WO2016004522A1

WO2016004522A1 - A light-weight air duct for ventilation, air conditioning and heating for use in a vehicle and a method of manufacturing same

Info

Publication number: WO2016004522A1
Application number: PCT/CA2015/050579
Authority: WO
Inventors: Patrick BLAIS; Omar Khennache; Sacha CARRIER; Martin Bernier; Richard DARVEAU
Original assignee: Exo-S Inc.
Priority date: 2014-07-11
Filing date: 2015-06-23
Publication date: 2016-01-14
Also published as: CA2916612A1

Abstract

An air duct, for supplying air from an air conditioning / heating unit to a desired location in a vehicle, having at least one of the following characteristics: light-weight, high compressive strength, energy absorption, noise attenuation, insulation properties and combinations thereof. The air duct is formed by assembling a plurality of sections of an air duct into the desired air duct. At least one of the sections of the air duct is manufactured using pre-expanded foam beads in steam chest moulding. The air duct may exhibit other characteristics and may have other functions, due to the process of manufacture allowing for a lower density and thinner thickness limitations compared to current blow moulding processing of typical solid plastic air duct walls. The present air duct fabricated by the pre-expanded foam beads using steam chest moulding may be used for any ventilation duct in the automotive sector, such as, but not limited to, cooling brakes, cooling batteries, seat cooling/heating as well as any vehicle where light weight is desirable (e.g. plane, train, truck).

Description

TITLE

A LIGHT-WEIGHT AIR DUCT FOR VENTILATION, AIR CONDITIONING AND HEATING FOR USE IN A VEHICLE AND A METHOD OF MANUFACTURING SAME

FIELD OF THE DISCLOSURE AND BACKGROUND

Air ducts in vehicles such as automobiles are typically injection-moulded with talc-filled polypropylene or blow moulded with unfilled polyethylene. The prior art air ducts are typically made of solid plastic walls with a thickness of between ] .0 to 2.0 mm. However, in order to achieve higher fuel economy for vehicles, weight reduction of such plastic parts is desirable.

Recently, a few processes to manufacture light-weight air ducts for the automotive industry have appeared on the market. Some are: foaming blow-moulding [US Patent #US 8,448,671 B2] of a mixed resin which includes such polymers as a polypropylene-based resin for foaming and styrene-bascd thermo-plastic elastomers; twin sheet foam thermoforming and felt compression processing (compression moulding, or the like). The industry is continually working to lower the material density and to reduce wall thickness of air ducts to reduce air duct weight There is therefore a need for an air duct that combines weight reduction, preferably >50% weight reduction compared to prior art air ducts, improved structural strength and at an acceptable cost.

Automotive manufacturers look for many characteristics and specifications in an air duct Some are mandatory to meet automotive safety requirements such as, but not limited to, chemical resistance, heat resistance, whereas others are preferred such as, but not limited to, acoustic attenuation and insulation of the air duct and acceptable cost of manufacturing the air duct.

Methods to manufacture articles of polypropylene resin pre -expanded foam beads are known in the art Steam chest moulding is a prior art process used to manufacture light weight plastic parts. In some instances, expanded foam beads are injected into a custom designed steam chest mould, where individual beads are fused together under steam, heat and pressure. When released from the mould, the solid moulded object has features as per the custom designed steam chest mould to serve the desired application.

Other moulding methods for particles or beads made of various plastics capable of melting at low temperature are known. For example, particle moulding processing has been used to form automobile vehicles passenger seats (from expanded polypropylene beads), spare tire trays and tool boxes in a vehicle trunk, sun visors, as well as vehicle bumper energy absorbing systems that include moulded foam and at least one integral reinforcing member. Typically, in the prior art, all are examples of parts designed and fabricated in single pieces. There is therefore also a need for a method allowing for the design, the fabrication and the assembly of the formed air duct sections of polypropylene resin pre-expanded foam beads via steam chest moulding to form an air duct.

Finally, there is a need for a light weight air duct that is mechanically resistant (having good structural strength), and which exhibits improved acoustic attenuation and insulation properties, while keeping the cost of the duct at an acceptable level.

SUMMARY According to one aspect, there is provided a method of fabricating a part for use in an air duct, formed of pre-expanded foam beads, preferably an air duct part, preferably for a vehicle, more preferably for an automotive vehicle, said method comprising the steps of:

i) injecting pre-expanded foam beads into at least one mould having a shape of a part for use in an air duct; preferably an air duct section part;

ii) injecting steam into the at least one mould for a period of time sufficient for the prc- cxpanded foam beads to partially melt and fuse together;

iii) cooling the at least one mould; preferably by allowing said at least one mould to cool; more preferably by introducing cooling to said at least mould; and

iv) removing the part from said at least one mould.

In one embodiment, said pre-expanded foam beads enter in direct contact with at least one mould surface, preferably a plurality of mould surfaces of the at least one mould and melt during said step of injecting steam into the at least one mould, forming at least one part wall and wall surface, preferably one air duct part wall surface, on each of said at least one mould surface, preferably on each of said mould surfaces, preferably said air duct part wall surface is a thin layer of plastic, preferably with air gaps between said pre-expanded foam beads forming said wall surfaces. In one embodiment said formed wall surfaces are substantially air tight In another embodiment said formed wall surfaces are substantially non-porous. In another embodiment, said formed wall surfaces are substantially porous. In another embodiment, said pre-expanded loam beads are selected from a group consisting of expanded polypropylene, expanded polyethylene, expanded polystyrene, expanded thermoplastic urethane and combinations thereof. In another embodiment, prior to said injecting steam, each of said pre-expanded foam beads is of a particle size with an average diameter range between about 1.5 mm and about 8 mm.

In another embodiment, each of said pre-expanded foam beads has a spherical diameter between about 1.5 mm and about 6 mm, prior to step ii.

In another embodiment, each of said pre-expanded foam beads has a spherical diameter between about 6 mm and about 8 mm, prior to step ii.

In another embodiment, each of said pre-expanded foam beads has a non-spherical diameter between about 1.5 mm and about 8mm, prior to said step ii, and said pre-expanded foam beads comprise non-spherical shapes.

In another embodiment, each of said pre-expanded foam beads may be of a shape including spherical, ellipsoidal, cylindrical, rectangular, cubic, other polyhedral shapes, irregular shapes and combinations thereof.

In another embodiment, each of said pre-expanded foam beads has an average density, prior to said injecting step of said pre-expanded foam beads into at least one mould, between about 1 pound per cubic feet to about 12 pounds per cubic feet.

In another embodiment, said at least one wall of the air duct has a thickness of at least about 0.6 mm.

According to another aspect, there is provided an air duct assembly method whereas at least one of said air duct parts described herein, made by steam chest moulding, is fastened together with at least another air duct part, preferably made by steam chest moulding, forming an air duct, preferably fastened together forming an air duct with at least one substantially air tight wall, more preferably forming an air duct with substantially air tight walls. In another embodiment, forming an air duct with at least one porous wall, preferably a plurality of porous walls. In one embodiment, said air duct parts are fastened together by a fastening method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, brackets, screwing, bolting and combinations thereof.

In one embodiment the produced air duct may serve for at least one of:

i) a ventilation, heating, cooling (air-conditioning) system and combinations thereof, for a vehicle cabin;

ii) cooling batteries;

iii) cooling brakes; and

iv) an air induction system of a vehicle, such as an automotive vehicle, a truck, a train, a bus, a recreational vehicle and an airplane.

According to yet another embodiment, there is provided an air duct assembly method, said method comprising fastening together at least one section of an air duct manufactured as described herein to at least another section of an air duct forming an air duct with a substantially air-tight wall, using a fastening method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof.

According to yet another embodiment, mere is provided an air duct assembly method, said method comprising fastening together at least one section of an air duct manufactured as described herein using porous pre-expanded foam beads, resulting in an air duct section with a porous wall, to another air duct section forming an air duct, using a fastening method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof.

According to yet another aspect, there is provided an air duct part, whenever produced by the method described herein.

According to yet another aspect, mere is provided an air duct, whenever produced by the method described herein.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 depicts the manufacturing process flow chart of the fabrication of a section of an air duct according to one embodiment. Figure 2 depicts two sections of an air duct according to Example 1 which is according to an embodiment, comprising a lower section and an upper section of an air duct moulded separately. Figure 3 depicts the air duct sections of Figure 2, after assembly of the lower section with the upper section of an air duct and installation of additional components and their specific location.

Figure 4 depicts two sections of an air duct according to Example 2 which is according to an embodiment, comprising a lower section and an upper section of an air duct which are moulded separately.

Figure 5 depicts the air duct of Figure 4, after assembly of the lower section with the upper section of an air duct. Figure 6 depicts two sections of an air duct according to Example 3 with components according to an embodiment, comprising a lower section and an upper section of an air duct which are moulded separately.

Figure 7 depicts the air duct of Figure 6, after assembly of the lower section with the upper section of an air duct and installation of additional components.

Figure 8 depicts two sections of an air duct of Example 4 with components according to an embodiment, comprising a lower section and an upper section of an air duct which are moulded separately, whereas the lower section further includes a protrusion to assist in the positioning of the air duct correctly in a vehicle and reducing, preferably removing the need of polyurethane insulation shims.

Figure 9 depicts the air duct of Figure 8, after assembly of the lower section with the upper section of an air duct

Figure 10 depicts two sections of an air duct of Example 5 with components according to an embodiment, comprising a lower section and an upper section of an air duct which are moulded separately. Figure 11 depicts the air duct of Figure 10, after assembly of the lower section with the upper section of an air duct.

Figure 12 depicts the air duct of Figure 11, with additional air ducts to bring air from the air conditioning/heating unit to the car passenger cabin through the instrument paneL

Figure 13 depicts the push pin of Figures 2, 3, 6 & 7.

Figure 14 depicts the transmission loss chart of Example 1.

DETAILED DESCRIPTION

Referring now to Figure 1, there is illustrated a process flow diagram of a manufacturing sequence used to produce at least one section of an air duct in accordance with one embodiment further described in the detailed description herein.

The purpose of this manufacturing sequence is to produce, by steam chest moulding, at least section of a desired air duct and then, assemble air duct sections together to form an air duct.

In one embodiment, the nianu&cturing sequence comprises the steps of. (1) pre-closing the mould cavity; (2) filling the mould cavity with the pre-expanded foam beads as described hereunder, (3) completely closing the mould cavity; (4) introducing steam, preferably pulsing steam into the mould cavity to melt and fuse the beads together; (5) cooling, preferably by pulsing a cooling mist into the mould cavity, preferably directly among the melted and fused beads; (6) opening the mould and; (7) and removing the melted and fused beads shaped in a section of an air duct from the mould cavity.

In some embodiments, at least one section of an air duct made by steps 1 to 7 above, is assembled together in a subsequent step (8) with another section of an air duct forming an air duct which includes a channel allowing air to move from an inlet of die air duct, through the channel of the air duct and out through the outlet of the air duct

According to one embodiment, the moulding system used herein is a steam chest moulding system. A steam chest moulding system comprises a shape moulding machine, a steam boiler and accumulator, a water cooling chiller and a compressed air accumulator. Such systems are widely available in the plastics industry. The present description is illustrative in manner and is to be understood that die terminology used herein is intended to be illustrative rather than in a limiting sense.

The shape moulding machine comprises a mould (preferably made of metal) comprising at least two mould parts (or two mould cavities) (one of the two mould parts is also called the movable cavity side and the other mould part is called the stationary cavity side); the interior surfaces of each mould have at least one core vent, preferably a plurality of core vents; at least one steam nozzle, preferably a plurality of steam nozzles; at least one rilling injector, preferably a plurality of filling injectors; and at least one ejector, preferably a plurality of ejectors mounted on a back plate in a manner as will be apparent to a person skilled in the art Each of such cavities may have a plurality of removable cores to allow opening of the mould and removal of the moulded section of the air duct upon completion of the steam chest injection mould process. Some sections of the air duct may be manufactured using a single mould having a plurality of cavities. For example, the upper and lower section of an air duct may be moulded side by side in a dual- cavity mould.

The shape of an air duct section is designed as per steam chest moulding specifications (one preferred process limitation is the draft angle) and vehicle specifications (location, spacing, routing, technical specifications), to form an air duct To be able to form the final air duct, at least two sections of an air duct, preferably multi-sections of air duct parts are typically required to be assembled together. In some embodiments, the air duct section has a wall thickness in the range of from about 2 mm to about 80 mm. In one embodiment, each section of the air duct has a wall thickness of 6 mm. In a preferred embodiment, the air duct section has a wall thickness of at least 0.6 mm based on the size of the beads used, although thinner walls arc possible if smaller beads are used.

Design of the air duct may include an improvement to wail stiffness (ribs, thickness), increased insulation characteristics (extra wall thickness) or other wanted characteristics in a vehicle (weight reduction, increased energy absorption, sealing between two air ducts). The design may also include features such as at least one quarter wave resonator or the like, at least one Helmholtz resonator or the like, and at least one smooth radius to reduce air turbulence throughout the air duct, such as a smooth radius at an elbow (or a plurality thereof) or the like to improve acoustic properties of the air duct. The design may also be selected according to the surrounding environment of the at least one selected area of die air duct and/or to accommodate other components, such as wires, metal brackets, or the like. Installation tabs and mounting holes may also be designed in the wall of the air duct section to facilitate installation of the air duct. A tab may be moulded into the wall structure of the air duct section or may be added after the moulding operation with a method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screws, bolts and combinations thereof. When the tab is added after the moulding operation, the tab may be made of metal, plastic and combinations thereof, although any suitable material may be used. Mounting holes on the air duct are preferred to be of sufficient diameter to facilitate push-pin installation. Preferably the material surrounding the mounting hole is sufficient to reduce any tearing proximate the mounting hole.

Referring still to Figure 1, one example of the preferred embodiment comprises the following steps: The first step is to partially close the mould. In this embodiment, the mould has a "telescope" built into it. Telescope is a term known to a person of ordinary skill in the art of steam chest moulding and is an extra metal depth that has zero and/or proximate zero degrees of draft, at all parting line surfaces. It is typically around 25mm deep. This will allow the mould to be opened upon the initial filling step.

In one embodiment, a reinforcement insert may be pre -installed in the mould cavity in either the movable cavity or stationary cavity or both. The insert may be made of any suitable material preferably metal or plastic, or both. Installing the insert in the mould before the injection step creates a mechanical and chemical bond between the insert and the pre-expanded foam beads as an integrated final piece. In one embodiment, the reinforcement insert serves to increase the stiffness of installation points of the air duct part

In the second step, pre-expanded foam beads are injected into the mould. Due to the telescope formed in the mould, extra foam beads are injected into the mould tool The pre-expanded foam beads may have a density from about 1 pound per cubic foot to about 15 pounds per cubic foot prior to the injecting step, preferably from about 1 to 12 pounds per cubic foot. In general, a lower density of the pre-expanded foam beads results in a lower density of the air duct section moulded from the beads. Filling injectors supply pressurized pre-expanded foam beads from a filling tank into the mould cavity. Filling of the mould cavity occurs because of a pressure gradient between the filling device and the interior of the mould itself, the latter being at a lower pressure then the filling injector pressure. The pressure within the mould cavity is increased by filling the cavhy with beads, but may also be increased by closing the mould over the beads (next step). Both methods allow a certain control over the density of the moulding material and allow for an increase in the strength (such as stiffness).

The pre-expanded foam beads used in steam chest moulding may have a large range of shapes including spherical, ellipsoidal, cylindrical, rectangular, cubic, other polyhedral shapes as well as irregular or other shapes. The pre-expanded foam beads may have imperfections and irregularities, such as dents, bumps, imperfectly aligned edges, corners or sides, and so forth. When non-spherical pre-expanded foam beads are used, for example ellipsoidal beads, the largest major diameter of a cross-section taken perpendicular to the longitudinal axis of the ellipsoid is defined as the diameter of the pre-expanded foam beads. In a preferred embodiment particular preference is given to beads of a spherical shape.

Each of the pre-expanded foam beads may have a diameter of from about 1.5 mm to about 8 mm, preferably from about 3 mm to about 6 mm. Each of the pre-expanded foam beads preferably have a compact outer skin. Here, reference to a compact outer skin means that the foam cells in the outer region of each of the pre-expanded foam beads are smaller than those in the interior region. Particular preference is given to the outer region of the pre-expanded foam beads having no pores, which will result in a substantially non-porous air duct section. In an alternative embodiment, a porous air duct section is achieved by using pre-expanded porous beads as raw material and by controlling the moulding parameters, such as the steam pressure and temperature of the mould, in order to avoid complete melting of the beads. In such embodiments, a portion of air may pass through the wall of the resulting air duct section. Such a porous air duct may be desirable in some applications, including, for example, but not limited to, noise control.

In one embodiment, said pre-expanded foam beads are selected from a group consisting of expanded polypropylene, expanded polyethylene, expanded polystyrene, expanded thermoplastic urethane and combinations thereof. In one embodiment, said pre-expanded foam beads may be closed cell, porous or combinations thereof. In the third step, the mould is fully "closed" such that the partition lines touch together on the pre-expanded foam beads. This is called "crack fill" and is one of two main pie-expanded foam beads moulding techniques known in the industry. The hydraulics of a moulding press, or the like is used to compress the pre-expanded foam beads during the fill stage to enhance final shape and performance. Once the mould is closed a locking pin may be inserted to keep the mould closed.

The pre-expanded foam beads density may have increased during the crack fill step and the final section of an air duct resulting may preferably have a density of from about 1 pound per cubic foot to about 15 pounds per cubic foot after injection step, most preferably from about I pound per cubic foot to about 12 pounds per cubic foot. However, a resultant higher density may also be possible. In general, the density of the final moulded air duct section increases during this step compared to the density of the pre-expanded foam beads previously introduced into the air duct section mould.

In one embodiment, a thinner wall thickness may be obtained by compressing and heating the desired areas during this step. The density of the desired areas may increase as high as 30 pounds per cubic foot. However, the maximum density that may be achieved is a function of the density of the starting material as understood by a person of ordinary skill

In one embodiment, an aesthetic wall surface may be obtained by compressing and heating the desired areas during this step. The resulting wall surface may have a substantially smooth surface on the outer skin, or may have a desired textured surface.

In the fourth step, steam, preferably superheated steam, is introduced under pressure into the mould via a steam nozzle, for a suitable period of time allowing for fusion of the particle foam beads. The particle foam beads are then fused in the mould with the help of the steam. Steam, in this embodiment, is water steam heated to temperatures higher than 100 Celsius at a pressure which may reach 60 pounds per square inch. When the fusing temperature is reached locally, the particle foam beads are fused together.

After the fusing step, in the fifth step, the mould is cooled, allowing for cooling and hardening of the moulded air duct section. Once cooled to achieve sufficient mechanical rigidity for subsequent handling, the moulded air duct section is removed from the mould cavity by opening the mould. The mould cooling method may be by spraying a suitable coolant, in one embodiment the coolant is -water, through nozzles onto the backside of the cavity of the mould. In another embodiment, the mould is allowed to cool naturally over time (such as by air- cooling).

In the sixth step, the mould is opened so as to create enough space between the two cavities, movable and stationary, allowing removal of the air duct section from the mould.

In the seventh step, the moulded air duct section is removed, or de-moulded, from the mould with the help of ejectors. A suitable draft angle previously incorporated into the design of the mould and air duct ensures an easy ejection phase. Ejection can be done by using one or a plurality of ejections pins (ejectors) or other suitable ejection methods as understood by a person of ordinary skill. In the eighth step (optional), at least one of said sections of an air duct described herein is fastened to another section of an air duct to form an air duct, preferably an air-tight air duct. In one embodiment, said fastening method is selected from the group consisting of pressure- snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof.

In a preferred embodiment, infrared welding may be used for fastening one section to another section. Infrared welding is the process of joining plastic components with the use of electric quartz glass infrared emitters known to persons of ordinary skill in the art. With the two sections in place, the emitters allow for the joint surfaces of each section to be heated above the melting point of the pre-expanded foam beads and after removing the emitters, both sections of the air duct, are squeezed together for a sufficient period of time allowing for the joint surfaces of the two sections to fuse together.

Preliminary testing has shown air ducts fabricated by some embodiments herein exhibit at least one, preferably a plurality of:

a. Reduced weight of final product when using pre-expanded foam beads described herein in comparison to the prior art solid and soft blow moulded foam; in some cases resulting in a weight reduction of up to 80%; b. Increased thermal insulation properties when using pre-expanded foam beads described herein when compared to the prior art solid and soft blow moulded foam; c. Increased audio insulation properties, also known as noise attenuation properties, when using pre-expanded foam beads described herein when compared to the prior art solid and soft blow moulded foam. In some cases noise attenuation levels are improved in comparison to the prior art (for example, as measured by ASTM E2611); d. Achieve or surpass common requirements for automotive air ducts, such as, but not limited to, heat resistance, chemical resistance and odours; c. 100% recyclable; f. Withstand multiple impacts without substantial damage; and/or g. Strong enough to bear structural support for other surrounding parts.

The air duct described herein may serve for the ventilation, heating and cooling (air- conditioning) system of automotive vehicles as well as other vehicles (e.g. truck, train, bus, recreational vehicles, airplanes, etc.). One advantage of such an air duct is its relative lightness compared to solid plastic air ducts of similar dimension of the prior art Furthermore, the random fusing of the pre-expanded foam beads within the walls of the air duct make the duct sufficiently rigid and suitable for automotive applications where loading, vibration and temperature changes are likely to happen. An example of such loading is when a passenger of an automotive vehicle places their feet on the top surface or extremity of an air duct in the vehicle. Other examples include having the air duct supporting fully or partially the weight of other components typically used in vehicles.

EXAMPLE 1

Referring now to Figures 2 and 3, the air duct (20) in this preferred embodiment has the function to bring the air from the HVAC front module to the knees of the second row passenger through the central console of an automobile. The walls have a thickness of about 5 mm (compared to the prior art conventional solid duct wall thickness of 1.5 mm). Without compromising the required inner surface area of a conventional solid duct, the extra space needed for the wall thickness is taken by increasing the outside dimensions of the air duct part while keeping the same inner surface area and the CFM needed. The air duct is designed in two sections of an air duct, lower (21) and upper (22), and the joining line (25) is located on the two opposite corners of the air duct sections to maximize the perpendicular moulding surface of the mould opening. An open cell foam strip (23) of very low density is attached with conventional adhesive to the outer side of the inlet air duct region (23'). The open cell foam strip (23) reduces any air leaking proximate the inlet air duct region (23') after assembling the air duct to the HVAC module (not shown).

A push-pin (24) is installed through an oval opening in the lower side of the inlet This push-pin has an extra length shoulder (best seen in Figure 13) to accommodate the extra wall thickness of the present air duct versus a conventional solid duct. This push-pin (24) secures the air duct in place inside the vehicle.

In one preferred embodiment, an air duct (20) for the automotive industry is fabricated, using pre-expanded polypropylene (ePP) in steam chest moulding as described above. More specifically, in this embodiment, two cavities in a mould, one cavity corresponding to a lower section (21) and another cavity corresponding to an upper section (22) of an air duct. Such mould allowing removal of a moulded air duct section from the cavity once the entire steam chest injection mould process is completed. As will be apparent to a person skilled in the art, each of such cavities may have a plurality of removable parts to allow opening of the mould and removal of the moulded air duct section upon completion of the steam chest injection mould process. One non-limiting example of commercially available pre-expanded foam beads suitable for making a section of an air duct is Ncopolen P - D-0040B™ which is available from Concepp Technologies Inc. The pre-expanded foam beads have a diameter between about 3 and about 6 mm. In this example, the density of the pre-expanded polypropylene foam beads prior to the injection step is about 5 pounds per cubic foot.

The final density after completion of the steam chest moulding process may be between about 5 and about 12 pounds per cubic foot. In one embodiment, the resulting air duct section had a final density of 6 pounds per cubic foot. In a preferred embodiment, to obtain a strong welding joint of the two sections of an air duct (21, 22) in pre -expanded polypropylene bead, infrared emitters are used to form a joint such that die infrared emitters power is set between 60 to 90% of its maximum power to allow for a surface temperature of the joining edges (25) of each section (21, 22) of at least 250°F but not higher than 350°F. The time needed to reach this range of temperature is less than 7 seconds. Once mis temperature range is achieved, both joining edges (25) are quickly squeeze together, with a small overlap (in one embodiment less than 1 mm of overlap) of the joining edges, creating a compressing force for as long as needed to obtain a joint. The joint is then cooled. In this embodiment, cooling time is in the range of 10 sec to 30 sec. The air duct made by Example 1 weighs about 93 g (contrasted to 334 g for an air duct manufactured from conventional blow moulding process with solid walls). In mis instance, a weight reduction of 72% was achieved. Typical industry testing (combustion behavior, mildew growth, odors characteristic, temperature and chemical resistance) passed successfully. Thermal conductivity of HDPE is normally between 0.46 to 0.51 W/(m.K) (0.39- 0.44 Kcal/m.hr.C). Thermal conductivity of ePP (PP pre-expanded foam beads) is around 0.042 Kcal/m.hr.C. It is expected that the temperature delta between the outlet and the inlet of an air duct may be smaller for an air duct made with ePP (PP pre-expanded foam beads) when compared to the same air duct made of solid HPDE. Condensation issues on the air duct wall may be less and passenger ambient air comfort may be improved with an ePP air duct versus an HDPE air duct. Testing showed that temperature loss when hot air was passed through the air duct was smaller with the present air duct versus an air duct made by the typical material used in the conventional duct fabrication. Transmission loss was tested on this air duct example per the ASTM E2611. Results show a better transmission loss (TL) in a range of 100 to 4100 HZ at the outlet of an air duct made with ePP (PP pre-expanded foam beads) in steam chest moulding when compared to the same air duct made by blow moulding HDPE solid (best seen in Figure 14). EXAMPLE 2

Referring now to Figures 4 and 5, the air duct (40) in this example has the function to bring the air from the second HVAC rear module to the roof duct of a vehicle such as a van or another large automotive vehicle. The walls have a thickness of about 5 mm (an increase of about 3.S mm wall thickness compared to a conventional solid duct). Without compromising the required inner surface area of a conventional solid duct, the extra space needed for the wall thickness is taken by increasing the outside dimensions of the air duct part while keeping the same inner surface area and the CFM needed. The air duct (40) is designed in two sections of an air duct, lower (41) and upper (42), and the joining line (44) maximizes the perpendicular moulding surface of the mould opening. This helps to obtain a S mm wall thickness on all walls of the air duct manufactured with a telescope mould. In this example, an air duct (40) for the automotive industry is fabricated, using porous pre- expanded polypropylene (ePP) foam beads using steam chest moulding. More specifically, in this embodiment, two cavities in a mould, one cavity corresponding to the lower section (41) and the other cavity corresponding to the upper section (42) of an air duct. Such mould allows for the removal of a moulded air duct section from the cavity once the entire injection process is completed. As will be apparent to a person skilled in the art, each of such cavities may have a plurality of removable parts to allow opening of the mould and removal of the moulded air duct section upon completion of the injection mould process.

In this example, pre-expanded polypropylene foam beads (ePP) have a diameter between about 3 mm and about 6 mm and the density, prior to injection, is about 3 pounds per cubic foot.

In this example, lower section (41) and upper section (42) of an air duct are assembled together using Injectiweld Drader™ plastic welding adding more weight than IR welding or hot glue.

The air duct made by this example weighs about 85 g (contrasted to 250 g for an air duct manufactured from conventional blow moulding process with solid walls). The weight reduction is 66% in this case.

EXAMPLE 3

Referring now to Figures 6 and 7, the air duct in this example (60) functions to bring the air from the HVAC front module to the feet of a passenger in the front area of a vehicle. The walls have a thickness between about 4 mm and about 8 mm. This is an average increase of 4.0 mm compared to the conventional prior art solid air duct. Without compromising the required inner surface area of a conventional solid duct, the extra space needed for the wall thickness is taken by increasing the outside dimensions of the air duct part while keeping the same inner surface area and the CFM needed. The air duct is designed in two sections, a lower section (61) and a upper section (62). In this example, the upper section (62) is a 'U' shape and the lower section (61) of an air duct is of a shape to accommodate the upper section and the shape of the location in the vehicle where the duct will be installed.

The visible side (63) of the lower section (61) also has an aesthetic appealing surface and replaces the hush panel (not shown). Lower section (61) of an air duct has at least one calibration hole (65) to diffuse air to the passenger feet Usually, polyurethane foam is installed on the prior art solid hush panel. Due to the properties and low density of the pre-expanded polypropylene (ePP), polyure thane foam is not mandatory in this design.

Push-pins (64) are installed through hole openings (64') in the lower section (61). Push-pins (64) have an extra length shoulder to accommodate the extra wall thickness versus the conventional solid duct The push-pins serve to secure the assembled air duct (Figure 7) in place inside the vehicle.

In this example, an air duct (60) for the automotive industry is fabricated, using pre-expanded polypropylene (ePP) via steam chest moulding as described herein. More specifically, in this embodiment, two cavities in a mould, each cavity corresponding to the lower section (61) and the upper section (62) of an air duct. Such that said mould allows removal of a moulded air duct section from the cavity once the entire injection process is completed. As will be apparent to a person skilled in the art, each of such cavities may have a plurality of removable parts to allow opening of the mould and removal of the moulded air duct section upon completion of the injection mould process.

In this example, an aesthetically appealing surface is obtained by compressing and heating the outer surface areas (63) during this injection and cooling step. The resulting wall having a substantially smooth surface on the outer skin. In an another embodiment, texture may be applied to the outer surface with the same method.

In this example, pre-expanded polypropylene foam beads have a diameter between about 3 mm and about 6 mm and the density, prior to injection, is about S pounds per cubic foot

In this example, lower section (61) and upper section (62) of an air duct are assembled together using hot glue applied along the joining line (65') to allow the lower section (61) and upper section (62) to be joined together, forming an air duct. The air duct of this example weighs about 93 g (contrasted to 220 g for an air duct manufactured from conventional blow moulding process with solid walls). The weight reduction is 58% in this case. The energy absorption of the air duct made of pre-expanded polypropylene beads by the process disclosed herein may exhibit a distinct advantage in case of a collision or impact In particular, the air duct may serve to reduce any impact to the knees of a passenger in a vehicle. EXAMPLE 4

Referring now to Figures 8 and 9, the air duct (80) in this example functions to bring the air from the HVAC front module to the second row area of a vehicle proximate the knees of the second row passenger, through the central console of an automobile. The walls have a thickness of about 5 mm. This is an increase of 4.0 mm compared to the conventional prior art solid duct Without compromising the required inner surface area of a conventional solid duct, the extra space needed for the wall thickness is taken by increasing the outside dimensions of the air duct part while keeping the same inner surface area and the CFM needed. The air duct is design in two sections of an air duct, lower (81) and upper (82). In this instance, each of the lower (81) and upper (82) sections are 'W' in shape to assemble 2 walls face-to-face in an effective way while increasing the length of the joining line while maintaining good shape for moulding.

The design also included a protrusion (83) to replace polyurethane foam (PUR) used in conventional air ducts of the prior art The protrusion (83) has two functions: (i) to level the car floor under the air duct, and (ii) to improve thermal insulation to reduce, preferably prevent, condensation on the duct.

In this example, an air duct (80) for the automotive industry is fabricated, using pre-expanded polypropylene (ePP) via steam chest moulding as described herein. More specifically, in this embodiment, two cavities are used in a mould, each cavity corresponding to the lower section (81) and the upper section (82) of an air duct such that said mould allows for the removal of a moulded air duct section from the cavity once the entire steam chest injection process is completed. As will be apparent to a person skilled in the art, each of such cavities may have a plurality of removable parts to allow opening of the mould and removal of the moulded air duct section upon completion of the steam chest injection mould process.

In the example, pre-expanded polypropylene foam beads have a diameter of between about 3 mm and about 6 mm and the density, prior to injection, is about 5 pounds per cubic feet In this example, the lower section (81) and upper section (82) of the air duct are assembled together using adhesive (such as hot glue) applied along the joining lines (84) allowing the lower (81) and upper (82) sections to be joined together. The air duct thereby made weighs about 190 g (contrasted to 271 g for an air duct manufactured from conventional blow moulding process with solid walls and with polyurethane foam). Weight reduction is 30% in this case.

Another benefit is also observed during installation of the air duct of this example in a vehicle; only one installation step is needed instead of two. Previously, car manufacturers would install PUR foam first and the air duct over the PUR foam. With the integral protrusion, the duct made with this design may be installed without the PUR foam.

The structural strength property of the pre-expanded polypropylene was demonstrated in this example. The protrusion (83) of the lower section of the air duct is capable of handling loads with little loss in form or shape.

EXAMPLE 5

Referring now to Figures 10, 11 and 12, the air duct in this example (100) functions to bring the air from the HVAC front module to multi conventional air ducts in the instrument panel of an automobile. The walls of 100 have a general thickness of 5 mm but may be more or less in some specific areas. This is a general increase of 4mm compared to the prior art solid air duct Without compromising the required inner surface area of a conventional solid duct, the extra space needed for the wall thickness is taken by increasing the outside dimensions of the air duct part while keeping the same inner surface area and the CFM needed. The air duct (100) is design in two sections, a lower section (101) and a upper section (102). Lower section (101) has a 'U' shape and the upper section (102) is more flat Both sections of an air duct were assembled face- to-face to form an air duct The air duct (100) is designed to direct the air from the HVAC unit to the front windshield defroster duct (110), passenger side window heating duct (111), driver side window heating duct (116), A.C. cross car duct right wing (112), A.C. cross car duct left wing (115), central A.C. right duct (113) and central A.C. right duct (114). In this example, 110 to 116 are conventional solid air ducts showing that the overall duct assembly may be a combination of conventional solid air ducts and an air duct made as described in the present disclosure. Lower section (101) may incorporate a resonance chamber to absorb noise corning from the air blower.

Upper section (102) includes a groove or channel (103) to direct and maintain at least one wire, reducing or eliminating the need of a retaining clip typically used in the prior art to harness wires or the like.

In this example, an air duct (100) for the automotive industry is fabricated, using pre-expanded polypropylene (ePP) via steam chest moulding as described herein. More specifically, in this embodiment, two cavities in a mould, each cavity corresponding to the lower section (101) and the upper section (102) of an air duct, such mould allowing for the removal of a moulded air duct section from the cavity once the entire steam chest injection mould process is completed. As will be apparent to a person skilled in the art, each of such cavities may have a plurality of removable parts to allow opening of the mould and removal of the moulded air duct section upon completion of the steam chest injection mould process.

In the example, pre- expanded polypropylene foam beads have a diameter from about 3 mm and about 6 mm and the density, prior to injection, is 5 pounds per cubic foot. In this example, lower section (101) and upper section (102) of an air duct (100) are assembled together using hot glue.

The air duct thereby made in this example weighs 323g compared to the 390g for an air duct manufactured by conventional blow moulding process with solid walls. Weight reduction is 17% in this case.

Referring now to Figure 13, pin 24 is depicted showing an extra length shoulder to accommodate the extra thickness of the walls of the air duct section made by the process described herein. Referring now to Figure 14, transmission loss of Example 1 was tested against the prior art using ASTM E2611 (although other transmission loss protocols as understood by a person of ordinary skill may be used), and one can see that in some frequencies, more sound decibels are stopped by the wall of an air duct manufactured by steam chest moulding of ePP, men the prior art Many modifications and variations arc possible in light of the above. Therefore, within the scope of the appended claims, the present disclosure may be practiced other than as specifically described.

The present disclosure has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is illustrative of preferred embodiments rather than limitative.

Claims

CLAIMS 1. A method for moulding a section of an air duct of using steam chest moulding, said method comprising the steps of:

i. closing the mould cavity;

ii. injecting the mould cavity with pre- expanded foam beads;

iii. introducing steam into the mould cavity among the beads to meh and fuse the beads;

iv. cooling the mould cavity and the fused beads;

v. opening the mould; and

vi. removing the melted and fused beads formed as a section of an air duct from said mould.

2. The method of claim I further comprising after step ii, compressing the pre-expanded foam beads into the mould cavity.

3. The method for moulding a section of an air duct of claim 1, wherein said pre-expanded foam beads are selected from the group consisting of expanded polypropylene, expanded polyethylene, expanded polystyrene, expanded thermoplastic urethane and combinations thereof.

4. The method for moulding a section of an air duct of claim I, wherein each of said pre- expanded foam beads has a spherical diameter between about 1.5 mm and about 6 mm, prior to step ii.

5. The method for moulding a section of an air duct of claim 1, wherein each of said pre- expanded foam beads has a spherical diameter between about 6 mm and about 8 mm, prior to step ii.

6. The method for moulding a section of an air duct of claim 1, wherein each of said pre- expanded foam beads has a non-spherical diameter from about 1.5 mm and about 8mm, prior to said step ii, and said pre-expanded foam beads comprise non-spherical shapes.

7. The method for moulding a section of an air duct of claim 1, wherein each of said pre- expanded foam beads may be of a shape including spherical, ellipsoidal, cylindrical, rectangular, cubic, other polyhedral shapes, irregular shapes and combinations thereof.

8. The method for moulding a section of an air duct of claim 1, wherein each of said pre- expanded foam beads has a density, prior to step ii, between about 1 pound per cubic feet and about 15 pounds per cubic feet

9. The method for moulding a section of an air duct of claim 1 , wherein said air duct section has a wall thickness of at least 0.6 mm.

10. The method for moulding a section of an air duct of claim I, wherein said air duct section wall has a thickness between about 2 mm and about 6 mm.

11. The method for moulding a section of an air duct of claim 1, further comprising compressing and heating during said injection and cooling steps obtaining a substantially smooth and/or textured outer surface.

12. The method for moulding a section of an air duct of claim 1, wherein at least one area of at least one section of air duct, has a density, after moulding, between about 1 pound per cubic feet and about 30 pounds per cubic feet.

13. The method for moulding a section of an air duct of claim 1, wherein at least one area of at least one section of air duct further comprises a reinforcement insert, preferably made of metal, plastic or a combination thereof.

14. The method for moulding a section of an air duct of claim 12, wherein said reinforcement insert is fastened to the air duct by a method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof.

15. An air duct assembly method, said method comprising fastening together at least one section of an air duct manufactured in accordance with any of claims 1-13 to at least another section of an air duct forming an air duct with a substantially air-tight wall, using a fastening method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof. An air duct assembly method, whereas aid method comprising fastening together at least one section of an air duct manufactured in accordance with any of claims 1-13 using porous pre-expanded foam beads, resulting in an air duct section with a porous wall, to another air duct section forming an air duct, using a fastening method selected from the group consisting of pressure-snapping geometrically engaging surfaces, welding, gluing, installing brackets, screwing, bolting and combinations thereof. An air duct comprising at least two connectable sections, wherein at least one section is manufactured in accordance with any of claims 1-13. An air duct assembled in accordance with any one of the claims 14 or 15.