WO2023113624A1

WO2023113624A1 - Shaped and machined acoustic panels

Info

Publication number: WO2023113624A1
Application number: PCT/NZ2022/050173
Authority: WO
Inventors: Neil Marcus Pennell Ridgway
Original assignee: Neil Marcus Pennell Ridgway
Priority date: 2021-12-16
Filing date: 2022-12-16
Publication date: 2023-06-22

Abstract

Prior-art acoustic panels include a fibrous mass of glass wool or equivalent, and decorative laminates as thin layers at the exposed surface. The layers are exposed at the edges. Acoustic panels are porous to gases. A method for firmly holding such panels on a vacuum bed of a CNC machine, employing an impervious film temporarily adhered to the decorative laminates, allows panels to be accurately machined. Machined panels have edges folded once or twice for increased rigidity and are finished along the side edges. The more rigid side edges permit use of a novel mounting accessory penetrating the side edges.

Description

TITLE: SHAPED AND MACHINED ACOUSTIC PANELS

FIELD:

For porous acoustic panels including layers of rock wool, glass wool or the like and a surface-enhancing laminate of thin layers at the exposed surface, as used inside buildings in order to attenuate sound waves incident on the panels, the invention relates to panels made temporarily attachable on to a table of a numerically controlled machine, thereby providing for accurate machining of the panels. Such panels may be machined to allow precise folds to be made.

DEFINITIONS

Four types of panel are separately classified for the reader’s convenience.

“Type A” acoustic panels are fixed or floating acoustic panels having a laminated exposed surface (usually including a decorative layer) and having naked surrounding edges with exposed fibrous materials, or edges covered with a paint or a separate paper or similar surface only. This Type includes many types of acoustic panel in the prior art.

“Type B” acoustic panels have modified edges. The edges of the panel, including the fibre mass and the laminated exposed surface are folded away from the exposed surface through 90 degrees with a single fold near each edge along a groove machined according to this invention, while the surface-enhancing laminate remains intact. Edges of the fold are then glued together.

“Type C” acoustic panels have modified with a twice folded edge, folded again over the back and toward the middle, using a pair of fold lines near each edge along grooves that are machined by this invention, while the surface-enhancing laminate remains intact. Adjacent edges of both folds are glued together.

“Type D” acoustic panels have a doubled thickness over the full area of the panel, for which the two sides are folded so that the fibrous back sides are in adherent contact, using a double fold line across the middle of a single-thickness panel; the product having the structure of the laminated exposed surface on both surfaces.

BACKGROUND For many years, Type A acoustic panels have been made using a mass of glass fibre, rock wool, or polyester fibre, that is concealed behind a flat surface including a decorative layer. The decorative layer is comprised of one or more adherent layers and obscures the fibrous rear of the panel from view.

Most attempts to configure Type B, C or D panels, seeking improved panel appearance, have failed because the material to be folded is a quite thick assembly of layers that will not accept sharp folds. It is difficult to hold and cut the mass of fibre.

For installations where an edge of an acoustic panel may be visible after installation, such as for panels suspended along one edge, a layer of paint or other heavy coating is often applied on the fibre surfaces at the exposed edges, both for aesthetic reasons and to prevent fragmentation of the panel over time. Such panels are type A. Use of high density board would be required in order to get better paint finish.

CNC (computer-numeric ally controlled) also known as NC (numerically controlled) machines for shaping materials including substantially impervious panels are well known, for working wood, plastics, or metals. Although a number of web sites are known depicting the machining of either front or back surfaces or edges of acoustic panels comprised of impervious materials, such as by cutting with a rotating cutter or disc saw or by use of a carbon dioxide laser, it has been found impossible to hold a fibrous and porous mass upon a well-known holding device such as a vacuum bed. One can hold a slab by clamping it between a flat bed and an overlying sheet but CNC shaping machinery used to hold and work such panels is likely to collide with the clamps. As a result, a limited range only of operations can be performed on acoustic panels during manufacture.

Also, clamping a slab of a porous, fibrous material compresses and distorts the material. After release, machined surfaces lose their shape.

OBJECT

A first object of the present application is to provide a method for accurately machining inherently porous acoustic panels.

A second object of the present application is to provide accurately machined inherently porous acoustic panels having accurate sizes and shapes. A particular object of the present application is to provide improved acoustic panels for which the edges are covered by a continuous extension of the laminated exposed surface, after a 90 degrees folding process.

Yet another object of the present application is to provide acoustic panels for which at least some edges are backed by a band or strip comprised of a second layer of the panel by a double folding process.

A further object of the invention is to provide concealed fasteners to hold the panels as described above on to a support structure or frame.

SUMMARY OF INVENTION

In a first broad aspect the invention provides an acoustic panel having an area, a decorative, layered front surface, side edges, and a thick, permeable, absorbent rear layer comprised of a material selected from a range of rock wool, glass wool, and fibrous plastics, wherein the acoustic panel includes a surface accessory layer comprising a relatively air-impermeable sheet or foil having a composition selected from a range of a plastic film, including polyester and terephthalate films, a cellulose film, a metallised plastics film, and a metal foil, bearing a selected adhesive coating; the surface accessory layer is applied over the decorative front surface of the panel thereby rendering the acoustic panel substantially impermeable to passage of gas through the tile.

Preferably the decorative front surface includes a thin fibrous layer capable in use of being folded over sharp bends formed about the front surface.

More preferably the layer comprises a sheet of tough, tear-resistant plastic fibres such as polyester fibres.

Preferably the selected adhesive coating on the surface accessory layer renders the surface accessory layer weakly adherent to the decorative front surface thereby allowing the surface accessory layer to be peeled away and removed.

Alternatively the selected adherent coating is permanent.

In a second broad aspect, the invention provides a method for machining an acoustic panel as previously described in this section, wherein the following steps are included: 1. mounting the decorative layered front surface of the acoustic panel against a surface of a vacuum bed of a numerically controlled shaping machine,

2. applying a vacuum to the vacuum bed thereby holding the acoustic panel against the bed by air pressure acting across the substantially impermeable surface accessory layer,

3. machining the acoustic panel from the rear surface,

4. releasing the machined acoustic panel from the vacuum bed for subsequent application of adhesive, folding and shaping, and

5. removing the weakly adherent impermeable sheet or foil from the decorative layered front surface before the acoustic panel is completely installed.

Preferably the cutting machine is a numerically driven (CNC or ) rotary machining or router device having a cutting tool selected from a range including a circular saw or an cylindrical router that operates on rails in three dimensions, including a height-controlled movement over a vacuum bed.

In a related aspect, the step of machining the acoustic panel forms at least one “V-cut” along a cutting line from the rear surface; said “V-cut” comprises a linear valley having plane walls at 45 degrees to the surface of the acoustic panel and a base of the valley extends as far toward the decorative front surface as the thin fibrous layer.

Other cuts can be made, but the “V-cut” appears to be the most useful option.

In one option, the manufacturing process creates one “V-cut” parallel to each side edge of the panel along a cutting line located at one panel thickness inward from each side edge, backing material is removed at comers of the acoustic panel for folding the decorative front surface, an adhesive is been applied on to the plane walls of each “V-cut” and the edges of the acoustic panel are folded away from the decorative front surface so that the plane walls of the “V-cut” are brought into adherent contact.

Preferably the machined and folded acoustic panel has the decorative front surface folded over the side edges of the acoustic panel thereby covering the side edges of the acoustic tile.

In another option, the manufacturing process machines a parallel pair of “V-cuts” parallel to at least one side edge of the panel along cutting lines; an outer cutting line being located at least one panel thickness inward from all side edges and an inner cutting line being located at one panel thickness inward from the outer cutting line; corner material is removed for accommodation of intended folds of the decorative front surface, an adhesive is applied on to the plane walls of each “V-cut” and the edges of the acoustic panel are folded back from the decorative front surface in two stages, bringing a side strip of the decorative front surface around the side edge of the acoustic panel with one fold and bringing a back strip on to a rear surface of at least one side edge of the acoustic panel with another fold.

Preferably the machined and folded acoustic panel is provided with a reinforcing back strip along at least one edge of the acoustic tile, after the edges of the acoustic panel have been folded twice away from the decorative front surface along the line of both “V-cuts” and the adhesive applied along the “V-cut” surfaces has made contact and formed joints.

In yet another option, the manufacturing process machines a parallel pair of “V-cuts” spaced apart by one panel thickness across a central portion of the acoustic tile, applying an adhesive on to the plane walls of each “V-cut” and over the entire rear surfaces of the acoustic panel and then of folding the two parts of the acoustic panel together, thereby creating a double thickness tile.

In a second broad aspect, the invention provides a mounting accessory, namely a penetrating clip for a machined and folded acoustic panel as previously described in this section; the mounting accessory relies on penetration of the sides of the machined and folded acoustic panel by sharp prongs directed in the plane of the panel; the mounting accessory is comprised of a flat shape with adherent properties (such as an fastener hole) , and is provided with at least one uplifted, broad penetrating prong raised from a base by about half an acoustic panel height and directed to one side of the clip.

Preferably a portion of the laminated structure is directed sideways and tucked or fixed into a joint made at each comer of the folded panel, thereby reinforcing the exposed corner of the acoustic panel.

PREFERRED EMBODIMENT

The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention. In particular the dimensions or described are purely illustrative. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Throughout this specification unless the text requires otherwise, the word "comprise" and variations such as "comprising" or "comprises" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference. Reference to cited material or information cited in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in New Zealand or in any other country.

DRAWINGS

Fig 1: shows cross-sectional detail of an acoustic panel including new layer 107.

Fig 2: shows a schematic cross section of part of a Type B panel with a covered edge.

Fig 3: shows a cross section of part of a Type C panel with a covered edge.

Fig 4: is an oblique view of a preferred fastener suitable for a fixing a panel to a substrate. Fig 5: is a rear face view diagram of part of a panel to show placement of a machined groove beside each edge of a Type B panel.

Fig 6: is a cross-section through the preferred fastener, when in use.

Fig 7 : is a rear face view diagram of part of a panel to show placement of two machined grooves near each edge of a Type C panel.

Fig 8: is a cross-section through the shaped Type C panel after making two folds along each edge.

Fig 9: is rear face view diagram of part of a Type D panel during manufacture, to show placement of two machined grooves across the middle of the panel.

Fig 10: is a cross-section through the shaped Type D panel after folding each side back on itself.

EXAMPLE 1

An acoustic panel is a building component intended to absorb at least some incident sound waves. This invention provides an improved type of acoustic panel that has been machined and shaped in order to better fulfil that function, while having a construction based on that of previous acoustic panels (Type A panels) based on a glass fibre (or rock wool fibre, or polyester fibre, or a blend) material having a mass and used for its property of providing sound attenuation, usually along with a decorative exposed surface.

Please see the cross-section 100 in Fig 1, oriented with the decorative surface down. The body of a typical prior-art acoustic panel and those according to this invention include the following porous, mutually adherent layers:

(1) a decorative layer, (layer 101 in Fig 1), often white although colours are acceptable, and perhaps including patterns.

(3) at least one and preferably several reinforcing layers of glass mat (layers 103 in Fig 1), and

(4) a thick “functional mass” of glass fibre, rock wool fibre, or polyester fibre, (layer 104 in Fig 1), typically 50 mm thick but dependent on the required acoustic objectives, and the type of acoustic panel to be made. This layer is porous and has an appreciable mass.

Layers 101-103 are collectively identified as “the surface layer” 106 to distinguish that layer from the rear layer 104. Mutual adherence is assured, as is well known to persons skilled in the relevant arts, through application of a selected adhesive coating such as a heat-fusible glue for each layer and then pressing as required to bring the layers together.

LAYER 107 (Impermeable Foil)

According to the invention, an additional non-porous and hence gas-impermeable layer shown as 107 in Fig 1 is attached on top of the decorative layer. The primary purpose of layer 107 is as an aid for use during manufacture. The non-porous layer serves as a distributed clamp during a machining process if carried out on top of a vacuum table. The layer is usually removed before the acoustic panel is put into service.

Although machining, and especially computerized - numerical control or “CNC” machining using routing tools is well known in manufacture as a way to create shapes in metals and in non-metallic materials to a high accuracy, for acoustic panels the nature of the “functional mass” layer 104 tends to preclude use of CNC machining during the manufacture of acoustic panels. One can clamp an acoustic panel between a top of a table and a flat, rigid clamping sheet above, but the clamps that hold the sheet in place present obstacles to passage of routing tools. Also, that form of clamping always involves some compression and distortion of the functional mass layer so that after cutting and on release, the functional mass layer (104 in Fig 1) assumes an unintended shape.

The concept of this invention is to provide the additional non-porous and hence gas- impermeable layer shown as 107 in Fig 1. When a panel provided with this extra layer is placed against a vacuum table for machining, room air pressure percolating through the porous mass of the acoustic panel presses against the layer 107, forcing layer 107 against an at least partially evacuated space; the spoil board or the vacuum table, beneath. Surprisingly, it has been found that the holding force is adequate for machining or routing of the functional mass. The acoustic panel is best machined with higher speed cutters taking small cuts. Without layer 107, room air is simply sucked into the vacuum table. Preferably, one would always use a flat and porous “spoil board” directly on top of the vacuum table to protect the table surface from inadvertent damage by cutters or when any object collides with the table surface. The spoil board is described below.

According to the invention, the entire surface layer of the acoustic panel is held with a consistent, distributed force as described above against the vacuum table (through the preferred spoil board) and no clamp structures are required. There is no clamping force applied against the rear side of the “functional mass” (layer 104 in Example 1) so that shaped forms are not distorted by subsequent release of pressure.

Layer 107 is selected from a range including a plastic film including polyester and terephthalate or other plastics films, a cellulose film, a metallised plastics film, and a metal foil. Minimal thickness is needed. The foil to be used as Layer 107 is treated with a dusting, spray or other coating of a selected heat-melted adhesive on the attachment side and can be applied over the decorative layer in a press. The selected adhesive has a rather weaker grip than the grip of the adhesives used when building up the permanent surface layer of the acoustic panel, so that after use it can be detached cleanly. A peeling operation applies a high load along a peeling line, whereas forces applied during milling are applied over large areas of the surface. Detachment of layer 107 should not disrupt the remainder of the laminate which will employ stronger adhesives. The adhesive should leave no trace on the decorative layer after the layer 107 foil has been detached, or if it does, any remaining adhesive should be easily removed.

Layer 107 is preferably discarded for recycling before the acoustic panel is completely installed. In that method, there is a need for the weak adhesive to completely part from the layer 101 beneath. The non-porous and gas-impermeable layer 107 may be peeled off the decorative layer 101 before installation is completed; perhaps as soon as a panel is manufactured. It may be left on the panel until all the dust of building or installation has been swept away. Continued presence of the non-porous and gas-impermeable layer 107 would tend to obstruct sound waves from entering the mass 104 of the panel although it may be possible to minimize or accept that effect and allow the layer 107, which may be printed with an attractive pattern or design, to remain in place through the life of the panel.

Also according to the invention, a “Layer 102” is optionally included in the layers of the panel, to help maintain the layered structure after folding around a sharp bend. Layer 102 is a flexible interlayer resistant to becoming torn. Preferred materials include polyester fibres which may be oriented. It may be that the layers of the glass mat provide sufficient resistant to tearing. Some decorative layers are not disrupted if bent sharply around a corner, but in the inventor’s experience, most require layer 102.

The invention provides an improvement rendering a laminated acoustic panel compatible with being accurately machined during manufacture, and provides a method for making machined acoustic panels.

MACHINERY

For shaping acoustic panels which is similar to a woodworking process, the inventor prefers to use a numerically controlled (“NC”) or computer-numerically controlled (“CNC”) machine. The maker is Homag Group, of Schopfloch, Germany; see www.homag.com/en . The product name is: “CNC Gantry-Processing Center CENTATEQ N-500”). That woodworking machine is claimed to provide precision machining to about 0.05 mm tolerance in three dimensions over the expanse of an acoustic panel. The head travels across the work held upon a vacuum bed under a gantry that runs along rails alongside the bed for typically about 2.5 to 3 metres.

For completeness, a vacuum bed as understood herein is a flat surface usually comprising an integral part of a machine. The surface has a thickness that is perforated by an array of apertures, all connected through fine drill holes to an air space which is evacuated by a vacuum pump. Atmospheric pressure then forces the article to be held against the flat surface, assuming that the article forms seals around the holes. The holes are relatively fine so that any hole not covered does not let much air flow through and destroy the vacuum.

Most machining operations that the inventor performs are intended to remove a valley shape having two plane walls at 45 degrees angle to a back plane of the panel from the back of an acoustic panel. One way to shape the fibrous working mass 104 of a “glass fibre” type acoustic panel when properly held is by using a fast-rotating saw blade at about 9000 rpm, making two cuts each at 45 degrees to the plane of the panel surface that intersect within the layer 1 of glass fibre. This method has the disadvantage of creating sticks comprised of offcuts of fibrous material which tend to become trapped within dust removal ducts.

An alternative is to take a cylindrical router tool, such as the type known as a “Spiral Tungsten Roughing Cutter” having a cutting side and a cutting end. The tool is operated at a 45 degrees angle to the perpendicular and to the direction of movement while cutting along the lines of the valleys. That converts all the removed material into dust. The diameter of the tool should be more than (1.42 x panel thickness) so that both sides of each valley are left as clean planes. Otherwise, two passes may be required. A fast rotation speed is used to provide a high cutter surface speed.

A router tool shaped like an inverted pyramid, with 45 degree sloping sides and used while rotating in a vertical axis, is less suitable because the radial cutting speed is relatively low near the axis of the tool and the cut is unlikely to be clean at the bottom of the valley. Imperfections may then be visible at the fold.

For any option, the cutting height is set to terminate precisely (such as within 0.05 mm tolerance) in relation to the underlying surface of the holding board (at 205 in Fig 2), at or within the glass mats layer 103. Using this criterion, cutting height is not affected by likely variations in thickness of the fibrous mass 104. Other cutting methods such as lasers and waterjets cannot terminate the depth of cutting precisely.

Preferably, a protective “spoil board”; a holding surface comprised of a panel of medium density fibre (MDF) board at least as broad as the acoustic panel is laid on the vacuum bed and held down with the applied vacuum, which passes through to the exposed side. For preparation of the spoil board, the CNC machine is fitted with a rotary plane tool that is used to configure the upper surface of the spoil board to be flat to preferably within 50 microns (0.05 mm) over the entire surface while it is held on the vacuum bed. It is then ready for use. The spoil board is sufficiently porous to allow the vacuum bed effect (suction from an underlying vacuum pump) to percolate through the board and create a pressure difference across the impermeable layer 107 that serves to grip the acoustic panel to the vacuum bed surface to hold the panel firmly and over its entire surface. At the same time, the spoil board protects the vacuum bed surface of the CNC machine from inadvertent damage such as from dropped cutters or cutters that come loose during use.

A firmly held acoustic panel held face down on a surfaced spoiler board with the rear side 105 exposed can be machined over its entire surface to a height accuracy, measured from the front or decorative surface of perhaps ± 0.1 mm from the decorative layer at 205 in Fig 2. It is an advantage that the decorative surface including impermeable layer 107 serves as the reference surface while held firmly against the now planed spoil sheet over its entire surface. As a result, thickness variations within the acoustic panel layer 104 are not important.

TYPE A ACOUSTIC PANELS

An obvious purpose of the CNC routing machine is to shape edges to fit exactly around, for example, curved ducts, or to cut panels to fit within concave surfaces. For that purpose a suitable cutter is a cylindrical routing tool having side cutter surfaces, rapidly rotated in a vertical axis while being driven along a specified course set down by programming. The tool is driven down to the height of the spoil board. The invention facilitates manufacture of this product which is still a “Type A” panel having exposed fibre edges. The product is hardly distinguishable from the prior art except by having vertical machined edges. Those edges may require sealing or painting as before.

TYPE B ACOUSTIC PANELS

The panel outline is rectilinear, although it may have a polygonal - such as triangular, trapezoidal, or a hexagonal profile. An advance made possible by this invention is “surface-coated sides”. The CNC routing machine is used to machine “V-cuts” comprising linear valleys having plane walls at 45 degrees to a surface of the panel, and a base that extends as far down as to the thin fibrous layer 102. The cuts are made through the rear layer of the clamped panel (by means of the accessory layer adherent to the vacuum table through a spoil board) along a cutting line. Each “V-cut” is a valley intended to serve as a fold line. All valleys having planar side walls at 45 degrees along cutting lines that are located one panel thickness in from the edges of the panel.

A Type “B” acoustic panel is a polygonal (almost always rectangular) shape that has the decorative surface folded away from the face at a sharp, perpendicular fold around all edges. The edge remains connected to the mass of the acoustic panel through the surface layers 106, so that the decorative surface along an edge of the panel remains outwardfacing and may be sharply bent through 90 degrees while retaining its integrity (optionally reliant on Layer 102). In the cross sections of Figs 2 (a Type “B” item) and 3 (a Type “C” item), layer 106 represents the decorative surface laminate of Fig 1 including layers 100 to 103 inclusive. A single valley 201 is machined around the edges, along a base line that leaves an outer slope of the “V-cut” 203 extending to the full height of the panel. Of course, attention to subsequent folding is required at comer edges such as removal of all fibres within a square (or other shape if not a rectangular panel) at each corner. Subsequent scraping to remove layer 104 may be required since clamping rigidity is compromised by removal of the backing. Optionally the remaining composite layers 106 at the corner are trimmed with scissors so that they can be wrapped around, or tucked inward and glued in place while making the folds, giving the corners more protection from impacts before installation is complete.

Fig 5 shows the rear surface appearance of a panel that has been milled but is not yet folded. 501 represents unaltered fibrous panel material. 502 is a cut line for the left “V-cut valley and 503 is a cut line for the right “V-cut valley.

Fig 2 shows, at the left, a cut and as yet not folded valley 201 having a base or cut line at 205 that preserves the layer 102 previously mentioned. The material formerly occupying the valley is discarded as router shavings, or dust. The walls 202, 203 of the valley are substantially planar after machining since the fibre mass had not been distorted by clamping pressures during routing. As a result, the valley side surfaces may be brought close together after application of adhesive and folding. In any finished panel, the original valleys 202 will have been obliterated. The fold is made at 90 degrees and is held in place with adhesive, possibly with temporary assistance from a jig. Glued joints may be visible in a cut section as profiles resembling mortice joints, with glued layers connecting the fibre masses together. The product is a machined and shaped acoustic panel having a structured edge that includes the layered structure 106, with the decorative surface outermost and bent so as to cover the edges. After folding, the surface layer 106 extends over the edges 206 of the panel and confers an improved appearance and improved rigidity as compared with the sides of a Type A panel. The height of the edge would preferably be the same as the thickness of the panel, so that none of the working mass 104 of fibrous material remains visible. But this dimension may be used to absorb small size or shape defects. The stronger edge construction is exploited in order to facilitate fastening along the side edges of the “Type B” or “Type C” panels to a substrate by hidden fasteners - see Figs 4 and 6.

TYPE C ACOUSTIC PANELS

A Type “C” acoustic panel is one that has an extra thickness of panel as a strip along the back, along at least one edge, which increases the inherent stiffness of the acoustic panel. Please refer to Fig 3 (section) and Fig 7 (rear view of a part). The CNC machine had been used to cut double valleys (again having side walls at 45 degrees) with the residue of one at 304 and the other at 305, with the base lines of the corresponding “V-cuts” separated by one panel thickness. The base line of the outer valley may be separated from the panel edge by one panel thickness or more, since that outermost material will, after folding and adhesive contact, form a rear strip 302 as shown in Fig 3. As before the surface layer has been brought around the sides, and some of the surface layer is now located on the rear of the panel.

In Fig 7 a rear surface view of a machined but as yet unfolded type “C” panel is shown. In Fig 7, dashed lines 702 and 703 are the cutting lines. Note that cut line 702 is spaced apart by a selected distance from the panel edge 704. That provides extra width to the strips 801 (see Fig 8) that have been created over the rear of the acoustic panel by the second fold. The manufacturer may add the extra thickness along one or both longer sides, or along all sides. An acoustic panel modified in this way is more stiff and can span a greater distance without support than can an unmodified panel. A “Type C” acoustic panel as described above along both long edges has been found capable of maintaining a flat surface (to within 1 mm) in an overhead installation under the influence of gravity when spanning a distance exceeding 1.5 metres, tested against a metal straightedge as a measuring tool.

TYPE D ACOUSTIC PANELS This type of panel is one that is folded like the covers of a book for a double thickness and has two decorative surface faces. See Fig 9 (rear face view) and Fig 10 (section). To make this type, a pair of valleys to become fold lines are machined as “V-cuts” along cut lines 902 and 903 that traverse the middle of the panel. The base lines of the valleys are preferably separated by a distance equal to the thickness of the acoustic panel so that after folding there are no voids. The valley sides and the entire fibrous surface are covered with adhesive and the front and back surfaces 900 and 901 are folded against each other and pressed together in a press. The exposed edges may also be covered by folded-up panel material, leaving the decorative surfaces exposed as for Type “C” panels. This Example allows simplified construction of panels having baffle beams that are extended outward from the general surface.

PENETRATING CLIP.

Enhanced side edge strengths of acoustic panels according to this invention as described above allow use of a penetrating clip as an invisible fastener to hold the acoustic panel on to a substrate. Preferably the clip as shown in Fig 4 is made of a corrosion-resistant bent metal sheet; for example 1 mm thick painted steel, galvanized steel, or stainless steel. The flat surface 401 is fixed to a substrate, optionally using the hole for a fastener 402, or an adhesive over the flat surface below. Fig 6 is a section through a penetrating clip in place, showing a substrate 601, a comer of a panel 206 with a decorative layer on the exposed side and exposed top surface, and the penetrated prong is shown as 405. The uprising portion 403 is intended to lift the re-entrant prongs so that they may enter and hold the middle of the fibrous mass of an already folded acoustic panel according to this invention. The prongs are orientated parallel to the substrate 601 to be covered with acoustic tiles. The panel edge and the prongs are pushed against each other. The adherent side edge facing helps to maintain the fibrous working mass in place by providing rigidity about the position of the prongs, and an capacity to distribute loads about the side of the clip. The clip may then be nailed through accessible hole 402 or otherwise fastened into place. The clip may already be loosely fastened to the substrate. In practice a row of such clips spaced apart at perhaps 100 mm centres are used along each join. Prongs on alternate clips may be aimed in opposite directions. No fixings will appear on an exposed surface of any panel, which is aesthetically desirable.

ADVANTAGES The invention provides a way to use a vacuum bed to simply hold a porous acoustic panel or panel for machining on a NC or CNC router machine.

By allowing a porous acoustic panel or panel to be accurately machined, substantial improvements in acoustic panel properties and appearance are possible. Edge formations are stronger.

Since the fibrous layers had not been distorted by compression under a clamp when being milled, cut surfaces remain as plane surfaces as machined after removal from the machine, which facilitates subsequent folding and glueing.

Machining allows “Type B” acoustic panels having visually acceptable finished edges to be easily made to a close tolerance, whereas the prior-art method required labour, involved paint drying, and limited the choice of the fibre layer.

Panels of the “Type B” type allows for quicker and neater installation, especially when used with the fixing clip described. There is less dust during installation.

“Type C” panels are markedly stiffer than prior-art glass fibre type panels of a similar weight because of the extra edge thickness. They can bridge a relatively wide gap between supports without any deflection associated with gravity when covering a ceiling.

Advantages of a lower mass per panel include that one man can lift a panel of standard dimensions easily since its mass is a little over half that of prior- art panels. The working time required to install the panels is reduced. That helps with installation. Transport to a site is made easier. The supporting structure or the building containing the acoustic tiles needs less weight-bearing capability and less bracing in case of an earthquake.

The cost per square metre of the materials used in the layers remains competitive in the acoustic panels industry.

Finally it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments.

Claims

M An acoustic tile having an area, a decorative, layered front surface, side edges, and a thick, permeable, absorbent rear layer comprised of a material selected from a range of rock wool, glass wool, and fibrous plastics, characterised in that the acoustic tile includes a surface accessory layer comprising a relatively air-impermeable sheet or foil having a composition selected from a range of a plastic film, including polyester and terephthalate films, a cellulose film, a metallised plastics film, and a metal foil, bearing a selected adhesive coating; the surface accessory layer is applied over the decorative front surface of the tile thereby rendering the acoustic tile substantially impermeable to passage of gas through the tile. An acoustic tile as claimed in claim 1, characterised in that the decorative layered front surface further includes a thin fibrous layer capable in use of being folded over sharp bends formed in the front surface. The surface accessory layer as claimed in claim 1, characterised in that the selected adhesive coating renders the surface accessory layer weakly adherent to the decorative front surface thereby allowing the surface accessory layer to be peeled away and removed. A method for machining an acoustic tile as claimed in claim 1; the method characterised in that the following steps are included: a. mounting the decorative layered front surface of the acoustic tile against a surface of a vacuum bed of a numerically controlled shaping machine, b. applying a vacuum to the vacuum bed thereby holding the acoustic tile against the bed by air pressure acting across the surface accessory layer, c. machining the acoustic tile from the rear surface, d. releasing the machined acoustic tile from the vacuum bed for subsequent application of adhesive, folding and shaping, and e. removing the weakly adherent impermeable sheet or foil from the decorative layered front surface before the acoustic panel is completely installed. The method as claimed in claim 4 characterised in that the step of machining the acoustic tile forms at least one “V-cut” along a cutting line from the rear surface; said “V-cut” comprises a linear valley having plane walls at 45 degrees to the surface of the acoustic tile and a base of the valley extends as far toward the decorative front surface as the thin fibrous layer.

6. The method as claimed in claim 5 characterised in that the manufacturing process creates one “V-cut” parallel to each side edge of the tile along a cutting line located at one panel thickness inward from each side edge, backing material is removed at comers of the acoustic panel for folding the decorative front surface, an adhesive is been applied on to the plane walls of each “V-cut” and the edges of the acoustic tile are folded away from the decorative front surface so that the plane walls of the “V- cut” are brought into adherent contact.

7. A machined and folded acoustic tile as claimed in claim 2 characterised in that the decorative front surface of the tile is folded over the side edges of the acoustic tile and covers the side edges of the acoustic tile.

8. The method as claimed in claim 5 characterised in that the manufacturing process further machines a parallel pair of “V-cuts” parallel to at least one side edge of the tile along cutting lines; an outer cutting line being located at least one panel thickness inward from all side edges and an inner cutting line being located at one panel thickness inward from the outer cutting line; comer material is removed for accommodation of intended folds of the decorative front surface, an adhesive is applied on to the plane walls of each “V-cut” and the edges of the acoustic tile are folded back from the decorative front surface in two stages, bringing a side strip of the decorative front surface around the side edge of the acoustic tile with one fold and bringing a back strip on to a rear surface of at least one side edge of the acoustic tile with another fold.

9. A machined and reinforced acoustic tile as claimed in claim 2 characterised in that the tile is provided with a reinforcing back strip along at least one edge of the acoustic tile, after the edges of the acoustic tile have been folded twice away from the decorative front surface along the line of both “V-cuts” and the adhesive applied along the “V-cut” surfaces has made contact and formed joints.

10. The method as claimed in claim 5 characterised in that the manufacturing process further machines a parallel pair of “V-cuts” spaced apart by one panel thickness across a central portion of the acoustic tile, applying an adhesive on to the plane walls of each “V-cut” and over the entire rear surfaces of the acoustic tile and then of folding the two parts of the acoustic tile together, thereby creating a double thickness tile. A machined and reinforced acoustic tile as claimed in claim 2 characterised in that the tile comprises a double-thickness tile, in which two fibre masses are adherent back-to-back and both exterior surfaces are covered with the decorative front surface. A penetrating clip for use with a machined and folded acoustic tile as claimed in claim 7 or in claim 9 or in claim 11, characterised in that the penetrating clip penetrates the sides of the machined and folded acoustic tile with sharp prongs directed within the plane of the panel and arising at a height of about half the thickness of an acoustic panel from a flat adherent shape fixed on to a substrate.