Field of the Present Invention

The present invention relates to a process and apparatus for laminating a core with a film using suction techniques, also known as vacuuming forming. For example the present invention can be used, but by no means exclusively, to laminate a core such an expanded polystyrene core with a single layer of film using vacuum forming.

Background of the Invention

Laminated core products can be used in range of different applications including structural building panels, containers, pallets and sporting equipment such as surfboards and alike. One of the benefits of laminated core products is that a low cost and low strength core material can be laminated with an outer skin to form a high strength and well refined product.

An existing process for making the laminated core product typically involves twin sheet thermo forming in which a first heat shrink skin is applied to one side of the core, followed by a second heat shrink skin being applied to the other side of the core with the skins overlapping to enclose the core. There are a number of heat shrink skins

commercially available including thermoplastic materials such as polyolefin, PVC, neoprene, silicone elastomers and fluoropolymers such as FEP, PTFE and so forth. These skins are pre-stretched and when heated, the skins shrink by relaxing back to their pre-stretched condition.

An improvement on the existing shrink lamination is the use of vacuum forming in which two female moulds are placed over the heat shrink skin and core. In order to enhance mechanical pressure applied by the moulds to the skin and core, a partial vacuum is created between the moulds and thereby improve the lamination of the skin to the core.

An object of the present invention is to provide an alternative process and apparatus for laminating a core. Summary of the Invention

The present invention relates to a process of laminating an air permeable core with a film, the process including the steps of: locating the core inside an enclosure that is at least in part defined by the film ; and applying suction to the core by positioning at least one suction passageway onto a surface of the core so as to draw air from within the enclosure into the core and create a pressure differential between i) the film that is exposed to ambient pressure and ii) the core, and cause the film to be pulled onto core to form a laminate core product.

In other words, applying suction to the core withdraws air from the core which in turn, draws air in the enclosure surrounding the core into the core.

Applying suction to the surface of the core may include applying suction in one or more lines along the surface of the core. For example, the suction passageway may be provided by multiple spatially separated dividers contacting the core along one or more lines and providing suction (or a partial vacuum) between the dividers. The dividers may have any shape, and are suitably planar bodies such as plates or blades.

The partial vacuum or suction may be provided by a pump or compressor that is connected to the suction passageway.

Applying suction to the surface of the core suitably includes applying suction along a perimeter on the surface of the core so as to draw air surrounding the core inwardly into the core and the film, disposed about separate parts of the core, so as to pull the film toward all outer surfaces of the core concurrently. The perimeter about the core contacted by the suction passageway may be any perimeter including the largest perimeter and smaller perimeters. One of the advantages in applying suction to the surface of the permeable core, such as about of the perimeter of the core, is that air can be drawn into parts of the core that are adjacent to, and remote from, where the suction passageway contacts the core. We have found that this can minimise the formation of air pockets between the film and the core. Moreover, the film can be pulled onto all surfaces of the core including cut outs, overhangs, undercuts, and other concave formations. The film can also be pulled onto the core at an even rate or an uneven rate depending on the shape and permeability distributions within the core.

The process may also include applying suction directly to space between the film and the core. The suction passageway contacting the surface of the core, or another suction passageway, may be open to space between the film and the core. For example, applying suction directly to space between the film and the core may be provided by an aperture in the suction passageway contacting the surface of the core. In other words, the suction applied directly to the space between the film and the core is independent of air being drawn into the core by suction being applied to the surface of the core. Applying suction to the space between the film and the core may be carried out while at least one suction passageway is being placed on the surface of the core.

Ideally, the film is relative non-permeable compared to the core.

The step of locating the core inside the enclosure may include locating a frame assembly about the core, and moving the suction passageway between a retracted position in which the passageway is spaced from the core, and an advanced position in which the suction passageway contacts the core. Suitably, the suction passageway extends from the frame assembly and when in contact with the core, the suction passageway can support the weight of the core while in a lifted position.

The frame assembly suitably defines a wall having a front side (or upper side) and a rear side (or a lower side), and the step of locating the core inside the enclosure may also include positioning sections of the film on the front and rear sides of the frame assembly so as to enclose the core. Suitably, the sections of the film located on the front and rear sides of the frame assembly from a seal with the frame assembly so that the enclosure about the core is airtight. The film may be located on the front and rear sides of the frame assembly after the frame assembly has been located about the core.

The sections of the film located on the front and rear sides of the frame assembly may be held by peripheral clamps that form a seal with the wall of the frame assembly.

Suitably, the process includes the peripheral clamps each picking up a sheet of the film and locating onto the front and rear sides of the frame assembly to form a seal therewith. Suitably, the peripheral clamps sealing engage the film and the peripheral clamps sealing engage the frame assembly.

Suitably, two separate sheets of the film are sealed to front and rear sides of the frame assembly.

The process may also include forming a seam between abutting sections of the film, the seam being formed by the sections of the film being pulled toward the suction passageway, and overlapped at, or adjacent to, the surface of the core contacted by the suction passageway.

The seam between the sections of the film may be formed adjacent to the surface of the core that is contacted by the suction passageway. In one example, in which two sections of the film are laminated to core, suitably the suction passageway extends about a perimeter of the core and a seam is formed extending about the perimeter of the core.

It is within the scope of the present invention that the core may be laminated by a single sheet of the film, for example, a single sheet folded over the core to provide a single layer of the film about the core. In another example, the film is a pre-form such as a bag, sleeve, or partially formed tube having one or more entrance. Suitably, the suction passageway applies suction in a line on the surface of the core adjacent to the or each entrance, and the film between abutting sections of the film closes the or each entrance of the pre-form.

Forming the seam suitably includes retracting the suction passageway away from

(and out of contact with,) the surface of the core, and a pressure reduction previously induced in the core by the suction passageway pulls the film toward the core previous contacted by the suction passageway so that abutting sections of the film overlap to form a seal. In one example, the overlapping portions are flush against the core so that one section lies adjacent to the core to from an inner portion of the seam, and the other overlaps to form an outer portion of the seam. In another example, the overlapping portions extend outwardly from the surface of the core and seal together. In other words, the overlapping portions that form a seal are not in direct contact with the core and rather form a protruding flange.

Forming the seam may include selectively opening the suction passageway to space between the core and the section of the film to at least one side of the suction passageway to draw air from the space and further pull the section of film from the side opened to the suction passageway toward the suction passageway.

Suitably, the suction passageway has two spatially separated dividers initially in contact with the core, and the step of forming the seam includes retracting one of the dividers from the surface of the core so as to open the suction passageway to one side of the passageway and, thereby further pull the section of film toward the opened passageway.

Forming the seam may also include retracting the other divider from the surface of the core so as to open the suction passageway to the other side of the suction passageway so that the sections of the film on two sides of the suction passageway abut against each other.

The step of forming the seam may be carried out after the film has been pulled onto surfaces of the film facing the film.

The step of forming the seam is carried out after suction applied to the core has pulled the film onto all surfaces of the core remote from where the suction passageway initially contacts the core.

The process may also include trimming excess extending from the seam formed between the abutting sections of the film.

Suitably, suction is applied to the surface of the core in a line that is spaced to a surface of the core onto which the film is first pulled onto the core. The process may also include heating the film prior to or during laminating the film to the core to increase stretchability of the film. Depending on the constituents of the film, the film may soften and become stretchable on exposure to the heat source. Suitably, the step of applying suction to the core and thereby pull the film onto the core occurs while the film is heated above ambient temperature. For example, the film may be heated to a temperature above ambient temperature and less than or equal to a temperature of 90°C.

Once the film has been laminated onto the core, the process may include cooling the film, for example by cooling the film to ambient temperature. Cooling the film can cause the film to harden or shrink so as to tension the film about the core.

The process may also include bonding two laminated core products together to form an assembly of laminated core products. For example, the assembly may be a pallet of which an upper and lower deck of the pallet may each comprise a laminated core product that are assembled together to form the assembled product. In this example, the upper and/or lower deck may also have the columns to form openings into which fork tines of the forklift may be received. The assembled product could also, for example, include a structural wall panel, a container such as intermediate bulk shipping container (IBCs) or a water craft product such as a surfboard onto which fins are bonded to a main body of the surfboard.

In any event, the bonding step may include applying heat to the external faces of the film and pressing heated surfaces of the laminated product together.

The core may have any suitable form and be made of any suitable material provided it has some degree of permeability or porosity. The core ideally has a shape that defines a final laminated product. The core is suitably relatively non-deformable compared to the film and may possess any three dimensional shape desired. The core may, for example, be made from any synthetic material such as foam, plastic and rubber materials; and naturally occurring materials such as timber. Polystyrene and, in particular, expanded polystyrene beads is an example of a particularly suitable material. An advantage in using expanded polystyrene beads for the core is that expanded polystyrene has significant load carrying properties, including both stress and strain on a mass basis compared to other materials. Expanded polystyrene is readily mouldable and will hold its shape precisely on being mould for a period of time, such as up to 20 minutes. The density and permeability of expanded polystyrene can also be adjusted and controlled depending on the form of the final laminated product required.

The film may be any suitable film, and ideally is stretchable film and heat softenable. Suitably, the film may be any polystyrene compatible formable plastic sheet. The present invention also relates to an apparatus for laminating an air permeable core with a film, the apparatus including: an enclosure in which, when in use, the core is located and wherein the enclosure is at least a part defined by the film to be laminated onto the core; a suction source; and a suction passageway connected to the suction source, wherein the suction source is operable to contact a surface of the core in the enclosure so as to draw air from within the enclosure into the core and create a pressure differential between i) the film that is exposed to ambient pressure and ii) the core, and thereby cause the film to be pulled onto the core and form a laminated core product.

The enclosure may include a frame assembly having a front side and a rear side that extends about the core being laminated, and a front clamp and rear clamp that are operatable to sealing hold sections of the film to the front and rear sides respectively to make the enclosure airtight. Suitably, the frame assembly has two sheets of the film, one on a front side and another on the rear side.

The front and rear clamps may also be operable to pick up and sealing hold sections of the film and sealing engage the frame assembly.

Suitably, the suction passageway extends from the frame assembly.

The suction passageway may include multiple spatially separated dividers between which the passageway is defined that can be moved between a retracted position in which the passageway is spaced from the core, and an advanced position in which the suction passageway contacts the core. When the suction passageway is in contact with the core, the suction passageway is able to support the weight of the core i.e., in an elevated position.

Suitably, the suction passageway includes multiple pairs of spatially separated dividers, and the pairs of separated dividers align to form a continuous suction passageway that extends about a perimeter of the core.

Suitably, the dividers are retained in contact with the core until the film has been pulled onto the surfaces of the core except for surfaces of the core about the perimeter of the core. Suitably, the dividers of the suction passageway can be moved between advanced and retracted positions independently so that retracting one of the dividers enables the suction passageway to be opened to the space between the core and the film to one side of the suction passageway, and thereby pull the film toward the suction passageway.

The other divider of the suction passageway can also be retracted so that the suction passageway opens to space between the core and the section of the film on another side and thereby pull the film toward the suction passageway from another side of the suction passageway.

By retracting the dividers in this way, the sections of the film can be placed in overlapping relationship to form a seam extending outwardly from the core.

The apparatus may also have a heater for heating the section of films prior to and/or while the suction passageway contacts the core.

The apparatus may also include a trimming station for trimming excess film from the seams.

The apparatus may also include a bonding station in which separate laminated core products are bonded together, for example, by heating outer film and pressing the heated outer surface together to form an assembly.

Brief Description of the Drawings

The present invention will now be described with reference to the following non- limiting drawings which exemplify a preferred form of the invention, of which:

Figure 1 is schematic perspective view of an apparatus for laminating a core with a film using vacuum or suction, in which the core is locating inside a frame assembly having upper and lower clamps for holding sheets of film, the sheets of film have been omitted so that the core to be laminated can be seen;

Figure 2 is a cross-section through arrows A-A in Figure 1 and illustrates the first step of forming an airtight enclosure about the core, and a suction passageway for applying suction to the core is located in an advanced position to make contact with an outer surface of the core;

Figure 3 is the cross-sectional view shown in Figure 2 in which suction is applied to the core and the film has been pulled onto outer surfaces of the core;

Figure 4 is the cross-sectional view shown in Figures 2 and 3 in which suction has continued to be applied to the core so that the film has begun to be pulled onto the surfaces inwardly of the outer surfaces of the core, and in addition, onto a downwardly facing surface of the frame assembly; Figure 5 is the cross-sectional view shown in Figures 2 to 4 in which further suction has been applied to the core and, in addition, an upper divider blade defining part of the suction passageway has been partially retracted from the surface of the core to further pull the film downwardly and the film on the lower face has been pulled further upwardly so as to being to contact a lower divider blade of the suction passageway, and thereby begin to form a seam between sections of the film above and below the suction passageway;

Figure 6 is the cross-sectional view shown in Figures 2 to 5 in which the lower divider blade of the suction passageway has been partially retracted and the film contacts opposite sides of the lower divider blade;

Figure 7 is a cross-sectional view shown in Figures 2 to 6 in which the upper and lower divider blades have been fully retracted from the core, and the film from the upper and lower halves have joined together to form a welded seam; and

Figure 8 is a schematic illustration of an apparatus for producing laminated core products, trimming the laminated products, and bonding the laminated products together to form an assembled product such as a pallet for moving material.

Detailed Description

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings which include reference numerals. Whilst the reference numerals have been used through the text in this section of the specification, for the purpose of maintaining clarity of the drawings, not all of the reference numerals have been used in each drawing.

The preferred embodiment includes an enclosure 20 having an outer frame assembly

10 with a top clamp 1 1 , a bottom clamp 12 and a mid clamp assembly 13 therebetween. The top clamp 1 1 and bottom clamp 12 can each hold a sheet of laminating film (not shown in

Figure 1 ) to laminate to a core 15. The mid clamp 13 encircles around the core 14, and the top clamp 1 1 and bottom clamp 12 sealing engage the mid clamp 15.

Figure 1 illustrates the situation in which the top clamp 1 1 and bottom clamp 12, without holding sheets of laminating film have been moved onto the mid clamp 13 so that the core 15 is left exposed. With reference to Figure 8, the core is moulded in an adjacent moulding station 16 comprising a two part mould in which moulding material, such as polystyrene beads are expanded into the desired shape. One of the advantages in using expanded polystyrene is that the core 14 can precisely retain its dimensions for

approximately 18 to 20 minutes after moulding. The mid clamp 13 includes a plurality of divider blades 17 that extend from the mid clamp 13 and encircle the core 15. The divider blades 17 can be moved between a retracted position and an advanced position in which the divider blades contact with a perimeter of the core 15. The perimeter may be any perimeter intermediate between upper and lower faces 15a, 15b of the core 15. The contours of the divider blades 17 and the core 15 have been coordinated so that the blades 17 can make contact with the core 15 without deforming or temporality depressing the core 15. The top and bottom clamps 1 1 , 13 also move independently of the mid clamp 13 and are adapted to engage and hold sheets of the laminating film 18. Once the core 15 is held by the blades 17 of the mid clamp 13, the top and bottom clamps 1 1 , 12, holding respective sheets of the film are then moved into sealing engagement with the mid clamp 13, and thereby locating the core 15 inside an airtight enclosure 20 in a laminating station 19.

Depending in the properties of the film 18, the preferred embodiment may also include heating the film with a heater (not shown in the Figures) prior to and/or whilst the top and bottom clamps 1 1 and 12 sealing engage the mid clamp 13. Heating the film 18 can increase the stretchability and flexibility of the film 18.

Figures 2 to 7 illustrate a cross-section in the direction of arrows A-A in Figure 1. The cross-section schematically illustrates the top clamp 1 1 holding a top sheet of the film 18 and sealing engaged with an upper surface of the mid clamp 13, and the bottom clamp 12 holding a bottom sheet of the film 18 and sealing engaging with a lower surface of the mid clamp 13. The mid clamp 13 has divider blades 17 that are separated by a spacing which defines a suction passageway 21 . At least four pairs of divider blades 17 are positioned around the mid clamp 13 and can contact a perimeter of the core 15. The pairs of divider blades 17 in essence form a suction passageway 21 that extends in a loop about the perimeter of the core 15. Applying suction to the core 15 is carried out by a vacuum source connected to an internal void 22 of the mid clamp 13 which communicates with the spacing between the divider blades 17.

Suitably actuators, not shown in the Figures, move the divider blades 17 between the advanced and retracted positions.

Figures 2 and 3 illustrate the divider blades 17 located in an advanced position and making contact with the perimeter of the core 15 to as to support the weight of the core 15. Figure 2 also illustrates the situation in which suction is yet to be applied to the core 15 and the sheets of film 18 are spaced from the core 15.

With the divider blades 17 in contact with the perimeter of the core 15, operation of the vacuum source applies suction to the passageway 21 which draws air from space between the permeable core 15 and the film 18 into the passageway via the permeable core 15. Applying suction to the core 15 creates a pressure differential between the inside of the enclosure and atmospheric pressure, which pulls the film 18 onto the core 15. Figure 3 illustrates the initial step of the applying suction to the core so as to pull the film 18 onto outer surfaces 15a, 15b of the core 15. As can be seen by the direction of the arrows, air is withdrawn from the core 15 which draws air surrounding the core 15, between the film 18 and the core 15 into an outer surfaces including surfaces 15a and 15b of the core 15.

Although it is not necessary, one or more of the divider blades 17 may also include apertures 23 that allow direct communication between the suction passageway 21 and the space between an outer surface of the core 15 and the film 18. In the case of the preferred embodiment apertures 23 are provided in the lower divider blade 17 which helps pull the lower film 18 upwardly against gravity and onto the outer face of the core 15.

Figure 4 illustrates the film 18 being pulled toward the outwardly facing side walls 15c of the core 15 and the inwardly facing walls of the mid clamp 13, particular the lower portion of the wall of the mid clamp 13. This process is facilitated by the film 18 stretching and the air between core 15 and the film 18 being pulled into the core 15 and, in turn, into the suction passageway 17. A follower bar, not illustrated in the figures, may also move between the mid clamp 13 and the outer face of the core 15 on the outside of the film 18 to assist in stretching the film 18 into the form shown in Figure 4.

While in the state shown in Figure 4, the film 18 may also be pulled into cut outs, overhangs and concave sections of the outer face of the core as a result of the permeability of the core 15 allowing air surrounding the core 15 to be drawn into the outer surface of the core 15.

Forming a seam 25 between the top and bottom sheets of the film 18 may be achieved by overlapping portions of the top and bottom sheet flush with an outer surface of the core 15. Alternatively, forming the seam 15 may include overlapping sections of the top and bottom film extending outwardly from the surface of the core 15 to form a flange.

It will be appreciated by those skilled in the art of the invention that the flush seam may be formed by overlaying the inner surface of either the top sheet or the lower sheet on the outer surface of the lower sheet or top sheet respectively.

Figures 5 to 7 illustrate the steps for forming the seam extending outwardly from a surface of the core in the form of a flange.

Specifically, Figure 5 illustrates applying suction to the core 15 so as to pull the film 18 onto the divider blade 17b and, in addition, the top divider blade 17a has been partially retracted so as to allow direction communication between the suction passageway 21 and - l i

the space between the top film 18 and the outer surface of the top part of the core 15. Figure 6 illustrates retracting the top plate 17a completely such that the top sheet of the film 18 has been completely pulled onto the lower divider blade 17b. The size of the portion of the lower sheet pulled onto the lower divider blade 17b has also increased and the lower blade 17b has been partially retracted.

Figure 7 illustrates the top and bottom divider blades 17a, 17b fully retracted. The reduced pressure that has been induced in the core 15, and ambient pressure acting on the outer surface of the film 18 cause the remaining air between the film and the core to be drawn into the core 15 and inner surfaces of the film abutting each other and extending outward to form the flange seam 25. The abutting sections can then self bond together to form an airtight weld. One of the numerous advantages of the preferred embodiment is that the seam 25 is formed without external mechanical pressure being applied to the seam 25.

The top and bottom clamps 1 1 , 12 may then be released to free the laminated core product 26 and processed in a trimming station 27. Specifically, the process may involve cutting excess film and reducing the size of the seam flange 25 to a suitable size.

Depending on the final product required, two or more laminated core products or components may be assembled and bonded together in an assembly station 28. For example, in the situation in which the laminating film is can be welded together, the assembly of the laminated core products may include applying heat to the laminated core products. The heated surfaces are then pressed together to form an assembled product. Applying heat to the laminated core products may involve applying heat to selected areas of the laminated core products to be bonded together. Applying heat to selected areas may, for example, involve shielding parts of the laminated core product from the heat source and exposing the selected areas to the heat source using a shroud.

Those skilled in the art of the present invention will appreciate that many modifications and variations may be made to the preferred embodiment described above without departing from the spirit and scope of the present invention.