Source: http://www.docstoc.com/docs/47247531/Heating-Apparatus---Patent-4639579
Timestamp: 2015-05-29 23:25:09
Document Index: 20951323

Matched Legal Cases: ['Application No. 8320717', 'Application No. 8320717', 'Application No. 8320717', 'Application No. 8320717', 'Application No. 8320717', 'Application No. 8320717']

Heating Apparatus - Patent 4639579 by Patents-154
47247531
This invention relates to improvements in heating apparatus and in particular though not exclusively, to heating apparatus of the type disclosed in our co-pending U.K. Patent Application No. 8320717 (PublicationNo. 2132060A), incorporating one or more sources of infra-red radiation.The heating apparatus disclosed in U.K. Patent Application No. 8320717 consists of, in one example, a shallow tray member containing a layer of thermally-insulative material, above which four infra-red-emitting, tungsten-halogen lamps aresupported. The tray member, usually along with a number of similar members may be mounted beneath a layer of glass ceramic to form a cooking hob.A thermal limiter is preferably provided in the heating apparatus to ensure that the maximum operating temperature of the glass ceramic is not exceeded. A number of discrete temperature settings are also provided by switching the lamps intoseries and/or parallel configurations, wherein one or more diodes are usually required to achieve one or more of the lower settings.However, some problems may be found to occur under particular circumstances of operation of the apparatus, such as operation of the limiter causing it to trip and disconnect the power supply to the lamps, which may be a source of annoyance for auser of the apparatus, or it may not be desirable to use the diodes in the switching arrangement, as they tend to interfere with the harmonics of the main supply.It is therefore an object of the present invention to provide heating apparatus which alleviates at least the above-mentioned potential problems, as well as being cost-effective.According to the present invention, there is provided a heating unit suitable for mounting in a cooking hob, said unit comprising a base layer of thermally-insulative material, a peripheral thermally-insulative wall to define a first hotplateregion, an inner thermally-insulative wall to define a second hotplate region located within said first region, at least one infra-
United States Patent: 4639579
4,639,579
A heating unit suitable for mounting in a cooking hob includes a circular
tray having a layer of thermally-insulative material disposed therein and
a peripheral thermally-insulative wall, within which four infra-red lamps,
each containing a tungsten filament, are supported. The tray also includes
an inner thermally-insulative wall, which encloses the length of each
filament. Between the peripheral and inner walls, two conventional,
wire-wound heating elements are disposed. The filaments and the elements
are energizable independently and/or concurrently, and series and/or
parallel combinations of the filaments and the elements may be switched to
provide various discrete power outputs.
Brooks; Steve M. (Essex, GB2), May; David R. (Cheshunt, GB2)
Thorn EMI Domestic Appliances Limited
06/733,802
219/462.1  ; 392/411
H05B 3/68&amp;nbsp(20060101); H05B 3/74&amp;nbsp(20060101); H05B 003/68&amp;nbsp()
219/354,449,461,464,524,553,445,446 313/315 337/394 99/425
3663798
Speidel et al.
Wortheimer et al.
2132060
1.  A heating unit suitable for mounting in a cooking hob, said unit comprising:
an electrical heating element;  means for supporting said heating element between said inner and peripheral walls adjacent said base layer,
a lamp emissive of infra-red radiation and having first and second ends, said lamp comprising a tubular envelope and a linear filament supported in said envelope;
means for supporting said lamp such that said envelope extends across said first hotplate region and said first and second ends are located outside of said first region, said filament being of length commensurate with said second hotplate region; and
means, connectable to said lamp and said heating element, for energising the filament and the heating element independently and concurrently, selectively.
2.  A heating unit as claimed in claim 1, wherein said energising means is adapted to switch said filament and said heating element into a number of selective series and parallel combinations to provide discrete heat outputs from said first and
second hot-plate regions, selectively.
3.  A heating unit as claimed in claim 1 wherein said heating element comprises a wire-wound element.
4.  A heating unit as claimed in claim 1 wherein said first and second hotplate regions are circular and concentric.
5.  A cooking hob comprising:
at least one heating unit disposed within said housing;  and
means for mounting said at least one heating unit adjacent the underside of said plate,
said heating unit comprising a base layer of thermally-insulative material, a peripheral thermally-insulative wall defining a first hot-plate region, an inner thermally-insulative wall defining a second hot-plate region located within said first
region, an electrical heating element, means for supporting said heating element between said inner and peripheral walls adjacent said base layer, a lamp emissive of infra-red radiation and having first and second ends, said lamp comprising a tubular
envelope and a linear filament supported in said envelope, said unit further including means for supporting said lamp such that said envelope extends across said first hotplate region and said first and second ends are located outside of said first
region, said filament being of length commensurate with said hotplate region, and means, connectable to said lamp and said heating element, for energising said lamp and said heating element independently and concurrently, selectively.
This invention relates to improvements in heating apparatus and in particular though not exclusively, to heating apparatus of the type disclosed in our co-pending U.K.  Patent Application No. 8320717 (Publication
No. 2132060A), incorporating one or more sources of infra-red radiation.
The heating apparatus disclosed in U.K.  Patent Application No. 8320717 consists of, in one example, a shallow tray member containing a layer of thermally-insulative material, above which four infra-red-emitting, tungsten-halogen lamps are
supported.  The tray member, usually along with a number of similar members may be mounted beneath a layer of glass ceramic to form a cooking hob.
A thermal limiter is preferably provided in the heating apparatus to ensure that the maximum operating temperature of the glass ceramic is not exceeded.  A number of discrete temperature settings are also provided by switching the lamps into
series and/or parallel configurations, wherein one or more diodes are usually required to achieve one or more of the lower settings.
However, some problems may be found to occur under particular circumstances of operation of the apparatus, such as operation of the limiter causing it to trip and disconnect the power supply to the lamps, which may be a source of annoyance for a
user of the apparatus, or it may not be desirable to use the diodes in the switching arrangement, as they tend to interfere with the harmonics of the main supply.
According to the present invention, there is provided a heating unit suitable for mounting in a cooking hob, said unit comprising a base layer of thermally-insulative material, a peripheral thermally-insulative wall to define a first hotplate
region, an inner thermally-insulative wall to define a second hotplate region located within said first region, at least one infra-red lamp each including a filament emissive of infra-red radiation and commensurate with said second hotplate region,
further heating means commensurate with said first hotplate region, further heating means commensurate with said first hotplate region, and means for energising said filament and said further heating means independently and concurrently, selectively.
FIG. 2 shows an alternative embodiment to that shown in FIG. 1,
Referring to FIG. 1, there is shown a heating unit consisting of a circular tray 1 having a layer 2 of thermally-insulative
material, such as microporous material, disposed therein and a peripheral thermally-insulative wall 3, within which four infra-red lamps, one shown at 4, are supported.  Each lamp 4 consists of tungsten filament 5 supported within a tubular quartz
envelope 6, and each end of each lamp 4 is formed with a pinch seal (not shown), having a connection between the respective end of the filament 5 and an electrical connector sealed therein, each pinch seal being housed within a ceramic end cap, such as
As shown in FIG. 6, the heating unit is preferably mounted beneath, and urged up towards, a glass ceramic plate 19, by a suitable mounting arrangement 20, to form a hotplate of a cooking hob.  The mounting arrangement 20 is fixed to a base 21 of
a housing for the cooking hob.
The four lamp filaments 5 and the two elements 9 and 10 may be energised independently and/or concurrently, by means of control 24, so that only the central hotplate region within the inner wall or alternatively the whole region may be heated.
Furthermore, any combination of one or more lamps and one or both elements may be energised to provide various discrete power outputs, and thus temperature settings, whilst maintaining an aesthetically pleasing balanced effect of the lamps, as seen
through the glass ceramic plate.
Preferably, a thermal limiter (not shown) either mechanical or electronic, is also employed within the heating apparatus to limit the operating temperature of the apparatus to prevent damage to the glass ceramic by overheating.  It may be
preferable for the limiter to control the heating elements 9 and 10 only, so that tripping of the limiter would not be so conspicuous, as only the elements, and not the lamps, would be de-energised if overheating occurred.
It may be preferable to arrange that switching of the lamp filaments into various series and/or parallel configurations provides relatively high power outputs and that energisation of one or both of the heating elements 9 and 10 provides lower
FIG. 2, wherein like parts are labelled with like reference numerals with respect to FIG. 1, shows an alternative embodiment to that shown in FIG. 1, wherein only three lamps, such as at 4, are provided in combination with only one heating
FIGS. 3a and 3b show the configurations of four lamp filaments 11 to 14 required to generate the third lowest and the lowest power outputs of the apparatus.  The remaining configurations for the power outputs provided are shown in our
above-mentioned co-pending U.K.  Patent Application No. 8320717, wherein the configurations giving the same power outputs as those shown in FIGS. 3a and 3b also include one or more diodes to generate the required power output.
The present configurations shown in FIGS. 3a and 3b overcome this disadvantage by including an additional element 15 in series with the configuration formed by lamp filaments 11 to 14, which, when switched into the two configurations generates
the same respective power outputs as when diodes are used.  The element 15 may be either a fifth lamp filament or a conventional heating element as shown in FIGS. 1 and 2.
A further use of the additional element 15 may be as a pre-heating device to produce faster warm-up periods of the apparatus.  The use of the element 15 would provide a high power output for an initial warm-up period, the length of which could be
controlled by a timer and/or a thermal sensor device.  The element 15 could also be used at various times during energisation of the lamp filaments 11 to 14, but preferably not continuously.  Subsequent use of the element 15 after the initial warm-up
period could be controlled manually.
The initial warm-up period could be controlled by any suitable type of timing device, so that the element 15 is de-energised at the end of a predetermined time, such as 6 mins.  for example.
Alternatively or additionally, the initial warm-up period could be controlled by any suitable thermal device, including a pre-set thermostat disposed at any suitable location within the apparatus to cause de-energisation of element 15 which a
certain operating temperature is attained.  Possible advantages of using a pre-heating element 15 may be that power outputs exceeding the limit that the glass ceramic is capable of withstanding may be utilised, because it is only energised until the
required operating temperature is attained, and additionally at lower outputs, a thermal limiter to protect the glass ceramic may not be required, as the glass ceramic should not exceed its limit at these lower outputs.  This therefore may provide an
additional cost saving.
However, it a limiter to protect the glass ceramic is employed, it may be necessary to cause the timer and/or thermal device controlling the pre-heating element 15 to by-pass the limiter, at least while the element 15 is initially energised, to
prevent nuisance tripping of the limiter.
FIGS. 4 and 5, wherein like parts are also labelled with like reference numerals with respect to FIGS. 1 and 2, show two alternative embodiments which include an additional filament accommodated within each lamp, instead of a conventional heating
Each lamp, as at 4 shown in FIG. 4 accommodates a filament 5, the length of which is commensurate with the area of the inner hotplate region within the wall 8, and a second filament 16, the length of which is commensurate with the area of the
whole hotplate region within the outer wall 3.  The two filaments may be energised independently and/or concurrently as required.
The embodiment shown in FIG. 5 is provided with a non-central inner hotplate region within the inner wall 8, which is integral around part of its circumference with the outer wall 3.  A lamp filament 18 is accommodated within each lamp 4, having
a length commensurate with the area of the whole hotplate region.  However, each filament 18 is tapped at a point 19 along its length, so that, if required only the filament length coinciding with the area of the inner hotplate region may be energised.
Filament 18 thus effectively consists of a filament 22 commensurate the inner hotplate region and an extended portion 23 thereof commensurate with the whole hotplate region.
The embodiments shown in FIGS. 4 and 5 may be advantageous in providing an increased number of switching combinations of the filaments, especially if they are maintained at a 100% output, as well as being cost-effective, because two filaments are
accommodated within only one lamp.
In the preferred embodiment of the heating apparatus disclosed in U.K.  Patent Application No. 8320717, each lamp is provided with an infra-red-reflective coating applied to the lower half of the quartz envelope, to reflect radiation emitted
downwardly from the filaments back in an upwards direction towards the glass ceramic plate.
"Heating Apparatus - Patent 4639579"