Baking oven having a lighting device with a low voltage and/or halogen bulb

A baking oven includes at least one boundary wall defining a baking space and at least one lighting device each including a first part in the form of a low-voltage bulb, a second part in the form of an electrical connection for the bulb, and a lamp socket disposed on the at least one boundary wall. The lamp socket receives the bulb from inside the baking space with the bulb protruding substantially completely into the baking space. The boundary wall has an opening formed therein for receiving and closely surrounding one of the parts of the lighting device.

SPECIFICATION: 
The invention relates to a lighting device for a baking oven having a bulb 
with a lamp socket on at least one boundary wall of the baking space, the 
bulb may be introduced into the lamp socket from the baking space. 
Incandescent bulbs that are typically used in conventional lighting devices 
for ovens have an operating voltage of 220 volts and a power consumption 
of 25 watts. To this end, a relatively large opening is provided in the 
muffle wall, which can be covered with a glass covering and behind which a 
metal holder for a lamp socket is mounted. The bulb is located essentially 
in a hollow space intended for lighting units, behind the muffle wall. A 
lighting device of this type is known from German Published, 
Non-Prosecuted Application DE-OS 29 13 542. During bulb operation in such 
a device, there is a relatively severe heat buildup, which also extends to 
the vicinity of the lamp socket and the metal holder. In order to avoid 
overheating at this point, the heat must be dissipated to the outside. In 
order to dissipate the heat, a break is typically made in the heat 
insulation layer that otherwise surrounds the baking oven muffle, in the 
vicinity of the metal holder. A pronounced thermal transport also takes 
place at this point because of the relatively large muffle opening leading 
from the baking space, especially during pyrolytic or self-cleaning 
operation of the oven. The muffle opening must be large enough to permit 
the relatively large-volume bulb to be easily mounted from the inside of 
the baking oven. This kind of thermal transport toward the outside is 
relatively unproblematic if the lighting device is located at the back of 
the baking oven, where heat dissipation does not present great 
difficulties. It becomes problematic if the lighting device is to be 
attached to one or both side muffle walls. In such a case, particularly in 
built-in ovens, lateral heat dissipation should be avoided as much as 
possible, because of the built-in furniture or appliances immediately 
adjacent the oven. To this end, the thermal insulation layer should remain 
uninterrupted along these side muffle walls as much as possible. 
Installing such lighting devices in the vicinity of the aforementioned 
side walls is also problematic, because little installation space is 
available on the sides in contrast to the back wall of the muffle. 
It is accordingly an object of the invention to provide a lighting device 
for an oven, which overcomes the hereinafore-mentioned disadvantages of 
the heretofore-known devices of this general type and which avoids further 
geometrical or thermal difficulties in terms of placing the lighting 
device so as to attain optimal illumination of the baking space. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a baking oven, comprising at least one 
boundary or limiting wall defining a baking space, at least one lighting 
device each including a first part in the form of a low-voltage bulb, a 
second part in the form of an electrical connection for the bulb, and a 
lamp socket disposed on the at least one boundary wall having means for 
receiving the bulb in the lamp socket from inside the baking space with 
the bulb protruding substantially completely into the baking space, the 
boundary wall having an opening formed therein for receiving and closely 
surrounding one of the parts of the lighting device. 
In accordance with another feature of the invention, the at least one 
boundary wall having the opening is a muffle wall with one surface facing 
toward the baking space and another surface facing away from the baking 
space, the lamp socket faces the other surface of the muffle wall, the 
bulb includes a lamp base portion and a connection portion, and only one 
of the portions protrudes through the opening up to the lamp socket. 
In accordance with a further feature of the invention, the low-voltage bulb 
has an operating voltage of substantially 12 volts. 
In accordance with an added feature of the invention, the low-voltage bulb 
has an installed power consumption of 5 watts. 
In accordance with an additional feature of the invention, the low-voltage 
bulb is a halogen lamp. 
The use of a low-voltage bulb, especially a halogen lamp which is known per 
se, makes it possible to keep the incident very low heat during operation 
of the bulb, so that special means for heat dissipation are unnecessary. 
In particular, there is no further necessity for interrupting the thermal 
insulating layer and therefore the lighting devices can preferably be 
disposed on the side muffle walls, where excellent illumination of the 
baking space is attained. Furthermore, such low-voltage bulbs and lamp 
sockets associated therewith are small enough to only require a very small 
installation space for the disposition thereof. At the same time, since 
the low-voltage bulb is so small, the opening in the particular muffle 
wall can be kept small enough to prevent a substantial emission of heat 
through the opening during operation of the baking oven. 
The small size of the low-voltage bulb, for instance a halogen lamp, also 
makes it possible to allow a substantial portion of the bulb to protrude 
into the baking space, so that the best possible illumination of the 
baking space can be obtained. 
In accordance with yet another feature of the invention, there is provided 
a reflector disposed in the vicinity of the opening. 
In accordance with yet a further feature of the invention, the reflector is 
part of the muffle wall and has the opening formed therein, and the muffle 
wall has another opening formed therein being larger than the opening in 
the reflector, the reflector being disposed in the other opening. In other 
words, in the vicinity of the opening, the muffle wall itself a reflector. 
In accordance with yet an added feature of the invention, the lighting 
device is disposed on at least one side muffle wall. 
In accordance with yet an additional feature of the invention, there is 
provided a an oven door, and a shade shielding the bulb from the oven 
door. 
In accordance with still another feature of the invention, the shade is 
part of a reflector disposed in the vicinity of the opening. 
Blinding brightness when a person looks into the baking space can be 
avoided by providing the shade. 
In accordance with still a further feature of the invention, there is 
provided an at least partially transparent glass covering mounted on the 
muffle wall and covering the bulb. 
In accordance with still an added feature of the invention, the part of the 
glass covering is in the form of a shade. 
In accordance with still an additional feature of the invention, the at 
least one boundary wall is an oven muffle having one surface facing toward 
the baking space and another surface facing away from the baking space, 
the lamp socket is secured so as to face the other surface of the muffle 
wall, and there is provided a thermal insulating layer covering the lamp 
socket and surrounding the oven muffle. 
In accordance with again another feature of the invention, there is 
provided an oven door in which the lighting device is disposed. 
In accordance with again a further feature of the invention, the oven door 
includes a viewing window having two sides and an inner glass panel, and 
the lighting device also includes another bulb in another lamp socket, one 
of the bulbs and one of the lamp sockets being disposed beyond each 
respective side of the viewing window, and the bulbs being covered by the 
inner glass panel. 
In accordance with again an added feature of the invention, the viewing 
window has an aperture, and the oven door has a strut or stringer 
surrounding the aperture, the strut having an outer surface in the form of 
a reflector facing toward the bulb bulbs. 
The small dimensions of low-voltage bulbs of the conventional type favors 
such a construction in a particularly advantageous manner. The result, in 
terms of the illumination of the baking space, is optimal lighting 
conditions, because the lighting device is disposed outside the viewing 
window of the baking door so that it is not visible to the observer, and 
the side of the food being baked that faces the observer is illuminated. 
In accordance with again an additional feature of the invention, there is 
provided a plug contact disposed between the oven muffle and the oven door 
for electrically connecting the lighting device. 
In accordance with another feature of the invention, there is provided a a 
current conducting rail disposed between the oven muffle and the oven door 
for electrically connecting the lighting device. 
In accordance with a further feature of the invention, there are provided a 
means for heating the oven by microwave energy. 
In accordance with an added feature of the invention, there is provided a 
grid-like, microwave-tight covering mounted on the boundary wall. 
In accordance with an additional feature of the invention, the boundary 
wall has one surface facing toward and another surface facing away from 
the baking space, and there is provided a holder plate secured on the 
other surface of the boundary wall in the vicinity of the opening formed 
therein for retaining the lamp socket. 
In accordance with a concomitant feature of the invention, the holder plate 
has a bent-over extension protruding through the opening formed in the 
boundary wall up to the grid-like covering, the extension being in the 
form of a shade and a reflector. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
lighting device for an oven, it is nevertheless not intended to be limited 
to the details shown, since various modifications and structural changes 
may be made therein without departing from the spirit of the invention and 
within the scope and range of equivalents of the claims.

Referring now to the figures of the drawings in detail and first, 
particularly, to FIG. 1 thereof, there is seen a cross-sectional plan view 
of a baking oven having a block-shaped metal oven muffle 1, the service 
opening 2 of which is to be closed with a baking oven door 3. The oven 
muffle 1 is surrounded toward the outside by a thermal insulating layer 4. 
Food 6 such as a cake that is to be baked, is placed in the interior of a 
baking space or chamber 5. The door 3 has a box-shaped structure and a 
door bottom 7, with which the door 3 is supported on an elastic gasket 8 
in the closing position. The elastic gasket 8 may be disposed on a muffle 
flange 9 of the oven muffle, so as to surround the opening. The door 
bottom has a recess 10 formed therein, which may be rectangular in shape 
and is defined by surrounding recess flanges 11, which are curved in 
approximately the shape of a semicircle and have another surrounding 
gasket 12 disposed therein. An inner glass panel 13 is supported on the 
gasket 12. The outer surface of the door 3 facing toward the front of the 
door 3 is formed by a further larger glass panel 14. In order to obtain an 
outlined viewing window 15 in the oven door 3, a surrounding window strut 
or crossbeam 16 is mounted in the hollow space of the box-like oven door 
3. The strut represents the outline of the viewing opening and extends 
between the two glass panels 13 and 14. 
One lighting device is disposed in the hollow spaces on each side of the 
corresponding sections of the window strut 16. For the sake of simplicity, 
the lighting device is merely diagrammatically indicated by the outline of 
a bulb 17. So-called low-voltage bulbs are used in this case, preferably 
halogen lamps, having an operating voltage of approximately 12 V and a 
power consumption of approximately 5 watts. According to one embodiment 
shown in FIG. 1, corresponding lamp sockets 18 for the low-voltage bulbs 
17 are mounted in the aforementioned hollow spaces. The supply of current 
to the lamp sockets 18 is provided by an electric supply line 19 as well 
as a plug contact 20 disposed between the oven muffle 1 and the oven door 
3. In order to obtain optimal illumination of the baking space 5, the 
outside of the window strut 16 in the vicinity of the lighting devices is 
constructed as a reflector and has oblique reflector surfaces 21. Arrows 
indicate the maximum illumination of the baking space 5 by the rays of 
light emanating from the bulbs 17. As the drawings show, the food 6 is 
optimally illuminated from both sides of the viewing window 15 and the 
lighting device or devices themselves need not be visible from outside. 
To this end, the outer glass panel 14 is only transparent in the vicinity 
of the viewing window 15, while it is colored outside the viewing window. 
The lighting devices are effectively protected from being spattered by the 
food 6 because the lighting devices are covered by the inner glass panel 
13. Since low-voltage bulbs are used, very little space is required for 
accommodating the lighting devices. The illumination of the baking space 5 
is of the best possible quality, especially when halogen lamps are used. 
Increased safety is provided because low voltage is used. Furthermore, the 
lighting device is relatively insensitive to jarring. 
In the embodiment of FIG. 2, part of the oven muffle is shown having a side 
muffle wall 22, a muffle flange 23 and a rear muffle wall 24. The oven 
muffle is again surrounded by a thermal insulating layer 4. In the FIG. 2 
embodiment, lighting devices are disposed in the two opposite side muffle 
walls 22. To this end, a lamp socket 18 is mounted behind a small opening 
25 in the muffle wall 22, or in a small reflector plate representing a 
part of the muffle wall 22. The lamp socket 18 is surrounded on the sides 
and toward the back by the practically uninterrupted thermal insulating 
layer 4. The opening 25 is used for plugging in a low-voltage bulb 17 in 
the form of a halogen lamp, which in the illustrated embodiment is plugged 
into the opening 25 in a practically flush manner with a tapered base 
portion 27. The bulb is provided with electrical contact via its 
electrical connection elements 28 in the lamp socket 18. The electrical 
supply line 19 leading away from the lamp socket 18 is disposed within the 
thermal insulating layer 4. In the illustrated embodiment, a low-voltage 
halogen lamp is once again used that has an operating voltage of 12 V and 
an installed power of 5 watts. Virtually all of the bulb 17 protrudes into 
the baking space 5 and is surrounded by a curved glass covering 29, which 
may be screwed into a tubular thread of the muffle wall in a 
non-illustrated manner or secured on the muffle wall in some other manner. 
A reflector plate 26 substantially closes a larger opening 30 for the 
glass covering 29 and reflects the rays of light emanating from the bulb 
17 in the direction toward the baking space 5. At the same time, the 
reflector plate forms a barrier for the heat or thermal radiation 
emanating from the baking space 5. A curved shade 31 projecting from the 
reflector plate and shielding the bulb 17 from the oven door is directly 
connected with the reflector plate 26, so that the bulb cannot be seen by 
the observer. 
In the embodiments described above, the standard main or network voltage 
must be transformed to a low voltage value. A transformer required for 
this purpose is installed at some suitable point, or the transformer 
already provided for the control panel of the oven may be used for this 
purpose as well. 
It is naturally possible within the scope of the invention to form the 
small opening 25 directly in the muffle wall. It is also possible for the 
lighting device described above to be used for ovens in which the food to 
be baked is heated by means of microwave energy, or with a combination of 
thermal and microwave energy. In these cases, it is an advantage that 
destruction of the bulb which protrudes virtually unprotected into the 
baking space due to the microwave energy is prevented because of the small 
size of the low-voltage bulbs, which may be halogen lamps. A further 
advantage is that when the bulb is disposed on the inside, microwave 
radiation out of the oven space is prevented without entailing complicated 
means of protection. 
FIG. 3 shows a portion of the side muffle wall 22 of a baking oven, with 
exclusively microwave heating or combined microwave and thermal heating. A 
covering 33, which rests with a cantilevered-like bent-over flange 34 on 
the rear or outer surface of the muffle wall 22, is inserted into an 
opening 32 formed in the muffle wall, from outside the muffle wall 22. A 
dome-like portion of the covering 33 is provided with a great number of 
openings 35 in grid-like fashion and protrudes into the baking space 5. A 
retainer ring 36 is mounted on the inside of the muffle wall 22 and has 
four stay bolts 37 with threads, for example, disposed about the periphery 
thereof. The stay bolts 37 can be welded to the retainer ring. Mounted on 
the stay bolts 37 and on the flange 34 is a holder plate 38 which holds a 
lamp socket 39 in the middle portion thereof. The holder plate 38, which 
is preferably formed of sheet aluminum, has an extension 40 bent over at 
right angles, which passes through most of the covering 33 and is 
constructed in gable or roof-like fashion, as shown in FIG. 3. The inside 
of the extension 40 provides a reflector 41 for the bulb 17 and the 
outside thereof has a shade oriented toward the baking oven door, through 
which the bulb 17 and especially the halogen lamp is shielded from the eye 
of the observer. The covering 33 prevents the escape of microwaves through 
the opening 32 of the muffle wall. The aforementioned parts are braced 
against one another and against the muffle wall 22 by means of nuts 42. 
The foregoing is a description corresponding in substance to German 
Application No. P 36 43 371.3, dated Dec. 18, 1986, the International 
priority of which is being claimed for the instant application, and which 
is hereby made part of this application. Any material discrepancies 
between the foregoing specification and the aforementioned corresponding 
German application are to be resolved in favor of the latter.