GB2349016A

GB2349016A - Mounting rail

Info

Publication number: GB2349016A
Application number: GB9908739A
Authority: GB
Inventors: Andrew Purdie Baker
Original assignee: Schneider Electric Ltd; Schneider Ltd
Current assignee: Schneider Electric Ltd
Priority date: 1999-04-17
Filing date: 1999-04-17
Publication date: 2000-10-18
Anticipated expiration: 2019-04-17
Also published as: GB9908739D0; GB2349016B

Abstract

A housing 10 for electrical distribution equipment includes a standard mounting rail 50, 55 for mounting a plurality of circuit breaking devices. The housing further includes at least one bus bar arranged alongside the rail with fixed contacts for mating with corresponding terminals of the devices. The standard mounting rail is modified by the provision of spaced projections 60 which engage parts of the circuit breaking device when mounted. The projections prevent longitudinal movement of the devices during assembly and wiring up, and so help to preserve reliable operation of the bus bar connections.

Description

ELECTRICAL DISTRIBUTION EOUIPMENT The invention relates to electrical distribution equipment and in particular to mountings for electrical circuit breaking components for connection to fixed bus bars.

The invention may be applied for example in electrical load centres and components thereof for domestic or industrial use.

Such load centres are for electrical distribution in buildings, and are arranged to house a number of"outgoers"or circuit breaking devices, which may be simple switches or, more typically circuit protection devices. The specific functions of these components are not material to the present invention. Many known examples use a DIN standard mounting rail, which provides two parallel upward facing projections with outwardly turned lips, thus forming an inverted top-hat cross section. The components for use with such a mounting are arranged to grip onto the DIN rail in a variety of ways.

Traditionally, the components have screw terminals for receiving cables coming from the supply, and going out to the load. The supply is generally common to all the outgoers, or to a group of them. Accordingly, other designs of load centre have been known in which a fixed bus bar is provided, and the components are adapted for plugging or screwing onto the bus bar, to simplify the installation process. At the same time, there are advantages in manufacture if the same basic design of component can be used for these fixed bus bar systems, as well as the conventional DIN rail systems.

Toward this end, various proposals have been made, adapting DIN mounting components for use with fixed bus bars. United Kingdom application GB-A-2328317 (Agents ref. 45794GB/GS-02) discloses a load centre wall mountable enclosure with means for connecting a circuit breaker mounted on conventional DIN rails to a live or neutral bus bar. The bus bars in that case (three phase plus neutral) are formed with tabs, which project directly into the screw terminal openings of the standard breaker housings. Alternative mounting systems for circuit breakers are disclosed in EP-A0748018 (45429EP/SWE-12-EPC) and EP-A-0472409 (Crabtree). These aim to provide a plug-in bus bar, associated with DIN rail mounting. Various forms of adapter are proposed so that the basic design of outgoer can be used with little or no modification.

The DIN rail was not conceived for mounting pluggable components, however, and the inventors have found that certain problems arise in such systems. In particular, although the supply side is directly connected to the bus bar as part of the mounting operation, screw connections to flying cables are still required to be made at the load side. The circuit breaker is not securely fixed against longitudinal movement on the rails, and mechanical strain is applied upon the circuit breaker/bus bar connection while making the cable connection. This will tend to distort the plug or other form of connection to the bus bar, leading to poor or broken connections, overheating and so forth.

According to one aspect of the invention there is provided a housing for electrical distribution equipment, the housing including a mounting rail for mounting a plurality of circuit breaking devices (outgoers) transversely across the rail, the mounting rail comprising a parallel pair of elongate, out-turned lips so that they may be gripped by appropriate gripping means on each device, wherein the housing further includes at least one bus bar arranged alongside a first one of said lips with fixed contacts for mating with corresponding terminals of devices when mounted on the mounting rail, and wherein the mounting rail is further provided with locating means for engaging predetermined parts of a device when mounted, so as to prevent movement of the mounted device in a direction parallel to the mounting rail.

The locating means prevent longitudinal movement of the devices during assembly and wiring up, and so help to preserve reliable operation of the bus bar connections. The locating means may comprise locating surfaces at regular intervals on or near the second of said lips. The locating surfaces may be formed by projections and/or apertures formed on the rail, depending on the detailed form of the outgoers and their gripping means. The locating surfaces may for example comprise projections on the underside of the second lip.

The locating surfaces on the rails may in alternative embodiments be provided by projections on the top of the rail, or by apertures or notches in the rail. In the case where the outgoers each comprise a movable tongue for engaging the underside of the second lip to grip the rail, such projections may be provided such that said tongue enters between them. With other designs, movable gripping lugs may project under the lip at either side of the outgoer body. In such embodiments, accordingly, the locating means may comprise projections centred between neighbouring device positions, or may be centred on the centre line of the respective device outgoer positions, respectively.

The invention further provides electrical distribution equipment comprising a housing according to the invention as set forth above, and one or more circuit breaking devices adapted for mounting on the mounting rail thereof, each circuit breaking device having a first terminal for contacting one of said fixed contacts and a second terminal for receiving a free cable connection, the device when mounted engaging said locating means so as to be prevented effectively from moving in a direction parallel to the mounting rail during connection of said cable to the second terminal.

Brief Description Of The Draines Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a known load centre housing and attached circuit breaker.

Figure 2 shows schematically the underside of the circuit breaker.

Figure 3 shows in detail a cut-away portion of the load centre housing with modified mounting rail, according to a first embodiment of the present invention.

Figure 4 is an enlarged schematic view of part of the circuit breaker attached to the modified mounting rail, as seen from below.

Figure 5 is an enlarged schematic view of part of a different standard circuit breaker, attached to a modified mounting rail according to a second embodiment of the invention, as seen from below.

Description of the Embodiments Figure 1 shows schematically part of a known load centre 10 which incorporates a DIN mounting rail 40, shown in cross section, carrying a typical outgoer in the form of a miniature circuit breaker (mcb) 20, shown in elevation. Figure 2 shows the circuit breaker in isolation, in a perspective view from below.

The circuit breaker 20 is of conventional form with generally flat and parallel faces. A mounting recess 30 is provided in the base of the breaker for receiving the mounting rail 40, the mounting rail being generally of inverted top-hat cross section, providing in effect two out-turned lips 50 and 55 running the length of the rail. At one end 70 of the recess, there is formed a re-entrant profile. At the other end 80 of the recess, a retractable tongue 90 is carried within a stationary part 100 of the breaker body.

To engage the breaker and fix it on the rail 40, the profile at 70 is first engaged under the lip 55. The second end 80 of the recess is then rotated into position over the other lip 50, with the tongue 90 in a retracted position. The tongue is then slid into a locked position (as shown) so that it projects under lip 50 to keep the breaker in place, in well-known manner. A plurality of circuit breakers can be attached to the load centre side-by-side along the mounting rail 40.

To disengage the circuit breaker 20 from the load centre 10, tongue 90, is unlocked from the closed position by means of a screwdriver or fingernail in slot 110, and is withdrawn to an open position thus allowing the body of the circuit breaker to be rotated and disconnected from the load centre in its entirety.

As disclosed in more detail in GB-A-2328317, mentioned above, the DIN rail mounting is nowadays being used in load centres that have an array of fixed terminal blades 44 connected to a bus bar 45, each blade being received and secured by the standard screw terminal of a respective breaker 20. At the load side of the circuit breaker a second screw terminal receives an outgoing cable 46 to connect to the load.

Note that the bus bar connection on the circuit breaker 20 may be placed differently, according to requirements and specifications.

As discussed in the introduction above, plug terminals or adapters providing plug terminals may be provided, to facilitate rapid assembly without operation of the screw terminal. Different types of bus bar will require different plug arrangements. As further discussed above, however, it has been found that the bus bar connections, made when the breaker is mounted on the rail, are susceptible to damage caused by movement of the breaker during assembly of the cable connection 46. In particular, the standard DIN rail and breaker designs provide nothing to stop the cable end 100 of the breaker sliding along the rail while heavy cables are fixed in the second terminal.

Figure 3 shows in detail a load centre 10'housing with modified mounting rail 40', which is intended to eliminate the sliding of the breakers mentioned above. Figure 4 is a schematic view from below, of the breaker 20 mounted on the modified rail. Parts corresponding to parts in Figure I are given like references. For clarity the internal assembly of the load centre housing is not shown, but is the same as described in GB A-2328317, mentioned above. As before, the mounting rail 40'forms an inverted top-hat cross section composed of two separate lips 50 and 55.

The modified rail 40'is further provided at regular intervals with protrusions 60 along the underside of the lip 50, each of which provides locating surfaces 62. The spacing between the protrusions 60 is such that the tongues 90 of the outgoer fit snugly between the protrusions. Accordingly, the locating surfaces 62 of neighbouring projections engage the tongue 90, thus ensuring a minimum of displacement of the circuit breaker during cable connection operations. The protrusions 60 are recessed slightly from the outlying edge of the lip 50, for compatibility with other types of DIN mounting components.

It will be appreciated that in this embodiment, when two circuit breakers are mounted adjacent to one another on the same load centre, their bodies lie against one another. This has the added advantage of limiting the effects of transverse movement of the circuit breakers even further.

In this embodiment the lip 55 of the mounting rail 40'is composed of a plain continuous lip without protrusion. In other embodiments, depending on the form of gripping means provided in the breaker design, notches, apertures or projections on one or both lips, or elsewhere on the rail or housing may be appropriate.

The load centre housing and the mounting rail 40'are in this example moulded out of a plastic material but may be manufactured from any suitable material, or composite of materials, for the purposes of the invention. The DIN rails and attendant protrusions, for example, may alternatively be formed by pressing from metal sheet.

Figure 5 shows schematically the underside of an alternative embodiment where tongue 90 is replaced by a slider 120 having two retractable projections 122. The stationary part 130 of the breaker resides centrally between the retractable projections 122. Such a form of slider is shown in more detail in EP-A-047209 (Crabtree), mentioned above. For use with this type of breaker, the dimensions and positions of the retractable projections 60'are such that they occupy fully the space between the retractable projections 120. Again, when two circuit breakers are fitted adjacent to each other on the load centre then one of the retractable projections 122 from each circuit breaker will abut on to the other forming a solid fit with each other, further limiting the possible effects of transverse movement upon the circuit breakers.

The invention is clearly not limited in detail to the embodiments described. For example, locating means in the form of protrusions may be on the upper side of the lip 50, on both lips, and/or on some other part of the housing. In yet other embodiments, the locating surfaces could be provided by apertures or notches in the mounting rail or housing, in addition or as an alternative to projections.

Claims

Claims 1. A housing for electrical distribution equipment, the housing including a mounting rail for mounting a plurality of circuit breaking devices transversely across the rail, the mounting rail comprising a parallel pair of elongate, out-turned lips so that they may be gripped by appropriate gripping means on each device, wherein the housing further includes at least one bus bar arranged alongside a first one of said lips with fixed contacts for mating with corresponding terminals of devices when mounted on the mounting rail, and wherein the mounting rail is further provided with locating means for engaging predetermined parts of a device when mounted, so as to prevent movement of the mounted device in a direction parallel to the mounting rail.
2. A housing as claimed in claim 1, wherein the locating means comprises locating surfaces at regular intervals on or near the second of said lips.
3. A housing as claimed in claim 2, wherein the locating surfaces are formed by projections formed on the mounting rail.
4. A housing as claimed in claim 3, wherein the locating surfaces comprise projections on the underside of the second lip.
5. A housing as claimed in claim 4, adapted for use where the devices each comprise a retractable projection for engaging the underside of the second lip to grip the rail, wherein the projections are provided such that said tongue enters between them.
6. A housing as claimed in claim 4, adapted for use where the devices each comprise retractable projections arranged to project under the second lip at either side of a body of the device.
7. A housing as claimed in any of claims 1 to 5, wherein the locating means comprise projections centred between neighbouring device positions as defined by said fixed contacts.
8. A housing as claimed in any of claims 1 to 4 and 6, wherein the locating means comprise projections centred on the centre lines of respective device positions as defined by said fixed contacts.
9. Electrical distribution equipment substantially as described herein with reference to Figures 3 and 4 or Figure 5 of the accompanying drawings.

9. A housing as claimed in any preceding claims, wherein said fixed contacts comprise tabs to be received in screw terminals of the circuit breaking devices.

10. A housing as claimed in any of claims 1 to 8, wherein said fixed contacts comprise contacts for engaging complementary plug contacts of the circuit breaking devices.

11. Electrical distribution equipment comprising a housing as claimed in any preceding claim, in combination with one or more circuit breaking devices adapted for mounting on the mounting rail thereof, each circuit breaking device having a first terminal for contacting one of said fixed contacts and a second terminal for receiving a free cable connection, the device when mounted engaging said locating means so as to be prevented effectively from moving in a direction parallel to the mounting rail during connection of said cable to the second terminal.

12. Electrical distribution equipment substantially as described herein with reference to Figures 3 and 4 or Figure 5 of the accompanying drawings.

Claims 1. A housing for electrical distribution equipment, the housing including a mounting rail for mounting a plurality of circuit breaking devices transversely across the rail, the mounting rail comprising a parallel pair of elongate, out-turned lips so that they may be gripped by appropriate gripping means on each device, wherein the housing further includes at least one bus bar arranged alongside a first one of said lips with fixed contacts for mating with corresponding terminals of devices when mounted on the mounting rail, and wherein the mounting rail is further provided with locating means for engaging predetermined parts of a device when mounted, so as to prevent movement of the mounted device in a direction parallel to the mounting rail, and wherein said locating means comprises projections formed at regular intervals on the underside of the second lip, and recessed from the edge of the second lip so as not to interrupt said edge.

2. A housing as claimed in claim 1, adapted for use where the devices each comprise a retractable projection for engaging the underside of the second lip to grip the rail, wherein the projections are provided such that said tongue enters between them.

3. A housing as claimed in claim 2, adapted for use where the devices each comprise retractable projections arranged to project under the second lip at either side of a body of the device.

4. A housing as claimed in any of claims 1 to 3, wherein the locating means comprise projections centred between neighbouring device positions as defined by said fixed contacts.

5. A housing as claimed in claim 1 or 3, wherein the locating means comprise projections centred on the centre lines of respective device positions as defined by said fixed contacts.

6. A housing as claimed in any preceding claim, wherein said fixed contacts comprise tabs to be received in screw terminals of the circuit breaking devices.

7. A housing as claimed in any of claims 1 to 6, wherein said fixed contacts comprise contacts for engaging complementary plug contacts of the circuit breaking devices.

8. Electrical distribution equipment comprising a housing as claimed in any preceding claim, in combination with one or more circuit breaking devices adapted for mounting on the mounting rail thereof, each circuit breaking device having a first terminal for contacting one of said fixed contacts and a second terminal for receiving a free cable connection, the device when mounted engaging said locating means so as to be prevented effectively from moving in a direction parallel to the mounting rail during connection of said cable to the second terminal.