GB2263826A

GB2263826A - Earth continuity connection

Info

Publication number: GB2263826A
Application number: GB9300067A
Authority: GB
Inventors: Brian David Hamblin; Reinhold Barlian
Original assignee: BARLIAN TECHNIK Ltd
Current assignee: BARLIAN TECHNIK Ltd
Priority date: 1992-01-10
Filing date: 1993-01-05
Publication date: 1993-08-04
Anticipated expiration: 2013-01-05
Also published as: GB9200436D0; GB9300067D0; GB2263826B

Abstract

An earthing connection for electrical equipment includes an earthing plate (10) to be received in an item of electrical equipment. Earth connection means (20) engage with an electrically conductive part (not shown) extending into the electrical equipment and with the earthing plate (10). The connection means may be formed as a split ring, hinged at (22), and connect to the part and to the plate (10) by a bolt (28), spacer (30) and nut (32). The plate (10) may be deposited on or moulded with the equipment. <IMAGE>

Description

EARTH CONTINUITY This invention relates to the provision of earth continuity in electrical equipment.

Traditionally, electrical equipment such as terminal boxes and junction boxes were made of metal and problems about electrical continuity did not arise.

With the replacement of metal equipment by equipment made of plastics it is now important to ensure that there is proper earth continuity between the conductors or other components, i.e. cable glands for armoured cable that are led into the equipment. Where regulations provide that earthing in such equipment is not permitted by trapping an earth plate against the inner wall of the equipment, which being non-metallic may be considered to be capable of relaxation thus giving an unstable connection.

The need for good earth connection in many kinds of equipment is becoming more important. For example with the increasing use of electrical and electronic equipment which is designed to operate at very low power it becomes highly important to ensure that parts of the equipment that are intended to be at earth potential do, in fact, meet that requirement. Imperfectly earthed equipment of this kind may not operate correctly or in some cases be damaged. The same is true of electrical protection systems and many other kinds of electrical and electronic equipment.

Earthing usually needs to be effected when equipment is installed. However, due to limitations of space the earthing, which requires the application of a tightening tool, such as a spanner, may not be possible.

With the introduction of new standards it may also be necessary to provide for improved earth connections in existing equipment.

The invention has been made in order to deal with these problems.

According to the invention there is provided an earthing connection for electrical equipment comprising an earthing plate adapted to be received in an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

A particularly preferred construction comprises an enclosure of plastics material with the earthing plate moulded into the enclosure so that at least a part of the earth plate is exposed inside the enclosure.

The earth plate may be provided on the interior faces of the enclosure or be captured in the walls of the enclosure so as to provide a sandwich type construction.

According to the invention there is further provided an earthing connection for electrical equipment comprising an earthing plate moulded into or onto an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

According to another aspect of the invention there is provided an earthing connection for electrical equipment comprising an earthing plate deposited onto an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

According to a further aspect of the invention there is provided an earthing connection for electrical equipment comprising an earthing plate about which an item of electrical equipment is moulded, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

When provided on the interior faces of the enclosure, the earthing plate may be held in position within the item of electrical equipment by means of grooves formed in the enclosure so that one or more edges of the earthing plate may be positioned within one or more grooves, respectively.

Preferably, at least some of the grooves extend adjacent to the corners of the enclosure. The grooves may be formed at the edges of the earthing plate during the moulding process.

Since there may be little or no bonding between the earthing plate and the item of electrical equipment, the grooves serve to retain the earthing plate in position so that, for example, the earthing plate does not tend to separate from the enclosure when an aperture is drilled through the item of electrical equipment and earthing plate.

In a preferred embodiment of the invention means is provided for connecting each earth connection means to the earth plate. The earth connection means is of the kind which can clamp onto the electrically conductive part which extends into the equipment. Examples of such earth connection means are disclosed in our co-pending UK Patent Applications 9102075.0 and 9012016.3.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawing in which: Fig.1 is a plan view of an earth plate; Fig.2 shows in exploded side elevation and part section earth connection means and link to an earth plate; and Fig.3 is a perspective view of another embodiment.

Referring to the drawing a metal earth plate 10 of generally cruciform shape is provided with apertures in the form of slots adjacent the free ends of the arms of the cross. The plate is sized and shaped in accordance with the equipment in which it is to be placed. Thus a cruciform shaped plate is intended for use in a piece of equipment such as a junction box of rectangular section so that when placed in the equipment the free ends of arms of the cross are disposed adjacent the walls of the equipment. It will be understood, therefore, that the invention is not limited to any particular size or shape of earth plate. It will also be understood that the metal earth plate can be deposited on or moulded into the equipment or that the equipment can be moulded about the metal earth plate.

In order to make an earth connection between the earth plate and an item projecting through the wall of the equipment an earth connection means is provided, for example in the form of a split ring 20 as shown in Fig.2. The split ring consists of two substantially semi-circular pieces of metal joined at one end by a hinge 22. A flange 24 is provided at the other, free end, of each semi-circular piece. Apertures 26 are provided in each flange. A threaded stud 28 extends from beneath the earth plate 10 through a slot 12, and then through a distance piece 30, through the apertures 26 in flanges 24. The assembly can be tightened together by a nut 32.

In use the earth connection means is positioned around the item to be earthed, for example the entry portion of a cable gland or other termination means which extends through the wall of the equipment in which the earth plate is located. The slot 12 in the earth plate enables the split ring 20 to be moved to the best position for engagement with the item to be earthed.

The nut 32 is then tightened thereby clamping the split ring onto the item to be earthed and at the same time making a sound earth connection to the earth plate.

In another embodiment of the invention as shown in Fig.3 the earth connection means, which may, as shown, be in the form of a split ring, can be fastened to the earth plate 10 by a rivet 32 or the like. In the embodiment illustrated the split ring is fixed to the upturned free end of one of the arms of the cruciform metal plate. The split ring can be pivotted around the riveted connection to the metal plate so as to bring it into the desired position for making connection to the item to be earthed.

It is to be understood that the above described embodiments are not the only ways of carrying out the invention and that many modifications and variations can be made. For example the split ring or other earth connection means can be arranged at any angle or position relative to the earth plate so as to receive items entering the equipment at any disposition. The earth connection means can be different. For example it can be in accordance with the assemblies described and claimed in our co-pending application No.9012016.3.

Included amongst the embodiments described in the aforesaid co-pending application 9012016.3 is a connection means which comprises two semi-circular pieces of metal joined together at their free ends to form a ring by fasteners, for example, nuts and bolts.

Such a connection means can be fastened to the earth plate in the present invention by one nut and bolt and the other nut and bolt used to tighten the connection means around an item to be earthed.

The invention can be usefully applied to existing equipment in which earthing does not meet the present requirements, for example because the earth connection relies on compression of the non-metallic wall of equipment. By fitting the present invention to existing equipment the earth requirements can, where necessary, be upgraded to meet the present requirements.

Claims

1. An earthing connection for electrical equipment comprising an earthing plate adapted to be received in an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

2. An earthing connection for electrical equipment comprising an earthing plate moulded into or onto an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

3. An earthing connection for electrical equipment comprising an earthing plate deposited onto an item of electrical equipment, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

4. An earthing connection for electrical equipment comprising an earthing plate about which an item of electrical equipment is moulded, earth connection means engageable with an electrically conductive part extending into the electrical equipment, said earth connection means being connectable to the earthing plate.

5. An earthing connection as claimed in any preceding claim wherein means is provided for connecting said earth connection means to the earth plate.

6. An earthing connection as claimed in any preceding Claim, wherein the earth connection means can be clamped onto the electrically conductive part.

7. An earthing connection as claimed in any preceding claim, wherein the earthing plate is of cruciform shape.

8. An earthing connection as claimed in Claim 7, wherein apertures are provided adjacent the free ends of the arms of the cruciform earthing plate.

9. An earthing connection as claimed in Claim 8, wherein the apertures are slots.

10. An earthing connection as claimed in any preceding claim, wherein the earth connection means is a split ring.

11. An earthing connection as claimed in Claim 10, wherein the split ring consists of two substantially semi-circular pieces of metal joined at one end by a hinge.

12. An earthing connection as claimed in Claim 10 or Claim 11 when dependent on any of claims 7, 8 or 9, wherein the split ring is fixed to the upturned free end of one of the arms of the cruciform earthing plate.

13. An earthing connection as claimed in any preceding claim, wherein retention means is provided to inhibit separation of the earthing plate from the item of electrical equipment.

14. An earthing connection as claimed in Claim 13, wherein said retention means comprises one or more grooves.

15. An earthing connection as claimed in any preceding claim, wherein the earthing plate is held in position within the.item of electrical equipment by means of one or more grooves.

16. An earthing connection as claimed in Claim 14 or Claim 15, wherein one or more edges of the earthing plate are located respectively in one or more of the grooves.

17. An earthing connection as claimed in any of Claims 14 to 16, wherein the grooves extend adjacent to corners of the item of electrical equipment.

18. An earthing connection as claimed in any of Claims 14 to 17, wherein the grooves are formed at one or more edges of the earthing plate by moulding.

19. An earthing connection for electrical equipment substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.