ARRANGEMENT WITH TWO OR MORE LAYERED NATURAL STONE SLABS

Abstract

The invention relates to the asymmetric structure, in terms of the layer structure, of two or more stone slabs—generally two—wherein the load-bearing bottom slab is designed to be thicker than the top slab which is to be stabilized and which forms the surface of an induction hob assembly. The thickness or stiffness of the bottom stone slab is designed in conjunction with an adequately dimensioned tension-resistant fibre layer such that the tensile stresses in the top slab resulting from the expansion of the top slab during cooking, especially on the surface, because of the bi-metal effect, that is to say from dishing up of the slab, are not exceeded to avoid any hairline crack formation. To this end, the cross-section and/or the stiffness of the bottom slab is to be designed to be so thick in the counter-stabilizing edge regions that the expansion forces of the top stone slab in the cooking zone are adequately compensated for by the compression zone beneath the tension-resistant fibre layer such that the maximum permissible tensile stress on the surface of the top stone slab, which makes up the hob, is not exceeded even if the maximum permissible cooking temperature is reached. In order to prevent deflection or dishing of the entire assembly as a result of the bi-metal effect, a sufficiently porous stone material is selected for the surface which is compressible in volume and/or preferably less resistant to compression than the bottom stabilizing slab, which provides the counter-pressure. To receive the induction coil, the slab assembly is milled out from below to close to the surface, so that the distance between the induction coil and the pan is as small as possible. The milled-out portion is designed to be domed to enhance mechanical stability against pressure and impact from above. Additional fibre reinforcement can be applied here to provide greater support. Circulating air layers are used beneath and, where necessary, on top of the stone surface to keep the surface temperatures on the hob and on the underside of the cooking zone as low as possible. These measures together serve the purpose of preventing the usual hairline cracking on the surface of the complete assembly.

Claims

1) Arrangement with two or more layered slabs of natural stone, artificial stone such as concrete or resin-bonded stone powder, glass or ceramic—hereinafter referred to as stone slab or stone slabs—whereby the overall arrangement of the stone slabs is mechanically stabilized across the cross-section of the overall structure through stabilizing fiber fabric layers to prevent the plates from exceedance of the allowable tensile elongation, with a cutout under the surface of the upper stone layer which breaks through the stabilizing fiber layer and which extends itself right below the surface of the uppermost stone layer, with an induction coil sitting within the cavity for induction heating of magnetizable induction dishes, characterized in that the rigidity of the stone geometry below the tensile-stable fiber layer is greater than the rigidity of the geometry of the upper cover layer, which forms the surface, whereby the fibers consist of carbon, glass or stone fibers.

2) Arrangement according to claim 1, characterized in that the ratio of the thickness of the stone layers in relation to the plate rigidity above and below the stabilizing carbon layer is designed so that the cross section of the temperature-expanding upper stone layer is so much smaller, than the minimum cross-section of the lower stone slab in the edge area between the cut and the stone slab edge, that the permissible tensile stress of the surface of the uppermost stone layer is not exceeded even if a surface temperature of 300° C. in the cooking zone is reached.

3) Arrangement according to claim 1 and 2, characterized in that the stone slab thickness above the tensile fiber layer is thinner than the stone slab thickness below the tensile fiber layer.

4) Arrangement according to claim 1 and 2, characterized in that the stone slab layer above the tensile fiber layer is a different material than the stone slab layer below the fiber layer.

5) Arrangement according to claim 1, 2, and 4, characterized in that the stone slab layer below the tensile fiber layer consists of a stiffer material than the stone slab layer above the fiber layer.

6) Arrangement according to claim 1 to 5, characterized in that the cavity of the milling is cooled by a circulating air stream in order to regulate and/or limit the maximum permitted temperature in the region of the cooking zone.

7) Arrangement according to claim 1 to 6, characterized in that the underside of the upper stone slab forms a concavely curved surface in the area of the milling, which ensures a natural mechanical stabilization against pressure from above onto the plate in the area of the milling against breakage or protect from breakthrough downwards.

8) Arrangement according to claim 1 to 7, characterized in that the underside of the milling is additionally stabilized against breakage due to impact in the cooking zone by a fiber matrix layer applied from below, which consists of either glass, stone or carbon fibers and a temperature-stable adhesive.

9) Arrangement according to claim 8, characterized in that the fiber-containing matrix of the fiber layer in the region of the cooking zone contains glass fibers, or stone fibers (basalt fibers) or a mixture of these different fiber materials and/or two layers of UD fabric carbon fibers in 0°/90° arrangement, wherein these two layers of UD carbon fabric are electrically insulated from one another by a layer of glass fibers or stone fibers or other fibers in order to exclude induced electric current flow in the carbon fabric.

10) Arrangement according to claim 1 to 9, characterized in that the surface of the upper stone slab is protected against the penetration of natural oils by a synthetic oil which is stable up to 300° C.

11) Arrangement according to claim 1 to 10, characterized in that the induction tableware used contains spacers which allow natural air convection between the stone surface and the pot material to additionally cool the upper stone slab on the surface, in order to avoid the burning in of natural and edible oils.

12) Arrangement according to claim 1 to 11, characterized in that the counter-stabilizing stone slab or the stone slabs below the top stabilizing carbon layer are made smaller in the horizontal XY coordinates, than the top stone slab.

13) Arrangement according to claim 1 to 12, characterized in that the coil shape is adapted to the curved shape of the milling and itself represents a curved plain.

14) Arrangement according to claim 1 to 13, characterized in that the coil in the middle carries a temperature sensor which measures the temperature at the bottom of the—if necessary. fiber-stabilized—measures the curvature of the underside of the upper stone slab and passes this measurement signal on to the induction control unit of the overall arrangement of the induction heating system, consisting of the induction control unit and induction coil, together with the necessary cable connection between the two, so that the induction control unit detects an exceeding of impermissibly high temperature to limit or switch off induction heating.

15) Arrangement according to claim 1 to 14, characterized in that the ratio of the thickness or rigidity of the stone slab or the stone slabs below the uppermost carbon layer in relation to the surface layer is so much larger that the deflection of the entire plate on the hob surface is de facto zero which is made possible by the fact that a stone structure with such a high pressure stiffness is used under the carbon layer that the bi-metal effect that usually occurs due to the compression of the stone material below the carbon layer is virtually zero, a correspondingly and sufficiently strong dimension

Description

[0014] One of the many possible embodiments of the invention is shown in FIG. 1 with a stone plate (1) as the hob surface and a second stabilizing plate made of stone (2) with cutouts (4) underneath the plates, a pot (8) standing on the plate (1) with spacers (9) attached to the bottom of the pot.

[0015] FIG. 2 shows the structure of FIG. 1 in cross section (A-A) with the carbon plates (3) mechanically connecting the two plates (1) and (2). Milled-out areas (4) house the induction coils (5), around which an air flow (6) flows in order to cool the stone of the plate (1) in the hob area from below. The thickness of the lower stone slab is significantly greater than that of the upper stone slab, in the form that the cross-section of the stone slab in the cooking zone is smaller than the cross-section of the lower stone slab in the edge areas between the cutout and the outer edge of the slab. For this purpose, the width of the edge area in relation to the diameter of the cut-out is dimensioned such that the counter-stabilizing minimum cross-section of the lower plate in the edge area (C) (viewed perpendicularly from the center of the cut-out on the long plate edge) is larger than the cross-section of the expanding stone mass in the area of the heating cooking zone (D).

[0016] FIG. 3 shows the milling (4) with coil (5) in a detailed view with a stabilizing fiber layer (7) under the hob and a rotationally symmetrical concave underside of the stone slab (1).

[0017] In the area of the milling (4) above the plate (1), due to the of the rigid carbon layer is necessary.

SUMMARY

[0018] The invention describes the asymmetrical structure of two or more stone plates—generally two—with respect to the layer structure, the load-bearing lower plate being designed stronger than the upper plate to be stabilized, which forms the surface of an induction cooking arrangement. The thickness or stiffness of the lower stone slab is designed in connection with an adequately dimensioned tensile fiber layer so that the tensile stresses in the upper slab due to the expansion of the upper slab when cooking—especially on the surface—due to the bimetal effect by bowl the plate—will not to be exceeded to avoid any hairline cracking. For this purpose, the cross-section and/or the rigidity of the lower plate in the counter-stabilizing edge areas must be designed so strongly that the expansion forces of the upper stone plate in the area of the cooking zone are sufficiently compensated by the pressure zone below the tension-resistant fiber layer, so that the maximum permissible tensile stress applied to the surface of the upper stone slab, which forms the hob, is not exceeded even when the maximum permitted cooking temperature is reached. In order to avoid deflection or curvature of the overall arrangement due to the bimetal effect, a sufficiently porous stone material is chosen on the surface, which is volume-compressible and/or preferably less pressure-resistant than the lower stabilizing plate, which builds up the counter pressure. To accommodate the induction coil, the plate arrangement is milled from below to just below the surface, so that the smallest possible distance between the induction coil and the pot is ensured. The cut-out is curved to increase the mechanical stability against pressure and impact from above. Additional fiber reinforcement can be attached here to help. Below and if necessary also above the stone surface circulating air is used in order to keep the surface temperatures on the hob and on the underside of the cooking zone as low as possible. Together, these measures serve the purpose of excluding the usual formation of hairline cracks on the surface of the overall arrangement.

[0019] distance between the pot (8) and the plate (1) through the spacers (9) below the pot, a natural convection flow (11) of the ambient air develops for the purpose of additional cooling the stone plate (1) in the cooktop area, the temperature of which in this area is measured, monitored and, if necessary, regulated with the aid of a temperature sensor (12) with a connecting cable connected to the induction electronics, and the induction can then be switched off if the temperature is, for example, due to an overheating pot, exceeding the limit values.