GB2082783A

GB2082783A - Improvements in Electricity Meters

Info

Publication number: GB2082783A
Application number: GB8114870A
Authority: GB
Original assignee: BARROW LUCIEN LEACOCK
Current assignee: BARROW LUCIEN LEACOCK
Priority date: 1980-08-29
Filing date: 1981-05-15
Publication date: 1982-03-10

Abstract

The meter(s) (21, 21a) of an electricity meter installation are fitted into a security container (10, 15) by a plug-and-socket connection so that the meters can be changed by a person other than an electrician. The container lid (15) being made of toughened glass or with glass windows (15a), as shown, to permit meter readings to be made without opening the lid. The lid (15) and the container base (10) are made of magnetically permeable material and/or are spaced so far from the meter mechanisms that the latter cannot be affected by magnets placed outside the casing. Provision may be made to prevent needle holes being drilled in the container. <IMAGE>

Description

SPECIFICATION Improvements in Electricity Meters This invention relates to electricity meter installations, such as may be used in factories, offices and domestic premises.

In the usual meter installations, the incoming mains cable is connected via a mains fuse to one or more meters whose output is connected to a fused distribution box. The mains cable, the meter, the mains fuse and the connecting wires from the latter to the meter must be rendered tamper proof. This is usually effected by seals but occasionally it is possible for persons with sufficient knowledge to "slow the meter down" by disposing magnets in the vicinity of the meter disc. Also it is not unknown for persons to drill a hole through the case and insert a needle which stops the meter disc from rotating. Installations having separate full rate (day-rate) and off-peak (night-rate) meters are common, the night-rate meter output being controlled by a time switch which must also be tamper-proof.Wiring of the two meters and the time switch is laborious and time-consuming as is the application of separate seals to each of such components.

One aspect of the present invention resides in an electricity meter box comprising a robust container having a base and a lid, and at least one power meter mechanism in the container, the lid being of substantially transparent glass or having a glass window to enable a meter reading to be made and the base and the lid being of such materials and/or so arranged that the magnetic field of any magnets, wherever they may be placed outside the container. does not reach the meter mechanism.

The glass of which the lid or the window in the lid is made can be a special magnetically permeable glass which substantially prevents any magnetic field from penetrating through the lid.

Additionally or alternatively the lid can be so far spaced from the meter mechanism that the field of any magnet placed on the outside of the lid cannot reach the meter mechanism across the large air gap thus formed. The glass of which the lid or the window in the lid is made is preferably toughened glass.

Another aspect of the invention consists in an electricity meter installation comprising a robust container having a base and a lid which is substantially transparent or which has a substantially transparent window, at least one meter mechanism in the container and a plugand-socket connection between the meter mechanism and terminals in the base, the meter mechanism being disposed so that a meter reading can be made by viewing through the lid or through the window in the lid, as the case may be.

Preferably a day-rate meter mechanism, a night-rate meter mechanism and a time switch are arranged in the container and each has a respective plug-and-socket connection with corresponding terminals. The terminals may be in line, four-square or triangular formation and can be suitably wired together during manufacture of the container and lead wires for connection to the main fuse and to the distribution box can be wired in at the same time. This minimises site work. The use of plug-and-socket connections also facilitates periodic meter-changing.

Alternatively a single combined day-and-nightrate meter mechanism having a time switch built in with two meters may be used, generally having five terminals which may be arranged in line.

Since the meter mechanisms and the time switch or the combined meter mechanism are arranged in a robust container they do not need to be individually protected by a casing and can simply have a respective chassis, thereby making the meter mechanism itself cheaper to offset the extra cost of the container.

An interlock switch can be associated with the lid so that the power supply to the meter mechanism(s) is automatically switched off before the lid can be opened. This enables nonelectricians to change the meter mechanism(s).

The invention is further described, by way of example, with reference to the drawings, in which Fig. 1 is a front perspective view of an electricity meter box according to the invention, Fig. 2 is a perspective rear view of the meter box, Fig. 3 is a front perspective view of the meter box with its cover opened.

Fig. 4 is a sectional view of the meter box, and Fig. 5 is a perspective view of one of the meter mechanisms to be plugged into the container of the box.

Referrinq first to Figs. 1, 2 and 3, an electricity meter installation comprises a robust container whose base 10 is intended to be permanently mounted by screws 11 or the like on a suitable wall or distribution board (not shown). These screws pass through holes in the container base.

Robust rubber or other suitable material packing 1 a is disposed on the screws 11 so that the meter box is resiliently mounted. Combined plug sockets and terminal blocks 12, 13 and 14 are recessed into holes in the base and secured in position with screws. The base is closed by a lid 1 5 provided with internal hinges 1 6 which are of the kind which are concealed when the lid is closed. The lid has a peripheral lip 17 so as to locate the lid over the upstanding wall 1 8 of the base. The lip 1 7 seats against a peripheral bead 1 7a on the upstanding wall 18, this bead making it difficult to insert a tool beneath the lid for the purpose of prising it open (see Fig. 4).The lid is held closed by an interlock switch 1 9 which is mounted on the base and which has an actuating stem 1 9a adapted to engage with a lock mechanism 20 on the lid 1 5. When the switch 19 is closed, the lid 1 5 cannot be opened and turning of the lock mechanism 20 to release the lid automatically opens the interlock switch. The lock mechanism 20 may be secured by a padlock 20a to prevent unauthorized opening of the lid.

Alternatively the illustrated lock mechanism could be replaced by a tumbler lock.

A full-rate or day-rate meter mechanism 21 (Fig. 5) having plug pins 22 is plugged into the socket 12 and a similarly constructed off-peak rate or night-rate meter mechanism 21 a is plugged into the socket 13. A time switch 21 b provided with suitable plug pins is plugged in the socket 14.

A mains cable 23 leads into a main fuse 24 mounted on the wall or distribution board. Input lead wires 25 connect the outlet side of the mains fuse 24 to the interlock switch whose output is connected to the sockets 12 and 13. The time switch socket 14 is connected to the socket 13 so that the time switch is in series with the nightrate meter. Meter output lead wires 26 and 27 extend from the socket 12 and the time switch 14 and are connected respectively to the consumers's day-rate and night-rate distribution boxes (not shown) mounted on the distribution board. In the case of a consumer who does not have separate day-rate and night-rate distribution systems, the time switch is arranged as a change over switch to connect one or other of the meter mechanisms to the distribution box, according to the switch position.The meter inlet lead wires 25 can be protected by a tamperproof shield 28, attached to the base 10 in a tamperproof manner or secured by security-sealed screws or the like, the main fuse 24 being likewise security-sealed.

The sockets 12, 13 and 14 are suitably wired together during manufacture of the container base 10 and the input and output lead wires 25, 26 and 27 can be wired in at the same time. Thus the only work which needs to be done on-site is the mounting of the base 10 on the wall or distribution board and the connection of the lead wires 25 to the main fuse 24 and the lead wires 26 and 27 to the distribution boxes.

Suitably rated meter mechanisms can be plugged in either at the factory or on-site immediately before locking the lid. If only a single meter is needed, the sockets 13 and 14 simply remain unused and are available for later use if the consumer desires to have a night-rate meter fitted.

Combined day and night-rate meters with built-in time switches are available and usually have five terminals. The invention is applicable to the use of such combined meter mechanisms in which case a single five-pin socket is provided in the base in place of the three sockets shown.

The base 10 can be made from a tough plastics material or from a ceramic material, such as porcelain, and can be of a magnetically permeable material if the meter mechanisms are so close to the wall 1 8 that the meter mechanism could otherwise be influenced by externai magnets placed against the outside of the wall 18. The lid 1 5 may be made of toughened glass which is of such a composition that it is magnetically permeable, but preferably, as illustrated, is made of the same material as the base but has windows 1 5a made of toughened glass to enable meter readings to be taken without opening the lid. The lid thereby prevents the magnetic field of any magnets which may be placed against the outside of the lid from penetrating the lid and reaching the meter mechanisms.If the lid is sufficiently spaced from the meter mechanism so that the resulting air gap between the lid and the meter mechanisms is at least 38 mm, the resulting air gap between any magnets placed against the outside of the lid and the meter mechanisms is so great that the magnetic field from the magnets cannot reach the meter mechanisms, ordinary toughened glass can be used. The shield 28 can also be made of magnetically permeable glass or ceramic.

Ledges 33 are attached to the lid 15 below the windows and, when the lid is closed, come close to the meter mechanisms (see Fig. 4) and are in alignment with the meter discs. The ledges 33 make it very difficult to drill the needle holes through the lid and into the meters for the purpose of inserting needles to stop the meter disc from rotating. The upstanding walls 18 can be internally reinforced at strategic places by means of toughened glass plates to prevent similar drilling from the sides.

It will be seen in Fig. 2 that the base 10 is provided with channels 30 at various places for the lead wires 25, 26 and 27. Any channels not used are closed by glass or ceramic blanks 31 which cannot be removed once the base 10 has been secured to the wall or distribution board.

A further feature of the invention is the provision of at least one switch to automatically place a short across the input lead wires 25 when the lid is removed, whereby the main fuse 24 is blown unless the fuse is removed before opening the lid. This will automatically foil any attempt to use electricity after unauthorised removal of the lid. Also it will ensure that the whole of the electrical installation can be automatically rendered dead simply by smashing the lid as may be appropriate in the case of fire or other emergency. To further this end, the lid could be of heat-sensitive glass which will automatically shatter when subjected to heat or shock. In carrying out this feature of the invention, springbiassed plungers are arranged in the base 10 so as to be depressed by the lid 1 5 when the lid is closed. Each of these plungers is arranged to actuate a respective switch (not shown) when the plunger is released, each such switch being connected across the input lead wires 25. When an authorised electricity engineer wishes to open the lid he must first remove the main fuse before opening the lid and must close the lid before replacing the fuse.

Claims

1. An electricity meter installation comprising a robust container having a base and a lid which is substantially transparent or which has a substantially transparent window, at least one meter mechanism in the container, and a plugand-socket connection between the meter mechanism and terminals in the base, the meter mechanism being disposed so that a meter reading can be made by viewing through the lid or through the window in the lid, as the case may be.

2. An installation as claimed in claim 1, in which a day-rate meter mechanism, a night-rate meter mechanism and a time switch are arranged in the container and each has a respective plugand-socket connection with corresponding terminals.

3. An installation as claimed in claim 1, in which a single combined day-and-night-rate meter mechanism having a time switch built in with two meters is arranged in the container and has a plug-and-socket connection with corresponding terminals.

4. An installation as claimed in claim 1, or 2, or 3, in which the terminals are wired together during manufacture of the container.

5. An installation as claimed in claim 4, in which lead wires for connection to the main fuse and to the distribution box are wired in during manufacture of the container.

6. An installation as claimed in any of claims 1 to 5, in which the base and the lid of the container are of such materials and/or so arranged that the magnetic field of any magnets, wherever they may be placed outside the container, does not reach the meter mechanism.

7. An electricity meter box comprising a robust container having a base and a lid, and at least one power meter mechanism in the container, the lid being of substantially transparent glass or having a glass window to enable a meter reading to be made and the base and the lid being of such materials and/or so arranged that the magnetic field of any magnets, wherever they may be placed outside the container, does not reach the meter mechanism.

8. An installation or box as claimed in claim 6 or 7, in which the glass of which the lid or the window in the lid is made is a magnetically permeable glass which substantially prevents any magnetic field from penetrating through the lid.

9. An installation or box as claimed in claim 6, 7 or 8, in which the lid is so far spaced from the meter mechanism that the field of any magnet placed on the outside of the lid cannot reach the meter mechanism across the large air gap thus formed.

10. An installation or box as claimed in any of claims 6 to 9, in which the glass of which the lid or the window in the lid is made is toughened glass.

11. An installation or box as claimed in any of claims 6 to 10, in which the container base is made of tough plastics material.

12. An installation box as claimed in any of claims 6 to 10, in which the container base is made of a ceramic material.

1 3. An installation or box as claimed in any of claims 6 to 12, in which the container base is made of a magnetically permeable material.

14. An installation or box as claimed in any of claims 6 to 13, in which the lid or the window therein, as the case may be, is spaced by at least 38 mm from the meter mechanism(s).

1 5. An installation or box as claimed in any of claims 6 to 14, in which a ledger is attached to the interior of the lid so as to lie in alignment with the disc(s) of the meter mechanism(s).

16. An installation or box as claimed in claim 15, in which the ledge is made of glass.

17. An installation or box as claimed in any of claims 6 to 1 6, in which the walls of the container base are strategically reinforced by glass plates.

1 8. An installation or box as claimed in any of claims 1 to 17, in which an interlock switch is associated with the lid so that the power supply to the meter mechanism(s) is automatically switched off before the lid can be opened.

19. An installation or box as claimed in any of claims 1 to 17, in which a switch is provided to automatically place a short circuit across the input lead wires should the lid be removed.

20. An installation or box as claimed in claim 19, in which the lid is made of heat-sensitive glass.

21. An installation or box as claimed in any preceding claim, in which the container base has holes to receive mounting screws and a robust packing is provided for disposition on the screws to resiliently mount the container.

22. An installation or box as claimed in any preceding claim, in which the terminals are combined with plug sockets of the plug-andsocket connection.

23. An installation or box as claimed in any preceding claim, in which the lid Is hinged to the base by internally disposed hinges.

24. An installation or box as claimed in any preceding claim, in which the base has a peripheral bead and the lid has a peripheral lip which seats against the bead when the lid is closed.

25. An electricity meter installation, constructed substantially as herein described with reference to and as illustrated in the drawings.