Abstrict
An asymmetric radiant electric heater has multiple heating zones
which can be arranged in a plurality of configurations. The heater
comprises a dish-like support having two orthogonal axes of symmetry,
a base of thermal and electrical insulation material in the dish-like
support, a first heating element and a second heating element supported
adjacent one another on a major surface of the base and forming
an asymmetric arrangement in the dish-like support, a terminal block
secured at a fixed location at an edge of the dish-like support,
and a wall arrangement of thermal insulation material supported
on the base and comprising a peripheral wall extending around the
heater and a dividing wall, integral therewith, extending between
the adjacent first and second heating elements to form at least
two asymmetric heating zones. The wall arrangement is adapted and
arranged to cooperate with the base and the terminal block whereby
the wall arrangement is fitted to the heater in a first position
to accommodate a first configuration of the adjacent first and second
heating elements and in a second position, representing 180 degrees
of rotation of the wall arrangement from the first position about
an axis perpendicular to a base of
Claims
I claim:
1. An asymmetric radiant electric heater with multiple heating
zones which can be arranged in a plurality of configurations, the
heater comprising: a dish-like support having two orthogonal axes
of symmetry; a base of thermal and electrical insulation material
in the dish-like support; a first heating element and a second heating
element supported adjacent one another on a major surface of the
base and forming an asymmetric arrangement in the dish-like support;
a terminal block secured at a fixed location at an edge of the dish-like
support; a wall arrangement of thermal insulation material supported
on the base and comprising a peripheral wall extending around the
heater and a dividing wall, integral therewith, extending between
the adjacent first and second heating elements to form at least
two asymmetric heating zones; the wall arrangement being adapted
and arranged to cooperate with the base and the terminal block whereby
the wall arrangement is fitted to the heater in a first position
to accommodate a first configuration of the adjacent first and second
heating elements and in a second position, representing 180 degrees
of rotation of the wall arrangement from the first position about
an axis perpendicular to a base of the dish-like support, to accommodate
a second configuration comprising a mirror image arrangement of
the adjacent first and second heating elements.
2. A heater according to claim 1, wherein the dish-like support
is of substantially oval shape.
3. A heater according to claim 2, wherein the first heating element
is of substantially circular configuration and the second heating
element is of substantially part-circular configuration.
4. A heater according to claim 2, wherein the dish-like support
has a long axis of symmetry and a short axis of symmetry.
5. A heater according to claim 4, wherein the terminal block is
secured at the edge of the dish-like support on the short axis of
symmetry.
6. A heater according to claim 4, wherein the wall arrangement
has a long axis of symmetry corresponding to the long axis of symmetry
of the dish-like support.
7. A heater according to claim 1, wherein the base of thermal and
electrical insulation material is dished.
8. A heater according to claim 7, wherein a lower edge of the dividing
wall is profiled to correspond to the dish-shape of the base.
9. A heater according to claim 1, wherein a recess is provided
in the peripheral wall at each end of the dividing wall at a lower
edge of the wall arrangement to selectively accommodate electrical
connections between the terminal block and at least one of the first
and second heating elements.
10. A heater according to claim 9, wherein a protrusion is provided
on the surface of the base of thermal and electrical insulation
material directly opposite to where the electrical connections to
the terminal block are provided and cooperating with an overlying
one of the recesses at the end of the dividing wall to substantially
fill such one of the recesses.
11. A heater according to claim 1, wherein a pair of matching elongate
projections are provided directly opposite each other on opposite
lower edges of an outer rim of the peripheral wall of the wall arrangement,
one of the projections being arranged to bear on the terminal block,
the other of the projections being accommodated in a substantially
complementary recess provided in the base layer of thermal and electrical
insulation material.
12. A heater according to claim 1, wherein a rod-like temperature-responsive
device is provided at least partly crossing one of the heating zones.
13. A heater according to claim 1, wherein the wall arrangement
comprises bound vermiculite.
14. A heater according to claim 1, wherein the base comprises microporous
thermal and electrical insulation material.
15. A heater according to claim 1, wherein the first heating element
and the second heating element are selected from wire, ribbon, foil
and film material.
16. A heater according to claim 15, wherein the first heating element
and the second heating element comprise corrugated ribbons supported
edgewise on the base of thermal and electrical insulation material.
Description [0001] This invention relates to an asymmetric radiant electric
heater with multiple heating zones.
DESCRIPTION OF PRIOR ART
[0002] Asymmetric radiant electric heaters, for example oval heaters,
with multiple heating zones are known, for example, from United
Kingdom Patent Publication No. 2,044,057 in which an additional
part-circular heated area is arranged to one side of the conventional
circular heated area. In practice, the additional part-circular
heated area can be arranged either to the left-hand side or to the
right-hand side of the circular area. A significant disadvantage
of such known oval heaters is that it is necessary to engineer,
or tool, the left-hand and right-hand additional areas as separate
products. It is also necessary to stock separate components for
use in left- and right-handed heaters.
[0003] It would result in a significant saving in terms of investment
and storage if the same components could be used for both left-and
right-handed heaters.
OBJECT OF THE INVENTION
[0004] It is therefore an object of the present invention to provide
an asymmetric radiant electric heater with multiple heating zones
in which the same components can be used for multiple configurations.
SUMMARY OF THE INVENTION
[0005] According to the present invention there is provided an
asymmetric radiant electric heater with multiple heating zones which
can be arranged in a plurality of configurations, the heater comprising:
[0006] a dish-like support having two orthogonal axes of symmetry;
[0007] a base of thermal and electrical insulation material in
the dish-like support;
[0008] a first heating element and a second heating element supported
adjacent one another on a major surface of the base and forming
an asymmetric arrangement in the dish-like support;
[0009] a terminal block secured at a fixed location at an edge
of the dish-like support;
[0010] a wall arrangement of thermal insulation material supported
on the base and comprising a peripheral wall extending around the
heater and a dividing wall, integral therewith, extending between
the adjacent first and second heating elements to form at least
two asymmetric heating zones;
[0011] the wall arrangement being adapted and arranged to cooperate
with the base and the terminal block whereby the wall arrangement
is fitted to the heater in a first position to accommodate a first
configuration of the adjacent first and second heating elements,
and in a second position, representing 180 degrees of rotation of
the wall arrangement from the first position about an axis perpendicular
to a base of the dish-like support, to accommodate a second configuration
comprising a mirror image arrangement of the adjacent first and
second heating elements.
[0012] The dish-like support may be of substantially oval shape.
[0013] The first heating element may be of substantially circular
configuration with the second heating element being of substantially
part-circular configuration.
[0014] The dish-like support may have a long axis of symmetry and
a short axis of symmetry and the terminal block may be secured at
the edge of the dish-like support on the short axis of symmetry.
The wall arrangement may have a long axis of symmetry corresponding
to the long axis of symmetry of the dish-like support.
[0015] The base of thermal and electrical insulation material may
be dished. The lower edge of the dividing wall may be profiled to
correspond to the dish-shape of the base.
[0016] A recess may be provided in the peripheral wall at each
end of the dividing wall at a lower edge of the wall arrangement
to selectively accommodate electrical connections between the terminal
block and one or more of the first and second heating elements.
[0017] A protrusion may be provided on the surface of the base
of thermal and electrical insulation material directly opposite
to where the electrical connections to the terminal block are provided
and cooperating with an overlying one of the recesses at the end
of the dividing wall to substantially fill such one of the recesses.
[0018] A pair of matching elongate projections may be provided
directly opposite each other on opposite lower edges of an outer
rim of the peripheral wall of the wall arrangement, one of the projections
being arranged to bear on the terminal block, the other of the projections
being accommodated in a substantially complementary recess provided
in the base of thermal and electrical insulation material.
[0019] A rod-like temperature-responsive device may be provided
at least partly crossing one of the heating zones.
[0020] The wall arrangement may comprise bound vermiculite.
[0021] The base may comprise microporous thermal and electrical
insulation material.
[0022] The first heating element and the second heating element
may comprise wire, ribbon, foil or film material. In particular,
the first heating element and the second heating element may comprise
corrugated ribbons supported edgewise on the base of thermal and
electrical insulation material.
[0023] As a result of the present invention, a standard base component
can be provided for a radiant heater, consisting of a dish-like
support containing a base layer of insulation material and arranged
to be fitted with a terminal block at a fixed symmetrical location.
Asymmetric heating elements can be arranged on the base layer in
a particular configuration, or a mirror image thereof. A single
wall member is provided which, by simple orientation into a selected
one of two positions, can be fitted to the base component to accommodate
a particular arrangement of asymmetric heating elements, or a mirror
image arrangement thereof.
[0024] 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
[0025] FIG. 1 is a top plan view of one embodiment of a base component
of an asymmetric radiant electric heater according to the present
invention in which a part-circular heating element is positioned
to the right hand side of a circular heating element;
[0026] FIG. 2 is a cross-sectional view of the heater base component
shown in FIG. 1 along the line A-A in FIG. 1;
[0027] FIG. 3 is a cross-sectional view of the heater base component
shown in FIG. 1 along the line B-B in FIG. 1;
[0028] FIG. 4 is a top plan view of another embodiment of a base
component of an asymmetric radiant electric heater according to
the present invention in which a part-circular heating element is
positioned to the left hand side of a circular heating element;
[0029] FIG. 5 is a top plan view of a wall arrangement for use
with the base components shown in FIGS. 1 and 4;
[0030] FIG. 6 is a bottom plan view of the wall arrangement shown
in FIG. 5;
[0031] FIG. 7 is a cross-sectional view of the wall arrangement
shown in FIG. 6 along the line C-C shown in FIG. 6; and
[0032] FIG. 8 is a top plan view of an embodiment of an asymmetric
radiant electric heater according to the present invention in which
the wall arrangement shown in FIGS. 5 and 6 is fitted to the base
component shown in FIG. 1.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] Referring to FIGS. 1 and 2, an asymmetric radiant electric
heater is constructed, starting with an oval metal dish-like support
1 having a long axis of symmetry 2 and a short axis of symmetry
3.
[0034] A base layer 4 of well-known microporous thermal and electrical
insulation material is provided in the support 1 and has an upwardly-extending
peripheral region 4A. The base layer 4 may be dished so as to provide
a greater distance between the surface of the base layer and the
plane in which the peripheral region 4A terminates in the central
region of the base than in the peripheral region thereof.
[0035] At least one first heating element 5 is arranged in substantially
circular configuration on the base layer 4 and at least one second
heating element 6 is arranged in substantially part-circular configuration,
adjacent the first heating element 5, on the base layer 4. The heating
elements 5 and 6 can comprise any of the well known materials, such
as wire, ribbon, foil or film materials. In particular, the heating
elements 5 and 6 may be of corrugated ribbon form and may be supported
edgewise, in well known manner, on the base layer 4.
[0036] A terminal block 7 is arranged at a fixed location at an
edge of the dish-like support 1. The terminal block 7 is secured
at the edge of the dish-like support 1 on the short axis of symmetry
3.
[0037] Heating element 5 has end portions 5A and 5B electrically
connected to terminals 8 and 9 respectively of the terminal block
7 and heating element 6 has end portions 6A and 6B electrically
connected to terminals 9 and 10 respectively of the terminal block
7. Thus, terminal 9 is common to both heating elements 5 and 6.
[0038] The terminals 8, 9, 10 of the terminal block 7 may be connected
to a voltage supply (not shown) such that heating element 5 is energisable
alone, or together with heating element 6. Terminal 9 of the terminal
block 7 is connected to the voltage supply by way of a well-known
form of rod-like temperature-responsive device 23 which extends
from the edge of the dish-like support 1 partly across the heating
element 5.
[0039] As shown in FIG. 4, a base component for a heater may be
constructed up to the same stage as that of FIG. 1 with the exception
that, whereas the arrangement of FIG. 1 has the substantially part-circular
heating element 6 situated at the right hand side of the circular
heating element 5, the arrangement of FIG. 4 has the substantially
part-circular heating element 6 situated at the left hand side of
the circular heating element 5.
[0040] Both forms of heater base component are constructed using
a common form of dish-like support 1, with base layer 4, only the
configuration of the heating elements being different, as required
for different user applications, such as in glass-ceramic cooking
appliances.
[0041] A wall arrangement 11 of thermal insulation material, as
shown in FIGS. 5, 6 and 7, is provided for adding to the base components
of FIGS. 1 and 4 to produce finished heaters. The wall arrangement
11 is constructed of bound vermiculite, suitably comprising exfoliated
particles of vermiculite bound with potassium silicate. The wall
arrangement 11 is symmetrical about the long axis.
[0042] The wall arrangement 11 is arranged for supporting on the
base 4 of insulation material of the base component of the heater
and comprises a peripheral wall 12 for extending around the heater,
and an integral dividing wall 13 for extending between the first
and second heating elements 5 and 6. Because the base 4 is dished,
the dividing wall 13 extends downwardly in the central region by
a greater distance than in the end regions thereof, by about 3 mm.
The wall arrangement is stepped so that an outer rim 12A of the
peripheral wall is supported by the upper surface of the upwardly-extending
peripheral region 4A.
[0043] Recesses 14 and 15 are provided in the peripheral wall 12
and the dividing wall 13 in the region of the ends of the dividing
wall 13, at a lower edge of the wall arrangement 11. When the wall
arrangement is fitted to the base component of the heater of FIG.
1, the recess 14 at the end of the dividing wall 13 allows the end
portions 5A, 5B of the first heating element 5 and the end portions
6A. 6B of the second heating element 6 to pass under the wall for
connection to the terminal block. In this orientation of the wall
arrangement 11, the corresponding recess 15 at the other end of
the dividing wall 13 overlies, and is substantially filled by, a
protrusion 16 provided on the surface of the base layer 4 of insulation
material directly opposite to where the electrical connections to
the terminal block 7 are provided. The protrusion 16 is suitably
formed integrally with the base layer 4.
[0044] A pair of matching elongate projections 17 and 18 are provided
directly opposite each other on opposite lower edges of the outer
rim 12A of the peripheral wall 12 of the wall arrangement 11 (FIG.
7). The projection 17 is arranged to bear upon the terminal block
7 of the base component of FIG. 1 while the projection 18 is accommodated
in a substantially complementary elongate recess 19 provided in
the upwardly-extending peripheral region 4A at the edge of the base
layer 4 of insulation material.
[0045] FIG. 8 shows a finished heater in which the wall arrangement
11 of FIGS. 5 to 7 is fitted to the base component of FIG. 1 and
first and second heating zones 20 and 21 are formed in the heater.
[0046] The wall arrangement 11 of FIGS. 5 to 7 also fits, without
modification, the heater base component of FIG. 4. The heating elements
5 and 6 of FIG. 4 comprise a mirror image arrangement of the heating
element 5 and 6 of FIG. 1. The wall arrangement 11 is fitted to
the base component of FIG. 4 in an orientation which represents
180 degrees of rotation of the wall arrangement about an axis perpendicular
to a base 22 (FIG. 2) of the dish-like support 1, compared with
the orientation when fitted to the base component of FIG. 1 (that
is, mirrored about a vertical plane through the short axis of the
oval heater). When the wall arrangement is fitted to the base component
of FIG. 4, the recess 15 at the end of the dividing wall 13 accommodates
the end portions 5A, 5B of the first heating element 5 and the end
portions 6A, 6B of the second heating element 6, while the corresponding
recess 14 at the other end of the dividing wall 13 overlies, and
is substantially filled by, protrusion 16 provided on the surface
of the base layer 4 of insulation material.
[0047] Elongate projection 18 on the lower edge of the outer rim
12A of the peripheral wall 12 of the wall arrangement 11 bears on
the terminal block 7, while the corresponding projection 17 at the
opposite side of the outer rim of the peripheral wall 12 is accommodated
in recess 19 provided at the edge of the base layer 4 of insulation
material.
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