GB2586826A

GB2586826A - Enclosure

Info

Publication number: GB2586826A
Application number: GB1912724.0A
Authority: GB
Inventors: Geoffrey Martell Andrew
Original assignee: EXTRONICS Ltd
Current assignee: EXTRONICS Ltd
Priority date: 2019-09-04
Filing date: 2019-09-04
Publication date: 2021-03-10
Also published as: GB201912724D0

Abstract

An enclosure assembly for housing electrical devices 31 in explosive environments e.g. paint spray booths or fuel tanks, comprising a first compartment 2 sealed from a second compartment 6. A circuit board 58 e.g. printed circuit board (PCB) is sealingly mounted to a dividing wall separating the compartments. The circuit board 58 comprises a first electrical connection point 64 in the first compartment 2 and a second electrical connection point 66 in the second compartment 6. The connection points are in electrical communication via the circuit board 58. The component 31 may be a transceiver in electrical communication with an antenna 84. The protection rating of the compartments may be different e.g. Ex nR or Ex ec rated. The enclosure may comprise an intrinsically safe RF output. The enclosure may be used as a wireless access point.

Description

Enclosure

Field of invention

The present invention relates to an enclosure for housing electrical devices in explosive environments. In addition, the invention relates to a wireless device.

Background

Hazardous environments exist in many sites, e.g. industrial sites. One type of hazardous environment is an explosive environment. Explosive environments can be present in a variety of different places including paint spray booths, near fuel tanks, in sumps, or in many places where aerosols, vapours, mists, gases, or dusts exist.

Electrical equipment, such as wireless access points, motors and enclosures for housing electrical components, present in explosive (or potentially explosive) environments is required to be certified as safe in order to be safely operated in an explosive environment. Explosive environments can be classified by zone. The zones include: zone 0, zone 1 and zone 2. By way of example, zone 2 is defined as "a place in which an explosive atmosphere consisting of a mixture with air or flammable substances in the form of gas, vapours and mists is not likely to occur in normal operation but if it does occur, it will be present for a short period of time only".

There are a number of industry standards which define the equipment, and the design considerations of the equipment, which is suitable to be used in a particular zone type. The equipment can include enclosures and electrical equipment such as electrical connection points and transceivers. Enclosures made to some of the industry standards are required by the industry standard to remain sealed from the surrounding environment when located in the hazardous environment. Different types of enclosure may be connected to one, with threaded gland entry or threaded pipe entry providing cable access between the enclosures. Each of the glands used to pass a cable between the enclosures present a potential failure point. In addition each grand needs to pass through a corresponding hole in each enclosure and so increasing the number of connections (and hence cables and glands) between the enclosures increases the complexity, cost and assembly time of the enclosures.

In light of the above, it is desirable to be able to provide electrical communication between multiple enclosures which are suitable for use in a hazardous environment whilst isolating the enclosures from one another and the surrounding environment. Such enclosures may solve problems with existing enclosures whether mentioned above or otherwise.

Summary

According to a first aspect of the invention there is provided an enclosure assembly for housing electrical devices in explosive environments, the enclosure comprising a first compartment; a second compartment, the first compartment being sealed from the second compartment; a dividing wall separating the first compartment and the second compartment; a circuit board sealingly mounted to the dividing wall; wherein the circuit board comprises a first electrical connection point and a second electrical connection point, the first electrical connection point being located in the first compartment and the second electrical connection point being located in the second compartment; wherein the first electrical connection member is in electrical communication with the second electrical connection member via the circuit board.

The term 'circuit board' is used herein to refer to a body which is capable of being sealingly mounted to the dividing wall and which includes electrical connections points in order to allow electrical communication between the first compartment and the second compartment. The circuit board may be electrically isolated from the dividing wall. An example of an appropriate circuit board is a printed circuit board, although any appropriate circuit board may be used.

Advantageously, the circuit board acts to both seal the first compartment from the second compartment and to place the first electrical connection point in electrical communication with the second electrical connection point. Therefore any components electrically connected to the electrical connection points are also placed in electrical communication. Known enclosures for housing electrical devices in explosive environments place components in electrical communication by passing a conductor, each end of which is connected to a respective electrical component, through a hole in the dividing wall, the hole comprising a suitable gland. The circuit board of the present invention serves the purpose of both the gland and the conductor from known enclosures.

Since the enclosure is provided with separate compartments, the enclosure is easily customisable. The compartments can be prepared separately by providing each compartment with the required components. For example, one of the compartments can be provided with standard components and the other one of the compartments can be provided with the more specialised components required for the specific application that the enclosure is being used for. It may be desirable to ensure that one of the compartments is not exposed to the surrounding environment. Therefore, allowing the compartments to be accessed independently advantageously allows this.

In addition, since the first compartment is sealed from the second compartment, components located in the second compartment can be accessed without exposing the other one of the compartments to the surrounding environment. This is particularly beneficial if the compartments and/or components which are located in the compartments are manufactured to different industry standards. The compartments can be accessed individually without compromising the other compartment.

The protection rating of the first compartment can be different to the protection rating of the second compartment.

The first compartment can be Ex nR rated and the second compartment can comprise an Ex ec rated environment.

Ex nR rated enclosures are enclosures which have been manufactured to a particular industry standard -BS EN 60079-15. The standard is well-known in the art. A person skilled in the art would understand the design features and requirements of an enclosure made to BS EN 60079-15. Ex nR enclosures are designed to restrict entry of a surrounding gas or vapour, in particular to restrict entry of an explosive gas and/or vapour, in to the enclosure. Any component can be placed in an Ex nR enclosure, provided that it does not raise the temperature of the surface of the enclosure such that the surface of the enclosure is 20K higher than the temperature of the surrounding environment. If an Ex nR rated enclosure is opened, its compliance with BS EN 600797 must then be re-tested.

Ex ec is a protection concept as defined by the industry standard BS EN 60079-7. This standard is well known in the art. A person skilled in the art would understand the design features and requirements of an enclosure made to BS EN 60079-7. Ex ec environments provide increased safety environments and are to be used in zone 2 areas. Zone 2 areas are defined as areas in which an explosive atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time. As mentioned above, suitable design considerations and components are used in order to create an Ex ec environment. For example, electrical connections are designed such that pulling of cables will not disconnect a cable from its connection point. In addition, components to be used in an Ex ec environment are designed such that they do not operate at unacceptably high temperatures and do not create sparks or arcs. This applies to both the internal and external parts of the components.

The combination of the first compartment being Ex nR rated and the second compartment being an Ex ec rated environment advantageously allows uncertified components, i.e. components which have not been designed and manufactured with compliance to an explosive environment standard in mind, to be placed in the Ex nR compartment. In addition, the Ex ec rated environment can be accessed without compromising the Ex nR compartment. It will be appreciated that compromising the Ex nR compartment means, as discussed above, exposing the Ex nR compartment to the surrounding atmosphere such that the compliance of the compartment with BS EN 60079-15 must be re-tested.

The first compartment and the second compartment can be sealed from the surrounding environment.

The second compartment may comprise a removable cover.

The circuit board may comprise a first plurality of electrical connection points located in the first compartment, the first plurality of electrical connection points being in electrical communication with at least one of a second plurality of electrical connection points which are located in the second compartment.

The first compartment may comprise a chassis on which electrical components can be mounted.

The first compartment can be defined by a body, an end plate and the dividing wall.

The end plate may comprise at least one intrinsically safe RF output.

The body of the first compartment can be formed of extruded box section.

Advantageously, extruded box section allows the body of the first compartment to be easily manufactured to a required length. The required length may be, for example, determined by the size and number of the components which, in use, will be housed inside the first compartment. It may also be determined by the heat generated, in use, by the components located in the first compartment. The length may be chosen such that the temperature of the exterior of the first compartment, in use, is less than a desired temperature (e.g. a temperature which is a particular amount above the temperature of the environment exterior to the first compartment).

The dividing wall may comprise an aperture, wherein the aperture can receive the circuit board An external surface of the first and/or second compartment can be provided with fins.

Advantageously, the fins can increase heat transfer between the first compartment and/or second component and the surrounding environment. Improving heat between the first compartment and the surrounding environment inhibits heat accumulation in the first and/or second compartment.

According to a second aspect of the invention there is provided a wireless access point comprising the enclosure assembly of the first aspect of the invention.

It will be appreciated that features described above with reference to one aspect of the invention may be combined with another aspect of the invention as appropriate.

Brief description of the drawings

Figure 1 depicts a cut-away view of an enclosure in accordance with an embodiment of the present invention; Figure 2 depicts an exploded view of the enclosure of Figure 1; Figure 3 depicts an alternative view of the cut-away view of the enclosure of Figure 1; Figure 4 depicts a perspective view of the enclosure of Figure 1; and Figure 5 depicts a cross-sectional view of the enclosure of Figure 1.

Detailed description

A perspective, cut-away view of an enclosure assembly 2 in accordance with an embodiment of the present invention is shown in Figure 1. The enclosure assembly 2 comprises a first compartment 4 and a second compartment 6. The enclosure further comprises a dividing wall 8. The dividing wall 8 separates the first compartment 4 and the second compartment 6. The enclosure assembly 2 further comprises a chassis. The enclosure assembly 2 can be suitable for housing an electrical device in an explosive environment.

Since the enclosure assembly 2 is provided with separate compartments, the enclosure assembly 2 is easily customisable. The first compartment 4 can be prepared separate to the second compartment 6. For example, one of the compartments 4, 6 can be provided with standard components and the other one of the compartments 4, 6 can be provided with the more specialised components as required for the specific application that the enclosure is being used for.

Referring now to Figure 2, an exploded view of the enclosure assembly 2 is shown. The first compartment 4 of the enclosure assembly 2 is defined by the dividing wall 8, a body 10 and an end plate 12. The second compartment 4 of the enclosure assembly 2 is defined by a cover plate 7, the dividing wall 8 and a body 9. The enclosure assembly 2 comprises an assembly axis 3. The assembly axis 3 extends perpendicular to, and, in the present case, through, the centre of area of the end plate 12.

In the depicted embodiment, the body 10 of the first compartment 4 is in the form of a box-section. The box-section can be extruded box section. Forming the body 10 of extruded box section allows the body to be easily manufactured to a required length. The length of the body may be determined, for example, by the number and size of the components which, in use, will be housed inside the first compartment 4. Alternatively, or in addition, the length of the body may be determined by the heat produced, in use, by the components housed inside the compartment. In some applications, it is desirable to keep heat radiated by the compartment into the external environment below a certain level -as such, the greater the heat produced by the components in use, the greater the length may be to increase the surface area of the compartment and thereby keep the heat radiated per unit area below a desired level.

It will be appreciated that the body 10 can be formed of other shapes. For example, the end plate 12 could be provided as an integral part of the body 10.

The body 10 comprises an external surface 14 and an internal surface 16. The body 10 further comprises a front section 28, a rear section 30 and side sections 32, 34. In use, the rear section 30 may be located adjacent to a structure on which the enclosure assembly is mounted. However, the enclosure assembly 2 need not necessarily be mounted on a structure. For example, the enclosure assembly 2 can simply be placed in a desired location for operation. The body 10 further comprises a first end 13 and a second end 15. The first end 13 may be located adjacent to the end plate 12 and the second end 15 may be located adjacent to the dividing wall 8. However, the body 10 has a plane of symmetry (not shown) located at the midpoint between the first end 13 and the second end 15, the plane of symmetry being perpendicular to the assembly axis 3. Therefore, it is irrelevant before assembly which end is the first end 13 and which end is the second end 15. It will be appreciated that in alternative embodiments, the body 10 may be asymmetric about said plane.

The body 10 can be provided with a first plurality of threaded recesses 22. The first plurality of threaded recesses 22 extends into the first end 13 of the body 10 of the first compartment 4. The body 10 can be provided with a second plurality of threaded recesses (not visible). The second plurality of threaded recesses extends into the second end 15 of the body 10.

In the depicted embodiment, the external surface 14 body 10 of the first compartment 4 comprises a plurality of fins 18. The fins 18 will be discussed in more detail below. It will be appreciated that the fins 18 need not be provided, and the outer surface 14 may be generally planar or flat.

In the depicted embodiment, the internal surface 16 is provided with a plurality of mounting portions 20. The mounting portions 20 may be provided so as to fix the position of the chassis 11 inside the body 10 of the first compartment 10, as will be discussed in more detail below. In the depicted embodiment, the mounting portions 20 each comprise slots. The slots are T-shaped in cross-section. However, it will be appreciated that the slots may be any other suitable shape in cross-section. The provision of slots with a constant shape of cross-section means that the slots are readily manufactured by extrusion processes.

The combination of an arrangement by which the size of the first compartment can be readily changed by increasing the length of the body of the first compartment (without having to change any other aspects of the design), together with the fact that the length of the chassis when extruded will match the length of the body of the first compartment, means that the design of the first compartment is such that it is readily scalable merely by changing the length of the body of the first compartment. Such a change in length is easily achievable when the length of the body is defined by the length of an extruded portion.

In the depicted embodiment, the mounting portions 20 extend from the first end 13 of the body 10 to the second end 15 of the body 10. It will be appreciated that the mounting portions 20 need not comprise slots and may instead be replaced with, for example, a series of threaded bores. Alternatively, the mounting portions 20 may not be provided at all. The chassis 11 may simply sit inside the body 10 and/or be mounted using suitable adhesive or the like. Alternatively, any appropriate arrangement for locating the chassis at a desired location within the body may be used.

The body 10 of the first compartment 4 comprises flanges 24, 26. The flanges 24, 26 extend from a respective side section 32, 34 of the body 10. The flanges 32, 34 extend from the body 10 adjacent to the rear section 30. However, it will be appreciated that the flanges 24, 26 can extend from any suitable position on the external surface 14 of the body 10. The flanges 24, 26 are each provided with apertures 36, 38. The apertures 36, 38 may each receive a respective fastener (not shown). The fastener can be received by a threaded member so as to secure the body 10 of the enclosure assembly 2 in a desired location. It will be appreciated that the flanges 24, 26 need not be provided and instead the enclosure assembly 2 may simply be placed in a desired location for operation. Alternatively, any appropriate arrangement for locating the enclosure assembly at a desired location may be used.

The body receives the chassis 11. The chassis 11 can be seen in Figure 3. The chassis 11 is provided so as to fix the position of components 31, such as transceivers or media converters, to be housed in the first compartment 4. The chassis 11 is formed of sheet metal. The chassis 11 can be provided with apertures or recesses such that fasteners 33 can be appropriately provided to fix the position of the components 31 on the chassis. The chassis 11 can be provided with fasteners 35. The fasteners 35 can extend through a portion of the chassis 11 which is positioned adjacent to the rear portion 30 of the body 10 of the first compartment 4. The heads of the fasteners are received in a respective T-slot of the mounting portions 20. The fasteners 35 can each receive a nut in order to fix the position of the fasteners. As discussed above, the T-slots may be replaced with threaded bores, in which case the fasteners 35 would extend through the portion of the chassis 11 and threadingly engage the threaded bores. In alternative embodiments, a chassis may not be provided. The components 31 may simply sit inside the first compartment 4 and/or be mounted to the body.

Referring now to Figure 2. A first side 39 of the end plate 12 sealingly engages the first end 13 of the body 10 of the first compartment 4. The end plate 12 comprises a plurality of apertures. The apertures are positioned around the periphery of the end plate 12. Each aperture is provided with a respective fastener 40. The fasteners 40 threadingly engage the threads of a respective one of the threaded recesses of the first end 13 of the body 10. The end plate 12 comprises a seal element 42. The seal element 42 is located adjacent to the first side 39 of the end plate 12. The seal element 42 extends around the periphery of the end plate 12. The seal element 42 may be a gasket. Once assembled, the seal element 42 sealingly engages the end plate 12 and the first end 13 of the body 10. Therefore, once assembled, the seal element 42 prevents ingress of fluid from the surrounding environment into the first compartment 4.

In an alternative, non-depicted embodiment, the end plate 12 can be integrally formed with the body 10, as discussed above. In which case, the seal element 42 is not provided.

The end plate 12 comprises a plurality of intrinsically safe RF outputs 44. The intrinsically safe RF outputs 44 extend from the first side 39 of the end plate 12 to a second side (not visible) of the end plate 12. In the depicted embodiment, the end plate 12 comprises four SF outputs 44. However, it will be appreciated that the end plate 12 can be provided with any suitable number of SF outputs 44. Each of the SF outputs receives a respective antenna (not shown) for radiating (and receiving) electromagnetic waves.

With continuing reference to Figure 2, the dividing wall 8 comprises a first side (not visible) and a second side 46. The first side is located adjacent to the second end 15 of the body 10 of the first compartment 4. The second side 46 is located on the opposite side of the dividing wall 8 to the first side. The dividing wall 8 comprises a plurality of apertures. The apertures are positioned around the periphery of the dividing wall 8. Each aperture is provided with a respective fastener 48. The fasteners 48 threadingly engage the threads of a respective one of the threaded recesses 22 of the second end 15 of the body 10. A seal element 49, which can be seen in Figure 1, is located adjacent to the first side of the dividing wall 8. The seal element 49 extends around the periphery of the dividing wall 8. Once assembled, the seal element 49 sealingly engages the second end 15 of the body 10 and the dividing wall 8. Therefore, once assembled, the seal element 49 prevents ingress of fluid from the surrounding environment into the first compartment 4. In an alternative embodiment, the dividing wall 8 can be integrally formed with the body 10. In a non-depicted embodiment, the dividing wall 8 and end plate 12 can be integrally formed with the body 10. The body 10 could then be provided with a separate access point in the form of a cover which sealingly engages the body.

With reference to Figure 2, the body 9 of the second compartment 6 extends from the second side 46 of the dividing wall 8. Therefore, at least part of the dividing wall 8 defines one of the walls of the second compartment 6. The remainder of the second compartment 6 is defined by the cover plate 7 and body 9 of the second compartment 6. A portion of the body 9 is open. The open portion therefore defines an aperture 51.

The perimeter of the aperture defines a rim 53. The rim 53 comprises a plurality of threaded apertures 52. In the depicted embodiment, the dividing wall 8 is integrally formed with body 9. However, in alternative, non-depicted embodiments, the dividing wall 8 may be formed as a separate component to the body 9. In such embodiments, the body 9 can be joined to the dividing wall 8 by any suitable means. For example, the body 9 can be welded on to the dividing wall 8, or may be fixed to the dividing wall by virtue of fasteners and appropriate seals. If the body 9 is fixed to the dividing wall 8 by fasteners, the cover plate 7 need not be provided. The user will be able to remove the body 9 in order to gain access to the second compartment 6. In the depicted embodiment, the overall shape of the body 9 is a cuboid. However, it will be appreciated that the body 9 can be any suitable shape as required by the application of the enclosure assembly 2. The overall shape of the body is used to refer to the shape that the body 9 occupies.

The cover plate 7 acts as a removable wall of the second compartment 6. The cover plate 7 therefore covers the aperture 51 of the open portion of the body 9 of the second compartment 6. The cover plate 7 comprises a plurality of apertures. The apertures are positioned around the periphery of the cover plate. Each of the plurality of apertures receive a respective fastener 50. The fasteners 50 threadingly engage the threaded bores 52. A seal 54 is positioned between the cover plate 7 and the body 9, which can be seen in Figure 1. When assembled, the seal 54 sealingly engages the body 9 and the cover plate 7.

The dividing wall 8 comprises an aperture 56. The aperture 56 extends between the first side and the second side 46 of the dividing wall 8. The aperture 56 is located in the dividing wall 8 such that the entirety of the aperture is located within the second compartment 6 (as discussed above, at least part of the dividing wall defines one of the walls of the second compartment).

Referring now to Figures 1 and 3, a circuit board 58 is provided to the dividing wall 8.

The circuit board 58 is positioned so as to cover the aperture 56. The circuit board 58 provides a fluid tight seal between the first compartment 4 and the second compartment 6. The circuit board 58 may therefore prevent fluid communication between the first compartment 4 and the second compartment 6. For example, the circuit board 58 may not comprise any through holes or through vias. In particular, if the circuit board 58 comprises a first side 60 located in use in the first compartment and a second side 62 located in use in the second compartment and there is no fluid communication possible between the first and second sides 60, 62 via the circuit board 58 itself. The circuit board 58 fully covers the aperture 56. Alternatively, a portion of the aperture 56 can be covered by the circuit board 58 and the remainder of the aperture 56 can be covered by another component such as a plate (not shown). The circuit board and other component Cif present) are mounted such that they seal the aperture 56.

The first side 60 of the circuit board 58 is located in the first compartment 4 and the second side 62 is located in the second compartment 6. In some embodiments the first side 60 of the circuit board 58 may merely face the first compartment 4 and the second side 62 may merely face the second compartment 6.

The first side 60 of the circuit board 58 comprises a plurality of electrical connection points 64. It will be appreciated that the first side 60 of the circuit board 58 may be provided with any suitable number of electrical connection points 64. For example, the first side 60 of the circuit board 58 may be provided with a single electrical connection point 64. The second side 62 of the circuit board 58 comprises a plurality of electrical connection points 66. It will be appreciated that the second side 62 of the circuit board 58 can be provided with any suitable number of electrical connection points 66. For example, the second side 62 of the circuit board 58 can be provided with a single electrical connection point 66.

It will be appreciated that the number of electrical connection points 66 provided to the second side 62 of the circuit board 58 can correspond with the number of electrical connection points 64 provided on the first side 60 of the circuit board 58. However, in some applications, the number of electrical connection points 64, 66 on one of the sides 60, 62 of the circuit board 58 can be different to the number of electrical connection points 64, 66 on the other side 60, 62 of the circuit board 58. Each of the electrical connection points 64, 66 can be in electrical communication with at least one of the electrical connection points 64, 66 located on the other side of the circuit board 58. Additionally, in some embodiments, one or more of the electrical communication points 64, 66 can be in electrical communication with one or more electrical communication points located on the same side of the circuit board 58. The second conductors are in communication with at least one of the electrical communication points 66.

Referring now to Figure 3. A frame 68 retains the circuit board 58 in the aperture 56 of the dividing wall 8. The frame 68 is provided with a series of apertures. The apertures are spaced around the frame. Each aperture is provided with a respective fastener 70.

A seal element 72, which can be seen in Figure 1, is provided. The seal element 72 is located between the dividing wall 8 and the circuit board 58. The seal element 72 can be adhered to the circuit board 58. Each fastener 70 extends from the first compartment 4 to the second compartment 6. The fasteners 70 threadingly engage threaded recesses (not visible) which are provided in protrusions 74, which are visible in Figure 1, provided on the second side 62 of the dividing wall 8. Once assembled, the seal element 72 sealingly engages the circuit board 58 and the dividing wall 8. Therefore, once assembled, the seal element 72 prevents the ingress of fluid from the second compartment 6 to the first compartment 4 (and, in some embodiments, vice-versa).

Advantageously, the circuit board 58 acts to both seal the first compartment 4 from the second compartment 6 and to place the electrical connection points 64, 66 in electrical communication. Therefore, any components electrically connected to the electrical connection points 64, 66 are also placed in electrical communication. Known enclosure assemblies allow electrical communication between compartments by passing a conductor through a hole in a dividing wall, the hole comprising a suitable cable gland. The circuit board (and any associated seal) of the present invention serves the purpose of both the gland and the conductor from known enclosures. That is to say, the circuit board both seals the first compartment 4 from the second compartment 6 and allows electrical communication between the first compartment and the second compartment.

Referring now to Figure 4. The body 9 of the second compartment 6 is provided with cable entry points 74. In the figure, the cable entry points 74 are shown with blanking plugs 76 received therein. In the depicted embodiment, the body 9 is shown as comprising two cable entry points 74. It will be appreciated that the body 9 can be provided with any suitable number of cable entry points 74. The cable entry points 74 can comprise cable glands (not shown). Each of the cable glands comprise an internal section and an external section. The internal sections are located within the second compartment 6. The external sections are exposed to the surrounding environment.

The cable glands can be Ex ec rated, as will be discussed in more detail below. In use, each of the cable glands 74 receive a conductor. The conductor can be a wire. The cable glands sealingly engage the conductor. The cable glands also sealingly engage the body 9. The cable entry points 74 prevent ingress of fluid from the surrounding environment into the second compartment 6, as is well known in the art. The cable glands are designed such that the conductor cannot be pulled out of the cable entry point when a force up to a predetermined threshold value is applied to the cable, this will be discussed in more detail below. The conductor can connect to at least one of the electrical connection points 66 of the circuit board 58. The conductor can also be connected to, for example, a router or power supply remote to the enclosure assembly Figure 5 schematically depicts the enclosure assembly 2. As can be seen, a wire 78 passes from the external environment into the second compartment 6 via a cable gland 80. The wire 78 is connected to an electrical connection point 66 of the second side 62 of the circuit board 58. The electrical connection point 66 is in electrical communication with an electrical connection point 64 of the first side 60 of the circuit board 58. A wire 82 is connected to the electrical connection point 64 and to a component 31. The component 31 may, for example, a transceiver. The component 31 is in electrical communication with an antenna 84.

The enclosure assembly 2 is suitable for use in an explosive environment. As discussed above, explosive environments are present in many sites, e.g. industrial sites. An environment need not be 'live' at all times to be considered an explosive environment. Where 'live' refers to an environment having a sufficient quantity of explosive gas or vapour is present which could result in an explosion if a spark or heat is provided to the environment. Explosive environments are classified by zone. The zones include: zone 0, zone 1 and zone 2. Where zone 0 provides the greatest likelihood of an explosive environment and zone 2 provides the least likelihood of an explosive environment. Zone 2 is an area that is classified 'as a place in which an explosive atmosphere consisting of a mixture with air or flammable substances in the form of gas, vapours and mists is not likely to occur in normal operation but if it does occur, it will be present for a short period of time only'.

Industry standards define the equipment and design considerations of equipment to be used in each of the above zones. For example, in the UK, BS EN 60079-7 and BS EN 60079-15 provide the requirements of equipment to be rated as Ex ec and Ex nR respectively. These standards are well-known in the art. A skilled person would understand the requirements set out in each of the standards such that electrical equipment complies with a respective standard. It will be appreciated that there are corresponding industry standards for other countries, and in such countries equivalent ratings to Ex ec and Ex nR will be used.

Ex nR is method of construction for an enclosure and, as noted above, is defined by BS EN 60079-15. Ex nR can be referred to as 'restricted breathing'. As a skilled person would understand, enclosures designed and manufactured to be Ex nR enclosures include a high level of sealing which limits the possible entry of explosive gases and/or vapours. If an Ex nR enclosure is opened, the enclosure must then be re-tested as Ex nR compliant.

The first compartment 4 can be Ex nR rated. The seals 42, 49, 72 can provide sufficient sealing to the first compartment so as to limit possible entry of gases and/or vapours to an extent which brings the first compartment 4 into compliance with BS EN 60079-15. Wien placed in a zone 2 environment, uncertified components (for example components not specified by BS EN 60079) can be placed inside an nR enclosure, provided that the components do not generate sufficient heat inside the enclosure so as to increase the external surface of the enclosure such that the external surface of the enclosure is 20K above the temperature of the surrounding environment. The fins 18 increase the surface area of the exterior of the first compartment. This maximises the surface area over which any heat generated with the compartment is dissipated, thereby minimising any temperature difference between the exterior of the compartment and the external environment.

In other words, the fins improve the heat transfer between the body 10 and the surrounding environment. Improving the heat transfer between the body 10 and the surrounding environment advantageously inhibits heat accumulation in the body 10 and distributes any radiated heat over as great an area as possible.

Ex ec is a protection concept and, as noted above, is defined by BS EN 60079-7. Ex ec can be referred to as 'increased safety'. As a skilled person would understand, for equipment to be Ex ec rated, the equipment must be non-sparking and non-arcing. In addition, cable connection points are required to be designed such that the cables will not be disconnected when the cables are pulled. Disconnection of the cables could result in a spark.

The second compartment 6 can be Execrated. This includes the sealing provided, the cable glands 80, and electrical connection points 66 being Ex ec compliant. As discussed above, Ex ec is a design concept. Therefore, the compliance of the second compartment 6 with BS EN 60079-7 is determined by multiple factors. For example, to be Ex ec compliant the cable glands 80 and the electrical connection points 66 should also be appropriately designed so as to be in compliance with BS EN 60079-7.

The enclosure assembly 2 can be used to house components which provide a wireless access point. The enclosure assembly 2 provides a versatile enclosure assembly for providing a wireless access point in an explosive environment. As discussed above, Ex nR enclosures can be provided with uncertified components (i.e. components which do not comply with BS EN 60079). Therefore, electrical components which are common to wireless access points, regardless of the specific application, can be placed in the first compartment 4. For example, the first compartment might house wireless devices, access points, RFID readers and/or loT gateways. The second compartment 6 can provide cable access to the electrical connection points 66 of the circuit board 58 which is Ex ec rated. This therefore allows the components housed in the first compartment 4 to be in communication with, for example, a power supply or router. Advantageously, the enclosure assembly 2 provided herein allows access to the second compartment 6 without also requiring access to the first compartment 4. As discussed above, if an Ex nR enclosure is opened, the enclosure must then be re-tested to ensure that it is still in compliance with the relevant industry standard. If a user of the present enclosure assembly 2 wishes to access the second compartment 6, they can simply remove the cover plate 7 in order to gain access and doing so will not expose the first compartment 4 to the surrounding environment.

It will be appreciated that there are numerous other industry standards for electrical equipment and enclosures to be used in explosive environments. For example. Ex d, Ex eb, Ex fr and Ex ta are alternative types of protection which can be used in explosive environments. In alternative embodiments, the first compartment 4 and/or second compartment 6 can be designed to an alternative protection rating as appropriate for the zone in which the enclosure assembly is to be used. The protection rating of the first compartment 4 can be different to the protection rating of the second compartment 6.

Another advantage of the present invention is that when manufacturing a wireless access point or other similar electrical assembly for a particular application, 'standard' components which are common to any application can be located in the second compartment (which can be pre-tested) and the application specific components can be located within an application specific (e.g. sized) first compartment. In this way, when catering for a particular application a common, pre-tested second compartment can be used in combination with an application specific first compartment. This makes assembly of an application specific enclosure more straightforward. Furthermore, being as the Ex ec rated second compartment doesn't need to be opened to make the application specific enclosure, the second component does not need recertification once it forms part of the enclosure.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS: 1. An enclosure assembly for housing electrical devices in explosive environments, the enclosure comprising a first compartment; a second compartment, the first compartment being sealed from the second compartment; a dividing wall separating the first compartment and the second compartment; a circuit board sealingly mounted to the dividing wall; wherein the circuit board comprises a first electrical connection point and a second electrical connection point, the first electrical connection point being located in the first compartment and the second electrical connection point being located in the second compartment; wherein the first electrical connection member is in electrical communication with the second electrical connection member via the circuit board.
2. The enclosure assembly of claim 1, wherein the protection rating of the first compartment is different to the protection rating of the second compartment.
3. The enclosure assembly of claim 2, wherein the first compartment is Ex nR rated and the second compartment comprises an Ex ec rated environment.
4. The enclosure assembly of claim 1 or claim 2, wherein the first compartment and the second compartment are sealed from the surrounding environment.
5. The enclosure assembly of any preceding, wherein the second compartment comprises a removable cover.
6. The enclosure assembly of any preceding claim, wherein the circuit board comprises a first plurality of electrical connection points located in the first compartment, the first plurality of electrical connection points being in electrical communication with at least one of a second plurality of electrical connection points which are located in the second compartment.
7. The enclosure assembly of any preceding claim, wherein the first compartment comprises a chassis on which electrical components can be mounted.
8. The enclosure assembly of any preceding claim, wherein the first compartment is defined by a body, an end plate and the dividing wall.
9. The enclosure assembly of claim 8, wherein the end plate comprises at least one intrinsically safe RF output.
10. The enclosure assembly of claim 8 or claim 9, wherein the body of the first compartment is formed of extruded box section.
11. The enclosure assembly of any preceding, wherein the dividing wall comprises an aperture and wherein the aperture receives the circuit board
12. The enclosure assembly of any preceding claim, wherein an external surface of the first and/or second compartment is provided with fins.
13. A wireless access point comprising the enclosure assembly of any preceding claim.