GB2135137A

GB2135137A - Electrical cable glands and their manufacture

Info

Publication number: GB2135137A
Application number: GB08303141A
Authority: GB
Inventors: Franz Lackinger
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-02-04
Filing date: 1983-02-04
Publication date: 1984-08-22
Also published as: GB8303141D0; GB2135137B

Abstract

An electrical cable gland (1) is provided in which one part (11) of the body of the cable gland has a tubular extension (13) extending away from the end (10) of the cable gland adapted for connection to an electrical box. The tubular extension has at its free end a seal assembly (14,15,16,17) for sealing onto the outer sheath (18) of an armoured electrical cable. The tubular extension and the part of the body of the cable gland carrying same are made as separate parts or alternatively of different materials and, in either case, the metal conductive cable gland part is united with the tubular extension by a fushion process, bonding process, or by injection moulding plastics material onto the conductive cable gland part. <IMAGE>

Description

SPECIFICATION Electrical cable glands and their manufacture This invention relates to electrical cable glands of the general type comprising an anchor assembly for armour wires of an electrical cable with an outer sheath over the armour wires and an inner sheath housing the individually insulated electrical conductors therein, and to the manufacture of such cable glands.

Cable glands are widely used at termination and junction points in electrical systems where armoured cables are used. In many instances it is unnecessary to protect the armourwiresfrom moisture and the like in which case a simple cable gland is employed.

However, it is often necessary to prevent moisture or any corrosive substances from entering the space between the outer sheath and the armour wires which, ultimately, has the effect of corroding or rusting the armour wires. It is to be noted that apart from providing mechanical strength the armour wires serve as an earth for an electrical system.

Different expedients have been employed in the past for preventing armour wires from becoming exposed, as indicated above, and these basically take one of two different forms.

The first is a shroud, made of elastomeric material and which sealingly engages a suitable co-operating formation on the periphery of the gland and also, sealingly engages the outer surface of the outer sheath. This prevents moisture from entering to the position between the outer sheath and armour wires. The disadvantage of such an expedient is the fact that the elastomeric material has a limited life and, in general, one can consider such life to be no longer than about five years. In view of the extremely long term nature of electrical installations this is, therefore, considered not suitable. Also such shrouds can easily be cut, dislodged, vandalised, or otherwise tampered with.

The second expedient is to provide an integral tubular extension onto the adjacent part of the cable gland and to provide, at the free end of the tubular extension, a compression type of seal adapted to seal onto the outer sheath of the armoured cable.

This expedient works extremely well as the elastomeric material is under compression and shielded to a large extent from ultraviolet radiation. It thus has a very much longer life than the elastomeric material forming the shrouds described above.

However, the disadvantage of the tubular exten sion expedient is that the relevant part of the cable gland is rendered extremely costly when compared to the analogous part of the cable gland without the tubular extension. This problem results from the fact that the part of the cable gland having the tubular extension is generally turned from hexagonal brass bar or tube and, apart from the relatively large weight of the material used to form the part, a large percentage of wastage is created by the turning operation as the tubular extension needs only a relatively thin wall.

It is the object of this invention to provide a cable gland having a tubular extension type of expedient for creating the so-called outer seal of the cable gland.

In accordance with this invention there is provided an electrical cable gland adapted for association with an electrical fitting, connection box or the like and wherein a part of the cable gland remote in use, from said fitting, connection box or the like has a tubular extension extending away from the cable gland and carrying at its free a seal assembly for sealing onto the outer sheath of an electrical cable, the cable gland being characterised in that the tubular extension is manufactured in a separate process from the part of the cable gland carrying it and is permanently secured to said part of the cable gland by a fusion or bonding process.

Further features of the invention provide for the tubular extension to be associated with a thimble part of a cable gland being a part of an armourwire anchor assembly; for the cable gland to be of a type which embodies a so-called inner seal adapted to seal between the inside of the cable gland and the inner sheath of an armoured cable; and for the seal assembly carried at the free end of the tubular extension to be a compression seal embodying an elastomeric ring and axially movable compressing nut.

It will be understood that there are numerous ways in which a tubular section could be made and, in some cases, depending on the manner of manufacture or, at least the materials of manufacture of the tubular extension, there are also numerous ways in which it can be secured to the adjacent part of the cable gland.

Thus, for instance, the tubular extension could be made of an injection moulded plastics material in which case an externally screw-threaded flange or the like could be made integral with the tubular extension at its free end. The end for attachment to the adjacent part of the cable of the cable gland can simply be flared thereby providing the additional advantage that a tapered locking surface is provided.

The tubular extension can, in this case, be adhesively secured or bonded to a complementary surface on the part of the cable gland and interengaging formations can be provided on the surfaces in order that they clip together.

Alternatively the tubular extension can be made from extruded or otherwise formed tubular stock in which case one end can be flared, if required, to be attached to the adjacent part of the cable gland and the other end could be provided, in any suitable manner, with an externally screw-threaded region forming part of the outer seal assembly. In the case of thermo-plastic or ductile materials the externally screw-threaded region could simply be made by deforming the region radially outwardly and forming external screw-threads in the periphery thereof.

In the case where the tubular extension is made of metal which is compatible with the metal from which the adjacent part of the cable gland is manufactured the securing of the two parts together could take place by means of solder, brazing or other fusion processes. Alternatively, adhesive can be employed for bonding the two parts together permanently.

In the case where the tubular extension is made of thermo-plastic material it could be injection moulded onto a prefabricated metal part defining the said part of the cable gland. In this event the part of the cable gland need have no hexagonal outer configuration as a hard plastic, defining the extension could also define the required hexagonal formation for co-operation with a spanner. The said part could be formed from drawn tube or round bar with the outer surface treated to ensure proper locking of the metal and plastic together.

In order that the invention may be more fully understood, two embodiments thereof are now described by way of exam ply with reference to the accompanying drawings in which: Figure 1 is a partly sectioned longitudinal elevation of a cable gland manufactured in accordance with the invention, and Figure 2 is a similar view of a slightly different embodiment.

As illustrated in Figure 1 a cable gland generally indicated by numeral 1, is composed of a thimble portion 2 having an internally screw-threaded socket formation 3 at one end thereof into which end a differenential nut 4 extends. The thimble 2 has a captive ring 5 defining an inner truncated conical surface of a cable anchor and the differential nut 4 carries captively a cone member 6 having a com plementarily tapered surface for clamping armour wires 7 of an armoured cable.

Within the differential nut is a space occupied by an elastomeric inner seal 8 which is, in use, com pressed longitudinally by the cone member 6. This seal is adapted to seal onto the outer surface of the inner sheath 9 of the armoured cable.

The differential nut has a screw-threaded spigot 10 extending away from the armour wire anchor arrangement so that it can be secured in an aperture in an electrical junction box or the like with the aid of a nut (not shown).

The end of the thimble member remote from the differential nut is provided with a stepped but tapering section 11 onto which is adhesively secured a co-operating flared end 12 of a tubular extension 13. In this embodiment of the invention the tubular extension is an injection moulded unit but, it could quite easily take any of the forms described above or, alternatively, any other suitable form.

The tubular extension has at its free end an enlarged externally screw-threaded ring section 14 with which a union type of nut 15 co-operates with a compression seal 16 of elastomeric material being positioned between an inwardly directed flange 17 of the union nut and the free end of the tubular extension.

It will be understood that by causing relative rotation of the thimble and differential nut, the inner seal is compressed axially so that it engages firmly the outer surface of the inner sheath 9, whilst the union nut 15 is similarly rotated to axially compress the elastomeric seal 16 to firmly engage the outer surface of the outer sheath 18.

It will be understood that with the modern adhe sives a satisfactory bond can easily be achieved between the separately manufactured tubular extension and the associated part of the cable gland.

Alternatively, the two parts could be interconnected by a fusion process as indicated above or even the tubular member could be sweated onto a suitable formation of the associated part of the cable gland.

Referring now to Figure 2, there is illustrated a slightly different embodiment of the invention insofar as the tubular extension and associated thimble portion of the cable gland are concerned. In this particular embodiment of the invention the metal thimble 19 itself which holds the ring 20 is machined of metal and can be made from tubular stock, or aiternatively, round bar stock. Since it is not of a solid hexagonal configuration an appreciable saving in material is achieved on the manufacture ofthe thimble part itself.

This thimble part 19 again defines an internally screw threaded socket formation with which the deferential nut 21 co-operates.

A tubular extension 22, together with an integral outer zone 23 to the thimble part 19 is moulded, by an injection moulding process, onto the thimble part 19. This outer zone 23 embodies an hexagonal formation 24 whereby the assembly of the tubular extension and the thimble part 19 can be rotated.

The outer surface of the thimble part is suitably treated, optionally by forming grooves or nailing the surface, so that the plastic is firmly secured thereto by bonding as well as interengagement of grooves, and nailed configuration or the like.

It will be understood that a suitable plastics material is employed to insure that the hexagonal formation does not break or deform to any appreciable extend during installation of the cable gland.

In use, the above described embodiment of the invention will operate in exactly the same manner as the embodiment described above with reference to Figure 1.

It will be understood that a substantial saving in stock of material from which the parts of the cable gland are manufactured is achieved and there is very little wastage, at least insofar as the manufacture of the tubular extension is concerned, and also in some cases in the manufacture of the gland itself. In all, a substantial saving in cost of manufacture is achieved which enables the more preferable expedient of providing the outer seal to be employed without the disadvantages exhibited by a shroud.

Claims

1. An electrical cable gland adapted for association with an electrical fitting, connection box or the like and wherein a part of the cable gland remote, in use from said fitting, connection box or the like has a tubular extension extending away from the cable gland and carrying at its free a seal assembly for sealing onto the outer sheath of an electrical cable, the cable gland being characterised in that the tubular extension is manufactured in a separate process from the part of the cable gland carrying it and is permanently secured to said part of the cable gland by a fusion or bonding process.

2. An electrical cable gland as claimed in Claim 1 in which the tubular extension is associated with a thimble part of the cable gland being apart of an armour wire anchor assembly and constiting said part of the cable gland.

3. An electrical cable gland as claimed in either of Claims 1 or 2 in which the tubular extension is made of metal and is soldered brazed, welded or otherwise secured to the said part of the cable gland by a fusion process.

4. An electrical cable gland as claimed in either of Claims 1 or 2 in which the tubular extension is adhesively or otherwise bonded to the said part of the cable.

5. An electrical cable gland as claimed in any one of Claims 1,2 or 4 in which the tubular extension is made of a plastics material.

6. An electrical cable gland as claimed in Claim 5 in which the plastics material is a thermo-plastic material.

7. An electrical cable gland as claimed in Claim 6 in which the tubular extension is injection moulded.

8. An electrical cable gland as claimed in either of Claims 1 or 2 in which the said part of the cable gland has moulded onto it, a covering or the like which is integral with a tubular extension formed simultaneously.

9. An electrical cable gland as claimed in Claim 8 in which the surface of the said part of the cable gland is prepared with bonding agents or by providing physical formations in the surface or both prior to moulding the thermo-plastic material thereon.

10. An electrical cable gland as claimed in any one of the preceding claims in which there is provided an inner seal adapted to seal between the inside of the cable gland and the inner sheath of an armoured cable.

11. An electrical cable gland as claimed in any one of the preceding claims in which the seal assembly at the free end of the tubular extension is a compression seal embodying an elastomeric ring and an axially movable compressing member.

12. An electrical cable gland as claimed in Claim 1 and substantially as herein described or as exemplified with reference to either Figure 1 or Figure 2 of the accompanying drawings.