Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2000-04-11
2001-02-13
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C392S435000
Reexamination Certificate
active
06188048
ABSTRACT:
This invention relates to a radiant electric heater such as of the type in which one or more radiant electric heating elements is or are supported relative to (that is, on or adjacent to) a base of thermal and/or electrical insulation and/or reflective material.
FIELD OF THE INVENTION
The invention is particularly, but not exclusively, applicable to such heaters for use in cooking appliances, such as grills or ovens, including microwave ovens. It is, however, also applicable to such heaters for general applications, such as space heating and industrial thermal processing.
DESCRIPTION OF PRIOR ART
It is well known, particularly in cooking appliances, to provide radiant heaters in which one or more heating elements, such as of wire form, or ribbon form, or lamp form, is or are supported on or adjacent to a base of insulation material and/or reflective material, which may be provided in a housing, such as a support dish, such as of metal. It is particularly well known and advantageous to use, as a base, compacted microporous thermal and electrical insulation material.
For safe and satisfactory operation of such heaters it is required that manual contact with energised heating elements therein should be prevented. Furthermore, particulates such as of food materials should be prevented from contacting the heating elements and any insulating and/or reflecting materials provided in the heater. Such particulates, and also liquids, may be splattered towards the heater during cooking operations and vapours may also be emitted towards the heater.
A further problem, particularly encountered with heaters for use in ovens and grills, is that particulate materials in the heater, such as particles of insulation material, may become dislodged and must be prevented from falling into the oven or grill and contaminating food being processed therein.
The aforementioned problems have hitherto been solved by operating the heater behind a sheet of glass-ceramic material. Such glass-ceramic material is expensive and also reduces the thermal performance of the heater.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to provide a radiant electric heater which eliminates or at least ameliorates the above problems without the use of a sheet of glass-ceramic material.
SUMMARY OF THE INVENTION
According to the present invention there is provided a radiant electric heater including a heating element, wherein at least one covering sheet is spaced from the heating element, the at least one covering sheet being in the form of a fabric comprising glass filaments, ceramic filaments or metal filaments.
The metal filaments may be of woven form in the fabric.
The metal filaments may comprise a high temperature withstanding alloy such as stainless steel.
The glass or ceramic filaments may be of woven, knitted or mat form in the fabric.
The ceramic filaments may comprise alumino-silicate material or alumino-boro-silicate material or zirconia.
The glass filaments may comprise glass fibres selected from E glass, C glass, R glass, S glass and modifications thereof.
The weight per unit area of the fabric may be generally both greater than 1 kg/m
2
and may preferably be in the range from 50 to 300 g/m
2
.
The heating element may be supported on or adjacent to a base of insulation material, such as of microporous thermal insulation material. The insulation material may be provided in a dish-like support, such as of metal.
A peripheral wall of thermal insulation material may be provided for the heater. The at least one covering sheet of the fabric may be arranged to overlie an outer surface of the peripheral wall.
The heater may include one or more heating elements of wire, ribbon or lamp form.
An apertured member may be provided in contact with, or adjacent to, the at least one covering sheet of the fabric. For example, the apertured member may serve as a support for the at least one covering sheet and/or as an electrical screen when formed of electrically conductive material and/or as protection, for the heater. The apertured member may comprise a perforated sheet or a lattice arrangement, of metal, ceramic or other suitable refractory material.
The heater of the invention is particularly applicable to cooking appliances, such as grills, ovens especially microwave ovens, deep fat fryers. However it is also applicable in other applications, such as in space heating and in industrial thermal processing operations.
The at least one sheet of the fabric serves as an efficient barrier to particulate materials and liquid splashing, such as arising from cooking operations. It also reduces passage into the heater of vapours.
The invention is now described by way of example with reference to the accompanying drawings, in which:
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Plumptre David Aubrey
Wilkins Peter Ravenscroft
Ceramaspeed Limited
Dorman Ira S.
Paik Sang
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