Cooking vessel with controlled deformation of the bottom.

A cooking vessel with a deformation-resistant bottom

Full description

Background of the invention

The present invention relates to a cooking vessel, the deformation of the bottom of which is prevented under the influence of heat and sudden temperature changes occurring during use. Cookware is generally produced from deep-drown aluminum sheet. During heating, the surface of the bottom of the pot, in contact with the cooking plate or burner, is exposed to a significantly higher temperature than the inner surface of said bottom. As a result, thermal expansion causes the bottom of the vessel to convex. To prevent this harmful phenomenon, the bottom of the vessel is provided with a slight concavity so that, during heating, this bottom becomes essentially flat under the influence of expansion. When it cools, the bottom theoretically regains its concavity.

However, experience has shown that, after a certain number of repeated cycles of heating and cooling, the concavity of the bottom of the vessel decreases, then becomes zero and finally the bottom becomes convex, so that the vessel becomes practically unusable. This result is explained by the properties of aluminum.

During repeated cycles of heating and cooling, the elastic area increases, resulting in irreversible deformation.

General description of the invention

The purpose of the present invention is to prevent irreversible deformation of the bottom of cooking vessels produced from a sheet of light alloy or light metal such as aluminium. The invention thus aims to provide a cooking vessel produced by deep-drawn thin sheet of light alloy or metal, which includes a bottom for the purpose of being placed on a cooking plate, stove or the like, such bottom being slightly concave. According to the invention, this cooking pot is characterized by the fact that the said bottom contains a plate that may consist of multiple elements, and this plate is centered and covers a small part of this bottom, and is made of a metal or alloy that has mechanical, thermal and physical properties different from those Of said thin sheet metal or alloy, and such sheet is incorporated into said bottom. This merger may be partial or complete.

Thanks to this plate integrated in the central area of the pot bottom and having mechanical, thermal and physical properties different from those of the metal or alloy forming the rest of the pot, any irreversible deformation of the bottom of the pot is prevented even after a large number of repeated heating cycles.

And cooling.

Tests have shown that it is important that the above board should be embedded over only a small portion of the bottom surface.

It is preferable that the thickness of the aforementioned bottom be such that, when placed on the cooking plate, the surface of this bottom around the plate with different mechanical, thermal and physical properties touches the cooking plate, while the previous plate does not touch the core of the cooking plate. Concavity is produced during deep drowning of a light alloy or light metal disc to which the aforementioned plate has been fully or partially embedded in advance.

The base metal or alloy of the vessel will generally be aluminum, and the plate partially or completely embedded in the bottom will generally be made of steel, preferably stainless steel. Preferably, the aforementioned board should cover between 5 and 30% of the bottom surface. It is possible to create a groove around the perimeter of the board.

Preferably, this board should have holes and be embedded in the bottom partially or completely so that the aforementioned bottom metal fills these holes completely. The merging done in this way makes the board slightly thicker than the bottom surface.

This plate can be integrated into the metal of the bottom of the vessel by cold striking, as described in European Patent Application No. 0.509.860 in the name of the applicant company, or by welding, braising, or bonding.

In a distinct version of the invention, the plate has a thickness of between 3/10 and 5/10 of a millimeter and is embedded in the bottom to a depth of between 0.5/10 and 1.5/10 of a millimeter, for an aluminum bottom with a thickness of between 2.5 and 5 mm.

Brief explanation of the drawings

Other features and advantages of the invention will also become clear in the following description. In the attached drawings, given by non-specific examples:

Figure 1: The vertical location of a disk for the purpose of deep drawing it into a bowl shape according to the invention;

Figure 2: A sectional view of the aforementioned disk. And

Figure 3: Partial sectional view of a cooking pot after deep drowning of the disk in Figure 2.

Detailed description

Figures 1 and 2 show a disk cut from a thin sheet made of a light alloy or metal, such as aluminum. This disc is drawn deeply, in a manner well known to an expert in this field, into the shape of a cooking vessel (Figure 3), such as a frying pan or a saucepan with a handle, which

It has a bottom for the purpose of placing it on a cooking plate or stove.

In Figure 1, the circumference of the bottom 1 of the vessel is marked with a dashed circle c. Also, it is well known in the field, that this bottom 1 is produced in a slightly concave shape during deep drowning of disk 3.

According to the invention, the bottom 1 contains, in its middle part, a plate 2 made of a metal or alloy having properties different from the metal or alloy of the disk 3.

As can be seen in Figure 2, disk 2 is embedded in the metal of the bottom 1 and the perimeter 2a of this disk 2 and is adjacent to a cavity 4 made in the aforementioned bottom 1.

After deep drawing of the plate 3, the concavity of the bottom 1 is such that, when placed on the cooking plate, the surface 5 of the bottom placed around plate 2 touches the cooking plate, while that of plate 2 does not touch the latter.

Preferably, disc 3 is made of aluminum and has a thickness between 2.5 and 5 mm. It is preferable to make plate 2 of stainless steel.

It is preferable that this plate 2 cover between 5 and 30% of the bottom surface 1. In fact, this small percentage of coverage of the bottom 1 by the plate 2 ensures the best results, with regard to the resistance of the plate 1 to deformation under the influence of repeated cycles of heating and cooling, and with regard to heat transfer and temperature distribution.

These results can be seen in particular by the partial embedding of plate 2 in the central region of the bottom of the vessel and by the different properties of steel compared to those of aluminium, which prevent the deformation of the bottom from becoming irreversible under the influence of repeated cycles of heating and cooling. In the embodiment of Figures 1 and 2, plate 2 has holes 6, i.e. round holes, spaced at regular intervals and distributed over the entire surface of the plate, and this plate 2 is partially incorporated into bottom 1. This plate 2 can be combined into bottom 1 by cold forging, as described in European Patent Application No. 0.5090860 in the name of the applicant company.

In this way, plate 2 is firmly attached to bottom 1 of the vessel at a large number of points and any deformation of bottom 1 is minimized thanks to the steel used for this plate.

It is sufficient for plate 2 to have a thickness between 3/10 and 5/10 of a millimeter (for an aluminum bottom, it has a thickness between 2.5 and 5 mm). Its integration into the bottom 1 will occur to a depth between 0.5/10 and 1.5/10 of

One millimeter is enough to get excellent results. Moreover, significant incorporation of plate 2 into bottom metal 1 becomes detrimental.

As shown in Figure 1, Plate 2 has a disc shape. However, plate 2 can have a polygonal or ring shape. Panel 2 can be divided into several sectors or can be produced in the form of a grid.

The size of holes 6 for panel 2 is not important. However, it is preferable that the holes 6 of plate 2 have a diameter two times less than the space between each two holes.

For example, holes 6 can have a diameter of approximately 3 mm and the gap between each hole can be approximately 2 mm.

Given below are the results of comparative tests between two frying pans, one conventional and the other produced in accordance with the invention.

The two frying pans were of identical size and were produced from an aluminum disc with a thickness of 3.4 mm. The frying pan according to the invention had, on its bottom, a stainless steel disc with a thickness of 0.5 mm and a diameter of 75 mm.

The two frying pans were subjected to repeated cycles of sudden heating and cooling (heating to 250°C, then cooling in tap water to approximately 20°C).

The irreversible deformation of the bottom of the conventional frying pan was detected after 30 of the above cycles.

In the case of the frying pan according to the invention, the irreversible bottom deformation was detected only after 300 repeated cycles of heating and cooling.

Of course, the invention is not limited to the examples just described, and many modifications can be made to them without deviating from the scope of the invention.

Therefore, plate 2 can take any shape and may not be centered on the bottom of the vessel. This vessel could, for example, be in the shape of a star with any number of branches. The shape of the plate can be asymmetrical and may, for example, have a single branch extending in one direction, for example the direction of the bowl hand.