Patent Publication Number: US-6656230-B1

Title: Method and device for transferring a color pattern on or into an object

Description:
The invention relates to a process and a device for applying and/or introducing a coloured decoration respectively to or into an article, in which a substrate with dye is applied against the article so as to transfer dye from the substrate to the article. 
     The invention is based on prior art as known from EP-A 0 282 859 “Process and device for applying decoration to an article”. In this prior art, a coloured decoration of sublimable dyes is initially applied to a substrate. The substrate may consist of paper, for example. This coloured decoration is then transferred from the substrate to the article to be decorated. The article may consist for example of a suitable plastics or of another material coated with plastics or lacquer for example. For transfer of the coloured decoration, the substrate is positioned over the article and the coloured decoration is transferred by temperature increase from the substrate to the article by means of sublimation. To achieve a uniform arrangement of the substrate against the article and homogeneous pressure distribution, in the cited prior art a cloth of resilient material (e.g. silicone) is positioned over the substrate. Using a vacuum pump, a vacuum is generated over the table on which the article is positioned with the substrate and covering cloth, which vacuum sucks up the substrate and the cloth lying thereover. The present invention may be applied to this prior art, for example, with or without a silicone cloth. 
     In addition, the invention is based on prior art as known from EP-A 0 573 676 “Use of a substrate with “release” properties for applying lacquer and paint to a substrate” In this prior art, substrates (e.g. of suitable paper) with so-called “release” properties are used for transfer of decoration onto an article. The “release” property of the substrate means that the decoration may be peeled off the substrate in the manner of a “decal” and transferred to the substrate in this way. 
     The object of the invention is to improve the processes or devices according to the above-mentioned prior art, in particular in relation to the quality of the coloured decoration. 
     The process according to the invention is characterised in claim 1. According thereto, at least one gas jet is used to promote application of the substrate with the coloured decoration against the article to be decorated. This technique may be used in particular both in the case of the above-mentioned sublimation transfer and in the case of “release” transfer of the coloured decoration. The gas jet causes the substrate to lie closely against the article over the entire area without gas inclusions or other non-uniformities. The gas jet may be passed over the article with the substrate lying thereon (and optionally the resilient cloth lying thereon) in the manner of a “doctor blade”. Gas inclusions are pressed out, ensuring that the substrate lies closely against the article all over. 
     It is preferably provided that the gas jet has a dimension, in at least one direction, which is small in comparison with the dimension of the article in this direction. It is particularly preferable for the gas jet to take the form of a knife and-to be passed in linear manner over the substrate or the cloth optionally lying thereon. The linear gas jet is preferably of a length which is greater than the width of the article plus the overlapping areas of the substrate or the cloth. 
     Moreover, if the gas jet takes the above-described knife form, the direction of the line of at least one gas jet forms an angle other than 0° and 90° with the direction of relative movement between gas jet and article. 
     A further preferred development of the invention, which is used in particular when sublimable dyes are used in the coloured decoration, provides for the gas jet to be heated to a temperature at which it ensures or at least promotes sublimation of the dye and thus transfer thereof from the substrate to the article. 
     The invention in particular allows the coloured decoration of the article to exhibit a high quality in the edge area, if the gas jet is directed appropriately obliquely at the edge area, wherein it presses the substrate down uniformly on both sides of the edge. 
     When a heated gas jet is used the jet is preferably positioned obliquely relative to the relative movement between article and jet in such a way that the areas of the substrate which extend towards the gas jet are subject to preheating. The hot air of the gas jet after impingement thus flows in an “upstream” direction with regard to the relative movement between article and gas jet. 
     The gas jet according to the invention may be used with or without the above-described suction effect using a vacuum pump. 
    
    
     The invention also relates to a device with a gas jet which promotes application of the substrate against the article to be decorated. The device may preferably comprise one or more of the above-mentioned features or also one or more features from the following description of preferred exemplary embodiments of the invention, given with reference to the drawings, in which: 
     FIG. 1 is a schematic representation of, a device for applying and/or introducing a coloured decoration respectively to or into an article; 
     FIG. 2 is a plan view of the device according to FIG. 1; 
     FIG. 3 is a schematic representation of a gas jet generator; 
     FIG. 4 shows a section along line I—I through the gas jet generator according to FIG.  3  and 
     FIG. 5 shows a modification of the device according to FIG. 1 with two gas jets. 
    
    
     FIG. 1 shows an article  10  to be decorated. In the exemplary embodiment shown, the article  10  is to be decorated with sublimable disperse dyes. The article  10  may consist of plastics, for example, into which the dye molecules may diffuse. First of all, the coloured decoration is printed onto a substrate  12 . In the exemplary embodiment shown, the substrate  12  consists of paper. The substrate  12  according to FIG. 1 is positioned over the article  10  with the printed side downwards, such that the paper projects beyond the edges. A resilient cloth  14 , e.g. of silicone, is positioned over the substrate  12 . The article  10 , with the substrate  12  and the cloth  14 , lies on a table  16 . A channel  18  with branches  18   a  is formed in the table  16 . The arrow  22  indicates a connection to a suction pump (not shown), which generates a vacuum directly over the table top via the channels  18  and the branches  18   a , such that the cloth  14  and the substrate  12  arranged therebelow are sucked up and drawn over the article  10 . This is described as such in the above-mentioned prior art. 
     A gas jet  20  acts on the cloth  14  and thereby presses the substrate  12  against the article  10 . As shown in the plan view according to FIG. 2, the gas jet  20  is linear in form, with a line width which is very small in comparison to the dimension of the article  10 . The narrow elongate gas jet  20  may have a width of a few millimetres, for example, e.g. a minimum width of approximately 1 mm and a maximum width of 10 mm or less. 
     The gas jet  20  is passed over the article  10  in such a way that it moves over the substrate  14  and the article  10  located therebelow gradually from left to right for example in FIGS. 1 and 2. The gas jet passes thereover in particular in such a way that it ensures a clean transfer of the coloured decoration in the critical edge area of the article. This is explained in more detail below with reference to FIG.  5 . 
     FIGS. 3 and 4 are schematic representations of an exemplary embodiment of a gas jet generator  24 . The gas jet generator comprises a connection piece  28 , into which hot air flows through an inlet  16  in the direction of the arrows. A blower (not shown) is arranged upstream of the connection piece. A heating device for the gas is indicated schematically by reference numeral  32 . The hot gas stream enters a funnel  30  through the connection piece  28 , said funnel  30  tapering according to FIG. 4 to form a nozzle  34  with the diameter “D”. This structure of the funnel  30  generates a linear gas jet  20  according to FIG.  2 . The gas passes through the funnel  30  in such a way that, owing to a suitable-structure of the funnel  30  and/or special chokes in the funnel, the hot gas stream exiting through the nozzle  34  is at least approximately homogeneous over the entire length of the linear gas jet  20  (c.f. FIG.  2 ), i.e. the gas jet has at least approximately the same intensity and speed in each surface unit, such that the distribution of pressure produced by the gas jet between substrate and article is substantially homogeneous over the entire extent of the gas jet. 
     The gas jet  20  is heated to a temperature at which it heats the substrate  12  and the coloured decoration printed thereon to such an extent that the desired sublimation of the dye molecules proceeds for the purpose of transfer to the article  10 . In this way, very homogeneous heating is achieved in the active area of the gas jet and sublimation may be performed very effectively in a short time. Energy consumption is reduced considerably in comparison with the IR light sources to be found in the prior art. 
     The gas jet may be easily controlled with regard to a series of parameters, such as for example with regard to the pressure produced at the substrate and/or the temperature of the gas. In this way, optimum adaptation to the conditions of the article to be printed and the substrate may be achieved. 
     FIG. 5 is a schematic representation of a modification of the above-described exemplary embodiment with two gas jets  20   a  and  20   b . The table  16  here takes the form of a trolley which moves in the direction of the arrow  36  in FIG.  5 . The two linear gas jets.  20   a ,  20   b  are stationary. The edges of the article  10  are designated with reference numerals  38 ,  40 ,  42 ,  44  in FIG.  5 . The two linear gas jets  20   a ,  20   b  form angles α and β respectively with the feed direction  36 , i.e. the direction of relative movement between the table  16  and the gas jets. The first gas jet  20   a  acts obliquely on the leading edge  42  and the side edge  38  of the article  10 , such that the substrate is pressed uniformly thereon also in the edge area. The oblique arrangement results in particularly high-quality dye transfer in the edge area. The likewise obliquely Positioned second gas jet  20   b  acts on the leading edge  42  and the other side edge  40  of the article  10 . 
     In addition to the oblique arrangement shown in FIG. 5 of the linear gas jets  20   a  and  20   b , the knife-form gas jets may also be positioned obliquely with respect to the plane of the drawing, i.e. the angle between the “knife blade” of the gas jet and the surface of the substrate  12  or cloth  14  is not necessarily equal to 90°. An oblique arrangement of the gas jet relative to the main plane of the substrate  12  has the result that the hot gases flow counter to the direction of relative movement  36  and thus the substrate  12  is preheated prior to entry into the active area of the gas jet. It goes without saying that air is suitable as the gas. The oblique arrangement of the gas jets also allows uniform heating in particular in the edge area. 
     The above-described process and the device may be modified, for example to the effect that, when a substrate with “release” properties is used, the process is performed without a silicone cloth. In this case, it is also frequently possible to dispense with heating of the gas.