Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-08-16
2004-06-22
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S448110, C219S460100
Reexamination Certificate
active
06753509
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a cooktop or hob with a cooktop plate, in particular, made from glass ceramic, beneath which at least one heating element is disposed, for heating a cooking vessel that can be placed on the cooktop plate, and having a temperature sensor for recording the temperature of the cooktop plate, which temperature sensor senses the temperature of the underside of the cooktop plate within the heating element and is shielded from the thermal radiation from a heating device of the heating element by insulating material, and is connected to a control unit for controlling the heating power of the heating element, and to a corresponding heating element and a suitable element.
German Patent DE 37 03 768 C2, corresponding to U.S. Pat. No. 4,851,645 to Wolf et al., discloses a device for recording the temperature of a glass ceramic plate that is heated by heating windings or halogen lamps using a temperature sensor. The Wolf device emits a signal that corresponds to the temperature of the glass ceramic to a control circuit. The heating windings or the halogen lamps are disposed in the interior of a pot-like insulating support and heat the glass ceramic plate by direct radiation. The edge of the insulating support bears against the underside of the glass ceramic plate under spring stress, and the temperature sensor is disposed outside the interior of the insulating support but inside the heating element. Furthermore, the temperature sensor is connected in a thermally conductive manner to the underside of the glass ceramic plate, the temperature sensor being disposed in a recess in the edge of the insulating support. The recess is disposed at a distance x from the inner side of the edge of the insulating support, the minimum value for which distance is selected such that the brief temperature changes that occur when the heating windings or the halogen lamps are switched on or off have only a negligible influence on the temperature sensor. The maximum value for the distance x is selected such that the delay in the control characteristic that is caused by the thermal conduction of the glass ceramic plate results in a small hysteresis. Widths from 3 mm to 6 mm have proven to be advantageous values for the distance x. The temperature sensor is introduced into the formed or pressed-in recess on the upper side of the attachment that projects into the interior of the insulating support, and is connected in a thermally conductive manner to the underside of the glass ceramic plate. The temperature sensor is held indirectly through spring stress against the underside of the glass ceramic plate to keep the heat transfer resistance between the glass ceramic plate and the temperature sensor low.
Furthermore, European Patent Application EP 0 021 107 A1. discloses a heating element for a cooker unit having a temperature sensor. To maintain complete heating of the entire surface of the heating element while, nevertheless, closely coupling the temperature sensor of the controller to the heating, a heat transfer element in the form of a metal sheet is used, which is disposed between the heating bodies and the glass ceramic plate, partially covering the heated area, but projects out of the heating element, where it is connected to the temperature sensor of the controller. The heat-transfer element is fastened by secure clamping on the edge of the shell carrying the heating device and normally bears against the underside of the glass-ceramic panel. An outer section projects outward, beyond the edge of the heating element, from the area of the heat transfer element that senses the heat. The outer section is formed integrally with the above mentioned area, substantially parallel thereto, but offset downward to a slight extent by a bend, so that the outer section does not bear against the underside of the glass ceramic plate. The sensor cell of the temperature sensor is pressed by a compression spring onto the underside of the heat-transfer surface of the heat-transfer element, which is supported against a holding mechanism that guides the sensor cell and is disposed on the outer section of the heat-transfer element. However, other sensor types and configurations are also possible. For example, it is also possible to use an electrical NTC or PTC sensor that is pressed on resiliently or securely attached to the outer portion of the heat transfer element. If desired, the heat transfer element may be grounded so that electric shocks are prevented.
Furthermore, U.S. Pat. No. 4,447,710 to McWilliams discloses a glass ceramic cooktop in which an insulating body, on which a temperature sensor, for example, a thermocouple, is positioned, is disposed in the edge region of the heating element. The thermocouple is kept in good thermal contact with the underside of the glass ceramic plate by the insulating block.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a cooktop with temperature sensor and a corresponding heating element that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that have good measuring accuracy.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a cooktop, including a glass ceramic cooktop panel having an underside, at least one heating element having a heating device for emitting thermal radiation, the heating element disposed beneath the cooktop panel for heating up a cooking vessel to be placed on the cooktop panel, a control unit electrically connected to the at least one heating element for controlling a heating power of the at least one heating element, a temperature sensor electrically connected to the control unit for controlling the heating power of the at least one heating element, a heat-conducting element holding the temperature sensor in heat-conducting contact at the underside of the cooktop panel within the at least one heating element, the temperature sensor sensing a temperature of the underside of the cooktop panel within the at least one heating element, and insulating material shielding the temperature sensor and the heat-conducting element from the thermal radiation. The insulating material can also substantially shield the temperature sensor and the heat-conducting element from the thermal radiation.
According to the invention, in the cooktop, the temperature sensor is in thermal contact with the underside of the cooktop plate by a thermally conductive element, and the element and the temperature sensor are shielded from the thermal radiation of the heating device by insulating material. Such a configuration ensures that the measuring configuration determines a temperature that, for example, corresponds to the temperature of a pan that has been placed on the cooktop plate above the heating element quickly and accurately enough. It is also ensured that the heat transfer from the pan or the cooktop plate to the temperature sensor is not limited to the very small area of the temperature sensor itself.
In accordance with another feature of the invention, the surface region A of the element that is in thermal contact with the underside of the cooktop plate is approximately at least 5 times, in particular, approximately 10 times larger than the base area B of the temperature sensor.
In accordance with a further feature of the invention, a lateral distance a between the element and the edge region of the insulating material is advantageously approximately 6 to 12 mm, in particular, approximately 8 mm. This value has surprisingly emerged if, on one hand, the shielding with respect to the thermal radiation from the heating device of the heating element is to be sufficiently great and if, on the other hand, the coupling of the thermally conductive element to the cooktop plate heated by the thermal radiation is to be sufficiently good.
In accordance with an added feature of the invention, to make it possible to provide ratios that are constant and defined by metrology over the ope
Grätz Franz
Has Uwe
Neumayer Dan
Theine Markus
Vetterl Peter
BSH Bosch und Siemens Hausgerate GmbH
Paik Sang
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