AU2019361731A1 - Sound panels and method for manufacture thereof - Google Patents

Abstract

The present invention relates to the field of sound attenuating, absorbing or reflecting panels, such as plastic or concrete panels, sound attenuation barriers or other wall structures. The present invention provides a mould with at least one protrusion configured to form at least one feature of the panel during production and provides an absorptive layer in a predetermined orientation relative to the protrusion. Panel material is added to the mould and then the panel is formed so as to retain the absorptive layer within at least a portion of the panel.

Description

SOUND PANELS AND METHOD FOR MANUFACTURE THEREOF

FIELD OF INVENTION

[0001] The present invention relates to the field of sound attenuating, absorbing or reflecting panels.

[0002] In one form, the invention relates to generally to plastic or concrete panels.

[0003] In one particular aspect, the present invention is suitable for use in plastic panels used in sound attenuation barriers or other wall structures.

[0004] It will be convenient to hereinafter describe the invention in relation to sound panels, however it should be appreciated that the present invention is not limited to that use only.

BACKGROUND ART

[0005] Throughout this specification the use of the word“inventor” in singular form may be taken as reference to one (singular) inventor or more than one (plural) inventor of the present invention.

[0006] The inventors have realised that noise reduction is seen as an important countermeasure against environmental noise pollution and noise pollution is becoming an important social problem.

[0007] Generally, sound reduction can be gained by erecting or positioning noise absorbing panels or structures nearby a source of noise pollution. US Patent No. 8167085 provides an example and describes some previous attempts at sound reduction with the use of typically inefficient and/or hazardous materials, in particular, materials that can be readily combustible such as paper, cellulose, viscose, foam, cotton wool, polyester and the like. [0008] In spite of these failings, sound-absorbing materials are often employed in situations where the reduction of noise pollution is considered of greater importance than the potential for the material to become as a fire hazard or less effective. For example, when shielding noisy machinery or selecting a noise insulator to surround an automotive engine, the machine or engine oil can be sprayed onto and be absorbed by the surrounding sound-absorbing material. The resultant effect being that not only does the sound absorbing material start to lose its sound-absorption capacity, but it becomes prone to catching alight.

[0009] The inventors also realise that in relatively large scale projects sound attenuation barriers are also used internationally to attenuate the transmission of noise from a noisy area, such as a roadway, industrial site or other high noise area. Such barriers are generally required to provide a certain specified degree of attenuation of noise passing from one side of the barrier to the other. Sound attenuation barriers common ly include support structure anchored to the ground and a series of panels spanning the support structure to provide a continuous barrier along a desired distance. In some instances, such sound attenuation barriers must extend for a number of kilometres.

[0010] The sound absorbing member functions to cut the propagation of sound energy by reflecting a sound propagated in air, and the sound transmission loss, which is an index of the sound insulation property, basically depends on mass low, and becomes greater as the mass becomes greater. Commonly, the panels used in existing sound attenuation barriers are formed of wood, concrete and/or steel.

[001 1] For example, a concrete sound-proof panel or a metal sound-proof panel, are used along a portion of a railway or a road for the purpose of reducing noise to inhabitants in the regions along the railway or road, and is considered well known.

[0012] These panels are formed at a remote site, transported to the place where the barrier is to be erected, the affixed relative to the support structure to form the sound attenuation barrier. Steel panels are heavy and expensive and subject to graffiti. Wood panels may be subject to burning, are more prone to deterioration from weather, bird attack and need significant maintenance. Concrete panels are quite heavy and can be prone to cracking or chipping. As it is commonly preferred to have sound attenuation barriers provide an aesthetically appealing appearance, cracking or chipping of the panels is undesirable and the panel manufacturer may be required to replace any such damaged panel at its own cost.

[0013] Further, concrete panel forming processes provide only limited flexibility to confer an appealing aesthetic appearance on an external face of the panel. Another problem encountered in relation to sound attenuation barriers is the potential for vandalism, such as spray painted graffiti. Removal of graffiti from concrete panels can be problematic and expensive. Similarly, where a sound attenuation barrier is adjacent an area that throws up air-born particulate, such as a roadway, airborne pollutants commonly accrete onto the panels over time and need to be cleaned in order maintain an aesthetically pleasing appearance. For some panel materials, it can be hard to clean the pollutants from the panel surfaces.

[0014] The weight of typical concrete, wood or metal panels are also considered a problem. For concrete panels, for example, the weight may be some 200 to 300 kg/m. Thus it is necessary to use heavy machinery to install the panels and where the installation is high on a bridge for example, this adds more complication to the installation process.

[0015] Other concrete or masonry walls are made from individual blocks laid in-situ. Some of the blocks are hollow and have insulation or sound absorbing material placed (manually) inside each block as the wall is built. This is considered manually intensive and lacks the overall consistency of build quality as would be provided from a prefabricated factory product.

[0016] The inventors are also aware of sandwich panels which are typically formed from a core sandwiched between two liner sheets. The core may be relatively thick, yet lightweight, as compared to the liner sheets. The liner sheets may be relative thin, yet stiff. Therefore, sandwich panels typically possess relatively high strength and stiffness at relatively low weight. As such, sandwich panels are widely used in various aerospace applications.

[0017] Like traditional sandwich panels, acoustic sandwich panels include a core sandwiched between two liner sheets. One of the liner sheets is perforated, while the other liner sheet is not perforated. The core provides bulk and defines a plurality of cavities. The apertures defined by the perforated liner sheet fluidly couple the cavities with the ambient environment. Therefore, when air flows across the perforated liner sheet of an acoustic sandwich panel, the cavities in the core act as Helmholtz resonators and attenuate the sound of the associated airflow.

[0018] The inventors are also aware of panels made from plastic, such as noise absorptive Rotational Moulded Panels (RMPs). RMPs are a noise wall products made from thermoplastic or thermoset material such as linear low-density polyethylene, typically mounted in a steel structure. RMPs are classified as a noise deflector and are used to reduce noise migrating to populated areas along freeways/highways. RMPs are restricted in their use due to production cost, ongoing maintenance cost and design constraints. A typical design has a metal insert containing surface penetrations and having a noise absorbing material. Fabrication of RMPs is considered labour intensive as it requires formation in two plastic parts, each separately moulded and then assembled with the metal insert placed between the two plastic parts.

[0019] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor’s knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

SUMMARY OF INVENTION

[0020] An object of the present invention is to alleviate at least one disadvantage associated with the related art. [0021] A further object of the present invention is to provide a sound panel and / or method of forming a sound panel in which an absorptive sound layer is moulded inside the sound panel.

[0022] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0023] In a first aspect of embodiments described herein there is provided a method of producing a sound panel, the method comprising the steps of providing a mould with at least one protrusion, the protrusion(s) being configured to form at least one feature of the panel during production; providing an absorptive layer in predetermined orientation with the at least one protrusion; adding panel material to the mould; and forming the panel so as to retain the absorptive layer within at least portion of the panel.

[0024] In another aspect of embodiments described herein there is provided a sound panel comprising a first surface having at least one panel feature provided integral with the surface, the panel feature serving to abut an absorptive layer internal of the panel; and a second surface formed integrally with the first surface; the first and second surfaces having been formed as the outer body of the panel during a moulding process.

[0025] In yet a further aspect of embodiments described herein there is provided a sound panel made in accordance with the method as disclosed herein.

[0026] In one embodiment, the sound panels are generally hollow, with reinforcing structure inside.

[0027] The present invention has particular application in rotational moulding which involves (i) loading a powdered thermoplastic or thermoset material into a mould and clamping it securely closed; (ii) heating the mould and material in an oven at the same time as the mould is rotated (usually around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mould. In order to attain one or more predetermined thicknesses in part, or all of the mould it is rotated at all times during the heating phase. To solidify the material, the mould is cooled, usually in a chamber in which air or water spray is circulated. The mould continues to rotate during the cooling step to ensure uniform cooling profiles throughout the mould and to avoid sagging or deformation.

[0028] The present invention therefore further provides a method of forming the aforesaid a sound panel, the method comprising the steps of:

(i) placing the absorptive layer in predetermined orientation in the mould;

(ii) adding panel material in the form of amount of particulate thermoplastic or thermoset material to the mould;

(iii) closing and securing the mould;

(iv) heating and rotating the mould is heated and rotated in two perpendicular axes so that the panel material forms a continuous coating on the inside of the mould;

(v) cooling and rotating the mould; and

(vi) halting rotation and opening the mould for removal for removal of the cooled coating, formed in the shape of the interior of the mould.

[0029] The present invention may also be fabricated by rotocasting (also known as rotacasting) techniques, which by comparison to rotational moulding, uses self-curing resins in an unheated mould, but the moulds are rotated at speeds similar to those used in rotational moulding.

[0030] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0031] In essence, embodiments of the present invention stem from the realization that the present invention seeks to combine some of the benefits of RMPs with an absorptive capability. The present invention is based on the ability to include in the rotational moulded product and/or process an absorptive material. Preferably, the panel has perforations through the moulded wall. This avoids the need for post mould installation of the absorptive material and or post mould coring of the holes to expose the absorptive material.

[0032] Advantages provided by the present invention comprise the following:

• One step moulding of sound panels or similar products that encapsulate a predetermined material inside;

• Design flexibility;

• Reduced production costs;

• Design capability both side;

• Reduced carbon footprint (less weight per sqm) per concrete;

• Colour through cress section so if damage there is no colour shift;

• Safety of operation because it is not necessary to handle the panel to split to post mould insert the absorptive material;

• One-piece construction of the finished part, makes it stronger, lighter, without the need for external fasteners or fixing systems;

• Reduced risk of ingress of fauna or flora;

• Improved aesthetics due to one-piece construction;

• Reduced capital investment due to post mould process elimination; and

• Reduced inventory due to reduced post mould activity.

[0033] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:

FIG 1 illustrates a first face of a panel body according to the present invention;

FIG 2 illustrates a second face of a panel body according to the present invention;

FIG 3 illustrates a cross sectional view A-A of the panel illustrated in FIG 1 and also illustrates the absorptive layer;

FIG 4 illustrates another view (from above) of the cross sectional view A-A of the panel 1 illustrated in FIG 3; and

FIG 5 illustrates a method according to another aspect of invention.

DETAILED DESCRIPTION

[0035] For purposes of description herein, the terms "upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” “interior,” “exterior,” and derivatives thereof shall relate to the invention as oriented in FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawing, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. Additionally, unless otherwise specified, it is to be understood that discussion of a particular feature of component extending in or along a given direction or the like does not mean that the feature or component follows a straight line or axis in such a direction or that it only extends in such direction or on such a plane without other directional components or deviations, unless otherwise specified.

LIST OF PARTS SHOWN IN THE DRAWINGS

I Panel Body 2 first face of panel body

3 second face of panel body 4 absorptive layer

5 first face holes 6 second face holes

7 decorative design, such as ribs 8 first legs

9 absorptive layer 10 hollow space

I I second legs

[0036] FIG 1 illustrates a first face 2 of a panel body 1 according to the present invention. The panel 1 of the present invention maybe of any size, shape, thickness and orientation. The panel 1 may also have an aesthetic or function design embossed or added to the face 2, however, as illustrated, the face 2 does not have any aesthetic design or embossing. The first face 2 has holes 5. The holes 5 may be of any size, shape, depth or configuration, depending on the design use of the panel 1 . The holes may be used to allow impinging sound to enter the interior of the panel, and to then strike the absorptive layer 9 (FIG 3) so the sound can be attenuated.

[0037] FIG 2 illustrates a second face 3 of a panel body 1 according to the present invention. The face 3 may also have an aesthetic or function design embossed or added to the face 3 and as illustrated, the face 3 has a rib design 7. It is important to note that design 7 may be of any shape, orientation or design and may be an aesthetic design or embossing suitable for the application of the panel 1 . The second face 3 has holes 6. The holes 6 may be of any shape, size, depth or configuration, depending on the design use of the panel 1 . The holes may be used to allow impinging sound to enter the interior of the panel, and to then strike the absorptive layer 9 (FIG 3) so the sound can be attenuated. The holes 6 maybe somewhat aligned with the holes 5 of the first face 2, however, they holes 5 and 6 may also be not aligned.

[0038] The design of the panel 1 is seen to include a compromise between a degree of absorption of sound and aesthetic design.

[0039] In another embodiment (not shown) the second face 3 may have very few, if any holes. The panel 1 could function then as a Helmholtz Resonator to have the impinging sound enter the panel 1 via holes 5, and the sound waves will be attenuated internal to the panel 1 . In yet another embodiment (not shown), the panel 1 could have thicker absorptive material which would then not need to function as a Helmholtz Resonator.

[0040] FIG 3 illustrates a cross sectional view A-A of the panel 1 illustrated in FIG 1 and also illustrates the absorptive layer 9. The cross sectional illustration shows ribs 7 of various shape and thickness. The rib design 7 may be of any type suitable for the panel application. Holes 5 of the first face 2 are shown. The holes 5 are formed by first legs 8. In between the legs 8 and around the absorptive layer 9 is a hollow space 10. Holes 6 of the second face 3 are also shown. The holes 6 are formed by second legs 1 1.

[0041] It can be seen in FIG 3 that the legs 8 and 1 1 serve to sandwich and hold the absorptive layer 9 in place. As will be later explained, the parts of the mould (not shown) which form the holes 5 and 6 have the legs 8 and 1 1 formed around those parts of the mould. The legs 8 and 1 1 serve to hold the absorptive layer 9 in place during the moulding process in which the plastic is moulded to eventually form the legs 8 and 1 1 and in turn contact and function to hold the absorptive layer 9 once the panel 1 is formed in the mould. Thereafter, when the panel 1 is taken out of the mould (not shown), the legs 8 and 1 1 hold the absorptive layer 9 in place. Hollow spaces 10 can then also be provided in the moulding process.

[0042] The absorptive layer may be any type of sound attenuating or sound absorbing material known in the art. For example, the absorptive layer may include but limited to manmade acoustic substances such as polymeric foam, fiberglass, or natural acoustic substances such as cotton, wool, mineral wool such as Rockwool, and combinations of manmade and natural acoustic substances. These include, for example, acousting fibre glass, polyester, acoustic foam, fabric covered panels, minereal fibre board, open cell polyethylene foam, EPDM (rubber) foam and mass loaded vinyl (MLV). The absorptive layer may be a composite, such as a combination of foam covered with mesh, textile or a metal/metallised layer. For example mesh coated sound proofing products such as those sold under the trade mark Megasorber may be suitable.

[0043] The absorptive layer need not be a contiguous layer, may be of any shape, thickness, orientation, material or composition dependent on the use of the panel and the degree of attenuation required. Preferably, the absorptive layer will additionally have other advantageous properties such as fire-resistance or thermal insulation.

[0044] FIG 4 illustrates another view (from above) of the cross sectional view A-A of the panel 1 illustrated in FIG 3 and also illustrates the absorptive layer 9 held between legs 1 1 and 8. The cross sectional illustration shows ribs 7 of various shape and thickness. Holes 5 and 6 are shown, formed by legs 8 and 1 1 respectively. The absorptive layer 9 is held between the legs 8 and 1 1 , with a hollow spaces 10 between. In the embodiment illustrated, in hole 6, a portion of the absorptive layer 9 can be seen and that the edge of the leg 1 1 which forms the hole 6 abuts the layer 9 to serve to sandwich and hold the absorptive layer 9 in place between legs 8 and 1 1 . It can also be seen that the holes 5 and 6 do not necessarily align. The legs 8 and 1 1 need to be formed either side of the layer 9 - but do not have to be axially aligned.

[0045] The panel may also have other formations formed (not shown), such as for mounting the panel, for decorative purposes. If any through holes are included into the design of the panel 1 , they are provided at an angle (up to 90 degree angle) to the sound source.

[0046] FIG 5 illustrates a method according to another aspect of invention. A mould is provided 501 , the mould having at least one protrusion (not shown) which will have the function of assisting to form either hole 5 or 6 and /or leg 8 or 1 1 . The protrusion can be of any shape, size, length and design but is formed in line with the hole 5, 6 and or leg 8, 1 1 required to be formed in the panel 1. Prior to rotational moulding, with the mould in the open position 502, the absorptive layer 9 can be placed in the mould 503, resting on the protrusion(s) provided in the mould. [0047] The method of the present invention can be performed according to the following steps:

(i) the absorptive layer is placed in the mould, resting on the protrusion(s) provided in the mould;

(ii) the mould is loaded with the requisite amount of particulate thermoplastic or thermoset material, such as powder, pellet or a mixture thereof combined with any desirable additive as is understood by those skilled in the art of rotary moulding products;

(iii) the mould is securely closed using clamps or other convenient fixing means;

(iv) the mould is heated and rotated in two perpendicular axes so that the material forms a continuous coating on the inside of the mould;

(v) the mould and coating continue to be rotated as they are cooled; and

(vi) rotation is stopped and the mould is opened for removal for removal of the cooled coating, formed in the shape of the interior of the mould.

[0048] The particulate material is typically linear low density polyethylene (LLDPE) and may include additives such as pigments for colouring, stabilisers to resist chemical reactions, anti-oxidants to counter oxidation during heating, agents to resist breakdown by ultraviolet radiation (sunlight), fillers, flame retarders and crosslinking agents. Other additives will be readily apparent to those skilled in the art.

[0049] The particulate material typically has a range of particle sizes appropriate for the size and shape of the mould to ensure that the entire interior surface of the mould is coated.

[0050] Preferably the molecular weight distribution of the thermoplastic or thermoset material (eg LLDPE) provides a Melt Flow Index of between 3 g/10 mins and 5 g/10 mins. [0051] Preferably the thermoplastic or thermoset material (eg LLDPE) is of medium density, typically from 0.935 to 0.945.

[0052] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0053] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0054] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus- function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface to secure wooden parts together, in the environment of fastening wooden parts, a nail and a screw are equivalent structures.

[0055] It should also be noted that where a flowchart is used herein to demonstrate various aspects of the invention, it should not be construed to limit the present invention to any particular logic flow or logic implementation. The described logic may be partitioned into different logic blocks (e.g., programs, modules, functions, or subroutines) without changing the overall results or otherwise departing from the true scope of the invention. Often, logic elements may be added, modified, omitted, performed in a different order, or implemented using different logic constructs (e.g., logic gates, looping primitives, conditional logic, and other logic constructs) without changing the overall results or otherwise departing from the true scope of the invention.

[0056] “Comprises/comprising” and“includes/including” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words‘comprise’,‘comprising’,‘includes’, ‘including’ and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to”.

Claims (14)

1. A method of producing a sound panel, the method comprising the steps of: providing a mould with at least one protrusion, the protrusion(s) being configured to form at least one feature of the panel during production;

providing an absorptive layer in predetermined orientation with the at least one protrusion;

adding panel material to the mould;

forming the panel so as to retain the absorptive layer within at least a portion of the panel.

2. A method as claimed in claim 1 , wherein the forming of the panel is by rotational moulding or rotocasting.

3. A method as claimed in claim 1 , wherein the at least one feature is a hole or a leg.

4. A method as claimed in claim 3, wherein the at least one feature serves to expose at least a portion of the absorptive layer.

5. A method as claimed in claim 1 , wherein the protrusion(s) are arranged to abut or hold the absorptive layer in place within the panel.

6. A sound panel comprising: a first surface having at least one panel feature provided integral with the surface, the panel feature serving to abut an absorptive layer internal of the panel; and - a second surface formed integrally with the first surface;

wherein the first and second surfaces are been formed as the outer body of the panel during a moulding process.

7. A sound panel as claimed in claim 6, wherein the body of the panel is made, at least in part, of plastic or resin.

8. A sound panel as claimed in claim 6, wherein the panel is made by rotational moulding or rotocasting.

9. A sound panel as claimed in claim 6, wherein the panel feature is a hole or a leg.

10. A sound panel as claimed in claim 6, wherein the at least one feature serves to expose at least a portion of the absorptive layer.

1 1 . A sound panel as claimed in claim 6, wherein the panel feature is arranged to abut or hold the absorptive layer in place within the panel.

12. A method of forming a sound panel according to claim 6, the method comprising the steps of:

(i) placing the absorptive layer in predetermined orientation in the mould;

(ii) adding panel material in the form of amount of particulate thermoplastic or thermoset material to the mould;

(iii) closing and securing the mould;

(iv) heating and rotating the mould is heated and rotated in two perpendicular axes so that the panel material forms a continuous coating on the inside of the mould;

(v) cooling and rotating the mould; and

(vi) halting rotation and opening the mould for removal for removal of the cooled coating, formed in the shape of the interior of the mould.

13. A method according to claim 13 wherein the panel material is linear low density polyethylene.

14. A sound panel made in accordance with the method as claimed in any one of claims 1 to 5, 12 or 13.