Heat conduction plate and cooking vessel with same

AREA

0001The present invention relates to a heat conducting plate and a cooking vessel formed therewith, particularly in the form of a pan.

BACKGROUND

0002Cooking vessels are typically placed on a hob for heating food, which heats the bottom of the cooking vessel. It can happen that the bottom of the cooking vessel warps. The warpage can cause the bottom of the cooking vessel to become uneven, with the result that the support properties and, as a result, the stability of the cooking vessel and also the heat transfer between the hotplate and the floor deteriorate. As a result, on the one hand, the heat distribution within the floor becomes uneven and, on the other hand, the energy consumption required increases. This affects both the function and the ecological fingerprint.

0003According to the state of the art, this can be remedied by making the floor thick enough, which on the one hand results in greater mechanical stability and on the other hand greater heat conduction in the horizontal direction. In most cases, aluminum is chosen as the material in order to achieve the best possible relationship between base thickness, heat conduction and weight. Copper is even more suitable under these parameters, but it is much more expensive. In this case, stable pan bottoms have a thickness of between 5 and 10 mm.

0004The situation is further complicated by the desired suitability for induction cooktops, which require a base with ferromagnetic properties. The required attachment of at least one layer of ferritic sheet metal causes additional soil movements, for example due to the bimetallic effect. Pans with good properties regarding the stability under heat input and with good heat distribution within the usable area are therefore heavy and slow in the heating rate, since a comparatively large inertial mass has to be heated. Conversely, the large heat capacity of a heavy pan is bad if the working temperature is to be changed downwards. All control processes are slow in this case.

0005Other common constructions only have a small indentation at room temperature, which then increases when heated, for example to values ​​over 1 mm, sometimes to more than 2 or even 3 mm. With increasing intake, these types of construction do not become unstable with regard to the support, but the efficiency and heat distribution deteriorate with increasing intake. In the worst case, the induction heat source can switch off because the center of the floor is too far away, resulting in the cookware being unusable.<patcit id="pcit0001" dnum="WO8704911A1"><text>WO87/04911A1</text></patcit> reveals a cooking vessel.

0006One aspect of the invention is a circular, oval or polygonal metal heat-conducting plate which can be used, for example, as an intermediate layer between a heating device, for example an induction or other cooker, and a cooking vessel in order to optimally transfer heat between the heating device and the cooking vessel. without there being direct contact between the cooking vessel and the heating device. In such a case, the heat-conducting plate should not warp when heated, so that the cooking vessel rests as completely as possible on an upper side of the heat-conducting plate when the heat-conducting plate and cooking vessel base are in the heated state, and the underside of the heat-conducting plate rests as completely as possible on the heating device.

SUMMARY

0007The object of the present invention is firstly to provide a heat-conducting plate which is not planar but is shaped or pre-deformed in such a way that, when heated, good contact properties on a planar heating device and good heat transfer properties are achieved.

0008According to the invention, this object is achieved by a heat-conducting plate according to claim 1 .

0009Preferred developments are described in the dependent claims.

0010Furthermore, it is the object of the present invention to provide a cooking vessel whose base is shaped in such a way that good support and heat transfer properties are achieved when heated. An improved shape is intended to ensure that the cooking vessel is particularly light, has a low heat capacity, has fast reaction times and at the same time has good heat distribution and is stable on the base at all temperatures of use without tipping over.

0011According to the invention, this object is achieved by a cooking vessel according to claim 15 .

0012The cooking vessel according to the invention comprises a base, which is formed in particular by a heat-conducting plate according to the invention and can be circular, oval or polygonal, with a peripheral edge extending upwards (away from the cooking area). The bottom has a first ring-shaped area, which runs with an underside in a support plane and which is designed to rest on a flat cooking surface on which the cooking vessel is placed during operation, a second ring-like area in the shape of a truncated cone or truncated pyramid is enclosed by the first annular, planar area and rises towards the center of the vessel with a first incline and a third area, which can be circular and is enclosed by the second area in the shape of a cone or truncated pyramid and whose slope in the direction of the center of the vessel is less than the first slope at every point. The first, second and third regions have a constant thickness.

0013The shape of the bottom can be created by embossing.

0014The described, approximately S-shaped course of the cross-sectional contour of the base between the first and third area ensures that a desired and reproducible distortion occurs when the base is heated. In particular, it has been shown that in the case of a heat-conducting plate according to the invention or a cooking vessel according to the invention, at least a partial area of ​​the third annular area, for example an innermost circular area, moves slightly downwards when the base is heated, so that the heat transfer between the hotplate and the base is improved. In particular, it was found that at a distance or Vertical distance of the third area of ​​the geometry according to the invention outside, i.e. at the transition from the second to the third area, from the deepest point/support surface of 0.2 to 0.7 mm or 0.8 mm a ground movement in the order of 0.2 to 0, 4 mm downwards towards the heat source and no further distortion occurs with further heating, i.e. the shape of the floor remains stable. Thus, at a preferred application temperature between 150° C. and 250° C., the geometry according to the invention only has a minimal indentation/distance from the base plate of 0.0 to 0.4 mm, better 0.1 to 0.2 mm, so that an optimal Heat transfer is guaranteed with a stable stand at the same time.

0015Furthermore, it has been measured that at a vertical distance of 0.8 mm at room temperature (e.g. 20°C to 25°C), this distance is stable and does not change when heated, whereas at a distance of 0.9 mm and more this increases with increasing temperature. With regard to the task at hand, an indentation of between 0.2 mm and 0.7 mm or a maximum of 0.8 mm is very well suited in connection with the cross-sectional contour according to the invention. The best efficiency results with a smallest distance, whereby the distance must never become negative in use. Measurements have shown that reducing the distance at room temperature from 0.4 mm to 0.3 mm brings practically no further advantage, but the risk of tipping in the event of improper overheating increases, so that a pull-in under series conditions from 0.4 - 0.5 mm or 0.6 mm is to be regarded as particularly advantageous.

0016In particular, the third area can initially run parallel to the support plane or horizontally in the direction of the center of the vessel,

0017Alternatively, the third area can initially rise in the direction of the center of the vessel.

0018As a further alternative, the third circular area can initially fall in the direction of the center of the vessel.

0019In particular, the cooking vessel can be an induction cooking vessel.

0020According to the invention, the bottom of the cooking vessel comprises a plurality of metal layers, one of the metal layers comprising aluminium. The metal layers include two steel layers enclosing the aluminum containing layer.

0021Due to the targeted thermal distortion due to the design of the cooking vessel according to the invention, the metal layers can be kept thin, which reduces the manufacturing effort and the weight of the cooking vessel. In particular, the steel layers must not be thicker than 0.7, 0.6, 0.5 or 0.4 mm and the layer containing aluminum must not be thicker than 2.5, 2.0, 1.5 or 1.4 mm. Furthermore, the metal layers do not have to be of the same thickness and can have different thicknesses.

0022Preferably one of the metal layers comprises a ferromagnetic material having a Curie temperature between 200°C and 300°C. Furthermore, the floor can have a Si-containing coating, in particular a black coating. Ceramics containing Si, Si resins, silanes, silixanes, polysiloxanes, etc., which can have a temperature resistance of at least 400° C., preferably at least 450° C. or 500° C., are well suited. It is also advantageous if this floor coating is dishwasher safe and has a non-stick effect. A non-stick coating in the inner area and on the outer walls is also advantageous, which is either ceramic or essentially composed of temperature-resistant polymers, in particular PAEK, PPS, PES, PAI, PI, PEI, PTFE, PFA, etc. and mixtures thereof in a single layer or in multiple layers can be. A calibration of the base contour after the coating and the necessary firing is advantageous, whereby the indentation can be enlarged or reduced by embossing in order to achieve the desired dimension described above.

0023Experiments have also shown that the geometry according to the invention also works advantageously with pure ferritic sheet steel in thicknesses between 1.0 and 3 mm, and also with aluminum sheet in thicknesses between 2 and 4 mm. However, the latter solution is not suitable for induction.

0024Due to the configuration according to the invention, the warpage can also be controlled or reduced to such an extent that stable cooking vessels can be produced in which no point on the underside of the base located within the annular first area at a temperature of the cooking vessel of more than 100 ° C, 150 °C or 200°C or 250°C in the vertical direction by more than 1 mm, 0.5 mm or 0.3 mm or 0.1 mm from the support plane.

0025Comparative tests have shown in particular that cooking vessels with the base geometry according to the invention and the multi-layer material described (0.4 mm thick steel layer, 1.8 mm thick aluminum layer, 0.4 mm thick steel layer) with a black base coating in the heating behavior up to 200 ° C around the Factor 2-3 faster than conventional comparison pans with correspondingly lower energy consumption on all types of stoves.

0026It can be provided that the first ring-shaped area is surrounded by a ring-shaped bead. The bead is preferably formed in the direction of an interior of the cooking vessel, ie away from the support plane. The bead can have a rectangular, trapezoidal or triangular cross-section.

0027As an alternative or in addition to a bead, it can be provided that the first annular region is surrounded by an annular recess on the bottom. The recess can have, for example, a rectangular, trapezoidal or triangular cross section.

BRIEF DESCRIPTION OF THE DRAWINGS

0028In the following the invention will be explained with reference to the accompanying drawings, in which:<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">1</figref> shows a cross-section of a first preferred embodiment of a cooking vessel according to the invention;</li><li><figref idref="f0001">2</figref> shows a cross-section of a second preferred embodiment of the cooking vessel according to the invention;</li><li><figref idref="f0001">3</figref> shows a cross-section of a third preferred embodiment of the cooking vessel according to the invention;</li><li><figref idref="f0002">4</figref> shows a cross-section of a fourth preferred embodiment of a cooking vessel not according to the invention;</li><li><figref idref="f0002">figure 5</figref> shows a cross-section of a fifth preferred embodiment of a cooking vessel not according to the invention;</li><li><figref idref="f0003">6</figref> shows a cross-section of a sixth preferred embodiment of a cooking vessel not according to the invention;</li><li><figref idref="f0003">7</figref> shows a cross-section of a seventh preferred embodiment of the cooking vessel according to the invention;</li><li><figref idref="f0003">8</figref> shows a cross-section of an eighth preferred embodiment of the cooking vessel according to the invention; and</li><li><figref idref="f0004">9</figref> shows a cross-section of a thermally conductive plate.</li></ul>

0029<figref idref="f0001 f0002 f0003">Figures 1 to 8</figref> show cross sections of preferred (rotationally symmetrical to a vertical axis A) embodiments 10, 12, 14, 112, 114 of the cooking vessel according to the invention. The cooking vessel comprises a heat-conducting plate according to the invention as a base 20, 22, 24, 26, 28, 120, 122, 124 and an upwardly extending, peripheral edge 30, 32, 34, 36, 38, 130, 132, 134. The base 20, 22, 24, 26, 28, 120, 122, 124 has an underside 40, 42, 44, 46, 48, 140, 142, 144 with a first annular area 50, 52, 54, 56, 58, 150, 152, 154, which runs in a support plane 10a and is designed to rest, during operation, on a plane heating device K on which the cooking vessel is placed. In the embodiments 10, 12, 14, 112, 114 according to the invention, the first annular region 50, 52, 54, 152, 154 is designed as a flat surface, while the first annular region 56, 58, 150 in the embodiments 16, 18 , 110 forms a substantially linear bearing surface.

0030Furthermore, the embodiments 16, 112, 114 comprise a fourth annular area 56', 152', 154', which encloses the first annular area 56, 152, 154 and is also set up to, during operation, on the planar heating device K on which the Cooking vessel is placed to rest. Between the fourth annular area 56', 152', 154', which is the first annular area 56, 152, 154, an annular bead 192 is stamped in the embodiments 16, 112, while in the embodiment 114 an annular recess 194 is provided on the contact surface side, which is preferably embossed. The edge 30, 32, 34, 36, 38, 132, 134, which adjoins the first annular area 50, 52, 54, 58 or the fourth annular area 56', 152', 154' is convex on the support side and ends with a concave termination on the support side, while the edge 130, which adjoins the first annular area 150, is frustoconical and then convex and ends with a concave finish on the support side.

0031The underside 40, 42, 44, 46, 48, 140, 142, 144 of the base 20, 22, 24, 26, 28, 120, 122, 124 also has a second annular area 60, 62, 64, 66, 68, 160, 162, 164, which is surrounded by the first annular region 50, 52, 54, 56, 58, 150, 152, 154 and rises at a first gradient in the direction of the center of the vessel (ie in the direction of the axis A). The first gradient of the second area 60, 62, 64, 66, 68, 160, 162, 164 can e.g. B. be at least 5°, 10°, 15°, 20° or 30°.

0032Furthermore, the underside 40, 42, 44, 46, 48, 140, 142, 144 of the base 20, 22, 24, 26, 28, 120, 122, 124 has a third circular area 70, 72, 74, 76, 78 , 170, 172, 174, which is enclosed by the second frustoconical region 60, 62, 64, 66, 68, 160, 162, 164 and the slope of which is less than the first slope of the second frustoconical region 60, 62 at every point , 64, 66, 68, 160, 162, 164. The third circular region 70, 72, 74, 76, 78, 170, 172, 174 may extend horizontally towards the center of the vessel, such as in embodiments 10, 12, 16, 18, 110, 112, 114, or rise or fall, such as shown in embodiments 12, 14. Furthermore, the third circular area 70, 72, 74, 76, 78, 170, 172, 174 includes a circular innermost area 80, 82, 84, 86, 88, 180, 182, 184. The innermost region 80, 86, 88, 180, 182, 184 of embodiments 10, 16, 18, 110, 112, 114 is flat, while the innermost region 82, 84 of embodiments 12, 14 is curved downwards or upwards is.

0033The contour of the bottom 40, 42, 44, 46, 48, 140, 142, 144 of the bottom 20, 22, 24, 26, 28, 120, 122, 124 can be formed by embossing. Furthermore, the underside 40, 42, 44, 46, 48, 140, 142, 144 can be coated with a coating containing Si.

0034An outer diameter of the heat conducting plate according to the invention or the cooking vessel according to the invention can be 200 mm - 220 mm, 220 mm - 240 mm, 240 mm - 260 mm, 260 mm - 280 mm, 280 mm - 300 mm, 300 mm - 320 mm, 320 mm - 340 mm, 340 mm - 360 mm, 360 mm - 380 mm or 380 mm - 400 mm. Furthermore, the outer diameter can be smaller than 200 mm or larger than 400 mm. The diameter of the first annular area can be between 70% - 85% of the outer diameter. The first annular region can have a radial width of more than 2%, 3%, 4%, 5%, 10%, 15%. 20% or 25% of the outer diameter. The second ring-like area shaped like a truncated cone can have a radial width of 1%-35%, preferably 5%-20% and particularly preferably 10%-15% of the outer diameter. The third region can have a diameter of more than 15%, preferably more than 30% and particularly preferably more than 50% of the outer diameter. The transitions between the areas can be rounded, for example with transitions of about 10 mm width.

0035<figref idref="f0004">figure 9</figref> shows a cross-sectional view of a heat-conducting plate 2 according to the invention, which can be circular, oval or polygonal, with a first annular region 50, the underside of which runs in a support plane 10a. The first annular area 50 encloses a second, ring-like, cone-shaped or truncated pyramid-shaped area 60, which rises towards a center with a first slope, and a third area 70, which runs parallel to the bearing plane 10a. The heat conducting plate can be used to act as an interface between a planar surface heating device and a cooking vessel to ensure optimal heat transfer. According to the invention, the heat-conducting plate is designed in such a way that it deforms in the heated state and rests on the heating device essentially over its entire surface.

0036The base of a cooking vessel described above is preferably formed by a heat-conducting plate 2, as shown in<figref idref="f0004">figure 9</figref> is shown as an example.