors are modular in construction and three units can snap-fit into each of the apertures 22 in the manner shown in Figure 1. As each unit can carry two sockets a total of 48 sockets can be mounted on the panel. Blind panels 70 (Figure 6) may be used to block off any unwanted apertures.

The socket units are connected to the wires of each cable through insulation displacement connectors 25 (Figures 5, 6). An example of a suitable connector is that described in our copending application GB 9112604 and sold by Mod-Tap Limited under the trade mark KATT.

Other connector types are also suitable.

The busbar serves two purposes. Firstly, it provides a connectidn point for the shielded cables on the patch panel and secondly it provides a common earth for all the cable shields. In the embodiment of Figure 7 a mounting screw 30 secures the busbar to the bottom wall of the patch panel via an end mounting hole 16 (Figure 2). Three further screws are provided along the length of the busbar corresponding to the remaining holes 16 on the bottom wall.

At each of the mounting points a non conductive bush and washer e.g.

a nylon bush 32 and a nylon washer 34 separates the busbar electrically from the patch panel providing separate earths for the shield and the panel.

The busbars of Figures 3 to 6 and Figure 7 are different. However, in principle they are the same, although the Figure 3 to 6 embodiment is the preferred construction. In that embodiment, two separate busbars 40, 41 are provided. The first busbar is mounted on the bottom wall 14 and the cabling attached. Then the second busbar is fitted above the first busbar, spaced apart by a series of tabs 42 (Figures 4 to 6). With the second busbar in position the remaining cables may be attached. In the arrangement of Figure 7 the busbar is a single C-shaped channel 60, which although adequate makes attachment of the cables to the lower wall 46 (Figure 7) more difficult than with the arrangement of Figures 3 to 6.

As the configuration of the two layers or two busbars is similar, the description will be restricted to the upper layer.

The busbar 40 of Figures 3 to 6 comprises a rectangular metal sheet having a side flange 44 from which depend a series of tabs 42 each tab has an aperture 46 and a U-shaped recess 48 for fixing the busbar to the lower busbar. The end tabs have projecting connecting points 50 which screw into the busbar and allow wires to be attached to the busbar, for example to earth the busbar to a desired point such as a mounting cabinet via an earthing lead 51 (Figure 5).

The busbar 40 is provided with a plurality of apertures 52 spaced in two rows along the length of the busbar 40. As can be seen from Figure 7, each of these apertures receives a cable retention clip 54. The apertures are shown as being circular although that shape is not mandatory. The underside of the clips carry a retaining tab (not shown) which slots into the aperture. The advantage of a circular aperture is that the orientation of the aperture with respect to the busbar is not important facilitating manufacture.

A pair of location tabs 56 are provided on each side of each aperture. In the embodiments shown, these tabs are formed by stamping the tab on the busbar and bending the tab upwards.

Alternatively, the tabs could be separate pieces attached to the busbar or could be formed on the clips, as shown in Figure 8.

Although the tabs are shown as being straight. They will in practice be curved or arcuate as the nature of the material is such that the bending in the metal will be radiused rather than concentrated along a line. The purpose of the tabs can be appreciated from Figures 5 to 7.

As can be seen from Figures 5a, 5b and 7, the clips comprise C-shaped spring clips, the upper end of which have an inwardly extending channel 58. When a cable is attached to the busbar, the outer sheath 28 is first cut away to expose the shield 26 (Figure 5a) and the cable inserted into the clip (Figure 5b).

Initially, the underside of channel 58 will abut the shield 26 forcing the spring clip to open against its natural resilience.

Once the cable has passed the channel 58 the clip close around the shield. The limit of movement of the cable in the clip is defined by the tabs 56. As these are arcuate, as described, they will fit around a portion of the cable circumference and, if correctly positioned with respect to the channel 58 of the clip, will prevent any lateral movement of the cable in the clip. Moreover, the tabs 56 prevent the cable being forced into the clip to the back 62 of the clip which is narrower than the cable and can cause crushing of the shield and a loss of shielding properties. Moreover, as the combination of the channel 58 and the tabs hold the cable firmly in position there is no need for the assembler to press down on the clips to secure the cable, an operation which is likely to crush the shield.

In the embodiment of Figure 8, the tabs are formed as an extension of the side of the clip which abuts the busbar. This arrangement eliminates the need to punch the tabs 56 out of the busbars reducing assembly time and cost.

Many modifications to the embodiments described are possible. For example, it is not necessary to have a tab on each side of the clip although this is preferred. Adequate cable retention can be obtained by a single tab.

The apparatus described may also be used for terminating unshielded cables. In such instances the insulation of the busbar from the remainder of the panel is of no consequence but the invention is useful as it allows cables to be arranged neatly along the busbar and the provision of tabs 56 ensure that the cables are retained firmly.

Claims (8)

1. A patch panel having a plurality of apertures for receiving electrical connectors, and means for terminating a plurality of electrical cables to be connected to the electrical connectors, the terminating means comprising a busbar mounted on the patch panel body and a plurality of cable retaining clips arranged on the busbar each to receive a cable, the busbar being electrically isolated from the patch panel body, wherein the cable retaining clips are generally C-shaped and include a portion limiting movemement of a cable within the clip, and in that the terminating means includes a tab arranged on at least one side of each clip, the tab and the limiting portion of the clip co-operating to prevent movement of a cable within the clip along the direction of insertion or removal of the cable into or from the clip.

2. A patch panel according to Claim 1, wherein the tabs are arcuate.

3. A patch panel according to Claim 1 or 2, wherein the tabs are integral with the busbar.

4. A patch panel according to Claim 1 or 2, wherein the tabs are integral with the clips.

5. A patch panel according to any preceding claim, wherein one tab is arranged on each side of each clip.

6. A patch panel according to any preceding claim, wherein the cables are shielded cables and the clips and tabs abut the cable shields.

7. A patch panel according to any preceding claim, wherein the busbar means comprises a first busbar having a plurality of clips arranged thereon and associated tabs, and a second busbar separable from the first busbar and having a further plurality of clips arranged thereon and associated tabs.

8. A patch panel, substantially as herein described with reference to Figures 1 to 6 or 1, 2 and 5 or 1, 2 and 8 of the accompanying drawings.