Electric resistance heating devices – Heating devices – Immersion heater details
Patent
1995-10-11
1998-08-11
Hoang, Tu B.
Electric resistance heating devices
Heating devices
Immersion heater details
392501, 219457, 219543, H05B 102
Patent
active
057939292
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to electric immersion heaters.
BACKGROUND AND SUMMARY OF THE INVENTION
Electric immersion heaters are very widely used in water heating electric appliances such as kettles, hot water jugs, washing machines, dish washers, urns etc. The standard form of immersion heater comprises an elongate metal sheathed element which is formed into a tortuous configuration to provide the required length of element within the size constraints of the water heating vessel. It is traditional that the element terminates in so-called cold leads by means of which electric connections are made to the heater. There is also generally provided an intermediate "hot return" portion which in use is in thermal contact with a thermally sensitive actuator of a control device which incorporates a switch for disabling the heater in the event of it overheating in consequence of there being insufficient water in the vessel to cover the element.
Such immersion heaters are used as standard in most electric kettles and hot water jugs. They are traditionally located in the lower part of such a vessel so that a minimum amount of water can be boiled. Since an immersion heater is substantially surrounded by water, heat generated from all sides of the heating element is dissipated which renders an immersion heater more efficient than heaters which are mounted externally of the water containing vessel and which heat the water via a vessel wall. This latter form of heater is less efficient in that heat dissipated from the side of the heating element remote from the vessel wall is essentially wasted. Such heaters are generally run at a higher temperature than immersion heaters and therefore more prone to failure.
Known immersion heaters do have certain drawbacks. In particular, they are, to an extent, aesthetically unpleasing. This is particularly so when they become covered in scale as is inevitable in the longer term. The shape of known heating elements makes them difficult to clean, and it is also difficult to clean the base of the vessel even though this remains visible through the heater. Whilst in the UK and other countries users of electric kettles and hot water jugs have to a degree accepted the unpleasing appearance of the lower region of the vessel interior, in some countries there is a strong reluctance for this reason to use immersion heaters and it is still more common to find the less efficient externally mounted heaters discussed above.
Viewed from one aspect the invention provides an electric immersion heater comprising a support plate which is provided on at least one side thereof with a heating element in the form of a printed circuit conductive track and incorporating a clamping part which is adapted to be clamped in relation to a control device of the type having a thermally sensitive actuator which cooperates with a switch diasabling the heater in the event of it overheating, the clamping part being effective to provide heating for the thermally responsive actuator of the control device.
The support plate should be heat conducting and is preferably formed of metal e.g. stainless steel. It is particularly advantageous, although possibly not essential in all applications, that the heating element is provided on the side of the plate which faces downwardly in normal use of the heater.
An immersion heater in accordance with the invention has a number of advantages compared with known immersion heaters. If mounted horizontally adjacent the base of an electric kettle or hot water jug, for example, the user sees the flat upper surface of the support plate which is aesthetically more appealing and easier to clean than known forms of heating element. If the printed circuit heating element is provided only on the underside of the plate, it is not visible to the user and is protected from damage. A heater in accordance with the invention is more compact than a traditional immersion heater of comparable power. As with known immersion heaters, heat dissipated from both sides of the element is uti
REFERENCES:
patent: 4621186 (1986-11-01), Taylor et al.
patent: 4859835 (1989-08-01), Balderson
patent: 5278941 (1994-01-01), Ward
Hoang Tu B.
Strix Limited
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