GB2298970A

GB2298970A - Slide cover for busbar

Info

Publication number: GB2298970A
Application number: GB9505412A
Authority: GB
Inventors: Kevin Brooks; Robert Butcher; Andrew Reynolds
Original assignee: Kloeckner Moeller GmbH; Barduct Ltd
Current assignee: Eaton Industries GmbH; Barduct Ltd
Priority date: 1995-03-17
Filing date: 1995-03-17
Publication date: 1996-09-18
Anticipated expiration: 2015-03-17
Also published as: TW308747B; GB2298970B; WO1996029762A1; GB9505412D0; ZA962130B; EP0815616A1; AU5010596A

Abstract

A slide cover assembly closes off tapping outlets of a busbar tapping outlet location. Actuator blades A on a tapping box 13 are introduced into associated slots in the cover assembly and engage main cover portions 12c to move said cover portion 12 across the busbar against spring action 14, to expose busbar conductors L1,L2,L3,E and N to contacts 15 through rectangular apertures. The actuator blades A each have a cam surface of two inclinations a,b in order to move the shutter at two different rates.

Description

IMPROVEMENTS IN OR RELATING TO BUSBARS This invention relates to improvements in or relating to busbars and is more particularly but not exclusively concerned with safety aspects in higher rating busbars.

Our Patent No. GB 2189091B relates to a slide cover assembly for a tapping outlet location of a busbar and to a method of selectively exposing and covering the tapping outlets of a busbar tapping outlet location. Such a slide cover assembly is suitable for bus bars of a lower rating of, for example, up to about 600 amps but it has not been practical to utilise such sliding covers on busbars of higher rating for various reasons. These reasons are linked to the inherent design constraints applicable for higher rating busbars, the main problem residing in being able to move a cover part including aperture means a sufficient amount to selectively expose and cover tapping outlets to tapping box plug-in connections bearing in mind the physical dimensional constraints involved.Thus, up to now, it has not been feasible to provide the clearly advantageous safety feature of a slide cover assembly (for selectively exposing and covering tapping outlets on a busbar tapping outlet location) on a busbar of higher rating up to, for example, 5,000 amps.

It is an object of the present invention to at least alleviate the aforementioned, or other, problem associated with a slide cover assembly or cover part for a busbar.

According to the present invention there is provided the combination of a slide cover assembly and cover actuator means, said slide cover assembly being for selectively exposing and covering the tapping outlets of a busbar tapping outlet location, said assembly comprising a slide cover or cover part movably mountable or mounted on a busbar, said slide cover or cover part having aperture means movable into and out of registration with said tapping outlets on relative movement of said slide cover/cover part and busbar, to thereby expose said tapping outlets to the plug-in connections of a plug-in tapping box and to cover the outlets when required, said actuator means being provided on the plug-in tapping box and having cam means co-operable with said slide cover/cover part in order to move said aperture means into and out of registration with said tapping outlets, said cam means having a variable action portion or profile enabling the slide cover/cover part to move a first amount for a first particular distance moved by the actuator means relative to the busbar, said first amount being less than a second amount moved by the slide cover in response to a second particular distance moved by the actuator means relative to the busbar, said second particular distance being equal to said first particular distance.

More generally, according to the present invention there is provided the combination of a slide cover or cover part and cover actuator means, said slide cover/cover part being for selectively exposing and covering the tapping outlets of a busbar tapping outlet location, said slide cover/cover part being movably mountable or mounted on a busbar, said slide cover/cover part having aperture means movable into and out of registration with said tapping outlets on relative movement of said slide cover/cover part and busbar, to thereby expose said tapping outlets to the plug-in connections of a plug-in tapping box and to cover the outlets when required, said actuator means being provided on the plug-in tapping box and having cam means co-operable with said slide cover/cover part in order to move said aperture means into and out of registration with said tapping outlets, said cam means having a variable action portion or profile enabling the slide cover/cover part to move variable amounts for equal distances moved by the actuator means relative to the busbar.

Further according to the present invention there is provided a busbar and at least one tapping box with at least one combination as related in either of the two immediately preceding paragraphs.

Further according to the present invention there is provided a method of moving a slide cover or cover part across a busbar to close off and expose tapping outlets, said method comprising engaging the slide cover or cover part with a first cam means portion or profile of actuator means and moving the slide cover or cover part across the busbar a first amount for a particular distance moved by the actuator means relative to the busbar, said method further comprising engaging the slide cover or cover part with a second portion or profile of said cam means and moving the slide cover or cover part across the busbar a greater amount for a second particular distance moved by the actuator means relative to the busbar, said second particular distance being equal to said first particular distance.

Still further according to the present invention there is provided a slide cover assembly for a busbar having a rating of 600 amps or above, said assembly including a slide cover or cover part that can be moved automatically, by actuator means on a tapping box, so that aperture means on the slide cover or cover part registers with tapping outlets on the busbar to expose said outlets to plug-in connections of the tapping box.

Preferably, the variable action portion or profile of the cam means is a double action mechanism. In one embodiment, the actuator means is, advantageously, provided by one or more actuator blades or plates (preferably two spaced actuator blades) having a first straight edge inclined portion adjoining a second straight edge inclined portion, the angle of the second inclined portion, preferably, being at a less steep incline than the first portion.The first inclined portion may be inclined at an angle of 45" + 5 and the second inclined portion may be at an angle of 22c + 5 (preferably 23.2 ). The first inclined portion may extend a particular depth of the actuator blade (for example 8mm) and the second inclined portion may extend an equal depth (for example about 8mm).

The ratio of the actuating movement of the actuator means from an initial engagement position with the slide cover or cover part to the movement of the slide cover or cover part across the busbar between open and closed positions is, preferably, .57 + .1.

Advantageously, the cam means has a variable action portion or profile to enable the slide cover or cover part to be moved a sufficient amount to expose and cover the tapping outlets without the actuator means jamming or sticking.

The slide cover assembly may be provided with at least one slot for receiving the actuator means in said form of at least one actuator plate or blade. The actuator blade or blades may be introduced automatically into the associated slot as the tapping box is engaged onto the slide cover assembly and importantly the tapping box may have guide means in the form of prongs engageable with guide slots in the busbar to guide the actuator blade or blades into said receiving slot or slots on introduction of the tapping box onto the slide cover assembly.

Preferably, the slide cover or cover part is provided with at least one head portion engageable in an associated one of said slots into which the associated actuator blade is introduced in use, said at least one head portion, preferably, having an inclined edge engageable with the variable action portion or profile of said cam means. The inclined edge may have an incline generally similar to said first straight edge inclined portion, where provided.

Preferably, the slide cover or cover part is movable across the busbar against the biasing action of a spring (usually a compression spring) which may have the general form of trapezoidal cross section.

The disposition of the actuator means in relation to the tapping box and slide cover or cover part is preferably, such as to introduce contact location pegs onto conductors of the busbar, in timed relationship just after the tapping outlets have been exposed by the movement of the slide cover/cover part induced by the actuator means.

Usually the aperture means of the slide cover or cover part will be a plurality of rectangular apertures of a size similar to tapping outlets.

Usually, a stop will be provided to limit the depth penetration of the actuator means into the busbar.

Many other advantageous method and apparatus features will be apparent from the following description and drawings.

An embodiment of apparatus and method in accordance with the present invention will now be described, by way of example only, with reference to FIGURES of the accompanying drawings in which: FIGURE 1 shows in somewhat diagrammatic form a cutaway plan view of a busbar showing a tapping outlet location fitted with a slide cover assembly but with a slide cover or cover part itself being omitted and tapping outlet locations exposed; FIGURE 2 shows a view which is similar to FIGURE 1 but drawn on a larger scale and being constructed in a schematic way as if a cover of the slide cover assembly were transparent in order to show the location of the slide cover closing off tapping outlets of a busbar tapping outlet location, with some hidden detail being shown;; FIGURE 3 is a sectional view through part of a tapping box and busbar tapping outlet location taken generally on line 111-Ill of FIGURE 2; FIGURE 4 is a view similar to FIGURE 3 but showing the slide cover moved to a position exposing the tapping outlets; FIGURE 5 shows sectional views of the slide cover in open and closed positions in relation to cover actuator means of the tapping box, and FIGURE 5a shows a plan view of the slide cover drawn to a different scale FIGURE 6 shows dimensional details of an actuator blade, and FIGURE 7 shows the dimensional and spatial relation of the actuator blade in relation to earth contact prongs of the tapping box.

FIGURE 1 shows a busbar 1 drawn schematically with the ends of the busbar length being cut away and depicting a slide cover assembly 2 at a tapping outlet location. As shown, the tapping outlet location is generally of known form save for upper slots 3 and 4 provided to receive slide cover actuator means in the form of spaced actuator blades or plates A (one actuator blade A being shown in FIGURES 3 and 4) in a manner to be described. The cover assembly 2 has a main cover portion 2a (see FIGURES 3 and 4) which is hinged about axis 5 in a generally known manner to allow access to the busbar conductor lengths numbers L1,L2,L3,E and N in known manner. The cover portion 2a is fastened down in position by catch 6 in known manner.FIGURE 1 shows generally rectangular apertures 7, 8, 9, 10 and 11 through which the busbar conductors L1,L2, L3,E and N are exposed to receive the phosphor bronze location pegs mounted in a contact block assembly of a tapping box (see earth location pegs 15 and sectional cut-away tapping box 13 in F FIGURES 3 and 4) in generally known manner. The designated reference numerals L1,L2,L3,E,N refer to three live busbar conductors, one earth and one neutral conductor respectively.

It is known to provide finger protection means at each of these rectangular apertures 7,8,9,10 and 11 in order to prevent contact of an operator's fingers with the busbar conductors L1,L2,L3,E,N, said finger protection means comprising insulator padding. However, such finger protection means is only able to prevent contact of a finger with the busbar conductors in the event that said finger is inserted directly through one of the rectangular openings 7,8,9,10 and 11 in a direction perpendicular to the associated busbar conductor length L1,L2,L3,E,N. The finger protection means is only partial protection since it is not effective to prevent finger contact with a busbar conductor length if said finger is inserted at an angle to the busbar length.

This embodiment of the present invention provides for a cover part in the form of a slide cover or shutter 12 to automatically cover the rectangular apertures 7,8,9,10, 11 (and thus the exposed busbar conductor lengths L1,L2,L3 E and N) thereby greatly increasing finger protection and enhancing aperture access safety (it is envisaged that the present invention may also be utilised with the aforementioned finger protection means provided at each of the rectangular apertures 7,8,9,10,11).

In the embodiment as shown in FIGURES 1 to 7 the slide cover 12 is automatically moved across the busbar 1 (from top to bottom as shown in FIGURE 1 and FIGURE 2) as a tapping box 13 (shown in part in FIGURES 3 and 4) is introduced onto the busbar cover assembly 2 with each actuator blade A engaging in an associated slot 3,4.As the slide cover 12 is moved across the busbar 1 against the spring action of compression spring 14 (see FIGURES 2,3 and 4) aperture means in the form of five rectangular windows W1,W2,W3,W4,W5 (see FIGURE 2) are moved into superimposed registration with the apertures 7,8,9,10 and 11 thereby exposing the conductor lengths L1,L2,L3 E and N in a manner which should be self-explanatory and in timed relationship with the location pegs or prongs (a pair of earth location pegs 15 being shown in FIGURES 3 and 4 as aforesaid). The location pegs are of a form known per se and there will be five strategically spaced pairs of pegs arranged to simultaneously engage associated ones of the five busbar conductor lengths L1,L2,L3 E and N in a manner which should be evident from the FIGURES of the drawings.

Thus, the important novel aspect of this embodiment of the present invention as aforedescribed, is the provision of the slide cover 12 within the cover assembly 2, said cover 12 closing off the rectangular apertures 7,8,9,10,11, and thus access to the busbar conductor lengths L1,L2,L3 E and N, until the tapping box 13 is itself introduced onto the cover assembly 2 with the actuator blades A appropriately engaging associated slots 3 and 4.

The slide cover 12 is generally rectangular in plan view (see FIGURE 5a) and has width and length dimensions X and Y as shown in FIGURE 2. The rear edge 12a of the slide cover 12 is engaged at spaced locations 16 and 17 (equidistantly spaced from the centre line Z of the cover assembly 2 - see FIGURE 2). Spring 14 has curved hooked ends 14a,b, which engage the rear edge 12a of the slide cover at the spaced locations 16 and 17. The spring 14 itself is of overall trapezoidal shape in cross section having a rear strip 14c engaging an inside rear wall of the cover assembly 2, said rear strip 14c finishing short of each end 2b,2c of the cover assembly 2.The strip 14c curves at each end into a straight inclined portion 14d,14e, said inclined portions 14d,14e merging into respective hooked ends 14a and 14b in a manner which should be self-evident from the FIGURES of the drawings. Spring 14 is symmetric about the central axis Z. In an alternative embodiment, it is possible that the spring could be replaced by two spring portions with the centre portion of strip 14c essentially being omitted. The spring 14 urges the slide cover 12 across the busbar conductors L2,L2,P3,E.N (i.e. in an upward direction in FIGURE 2) until the front edge 12b of the slide cover engages the inside front wall of the cover assembly 2 (see FIGURE 3).

It is to be noted that the slide cover 12 is provided with spaced head portions 12c and 12d which protrude upwardly into respective slots 3 and 4. Thus, the slide cover 12 is arranged to move from a first position shown in FIGURES 2 and 3 in which the rectangular apertures 7,8,9,10 and 11 are fully closed to a second "actuator finish" position as shown in FIGURE 4 in which the rectangular apertures W1,W2,W3,W4,W5 are in superimposed registration with the apertures 7,8,9,10 and 11. The movement between the first and second positions is governed by the forward to rearward length of each slot 3,4 with the rear face 12'c,12'd of each head portion 12c,12d engaging an associated rear wall 3a,4a of the associated slot 3,4.For ease of illustration the rectangular aperture W4 is depicted in FIGURES 3 and 4 by a solid thick black line in order to illustrate the position of this rectangular aperture relative to the rectangular aperture 10 of the busbar earth conductor E in the closed (FIGURE 3) and fully open (see FIGURE 4) positions.

Each head portion 12c,12d of the slide cover 12 has an upper, forward, inclined edge 12e,12f which is arranged to initially engage a first inclined profile portion a of cam profile a,b of each actuator blade A. Each actuator blade A is provided with a two-portion cam profile a,b owing to the dimensional constraints involved in sliding the cover 12 a sufficient amount to expose the busbar conductor lengths L1,L2,L3,E and N through the apertures 7,8,9,10 and 11 for the introduction of the associated pairs of contact location pegs. More specifically, if each actuator blade A were only provided with a single inclined cam profile at a similar angle to profile portion b the angle would be too shallow to move the slide cover 12 across the busbar 1 and each actuator blade A would stick or jam in its associated slot 3,4.If each actuator blade A were provided with a single cam profile having an angle the same as cam profile portion a, the slide cover 12 would not move a sufficient amount across the busbar 1, so that the apertures W1 to W5 would not register with the rectangular apertures 7 to 11 after each actuator blade A had passed completely through the slots 3 and 4.

The present invention solves the aforementioned problem in the embodiment as shown by providing a variable action profile a,b which is in this instance a double action profile. Cam profile portion a is at a sufficient angle relative to engagement edge 12b to enable the slide cover to begin moving across the busbar a and, after this movement is initiated cam profile portion b then acts to move the slide cover 12' at a greater rate across the busbar (without jamming) in a manner which should be evident from the drawings. In this way, the depth of penetration of each actuator blade A into the busbar 1 is reduced, this distance being critical and limited by the design constraints of the busbar.Thus, the cam profile a,b on each actuator blade A allows the slide cover 12 to move a first amount across the busbar 1 governed by the straight cam profile portion a until the junction C of the cam profile portions a and b is reached. The slide cover 12 is moved at a relatively slow rate and is then engaged by the straight cam profile portion b. Up until this point the actuator blades A will have moved a first particular distance relative to the busbar 1 and on moving a second particular distance relative to the busbar equal to said first particular distance (during which time cam profile portion b engages head 12c) the slide cover will be moved at a greater rate.Because the slide cover moves across the busbar at a greater rate, it will move a second amount across the busbar greater than said first amount, in response to a second particular distance moved by the actuator blades A relative to the busbar, which second particular distance is equal to said first particular distance.

FIGURE 4 shows the actuator finish position for the actuator blade A and it is to be noted that the pointed end P of each actuator blade does not protrude beyond the back B of the busbar section. Slots S are arranged to receive associated actuator blades A after travelling through the slots 3 and 4 with a stop T being provided as shown in FIGURE 4, limiting the downward travel of the actuator blades A. Distance f in FIGURE 5 is 27 mm and distance g is 22.47 mm. Distance h in FIGURE 4 is 28.71 mm. Distance i in FIGURE 4 is 7.47 mm. Distance j in FIGURE 3 is 21.25 mm. Thus a movement of 16.05 mm of each actuator blade relative to the busbar 1 produces 28 mm of movement of the slide cover 12 across the busbar, which is a ratio of about .57.Initially the slide cover is moved at an equal rate across the busbar for movement of the actuator blade towards the busbar since the cam profile part a is at 45".

The initial movement is 8 mm. The slide cover then moves at a greater rate (about twice the initial movement) because a movement of about 8 mm of the actuator blade relative to the busbar produces 16 mm of movement of the slide cover 12. Thus, the ratio of movement of the actuator blade A to movement of slide cover 12 during engagement of cam profile part b with the slide cover is about .5.

It is possible that the cam profile portions a,b may be replaced by an alternative, for example curved, profile.

In addition to the actuator blades A engaging in slots 3 and 4 on introduction of the tapping box 13 onto the slide cover assembly 2 prongs 13a engage in the slots la (see FIGURES 1 and 2) in order to correctly align and maintain alignment of the actuator blades A in the slots 3 and 4 as the tapping box 13 is introduced onto the slide cover assembly 2.

It should be evident that movement of the slide cover 12 across the busbar by the actuator blades A is against the spring biasing provided by spring 14 and that this spring will act to return the slide cover 12 to the position as shown in FIGURE 3 automatically as the tapping box 13 is withdrawn from the busbar 1.

FIGURE 6 shows the dimensions in millimetres, of the actuator blade, and angles (in degrees) of the cam profile portions a,b in a manner which should be evident. Each actuator blade A is made from 3 mm thick steel. FIGURE 7 shows the dimensional and spatial relationship of the actuator blade A to the earth contact prongs 15 in a manner which should be evident.

It is believed that the particular relative dimensions of the cam profile, a,b and form thereof are particularly advantageous.

It is to be understood that the scope of the present invention is not to be unduly limited by the particular choice of terminology and that a specific term as used herein may be replaced or supplemented by any equivalent or generic term. Further it is to be understood that the individual features, method or functions related to the slide cover assembly, the slide cover or the actuator means or combination thereof might be individually patentably inventive. The singular may include the plural or vice versa. Moreoever, any disclosure in this specification of a range for a variable or parameter shall be taken to include a disclosure of any selectable or derivable subrange within that range and shall be taken to include a disclosure of any value for the variable or parameter lying within or at an end of the range.

Claims

1. A combination of a slide cover assembly and cover actuator means, said slide cover assembly being for selectively exposing and covering the tapping outlets of a busbar tapping outlet location, said assembly comprising a slide cover or cover part movably mountable or mounted on a busbar, said slide cover or cover part having aperture means movable into and out of registration with said tapping outlets on relative movement of said slide cover/cover part and busbar, to thereby expose said tapping outlets to the plug-in connections of a plug-in tapping box and to cover the outlets when required, said actuator means being provided on the plug-in tapping box and having cam means co-operable with said slide cover/cover part in order to move said aperture means into and out of registration with said tapping outlets, said cam means having a variable action portion or profile enabling the slide cover/cover part to move a first amount for a first particular distance moved by the actuator means relative to the busbar, said first amount being less than a second amount moved by the slide cover in response to a second particular distance moved by the actuator means relative to the busbar', said second particular distance being equal to said first particular distance.

2. A combination of a slide cover or cover part and cover actuator means, said slide cover/cover part being for selectively exposing and covering the tapping outlets of a busbar tapping outlet location, said slide cover/cover part being movably mountable or mounted on a busbar, said slide cover/cover part having aperture means movable into and out of registration with said tapping outlets on relative movement of said slide cover/cover part and busbar, to thereby expose said tapping outlets to the plug-in connections of a plug-in tapping box and to cover the outlets when required, said actuator means being provided on the plug-in tapping box and having cam means co-operable with said slide cover/cover part in order to move said aperture means into and out of registration with said tapping outlets, said cam means having a variable action portion or profile enabling the slide cover/cover part to move variable amounts for equal distances moved by the actuator means relative to the busbar.

3. A combination as claimed in Claim 1 or Claim 2 in which the variable action portion or profile of the cam means is a double action mechanism.

4. A combination as claimed in Claim 3 in which the actuator means is provided by one or more actuator blades or plates having a first straight edge inclined portion adjoining a second straight edge inclined portion.

5. A combination as claimed in Claim 4 in which the angle of the second inclined portion is at a less steep incline than the first portion.

6. A combination as claimed in Claim 5 in which the first inclined portion is inclined at an angle of 45" + 5 and the second inclined portion is at an angle of 224" + 5.

7. A combination as claimed in any one of Claims 4 to 6 in which the first inclined portion extends a particular depth of the actuator blade and the second inclined portion extends an equal depth.

8. A combination as claimed in any one of the preceding claims in which the ratio of the actuating movement of the actuator means from an initial engagement position with the slide cover or cover part to the movement of the slide cover or cover part across the busbar between open and closed positions is .57 + .1.

9. A combination as claimed in Claim 4 or any claim dependent therefrom in which a, or the, slide cover assembly is provided with at least one slot for receiving the actuator means in said form of at least one actuator blade or plate.

10. A combination as claimed in Claim 9 in which the said at least one actuator blade/plate can be introduced automatically into the associated slot as the tapping box is engaged onto the slide cover assembly.

11. A combination as claimed in Claim 10 including guide means on the tapping box said guide means being in the form of prongs engageable, in use, with guide slots in the busbar to guide the at least one actuator blade or plate into the said associated receiving slot on introduction of the tapping box onto the slide cover assembly.

12. A combination as claimed in any one of Claims 9 to 11 in which the slide cover or cover part is provided with at least one head portion engageable in the associated receiving slot into which the associated actuator blade or plate is introduced in use.

13. A combination as claimed in Claim 12 in which said at least one head portion has an inclined edge engageable with the variable action portion or profile of said cam means.

14. A combination as claimed in Claim 13 when dependent from Claim 4 in which the inclined edge has an incline generally similar to said first straight edge inclined portion.

15. A combination as claimed in any one of the preceding claims in which the slide cover or cover part is movable across the busbar against the biasing action of a spring.

16. A combination as claimed in Claim 15 having the general form of trapezoidal cross section.

17. A combination as claimed in any one of the preceding claims in which the disposition of the actuator means in relation to the tapping box and slide cover or cover part, in use, is such as to introduce contact location pegs onto conductors of the busbar, in timed relationship just after the tapping outlets have been exposed by the movement of the slide cover/cover part induced by the actuator means.

18. A combination as claimed in any one of the preceding claims in which the aperture means of the slide cover or cover part is a plurality of rectangular apertures of a size similar to the tapping outlets.

19. A combination as claimed in any one of the preceding claims including a stop to limit the depth penetration of the actuator means into the busbar.

20. A combination as claimed in Claim 1 or Claim 2 and substantially as shown in the accompanying drawings.

21. A kit of parts comprising a busbar and at least one tapping box and at least one combination as claimed in any one of the preceding claims.

23. A slide cover assembly for a busbar having a rating of 600 amps or above, said assembly including a slide cover or cover part that can be moved automatically, by actuator means on a tapping box, so that aperture means on the slide cover or cover part registers with tapping outlets on the busbar to expose said outlets to plug-in connections of the tapping box.

24. A method of moving a slide cover or cover part across a busbar to close off and expose tapping outlets, said method comprising engaging the slide cover or cover part with a first cam means portion or profile of actuator means and moving the slide cover or cover part across the busbar a first amount for a particular distance moved by the actuator means relative to the busbar, said method further comprising engaging the slide cover or cover part with a second portion or profile of said cam means and moving the slide cover or cover part across the busbar a greater amount for a second particular distance moved by the actuator means relative to the busbar, said second particular distance being equal to said first particular distance.

25. A method as claimed in Claim 24 in which the ratio of the actuating movement of the actuator means from an initial engagement position with the slide cover or cover part to the movement of the slide cover or cover part across the busbar between open and closed positions is .57 + .1.

26. A method as claimed in Claim 24 or Claim 25 said actuator means being introduced automatically into an associated slot in the slide cover or cover part as a tapping box is engaged onto the slide cover.

27. A method as claimed in Claim 26 including guiding the actuator means into the said associated receiving slot on introduction of the tapping box onto the slide cover assembly.

28. A method as claimed in Claim 26 or Claim 27 comprising engaging at least one head portion of the slide cover or cover part in the associated receiving slot into which the associated actuator means is introduced.

29. A method as claimed in Claim 28 comprising engaging an inclined edge of said at least one head portion with the first and second cam means portion or profile of said cam means.

30. A method as claimed in any one of Claims 24 to 29 comprising moving the slide cover or cover part across the busbar against the biasing action of a spring.

31. A method as claimed in any one of Claims 24 to 30 comprising introducing contact loaction pegs onto conductors of the busbar, in timed relationship just after the tapping outlets have been exposed by the movement of the slide cover/cover part induced by the actuator means.

32. A method of moving a slide cover or cover part across a busbar to close off and expose tapping outlets substantially as herein described.