GB2351189A

GB2351189A - Test terminal block (TTB) with reduced height connectors that are covered to prevent unintentional contact

Info

Publication number: GB2351189A
Application number: GB0010499A
Authority: GB
Inventors: Roger John Wood
Original assignee: CAMPBELL YORK Ltd
Current assignee: CAMPBELL YORK Ltd
Priority date: 1999-05-01
Filing date: 2000-05-02
Publication date: 2000-12-20
Anticipated expiration: 2020-05-02
Also published as: GB2351189B; GB0010499D0; GB9910427D0

Abstract

A test terminal block (TTB) connecting mains electricity cables and electrical meters to allow testings of the circuits comprises connector blocks 1-13 arranged on a base (14, fig 2) within a casing (48, fig 2). Some of the connector blocks 10-13 are covered by a cover part 60; to allow the cover part 60 to fit inside the casing, the connector blocks 10-13 that are covered are made to a reduced height compared to those blocks 1-9 which are not covered. Sheathed socket connectors 82,84,86,88 are provided which have a depth capable of receiving the majority of the conducting shank of a shrouded connector plug (90, fig 14). The cover part 60 can be held in place by a toe edge 74 which rests on ribs 20 dividing the connector blocks; and by a heel edge 76 which has a hole 72 to allow casing post 18 to pass through. Oval apertures 32,34,36,38 are provided to allow screwdriver access to the connector blocks 10-13.

Description

2351189 Terminal Block This invention relates to a terminal block

connection means, and to a terminal block provided with such connection means.

Test terminal blocks (hereinafter known as TTBs) are well known in the field of electrical meters, especially industrial and commercial meters which are provided in such premises to monitor and measure the amount of electrical current consumed by those premises. Such meters are commonly provided in two different forms, being those which are provided with an external current transformer and those which are not. These meters are known as CT Op meters, and whole current meters respectively, and typical ratings may range from 5A500A. The invention is applicable to all such meters, and additionally to phase rotation meters, phased sequence meters, power factor meters, industrial and commercial voltmeters and the like.

In either case the CTs and meters themselves are highly sensitive and accurate electrical apparatus which must be connected and disconnected to electrical supplies without damage to any of the working components therein. Such damage can be caused by electrical power current surge through the meter during disconnection or connection, and furthermore can result in incorrect meter readings.

TTBs are typically provided together with such meters to permit safe connection and disconnection of the meter both to the mains power supply but their primary function is to facilitate the electrical connection and disconnection of test apparatus to ensure that the meter measuring power consumption is functioning correctly and measuring accurately.

2 As their name suggests, TTBs comprise a plurality of individual and discreet electrically conducting connector blocks mounted side by side on an insulating, commonly plastic, moulding. The moulding is provided with dividers which separate each of the blocks which are screwed to one surface of the moulding, said dividers being generally of a height greater than the block and any electrical connection screws disposed therein to minimise the likelihood of accidental contact therewith. Each TTB is provided with 13 blocks, the first nine of which are provided for the connection of the meter to the three different phases of industrial and commercial current supply. Three blocks are provided for each phase, each of these three blocks being provided with two pairs of screws at either end of the block for electrical connection of the meter to the power supply. Two of the three blocks in the group of three are provided with additional interconnecting hooks which can be rotated in electrical contact with posts provided on an adjacent block which stand proud of the block and the dividers of the mould to allow for those adjacent blocks to be electrically connected together. The screws in each block provide a wiring point for each block and the provision of hooks allows for the shorting in and out of secondary and tertiary terminals on the current transformer of the CT Op meters thus safe connection can be ensured. Each of the three groups of three blocks are provided with similar hook and post connectors.

The remaining 4 blocks are provided for the each of the three phases of voltage which drive each current phase through the meter and ultimately the premises in which the power supply is installed, the final 13 th terminal being provided as a neutral connection across which the voltage is applied to drive said currents. It is these four blocks which pose the greatest risk of electrocution to humans, because there may be significant potential differences between any respective pair of blocks.

3 At either end of the TTB there are provided posts which allow for the connection of a casing provided with a pair of suitably disposed apertures through which the posts pass. A pair of knurled nuts are screwed onto the posts and a security wire, to prevent unauthorised access to the TTB, passes through both the nuts and an aperture provided in each of the posts. The security wire must be cut if access is to be gained to the TTB.

An insulating cover is therefore commonly provided above said four blocks and secured thereto by means of screws which pass through the said cover and into the respective blocks underneath.

Said cover is screwed against the upper edges of the dividers provided between the voltage blocks, but because it is the voltage connection of the supply and meter which are most commonly tested, a means must be provided to allow for connection of test wires to said voltage blocks. Although the screws provide an ideal electrical connection means, the safety implications discussed above must be taken into consideration. Accordingly the cover is provided with countersunk portions into which the screws are deposited, the cover being disposed at a suitable height above the voltage blocks and being of a suitable thickness such that when the screws are fully tightened within the voltage blocks, their uppermost portions are recessed in the upper surface of the cover. In this manner, accidental contact with the now electrically live screws is minimised.

The in the upper surface of the screws there is also provided with a recess which receives the nose and a portion of the shank of a commonly available electrical plug connector. The problem with the connection made between the screw and ultimately the voltage block, and the plug is that the depth of the recess in the screws which hold the cover in place is limited by the height of blocks 4 which receive said screws. Additionally, the nose of conventional electrical plug connectors is insulated to ensure that the electrical connection is made only between the side walls of a socket which conventionally receives the plug, and the shank thereof which is provided expanded laminated portions which bow outwardly of said shank and elastically deform as the shank is inserted within the socket to provide a frictional engagement therebetween on complete insertion of the shank therein. In the circumstance where the convention plug connectors are used to make the electrical connection between test apparatus and the cover screws of TTBs, the recess of said screws is of insufficient depth to completely receive the shank of the plug, and therefore the plug is easily and/or accidentally dislodged from the screw. The dangers and risks posed by a free, unsheathed plug end are obvious, and such are increased if it is the connection to the neutral block which has become dislodged because in this case, the alternate connections of the test apparatus are to live voltage blocks.

The current means of connection of test apparatus to voltage and neutral blocks is therefore entirely inadequate, and this invention has as its primary object the improvement of said connection.

According to the present invention there is provided a TTB comprising a plurality of connector blocks adjacently disposed and at least one post for connection of a casing to completely cover said blocks, a cover being provided over one or more of said blocks to prevent accidental contact therewith, characterised in that the covered blocks are provided with a reduced height portion within which sheathed socket connectors are attached and make electrical contact with said blocks, said socket connectors being of a depth capable of receiving at least the majority of the shank of a suitable sheathed plug and furthermore having their electrically conducting parts beneath the upper surface of the cover which is provided with suitable apertures to allow access to the sheathed socket connectors.

Preferably, at least a pair of said blocks is separated by a divider rib therebetween, the cover having an edge portion which abuts the upper edge of said rib and being provided with an aperture proximate an opposite edge through which the post of the TTB can pass.

Preferably the cover is support along one edge by the divider rib between a pair of blocks and along its opposite edge by a spacer element provided around the base of the post which passes through the aperture proximate said opposite edge.

Preferably the cover is provided in its upper surface with a plurality of oval apertures which allow screwdriver access to the screws within the block beneath which permit electrical connection of the TTB to wires.

The invention will be better understood with reference to the following specific embodiment which is described with reference to the accompanying diagrammatic illustrations wherein:

Figure 1 shows a plan view of a current TTB, Figure 2 shows a side elevation of the TTB of Figure 1, Figure 3 shows a sectional view of the TTB of Figures 1 and 2 Figure 4 shows a rear elevation of the TTB of Figures 1-3.

Figure 5 shows a plan view of a TTB according to the invention, 6 Figure 6 shows a side elevation of the TTB of Figure 5, Figure 7 shows a sectional view of the TTB of Figures 5 and 6 Figure 8 shows a rear elevation of the TTB of Figures 5-7, Figures 9-10 show respectively plan, sectional and rear elevations of a casing applied over the connection blocks of a TTB, Figure 11 shows a rear face cover to conceal connector screws on the base of the TTB, Figures 12 shows a plan view of a TTB with the shrouded connector plugs, Figure 13 shows a side elevation of the TTB of Figure 12, Figure 14 shows example shrouded connector plugs to be connected to the TTB of Figure 13, Figures 15A-E shows different views of the cover according to the invention, Figures 16A-C show respectively a sectional view, a side elevation, and an end elevation of a socket connector used in the invention before application of an insulating sheath, Figures 17A-C show the same views as Figures 16A-C of the socket with insulating sheath applied for use in the invention, and Figures 18A-D show respectively a plan view, a side elevation, an underside view, and an end elevation of a block connector according to the invention.

7 Referring firstly to Figure 1, there is shown a test terminal block T comprising a plurality of individual electrical connector blocks 1 to 13 attached to a moulded plastic base 14 provided with a pair of casing connection posts 16, 18 and having a plurality of divider ribs 20 integrally moulded with said base 14. As can be seen in Figure 1, and more clearly in Figure 2, connector blocks 10 to 13 by which a meter is connected to a live three phase voltage supply (connector 13 typically serves as a neutral connection), are concealed by a cover 22 which prevents accidental contact by a human or other stray electrically conducting means with said connector blocks 10 to 13. Said cover 22 is screwingly connected with screws 24 to 30 which are received in apertures in the upper surface of the said connector blocks 10 to 13. The underside of said cover 22 is supported by the upper edges of the divider ribs 20 which are of a greater height than the divider ribs which separate any pair of adjacent connector blocks 1 to 9.

Oval apertures 32 to 38 are additionally provided in the cover to permit access to the pairs of screws 40 to 46 which are provided in the upper surface of the connector blocks to allow for the electrical connection of the TTB between a meter and a power supply. It will be seen in Figure 2 that an aperture 1X to 13X is provided through the body of the connector blocks 1 to 13, and it is in this aperture that a bare wire may be clamped by means of the pairs of screws provided in each connector block. A casing 48 provided with a pair of apertures (not shown) proximate its ends to receive the upper ends of the posts 16, 18 generally encases all the connector blocks of the TTB. Unauthorised access to the electrical connections made by the connector blocks is prevented by means of security wires which pass through apertures 17, 19 provided in the upper ends of the posts 16, 18 after a pair of knurled nuts 50, 52 have been screwed onto the posts to retain the casing against the base 14.

8 This type of security connection will be instantly understood by those skilled in the art, and therefore no further description is necessary.

The thickness of the cover 22 and the height of the divider ribs 20 adjacent the connector blocks 10 through 13 allow for said screws 24, 26, 285 30 to be recessed within said cover 22 and this is so because said screws make electrical contact with and can conduct an electricity from the connector blocks 10 to 13, and hence it is important that the possibility of accidental contact with said screw is minimised. Each of said screws 24, 26, 28, 30 is provided with a central recess 25, 27, 29, 31 which is capable of receiving the nose of a conventional connector plug (not shown) and part of the electrically conducting shank thereof such that a test connection can be made between test apparatus and the voltage connector blocks 10 to 13. However, as previously described, the configuration of the connector blocks, which are of uniform height, the height of the divider rib, the thickness of the cover 22, the length of the screws 24, 26, 28, 30 and the limited penetration with which said screws enter the connector blocks 10 to 13 limits the depth of recesses 25, 27, 29, 31 to such an extent that only a portion of the shank of a conventional plug connector is received therein. As the nose of a conventional connector plug is typically of an insulating material, only the shank being of a conductive material, such electrical connector plugs are insecurely retained within said recesses, and can easily be dislodged therefrom.

Accordingly, a modified arrangement is shown in Figures 5 to 8 in which like reference numerals have been used to reference like parts of the construction of a TTB.

Referring to Fig. 5, the TTB T, again provided with a plurality of separate electrical connector blocks 1 to 13 is provided with a 9 modified cover 60 having respective pairs of oval apertures 32, 34, 36) 38, and being further provided with enlarged apertures 62, 64, 66, 68 and an enlarged end portion 70 having a further aperture 72 therein through which the connection post 18 can pass. In the configuration of the TTB T according to the invention, the said cover 60 is clamped against the upper edges of the increased height ribs 20 adjacent the connector blocks 10 to 13 by means of a toe formation 74 along the distal edge of the cover 60 and a heel formation 76 provided around the curved edge of the enlarged portion 70. Said heel formation 76 abuts an insert 78 which effectively reduces the height of the post 18 and supports said cover 60 at a suitable height in relation to the upper edges of the increased height divider ribs 20. A nut 80 may then be screwed down over the post and into contact with the upper surface of the cover 60 to secure same in place.

In order to provide a means of electrical connection between the connector blocks 10 to 13 and test apparatus, each of the connector blocks 10 to 13 is provided with a shrouded test socket 82, 84, 86, 88 which can be seen more clearly in Figures 13, 16 and 17 which allows the connection of a shrouded safety plug 90 thereto. Such shrouded safety plugs are equally as commonly available as a conventional connector plug provided with a shank and indeed may be even more widely available, but in any event there is a desire among test personnel to use said shrouded safety plugs on account of the safety benefits provided thereby. In particular the electrical conducting shank of the plug is shrouded and accidental electrical contact therewith is thus minimised.

The particular configuration of the cover 60 is seen clearly in Figures 15A to 15E, and it will be appreciated from these figures that the enlarged aperture 62, 64, 66, 68 are of a greater diameter than the corresponding apertures provided in the cover 22 of the prior art configuration. The reason for the enlarged size of the apertures 62, 64, 66, 68 is the requirement for the shrouded safety plugs 90, which are necessarily of a greater diameter than the conventional connection plug provided with a simple shank, to be inserted therethrough to make electrical contact with the shrouded test sockets 82, 84, 86, 88.

Specific examples of such shrouded test sockets are shown in Figures 16 and 17 where it can be seen that each of the sockets is provided with an electrically conducting inner surface 100 which defines a recess 102 which is capable of receiving the majority of the length of the shank within the shrouded safety plugs 90 to allow for a firm and secure electrical connection therebetween. Said shrouded test socket is provided with a threaded end portion 104 and a nut hexagonal formation 106 to allow for connection of said socket to its respective electrical connector block 10 to 13. Said shrouded test sockets 82, 84, 86, 88 could not ordinarily be connected to the conventional connector blocks 1 to 13 which have a uniform height in the prior art configuration because their length is such that they would stand a considerable distance proud of the upper surface of the cover 22 and inhibit the connection of the casing 48 to the base 14 as shown in Figure 2. Accordingly, said shrouded test sockets 82, 84, 86, 88 are connected to specifically designed connector blocks 110 shown in Figures 18A to D. Said connector plugs are provided substantially centrally with a reduced height portion 112 to compensate for the increased height of the shrouded test sockets connected thereto, and it is the combination of the connector blocks 110 therewith which form an essential element of this invention. Furthermore, it is to be mentioned that the enlarged aperture 62, 64, 66, 68 provided in the cover 60 provide a location means for the shrouded safety plugs 90 as they are inserted therethrough because the shrouds thereof, being of marginally lesser diameter than the said apertures are guided thereby

11 during insertion such that the shanks disposed within said shrouds locate precisely within the recess 102 of the shrouded test sockets 82, 84, 86, 88 and thus make secure electrical connection therewith. Furthermore, the respective height of the reduced height portion, the overall length of the shrouded test sockets, and the height of the increased height divider ribs 20 is such that the electrically conducting surface 100 of the shrouded test sockets is disposed well beneath the upper surface of the cover 60 and accidental contact therewith is thus minimised and even eradicated.

The shrouded test sockets 82, 84, 86, 88 are shown in Figures 17A to 17C with an additional insulating shroud 108 provided around the electrically conducting surface 100 of the recess 102 to ensure that accidental contact with said electrically conducting surface is practically impossible without concerted effort to make contact with same. Therefore, as the shrouded plug 90 is urged through the aperture in the cover 60, the shroud of the connector is disposed to the outside of the insulating shroud 108, while the shank of the connector is received in the recess 102 and makes secure electrical connection therewith.

Accordingly, it will be appreciated that the means of connection is substantially improved, and the risk of any of the shrouded test connectors becoming dislodged or working themselves free from the shrouded test sockets 82, 84, 86, 88 is minimised.

12

Claims

1. A test terminal block (TTB) comprising a plurality of connector blocks adjacently disposed and at least one post for connection of a casing to completely cover said blocks, a cover being provided over one or more of said blocks to prevent accidental contact therewith,, characterised in that the connector blocks underneath the cover are provided with a reduced height portion within which socket connectors are attached and make electrical contact with said blocks, said socket connectors being of a depth capable of receiving the majority of an electrically conducting shank and furthermore having their electrically conducting parts beneath the upper surface of the cover which is provided with suitable apertures through which the electrically conducting shank can be passed before being received in said socket connectors.

2. A TTB according to claim 1 wherein the electrically conducting shanks are concealed within a sheathed plug.

3. A TTB according to either of claims 1 or 2 wherein the electrically conducting portions of the socket connectors are sheathed so as to be insulated.

4. A TTB according to any preceding claim wherein at least a pair of the blocks underneath the cover is separated by a divider rib therebetween, said cover having an edge portion which abuts the upper edge of said rib and being provided with an aperture proximate a further edge of said cover through which the connecting post of the TTB can pass.

5. A TTB according to claim 4 wherein the cover is supported along said edge portion by the divider rib between a pair of blocks and along its opposite edge by a spacer element provided around the base of the connecting post which passes through the aperture proximate said further edge.

6. A TTB according to any preceding claim wherein the cover is provided in its upper surface with a plurality of oval apertures which allow screwdriver access to the screws within the blocks beneath the cover by which electrical connection of the TTB to wires is facilitated.

7. A TTB as herein described with reference to the accompanying drawings.