Patent Description:
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 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 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 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.

Documents <CIT>, <CIT> and <CIT> disclose respective solutions according to the state of the art.

The technical aim of the present invention is to improve the state of the art in 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 <NUM>.

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

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:.

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

With reference to <FIG>, the number <NUM> generally indicates a container for cooking food according to the present invention.

The container <NUM> comprises a main element <NUM>, made of a first material.

The main element <NUM>, as long as the process for making the container <NUM> 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 <NUM> and a side wall <NUM> of the container <NUM> inside which the food for cooking can be housed.

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

By way of example, <FIG> illustrates a container <NUM> obtained from the main element <NUM> illustrated in <FIG>.

The container <NUM> 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 <NUM> comprises a layer <NUM>, positioned on the external side of the bottom <NUM>, made with powders <NUM> 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 <NUM> for cooking food comprising a main element <NUM>, equipped with a first surface 2a, this element <NUM> being intended to define a bottom <NUM>, a side wall <NUM> and to be shaped with a substantially concave conformation, inside the container <NUM> being possible to house the food for cooking, and a layer <NUM>, positioned on the outside of the bottom <NUM> in a portion 2b of the first surface 2a and obtained with powders <NUM> which are heated if subjected to magnetic fields, comprises the steps of:.

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 <NUM> can have a particle size between <NUM>-<NUM>.

The first metal material with which the main body <NUM> is made is of the non-ferromagnetic type, and for example comprises aluminum or aluminum alloy, for example aluminum alloys of the <NUM> series or of the <NUM> series.

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

<FIG> show the mould <NUM> of the first type in which the pressing mould is dedicated only to the pressing step.

<FIG> show the mould <NUM> of the second type in which the pressing mould is dedicated to the step of pressing and forming the container <NUM>.

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

The sintering step of the powders <NUM> can take place during or after the pressing step.

The sintering means, not shown in the figures, can be provided directly in the mould <NUM> 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 <NUM>° C and <NUM>° C for a time interval between <NUM> and <NUM> 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 <NUM>, 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 <NUM>° and <NUM>° C and for a time of at least <NUM> 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 <NUM> of powders <NUM>, thereby improving the operating performance on the electromagnetic induction plates.

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

The process can also comprise a step of adding the powders <NUM> 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 <NUM>-<NUM>% by weight of the powders <NUM>, and graphite to be added in an amount equal to <NUM>-<NUM>% by weight of the powders <NUM>.

The pressing step can be carried out with a pressing force F between <NUM> tons force and <NUM> tons force, for example <NUM> tons force on a powder coating diameter of <NUM>.

As mentioned, the main element <NUM> has an initial flattened conformation, for example discoidal having, by way of non-limiting example, a diameter between <NUM> and <NUM>, and the layer <NUM> of the pressed powders <NUM> can for example have a circular conformation with a diameter between <NUM>-<NUM>.

Said layer <NUM> of pressed powders <NUM> can have, again by way of non-limiting example, a thickness between <NUM> and <NUM> and a weight between <NUM> and <NUM> grams.

The process also includes a step of extracting the main element <NUM> from the mould <NUM> after the pressing step.

A step of forming the container <NUM> is also provided in which a substantially concave conformation of the main element <NUM> is achieved.

A step of painting with lacquer and/or surface protective treatment of the layer <NUM> of powders <NUM> 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:.

The subject-matter of the present invention is also a mould <NUM> for processing a container <NUM> comprising at least one main element <NUM> made of the first material and a layer <NUM> of powders <NUM> in the second material.

<FIG> 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 <NUM> of the container <NUM>, while the final forming step of the container will be carried out with another mould (not illustrated).

The mould <NUM> comprises at the bottom a support base <NUM> to which a piston <NUM> is fixed, equipped with axis <NUM>, by means of fixing screws <NUM>, and a mobile die <NUM>, which has an internal through shaped cavity <NUM> for a sliding coupling with piston <NUM>.

The cavity <NUM> and the piston <NUM> define at least one chamber <NUM> for loading the powders <NUM> of the second material.

On the opposite side to the coupling side on the piston <NUM>, the matrix <NUM> comprises centring means <NUM> to house and center the main element <NUM> of the container <NUM>.

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

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

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

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

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

However, since the rods <NUM> can re-enter inside the matrix <NUM>, during the step of pressing the powders <NUM>, the main element <NUM> can rest on the upper surface of the matrix <NUM>, also allowing the correct pressing of the powders <NUM> in the foreseen portion 2b.

The mould <NUM> comprises at the top a punch <NUM> which is movable, along the axis <NUM> of the piston <NUM>, from an inactive configuration, in which the punch <NUM> is separated from the main element <NUM> housed on the die <NUM> and the volume of the aforementioned chamber <NUM> loaded with the powders <NUM> is maximum, to a pressing configuration, in which said punch <NUM> is pressed on the main element <NUM> so as to push the die <NUM> towards the base <NUM>, reduce the volume of the chamber <NUM> and press the powders <NUM> between the main element <NUM> and the piston <NUM>, in this way the powders <NUM> are pressed and coupled to the main element <NUM> so as to form the layer <NUM> of the second material joined on the external side of the main element <NUM>.

The chamber <NUM> has a reduction ratio for example between <NUM>-<NUM>.

The mould <NUM> also comprises contrast means <NUM> of the elastic type that oppose the movement of the matrix <NUM> towards the base <NUM> according to the axis <NUM> of the piston <NUM>.

In particular, the contrast means <NUM> comprise a distribution of springs <NUM> inserted on respective spring-guide screws <NUM> parallel to the axis <NUM>; the spring-guide screws <NUM> are inserted from one end into provided first holes <NUM> of the mobile matrix <NUM> and from the other end into provided second threaded holes <NUM> formed in supports <NUM>, in turn fixed to the base <NUM>.

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

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

It should be noted that the contrast means <NUM> also cause the detachment of the main element <NUM> from the matrix <NUM>, after the pressing step, and therefore the main element <NUM> 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 <NUM> into the chamber <NUM>; the hopper is not shown in the figures.

<FIG> 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 <NUM> of the container <NUM>, and the step of forming the container <NUM>.

In these <FIG> the identical components are identified by the same reference numbers as in <FIG>.

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

The matrix <NUM> defines a chamber <NUM> which has a first loading zone 114a for pressing the powders <NUM> of the second material on the main element <NUM> and a second zone 114b for the final forming of the container <NUM>.

Furthermore, since the punch <NUM> performs a longer stroke, the first holes <NUM> which are in the die <NUM> 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 <NUM> from the matrix <NUM>, after the forming step, is produced by the contrast means <NUM>, so the container <NUM> can be taken, for example, by means of a robotic arm (not shown) which acts on the matrix <NUM>.

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

The container <NUM>, at the end of the manufacturing process, comprises a main element <NUM> having a substantially concave conformation made in the described first metal material and defining a bottom <NUM> and a wall <NUM> connected to each other; on at least the portion 2b of the main element <NUM> is coupled at least one layer <NUM> of pressed powders <NUM> 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 <NUM> on the bottom <NUM> of the container <NUM> in a simple and economical way, with respect to the known methods, starting from powders <NUM> 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 <NUM>, to the main element <NUM>.

The container <NUM>, made with the described procedure, comprising on the bottom <NUM> the layer <NUM> of pressed powders <NUM>, is suitable for use on plates operating by electromagnetic induction, but also other traditional fires; and again thanks to the presence of the layer <NUM>, the container <NUM> 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 <NUM>, and to the possible mixing of the additive described, the bottom <NUM> is less subject to deformation when using the container <NUM> for cooking food.

The layer <NUM> of powders <NUM> 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.

Claim 1:
Process for making a container (<NUM>) for cooking foods comprising a main element (<NUM>), provided with a first surface (2a), such element (<NUM>) being intended to define a bottom (<NUM>), a lateral wall (<NUM>) of the container (<NUM>) and to be shaped with substantially concave conformation, within said container (<NUM>) it being possible to house said foods for cooking, and a layer (<NUM>), positioned on the outside of the bottom (<NUM>) in a portion (2b) of the first surface (2a) and attained with powders (<NUM>) which are heated if subjected to magnetic fields, the process comprising the steps of:
providing at least one main element (<NUM>) of said container (<NUM>) made of a first metal material and defining at least one first surface (2a) which at the end of processing will correspond with the outside of said bottom (<NUM>);
providing powders (<NUM>) of a second material selected from the group consisting of ferromagnetic materials, ferromagnetic ceramic materials and mixtures of ferromagnetic materials and ferromagnetic ceramic materials; the process being characterized in that it further comprises the steps of:
providing at least one mould (<NUM>),
arranging at least said main element (<NUM>) and said powders (<NUM>) in said at least one mould (<NUM>),
pressing in said mould (<NUM>) said powders (<NUM>) of said second material on at least one portion (2b) of at least said first surface (2a) of said main element (<NUM>), so as to attain at least one layer (<NUM>) of said second material associated with at least said portion (2b).