MEMBRANE MACHINE

Abstract: A method and apparatus for applying a membrane film to the surface of a porous object, involving supporting an object (20) on supporting means (4), applying a sheet of membrane film (14) over the object (20) and applying a vacuum which acts through the object (20), drawing the membrane film (14) into contact with the surface of the object (20). Then bonding the membrane film (14) to the object (20).

Description: MEMBRANE MACHINE The present invention relates to method and apparatus for applying a membrane film to the surface of a porous object. The invention is particularly applicable to the application of membrane films to porous wooden objects such as cupboard doors and other like furniture or fixtures, and it will be convenient to describe the invention with that application in mind. It is known to apply membrane films such as vinyl or plasticised synthetic sheets to cupboard doors or the like for decorative and protective purposes and to simulate a painted surface. The application of such a film is preferred in some circumstances over the application of paint, because painting is time consuming and inefficient during medium to large scale production runs, but more importantly, film application generally provides a higher quality surface finish to the door and also provides a more durable protective surface compared to that of paint. Further, vinyl or other like membrane films can be produced in a range of colours and patterns for direct application to the door. Known methods and apparatus for the application of membrane films to wooden doors generally require the application of extremely high pressure to force the membrane film into sealing contact with the surface of the door. The extreme high pressure is principally required to ensure that the membrane film is satisfactorily attached to every surface of the door, in particular decorative cavities, recesses or grooves or the like which deviate from the planar surface of the door. The existence of such cavities has previously resulted in ineffective attachment of the membrane film to the surface of the door, because it is not always possible, even under extreme pressure, to fully extend the film into each cavity for attachment to the surface thereof. Clearly, the greater depth the cavity has, the more difficult it becomes to attach a membrane film thereto, although the width of the cavity also contributes to that degree of difficulty. One type of known machine for applying membrane films includes a silicon rubber mat which presses the membrane film against the planar surface of the door. The rubber mat is required to be sufficiently malleable to ingress under pressure applied to it into any decorative cavities or the like which may be present on the surface of the object, while the pressure exerted on the mat must be sufficient to ensure that ingress of the mat into such cavities is achieved fully. That ensures that adequate surface contact between the mat and the cavities is achieved, thereby ensuring that the membrane film is pushed into and against the entire surface area of each cavity. In the above described machine, above the rubber mat there is normally located a heating mat which applies heat to the rubber mat. That heat is conducted through the rubber mat and heats the membrane film to assist in adhering the film to the surface of the door. In this respect, a surface of the door is normally coated with an adhesive layer to adhere the membrane film thereto under the application of pressure and heat. In this known process, the adhesive is heat activatable, so as to bond at a certain temperature. Thus, when the adhesive layer applied to the surface of the door reaches the correct activation temperature, the membrane film bonds to the surface of the door under assistance of the pressure exerted on it by the silicone mat. Once bonded, the pressure exerted on the rubber mat is released and the door is allowed to cool to a stable temperature, after which it may be removed from the machine. It is therefore clear, that if the membrane film is not fully pressed into contact with all surfaces of the door, particularly the cavities, then bonding to those surfaces will not take place. The pressure applied to the silicone rubber mat is normally pneumatic pressure in the order of 80 to 100 bar. To generate and constrain this extreme pressure, the construction of the machine must be particularly heavy and in that respect, known machinery includes upper and lower metal panels defining a pressure vessel, each panel being in the order of 200mm to 250mm thick. Additionally, the hydraulics and pneumatics necessary to operate the machinery are of a very heavy nature. Consequently, the machinery is quite expensive. Further, given the temperature and the high pressure involved in the operation of the known machinery, the silicon mat and the heating mat tend to wear relatively quickly and must therefore be replaced on a regular basis. This results therefore additionally, in expensive operation of this type of machine. The above type of known machinery is additionally regularly ineffective where the decorative cavities as previously referred to are of such a depth or configuration that the silicon mat cannot penetrate into them to a sufficient degree that the membrane film is adequately adhered to the surface of the cavity. Thus, the design of doors to be treated by the known machinery is limited because of the operational restrictions of that machinery. The present invention is primarily concerned with objects constructed from a porous material such as wooden product, or manufactured wood, eg. chipboard or kraftwood. However, the present invention is only limited to porous materials in as much as their use in the present invention is likely to generate the most substantial benefits, compared to that of non-porous materials. It is an object of the present invention to provide a machine and a process for applying a membrane film to a porous object, which overcomes one or more of the disadvantages of the known processes and machinery. According to the present invention there is provided a method of applying a membrane film to a surface of a porous object, the method including supporting said object on supporting means, applying a sheet of membrane film over said object and applying a vacuum which acts through said object drawing said membrane film into contact with the surface of the object and bonding said membrane film to said object. The membrane film is preferably of a substantially non-porous nature to ensure that it is adequately drawn into contact with the surface of the object. The membrane film is preferably bonded to the object surface by virtue of an adhesive and in one embodiment, that adhesive may be applied to the particular surface prior to the membrane film being applied to the object. In one embodiment, the adhesive may be an adhesive that only bonds under certain conditions such as a particular heat or pressure. In that embodiment, the adhesive may be applied to the object well before the membrane film is applied. The adhesive is preferably of a heat activated nature and the method thus preferably includes means to heat the membrane film to a suitable temperature to react with the adhesive and to thereto bond to the object. Any suitable means are used for this purpose, but in one particular embodiment, infra-red heating means are used. Such infra-red heating means may be used to heat the membrane film prior to adhesion with the object and upon reaching the reactive temperature, the vacuum may be then applied, thus bringing the membrane film into contact with the object surface and bonding thereto. The temperature of the membrane film may be maintained by infra-red sensing means which can accurately determine when the vacuum should be applied. The support means may take any suitable form, but in one embodiment, it may be a supporting deck upon which the object or objects may be located. In one embodiment, the support deck may include means to enable the vacuum to pass through it and in that embodiment, the support deck may include one or more openings which communicate with a vacuum generating source preferably located beneath the support deck. The vacuum may be generated between the membrane film and the supporting deck by providing sealing means to entrap the vacuum therebetween. In one embodiment, the membrane film seals against the supporting deck about the object upon generation of the vacuum. Alternatively, a vacuum chamber may be created about the supporting means by providing a cover which cooperates with the supporting means for that purpose. In that embodiment, sealing means should be provided to seal the cover to the supporting means and to create a vacuum chamber in which the vacuum can be applied. Where the membrane film is sealable against the support deck, the cover need not form a vacuum chamber with the supporting means, although it may still be preferable to provide a cover and in one embodiment, the cover may advantageously include heating means to heat the membrane film as may be required. The present invention further provides apparatus for applying a membrane film to the surface of a porous object, said apparatus including supporting means for supporting said object and vacuum generation means for generating a vacuum which acts through said object, the apparatus being arranged so that a sheet of membrane film placed over said object is drawn into contact with a surface of said object for bonding thereto upon generation of a vacuum by said vacuum generation means. In order to assist in arriving at an understanding of the present invention, a preferred embodiment is illustrated in the attached drawings. However, it should be understood that the following description is illustrative only and should not be taken in any way as a restriction on the generality of the invention as described above. Figure 1 is a perspective view of one embodiment of apparatus according to the invention. Figure 2 is a further perspective view of the apparatus according to Figure 1. Figures 3 and 4 are cross-sectional views of the apparatus illustrated in Figures 1 and 2. Figure 5 illustrates an object to which a membrane film may be applied. Figure 6 is a cross-sectional view of the object of Figure 5. Figure 1 is an illustration of a membrane machine 1 according to the invention. The machine 1 includes a housing comprising a cover 2 and a base 3. The base 3 encloses a plurality of parts necessary for the function of the machine 1, but in particular, it encloses the vacuum generation means. The vacuum generation means may include any suitable components to generate the required vacuum, which will generally be in the order of 0.9 bar, which is a dramatic reduction in pressure compared to previously known machinery. The base 3 includes a support deck 4 for supporting objects which are to have a membrane film applied thereto. The supporting deck 4 includes a plurality of openings to and in communication with the vacuum source so that the vacuum generated by the vacuum source can pass through the support deck 4. The support deck 4 is preferably constructed from aluminium, as that metal reflects infra-red heat, the advantage of which will become apparent later. The support deck 4 preferably includes a raised edge 6 which is raised above the flat surface of the support deck 4. The raised edge 6 provides a sealing surface for cooperation with a complimentary sealing surface of the cover 2, although other arrangements to seal the cover 2 and base 3 together may be adopted. Upon sealing of the cover 2 and the base 3 together, a chamber is formed between those two parts for the accommodation of a vacuum generated by the vacuum source. It is preferable that vacuum is retainable within the vacuum chamber for a time period necessary to bond the membrane film to the object surface, which period will be determined by the type of object to which the membrane is to be adhered to, although where the membrane film is sealable against the surface of the support deck 4, the vacuum can be retained between that surface and the film and therefore the cover 2 need not seal hermetically against support deck 4. The cover 2 preferably includes heating means to heat the membrane film to the temperature necessary to bond with the object. That heating means is, in one embodiment, in the form of a bank of infra-red heaters extending across the full cross-sectional area of the cover 2. Infra-red heat is advantageous in the arrangement illustrated, because the heat generated is not absorbed by the aluminium support deck 4, but is instead reflected. Thus, the support deck 4 does not heat to any significant degree due to the existence of the heating arrangement. This enables objects to be manually placed on and removed from the support deck 4 with little risk of bums from contact with the support deck. Further, the temperature of the heating arrangement may be easily monitored with the use of an infra-red sensor. The cover 2 may be raised and lowered as necessary by a supporting structure 7. The supporting structure may be of any suitable form, but will generally include hydraulic or pneumatic rams connected at one end to the cover 2 and at the other end to the base 3 or the surface upon which the base 3 is supported. Arms 8 serve to stabilise the cover 2 as it is raised and lowered. The cover 2 is raised sufficiently to allow access to the support deck 4 so that objects may be placed on the support deck 4 and removed therefrom as necessary. The cover 2 is preferably lowerable sufficiently to engage the raised edge 6 of the base 3 and preferably engages that edge in such a manner that a sealed vacuum chamber is formed that can retain the vacuum subsequently generated, although as discussed previously, that type of hermetically sealed arrangement is not entirely necessary. For sealing purposes, the cover 2 may include a flexible seal 9 about the lower edge 10 thereof for sealing with the raised edge 6 of the base 3. Other types of sealing means may also be appropriate. Figure 2 is an illustration of the machine 1 of Figure 1 with the cover 2 lowered and in sealing contact with the raised edge 6 of the support deck 4. Features corresponding to those illustrated in Figure 1 have been referenced by the same numerals. The machine 1 may further include means to securely locate a web of membrane film over the surface of the support deck 4 and that means may include a locating arrangement 11 at either end of the support deck 4. Each locating arrangement comprises a bar 12 extending across the width of the support deck 4 and each bar 12 carries a series of suction cups 13. To secure the web of membrane film across the support deck 4, the web is extended between the opposing bars 12 and the face of the web is placed in contact with the suction cups 13 through which suction is applied to the web. This arrangement is better illustrated in Figure 3. In Figure 3, a web of membrane film 14 is stretched from a supply roll 15 over the support deck 4 between opposing locating arrangements 11. The supply roll 15 is a convenient way of providing a continuous web, although separate sheets of membrane film may alternatively be used. As is apparent from this Figure, the suction caps 13 secure the web above the surface of the support deck 4. The web 14 is not required to be taut, as it must include enough slack to enable it to be brought into contact under vacuum force with objects supported on the support deck 4. Figure 3 also illustrates the vacuum generator vessel 16 and shows that in communication through passages 17 with a vacuum chamber 18. The vacuum chamber 18 is in communication with a basin 19 formed by the support deck 4 and the raised edge 6, through the openings 5 (not seen in this figure). It is considered that further detail surrounding the means for generating a vacuum is not required, but is within the general knowledge of a person skilled in this field. The requirement is to generate a vacuum which communicates with the vacuum chamber 18 and any means suitable to achieve that requirement will suffice for the purposes of the present invitation. Figure 3 also illustrates objects 20 which might typically be subject to a membrane film covering. These objects might be cupboard doors for example, and the following description will relate to the covering of such an object. It is to be appreciated however, that other objects of many sizes could also be covered by the method and apparatus of the present invention. In this respect, tests have satisfactorily applied a membrane covering to a household door measuring 1800mm x 900mm x 33mm and made of kraftwood. In use, the doors 20 are placed on the supporting deck 4. The number of doors placed on the supporting deck is dependent only on the size of the deck compared to the size of the door and therefore any number of doors may be placed on the deck 4. The doors are preferably spaced from each other at least a small distance (typically 4 or 5 centimetres) to enable the membrane film to be brought into contact under vacuum with the side edges of each door, for application to those side edges, although if it is not necessary to cover the side edges of each door, then a plurality of doors may be placed immediately adjacent one another. The web 14 is stretched over the support deck 4 and the door 20, with enough slack to enable the web to be wrapped around the doors 20 under vacuum force. That may mean that the web 14 rests under its own weight against the upper surface of the doors 20 prior to application of the vacuum, but that does not create any problems while the temperature of the web 14 and door 20 is below that of the activation temperature. The suction caps 13 are then activated to secure the web 14 in place. The web 14 is severed from the supply roll 15, although this may be completed prior to or following vacuum generation as appropriate. It is to be noted that the doors 20 are elevated above the level of the support deck 4 on blocks 21 and the reason for this will become apparent later. When the apparatus is set as in Figure 3, the cover 2 may be brought into the position as illustrated in Figure 2. In that position, the infra-red heaters commence heating of the web 14 to the desired bonding temperature, although alternatively, the door 20 may be heated separately or in addition to the web 14. The heating temperature for vinyl webs is preferably approximately 100°C to 120°C and the heat-up time is typically approximately 30 seconds. While the web 14 is undergoing heating, it may tend to sag and, if not already, it may tend to come into contact with the objects 20 and/or the support deck 4. Given that heating of the web 14 will eventually bring it to the activation temperature of the adhesive, it must be prevented from contact with the door 20 until the vacuum is generated. Thus, a gentle air force is blown out of the support deck 4 through the openings 5 to ensure that the web 14 floats above the doors 20 and the support deck 4 to prevent contact therewith. This may or may not be necessary depending on the flexibility of the web 14. When the bonding temperature is reached, the vacuum may be generated within the vacuum chamber 18 to act on the web 14, The manner in which that acts on the web 14 is illustrated in Figure 4. In Figure 4, the vacuum generated draws the web 14 in the direction of the support deck 4 which means the web wraps around each door 20. The blocks 21 elevating the doors 20 enable the web 14 to wrap fully around the side edges of the objects 20 which, without the blocks, would not result in an entirely satisfactory bond because the web tends to pull away from the corners under the effect of the vacuum. With known machinery, a frame is generally constructed around the door, but spaced from the edge thereof, so that a recess is created between the frame and the edge of the door. That enables the rubber mat used in known machinery to be pressed into the recess to bond the membrane film to the edge surface of the object. While the end result is generally adequate, the assembly of the frames is tedious and time consuming and each frame must be constructed to suit the particular object being covered. It is therefore a relatively unsatisfactory arrangement which is entirely dispensed with the method and apparatus of the present invention. The vacuum is maintained for a period of time suitable to ensure adequate bonding between the membrane film 14 and the door 20. A period of approximately 30 seconds to 2 minutes is normally sufficient for the door to cool to a temperature at which it can be removed from the support deck 4. The cover 2 may be raised at this stage so that the door 20 can cool. After sufficient time has elapsed, the vacuum may be released and the membrane film 14 trimmed from about the edge of the door 20. The arrangement illustrated in Figure 4 is advantageous for the application of a membrane film to a door or other object, but it is particularly advantageous in relation to objects which include cavities or grooves for decorative or other purposes. A typical cupboard door including such recesses is illustrated in Figures 5 and 6. The door 30 in Figure 5 is of a porous nature and includes a decorative recess 31 recessed into the outside surface thereof. With normal membrane application apparatus, a malleable silicone mat would press the membrane web into the recess 31 under pressure. The membrane may well be adequately bonded over the full surface 32 of the door 30, although that is not always the case, particularly if the recess 31 is of a sufficient depth and if the walls 33 of the recess 31 are so upright that the silicon mat could not adequately ingress into the recess, particularly into the corners, then the likelihood of adequate bonding is reduced. In that case, the arrangement of the present invention overcomes that problem because the web is pulled onto the surface 32 by the vacuum force which operates through the full cross-section of the porous door 30. Thus, the web is neatly bonded to every surface, including the corners. Comparative tests conducted to date show that membrane film applied to doors having cavities such as those illustrated in Figures 5 and 6, is applied far more consistently to the full surface of the cavities compared with film applied by the known machinery. ln addition to the sealing arrangement already described, a sealing bead 34, such as a concave recess, can be located on the support deck 4 preferably adjacent the raised edge 6. The bead 34 preferably extends fully about the circumference of the support deck 4 and when vacuum is applied to the web 14, it is drawn into the bead 34 which seals the web 14 against the support deck 4. With an adequate seal generated between the bead 34 and the web 14, the vacuum is contained between the web and the support deck 4 about the door 20. That arrangement therefore negates the necessity to provide a cover, in as much as that cover is required to provide a vacuum chamber. The cover is still likely to be necessary for the location of heating means if the adhesive for bonding the web to the door is heat activatable. The cycle time for the apparatus and method of the present invention is in the order of VΛ minutes which is much reduced over that of known cycles which are generally in the order of 4 minutes. Clearly, the process as above described is dependent on the door material being of a porous nature. The invention is particularly applicable to manufactured woods such as chipboard or kraftwood and the invention has been developed with that type of material in mind. However, the invention could clearly be used with other types of material with suitable adjustments in the vacuum pressure. Regardless of the material which is used with the process of the invention, it is the mechanism of the vacuum force pulling through the object which enables such precision bonding of membrane film to object surfaces, particularly recessed surfaces. It should be noted that in many cases, the door 30 of Figures 5 and 6 will require membrane film adhesion to both the front and rear side thereof. In that case, it is generally preferable to apply membrane film to one side and then repeat the process to the other side. Given that the membrane film is normally of a non-porous nature, the vacuum will not pull through the first applied layer and in that situation, it is necessary to provide openings in the membrane film on the first applied layer to enable passage of the vacuum force through the object. Such an opening need simply be the size of a relatively small drill hole and for cupboard doors, that opening may be provided by drill holes already provided for hinges or other fittings that might be attachable to the door. The opening need not have a substantial cross-section compared to the cross-section of the door itself, but must provide a passage for vacuum through the membrane film. The present invention thus enables a membrane film to be applied to the surface of a porous object and particularly enables the membrane to be applied and securely bonded to cavities and recesses which may form part of the surface of the object. The apparatus of the invention is of a far lighter construction than the presently known machinery and operates on a reduced cycle time, the end result of which is that of a significantly cheaper machine and product. Those skilled in the art will appreciate that there may be many variations and modifications of the configuration described herein which are within the scope of the present invention.

Claims: CLAIMS 1. A method of applying a membrane film to a surface of a porous object, the method including supporting said object on supporting means, applying a sheet of membrane film over said object and applying a vacuum which acts through said object drawing said membrane film into contact with the surface of said object, and bonding said membrane film to said object. 2. A method according to claim 1 , wherein said vacuum is applied through said supporting means. 3. A method according to claim 1 or 2, wherein said membrane sheet completely surrounds and overlaps said object such that upon application of said vacuum, the overlapping portion of said membrane film is drawn into contact with said supporting means to substantially contain said vacuum between said membrane film and said supporting means. 4. A method according to any one of claims 1 to 3, wherein bonding of said membrane film to said object occurs by way of adhesive existing between said membrane film and said object surface and wherein said adhesive is activated by heat applied to said membrane film or said object. 5. A method according to claim 4, wherein said heat is applied prior to the generation of said vacuum. 6. A method according to claim 4 or claim 5, wherein said heat is infra-red heat. 7. A method according to any one of claims 4 to 6, wherein said object is cooled for a period after activation of said adhesive, whereafter said vacuum is released. 8. A method according to any preceding claim, wherein a vacuum chamber is created about said object in order to contain said vacuum about said object. 9. A method according to any preceding claim, wherein said supporting means includes a supporting surface and means to elevate said object above that supporting surface so that said membrane film may be fully bonded to edge portions of said object. 10. A method according to claim 9, wherein said elevation means comprises a porous or perforated member which is placed between said supporting surface and said object and is of such a size that said edge portions overlap said porous member. 11. A method according to any preceding claim, wherein the membrane film is substantially non-porous such that said vacuum is substantially prevented from passing through it. 12. Apparatus for applying a membrane film to the surface of a porous object, said apparatus including supporting means for supporting said object and vacuum generation means for generating a vacuum which acts through said object, the apparatus being arranged so that a sheet of membrane film placed over said object is drawn into contact with a surface of said object for bonding thereto upon generation of a vacuum by said vacuum generation means. 13. Apparatus according to claim 12, wherein said supporting means includes elevation means suitable to elevate said object above said supporting surface. 14. Apparatus according to claims 12 or 13, wherein said supporting means includes openings extending between said vacuum generating means and an upper supporting surface of said supporting means upon which said object is supported. 15. Apparatus according to claim 14 when dependent on claim 13, wherein said openings extend through said elevation means. 16. Apparatus according to any one of claims 13 to 15, wherein said apparatus includes heating means for heating said membrane film or said object to assist in bonding of said membrane film to said object surface. 17. Apparatus according to claim 16, wherein said heating means provides infra-red heat. 18. Apparatus according to claim 16 or 17, wherein said apparatus includes heat sensing means for determining the surface temperature of said membrane film or said object. 19. Apparatus according to any one of claims 12 to 18, wherein said apparatus includes a retractable cover for cooperation with said supporting means to create a chamber about said supporting means. 20. Apparatus according to claim 19, wherein said cover includes sealing means for sealing with corresponding sealing means depending from said supporting means. 21. Apparatus according to claim 20, wherein said supporting means sealing means includes a raised lip extending about the periphery of said supporting means for cooperation with said cover sealing means. 22. Apparatus according to any one of claims 19 to 21, when dependent on any one of claims 16 to 18, wherein said heating means are located within said cover. 23. Apparatus according to any one of claims 14 to 22, wherein said supporting surface includes a sealing channel and wherein upon generation of said vacuum, said membrane film seals against the surface of said channel. 24. Apparatus according to claim 23, wherein said openings are provided in said channel so that a vacuum force is generated within said channel in order to draw said membrane film into said channel for sealing thereagainst. 25. Apparatus according to any one of claims 12 to 24, further including membrane sheet clamping means for clamping said membrane sheet relative to said supporting means. 26. Apparatus according to any one of claims 12 to 25, wherein said supporting surface includes an aluminium supporting deck. 27. Apparatus according to any one of claims 12 to 26, further including means to apply a lifting force suitable to lift the membrane sheet away from said supporting means prior to generation of the vacuum. 28. Apparatus according to claim 27, wherein said lifting means includes means to apply an air stream to the underside of the membrane film in a direction substantially opposite to that of the vacuum force. 29. Apparatus according to claim 28, wherein said air stream is applied through said openings in said supporting means. 30. A method substantially as herein described with reference to any one of the accompanying drawings. 31. Apparatus as herein described with reference to any one of the accompanying drawings.

Inventors: HUNTER JOSEPH, HUNTER, JOSEPH
Applicants: HUNTER JOSEPH, HUNTER, JOSEPH
Application year: 1995
Main classification: B29C51
IPC codes: B29C35, B29C51