GB2323977A - Cable glands - Google Patents

Abstract

A cable gland comprises an annular body 1 with means for securing an electric cable end (not shown) passing through the bore of the body is characterised by a flange 2 at one end of the body and mounting means 6 for securing the body in an aperture in the wall 3 of apparatus to which the cable is to be connected with the said flange inside the wall and the said mounting means outside. The flange may be no thicker than the backnut that would be used to fix an equivalent size of conventional gland (having a threaded spigot projecting through the aperture from the outside) and may be thinner, so reducing projection of the gland inside the apparatus wall. The annular body may be the main body of the gland without requiring a larger size of aperture, and thereby save material.

Description

Cable Glands This invention relates to electric cable glands for use in terminating cables into connecting boxes or other apparatus having a wall with an aperture for receiving the gland. It includes termination methods and terminations in which the glands are used.

In current practice, cable glands (whether of metal, plastics material or a combination) are mounted in circular apertures by means of a threaded annular spigot projecting from one end of the gland to pass inwardly through the mounting aperture and a mating threaded backnut on the inside of the wall. This implies that the gland must project into the apparatus at least the thickness of the backnut (and typically more than that, as the wall thickness may vary and the spigot length, generally speaking, does not). It also requires access to the inside of the apparatus for the placing and tightening of the backnut, usually requiring one spanner inside the apparatus and another outside. This can often be difficult and can require a considerable time to complete satisfactorily in some site conditions.

In accordance with the invention, a cable gland comprises an annular body with means for securing an electric cable end passing though the bore of the body and is characterised by a flange at one end of the body and mounting means for securing the body in an aperture in the wall of apparatus to which the cable is to be connected with the said flange inside the wall and the said mounting means outside.

The flange need be no thicker than the backnut that would be used to fix an equivalent size of conventional gland and may often be appreciably thinner, so reducing projection of the gland inside the apparatus wall. Nor need it be larger in diameter; in some cases it may be substantially smaller.

We have found that in many cases it is possible for the annular body to be the main body of the gland without requiring a larger size of aperture, and in these cases the saving in material (and so weight and cost) can be considerable.

In cases where this is not possible (and enlargement of the aperture is not possible or not desired) the annular member may be an auxiliary member connected to a main body member outside the apparatus wall. In such cases, the main body member may if desired be the mounting means for the annular member.

The mounting means may in general be a screw-threaded member (a backnut) engaging a mating thread on the annular member, giving all the strength and security expected of a conventional cable gland, but other mounting means may be used. In particular, when the annular member is the main body of the gland the mounting means does not contribute to the tensile strength of the assembly (that is, its resistance to pulling on the cable) and may be of relatively low strength and/or rigidity.

For example, the mounting means may consist of an axially compressible ring (such as a metal spring or a rubber ring) trapped between the enclosure wall and a gland nut or other functional member of the gland.

When the mounting means is in screw-threaded relation with the annular member, the flange will usually need to be shaped for engagement with a spanner or other tool or means to facilitate screwing action. For instance it may be hexagonal (or at least have a pair of flats) for engagement with a conventional spanner, it may have at least one edge that will engage the side of a mounting box or the part of another gland projecting inside a mounting box so as to resist rotation, or it may have one or more notches into which a screwdriver or other tool can be inserted to resist rotation. If neither the mounting means nor any other function of the gland requires relative rotation of the annular member, the flange can be circular to minimise material.

The components of the glands in accordance with the invention (excluding any sealing rings) may be of metal or suitable plastics material, or a combination, as appropriate to the requirements of the particular installation, and the glands may be provided with any of the facilities (such as inner and/or outer seals, grips for any class of armour or concentric conductor, and earthing facilities).

The invention will be further described, by way of example, with reference to the accompanying drawings in which each of figures 1-7 is a partly sectioned "exploded view of a different form of gland in accordance with the invention, showing the parts separated but in order for assembly, and figures is an end-view of an alternative component usable in modification of some forms of gland.

The gland of Figure 1 is an "indoor" gland for terminating a cable having a single layer of armour wires without providing any fluid-tight seal. The annular member 1 is the main body of the gland and has a flange 2 for engaging the interior of an enclosure wall 3, an external screw thread 4 and an armour cone 5. The mounting means for the annular member is a conventional threaded nut 6 engaging the thread 4 and optionally trapping an earthing tag 7; a rubber sealing washer can be interposed on either side of the wall 3 if required. To enable the nut to be tightened using a pair of spanners, the flange 2 is hexagonal. The remaining gland member is a gland nut 8 having a frustoconical surface 9 designed to grip the ends of armour wires splayed out onto the armour cone 5 when the gland nut is screwed onto the thread 4.

The design of Figure 2 is similar but the nut 6 is replaced by an axially compressible flat-wire spring 10 which does not engage the thread 4 but is urged towards the enclosure wall 3 by engagement with the gland nut 8 when that is screwed up.

The gland of Figure 3 is for unarmoured cable and the annular member 11 (which is again the main gland member) instead of having an armour cone has a threaded counterbore 12 which receives a resilient sealing ring 13, a skid washer 14 and a male gland nut 15 by which the sealing ring is compressed to secure the cable. As in Figure 1, the mounting means is a threaded nut 6 engaging the external thread 4.

The gland of Figure 4 is similar to that of Figure 3, except that the nut 16 is a more conventional female gland nut and the sealing ring 13 bears on the end face 11 of the body 11, obviating the need for a counterbore. This reduces manufacturing operations but has the disadvantge that the backnut 6 has to be rotated many more times to reach its working position on the thread 4.

Figure 5 shows a modification of the gland of Figure 1 suitable for use when it is not possible for the gland body 18 to be small enough to enter the aperture in the enclosure 3 from the inside (either because its main diameter must be larger than the diameter of the aperture or because there is insufficient longitudinal clearance inside the enclosure) ; an auxiliary male nut 19 is inserted from inside the enclosure and screwed into a threaded counterbore 20 in the body 18.

The gland of Figure 6 may be considered a modification of that of Figure 1 and provides, in a fairly conventional way, for the adddition of an "outer" seal onto a cable sheath enclosing the armour wires. The gland nut 8(in figure 1) is replaced by a barrel member 21 and a separate armour ring 22, the barrel member having an external thread 23 which receives a gland nut 24 that encloses and compresses a sealing ring 25, with which the usual skid washer 26 is used.

The gland of Figure 7 is similar to that of Figure 6 but provides additionally for an "inner" seal to a bedding layer (or inner sheath) inside the armour wire layer of the cable.

The armour cone is separated from the body 1 and forms a separate component 27, and an additional sealing ring 28 (with a skid washer (not shown) if required) is compressed between the component 27 and the body 1; as shown, the body may be provided with a tapered (or plain) counterbore to receive the sealing ring 28.

Figure 8 shows an altenative profile for the nut 6 which provides both flats 29 for engagement by a spanner and grooves for engagement by a screwdriver or similar tool. This profile is also suitable for use on any of the flanges or other parts shown as being hexagonal in the other figures.

Claims (8)

1 A cable gland comprising an annular body with means for securing an electric cable end passing though the bore of the body characterised by a flange at one end of the body and mounting means for securing the body in an aperture in the wall of apparatus to which the cable is to be connected with the said flange inside the wall and the said mounting means outside.

2 A cable gland as claimed in claim 1 in which the said annular member is the main body of the gland.

3 A cable gland as claimed in claim 1 in which the annular member is an auxiliary member connected to a main body member outside the apparatus wall.

4 A cable gland as claimed in claim 3 in which the main body member of the gland constitutes the said mounting means for the annular member.

5 A cable gland as claimed in any one of claims 1-4 in which the said mounting means is a screw-threaded member engaging a mating thread on the annular member.

6 A cable gland as claimed in any one of claims 1-4 in which the said mounting means consists of an axially compressible ring trapped between the enclosure wall and a gland nut or other functional member of the gland.

7 A cable gland substantially as described with reference to any one figure of the drawings.

8 A cable termination comprising a cable end entering through an aperture in a housing of apparatus to which it is electrically connected and secured in that aperture by a cable gland as claimed in any one of claims 1-7, the said annular member of the gland having its flange inside the said housing.