Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1989-08-16
1991-01-08
Walberg, Teresa J.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
219453, H05B 368
Patent
active
049838121
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to control systems for ceramic hob electric cookers and, more particularly, to the switch actuating mechanism for selecting various functions of the cooker.
Conventional electric cooker control system usually comprise manually operable switches or dials which are set by the user to determine which cooker elements are on and to control the temperature reached. Such mechanical controls suffer from the problem that they can be inadvertently operated giving rise to a risk that a user who comes into contact with an element that has been turned on accidentally will suffer burns. Such inadvertent operation of the controls of a cooker is a particular problem where children are present.
The present invention is for use with the type of electric cooker which has a planar, glass ceramic hob covering at least part and sometimes all the upper surface of the cooker. The electric heater elements are positioned underneath the hob. It is a considerable advantage if the hob can be completely uninterrupted by holes or projections as this enables any accidental spillages to be removed easily without any risk of contaminating other parts of the cooker. If projecting controls are provided on the glass ceramic surface then they represent regions which become difficult to clean and allow accumulation of food deposits around them. Nevertheless, there are considerable advantages in positioning the controls on the hob surface since, in such a position, they are readily accessible to the user who can quickly see what settings have been established. It is also extremely difficult to drill holes in glass ceramic material in order to allow mechanical controls to be positioned on the hob surface.
In order to overcome these technical problems the control system of the present invention uses an array of magnetic field sensitive switches.
BACKGROUND OF THE INVENTION
The concept of using an array of magnetic field sensitive switches in a control system is not, of itself, novel. A proposal has been made, for example, in DE-B-1 463 275 to use an actuating member in the shape of a tile which houses several distinct permanent magnets and which can be positioned in a recess formed in a front panel in order to select a particular control programme for a washing machine. FR-A-2 556 127 describes an entry control system which employs an array of magnetic field sensitive switches which are actuated by magnets which are received within sockets in a vertical front panel.
In such prior art systems a socket or other modification to the surface of the equipment is always employed and, as previously discussed, the construction of such recesses or sockets represents a technical problem when the surface is made of glass ceramic.
SUMMARY OF THE INVENTION
The system of the present invention solves these problems by the use of a simple actuator key that can rest on the marked surface of the hob. Such a system requires no holes in the hob, recesses or sockets of any other type. The user can be provided with a number of actuator keys which can be used as required to set the control functions of the elements of the cooker hob. When the cooker is not in use the actuator keys can be removed to a safe place thereby eliminating the risk of inadvertent operation of the controls and allowing the planar surface of the hob to be easily cleaned.
The actuator keys may be rectangular in form so that they can slide along a linear path underneath which the magnetic field sensitive switches are located. Alternatively the actuator key may be circular and rotatable with the permanent magnet being housed near the periphery so as to co-operate with an array of field-sensitive switches which are arranged around the circumference of a circle.
In a preferred embodiment feedback means are provided for giving a visual indication of which switch or switches of the array have been actuated. Such feedback may be provided by a corresponding array of LEDs positioned underneath the hob each of which illuminates when its associated switch is closed.
The magn
REFERENCES:
patent: 3711672 (1973-01-01), Moreland
patent: 4295118 (1981-10-01), Herr
Crossley Peter W.
Worrall Peter W.
Aktiebolaget Electrolux
Walberg Teresa J.
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