GB2075770A

GB2075770A - Improvements in or relating to cable glands

Info

Publication number: GB2075770A
Application number: GB8114106A
Authority: GB
Original assignee: Hawke Cable Glands Ltd
Current assignee: Hawke Cable Glands Ltd
Priority date: 1980-05-10
Filing date: 1981-05-08
Publication date: 1981-11-18

Abstract

To prevent hot gases being transmitted along a cable from equipment to which the cable has been connected a cover (42) is provided for the gap between a terminal (40) at the end of the cable and the end of the insulation (36) around a conductor of the cable, the cover comprising a fluid tight thermally stable,material which will prevent hot gases escaping through said gap and into the conductors. The cable passes through a gland which prevents escape of hot gases from the equipment. <IMAGE>

Description

SPECIFICATION Improvements in or relating to cable glands This invention relates to cable glands.

It has recently been proposed, for example in our British Patents Nos. 1528347 and 1528348 to provide a cable gland which is used in such a way to form a barrier around the core or cores of a cable to prevent hot gases being transmitted along a cable. In practice the outer sheath and armour if present are stripped back to expose the individual conductors which are themselves surrounded by insulation. The conductors are led through the gland body and a barrier of resin is formed therearound. The insulation at the ends of the conductors is removed and a terminal lug or the like fixed thereto by which the conductor can be connected to some piece of electrical equipment.

With large size cables each individual conductor is made up from a number of strands. It is, therefore, possible for such conductors to allow transmission of hot gases therealong. Such hot gases can enter the conductors at the point where they are exposed between the terminal lug and the end of the stripped-back, surrounding insulation. It will be appreciated that the barrier formed around the conductors where they are insulated cannot prevent transmission of gases along the conductors themselves.

The present invention has been made from a consideration of this problem.

According to the invention them is provided a barrier assembly for a conductor comprised of a plurality of strands comprising a cover of fluid tight, thermally stable material adapted to surround the conductor strands between the terminal means fixed to the end of the conductor and the end of strippedback insulation surrounding the conductor.

The cover forming the barrier is preferably in the form of a sleeve which can be positioned over the exposed conductor strands either before or after the terminal means is fixed to the conductor end. The material of the cover must be fluid tight and must also be thermally stable that is to say it must remain fluid tight in the presence of hot gases such as might be generated from a fault in the electrical equipment to which the conductor is to be connected.

Preferably the cover is secured in place so as to prevent any gases penetrating under the ends of the cover. The cover can be secured as aforesaid by adhesive, by mechanical means such as a clamp, or a combination thereof.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows in longitudinal section a gland equipped with the present invention.

Referring to the drawing the gland shown is of the kind known per se and will not, therefore, is described in great detail. The gland comprises a hollow gland body 10 having an externally threaded end 12 for engagement in a tapped hole in the wall 14 of the piece of electrical equipment. The other end 16 of the gland body, which is of larger dimensions than end 12, is externally threaded to receive a cap 18 for tightening together inner and outer clamping rings 20, 22 for cable armour 24. Ring 20 has a projecting sleeve 26 which extends into the end 16 of the gland body. A second sleeve or liner 28has an out-turned end 30. The sleeve 28 is located inside end 12 of the gland body-with the out-turned.end disposed inside the projecting sleeve 26 of the armour clamping ring 20.

In use the inner and outer cable sheaths 32 and 34 are cut back to expose the conductors 36 which are surrounded by insulating material. When the gland is "made off" a barrier 37 of for example resin is formed inside sleeves 26 and 28 around the conductors. At the ends of each conductor the surrounding insulation is stripped back to reveal the individual strands 38 making up the conductor. A terminal lug 40 is crimped onto the end of the exposed conductor strands.

If a fault should occur within the equipment housing the barrier 37 prevents hot gases being transmitted albng the cable inside the inner or outer cable sheath. However, the barrier cannot prevent such gases entering the conductors at the gap between the terminal 40 and the stripped back insulation and being transmitted along the conductors through the gaps between the strands thereof.

To prevent that a cover 42 is provided over the gap orjunction between each lug 40 and the end of the insulation covering the strands.

The cover 42 is of fluid tight preferably electrically insulating material which is also preferably resilient, for example rubber. The cover is preferably in the form of a tubular sleeve which extends at lest across the-gap between the insulation surrounding the conductor and the terminal lug 40. The cover is placed on the conductor prior to the terminal lug 40 being crimped thereon. When the terminal lug 40 is in place the cover is located in its correct position.

If desired the cover can be formed from heat shrinkable polymeric tubing, self-vulcanizing tape, self-adhesive tape. A convenient form of cover can be obtained from tubing of a kind known per se which is expanded by a removable spring. On removal of the spring the tube contracts.

A sealing material such as paste or the like or a hot melt material may be disposed between the cover and the conductor.

1. A barrier assembly for a conductor comprised of a plurality of strands comprising a cover of fluid tight, thermally stable material adapted to surround the conductor strands between terminal means fixed to the end of the conductor and the end of strippedback insulation surrounding the conductor.

2. A barrier assembly as claimed in Claim 1 wherein the cover material is electrically insulating.

3. A barrier assembly as claimed in Claim 1 or Claim 2, wherein the cover material is natural rubber, synthetic rubber, plastics, self-vulcanizing tape or self-adhesive tape.

4. A barrier assembly as claimed in any preceding claim wherein the cover is in the form of a tube.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to cable glands This invention relates to cable glands. It has recently been proposed, for example in our British Patents Nos. 1528347 and 1528348 to provide a cable gland which is used in such a way to form a barrier around the core or cores of a cable to prevent hot gases being transmitted along a cable. In practice the outer sheath and armour if present are stripped back to expose the individual conductors which are themselves surrounded by insulation. The conductors are led through the gland body and a barrier of resin is formed therearound. The insulation at the ends of the conductors is removed and a terminal lug or the like fixed thereto by which the conductor can be connected to some piece of electrical equipment. With large size cables each individual conductor is made up from a number of strands. It is, therefore, possible for such conductors to allow transmission of hot gases therealong. Such hot gases can enter the conductors at the point where they are exposed between the terminal lug and the end of the stripped-back, surrounding insulation. It will be appreciated that the barrier formed around the conductors where they are insulated cannot prevent transmission of gases along the conductors themselves. The present invention has been made from a consideration of this problem. According to the invention them is provided a barrier assembly for a conductor comprised of a plurality of strands comprising a cover of fluid tight, thermally stable material adapted to surround the conductor strands between the terminal means fixed to the end of the conductor and the end of strippedback insulation surrounding the conductor. The cover forming the barrier is preferably in the form of a sleeve which can be positioned over the exposed conductor strands either before or after the terminal means is fixed to the conductor end. The material of the cover must be fluid tight and must also be thermally stable that is to say it must remain fluid tight in the presence of hot gases such as might be generated from a fault in the electrical equipment to which the conductor is to be connected. Preferably the cover is secured in place so as to prevent any gases penetrating under the ends of the cover. The cover can be secured as aforesaid by adhesive, by mechanical means such as a clamp, or a combination thereof. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows in longitudinal section a gland equipped with the present invention. Referring to the drawing the gland shown is of the kind known per se and will not, therefore, is described in great detail. The gland comprises a hollow gland body 10 having an externally threaded end 12 for engagement in a tapped hole in the wall 14 of the piece of electrical equipment. The other end 16 of the gland body, which is of larger dimensions than end 12, is externally threaded to receive a cap 18 for tightening together inner and outer clamping rings 20, 22 for cable armour 24. Ring 20 has a projecting sleeve 26 which extends into the end 16 of the gland body. A second sleeve or liner 28has an out-turned end 30. The sleeve 28 is located inside end 12 of the gland body-with the out-turned.end disposed inside the projecting sleeve 26 of the armour clamping ring 20. In use the inner and outer cable sheaths 32 and 34 are cut back to expose the conductors 36 which are surrounded by insulating material. When the gland is "made off" a barrier 37 of for example resin is formed inside sleeves 26 and 28 around the conductors. At the ends of each conductor the surrounding insulation is stripped back to reveal the individual strands 38 making up the conductor. A terminal lug 40 is crimped onto the end of the exposed conductor strands. If a fault should occur within the equipment housing the barrier 37 prevents hot gases being transmitted albng the cable inside the inner or outer cable sheath. However, the barrier cannot prevent such gases entering the conductors at the gap between the terminal 40 and the stripped back insulation and being transmitted along the conductors through the gaps between the strands thereof. To prevent that a cover 42 is provided over the gap orjunction between each lug 40 and the end of the insulation covering the strands. The cover 42 is of fluid tight preferably electrically insulating material which is also preferably resilient, for example rubber. The cover is preferably in the form of a tubular sleeve which extends at lest across the-gap between the insulation surrounding the conductor and the terminal lug 40. The cover is placed on the conductor prior to the terminal lug 40 being crimped thereon. When the terminal lug 40 is in place the cover is located in its correct position. If desired the cover can be formed from heat shrinkable polymeric tubing, self-vulcanizing tape, self-adhesive tape. A convenient form of cover can be obtained from tubing of a kind known per se which is expanded by a removable spring. On removal of the spring the tube contracts. A sealing material such as paste or the like or a hot melt material may be disposed between the cover and the conductor. CLAIMS

5. A barrier assembly as claimed in Claim 4, wherein the cover is a shrinkable tube.

6. A barrier assembly as claimed in -any preced- ing claim, wherein a sealing material is disposed between the cover and the conductor.

7. A barrier assembly as claimed in any preceding claim in combination with a cable gland.

8. A barrier assembly as claimed in Claim 7, wherein the gland includes two hollow interconnecting parts defining a chamber through which the conductor extends, a filler compound being provided in said chamber to form a barrier around-said conductor.

9. A barrier assembly as claimed in Claim 7 or Claim 8, wherein the conductor extends through the gland and the cover is provided- on a part of the conductor outside the gland.

10. A barrier assembly substantially as described herein with reference to the accompanying drawing.