TECHNICAL FIELD OF THE INVENTION 5 The present invention relates to the process for making a container for cooking foods or aliments, and to the container itself. More specifically, the present invention relates to the process for making a container, as well as the container itself, particularly suitable for cooking food on plates operating by electromagnetic induction, but also other traditional fires.

10 STATE OF THE ART

In the state of the art, different types of containers for cooking food, as well as processes for their realization, particularly suitable for being used on electromagnetic induction plates, such as pans, pots, skillets and the like are known.

Some types of container provide a bottom comprising or consisting of 15 ferromagnetic material, associated on a main body of bowl shape and of non ferromagnetic material according to different manufacturing processes.

The coupling of the bottom comprising ferromagnetic material with the main body allows to obtain a good technical result in the use of the container, in particular with induction-type heat sources, since the bottom with the ferromagnetic material 20 heats up directly due to the eddy currents that are generated by the effect of the magnetic field produced by the induction source, thus transferring the heat in a very efficient way to the bowl in non-ferromagnetic material, which finally cooks the food.

The process for coupling the bottom to the main body can, for example, take 25 place through moulding, brazing, impact bonding, and other ways, which include a series of laborious and expensive operations for processing the bottom and specific construction steps.

OBJECTS OF THE INVENTION

The technical aim of the present invention is to improve the state of the art in 30 the sector of making containers for cooking food. Within this aim, it is an object of the present invention to develop a process for the production of a container for cooking food which allows to realize in a simple and economical way a bottom of the container suitable for being used on plates operating by means of electromagnetic induction, but also other traditional fires.

Another object of the present invention is to develop a process for making a container characterized by optimum stability of the bottom during use, i.e. during cooking on an energy source such as an induction plate or others, i.e. equipped with greater resistance to deformation of the bottom.

Another object of the present invention is to provide a container for cooking food having a high thermal efficiency for use with electromagnetic induction plates.

This aim and these objects are achieved by a process for making a container for cooking food according to claim 1.

Furthermore, this aim and these objects are achieved by a mould according to claim 13, and by a container for cooking food according to claim 18.

The dependent claims refer to preferred and advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be more evident from the description of an example of construction of a unit, illustrated as an indication in the accompanying drawings in which:

Figure 1 is an axonometric view from below of the main element of the container with the associated layer of pressed powders, according to the present invention;

Figure 2 is an axonometric view from below of a container made with the main element of Figure 1, according to the present invention;

Figure 3 is an axonometric view from above of a first type of mould to carry out a step of pressing a layer of powders on a main element of the container for cooking food, according to the present invention;

Figure 4 is a sectional side view of the mould of Figure 1; Figure 5 is an axonometric view from above of a second type of mould to carry out a step of pressing a layer of powders on a main element of the container for cooking food and forming the container, according to the present invention; and

Figure 6 is a sectional side view of the mould of Figure 5.

In the accompanying drawings, identical parts or components are indicated by the same reference numbers.

EXAMPLES OF EMBODIMENT OF THE INVENTION

With reference to Figure 1, the number 1 generally indicates a container for cooking food according to the present invention.

The container 1 comprises a main element 2, made of a first material.

The main element 2, as long as the process for making the container 1 is not completed, has a substantially flattened discoidal shape, or the like, and which, once the manufacturing process has been completed, has a substantially concave shape, defining a bottom 3 and a side wall 4 of the container 1 inside which the food for cooking can be housed.

In order to make different types of containers 1, there is no restriction on the size or proportions of the bottom 3 and the side wall 4, thereby making it possible to produce, based on the need, pots, pans, skillets and the like.

By way of example, figure 2 illustrates a container 1 obtained from the main element 1 illustrated in figure 1.

The container 1 can be provided with any further accessory element, such as a permanent handle (not shown in the figures), which can be fixed with means and techniques known in the field, or even a removable handle or grip.

Furthermore, the container 1 comprises a layer 7, positioned on the external side of the bottom 3, made with powders 5 of a second material which heats up if subjected to magnetic fields, as will be described in more detail below.

According to the present invention, the process for making a container 1 for cooking food comprising a main element 2, equipped with a first surface 2a, this element 2 being intended to define a bottom 3, a side wall 4 and to be shaped with a substantially concave conformation, inside the container 1 being possible to house the food for cooking, and a layer 7, positioned on the outside of the bottom 3 in a portion 2b of the first surface 2a and obtained with powders 5 which are heated if subjected to magnetic fields, comprises the steps of: providing at least one main element 2 of the container 1 made of a first metal material and defining at least one first surface 2a, which at the end of the processing will correspond to the outside of the bottom 3, providing powders 5 of a second material selected from the group consisting of ferromagnetic materials, ferromagnetic ceramic materials and mixtures of ferromagnetic and ceramic materials and/or ferromagnetic ceramic materials, providing at least one mould 6, arranging at least the main element 2 and the powders 5 in the mould 6, pressing the powders 5 of the second material into the mould 6 on at least one portion 2b of the first surface 2a of the main element 2, so as to attain at least one layer 7 of the second material associated at least with the portion 2b.

In particular, the second material is selected from the group composed of ferromagnetic materials such as inoxidizable ferromagnetic alloys and oxidizable ferromagnetic alloys, other ferromagnetic materials such as those based on carbon, for example graphite or graphene, ferromagnetic ceramic materials such as magnetite, and mixtures of such ferromagnetic materials and ferromagnetic ceramic materials.

Furthermore, mixtures of non-ferrous metal powders can be added for decorative purposes, such as for example Cu and related alloys.

The powders 5 can have a particle size between 45-200 pm.

The first metal material with which the main body 2 is made is of the non ferromagnetic type, and for example comprises aluminum or aluminum alloy, for example aluminum alloys of the 3000 series or of the 4000 series.

More generally, the main body 2 comprises a metal material or metal alloy with high thermal conductivity, good workability and compatible with contact with food.

Figures 3 and 4 show the mould 6 of the first type in which the pressing mould is dedicated only to the pressing step.

Figures 5 and 6 show the mould 6 of the second type in which the pressing mould is dedicated to the step of pressing and forming the container 1.

The process can also comprise a step of sintering the powders 5 carried out at predetermined temperature and duration and carried out by respective sintering means.

The sintering step of the powders 5 can take place during or after the pressing step.

The sintering means, not shown in the figures, can be provided directly in the mould 6 and, for example, can comprise an induction oven, or a roller oven, or can be of the HFHIS (High-Frequency Induction Heated Sintering) type, or of the laser- welded type, or even of another type.

More in detail, the sintering step takes place at a temperature between 900° C and 1300° C for a time interval between 0 and 10 seconds, and can be carried out in an ambient atmosphere, or in a controlled reducing atmosphere, or in a controlled atmosphere in oxygen debt.

If the process does not provide for a sintering step of the powders 5, i.e. the pressing step is not followed by a sintering step, then the process according to the present invention can comprise a heat treatment step at a temperature between 180° and 200° C and for a time of at least 20 minutes.

Thanks to the aforementioned heat treatment, there is a release of the deformation stresses accumulated during the pressing step and a principle of sintering which determines the formation of micro-welds, this contributes to the reduction of the electrical resistance of the layer 7 of powders 5, thereby improving the operating performance on the electromagnetic induction plates.

The process may further comprise a step of lubricating the powders 5 and/or the mould 6 with at least one lubricant, for example comprising organic and non- organic compounds; the lubricant can be mixed with the powders 5, and/or even distributed on the surfaces of the mould 6.

The process can also comprise a step of adding the powders 5 with an additive, which allows to increase the mechanical resistance of the layer being formed, in the pressing and sintering steps.

This additive can be, for example, copper or phosphorus to be added in an amount equal to 2-3% by weight of the powders 5, and graphite to be added in an amount equal to 0.2-0.8% by weight of the powders 5.

The pressing step can be carried out with a pressing force F between 1000 tons force and 5000 tons force, for example 3000 tons force on a powder coating diameter of 200 mm.

As mentioned, the main element 2 has an initial flattened conformation, for example discoidal having, by way of non-limiting example, a diameter between 175 and 570 mm, and the layer 7 of the pressed powders 5 can for example have a circular conformation with a diameter between 140-210 mm.

Said layer 7 of pressed powders 5 can have, again by way of non-limiting example, a thickness between 0.3 and 0.5 mm and a weight between 30 and 150 grams.

The process also includes a step of extracting the main element 2 from the mould 6 after the pressing step.

A step of forming the container 1 is also provided in which a substantially concave conformation of the main element 2 is achieved.

A step of painting with lacquer and/or surface protective treatment of the layer 7 of powders 5 can also be envisaged to increase its corrosion resistance properties.

The painting step can be carried out with silicone-polyester lacquers, silicone lacquers, porcelain enamel, Sol-gel coating, with PTFE (polytetrafluoroethylene), PES (polyetheresulfone), PFA (Perfluoroalkoxy).

The surface protective treatment step can be carried out through a plasma coating of ceramic materials, metallic materials or compounds of the two.

Furthermore, the surface protective treatment step can be carried out through one or more of the following processes: physical vapor deposition (PVD), a deposition process in which the material is evaporated in the form of atoms from a solid source and transported in vapor form through a vacuum environment or in a controlled atmosphere to the substrate where it condenses; the evaporation of the source is generally obtained thermally by the Joule effect, for example through an electric discharge, a high-power laser or a plasma, by way of example, the following metallic materials can be deposited: Ti, Al, Cu, Au, Ag, etc. and the ceramic materials: TiN (titanium nitride), AIN (aluminum nitride), Si3N4 (silicon nitride), SiC (silicon carbide), TiCN (titanium carbo-nitride); chemical vapor deposition (CVD), the chemical vapor deposition process is an atomic deposition process in which the synthesis material deposited on the substrate derives from the decomposition and condensation of one or more gaseous precursors in a controlled atmosphere and temperature; this type of coatings has high corrosion resistance, mechanical and adhesion properties to the substrate, by way of example, the following metallic materials: Ti, Al, Cu, Au, Ag, etc., and ceramic materials: TiN (titanium nitride ), AIN (aluminum nitride), Si3N4 (silicon nitride), SiC (silicon carbide), TiCN (titanium carbo-nitride) can be deposited; tempering to blue or bluing, is a tempering treatment carried out in an ambient atmosphere around 300-350 ° C which in carbon steels determines the formation of a compact layer of magnetite (Fe[04) adhered to the surface of the product; the aforesaid layer has a better resistance to corrosion and better paintability, that is a better aptitude to be painted.

The subject-matter of the present invention is also a mould 6 for processing a container 1 comprising at least one main element 2 made of the first material and a layer 7 of powders 5 in the second material.

Figures 3 and 4 show a first type of mould which is capable of carrying out only the step of pressing a layer of powders onto a main element 2 of the container 1, while the final forming step of the container will be carried out with another mould (not illustrated).

The mould 6 comprises at the bottom a support base 8 to which a piston 9 is fixed, equipped with axis 11, by means of fixing screws 24, and a mobile die 10, which has an internal through shaped cavity 12 for a sliding coupling with piston 9. The cavity 12 and the piston 9 define at least one chamber 14 for loading the powders 5 of the second material.

On the opposite side to the coupling side on the piston 9, the matrix 10 comprises centring means 15 to house and center the main element 2 of the container 1.

The centring means 15 comprise at least three rods 23 arranged substantially at an angular distance equal to each other, on a circumference concentric with the axis 11, each rod 23 is equipped with a frustoconical tip to facilitate the centring of the main element 2.

More in detail, to constitute an effective centring of the main element 2, the rods 23 must be at least three, arranged at about 120°, naturally the rods 23 can also be more than three, always arranged on a circumference concentric with respect to the axis 11, and substantially at an angular distance equal to each other, for example: four rods 23 arranged at 90°, five rods 23 arranged at 72°, and so on.

Each rods 23 can also re-enter the upper surface of the matrix 10 and, for this purpose, the matrix 10 comprises holes 25, a hole 25 for each rod 23.

Each rod 23 is therefore sliding within its own hole 25 and is pressed upwards by a respective spring 26 which is in turn blocked within the hole 25 by means of a locking grub 27; in proximity to the upper surface of the matrix 10, the hole 25 has a smaller diameter, with an annular seat 28, and a corresponding projection in the rod 23 which prevents the rod from coming out from above.

The main element 2 can have an external diameter greater than the diameter defined by the internal portions of the rods 23 and, therefore, when the element 2 is inserted into the matrix 10, it can rest on the conical parts of the rods 23, being raised with respect to the upper surface of the matrix 10, as illustrated for example in figure 4.

However, since the rods 23 can re-enter inside the matrix 10, during the step of pressing the powders 5, the main element 2 can rest on the upper surface of the matrix 10, also allowing the correct pressing of the powders 5 in the foreseen portion 2b. The mould 6 comprises at the top a punch 16 which is movable, along the axis 11 of the piston 9, from an inactive configuration, in which the punch 16 is separated from the main element 2 housed on the die 10 and the volume of the aforementioned chamber 14 loaded with the powders 5 is maximum, to a pressing configuration, in which said punch 16 is pressed on the main element 2 so as to push the die 10 towards the base 8, reduce the volume of the chamber 14 and press the powders 5 between the main element 2 and the piston 9, in this way the powders 5 are pressed and coupled to the main element 2 so as to form the layer 7 of the second material joined on the external side of the main element 2.

The chamber 14 has a reduction ratio for example between 2-2.5.

The mould 6 also comprises contrast means 17 of the elastic type that oppose the movement of the matrix 10 towards the base 8 according to the axis 11 of the piston 9.

In particular, the contrast means 17 comprise a distribution of springs 18 inserted on respective spring-guide screws 19 parallel to the axis 11; the spring- guide screws 19 are inserted from one end into provided first holes 20 of the mobile matrix 10 and from the other end into provided second threaded holes 21 formed in supports 22, in turn fixed to the base 8.

According to another version of the present invention, the contrast means 17 comprise a plurality of pneumatic elements (not shown), for example gas springs.

The spring-guide screws 19 comprise collars 19a for holding the matrix 10 which slides for a predefined travel within the first holes 20.

It should be noted that the contrast means 17 also cause the detachment of the main element 2 from the matrix 10, after the pressing step, and therefore the main element 2 can be picked up, for example, by means of a robotic arm (not shown).

The mould can also comprise a hopper for loading the powders 5 into the chamber 14; the hopper is not shown in the figures.

Figures 5 and 6 show a second type of mould which is capable of carrying out both the step of pressing a layer of powders onto a main element 2 of the container 1, and the step of forming the container 1. In these figures 5, 6 the identical components are identified by the same reference numbers as in figures 3, 4.

It can be noted a different punch 116, which has a convex conformation, and a different die 110, which has a concave conformation, both of the aforementioned elements, punch 116 and die 110, are thus made to provide the final concave shape to the container 1, starting from the main element 2, flat, with the layer 7 of powders 5 fixed to the portion 2b of the main element 2.

The matrix 110 defines a chamber 114 which has a first loading zone 114a for pressing the powders 5 of the second material on the main element 2 and a second zone 114b for the final forming of the container 1.

Furthermore, since the punch 116 performs a longer stroke, the first holes 20 which are in the die 110 are deeper to allow for a longer predefined travel than that of the first type of mould described above.

Also the extraction of the container 1 from the matrix 110, after the forming step, is produced by the contrast means 17, so the container 1 can be taken, for example, by means of a robotic arm (not shown) which acts on the matrix 110.

The container 1 for cooking food is therefore made, as mentioned, according to the method described above, starting from a main element 2 having a substantially flattened conformation, for example discoidal, or the like.

The container 1, at the end of the manufacturing process, comprises a main element 2 having a substantially concave conformation made in the described first metal material and defining a bottom 3 and a wall 4 connected to each other; on at least the portion 2b of the main element 2 is coupled at least one layer 7 of pressed powders 5 of the second material.

As mentioned, the second material is selected from the group composed of ferromagnetic materials, ceramic materials and mixtures of ferromagnetic and ceramic materials.

It has thus been seen how the invention fully achieves the proposed purposes.

The described process allows to realize a layer 7 on the bottom 3 of the container 1 in a simple and economical way, with respect to the known methods, starting from powders 5 of a suitable second material, selected from the group composed of ferromagnetic materials, ceramic materials and mixtures of ferromagnetic and ceramic materials, pressed and joined, in the mould 6, to the main element 2. The container 1, made with the described procedure, comprising on the bottom 3 the layer 7 of pressed powders 5, is suitable for use on plates operating by electromagnetic induction, but also other traditional fires; and again thanks to the presence of the layer 7, the container 1 allows a high thermal efficiency when using the container on electromagnetic induction plates. Furthermore, thanks to the characteristics of the second material of the layer

7, and to the possible mixing of the additive described, the bottom 3 is less subject to deformation when using the container 1 for cooking food.

The layer 7 of powders 5 can also be painted with lacquer and/or provided with a protective surface treatment to increase its corrosion resistance properties, with the materials and protective processes described above.

Changes and variants of the invention are possible within the scope defined by the claims.