WO1991017060A1

WO1991017060A1 - Method for making a relief

Info

Publication number: WO1991017060A1
Application number: PCT/FI1991/000140
Authority: WO
Inventors: Veikko Hakkarainen
Original assignee: Serikansi Oy
Priority date: 1990-05-03
Filing date: 1991-05-03
Publication date: 1991-11-14
Also published as: FI86270B; FI912166A; FI912166A0; FI86270C

Abstract

The object of the invention is a method whereby a hot-welding device for making relief images (5, 6, 7) onto plastic covers, for example. The filling material used between the base and surface layers of the covers is composed of a combination of open-cell and closed-cell plastic (2, 3, 3') for the purpose of achieving clearly visible three-dimensional images.

Description

METHOD FOR MAKING A RELIEF

The object of this invention is a method for making a relief image in which method elastic filling material is placed upon material forming a frame, the frame and the filling material are covered with a surface layer, and this is followed by hot- welding using a press die embodying the desired image.

This kind of a method is used commonly in the manufacturing of so-called rigid plastic binders and plastic covers, for ins¬ tance. Instead of welding the surface layer made of glossy plastic or flock plastic directly onto a frame made of cardbo¬ ard, for instance, elastic filling material is placed between these in order to achieve a certain softness and to ease the embossing of letter characters or other such patterns. The said softness enhances the appearance of the binder or cover, and also makes them more pleasant to handle. Letter characters and patterns can be used as means of designating the purpose of use of the product and, for example, to put across a speci- fie message, and simply to make the product more decorative.

Prior art methods do, however, have their limitations. The profile depth of letter characters and patterns when viewing the product in cross-section remains rather insignificant, the said depth being generally no more than in the order of one millimetre. This being so, it is not possible in practice to achieve noticeable variation in the profile depth of different letter characters or between different parts of patterns, for ins ance.

The purpose of this invention is to bring about a method using which the aforementioned limitations can be avoided and consi¬ derably more versatile implementation possibilities with respect to letter characters and patterns, for instance, are enabled in simple manner. This purpose is achieved when using the method in accordance with the invention, the said method being characterized in that the elastic filling material is formed of at least one layer of closed-cell plastic next to the frame and of one layer of open-cell plastic fitted on top of it, whereupon the profile depth of the relief made using hot-welding is determined mainly by the thickness of the layer of open-cell plastic and the depth of the picture in the press element.

The invention is based on the realization that the joint- effectual properties of open-cell plastic and closed-cell plastic can be made use of in conjunction with hot-welding with regard to the achieving of distinctly distinguishable three-dimensionality especially when producing letter cha¬ racters and patterns onto plastic binders and covers. The range of uses to which products manufactured using the said method can be put to can be widened and, owing to the clearly observable three-dimensionality, the visual impact achieved can be improved.

In the following, the method in accordance with the invention is described by means of an example. In this connection, references are also made to the figures contained in the appended drawing.

Figure 1 shows a schematic presentation of the manner in which the materials used are placed into the welding device in preparation for hot-welding, and

figure 2 serves to illustrate in cross-section the so-called profile depth of the manufactured product.

In figure 1, the reference designation 7 indicates the lower die of a so-called industrial channel connectable high fre¬ quency welding machine (27 MHz) commonly used, especially in the plastics industry. Reference designation 5 indicates the press element or die used to manufacture the desired image 6. In accordance with the method in accordance with the inventi¬ on, the relief image is manufactured onto the product in question, e.g. a plastic binder or cover, by positioning a layer 2 composed of closed-cell plastic, advantageously about 1 - 1.5 mm in thickness, onto the lower die 7 of a high fre¬ quency welding device. If the purpose is to manufacture a cover that is soft throughout and bears distinctly raised letter or numeral characters or patterns, the procedure is as follows. In order to achieve the desired softness, a thin layer of open-cell plastic 3 is first laid onto the layer of closed-cell plastic 2. This is followed by placing strips 3' of open-cell plastic in the actual pattern places so that they become positioned in places corresponding to the patterns 6 (plate etchings) formed in the press element 5. This results in these open-cell plastic layers filling the letter character or pattern "mould cavities" (i.e. plate etchings) in the press element 5 once the hot-welding operation is executed. The product gets the desired surface when the above set-up is covered with a surface layer 4 composed, for instance, of flock plastic prior to the hot-welding operation.

The aforementioned plate etchings are formed in the press element 5 applying methods well known to professionals in the field, it not being necessary in this connection to describe these methods in more detail. The same applies to the hot- welding operation itself which is a technique well known in the field.

On applying the method in accordance with the invention, it has been possible to achieve profile depths within the range of c. 0.1 to 10 mm with accompanying temperatures being c. 40 to 90°C. It is clear that different plastics, temperature and high frequency can be used to influence the profile depth. Essential to the method is, however, the combination of the properties of the closed and open-cell plastics. Figure 2 shows a cross-sectional view of a manufactured product to illustrate the profile depth h.

The following is an example of an advantageous method of manufacture:

A selection of PVC-based plastics is acquired. Open-cell plastic or strips of the plastic, the said plastic being characterized in that it melts when exposed to the heat produ¬ ced by a high frequency heating device, are placed on top of a sheet of closed-cell plastic so as to coincide more or less with those spots where the purpose is to achieve relief ima¬ ges. Following this, PVC plastic, a known material used in the manufacture of covers, is placed on top of the closed-cell plastic and the open-cell plastic. The thus formed entity is then transferred into a high frequency heating device. First, it is preheated for a few seconds. Then the device is switched into the high frequency mode. The time of exposure depends on the temperature, depth of profile, properties of the plastic, etc. During the hot-welding stage, the plastic will melt in those places where there is too much of it (i.e. where the profile depth is small or where there is no etching at all) . Thus, it retains its shape, at least partly, in those places where the profile depth is great and in so doing the pieces of closed-cell plastic become fused to one another in those places where there are no etchings. The air discharged from the open-cell plastic is directed into the space occupied by the relief image. Following the welding operation, the product is allowed to cool down for a moment before it is removed from the high frequency heating device. Having been removed, the product is ready to be used as a cover decoration, for exam¬ ple. It keeps its shape when compared to a deep drawn product, for instance. The pattern resumes its original shape after being compressed.

In the case of small images especially, it is also possible that open-cell plastic is not required and that a layer of air instead is used to bring about the relief image along the welded spots within the layers of welded closed-cell plastic. An example of a means whereby the thus achieved relief image can be made to retain its advantageous shape is to place a sheet of rigid PVC, the said sheet being characterized in that it will melt during the hot-welding operation, for example, underneath the welded closed-cell plastic layer. The said PVC sheet supports the relief image so that the top layer retains the relief image achieved.

The achieved relief image can thereafter be used to decorate various types of covers and in the dissemination of informati¬ on.

In accordance with the invention, no glues are required cont¬ rary to the practice with regard to several other solutions.

The drawing and the description accompanying it are intended only to illustrate the fundamental inventive idea. Details such as the number of layers of closed and open-cell plastic, their thickness, and the material used to form the top layer, can, naturally, vary within the framework of the accompanying patent claims.

Claims

1. A method for making relief images in which method layers (2,4) composed of PVC-based plastic are welded using a high frequency device and a press element (5) embodying the desired image (6) , characterized in that a layer of plastic (4) is placed on top of a closed-cell plastic layer (2) and at least one layer of open-cell plastic (3, 3 ' ) whereupon the profile depth (h) of the relief image produced by preheating and high frequency welding is determined in the main by the thickness of the layer of open-cell plastic and depth of the image (6) embodied in the press element (5).

2. A method as claimed in claim 1, characterized in that the profile depth (h) is increased at least in the case of certain image components by using more than one layer (3') of open- cell plastic.

3. A method as claimed in claims 1-2, characterized in that the open-cell plastic layer is at least partially rep¬ laced by air.

4. A method as claimed in claims 1-3, characterized in that a layer of rigid PVC is placed beneath the layer of closed-cell plastic.

5. A method as claimed in claim 1, characterized in that the layer of plastic (4) is composed of PVC plastic.