Abstrict
An electric heater (2) is arranged for location in an oven (4)
intermediate a cavity (6) of the oven and a flue arrangement (8)
for venting the cavity (6). The heater (2) comprises a dish-like
support (14) containing at least one electric heating element (22)
and having a first face (24) open to the cavity (6) and a second
face (16; 18) having an aperture (26) adapted to interface with
the flue arrangement (8). Catalyst means (28) is provided incorporated
in the heater (2).
Claims
I claim:
1. An electric heater for location in an oven intermediate a cavity
of the oven and a flue arrangement for venting the cavity, the heater
comprising a dish-like support containing at least one electric
heating element and having a first face open to the cavity and a
second face having an aperture adapted to interface with the flue
arrangement, catalyst means being provided incorporated in the heater.
2. The heater of claim 1, wherein the aperture adapted to interface
with the flue arrangement is provided in the second face of the
dish-like support selected from a base and a peripheral wall of
the dish-like support.
3. The heater of claim 2, wherein the aperture includes a rimmed
portion projecting outwardly from the dish-like support.
4. The heater of claim 2, wherein the catalyst means is located
at or in the aperture in the base or the peripheral wall of the
dish-like support.
5. The heater of claim 4, wherein the aperture is at least partly
bordered by thermal insulation material.
6. The heater of claim 5, wherein the thermal insulation material
comprises microporous thermal insulation material.
7. The heater of claim 2, wherein a base layer of thermal insulation
material is provided in the dish-like support and having an opening
coinciding with the aperture in the base or the peripheral wall
of the dish-like support.
8. The heater of claim 7, wherein the at least one electric heating
element is supported on or adjacent to the base layer of thermal
insulation material.
9. The heater of claim 8, wherein the at least one electric heating
element is arranged with at least one part thereof traversing the
opening in the base layer coinciding with the aperture when provided
in the base of the dish-like support.
10. The heater of claim 9, wherein a supporting member is arranged
in the opening in the base layer for supporting the at least one
part of the at least one electric heating element where traversing
the opening in the base layer.
11. The heater of claim 10, wherein the supporting member comprises
ceramic material.
12. The heater of claim 11, wherein the supporting member is moulded
into, or pressed into, the base layer of thermal insulation material.
13. The heater of claim 2, wherein the catalyst means provided
at or in the aperture in the base or the peripheral wall of the
dish-like support comprises catalyst material on a support means.
14. The heater of claim 13, wherein the support means is selected
from a ceramic member of honeycomb form, a helically coiled metal
foil member, a wire mesh member, and ceramic mesh member.
15. The heater of claim 14, wherein the metal foil member is of
crinkled form.
16. The heater of claim 1, wherein there is provided at least one
apertured member overlying the first face thereof and spaced from
the at least one electric heating element.
17. The heater of claim 16, wherein the apertured member(s) overlie(s)
a peripheral wall of the dish-like support.
18. The heater of claim 17, wherein the at least one apertured
member is selected from woven glass filament material, woven ceramic
filament material and wire mesh material, and combinations thereof.
19. The heater of claim 1, wherein the catalyst means is arranged
at the first face of the heater.
20. The heater of claim 19, wherein the catalyst means overlies
the first face of the heater.
21. The heater of claim 20, wherein the catalyst means is in the
form of a mesh comprising or supporting catalyst material.
22. The heater of claim 20, wherein the catalyst means overlies
a peripheral wall of the dish-like support.
23. The heater of claim 19, wherein at least one apertured member
is additionally provided overlying the catalyst means at the first
face of the heater.
24. The heater of claim 23, wherein the at least one apertured
member is selected from woven glass filament material, woven ceramic
filament material and wire mesh material, and combinations thereof.
25. The heater of claim 1, wherein the catalyst means comprises
a coating on at least part of the at least one electric heating
element.
26. The heater of claim 1, wherein the catalyst means comprises
one or more catalyst materials selected from platinum, palladium,
osmium, iridium, ruthenium, rhodium and mixtures thereof.
27. The heater of claim 1, wherein the at least one electric heating
element is selected from ribbon, wire, foil, lamp and metal-sheathed
form.
28. The heater of claim 1, wherein the dish-like support comprises
metal.
29. The heater of claim 1, wherein a fan means is provided associated
with the flue means.
Description BACKGROUND TO THE INVENTION
More particularly, the invention relates to an electric heater
for an oven in which smoke or fumes are generated in a cavity of
the oven and are treated by a catalyst assembly during exit from
the oven cavity through a flue arrangement which is provided to
vent the oven cavity.
DESCRIPTION OF PRIOR ART
It is well known to provide a catalyst assembly in the flue of
an oven to reduce or eliminate smoke or fumes generated either during
a normal cooking operation, or during a high temperature self-cleaning
cycle effected in the oven. Such a catalyst assembly requires to
be heated before it can operate effectively. This is usually achieved
by locating the catalyst assembly in the flue sufficiently close
to the outlet from the oven such that hot air from the oven heats
the catalyst assembly, but such an arrangement is not altogether
satisfactory. In another arrangement, a separate heating element,
such as of metal-sheathed form, is known to be provided up-stream
of the catalyst assembly to more rapidly heat the air approaching
the catalyst assembly. However, such an arrangement is expensive
to implement.
It is also known to locate a heating element near the top wall
of an oven cavity, with part of the element overlying a flue opening
provided in the top wall of the oven cavity. A catalyst assembly
is again provided in the flue. This can improve the heat-up rate
of air entering the flue and thus accelerate heating of the catalyst
assembly. However, the heating element and the catalyst assembly
are provided as separate components and subsequently mounted relative
to the flue. Such an arrangement is inconvenient to implement.
OBJECT OF THE INVENTION
It is an object of the present invention to overcome or minimise
the aforementioned disadvantages.
SUMMARY OF THE INVENTION
According to the present invention there is provided an electric
heater for location in an oven intermediate a cavity of the oven
and a flue arrangement for venting the cavity, the heater comprising
a dish-like support containing at least one electric heating element
and having a first face open to the cavity and a second face having
an aperture adapted to interface with the flue arrangement, catalyst
means being provided incorporated in the heater.
The electric heater may be arranged for location at a wall of the
oven cavity, such as a wall at the top of the oven cavity and may
be adapted for a cooking purpose, such as grilling.
The catalyst means may be adapted to reduce or eliminate passage
into the flue arrangement of smoke or fumes generated in the oven
cavity.
The aperture adapted to interface with the flue arrangement may
be provided in the second face of the dish-like support comprising
a base or a peripheral wall of the dish-like support and may include
a rimmed portion projecting outwardly from the dish-like support.
The catalyst means may be located at or in the aperture in the
base or the peripheral wall of the dish-like support and may be
at least partly bordered by thermal insulation material, such as
microporous thermal insulation material.
A base layer of thermal insulation material may be provided in
the dish-like support and having an opening coinciding with the
aperture in the base or the peripheral wall of the dish-like support.
The at least one electric heating element may be supported on or
adjacent to the base layer of thermal insulation material and may
be arranged with at least one part thereof traversing the opening
in the base layer coinciding with the aperture when provided in
the base of the dish-like support.
A supporting member, such as of ceramic material, may be arranged
in the opening in the base layer for supporting the at least one
part of the at least one electric heating element where traversing
the opening in the base layer. Such supporting member may be moulded
into, or pressed into, the base layer of thermal insulation material.
The catalyst means provided at or in the aperture in the base or
the peripheral wall of the dish-like support may comprise catalyst
material on a support means. Such support means may comprise a ceramic
member of honeycomb form, a helically coiled metal foil member which
may be of crinkled form, or a wire or ceramic mesh member.
The electric heater may be provided with at least one apertured
member overlying the first face thereof and spaced from the at least
one electric heating element. Such apertured member(s) may overlie
a peripheral wall of the dish-like support and may comprise woven
glass or ceramic fibre or filament material, and/or wire mesh material.
The catalyst means may alternatively be arranged at the first face
of the heater, for example overlying the first face of the heater,
such as in the form of a mesh comprising or supporting catalyst
material, and which may be arranged to overlie a peripheral wall
of the dish-like support. At least one apertured member, such as
of woven glass or ceramic fibre or filament material, and/or wire
mesh material, may be additionally provided overlying the catalyst
means at the first face of the heater.
In a further alternative embodiment, the catalyst means may comprise
a coating on at least part of the at least one electric heating
element.
The catalyst means may comprise one or more catalyst materials
selected from platinum, palladium, osmium, iridium, ruthenium and
rhodium and mixtures thereof.
The at least one electric heating element may be of ribbon, wire,
foil, lamp or metal-sheathed form.
The dish-like support of the heater may comprise metal.
A fan means may be provided associated with the flue arrangement
in the oven.
For a better understanding of the present invention and to show
more clearly how it may be carried into effect, reference will now
be made, by way of example, to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an oven provided with an embodiment
of an electric heater according to the present invention located
outside an oven cavity;
FIG. 2 is a cross-sectional view of an oven provided with an embodiment
of an electric heater according to the present invention located
inside an oven cavity;
FIG. 3 is a plan view of the electric heater provided in the ovens
of FIGS. 1 and 2;
FIGS. 4A, 4B and 4C are perspective views of alternative catalyst
means for use in the heater of FIG. 3;
FIG. 5 is a plan view of an alternative arrangement of a heating
element in the heater of FIG. 3;
FIGS. 6A and 6B are perspective views of embodiments of supporting
members for use in the arrangement of FIG. 5;
FIGS. 7A and 7B are cross-sectional views of alternative aperture
arrangements in a dish-like support of a heater of the present invention;
FIG. 8 is a cross-sectional view of an alternative embodiment of
an electric heater according to the present invention, having an
aperture provided in a peripheral wall thereof;
FIG. 9 is a cross-sectional view of a further embodiment of an
electric heater according to the present invention;
FIG. 10 is a cross-sectional view of an alternative arrangement
of catalyst means in the heater of FIG. 9; and
FIG. 11 is a cross-sectional view of a still further embodiment
of an electric heater according to the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIGS. 1 to 3, a radiant electric heater 2 is located
in an oven 4, for example for performing a grilling or other cooking
function. The heater 2 is located in the oven 4 intermediate a cavity
6 of the oven and a flue arrangement 8 for venting the cavity 6.
Such venting of the cavity 6 is required as a result of smoke or
fumes being generated in the cavity 6 during a cooking operation
or during a high temperature self-cleaning cycle effected in the
cavity 6. A fan 10 may be provided in the flue arrangement 8 to
promote exit of air through the flue arrangement 8.
The oven 4 of FIG. 1 has the heater 2 located at the top of the
oven cavity 6 in a recess in a top wall 12 of the cavity 6, whereas
the oven 4 of FIG. 2 has the heater 2 located at the top of the
oven cavity 6, inside the oven cavity 6 and against the top wall
12 thereof.
The heater 2 is arranged in the oven 4 between the cavity 6 of
the oven and the flue arrangement 8 and comprises a dish-like support
14, such as of metal, having a base 16 and a peripheral wall 18.
A base layer 20 of thermal insulation material, such as microporous
thermal insulation material, is provided inside the dish-like support
14.
At least one electric heating element 22 is supported on or adjacent
to the base layer 20. Such heating element or elements 22 can comprise
any of the well-known forms, such as ribbon, wire, foil, lamp or
metal-sheathed forms, or combinations thereof. As illustrated, the
heating element 22 is provided of corrugated metal ribbon form.
The heater 2 has a front face 24 open to the oven cavity 6 and
has an aperture 26 extending through the base 16 of the dish-like
support 14 and the base layer 20 and interfacing with the flue arrangement
8.
A catalyst means 28 is incorporated in the heater 2 and is arranged
in the aperture 26 and bordered by the base layer 20 of thermal
insulation material. Such catalyst means 28 is heated by air drawn
through the heater 2 from the oven cavity 6 into the flue arrangement
8. The catalyst means 28 comprises a catalytically active material
which, when heated and contacted by smoke or fumes from the oven
cavity 6, operates to reduce or eliminate the smoke or fumes which
are generated in the cavity 6 during a cooking operation or during
a high temperature self-cleaning cycle effected in the oven cavity
6.
The catalyst means 28 suitably comprises a catalyst material on
a support. Such catalyst material may, for example, comprise one
or more of platinum, palladium, osmium, iridium, ruthenium and rhodium,
preferably platinum.
Examples of catalyst means 28 are illustrated in FIGS. 4A, 4B and
4C. In FIG. 4A, the catalyst means 28 comprises a ceramic member
of honeycomb form coated with catalyst material. In FIG. 4B, the
catalyst means 28 comprises a helically coiled metal foil member,
such as of crinkled or corrugated form, coated with catalyst material.
In FIG. 4C, the catalyst means 28 comprises a wire or ceramic mesh
member coated with catalyst material.
For effective operation, the catalyst means 28 must be heated to
and maintained at as high a temperature as possible. This is assisted
by the thermally insulating base layer 20 which surrounds the catalyst
means in the heater 2.
The electric heater 2 can be provided with at least one apertured
member 30 overlying the front face 24 of the heater 2 and spaced
from the heating element or elements 22. Such one or more apertured
members 30 is or are arranged to be permeable to smoke and/or fumes
generated in the oven cavity 6 and suitably overlie(s) the peripheral
wall 18 of the dish-like support 14 of the heater 2. The one or
more apertured members 30 suitably comprise(s) woven glass or ceramic
fibre or filament material and/or wire mesh material.
Referring now to FIG. 5, in order to ensure that air passing through
the catalyst means 28 is heated to as high a temperature as possible,
at least part of the heating element or elements 22 is arranged
to traverse the aperture 26 in which the catalyst means 28 is provided.
To prevent sagging of the at least part of the heating element 22
where crossing the aperture 26, a support member 32, such as of
ceramic material, can be provided, as shown in FIGS. 6A and 6B.
In FIG. 6A, the support member 32 is in the form of a frame arranged
in the aperture 26 in the heater 2 and provided with recesses 34
for receiving and supporting the heating element 22. In FIG. 6B,
the support member 32 is in the form of a beam across the aperture
26 in the heater 2 and provided with recesses 34 for receiving and
supporting the heating element 22. The support member 32 in FIGS.
6A and 6B may be moulded into, or pressed into, the base layer 20
of thermal insulation material.
Referring now to FIGS. 7A and 7B, the aperture 26 in the base 16
of the dish-like support 14 may include a rimmed portion 36 projecting
outwardly from the dish-like support 14 and supporting the catalyst
means 28. As shown in FIG. 7B, the catalyst means 28 is bordered
by thermal insulation material 38, for example microporous thermal
insulation material, in the rimmed portion 36 of the aperture 26
in the dish-like support 14. Such thermal insulation material 38
assists in maintaining the catalyst means 28 at as high a temperature
as possible.
Referring now to FIG. 8, instead of the aperture 26 and the catalyst
means 28 being provided in the base 16 of the dish-like support
14 of the heater 2, the aperture 26 and the catalyst means 28 are
provided in the peripheral wall 18 of the dish-like support 14 and
interfacing with the flue arrangement 8. The flue arrangement 8
is arranged for sideways connection to the heater 2. The catalyst
means 28 is bordered by thermal insulation material of the base
layer 20.
An alternative embodiment of the heater 2 of the present invention
is shown in FIG. 9. This is substantially the same as the heater
shown in FIG. 3 with the important difference that, instead of the
catalyst means 28 being provided in the aperture 26 through the
base 16 of the dish-like support 14, the catalyst means 28 is arranged
to overlie the front face of the heater 2, suitably in the form
of a mesh permeable to smoke and/or fumes and comprising or supporting
catalyst material. Such catalyst means 28 suitably overlies the
peripheral wall 18 of the dish-like support 14 and is heated to
an effectively high temperature by direct radiation from the heating
element or elements 22.
In a modification of the heater 2 of FIG. 9, as shown in FIG. 10,
at least one apertured member 40, such as of woven glass or ceramic
fibre or filament material and/or wire mesh material, is additionally
provided overlying the catalyst means 28 at the front face of the
heater. Such apertured member(s) 40 must of course be permeable
to smoke and/or fumes from the oven cavity.
A further embodiment of the heater 2 is illustrated in FIG. 11.
The heater 2 of FIG. 11 is similar to that of FIG. 3 or FIG. 5,
with the significant difference that, instead of the catalyst means
28 being provided in the aperture through the base 16 of the dish-like
support 14 (or indeed through the peripheral wall 18 of the dish-like
support 14 as shown in FIG. 8), the catalyst means is arranged as
a coating of catalyst material on the surface of at least part of
the heating element or elements 22. In particular, where part of
the heating element or elements 22 traverses the aperture 26 through
the base 16 of the dish-like support 14, as shown in FIG. 5, the
catalyst means 28 may be substantially confined to the surface of
that part of the heating element or elements 22 overlying the aperture
26.
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