GB2566547A - Enclosure - Google Patents

Abstract

A smoke and/or fire alarm enclosure comprises a base 1 for mounting the enclosure, and a housing 2 for supporting smoke and/or fire detection components. The base 1 comprises an upstanding guide wall 15 at, adjacent or towards its periphery and the housing 2 comprises a peripheral wall 21. When the housing 2 is releasably retained by the base 1, the guide wall 15 surrounds the peripheral wall 21. The base 1 may comprise an abutment 16 lying within the peripheral wall 21 when the housing 2 is retained by the base 1, extending parallel to the guide wall 15. The base 1 and housing 2 may be attached to one another by a snap-fit connection, and one of the components may comprise a hook 18 and the other comprises a latch 22, wherein the hook 18 is resiliently biased towards a retention position. The enclosure may also comprise a keying mechanism 19 for ensuring correct orientation of the housing 2 relative to the base 1, and may further comprise a cover configured to attach to the housing 2, thereby covering the enclosure.

Description

This invention relates generally to an enclosure. More specifically, although not exclusively, this invention relates to a smoke and/or fire alarm enclosure.

It is important to rapidly detect the presence of undesirable fire and/or smoke, for example within buildings. Such rapid detection keeps the time between the start of fire and/or smoke generation and the time by which action can be taken to combat the source of the fire and/or smoke and/or to evacuate the vicinity of the fire and/or smoke. In order to detect smoke and/or fire it is known to install smoke and/or fire alarms, for example on ceilings or other surfaces within buildings. In some jurisdictions it is a legal requirement to install smoke and/or fire alarms in certain types of buildings.

Smoke and/or fire alarms are known which detect, respectively, smoke and/or heat based upon a number of different operating principles. It is known to electrically power smoke and/or fire alarms, where the electrical energy is used in the detection of, respectively smoke and fire. Such smoke and/or fire alarms may include their own power supply (e.g. one or more battery) or may be connected or connectable to an external source of electrical power (for example).

Smoke and/or fire alarms typically include an enclosure for retaining detection components, where the enclosure is secured or securable to a site of use, e.g. to a ceiling. Smoke and/or fire alarms which are electrically powered by either an internal or an external source of electricity typically have an enclosure formed typically of two parts, in order to facilitate their installation. The two parts of the enclosure are a base part and a housing or holder part in which the components of the alarm are housed. During installation the first, base part is secured to a site of use and the second, holder or housing part is then attached to the base part in order to locate the alarm. Attachment between the two components may be effected by a screw fit connection, where the housing part includes an internal thread for engaging around an external thread on the base part. In other cases, push fit connections are used.

Installation of a smoke and/or fire alarm as described above may be challenging, particularly when installation is to a ceiling, where an installer may be installing the alarm at a location above his or her head. Moreover, removal of the housing part (for example to access the housing part for cleaning and/or to remove the alarm) may also be challenging. As will be appreciated, when manipulating objects above one’s head the degree of control afforded is relatively reduced whilst even relatively simple movements are more tiring than when effected below head height. Accordingly, installation and/or removal of known smoke and/or fire alarms may be time consuming, difficult and/or tiring for the installer. Moreover, it has been found that during installation of alarms of this type it is difficult to correctly align the housing part with the base part, especially where it is necessary to effect an electrical connection. Accordingly, the screw threads on the two parts can become cross threaded which can result in damage and/or in alarms in which the housing part cannot be readily removed from the base part. In the case where a push-fit is used, it is typical for the base part and the housing part to have alignment indicators (such as arrows) to ensure alignment of the parts. These are difficult to identify and are usually difficult to align when working at elevated positions and above one’s head.

It is therefore a first non-exclusive object of the invention to provide an improved fire and/or smoke alarm enclosure and/or to provide a fire and/or smoke alarm enclosure which overcomes one or more of the above-identified problems.

Accordingly, a first aspect of the invention provides a smoke and/or fire alarm enclosure comprising a base for mounting the enclosure to or at a site of use and a housing or holder for supporting smoke and/or fire detection components, the base comprising an upstanding guide wall at, adjacent or toward its periphery and the housing comprising a peripheral wall, wherein, when the housing is releasably retained by the base, the guide wall surrounds the peripheral wall.

The invention thereby provides improved alignment of the housing relative to the base during attachment of the housing thereto. Accordingly, attachment is relatively more easy and more rapid and with a reduced likelihood of misalignment than is the case with prior art smoke and/or fire alarm enclosures.

The base may comprise an abutment, for example which may lie within the peripheral wall when the housing is releasably retained by the base. Provision of such an abutment may therefore, when the housing is releasably retained by the base, restrict movement of the peripheral wall away from the guide wall. The abutment may extend parallel (e.g. substantially or at least partially parallel) to the guide wall. The abutment may be elongate. The abutment may comprise a support wall. The abutment may be spaced from the guide wall, for example by a distance just greater than the thickness of the peripheral wall.

The base and housing may be configured to be attached to one another by snap-fit connection.

One of the base and holder may comprise a latch and the other of the base and housing may comprise a hook configured to engage the latch when the housing is releasably retained by the base.

The hook may be resiliently biased toward a retention position, for example wherein the hook engages the latch when the housing is releasably retained by the base. The enclosure may comprise a ramp, for example arranged to deflect, during attachment of the housing to the base, the hook away from the retention position (e.g. toward a position where the hook is clear of the latch). The enclosure may comprise plural ramps, for example arranged to deflect, during attachment of the housing to the base, the hook away from the retention position (e.g. toward a position where the hook is clear of the latch).

The hook may comprise an aperture or slot, e.g. engageable so as to move the hook from the retention position to enable removal of the housing from the base. The aperture or slot may be provided on an external or outer (when the housing is releasably retained by the base) surface of the hook.

The guide wall may comprise one or more interruptions or depressions extending into the guide wall from its terminal edge. For example, the guide wall may be discontinuous. A hook may be provided at or in the, some or each interruption.

The base may comprise the hook, e.g. and the housing may comprise the latch.

The hook may be integrally formed with the base. The base may comprise a skirt at its periphery, e.g. a peripheral skirt. The hook may be integrally formed with the skirt. The base may comprise a recess into the skirt on one or both sides of the hook. The skirt may extend around the periphery of the base, for example around part or all of the periphery of the base. The hook may be recessed with respect to the top edge of the guide wall.

The base may comprise a flange, for example which may extend from the skirt. The guide wall may extend or upstand from the flange. The guide may extend or upstand from the flange by a distance of between about 5 and 20 mm, for example between about 7 and 15 mm, say between about 10 and 15 mm (i.e. the distance between the flange and the terminal edge of the guide wall). The abutment (where provided) may extend from the flange. The abutment may extend from the flange by a distance of between about 1 and 5 mm (i.e. the distance between the flange and the terminal edge of the abutment).

The housing may comprise one or more guides, for example projecting from the outer major surface of the peripheral wall. The or each guide may be arranged to guide the hook into engagement with the latch, e.g. during attachment of the housing to the base. Where the housing comprises the latch, the housing may comprise a guide on either side of the latch. The or each guide may be spaced from the latch. The latch may extend from the peripheral wall of the housing, for example by a first distance. The or each guide may extend from the peripheral wall of the housing by a second distance. The first distance may be less than the second distance.

The housing and the base may comprise a keying means or mechanism, for example for ensuring correct orientation of the housing relative to the base. Correct orientation of the housing relative to the base may comprise correct rotational alignment of the housing relative to the base. The keying means or mechanism may comprise a key and a key way. One of the housing and the base may comprise the key and the other of the housing and the base may comprise the keyway. The key may comprise a projection or abutment. The keyway may comprise a recess or rebate. The key may be configured to fit (e.g. fit within) the keyway. The key way may be provided by an interruption or depressions in the guide wall.

In embodiments, one of the housing and the base may comprise plural hooks and the other of the housing and the base may comprise plural latches, e.g. where each hook may be configured to engage with one of the latches.

The base may comprise a recess, e.g. for the location of an electrical connection and/or cable. The recess may have a height, when the housing is removably retained in the base, of between about 10 and 40 mm, say between about 12 and 35 mm, for example between about 15 and 25 mm.

The enclosure may comprise a cover, for example configured to attach to the housing and thereby cover the enclosure. Attachment of the housing to the cover may be permanent, e.g. non-releasable. One of the housing and the cover may comprise a hook whilst the other of the housing and the cover may comprise a latch, for example configured to engage the hook. The latch may extend from an interior or inner surface (when the cover is attached to the housing) of the cover or the housing.

The enclosure may comprise a paint cover, for example for temporarily attaching to the enclosure. The paint cover may comprise a substantially frusto-conical peripheral wall, for example closed at one end by an end cover. The paint cover may be configured to engage the housing and/or the cover (where provided) by push fit.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one aspect or embodiment of the invention are applicable to all aspects or embodiments, unless such features are incompatible.

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 perspective view of a base of a smoke alarm according to an embodiment of the invention;

Figure 2 is a plan view of the base shown in Figure 1;

Figure 3 is a partial view of the periphery of the base shown in Figure 1;

Figure 4 is perspective view of a housing for smoke and/or fire alarm electronics according to an embodiment of the invention;

Figure 5 is a partial side view of the housing shown in Figure 4;

Figure 6 is a partial side view of the housing shown in Figure 4;

Figure 7 is a perspective view of a cover for fire alarm according to an embodiment of the invention;

Figure 8 is a reverse plan view of the cover shown in Figure 7;

Figure 9 is a partial view of the periphery of the cover shown in Figure 8;

Figure 10 is a perspective view of a paint cover for a smoke and/or fire alarm according to an embodiment of the invention;

Figure 11 is a reverse plan view of the paint cover shown in Figure 10;

Figure 12 is a perspective view of the housing shown in Figure 4 attached to the base shown in Figure 1;

Figure 13 is a perspective view of the cover shown in Figure 7 attached to the housing shown in Figure 4 and the base shown in Figure 1;

Figure 14 is a perspective view of the paint cover shown in Figure 10 attached over the assembly shown in Figure 12; and

Figure 15 is a perspective view of a cover of a smoke alarm according to a further embodiment of the invention.

Referring now to Figures 1 to 11, there is shown a fire alarm enclosure comprising a base

I, a housing 2, a cover 3 and a paint cover 4.

Some or all of the above described components may be formed from plastic, wood, metal or any suitable material or any combination thereof. In this embodiment, each of the components is formed from plastic and as a unitary structure by moulding. However, in embodiments, one, some or each component may be formed from plural pieces and/or may be formed by any suitable manufacturing process. In this embodiment, each of the components is generally circular, in plan. However, in embodiments, the components may have any suitable shape, in plan, for example rectangular, oval or the like.

The base 1 (as shown in Figures 1 to 3) comprises a peripheral skirt 10 from which extends a flange 11, which has an annular shape, in plan. A side wall 12 extends from the flange

II, in a direction generally parallel to the skirt 10, with a central base plate 13 extending from the side wall 12 in a substantially perpendicular direction thereto. A recess 14 for housing electrical connections and/or connectors is thereby defined within the flange 11 and above the base plate 13. The recess has a height of about 18 mm, as defined by the distance between the base plate 13 and the flange 11, in this embodiment. In embodiments, however, the height of the recess may be any suitable height, for example between about 10 and 40 mm, say between about 12 and 35 mm, e.g. between about 15 and 25 mm.

A guide wall 15 extends from the flange 11 in a direction generally perpendicular thereto and substantially around the circumference thereof. Three interruptions 15a are provided in the guide wall 15, at regularly spaced intervals around its circumference. However, in embodiments, any suitable number of interruptions 15a may be provided and/or the interruptions 15a need not be provided at regularly spaced intervals around the circumference of the guide wall 15. The guide wall 15 extends from the flange 11 by a distance of between about 5 and 20 mm, for example between about 7 and 15 mm, say between about 10 and 15 mm.

An abutment 16, which is a support wall 16 in this embodiment, extends from the flange 11, inside of and spaced from the guide wall 15. The support wall 16 thereby defines a groove 17 adjacent the inside of the guide wall 15. The support wall 11 extends from the flange 11 by a distance of between about 1 and 5 mm.

Hooks 18 are provided in the interruptions 15a in the guide wall 15. In this embodiment three such hooks 18 are shown, one at each interruption 15a. In embodiments, however, any suitable number of hooks 18 may be provided.

Each hook 18 has a width which is less than the width of the interruption 15a in the guide wall 15 at which it is provided. In this way spaces are provided between either side of each hook 18 and the adjacent portion of the guide wall 15.

Each hook 18 is integrally formed with the skirt 10. The plastic from which the base 1 is formed allows each hook 18 to flex resiliently, in use, toward and away from a central axis A through the base 1. Said flexing is enhanced by the provision of cut-out portions into the skirt 10 on either side of each hook 18. Each hook 18 comprises, at a distal, free end thereof, a sloped lead-in portion 18a and an engagement lip 18b. The distal, free end of each hook 18 is recessed with respect to the top edge of the guide wall 15. Advantageously, the hooks 18 are thereby at least partially protected from impact damage, for example during misaligned attempted installation of the housing 2 to the base 1.

The distal, free end of each hook 18 has a natural or starting position relative to the skirt 10. The hooks 18 are each biased toward the starting position due to the material properties of the plastic from which the base 1 is formed. When the distal, free end of a hook 18 is displaced from its starting position by a displacement force the bias generates a reaction force acting against the retention force, thereby biasing the hook 18 back toward its starting position. In embodiments, however, each hook 18 may comprise a separate component to that of the skirt 10 and may be connected thereto by a resilient connection, thereby providing resilient flexibility of the distal, free end of each hook relative to the skirt 10.

Each hook 18 comprises an aperture 18c on an outer surface for an installer or user of a smoke alarm including the base 1 to manually move the hook 18, e.g. via insertion of finger or device into the aperture 18c.

A keying feature 19 is provided in the guide wall 15, where the keying feature 19 is a rebate 19 into the guide wall 15, in this embodiment. In embodiments, one or more of the hooks 18 and/or the interruptions 15a in the guide wall 15 may provide a keying feature 19 (and in embodiments the guide wall 15 may be absent a rebate 19).

Apertures AP through the base plate 13 provide locations for attaching, in use, the base 1 to a site of use such as a ceiling. Attachment may be effected by any suitable attachments, for example screws. In embodiments, the base 1 may be attached to a site of use by adhesive and may be provided absent apertures. The base plate 13 includes a cut-out C, which may be any suitable shape but is circular in plan in this embodiment. The cut-out C comprises a line of weakness into and/or through the base plate 13, for example thereby defining a frangible portion of the base plate 13. In use an installer may push the cut-out C in order to form an aperture through the base plate 13 through which cables to an external source of electrical energy may be inserted.

An opening O in the skirt 10 and base plate 13 provides a location whereby electrical cables connected or connectable to an external source of electricity may be fed into the recess 14 in the interior of the base 1. In embodiments, the skirt 10 and/or base plate 13 may be absent such an opening O, for example where the fire alarm is powered by an internal source of electricity such as a battery.

The housing 2 (as shown in Figures 4 to 6) comprises a base plate 20 with a peripheral side wall 21 extending perpendicularly therefrom at and around the base plate’s 20 periphery.

The housing 2 further comprises three latches 22 at evenly spaced locations on the outer surface 21a of the side wall 21. Each latch 22 comprises an abutment 22a extending from the outer surface 21a of the side wall 21. A ramp 23 is provided adjacent each abutment 22a, where the ramp 23 tapers from the abutment 22a toward the outer surface 21a of the side wall 21. Guides 24 are provided on either side of each latch 22. The guides 24 are configured (e.g. shaped, sized and spaced) to engage, in use, the spaces between each hook 18 and the adjacent portion of the guide wall 15 of the base 1.

Four hooks 25 extend from a first, free end of the side wall 21 in a direction generally parallel thereto. In embodiments, however, any suitable number of hooks 25 may be provided, for example one, two, three, five or more hooks 25. The hooks 25 are positioned at evenly spaced locations around the periphery of the housing 2. The hooks 25 are integrally formed with the side wall 21. The plastic from which the housing 2 is formed allows each hook 25 to flex resiliently, in use, toward and away from a central axis B through the housing 2 (in a manner similar to that described above in respect of the hooks 18 of the base 1). In embodiments, however, each hook 25 may comprise a separate component to that of the side wall 21 and may be connected thereto in such a way as to provide resilient flexibility thereto. Each hook 25 comprises, at a distal, free end thereof, a sloped lead-in portion 25a and an engagement member 25b. None of the hooks 25 are aligned with any of the latches

22.

A keying feature (not shown) is provided on the side wall 21 of the housing 2. The keying feature is a projection (not shown) from the outer surface 21a of the side wall 21 and is arranged to engage, during attachment of the housing 2 to the base 1, the rebate 15 into the guide wall 13 of the base 1. In embodiments, however, the keying feature may be provided exclusively by one or more of the latches 22 and/or the guides 24 (for example, and the side wall 21 may be absent the projection).

An aperture 26 through the base plate 20 is provided to allow the passage therethrough of an electrical connection from the base 1, in use.

The base plate 20 of the housing includes a structure for holding a battery in the embodiment shown in the Figures. However, in embodiments, the base plate 20 may be absent such a structure.

The cover 3 (as shown in Figures 7 to 9) is for use with a fire alarm and comprises a top plate 30 from which extends a peripheral side wall 31.

Four latches 32 are provided on the inner surface 31a of the side wall 31, positioned at evenly spaced locations around the periphery of the top plate 30 (where the locations are selected to conform to those selected for the hooks 25 on the housing 2). Each latch 32 comprises an abutment 32a extending from the inner surface 31a of the side wall 31. A ramp 33 is provided adjacent each abutment 32a, where the ramp 33 tapers from the abutment 32a toward the inner surface 31 a of the side wall 31. Guides 34 are provided on either side of each latch 32. The spacing between each pair of guides 34 is selected to be just greater than the width of each latch 25 on the housing 2.

The top plate 30 comprises a grill 35 through which, in use, ambient air surrounding the cover 3 may enter a fire alarm comprising said cover 3. Power and alarm lights 36, 37 are also included, which provide a visual indication to a viewer of the fire alarm as to its status with regard to power supply and detection of fire. A button 38 is provided for periodically testing the fire alarm.

The paint cover 4 (shown in Figures 10 and 11) comprises a substantially frusto-conical side wall 40 closed at its narrower end by an end plate 41. A row of plural projections 42 extend inwardly from the inner surface 40a of the side wall 40. The row of projections 42 extends around the circumference of the side wall 40 and in a plane substantially parallel to a plane defined by the open end of the paint cover 4. A row of plural depressions 43 are formed in the outer surface 40b of the side wall, each depression 43 corresponding to a projection 42 on the obverse, inner surface 40a. In embodiments, however, one, some or each projection 42 may be formed without a corresponding depression. At least part of each projection 42 and/or the side wall 40 is resiliently flexible. The internal diameter of the side wall 40 of the paint cover 4 is greater at both of its ends than is the external diameter of the cover’s 3 side wall 31 and the housing’s 2 side wall 21. The projections 42 reduce the internal diameter to a distance less than the external diameter of the cover’s 3 side wall 31. At the open end of the paint cover 4 grip tabs 44 extend outwardly from the outer surface 40b of the side wall 40.

The fire alarm enclosure is assembled during installation at a site of use. In one example, the base 1 is mounted to a ceiling via screws (not shown) through the apertures AP in the base plate 13. Electrical connectors (not shown) from a source of electrical energy (e.g. the mains or other electrical, cables, not shown) are fed through the opening O in the skirt 10 and base plate 13 and thence into the recess 14 in the base 1. The electrical connectors are then attached to an electrical connection (not shown) within the recess 14 in the base

1. The electrical connection may comprise a junction block into which the free ends of the electrical connectors are attached. The junction block may have been previously electrically connected to a further electrical connection for transmitting electrical energy to components of the alarm. The further electrical connection may be secured to the base plate 13, for example by attachments such as screws.

We have surprisingly found that, using the invention, installation of a fire and/or smoke alarm is relatively more easily accomplished at a site of use than is the case with prior art alarms. The length of the electrical connection from an external source of electrical energy into the base 1 (for example the length of an electrical connection fed into the base 1 from external thereto) can be relatively longer than is possible with prior art alarm enclosures. Accordingly, connection of the electrical connector or connection to an electrical connection in the housing 2 is made relatively more easy and rapid. Any excess length of electrical connection may then be stored within the recess of the base 1, for example folded thereinto. In an attached condition the side wall 21 of the housing 2 is configured to seat against the flange 11 of the base 1, inside the guide wall 15. Hence, the recess 14 in the base 1 provides a volume into which the housing 2 does not impinge (at least substantially), when the housing is removably retained in the base 1. In this way, the recess 14 provides a useful volume for storage of excess electrical connection and/or connectors. The electrical connection from the external source of electrical energy does not, therefore, have to be of a specific length (or cut to a specific length), as with prior art enclosures. Accordingly, installation is quicker and simpler. Enclosures for alarms are typically designed to have as low a profile as possible, such that there is a prejudice against providing excess space within an enclosure. This is due to a perceived consumer desire for low profile alarms. Accordingly, provision of a recess 14 within the base 1 is in stark contrast to prejudices within the design industry for alarm enclosures.

Attachment of the housing 2 to the base 1 comprises a snap-fit connection between the hooks 18 of the base 1 and the latches 22 of the housing 2. The housing 2 is offered up to the base 1 such that the side wall 21 of the housing 2 is aligned with the guide wall 15 of the base 1. The side wall 21 of the housing 2 is inserted inside of the guide wall 15 of the base 1. The housing 2 is rotated relative to the base 1 until the rebate 15 in the guide wall interacts with the corresponding projection (not shown) on the housing, thereby keying the two components to one another and ensuring correct rotational alignment of the housing relative to the base 1. In this way, the hooks 18 of the base are aligned with the latches of the housing 2. The guides 24 of the latch 22 also act to key rotational alignment of the housing 2 relative to the base 1 by engaging in the spaces either side of the hooks 14. In embodiments, correct rotational alignment of the housing 2 relative to the base 1 may be provided only by the guides 14 interacting with the spaces either side of the latches 14 (for example, where the recess 15 and projection may not be provided).

Provision of the rebate 15 and corresponding projection (not shown) allows relatively more rapid and easy attachment of the housing 2 to the base 1. Through use of the keying action provided by the rebate 15 and corresponding projection, the correct alignment of the housing 2 relative to the base 1 may be felt and/or heard during attempted alignment. Advantageously, this alignment does not rely upon any visual cues, which may be difficult to see whilst installing the alarm.

In the aligned condition the housing 2 is then pushed into engagement with the base 1. As the side wall 21 of the housing 2 is pushed into the interior of the base 1, within the guide wall 13, the lead-in portions 18a at the distal, free ends of the hooks 18 to contact the ramps of the housing. Subsequent force pushing the housing 2 toward the base 1 causes the hooks 18 to resiliently bias away from the central axis A of the base, and hence away from their starting positions. When the distal, free end of the hooks 14 has been pushed beyond the abutments 22a the hooks 18 resiliently return toward their starting position into a retention position. As will be appreciated, in the retention position the distal ends of the hooks 18 may remain at least slightly deflected from their starting position relative to the skirt 10 of the base 1. The engagement lips 18b of the hooks 18 thereby engage with the abutments 22a of the latches 22, thereby restraining the housing 2 from being withdrawn from the base 1. As the housing 2 is pushed into the interior of the base 1 the free end of the further electrical connection (which is secured to the base plate 13 of the base 1) engages into the aperture 26 in the base plate 20 of the housing. The aperture 26 may comprise a socket. In this way, electrical connection between the base 1 and the housing 2 (e.g. between the further electrical connection and the socket is effected. Components supported by the housing may thereby be supplied by electrical energy from the external source of electrical energy.

We have surprisingly found that provision of a guide wall 15 on the base 1 which is configured to seat around the side wall 22 of the housing 2, when the housing 2 is attached to the base 1, reduces the time required for installation. Advantageously, we have found that provision of the guide wall 15 acts to allow rapid and accurate initial alignment of the housing 2 relative to the base 1, prior to final attachment of the housing 2 into the base 1. In this way, the time of installation is beneficially reduced and an installer consequently expends relatively less energy installing an enclosure according to the invention than is the case with prior art enclosures.

When attached to the base 1 the side wall 22 of the housing 2 is located inside and adjacent the guide wall 15 of the base 1. The free edge of the side wall 22 engages into the annular groove 17 on the annular shaped flange 11. In this way, the side wall 21 of the housing 2 is located between the guide wall 15 and the annular support wall 16 of the base 1 and is thereby restrained from axial movement relative to the base 1. The housing 2 is thus removably retained by the base 1.

The cover 3 is then aligned with the housing 2 and attached thereto by snap-fit connection between the hooks 25 of the housing 2 and the latches 32 of the cover 3 in a similar manner to that described above in respect of the snap-fit attachment of the housing 2 to the base 1.

The paint cover 4 is intended for temporary use when an area near the fire alarm is being painted or otherwise decorated or altered. Under such circumstances the paint cover 4 is pushed over the cover 3 and housing 2 of the fire alarm such that the projections 42 and/or the side wall 40 of the paint cover 4 at least partially and resiliently deform. The paint cover 4 is pushed onto the fire alarm until the projections 42 are beyond the side wall 31 of the cover 3. In this position the projections 42 resiliently return to their original shape or orientation such that they retain the paint cover 4 on the fire alarm. When installed thereon, the paint cover 4 militates against paint and other detritus entering the fire alarm and/or from blocking the grill 35 of the cover 3.

When painting has ceased the paint cover 4 is removed by gripping the grip tabs 44 and pulling the paint cover 4 away from the fire alarm. The projections 42 and/or the side wall of the paint cover 4 resiliently deforms, again, thereby allowing the paint cover 4 to be pulled past the cover 3 of the fire alarm and hence removed therefrom.

The housing 2 may be removed from the base 1 (for example to replace and/or repair the fire alarm) by disengagement of the hooks 18 of the base 1 from the latches 22 of the housing 2. To remove the housing 2 a finger or implement (such as a screwdriver) is inserted into the aperture 18c on the outer surface of one hook 18 and said hook 18 is levered away from its retention position and away from its starting position (e.g. away from the central axis A of the base 1). The hook 18 is thereby disengaged from the adjacent latch 22 on the housing 2, which is therefore no longer retained relative to the base 1 and may be withdrawn therefrom.

Forming each hook 18 integrally with the skirt 10 advantageously increases the flexibility of the hooks 18 with respect to the base 1. Accordingly, the hooks 18 are capable of deflecting more readily and are, therefore, less susceptible to failure during use than are hooks attached or formed integrally with the flange 11 of the base 1.

Referring now to Figure 15, there is shown a cover 53 according to a further embodiment of the invention, wherein like features to those of the cover 3 shown in Figure 7 are referred to by like references preceded by a ‘5’, which will not be referred to further herein. The cover 53 is adapted to be suitable for use with a smoke alarm and differs from the cover 3 shown in Figure 7 by comprising a test button T and a centrally disposed grill G for the flow therethrough of gaseous substances and vapours.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, although the enclosure shown in Figures 1 to 11 is described as comprising a paint cover 4 this need not be the case and instead the enclosure may be absent such a component.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims (17)

1. A smoke and/or fire alarm enclosure comprising a base for mounting the enclosure to or at a site of use and a housing for supporting smoke and/or fire detection components, the base comprising an upstanding guide wall at, adjacent or toward its periphery and the housing comprising a peripheral wall, wherein, when the housing is releasably retained by the base, the guide wall surrounds the peripheral wall.

2. An enclosure according to Claim 1, wherein the base comprises an abutment which lies within the peripheral wall when the housing is releasably retained by the base.

3. An enclosure according to Claim 2, wherein the abutment extends parallel to the guide wall.

4. An enclosure according to any preceding Claim, wherein the base and housing are configured to be attached to one another by snap-fit connection.

5. An enclosure according to any preceding Claim, wherein one of the base and housing comprises a latch and the other of the base and housing comprises a hook configured to engage the latch when the housing is releasably retained by the base.

6. An enclosure according to Claim 5, wherein the hook is resiliently biased toward a retention position.

7. An enclosure according to Claim 6, comprising a ramp arranged to deflect, during attachment of the housing to the base, the hook away from the retention position toward a position where the hook is clear of the latch.

8. An enclosure according to either of Claims 6 or 7, wherein the hook comprises an aperture or slot engageable so as to move the hook from the retention position to enable removal of the housing from the base.

9. An enclosure according to any of Claims 5 to 8, wherein the guide wall comprises one or more interruptions.

10. An enclosure according to Claim 9, wherein a hook is provided at or in the, some or each interruption.

11. An enclosure according to any of Claims 5 to 10, where the base comprises the hook and the hook is integrally formed with the base.

12. An enclosure according to any of Claims 5 to 11, comprising one or more guides projecting from the outer major surface of the peripheral wall, where the or each guide is arranged to guide the hook into engagement with the latch during attachment of the housing to the base.

13. An enclosure according to any preceding Claim, comprising a keying mechanism for ensuring correct orientation of the housing relative to the base.

14. An enclosure according to any preceding Claim, wherein the base comprises a recess for the location of an electrical connection and/or cable.

15. An enclosure according to Claim 14, wherein the recess has a height, when the housing is removably retained in the base, of between about 10 and 40 mm.

16. An enclosure according to any preceding Claim, comprising a cover configured to attach to the housing and thereby cover the enclosure.

17. An enclosure according to any preceding Claim, comprising a paint cover for temporarily attaching to the enclosure.