GB2577501A

GB2577501A - An electrical earthing device

Info

Publication number: GB2577501A
Application number: GB1815637.2A
Authority: GB
Inventors: Rutter Jake
Original assignee: Acumen Electrical Innovations Ltd
Current assignee: Acumen Electrical Innovations Ltd
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2020-04-01
Also published as: GB201815637D0

Abstract

An electrical earthing device includes an earthing nut 1. The earthing nut comprises a nut body 2 with an internal screw thread 3 and a connector 5 configured to receive an earth wire (6, Fig 7). The connector may have apertures 11, 12 for bolts (14, 15, Fig 7), or it may have a resilient retaining member (130, Fig 14) allowing the wire to be connected by a push-fit. The nut may have serrated teeth (26, Fig 5) and be used (Fig 8) with a cable gland (4, Fig 9).

Description

AN ELECTRICAL FARTHING DEVICE

Field of the Invention

The present invention relates to an electrical earthing device in particular, but nor_ exclusively, for providing an earthing connection for an electrical cable at a location at which the electrical cable is connected to an electrical junction box or electrical appliance. The present invention also relates to an earthed cable assembly comprising an electrical earthing device.

The present invention also relates to an electrical earthing nut for use as the, or part of the, electrical earthing device.

The present invention also relates to a method of connection 15 of an electrical earth wire to an electrical earthing device and to a method of installation of an electrical earthing device.

Background of the Invention

When connecting a cable, typically a steel wire armoured 20 (SWA) cable, to an electrical junction box or electrical appliance, it is known to use a cable gland. The cable gland comprises a threaded shaft and a cable retention section. The gland is inserted into an aperture in a wall of the junction box (or electrical appliance) and a nut is screwed onto the threaded 25 shaft to secure the gland to the wall. The cable is passed through the gland into the junction box (or appliance). The cable retention section clamps the cable in the gland by a nut that is screwed onto the cable retention section.

Safety regulations in many jurisdictions require that the 30 cable is earthed. Current methods of earthing the cable use a -2 -type of washer, typically referred to as a 'banjo washer' that is a washer provided with an arm that extends out radially from the washer body. The arm is provided with an aperture for receiving a bolt that also passes through a connection terminal mounted on the end of an earth cable.

However a banjo washer suffers from a number of problems. Firstly, it requires multiple tools and is time consuming to drill the hole in the arm of the banjo washer and to connect the earth cable, which requires stripping the end of the cable, inserting the stripped end into a connection terminal, aligning the connection terminal with the hole, passing a bolt through the connection terminal and hole and securing the bolt so as to fix the connection terminal to the arm of the banjo washer.

Furthermore, the arm of the washer is susceptible to 15 breakage. Also if the washer and/or gland becomes loose, then this can result in a sub-optimal earthing connection.

EP1790053 (Cable Terminology Limited) attempts to address some of the above problems by providing an electrical earthing nut that has a nut body with an internal screw thread for attachment to the threaded shaft of the gland. The earthing nut has a threaded aperture that extends from the radially outer periphery of the nut body, into the nut body. The threaded aperture is for receiving a boll that passes through a connection terminal at the end of an earth cable, so as tc retain the connection terminal in contact with the earthing nut. Accordingly, the earthing nut removes the need for a separate banjo washer.

However, it is still necessary to strip the end of the earth cable, insert the stripped end into a connection terminal, align 30 the connection terminal with the hole in the nut body, pass a bolt through connection terminal and hole and secure a bolt so as to fix the connection terminal to the nut body. This requires multiple tools and is fiddly and time consuming.

The present invention seeks to address or mitigate at least some of the above mentioned problems. Alternatively, or additionally, the present invention seeks to provide an improved electrical earthing device. Alternatively, or additionally, the present invention seeks to provide an improved method of installation of an electrical earthing device.

Summary of the Invention

According to a first aspect of the invention there is provided an electrical earthing device comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; wherein the earthing nut comprises a connector configured to receive an earth wire in the connector; and wherein the earthing device comprises a retaining arrangement for retaining an earth wire, that is in the connector, in electrical connection with the earthing nut.

The electrical earthing device is advantageous in that it may allow for an earth wire to be retained in electrical connection with the earthing nut in a relatively fast and efficient manner that reduces the number of tools that would otherwise be required.

In this respect, it removes the need to fit a stripped end of an earth cable to a connection terminal, align the connection terminal with a hole in the nut body, pass a bolt through the hole and connection terminal and secure a bolt so as to fix the connection terminal to the nut body. -4 -

Instead, a stripped end of an earth cable (i.e. an earth wire) may simply be inserted into the connector and retained in electrical connection with the earthing nut by the retaining arrangement.

Preferably the retaining arrangement is for retaining an earth wire, that is in the connector, in contact with the earthing nut.

Preferably the retaining arrangement is for retaining an earth wire, that is in the connector, in contact with the 10 connector.

The connector may comprise the, or part of the, retaining arrangement.

Preferably the earthing wire is retained in contact with (i.e. in direct contact with) the earthing nut, preferably the 15 connector housing, to provide said electrical connection.

In this respect, preferably the retaining arrangement is for retaining an earth wire, that is in the connector, in contact with the earthing nut, preferably in contact with the connector, preferably in contact with a housing of the connector or in contact with the retaining arrangement.

Optionally the connector is a push-fit connector that comprises a resiliently deformable retaining member arranged such that when an earth wire is inserted into the connector, the retaining member urges the earth wire into electrical connection with the earthing nut, preferably by urging the earth wire into contact with the retaining member. Preferably the retaining member is in contact with the connector housing.

In this respect, in embodiments of the invention the retaining member is configured such that when the earth wire is 30 inserted into the connector, the retaining member automatically -5 -urges the earth wire into electrical connection with the earthing nut and then retains said electrical connection.

This is advantageous in that it provides for fast and simple connection of the earth wire, to the earthing nut, as no tools 5 are required.

Optionally the connector comprises a housing that houses a space for receiving the earth wire, and wherein the resilient retaining member is mounted in the housing.

It will be appreciated that the resiliently deformable 10 retaining member forms the retaining arrangement.

Preferably the resilient retaining member is flexible.

Optionally the resilient retaining member is configured to urge an earth wire into electrical connection with the earthing nut, as the earth wire is inserted into the connector.

Optionally the resilient member is configured such that as the earth wire is inserted into the connector, the resilient member urges the earth wire inco electrical connection with the earthing nut.

Optionally the resilient retaining member is mounted in the 20 connector.

Optionally the resiliently deformable retaining member is a spring.

Optionally the retaining member comprises at least one resilient arm that is configured to be deformed by an earth wire, as the earth wire is inserted into the connector, such that the arm urges the earth wire into electrical connection with the earthing nut.

Optionally the arm extends along a longitudinal axis that is inclined relative to the longitudinal axis of the wire 30 receiving space. -6 -

The arm may be formed by part of a deformed sheet. The arm may be a folded or bent part of a sheet.

Optionally the resilient member comprises a plurality of said arms. Optionally the resilient member is a deformed sheet, preferably a folded or bent sheet. The resilient member may be a sheet formed into a general U-shape, where one or more sides are deformed to form said resilient arms.

Optionally the connector comprises a housing and the resilient retaining member is releasably mounted in the housing. 10 Optionally the resilient retaining member is an insert that is detachable from the housing of the connector.

Optionally the resilient retaining member is mounted in the connector housing under compression, preferably such that it can be removed by being further compressed and then removed from the 15 connector housing.

Preferably the resilient retaining member is configured to retain the earth wire in contact with the retaining member and wherein the retaining member is in electrical connection with the connector housing.

In embodiments of the invention the resilient member is made of an electrically conduc-ive material.

The resilient member may be made of steel.

It will be appreciated that, where the connector is a push-fit connector, the connector comprises the retaining arrangement. In this respect, the earthing nut comprises the retaining arrangement and the electrical earthing device is the electrical earthing nut.

Optionally the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mounted 30 in the aperture and is movable to a retaining configuration to -7 -retain an earth wire, that is in the connector, in electrical connection with the earthing nut, preferably by retaining the earth wire in contact with the connector housing.

Preferably the aperture is provided in the connector 5 housing, preferably a side of The connector housing.

Optionally the earthing nut comprises an abutment surface that is arranged such that when the retaining member is in said retaining configuration, the earth wire is clamped between the retaining member and the abutment surface, so as to retain the earth wire in electrical connection with the earthing nut.

Preferably the retaining arrangement is for retaining an earth wire, that is in the connector, in contact with the connector housing.

Preferably the abutment surface is a surface of the 15 connector, preferably a surface of the connector housing.

Optionally the retaining member is moveable to a releasing configuration to allow the earth wire to be moved out of electrical connection with the earthing nut.

Optionally the aperture is a threaded aperture and the retaining member is a threaded fastener configured to engage with the threaded aperture so that the fastener can be moved between the retaining and releasing configurations by screwing and unscrewing the fastener in the aperture.

Preferably the retaining member is a threaded bolt or screw.

Optionally the connector housing houses a space for receiving the earth wire.

In embodiments of the invention the wire receiving space is an internal space in the housing.

Optionally the nut body extends generally in a plane and 30 wherein the wire receiving space has a longitudinal axis that is -8 -transverse to said plane. Optionally the longitudinal axis is substantially perpendicular to said plane. Optionally the wire receiving space has a longitudinal axis that is substantially parallel to the longitudinal axis of the nut body.

In embodiments of the invention the wire receiving space is open at a receiving end that forms a first aperture in the connector, and wherein the aperture of the retaining arrangement forms a second aperture in the connector housing.

Optionally the longitudinal axis of the aperture of the retaining arrangement is transverse to the longitudinal axis of the wire receiving space. Preferably the longitudinal axis of the aperture of the retaining arrangement is substantially perpendicular to the longitudinal axis of the wire receiving space.

Optionally the retaining arrangement comprises a plurality of said apertures and retaining members. Optionally the plurality of apertures are provided in the same side of the housing of the connector.

Optionally a surface of the nut body is provided with 20 serrated teeth configured to contact a surface, against which the electrical earthing nut is tightened in use.

The serrated teeth are advantageous in that they may prevent rotation of the electrical earthing nut relative to the surface. Furthermore, the serrated teeth may act to reduce vibration 25 of the earthing nut, to prevenr_ it shaking loose in use.

Optionally the nut body has an external perimeter shape configured to fit a tool such that the nut can be screwed or unscrewed, on a threaded shaft, by the tool. The tool may be a tensioning device, for example a spanner. The nut body may have -9 -at least two sides. The nut body may have a polygonal outer perimeter. The nut body may have a hexagonal outer perimeter. In embodiments of the invention the connector is in electrical connection with the nut body. In embodiments of the 5 invention the connector is in contact with the nut body.

It will be appreciated that, in the context of this application, an 'electrical connection' between two things (or electrically connecting' two things) refers to those things either being in direct contact, or with one or more electrically conductive intermediary solid bodies (i.e. not air), that are between them, and provide a continuous path between the two things, such that an electric current applied to one thing passes to the other thing. In this respect it will be appreciated that, in the context of this application, an 'electrical connection' between two things (or 'electrically connecting' two things) does not refer to a connection of either of those things to an electrical power supply.

The connector may be mounted on the nut body, preferably on a side of the outer perimeter of the nut body. The connector may 20 be mounted on a planar side face of the nut body.

The connector may extend radially outwardly from the nut body. The connector may extend above and/or below the nut body. This is advantageous in that it may allow a person to grip the the connector, when tightening the shaft nut and/or earthing nut. This may remove the need 7_40 use a tool, such as a spanner, to hold the earthing nut in place, or to tighten or loosen the earthing nut.

In embodiments of the invention the connector is fixed to the nut body. In embodiments of the invention the connector and -10 -the nut body form a single piece. The connector may be integrally formed with the nut body.

In embodiments of the invention the earthing nut is made of an electrically conductive material. In embodiments of the 5 invention the nut body is made of an electrically conductive material. Preferably the nut body is made of brass or steel. In embodiments of the invention the connector, preferably the connector housing, is made of an electrically conductive material. Preferably the connector is made of brass or steel.

In embodiments of the invention the retaining member, of the retaining arrangement, is made of an electrically conductive material. Preferably the retaining member is made of brass or steel.

According to a second aspect of the invention there is provided an assembly comprising an earthing device according to the first aspect of the invention and an earth wire received in the connector and retained in electrical connection with the earthing nut by the retaining arrangement.

According to a third aspect of the invention there is provided an earthed cable assembly comprising: a shaft mounted in an aperture in a wall; an assembly according to the second aspect of the invention, where the earthing nut is mounted on a threaded section of the shaft, on a first side of the wall; a shaft nut provided on the shaft on a second side of the wall, opposite to the first side, to retain the earthing nut in position; and an electrical cable mounted in the shaft.

The shaft nut may be fixed to the shaft. Alternatively the shaft nut may be a nut that is a separate component to the shaft, that is screwable onto the shaft.

The electrical cable may pass through the shaft.

The shaft may be part of a gland. In this respect, the earthed cable assembly may comprise a gland that has a first section that forms the shaft and second section that is a cable retention section configured to retain a cable in the gland. The earthed cable assembly may comprise a cable retention nut screwed onto the cable retention section of the gland so as to retain the cable in the gland.

The electrical cable may pass through the gland.

The electrical cable may be a multi-core cable. The 10 electrical cable may be a steel wire armoured cable.

Optionally the wall is a wall of a junction box or other electrical appliance. The wall may be plastic. The wall may be metal.

According to a fourth aspect of the invention there is 15 provided an earthing nut for use as the earthing nut in any of the preceding aspects of the invention.

According to a fifth aspect of the invention there is provided an earthing nut for use as the earthing nut in the first aspect of the invention, the earthing nut comprising: a nut body with an internal screw thread; and a connector configured to receive an earth wire in the connector; wherein an aperture is provided in the connector, for receiving a retaining member such that the retaining member is movable to a retaining configuration to retain an earth wire, that is in the connector, in electrical connection with the earthing nut.

According to a sixth aspect of the invention there is provided a kit of parts comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; wherein the earthing nut comprises a connector configured to receive an earth wire in the connector; and wherein -12 -the kit of parts comprises a retaining arrangement for retaining an earth wire, that is in the connector, in electrical connection with the earthing nut.

Optionally the retaining arrangement comprises a resilient retaining member that is mountable in the connector such that, in use, it urges the earth wire into electrical connection with the connector.

Optionally the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mountable in the aperture such that it is movable tc a retaining configuration to retain an earth wire, that is in the connector, in electrical connection with the earthing nut.

Optionally the retaining member is mountable in the aperture such that it is moveable to a releasing configuration, to allow the earth wire to be moved out of electrical connection with the connector.

Optonally the kit of parts comprises a shaft provided with a screw thread for attachment of the earthing nut to the shaft. Optionally the kit of pares comprises a shaft nut.

Optionally the kit of parts comprises an earth wire, for being received in the connector of the earthing nut.

Optionally the kit of parts comprises an electrical cable for mounting in the shaft.

According to a seventh aspect of the invention there is provided a method of electrical connection of an earth wire to an electrical earthing device, the electrical earthing device comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; the earthing nut comprising a connector configured to receive an earth wire in the connector; and the earthing device comprising a retaining -13 -arrangement for retaining an earth wire, that is in the connector, in electrical connection with the earthing nut; wherein the method comprises inserting an earth wire into the connector and using the retaining arrangement to retain the earth wire in electrical connection with the earthing nut.

Optionally the connector is a push-fit connector and the method comprises inserting the earth wire into the push fit connector, wherein the push fit connector retains the earth wire in electrical connection with the earthing nut.

Optionally the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mounted in the aperture, and wherein the method comprises moving the retaining member to a retaining configuration in which it retains the earth wire in electrical connection with the earthing nut.

According to an eighth aspect of the invention there is provided a method of installation of an electrical earthing device, the method comprising: (a) inserting a shaft through an aperture in a wall; (b) screwing an electrical earthing nut, of an electrical earthing device according to the first aspect of the invention on a threaded section of the shaft, on a first side of the wall; (c) arranging a shaft nut on the shaft on a second side of the wall, so as to retain the earthing nut in position; (d) electrically connecting an earth wire to the electrical earthing device according to the method of the seventh aspect of the invention; (e) mounting an electrical cable in the shaft.

-14 -Optionally the shaft nut is fixed to the shaft and wherein step (c) comprises rotating the shaft nut so as to rotate the shaft relative to the earthing nut so that the thread of the shaft is screwed along the thread of the earthing nut to clamp the earthing nut in position.

Optionally the wall is a wall of a junction box or other electrical appliance.

Alternatively, the shaft nut may be a separate component to the shaft, that is screwable onto the shaft. In this case, step (c) may comprise screwing the shaft nut onto the shaft so as to clamp the earthing nut in position.

Preferably step (c) comprises holding the electrical earthing nut in place whilst the shaft nut is rotated. Preferably step (c) comprises tightening the earth nut 15 and/or shaft nut against a respective side of the wall. Preferably, the earthing nut and/or shaft nut are in contact with the wall, i.e. with respective sides of the wall. In this case, step (c) may comprise screwing the shaft nut and/or electrical earthing nut against the side of the wall that they are on.

Alternatively an intermediary member may be mounted between the wall and the earthing nut and/or shaft.

Preferably the steps occur in the order (a) then (b) then (c) then (d) then (e). However, the steps may occur in a 25 different order. For example, step (d) may occur before step (c). Step (e) may occur before any of steps (b) to (d).

In embodiments of the invention step (e) comprises passing the electrical cable through the shaft such that it passes through the wall.

-15 -The method may comprise screwing a cable retention nut onto the cable retention section so as to retain the cable in the gland.

In embodiments of the invention the nut body is made of an 5 electrically conductive material. In embodiments of the invention the gland is made of an electrically conductive material. In embodiments of the invention the threaded shaft is made of an electrically conductive material. In embodiments of the invention the cable retention section is made of an 10 electrically conductive material. Preferably the electrically conductive material is brass or steel.

The earth wire may be an exposed section of an electrical earth cable, i.e. a section where an insulating outer cover has been removed.

In embodiments of the invention the earth wire is electrically connected to earth.

In embodiments of the invention the earth wire is not connected to the connector via a connection terminal.

According to a ninth aspect of the invention there is provided an electrical earthing device comprising: an electrical earthing nut, the earthing nut comprising a nut body with an Internal screw thread; wherein the earthing nut comprises a connector configured to receive an electrical earth wire in the connector; and wherein the earthing device comprises a retaining arrangement for retaining an electrical earth wire, that is in the connector, in contact with the earthing device.

According to a tenth aspect of the invention there is provided a method of connecting of an electrical earth wire to an electrical earthing device, the electrical earthing device 30 comprising: an electrical earthing nut, the earthing nut -16 -comprising a nut body with an internal screw thread; the earthing nut comprising a connector configured to receive an earth wire in the connector; and the earthing device comprising a retaining arrangement for retaining an earth wire, that is in the connector, in contact with the earthing device; wherein the method comprises inserting an electrical earth wire into the connector and using the retaining arrangement to retain the earth wire in contact with the earthing device.

The features of any of the above aspects of the invention 10 may be combined with one or more features of any of the other aspects of the invention, in any combination.

Other preferred and advanrageous features of the invention will be apparent from the following description.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the description and drawings.

Figure 1 shows a front view an electrical earthing nut of 20 an electrical earthing device according to a first embodiment of the present invention; Figure 2 shows a cross-sectional view taken along section A-A in Figure 1; Figure 3 shows a plan view (with part of the internal 25 structure of the nut shown) of the electrical earthing nut shown in figure 1; Figure 4 shows a bottom view of the electrical earthing nut shown in figure 1; Figure 5 shows a perspective view, from below, of the 30 electrical earthing nut shown in Figure 1; -17 -Figure 6 shows a perspective view, from above, of the electrical earthing nut shown in Figure 1; Figure 7 shows a cross-sectional view corresponding to the view shown in Figure 2, but with an electrical earth wire received in a connector of the electrical earthing nut and first and second retaining bolts engaged in retaining apertures in the connector, so as to retain the earth wire in electrical connection with the earthing nut; Figure 8 shows a front view of the electrical earthing nut, shown in Figures 1 to 7, installed as part of an earthed cable assembly according to a further embodiment of the invention, but where the retaining bolts of the electrical earthing device are omitted for illustrative purposes; Figure 9 shows a side view of a cable gland of the earthed 15 cable assembly shown in Figure 8; Figure 10 shows a plan view of a wall of an electrical junction box of the earthed cable assembly shown in Figure 8; Figure 11 shoes a flow chart illustrating the steps in the method of installation of the first embodiment of the electrical earthing device; Figure 12 shows a perspective view, from above, of an electrical earthing device according to a second embodiment of the present invention; Figure 13 shows a front view of the second embodiment of 25 the electrical earthing device shown in Figure 12; Figure 14 shows a cross-sectional view taken along the line C-C in Figure 13; Figure 15a shows a side view of a steel spring insert of the connector of the second embodiment of the earthing device 30 shown in Figures 13 and 14; -18 -Figure 15b shows a perspective view of the spring steel insert shown in Figure 15a; Figure 16 shows a view corresponding to that of Figure 14, but where an electrical earth wire is connected to the earthing 5 device; Figure 17 shows a front view of the second embodiment of the electrical earthing device, shown in Figures 12 to 16, installed as part of an earthed cable assembly according to a further embodiment of the invention, and Figure 18 shoes a flow chart illustrating the steps in the method of installation of the second embodiment of the electrical earthing device.

Detailed Description

Referring to Figures 1 to 6 there is shown an electrical earthing nut 1 of an electrical earthing device 100 (see Figure 7) according to a first embodiment of the present invention. The electrical earthing nut 1 comprises a nut body 2 20 provided with an internal screw thread 3 (see Figure 6) for attachment of the earthing nut 1 to a threaded shaft 54 of a gland 4 (see Figure 8).

The nut body 2 extends in a thickness direction, along a central longitudinal axis B, from a first surface 24 to a second 25 surface 25 (which, in the orientation shown in the Figures, are upper and lower surfaces of the nut body 2 respectively).

The nut body 2 has a radially inner surface that defines an internal generally cylindrical aperture 10, that has a longitudinal axis that is co-axial with the longitudinal axis B 30 of the nut body 2, and a generally hexagonal radially outer -19 -perimeter, formed by six substantially planar outer faces 23. The hexagonal outer perimeter is sized and shaped to fit a spanner such that the electrical earthing nut 1 can be screwed or unscrewed on the threaded shaft 54 of the gland 4 by the spanner (discussed in more detail below). It will be appreciated that the nut body 2 may have any suitable shape, for example the outer perimeter may have a polygonal shape.

The second surface 25 of the nut body 2 is provided with a set of serrated teeth 26 (see Figure 4), comprising a plurality of serrated teeth 26, that each extend generally in the radial direction (relative to the longitudinal axis B of the nut body 2), distributed circumferentially around the second surface 25, about the longitudinal axis B of the nut body 2. The set of teeth 26 form a continuous ring of teeth around the longitudinal axis B of the nut body 2.

The earthing nut 1 further comprises a connector 5 for an electrical earth wire 6 of an electrical earth cable 40(see Figure 7). The earth cable 40 comprises an earth wire housed in an insulating sheath 41. At an end of the earth cable 40, a section of the insulating sheath 41 has been removed, so as to expose an end section of the earth wire 6. It will be appreciated that references to the earth wire 6 are to the exposed end section 6 of the earth wire 6.

The connector 5 is mounted on a side of the nut body 2. In this respect, the connector 5 is mounted on one of the planar outer faces 23 of the hexangonal outer perimeter of the nut body 2. The connector 5 comprises a housing 7 that has a cuboidal shape, extending in a length direction (i.e. the longer dimension of the housing 7) from a first end 21 to a second end 22, along a longitudinal axis A (see Figure 2).

-20 -The housing 7 is oriented such that its longitudinal axis A is substantially parallel to (but offset from) the central longitudinal axis B of the nut body 2 (see Figure 2).

An inner surface 65 of the housing 7 defines a wire 5 receiving space 8, inside the housing 7, for receiving the earth wire 6.

The connector 5 is integrally formed with the nut body 2 The connector 5 and nut body 2 are each made of an electrically conductive material. In the currently described embodiment, the connector 5 and nut body 2 are each made of brass. However, it will be appreciated that other electrically conductive materials may be used.

The connector housing 7 protrudes radially outwardly from the radially outer perimeter of the nut body 2 and extends past the first surface 24 of the nut body (i.e. above the nut body 2, in the orientation shown in the Figures). This is advantageous in that it may aid a person to grip the earthing nut 1, when tightening the gland nut 53 and/or earthing nut 1 (see below). This may remove the need to use a tool, such as a spanner, to hold the earthing nut 1 in place, or to tighten or loosen the earthing nut 1.

The wire receiving space 8 extends from an open end, that forms a circular aperture 9 in the first end 21 of the housing 7, to a closed end formed by the second end 22 of the housing 7.

The open end of the wire receiving space 8 is a wire receiving end.

The wire receiving space 8 is substantially cylindrical and has a central longitudinal axis C that is substantially coaxial with the longitudinal axis A of the housing 7. In this respect, 30 the longitudinal axis C of the wire receiving space 8 is -21 -substantially parallel to (but offset from) the longitudinal axis B of the nut body 2. The inner surfaces of the housing 5 that define the wire receiving space 8 are not threaded, and instead present a generally smooth surface.

First and second retaining apertures 11, 12 are provided in a radially outer side of the connector housing 7 (radially outer relative to the longitudinal axis B of the of the nut body aperture 10). The first and second retaining apertures 11, 12 each extend radially inwardly (relative to the longitudinal axis A of the connector 5) from a respective opening in the radially outer side of the connecter housing 7, through the thickness of that side of the connecter housing 7 such that they open into the wire receiving space 8 (i.e. they are in communication with the wire receiving space 8).

Each of the retaining apertures 11, 12 is generally cylindrical and threaded so as to receive a respective retaining member in the form of a threaded bolt 14, 15 (see Figure 7), screwed into it.

The first and second retaining apertures 11, 12 and the first and second retaining bolts 14, 15 together form a retaining arrangement of the earthing device 100, for retaining the electrical wire 6, that is in the wire receiving space 8, in contact with the housing 7 and so in electrical connection with the nut body 2 (as described in more detail below). The earthing nut 1 and retaining bolts 14, 15 together form the electrical earthing device 100.

It will be appreciated that the first and second apertures 11, 12 of the retaining arrangement 13, are distinct and separate apertures to the aperture 9 formed by the open end of the wire 30 receiving space 8.

-22 -Each of the first and second apertures 11, 12 is oriented such that its central longitudinal axis is substantially perpendicular to the longitudinal axis C of the wire receiving space 0.

Figure 7 shows the earth wire 6 received in the connector and the first and second retaining bolts 14, 15, received in the retaining apertures 11, 12 of the connector 5, so as to retain the earth wire 6 in contact with an opposed inner surface 16 of the connector 5, which forms an abutment surface 16. The abutment surface 16 is part of the inner surface 65 of the housing 7.

The abutment surface 16 is on an opposite side of the connector 5 to the side provided with the retaining apertures 11, 12. As the retaining bolts 14, 15 are screwed into the retaining apertures 11, 12, the retaining bolts 14, 15 push the earth wire 6 against the abutment surface 16. This acts to clamp the earth wire 16 between the bolts 14, 15 and The abutment surface 16, thereby acting to retain the earth wire 6 in contact with the abutment surface 16 and thereby in electrical connection with the connector 5. Since the connector 5 is in electrical connection with the nut body 2 (the connector 5 and nut body 2 are in contact with each other and are made of an electrically conductive material, in this case brass), this thereby retains the earth wire 6 is in electrical connection with the nut body 2.

The earthing nut 1 is for use in electrically earthing an electrical cable 58 (see Figure 8), in particular a steel wire armoured cable (SWA), where it passes to an electrical junction box or electrical appliance.

-23 -In this respect, referring to figure 8 the electrical earthing nut 1 is shown installed as part of an earthed cable assembly 50.

A gland 4 is mounted in a circular aperture 51 in a wall 52 (see Figure 10) of a housing of an electrical junction box. The gland 4 is shown in more detail in figure 9.

The gland 4 comprises a gland nut 53, located substantially midway along the length of the gland 4. The gland nut 53 has a generally hexagonal outer perimeter.

The gland 4 also comprises a threaded shaft 54, on a first side of the gland nut 53, that extends away from the gland nut The threaded shaft 54 is hollow and substantially cylindrical and has an external screw thread for engagement with the internal screw thread 3 of the earthing nut 1 so that the earthing that 1 can be screwed onto (and unscrewed from) the threaded shaft 54.

The gland 4 also comprises a cable retention section 55 that located on a second side of the gland that 53, opposite the first side, extends from the gland nut 53. The cable retention section 55 has the general shape of a hollow truncated cone, which tapers away from the gland nut 53.

A radially inner surface of the gland nut 53 forms a central aperture and the inner bores defined by the inner surfaces of the threaded shaft 54 and cable retention section 55 are in communication with each other (and the aperture in the gland nut 53) such that an electrical cable 58 can be passed through the gland 4 (see figure 8). In the current described embodiment the electrical cable 58 is a steel wire armoured (SWA) electrical cable.

-24 -The cable retention section 55 has a threaded section 56 that extends from the gland nut 53, partway along the length of the cable retention section 55. The threaded section 56 is for engagement with the internal thread of a cable retention nut 57 (see figure 8) such that when the cable retention nut 57 is screwed onto the threaded section 56 and is tightened against the gland nut 53, this acts to compress the cable retention section 55 radially inwardly, so as to retain the cable 58, passing through the gland 4, in position in the gland 4 (see figure 8).

The gland 4 is made of an electrically conductive material. In the currently described embodiment the gland 4 is made of brass. However, it will be appreciated that any suitable electrically conductive material may be used.

The threaded shaft 54 of the gland 4 passes through the aperture 51 in the wall 52 of the electrical junction box, with the gland nut 53 abutting against a second surface of the wall (in the orientation shown this is the lower surface of the wall 52). The earthing nut 1 is mounted on the threaded shaft 54, 20 with its serrated teeth 26 biting into a first surface of the wall 52, which is opposite to the second surface (in the orientation shown the first surface is the upper surface of the wall 52).

The SWA cable 58 passes through the gland 4 (i.e. into the 25 gland 4 through the open (lower) end of the cable retention section 55 and out of the gland 4 through the open (upper) end of the threaded shaft 54, thereby passing through the wall 52. The gland 4, earthing device 100, earth wire 6, SWA cable 58 and the wall 52 of the junction box form an earthed cable 30 assembly 50 according to an embodiment of the invention.

-25 -The earth wire 6 is electrically connected to the earthing nut 1, as described above. Since the earthing nut 1 is in contact with the gland 4, which is also made of an electrically conductive material, the earth wire 6 is thereby electrically connected to the gland 4. Due to the contact of the earthing nut 1 with the wall 52, the earth wire 6 is also electrically connected to the wall 52. Accordingly the earthing rut 1 thereby provides an electrical earth connection for the SWA cable 58.

Referring to figure 11, there is shown a flowchart 10 illustrating the steps in the method of installation 200 of the first embodiment of the electrical earthing device 100.

The gland 4 is mounted to the wall 52 of the junction box by passing the threaded shaft 54 of the gland 4 through the aperture 51 in the wall 52 until the gland nut 53 abuts against the lower surface of the wall 52 (step 201). The electrical earthing nut 1 is then screwed onto the threaded shaft 54 of the gland 4 until the serrated teeth 26 of the earthing nut 1 bite into the upper surface of the wall 52 (step 202). The earthing nut 1 may be screwed by hand and/or with a tensioning device (e.g. a spanner) that fits the hexagonal outer perimeter of the electrical earthing nut body 2.

The earthing nut 1 is held in place (i.e. to prevent its rotation relative to the wall 52) whilst the gland nut 53 is then tightened against the lower surface of the wall 52 (step 203). This screws the shaft 54 through the earthing nut 1 and secures the earthing nut 1 and gland 4 in position, by clamping them either side of the wall 52.

The connector 5 facilitates holding the earthing nut 1 in place, as it can be readily gripped by a user's fingers, due to 30 it protruding above and radially outwardly from the nut body 2.

-26 -The earth wire 6 is then inserted into the wire receiving space 8 of the connector 5 of the earthing nut 1 (step 204). The retaining bolts 14, 15 are then screwed into the retaining apertures 11, 12 to press the earth wire 6 into contact with the abutment surface 16 of the connector 5, so as to retain the earth wire 6 in direct contact with the abutment surface 16 of the housing 7 (step 205).

The SWA cable 58 is then passed through the gland 4, by passing it through the open end of the cable retention section 55 and out of the open end of the threaded shaft 54. In this way, the SWA cable 58 passes through the wall 52 of the junction box (step 206).

The cable retention nut 57 is then screwed onto the cable retention section 55 so as to secure the cable 58 in position in the gland (step 207).

An insulating sheath 60 (shown as a dotted line figure 8) is then slid up the cable 58 to the end of the cable retention section 55 (step 208).

It will be appreciated that once the SWA cable 58 has been passed through the gland 4 into the junction box, it is connected to additional cables and/or components in the junction box as required. Once the earthed cable assembly 50 has been installed, the junction box is then closed.

Referring to Figure 12 there is shown an electrical earthing 25 nut 101 that forms an electrical earthing device 101 according to a second embodiment of the invention.

The electrical earthing device 101 of the second embodiment has identical features to that of the electrical earthing device 100 of the first embodiment, except for the features described -27 -below. Corresponding features are provided with corresponding reference numerals increased by 100.

In the second embodiment, the wire receiving space 108 has a generally cuboidal shape and its open end forms a rectangular 5 aperture 109 in the first surface 121 of the housing 107.

The electrical earthing nut 101 of the second embodiment is identical to that of the first embodiment except in that its connector 105 is a push-fit connector.

In this respect, in the second embodiment, the connector 10 105 does not have the first or second retaining apertures 11, 12 (and its retaining arrangement does not comprise the first or second threaded bolts 14, 15). Instead, the connector 105 has a retaining arrangement in the form of a resilient retaining member 130.

The retaining member 130 is a flexible resilient insert, that lines, and abuts against, a pair of opposed inner surfaces and a lower inner surface of the connector housing 107. The retaining member 130 is made of an electrically conductive material. In the current embodiment the retaining member 130 is made of steel. However, it may be made of any suitable electrically conductive material.

The retaining member 130 is a sheet that is folded into a general U-shape. The retaining member 130 comprises a base section 131 with opposed first and second sides 142, 143 that extend from the base section 131, on either side of the base section 131 (see Figure 14).

The upper end sections of the first and second sides 142, 142 are bent and/or folded so as to form respective resilient arms 132, 133.

-28 -In this respect the first arm 132 is bent inwardly and then outwardy and the second arm 133 is folded and bent inwardly. The retaining member 130 is resiliently deformable and forms a spring. When the earth wire 6 is inserted into the wire 5 receiving space 108, the arms 132, 133 are deflected by the earth wire 6 and, due to their resilience, the arms 132, 133 push back against the earth wire 6 so as to force it into contact with a surface 116 of the retaining member 130 (see Figure 16).

In this way, the earth wire 6 is retained in contact with 10 the retaining member 130 and thereby the connector housing 107 (because the retaining member 130 is electrically conductive). As with the first embodiment, The connector housing 107 and nut body 102 are also made of an electrically conductive material, namely brass. Accordingly, the earth wire 6 is retained in 15 electrical connection with the nut body 102.

The retaining member 130 is mounted in the connector housing 107 under compression, with the sides of the retaining member 130 pushing against the respective adjacent sides of the housing 107 of the connector 105. In this way, the retaining member 130 is retained in the connector housing 107 without requiring any separate fasteners, such as screws or bolts for example. Furthemore, the retaining member 130 can be removed by being further compressed, e.g. by applying force from a screw-driver or other tool that is slide inr_o the connector 105, between the retaining member 130 and the housing 107, and then slid out of connector 105.

Apart from the above differences in the retaining arrangement, the electrical earthing device 101 of the second embodiment works in the same way as the electrical earthing 30 device 100 of the first embodiment. In this respect, figure 17 -29 -shows a view of an earthed cable assembly corresponding to that of figure 8, but with the electrical earthing nut 101 of the second embodiment.

Referring to figure 10, there is shown a flowchart 5 illustrating the steps in the method of installation 300 of the second embodiment of the electrical earthing device 101.

The method of installation of the electrical earthing device 101 of the second embodiment is identical to that of the first embodiment, except in the method of connection of the earth 10 wire 6 to the connector 105.

In more detail, as with the first embodiment, the gland 4 is mounted to the wall 52 of the junction box by passing the threaded shaft 54 of the gland 4 through the aperture 51 in the wall 52 until the gland nut 53 abuts against the lower surface of the wall 52 (step 301). The earthing nut 101 is then screwed onto the threaded shaft 54 of the gland 4 until the serrated teeth 26, on the second surface 26 of the electrical earthing nut 101, bite into the upper surface of the wall 52 (step 302). The electrical earthing nut 101 may be screwed by hand and/or with a tensioning device (e.g. a spanner) that fits the hexagonal outer perimeter of the earthing nut body 102.

Whilst the earthing nut 101 is held in place (i.e. to prevent its rotation relative:,c) the wall 52), the gland nut 53 is tightened against the lower surface of the wall 52 (step 303) by screwing the shaft 54 through the earthing nut 101. This secures the electrical earthing nut 101 and gland 4 in position, by clamping them either side of the wall 52.

The earth wire 6 is inseced into the wire receiving space 108 of the connector 105.

-30 -As the wire 6 is inserted into the wire receiving space 108, the arms 132, 133 of the retaining member 130 are deflected by the earth wire 6 and, due to their resilience, the arms 132, 133 push back against the earth wire 6 so as to force it into contact with the surface 116 of the retaining member 130. In this way, the earth wire 6 is retained in contact with the resilient member 130 and therefore in electrical connection with the connector 105 (step 304).

The SWA cable 58 is then passed through the gland 4, by passing it through the open end of the cable retention section 55 and out of the open end of the threaded shaft 54. In this way, the SWA cable 58 thereby passes through the wall 52 of the junction box (step 305).

The cable retention nut 57 is then screwed onto the cable 15 retention section 55 so as to secure the cable 58 in position (step 306).

An insulating sheath 60 (shown as a dotted line figure 8) is then slid up the cable 58 to the end of the cable retention section 55 (step 307).

It will be appreciated that once the SWA cable 58 has been passed through the gland 4 into the junction box, it is connected to additional cables and/or components in the junction box as required. Furthermore, once the earthed cable assembly 150 has been installed, the junction box is then closed.

The electrical earthing devices 1, 101 of the first and second embodiments of the invention are advantageous in that they may each allow for an earth wire to be retained in electrical connection with an earthing nut in a relatively fast and efficient manner that reduces the number of tools that would otherwise be required.

-31 -In this respect, it removes the need to fit a stripped end of an earth cable to a connection terminal, align the connection terminal with a hole in the nut body, pass a bolt through the connection terminal and hole and secure the bolt so as to fix the connection terminal to the nut body.

Instead, a stripped end of an earth cable (i.e. an earth wire) may simply be inserted into the wire receiving space of the connector of the earthing nut and retained in contact with the connector by the respective retaining arrangement.

The earthing nut 101 of the second embodiment is particularly advantageous in this respect, as it provides for fast and simple connection of the earth wire 6, to the earthing nut 101, as no tools are required.

It will be appreciated that numerous modifications to the 15 above described design may be made without departing from the scope of the invention as defined in the appended claims.

For example, in the described embodiments the earth wire 6 is electrically connected to the connector 5, 105 by being in direct contact with a surface 16, 116 of the connector 5, 105.

Alternatively one or more intermediate members, that are electrically conductive, may be located between the earth wire and the respective surface 16, 116 of the connector, whilst still allowing the earth wire to be electrically connected to the connector 5, 105. However, preferably the earth wire 6 is electrically connected to the connector 5, 105 by being in direct contact with the respective surface 16, 116.

Furthermore, in the described embodiments the gland nut 53 is part of the gland 4 (i.e. it is rotationally fixed relative to the gland 4). Alternatively, the gland not 53 may be a -32 -separate nut that is screwed onto the threaded shaft 54 of the gland nut 4.

In the method of installation of the earthed cable assembly 50, the gland nut 53 is tightened against the lower surface of the wall 52 (whilst the electrical earthing nut 1 is held in place). Alternatively, or additionally, the earthing nut 1 may be tightened against the upper surface of the wall 52, for example whilst the gland nut 53 is held in place.

Preferably the earthing nut 1 is fixed in position on the wall 52 (by the clamping of the electrical earthing nut 1 and gland nut 4 against the wall 52) before the earth wire 6 is connected to the connector 5 of the earthing nut 1. However the earth wire 6 could be connected to the connector 5 of the electrical earthing nut 1 before the electrical earthing nut is fixed in position on the wall 52 (by clamping the electrical earthing nut 1 and gland nut 4 against the wall 52), although this is not preferred.

Furthermore, preferably the SWA cable 58 is passed through the gland 4 after the earthing nut has been fixed in place on the wall by the gland nut 53 and/or after the electrical wire 6 has been connected to the connector 5 of the electrical earthing nut. However, it will be appreciated that the SWA cable 58 may be passed through the gland 4 before the earthing nut 1, 101 has been fixed in place on the wall by the gland nut 53 and/or before the electrical wire 6 has been connected to the connector 5, 105 of the earthing nut.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if 30 individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

-34 -CLAIMS1. An electrical earthing device comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; wherein the earthing nut comprises a connector configured to receive an electrical earth wire in the connector; and wherein the earthing device comprises a retaining arrangement for retaining an electrical earth wire, that is in the connector, in electrical connection with the earthing nut.
2. An earthing device according to claim 1 wherein the connector is a push-fit connector that comprises a resiliently deformable retaining member arranged such that when an earth wire is inserted into the connector, the retaining member urges the earth wire into electrical connection with the earthing nut.
3. An earthing device according to claim 2 wherein the retaining member comprises at least one resiliently deformable arm that is configured to be deformed by an earth wire, as the earth wire is inserted into the connector, such that the arm urges the earth wire into electrical connection with the earthing nut.
4. An earthing device according to either of claims 2 or 3 wherein the connector comprises a housing that houses a -35 -space for receiving the earth wire, and wherein the retaining member is mounted in the housing.
5. An earthing device according to claim 4 wherein the retaining member is releasably mounted in the housing.
6. An earthing device according to claim 1 wherein the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mounted in the aperture and is movable to a retaining configuration to retain an earth wire, that is in the connector, in electrical connection with the earthing nut.
7. An earthing device according to claim 6 wherein the earthing nut comprises an abutment surface that is arranged such that when the retaining member is in said retaining configuration, the earth wire is clamped between the retaining member and the abutment surface, so as to retain the earth wire in electrical connection with the earthing nut.
8. An earthing device according to either of claims 6 or 7 wherein the retaining member is moveable to a releasing configuration to allow the earth wire to be moved out of electrical connection with the earthing nut.
9. An earthing device according to claim 8 wherein the aperture is a threaded aperture and the retaining member is a threaded fastener configured to engage with the threaded aperture so that the fastener can be moved between the retaining and -36 -releasing configurations by screwing and unscrewing the fastener in the aperture.
10.An earthing device according to any of claims 6 to 9 wherein the connector houses a space for receiving the earth wire and wherein the longitudinal axis of the aperture of the retaining arrangement is transverse to the longitudinal axis of the wire receiving space.
11.An earthing device according to any of claims 6 to 10 wherein the retaining arrangement comprises a plurality of said apertures and retaining members.
12.An earthing device according to any preceding claim wherein a surface of the nut body is provided with serrated teeth configured to contact a surface, against which the earthing nut is tightened in use.
13.An earthing device according to any preceding claim wherein the nut body has an external perimeter shape configured to fit a tool such that the nut can be screwed or unscrewed, on a threaded shaft, by the tool.
14.An assembly comprising an earthing device according to any preceding claim and an earth wire received in the connector and retained in electrical connection with the earthing nut by the retaining arrangement.
15.An earthed cable assembly comprising: -37 -a shaft mounted in an aperture in a wall; an assembly according to claim 14, where the earthing nut is mounted on a threaded section of the shaft, on a first side of the wall; a shaft nut provided on the shaft on a second side of the wall, opposite to the first side, to retain the earthing nut in position; and an electrical cable mounted in the shaft.
16.An earthed cable assembly according to claim 15 wherein the wall is a wall of a junction box or other electrical appliance.
17.An earthing nut for use as the earthing nut in any preceding claim.
18.An earthing nut for use as the earthing nut in any of claims 6 to 11, the earthing nut comprising: a nut body with an internal screw thread; and a connector configured to receive an earth wire in the connector; wherein an aperture is provided in the connector, for receiving a retaining member such that the retaining member is movable to a retaining configuration to retain an earth wire, that is in the connector, in electrical connection with the earthing nut.
19.A kit of parts comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; -38 -wherein the earthing nut comprises a connector configured to receive an earth wire in the connector; and wherein the kit of parts comprises a retaining arrangement for retaining an earth wire, that is in the connector, in electrical connection with the earthing nut.
20.A kit of parts according:,c) claim 19 wherein the retaining arrangement comprises a resilient retaining member that is mountable in the connector such that, in use, it urges the earth wire into electrical connection with the connector.
21. A kit of parts according to claim 19 wherein the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mountable in the aperture such that it is movable to a retaining configuration to retain an earth wire, that is in the connector, in electrical connection with the earthing nut.
22.A kit of parts according r_o claim 21 wherein the retaining member is mountable in the aperture such that it is moveable to a releasing configuration, to allow the earth wire to be moved out of electrical connection with the connector.
23.A kit of parts according co any of claims 19 to 22 wherein the kit of parts comprises a shaft provided with a screw thread for attachment of the earthing nut to the shaft.
24.A kit of parts according to claim 23 wherein the kit of parts comprises a shaft nut.
-39 - 25.A kit of parts according co any of claims 19 to 24 wherein the kit of parts comprises an earth wire, for being received in the connector of the earthing nut.
26.A kit of parts according co any of claims 19 to 25 wherein the kit of parts comprises an electrical cable for mounting in the shaft.
27.A method of electrical connection of an electrical earth wire to an electrical earthing device, the electrical earthing device comprising: an electrical earthing nut, the earthing nut comprising a nut body with an internal screw thread; the earthing nut comprising a connector configured to receive an earth wire in The connector; and the earthing device comprising a retaining arrangement for retaining an earth wire, that is in the connector, in electrical connection with the earthing nut; wherein the method comprises inserting an electrical earth wire into the connector and using the retaining arrangement to retain the earth wire in electrical connection with the earthing nut.
28.A method according to claim 27 wherein the connector is a push-fit connector and the method comprises inserting the earth wire into the push fit connector, wherein the push fit connector retains the earth wire in electrical connection with the earthing nut.
-40 - 29.A method according to claim 27 wherein the retaining arrangement comprises an aperture provided in the connector and a retaining member that is mounted in the aperture, and wherein the method comprises moving the retaining member to a retaining configuration in which it retains the earth wire in electrical connection with the earthing nut.
30.A method of installation of an electrical earthing device, the method comprising: (a) inserting a shaft through an aperture in a wall; (b) screwing an electrical earthing nut, of an electrical earthing device according to any of claims 1 to 13, on a threaded section of the shaft, on a first side of the wall; (c) arranging a shaft nut on the shaft on a second side of the wall, so as to retain the earthing nut in position; (d) electrically connecting an earth wire to the electrical earthing device according to the method of any of claims 27 to 29; (e) mounting an electrical cable in the shaft.
31.A method according to claim 30 wherein the shaft nut is fixed to the shaft and wherein step (c) comprises rotating the shaft nut so as to rotate the shaft relative to the earthing nut so that the thread of the shaft is screwed along the thread of the earthing nut to clamp the earthing nut in position.-41 - 32.A method according to either of claims 30 or 31 wherein the wall is a wall of a junction box or other electrical appliance.