Note: Descriptions are shown in the official language in which they were submitted.
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HOUSEHOLD BROILING AND/OR BAKING OVEN
Description
This invention relates to a household broiling and/or baking oven and a method
for the
interior illumination of said broiling and/or baking oven.
Lighting the interior of a broiling, baking or roasting oven typically employs
incandescent or
halogen lamps. For installing these lamps, i.e. for illuminating the interior
of the oven, it is
necessary to punch holes in the oven wall or inner oven chamber. Production
tolerances
may leave a gap between the lamp and the chamber or between the enclosure and
the
chamber. It is there that moisture from the oven interior can penetrate into
the insulation
where it can cause problems. That gap can also lead to unwanted heat loss from
inside the
oven. Moreover, the lamps are often mounted on the oven back or side wall so
that, from
an outside observer's view, the food is illuminated only indirectly. In the
worst case, the
observer is even blinded when looking inside the oven through the glass door.
DE 38 08 717 Al, for example, describes a roasting and baking oven chamber in
which the
lighting system is mounted behind a side wall of the chamber. The lighting
system consists
of an elongated reflector housing serving as the lamp support fixture and a
protective glass
plate shielding the lamp from the baking or cooking chamber of the oven. To
further
improve the illuminating range of the light source and to avoid blinding the
observer looking
into the cooking area, the lighting system is positioned in the front section
of the oven
chamber. The light source employed is a halogen lamp.
The lighting system described in DE 38 08 717 Al may well provide better
illumination of
the oven interior and reduce the blinding effect, yet it still has to be
installed through an
opening in the oven chamber.
Then, too, halogen and incandescent lamps suffer from considerable power
dissipation,
meaning that only a small portion of the power is converted into light while
the remaining
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energy undesirably exits into the surroundings outside the oven in the form of
heat. Since
the lamps are restricted to certain temperatures, they cannot be insulated on
the enclosure
side.
It is therefore the objective of this invention to improve the illumination in
the interior of a
broiling, baking or roasting oven in a manner whereby the aforementioned prior-
art
shortcomings are at least in part avoided or at least minimized. In
particular, the invention
is also intended to provide good full-range illumination while at the same
time saving
energy to the best extent possible.
This objective is achieved with a broiling, roasting and/or baking oven
according to claim 1
and the method described in claim 19. Advantageous design variations and
enhancements
are covered in the dependent sub-claims to claims 1 and 19.
The novel broiling, roasting and/or baking oven, in particular a household
appliance-type
broiling, roasting and/or baking oven according to claim 1, includes at least
one lighting
system, in particular for illuminating at least one interior space of the
broiling, roasting
and/or baking oven, said illumination system incorporating at least one
electroluminescent
light source.
The term electroluminescence refers to the direct luminescent excitation of
luminescence
pigments or luminophores by means of an electric alternating field. Known
examples
include electroluminescence elements based on inorganic luminescent pigments
or
luminophores stimulated with alternating-current. The luminescent pigments or
luminophores may be embedded in a transparent organic or ceramic i.e.
inorganic bonding
compound. Among others, these may be in the form of foils, lacquers or even
ceramic and
other suitable support materials. An electric current stimulates the pigments
into
luminescence. The higher the voltage applied, the greater the potential
luminance or light
intensity of these light sources. A change in the frequency of the alternating
field can bring
about a color shift. Electroluminescent light sources of this type have been
described for
instance in DE 10 2004 019 611 Al or DE 10 2004 016 709 A1.
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The advantage of electroluminescent light sources lies in the fact that they
emit relatively
non-dazzling, flicker-free light and offer homogeneous luminosity over their
entire surface.
They also permit implementation in different colors. Another advantage of
electroluminescent light sources is their modest energy consumption and near-
absent heat
generation. Moreover, they are extremely robust.
The use of an electroluminescent light source permits the illumination of an
oven chamber
without the need to punch holes into the oven wall of chamber to accommodate
the
installation of lamps. It also means that condensation problems or heat loss
due to air
movement can be prevented. In addition, it permits uninterrupted insulation of
the oven
chamber and oven walls, ensuring improved energy efficiency. Finally, an
electroluminescent light source permits better and more even illumination of
the oven
interior, perhaps from several sides if so desired.
In a particularly preferred embodiment of this invention the minimum of one
electroluminescent light source is positioned on at least one section of at
least one wall
delimiting the oven interior and/or it constitutes at least one section of at
least one wall
delimiting the oven interior. This may mean that the electroluminescent light
source is
mounted directly on a wall of the oven interior, illuminating that interior
space from there or
through the wall if the latter is at least in part transmissive to light, or
that the light source is
integrated or embedded in a section of a wall or in a wall element of a wall
composed of
several elements, or mounted thereon. The reference to a wall delimiting the
oven interior
includes all oven walls such as side walls, bottom and top panels, partitions
and even
doors etc. The wall may be composed of one wall element or of several wall
elements,
which may be positioned side-by-side or one behind the other as viewed from
the interior.
The wall often encompasses at least one wall element directly adjoining the
oven interior,
at least one insulating element or at least one insulating air space and at
least one wall
element separating the oven from the outside. The heating device serving to
heat the oven
interior may on its part perhaps be at least partially integrated into a wall
element.
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As another possible, particularly advantageous feature the minimum of one wall
delimiting
the interior is an access door to the interior and the minimum of one
electroluminescent
light source is provided on at least a partial section of that door and/or
constitutes a partial
section of the door. As described above, the door on its part may be composed
of several
door elements.
In addition, as a particularly preferred feature, the minimum of one wall
and/or the door,
and especially a section of the wall or door facing the oven interior,
consists at least in part
of at least one transparent material. Accordingly, it is possible for the
electroluminescent
light source to emit enough light into the interior of the broiling, roasting
and/or baking
oven, illuminating its contents of food that is being cooked, roasted or
baked.
In a preferred embodiment, the minimum of one electroluminescent light source
is covered
or surrounded by a transparent material, especially glass. At least one
transparent
material, especially in the form of at least one pane or at least one coating,
is preferably
positioned between the minimum of one electroluminescent light source and the
interior of
the household broiling and/or baking oven. This is to ensure that the light
emitted by the
light source reaches the inside of the oven. It also prevents the light source
from being
directly exposed to the atmosphere in the oven interior which may not only be
very hot but
may also contain moisture as well as other substances such as oil droplets or
particles etc.
emanating from the food being cooked. While on the one hand protecting the
light-source
from soiling or damage, it also protects the food in the oven from
contamination by
abrasion particles or fumes released by the light source.
In a particularly advantageous design version of the household broiling and/or
baking oven
according to the invention, at least a partial section of the minimum of one
wall or of the
minimum of one door consists of a transparent material over its entire area.
It is thus
possible, even when the oven chamber is closed, to see the oven interior from
the outside,
which interior can preferably be illuminated even when closed.
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It may also be particularly advantageous to provide a cooling system for
cooling the
minimum of one electroluminescent light source. As a rule, electroluminescent
light
sources are restricted to a maximum operating temperature beyond which their
performance may deteriorate. A cooling system can make certain that, when the
temperature prevailing inside the broiling or roasting oven is very hot, that
maximum
operating temperature of the light source is not exceeded. For example, such
cooling can
be achieved by means of a fluid such as air, gas or a suitable liquid caused
to flow directly
along the light source or along the adjoining material. It is equally
possible, however, to
suitably cool a wall or door section positioned at a distance from the light
source but in
contact with or near the oven interior, so that the heat does not even reach
the light source
in the first place. It is further possible to specially configure the glass
panes in a way as to
protect the light source from overheating. Ultimately, the glass pane or
window functions as
thermal insulation as well. The air cushion between the panes reinforces this
thermal
insulation.
In a particularly advantageous form of implementation, the minimum of one
electroluminescent light source is constituted of at least one
electroluminescent foil applied
in particular on a glass, ceramic or synthetic-material element, preferably on
a glass,
ceramic or plastic disk. Specifically, the electroluminescent foil may be up
to 1 mm thick
and/or carry an operating voltage of 60V to 100V. The operating frequency is
preferably in
a range between 50 Hz and 3000 Hz. This permits the attainment of a high
luminance level
and thus good and even illumination of the oven interior. Using an
electroluminescent foil
has the advantage that it is easy to process in a manufacturing operation and
that by
relatively simple methods it can be produced in a variety of shapes. It would
also be
possible in the event of a malfunction of the electroluminescent foil to
replace it with a new
foil.
In another, equally preferred form of implementation, the minimum of one
electroluminescent light source consists of an electrode layer, preferably a
lacquer
containing electroluminophores, that is applied in particular on a glass,
ceramic or
synthetic-material element, preferably on a glass, ceramic or plastic disk. A
layer of this
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type may be embedded in or between several transparent panes. The result is a
very
robust light source. It also allows for a lighting effect in two mutually
opposite directions.
As another perhaps preferred possibility, one or several electroluminescent
light sources
may be implemented in one or several shapes and/or colors. The light sources
may be
mounted on only one or on several walls bounding on the oven interior. For
example,
different colors or configurations can indicate different operating phases or
operating
programs.
It may also be desirable to be able to vary the luminance or light intensity
and/or luminous
color of the electroluminescent light source. Such difference may be effected
for instance
by the open and, respectively, closed state of the oven. For example, the
brightness may
be lower when the oven is opened so as not to blind the user. Or, when the
oven is
opened, the luminous color may change to one that is more pleasing on the eye
or
indicates that the oven door is open. In addition, different light intensities
may serve to
indicate different operating phases or operating programs.
In a particularly preferred design version of the household broiling and/or
baking oven the
minimum of one electroluminescent light source is mounted, farthest from the
oven interior,
on a section of a glass, ceramic or synthetic-material element of a wall
and/or door
consisting at least in part of transparent elements and adjoining at least one
interior space,
with the wall and/or door section encompassing the minimum of one
electroluminescent
light source being opaque toward the outside, while another section of the
wall and/or door,
preferably not encompassing an electroluminescent light source, consists
entirely of a
transparent material. Positioning the light source on a section, farthest from
the oven
interior, of a glass, ceramic or synthetic-material element of a door
consisting of several at
least in part transparent elements has the advantage that it is farthest
removed from the
heat source. The interpositioned door elements alone, or an air space, can
shield the light
source from exposure to the heat. Alternatively, a cooling system may be
provided in the
intervening space. Since the section of the wall and/or door encompassing the
minimum of
one electroluminescent light source is opaque toward the outside, the light
will not radiate
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toward the outside and the user of the oven will not be blinded. At that
particular point the
light penetrates into the oven interior only. Through the section that is
entirely transparent
the user can look into the oven interior and observe the broiling, roasting
and/or baking
process, again without being blinded.
It may also be particularly advantageous to provide at least one power supply
for the
electroluminescent light source feeding power through the wall and/or door
adjoining the
minimum of one oven interior, and in particular through at least one door
hinge. This
obviates the need for providing an opening in the wall or door to the oven
interior to
accommodate for instance a cable or wires. It also prevents heat loss, or
moisture
penetration, through the wall or door.
Preferably, the power input is controlled by a microswitch specifically
activated by opening
and/or closing the door. That microswitch may be positioned in the door hinge
or at some
other point in the door frame, etc. It may also be particularly desirable if
at least part of the
minimum of one light source, especially of the light source located on the
door, is switched
on or off, and/or its brightness is increased or lowered, in a predefined or
predefinable
position of the door. This means that, specifically from a predefined or
predefinable
opening angle of the door, at least part of the light source in or on the door
is switched off
or dimmed so as not to blind the user. The microswitch serves to turn the
light on or off,
and to vary the light intensity or luminance or even the luminous color.
Preferably,
however, the minimum of one oven interior remains illuminated in both the open
and the
closed state. This can be achieved for instance by providing several
electroluminescent
light sources, perhaps in the door for directly activated illumination and on
the lateral walls
or ceiling of the oven interior for illumination even in the open state.
Alternatively it may be
desirable if the electroluminescent light sources on the lateral walls or on
the interior ceiling
as well are turned on or off or their brightness increased or dimmed in the
predefined or
predefinable position of the door. In that case, for example, primarily the
light source in the
door may be lit when the interior is closed while the light sources on the
other walls would
be on when the interior is open.
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In another preferred design version at least one electroluminescent light
source of a
predefined or predefinable shape and/or color is provided on a transparent
section of a
door. That light source may be activated perhaps by switching on the broiling
or baking
oven and may for instance indicate an operating state, an operating program,
or even the
manufacturer's logo, etc.
In applying the method according to claim 19, a broiling, roasting and/or
baking oven and in
particular a household broiling, roasting and/or baking oven preferably as
described in one
of the claims 1 to 18, is illuminated by at least one electroluminescent light
source.
The electroluminescent light source employed is preferably at least one
electroluminescent
foil applied in particular on a glass, ceramic or synthetic-material element
and/or an
electrode layer preferably in the form of a lacquer containing
electroluminophores, applied
in particular on a glass, ceramic or synthetic-material element.
In a particularly preferred form of implementation of the device the minimum
of one
electroluminescent light source is specifically cooled by means of an
appropriate cooling
system.
As an additional desirable feature, at least one microswitch serves to turn
the power to at
least one electroluminescent light source on or off or to regulate it up or
down, in particular
when at least one door to the interior of the broiling, roasting and/or baking
oven is closed
and/or opened.
The following will explain the invention in more detail with the aid of an
implementation
example and with reference to the attached schematic illustrations in which:
FIG. 1 depicts one advantageous design version of a household broiling,
roasting and/or
baking oven according to the invention;
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FIG. 2 is a perpendicular view of part of the household broiling, roasting
and/or baking oven
in FIG. 1.
Identical parts and parameters in FIG. 1 and 2 bear identical reference
numbers.
FIG. 1 shows a door 1 to the interior of a household broiling, roasting and/or
baking oven.
One section of the door 1 is equipped with an electroluminescent foil 2
serving as the
electroluminescent light source. This type of electroluminescent foil can have
a life span for
instance of 2,500 hours, withstanding an operating temperature from -50 C to
65 C and a
storage temperature from -65 C to 85 C. The foil may be about 1 mm thick. The
operating
voltage is preferably in the range between 60 V and 100 V, the operating
frequency in the
range between 50 Hz and 3000 Hz. FIG. 1 is a top view of the inside 6 of the
door (also
refer to FIG. 2). The light source transmits light into the oven interior. The
outside 7 of the
door is opaque at least in the section encompassing the electroluminescent
foil 2 so as not
to blind the operator of the oven. Another section 3 of the door, not equipped
with an
electroluminescent foil 2, consists entirely of a transparent material, which
in this case is
glass, allowing the operator to view the illuminated oven interior from the
outside. The
power for the electroluminescent foil 2 is fed in by way of a door hinge 4
which also
encompasses the microswitch, not illustrated, that deactivates the
electroluminescent foil 2
when the door 1 is opened at a predefined opening angle and reactivates it
when the door
1 is closed.
FIG 2 is a bottom view of the door 1. It shows, among others, the door hinges
4. The door
is composed of several door elements, in this case several transparent glass
panes 5 with
insulating air spaces 8. The electroluminescent foil 2 is mounted on the door
element 8 that
is farthest from the inside 6 of the door, thus protecting it from direct
exposure to the heat in
the oven.
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