GB2241388A - Shroud for a cable gland - Google Patents

Abstract

A shroud 10 located on the cable gland 12 for attaching a cable 14 to an apparatus (not shown) comprises a sleeve 24 having a first end 26 and a second end 28. The first end 26 includes three co-axial sealing rings 30, 32 and 34 which are designed to grip on to the outer sheath of the cable 14. The second end 28 of the sleeve 24 is designed to seal on to the apparatus to which the cable gland 12 is attached. A section 29 of the sleeve 24 is internally hexagonally shaped to conform to the external hexagonal shape of a section 22 of the body 18 of the cable gland 12 so that the section 29 of the sleeve 24 holds or grips on to the body 18 in use. There is also provided a sealing ring 36 which fits into a groove 38 on the cable gland body 18 to provide additional holding and sealing effect. The shroud 10 is designed to protect the cable gland 12 against attack by corrosive agents. <IMAGE>

Description

"SHROUD FOR A CABLE GLAND" This invention relates to a shroud for a cable gland for protecting the cable gland and/or a cable armouring against the adverse effects of corrosive liquids, vapours or atmospheres.

Cable glands may be made from a variety of metallic and non-metallic materials.

Typically however cable glands are manufactured from brass because of its superior machining characteristics or from a rigid plastics material because of its production mouldability. Cable glands for use with armoured cable are usually metallic as they are frequently required to be electrically conductive in order to ensure electrical continuity between the cable armouring and the apparatus to which the cable is attached. For this reason, it is important that neither the cable gland nor the cable armouring should corrode during its installed lifetime. Such corrosion is known to interfere with the electrical continuity between the cable armouring and apparatus to which it attaches by means of a cable gland.

One method of protecting cable armouring when fitted to a cable gland is to provide the cable gland with an elastomeric sealing bush or outer seal. When a cable gland nut is screwed or otherwise attached to a cable gland body, the aforementioned seal is compressed and forced to seal against the outer sheath of the cable at its point of entry into the cable gland. This type of arrangement does not however protect the cable gland itself from possible attack by corrosive agents. Furthermore, such an outer seal only prevents the ingress of corrosive agents by the rear (cable entry side) of the cable gland.

Most cable glands rely on screw thread action to grip the cable armouring and unless further measures are taken, such screw threads are not sealed against ingress of corrosive agents, merely by the provision of an outer seal.

An alternative method of protection requires the employment of an elastomeric shroud which covers the entire cable gland and elastomerically grips onto the exterior of the cable gland and the outer sheath of the cable. Such an arrangement effectively protects both the cable armouring and the cable gland body from the harmful effects of corrosive agents. Shrouds are typically made of synthetic rubber and are flexible so that they may seal on to a variety of cable sheath diameters and cable gland body sizes.

One type of elastomeric shroud is that disclosed in South African Patent No 80/6478.

This shroud comprises a tapered sleeve having one end which is a tight fit around the cable, a belled end with a projection or projections to engage with a formation or formations on a gland part to hold the shroud in position, and a cylindrical extension to the belled part projecting from the formation or formations to such an extent that when the shroud is installed, the extension is compressed between the formation or formations and the apparatus to which the gland is attached.

One disadvantage of elastomeric shrouds is that under the influence of prolonged exposure to weather, ultraviolet light and certain chemicals, the highly stressed elastomeric material tends to deteriorate and crack. Such cracks typically occur around the periphery of the shroud skirt which is in tension around the outer sheath of the cable.

Another method of protection relies on encapsulating the metallic parts of the cable gland in a chemically resistant non-metallic polymer. Such a cable gland is described in SA Patent No 73/3028. Further refinements of this concept employ encapsulation of the cable gland parts together with an outer seal plus further elastomeric seals, which seal all exposed threads and thereby prevent the ingress of corrosive agents. Such a cable gland is described in SA Patent No 87/0687. These cable glands suffer from the disadvantage that they are expensive to make and rely to an extent on non-metallic polymers for strength. They also rely on stressed elastomeric components for sealing and like the shrouds, these elastomeric components are subject to deterioration with age and environmental exposure.

According to the invention there is provided a shroud for a cable gland for attaching a cable to an apparatus, the cable gland comprising a nut and a body, the shroud comprising a sleeve having a first end and a second end, the first end including one or more internal sealing rings adapted to provide a seal on to the cable in use, and holding means inside the sleeve intermediate the first end and the second end adapted to cooperate with the cable gland to hold the shroud on the cable gland in use, the sleeve comprising an elastomeric material.

The apparatus to which the cable gland to be covered by the shroud of the invention is attached, may be an item of electrical equipment or may be a conventional cable termination box or a so-called integral cable gland.

Preferably, the second end of the sleeve is adapted to seal on to the apparatus in use.

The holding means of the shroud may comprise the internal shape of a section of the sleeve which conforms to the external shape of a section of the cable gland body so that the sleeve grips on to the cable gland body in use. For example, generally a cable gland body includes a section which has externally a hexagonal axial cross-sectional shape, i.e.

its shape at right angles to the axis of the bore of the body is hexagonal, in which case a section of the sleeve is shaped to be hexagonal in axial cross-section to conform to the hexagonal axial cross-sectional external shape of the section of the cable gland body.

Alternatively, the holding means may comprise an annular protrusion adapted to fit into a groove on the cable gland in use. Further, alternatively, the holding means may comprise the combination of the internal shape of a section of the sleeve which conforms to the external shape of a section of the cable gland body as well as an annular protrusion adapted to fit into a groove on the cable gland in use.

Preferably, the first end of the shroud includes two or more internal sealing rings adapted to provide a labyrinth seal on to the cable in use.

More preferably, the first end of the shroud includes three co-axial internal sealing rings to provide the labyrinth seal on the cable in use.

The shroud may include a casing of a suitable material, preferably a rigid plastics material or stainless steel, encircling the sleeve further to protect the sleeve in use.

The sleeve of the shroud is made of any suitable elastomeric material such as a suitable natural or synthetic rubber or a suitable plastics material.

Figure 1 is a partially sectioned side view of a shroud of the invention located on a cable gland and cable assembly; Figure 2 is a cross-sectional view along the line AA in Figure 1; Figure 3 is a partially sectioned side view of another shroud according to the invention; Figure 4 is a cross-sectional view along the line BB in Figure 3; and Figure 5 is a partially sectioned side view of another shroud of the invention.

Referring to Figures 1 and 2 there is shown a shroud 10 located on a cable gland 12 for attaching a cable 14 to an apparatus (not shown).

The cable gland 12 comprises an externally threaded compression nut 16, a complementarily internally threaded body 18 and an externally threaded nipple 20.

Located between the nut 16 and the body 18, and not shown, is means for gripping the cable armouring of the cable 14. The body 18 includes a section 22 which is hexagonal in external shape, in other words this section has a hexagonal cross-sectional shape at right angles to the axis of the bore of the body 18.

The shroud 10 comprises a sleeve 24 having a first end 26 and a second end 28. The first end 26 includes three co-axial sealing rings 30, 32 and 34 which are designed to seal on to the outer sheath of the cable 14. By utilising three sealing rings 30, 32, 34 a labyrinth effect is achieved whereby the concentration and effect of any corrosive agent present in the vicinity of the cable gland 12 is reduced as it progresses along the bore of the shroud 10 should a leak in the seal occur. The second end 28 of the sleeve 24 is designed to seal on to the apparatus to which the cable gland 12 is attached. A section 29 of the sleeve 24 is internally hexagonally shaped to conform to the external hexagonal shape of the section 22 of the body 18 so that the section 29 of the sleeve 24 holds or grips on to the body 18 in use. The internal shape of the section 29 of the sleeve 24 is best illustrated in Figure 2. Located adjacent the section 29 is an annular protrusion or sealing ring 36 which fits in use into a groove 38 on the body 18, to provide an additional holding and sealing effect.

The shroud 10 may be made of any suitable elastomeric material such as a natural or synthetic rubber or a plastics material. The elastomeric material may include additives to render it resistant to corrosive attack. Suitable elastomeric materials include ethylenepropylene terpolymers, Hypalon (a product of Du Pont) and neoprene.

As the shroud 10 is made of elastomeric material, the annular sealing rings 30, 32 and 34 place the elastomeric material into compression and thereby reduce the incidence of tensile stress related to cracking associated with elastomeric shrouds.

The shroud 10 is designed to protect both the cable gland 12 and the cable armouring of the cable 14 against attack by corrosive agents.

Referring to Figure 3 there is shown a shroud 10A in which like parts to the shroud 10 are marked with the same numbers. The section 42 of the shroud 10A which corresponds to the section 29 of the shroud 10 is not shaped to conform to the external hexagonal shape of a section of a cable gland body, as is clearly shown in Figure 4 where the external hexagonal shape of the section of the cable gland body is shown in dotted outline. Thus, the shroud 10A is held on a cable gland in use solely by the sealing ring 36 located in a groove on the cable gland. The shroud 10A includes a casing 40 encircling the sleeve 24 to protect the sleeve 24 in use. The casing 40 may be made of any suitable material such as stainless steel or a suitable rigid plastics material.The shroud 10A functions in exactly the same manner as the shroud 10 to protect a cable gland and cable against corrosive agents, in use.

Referring to Figure 5 there is shown a shroud 10B in which like parts to the shroud 10 and 10A are marked with the same numbers. The shroud 10B includes a second end 28B which is an elastomeric sealing ring attached to the sleeve 24 of the shroud 10B to provide a seal against an apparatus in use. The casing 40 of the shroud 10B includes an extension 44 to protect the first end 26 of the sleeve 24 in use.

The outer wall of the sleeve of the shroud of the invention may be shaped to enhance the appearance of the shroud or may be shaped for functional reasons.

The provision of an internal sealing ring or rings in the shroud of the invention provides an effective means of sealing the cable in use again to prevent the ingress of corrosive agents into the cable gland and the cable armouring of the cable.

In addition, the thickness of the sleeve of the shroud makes the shroud easier to fit in use and renders the shroud less vunerable to degradation.

It is to be noted that the shroud of the invention, while of particular use with cable glands for armoured cable, may also be used with cable glands for unarmoured cables.

Claims (10)

1.

A shroud (10, 10A, 10B) for a cable gland (12) for attaching a cable (14) to an apparatus, the cable gland (12) comprising a nut (16) and a body (18), comprises a sleeve (24) having a first end (26) and a second end (28, 28B), the first end (26) including one or more internal sealing rings (30, 32, 34) adapted to provide a seal on to the cable (14) in use, and holding means (29, 36) inside the sleeve (24) intermediate the first end (26) and the second end (28, 28B) adapted to co-operate with the cable gland (12) to hold the shroud (10, 10A, 10B) on the cable gland (12) in use, the sleeve (24) comprising an elastomeric material.

2.

A shroud (10, 10A, 10B) according to claim 1 wherein the first end (26) of the sleeve (24) includes two or more internal sealing rings (30, 32, 34) adapted to provide a labyrinth seal on to the cable (14) in use.

3.

A shroud (10, 10A, 10B) according to claim 1 or claim 2 wherein the second end (28, 28B) of the sleeve (24) is adapted to seal on to the apparatus in use.

4.

A shroud (10, 10A, 10B) according to any one of claims 1 to 3 wherein the holding means (29) comprises the internal shape of a section of the sleeve (24) which conforms to the external shape of a section of a cable gland body (18) so that the sleeve (24) grips on to the body (18) in use.

5.

A shroud (10, 10A, 10B) according to claim 4 wherein the internal shape of a section (29) of the sleeve is hexagonal in axial cross-section to conform to the hexagonal axial cross-sectional external shape of a section of the cable gland body (18).

6.

A shroud (10, 10A, 10B) according to any one of claims 1 to 3 wherein the holding means (36) comprises an annular protrusion adapted to fit into a groove (38) on the cable gland (12) in use.

7.

A shroud (10, 10A, 10B) according to any one of claims 1 to 3 wherein the holding means comprises a combination of the internal shape of a section (29) of the sleeve (24) which conforms to the external shape of a section of the cable gland body (18) so that the sleeve (24) grips on to the body (18) in use and an annular protrusion (36) adapted to fit into a groove (38) on the cable gland (12) in use.

8.

A shroud (10, 10A, 10B) according to any of claims 1 to 7 wherein the first end (26) of the sleeve includes three co-axial internal sealing rings (30, 32, 34).

9.

A shroud (10, 10A, 10B) according to any one of claims 1 to 8 which includes a casing (40) of a suitable protective material encircling the sleeve (24).

10.

A shroud (10, 10A, 10B) for a cable gland (12) substantially as herein described with reference to Figures 1 and 2 or Figures 3 and 4 or Figure 5 of the accompanying drawings.