GB2304467A

GB2304467A - Electrical apparatus enclosure

Info

Publication number: GB2304467A
Application number: GB9516769A
Authority: GB
Inventors: Stuart Frank Copping; Michael Richard Taylor
Original assignee: Malcoe Precision Fabrications Ltd
Current assignee: Malcoe Precision Fabrications Ltd
Priority date: 1995-08-16
Filing date: 1995-08-16
Publication date: 1997-03-19
Also published as: GB9524765D0; GB2304469A; GB9516769D0; GB2304469B

Abstract

Electrical apparatus 2 has double-walled panels 4, 6 with an injected setting foam between the walls 4, 6. An electromagnetic radiation screening mesh may be embedded within the foam. Metal Castings 8, 10, 22 are used at the edges of the panels. The resultant enclosure is resistant to attack by vandals.

Description

ELECIwRICAL APPARATUS ENCLOSURE This invention relates to the field of electrical apparatus enclosures.

It is known to provide electrical apparatus enclosures for housing electrical equipment, such as telephone junction/switching equipment and traffic signalling equipment, in outdoor locations, typically by the side of a road. Such an environment is harsh and the enclosures must provide a high degree of protection for what can be expensive and sensitive electrical apparatus. The enclosures must protect their contents from damage by moisture or dust penetrating the enclosures, temperatures that are too high or too low and similar environmental factors consequential upon their exposed location.

Another aspect of the protection that must be provided by the electrical apparatus enclosure is protection against damage by vandals or other malicious persons. The enclosures may be fitted with security locks that resist picking but must also be made sufficiently mechanically strong that they can resist direct attempts to breach their security, such as forcing the locks or hinges or attack with device trying to penetrate the enclosure walls.

In order to meet these challenges, it is known to provide electrical apparatus enclosures having galvanised steel carcass constructions. If an appropriate gauge of steel is used, then such enclosures can provide a very high degree of physical security.

It is also known to provide welded aluminium enclosures. In order to provide sufficient strength to give the required degree of resistance to malicious attack, a heavy gauge of aluminium must be used. This is both expensive in terms of materials and requires a large amount of skilled and expensive labour to weld together the panels to form such enclosures. As an alternative to welding together the aluminium panels, it is known to use a framework of aluminium extrusion into which the aluminium panels are fixed. However, such aluminium extrusions are expensive to produce and complicate the design.

An emerging requirement for electrical apparatus enclosures in particular circumstances is that they should be as light as possible. It is increasingly common to install such electrical apparatus enclosures on rooftops where a high weight causes significant problems. The weight of a steel enclosure or a heavy gauge aluminium enclosure can introduce a requirement for special strengthening of the roof on which the enclosure is to be installed in order to support the load. Furthermore, access to such locations is often restricted and so it can be very difficult to lift a heavy enclosure into position. Both of these factors make it more difficult and expensive to install known enclosures in such locations.

The invention addresses the problem of providing a lightweight enclosure that nevertheless maintains a high degree of environmental and security protection desired.

Viewed from one aspect the present invention provides an electrical apparatus enclosure comprising: a plurality of double-walled panels having an internal cavity containing an injected setting foam.

It has been found that the use of an injected and setting foam between doublewalled panels greatly enhances the physical security of the enclosure whilst only slightly increasing the weight. Accordingly, much thinner and lighter materials may be used for the walls of the panel whilst relying upon the foam filled core to make an attack seeking to damage or to penetrate the panel difficult. If the outer skin is penetrated, then it must be peeled back against the action of the foam and then all of the foam must be removed before the inner skin can be attacked. Furthermore, the support provided by the foam to the outer skin makes its initial penetration more difficult.

In addition to the security advantages provided by the invention, the doublewalled panels also have a significantly improved mechanical strength and rigidity due to their foam filling. Accordingly, the enclosure is more able to resist an attack that seeks to force apart and distort panels to gain access. The foam filling also provides a high degree of thermal and noise insulation that can be particularly advantageous in the field of electrical apparatus enclosures.

Another performance parameter for conventional electrical apparatus enclosures is the degree of electromagnetic screening that they provide. This electromagnetic screening operates in two senses, i.e. to stop unwanted interference escaping from the enclosure and to stop unwanted interference entering the enclosures and disrupting the operation of the apparatus inside. Conventional heavy gauge steel enclosures inherently provide a high degree of electromagnetic screening both against radio frequency interference and magnetic fields. Such lightweight materials as are desired to provide the walls of the panels in accordance with the present invention tend to provide a lower degree of electromagnetic screening. Accordingly, in preferred embodiments of the invention an electromagnetic radiation screening mesh is embedded within said foam.

Embedding of a screening mesh within the foam is highly effective in compensating for the lack of heavy gauge material used in the construction. In addition, there is a significant synergy between the foam and the mesh in the functions that they are able to perform. Since the foam is injected, it flows easily around the mesh and when set holds it firmly in position to perform its desired function. The screening mesh also provides a back-up in the security improvements provided by the foam. With an embedded mesh, an attacker will have an increased difficulty in penetrating the foam layer to gain access to the inner wall of the panel.

It will be appreciated that the double-walled panels could be constructed in many different ways. In particular, the wall skins could be moulded. However, it is particularly economic and convenient to use embodiments in which said plurality of double walled panels have walls formed of sheet material.

The sheet material from which the panels are formed could have many different compositions. For example, light gauge steel or sheet plastics materials could be used. However, in preferred embodiments of the invention said sheet material comprises aluminium or aluminium alloy.

Aluminium or aluminium alloy sheet material would normally have the significant disadvantage of relatively low physical strength compared to sheet steel material. However, due to the security and strength improvements made by the presence of the foam, the use of aluminium or aluminium alloy becomes desirable due to its properties of low weight and inherent corrosion resistance.

If the panels are to have a double-walled foam filled construction, then a particular point of low strength will be a their edges. Furthermore, it is difficult to produce complex shapes from simple sheet materials as are often required at edges.

Accordingly, in preferred embodiments of the invention said walls of sheet material are held captive within a moulding at at least one edge thereof.

Such mouldings are able to provide a high degree of mechanical strength at the edge portions and also may be relatively easily made to have a complicated three dimensional shape.

Electrical apparatus enclosures often incorporate a lock mechanism. In order that a lock mechanism should be physically strong, it is advantageous that it is attached to a firm location. In preferred embodiments of the invention a lock mechanism is housed within said moulding.

Given the construction of the double-walled panels, these do not provide a strong fixing point for any lock mechanism and so it has been found advantageous to dispose the lock mechanism within the moulding.

As previously mentioned, mouldings may be used at the edges of the doublewalled panels to increase their strength. However, for those edges where strength is less critical or where strength can be achieved by other means, then it is found convenient that said walls of sheet material are held by said foam in an interlocking abutting relationship at at least one edge thereof.

Abutting the walls together an then injecting the foam which when set holds the walls in place is a advantageously simple manufacturing process.

As mentioned, alternatives to using a moulding to strength the panels may be provided. This is particularly the case for positions on the panels where fixings are to be placed. Accordingly, in preferred embodiments of the invention a backing plate is provided behind an area of a wall of sheet material through which a fixing passes, such that said fixing passes both through said backing plate and through said wall.

Using backing plates behind areas where fixings are to be made allows the thickness of the rest of the panel wall to be reduced to give a reduced weight and yet provides sufficient strength at the point at which it is needed.

With the double-walled panels according to the invention it is possible to produce an enclosures of a carcass structure for reduced overall weight since a separate frame is not required to achieve the desired strength.

The double-walled panels may also be utilised in the doors of the enclosure.

The advantages of security, strength and lightness apply to the enclosures doors in the same manner as to the fixed panels of the enclosure. Furthermore, the doors of an enclosure are often the focus of any malicious attack and so improvements in their security are particularly advantageous. Lightweight doors are also easier and safer to use when authorised access to the enclosure is needed.

In order to provide convenient working access to the enclosure, it is desired to provide a hinged lid to the enclosure. This hinged lid may also be in the form of one of the double-walled panels.

In an enclosure having both a hinged lid and doors, it has been found advantageous to provide a manually actuated crank for engaging said one or more doors and holding said one or more doors compressed shut, said crank being disposed beneath said lid such that said crank may not be accessed when said lid is shut.

In this way, the mechanism for opening the doors is not accessible when the enclosure is in its normal locked state with the consequence that the number of potential weaknesses in the security of the enclosure is reduced and a lock need only be provided for the lid.

In order to increase the mechanical strength of the closing of the doors whilst not making the doors unduly difficult to open by an authorised person, it is preferred that when shut, said one or more doors sit within a groove, said crank serving to lift said one or more doors out of said groove when operated to open said one or more doors.

The locating of the doors in a groove when they are shut means that they will be prevented from being forced open unless they are lifted out of the groove. This will not be possible without lifting the lid. However, when the lid is lifted by an authorised person, then the doors may be relatively simply lifted via the crank.

Springs may be provided to hold the doors up in a lifted position once doors have been lifted out of their tight engagement with the groove.

In this arrangement with the hinged lid, crank and doors, it has been found advantageous to provide embodiments in which a lock mechanism is housed within a moulding at each lateral edge of said lid, each respective lock mechanisms engaging with a respective catch fixed to a moulding at a top edge of a respective side panel.

This arrangement provides that the doors are mechanically clamped in position by the groove and compressed shut giving a high degree of security and weather resistance whilst the lid is held secure by lock mechanisms fixed within the relatively strong mouldings at the lateral ends of the lid.

In order to provide a convenient arrangement for installations where the cables may not be routed underground, e.g. on top of a roof which it is desired not to unduly disturb, it is preferred that cabling entry ports are provided under lateral edges of said lid.

Whilst it would be possible to route such cable entry ports through the walls of the panels, it is advantageous that cabling entry ports are provided in moulding at a top edge of side panels of said enclosure.

Since the mouldings already have to be formed for other purposes, it is relatively easy to incorporate the cabling entry ports within them compared to the additional complication that would be involved in providing these cable entry ports elsewhere.

It will be appreciated that whilst the mouldings could be formed of many different materials, it is preferable that the mouldings comprise metal castings.

Metal castings provide a high degree of mechanical strength and corrosion resistance whilst being relatively easy to produce with complex shapes.

Given that many places where the lightweight enclosures of the present invention may be desired to be installed are relatively inaccessible, it is advantageous that the panels forming said enclosure is fixed in place such that said enclosure may be assembled from and disassembled to substantially flat panels.

In this way, an enclosure may be completely dissembled and the individual panels passed through a relatively small access hatch with the full enclosure then being assembled on site.

The strength of the double-walled panels is enhanced when said double walled panels have a curved outer wall.

Utilising a curved outer wall on several adjoining panels is made considerably easier by the use of mouldings at the edges joining these adjoining panels since these mouldings may be relatively easily made to have the complex double curvatures required to accommodate such joints.

Viewed from another aspect the present invention provides a method of manufacturing an electrical apparatus enclosure, said method comprising the steps of: forming double-walled panels having an internal cavity from sheet material; injecting foam into said internal cavity; leaving said foam to set within said internal cavity; and assembling a plurality of said double-walled panels to form said enclosure.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 illustrates an electrical apparatus enclosure in accordance with one embodiment of the present invention; Figure 2 illustrates the principle of construction of a double-walled panel of the enclosure of Figure 1; and Figure 3 illustrates the fixing used between two double-walled panels of the embodiment of Figure 1.

Figure 1 shows exploded view of an electrical apparatus enclosure 2 having a carcass construction of double-walled panels. An end wall of the enclosure 2 comprises an outer skin 4 and an inner skin 6. The outer skin 4 and the inner skin 6 are made of sheet aluminium or aluminium alloy bent into the required shape. The outer skin 4 and the inner skin 6 include only simple curves in one direction making their fabrication easier. A metal casting 8 (e.g. aluminium alloy) is provided at the top of the end panel and a metal casting 10 is provided at the bottom of the end panel.

The shape of the outer skin 4 is formed so as to be held captive by respective portions 12 of the top casting 8 and the bottom casting 10.

The top casting 8 includes a number of cabling entry ports 14 that may be closed off with a blanking plate 16 if they are not required. The cabling entry ports 14 lead into an upper roof space 18 of the enclosure 2 that is position beneath a hinged lid 20. The hinged lid 20 includes a casting 22 at each end. The castings 22 incorporate a lock (not shown) that co-operates with a catch within the top casting 8 of the end panel. This lock and catch arrangement may have the form of operation found in a vehicle luggage compartment whereby a key must be used to open the lid but the lid is shut and locked merely be slamming the lid closed.

The enclosure 2 incorporates two double-walled doors 24 that are hinged about a vertical axis. When shut, the doors 24 sit within a groove 26 in the bottom panel of the enclosure 2. A manually actuated crank engages with the doors 24 and serves to lift them out of the groove 26 so that they may be opened. The crank 28 is positioned beneath the lid 20 and so is not accessible when the lid 20 is shut. Springs 27 are provided between the groove 26 and the doors 24 to hold the doors in their lifted position when open and so avoid them dragging on the lip of the groove 26.

If an appropriate strength of spring 27 is used, then the crank 28 may be omitted with the springs 27 serving to lift the doors 24 out of the groove 26.

The enclosure 2 has a carcass construction whereby it is assembled from and may be disassembled to individual, substantially flat panels, e.g. end panels, lid, doors, back, bottom, etc.

Each of the double-walled panels of the enclosure 2 of Figure 1 is filled with foam that is introduced between the panelled walls and then sets. This foam serves to enhance the security offered by the panel and also increases it strength, insulation and noise blocking properties. Figure 2 schematically illustrates the production of such a panel.

An outer skin 4 is formed by a pressing process from flat sheet aluminium alloy. The outer skin 4 is then placed in a jig (not shown) and an electromagnetic radiation screening mesh 30 (this may be formed embedded with a sheet of backing material such as rubber or plastic or could possibly be a continuous thin metal sheet) is clipped into place within it followed by the inner wall 6. At this stagc, the assembly has relatively little strength.

The open ends of the double-walled panels are then closed with temporary plugs associated with the jig and a predetermined volume of foam is injected using a system such as that designed for packaging and sold as Instapak 808 by Sealed Air Limited of Northants, England. The quantity of this foam that is injected may be empirically determined such that when it has expanded and set it fills substantially all of the volume between the outer wall 4 and the inner wall 6 without excessive overflow. The set foam 32 flows around the mesh 30 and so embeds this securcly in position. The non-compressibility of the foam 32 also serves to hold the inner skin 6 in an interlocking and abutting relationship with the outer skin 4. The doublewalled and foam filled panel has a high degree of strength and offers good security.

The electromagnetic radiation screening mesh 30 may be manufactured of a number of different materials. The screening mesh 30 serves to block the passage both in and out of radio frequency radiation and also magnetic fields. Accordingly, a suitable substance for the screening mesh 30 conductive wire embedded within a plastic carrier sheet for ease of handling.

Figure 3 illustrates a joint between two panels. Since the aluminium alloy sheet material from which the outer wall 6 and the inner wall 4 are manufactured is relatively soft, then a normal nut and bolt fixing would be susceptible to the holes being enlarged by applied force and the bolt being pulled through to the break the joint. In order to protect against this and reinforce the joint, backing plates 34 are provided within each panel behind the point at which the fixing (in this case a bolt 36 and a nut 38) are provided. These backing plates 34 may be made of steel (preferably nitrotech treated for increased strength) which will be resistant to having the holes within it enlarged.

Claims

1. An electrical apparatus enclosure comprising: a plurality of double-walled panels having an internal cavity containing an injected setting foam.

2. An electrical apparatus enclosure as claimed in claim 1, wherein an electromagnetic radiation screening mesh is embedded within said foam.

3. An electrical apparatus enclosure as claimed in any one of claims 1 and 2, wherein said plurality of double walled panels have walls formed of sheet material.

4. An electrical apparatus enclosure as claimed in claim 3, wherein said sheet material comprises aluminium or aluminium alloy.

5. An electrical apparatus enclosure as claimed in any one of claims 3 and 4, wherein said walls of sheet material are held captive within a moulding at at least one edge thereof.

6. An electrical apparatus as claimed in claim 5, wherein a lock mechanism is housed within said moulding.

7. An electrical apparatus enclosure as claimed in any one of claims 3 to 6, wherein said walls of sheet material are held by said foam in an interlocking abutting relationship at at least one edge thereof.

8. An electrical apparatus enclosure as claimed in any one of claims 3 to 7, wherein a backing plate is provided behind an area of a wall of sheet material through which a fixing passes, such that said fixing passes both through said backing plate and through said wall.

9. An electrical apparatus enclosure as claimed in any one of the preceding claims having a carcass structure formed of a plurality of said double-walled panels.

10. An electrical apparatus enclosure as claimed in claim 9, having one or more doors formed of said double-walled panels.

11. An electrical apparatus enclosure as claimed in any one of the preceding claims having a hinged lid formed of one of said double-walled panels.

12. An electrical apparatus enclosure as claimed in claims 10 and 11, comprising a manually actuated crank for engaging said one or more doors and holding said one or more doors compressed shut, said crank being disposed beneath said lid such that said crank may not be accessed when said lid is shut.

13. An electrical apparatus as claimed in claim 12, wherein, when shut, said one or more doors sit within a groove, said crank serving to lift said one or more doors out of said groove when operated to open said one or more doors.

14. An electrical apparatus as claimed in claim 6 and any one of claims 11 to 13, wherein a lock mechanism is housed within a moulding at each lateral edge of said lid, each respective lock mechanisms engaging with a respective catch fixed to a moulding at a top edge of a respective side panel.

15. An electrical apparatus enclosure as claimed in any one of claims 11 to 14, wherein cabling entry ports are provided under lateral edges of said lid.

16. An electrical apparatus enclosure as claimed in claim 5 and claim 15, wherein said cabling entry ports are provided in moulding at a top edge of side panels of said enclosure.

17. An electrical apparatus enclosure as claimed in any one of the preceding claims, wherein said one or more mouldings comprise metal castings.

18. An electrical apparatus enclosure as claimed in any one of the preceding claims, wherein each panel forming said enclosure is fixed in place such that said enclosure may be assembled from and disassembled to substantially flat panels.

19. An electrical apparatus enclosure as claimed in any one of the preceding claims wherein said double walled panels have a curved outer wall.

20. A method of manufacturing an electrical apparatus enclosure, said method comprising the steps of: forming double-walled panels having an internal cavity from sheet material; injecting foam into said internal cavity; leaving said foam to set within said internal cavity; and assembling a plurality of said double-walled panels to form said enclosure.

21. A method as claimed in claim 20, further comprising the step of: placing an electromagnetic screening mesh within said internal cavity before injecting said foam.

22. An electrical apparatus enclosure substantially as hereinbefore described with reference to the accompanying drawings.

23. A method of manufacturing an electrical apparatus enclosure substantially as hereinbefore described with reference to the accompanying drawings.