Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-08-21
2001-11-13
Huson, Gregory L. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S612000, C029S613000, C029S614000, C029S615000
Reexamination Certificate
active
06314636
ABSTRACT:
This invention concerns a method of manufacturing an electric heater assembly with a plurality of electric heating units, for use behind a plate such as a glass-ceramic plate in a cooking appliance, to provide a plurality of discrete heating zones on the plate.
DESCRIPTION OF PRIOR ART
For many years it has been most common practice to design glass-ceramic top cooking appliances in which a plurality of discrete electric heating units are provided underneath and in contact with a sheet of glass-ceramic and in which each heating unit is formed in an individual metal dish-like support and individually held against the underside of the glass-ceramic sheet. Recent trends have been aimed at simplifying manufacture by forming a plurality of heating units directly on a common supporting tray which is then secured in contact with the underside of the glass-ceramic sheet. One such arrangement is described in European Patent Publication No. 0757508 in which individual components of a plurality of heating units are built up on a common tray-like support. In this arrangement, for each heating unit a tablet-form base of insulation material and a separate insulating wall are assembled on the base of the support, one or more heating elements being secured to the base.
An arrangement of securing clips is used to secure the components to the support.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a method of manufacturing a heater assembly in which rather than separately form the insulation components and then build them up on the tray-like support, the insulation components are integrally formed directly on the support and no securing clips are required.
SUMMARY OF THE INVENTION
The present invention provides a method of manufacturing an electric heater assembly with a plurality of electric heating units, for use behind a plate, in particular a glass-ceramic plate, to provide a plurality of discrete heating zones on the plate, the method comprising:
providing a tray-like support having formed therein a plurality of dish-like recesses, each dish-like recess comprising a base and a surrounding wall;
moulding into each dish-like recess microporous thermal and electrical insulation material to form a base layer against the base of each dish-like recess and an upstanding wall layer against the surrounding wall of each dish-like recess, the base layer being formed integrally with the wall layer; and
providing in each dish-like recess at least one electric heating element supported relative to (that is, on or adjacent to) the base layer.
The microporous thermal and electrical insulation material may be moulded into the dish-like recesses one at a time, or all or a plurality thereof at the same time.
The upstanding wall layer of insulation material may be provided of a height in each dish-like recess such that it has an upper surface for contacting the plate, such as the glass-ceramic plate, when the heater assembly is arranged for operation. The upper surface of one or more of the wall layers may be profiled such as to be higher at the centre than at the edges.
The base layer in each dish-like recess may be provided having a compaction density substantially the same as, or different from, that of the upstanding wall layer. It may be preferred for the wall layer to have a compaction density greater than that of the base layer.
The base layer in each dish-like recess may have a composition substantially the same as, or different from, that of the upstanding wall layer, although formed integrally therewith.
The base layer and/or the wall layer in each dish-like recess may include reinforcing glass filaments. Such filaments may, for example, be selected from E glass, R glass, S glass and silica.
The microporous insulation material may be moulded into each dish-like recess as described in British Patent Application No. 9705923.2.
The at least one electric heating element provided in each dish-like recess may be of ribbon form and may be secured to the base layer in each dish-like recess by partial embedding in the base layer. Such partial embedding of the at least one heating element may be effected during moulding of the insulation material into each dish-like recess.
The at least one ribbon-form heating element may be provided partially embedded edgewise in the base layer of each dish-like recess and may be of corrugated form.
The tray-like support may be of metal and may be fabricated from component parts or the plurality of dish-like recesses may be formed, for example, by stamping, drawing, pressing, or otherwise shaping, a basic sheet-form metal component.
The tray-like support may be formed with a peripheral edge adapted to receive the plate. The plate may be secured to the peripheral edge by means of an adhesive or may be secured by mechanical fixing means. Sealing means, such as a gasket, may be provided between the plate and peripheral edge.
The plate may preferably be a glass-ceramic plate and may be for use in a cooking appliance.
REFERENCES:
patent: 1021230 (1912-03-01), Ball
patent: 4150280 (1979-04-01), Hurko
patent: 5296684 (1994-03-01), Essig et al.
patent: 0625865 (1994-11-01), None
patent: 0757508 (1997-02-01), None
patent: 2270824 (1994-03-01), None
Search Report, Nov. 4, 1997.
Ceramaspeed Limited
Dorman Ira S.
Huson Gregory L.
Smith Sean
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