Field of the Invention

The invention concerns the field of technology designed to modify surfaces of materials and semi-finished products using relief stamping.

Background of the Invention

The method of relief stamping execution has been known for a long time. During relief stamping the surface of pliable material is modified by creating a relief on the surface as a result of the relief stamping process. Relief stamping is executed by stamping dies. The bottoms of stamping dies are equipped with matrices that are pressed into the respective surface of pliable material either by the action of an increasing pressure applied onto the stamping die, or by hitting the stamping die. Relief stamping can be performed at normal temperature or at higher temperatures of either the material or the matrix, for example when stamping leather material.

Among other methods is dry relief stamping process, or where applicable relief printing, where the relief is created on the stamped surface that retains the appearance of the original material into which relief stamping was performed. Another known alternative technology is colour relief stamping process where a layer of colour is applied onto the matrix and the layer of colour is applied to the relief in the material by the action of pressure during the relief stamping process.

Based on the close state of the art presented by document CZ 283220, engraving in leather with the subsequent treatment of the leather surface with a relief using paint coat is known. Among other known procedures for the application of colours or surface-treatment preparations onto surface are printing, spraying, immersion, etc. Disadvantages of dry stamping include the fact that the resulting relief keeps its original colour appearance, or an appearance modified due to exposure to pressure exerted by the matrix, either under cold conditions or at higher temperatures. If a colour relief should be created, additional labour is required, which must be precise in particular in the case of minor reliefs. Deployment of machines for automatic colour modifications of relief graphics is difficult as pliable materials, into which relief stamping is executed, do not have constant and fixed dimensions. Moreover, there are requirements concerning the quality and properties of the used colours that should not cause the relief become stuck over by the colour to prevent the colour peeling off from the stamped relief, which means that completing colours into reliefs created by relief printing is time-consuming and expensive.

As far as colour relief stamping process is concerned, automation is feasible as this technology combines the creation of a relief and its colour modification in one process step, which means that although pliable material has not constant and fixed dimensions, colour is applied to the exact place in the relief. Disadvantages of the colour relief stamping process rest in the fact that the colour for the hot relief stamping process must have special properties, which increases its price and consequently production costs of the colour relief stamping process. Another disadvantage is that the application of colour onto the matrix is complicated as the colour is prone to mixing and creeping. In the case of stamping minor reliefs with numerous details blurring of colours may appear with the colour potentially overflowing into the adjacent places of the relief due to the non-constant pliability of the material, etc.

The task of the invention is to create a method of colour relief stamping which would be suitable for the automated production of colour reliefs of various sizes and with a different degree of detail, with exact application of colours that would utilize the well-known procedures for relief stamping and application of colours and combine them in a manner allowing the given procedures to be consecutive and mutually compatible. Summary of the Invention

The set goal has been achieved by developing a method of colour relief stamping according to the present invention.

The method of colour relief stamping is intended for the creation of a coloured relief stamped on the surface of material or a semi-finished product.

The essence of the invention rests in the following working steps, during which the material or semi-finished product is at first fixed into a fixture for its positioning in the system of coordinates determined by the fixture. The fixing maintained over the entire time of the method execution is the comer-stone of the invention as the relief stamping is implemented into pliable materials that cannot be repeatedly fixed in an identical manner. In addition, the material is positioned in the system of coordinates that allows printing to be accurately aligned with the stamped relief created during the relief stamping operation. The next step is the determination of working coordinates in the system of coordinates given by the relief stamping specification. The working coordinates are used for the alignment of work operations in an exact place when implementing the colour relief stamping operation based on the graphic model for the relief stamping operation. The next steps of the working procedure include the alignment of the matrix performing the relief stamping operation with the working coordinates and the execution of the relief stamping operation. After the relief stamping operation is executed, the print head of the machine performing printing is aligned with the working coordinates and printing into the relief stamped into the material or semi finished product is performed. The last step of the working procedure comprises the removal of the material or semi-finished product from the fixture.

Considering the fact that the machines for the execution of the relief stamping and printing operations are usually independent, a preferred embodiment of the invention of colour relief stamping includes a step comprising the transfer of the fixture from the machine performing the relief stamping operation to the machine performing printing operation that is inserted between the working step comprising the execution of the relief stamping operation and the working step comprising the alignment of the print head of the machine performing the printing operation.

In another preferred embodiment of the invention of colour relief printing the working step of serial production comprising the determination of working coordinates in the system of coordinates as per the relief stamping specification is omitted for the second and any following repetition of the method of colour relief stamping.

When executing the invention of colour relief stamping, it is preferred if the working step is implemented using the UV LED printing technology. This technology is suitable for colouring stamped reliefs as the application of colour is accurate and its curing immediate.

Among the benefits of the invention is the provision of the colour relief stamping method where the relief is coloured by the machine performing printing, which results in a wide range of design alternatives that can be offered to customers. Colour is applied with high precision into stamped reliefs that can have details to be coloured in the order of several hundredth of millimetre and the UV LED printing technology is capable of printing even a photograph into a dry-stamped relief. Such accuracy with pliable materials has not been attained yet.

Explanation of Drawings

The present invention will be explained in detail by means of the following figures where:

Fig. 1 shows a view of a semi-finished product fixed in the fixture.

An Example of the Invention Embodiment

It shall be understood that the specific cases of the invention embodiments described and depicted below are provided for illustration only and do not limit the invention to the examples provided here. Those skilled in the art will find or, based on routine experiment, will be able to provide a greater or lesser number of equivalents to the specific embodiments of the invention which are described here. Also such equivalents will be included in the scope of the following claims.

Fig. 1 shows the fixing of the semi-finished product 2 in the fixture. The fixture consists of the body 1 with a rectangular plan view and of the stops 3. The stops 3 can be fastened on the body 1 of the fixture in an adjustable manner so that they can adapt to materials or semi finished products of various dimensions. The fixture is made of, for example, metal (steel, aluminium) or hard plastic material.

An example of the semi-finished product 2 can be a diary with leather covers that is to be equipped with a stamped relief according to the client's wish. The graphic model of the stamped relief includes the“Praha” inscription and the coat of arms of the Capital City of Prague. The inscription should be made in black colour and the colours of the coat of arms should correspond to the original. The stamped relief should be situated in the right bottom corner of the outer side of the diary cover.

After the execution of colour relief stamping operation on the diary cover, the diary is first fixed on the body 1 of the fixture using the stops 2. By fixing, the diary is positioned in the system of coordinates. The origin of coordinates can be positioned for example in the centre of the body 1 of the fixture or in one of its corners. The fixing must be the only one for the whole sequence of working steps as the leather covers are pliable and during the second round of fixing, the diary may be squeezed and displaced by a millimetre, which means that the printing operation would not be made exactly into the stamped relief.

Subsequently, the working coordinates defines the place in the system of coordinates where the relief is to be stamped as per the relief stamping specification. The matrix of the machine performing the relief stamping operation is aligned with the working coordinates, the fixture is put into the machine executing the relief stamping operation and the relief itself is stamped. The machine for performing the relief stamping operation can be manufactured by Printek, e.g. the SH 12 model. Then the fixture is transferred into the machine performing the printing operation, whose print head is aligned with the working coordinates, and printing into the stamped relief is executed. The machine for the performance of the printing operation can be for example the UV LED printer, model UJF-6042 manufactured by Mimaki. UV LED printing is printing technology based on the injection of colour droplets with the volume of picoliters at a high speed onto the printing area. The colour is UV-sensitive, i.e. it is cured by UV radiation.

During serial production the machines are left aligned and are only fed with new semi finished products fixed in the fixtures.

Industrial Applicability

The invention can be applied in the area of the manufacture of advertising articles and also in the area of the manufacture of handbags, waist belts and shoes.

Overview of the Positions

1 Body of the fixture

2 Semi-finished product

3 Stops of the fixture