GB2128281A

GB2128281A - Sealed threaded joints - electrical continuity

Info

Publication number: GB2128281A
Application number: GB08227254A
Authority: GB
Inventors: Brian David Hamblin
Original assignee: Hawke Cable Glands Ltd
Current assignee: Hawke Cable Glands Ltd
Priority date: 1982-09-24
Filing date: 1982-09-24
Publication date: 1984-04-26
Also published as: NO833413L

Abstract

A seal is formed by sealing material (16) pre-applied to the threads of one or both parts (10) of a cable gland, the material is covered by a protective cover (18). When the parts are interengaged the sealing material deforms to form a seal and preserves electrical continuity. The amount of sealing material pre- applied will determine in advance the pressures that the seal will withstand. <IMAGE>

Description

SPECIFICATION Seal This invention relates to the provision of a fluid-tight seal between threadedly engaged members while preferably maintaining electrical continuity between such members and more particularly, but not exclusively, the provision of a fluid-tight seal between parts of an electrical cable gland or between part of a cable gland and a fitting to which the gland part is fixed.

Where, in order to meet British Standard or other such requirements, a fluid-tight seal is to be provided between threadedly engaged parts of a cable gland, the present practice is to apply an appropriate sealing compound to the threads just prior to installation of the gland into service. Once the gland has been made off there is no way of telling whether adequate sealing material has been applied to meet the necessary standard.

Inadequate sealing may only become apparent when the gland is actually in service.

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

The present invention provides for a seal to be formed between two threadedly engageable parts wherein a sealing material is pre-applied to at least a portion of the threads of one or both parts, said portion including threads that are interengaged with threads of the other part when the two parts are engaged together, said sealing material being covered by a protective cover, which cover prevents premature dispersal of the sealing material but which will deform to allow the sealing material also to deform and form a seal between interengaged threads of the parts.

Preferably said sealing material is further arranged or adapted to permit electrical continuity between said parts when in said engaged condition.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which:~ Fig. 1 is a longitudinal section through a part of a cable gland; Fig. 2 shows a threaded part of the section of Fig. 1 but on an enlarged scale; and Fig. 3 shows the threaded part of Fig. 2 engaged in a complementary threaded member.

Referring to the drawings a cable gland body of typical form is shown in Fig. 1. The body is of hollow tubular shape externally threaded at one end 10 for engagement in the wall of a junction box or other fitting. The other end 12 of the body is also externally threaded for engagement with other gland parts (not shown).

A composite sealing strip 14 is applied to the threads 10. The strip comprises a layer 16 of paste-like sealing material, such as mastic, uncured rubber or other material that will flow under pressure, covered by a thin protective layer 18 for example of a plastics material such as polyvinyl chloride, a powder gel or other suitable material. The layer 16 of paste-like material is readily embedded on the peaks of threads and sticks to said threads. At this stage it does not matter if, as illustrated in Fig. 2 the layer 16 does not extend down to the troughs of the threads. In this condition the gland body is supplied to the user who will install it. The cover layer 18 prevents the layer 16 from being unduly disturbed during storage and transport prior to the gland body being used.

As illustrated in Fig. 3, when the threaded end 10 of the gland body is engaged in the threads 20 of a tapped bore, for example, in the wall of a junction box or other fitting, the composite strip is compressed, the layer 18 is broken up and the layer 16 flows over the surfaces of the threads forming a fluid-tight seal therebetween. As can be seen in Fig. 3 there are threads of the gland body which bear directly on the threads 20 without any interposition of sealing material so that electrical continuity is maintained between the two parts. In order to ensure that such electrical continuity will be present in the assembled parts the positioning of the sealing strip on the threads 10 and the size of the strip must be appropriately selected. There are many ways in which this can be brought about.As illustrated in the drawings, the axial width of the sealing strip may be less than the axial length of engaged threads. However, the sealing strip need not extend entirely around the threads but may be in the form of a pad. In that case the pad may extend over the entire axial length of the engaged parts. Another way of obtaining electrical continuity is through the sealing material itself by incorporating an electrically conductive substance such as metal powder or graphite in the sealing material.

The selection of sealing material and application thereof is also chosen having regard to the seal that is required. For cable glands, the seal is primarily intended to prevent ingress of moisture dust and the like into the gland and is, therefore, unlikely to be subjected to very high pressures. Nevertheless a seal of the kind described with reference to the drawings has been tested and found to withstand pressures of up to 150 psi. The invention is not confined to cable glands and can be used in other circumstances where higher or lower pressures may be experienced. Examples of other items to which the invention can be applied include conduit, and pipes for conducting a fluid such as water.

Although particularly applicable to metal parts the invention can be used with non-metal, such as plastic, items.

Claims (Filed on 21 Sept 1983) 1. A seal formable between two threadedly engageable parts wherein a sealing material is pre-applied to at least a portion of the threads of one or both parts, said portion including threads of the other part when the two parts are engaged together, said sealing material being covered by a protective cover, which cover prevents premature disposal of the sealing material but which will allow the sealing material also to deform and

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

Claims

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

SPECIFICATION Seal This invention relates to the provision of a fluid-tight seal between threadedly engaged members while preferably maintaining electrical continuity between such members and more particularly, but not exclusively, the provision of a fluid-tight seal between parts of an electrical cable gland or between part of a cable gland and a fitting to which the gland part is fixed.

Where, in order to meet British Standard or other such requirements, a fluid-tight seal is to be provided between threadedly engaged parts of a cable gland, the present practice is to apply an appropriate sealing compound to the threads just prior to installation of the gland into service. Once the gland has been made off there is no way of telling whether adequate sealing material has been applied to meet the necessary standard.

Inadequate sealing may only become apparent when the gland is actually in service.

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

The present invention provides for a seal to be formed between two threadedly engageable parts wherein a sealing material is pre-applied to at least a portion of the threads of one or both parts, said portion including threads that are interengaged with threads of the other part when the two parts are engaged together, said sealing material being covered by a protective cover, which cover prevents premature dispersal of the sealing material but which will deform to allow the sealing material also to deform and form a seal between interengaged threads of the parts.

Preferably said sealing material is further arranged or adapted to permit electrical continuity between said parts when in said engaged condition.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which:~ Fig. 1 is a longitudinal section through a part of a cable gland; Fig. 2 shows a threaded part of the section of Fig. 1 but on an enlarged scale; and Fig. 3 shows the threaded part of Fig. 2 engaged in a complementary threaded member.

Referring to the drawings a cable gland body of typical form is shown in Fig. 1. The body is of hollow tubular shape externally threaded at one end 10 for engagement in the wall of a junction box or other fitting. The other end 12 of the body is also externally threaded for engagement with other gland parts (not shown).

A composite sealing strip 14 is applied to the threads 10. The strip comprises a layer 16 of paste-like sealing material, such as mastic, uncured rubber or other material that will flow under pressure, covered by a thin protective layer

18 for example of a plastics material such as polyvinyl chloride, a powder gel or other suitable material. The layer 16 of paste-like material is readily embedded on the peaks of threads and sticks to said threads. At this stage it does not matter if, as illustrated in Fig. 2 the layer 16 does not extend down to the troughs of the threads. In this condition the gland body is supplied to the user who will install it. The cover layer 18 prevents the layer 16 from being unduly disturbed during storage and transport prior to the gland body being used.

As illustrated in Fig. 3, when the threaded end 10 of the gland body is engaged in the threads 20 of a tapped bore, for example, in the wall of a junction box or other fitting, the composite strip is compressed, the layer 18 is broken up and the layer 16 flows over the surfaces of the threads forming a fluid-tight seal therebetween. As can be seen in Fig. 3 there are threads of the gland body which bear directly on the threads 20 without any interposition of sealing material so that electrical continuity is maintained between the two parts. In order to ensure that such electrical continuity will be present in the assembled parts the positioning of the sealing strip on the threads 10 and the size of the strip must be appropriately selected. There are many ways in which this can be brought about.As illustrated in the drawings, the axial width of the sealing strip may be less than the axial length of engaged threads. However, the sealing strip need not extend entirely around the threads but may be in the form of a pad. In that case the pad may extend over the entire axial length of the engaged parts. Another way of obtaining electrical continuity is through the sealing material itself by incorporating an electrically conductive substance such as metal powder or graphite in the sealing material.

The selection of sealing material and application thereof is also chosen having regard to the seal that is required. For cable glands, the seal is primarily intended to prevent ingress of moisture dust and the like into the gland and is, therefore, unlikely to be subjected to very high pressures. Nevertheless a seal of the kind described with reference to the drawings has been tested and found to withstand pressures of up to 150 psi. The invention is not confined to cable glands and can be used in other circumstances where higher or lower pressures may be experienced. Examples of other items to which the invention can be applied include conduit, and pipes for conducting a fluid such as water.

Although particularly applicable to metal parts the invention can be used with non-metal, such as plastic, items.

Claims (Filed on 21 Sept 1983) 1. A seal formable between two threadedly engageable parts wherein a sealing material is pre-applied to at least a portion of the threads of one or both parts, said portion including threads of the other part when the two parts are engaged together, said sealing material being covered by a protective cover, which cover prevents premature disposal of the sealing material but which will allow the sealing material also to deform and form a seal between interengaged threads of the parts.
2. A seal as claimed in Claim 1, wherein the sealing material is arranged or adapted to permit electrical continuity between said parts when in the engaged condition.
3. A seal as claimed in Claim 1 or Claim 2, wherein the sealing material comprises material which will flow under pressure.
4. A seal as claimed in any preceding claim, wherein the protective cover is of plastics material.
5. A seal as claimed in any preceding claim wherein the sealing material is pre-applied to the peaks of the threads of one or both parts.
6. A seal as claimed in any preceding claim, wherein the axial width of the sealing material and cover is less than the axial length of the threads which interengage.
7. A seal as claimed in any preceding claim, wherein the sealing material and cover does not extend entirely around the threads.
8. A seal as claimed in any preceding claim, wherein the sealing material incorporates an electrically conductive substance.
9. A seal substantially as described herein with reference to the accompanying drawing.
10. A cable gland incorporating a seal as claimed in any preceding claim.