GB2541718A

GB2541718A - Housing unit

Info

Publication number: GB2541718A
Application number: GB1515273.9A
Authority: GB
Inventors: Howard Porter Glenn
Original assignee: Crosswater Ltd
Current assignee: Crosswater Ltd
Priority date: 2015-08-27
Filing date: 2015-08-27
Publication date: 2017-03-01
Anticipated expiration: 2035-08-27
Also published as: GB201515273D0; GB2541718B

Abstract

The unit 10 comprises outer 20 and inner 18 housings. The outer housing is for fixing to a wall and the inner housing is configured to be located within the outer housing. One housing includes a series of engagement features 22 spaced apart in a first pattern. The other housing, preferably the inner one, includes a protrusion 24 for engagement with the features. The protrusion and engagement features are configured to permit incremental movement of the housings relative to each other. The engagement/protrusion features are preferably located in the corners of their respective housings. The units protrusion may include a locking feature operable between a first orientations where it is free of the engagement features and allows relative movement of the housings and a second orientation where movement is prevented. The telescopic movement of the housings allows adjustment to the length of the device.

Description

HOUSING UNIT

The present disclosure relates to a housing unit.

In particular the disclosure is concerned with a telescopic housing unit for housing plumbing, electrical or the like installations.

Background

Conventionally, pipes and ducts for fluids and cabling in buildings may be hidden under plaster work or plasterboard walls. For example it is common to have pipes hidden beneath an outer surface of a wall in order to protect a user against accidentally touching hot or cold pipes whilst getting washed, and to provide an aesthetically pleasing design. Often it is desirable to maintain access to part of the ducting or pipe, for example a stop tap which can be used to control fluid supply.

To achieve this a housing unit may be fixed to the wall, and valves, control units or the like are mounted within the housing and connected to pipework and/or electrical supply cables as required. Plaster work, plaster board and/or tiling can then be applied to the wall around the housing leaving an opening for access to the installation which can then be covered with a panel.

However, in order to that such housings are always proud of the outer surface of the wall, they must either be made longer than required and/or be mounted on batons or mounted with adjustable studs.

Hence a housing unit which is adjustable in length, thus obviating the need for excess material to be trimmed, or complex mounting solutions, is highly desirable.

Summary

According to the present disclosure there is provided an apparatus as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Accordingly there may be provided a housing unit comprising : an outer housing for fixing to a wall; an inner housing which is configured to be located within the outer housing; one of the housings being provided with a first series of engagement features spaced apart in a first pattern; the other housing being provided with a first protrusion feature for engagement with the engagement features; the engagement features and protrusion feature being configured to permit incremental movement of the housings relative to one another in a longitudinal direction.

The housing may further comprise a second series of engagement features spaced apart in a second pattern different to the first pattern.

The first series of engagement features may be spaced apart from each other by a first distance; and the second series of engagement features are spaced apart from each other by the first distance, and are longitudinally offset from the first series of engagement features.

The first protrusion feature may comprise a first series of protrusions spaced apart from each other by a distance which is the same as, or a multiple of, the first distance.

There may be further provided a second protrusion feature on the same housing as the first protrusion feature for engagement with engagement features provided on the other housing.

The second protrusion feature may comprise a second series of protrusions spaced apart from each other by a distance which is the same as, or a multiple of, the first distance; and the second series of protrusions may be longitudinally offset from the first series of protrusions.

In each series of engagement features there may be provided at least one engagement feature for every protrusion.

The housings may be substantially polygonal in cross section, with the same number of sides; at least one corner region of one of the housings may be provided with the first series of engagement features; and the first protrusion feature may be provided in a corner region of the other housing.

First protrusion features may be provided in two or more corner regions of the other housing.

The housings may be substantially polygonal in cross section, with the same number of sides; at least one corner region of one of the housings may be provided with the first series of engagement features; the housing provided with the first series of engagement features may be further provided with the second series of engagement features on a different corner region to the first series of engagement features; and the first protrusion feature may be provided in a corner region of the other housing.

The first and second protrusion features may be provided in different corner regions of the same housing.

The housing unit may further comprise : a locking feature provided on the housing provided with the protrusion feature; the locking feature operable to move between : a first orientation relative to its housing in which it is free of the engagement features to thereby permit relative longitudinal movement of the housings; and a second orientation relative to its housing in which it engages with the engagement features to thereby prevent relative longitudinal movement of the housings.

Two or more locking features may be provided on the housing provided with the protrusion feature for releasable engagement with the engagement features on the other housing.

The locking feature may comprise a tab which in the first orientation is free of the engagement features; and in the second orientation engages with one of the engagement features.

The locking feature may be provided in the same corner region of the housing as the corner region which the protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with the same series of engagement features.

The locking feature may be provided in a different corner region of the housing to the corner region which the first protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with different series of engagement features.

The first series of engagement features may be provided on the outer housing, and the protrusion feature is provided on the inner housing. A flange may extend around the outer housing for fixing the outer housing to a wall.

The flange may be located at one end of the outer housing, and the engagement features extend in a line away from the flange towards a free end of the outer housing distal to the flange end.

The or each series of protrusions may extend in a line such that, when the inner and outer housings are assembled, the or each series of protrusions are aligned with the or each series of engagement features respectively.

Hence there is provided a housing unit which may be adjusted in length before or after fitting, thus making it easy for an installer to make the free end of the housing, i.e. the end which is not attached to the wall, positioned as desired relative to any plaster work, plaster board, tiling or other surface finish which has been built up on the wall.

Brief Description of the Drawings

Examples of the present disclosure will now be described with reference to the accompanying drawings, in which:

Figure 1 shows a cross section of a housing unit according to the present disclosure mounted to a wall;

Figure 2 shows a perspective view of the housing unit shown in Figure 1;

Figures 3 to 6 show different views of an outer housing of the housing unit;

Figures 7 to 10 show different views of an inner housing of the housing unit;

Figure 11 shows a view of the outer housing and inner housing when assembled in a first configuration;

Figure 12 shows an enlarged view of an engagement feature and complementary protrusion feature provided on the housing unit;

Figure 13 shows a similar view to that shown in Figure 11 but with the outer housing and inner housing in a different configuration;

Figure 14 shows a plan view of the assembled housing unit;

Figure 15 shows an enlarged view of a corner of the assembled housing unit which has a locking feature;

Figure 16 shows a perspective view of the region shown in Figure 15 with the locking feature in a first orientation;

Figure 17 shows a view similar to that of Figure 16 with the locking feature in a second orientation;

Figure 18 shows a pair of housing units with equipment installed within the housing unit;

Figure 19 shows an isometric view of an alternative example of a housing unit according to the present disclosure;

Figure 20 shows a similar view to that of Figure 19 but with equipment installed within the housing unit;

Figure 21 shows a cross section of an alternative example of a housing unit according to the present disclosure when fitted to a wall;

Figure 22 shows a perspective view of the housing unit shown in Figure 21;

Figure 23 shows a side view of the housing unit shown in Figures 21,22;

Figure 24 shows an underside view of the housing unit shown in Figures 21 to 23; and

Figures 25 to 30 show different views of a housing unit according to an additional example of the present invention.

Detailed Description

Figure 1 shows a cross sectional view of a housing unit 10 according the present disclosure. The housing unit 10 is fixed to a wall 12, for example by an adhesive or by being screwed to the wall 12. Plaster 14 may then be applied to the surface of the wall 12 and part way up the height of the housing unit 10. A further plaster or tiling layer 16 may then be applied to the plaster 14 to a desired height. Alternatively, the layer 16 may be provided spaced apart from the wall 12, for example by batons, with no intermediate layer 14.

In Figure 1 the tiling 16 comes to the height of an outer housing 18 of the housing unit 10. Flowever the housing 18 may be proud of or below the surface of the tiling 16. An inner housing 20 is moveable within the outer housing 18 to reach the desired height for the component being fitted inside of the housing unit 10.

Figure 2 shows a perspective view of the housing unit 10. As described above, the housing unit 10 comprises the outer housing 18 for fixing to the wall 12, and an inner housing 20 which is configured to be located within the outer housing 18. Figures 3 to 6 show a perspective view, plan view, first side view and second side view respectively of the outer housing 18. Figures 7 to 10 show a perspective view, plan view, first side view and second side view respectively of the inner housing 20. Figures 11 to 13 show a side view of the housing unit when assembled.

One of the housings 18, 20 is provided with a first series of engagement features 22 which are spaced apart in a first pattern. The other housing 18,20 is provided with a protrusion feature 24 for engagement with the engagement features 22.

In the example shown the first series of engagement features 22 are provided on the outer housing 18, and the protrusion feature 24 is provided on the inner housing 20. Flowever, in a different example (not shown) the first engagement features 22 may be provided on the inner housing 20 and the protrusion feature 24 may be provided on the outer housing 18.

The engagement features 22 and protrusion feature 24 are configured to permit incremental movement of the housings 18, 20 relative to one another in a longitudinal direction, thereby providing an arrangement in which the housing unit is “telescopic”. That is to say, the housing unit 10 is expandable and contractible in length by virtue of the movement of the protrusion feature 24 along the line defined by the series of engagement features 22, 26.

The housing 18, 20 comprising the first series of engagement features 22 further comprises a second series 26 of engagement features which may be spaced apart in a second pattern which is different to the first pattern. The first series of engagement features 22 and second series of engagement features 26 may be provided as slits, holes, apertures or indentations. The first series of engagement features 22 and second series of engagement features 26 may each be spaced apart in a line which extends along a wall of the housing in which they are provided.

The protrusion feature 24 may be provided as a “p/p” which extends above the height of the wall of the housing upon which it is provided.

The first series of engagement features 22 are spaced apart from each other by a first distance. The second series of engagement features 26 are spaced apart from each other by the first distance, and are longitudinally offset from the first series of engagement features 22. This is best shown in Figures 5, 6. In Figure 5 on the left hand side of the outer housing 18 the first series of engagement features 22 are shown as slits in a solid line, and the second series of engagement features 26 are shown as a dotted line. The first series of engagement features 22 and second series of engagement features 26 are provided on different corners of the outer housing 18. However the dotted line on the left hand side of Figure 5 show how the different series 22,26 are offset from one another in the longitudinal direction. That is to say, the first series of engagement features 22 and second series of engagement features 26 comprise the same number of slits, holes, apertures or indentations, and are spaced apart by the same amount. However the first series of engagement features 22 extends further up the wall of the housing on which it is provided than the second series of engagement features 26.

Figures 7, 9, 10 show the protrusion feature 24 on the outer surface of the inner housing 20. It is provided towards one end of the inner housing 20. Ports 30, 32 are provided in the walls of the inner housing 20. In use pipes will extend through the ports 30, 32 and into the equipment located in the housing unit 10. Cut out regions 34 on the outer housing 18 correspond to the ports 30, 32 such that pipes may pass through the cut out regions 34 and through the ports 30, 32 into the housing unit 10.

The housings 18, 20 are substantially polygonal in a cross section, with the same number of sides. In the example shown in Figures 1 to 18 the housings are substantially square. However the housings may also be rectangular, triangular or other polygon having any number of sides. Optionally the housings may be circular or oval.

In the example shown the housings are substantially cubic, with four sides and four corner regions defining the perimeter of the housing. The term “corner region” is intended to refer to an area of the side walls of the housing which leads up to, and includes, where the walls of the housing meet. That is to say, the corner region includes the geometric corner of the housing, and also a region of the side walls of the housing to either side of the geometric corner.

At least one corner region of one of the housings 18, 20 is provided with the first series of engagement features 22. In the example shown, two opposite corner regions of the outer housing 18 are provided with engagement features 22 of the first series pattern, spacing and longitudinal location, and the protrusion feature 24 is provided on a corner region of the inner housing 20. In the example shown the protrusion 24 is shown at the geometric corner of the inner housing 20. However, it may also be provided on the side wall of the housing adjacent the geometric corner.

The housing provided with the first series of engagement features 22 may also be provided, and as shown in the figures, with the second series of engagement features 26 on a different corner region to the first series of engagement features 22. In the example shown, two opposite corners of the outer housing 18 are provided with engagement features 26 of the second series pattern, spacing and longitudinal location.

In the example shown, the engagement features 22,26 are slots which extend around the geometric corners of the housings 18,20 within the corner region of the housing. A flange 40 extends around the outer housing 18 for fixing the outer housing 18 to the wall 12. The flange 40 is located at one end of the outer housing 18. The series of engagement features 22, 26 extend in a line away from the flange 40 towards a free end 42 of the outer housing 18 distal to the flange end 44. The flange 40 may comprise apertures 46 through which fixing means, for example screws, may extend to fix the flange 40 and hence the outer housing unit 18 to the wall 12. A locking feature 50 may be provided on the housing provided with the protrusion feature 24. In the example shown, the locking feature 50 is provided on the inner housing 20. However in an alternative example, the locking feature 50 may be provided on the outer housing 18.

The locking feature 50 is operable to move between a first orientation relative to its housing 18,20 in which it is free of the engagement features 22, 26 to permit relative movement of the housings 18, 20 in a longitudinal direction, and a second orientation relative to its housing 18, 20 in which it engages with one of the first or second series of engagement features 22, 26 to thereby prevent relative movement of the housings 18, 20 in the longitudinal direction.

Two or more locking features 50 may be provided on the housing 20 provided with the protrusion feature 24 for releasable engagement with the series of engagement features 22,26 on the other housing 18. The locking feature 50 comprises a tab 52 which in the first orientation is free of the series of engagement features it is proximate to, and in the second orientation the tab 52 engages with one of the series of engagement features 22, 26. As shown in Figures 14 to 17, the tab 52 is connected to a rotatable screw 54. Hence the tab 52 may be rotated from one orientation to another orientation to move the tab 52 to sit within the housing 20 or to slide into position in the series of engagement features 22, 26 which it is adjacent to. For example, as shown in Figures 14,16, in the top right corner the tab 52 is shown rotated to a first orientation where it sits within the inner housing 20. That is to say Figures 14,16 show the tab in a stowed position such that it does not engage with the engagement features of the outer housing 18. In the bottom left hand corner of Figure 14 and in Figures 15,17 the tab 52 has been rotated to a second orientation relative to its housing in which it extends through one of the engagement features in the outer housing 18. The same can be seen in Figure 2 where the tab 52 can be seen extending through the slits which form the first series of engagement features 22.

The locking feature 50 may be provided on a different corner region of the housing to the corner region which the protrusion feature 24 is provided on. Hence, in use, the locking feature 50 and protrusion feature 24 may engage with different series of engagement features. For example, the locking feature 50 may engage with a series of engagement features provided on one corner of the outer housing 18, and the protrusion feature 24 will thus engage with another series of engagement features provided on a different corner of the outer housing 18.

The two series of engagement features may be aligned with each other. In such an example, the locking feature 50 may be provided in the same plane as the protrusion feature 24. That is to say, the tab 52 of the locking feature 50 and protrusion feature 24 may be provided at the same distance from a free end of the housing wall on which they are provided, albeit on different corners of the same housing.

Alternatively, the two series of engagement features may be provided as the first and second series of engagement features described above, and hence are longitudinally offset from each other. In such an example, the locking feature 50 and protrusion feature 24 may be provided offset from one another in the longitudinal direction by the same amount as the first series and second series of engagement features.

In some examples, only one locking feature 50 is provided in one corner of the inner housing 18. In other examples locking features 50 may be provided in two adjacent corners along the same side of the housing, or in opposite corners of the housing. In examples where two locking features 50 are provided, the locking features 50 may be provided in the same plane as one another.

Depth dimensions may be embossed on one or other of the housings.

In use, and as shown in Figures 11 to 13, the inner housing 20 is inserted in the free end of the outer housing 18 and urged in a longitudinal direction such that the inner housing 20 slides relative to the outer housing 18. The protrusion feature 24, provided as it is on a corner of the inner housing 20, will push past the outer housing 18 and extend through, and hence engage with, the series of engagement features 22, 26 on the corresponding corner of the outer housing 18. The user can urge the inner housing 20 further to disengage the protrusion feature 24 from the engagement feature it is engaged with, such that it moves out of engagement with the slot and pushes past the wall of the housing 18 until it reaches the next slot in the series of engagement features 22, 26. When a desired height of housing unit 10 is achieved, the locking feature 50 is rotated such that the tab 52 is extended through one of the engagement features 22,26 of the series of engagement features which it is adjacent to.

The inner housing unit 20 and outer housing unit 18 may be assembled prior to the outer housing unit 18 being fixed to the wall 12. Hence the inner housing unit 20 may be moved longitudinally relative to the outer housing unit once the outer housing unit 18 is fixed to the wall 12. When in the correct position, the device to be installed in the housing unit may be fitted and connected to supply pipework etc. The extent to which the inner housing extends out of the outer housing 18 may be adjusted at any time throughout or after the installation process. A cover may be installed on the end of the inner housing as required.

The housing unit 10 may be used in isolation, or multiple housing units may be located next to each other as shown in Figure 18. In the example shown in Figure 18 the higher housing unit 10 holds a thermostat for a shower unit, and the lower housing unit 10 houses a water flow control dial. However any fitting may be located within the housing unit as required. The ports 30, 32 and slot 34 may be sized according to the requirements of the installation.

As shown in Figure 14, the locking features 50 are shown adjacent to the second series of engagement features 26. However if a different height is required to that which can be provided with this arrangement, then the inner housing 20 can be inserted such that the locking features are adjacent to the first series of engagement feature 22. That is to say, since the outer housing 18 and the inner housing 20 are both square, the inner housing 20 may be inserted as shown in Figure 14, or may be inserted in the outer housing 18 after having been rotated through 90 degrees so that the locking features 50 are adjacent to the first series of engagement features 22. Since the first series of engagement features 22 are longitudinally offset relative to the second series of engagement features 26, the engagement of the locking feature 50 with either series of engagement features enables the inner housing 18, in the example shown, to be located at a different range of heights relative to the outer housing 22.

The arrangement shown in Figures 19, 20 is essentially the same as that shown in Figures 1 to 18. The housings 18, 20 are rectangular rather than square, and locking features 50 are provided in each corner of the inner housing 20. A different series of engagement features 22, 26 are provided on adjacent corners of the outer housing 18. Hence one pair of opposite corners of the outer housing 18 have a first series of engagement features 22, and the other pair of opposing corners have a second series of engagement features 26 which are longitudinally offset from the first series. Thus a variety of relative positions of the inner housing 20 relative to the outer housing 18 are possible by engaging one set of locking features into either the first series of engagement features 22 or the second series of engagement features 26. Figure 20 shows a thermostat and dial installed in the example housing shown in Figure 19.

Figures 21 to 24 show a further example of a housing unit 110 according to the present disclosure. Features common to previous examples will be indicated using common reference numerals.

As in the preceding examples, the first and second series of engagement features 22,26 are provided extending in a line away from the flange 140 towards one end of the outer housing 118 on one side of the flange only. Protrusion features 24 and locking features 50 are also provided as in preceding examples.

In this example, in use, the flange 140 is fitted to the “rear” of the wall 12 such that the portion of the outer housing 118 which comprises the series of engagement features extends from the rear of the wall 12, and the inner housing 120 extends from the flange end 140 of the inner housing 118, and not from the free end at the opposite end of the outer housing 118. Hence in use the inner housing 120 extends from the rear of the wall 12 through an aperture provided in the wall so that plaster 14 and tiles may be provided up to the sides of the inner housing 120.

In this arrangement the pipework may be provided “behind” the wall 12 with control features extending through the housing 110 towards the tile side 16 of the unit.

Figures 25 to 30 show a further example of a housing unit 210 according to the present disclosure. Features common to previous examples will be indicated using common reference numerals.

The example of shown in Figures 25 to 30 differs from the preceding example in that, whereas in the preceding examples the protrusion feature comprises a single protrusion 24, the example of Figures 25 to 30 comprises multiple protrusions 24a, 24b.

That is to say, there may be provided protrusion features 24a, 24b in different corner regions of the same housing 18,20. Put another way, the protrusion features 24a, 24b may be provided in two or more corner regions of the same housing. The protrusion feature 24a, 24b may be provided at the geometric corner of the housing, or (as shown in Figure 25 to 30) on the side wall of the housing adjacent the geometric corner.

There may be a first protrusion feature 24a and a second protrusion feature 24b on the same housing as each other, in different corner regions. Put another way, the first and second protrusion features 24a, 24b may be provided in different corner regions of the same housing.

The first protrusion feature 24a may comprise a first series of protrusions 24a spaced apart from each other by a distance which is the same as, or a multiple of, the first distance (i.e. having the spacing between the engagement features 22, 26).

The second protrusion feature 24b may comprise a second series of protrusions 24b spaced apart from each other by a distance which is the same as, or a multiple of, the first distance (i.e. having the same spacing as engagement features 22, 26). The second series of protrusions 24b may be longitudinally offset from the first series of protrusions 24a.

The or each series of protrusions 24a, 24b extend in a line along such that, when the inner and outer housings 18,20 are assembled, the or each series of protrusions 24a, 24b are aligned with the or each series of engagement features 22,26.

For each series of engagement features 24a, 24b on the housing, there is provided at least one engagement feature 22 for every protrusion 24, 24b. In the example shown there is provided the same number of engagement features 22 for each protrusion 24a, 24b, plus additional engagement features 22 for each locking feature tab 52. That is to say, the number of engagement features 22 provided may be equal to, or greater than, the number of protrusions 22 provided plus the number of locking features 50 provided.

In the example shown locking features 50 are provided in all of the corner regions of the housing, and so share corner regions with the protrusion features 24a,24b. Flence, in use, locking features 50 and protrusion features 24a,24b in each corner engage with the same series of engagement features 22, 26. The locking feature 50 is provided at the end of the line defined by the series of protrusions 24a,24b.

In a different example, not shown in the figures, the locking feature 50 may be provided in a different corner region of the housing to the corner region which the protrusion feature(s) 24a, 24b is/are provided such that, in use, the locking feature 50 and protrusion feature(s) 24a, 24b engage with different series of engagement features 22,26.

Hence there is provided a housing unit which may be telescopically altered in length, and which may be used for housing control features for plumbing and electrical installations. The combination of engagement features 22, 26, protrusion feature(s) 24, 24a, 24b and locking features 50 enables the positioning and fixing of the inner housing and the outer housing relative to one another. The device of the present invention obviates the need for complex mounting arrangements for the housing boxes and thus allows for a more easily achievable tidy finish to an installation.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS 1 A housing unit comprising : an outer housing for fixing to a wall; an inner housing which is configured to be located within the outer housing; one of the housings being provided with a first series of engagement features spaced apart in a first pattern; the other housing being provided with a first protrusion feature for engagement with the engagement features; the engagement features and protrusion feature being configured to permit incremental movement of the housings relative to one another in a longitudinal direction. 2 A housing unit as claimed in claim 1 wherein : the housing further comprises a second series of engagement features spaced apart in a second pattern different to the first pattern. 3 A housing unit as claimed in claim 2 wherein : the first series of engagement features are spaced apart from each other by a first distance; and the second series of engagement features are spaced apart from each other by the first distance, and are longitudinally offset from the first series of engagement features. 4 A housing unit as ciaimed in any one of the preceding ciaims wherein : the first protrusion feature comprises a first series of protrusions spaced apart from each other by a distance which is the same as, or a muitipie of, the first distance. 5 A housing unit as ciaimed in ciaim 4 wherein : there is further provided a second protrusion feature on the same housing as the first protrusion feature for engagement with engagement features provided on the other housing. 6 A housing unit as ciaimed in ciaim 5 wherein : the second protrusion feature comprises a second series of protrusions spaced apart from each other by a distance which is the same as, or a muitipie of, the first distance; and the second series of protrusions are iongitudinaiiy offset from the first series of protrusions. 7 A housing unit as ciaimed in any one of ciaims 4 to 6 wherein : in each series of engagement features there is provided at ieast one engagement feature for every protrusion. 8 A housing unit as ciaimed in any one of ciaims 1 to 7 wherein : the housings are substantiaiiy poiygonai in cross section, with the same number of sides; at least one corner region of one of the housings is provided with the first series of engagement features ; and the first protrusion feature is provided in a corner region of the other housing. 9 A housing unit as claimed in claim 8 wherein first protrusion features are provided in two or more corner regions of the same housing. 10 A housing unit as claimed in any one of claims 2 to 7 wherein : the housings are substantially polygonal in cross section, with the same number of sides; at least one corner region of one of the housings is provided with the first series of engagement features; the housing provided with the first series of engagement features is further provided with the second series of engagement features on a different corner region to the first series of engagement features; and the first protrusion feature is provided in a corner region of the other housing. 11 A housing unit as claimed in claim 10 when dependent upon claim 5 wherein the first and second protrusion features are provided in different corner regions of the same housing. 12 A housing unit as claimed in any one of the preceding claims further comprising : a locking feature provided on the housing provided with the protrusion feature; the locking feature operable to move between : a first orientation relative to its housing in which it is free of the engagement features to thereby permit relative longitudinal movement of the housings; and a second orientation relative to its housing in which it engages with the engagement features to thereby prevent relative longitudinal movement of the housings. 13 A housing unit as claimed in claim 12 wherein : two or more locking features are provided on the housing provided with the protrusion feature for releasable engagement with the engagement features on the other housing. 14 A housing unit as claimed in claim 12 or claim 13 wherein : the locking feature comprises a tab which in the first orientation is free of the engagement features; and in the second orientation engages with one of the engagement features. 15 A housing unit as claimed in any one of claims 12 to 14 : the locking feature is provided in the same corner region of the housing as the corner region which the protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with the same series of engagement features. 16 A housing unit as claimed in any one of claims 12 to 14 when dependent on claim 2 wherein : the locking feature is provided in a different corner region of the housing to the corner region which the first protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with different series of engagement features. 17 A housing unit as claimed in any one of the preceding claims wherein the first series of engagement features are provided on the outer housing, and the protrusion feature is provided on the inner housing. 18 A housing unit as claimed in any one of the preceding claims wherein a flange extends around the outer housing for fixing the outer housing to a wall. 19 A housing unit as claimed in claim 18 wherein : the flange is located at one end of the outer housing, and the engagement features extend in a line away from the flange towards a free end of the outer housing distal to the flange end. 20 A housing unit as claimed in claim 17 when dependent upon claim 4 or claim 6 wherein : the or each series of protrusions extend in a line such that, when the inner and outer housings are assembled, the or each series of protrusions are aligned with the or each series of engagement features respectively. 21 A housing unit substantially as hereinbefore described and/or as shown in the accompanying drawings. Amendments to the claims have been made as follows: CLAIMS 1 A housing unit comprising : an outer housing for fixing to a wall; an inner housing which is configured to be located within the outer housing; one of the housings being provided with : a first series of engagement features spaced apart in a first pattern; and a second series of engagement features spaced apart in a second pattern; the other housing being provided with a first protrusion feature for engagement with the engagement features; the engagement features and protrusion feature being configured to permit incremental movement of the housings relative to one another in a longitudinal direction. 2 A housing unit as claimed in claim 1 wherein : the first series of engagement features are spaced apart from each other by a first distance; and the second series of engagement features are spaced apart from each other by the first distance, and are longitudinally offset from the first series of engagement features. 3 A housing unit as claimed in any one of the preceding claims wherein : the first protrusion feature comprises a first series of protrusions spaced apart from each other by a distance which is the same as, or a multiple of, the first distance. 4 A housing unit as claimed in claim 3 wherein : there is further provided a second protrusion feature on the same housing as the first protrusion feature for engagement with engagement features provided on the other housing. 5 A housing unit as claimed in claim 4 wherein : the second protrusion feature comprises a second series of protrusions spaced apart from each other by a distance which is the same as, or a multiple of, the first distance; and the second series of protrusions are longitudinally offset from the first series of protrusions. 6 A housing unit as claimed in any one of claims 3 to 5 wherein : in each series of engagement features there is provided at least one engagement feature for every protrusion. 7 A housing unit as claimed in any one of claims 1 to 6 wherein : the housings are substantially polygonal in cross section, with the same number of sides; at least one corner region of one of the housings is provided with the first series of engagement features ; and the first protrusion feature is provided in a corner region of the other housing. 8 A housing unit as claimed in claim 7 wherein first protrusion features are provided in two or more corner regions of the same housing. 9 A housing unit as claimed in any one of claims 1 to 6 wherein : the housings are substantially polygonal in cross section, with the same number of sides; at least one corner region of one of the housings is provided with the first series of engagement features; the housing provided with the first series of engagement features is further provided with the second series of engagement features on a different corner region to the first series of engagement features; and the first protrusion feature is provided in a corner region of the other housing. 10 A housing unit as claimed in claim 9 when dependent upon claim 4 wherein the first and second protrusion features are provided in different corner regions of the same housing. 11 A housing unit as claimed in any one of the preceding claims further comprising : a locking feature provided on the housing provided with the protrusion feature; the locking feature operable to move between : a first orientation relative to its housing in which it is free of the engagement features to thereby permit relative longitudinal movement of the housings; and a second orientation relative to its housing in which it engages with the engagement features to thereby prevent relative longitudinal movement of the housings. 12 A housing unit as claimed in claim 11 wherein : two or more locking features are provided on the housing provided with the protrusion feature for releasable engagement with the engagement features on the other housing. 13 A housing unit as claimed in claim 11 or claim 12 wherein : the locking feature comprises a tab which in the first orientation is free of the engagement features; and in the second orientation engages with one of the engagement features. 14 A housing unit as claimed in any one of claims 11 to 13 : the locking feature is provided in the same corner region of the housing as the corner region which the protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with the same series of engagement features. 15 A housing unit as claimed in any one of claims 11 to 13 when dependent on claim 2 wherein : the locking feature is provided in a different corner region of the housing to the corner region which the first protrusion feature is provided on such that, in use, the locking feature and protrusion feature engage with different series of engagement features. 16 A housing unit as claimed in any one of the preceding claims wherein the first series of engagement features are provided on the outer housing, and the protrusion feature is provided on the inner housing. 17 A housing unit as claimed in any one of the preceding claims wherein a flange extends around the outer housing for fixing the outer housing to a wall. 18 A housing unit as claimed in claim 17 wherein : the flange is located at one end of the outer housing, and the engagement features extend in a line away from the flange towards a free end of the outer housing distal to the flange end. 19 A housing unit as claimed in claim 16 when dependent upon claim 3 or claim 5 wherein : the or each series of protrusions extend in a line such that, when the inner and outer housings are assembled, the or each series of protrusions are aligned with the or each series of engagement features respectively. 20 A housing unit substantially as hereinbefore described and/or as shown in the accompanying drawings.