Apparatus for Mounting Cables

This invention relate to telecommunications apparatus.

Network interface units constitute the demarcation between the customer's equipment and a telecommunications network. In buildings including multiple subscribers, the interface unit is typically mounted in a basement and includes an array of customer bridges, each bridge being coupled to an individual subscriber's line. The bridges are coupled to the network through an RJ11 jack and plug so that the customer can plug a working phone into the jack to determine if any problem lies in the customer or network side of the telecommunications system. Network interface units also typically include a building entrance protector portion which comprises a cable splice chamber and a protector field for providing surge protection for each customer. (For an example of a network interface unit, see U.S. Pat. No. 5,363,440 issued to Daoud).

In the splice chamber, it is usually desirable to provide strain relief for the incoming cable to prevent damage thereto. Standard brackets for holding the cable are effective, but expensive. It is also desirable to provide a grommet at the entry point of the cable in order to prevent the entry of pests or dust into the unit and prevent fire from escaping the splice chamber. A typical grommet comprises a compliant material with a series of perforations in the shape of concentric circles which can be cut out to define an opening according to the size of the cable. (See, U.S. Pat. No. 4,704,499 issued to Faust, and U.S. Pat. No. 4,988,834 issued to Birch.)

The invention is an apparatus for mounting a cable within an electronic enclosure having a splice chamber. The chamber includes a surface and an opening for receiving the cable. A recessed portion is formed in the surface in close proximity to the opening. A tie bar is formed across the recessed portion to form a gap therebetween, the gap being sufficient for insertion of a tie wrap or hose clamp which is capable of securing the cable. The opening may be covered by a grommet made of a compliant material with perforations defining non-concentric circles of increasing diameter in the material. The perforations also include a series of radial lines defining segments which, upon removal of at least one of said circles, form flaps in the material adjacent an aperture formed by the removal.

These and other features of the invention are delineated in detail in the description to follow. In the drawing:

FIG. 1 is a perspective view of a portion of a network interface unit in accordance with an embodiment of the invention;

FIG. 2 is a cross sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is a frontal view of a grommet which may be included in the network interface unit of FIG. 1.

It will be appreciated that, for purposes of illustration, these figures are not necessarily drawn to scale.

Referring now to the drawings, in which like reference numerals identify similar or identical elements, FIG. 1 illustrates a portion of a network interface unit, 10, which embodies the present invention. Specifically, FIG. 1 shows the bottom layer of a two-layer design, where the bottom layer includes a splice chamber, 11, a plug-in socket field, 12, for mounting protectors, e.g., 13, and a cross-connect field, 14. The array of protectors are electrically coupled to a bundle of wires, 15, which terminate in a splice connector, 16. The splice chamber, 11, includes at least one, and preferably two, ports, 17 and 18, for permitting ingress and egress of the telecommunications cable (not shown). (For more details of a network interface unit, see U.S. Pat. No. 5,363,440, cited above, and incorporated by reference herein.)

The splice chamber, 11, is defined by two side walls, 19 and 20, and a bottom surface, 21. Adjacent to each port, e.g., 17, is a recessed portion including an arcuate surface, 22, which is formed in the bottom surface, 21. Shaped across the recessed portion is a tie bar, 23, which forms a gap, G, with the arcuate surface, 22. The gap, G, is sufficient to allow a tie wrap, 25, to be threaded therethrough, i.e., a dimension typically in the range 12 mm to 58 mm. The tie bar, 23, and recessed portion are preferably formed integrally with the bottom surface, 21. The tie bar, 23, preferably includes a series of sharp projections, 24, which provide a gripping surface for the cable.

Thus, a cable entering or exiting the ports, 17 or 18, can be secured to the bottom surface, 21, by wrapping the tie wrap, 25, around the cable and tightening according to the diameter of the cable. The combination tie wrap and tie bar, 23, thus provides strain relief for the cable at minimal expense.

In accordance with a further feature of the invention, grommets, e.g., 30, are provided at the ports, e.g., 18. (In FIG. 1, only a single grommet is shown for purposes of illustration, but it will be realized that an identical grommet would be provided at port 17.) Reference is also made to FIG. 3 which illustrates the face of the grommet, 30, opposite to that shown in FIG. 1. The grommet includes a frame, 31, typically made of plastic, which supports a compliant material, 32, typically made of polyvinyl chloride. The frame, 31, and the compliant material, 32, are preferably the same material. However, the frame, 31, is made stiffer due to the material thickness and the confirguration of the struts, 50. The frame, 31, and compliant material, 32, are separated by a slot, 33. The grommets may be inserted by sliding the slot over a flange (see, e.g., 53, at port 17) at the entrance to the ports.

As best seen in FIG. 3, most of the compliant material, 32, includes a series of perforations in the shape of non-concentric circles, 34-39, having increasing diameters and a common portion near the bottom of the compliant material, 32. In a typical example, the smallest circle, 34, would have a diameter of 2.54 cm (1 inch) and each succeeding circle would have a diameter which increases by 0.64 cm (0.25 inches). Further perforations are provided in the form of radial lines, in this example, four such lines designated 40-43, which pass through the center of the smallest circle, 34, and extend essentially the full distance occupied by the circles, 34-39. Since four lines are provided in this example, it is convenient to have the lines at 45 degree angles to the adjacent lines. It will be appreciated that the angles and the number of lines can be varied, but preferably there should be at least two radial lines. The radial lines, 40-43, divide the circles into segments, e.g., 44 and 45.

When it is desired to introduce or exit a cable from the splice chamber, 11, the appropriate circular perforations can be cut to remove a number of circles defined thereby depending upon the diameter of the cable. For example, if the cable has a diameter greater than 3.2 cm (1.25 inches), but less than 3.8 cm (1.50 inches), the circles defined by perforations 34 and 35 will be removed to provide the appropriate sized hole. The portion of the radial lines, 40-43, between perforations 35 and 36 are then cut so that the segments, e.g., 44 and 45, defined by the radial lines can now act as flaps to plug the space which would have been present between the cable and the perforation 36. Thus, the presence of radial lines, 40-43, ensures an effective barrier against dust entering the splice chamber regardless of the size of the cable.