Method for surface-treating a functional surface of a cooking apparatus, and cooking apparatus for cooking food to be cooked

Abstract

The invention relates to a method for surface-treating a functional surface of a cooking apparatus for cooking food to be cooked. The method according to the invention comprises the following steps: structuring the functional surface by means of a laser-processing apparatus, the functional surface being structured by at least one laser beam, the at least one laser beam comprising at least temporary pulse durations of at most 500 ns, and the structuring producing a profile having at least one indentation, applying a lubricant to the structured functional surface, thermally treating the structured functional surface having the lubricant at a temperature between 50°C and 700°C in order to obtain the treated functional surface. The cooking apparatus according to the invention comprises an functional surface treated in accordance with the method according to the invention.

Description

[0001]Method for the surface treatment of an active surface of a cooking device and cooking device for cooking food The invention relates to a method for the surface treatment of an active surface of a cooking device for cooking food and to a cooking device for cooking food. Cooking devices are known from the prior art, for example as stainless steel pots, for example for boiling food, wherein the active surface of the stainless steel pot is made smooth by polishing carried out during its manufacture. After prolonged use, the active surface becomes uneven due to scratches and dirt spots, so that food residues from the food stick to the active surface of the stainless steel pot and this surface is difficult to clean. Several designs are known from the prior art to improve the non-stick properties of cooking devices.EP 0365 458 proposes a roughened active surface onto which a ceramic material, for example, an aluminum oxide-titanium oxide powder mixture, is thermally sprayed. EP 1048 751 proposes coating an active surface with diamond crystals to obtain a hard and highly thermally conductive coating. Furthermore, coatings of active surfaces are known that contain per- and polyfluorinated alkyl compounds, also known as "PFAS" ("per- and polyfluoroalkyl substances"). Although these components improve the non-stick properties of the active surface, they are highly harmful to health and the environment. The known cooking devices from the prior art have depressions with a largely uncontrolled distribution of dimensions due to the comparatively macroscopic manufacturing processes for producing depressions on the active surface of the cooking devices.The dimensions of the recesses are highly statistically distributed and subject to significant fluctuations. Furthermore, the known coatings of the active surfaces are neither sustainable nor durable. In most cases, with increasing service life of the known cooking devices, the non-stick surface and / or the active surface of the cooking device itself detaches or wears, so that the non-stick properties of the known cooking devices are severely impaired over a longer service life. Therefore, the object of the invention is to develop a method for surface treatment of an active surface of a cooking device and a corresponding cooking device in order to obtain improved non-stick properties of the cooking device, in particular for a longer service life of the cooking device and with a lower environmental impact. The object of the invention is achieved by a method having the features of claim 1.This provides a method for the surface treatment of an active surface of a cooking device for cooking food, comprising the following steps: providing the cooking device in a laser processing device, structuring the active surface of the cooking device by means of the laser processing device, wherein the laser processing device structures the active surface by means of at least one laser beam, wherein the at least one laser beam at least temporarily has pulse durations of at most 500 ns and wherein a profile with at least one depression is produced on the active surface by means of the structuring, applying a lubricant to the structured active surface and thermally treating the structured active surface with the lubricant at a temperature between 50°C and 700°C while maintaining the treated active surface.The object of the invention is further achieved by a cooking device with the features of claim 13. This provides a cooking device with an active surface for cooking food, wherein the active surface is treated according to the method according to the invention. The inventive structuring of the active surface of the cooking device by means of the at least one laser beam within the laser processing device ensures that the at least one depression, in particular all of the designed depressions, are formed with an identical dimension within the manufacturing tolerance. The formation of the at least one depression of the profile is therefore reproducible, in particular with regard to several depressions of the same profile and / or with regard to several cooking devices structured one after the other according to the invention.For example, the structuring of the active surface can be carried out using a single laser beam, which is also referred to in particular as “direct laser writing”. To structure the active surface, the laser beam can be focused on the position of the processing of the active surface in order to increase the energy and power density. The structuring of the active surface can provide for the laser beam to be moved relative to the active surface, which is also referred to as “rasterizing”. This can be carried out, for example, using a laser scanner, in particular using a mirror scanner, which can be designed as a galvo scanner and / or as a polygon scanner. The laser scanner is preferably designed for one-dimensional or two-dimensional deflection of the at least one laser beam.In a further embodiment of the invention, the active surface of the cooking device can be moved translationally - relative to the at least one, in particular spatially fixed laser beam - for example by means of at least one servo motor. In a particularly advantageous development of the invention, the at least one laser beam and the cooking device are movable in one and / or two dimensions in order to be able to carry out particularly rapid structuring of the active surface. To increase process efficiency, at least two laser beams in the sense of the "direct laser writing" described above can also be used to structure the active surface. In a development of this feature, several laser sources of the laser processing device connected in parallel to one another can be used to generate the at least two laser beams in order to structure the active surface.The number of laser beams preferably corresponds to the number of laser sources of the laser processing device. In an alternative embodiment, the laser processing device has a laser source whose beam, also referred to as a "seed beam," is split into at least two partial beams, for example, through the use of diffractive optical elements. The partial beams obtained on the basis of the original laser beam from the laser beam source can be used to structure the active surface, wherein it can be provided that at least one of the partial beams, in particular several partial beams, is or are focused independently of one another. The at least two laser beams of the laser processing device can be in a specific spatial relationship to one another, in particular with the use of diffractive optical elements as already described.It can be provided that the temporal pulse duration of the at least one laser beam is a maximum of 15 ps. This ensures that thermal effects are prevented as far as possible during profile generation, which improves the manufacturing quality of the depressions. Furthermore, the formation of melting and thermally induced material damage, in particular stress cracks, is prevented. It is known that with shorter pulse durations, thermal effects are increasingly neglected, so that the active surface of the cooking device is increasingly mechanically processed. This effect is therefore also referred to as cold ablation. From this perspective, it can be provided that the temporal pulse duration of the laser beams is a maximum of 10 ps, ​​so that even fewer thermal effects occur. In addition, the accuracy of the structuring is improved.For the same reason, it can be provided that the temporal pulse duration of the laser radiation is at most 1 ps, whereby an even better surface quality of the active surface can be achieved. Preferably, a temporal pulse duration between 100 fs and 15 ps, in particular between 100 fs and 1 ps, is provided. Furthermore, the power of the laser radiation can be between 1 W and 5 kW, in particular between 1 W and 500 W, and / or the energy of the pulses of the laser radiation can be between 10 µJ and 200 mJ, in particular between 10 µJ and 100 mJ. The at least one laser beam can have a beam diameter between 2 µm and 6 µm when structuring the active surface, in particular in the region of the active surface. When generating the structuring according to the invention, between 2 and 1000 individual pulses can be superimposed in a spatial area in order to obtain high structure aspect ratios through a correspondingly high material removal.Furthermore, it can be provided that exactly two interfering laser beams are used to structure the active surface of the cooking device by means of the laser processing device. A further development of the invention provides that three interfering laser beams are used, whereby, for example, a structuring of the active surface with depressions in a hexagonal pattern can be created. In this case, the structuring has three axes along the surface, along which the depressions are each arranged in a lateral period, wherein, within the meaning of the invention, the lateral periods for the three axes are identical in the hexagonal pattern. In addition, it can be used that four interfering laser beams are used to create a square pattern of depressions when structuring the active surface.Finally, it can be provided that a maximum of nine interfering laser beams are used. By structuring the active surface, this is enlarged due to the at least one depression and allows better wetting of the active surface by the lubricant. To the applicant's knowledge, in the case of the active surface structured according to the invention, the lubricant is "drawn" into the depressions by means of capillary forces occurring in the microstructure area and remains stored there at least temporarily. This improves the non-stick properties compared to the known cooking device. A further basic idea of ​​the invention is that polymerizations, oxidations, and hydrolysis can occur through the thermal treatment of the lubricant, which is introduced in particular into the active surface structured according to the invention.As a result, reaction products are embedded in at least one depression in the profile of the active surface and, due to the aforementioned surface enlargement, adhere particularly well to the active surface, so that the applied lubricant forms a lubricating film, also referred to as a tribofilm. Due to the structuring of the active surface according to the invention, these properties are particularly long-lasting and protect the topography of the active surface from mechanical wear for as long as possible. The invention thus enables the creation of an environmentally friendly and long-lasting cooking device with stable non-stick properties even after prolonged use. In addition, no further cleaning steps are required according to the method according to the invention, so that the cooking device surface-treated according to the invention is immediately ready for use after the end of the method.The structuring of the active surface of the cooking device is preferably carried out by means of the laser processing device through the interference of at least two laser beams. By using at least two interfering laser beams to structure the active surface, a large area of ​​the active surface can be processed in a comparatively short time, thus also improving the process efficiency of the surface structuring in the course of the method according to the invention. In particular, the active surface of the cooking device can be provided with a full-surface surface structuring in the micrometer and / or nanometer scale range in a short processing time, which leads to significantly higher process efficiency and thus lower manufacturing costs compared to other known treatment methods.For the purposes of the invention, the cooking device comprises all utensils for cooking food, such as frying, cooking, grilling, baking, roasting, and braising utensils. The active surface refers to the surface of the cooking device that comes into contact with the food to be fried, i.e., the food, during the cooking process. For the purposes of the invention, cooking includes, on the one hand, moist cooking techniques in which the food is cooked with the aid of drinking water, for example, boiling or steaming. In addition, cooking also includes dry cooking techniques in which the food is cooked without the addition of drinking water, for example, frying, baking, or grilling. Preferably, the at least one laser beam, in particular the at least two interfering laser beams, at least temporarily have pulse durations between 1 ns and 20 ns, in order to achieve a greater processing speed when structuring the active surface.The use of pulse durations between 1 ns and 20 ns also enables the structuring of the active surface with a greater depth of field, i.e. greater flexibility in structuring the active surface along the depth. It is preferably provided that the at least one depression in the active surface is produced with a dimension, in particular with a depth compared to an unstructured region of the active surface, between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm. In further embodiments of the invention, it can be provided that the dimension of the depression corresponds to its length in the x and / or y direction, wherein, within the meaning of the invention, in the case of multiple depressions, the y direction corresponds to the offset direction of the depressions, while the x direction is arranged perpendicular thereto.The x- and y-directions are each perpendicular to the normal of the active surface and thus each extend along the active surface. In the sense of the invention, a dimension can also refer to a direction as a combination of the x- and y-directions, which in this respect corresponds to a generally lateral direction. In a further embodiment of the invention, at least two depressions with essentially identical dimensions, in particular with essentially identical depths, are produced. In the sense of the invention, two dimensions have essentially identical dimensions if their deviations do not exceed the processing tolerance customary in comparable processes. At least two adjacent depressions can be arranged at a distance of 10 nm to 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm.Due to the structured active surface, structural geometries in the order of magnitude between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm, can be realized on the cooking device at an industrially relevant process speed while simultaneously ensuring reproducibility. Preferably, at least one group of depressions is created in a periodic pattern on the active surface, since this structure can be created particularly easily using the interfering laser beams. In the context of the present invention, the period refers to the distance between two identical structural features of different depressions of the periodic pattern, for example the distance between the beginning of a first depression of the periodic pattern and the beginning of the depression of the same periodic pattern adjacent to this depression.Alternatively or additionally, the period within the meaning of the invention can refer to the distance between a center point of the first depression of the periodic pattern and the center point of the depression of the same periodic pattern adjacent to this depression. Since the depressions of the periodic pattern are laterally offset, the term lateral period is also used within the meaning of the invention, which, as already stated, refers to the distance between recurring structural features of adjacent depressions of the periodic pattern. Preferably, the group of depressions in the periodic pattern is produced on the active surface with a lateral period between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm, in at least one direction along the active surface.A periodic structuring of the active surface with a lateral period of this magnitude enables the formation of the advantageous surface functionalities mentioned above, with which the cooking device is to be provided. The group of depressions in the periodic pattern can furthermore have different periods in different directions, for example when three, four or more interfering laser beams are used to structure the active surface. In an advantageous development, the group of depressions in the periodic pattern has identical periods in two different directions. Furthermore, it can be provided that the group of depressions in the periodic pattern has identical periods in three different directions, which corresponds, for example, to a hexagonal arrangement of the depressions.The group of depressions is designed, for example, as a sinusoidal line structure in which depressions and elevations are each arranged one behind the other in the same lateral period. In a further embodiment of the invention, it can be provided that at least one group of depressions is produced on the active surface of the cooking device with a linear course and / or with a rectangular, preferably square, basic shape and / or with a circular basic shape. The basic shape of the depressions can be polygonal, in particular hexagonal. As a special case, the depressions can be designed as lines, which can in particular be offset perpendicular to their direction of extension and / or arranged in a defined lateral period.Preferably, the depressions, in particular the group of depressions, have a lateral extent, in particular in a direction parallel to the direction of the lateral period, of between 10 nm and 49 µm, in particular between 10 nm and 10 µm or between 1 µm and 25 µm, in order to obtain particularly advantageous non-stick properties of the cooking device. Particularly preferably, all depressions each have a lateral extent of substantially 10 nm to 49 µm, in particular between 10 nm and 10 µm or between 1 µm and 25 µm. Preferably, the depressions, in particular the group of depressions, have an aspect ratio between 0.01 and 5, in particular between 0.01 and 1, wherein the aspect ratio in the sense of the invention corresponds to the ratio of the depth of the depression to a lateral extent of the depression.The structuring of the active surface is preferably carried out in a single work step in order to improve the efficiency of the method. In a further development of the invention, it can be provided that at least two first depressions, in particular a first group of depressions, are produced with a first lateral period between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm, and at least two second depressions, in particular a second group of depressions, are produced with a second lateral period, wherein in particular the second lateral period is smaller than the first lateral period. The first lateral period can be between 100 nm and 999 µm. However, the second lateral period can also be larger than or identical to the first lateral period.The second group of depressions can be configured mathematically similarly to the first group of depressions, so that the second group of depressions results from the first group of depressions by means of at least one mathematical similarity transformation, for example, translation, rotation, stretching, and / or scaling. Preferably, the second group of depressions corresponds to a 90° rotation of the first group of depressions around an axis perpendicular to the tool surface.Alternatively or additionally, it can be provided that at least two first depressions, in particular a first group of depressions, are produced with a first dimension between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm, and at least two second depressions, in particular a second group of depressions, are produced with a second dimension, wherein the second dimension is in particular smaller than the first dimension. As already stated, the dimension of the depression within the meaning of the invention can correspond to its depth. In addition, it can be provided that, in addition to the second depressions, at least two third depressions, in particular a third group of depressions, are produced with a third lateral period and / or a third dimension, wherein the third lateral period and / or the third dimension are in particular smaller than the second lateral period and / or the second dimension.In further developments, up to ten groups of depressions can be created, each with a lateral period and / or a dimension, wherein, in particular, the lateral period and / or the dimension of a group are always smaller than the lateral period and / or the dimensions of the previous groups. Preferably, the area of ​​the second depressions, in particular the second group of depressions, at least partially overlaps the area of ​​the first depressions, in particular the first group of depressions. The same applies to any third depressions that may be created, in particular the third group of depressions.Such an overlap makes it possible to combine structures with different lateral periods and / or dimensions, in particular to modulate them mathematically, and to provide the active surface of the cooking device with complex surface structures that are not possible with simple structuring. This expands the possibilities for improving the non-stick properties of the cooking device. Preferably, the production of the first depressions, in particular the first group of depressions, and the production of the second depressions, in particular the second group of depressions, take place in a single work step or in separate work steps. The production of the first depressions and the second depressions in a single work step increases the process speed.In contrast, the design of the production of the first depressions and the second depressions in separate work steps includes, in particular, that the active surface is structured with different interference patterns. For example, it can be provided that the cooking device is moved between two successive work steps. Preferably, it can be provided that the cooking device is rotated between two work steps, in particular by an angle of 90°, so that depressions can be formed particularly easily, for example as cross-structure patterns and / or so-called Penrose structure patterns. The depressions of the second group can be arranged perpendicular to the depressions of the first group, so that the lateral period of the second group of depressions is arranged perpendicular to the lateral period of the first group of depressions.In addition, the lateral period of the second group of depressions can be aligned parallel to the lateral period of the first group of depressions or can enclose an angle between 0° and 180°. The second group of depressions is preferably created by a polarization of the laser beams selected depending on the material of the active surface to be structured, whereby, in particular, laser-induced periodic surface structuring can be formed, in particular in a joint work step with the formation of the first group of depressions. The lateral period of the second group of depressions corresponds, for example, at most to the wavelength of the laser beams used.The polarization of the laser beams can be aligned linearly, with the polarization vector being arranged substantially perpendicular to the direction of extension of the laser-induced periodic surface structuring and / or parallel to the lateral period associated with the laser-induced periodic surface structuring. In addition, the direction of the polarization vector of the laser beams can be aligned at an angle between 0° and 180° relative to the lateral period of the first group of depressions, so that the arrangement of the second group of depressions can be adjusted, particularly relative to the first group of depressions, by aligning the polarization vector of the laser beams.For example, it can be provided that the first depressions, in particular the first group of depressions, are produced by means of interference of the at least two laser beams, wherein the second depressions, in particular the second group of depressions, are produced by means of interference of at least two laser beams and / or by means of a single laser beam. This means that the first depressions are always produced with the laser beams interfering with one another, whereas this does not necessarily have to be the case for the production of the second depressions. The production of the second depressions by means of a single laser beam can be expedient if the number of second depressions is small compared to the number of first depressions and / or if the area of ​​the second depressions is small compared to the area of ​​the first depressions.If the second depressions are also created by means of interfering laser beams, it can be provided that the number of interfering laser beams differs from or is identical to the number of laser beams used to create the first depressions. Preferably, at least two groups of depressions are created, each in a periodic pattern, wherein the lateral period of the first group of depressions is arranged at an angle other than 0° to the lateral period of the second group of depressions, in particular at an angle of 90°.The lubricant preferably comprises at least one component from the following group: oil-based lubricant, oil, food-grade oil, vegetable oil, sunflower oil, rapeseed oil, food-grade chain oil, grease, food-grade fat, vegetable fat, animal fat, synthetic fat, polyalkylene glycol, dry lubricant, food-grade dry lubricant, solid lubricant, carbon-based lubricant, graphite. For the purposes of the invention, lubricants that correspond to the H1 classification and / or satisfy the requirements of EC Directive 93 / 43 EEC can be considered food-grade. For the purposes of the invention, lubricants are considered food-grade in particular if unintentional contact with food is possible and humanly acceptable.Food-grade lubricants may contain additives that are safe for human consumption and may only be transferred to the food in limited quantities. In particular, it can be provided that the preferably fat-containing lubricant is applied to the structured active surface of the cooking device in such a way that the lubricant forms a flat surface, which improves the non-stick properties of the cooking device. The thermal treatment of the structured active surface preferably takes place for a duration of at least 1 minute. The cooking device according to the invention, in particular its active surface, preferably comprises at least one component from the following group: aluminum, iron, cast iron, stainless steel, carbon steel, carbon steel, in particular provided with a magnetic component, ceramic, fiber-reinforced material.The cooking device preferably has a layer system with at least two layers, wherein in particular a first layer made of aluminum and a second layer made of stainless steel are provided, wherein in particular the active surface corresponds to the second layer. The active surface of the cooking device preferably has at least one group of depressions, wherein the depressions in particular have a lateral period between 100 nm and 50 µm and / or a lateral dimension, in particular a lateral width between 10 nm and 49 µm, in particular between 10 nm and 10 µm or between 1 µm and 25 µm, and / or an aspect ratio between 0.01 and 5, in particular between 0.01 and 1, wherein the aspect ratio corresponds to the ratio of the depth of the depression to the lateral dimension of the depression. The lubricant on the active surface preferably has a layer thickness of between 10 nm and 500 µm after the thermal treatment.The cooking device is preferably at least one member of the following group: cooking device, grilling device, frying device, baking device, braising device. The cooking device is preferably a member of the following group: cooking pot, roasting pan, baking tray, pan, grill rack. Further advantages and features emerge from the claims and from the following description, in which exemplary embodiments of the invention are explained in detail with reference to the drawings. Therein: Fig. 1 shows schematic representations a) to d) of steps of the method according to the invention in connection with a cooking device according to the invention, Fig. 2 shows a schematic representation of a structured active surface of the cooking device according to the invention, Fig. 3 shows the active surface according to Fig. 2 in a schematic section, Fig. 4 shows the active surface of Fig. 3 after application of a lubricant, Fig.5 shows a cooking pot with an untreated active surface, Fig. 6 shows the cooking pot according to Fig. 5 with an active surface treated according to the invention, Fig. 7 shows a baking tray with an untreated active surface, Fig. 8 shows the baking tray according to Fig. 7 with an active surface treated according to the invention, Fig. 9 shows a frying pan with an untreated active surface, Fig. 10 shows the frying pan according to Fig. 9 with an active surface treated according to the invention, Fig. 11 shows a grill grate with an untreated active surface, Fig. 12 shows the grill grate according to Fig. 11 with an active surface treated according to the invention, Fig. 13 shows a pan according to the invention with an active surface treated according to the invention, Fig. 14 shows another pan according to the invention with an active surface treated according to the invention and Fig. 15 shows a baking pan according to the invention with an active surface treated according to the invention.1 shows, in four representations a) to d), the sequence of one embodiment of the method according to the invention for the surface treatment of an active surface 10 of a cooking device 11, which in the exemplary embodiment shown is the surface 10 of a frying pan on which food is to be fried. In representation a) of FIG. 1, the cooking device 11 is provided with an as yet untreated active surface 10. In this state, the active surface 10 does not yet have a structuring 12 and is, for example, polished during the manufacture of the cooking device 11. The cooking device 11 is provided according to the method according to the invention in a laser processing device 13, which is shown schematically in representation b) of FIG. 1.With the aid of the laser processing device 13, the active surface 10 of the cooking device 11 is structured by means of interference from two laser beams 14, 15, which, as shown in illustration b), are deflected at a finite angle to one another and each have pulse durations of approximately 10 ns. These are therefore short pulses that interfere with one another in the region of the active surface 10 in order to carry out a structuring 12 of the active surface 10 of the cooking device 11. In the exemplary embodiment of Fig. 1, a profile 16 with linear depressions 17 is created, which are arranged offset from one another perpendicular to their direction of extension. The profile 16 of the active surface 10 of the cooking device 11 created by the structuring 12 is shown enlarged in Fig. 2. The depressions 17 each have a depth of 1 µm, a width of 5 µm and an approximately sinusoidal profile in cross-section; this profile is shown in Fig.3, wherein for illustration reasons the y-axis, which is aligned normal to the active surface 10, is scaled differently to the x-axis, wherein the x-axis is aligned parallel to the width of the depressions 17. The aspect ratio of the depressions 17, i.e. the ratio between the depth and the width of the depression 17, essentially corresponds to 0.2. Perpendicular to their direction of extension, the depressions 17 are arranged at a distance of 5 µm, so that a lateral period l of the profile of the active surface in the sense of the invention of 5 µm results. Fig. 3 shows a schematic section through the structured active surface 10 of the cooking device 11, from which in particular the sinusoidal course of the depressions 17 and their lateral period l can be seen.The structuring 12 takes place in a single work step essentially on the entire active surface 10 of the cooking device 11, leads to a surface activation of the active surface 10 due to an enlargement of the active surface 10, and thus serves as a surface pretreatment within the meaning of the invention. After the structuring of the active surface 10 by the laser processing device 13, a fatty lubricant 18, which in the present embodiment is cooking oil, is applied to the thus structured, pretreated active surface 10. The lubricant 18 penetrates in particular into the recesses 17 and wets the entire active surface 10 of the cooking device 11 as evenly as possible.The lubricant 18 forms an approximately flat layer 19 on the cooking device 11 with a thickness of 100 nm, which, in the sense of the invention, corresponds to the distance from the tip 20 of a depression 17 to the surface of the layer 19 of the lubricant 18. This is due, for example, to capillary forces that develop as a result of the structuring 12 of the active surface 10 in the microstructure area and draw the lubricant 18 into the depressions. The lubricant 18 remains adhered there, at least temporarily. The active surface 10 modified in this way is shown in illustration c) of Fig. 1. The flat layer 19 of the lubricant 18 is also shown schematically in the section of the active surface 10 according to Fig. 4. Subsequently, according to illustration d) of Fig.1 illustrates a thermal treatment of the cooking device 11 with the lubricant 18 at 250°C for a duration of 30 minutes, which in the illustrated embodiment is carried out by means of a heating means 20 arranged at a distance from the cooking device 11, the heating means 20 being shown schematically in illustration d). The temperature is selected such that it is below the smoke point of the lubricant 18, here the cooking oil, but is still sufficiently high to cause, for example, polymerization, oxidation, and hydrolysis of the lubricant 18. Decomposition products of these reactions are stored in the depressions 17, also referred to as microcavities, of the structured active surface 10 and adhere particularly well due to the surface area enlarged by the structuring 12 and form a friction-reducing layer 19 or film, which is also referred to as a “tribo-film”.This layer 19, in combination with the structuring 12 of the active surface 10 in the micrometer range, improves the non-stick properties and also improves the corrosion properties of the active surface 10 of the cooking device 11 treated according to the invention. Fig. 5 shows a cooking pot 21 with an untreated active surface 10, which can also be used as a casserole dish or roasting pan. In contrast, Fig. 6 shows the cooking pot 21 from Fig. 5 with an active surface 10 treated according to the invention, which in particular has the profile 16 with the depressions 17 and the lubricant 18 applied thereto. Fig. 7 shows a baking tray 22 with an untreated active surface 10, and Fig. 8 shows the baking tray 22 with an active surface 10 treated according to the invention, which is provided with the profile 16 with the depressions 17 and to which the lubricant 18 is applied. Fig. 9 shows a frying pan 23 with an untreated surface 10 and Fig. 10 with an active surface 10 treated according to the invention. Fig.11 shows a grill grate 24 with an untreated active surface which corresponds at least to the top side of the grill grate 24. Fig. 12 shows the grill grate 24 of Fig. 11 with an active surface 10 treated according to the invention, which is shown enlarged in a section in Fig. 12 and has the already described profile 16 with the depressions 17 and with the lubricant 18. Fig. 13 shows a photographic representation of a frying pan 23 made of stainless steel, the active surface 10 of which is largely treated according to the invention and as such has the profile 16 with the depressions 17 and the lubricant 18. Fig. 14 shows a photographic representation of another frying pan 23 which, however, in contrast to the frying pan 23 of Fig. 13, is made of carbon steel, which is also referred to as carbon steel. The active surface 10 of this pan 23 is also provided with the profile 16 with the recesses and with the lubricant 18. Fig.15 shows a photographic representation of a baking mold, the active surface 10 of which is largely treated according to the invention and has the profile 16 with the recesses 17 and the lubricant 18.

Claims

Patent claims 1.Method for the surface treatment of an active surface (10) of a cooking device (11) for cooking food, comprising the following steps: providing the cooking device (11) in a laser processing device (13), structuring the active surface (10) of the cooking device (11) by means of the laser processing device (13), wherein the laser processing device (13) structures the active surface (10) by means of at least one laser beam (14, 15), wherein the at least one laser beam (14, 15) has, at least temporarily, pulse durations of at most 500 ns, and wherein a profile (16) with at least one depression (17) is generated on the active surface (10) by means of the structuring (12), applying a lubricant (18) to the structured active surface (10), and thermally treating the structured active surface (10). with the lubricant (18) at a temperature between 50°C and 700°C while preserving the treated active surface (10). 2024004161.2 2. The method according to claim 1, characterized in that the structuring of the active surface (10) of the cooking device (11) by means of the laser processing device (13) is carried out by means of interference of at least two laser beams (14, 15).

3. The method according to one of claims 1 or 2, characterized in that the at least one laser beam (14, 15), in particular the at least two interfering laser beams (14, 15), at least temporarily have pulse durations between 1 ns and 20 ns.

4. Method according to one of the preceding claims, characterized in that the at least one depression (17) of the active surface (10) is produced with a dimension, in particular with a depth relative to an unstructured region of the active surface (10), between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm. 5.Method according to one of the preceding claims, characterized in that at least one group of depressions (17) is produced in a periodic pattern on the active surface (10).

6. Method according to claim 5, characterized in that the group of depressions (17) in the periodic pattern on the active surface (10) has a lateral period (Δd) between 10 nm and 50 µm, in particular between 100 nm and 15 µm or between 1 µm and 25 µm. 3 is generated in at least one direction along the active surface (10).

7. Method according to one of the preceding claims, characterized in that the depressions (17), in particular the group of depressions (17), have a lateral extent, in particular in a direction parallel to the direction of the lateral period, between 10 nm and 49 µm, in particular between 10 nm and 10 µm.

8. Method according to one of the preceding claims, characterized in that the depressions (17), in particular the group of depressions (17), have an aspect ratio between 0.01 and 5, wherein the aspect ratio corresponds to the ratio of the depth of the depression (17) to a lateral extent of the depression (17).

9. Method according to one of the preceding claims, characterized in that the structuring (12) of the active surface (10) takes place in a single work step.Method according to one of claims 5 to 9, characterized in that at least two groups of depressions (17) are produced in a periodic pattern, wherein the lateral period of the first group of depressions (17) is arranged at an angle other than 0° to the lateral period of the second group of depressions (17), in particular at an angle of 90°. 4 11. Method according to one of the preceding claims, characterized in that the lubricant (18) comprises at least one component from the following group: oil-containing lubricant, oil, food-grade oil, vegetable oil, sunflower oil, rapeseed oil, food-grade chain oil, fat, food-grade fat, vegetable fat, animal fat, synthetic fat, polyalkylene glycol, dry lubricant, food-grade dry lubricant, solid lubricant, carbon-based lubricant, graphite.

12. Method according to one of the preceding claims, characterized in that the thermal treatment of the structured active surface (10) takes place for a duration of at least 1 minute.

13. Cooking device (11) with an active surface (10) for cooking food, wherein the active surface (10) is treated according to a method according to one of claims 1 to 12. 14.Cooking device according to claim 13, characterized in that the cooking device (11), in particular its active surface (10), comprises at least one component from the following group: aluminum, iron, cast iron, stainless steel, in particular with a magnetic component, ceramic, fiber-reinforced material.

15. Cooking device according to one of claims 13 or 14, characterized in that the cooking device (11) has a layer system with at least two layers. 5, wherein in particular a first layer of aluminum and a second layer of stainless steel are provided, in particular wherein the active surface (10) corresponds to the second layer.

16. Cooking device according to one of claims 13 to 15, characterized in that the active surface (10) of the cooking device (11) has at least one group of depressions (17), wherein the depressions (17) in particular have a lateral period between 100 nm and 50 µm, and / or a lateral dimension, in particular a lateral width between 10 nm and 49 µm, in particular between 10 nm and 10 µm or between 1 µm and 25 µm, and / or have an aspect ratio between 0.01 and 5, in particular between 0.01 and 1, wherein the aspect ratio corresponds to the ratio of the depth of the depression (17) to the lateral dimension of the depression (17).Cooking device according to one of claims 13 to 16, characterized in that the lubricant (18) on the active surface (10) has a layer thickness (d) between 10 nm and 500 µm after the thermal treatment.

18. Cooking device according to one of claims 13 to 17, characterized in that the cooking device (11) is at least one member of the following group: cooking device (21), grilling device (24), roasting device. 6 device (23), baking device (22), braising device (21).

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