GB2224894A

GB2224894A - Corrosion-protected electrical cable gland

Info

Publication number: GB2224894A
Application number: GB8920926A
Authority: GB
Inventors: Franz Lackinger
Original assignee: WESTWARD INVESTMENTS; Westward Investments Ltd
Current assignee: WESTWARD INVESTMENTS; Westward Investments Ltd
Priority date: 1988-09-15
Filing date: 1989-09-15
Publication date: 1990-05-16
Anticipated expiration: 2009-09-15
Also published as: AU4141289A; GB8920926D0; GB2224894B

Abstract

An electrical cable gland (1) and protective sleeve (10) therefor are provided. The cable gland has formations, generally screw-threads (8), on its outer surface for co-operation with complementary formations (9) on the protective sleeve for use to urge the sleeve axially with respect to the cable gland. The protective sleeve is substantially rigid and made of corrosion resistant material such as glass fibre reinforced plastics. It has a seal (15) at one end for sealing to the outer sheath (16) of an armoured cable by means of a nut (13) and a second seal (18) at its other end for sealing onto the surface (20) of a termination box or the like around the position where the gland is secured thereto in use. Said second seal is rendered operative by urging the sleeve axially relative to the cable gland by means of said co-operating formations (8, 9). <IMAGE>

Description

"ELECTRICAL CABLE GLAND" FIELD OF THE INVENTION This invention relates to electrical cable glands and, more particularly, to electrical cable glands adapted for co-operation with a protective sleeve for inhibiting the ingress of corrosive materials to an electrical cable gland. The invention also relates to protective sleeves adapted to serve such a purpose.

BACKGROUND TO THE INVENTION Electrical cable glands, particularly those adapted for use on armoured cables and embodying an armour anchor arrangement, of necessity need to embody metallic parts, at least for the purpose of establishing electrical continuity between the armour wires, which serve as an earth connection, and electrically conductive zones of an electrical termination box box or the like. It is well known that such metallic parts of an electrical cable gland are susceptible to corrosion and, accordingly, when used in corrosive atmospheres, the metallic parts should be protected against attack by such corrosive atmosphere.

The use of elastomeric shrouds has been extensively employed but has, as far as applicant is concerned, not been adequately effective, at least on a reasonably long term basis. The reason for this is that the shrouds generally perish over an extended period.

With a view to improving the situation applicant has devised, and is currently marketing, electrical cable glands in which the metallic parts carry, generally moulded on to the outside thereof, a corrosion resistant, fibre reinforced synthetic plastics material.

However in such an arrangement, certain co-operating threads are of the reinforced plastic material and for certain applications where above average mechanical strengths are required, such plastic material may not stand up to the mechanical specifications prescribed. One such application is to electrical cable glands of the so-called "flame-proof" category as provided for in various standard specifications, for example that of the United Kingdom.

To CeSe this, a cable gland, and a protective sleeve therefor, is provided in which effective protection is provided without any unacceptable mechanical weakening of an electrical cable gland being necessary.

SUMMARY OF THE INVENTION In accordance with one aspect of this invention there is provided an electrical cable gland assembly comprising a cable gland and a substantially rigid, corrosion resistant protective sleeve therefor, the cable gland having connection means at one end thereof for connecting same to an electrical termination box or the like, the sleeve substantially enclosing the cable gland and having first sealing means at its end opposite the connection means adapted for co-operation with the outer sheath of an electrical cable in use, second sealing means at its end corresponding to the connection means, and co-operating formations on the cable gland and sleeve for urging the sleeve axially towards the end corresponding to the connection means to effectively seal said second sealing means to a surface surrounding the connection means in use.

Further features of the invention provide for the cable gland to be made of metal and to embody both an armour anchor and an inner compression seal for sealing the gland onto the outer surface of the inner sheath of an armoured cable, in use; for the said first sealing means to be an elastomeric compression seal operatively located between the associated end face of the sleeve and an inwardly directed flange of a union nut having screw-threads co-operating with complementary screw-threads on the outer surface of the sleeve; for the said co-operating formations on the cable gland and sleeve to be co-operating screw-threads; and for the said second sealing means associated with the sleeve to be an elastomeric ring or the like carried at the appropriate end of the sleeve.

It is an important feature that the protective sleeve and, where same is present, the union nut for the compression seal defining said first sealing means, be made of corrosion resistant fibre, preferably glass fibre, reinforced, filled synthetic resin material of a type commonly referred to as "dough" moulding composition.

It will be understood that it is the intention that protective sleeves and cable glands of the type defined above will be sold separately in the marketplace and, accordingly, are intended to be individually included within the scope of this invention separately and apart from each other.

Accordingly, a second aspect of this invention, provides a protective sleeve made of corrosion resistant material and having first sealing means at one end thereof, second sealing means at the opposite end thereof and formations for co-operation with complementary formations on a cable gland for urging it axially with respect thereto.

The inentkn Ian, still further provide an electrical cable gland having formations on the outside thereof for co-operation with complementary formations on a protective sleeve, the formations being such that they serve to enable a protective sleeve to be urged axially with respect to the cable gland, in use.

In order that the invention may be more fully understood one embodiment thereof will now be described with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a partly sectioned longitudinal elevation of a cable gland and protective sleeve according to this invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWING In the embodiment of the invention illustrated in the drawing a cable gland, generally indicated by the numeral 1, is made in substantiall conventional manner of metal component parts having their required mechanical strength for the particular purpose for which the cable gland is designed.

The cable gland is of a type having a connection spigot 2 at one end thereof for co-operation with the screw-threaded access aperture 3 in an electrical termination box 4 or the like.

The cable gland has an armour anchor 5 and an inner compression seal 6 located in its axial passage 7.

The only additional feature of the cable gland, over and above a conventional cable gland, is the provision of an external screw-thread 8 on its outer surface towards the end thereof remote from the connection spigot 2.

This external screw-thread 8 co-operates with an internal screw-thread 9 on the inner surface of a protective sleeve 10 which, in the operative position encloses the entire cable gland as illustrated.

The sleeve reduces in diameter at its end remote from the termination box, as indicated by numeral 11, and ends in a smaller diameter tubular section 12 having an external screw-thread co-operating with the inner screw-thread of a union nut 13, the flange 14 of which is arranged to compress an elastomeric compression seal 15 between it and the end face of the reduced diameter tubular section 12. This compression seal defines the first sealing means referred to above and is so axially located that it co-operates, in use, with the outer sheath 16 of an armoured electrical cable 17 being terminated.

The other end 18 of the sleeve 10 has a seal 19 associated therewith and adapted to seal the end face of the sleeve onto the outer surface 20 of the electrical termination box in a path encircling the connector spigot.

It will be understood that the latter seal defines the said second sealing means referred to above and these sealing means are urged into firm sealing contact by rotating the sleeve relative to the cable gland so that the co-operating screw-threads 8 and 9 urge the sleeve axially towards the termination box to cause compression, and accordingly effective sealing of the second sealing means.

In the present embodiment of the invention the sleeve and union nut, which must in any event be made of corrosion resistant material, are made of a "dough" moulding compound composed of a thermosetting synthetic resin reinforced with glass fibres and filled with a suitable non-inflammable filler material. Whilst the mechanical strength of such a compound is insufficient for certain applications for manufacture of the outer surface portions of the cable gland itself, it is strong enough for the purposes of an arrangement according to this invention.

It will be understood that, in use, a cable 17 is secured to a termination box in the usual way with the inner seal 6 automatically becoming compressed and sealing onto the outer surface of the inner sheath 21 of the electrical cable 17 as the armour anchor is tightened on the armour wires 22. The sleeve is then installed in position, having previously been threaded onto the cable, and is rotated to urge the sealing means 19 in at the end thereof adjacent the termination box into firm sealing contact with the surface of the latter. The union nut 13 is then tightened to effectively cause the compression seal 15 to effectively engage the outer surface of the outer sheath 16.

Numerous variations may be made to the above described embodiment of the invention without departing from the scope hereof. In particular the nature of the sealing means at the two ends of the sleeve could be varied widely and, in addition, the co-operating formations provided on the cable gland and protective sleeve could be varied as may be required. Also the material of manufacture of the protective sleeve could be any suitable material which is corrosion resistant and the cable gland could be of any type other than that described above.

Claims

1. An electrical cable gland assembly comprising a cable gland and a substantially rigid, corrosion resistant protective sleeve therefor, the cable gland having connection means at one end thereof for connecting same to an electrical termination box or the like, the sleeve substantially enclosing the cable gland and having first sealing means at its end opposite the connection means adapted for co-operation with the outer sheath of an electrical cable in use, second sealing means at its end corresponding to the connection means, and co-operating formations on the cable gland and sleeve for urging the sleeve axially towards the end corresponding to the connection means to effectively seal said second sealing means to a surface surrounding the connection means in use.

2. An electrical cable gland assembly as claimed in claim 1 in which the cable gland is made of metal.

3. An electrical cable gland assembly as claimed in either of claims 1 or 2 in which the cable gland embodies an armour anchor and an inner compression seal for sealing the gland onto the outer surface of the inner sheath of an armoured cable.

4. An electrical cable gland assembly as claimed in any one of the preceding claims in which said first sealing means is a compression seal for sealing the sheath onto the outer surface of the outer sheath of an armoured cable.

5. An electrical cable gland assembly as claimed in claim 4 in which the said compression seal comprises an elastomeric compression seal operatively located between the associated end face of the sleeve and an inwardly directed flange of a corrosion resistant union nut having screw-threads co-operating with complementary screw-threads on the outer surface of the sleeve.

6. An electrical cable gland assembly as claimed in any one of the preceding claims in which the said co-operating formations on the cable gland and sleeve are co-operating screw-threads.

7. An electrical cable gland assembly as claimed in any one of the preceding claims in which the said second sealing means comprises an elastomeric ring or the like carried at the end of the sleeve corresponding to the connection means of the cable gland.

8. A protective sleeve made of corrosion resistant material and having first sealing means at one end thereof, second sealing means at the opposite end thereof and formations for co-operation with complementary formations on a cable gland for urging it axially with respect thereto said protective sleeve being suitable for use as the sleeve of an electrical cable gland assembly as claimed in any one of claims 1 to 7.

9. An electrical cable gland having formations on the outside thereof for co-operation with complementary formations on a protective sleeve, the formations being such that they serve to enable a protective sleeve to be urged axially with respect to the cable gland in use said cable gland being suitable for use as the cable gland of an electrical cable gland assembly as claimed in any one of claims 1 to 7.

10. An electrical cable gland assembly substantially as herein described and exemplified with reference to the accompanying drawing.

11. A protective sleeve substantially as herein described and exemplified with reference to the accompanying drawing.

12. An electrical cable gland substantially as herein described and exemplified with reference to the accompanying drawing.