WO1999020165A1

WO1999020165A1 - High-performance cooking pot

Info

Publication number: WO1999020165A1
Application number: PCT/CH1998/000449
Authority: WO
Inventors: Dusko Maravic
Original assignee: Dusko Maravic
Priority date: 1997-10-21
Filing date: 1998-10-21
Publication date: 1999-04-29
Also published as: AU9427198A

Abstract

The bottom (2) of the cooking pot (1) is in linear contact along its outermost edge with a flat bottom plate (3) of the pot. A tough compensation medium (4) with good heat-conducting properties is located between the bottom (2) and the flat bottom plate (3). The bottom plate (3) and the body (1) of the pot are held together by an outer jacket (5) in such a way that displacements of the bottom (2) do not subject the bottom plate (3) to any bending loads.

Description

High performance cookware

The invention relates to a cooking container for food preparation by means of heating with a base part through which the heat is supplied to the interior of the container.

For the purpose of this description, the term cooking is intended to include other types of preparation, such as braising, roasting, etc.

Experience with cooking and roasting has clearly confirmed that the quality of the pot, regardless of the type of heating, plays a crucial role. For example, the properties of energy consumption, parboiling time and temperature level vary by a factor of 2 and more when comparing good and bad pots. With a bad saucepan, twice as much energy can be used during a double cooking time, although it is usually not known whether you have a good or a bad saucepan.

Since the liberalized market allows the sale of a wide variety of pots, the consumer is always at risk of buying a bad pot. However, it can be assumed that in times of reasonable

Dealing with energy consumption, increasing attention is also paid to the quality of such products.

The quality of a saucepan or frying pan, in terms of its energetic properties, is determined by the quality of its base. A good pot today takes on a shape that gives it the best properties in conjunction with all heating systems. Its floor deflection (so-called floor indentation), its floor thickness and its floor material are optimized as far as possible. This optimization is not only related to the "external" influences (type of heating), but also to the manufacturing technology. The latter is becoming increasingly important for cost reasons. The Most pots made in Europe are made by deep drawing the body of the pot and then connecting it to the base by beating. However, this production technology limits the possibilities for an optimal design of the pot, and the proposed solution of this invention should bring about an improvement.

Pots made of metal and non-metallic materials are known. Metal pots are either steel or aluminum. Both are either bare or protected, for example enamelled. Non-metallic pots are made of glass, glass ceramics or various ceramic materials, such as clay ceramics and porcelain. There are also pots made of plastic, but they have not really caught on. Pots have recently been designed which are a combination of different materials. This solution provides for the bottom of a pot to be provided with the heat-conducting, level, high-tech ceramic. The disadvantages of this solution are the relatively high purchase price on the one hand and the reduced safety in extreme cases on the other hand (leakage of the hot pot contents when the pot base is destroyed).

However, if you design the pan base from two parts, in that the inner part consists of the bottom part of the deep-drawn pot body and the outer part is made of high-tech ceramic, the two parts must be connected to each other. If the connection is achieved by soldering, thermally induced forces arise in the solder due to the enormous elongations of the two different materials, which sooner or later make such a solder connection unsafe and question it. The frequent temperature changes add an additional difficulty. There is still no saucepan or frying pan on the market that is made on this basis. Exceptions are prototypes in laboratories from leading manufacturers. The object of the present invention is to provide a solution which is reliable over the long period of the life of a pot and which can also be produced at prices which are acceptable on the market.

According to the invention, this object is achieved by the features of the characterizing part of the patent claim.

Preferred exemplary embodiments of the invention are described below with reference to the accompanying drawings. Show it:

Figure 1 shows the design of the pot. 2 and 3 the compensation of the floor curvature; Fig. 4 is a pot base plate; 5 and 6 embodiments for the attachment of the annular outer shell and Fig. 7 shows another form of the pot base plate.

In addition to its base 2, a deep-drawn metallic container 1 is provided with a separate pan base plate 3 arranged below the base. The bottom 2 and the pot bottom plate 3 are also referred to collectively as bottom parts in the following description. So that there is maximum contact despite any unevenness, a layer of a compensation medium 4 is arranged between the mutually facing surfaces of the two base parts. The pot base plate 3 is connected to the cylindrical wall of the container 1 by means of an essentially annular outer jacket 5.

The layer of the compensation medium 4 is highly heat-conductive, heat-resistant and sufficiently deformable so that a constant and steady connection with the surfaces of the two base parts is guaranteed. Good surface wetting is also required. The compensation medium 4 can, for example, be a thermal paste (WLP). It can consist of metal, for example mercury, salt or molten salt or low-melting alloy, such as, for example, Wi alloys, wood metal, rose metal, lipnitzer metal, etc.

The compensation medium 4 must on the one hand ensure good heat conduction between the two base parts and on the other hand allow the relative movement of the two base parts with respect to one another without significant internal stresses. The type of relative movement, surface-oriented or perpendicular to the surface, does not play a decisive role.

As a rule, the above-mentioned compensation media are liquid and can meet the required conditions. Thermal conductivities range from 3 W / mK (WLP) to 15 W / mK (Rose metal). In addition, they are heat-resistant up to 250 ° C and easily deformable. Since the functioning of the compensation medium must be guaranteed at temperatures in the pot bottom of over 100 ° C, the Wi alloys are also used. Although they are rigid below 100 ° C, they have completely filled the space between the two bottom surfaces and the pot can be reheated optimally. In terms of heat transfer, there is therefore no significant difference to compensation media that are liquid when the pot is cold.

The compensation medium 4 is also located between the base parts and the outer casing 5. Its volume is adapted to the geometric boundary conditions of the pot. A dilatation volume Δv is defined based on the material-specific circumstances. It is ensured that there is no significant overpressure in the Δv. The connection 6 of the outer jacket to the cylindrical wall of the container 1 can be a fixed connection. It is achieved either by soldering, welding or gluing. However, it can also be elastic, ie detachable in nature. This is achieved, for example, with silicone rubber 10. A Tolerance connection could also be advantageous, since it is quite possible to mount the outer jacket at an elevated temperature, for example at 250 ° C.

The connection 7 between the outer casing and the pot base plate can also be achieved by soldering, welding or gluing. An elastic connection (for example silicone rubber) is also conceivable here. Metals or non-metals can be used as the material of the outer jacket. Steel, aluminum or other non-ferrous metals or non-ferrous metal alloys can preferably be used. In addition to the properties mentioned, such as compatibility with compensation media, all of them must also have appropriate mechanical (dimensional stability) and chemical (reaction behavior) resistance.

The thermo-induced forces that occur on the pot body as a whole must not be passed on to the outer jacket and the pot base plate. The purpose of this design of the pot base plate is not to direct these forces and the resulting movements (of the base and the cylinder part) to the pot base plate. This must be largely free of residual stress. In addition, the base plate of the pot must be good heat conductor and very flat. Materials that come into question here are good heat-conducting metals, such as aluminum and aluminum alloys, non-ferrous metals, all good heat-conducting iron alloys, gray cast iron, and good heat-conducting high-tech ceramics, such as silicon carbide and nitride. Ultimately, it is unimportant from which materials the base plate is made as soon as it is good heat conductor, impact and temperature resistant and of course inexpensive. The flatness of such a plate, which is at least on one side, can be achieved without problems with all materials today. The pan base plate, which is not in a fixed connection with the bottom of the pan, must not bend. As soon as it gets an impermissible deformation, the pot is no longer an energetically optimal pot. In view of the requirement for greater flatness of the base plate 3 and the expectation of an equally flat heating plate, so that the maximum possible contact area of the two plates can be achieved, one must automatically expect a not insignificant side effect, namely the adhesive liability. In order to avoid this problem, 3 relief channels 11 are embedded in the pot base plate, as shown in FIG. 7. These ensure that the saucepan can be easily separated from the hotplate. As a rule, one is inclined to lift a saucepan almost vertically upwards, and this habit should be maintained. Accidents could often occur if one tried to force the "sticky" pot off the stove and therefore relief channels should be provided, regardless of which plate they are housed in.

The linear expansion of the pan base plate no longer plays a significant role. In contrast to the permanent connection by soldering etc., in which the thermo-induced forces in the solder are of great importance, the surface-oriented relative movement no longer plays a role here. This is such an important advantage that reliable long-term stability of the pot can be expected.

It is known that the bottom movement of a pot is due to at least two mechanisms. On the one hand there are temperature differences across the base thickness, i.e. axially, and these can cause a base curvature

(Bimetal effect). On the other hand, there is a temperature difference in the radial direction, where the warm pot base "moves" in relation to the cold pot cylinder, with the result that both are subjected to a deformation (base: deflection, cylinder deformation). As a rule, however, both deformation mechanisms prevail at the same time. The degree to which the individual works is often insignificant. The well-known pot manufacturers have accepted a basic rule: the induction cooking pots move away from the cooking surface and the others towards the cooking surface.

The proposed solution provides that a deep-drawn base is connected to the pot base plate regardless of its flatness. If the floor is facing outwards, see Fig. 2, or inwards, see. Fig. 3, arched, moves from below when warming up, i.e. always inside via the hotplate. The same applies to the case of a flat floor, see. Fig. 1.

4 shows that one of the two surfaces in contact is provided with a number of differently arranged depressions. This ensures that the

Movement of the base in the axial direction, irrespective of whether in the direction of the pot base plate or away from it, can inject the compensation medium into newly created spaces or can measure from the displaced spaces. In the embodiment according to FIG. 4, the inflow and outflow channels are accommodated in the pot base plate. They can also be in floor 2. If the replenishment or drainage movement of the compensation medium is not guaranteed, mechanically induced forces can occur which lead to a curvature of the pot base plate 3. This deformation must be avoided.

The depth s and the width h of the inflow and outflow channels 8 and the number and arrangement of the channels among one another were determined experimentally. At D in the range 100 to 300 mm, the depth s is preferably in the range of a few tenths of a mm, and h in the range of a few mm.

The outer jacket takes on an important function in that it is designed (material, shape and dimensioning) in such a way that it enables the cylindrical wall of the container 1 to move relative to the base 2 without

the pot base part 2 and the pot base plate 3 is selected so that it is in operation of the pot, i.e. when cooking and roasting, there is never any contact between the two parts, i.e. m = 0. Because when the two parts 2 and 3 are touched, the thermoinduced forces can stress the base plate 3 on bending, which would result in the loss of the contact surface between the base plate 3 and the heating plate. In theory, it would even be possible for the two parts, namely both the base plate 3 and the heating plate, to bend both simultaneously and uniformly and for the contact area to be kept the same size. But in practice, especially when using different materials, this possibility is not very likely. As soon as there is only a tiny gap between the two surfaces, heat is no longer transferred by heat conduction, but according to the laws of convection. This means that the heat transfer from the heating plate deteriorates significantly and as a result, significantly higher heating plate temperatures arise. This example shows how important good contact is. The following numerical example underpins this: Even at m = 0.1 mm, temperature differences of the heating plate, when boiling 1 liter of water, of more than 200 ° K have been measured; in one case (m> 0) the heating plate temperature was 120 ° C and in the other (m = 0) 350 ° C.

Production experience shows that it is not always possible to maintain the shape and deflection of the pan base precisely. For this reason, this invention provides for the use of a spacer ring 9. His

The task is to ensure that the contact of the bottom 2 and the bottom plate 3 is excluded. The geometric dimensions of this ring are chosen so that all of the requirements mentioned are taken into account.

Claims

claims

1. Cooking container for food preparation by heating with a bottom through which the heat supply to the

The inside of the container takes place, characterized in that the bottom (2) of the container (1) is provided with a flat pot bottom plate (3), that between the two there is a tough, heat-conductive compensation medium (4) that it is touch linearly only at their outermost edge and that they are held together by an annular outer jacket (5), which presses the pan base plate (3) against the pan body (1), such that the floor movement of the base part (2) does not cause any bending stress on the pan base plate ( 3) can cause.