Temperature indicating device

ES 2 215 826 T3

DESCRIPTION

Temperature indicating device.

The invention concerns a temperature indicating device on a glass door of a heating and / or cooling appliance, in which a variation in color visible from the outside serves to indicate the temperature.

A temperature indicating device is described in DE 198 36 732 A1. A temperature sensor element is mounted in the area of ​​the surface of a door which, as the door temperature increases, indicates the increased temperature of the door by means of a color variation. Essential here is the fact that the temperature of the interior enclosure is not indicated, but the temperature of the door. The element is preferably a sheet applied to the inner side of the door that contains chemicals that visibly change color with varying temperature. Consequently, the element has to be designed in such a way as to withstand the high temperatures prevailing in the firing oven. This temperature sensing element is complicated and expensive.

In US 5 499 597 thermochromic materials for indicating temperature are described, with which dangerous temperatures in heating elements are disclosed.

According to the state of the art, bimetallic or electronic sensors are used as temperature sensors to indicate the temperature of the interior chamber of a cooking oven, which act on a display screen through corresponding electronics. Such circuits are complicated, energy dependent, and expensive to manufacture.

Different requirements for temperature indicating devices on the door of a domestic cooking oven are known from WO 97/26 486 and WO 97/34 490.

In AT 202 660 a rotisserie tube for electric cookers with door mounted thermostatic regulators is described. The regulator is arranged between two door covers. A heat conducting body transmits the heat from the inner door cover to a switching bimetal. A warning lamp is provided to display the switching state.

Document US 5 589 958 describes a kitchen installation in which front windows are switchable to a transparent or non-transparent state.

A self-adhesive sheet for temperature indication is known from DD 234 298 A1. This is used to indicate the temperature in household appliances.

JP 11351729 A describes a device for indicating the interior temperature of a refrigerator. It has a thermochromic member for this.

The object of the invention is to provide a temperature indicating device that indicates by color variation that a certain temperature range has been reached in the interior enclosure of a heating and / or cooling device, preventing the temperature indicating device from temperature may be damaged in a heating appliance by the high temperatures inside the oven.

According to the invention, the above problem is solved in a temperature indicating device of the kind indicated at the beginning by means of the features of claim 1.

Since the thermochromic layer is provided between two panes of the glass door, said layer is only indirectly exposed to the temperature of the interior chamber of the oven. The maximum temperature of said enclosure is not presented in it. For this reason, an inexpensive heat-sensitive color layer can be used as a thermochromic layer, which can be applied to the corresponding glass, for example by screen printing or as a foil, preferably a polymer foil. Therefore, the temperature indicating device is significantly cheaper than a corresponding electronic temperature indicating device.

The thermochromic layer does not indicate the temperature of the door, but rather the temperature of the interior of the oven. Glass doors with two or more panes are designed in such a way that their outside temperature is not dangerous for the user. For this reason, it is not necessary to warn the user of a high door temperature.

Preferably, the site where the thermochromic layer is applied is chosen so that, at a maximum temperature of the interior oven chamber of approximately 280 'to 300' C, the temperature in the layer does not exceed 120 ° C. Thermosensitive inks are known on the market that are not damaged at 120^' C.

In a preferred embodiment of the invention the thermochromic layer is applied on the inside on the outermost pane of the glass door.

In the operation of a domestic cooking oven, deposits or incrustations form on the interior. A cleaning procedure for their disposal is known. In this procedure, a cleaning liquid is introduced into the interior of the oven, which evaporates there and dissolves the incrustations. The best cleaning results can be achieved when the cleaning liquid is introduced at an oven interior temperature of approximately 40^' C. The described temperature indicating device is especially suitable for making this temperature known by means of a color change of the thermochromic layer.

The described temperature indicating device can also be used in other ovens to indicate a characteristic internal temperature or the internal temperature prevailing at the moment in question. An example of application of the indicating device according to the invention is the indication of so-called residual heat. Residual heat is the heat that remains in the interior of the oven after it has been switched off.

Other advantageous embodiments of the invention appear from the drawing and its description, as well as from the dependent claims.

In the drawing they show:

Figure 1, a front elevation of a domestic cooking oven with a glass door and

Figure 2, a longitudinal section of the glass door of a domestic cooking oven and a plan view.

Figure 3, a front elevation of a refrigerator and

Figure 4, a longitudinal section of the glass door of a refrigerator and a plan view.

A domestic cooking oven presents

ES 2 215 826 T3 a glass door 1 according to FIG. 1 to which a handle 2 is attached. Different adjusting elements are provided above this. The glass door 1 has a central area 4 that is transparent like clear glass. and edge areas 5 provided with a decoration.

The glass door 1 consists of two panes or in general of three panes, namely an outer pane 6, a central pane 7 and an inner pane 8. On the outer pane 6 it is applied from the inside, in the lower edge area. 5, a thermochromic layer 9 consisting of a thermosensitive ink that has been printed on the outer glass 6, for example by the screen printing process, or that has been applied on said glass as a polymeric sheet. The surface area that the thermochromic layer 9 occupies is large enough that it can be seen well from the outside. The thermochromic layer 9 can be configured in the form of a writing line or a symbol.

The maximum temperature that can be reached in the interior chamber 10 of the furnace is, for example,

280 'C. The tests carried out have shown that at point 11 of the outer glass 6, where the thermochromic layer 9 is provided, 105' C is not exceeded at the maximum temperature of the interior oven chamber, which can be attributed to the low position of point 11 and the thermal insulation of the central pane 7 and the inner pane 8, as well as the distances between the inner pane 8 and the central pane 7, and also between the central pane 7 and the outer pane 6. A heat-intensive surface can be used which is reversibly color stable up to 105^' C.

The thermochromic layer 9 has been chosen such that, at an internal oven temperature of approximately 45^' C, change from a color, for example white, to green. At an internal oven temperature of 40^' C to 45^' C, the temperature in the thermochromic layer 9 is about 30^' C. As the oven interior temperature drops from 280^' C, the thermochromic layer 9 turns from white to green when the color change temperature is reached. The heat-intensive ink has been chosen so that the color change temperature is reached when the temperature of the interior chamber of the oven is approximately 50^' C to 60^' C. This is the temperature at which the best results are achieved in an oven cleaning program. The user recognizes by the color change that the correct temperature has been reached for introducing a cleaning liquid into the interior chamber 10 of the oven. Then open the glass door 1, insert the cleaning liquid and close the glass door 1. Subsequently, the oven heating system is switched on again by hand or under program control, the cleaning liquid evaporating and its vapors dissolving the incrustations existing in the interior chamber of the oven.

The indicating device according to the invention can also be used to indicate the residual heat in the inner chamber 10 of the furnace. The display color then changes as the residual heat temperature goes from approx. To 160^' at a lower temperature. Thus, the residual heat can be used.

In other exemplary embodiments, depending on the temperature conditions and the thermochromic layer 9 to be used, it may be provided in other places on the crystals 6, 7, 8.

A refrigerating appliance has a glass door 1 according to FIG. 3, to which a handle is attached.

two. The glass door 1 consists of two panes or in general three panes, namely an outer pane 6, a central pane 7 and an inner pane 8. On the outer pane 6 preferably four thermochromic layers 9 consisting of: a heat-sensitive ink and which have been printed on the outer glass 6, for example by the screen printing process, or which have been applied as a polymer foil. The surface that the thermochromic layer 9 occupies is large enough so that it can be seen well from the outside. The thermochromic layer 9 can be configured in the form of a writing line or a symbol. The thermochromic layer 9 has been chosen so that it changes color at an internal temperature of approximately 5^' C.