AU2021107471A4 - Stackable diffuser plenum unit - Google Patents

Abstract

A stackable diffuser plenum unit comprising a housing, at least a top portion of the housing having a shape of a truncated four-sided pyramid, the housing defining an 5 inner surface, the unit further comprising an acoustic damper attached to the inner surface, wherein the housing has a void formed therein and wherein the void is shaped so that, when a first stackable plenum unit is stacked on top of a second stackable plenum unit, the void of the 10 second unit accommodates at least a portion of the acoustic damper of the first unit. The unit may comprise an adaptor for connecting an air duct to the housing 26 2 4d1a &-2 4c1 T / 10 4,bIl lib" b C; 66 Fig la Section X-X Fig lb Section X-X 2 lb Il4b 4c1 I-)" lb' 9 4c 4a 4d1 I1k 6 3a x x 8' 4b1 Fig Ic Fig Id y 4dcb Tft~ 4d 4a' 4a 8 Ila fP Section Y-Y Section X-X TB p CO C8 Fig~a Fig a

Description

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STACKABLE DIFFUSER PLENUM UNIT

Technical Field Embodiments of the invention relate to a plenum units

for use in air conditioning units.

Background Art

Connection boxes for air diffusers in HVAC

applications are increasingly being manufactured of rigid

foam board. Advantageously, such board typically provides

higher thermal insulation for a given thickness than

comparable metal connection boxes lined or lagged with

thermally insulating material, and is less expensive.

Additionally, connection boxes fabricated using rigid foam

board are substantially lighter than their sheet-metal

counterparts, which reduces installation costs and time,

and reduces structural requirements and costs to support

the connection box weight. Rigid foam board also lends

itself to flat-packing of pre-cut elements, for later

assembly into a connection box. Rigid foam board, however,

has rigid surfaces that are highly reflective to noise,

and it is therefore ineffective at attenuating noise,

especially that entering the connection box through the

spigot, such as noise generated upstream of the diffuser

or proximate to the diffuser spigot, where high air

velocities and adverse velocity profiles frequently

generate excessive noise (such as due to an ovalised

spigot to achieve reduced connection box height, or a bend

in a flexible duct directly upstream of a connection box).

This noise is then emitted by the diffuser into the

occupancy space, causing acoustic discomfort to occupants.

In contrast, sheet-metal connection boxes are often lined

with thermal insulation that has an open cell structure to additionally provide acoustic absorption, thereby reducing the risk of excessive noise being emitted from the diffuser.

Many connection boxes are manufactured substantially

in the shape of a four-sided truncated pyramid, to allow

them to be stackable, thereby reducing the volume required

for storage and transport. This substantially reduces

costs. Such stackable connection boxes of the prior art,

however, suffer from several shortcomings:

1. It is generally not feasible to line the rigid foam

board box with acoustically absorptive material, such

as polyester matting, as the combined thickness of the

rigid foam board and the acoustically absorptive

material severely reduces the number of connection

boxes that can be stacked on top of one another for a

given stack height.

2. Connection boxes often get "stuck" inside one another,

or are pulled apart, due to the high forces and static

friction on the wall surfaces generated by the weight

of the stack acting in shear on the inclined connection

box walls, prising them apart.

3. The side-entry spigot (for attachment of the duct

supplying air to the diffuser) directs supply air

partially downwards directly onto at least part of the

diffuser, due to the inclined orientation of the

connection box side walls. This may generate noise and

an unfavourable asymmetric discharge pattern from the

diffuser. For this reason, many specifications for air

conditioning projects stipulate that each connection

box spigot must be located on a vertical wall. This is

so that the supply airstream into the connection box is

directed above the diffuser, for supply velocity to be broken down in the connection box. The connection box then acts substantially as a pressure plenum, resulting in lower noise and better diffuser performance.

4. The width of the connection box walls reduces with

increasing box height, due to pyramid taper. This

severely restricts the maximum spigot size (round or

ovalised) that can be accommodated, in comparison to a

connection box of equal height but with vertical walls.

Stackable connection boxes of the prior art, therefore,

often tend to be higher than their non-stackable

counterparts, thereby requiring more ceiling void space

(which may not be available) and delivering lower air

quantities, which may necessitate the use of more

diffusers, increasing overall costs.

Conventional connection boxes with vertical walls

tend not to suffer from the above list of shortcomings.

However, in addition to requiring significant storage and

transport volume, they are also often too bulky (if sized

for high airflow rates) to install into a ceiling from

below without the need to dismantle the ceiling grid. This

increases installation costs and potentially causes damage

to the ceiling.

Due to the high costs associated with bulky

connection boxes, a multitude of different connection box

sizes is often used, so that each connection box is as

small as possible for the required airflow rate. This

increases co-ordination issues on site and reduces

flexibility, as each connection box type must be correctly

located.

The substantial height requirement of connection

boxes - including those with vertical walls - suitable for high airflow rates often causes clashes with the structure or other services in the ceiling void (such as structural beams, sprinkler pipes or cable trays) causing costly installation delays and rectification works.

Summary

A stackable diffuser plenum unit comprising a

housing, at least a top portion of the housing having a

shape of a truncated four-sided pyramid, the housing

defining an inner surface, the unit further comprising a

damper attached to the inner surface, wherein the housing

has a void formed therein, the void being defined by one

or more edges of the housing and wherein the void is

shaped so that, when a first stackable plenum unit is

stacked on top of a second stackable plenum unit, the void

of the second unit accommodates at least a portion of the

damper of the first unit.

The damper may be an acoustic damper.

The damper may be located on an inner surface of the

housing opposite the void.

The void may be shaped to accommodate at least the

portion of the damper of the first unit when the first

unit is stacked on top of the second unit with an altered

orientation.

The altered orientation may be a rotation through

1800.

The rotation may be a rotation about a central axis of the four-sided pyramid of the housing.

In an embodiment, one or more edges of the housing

defining the void may be located on a plane defined by a

side wall of the truncated four-sided pyramid. In a

further embodiment one or more edges of the housing

defining the void may be recessed relative to a plane

defined by a side wall of the truncated four-sided

pyramid.

The one or more edges may be recessed relative to the

plane by an amount corresponding to a thickness of the

damper.

The stackable diffuser plenum unit may further

comprise a ledge formed in a bottom portion, wherein the

ledge is configured to provide a stop for a similar unit

stacked onto the diffuser plenum unit.

The stackable diffuser plenum unit may further

comprise an adaptor for fitting an air duct to the

housing.

The adaptor may be attached to the housing at a

location corresponding to the void. The void may

accommodate the adaptor.

The adaptor may comprise a spigot wall for supporting

a spigot.

The spigot wall may be substantially perpendicular to

the bottom portion.

The adaptor may comprise a spigot. The spigot may define an oval or round shape.

The bottom portion may be configured to receive a

diffuser.

The housing may be constructed from rigid foam board.

A further aspect of the disclosure extends to a

housing for a diffuser plenum unit, the housing having a

bottom portion, the housing being configured to receive a

diffuser at the bottom portion, the housing having side

walls with at least one side wall configured to receive a

spigot adaptor.

A further aspect of the disclosure extends to a

spigot adaptor for a diffuser plenum unit, the spigot

adaptor comprising a spigot wall and a spigot attached to

the spigot wall.

A further aspect of the disclosure extends to a

diffuser plenum unit comprising a housing as herein

described and a spigot adaptor as herein described.

The spigot wall may be substantially perpendicular to

a diffuser, when installed in the bottom portion.

Detailed Description of the Drawings

In the following detailed description, reference is

made to accompanying drawings, which are not to scale and

which form a part of the detailed description.

The same part number is used for the same part if it

appears across multiple figures.

The illustrative embodiments described in the

detailed description, depicted in the drawings and defined

in the claims, are not intended to be limiting. Other

embodiments may be utilised, and other changes may be made

without departing from the spirit or scope of the subject

matter presented. It will be readily understood that the

aspects of the present disclosure, as generally described

herein and illustrated in the drawings can be arranged,

substituted, combined, separated and designed in a wide

variety of different configurations, all of which are

contemplated in this disclosure.

Embodiments will now be described, by way of example

only, with reference to the accompanying drawings in

which:

Figure la is a diagram illustrating a side cross

section of a spigot adaptor suitable for attachment to a

connection box;

Figure lb is a diagram illustrating a side cross

section of a connection box attached to a diffuser, and

suitable for attachment of a spigot adaptor, such as

depicted in figure la;

Figures 1c and 1d are diagrams illustrating top views

of the spigot adaptor and connection box attached to a

diffuser depicted in figures la and lb, respectively;

Figures 2a and 2b are diagrams illustrating side

cross-section views of stacked connection boxes and a

connection box above the stack, suitably orientated to be

added to the stack;

Figures 3a and 3b are diagrams illustrating a top

view and a top cross-section view of a diffuser unit

comprising a spigot adaptor attached to a connection box

with diffuser;

Figures 3c and 3d are diagrams illustrating a front

view and a side view of a diffuser unit comprising a

spigot adaptor attached to a connection box with diffuser;

Figures 3e and 3f are diagrams illustrating a front

cross-section view and a side cross-section view of a

diffuser unit comprising a spigot adaptor attached to a

connection box with diffuser;

Figures 4a and 4b are diagrams illustrating a front

view and a side cross-section view of an alternative

embodiment of a diffuser unit comprising a spigot adaptor

attached to a connection box with diffuser;

Figures 5a is a top view of a ceiling grid with a

diffuser unit shown during installation from below,

without requiring dismantling of the ceiling grid;

Figure 5b is a side view of an alternative embodiment

of a diffuser unit, also suitable for installation from below into the ceiling grid shown in figure 5a, without requiring dismantling of the ceiling grid

Figure 6 is an isometric view of a diffuser plenum

unit in accordance with an embodiment;

Figure 7 is an isometric view of a diffuser plenum

unit in accordance with an alternative embodiment;

Figures 8a and 8b are isometric views of a diffuser

plenum unit in accordance with a further alternative

embodiment, including assembly of a spigot adaptor to a

connection box.

Detailed Description of the Embodiments

The embodiments, as described herein, relate

generally to an air diffuser assembly for ceiling

discharge with an air supply supplied from a duct.

For reasons of simplicity, the illustrations below

show the diffuser as a swirl diffuser with discharge

openings largely coincident with a plane that is

coincident with the diffuser discharge plane. It will be

appreciated by persons skilled in the art that the

diffuser need not be a swirl diffuser (for example, it may

be a four-way blow diffuser or multi-cone diffuser) and

discharge openings need not be coincident with a plane

(for example, they may lie on a curved surface) and that

they need not be coincident with the diffuser discharge

plane (which, for example, may be a perforated plate

further downstream).

For reasons of simplicity, connection ducts

(typically in the form of flexible ducts) and ceiling

panels are not shown.

While multiple figures show the diffuser unit

installed in a ceiling grid, it is to be understood that

the diffuser unit need not be installed in a ceiling grid.

It may, for example, be installed in a plaster board

ceiling, or it may not be installed in a ceiling at all

(for example, it may be freely suspended).

While reference is made to walls and top constructed

of rigid foam board, typically of 20 mm to 25 mm thickness

to achieve an R1 thermal insulation rating, it will be

appreciated that these thicknesses may differ from one

another, may be greater than or less than the 20 mm to 25

mm range, and may achieve a thermal insulation rating

other than R1. Furthermore, walls and top may be

constructed of a material other than rigid foam board, for

example these may be constructed of flexible foam sheets

or of sheet-metal.

While ceiling grid spacing of approximately 600 mm

square is referred to, as is typically used in many

commercial buildings, it will be appreciated that ceiling

grid spacing may be smaller or greater than this value,

and may not be square.

While reference is made to acoustic insulation being

attached to connection box walls and top (which acts as a

roof), it will be apparent that acoustic insulation could

be combined into a wall or top, and that the two elements

of wall and insulation, or of top and insulation, should

therefore, in each case, be taken as a single element.

It will be appreciated by persons skilled in the art

that numerous variations and/or modifications may be made

as shown in the specific embodiments without departing

from the spirit or scope of the description. The present

embodiments are, therefore, to be considered in all

respects as illustrative and not restrictive.

Figure la is a diagram illustrating a side cross

section view of a spigot adaptor 2 in accordance with an

embodiment, in which spigot adaptor 2 comprises adaptor

top 4dl, spigot wall 4c1, side-entry spigot 9 (to which a

duct, not shown, attaches to connect spigot adaptor 2 to

the cooling, heating or ventilation system) and perforated

baffle plate 10. Adaptor top 4dl and spigot wall 4cl may

be constructed of rigid foam board, typically of 20 mm to

25 mm thickness to achieve a thermal insulation rating of

R1. Thicknesses of up to 50 mm or of less than 20 mm may

be used to achieve a thermal insulation of up to R2, or of

less than R1, respectively.

Figure lb is a diagram illustrating a side cross

section view of connection box 1 connected by threaded rod

3, screwed into connection box threaded socket 3a, to

diffuser 6 (shown as a swirl diffuser). Connection box 1

comprises connection box top 4d, which acts as a roof,

substantially perpendicular to central-axis C0, rear wall

4a and two side walls 4b, all three of which are inclined

at acute angle a (typically between 150 and 350,

preferably between 200 and 30°, most preferably at

approximately 250) to central-axis C0, and front wall 4c,

which may be substantially parallel to central-axis C0,

all of which may be constructed of rigid foam board, which

typically has connection top thickness Ti and wall

thickness Ti' of 20 mm to 25 mm to achieve a thermal insulation rating of Ri, although thicknesses of up to 50 mm or of less than 20 may be used to achieve a thermal insulation of up to R2 or of less than Ri.

Attachment opening lic is bounded by edges 8 of side

walls 4b and connection box top 4d, as well as by front

ledge lib and top edge lib'.

Ledge lib and rear ledge 11a lie substantially on a

plane perpendicular to central-axis CO. Top edge lib' may

also lie on this plane. The portion of the connection box

that lies substantially above this plane is referred to as

top portion Tp, whereas that which lies substantially

below this plane is referred to as bottom portion Bp

(refer to figure 2b) and is flared.

The outer surfaces of connection box top 4d, rear

wall 4a and two side walls 4b, in particular in relation

to top portion Tp, lie substantially along the top and

three side planes of a four-sided truncated pyramid, with

sides inclined by angle a relative to a central-axis CO.

In relation to top portion Tp, attachment opening lic is

located proximate to the fourth side plane 4a' of the

truncated pyramid, and may lie substantially on the fourth

side plane 4a', or may be recessed by depth Ti'', thereby

defining the location of edges 8 of side walls 4b and

connection box top 4d.

In some embodiments, recess depth Ti'' is

substantially equal to acoustic insulation thickness T2',

especially if acoustic insulation thickness T2' is

substantial equal to wall thickness Ti' of rear wall 4a.

In some embodiments, wall thickness Ti' of rear wall

4a is less than the thickness of each side wall 4b, and acoustic insulation thickness T2' of acoustic insulation 5

on rear wall 4b is increased accordingly, providing

greater acoustic absorption, without increasing the

combined thickness of rear wall thickness Ti' and rear

wall acoustic insulation thickness T2', and without

reducing the combined thermal insulation rating of rear

wall 4a plus acoustic insulation 5 attached to rear wall

4a to less than the thermal insulation rating of side

walls 4b (typically rated at Ri), given that acoustic

insulation 5 also has thermally insulating properties

(albeit of a lower value, typically, then rigid foam board

of a similar thickness). In such embodiments, recess

thickness Ti'' may be less than acoustic insulation

thickness T2' of acoustic insulation 5 on rear wall 4a.

In an alternative embodiment, not shown, the acute

angle a of rear wall 4a and fourth side plane 4a' to

central-axis CO is different to the acute angle of side

walls 4b to central-axis CO.

Foam seal 7, fixedly attached to four wall edges of

bottom portion Bp in a plane substantially perpendicular

to central-axis CO seals connection box 1 to the rear of

face plate 6a of diffuser 6, which in turn is orientated

substantially perpendicular to central-axis CO.

In some embodiments (not shown), foam seal 7 is

fixedly attached to the rear of face plate 6a of diffuser

6. In some further embodiments (not shown), foam seal 7 is

not present.

Acoustic insulation 5 of insulation thicknesses T2

and T2' may be attached to all or part of the inner surfaces of connection box top 4d and rear wall 4a, respectively. Rear wall 4a is the most effective location upon which to attach acoustic insulation 5 as it is located directly opposite attachment opening 11c, from which noise generated by or transmitted through spigot 9 will be projected into connection box 1 and most powerfully onto rear wall 4a.

Figure 1c, which is a diagram illustrating the top

view of spigot adaptor 2 shown in figure la, additionally

shows adaptor side walls 4bl, which may also be

constructed of rigid foam board as described in figure la.

Side and top edges 8' of spigot adaptor 2 follow the same

profile as side and top edges 8, and wall underside

lb'' (figure la) follows the same profile as front ledge

lb and top edge lb' of front wall 4c (figures lb and

ld), to allow these to seal to one another when spigot

adaptor 2 is attached to connection box 1, as shown in

figures 3 and 4.

Figure 1d is a diagram illustrating a top view of

connection box 1 attached to diffuser 6.

Figures 2a and 2b are diagrams illustrating side

cross-section views of four connection boxes 1 stacked, as

well as of one connection box 1 suitably orientated to be

added to the stack. Foam seal 7 of each stacked connection

box 1 rests on front ledge lb and rear ledge 11a of

connection box 1 upon which it is stacked, cupping upper

portion Tu of the latter to be contained within connection

box 1 of the former. (In an alternative embodiment, not

shown, rear wall 4a and front wall 4c rest directly on

front ledge 11b and rear ledge 11a, respectively.) The

orientation of stacked connection boxes 1 alternates by

1800 such that rear wall 4a of each successive connection

box 1 is located proximate to the side and top edges 8 of

side walls 4b and top 4d of connection box 1 upon which it

is stacked, and, if present, acoustic insulation thickness

T2' of the former is substantially accommodated by recess

depth Ti'' of the latter.

Figures 3a and 3b, 3c and 3d, and 3e and 3f, are a

top view and a top cross-section view, a front view and a

side view, and a front cross-section view and a side

cross-section view, respectively, of a diffuser unit l'

comprising spigot adaptor 2 and connection box 1, which

together define a diffuser plenum unit, plus diffuser 6.

Diffuser unit l' has a profile height equal to connection

box height Hi, which would typically be of 200 mm to 400

mm height, preferably 250 mm to 350 mm, depending on the

application and airflow rate. Spigot 9 is shown

substantially "ovalised" to fit into the low profile

height of connection box height Hi. Such ovalisation may

substantially reduce the cross-sectional area of spigot 9

relative to the cross-sectional area of a round spigot of

equal perimeter, thereby resulting in an elevated velocity

of supply airstream 100 (figure 3f) which may cause noise

generation upon being deflected towards diffuser 6 by end

wall 4a (and insulation 5, if present) and the associated

high dynamic pressure may result in substantially

asymmetric discharge from diffuser 6. Perforated baffle

plate 10, which may be attached to adaptor 2, may spread

supply airstream 100, dispersing it across the full area

of perforated baffle plate 10, substantially reducing

airstream velocity into connection box 1 and dissipating

dynamic pressure to reduce noise and improve the discharge

pattern from diffuser 6.

Figures 4a and 4b are a front view and a side cross

section view of an alternative embodiment of diffuser unit

l' which may accommodate a spigot size or shape (for

example, round rather than ovalised) providing a larger

cross-sectional area than ovalised spigot 9 in figure 3f,

thereby being suitable for an increased airflow rate 100'

relative to airflow rate 100 through ovalised spigot 9 in

figure 3f. Additionally, airflow rate 100' may be achieved

at a reduced velocity, which may obviate the need for

perforated baffle plate 10 shown as part of spigot adaptor

2 in figures la, 3b, 3c and 3f, and is therefore not

included in the embodiment shown in figures 4a and 4b.

Figures 4a and 4b show an alternative embodiment of

diffuser unit 1', which may be preferable to a

conventional diffuser unit of the prior art comprising

four walls and top parallel and perpendicular,

respectively, to central-axis C0, and top at height H2.

Furthermore, diffuser unit l' may be preferable to a

tapered connection box of the prior art with connection

box height Hi and with spigot 9 located directly in a

tapered wall of the connection box (which may require

spigot 9 to be of a smaller size than could be

accommodated by the embodiment shown in figures 4a and

4b). By way of example, the embodiment of diffuser unit l'

shown in figures 4a and 4b may have diffuser unit height

H2 of 350 mm to 400 mm for substantially round spigot 9 of

approximate diameter 300 mm, suitable for an airflow rate

of up to approximately 200 L/s; or may have diffuser unit

height H2 of 400 mm to 450 mm for substantially round

spigot 9 of approximate diameter 350 mm suitable for an

airflow rate of up to approximately 300 L/s. These

respective diffuser unit heights H2 are substantially

greater than associated connection box heights Hi of 250 mm and 350 mm that would typically be suitable for up to

200 L/s and 300 L/s in an office application of NC30 to

NC35 sound pressure level, respectively. Connection box

heights Hi are reduced, relative to associated diffuser

unit heights H2, due to attachment opening lic (refer to

figures lb and ld) being substantially equal to or larger

than the cross-sectional area of spigot 9. A connection

box height Hi that is lower than diffuser unit height H2

and suitable for the required airflow rate may reduce

costs (storage and transport costs may be lower due to

decreased volume) and may overcome clashes with other

services on site (reduced connection box height Hi may fit

under a sprinkler pipe, cable tray or beam that diffuser

unit Height H2 is not able to fit under, and simply

rotating the diffuser unit about its central-axis CO may

achieve an orientation that does fit). Furthermore, a

common connection box 1 may be used for both small and

large airflow rates, rather than requiring connection

boxes of the prior art of differing connection box height

Hi, thereby reducing co-ordination issues on site.

Figure 5a is a diagram showing a top view of a

ceiling grid 13, which would typically have ceiling grid

central-axis spacing G1, typically, of approximately 600

mm, with diffuser unit l' being installed from below by

orientating it diagonally relative to the ceiling grid.

Diffuser unit l' fits into the footprint of ceiling grid

13, thereby allowing installation of diffuser unit l' from

below without the need to dismantle part of ceiling grid

13.

Figure 5b is a diagram showing a side view of the

alternative embodiment of diffuser unit l' described in

figure 4b, which may also be installed into ceiling grid

13 (typically with central-axis spacing Gl of approximately 600 mm) from below without the need to

dismantle part of the grid. Installation is achieved by,

for example, first inserting the top end 2' of diffuser

unit 1', oriented diagonally, in plan view, relative to

the ceiling grid. Installation of diffuser unit l' of high

diffuser unit height H2 is possible as a single unit,

without the need to dismantle part of the ceiling grid

13due to low connection box height Hi.

Figure 6 is an isometric view of an embodiment in

which diffuser plenum unit height H2 is greater than

connection box height Hi. Details not shown in figures 1

to 5 include mounting brackets 300, for suspension of the

diffuser plenum unit from above, as well as adaptor foam

seal 7', clip nipples 200 and clip arms 201.

Figure 7 is an isometric view of an embodiment in

which diffuser plenum unit height H2 is equal to

connection box height Hi. Details not shown in figures 1

to 5 include mounting brackets 300, for suspension of the

diffuser plenum unit from above, as well as adaptor foam

seal 7', clip nipples 200 and clip arms 201.

Figures 8a and 8b are isometric views of an

embodiment in which diffuser plenum unit height H2 is

equal to connection box height Hi, and in which spigot

size 9 is restricted (potentially leading to excessive

inlet velocity), thereby additionally being equipped with

perforated baffle plate 10 connected to spigot adaptor 2.

Details not shown in figures 1 to 5 include mounting

brackets 300, for suspension of the diffuser plenum unit

from above, as well as adaptor foam seal 7', clip nipples

200, clip sockets 202 and clip arms 201, for attachment of spigot adaptor 2 to connection box 1, as well as nipples

301 that insert into sockets 302 for alignment of spigot

adaptor 2 when attached to connection box 1.

Potentially Advantageous Features of the Embodiments

Described Herein

A diffuser unit in accordance with embodiments may be

constructed of light and low-cost rigid foam board.

By separating the spigot from the connection box, the

connection box may be configured substantially as a four

sided truncated pyramid that is stackable, reducing

storage and transport costs.

Each connection box has only three walls and a

substantially open side suitable for attachment of a

spigot adaptor. Different sized spigot adaptors may be

attached to the substantially open side, depending on the

duct size to be attached to the spigot. This increases

flexibility on site by allowing a common connection box

size to be used for a wide range of duct sizes and hence

airflow rates.

In order not to increase the height of stacked

connection boxes that include acoustically absorptive

material, such as polyester matting, the edges of the top

and side walls that define the substantially open side of

each connection box may be recessed to accommodate the

acoustically absorptive material of the connection box

that may be stacked on top. Connection boxes are stacked,

successively alternating 180 degrees with one another, so

that the acoustic insulation on the rear wall of one box

projects into the recessed edges of the open side of the

connection box upon which it is stacked. This allows

acoustic attenuation to be attached to the most

acoustically significant surface, viz. the wall directly

opposite the spigot (as the spigot, during use, projects sound onto this wall in particular) or if the wall opposite the spigot incorporates acoustic attenuation, this allows for this wall to be thickened, in each case increasing the attenuation provided without increasing the stack height for a given number of stacked connection boxes, or without reducing the number of connection boxes in a stack for a given stack height.

Stacked connection boxes do not get stuck in one

another, or get prised apart, as stack weight is not

transferred from one connection box to the next through

shear forces between inclined side walls acting on

respective connection boxes in the stack. Instead, each

stacked connection box (or the foam seal, if present, on

the underside of each stacked connection box) rests on

four ledges protruding from the connection box directly

beneath it, so that the inclined walls of successive

connection boxes do not transmit shear forces from one to

another.

A diffuser unit in accordance with embodiments may be

installed into a ceiling grid from below, without

requiring partial dismantling of the ceiling grid, even

for diffuser units suited to high airflow rates. This

facilities ease of installation and reduces costs.

A diffuser unit in accordance with embodiments may be

assembled on site by clipping a spigot attachment (which

may be connected to a flexible duct and which may be

located in the ceiling void) onto a connection box (which

may already have a diffuser attached). This provides a

quick and simple installation method whereby commonly

sized connection boxes (potentially with diffusers already

attached) may be clipped onto spigot attachments of different sizes that have been pre-installed and that may have been installed prior to the ceiling grid being ready for diffuser installation.

For diffusers located under restrictions (such as

structural beams, cable trays or sprinkler pipes) low

height connection boxes, even if connected to spigot

attachments of greater height, may reduce the risk of

clashes.

For highly restricted ceiling void heights, a spigot

attachment that has a highly ovalised spigot, and that may

be of reduced height (potentially as low as the height of

the connection box itself) may include a perforated baffle

plate that dissipates the higher velocity supply air in

the spigot into a lower velocity, broadly spread airstream

in the connection box, thereby reducing noise and

improving the discharge pattern from the diffuser.

It is to be understood that, if any prior art

publication is referred to herein, such reference does not

constitute an admission that the publication forms a part

of the common general knowledge in the art, in Australia

or any other country.

In the claims which follow and in the preceding

description, except where the context requires otherwise

due to express language or necessary implication, the word "comprise" or variations such as "comprises" or

"comprising" is used in an inclusive sense, i.e. to

specify the presence of the stated features but not to

preclude the presence or addition of further features in

various embodiments. Similarly, the word "device" is used

in a broad sense and is intended to cover the constituent parts provided as an integral whole as well as an instantiation where one or more of the constituent parts are provided separate to one another.

Claims (5)

1. A stackable diffuser plenum unit comprising a

housing, at least a top portion of the housing having a

shape of a truncated four-sided pyramid, the housing

defining an inner surface, the unit further comprising an

acoustic damper attached to the inner surface, wherein the

housing has a void formed therein and wherein the void is

shaped so that, when a first stackable plenum unit is

stacked on top of a second stackable plenum unit, the void

of the second unit accommodates at least a portion of the

acoustic damper of the first unit.

2. The stackable diffuser plenum unit according to

claim 1 wherein the acoustic damper is located on an inner

surface of the housing opposite the void, the void is

shaped to accommodate at least the portion of the damper

of the first unit when the first unit is stacked on top of

the second unit with an altered orientation, and wherein

the altered orientation is a rotation through 1800.

3. The stackable diffuser plenum unit according to

claim 1 or claim 2 wherein one or more edges of the

housing defining the void are recessed relative to a plane

defined by a side wall of the truncated four-sided

pyramid.

4. The stackable diffuser plenum unit according to

any preceding claim further comprising a ledge formed in a

bottom portion, wherein the ledge is configured to provide

a stop for a similar unit stacked onto the stackable

diffuser plenum unit.

5. The stackable diffuser plenum unit according to any preceding claim further comprising an adaptor fitted at a location corresponding to the void for connecting an air duct to the housing.