WO1994005483A1

WO1994005483A1 - Method and machine for laminating a decorative layer to the surface of a three-dimensional object

Info

Publication number: WO1994005483A1
Application number: PCT/EP1993/001173
Authority: WO
Inventors: Spyros Bitzounis; Athanasisos Bitzounis; Roy Elwyn Williams; Wilfried SPÄLTE; Heinrich Wild
Original assignee: Leonhard Kurz Gmbh & Co.
Priority date: 1992-09-03
Filing date: 1993-05-12
Publication date: 1994-03-17
Also published as: ZA936264B; EP0659112A1; AU4066893A; JPH08500784A

Abstract

There is described a method and a machine for laminating a decorative layer to the surface of a three-dimensional object (31) in a membrane press by use of pressure-difference in two chambers (38, 43) acting on the membrane, in which as membrane there is used a laminate (10) comprising a carrier film as well as at least one decorative lacquer layer and a heat-activateable adhesive layer laminate to the carrier film. The machine is adapted for use of the laminate (10) instead of a membrane by using a supporting plate (14) which is cooled as well as by provision of feeding means (11, 12, 13) for the laminate and radiation heating means (4a, 4b).

Description

Method and machine for laminating a decorative layer to the surface of a three-dimensional object.

This invention refers to a method for laminating a decorative layer to the surface of a three-dimensional object in a membrane press comprising two chambers which are separated by a membrane and can be subject to different air pressures, one of the chambers containing the object to be decorated, wherein the object to be decorated is brought into contact with the decorative layer, which is pressed against the said surface of the object by a pressure difference in the two chambers acting on the membrane.

A further subject of the invention is a machine for applying at least one decorative layer to a surface of a three-dimensional object comprising an upper, hood shaped pressure chamber, heating means within the pressure chamber, means for tightly clamping a membrane forming the decorative layer to lower edges of the pressure chamber, a supporting plate for the object to be decorated, means for vertically moving the pressure chamber and the supporting plate, resp., in order to bring the supporting plate and the pressure chamber into and out of contact with each other and to bring the surface of the object to be decorated into contact with the decorative layer, and pressure means for applying pressure to the space limited by the pressure chamber and the membrane as well as suction means for applying suction to the space between the membrane and the supporting plate for the object.

Many different laminating methods and machines are known in the trade. Machines for laminating decorative sheet material to large flat surfaces usually employ one or more rollers for rolling the sheet material onto the said flat surfaces. However, where the surface of the object is sharply curved or angled, it is not always possible to make use of rollers to apply the decorative sheet material since the rollers are not designed to reach into all the sharp curves and corners.

There are also known machines for laminating decorative sheet material to an object which includes sharply curving or angled surfaces. Such machines comprise a base and a hollow head, the open bottom of which is sealed by a flexible diaphragm or membrane (EP-A2 0.302.703). In use the three-dimensional object to be laminated is placed on the base and the decorative sheet material to be laminated to the surface of the object is placed over the object. Thereafter the hollow head is placed over the object with the membrane engaging the object. Thereafter air is pumped into the hollow head thus causing the diaphragm to snugly engage and take on the form of the object thereby applying the sheet material to the object. Such machines comprising membranes and thereafter called membrane presses have also been used for applying the decorative layer of hot stamping foils onto the surface of an object. Hot stamping foils tack onto the surface of an object to be laminated when the foil is subjected to heat treatment. Therefore the known laminating machines usually include a heating means for applying heat to the foil when it is applied to the object. One disadvantage of the membrane presses described herein- above is that the membranes used in the machines have to be relatively thick. The disadvantage of the use of such thick membranes is that these menbranes do in use not always take on the exact shape of the object to be laminted, especially in very sharp curves or corners, with the result that the lamination is not always smooth and that small creases and bubbles may form in the difficult to reach places.

It has also been known to dispose of separate membranes in such machines and instead of using the decorative sheet material to be laminated to the surface of the three- dimensional object as the membrane. Examples for respective machines are e.g. described in US-A 1.856.694, EP-B1 0.309.601, EP-A2 0.379.844, DE-A1 37.06.443 and DE-A1 38.01.518.

A common feature of these known methods or machines has to be seen in the fact that the decorative sheet material must be relatively thick in order to have the necessary stability for withstanding the forces exerted by the pressure-difference between the upper pressure and lower suction chamber. These problems are especially remarkable in case the decorative sheet material is heated for softening purposes, such heating leading to a remarkable reduction in strength of the sheet material. Use of relatively thick sheet material as decorative layer and membrane means, however, that there must also be counted with problems in case there are very sharp curvings or angles on the surface to be decorated of the three- dimensional object. If the decorative sheet material shall follow very sharp angles, this can only be achieved if a very high pressure-difference is used between the pressure and the suction chamber, such high pressure-difference, however, possibly causing the sheet material to rupture, in which case the pressure difference between the two chambers of the membrane press would immediately be equalized with the result that the decorative sheet material would not firmly adhere to the surface of the object.

It is accordingly a main object of the present invention to overcome or a least reduce the above described disadvantages in offering a method and a machine with which it is possible to laminate a relatively thin and therefore flexible decorative layer to practically any kind of surface of a three-dimensional object.

In order to achieve this object there is proposed according to the invention to perform the above mentioned method such that there is used as the membrane a laminate comprising a carrier film as well as at least one decorative lacquer layer and a heat-activateable adhesive layer laminated to the carrier film, that the laminate as a whole is pressed against the surface of the object by a pressure-difference in the two chambers, such pressure-difference being generated by a pressure higher than atmospheric pressure in the pressure chamber on the carrier film side of the laminate and/or by suction in the suction chamber on the side of the laminate with the adhesive layer, and that the carrier film is peeled off the decorative layer after setting of the adhesive layer and respective fixation of the decorative layer to the surface of the object.

When proceeding according to the invention there is neither used a separate, relatively thick membrane nor a comparatively thick decorative sheet material. Instead of it is proposed to make use of a laminate comprising on the one hand a carrier film and on the other hand a combination of at least one decorative lacquer layer and a thermo- activateable adhesive layer. The combination of the decorative lacquer layer and the adhesive layer can be easily separated from the carrier film so that the carrier film can be peeled off from these layers after the at least one lacquer layer has been tacked to the surface of the object by setting of the adhesive material. As can be easily understood the decorative layer can be very thin, as it needs not be very strong, the strength of the laminate being only dependant from the strength and stability of the carrier film. As such carrier film will only be used once, it is not necessary to make use of an elastic material which can be stretched and thereafter returns to its original shape and dimensions. Therefore the carrier film of the laminate used according to the invention can be selected only with the view of being extended for completely covering the three-dimensional surface of the object. Such film can be rather thin, e.g. consisting from polyester. This means, however, that the laminate used according to the invention can very closely follow the surface of the object. Nevertheless there is no danger that the carrier film or the laminate will be destroyed during the application of the laminate to the surface of the object. Another, very important advantage of the invention has to be seen in the fact that the at least one decorative lacquer layer can be freely varied and therefore there is a great variety for the decoration of the object.

Advantageously there is used a continuous strip of laminate, which is transported in a stepwise manner after each decoration cycle for an object to release the carrier film from the decorative layer and simultaneously provide a fresh laminate section for decorating the surface of another object. Preferably the laminate used is a hot stamping foil which may comprise a transparent carrier film. Suitable hot stamping foils can easily be developed considering the properties they must have, namely high stretchability of the carrier film and the lacquer layer as well as sufficient strength of the carrier film. If the carrier film is transparent, this is especially advantageous for radiation heating of the decorative lacquer layer and the adhesive layer.

If the laminate is heated prior to being pressed against the surface of the object, there can be a softening of the carrier film and simultaneously an activation of the adhesive layer, which helps more closely adapting the decorative layer to the uneven surface of the three- dimensional object.

Preferably heating of the laminate is effected in at least two steps with different heating energy simultaneously varying the pressure-difference in the two chambers. When proceeding this way the decorative laminate can best follow the surface irregularities of the object. Additionally the laminate progressively comes into contact with the surface of the object, thus avoiding undue load on the laminate.

It is further suggested that heating of the laminate should be effected by means of heat emitting lamps, preferably by lamps emitting infrared radiation of short wavelength ( J^ = 0.9 to 1.6 μm) . Use of heat emitting lamps has the advantage that the heating energy can quickly be changed and especially that, when the heating means have been switched off, the laminate can rapidly cool, which is advantageous in order to firmly tack the decorative layer to the surface of the object within a short term. Quite contrary thereto in cases where thick membranes or decorative layers have been used, heating of the membranes or decorative layers is normally effected using a hot surface transferring heat by contact to the membrane or decorative layer. Such hot surfaces cannot rapidly cool down. Similarly thick membranes or layers store the heat for a considerable time which means, of course, that the adhesive will during a relatively long period not firmly tack the decorative layer to the object, which would, when using a laminate according to the invention, mean that the working cycles would be rather long.

In order to further shorten the working cycles the laminate is preferably cooled down substantially to room temperature prior to the peeling off of the carrier film from the decorative layer tacked to the surface of the object.

A preferred working cycle of the method according to the invention comprises the following steps -:

a) Pre-heating the laminate without exerting pressure or suction on the laminate (in order to soften the carrier film and improve its stretchability) , b) bringing the surface of the object at least partly into contact with the adhesive and decorative layer of the laminate (to roughly adhere the decorative layer to the object) , c) further heating of the laminate in at least two steps with increased heating energy and simultaneously applying suction and pressure, resp., to the both sides of the laminate in order to press the laminate against the surface of the object (so that the laminate will smoothly follow the three-dimensional surface of the object) , d) cooling the laminate while at least the suction is maintained (in order to keep the decorative layer in intimate contact with the surface of the object to be decorated) , e) venting the chambers on both sides of the laminate (i.e. providing regular pressure conditions) and f) peeling off of the carrier film after sufficient setting of the adhesive to firmly adhere the decorative layer to the object.

Peeling off of the carrier film is normally effected by proceeding the laminate transversely to the decorated surface of the object and bringing a new section of laminate in the decoration-position. For cooling the laminate according to step d) above the pressure chamber of the membrane press is preferably vented with cool air, while maintaining the suction in the suction chamber.

A preferred machine for applying at least one decorative layer to a surface of a three-dimensional object using the above described method and comprising the features stated above is characterized in that the membrane being a laminate, comprising a carrier film as well as at least one decorative lacquer layer and a heat activateable adhesive layer laminated to the carrier film, is directly clamped between the lower edges of the pressure chamber and the supporting plate with the adhesive layer contacting the supporting plate, that at least the surface of the supporting plate contacting the adhesive layer is cooled below the softening temperature of the adhesive layer, that there are provided feeding means for transporting and stretchinng the laminate serving as membrane across the opening surrounded by the lower edges of the pressure chamber, and that the heating means are radiation heating means.

Such a machine is relatively simple in construction, nevertheless guarantees, however, good results in decorating a three-dimensional surface of an object with a laminate as described, especially with a hot stamping foil. In this connection the cooled supporting plate is important, because only in case the decorative layer of the laminate does not adhere to the supporting plate it is possible to permanently work with the machine and easily peel the carrier film off the decorative layer adhered to the object by the adhesive layer. Further the direct clamping of the laminate between the pressure chamber and the supporting plate is only possible if the laminate does not adhere to the supporting plate, this fact also being helpful for a simple construction of the feeding means.

In order to use laminates of different sizes the pressure chamber preferably comprises means for interchangeably mounting intermediate partitions having lower edges for clamping the laminate to the supporting plate. The partitions can be of a very simple construction because they only must press the laminate against the supporting plate so that suction can be applied to the space between the laminate and the supporting plate.

The feeding means preferably comprise a winding equipment with a storage roll for the laminate, guiding rolls in alingement with the lower end of the pressure chamber and a wind up roll for the carrier film and rests of the decorative and adhesive layer left on the carrier film after its peeling off from the object. Such winding equipment is known per se and can easily be adapted to the machine of the invention.

As already described in connection with the method it is advantageous to use as heating means infrared lamps with a wavelength -A of 0.9 to 1.6 μm. This heating means are in a preferred embodiment of the invention horizontally and/or vertically and/or angularly adjustable so that they can be adapted to the shape and size of the object to be decorated. This adaptation can be improved by dividing the heating means, preferably lamps, into different groups, which can additionally be energized differently.

If, as provided according to the invention, the object rests on a base plate adapted to the shape of the object such that the subject is vertically spaced from the supporting plate and projects horizontally along its periphery over the base plate, the laminate will when applying the pressure-difference according to the invention follow the surface of the object even beyond the peripheral edges so that also the edges are completely covered by the decorative layer.

A very simple construction is achieved if the supporting plate has a central suction opening and the base plate is placed over the suction opening and provided with air passages leading from the suction opening to all parts of the space around the object and between the supporting plate and the laminate. The use of a central suction opening especially makes it possible to provide base plates of different shape depending on the shape of the object, all such base plates fitting the same supporting plate. The air passages simultaneously make sure that suction or vacuum, resp., is in the whole space between the supporting plate and the laminate.

In this construction suction air passages can consist from distance elements between the base plate and the supporting plate and, the case being, from bores connecting the upper and lower surface of the base plate.

An easy and fast replacement of the object after decoration can be achieved by holding the object at the supporting or base plate, resp., by suction elements, such suction elements preferably consisting from a surface area of the supporting or base plate, resp., surrounded by a gasket and connected by a suction duct and a valve to suction means. In case the machine comprises a base plate for the object, the suction elements are preferably provided at the top surface of the base plate which has at least one separate suction channel connecting the suction elements with a suction joint on the supporting plate, said suction channel not intersecting the suction air passages in and below the base plate. Also the suction joint can be unitary for different base plates, thus making also a fast change of the base plate possible, as it is only necessary to place the base plate onto the supporting plate, at this occasion connecting the suction channel of the base plate to the suction joint in the supporting plate. The suction vacuum between the supporting plate and the laminate can in any event be achieved because the base plate has the necessary suction air passages. Nevertheless the suction in the space between the laminate and the supporting plate on the one hand and at the suction joint for the suction elements can of course be separately controlled. Finally the machine according to the invention is characterized by control means for controlling time and intensity of the heating radiation as well as variation over the time of the pressure in the pressure chamber and the suction in the suction chamber. Such control means can be computer-controlled with the possibility of relatively free variation. Such control means can e.g. also comprise several separate control circuits for several groups of heating means.

Without thereby limiting the scope of the invention and by means of example only, one embodiment of a machine according to the invention will now be described with reference to the accompanying drawings, simultaneously describing the inventive method in more detail.

In the accompaying drawings

Figure 1 shows a schematic front elevational view of a machine according to the invention, partly in vertical section,

Figure 2 shows a schematic side elevational view of the machine,

Figures

3a and 3b show in a vertical schematic section and in more detail in two different positions the most essential parts of the machine, namely the hood-shaped pressure chamber, the supporting plate, the base plate, and the heating means, Figure 4 shows diagramatically the pressure variations over the time in the two chambers during a working cycle, and Figure 5 shows diagramatically the intensity of the heating means (two groups) depending on the time in a working cycle.

In the drawings the machine is shown in use for lamination of a decorative layer of a hot stamping foil to a toilet- seat because when decorating ring-shaped parts like toilet- seats some special provisions are necessary with respect to the construction of the base plate. Nevertheless the basic construction of the machine is the same irrespective of the three-dimensional object to be decorated. The expression "three-dimensional object" shall always mean an object havinσ a thickness of at least several mm and a surface to be decorated which extends out of a plane, so that known rolling methods for application of a decorative layer cannot be used.

As can be seen in the schematic representations of figures 1 and 2 the machine comprises a frame 1. In the upper part of the frame 1 there is mounted a hood-shaped pressure chamber 2 consisting from a top plate 2a and side walls 2b. As can be seen in the representations of figures 1 to 3 the lower edges of the side walls 2b of the pressure chamber 2 are all on the same level and bearing gaskets 3, the purpose of which will be described later on.

The pressure chamber 2 houses radiation heating means 4a, 4b. In the embodiment shown the heating means are tube- shaped twin infrared lamps emitting short wave infrared radiation of a wave-length , between 0.9 and 1.6 μm. The lamps are arranged in two groups, namely an outer group of lamps 4a and an inner group of lamps 4b. Both groups consist from four twin-lamps, the outer lamps 4a being arranged in a square along the walls 2b of the pressure chamber 2, the inner lamps 4b being arranged in parallel. According to a special feature of the machine described the lamps 4a of the outer group and the lamps 4b of the inner group can be independently energized in order to transmit radiation or heat of different intensity to the outer and inner regions of the object to be decorated.

The lamps 4a and 4b are mounted to the top plate 2a or the side walls 2b of the pressure chamber 2 such that their position can be varied horizontally as well as vertically and/or angularly. According to figures 3a and 3b this is e.g. made possible by use of guide rails 5 along which the lamps 4a and 4b can be displaced horizontally. For vertical adjustment of the lamps 4a and 4b there are provided holders 6 of variable length. The lamps 4a, 4b are connected with the holders 6 by joints 7 so that the lamps 4a, 4b can be tilted with respect to the holders 6 for ajusting them angularly, as evidenced by the difference in the position of the lamps 4a when compared to the position of the lamps 4b.

As shown schematically in figures 1 and 2 the pressure chamber 2 is provided with means 8 for interchangeably mounting additional partitions 9 having in the embodiment shown the shape of vertical walls, the lower edges of which are also provided with gaskets 3 and are flush with the lower edges of the side walls 2b of the pressure chamber 2. The purpose of these additional partitions 9 is to give the possibility of adapting the pressure chamber 2 to different sizes of laminate used and to guarantee that, even if a laminate of a smaller size is used, such laminate is firmly clamped to the supporting plate.

In the frame 1 there are additionally provided feeding means for the laminate 10. These feeding means comprise a winding equipment with a storage roll 11 on which the laminate to be used can be stored in a sufficient quantity. Further there are provided some guiding rolls 12, two of which are, as can most clearly be seen from figures 3a and 3b, aligned with the lower edges of the side walls 2b or partitions 9 of the pressure chamber 2. Further the winding means have a wind up roll 13 for winding up the carrier film of the laminate 10 together with rests of the decorative and adhesive layer, which are left on the carrier film after the carrier film has been peeled off from the object to be decorated. The winding means must, of course, additionally be provided with tension means known per se and not shown to guarantee that the laminate 10 is in the position shown in figure 2 prior to application of the decorative layer to the object.

The machine additionally comprises a supporting plate 14 which is, as shown in figures 1 and 2, mounted on a traverse 15 for vertical movement by means of a piston/cylinder unit 16. For correctly guiding the traverse 15 with the supporting plate 14 there are additionally provided guiding rods 17 cooperating with guides 18 on the frame 1.

As can be seen from figurs 3a and 3b the supporting plate 14 has a plane surface 19 cooperating, as shown in figure 3b, with the gaskets 3 at the lower edges of the side walls 2b or the partitions 9 of the pressure chamber 2 for clamping the laminate 10 in between.

In order to make sure that the adhesive layer of the laminate 10, which consists from a heat activateable cement, does not tack or adhere to the surface 19 of the supporting plate 14, the supporting plate 14 is, when working, cooled to a temperature below the softening temperature of the adhesive layer. For this purpose the supporting plate 14 is provided with ducts 20 for a cooling fluid entering the series of ducts 20, e.g. via the pipe 21 with a valve 22 and leaving through the pipe 23 with the valve 24. The valves 22, 24 allow respective controlling of the flow of cooling fluid through the ducts 20. Figures 3a, 3b further show that at the surface 19 of the supporting plate 14 there is a suction opening 25 connected to a suction means (now shown) by a conduit 26 and controllable by a valve 27. Further there is provided a suction joint 28 for connecting suction elements of the base plate 29 to the suction .conduit 26 and therefore also to the suction means (not shown). The suction at the suction joint 28 can be controlled by a valve 30.

In figures 3a and 3b there is shown the arrangement of the object 31 to be decorated on the base plate 29. It is essential that the object 31 projects horizontally over the base plate (as shown in figures 1 to 3b). Further the base plate 29 makes sure that the object 31 is placed in a certain distance vertically above the surface 19 of the supporting plate 14.

The shape of the top surface 32 of the base plate 29 is, as shown in figures 3a and 3b, adapted to the shape of the object 31 to be decorated. As the object is in the described case a toilet-seat and therefore essentially ring-shaped, also the top surface 32 of the base plate has ring shape with a center depression 33.

For fixing the object 31 on the base plate 29 special suction elements are provided. For this purpose the base plate has a suction channel 34 leading from the surface 32 adapted to the object 31 to the suction joint 28. As clearly shown in figures 3a and 3b, the suction channel 34 ends on the surface 32 of the base plate 29 in an area confined by two gaskets 35, which means that the space between the two ring-shaped gaskets 35, the top surface 32 of the base plate 29 and the lower surface of the object 31 can be evacuated via the suction joint 28 and the valve 30, which allows fixation of the object 31 to the base plate 29 by suction.

The base plate 29 is further arranged such that between the lower surface of the base plate 29 and the upper surface 19 of the supporting plate 14 there are left suction air passages 36. These air passages 36 are in the embodiment shown formed by distance elements 44. It is, however, also possible to form such passages by other means, e.g. in placing a corrugated, perforated sheet metal between the supporting plate 14 and the base plate 29. Further the depression 33 of the base plate 29 is connected by bores 37 with the air passages 36 at the underside of the base plate 29. Through the air passages 36 and the bores 37 the suction opening 25 at the top surface 19 of the supporting plate 14 is connected with all parts of the space below the laminate 10 in the position shown in figure 3b so that suction or vacuum can be generated in the whole space between the top surface 19 of the supporting plate 14 and the laminate 10. There is therefore constituted a suction chamber 38 containing the base plate 29 and the object 31 to be decorated, this suction chamber 38 being confined by the supporting plate 14 and the laminate 10 pressed against the supporting plate 14 by the gaskets 3 at the lower edges of the side walls 2b or partitions 9, resp., of the pressure chamber 2.

The pressure in the pressure chamber 2 can be controlled by introducing or removing air using pipes 39, 40 with valves 41, 42, resp.. Preferably the pipes 39, 40 are connected to the interior of the pressure chamber 2 on opposite sides for enabling an efficient venting of the space within the pressure chamber 2.

Decoration of an object using the machine described above is effected in the following way -:

The supporting plate 14 is brought into its lower position shown in figures 1 and 2, this position being below the position shown in figure 3a. In this position the object 31 to be decorated is placed on the base plate 29 and fixed on the base plate 29 by suction. For this purpose the valve 30 is opened so that the space between the underside of the object 31, the two ring gaskets 35 and the top surface 32 of the base plate 29 is evacuated.

Further a fresh piece of laminate is brought in position such that it adheres to the lower edges and gaskets 3 of the side walls 2b or partitions 9 of the pressure chamber 2. For this purpose a sufficient length of laminate is unwound from the storage roll 11 and a corresponding length of carrier film is wound onto the roll 13. The laminate 10 must be on the storage roll 11 in a position such that in use the carrier film is on the side of the pressure chamber 2, whereas the decorative layer and the adhesive layer point downwardly and come during the lamination procedure into contact with the surface of the object 31 to be decorated.

The laminate 10 is normally a hot stamping film known per se and comprising at least a transparent carrier film, one decorative lacquer layer, and the case being, a heat activateable adhesive layer (in this sequence). As is known from the manufacture of hot stamping foils, the decorative lacquer layer can simultaneously be of such a nature that when activated by heat it gets tacky and adheres to the surface. Further it is known from hot stamping foils to provide not only one decorative lacquer layer but several such layers or to have layers with a special design.

Details of such hot stamping foils shall not be described because they are known to a person skilled in the art.

It is, of course, also possible to use other kinds of laminates especially adapted to the respective purposes, e.g. by using very specific decorative lacquer layers or very special adhesives adapted to the surface or object to be decorated. In any event it must be possible to easily peel the carrier film off from the decorative lacquer layer after lamination of the decorative lacquer layer to the object.

After having the object 31 placed on the base plate 29 and brought a sufficient length of laminate 10 in working position at the underside of the pressure chamber 2, the supporting plate 14 with the base plate 29 and the object 31 is moved upwards against the pressure chamber 2 by activating the piston/cylinder unit 16. This upward movement of the supporting plate 14 brings the top surface of the object 31 slowly into contact with the adhesive and decorative lacquer layers of the laminate 10, as shown in figure 3a. During this upward movement tensioning means (not shown) provided in the winding or feeding means for the laminate 10 allow that the laminate bridging the bottom of the pressure chamber 2 is kept stretched, may, however, follow the upward movement of the object 31 into the pressure chamber 2 in order to reach the position shown in figure 3b.

As soon as the supporting plate 14 has reached the position of figure 3b, the laminate 10 is clamped between the gaskets 3 at the lower edges of the side walls 2b or partitions 9 of the pressure chamber 2 and the top surface 19 of the supporting plate 14, which means that the space within the pressure chamber 2 is separated by the laminate 10 in a membrane-like manner into two chambers, namely the real pressure chamber 43 above the laminate 10 and the suction chamber 38 below the laminate, the suction chamber containing the object 31 to be decorated resting on the base plate 29.

As soon as the position of figure 3b is reached, the real laminating cycle can be started.

In order to make the stretching of the laminate easier and make the laminate 10 more flexible, it is possible to energize the heating lamps 4a and 4b already at a time prior to the final closure of the suction chamber 38 (figure 3b). Such pre-heating may e.g. last about 5 seconds.

As soon as the chambers 38 and 43 have been closed the intensity of the heating is increased, preferably in at least two steps. As the heating lamps 4a and 4b are divided into two groups, it is also possible to heat the two groups with different intensity, which may be necessary depending on the shape of the object 31 to be decorated. Simultaneously with strong heating of the laminate 10 by the heating lamps 4a and 4b pressure is applied to the chamber 43 above the laminate 10 in pressing air into this space 43, e.g. in opening the valve 41 of pipe 39 for compressed air, simultaneously keeping valve 42 of pipe 40 closed. At the same time also valve 27 is opened so that suction from the suction means is applied to the space 38 via the air passages 36 and the bores 37 of the base plate 29.

Caused by the action of the suction in the space 38 and the pressure in the space 43 the laminate 10, having become rather flexible and elastic because of its heating, is sucked and pressed down against the upper surface of the object 31 (as shown by the interrupted lines 10' in figure 3b).

When the pressure in the space 43 and the vacuum or suction in the space 38 have reached their final value, this value is kept for a while. Then the heating lamps 4a and 4b are switched off, while maintaining at least the suction in the space 38.

It is now necessary to cool the adhesive layer of the laminate 10 in order to make sure that the decorative layer firmly sticks to the decorated surface of the object 31.

In order to shorten the period, it is preferred to vent the space 43 within the pressure chamber 2 by cool air. For this purpose it is sufficient to simply open the valve 42 in the pipe 40 so that cool air can circulate through the space 32. During this venting the suction in the space 38 is, however, maintained.

After sufficient venting, the valve 42 is again closed, whereafter pressure is again created in the space 43, such pressure one again acting on the laminate 10 and pressing it again against the surface to be decorated. This further pressing action is e.g. for about 10 seconds.

After this time it can be assumed that the decorative lacquer layer firmly adheres to the surface of the object 31 to be decorated. Therefore it is now possible to return to normal pressure. For this purpose at least valve 42 is opened. It is, however, possible to simultaneously close valve 41. At the same time valve 27 is closed. Venting of the space 38 can then be achieved simply in moving the supporting plate 14 downwardly with respect to the pressure chamber 2 and the gaskets 3. As the laminate 10 is stretched by tension over the bottom opening of the pressure chamber 2, this movement will cause the laminate 10 to at least partly move away from the top surface 19 of the supporting plate 14. When moving the supporting plate 14 further downwardly, the carrier film of the laminate 10 will be peeled off from the surface of the object 31 and the decorative layer and the adhesive layer, resp., will tack to the object 31. As soon as the supporting plate 14 has reached the position shown in figures 1 and 2, the laminate 10 will have been completely separated from the object 31 and again rest in a basically horizontal position closing the bottom opening of the pressure chamber 2. Now valve 30 has to be closed to stop suction on the underside of the object 31, which can then be easily removed from the base plate 29.

After removal of the object 31, a new working cycle can be started by placing a new object 31 on the base plate 29 and moving the laminate 10 a sufficient length to have a new piece of laminate 10 cover the bottom opening of the pressure chamber 2.

As already mentioned the working cycles can be adapted to different laminates and objects to be decorated in varying the heating periods and intensities as well as the pressure and suction, resp.. Further it is possible to work with at least two groups of heating elements radiating at different intensity.

A typical working cycle is shown in the diagrams of figures 4 and figures 5, the diagram of figure 4 showing the pressure in the pressure chamber of space 43 as well as the suction in the suction chamber 38, resp., whereas the diagram of figure 5 represents the heating cycles of an inner and outer group of infrared lamps.

When looking at figures 4 and 5 there can be seen that a first time period t-^ is a preperatory period in which the necessary movement of the supporting plate 14 and placement of the object 31 on the base plate 29 take place. Already during this movement, the heating means can, however, be energized in the period p^ at relatively low energy, the intensity of the heaters of the inner group being lower than the intensity of the heaters of the outer group. As soon as the spaces 38, 43 have been closed, pressure in the space 43 and suction in the space 38 are generated during the period t (figure 4), the pressure in space 43 already being achieved prior to the full suction in space 38. During the time period t2 of about 35 seconds there are four different heating periods, namely on the one hand part of the low energy heating period p-^, then the heating period P2 with higher energy of the inner and outer group of the lamps, resp.. As soon as nearly the full pressure in the pressure chamber or space 43 is reached, the third heating period p^ is started, in which the inner lamps are working with an intensity of about 80 % and the outer lamps are working with an intensity of about 90 %. It would according to the invention also be possible to work in the periods p^ and p^ with different intensities, depending on the decorative layer and the object to be decorated.

After sufficient heating time, i.e. at the end of period p_^ a further pressure condition is generated in starting period t_β, during which period fresh air is venting the space 43 in the pressure chamber 2 by opening valves 41 and 42. This venting period is about 10 seconds and causes substantial cooling of the laminate to a temperature guaranteeing sufficient tacking of the layer to the surface of the object 31. Without any change in the heating conditions (i.e. with the heating means being switched off) within the fourth time period t₄, pressure in the pressure chamber is again increased in closing valve 42, the period t^ being also about 10 seconds. As soon as a sufficiently high pressure is reached, the final venting of the pressure space 43 and the suction chamber 38 is started (time period tc in figure 4) , which period tr is about 15 seconds. As can be seen from figures 4 and 5 it is very essential that heating is switched off as soon as the pressure difference between pressure chamber and suction chamber is diminished in order to make sure that the decorative layer firmly adheres to the object.

Control of the different pressure and heating conditions as well as of the movement of the supporting plate 14 by means of the piston/cylinder 16 unit is best achieved with the help of a computer, which allows a lot of variations. Tests of applicants have shown that the intensity of the heating means should be variable between 0 and 100 % and the different periods for changes in the pressure conditions (t_j to t^) and heating conditions (p-^ to p^) should be variable between 0 and about 60 seconds.

Claims

C L A I M S

1. A method for laminating a decorative layer to the surface of a three-dimensional object in a membrane press comprising two chambers which are separated by a membrane and can be subject to different air pressures, one of the chambers containing the object - to be decorated, wherein the object to be decorated is brought into contact with the decorative layer, which is pressed against the said surface of the object by a pressure-difference in the two chambers acting on the membrane, c h a r a c t e r i z e d i n t h a t there is used as the membrane a laminate comprising a carrier film as well as at least one decorative lacquer layer and a heat-activateable adhesive layer laminated to the carrier film, that the laminate as a whole is pressed against the surface of the object by a pressure-difference in the two chambers, such pressure-difference being generated by a pressure higher than atmospheric pressure in the pressure chamber on the carrier film side of the laminate and/or by suction in the suction chamber on the side of the laminate with the adhesive layer, and that the carrier film is peeled off from the decorative layer after setting of the adhesive layer and respective fiaxtion of the decorative layer to the surface of the object.

2. A method according to claim 1, wherein a continuous strip of laminate is used, which is transported in a stepwise manner after each decoration cycle for an object to release the carrier film from the decorative layer and simultaneously provide a fresh laminate section for decorating the surface of another object.

3. A method according to claim 1 or 2, wherein the laminate used is a hot stamping foil.

4. A method according to claim 3, wherein as laminate there is used a hot stamping foil comprising a transparent carrier film.

5. A method according to one of claims 1 to 4, wherein the laminate is heated prior to being pressed against the surface of the object.

6. A method according to claim 5, wherein heating of the laminate is effected in at least two steps with different heating energy simultaneously varying the pressure-difference in the two chambers.

7. A method according to claim 5 or 6, wherein heating of the laminate is effected by means of heat emitting lamps, preferably by lamps emitting infrared radiation of short wavelength ( = 0.9 to 1.6 μ ) .

8. A method according to one of claims 4 to 7, wherein the laminate is cooled down substantially to room temperature prior to the peeling off of the carrier film from the decorative layer tacked to the surface of the object.

9. A method according to any of claims 4 to 8 comprising the following working steps a) pre-heating the laminate without exerting pressure or suction on the laminate, b) bringing the surface of the object, at least partly, into contact with the adhesive and decorative layer of the laminate c) further heating of the laminate in at least two steps with increased heating energy and simultaneously applying suction and pressure, resp., to the both sides of the laminate in order to press the laminate against the surface of the object, d) cooling the laminate while at least the suction is maintained e) venting the chambers on both sides of the laminate and f) peeling off of the carrier film after sufficient setting of the adhesive to firmly adhere the decorative layer to the object.

10. A method according to claim 8 or 9, wherein for cooling the laminate the pressure chamber of the membrane press is vented with cool air while maintaining suction in the suction chamber.

11. A machine for applying at least one decorative layer to a surface of a three-dimensional object (31) using the method of claims 1 to 10, comprising an upper, hood-shaped pressure chamber (2), heating means (4a, 4b) within the pressure chamber (2), means for tightly clamping a membrane (10) forming the decorative layer to lower edges of the pressure chamber (2), a supporting plate (24) for the object to be decorated, means (16) for vertically moving the pressure chamber or the supporing plate (14), resp., in order to bring the supporting plate (14) and the pressure chamber (2) into and out of contact with each other and to bring the surface of the object (31) to be decorated into contact with the decorative layer, and pressure means (41, 42) for applying pressure to the space (43) limited by the pressure chamber (2) and the membrane (10) as well as suction means (26) for applying suction to the space (38) between the membrane (10) and the supporting plate (14) for the object (31) c h a r a c t e r i z e d i n t h a t the membrane, being a laminate (10) comprising a carrier film as well as at least one decorative lacquer layer and a heat-activateable adhesive layer laminated to the carrier film, is directly clamped between the lower edges of the pressure chamber (2) and the supporting plate (14) with the adhesive layer contacting the supporting plate (14) that at least the surface (19) of the supporting plate (14) contacting the adhesive layer is cooled below the softening temperature of the adhesive layer, that there are provided feeding means (11 to 13) for transporting and stretching the laminate (10) serving as membrane across the opening surrounded by the lower edges (2a, 9) of the pressure chamber (2), and that the heating means (4a, 4b) are radiation heating means .

12. A machine according to claim 11, wherein for adaptation to different laminate sizes the pressure chamber (2) comprises means (8) for interchangeably mounting intermediate partitions (9) having lower edges for clamping the laminate (10) to the supporting plate (14).

13. A method according to claim 11 or 12, wherein the feeding means comprises a winding equipment with a storage roll (11) for the laminate (10) guiding rolls (12) in alignment with the lower edges of the pressure chamber (2) and a wind up roll (13) for the carrier film and rests of the decorative and adhesive layer left on the carrier film after its peeling off from the object (31).

14. A machine according to any of claims 11 to 13, wherein the heating means (4a, 4b) are infrared lamps with a wavelength Λ of 0.9 to 1.6 μm.

15. A machine according to any of claims 11 to 14, wherein the heating means (4a, 4b) are horizontally and/or vertically and/or angularly adjustable.

16. A machine according to any of claims 11 to 15, wherein the object (31) rests on a base plate (29) adapted to the shape of the object (31) such that the object (31) is vertically spaced from the supporting plate (14) and projects horizontally along is periphery over the base plate (29).

17. A machine according to claim 16, wherein the supporting plate (14) has a central suction opening (25) and the base plate (29) is placed over the suction opening (25) and provided with air passages (36) leading from the suction opening (25) to all parts of the space (38) around the object (31) and between the supporting plate (14) and the laminate (10).

18. A machine according to claim 17, wherein distance elements (44) between the base plate (29) and the supporting plate (14) and, the case being, bores (37) connecting the upper and lower surface of the base plate (29) are provided as suction air passages (36).

19. A machine according to any of claims 11 to 18, wherein the object (31) is held at the supporting or base plate (14, 29), resp., by suction elements (30, 34, 35).

20. A machine according to claim 19, wherein the suction elements consist from a surface area of the supporting or base plate (14, 29), resp., surrounded by a gasket (35) and connected by a suction duct (34) and a valve (30) to suction means (26).

21. A machine according to claim 20 and comprising a base plate (29) for the object (31), wherein the suction elements are provided at the top surface (32) of the base plate (29) which has at least one separate suction channel (34) connecting the suction elements with a suction joint (28) on the supporting plate (14), said suction channel (34) not intersecting the suction air passage (36, 37) in and below the base plate (29).

22. A machine according to any of claims 11 to 21, c h a r a c t e r i z e d b y control means for controlling time and intensity of the heating radiation as well as variation over the time of the pressure in the pressure chamber (2) and the suction in the suction chamber (38) (Figures 4, 5).