GB2224893A

GB2224893A - Electrical earth bonding device

Info

Publication number: GB2224893A
Application number: GB8920010A
Authority: GB
Inventors: Barry Dobson; John Sandor
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-09-09
Filing date: 1989-09-05
Publication date: 1990-05-16
Anticipated expiration: 2009-09-05
Also published as: GB8920010D0; GB2224893B

Abstract

An earth bonding device for securing an earth cable to an electrical conducting pipe (13A) comprises a pipe securing member (11A) and a cable securing member (12A), the cable securing member (12A) comprising an electrically conducting flexible strip (10A) which can be clamped around the earth cable and pressed into electrical contact with the pipe (13A) by the pipe securing member (11A). <IMAGE>

Description

ELECTRICAL EARTH BONDING DEVICE This invention relates to an electrical earth bonding device such as is required to earth electrical wiring via an electrically conducting pipe (e.g. a water pipe).

British Standard BS951:1986 relates to earth bonding devices of the kind to which this invention relates.

Earth bonding clips (or clamps) are needed in many electrical wiring installations for earthing the installation through metal water pipes. This is achieved by providing good electrical contact between the metal pipe on the one hand and an earth cable of the installation on the other, using an appropriate earth bonding device.

Embodiments of the present invention provide, inter alia, an earth bonding device which is timesaving to install, which readily accommodates varying sizes of metal pipe and earth cable and which can be used in places where access to work is difficult.

According to the present invention an earth bonding device has a pipe securing member and a cable securing member, the cable securing member comprising an electrically conducting flexible strip which is pressed into electrical contact with the pipe by the pipe securing member.

Conveniently the pipe securing member comprises a flexible band co-acting with a tensioning member for drawing the band tightly around the surface of the pipe.

Suitably the flexible band has parts of a screw thread formed therein and the tensioning member includes a threaded tightening screw to engage said screw thread parts.

The pipe securing member may be a flexible band secured at one end to a cradle and tightened around the pipe by pressure exerted on the band by a screw threaded in the cradle.

Means may be provided to lock the pipe securing member in tightened condition about the pipe.

Where the pipe securing member includes a band, the electrical conducting flexible strip of the cable securing member can embrace the band of the pipe securing member and thereby be pressed into good electrical contact with the pipe as the band is tightened around the pipe.

Suitably the flexible strip of the cable securing member is reinforced with a core plate. The flexible strip may be bent around an end of the core plate remote from the pipe securing member, means being provided to secure the cable between the bent-back end of the strip and the core plate. The means to secure the cable in place can include a screw threaded into a hole in the core plate and passing through a hole and/or an elongate slot in the flexible strip.

Some forms of electrical earth bonding device according to our invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a first embodiment of device which uses a Jubilee clip (or the like) as the pipe securing member, Figure 2 is an enlarged sectional view on the line II-II of Figure 1, Figure 3 is a perspective view of a second embodiment, Figure 4 is a detail of part of the embodiment of Figure 3 with obscuring parts removed for clarity, Figure 5 is a front elevation of a third embodiment of earth bonding device, Figure 6 is an enlarged section on the line VI-VI of Figure 5, Figure 7 is a plan view of the device of Figure 5 seen from above, Figure 8 is a view of a fourth embodiment of device which also uses a Jubilee clip (or the like) as the pipe securing member, and Figure 9 is a view similar to Figures 2 and 6 of a part of a fifth embodiment of device.

The inventive feature of each of the illustrated embodiments is that a flexible strip of electrically conducting material is used to contact both the cable and the pipe to be secured to the device. In all the Figures this strip is designated 10, the reference 10A being used in Figures 1 and 2, 10B in Figures 3 and 4, 10C in Figures 5 to 7, 10D in Figure 8 and 10E in Figure 9. In all Figures, the pipe securing member is designated 11, the cable securing member 12 and the pipe 13, the letters A, B, C, D and E again being used to qualify the five embodiments.

In Figures 1 and 2 a flexible band 14 is used to embrace the pipe 13A, this band having parts of a screw thread formed therein which parts engage with a threaded tightening screw 15 shown in Figure 1. As the screw 15 is turned in one direction it reduces the size of the loop of the band 14 surrounding the pipe and as it is turned in the opposite direction, it increases the size of that loop. A Jubilee clip is one example of the pipe securing member 11A shown in Figures 1 and 2.

To provide rigidity to the strip 10A a core plate 16 is incorporated therein, this plate being threaded with holes 17A, 17B and 17C in Figure 1. The provision of a choice of holes for a flanged securing screw 18 allows a range of different gauges of wire and/or a range of different numbers of wire to be electrically connected to each cable securing member 12A. The strip 10A embraces the band 14 (i.e. it is pressed into good electrical contact with the pipe 13A) and is tacked to the core plate 16 (e.g. by rivet, solder, welding or screwing) at the locations indicated by arrows 19.

The embodiment of Figures 3 and 4 has a pipe securing member 11B which includes a flexible metal band 24 secured at one end to a cradle 20 and tightened around the pipe 13B by pressure exerted on the band 24 by a screw 25 threaded in the cradle 20. Pipe securing members of the kind shown in Figures 3 and 4 are known in the art. A rigid core plate 26 partially surrounded by the flexible strip 10B provides the cable securing member 12B and Figure 4 shows the lower end of this without the cradle 20 in place. A flanged screw 28 and tacked regions 29 are similar to those described previously with reference to Figures 1 and 2.

Only one screw-threaded hole is needed in the core plate 26 for the flanged screw 28, an elongate slot 23 being provided in the strip 10B to allow for varying gauges and/or numbers of cable(s).

The embodiment of Figures 5, 6 and 7 uses a pipe securing member 11C which embodies a band 34 tightenable about the pipe 13C in any convenient way (e.g. by a Jubilee-type fitting as described with reference to Figure 1) and has a flexible strip 10C partially surrounding a rigid core plate 36. Tack areas 39, a flanged screw 38 ana a threaded hole 37 enable ranges of cable thicknesses to be secured to the member 12C. The upper end of the core plate 36 has ears 36A which bear against the pipe when pressure is applied to the screw 38 during a tightening operation.

Figure 8 illustrates a fourth embodiment of device (without the metal pipe) together with an electric earth cable E stripped ready for an earthing installation. A metal band or Jubilee clip 44 (i.e. the pipe securing" member 11D) has parts 70 of a screw thread formed therein and conductively attached to it a thin flexible metal strip 10D containing a series of holes 47. The strip 10D is attached to a collar of the member 11D which includes a screw 45 whose threads are adapted to engage the thread parts 70 on the band 44. The screw 45 acts as a tensioning member for the band 44. The strip 10D extends parallel to the axis of a cylinder formed by the pipe securing member 11D. The strip 10D can be readily bent back on itself, as shown to provide a loop around the stripped earth cable E.

Once the strip 10D is bent, a nut and bolt 48 can be applied to hold in position any cable E within a range of sizes, by means of the appropriate holes 47 selected for the purpose. The flexible strip 10D near its distal edge is slightly deformed and/or narrowed and/or cut in; and is provided with a crimped or welded or brazed metal plate 71 with a threaded screwhole containing a bolt 72, The cut-in part of the flexible strip 10D behind the plate 71 gets further deformed, essentially into a V-shape with the apex pressing against the bare wires of the cable E as the bolt 72 is being tightened, to provide good electrical contact.

Figure 9 shows part of a fifth embodiment of device.

The pipe securing member 11E comprises a flexible band 54 which is secured at one end to a flexible strip 10E of the cable securing member and after embracing the pipe 13E passes between a core plate 56 and a length of the flexible strip 10E close to said one end. Thus two layers of the band 54 are pressed together as the band is manually pulled tight around the pipe 13E. The band 54 is locked in the tightened condition by a screw 55 threadedly engaged in a captive nut 55a. The nut 55a is non-rotatably held adjacent to the front face of the core plate 56 and the return length of the strip lOE by ears 73 projecting outwardly from the core plate 56 (only one of which is shown in Figure 9) and is prevented from moving too far away from the front face of the core plate 56 by an inwardly turned edge 73a of each ear 73.The screw 55 passes through clearance holes in the strip 10E and plate 56 so that the inner end of the screw 55 can bear against the lapped layers of the band 54 and press the strip 10E firmly against the pipe 13E. The pipe securing member 11E is thus similar to that shown at 11B in Figure 3, but there is now no need for the cradle 20, resulting in considerable costsaving. A lock nut 55b is also provided to ensure that the screw 55 is held locked tight against the pipe lapped layers of the band 54 thus holding the strip 10E in good electrical contact with the pipe 13E.

The flexible strip 10E is tacked (e.g. welded) to the core plate 56 at the places indicated by the arrows 59 and the strip 10E will be bent around the upper end of the core plate 56 (i.e. the end remote from the pipe securing member 11), means (not shown) being provided to secure the cable within the loop between the bent-back end of the strip and the core plate in a manner similar to that shown in Figures 1 and 2, Figure 3 or Figures 5, 6 and 7.

It will be appreciated that in each of the embodiments of Figures 3, 4 and 9, the band of the pipe securing member 11 and the flexible strip 10 are jointly pressed into electrical contact with the pipe 13 by a screwthreaded member (25, 55).

In a modification of the arrangement shown in Figure 9, the captive nut 55a is dispensed with (as are the ears 73), the screw 55 now being threadedly engaged in the core plate 56. The nut 55b again acts as a lock nut.

Phosphor bronze is a suitable material for the members 11 and 12 in all five illustrated embodiments. Stainless steel is a possible substitute material.

It may be necessary or desirable to provide some means to lock the respective pipe securing member 11 in tightened condition about the pipe 13. In the case of the embodiment of Figures 1 and 2 this can be effected by a lock nut 15a engaging with a special threaded region 15b of the tightening screw 15. In the case of the embodiment of Figures 3 and 4 this can be a lock nut 25a engaging with the thread of the screw 25 and bearing against the cradle 20 in its tightened condition.

An advantage of all five embodiments disclosed is that each can be used with others of the same or a similar nature on parallel pipes to connect a single run of earthed cable to each pipe in turn without the need for any significant bending of the earthed cable between devices or in making connection to the member 12 of each device.

Claims

1. An earth bonding device having a pipe securing member and a cable securing member, the cable securing member comprising an electrically conducting flexible strip which is pressed into electrical contact with the pipe by the pipe securing member.

2. A device as claimed in claim 1, in which the pipe securing member comprises a flexible band co-acting with a tensioning member for drawing the band tightly around the surface of the pipe.

3. A device as claimed in claim 2, in which the flexible band has parts of a screw thread formed therein and the tensioning member includes a threaded tightening screw to engage said screw thread parts.

4. A device as claimed in claim 1, in which the pipe securing member is a flexible band secured at one end to a cradle and tightened around the pipe by pressure exerted on the band by a screw threaded in the cradle.

5. A device as claimed in any preceding claim, in which means is provided to lock the pipe securing member in tightened condition about the pipe.

6. A device as claimed in any of claims 2 to 5, in which the electrical conducting flexible strip of the cable securing member embraces the band of the pipe securing member and is thereby pressed into good electrical contact with the pipe as the band is tightened around the pipe.

7. A device as claimed in claim 6, in which the flexible strip of the cable securing member is reinforced with a core plate.

8. A device as claimed in claim 6 or 7, in which the band of the pipe securing member and the flexible strip of the cable securing member are jointly pressed into electrical contact with the pipe by a screwthreaded member.

9. A device a claimed in claim 7 or 8, in which the flexible strip is bent around an end of the core plate remote from the pipe securing member, means being provided to secure the cable between the bent-back end of the strip and the core plate.

10. A device as claimed in claim 9, in which the means to secure the cable in place includes a screw threaded into a hole in the core plate and passing through a hole in the flexible strip.

11. A device as claimed in claim 10, in which an elongate slot is provided in the flexible strip.

12. A device as claimed in claim 10 or claim 11, in which a plurality of screw threaded holes is provided in the core plate for the cable securing means.

13. A device as claimed in claim 1, in which the flexible strip extends parallel to the axis of a cylinder formed by the cable securing member.

14. A device as claimed in claim 13, in which the flexible strip is bent back on itself to provide a loop to receive the electrical cable, and means is provided to clamp the loop around the cable.

15. An earth bonding device substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 and 2, Figures 3 and 4, Figures 5, 6 and 7, Figure 8 or Figure 9 of the accompanying drawings.

16. A device as claimed in any preceding claim, in which phosphor bronze or stainless steel is used for making the pipe securing member and the cable securing member.