1 TITLE OF IN TION Air Duct TECHNICA IELD [0001] Thi i nation concerns blow moulded products and methods for making the same. BACKGROb [0002] In nu storey dwellings such as apartment blocks, exhaust air cannot be vented into roof space and nust be ducted across ceilings to reach wall vents. In this way range hoods and bathroom ex nators send air through ducts installed between floors. Ducts of this type are made of sheet steel. ,ints between sections of duct must be taped or other wise sealed. Steel is unsuitable at o ically tending to resonate too readily. The high thermal conductivity of steel leads to conc esttion and this is an unwelcome disadvantage where access for inspection and repair is rest ic eI as in wall and ceiling flow paths. SUMMARY 0FINVENTION [0003] The a paratus aspect of this invention provides a moulded air duct of elongated cross section capable I of installation in wall or ceiling space which duct comprises an effective quantity of flame retard t, having maleland/or female joins at the end. [0004] Mot lig by injection is feasible but blow moulded ducts are preferred in that acceptable u i nnity in wall thickness is achievable at lower cost. Wall thickness may be 2.00 3.00mm. T e citets may have male/female joins at the ends of the ducts which will allow sealant to fill the cle at alce between the overlapping parts. [0005] Ind vi lual ducts may be 1000-1500mu in length, but 1200mm is preferable. The duct may have a ma e join at one end, a female join at the opposite end and one or more joint sites at 2013-02-28,C:\Uers\Sharlene\Documads\SPECMICATIONSiscot.unnat.wpd, I -2 predetermined spacings. The joint site may be of enlarged section so that cutting the duct through the joint site generates a female join. The joint sites stiffen the duct. Further stiffening is made possible by the inclusion of tubular supports extending from opposite internal faces of the duct. These are created during the blow moulding operation. The sides of the duct may be curved, preferably semi-circular section. [0006] The ducts may be moulded from polyolefins such as polyethylene, preferably HDPE. Suitable flame retardants are that the flame retardants are halogenated aromatic flame retardants including tetrabromobisphenol A polycarbonate oligomer, polybromophenyl ether, brominated polystyrene, brominated BPA polyepoxide, brominated imides, brominated polycarbonate, poly (haloaryl acrylate), poly (haloaryl methacrylate), or mixtures thereof. Poly (haloaryl acrylate) is preferred with the most preferably being poly (pentabromobenzyl acrylate). PBB-PA has been known for some time and is a valuable flame retardant material useful in a number of synthetic resins. PBB-PA is prepared by the polymerisation of pentabromobenzyl acrylate ester (PBB MA). The PBB-PA polymeric flame retardant material is incorporated into the synthetic resin during processing to impart flame retardant characteristics. These are described in the literature. They are added to the moulded beads to make up 6-10% of the moulding mix. [0007] The ducts may be modified by moulding corner components which turn the flow path through 450 or 900. The ducts may be joined to ducts of both substantially square section and round section by an adapter. [0008] When one end is male and the opposite end is female the ducts join end to end. When the ducts have like ends an all male duct is joined to an all female duct to create a run. Alternatively a separate connector component is interposed between successive ducts. [0009] A ducting system using the components described above permits the installation of a cooling distribution circuit in the ceiling with wall supplied outlets just above floor level, together with underfloor heating distribution circuit with wall supplied outlets at any desired height. Accordingly the ducts run up and down walls and across ceilings within the existing structure bringing cooling, heating and ventilation.
-3 [0010] The method aspect of this invention provides a method of making a duct of elongated section by blow moulding a parison to form a duct which is closed at both ends with a joint site at one end and at least one other joint site intermediate the ends and removing both ends to create a male join at one end and a female join at the opposite end. [0011] The method may include the step of connecting the internal faces of the duct with a tubular support in the central area of the duct. Advantageous Effects of Invention [0012] 1. The components are easier to handle than metal components in that the formation of a chain is easier. [0013] 2. The components have poor thermal conductivity and therefore improve the thermal efficiency of the system and reduce condensation. [0014] 3. The finished duct work has better acoustic performance than metal duct work. [0015] 4. The ducts fit between studs in a stud wall. [0016] 5. Although the ducts provide an air path during a fire, the duct itself will not spread the fire through the building. BRIEF DESCRIPTION OF DRAWINGS [0017] Various embodiments of the invention are now described with reference to the accompanying drawings, in which: [0018] Figure 1 is a plan of a piece of duct. [0019] Figure 2 is an end view of the duct of Figure 1. 2012-05-02,H:\Specifications\scott.divisional3.wd3 -4 [0020] Figure 3 is a 450 corner component in the same plane. [0021] Figure 4 is a perspective of a 900 corner in a different plane. [0022] Figure 5 is a perspective of an adapter. [0023] Figure 6 is a side view of a moulding before conversion to a duct. [0024] Figure 7 is a section through part of a two storey building with in wall ducting. [0025] Figure 8 is a section through part of a single storey building with ducting in the roof space. [0026] Figure 9 is a perspective of a specialised air duct containing a butterfly valve. [0027] Figure 10 is a section through part of a multi-storey apartment building with an air duct in the suspended ceiling space. [0028] Figure 11 is a plan of a department with air ducts exhausting the outside air through the ceiling space. DESCRIPTION OF EMBODIMENTS [0029] Referring now to Figures 1 and 2, the duct is 1200mm long, 335mm wide and 60mm deep. End 2 is square and constitutes a male join 4. End 6 is also square and is enlarged in section to form a female join 8. The intermediate female joins 10 are equally spaced along the length of the duct. The three areas between joins are each stiffened by the formation, during moulding, of a tubular post 12 which extends from wall 14 to opposite wall 16. The junction 18 between the wall and the post is radiussed to reduce drag. 8% of poly pentabromobenzyl acrylate ester is dispersed in the mix at the moulding stage. [0030] In Figure 3 the corner component 20 turns the duct flow direction through 450 and can 2012-05-02,H:\Specifications\scott divisiona3wod,4 -5 be used with a second component to achieve a 900 change. One end has a male join 4. The opposite end has a female join 8. Again an intermediate female join 10 and a post 12 import the necessary stiffness and shape to become part of a chain of duct work. [0031] In Figure 4 a 90' bend component 22 is shown. [0032] In Figure 5 the adapter 24 has a neck 26 which takes the cross section of the male join into a box-section spigot 28 (170 x 100mm). [0033] Figure 6 shows a side view of the moulded duct precursor from which the 1200mm duct is cut. The ends 30 are excised. [0034] In Figure 7, a two storey dwelling has a suspended floor 32 and a ceiling fixed to ceiling joists 34. The timber frame 36 stands inside the outer brick veneer 38. The plasterboard lining is pierced to receive a duct outlet 40 which discharges air from duct run 42. Duct run 42 is turned through 90' by bend 22 and bend 22 is connected to adapter 24. Circular flexible pipe 44 is taped to the adapter. The opposite end of the pipe is taped to the outlet of a gas fuelled heater (not shown). The flattened section of the duct fits within the stud depth. Gaps in the floor plate allow the duct to reach the space under the floor. [0035] In Figure 8, the space heater 46 warms the air in the room 48 which is to be transferred to room 50 through ceiling vents 52 joined by the duct run 42. The ends of the ducts open into adapters 24 and flexible pipes 44 join the adapters to fan box 54. The fan box is concealed in cupboard 56. [0036] Duct runs also discharge room air outside the building. Regulations require that the duct contains a barrier to the reverse flow of air into the building so that for example prevailing winds will not drive unwanted air into the building. Figure 7 shows the valve component which forms part of the duct run for an extraction layout. The component is a blow moulding in polyethylene containing flame retardant as described above. The main tube 60 is 150mm in diameter and 440mm long. One end 62 is plain for the connection of flexible tubing and the opposite end 64 is enlarged and of capsule section being 135 x 220mm. Transverse branches 64 2012-05-02,H:\Specifications\scott divisional3 wpd,5 -6 are of circular section and likewise of 150mm diameter. The air barrier in the main tube is a gravity biassed circular plastic disc 66 mounted 30mm off centre. The main tube has two sites 68 where the wall thickening of the tube is increased. Both sites have a central point of weakness which is broken through in order to admit the axle 70 of the disc. [0037] The manner of use of the valve component is shown in Figures 10 and 11. [0038] Room 50 has a suspended ceiling 72 with a vent 52. Fan box 54 is fixed to the ceiling slab 74 as is the duct run 42. The valve component 60 is connected between the fan box input and the vent with the valve disc disposed to close when the fan stops. [0039] In Figure 11 the duct runs 42 are evident in plan extending from the cooler's extractor fan 76 to the outside vent 78 utilising corners 20. Valve component 66 utilises shaped end to connect to shower vent 52 via a flexible tube 44 and branch 54 to connect a toilet vent 52. [0040] It is to be understood that the word "comprising" as used throughout the specification is to be interpreted in its inclusive form, ie. use of the word "comprising" does not exclude the addition of other elements. [0041] It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. these modifications and/or additions are therefore considered to fall within the scope of the invention.