GB2351852A

GB2351852A - Electrical distribution apparatus

Info

Publication number: GB2351852A
Application number: GB9915757A
Authority: GB
Inventors: Keith Wray Ball; Paul S Ritchie-Haydn; Kenneth Neill
Original assignee: Schneider Electric Ltd
Current assignee: Schneider Electric Ltd
Priority date: 1999-07-07
Filing date: 1999-07-07
Publication date: 2001-01-10
Also published as: GB9915757D0

Abstract

A mechanically stable panelboard incorporates safety features, particularly for heavy duty applications. A four-way bus bar assembly is disclosed in which a plurality of bus bars 10 are spaced so as to lie parallel with one another, each bus bar providing contact surfaces on two sides thereof for corresponding electrical contact jaws of circuit breaking devices. The apparatus further comprises finger safety panels 30 including insulating portions 37 overlying the bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by the circuit breaking device while permitting entry of the contact jaws through apertures 35 either side of said insulating portions. The safety panels are attached to the bus bar assembly by fingers 80 which engage spacing elements 60 between the bus bars. In this way, a simple but robust fixing is achieved, in which the forces tending to pull the finger safety panel away from the bus bars are transmitted to the bus bar assembly locally. In alternative embodiments, the fingers engage the bus bars directly, rather than the spacing elements.

Description

2351852 ELECTRICAL DISTRIBUTION APPARATUS

Description

This invention relates to electrical switch gear and bus bar assemblies, in particular panelboardswith safety features.

In order to distribute electrical power to various locations and equipment it is necessary to employ robust circuits capable of withstanding the levels of power involved. A means for interconnecting the live supply via circuit breakers or other switching devices to sub-circuits is provided by bus bars, manufactured in the form of strips to which such circuit breakers can be connected by means of spring contacts.

Bus bars distributing electrical power to sub-circuits may carry dangerous voltages and currents. There is generally a panel of insulating material over the bus bar assembly to prevent accidental finger contactwith the live bus bars, the panel having small apertures sufficient for the contacts to reach the bus bars.

Previous examples of safety panels in electrical bus bar equipment are disclosed in GB 2 305 008 A and GB 2 264 399 A (Square D). Known safty panels and the methods of affixing safety panels over bus bar assemblies suffer from a number of disadvantages. GB 2 305 008 A attached the panel on to the sides of the panelboard.

The stresses on the panelboard when various equipment has been attached may have a detrimental effect on the quality of the plug-in connection, or the robustness of the finger safety protection.

These problems can become more acute when trying to apply similar features in multi-phase and heavier duty equipment where larger distances must be spanned.

GB 2 264 399 A proposes a self-adbesive safety blank. This construction a] so suffers from drawbacks, and is not suitable for all applications.

The invention aims to provide a mechanically stable panelboard incorporating safety features, particularly for heavy duty applications.

2 The invention in a first aspect provides an electrical distribution apparatus for the mounting of at least one circuit breaking device, the apparatus comprising a bus bar assembly in which a plurality of bus bars are spaced so as to he parallel with one another, each bus bar providing contact surfaces on two sides thereof for corresponding electrical contact jaws of said circuit breaking device, the apparatus fin-ther comprising a finger safAy panel including insulating portions overlying the bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by said circuit breaking device while permitting entry of said contact jaws through apertures either side of said insulating portions, the safety panel being attached 10 the bus bar assembly at least in part by means which extend into a space between adjacent bus bars.

By providing attachment means in the spaces between the bus bars, a robust fixing can be readily achieved, in which the forces tending to pull the finger safety panel away from the bus bars are transmitted to the bus bar assembly locally. This provides a robust and reliable connection, even where the safAy panel spans a relatively large distance from end to end, without special reinforcement of the panel and its fixings.

The attaching means may comprise at least one projection on the safety panel which extends into the space between at least one pair of the bus bars and which engages part of the bus bar assembly. In embodiments wherein said bus bar assembly includes spacing means between the bus bars, and said projection may be arranged to engage said spacing means. Said projection may be provided with surfaces facing towards the safety panel and arranged to engage positively behind an edge of the spacing means.

In alternative embodiments, said projection is arranged to engage directly onto one of said bus bars. The bus bar and projection may be shaped so as to provide positive engagement of the projection behind a surface on the bus bar. In a particular embodiment of this type, the bus bar is provided with at least one groove running parallel to the length of the bar, and wherein part of said projection is arranged to lie in said groove.

In either case, said projection may be one of a pair of projections, arranged to engage a part of said bus bar assembly on two sides.

3 The attaching means may be arranged to operate by push-fitting or snaplocking of the safety panel onto said bus bar assembly.

The invention further provides a finger safety panel suitable for use in an electrical distribution apparatus according to the invention as set forth above, the panel including insulating portions arranged to overly a plurality of spaced bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by circuit breaking devices, apertures either side of said insulating portions to permit entry of contact jaws of circuit breaking devices through the safiAy panel, and means for attaching the safety panel to the bus bar assembly at locations between at least one pair of the bus bars.

The invention in a second aspect provides an electrical distribution apparatus comprising a bus bar assembly in which a plurality of bus bars are spaced so as to lie parallel with one another, each bus bar providing contact surfaces on two sides thereof for corresponding electrical contact jaws of said circuit breaking device, the apparatus further comprising a finger safety panel including insulating portions overlying the bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by said circuit breaking device while permitting entry of said contact jaws through apertures either side of said insulating portions, the apparatus further including a circuit breaking device having electrical contact jaws for projecting through the apertures in said sa&ty panel, wherein a housing of said device is provided with insulating projections arranged to project through said apertures alorkode at least one of said electrical contact jaws to such an extent that the electrical contact jaws are shielded from accidental human contact from the side until they have been fully disengaged from electrical contact with the bus bar. The finger safety panel may or may not be attached in accordance with the first aspect of the invention as set forth above.

Brief Desaiption Of The Drawinas Embodiments of the invention -will now be described, by way of example only, with reference to the following drawings, in which:- 4 Figure I shows the general arrangement of a four-way panelboard with finger safety features, with a circuit breaker mounted thereon.

Figure 2 shows in more detail a section of four-way panelboard with two sections of finger safety panel attached, according to a first embodiment of the present 5 invention.

Figure 3 is a rear view of the safety panel shown in Figure 2.

Figure 4 shows in more detail a spacer element of the assembly of Figure 2.

Figure 5 shows the attachment of safety panels directly to bus bars by means of grooves in the bus bar according to a second embodiment of the invention- Figure 6 shows the attachment of safety panels directly to bus bars by means of friction according to a third embodiment of the invention Figure 7 shows the safety shroud of the typical circuit breaker with added side protection features, suitable for use in any of the above embodiments.

Detailed Description Of The Embodiments

Figure I shows the general arrangement of electrical distribution apparatus in the form of a four-way partelboard I with a circuit breaker 5 mounted thereon. The panelboard includes a bus bar assembly which provides four conducting bus bars tO and spacing means 20, so that the bus bars lie parallel with one another and provide contact surfaces for the corresponding jaws (not shown) of the circuit breaker 5 and others like it. In the embodiment, two banks of circuit breakers can be attached to the bus bar assembly, at front as shown, and at the rear.

Safety panels 30 manufactured from an insulating material such as plastic are attached onto the bus bar assembly at front and rear. Apertures 35 in the safety panels allow access for the contact jaws of the circuit breaker but are sized such that accidental human contact with the underlying bus bars is prevented at unoccupied locations. In particular, each contact location is provided with a pair of apertures, which are separated by a bridging portion 37 which overlies the edge of the bus bar, while the contact jaws can enter to engage the bus bar to either side. There are projections 39 with chamfered edges which act as a barrier during the transition stages (plugging on), this preventing finger contact from top and bottorn. There are also provided additional insulating safety covers 40 for the top and bottom of the assembly.

The safety panel 30 and the top panel 40 may be integrated into a single piece.

It will be appreciated that the contact jaws will tend to knock and/or grab at the safety panel during attachment and removal of circuit breakers over a long period of operation, so that the safety panels and their attachment should be resistant to distortion and damage.

Figure 2 shows in greater detail a section of four-way panelboard 1 according to the embodiment shown in Figure 1. The bus bar assembly is held together by means of bolts 50 which are placed within insulating sleeves to ensure that the bolt does not short circuit the individual bus bars.

The safety panel 30 is fixed onto the bus bar assembly by attachment to spacing elements (spacers) 60 which form the spacing means 20 within the bus bar assembly.

The electrically insulating spacers 60 in this embodiment not only position the bus bars relative to each other, but are shaped so as to allow the safety panels 30 to be attached securely in place.

In use the bus bars are separated and supported by means of spacers 60 placed at intervals along the length of the bus bar assembly. The spacers also serve as a means for attaching the front safety panel, as will be described in more detail below, with reference to Figures 3 and 4. The support for the saflty panels thus provided is over many points of the bus bar assembly, distributing the mechanical load on the panels evenly.

Figure 3 shows in detail the safety panel 30, the view orientated to show the inner side of the panel and the specific parts which grip onto the bus bar assembly in the spaces between the bus bars 10- Resilient fingers 80 on the inner side of the sa&ty panel face towards the bus bar assembly. The fingers are grouped in pairs, as shown in Figure 4, such that each pair of fingers may firmly mate with and grip a corresponding formation on the bus bar assembly.

The end of each finger is provided with a forward-facing lip 82 and a chamfer 84. The pairs of fingers thus provide a spring clip which can pass over and lock securely into place behind complementary formations of the bus bar assembly.

6 Figure 4 shows in detO one of the spacers 60. The spacer is formed such that there are complementary projections 100 and recesses 105 allowing two or more spacers to be stacked together between bus bars such that recesses 105 receive projections 100 and the resultant assembly is held firmly in place. There is also provided a hole 110 through the vertical axis of the spacer so that the spacers are held in place by the bolts 50.

There are pairs of receiving edges 120 on the spacer which can be gripped by the fingers 80 formed on the safety panel 30, positively holding said safety panel 30.

Each receiving edge 120 is formed with a chamfer 122 leading to a lip 126 facing inwards in the completed bus bar assembly. During assembly of the safiAy panel onto the bus bar assembly, the charnfers 82 on the fingers 80 of the safety panel guide the fingers over the edges 120 of the spacers, while the pairs of fingers 80 bend slightly apart. Eventually, the lips 84 and 126 of the two components lock into place one behind the other, forming a snap-lock to hold the safty panel 30 securely against the bus bars.

The spacer is formed symmetrically such that safety panels may be fitted on opposite sides of the bus bar assembly.

The safety panel 30 can be attached onto the bus bar assembly in alternative ways.

Figure 5 shows the safty panel 30 attached directly onto the bus bars 10 according to a second embodiment. In place of the fingers 80 which are arranged to engage with the spacers, there are provided pairs of resilient fingers 150 so formed so as to lock into grooves 160 extending along the length the bus bars as shown, and formed in the bus bar 10 such that the safL-ty panel 30 is attached to the bus bars and firmly held in position The grooves 160 are of a depth and profile, for example semi-circuLar, sufficient to provide adequate purchase for the fingers 150 which have a similarly and complementarily modified profile.

7 Figure 6 shows the safety panel 30 attached directly onto the bus bars 10 according to a third embodiment. This is similar to the second embodiment but avoids the need to provide grooves or otherwise modify the cross- section of the bus bars, reducing cost and electrical losses. In this case, the panel 30 is attached by resilient fingers 170 which grip both sides of the bus bars 10 by means of ftiction only. The fingers are designed so as to provide a positive holding force at regular locations close to the apertures 35, and so keep the safety panel 30 firmly in place. The surfaces of the fingers 170 which interface with the bus bars may be smooth or contoured, for example ridged.

Figure 7 shows an extra feature on an insulating shield 170 as fitted to a circuit breaker 5, which may be used with a panelboard of the type just described to provide an additional degree of finger safiAy. A forked projection 190 is fitted to or formed in the insulating shield so as to project into the apertures 35 of the saflAy panel 30 either side of the bridging portion 37, alongside the contact jaws (not shown). The projections 170 prevent accidental contact with the live bus bars from the sides during insertion or extraction of the circuit breaker. The projections 180 are of a length such that the electrical contact jaws of the circuit breaker or other electrical equipment are shielded from human or other outside contact until they have been fidly disengaged and electrical contact with the bus bars broken. As can be seen in Figure 7, this extra protection is provided only at the two outer contact positions, of a four-way device.

Those skilled in the art will appreciate that othcr'different embodiments are possible, within the scope of the invention, and the specific embodiments above are presented as examples only. For example, mating portions on the bus bar assembly and the safiAy panel may be reversed, so that fingers on the spacer elements engage appropriate formations on the safety paneL In embodiments where safety panels are provided front and rear, each safety panel may engage formations on the other, rather than engaging the bus bar assembly directly. The safL-ty panels need not attach to the bus bar assembly at points between every pair of bus bars, or at every contact or spacer location. The attaching points may be distributed more sparsely while still 8 providing sufficient attachment to reduce the risk of the safety panel becoming damaged or con-dng away with the circuit breaker.

9

Claims

1. An electrical distribution apparatus for the mounting of at least one circuit breaking device, the apparatus comprising a bus bar assembly in which a plurality of bus bars are spaced so as to he parallel with one another, each bus bar providing contact surfaces on two sides thereof for corresponding electrical contact jaws of said circuit breaking device, the apparatus ftu-ther comprising a finger safety panel including insulating portions overlying the bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by said circuit breaking device while permitting entry of said contact jaws through apertures either side of said insulating portions, the safity panel being attached to the bus bar assembly at least in part by means which extend into a space between adjacent bus bars.

2. An apparatus as claimed in claim 1, wherein said attaching means comprises at least one projection on the safety panel which extends into the space between at least one pair of the bus bars and which engages part of the bus bar assembly.

3. An apparatus as claimed in claim 2, wherein said bus bar assembly includes spacing means between the bus bars, and wherein said projection is arranged to engage said spacing means,

4. An apparatus as claimed in claim 3, wherein said spacing means comprises of a plurality of spacing elements which separate and support the bus bars of said apparatus and are held in place by means of bolts placed through an axis of said elements and through apertures in the bus bars.

5. An apparatus as claimed in claim 4, wherein said spacing elements are provided with complementary recesses and projections allowing two or more spacers to be stacked together between successive pairs of bus bars, the projection of one spacing element extending through an aperture in the bus bar and into the recess of another spacing element.

6. An apparatus as claimed in claim 3, 4 or 5, wherein said projection is provided with surfaces facing towards the safety panel and arranged to engage positively behind an edge of the spacing means.

7. An apparatus as claimed in claim 2, wherein said projection is arranged to engage directly onto one of said bus bars.

8. An apparatus as claimed in claim 7, wherein the bus bar and projection are shaped so as to provide positive engagement of the projection behind a surface on the bus bar.

9. An apparatus as claimed in claim 8, wherein the bus bar is provided with at least one groove running parallel to the length of the bar, and wherein part of said projection is arranged to he in said groove.

10. An apparatus as claimed in claim 7, wherein said projection is arranged to grip onto the bus bar by friction, without positive engagement.

11. An apparatus as claimed in any of claims 2 to 10, wherein said projection is one of a pair of projections, arranged to engage a part of said bus bar assembly on two sides.

12. An apparatus as claimed in any of claims 1 to 11, wherein said attaching means is arranged to operate by push-fitting of the safety panel onto said bus bar assembly.

13. An apparatus as claimed in any of claims 1 to 9, wherein said attaching means is arranged to operate by snap-locking of the safety panel onto said bus bar assembly.

14. An electrical distribution apparatus as claimed in any preceding claim, the apparatus fiu-ther including a circuit breaking device having electrical contact jaws for projecting through the apertures in said panel, wherein a housing of said device is provided with insulating projections arranged to project through said apertures alongside at least one of said electrical contact jaws to such an extent that the electrical contact jaws are shielded from accidental human contact from the side until they have been fully disengaged from electrical contact with the bus bar.

15. An electrical distribution apparatus as claimed in any preceding claim, wherein said bus bar assembly comprises a stack of bus bars and spacing means arranged between an elongate base member and an elongate upper structural member, said members being held together by bolts extending through said members and through the bus bars and spacing means of the bus bar assembly.

16. An apparatus as claimed in claim 15, wherein said finger safety panel is attached to at least one of said members above or below the bus bar stack, in addition to being attached to the bus bar assembly in the space between the bus bars.

17. An apparatus as claimed in claim 15 or 16, wherein a top safety panel is provided which extends perpendicular to said finger safety panel along the top of the bus bar stack.

18. A finger safety panel suitable for use in an electrical distribution apparatus as claimed in any preceding claim, the panel including insulating portions arranged to overly a plurality of spaced bus bars so as to prevent accidental human contact with said bus bars at locations unoccupied by circuit breaking devices, apertures either side of said insulating portions to permit entry of contact jaws of circuit breaking devices through the safety panel, and means for attaching the safety panel to the bus bar assembly at locations between at least one pair of the bus bars.

19. A finger safety panel as claimed in claim 18, wherein the attaching means is arranged to operate by snap4ocking of the safety panel onto said bus bar assembly.

20. A finger safety panel as claimed in claim 18 or 19, wherein the attaching means includes at least one pair of projections formed on a rear side of the panel so as to 12 extend into the space between adjacent bus bars and engage corresponding portions of the bus bar assembly.

21. A finger safety panel as claimed in claim 20, wherein said projections are arranged to engage spacing means forming part of the bus bar assembly between the bus bars.

22. An electrical distribution apparatus comprising a mulfi-phase panel board with finger safety panel substantially as described herein with reference to any of the 10 accompanying drawings.

23. A finger safety panel for use in a mulfi-phase panel board, substantially as described herein with reference to any of the accompanying drawings.