Patent Publication Number: US-2011052816-A1

Title: Method and apparatus for treating the peripheral region of a sandwich component

Description:
The present invention relates to a method for treating an peripheral region of a sandwich component, in particular of a sandwich component having a honeycomb structure and two spaced-apart coating layers and a core structure having a plurality of cavities. 
     The invention further relates to a device for treating the peripheral region of the sandwich component, in particular for performing the method of any of the above claims, comprising a conveying means for transporting the sandwich component being treated. 
     Sandwich components are well-known and used in different technical fields and industries as workpieces. A sandwich component has a relatively low weight and at the same time has a relatively high strength. An example of such sandwich component is of the type having a to honeycomb structure. Typically, the sandwich components comprise a core structure, such as a honeycomb, which are covered by two spaced-apart outer coating layers. Such sandwich components may be used for example in the automotive industry or airplane industry as structural elements or in the furniture industry as workpieces to produce e.g. tables, shelves, doors or other products. 
     In the prior art, it is often necessary to prepare the sandwich component to make it suitable for this specific use and application. For many applications, for example in the furniture industry, it is desired to prepare and treat the peripheral region of the sandwich component. In order to cover the cavities within the core structure at the peripheral region, a so-called support edge is bonded to the peripheral region by means of a glue. Before the support edge is glued into the peripheral region, it is necessary to mill the peripheral region of the core structure by means of a milling machine or other tooling. The core structure is milled in a depth, which corresponds to the thickness of the support edge. The support edge is for example made of wood. After the milling step, glue is applied to the milled region, and the support edge is pressed into the milled region. 
     This known method of milling and subsequently gluing the support edge into the peripheral region is quite complicated. The milling step is expensive and requires complex machinery. The support edge must be prepared in the specific dimensions of the sandwich components, which makes this matter even more complicated. After the support edge has been attached to the sandwich component, a decor edge must further be attached to the support edge, which makes the preparation of the sandwich component even more complicated and expensive. Furthermore, different decor edges in different width and thicknesses must be to provided. 
     There exists a need to provide a method and apparatus for treating the peripheral region of a sandwich component which is simpler and less complicated. 
     Thus, it is the object of the present invention to provide a method and apparatus for treating a peripheral region of a sandwich component, in particular a sandwich component having a honeycomb structure, which has two spaced-apart coating layers and a core structure having a plurality of cavities. 
     The invention solves this problem by providing a method having the features of claim  1 , in particular by the steps of applying a layer of liquid thermoplastic material onto an peripheral region of the sandwich component such that thermoplastic material penetrates into cavities in the core structure of the sandwich component, and hardening the applied thermoplastic material. 
     The invention further solves this problem by providing a device having the features of claim  23 , which is characterized by two dispensing apparatuses arranged adjacent to the conveying means in order to dispense thermoplastic material onto opposite peripheral regions of the sandwich component, wherein each applying device has a transfer device, which receives thermoplastic material from a material dispensing device and transfers the material to the peripheral region of the sandwich component. 
     By applying a layer of liquid thermoplastic material onto the peripheral region, the thermo-plastic material penetrates into cavities or voids in the core structure. The cavities are at least partly closed by the thermoplastic material. The thermoplastic material then hardens. The result is a layer of hard or stiff thermoplastic material in the peripheral region at the edge. As a result, the sandwich component is ready for further processing. In particular, the sandwich component is ready for applying a decor edge, if desired. The invention avoids a complicated preparation of the edge region by milling and by putting a support edge into the milled region and bonding it in by means of adhesive material. The invention results in a much easier treatment of the sandwich component. By pressing thermoplastic material into the cavities, the honeycomb structure is hardened and has a higher strength. All open cores can be closed, so that a very smooth and even surface is obtained. While the open cores, cavities or voids can be closed, they do not have to be completely filled with thermoplastic material. It would be sufficient if these cores voids or cavities are partly filled with thermo-plastic material. 
     Further, the applied and hardened thermoplastic material results in an additional structural support of the peripheral region of the sandwich component, thus not only closing or sealing the peripheral region but also providing a higher strength and improved mechanical properties. 
     The invention can be used in particular to make sandwich components for use in the furniture industry, in particular for use in finished boards for furniture. Furthermore, as an example, the invention can be applied to manufacture and treat sandwich components made of wooden and/or paper structures. For example, the honeycomb core structure may be made of paper. By applying the thermoplastic material into the voids of such honeycomb structure, the voids are at least partly filled and/or closed, resulting in a proper even surface and additional mechanical strength. 
     In accordance with the preferred embodiment of the method, the thermoplastic material is applied onto the peripheral region in such an amount that a substantially closed peripheral coating layer which closes and/or seals the cavities of the core structure to the outside is formed in the region of the outer surface of the applied thermoplastic material after hardening. By creating of the substantially closed coating layer, the core structure is completely sealed and thus fully prepared for attaching a decor edge. The smooth and even surface is generated by the sealing layer of adhesive material. 
     Preferably, the thermoplastic material is applied onto the peripheral region in such a manner that it is substantially aligned with the peripheral surface of the coating layers. After the alignment, a further decor edge can simply be attached to the pre-treated edge region. 
     In a further preferred embodiment, in that the thermoplastic material is applied onto the peripheral region of the sandwich component substantially in the region of the core structure only. A minimum amount of material is applied in this way, and the outer dimensions of a component are not changed by the application of the thermoplastic material. 
     In another alternative embodiment, the thermoplastic material is applied onto the peripheral region of the coating layers and the peripheral region of the core structure. A completely coated edge region is achieved. 
     In accordance with another embodiment, the thermoplastic material is applied in a thinner layer in the peripheral region of the coating layers than in the peripheral region of the core structure. 
     It is further preferred that the thermoplastic material is applied onto the peripheral region of to the core structure and penetrates into the cavities in such an amount that the core structure in the peripheral region is embedded in the hardened thermoplastic material. The strength and stiffness of the component in particular within the core structure is enhanced by embedding the core structure within the thermoplastic material. 
     In accordance with a further embodiment, the thermoplastic material is applied in such an amount that a peripheral coating layer with a thickness ranging from 0.01 mm to 40 mm, preferably in a range between 2 mm and 4 mm is formed in the hardened state. 
     In accordance with an alternative embodiment, the thermoplastic material is a hot-melt adhesive, an ethylene-vinyl-acetate hot-melt adhesive, a wax, a polyamide, a polyester, a polyurethane or a polyolefine. 
     The advantages of the invention apply in particular in an embodiment in which the core structure is embodied as a honeycomb structure or a foam structure. 
     Preferably, the thermoplastic material is applied by means of a slot nozzle arrangement or by means of a roller dispenser apparatus. The slot nozzle arrangement is preferably having a slot nozzle which is adjustable in width. The width of the layer of adhesive material can easily be adjusted to the width of the sandwich component. The adjustment is developed further in that the width of the slot nozzle can be modified on one side by means of a stopper member and that the entire slot nozzle can be linearly displaced and fixed. 
     In accordance with a further embodiment, the outlet opening of the slot extends in a substantially vertical direction during operation. This allows a simple transport of the sandwich component in a horizontal orientation, and a thermoplastic material is applied from opposite sides of the transport path. 
     Preferably, the transfer device comprises a transfer element in the form of a belt, rail or band, onto which the thermoplastic material is applied and which can be brought into contact with the peripheral region of the sandwich component. 
     In particular, it is preferred that the transfer device has an endless circulating belt, and thermoplastic material can be applied to each endless belt, said endless belts being disposed adjacent to the path of movement of the sandwich component such that the thermo-plastic material can be applied onto the respective peripheral region by the endless belt to contacting the peripheral region of the sandwich component. 
     In a further preferred embodiment the step of temperature conditioning the transfer device is suggested. 
     In a preferred embodiment, the thermoplastic material is applied onto the peripheral region of the sandwich component by means of an endless circulating belt. The endless or non endless circulating belt allows a simple application of the layer in a continuous process. The endless belt is preferably made of sheet metal which has the characteristic that the hot melt thermoplastic material is cooled instantaneously and does not adhere to the belt. If necessary, the sheet metal has an anti-stick coating. 
     The process can be further enhanced, if the endless belt is cooled by means of a cooling device. The hardening of the adhesive material can be expedited and controlled by the cooling device. 
     Preferably, the cooling device can be controlled in such a manner that the thermoplastic material can be cooled to a given temperature during contact with the endless belt. Positive results are achieved if the temperature is in a range between 90° C. and 250° C. and/or if the duration that the endless belt is in contact with the sandwich component is in a range between 1 and 10 seconds, preferably 3 to 4 seconds and/or if the length of contact when the endless belt is in contact with the sandwich component is in a range between 50 and 1000 mm. Thus, the invention allows that the method and device is controlled and adjusted depending on the parameters of the method and device and temperature, in particular the application temperature of thermoplastic material, preferably a thermoplastic adhesive material. The method and apparatus can be controlled depending on all these parameters to achieve the above described temperature values, contact times and length of contact. 
     In accordance with an apparatus according to claim  23 , the sandwich component is pre-treated at both edge regions at the same time, so that subsequently after applying the layer of thermoplastic material a further treatment may take place such as attaching a decor edge. 
     In accordance with a preferred embodiment each dispensing apparatus has a slot nozzle arrangement or a roller dispensing apparatus adjacent to the endless belt or other transfer device. An easy adaption to the size of the workpiece is achieved if the distance of the dispensing apparatus from the path of movement is adjustable. In accordance with a method, it is preferred to provide a cooling device disposed adjacent to the endless belt or other transfer device in order to cool the endless belt. 
    
    
     
       The invention is further described with reference to a preferred embodiment of the apparatus and method which are illustrated with reference to the attached drawings. The drawings show: 
         FIG. 1  a device for treating the peripheral region of a sandwich component in a perspective view; 
         FIG. 2  the device of  FIG. 1  as top view; 
         FIG. 3  an enlarged detail of the view according to  FIG. 2 ; 
         FIG. 4  an example of a sandwich component having a honeycomb core in a perspective view and with an enlarged section; 
         FIG. 5  a sandwich component treated in accordance with the method for treating the peripheral region of the component in a cross-sectional view. 
     
    
    
     As can be seen in  FIG. 1 , the apparatus or device  1  for treating the peripheral region of the sandwich component in accordance with the invention comprises a conveying means  2  for transporting the sandwich component being treated. The conveying means  2  comprises a conveyer belt (not shown), a plurality of rollers and drive means for moving the conveyer belt such that the sandwich components  3  can be transported horizontally in a linear path of movement, illustrated by arrow  4 . Apparatus  1  comprises a controlling device (not shown) for controlling all components such as the conveying means  2 . 
     Two dispensing devices  6 ,  8  are arranged adjacent to the conveying means  2 , in order to dispense thermoplastic material onto opposite peripheral regions of the sandwich component  3 , as the components are moved along applying devices  6 ,  8 . Each dispensing device  6 ,  8  has a transfer device for transferring thermoplastic material to the sandwich component, which in the shown embodiment has an endless circulating belt  10 . Each endless circulating belt  10  is guided by rollers  12 ,  14 ,  16 , each roller having a vertical axis of rotation. The rollers  12 ,  14 ,  16  can be adjusted such that the endless belt  10  has a desired tension. At least one of the rollers  12 ,  14 ,  16  is driven by means of driving means, preferably an electric motor, and controlled by the controlling device such that the speed of the belt  10  can be varied and adjusted to the speed of the sandwich components  3 . The direction of movement of belts  10  is such that the sections of the belt  10  which are positioned parallel with respect to the opposite peripheral regions  18 ,  20  of the component, move in the same direction  4  as the component  3 . 
     As can also be seen from  FIGS. 1 and 2 , each applying device  6 ,  8  comprises a slot nozzle arrangement  22 ,  24 . The slot nozzle arrangement  22 ,  24  is connected to a source of thermoplastic material such as a melter or bulk melter for providing liquid thermoplastic material. Such slot nozzle arrangement  22 ,  24  are also referred to as application heads and comprise a valve arrangement (not shown) in order to control the flow and applying of material. The slot nozzle can be for example the Nordson slot nozzle EB 60 V. 
     As  FIG. 3  illustrates, each slot nozzle arrangement  22 ,  24  has a slot-shaped outlet channel  26  through which liquid material is applied. The applied thermoplastic can be applied to each endless belt  10 . Because said endless belts  10  are disposed adjacent to the path of movement of the sandwich component  3 , the thermoplastic material can be applied onto the respective peripheral region  18 ,  20  by the endless belt contacting the peripheral region of the sandwich component. The thermoplastic material moves on the outer periphery of belt  10  along the direction of arrow  30  and comes at a contact portion  32  in contact with the outer periphery  18  of component  3 . 
     As  FIG. 1  and  FIG. 2  illustrate, the distance of the dispensing apparatus from the path of movement is adjustable. The rollers  12 ,  14 ,  16  and the slot nozzle arrangements  22 ,  24  are mounted onto a mounting structure  34 ,  36  which has the form of a plate. This mounting structure  34 ,  36  can be adjusted at different positions and at different distances to the path of movement of the components  3 . To this end, mounting structures  34  and  36  are moveable and can be fixed to a supporting structure  38 , e.g. a frame. Thus, it is possible to treat components  3  having different widths (W) (see  FIG. 2 .). 
     Further, the applying devices are designed to be vertically adjustable, such that the height of the endless belt can be varied. The support structure  34 ,  36  can be fixed at different heights to the supporting frame structure  38 . As can be seen from  FIG. 1 , a vertical post  40  is connected to the support structure  34 ,  36 . The slot nozzle arrangement  22  can fixed at different positions to the post  40  by means of a clamping device  42  comprising bolds in order to fix the slot nozzle arrangement  22 ,  24  at a desired height. 
     The clamping devices  42  allow positioning the slot nozzle arrangement  22 ,  24  in different angular positions with respect to posts  40 , so that it is possible to adjust the distance between the outlet channels  26  ( FIG. 3 .) of the slot nozzle arrangement  22 ,  24  with respect to the roller  12  and belt  10 . This maybe required in order to adjust the slot nozzle arrangements  22 ,  24  to different belts  10  having different thicknesses or to the actual properties of to the thermoplastic material. The outlet channels  26  or openings of the slot extend in a substantially vertical direction during operation. 
     The slot nozzle arrangement  22 ,  24  allows an adjustment of the length of the outlet channel  26 , in  FIG. 3 . in the vertical direction. To this end, the width of the slot nozzle can be modified on one side by means of a stopper member and that the entire slot nozzle can be linearly displaced and fixed. The stopper member  44  is positioned within an internal channel of slot nozzle arrangement  22 ,  24 . Stopper member  44  is connected to a rod which is moveable along its longitudinal axis such that the length of the internal flow channel can be varied. Thus, the effective length of the outlet channel  26  can be adjust and adapted to the height H (see  FIGS. 1 ,  4  and  5 ) as is explained above, the whole slot nozzle arrangement  22  can be vertically adjusted by means of post  40  and clamping unit  42 . In combination with moveable stopper member  44  the effective width of the applied material flows out of auto channel  26  can be adjusted. The endless belt or transfer device is made of sheet metal. The sheet metal may have an anti-stick coating, if desired. 
     A cooling device  46  (see  FIG. 2 ) is disposed adjacent to the endless belt or the transfer device  10  in order to cool the endless belt. As an example, each cooling device  46  comprises an air slot nozzle device which is connectable to a source of pressurized air and which has a slot-shaped outlet channel through which an air sheet is applied towards the inner periphery of belt  10 . The air sheet cools the belt. As an example, the slot shaped outlet channel is arranged perpendicularly with respect to the belt  10 , such that the air flowing out of the slot nozzle flows in an right angle towards the belt  10 . Instead of a slot-shaped outlet channel, air can alternatively flow out of one or more cylindrical orifices and flow towards the transfer belt in order to cool it. The flow of air can be controlled in a way that the thermoplastic material is sufficiently hardened and that a desired through put off sandwich components  3  can be achieved. This can be achieved by adjusting the volume flow and/or the velocity of air flow being dispensed from the outlet channel cooling device  46 . The cooling device can be controlled in such a manner that the thermoplastic material can be cooled to a given temperature during contact with the endless belt. The temperature is in a range between 140 and 190° C. Instead of air, a liquid cooling material might be employed, e.g. water which can be sprayed to the inner peripheral surface of belt  10 . 
       FIGS. 4 and 5  illustrate a sandwich component which is treated and manufactured in accordance with the method. The sandwich component  3  has a honeycomb core structure  50  and two spaced-apart outer coating layers  52 ,  54 . The two coating layers  52 ,  54  are formed of sheets or skins, e.g. made of wood or metal or plastic material and are relatively stiff. The core structure  50  maybe a honeycomb structure. Alternatively, it may have an open or closed cell structure. The honeycomb structure may be made of paper, plastic material, glass or carbon reinforced laminates and the like. 
     The method and apparatus for treating the sandwich component is further explained in the following with reference to the figures. 
     Thermoplastic material is applied as a layer by means of the slot nozzle arrangement  22 ,  24  onto the belt  10  and then transferred along arrow  30  with the belt  10  towards contact region  32 . When the component  3  reaches the contact region  32 , the layer of liquid thermoplastic material is applied and deposited onto both peripheral regions  18 ,  20  of the sandwich component  3  such that thermoplastic material penetrates into cavities  51  in the core structure of the sandwich component. The thermoplastic material hardens within the cavities  51 . 
     The thermoplastic material is applied onto the belts  10  and then onto the peripheral regions  18 ,  20  in such an amount that a substantially closed peripheral coating layer is formed, which closes and/or seals the cavities of the core structure to the outside, after hardening, as best can be seen in  FIG. 4  and  FIG. 5 . The thermoplastic material is applied onto the peripheral region in such a manner that it is substantially aligned with the peripheral surface of the coating layers  52 ,  54 . A flat outer surface is created, whereas the inner surface of hardened thermoplastic material may be at least partly curved (see  FIG. 5 ). The thermoplastic material is applied onto the peripheral region of the core structure  50  and penetrates into the cavities  51  in such an amount that the core structure in the peripheral region is embedded in the hardened thermoplastic material.  FIG. 5  illustrates, that the thermoplastic material is applied onto the peripheral region of the sandwich component substantially in the region of the core structure  50  only. 
     As in not shown, the thermoplastic material can be applied onto the peripheral region of the coating layers  52 ,  54  and the peripheral region of the core structure  50 . In this case, the thermoplastic material is applied in a thinner layer in the peripheral region of the coating layers  52 ,  54  than in the peripheral region of the core structure  50 . 
     In the shown embodiment, the thermoplastic material is applied in such an amount that a peripheral coating layer with a thickness or an average thickness T (see  FIG. 5 ) ranging from 0.01 mm to 40 mm, preferably in a range between 2 mm and 4 mm is formed in the hardened state. The thermoplastic material is e.g. a hot-melt adhesive, an ethylene-vinyl-acetate hot-melt adhesive, a wax, a polyamide, a polyester, a polyurethane or a polyolefin. 
     The cooling device  46  can be controlled in such a manner that the thermoplastic material is to cooled to a predetermined temperature during contact with the endless belt. The temperature is in a range between 90° C. and 250° C. 
     The controlling device (not shown) controls the components such that the duration that the endless belt is in contact with the sandwich component is in a range between 1 and 10 seconds, preferably 3 to 4 seconds, and/or that the length L (see  FIG. 2 ) of contact when the endless belt is in contact with the sandwich component is in a range between 50 and 1000 mm. 
     As  FIG. 4  shows, a further edge band or edge protection  56  is attached to the edge region, in particular the layer of thermoplastic material applied as described above. This requires a further step subsequently to the deposition of the thermoplastic material  5  within the cavities  51 .