GB2285713A

GB2285713A - Improved electricity supply outlet points

Info

Publication number: GB2285713A
Application number: GB9400401A
Authority: GB
Inventors: Derek Leslie Arthur Barber; Ann Barber
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-01-11
Filing date: 1994-01-11
Publication date: 1995-07-19
Also published as: GB9400401D0

Abstract

The provision, at the periphery of electricity supply wiring systems, of a circuit protection arrangement such as a fuse (2) or a circuit breaker (3) resettable by a pin (5). These may be provided in an outlet socket (1), or located in an adaptor permanently fixed to each outlet socket eg by screws. Each outlet/adaptor can include different types of socket (including an unprotected socket) or ratings of protection and the latter can be selected by the user via a switch. These provisions offer advantages over the necessary provision of a fuse in all plugs. <IMAGE>

Description

IMPROVED ELECTRICITY SUPPLY OUTLET POINTS DLA Barber and A Barber - 8th January 1994 This invention relates to the design of new types of electricity outlet points and outlet point adaptor units for use with electrical power distribution systems.

There are two basic kinds of electricity distribution wiring system used for connecting a number of outlet points (or sockets) to the common fuse box and mains switch, which are associated with the mains supply cable from an electricity supply company. One, known as the Radial system, employs a separate set of wires, or cables, to connect each of several outlet sockets to the common (central) fuse box. The other, known as the Ring Main system, uses a set of wires which passes from a given fuse in the central fusebox to each one, in turn, of a group of outlet sockets, before returning to the same fuse in the fusebox; there may be more than one ring-main at a site.

The ring-main scheme generally requires less connecting cable and so is normally less expensive than the radial scheme, particularly when a large number of outlet sockets are installed. It is also generally easier to add extra sockets at a later date, either by connecting them into the ring-main, or by attaching one or two of them via a spur cable taken from one of the existing sockets.

However, the fuse in the central fusebox which serves each ring main must be of sufficient capacity to support the maximum load provided by the total number of items of equipment connected to the ring-main sockets. As a result, this fuse will be of too large a capacity to adequately protect any individual socket. Also, if this common fuse should fail, all the sockets on the ring-main will suffer a loss of power supply. Therefore, to protect this common fuse and to provide adequate protection to equipment attached to the ring-main, the specification of the standard ring-main system calls for fuses to be fitted in all of the plugs on equipment which may be plugged into the ring-main sockets. In the interests of increased safety, the fuse in each "fused" plug should be chosen properly to match the electrical current loading provided by the associated item of equipment.

With the radial type of electrical power connection, each socket is allocated its own fuse in the central fusebox. This could permit each individual fuse to be chosen to match a particular type of attached equipment; but, more commonly, the fuse is selected to accommodate a maximum allowed loading (usually of around three kilowatts) at each of the outlet sockets. As a result, of course, equipment having a much lower loading will be less well protected.

The ring-main approach using fused plugs is the standard adopted in the United Kingdom: tile radial system is commonplace in many other countries.

Recently, there have been reports in the Press of a possible move towards a European Union standard power plug and socket. These reports have suggested that such a European Standard is likely to be based on the use of the radial system: therefore, the plug will not contain a fuse.

If such un-fused plugs were to be used in the United Kingdom, with an existing standard socket on a ring-main (or with a new "radial system" socket introduced to conformed with a new standard), a potentially dangerous situation would arise. This is because there would no longer be the protection provided by the present fused plugs. The solution to restoring this protection for users, being discussed at present, is the replacement of the UK ring-mains by radial systems. This would be extremely expensive for the UK economy.

The prime purpose of the present invention, described below, is to provide an alternative solution which allows existing ring-main wiring systems to be safely retained; but it may also be used advantageously with radial wiring systems.

According to the invention a fuse (or other form of circuit breaker) is included in each new type of outlet socket, or in an adaptor which is permanently fixed over an existing type of outlet socket. An outlet point, protected in such a way, has significant advantages compared with the various kinds of unprotected outlet points used world-wide at the present time.

The protected outlet points of this invention are specially important in the context of ringmain wiring systems, for these systems may be altered to conform with any new standard, which specifies the use of un-fused plugs, either by changing the existing sockets to new ones, which incorporate protection according to the present invention, or by fitting existing sockets with adaptors which incorporate protection according to present invention; the use of these procedures, as appropriate, will avoid the need for the expensive rewiring of existing systems in premises in the United Kingdom, where there is a requirement to change to a new standard.

However, the protected sockets of this invention could also usefully be used with new radial wiring systems to provide increased safety. In addition, the use of protected sockets would allow installed radial systems to be enhanced by adding spurs to existing wiring, in a manner similar to that adopted with ring-main systems. Also, the replacement of a blown fuse, or the resetting of a tripped circuit breaker, in a protected socket, designed in accordance with the present invention, is likely to be much easier than carrying out such operations at a central fusebox.

It should be noted that the use of a low-rated fuse with a spur to a ring-main system is not a new idea, for it is customary to provide a supply for an electric clock in this way. A clock point has a recess which accommodates a "plug-in" fuse holder, which is held in the recess by a screw to prevent easy removal. The fuse holder, which contains a suitably low-rated fuse, is permanently attached to the clock by a lead. In order to change the fuse, it is necessary to unscrew the fuse holder and remove it from the outlet point, together with the attached connecting lead and clock. Therefore, the fuse holder performs the function of a plug; it is, in essence, a fused plug.

The present invention allows the safe use of unprotected plugs which may be readily inserted into, and removed from, any of the protected sockets, or protected adaptors, which are the subject of this patent application, or which embody variations of the the concepts exposed in this patent application.

The essence of the invention is the provision of circuit protection arrangements at the periphery of electricity supply wiring systems; for example, by making the protection arrangements an integral part of the design of an outlet socket, rather than by having a fuse fitted in every one of the mating plugs.

A variation of the concept, also claimed to be novel, is the inclusion of protection facilities in the form of an adaptor unit, which can be permanently fixed onto an existing un-protected socket (for example, by using long screws through the existing fixing holes of that socket) to provide the required protection to that outlet point.

A protected adaptor may support a socket which is of the same type as the socket to which it is fixed; in this case, its purpose is simply to provide protection in the form of a fuse, contact breaker, or other form of protection mechanism. Alternatively, the adaptor may provide a socket, or sockets, of a type which is different from the socket to which it is fixed. In this case, in addition to providing protection, it may also convert the existing outlet point into one that accepts a different type of plug; for example, one conforming to a new standard,. In this way, some or all of the outlet points in a building could be converted safely to accept the use of un-fused plugs, regardless of whether the building was wired according to the ring-main or radial wiring schemes.

A further development of the invention could be to provide, at one outlet point, or in one outlet point adaptor, more than one type of outlet socket; each separately protected to a level appropriate for that type of socket. This would allow, for example, a lighting fitting to be connected by a two-pin un-fused plug to a protected "two-pin" socket on a power outlet point adaptor, which was also fitted with a protected power outlet socket.

Another example of the application of this invention is the provision, at one outlet point, or in one outlet-point adaptor, of two types of outlet socket: one type according to a previous standard, to accommodate existing equipment having fused plugs; the other type according to a new standard specifying un-fused plugs. Protection is provided for one or both types of socket as appropriate to meet any relevant safety requirements. This would allow equipment fitted with either type of plug to be connected to that outlet point. This is likely to contribute significantly towards the smooth transition to a new standard, by allowing the easy co-existence of installed equipment, which meets the old standard, with new equipment conforming to the new standard.

A particular advantage, which derives from the use of a circuit breaker, rather than a fuse, in an outlet socket, or outlet-socket adaptor, is the possibility of providing switched levels of protection. For instance, a switch could be provided to allow users to select, for example, 2 amps, 5 amps or 13 amps as the current level at which a breaker disconnected the circuit. This might encourage users to chose a level of protection appropriate to the type of connected equipment, rather than, as is all too often the case with fused plugs, using, indiscriminately, the 13 amp fuse generally supplied with new plugs.

Some examples of the embodiment of the invention in practical outlet sockets and adaptors are shown in figures 1 and 2, and are described below. For the purposes of illustration, the power sockets shown are of the type standardised in the United Kingdom.

However, it is clearly possible to apply the invention to other types of outlet point which already exist, or may be devised in the future.

Figure 1 shows two examples of a protected socket. The one on the left contains a fuse; that on the right has a circuit breaker. The main component parts are as follows: 1 - A socket to a new design incorporating protection, or an existing typed of socket redesigned, or modified, to incorporate protection.

2 - A fuse holder.

3 - A circuit breaker.

4 - A hole through which a pin may be pushed to reset the circuit breaker.

5 - A pin for resetting the circuit breaker.

Figure 2 shows an example of a protected adaptor. The main component parts are as follows: A - The existing outlet socket, which is being adapted by fitting an adaptor over it.

B - The body of the adaptor.

C - A push-button in the body of the adaptor, to reset the circuit breaker.

D - A hole for a fixing screw to attach the adaptor to an existing socket.

E - A long fixing screw to replace the original fixing screw of the socket.

F - The fixing lugs in the existing socket housing.

Note that the original fixing screws are discarded. The new longer screws pass through the fixing holes in the adaptor and the holes in the existing socket to fix the whole assembly into the existing socket housing. There is no need for the existing socket to be removed; therefore, the process of fitting the adaptor is a very safe one.

Claims

1. The provision of circuit protection facilities at the periphery of electricity supply wiring systems, as an integral part of the design of the outlet point arrangements, rather than providing protection by having a fuse fitted in every one of the possible mating plugs.

2. An electrical outlet point, for use at the periphery of electricity supply wiring systems, that comprises an outlet socket which incorporates circuit protection arrangements within the outlet socket, rather than in an associated plug.

3. An adaptor which incorporates circuit protection arrangements and which can be permanently attached to an existing un-protected outlet socket to convert it into a protected power outlet point.

4. A protected outlet point, as in (2), which is fitted with more than one type of separately-protected outlet socket.

5. A protected adaptor, as in (3), which is fitted with more than one type of separatelyprotected outlet socket.

6. A protected adaptor, as in (3), which supports a socket which is of the same type as the socket to which it is fixed; in this case, its purpose is simply to provide protection in the form of a fuse, contact breaker, or other form of protection mechanism.

7. A protected adaptor, as in (3), which supports a socket of a type which is different from the socket to which it is fixed. In this case, it converts the existing socket to accept a different type of plug; for example, one conforming to a new standard, in addition to providing protection.

8. An outlet point, as in (2), with more than one type of outlet socket; each separately protected to a level appropriate for that type of socket.

9. An outlet point adaptor, as in (3) with more than one type of outlet socket; each separately protected to a level appropriate for that type of socket.

10. An outlet point with two types of outlet socket: one type according to a previous standard, to accommodate existing equipment having fused plugs; the other type according to a new standard specifying un-fused plugs. Protection would be provided for one or both types of socket as appropriate to meet any relevant safety requirements.

11. An outlet-point adaptor with two types of outlet socket: one type according to a previous standard, to accommodate existing equipment having fused plugs; the other type according to a new standard specifying un-fused plugs. Protection would be provided for one or both types of socket as appropriate to meet any relevant safety requirements.

12. An outlet point, incorporating protection arrangements, fitted with more than one type of outlet socket: each type of socket meeting the requirements of a particular type of connected equipment.

13. An outlet-point adaptor, incorporating protection arrangements, with more than one type of outlet socket: each type meeting the requirements of a particular type of connected equipment.

14. An outlet-point adaptor incorporating protection in the form of a circuit breaker which provides a facility for selecting different levels of protection, at one or more outlet sockets.

Amendments to the claims have been filed as follows 1. The provision of circuit protection facilities at the periphery of electricity supply wiring systems, as an integral part of the design of the outlet point arrangements, rather than providing protection by having a fuse fitted in every one of the possible mating plugs.