Improvements relating to electric heating elements
An element and heater technology, applied in the field of thick film heating elements and thick film electric heating elements, can solve the problems of slow response, tolerance and cost increase of bimetal parts
Inactive Publication Date: 2004-03-24
OTTER CONTROLS LTD
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- Abstract
- Description
- Claims
- Application Information
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Problems solved by technology
This means that a very high operating temperature needs to be set for the thermal actuator, which brings difficulties at least increased cost, and the manufacture and adjustment of a stable, fast-acting bimetallic device capable of operating at the required temperature. The problem
Typical temperature settings for overheat protection of mineral isolated, metal shielded resistive heating type immersion heating elements, or an under-panel heating element with a securely secured metal shielded heating element underneath are 135±15℃, while the equivalent temperature setting value of the thick film heating element is about 180±5℃, the slow response problem caused by the high setting value of the bimetal parts will cause more stringent tolerances
[0005] From the specific problems to be solved above, it can be seen that if effective overheating protection of the heating element is to be provided for the thick-film heating element which is susceptible to working on an inclined surface in use, an indeterminate part of the heating element will Overheating occurs earlier than other parts
Method used
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[0013] see first figure 1 , which shows a plan view of the track layout of the thick film heating element according to the embodiment of the present invention. It is worth noting that the dimensions and proportions of the traces are only schematic rather than actual dimensions, and those of ordinary skill in the art who are familiar with the design of thick film heating elements will be able to figure 1 Transform the schematic arrangement in a practical form.
[0014] figure 1 The thick film heating element 1 may for example comprise a stainless steel disc substrate with an electrically insulating layer of glass on one or both sides of its main surface. Then, the track pattern is formed on the insulating layer through a screen printing process using the conductive ink paste that is sintered after deposition. An electrically insulating layer of glass can then be covered on top of the track pattern as a protective layer.
[0015] As shown, the trace pattern includes a main h...
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Thick film heating elements can cause problems if associated water heating vessels are used on a sloping surface so that if the vessel boils dry an elevated part of the heating element is first exposed to overheating and self-destructs. To protect against this the invention proposes to divide the heating element track into parallel-connected main heater and sensor portions, the sensor portion surrounding the main heater portion and comprising a plurality of parallel-connected track portions having NTCR (negative temperature coefficient of resistance) characteristics and connected in series therewith a track portion having a PTCR (positive temperature coefficient resistance) characteristic. By virtue of this arrangement, if one of the NTCR track portions begins to boil dry, so its temperature will increase and its resistance reduce so that more current flow through the PTCR track portion and its temperature rises. With a bimetallic thermally-responsive control arranged to sense the temperature of the PTCR track portion and to switch off at least the main heater portion if it overheats, effective control of the heater operation can be achieved by use of a bimetallic control.
Description
technical field [0001] The present invention relates to improvements in electric heating elements, and in particular to thick film electric heating elements comprising resistive heating tracks or layers formed on a substrate, such as a printing ink formed on a stainless steel substrate The track, while having an insulating layer between the substrate and the track, preferably also covering the track with an insulating layer. The invention relates in particular to thick film heating elements for boiling water vessels, such as domestic kettles and kettles, but has wide application. Background technique [0002] Control techniques for cutting power to an electric heating element when it overheats are known. Further investigation will also reveal a specific problem if thick film heating elements in kettles and hot water jugs are operated at a slant, such as when the appliance is placed on a sloping drainboard, if any part of the heating element track is exposed to the appliance...
Claims
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Patent Timeline
Login to View More IPC IPC(8): H05B1/02
CPCH05B2203/019H05B2203/017H05B1/0269H05B1/0213H05B2203/02H05B2203/013
Inventor R·A·奥内尔
Owner OTTER CONTROLS LTD