GB2409113A

GB2409113A - Cable gland

Info

Publication number: GB2409113A
Application number: GB0328462A
Authority: GB
Inventors: Edward Hand
Original assignee: Hubbell Ltd; Hawke Cable Glands Ltd
Current assignee: Hubbell Ltd; Hawke Cable Glands Ltd
Priority date: 2003-12-09
Filing date: 2003-12-09
Publication date: 2005-06-15
Also published as: GB0328462D0

Abstract

A cable gland 101 for armoured electrical cable 102 has inner and outer clamping members 109, 110 for clamping armour 103 therebetween. The outer clamping member 110 is expandable radially outwards on being urged towards a tapered surface 126 of the other clamping member 109 during assembly of the gland 101 to accommodate different thicknesses of cable armour 103. The outer clamping member may be a split ring or a coil.

Description

24091 1 3

CABLE GLAND

The present invention relates to cable glands for electric cable. The invention has particular application to armoured electric cable.

Cable glands for armoured cable are known in which the cable armour is clamped between a pair of clamping members, typically a spigot and a ring, having opposed taper surfaces to secure the cable in the assembled gland.

A problem with this design is the limitation on the thicknesses of cable armour that can be accommodated by one pair of clamping members.

One solution to this problem is to provide a set of rings having taper surfaces of different sizes for selection and fitment of the ring with the appropriate size taper surface. This results in a number of different assemblies to accommodate a range of thicknesses of cable armour with increased inventory and greater risk of fitting the wrong size of ring.

Another solution is to provide the ring with different size taper surfaces at opposite ends with the ring being reversible to present one of the taper surfaces to the spigot.

Alternatively or in addition to such reversible ring, the spigot may be provided with different size taper surfaces. This results in an increase in the overall length and cost of the gland.

Yet another solution is to provide an elongated spigot for extended travel of the ring but this suffers from the same problems of increased overall length and cost of the gland.

It is an object of the present invention to provide a cable gland which mitigates the problems and disadvantages of the known cable glands above discussed.

According to the present invention a cable gland for armoured electric cable comprises a clamp for securing cable armour, the clamp comprises first and second members arranged to be urged axially towards one another when the gland is tightened for clamping cable armour therebetween, the first member having a tapered surface and the second member being cooperable with the tapered surface when the members are urged together to expand radially outwards.

The main advantage of the invented gland is that one assembly can accommodate different thicknesses of cable armour without any significant increase in the overall length of the gland.

The second member preferably comprises a split ring arranged so that the ring can expand radially outwards, preferably without opening in the circumferential direction, and is advantageously made of any material which retains its memory when heat treated.

For example, the ring may comprise a coil having one or more turns of wire of circular or non-circular cross-section and preferably at least two turns with the ends of the coil arranged on opposite sides of a crossover between adjacent turns. In this way, the ring is reversible having substantially planar end faces for assembly either way round.

The tapered surface of the first member preferably has a frustoconical shape with the ring being urged axially towards the wider end causing the ring to expand to clamp the armour therebetween on tightening threadably engaged gland parts having respective through bores for passage of the cable.

The tapered surface may be integral with one of the gland parts which preferably has an external screw thread engaged by an internal screw thread of the other gland part. Alternatively, the tapered surface may be provided by a bushing axially located by engagement with said one gland part.

The other gland part preferably has an internal shoulder providing an abutment for the ring. The contacting surfaces of the ring and shoulder are preferably of similar radial or angular section to assist in armour clamping.

Other features, benefits and advantages of the invention will be apparent from the following description, given by way of example only, with reference to the accompanying drawings in which: FIGURE 1 is an exploded isometric view of the parts of a known cable gland; FIGURE 2 is a longitudinal section of one half of the cable gland depicted in Figure I partially assembled; FIGURE 3 is an exploded isometric view of the parts of a.cable gland embodying the invention; FIGURE 4 is a longitudinal section of one half of the cable gland depicted in Figure 3 partially assembled for comparison with Figure 2; FIGURES 5, 6 and 7 show various forms of the expandable clamping ring shown in Figures 3 and 4; and FIGURES 8,9 and 10 show alternative forms of the clamping ring shown in Figures S,6 and 7 respectively.

With reference to Figures 1 and 2 of the drawings, there is shown a cable gland 1 for terminating electric cable 2 having armour 3 disposed between an outer sheath 4 of electrically insulating material and an inner sheath 5 of electrically insulating material surrounding one or more conductor cores (not shown).

The armour 3 may be of any known type including wire, tape or strip of metal or non-metal as will be familiar to those skilled in this field.

The cable gland 1 comprises an entry adaptor 6, a sleeve nut 7 and a cap nut 8 defining a central passageway for the cable 2, and a clamp assembly 9, 10 for gripping the cable armour 3.

The entry adaptor 6 has a flatted flange 11 for engagement by a spanner or like tool to rotate the adaptor 6 during installation of the gland 1. One end of the adaptor 6 has a cylindrical bore 12 and a male thread 13 for threaded engagement with a threaded hole (not shown) in a wail of electrical equipment to which the cable 2 is to be connected. Alternatively, the thread 13 may extend through the hole to engage a retaining nut.

The other end of the entry adaptor 6 has a counterbore 14 terminating in a shoulder 15 for locating a seal 16 engageable with the inner sheath 4 of the cable and this end has a male thread 17 for threaded engagement with a female thread 18 at one end of the sleeve nut 7.

The female thread 18 terminates in an inclined shoulder 19 leading to 25a cylindrical bore 20 at the other end of the sleeve nut 7 and this end has a male thread 21 for threaded engagement with a female thread 22 at one end of the cap nut 8.

The sleeve nut 7 and cap nut 8 have hexagonal bodies for engagement by a spanner or like tool to rotate the sleeve nut 7 and cap nut 8 during assembly of the gland 1.

The female thread 22 terminates in an annular recess 23 for reception of an annular seal (not shown) engageable with the other sheath 3 of the cable and this seal is retained by an internal annular flange or lip 24 at the other end of cap nut 8.

The clamp assembly 9,10 comprises an inner bush 9 and a reversible outer ring 10 located in the central passageway between the entry adaptor 6 and the sleeve nut 7.

One end of the bush 9 is cylindrical complementary to the counterbore 14 of the adaptor 6 and terminates in an annular collar 25. This end is a sliding fit in the counterbore 14 so that, in the assembled gland, the seal 16 is compressed between the shoulder 15 and the bush 9 to engage the inner sheath 5 with the collar 25 locating against the end of the adaptor 5 to prevent over compression of the seal 16.

The other end of the bush 9 is of frusto-conical shape providing an external clamping surface 26 tapering from the collar 25 to the end of the bush 9 over which the armour 3 is located.

The ring 10 is provided at opposite ends with two internal clamping surfaces 27,28 of frusto-conical shape complementary to the external clamping surface 26 on the bush 9 so that the ring 10 is reversible to position either one of the clamping surfaces 27,28 opposite the clamping surface 26 with the other end seating against the shoulder 19 within the sleeve nut 7.

The ring 10 is urged axially relative to the bush 9 on tightening the sleeve nut 7 on the entry adaptor 6 to clamp the armour 3 in an annular clearance gap between the opposed clamping surfaces 26 and 27 or 28.

The clamping surfaces 27,28 are of different axial length so that the size of the clearance gap can be altered to accommodate different thicknesses and/or types of armour 3 by reversing the ring 10 and/or by adjusting the axial position of the ring in each orientation.

Thus, relatively thick wire armour may be clamped by the clamping surface 27 and relatively thin braid or tape armour may be clamped by the shorter clamping surface 28.

As will be appreciated this arrangement causes a variation in the threaded engagement of the sleeve nut 7 and adaptor 6 for different thicknesses of armour 3 with the result that the engaged threads 17,18 and/or the armour 3 may be damaged by overtightening the sleeve nut 7.

To facilitate correct assembly of the gland for a given type of armour 3, a visual indication of the orientation of the ring 10 is provided by an external annular groove 29.

To assist clamping the armour 3 to meet the pull-out requirements for a particular application, the clamping surface 26 is provided with a series of annular grooves 30 or other suitable formations. Alternatively, the clamping surface 26 may be smooth.

Referring now to Figures 3 to 10 of the accompanying drawings, embodiments of a cable gland according to the present invention are shown in which like reference numerals in the series 100 are used to indicate parts corresponding to the gland shown in Figures I and 2.

As best shown in Figures 3 and 4, the invented cable gland 101 comprises an entry adaptor 106, a sleeve nut 107 and a cap nut 108 defining a ccutral passageway for the cable 102, and a clamp assembly 109,110 for gripping the cable armour 103.

The clamp assembly lO9,110 comprises an inner bush 109 providing a tapered surface 126 and an outer ring 110 formed by a coil of wire of circular cross-section (Figure 5) or non-circular cross-section (Figures 6 and 7) which retains its memory when heat treated.

As shown, the coil comprises two substantially complete turns with the ends of the wire arranged on opposite sides of a cross-over between the turns. In this way, both sides of the ring 110 are substantially planar with external corners of a known radial or angular section conforming to a similar but not necessarily the same angle as the shoulder 119 within the sleeve nut 107. As a result, the ring l lO is reversible and can be fitted either way round.

The coil provides the ring llO with a split which enables the ring llO to expand radially outwards when the sleeve nut 107 is tightened on the adaptor 106 during assembly al the gland 101 to force the ring 110 up the taper of the clamping surface 126 without opening the ring l l O. As a result, the armour 103 is gripped between the clamping surface 126 and the ring l l O with sufficient tension to meet the pullout requirements for a given 1 5 application.

Furthermore, when pullout forces are exerted, the engagement of the external peripheral corners of the ring 110 with the angled shoulder 119 assists in applying pressure to the armour 103 to meet the pullout requirements.

By this invented feature of the split ring 110, the clamp assembly 109, 110 can adjust automatically to the thickness of the arrnour 103 during assembly of the gland 101.

As a result, the sleeve nut 107 can be fully tightened on the adaptor 106 for different thicknesses of armour 103 without damage to the threads 117, 118 or armour 103.

This enables the length of the sleeve nut 107 to be reduced as shown by a comparison of Figures 2 and 4.

Figures 8 to 10 show alternative split rings 110 formed by coils having four substantially complete turns of wire of similar section to that shown in Figures S to 7 arranged so that the rings 110 are reversible as above described.

It will be understood that the invention is not limited to the embodiments above- described. For example, the split ring may be formed from one or more coils of wire of any desired cross-section.

It will further be understood that the invention is not limited to such construction of the split ring and that the benefits and advantages of the invention may be obtained with other types and constructions of split ring which allow the ring to expand radially outwards by co-operation with the taper of the opposed clamping surface.

It will also be understood that the invention is not limited to the cable gland above described but is applicable equally to other types and constructions of cable gland as

will be familiar to those skilled in this field.

Claims

Claims: 1. A cable gland for armoured electric cable comprises a clamp for

securing cable armour, the clamp comprises first and second members arranged to be urged axially towards one another when the gland is tightened for clamping cable armour therebetween, the first member having a tapered surface and the second member being co-operable with the tapered surface when the members are urged together to expand radially outwards.
2. A cable gland according to Claim I wherein the second member comprises a split ring.
3. A cable gland according to Claim 2 wherein the ring is split to allow the ring to expand radially outwards without opening the ring in the circumferential 1 5 direction.
4. A cable gland according to Claim 2 or Claim 3 wherein the ring comprises a coil having one or more turns.
5. A cable gland according to Claim 4 wherein the coil has at least two turns with the ends of the coil arranged on opposite sides of a crossover between adjacent turns.
6. A cable gland according to Claim 4 or Claim 5 wherein the coil is made of a material which retains its memory when heat treated.
7. A cable gland according to any one of Claims 4 to 6 wherein the coil comprises wire of circular eross-seetion.
8. A cable gland according to any one of Claims 4 to 6 wherein the coil comprises wire of non-circular cross-section.
9. A cable gland according to any one of Claims 2 to 8 wherein the ring is reversible.
10. A cable gland according to any one of Claims 2 to 9 wherein the tapered surface of the first member is of frusto-conical shape surrounded by the ring to clamp the armour therebetween.
I 1. A cable gland according to Claim 10 wherein the ring is urged axially towards the wider end tapered surface causing the ring to expand to clamp the armour therebetween on tightening threadaby engaged gland parts having respective through bores for passage of the cable.
1 2. A cable gland according to Claim 11 wherein the tapered surface is associated with one of the threadably engaged gland parts and the ring is engaged by the other gland part.
13. A cable gland according to Claim 12 wherein the tapered surface is integral with said one gland part.
14. A cable gland according to Claim 12 wherein the tapered surface is provided by a bushing axially located by engagement with said one gland 5 part.
15. A cable gland according to any one of Claims 12 to 14 wherein said one gland part has an external screw thread engaged by an internal screw thread of the other gland part.
16. A cable gland according to any one of Claims 12 to 15 wherein the other gland part has with an internal shoulder providing an abutment for the ring.
17. A cable gland according to Claim 16 wherein contacting surfaces of the ring and shoulder are of similar radial or angular section.
18. A cable gland for armoured electrical cable comprises inner and outer clamping members wherein the outer clamping member is caused to expand radially outwards during assembly of the gland to clamp cable armour between the clamping 1 0 members.
l 9. A cable gland for armoured electric cable substantially as hereinbefore described with reference to Figures 3 to 7 ol the accompanying drawings.
20. A cable gland for armoured electric cable substantially as hereinbefore described with reference to Figures 3 to 7 of the accompanying drawings as modified by Figures 8 to l O of the accompanying drawings.