Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1990-01-17
1990-10-09
Walberg, Teresa J.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
219464, H05B 370
Patent
active
049622978
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a temperature controlled hot plate.
Temperature controlled hot plates are known in which there is provided a recess in the center of the hot plate for a temperature sensor. By a spring the sensor is pressed into engagement with a cooking utensil placed on the hot plate. An example of such a hot plate is given in the Swedish patent No. 448 508. In a hot plate of this kind, according to the principle of regulation used the parameter of regulation is the temperature prevailing on the bottom surface of the cooking utensil. When the control temperature has been reached the hot plate body, most often being made of cast iron, has a heat content stored which continues to supply heat to the cooking utensil even after the disconnection of the hot plate. This gives rise to undesirable overshoots in the control temperature graph of the hot plate.
As appears from the Swedish patent No. 446 243, for example, the heating of liquid in a cooking utensil to cooking temperature can be performed at maximum power up to a predetermined temperature and from this point the continued cooking can take place at this predetermined temperature without any appearance of overshoots in the control temperature graph. However, in connection with this heating process there is a demand for advanced electronic control arrangements to be provided which for cost reasons are considered unrealistic in common ranges and cooking hobs.
Another disadvantage in the arrangement described in the first-mentioned patent is the requirement for an operation to be performed in the hot plate for mounting of the temperature sensor which, in addition, has a relatively complex design with a cup-shaped thin plate which is to be pressed upwards into contact with a cooking utensil. Here, the arrangement is unnecessarily complicated and, accordingly, costly in relation to ordinary power-regulated hot plates.
SUMMARY
The object of the invention is to remedy the drawbacks indicated and to provide a temperature controlled hot plate wherein the temperature sensor has been given a different design which makes possible the mounting of the temperature sensor on a common hot plate which does not need to be modified. In addition, the sensor need not to be movably mounted.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described more in detail in connection with a few embodiments with reference to the enclosed drawings.
FIG. 1 shows a cast iron hot plate as seen from below.
FIG. 2 is a side view of the hot plate of FIG. 1.
FIGS. 3, 4 and 5 are detail sectional views showing the mounting on the hot plate of the temperature sensor of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIGS. 1 and 2 a common cast iron hot plate 10 is shown comprising a plate body 11 having an upper plane heat emitting surface 12 on which a cooking utensil is to be placed. The body also has a lower surface on which a heating coil is disposed along a helical path. The heating coil is enclosed in an electrically insulating substance 14 and the heat generating area i surrounded by an angular flange 15 being an integral part of the hot plate body. Of course, instead of a single heating coil also several different coils can be provided which can be interconnected in different ways to give different nominal power ratings for the hot plate.
An elongated tubular temperature sensor 16 is being secured to the bottom of the hot plate in such a way that is contacts the insulating substance 14 and follows the angular flange 15. The temperature sensor contains an expandable medium, such as a liquid or a cream-like mixture of sodium and potassium which is particularly useful at high temperatures. As shown in FIGS. 3-5 essentially one turn of the heating coil 13 is situated adjacent to the flange and hence straight below the temperature sensor 16. As a result the temperature sensor will be in heat conducting connection both with the heating coil, via the insulating substance 14, and with the hot plate body 11 via the flange
REFERENCES:
patent: 3885128 (1975-05-01), Dills
patent: 3895216 (1975-07-01), Hurko
patent: 4716277 (1987-12-01), Schreder
Aktiebolaget Electrolux
Walberg Teresa J.
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