GB2140115A

GB2140115A - Conduit coupling-electrical continuity

Info

Publication number: GB2140115A
Application number: GB08410427A
Authority: GB
Inventors: Stanley James Mitchell; Alan Terry
Original assignee: IMI Components Ltd
Current assignee: IMI Components Ltd
Priority date: 1983-04-25
Filing date: 1984-04-24
Publication date: 1984-11-21
Also published as: GB8410427D0

Abstract

A coupling for connecting electrical conduit, said coupling typically being manufactured by die-casting. The coupling comprises a hollow cylindrical male member 1 and a co-operating female member 10 which is screwed onto the male member. The interior of the female member additionally carries wedge- shaped projections 14, 15 on taper 8 which upon tightening of the coupling are deformed against a surface on the male member to provide a water-tight seal between the two members. <IMAGE>

Description

SPECIFICATION Couplings for conduit This invention relates to couplings for conduit, and especially to couplings for conduit adapted to carry electricity cable.

Cable conduits are known which are sandwich construction comprising a waterproof outer synthetic rubber layer, a helical wire reinforcement which is flexible to some extent, and a synthetic rubber or plastics inner lining.

The cable is carried within the conduit, and is typically connected to terminals on an electrical supply at one end and to terminals on a machine at the other. It is desirable that the conduit is satisfactorily connected to the supply housing and the machine housing, preferably in a water tight manner, so that from sprays etc cannot enter the interior of the conduit and cause electrical problems.

Where the coupling is in two parts it is also desirable to provide electrical continuity between them.

According to one aspect of the invention, we provide a metal coupling for conduit, said coupling comprising a generally cylindrical male member having a passageway extending through it in the direction of its principal axis, and a co-operating female member which fits around a portion of said male member, an end of the conduit being retained between the male and female members, said male member and female member having respective means for engaging one another so as to prevent their being pulled apart, the female member having a surface with one or more integral projections formed thereon, which when the male and female members are fully engaged, is or are urged into contact with a surface on the male member, so as to provide electrical continuity between the male and female members.

Where a single projection is formed, it may comprise an annular projection having a plane surface which engages with and is urged into contact with a plane surface on the male members. The contacting plane surface may be parallel, or inclined to one another. Where the projection is formed with a surface nonparallel to the surface on the male member, the projection preferably has a sharp edge which is urged into contact with the surface of the male member. The single projection may alternatively comprise an annular or part annular wedge shaped element with an edge which is urged into contact with the surface on the male member. Where two or more projections are employed both or all the projections may be of wedge-shaped annular configuration. The angle at the edge of the wedge may be a right angle.

The present invention further provides a metal coupling for conduit such coupling comprising a generally cylindrical male member having a passageway extending through it in the direction of its principal axis and a die cast co-operating metal female member which fits around a portion of said member, an end of the conduit being retained between the male and female members, said male member and female member having respective means for engaging one another so as to prevent their being pulled apart, the die cast female member having a surface which, when the male and female members are fully engaged, is deformed upon contact with a surface of the male member so as to provide a watertight seal and electrical continuity between the male and female members.

Preferably the male member is also a die cast member. Both members may be formed or zinc or a zinc alloy and particularly the zinc alloy BS 1004.

The deformable projection may be located on a tapered portion and may comprise an annular ring extending inwardly of the female member. The annular ring may be wedgeshaped so as to have a face parallel to the principal axis of the female member and a further face at an angle to the first face. The angle may be a right angle. There may be provided two or more annular projections.

Heretofor die cast couplings have utilised 0rings to form efficient water-tight sealing between the two members. It has not been posisble heretofor to rely on male to female contact on a metal to metal sense to produce water-tight seals between the two members.

By way of example embodiments of the present invention will now be described with reference to the accompanying drawings of which: Figure 1 is a side elevational view of a male member; Figure 2 is a cross-sectional view of a cooperating female member (Fig. 2 does not show the feature of the present invention); Figure 3 is a partial cross-section of a male and female member in contact and Figures 4 and 5 show alternative embodiments of the female member.

Referring to Figs. 1 and 2 these show a male member 1 having a principal longitudinal axis and a bore 2 therethrough. One end of the member 3 is threaded for connection to a suitable socket. The other end of the member is provided with a longitudinally extending portion 4 which is adapted to engage the inside of a conduit. Threaded portions 5 are provided to enable the portion 4 to be screwed into the conduit. The conduit comes into engagement with a tapered portion 6.

The female member 10, Fig. 2, has a first tapered portion 7 and a second tapered portion 8. The two tapered portions are separated by a die cast single thread 9 the function of which will be described in more detail below.

As is shown clearly in Fig. 3 the female member 10 is screwed on to the male mem ber 1 by means of a thread 9 which engages with a co-operating thread 11 on the male portion. The tapered portion 8 of the female member co-operates with the tapered portion 12 of the male member. The tapered portion 8 is provided with an inwardly directed ridge 13 which is arranged to be deformed when the two members are screwed together. As full metal to metal contact is made between the ridge 13 and the tapered portion 12 good sealing and electrical continuity are provided.

Instead of a single large member 13 a pair of inwardly directed projections 14, 15 may be provided. It will be noted that the faces 16, 17 are parallel to the principal axis of the female member. This enables the core to be withdrawn after die casting. In the embodiment illustrated in Fig. 5 only a single inwardly directed projection 18 is provided.

It will be appreciated that as the two members, male and female, are screwed together the projections 16, 17 and 18 are deformed to produce a good water-tight seal and proper electrical continuity.

It is preferred that the projection be provided on the female member as the core for the die-casting machine is a cylindrical member which may readily be machined to accurate tolerances. It is easier to machine cylindrical cores then the tubular cores required for the male members.

By providing a deformable member on the female coupling portion slight variations in the size of the male member and mis-match in alignment of the cores in die-casting can be accommodated.

It will be appreciated therefore that the invention is particularly directed to die-cast conduits by providing means for sealing which can be formed integrally and obviate the need for the O-rings proposed hitherto.

Claims

1. A metal coupling for conduit, said coupling comprising a generally cylindrical male member having a passageway extending though it in the direction of its principal axis, and a co-operating female member which fits around a portion of said male member, an end of the conduit being retained between the male and female members, said male member and female member having respective means for engaging one another so as to prevent their being pulled apart, the female member having a surface with one or more integral projections formed thereon, which when the male and female members are fully engaged, is or are urged into contact with a surface on the male member, so as to provide electrical continuity between the male and female members.

2. A coupling as claimed in Claim 1 wherein single projection is formed on the female member, said projection being annular and having a plane surface which engages with and is urged into contact with a plane surface on the male member.

3. A coupling as claimed in Claim 2 wherein the contacting plane surfaces are inclined to one another.

4. A coupling as claimed in Claim 2 wherein the contacting plane surfaces are parallel to one another.

5. A coupling as claimed in Claim 3 wherein the projection has a sharp edge which is urged into contact with the surface of the male member.

6. A coupling as claimed in Claim 1 wherein the projection comprises an annular wedge-shaped element with an edge which is urged into contact with a plane surface on the male member.

7. A coupling as claimed in Claim 6 wherein the projection has a surface parallel to the principal axis of the female member.

8. A coupling as claimed in Claim 6 or Claim 7 wherein the angle of the edge of the wedge is a right angle.

9. A metal coupling for conduit such coupling comprising a generally cylindrical male member having a passageway extending through it in the direction of its principal axis and a die cast co-operating metal female member which fits around a portion of said member, an end of the conduit being retained between the male and female members, said male member and female member having respective means for engaging one another so as to prevent their being pulled apart, the die cast female member having a surface which, when the male and female members are fully engaged, is deformed upon contact with a surface of the male member so as to provide a water-tight seal and electrical continuity between the male and female members.

10. A coupling as hereinbefore described with reference to and as shown in Figs. 1 and 2 in combination with Fig. 3, Fig. 4 or Fig. 5 of the accompanying drawings.