Specification
The present invention concerns a cooking appliance with at least one gas sensor
array and a sampling system for a cooking appliance with at least one gas sensor array.
Furthermore, the invention concerns a method for cooking with the cooking appliance
according to the invention, as well as a method for cleaning the same.
The ability to track the cooking process of cooking products exactly, for example
in order to determine the desired final cooking state and to remove the cooking product
from the cooking appliance in time, is of great importance especially for large kitchens
and canteen operations. Namely, if the desired final cooking state is not realized,
frequently the cooking product has defective taste, for example a degree of browning that
is too strong, and in the extreme case it has to be discarded completely. In the case of
large cooking product loads, as is customary in large kitchens, the economic damage is
not insignificant. A frequent cause is that the cooking processes cannot be standardized
completely, which again can be attributed to the non-uniform size of cooking products,
different initial cooking states and the rarely completely uniform total amount of cooking
products to be cooked.
In order to achieve reproducible cooking results nevertheless, independently of
the type, size and number of the cooking products used, so-called cooking process
sensors are used increasingly, for example, in the form of core temperature sensors. Such
cooking process sensors are described, for example, in DE 202 04 393 Ul, DE 299 23
215 Ul or DE 199 45 021. With the aid of these core temperature sensors, using
predetermined guide values, one can determine when a cooking product has reached the
desired predetermined target cooking temperature in its core during a cooking process.
For this purpose, it is generally required that the core temperature sensor is inserted
mechanically into the cooking product in such a way that it actually reaches to the center
of same. Naturally, in this type of measurement the cooking product is partially
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destroyed by the insertion process. Frequently, even after the end of the cooking process,
the insertion point can be recognized on the surface of the cooking product. Since the
core temperature sensor is often located in the inner cooking compartment during the
entire cooking process, sometimes injury to the operating personnel occurs due to
inattention. Also, the insertion of the cooking process sensor during the cooking process
is not always optimal, so that, for example, the cooking process sensor is inserted at a
distance from the actual center of the cooking product. Furthermore, it may occur that
the core temperature sensor cannot be placed at all into the cooking product because of its
small cross-section. Also, the core temperature is not necessarily representative of the
state of cooking, that is, a correlation between the core temperature and the state of
cooking is possible only with accurate knowledge of the cooking product.
At the present time, an attempt is also being made to determine the state of
cooking of foods with the aid of gas sensors. In any case, these efforts at the present time
have not gone beyond the project stage. For example, in the project supported by the
Federal Ministry for Education and Research of the Federal Republic of Germany
"Sensor system for the control of frying, baking and roasting processes with the aid of
primary aroma standards" it is supposed to be determined if, with the aid of suitable gas
sensors, the time endpoint of cooking can be determined during the cooking of foods with
the aid of the odor of the finished food. Within the framework of the above project,
furthermore, the process of roasting of coffee as well as the product control of foods with
the aid of gas sensors was investigated (see also wvvw.mst-innovationen.de, Infoborse,
Mikrosystemtechnik, 43 - 2003, L. Heinert, N. Felde, "Use of semiconductor gas sensors
for the recognition of roasting, frying and baking processes in the food industry
(SPAN)").
In the method named above, use is made of the fact that when foods are heated
numerous volatile substances are liberated, but normally only a few of these contribute to
their characteristic odor. For example, the odor of butter is composed of a total of 230
volatile substances, but only a total of 19 of these can be described as contributing to the
odor (L.M. Nijssen et al., Volatile Compound in Food, 7th Edition, TNO Nutrition and
Food Research Institute, Zeist, The Netherlands). Such odorants can be detected with the
aid of metal oxide gas sensors, for example based on tin dioxide or zinc oxide (see also T.
Hofmann et al., "High resolution gas chromatography/selective odorant measurement by
multisensor array (HRGC/SOMSA): a useful approach to standardize multisensor arrays
for use in the detection of key food odorants", Sensors and Actuators B 41 (1997), pages
3

81 to 87). The method described above is based on the use of so-called chemical leads.
The characteristic components or basic structures responsible for the odor are recognized
here by the gas sensors used in order to be able to derive the desired conclusions from the
detected signals. This requires, at least in the beginning, the parallel use of an HR gas
chromatograph. As soon as the basic structure signal determined with the gas
chromatography can be assigned to the corresponding signal of the gas sensor, the use of
the gas chromatograph can be omitted.
As described by Lemme in Elektronik/17 2002, pages 42 to 48, when using a gas
sensor array called KAMINA of the Karlsruhe Research Center, the prior determination
of guide components is eliminated. Rather, the patterns detected with this gas sensor are
simply compared to one another. Located above a frying pan that is filled with steaks,
the above KAMINA sensor array, after an initial learning phase, should be able to
determine the various states of frying from "raw" through "medium" and "well done" to
"overdone." The heating of the frying pan should shut off automatically exactly at the
desired moment with the aid of the said sensor array. Information on further suitability of
the described sensor array for the determination of states of cooking are not described in
the quoted literature citation or in the German Patent Application DE 44 23 289 Cl based
on the above gas sensor. It is already questionable if the possibilities of use of this type
of sensor can be extended to completely different types of situations. For example, the
cooking atmosphere in the internal compartment of especially industrial cooking
appliances is not comparable to the atmosphere existing above an open frying pan. This
applies even more to the so-called convection cooking appliances in which regularly a
rapidly-rotating fan is used. Also, the moisture content in such appliances is usually very
high and is not infrequently in the saturation range. So far, in such hot air convection
steam appliances the cooking process could be controlled somewhat satisfactorily only
with the aid of core temperature sensors. Accordingly, the gas sensors that are used in
cooking appliances in US 6,784,404 and US 2004/0144768 Al are used exclusively for
the determination of the carbon monoxide content, with the purpose of being able to
establish the duration of the cleaning cycle of a self-cleaning cooking appliance by
determination of the degree of contamination of the cooking compartment.
It would therefore be desirable, especially also due to the inadequacies observed
when using core temperature sensors, to have a means for monitoring the cooking process
that yields reproducible, reliable results, without having to specify previously the cooking
product, for example regarding size or initial cooking state.
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For example, a multifunctional sensor is known from US 4,378,691 which
comprises a single sensor element which is heated by a heating element. This sensor
element can be used to control a cooking appliance as a function of the moisture content
in a cooking compartment.
In DE 103 07 247 Al, a vapor ventilation hood of an electric oven with a waste
air tube is disclosed which has a number of sensors that are designed for the evaluation of
gaseous media or substances in the gaseous media. Based on the data detected and
evaluated through the sensor, a fan in the exhaust tube of the electric oven can, for
example, be controlled. Similarly, according to DE 103 07 247 Al, based on the
measured data, the power of the electric oven can be controlled.
US 6,170,318 Bl discloses a generic cooking appliance as well as generic
sampling system using a gas sensor array with a number of gas sensors, which is
supposed to be able to detect various substances after a learning phase. For example,
such a gas sensor array can be used in a microwave appliance or a roasting appliance in
order to control the corresponding cooking appliance based on the measured data or to
determine if a cooking product is still fresh.
Therefore, the task of the present invention is to further develop the generic
cooking appliance or the generic sampling system in such a way that the disadvantages of
the state of the art are overcome. Especially, a contactless control of a state of cooking
should be permitted independently of external disturbing influences, above all also for
larger cooking product loads in the internal chamber of a cooking appliance and greater
process reliability should be provided.
The task concerning the cooking appliance is solved by the characteristics of
Claim 1.
Advantageous embodiments of the cooking appliance according to the invention
are described in Claims 2 to 20.
Fundamentally, all cooking appliances that have an inner cooking compartment
and an installation compartment come into consideration as starting point for the cooking
appliances according to the invention. Especially preferred are those cooking appliances
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that are further equipped with at least one aeration system, that is, so-called hot air
convection steamers. Suitable hot air convection steamers which form the starting basis
of the cooking appliances according to the invention, are described, for example, in DE
196 515 14 Al. The fan wheels used in conventional hot air convection steamers
operating at high velocities sometimes produce very high air velocities in the inner
cooking compartment, as a result of which sometimes fat and other liquid droplets are
swirled in the inner cooking compartment.
Naturally, a memory and evaluation unit as well as a control system of a cooking
appliance according to the invention can be present in a single processor. With the aid
the control system, for example, the heating of the cooking compartment, the speed of the
fan, the steam generator, the aeration, for example with fresh air, the misting nozzle
and/or the cleaning nozzle can be controlled.
A cooking appliance according to the invention, comprising at least one gas
sensor array, permits the monitoring of the gas atmosphere in and at the cooking
appliance and thus can orient itself both with respect to guide structures, the signal of
which was previously determined and entered into the memory unit of the cooking
appliance, as well as preferably with regard to the entirety of the detected signal. In the
latter case, the desired information is determined without the use of a guide structure,
based on the change of the complex signal pattern over time during the cooking process,
for example, in order to be able to draw conclusions about the state of cooking. That is, a
number of signals originating from volatile, especially oxidizable and/or reducible
substances, are regularly recorded with the gas sensor arrays. Signals of certain
individual compounds cannot be extracted from these total spectra. Generally, this is also
not required due to the detection of the total patterns by the sensor array. At least two,
especially a multiple number of individual sensors or sensor segments of a gas sensor
array yield a different measured signal under essentially identical conditions and for an
essentially identical atmosphere to be measured. In this way, a characteristic total
measurement result is obtained for each specific situation or atmosphere to be measured.
Frequently, even 5 to 100, for example also 10 to 50 individual sensors or sensor
segments, are sufficient for the recording of signal patterns with sufficient information
about a time period.
In order to be able to draw a conclusion about a state of cooking, generally first of
all a so-called learning phase is required. The states to be determined in the cooking
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appliance, especially the cooking states, will hereby be first run experimentally and the
time development of the detected signal pattern for an optimum cooking process as
normal state is determined and stored. Then the time courses of the signal patterns for
cooking processes that deviate from this optimum state are determined and stored.
Accordingly, if in a cooking process the time change of the detected signals remains
within the desired limits or tolerances, the intended desired cooking process control is
being maintained. Otherwise, alternative solutions are used. Thus, it is of particular
importance to follow the time development or time change of the entirety of the detected
signals. In general, it is sufficient to perform the above learning phase for a certain
cooking appliance type only once. The obtained signal patterns can then easily be used
for all other cooking appliances and for example can be entered into their memory unit.
It was found to be especially advantageous when at least one gas sensor array is
introduced into the inner cooking compartment, in the installation compartment, in the
aeration system and/or outside the cooking appliance.
Also preferably the gas sensor array has several fields made of a semiconducting
metal oxide film, each of which are connected to two electrodes, whereby the fields form
an essentially continuous flat surface, the electrodes have a band-shaped form and the
continuous surface is divided into fields in such a way that each field in the continuous
surface is delineated by two electrodes in each case.
Correspondingly, suitable gas sensor arrays may comprise an arrangement of
several, for example eight, individual sensors, which are arranged pairwise on a silicon
chip. Each of these individual sensors consists of one or several of the semiconducting
oxides SnO2, ZnO, TiO2, WO3 and is applied as a thin film on the chip, which is covered
at least partially with palladium or platinum as catalyst. All the individual sensors used
differ in their composition or in their structure. Upon contact with the gases measured,
the conductivity of the semiconducting oxides changes as a function of their composition
and of the catalytic palladium coating that is optionally applied on them; therefore, each
individual sensor in contact with a gas to be measured provides a different signal, which
is proportional to the change of the conductivity. Such a gas sensor array is described,
for example, in X. Wang et al., Sensors and Actuators B 13 - 14 (1993) 458 - 461.
Especially preferred for use are those gas sensor arrays in which different fields,
comprising semiconducting metal oxide thin films, each of which is connected to two
7

electrodes, will show different changes in conductivity upon contact with reducing or
oxidizing gases as a function of the temperature, composition, dosage and/or coating.
The sensitive layer of a preferred gas sensor array is composed especially of a
single continuous layer of one or several semiconducting oxides, for example tin dioxide,
whereby this continuous layer is subdivided into individual fields by band-shaped
electrodes. The electrodes can be applied directly to or below the surface of the
continuous layer. The continuous surface is divided into the above fields especially in
such a way that each field in the continuous surface is delineated preferably by two
electrodes. According to one advantageous embodiment, the gas sensor array is provided
with a coating, the permeability of which for reducing or oxidizing gases changes
continuously between the two outer electrodes.
Especially in the analysis of complex gas systems, it is advantageous when the
individual fields of the sensor array differ from one another in their structure or in their
composition. Each field then will provide a different change in conductivity in
comparison to the other fields, when the sensor is brought into contact with a single gas.
A different composition of the fields can be achieved, for example, by evaporation of
noble metals, that is, a doping of the metal oxide film over time periods of different
lengths. A continuous change of the composition along the continuous surface of the gas
sensor array can be achieved with the aid of chemical vapor deposition.
It can also be of advantage to adjust the sensitivity of a gas sensor array for
certain gases by application of certain temperatures, especially by application of different
temperatures to the different fields. For this purpose it should be mentioned first of all
that the sensitivity of a gas sensor array is fundamentally high when:
a strong change in the signal of the gas sensor array, for example in the
resistance of an individual sensor, can be recognized as a function of the
time of a progressing chemical reaction;
a signal of the gas sensor array is strong in itself, that is, a defined
concentration produces as strong a signal as possible;
different, simultaneously-produced gases produce signal patterns in the gas
sensor array that are as different as possible, or
8

the detection limit of a gas is so low that the identification of the gas can be
done even at low concentrations.
It has been found that one and the same sensor of a gas sensor array has opposite
sensitivities for different gases depending on the temperature, as a result of which the
temperature of each sensor should be adjustable advantageously. For this purpose, the
temperature of each field of the gas sensor array should be determined, for example,
using a thermocouple, and each field then can be heated in a designed manner, for
example with the aid of a heating wire.
Especially suitable gas sensor arrays are described, for example, in DE 44 23 289
Cl and are also known as the so-called Kamina sensors of the Karlsruhe Research
Center.
According to a further aspect of the present invention, the cooking appliances
according to the invention are also characterized by at least one second line for the
atmosphere from the installation compartment to at least one first, second, third and/or
fourth gas sensor array, at least one third line for the atmosphere from the aeration system
to at least one first, second, third and/or fourth gas sensor array and/or at least one fourth
line for the atmosphere surrounding the cooking appliance to at least one first, second,
third and/or fourth gas sensor array.
Furthermore, suitable cooking appliances are equipped with at least one first
discharge from the first, second, third and/or fourth gas sensor array.
In order to protect the measuring surface of the gas sensor array against
permanent contamination, it was found to be advantageous to install at least one filter in
front of at least one gas sensor array, especially in front of its measuring surface, and/or
to install it at the inlet to the first, second, third and/or fourth feed. Suitable filters are, for
example, plastic membranes, for example made of Teflon, ceramic filters, for example a
porous aluminum oxide ceramic, or metallic filters, for example a porous metal foam.
Sintered metal filters are especially suitable.
9

Furthermore, the cooking appliances according to the invention are characterized
by at least one valve that can be controlled with the control unit, at the inlet and/or in the
area of the second, third and/or fourth feed and/or the discharge.
With the aid of the above valves, especially in the course of the discharge, for
example the entry of waste air into the gas sensor array, can be prevented. The feeds to
the gas sensor arrays are preferably designed to be very short in order not to
unnecessarily delay or spread the detected signal.
Suitable cooking appliances comprise in another embodiment in addition at least
one pump unit in working connection with a first, second third and/or fourth line for the
transportation of the atmosphere to be analyzed to the gas sensor array(s). For example,
with the aid of a pump, the atmosphere from the cooking compartment or the installation
compartment or even outside air can be introduced to the gas sensor array through a filter
that does not change the characteristic composition of the sample volume. In this case,
the filter may retain for example solid particles as well as fat and liquid droplets.
According to the invention it is also provided that at least two lines are connected
directly or indirectly to the gas sensor array.
For example, at least one sensor array is integrated in the inner wall of the inner
cooking compartment or the installation compartment. Naturally, in order to determine
or analyze the atmosphere in the area outside the cooking appliance, the gas sensor array
may also be present on the outer wall of the cooking appliance or can be integrated into
this wall. Furthermore, according to another embodiment, the gas sensor arrays arranged
in the inner wall or outer wall of the cooking appliance can also have feeds for the
purpose of introduction of the atmosphere to be analyzed. This is especially
advantageous when the gas sensor array does not lie on the wall surface but is integrated
into it. These feeds can also be used to introduce suitable filters before the gas sensor
array.
Preferably at least two inner walls of the inner cooking compartment are equipped
with a gas sensor array. In this way, the cooking progress can be detected depending on
the location.
10

The task concerning the sampling system is solved by a sampling system for a
cooking appliance comprising at least one first gas sensor array for detection of the
atmosphere from a cooking compartment of the cooking appliance, a second gas sensor
array for the detection of the atmosphere from an installation compartment of the cooking
appliance, a third gas sensor array for the detection of the atmosphere from an aeration
system of the cooking appliance and/or a fourth gas sensor array for the detection of the
atmosphere surrounding the cooking appliance and at least one feed for the atmosphere
from the cooking compartment to the first, second, third and/or fourth gas sensor array, at
least one second feed for the atmosphere from the installation compartment to the first,
second, third and/or fourth gas sensor array, at least one third feed for the atmosphere
from the aeration system to the first, second, third and/or fourth gas sensor array, and/or
at least one fourth feed for the atmosphere surrounding the cooking appliance to the first,
second, third and/or fourth gas sensor array, whereby at least one valve is arranged at the
inlet and/or in the area of the first, second, third and/or fourth feed.
Hereby at least one discharge from the first, second, third and/or fourth gas sensor
array can be provided, whereby preferably at least one valve is arranged at the inlet
and/or in the area of the discharge.
With the invention, it is also proposed that at least one filter [be arranged] before
at least one gas sensor array, especially before its measuring surface and/or in or on the
inlet of the first, second, third and/or fourth feed.
Furthermore, it can be provided that at least one valve is controllable.
With the invention it is also proposed that at least one pump unit [be arranged] in
combination with the first, second, third and/or fourth feed for the transportation of the
atmosphere to be analyzed to the gas sensor arrays.
Preferred sampling systems according to the invention are characterized by the
fact that the gas sensor array comprises several fields consisting of semiconducting metal
oxide film, each of which is connected to two electrodes, whereby the fields form an
essentially continuous surface, the electrodes have a band-like shape and the continuous
surface is divided into fields in such a way that each field is delineated in the continuous
area by two electrodes.
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According to the invention it is also proposed that different sensors, sensor
segments and/or fields of each gas sensor array exhibit different conductivity changes as
a function of temperature, composition, doping and/or coating when they come into
contact with reducing or oxidizing gases.
Furthermore, it can be provided that the temperature of each sensor, sensor
segment and/or field of the gas sensor array be adjustable, preferably that a specific
temperature or a specific temperature profile can be applied to the gas sensor array.
With the invention it is also proposed that each sensor, each sensor segment
and/or each field be in working connection with a preferably controllable thermocouple
and/or heating element.
Moreover, according to a further aspect, a method for the cooking of cooking
product with a cooking appliance according to the invention is proposed in which at least
the cooking compartment atmosphere is introduced to a sensor, sensor segment or field of
at least one gas sensor array and is detected at intervals or continuously during the
cooking, the analysis result is compared in the evaluation unit with a standard stored in
memory unit and the cooking process is conducted as a function of the analysis result.
Hereby it can be provided that the analysis results do not deviate from a selected
standard or deviate only within a predetermined band width.
Furthermore, it can be provided that the temperature of the sensor, sensor segment
or field and/or of the standard used for comparison is/are varied, especially before or
during the cooking process.
Furthermore, it is proposed according to the invention that standards be stored in a
learning phase in the form of profiles or patterns of detected signals of each gas sensor
array, especially as a function of the type of cooking product, amount of cooking product,
cooking product quality and/or the desired degree of cooking, preferably for different
temperatures of each sensor, sensor segment and/or field.
It can also be provided that, after introduction of the cooking product into the
internal compartment of the cooking appliance, especially during a first heating phase,
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the nature and/or initial state of the cooking product be determined, especially during a
first heating phase, through the use of the gas sensor array(s).
Hereby it is proposed that the determined nature and/or the determined initial state
can be taken into consideration during the control of the cooking process.
Furthermore it is proposed with the invention that when the initial state of a
cooking product is qualified as spoiled, the cooking process be stopped and/or a warning
signal be emitted.
Furthermore, it can be provided that a cooking program is assigned to each
standard in a learning phase.
Thus, it is especially advantageous when, during learning, different temperature
profiles are applied to a gas sensor array, the signals of the gas sensor array are stored and
a cooking program is assigned to each signal pattern of the gas sensor array, which forms
a standard. In normal operation of the cooking appliance according to the invention, then
information from a control panel of it and from the gas sensor array are used to classify
chemical processes which occur in the cooking compartment by comparison with the said
standards. As soon as a classification has occurred, then one can use a suitable
experimentally determined temperature profile which optimizes the sensitivity of the gas
sensor array and makes the selection of an optimum cooking program possible. With the
aid of a multiple number of thermocouples and heating elements, the temperature profile
of the gas sensor array can be adjusted at any time, also many times during a cooking
process, namely when a classification is to be adapted.
For example, if according to an input through the control panel of a cooking
appliance in a time-controlled cooking program, only the moisture content in the cooking
compartment is to be controlled, then, according to the invention, the temperature profile
is selected automatically from a multiple number of stored temperature profiles with
which the H2O content of the cooking atmosphere can be determined as accurately as
possible, while larger hydrocarbons, which are themselves caused by the cooking of the
cooking product, should contribute as little as possible to the signal.
On the other hand, if it is entered through the control pattern that the meat is to be
roasted, and one can recognize from the profile or pattern of the gas sensor array that,
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with high probability, the meat is beef, then the control device of the cooking appliance
according to the invention will select automatically a temperature that has proven itself in
its sensitivity for roast beef. Hereby, larger hydrocarbons that occur during cooking
contribute especially strongly to the formation of the signal pattern.
A further aspect provides a cleaning method of a cooking appliance according to
the invention according to which, after the end of a cooking process, the degree of
contamination of the cooking compartment is determined through the gas sensor array(s),
and through the evaluation unit a cleaning program is selected that corresponds to the
degree of contamination and then this cleaning program is run by the control unit.
Hereby it can also be provided that the degree of contamination is determined by
a comparison with standards, preferably in the form of profiles or patterns of the signals
of each gas sensor array, these profiles having been stored specifically in a learning
phase.
With the previously outlined embodiments of the cooking appliance, sampling
systems or methods according to the invention, it is possible to detect odors at various
locations in or by the cooking appliance. This can be done either with the aid of several
gas sensors, optionally equipped with their own feeds for sampling, which are attached at
the measuring locations or with the aid of a number of feeds, which together serve a
central gas sensor array.
According to the invention an optimum cooking result is also obtained when the
atmosphere in the inner cooking compartment is disturbed or altered during the cooking
process, for example, by frequent opening and closing of the door of the cooking
compartment. Upon such changes in the cooking compartment atmosphere, which are
not known to the cooking appliance and/or are not stored in the memory unit, an error
message can be produced for the operating personnel. Furthermore, it is of advantage
that through the detected odor pattern during the initial heating of the cooking product, its
initial state, for example frozen, marinated, etc., can be determined. If it is determined
with the aid of the time development of the detected total pattern, that, for example, we
are dealing with a frozen product, first a thawing or heating phase can be initiated by the
control. If marinated product is detected, one can ensure that this is not overheated.
Also, in this early stage of the cooking process, it can also be determined if the food to be
14

cooked is possibly already spoiled and/or if poorly aged meat should possibly be exposed
to a holding phase in order to obtain the desired cooking result nevertheless.
Thus, it is an advantage that the initial state of the cooking product, for example
of the meat, no longer has to be determined by the user visually or haptically but can be
determined with the aid of the cooking appliance according to the invention.
Since the speed with which the known or stored signal courses change also
depends on the amount of the cooking products introduced into the inner cooking
compartment, already in the initial phase of the cooking product a so-called load
recognition can be performed with the cooking appliances according to the invention.
Then the cooking program can be adjusted individually to the determined load.
The determination of odorant compounds can also be used in order to detect the
surface state as well as the cooking of the particular cooking product. For example, if a
cooking product is already sufficiently browned, but cooking is not yet complete, the
cooking compartment temperature must be reduced correspondingly so that the browning
will not become too strong. From the detectable rate of the surface reaction and the rate
of cooking, furthermore, one can also determine the size of the cooking product.
Furthermore, it is of advantage that processes, such as flavoring, moistening or basting of
the cooking products no longer have to occur as a function of time but as a function of the
actual cooking state, always at the correct point in time. This process can of course also
be automated with the aid of the cooking appliances according to the invention.
Since the sampling at several locations in the cooking internal compartment can
be performed simultaneously or almost simultaneously, the operating personnel using the
cooking appliances according to the invention are easily informed as to whether the
cooking product is being cooked uniformly or if there are areas with more highly cooked
or less highly cooked cooking product. Using deflectable or adjustable deflectors, for
example, the cooking products that have been cooked less can be provided with energy in
a hot air convection steamer in a targeted manner.
With the aid of the gas sensor arrays used in the cooking appliance according to
the invention, after the end of the cooking process, the degree of contamination of the
cooking compartment can be determined. For example, a simple comparison of stored
initial state and end state can be used for this. With the aid of this degree of
15

contamination, a cleaning program can be proposed or carried out by the cooking
appliance automatically, adjusted to this degree of contamination. For example, if a high
fat content is detected, automatically a corresponding amount of emulsifier can be
proposed or used. Similarly, when a protein-containing contamination is detected, a
cleaning agent containing enzymes can be proposed.
Moreover, with the cooking appliance according to the invention, erroneous
operations as well as disturbances, for example smoldering odors, overheating or leakage
of the cooking system into the installation compartment as well as the cooking
compartment can be immediately detected. It has been found to be especially
advantageous that the initial state of cooking and the final state of cooking can generally
be determined and compared to one another, which gives an indication whether or not all
desired hygienic prerequisites have been observed.
For example, if a steam generator is used in a cooking appliance, with the aid of
the gas sensor array present in the cooking appliance according to the invention, the
quality of the water can also be determined directly.
Reliable data recording is provided especially through the combined use of at
least one pump, at least one filter and at least one valve.
Other characteristics and advantages of the invention follow from the
specification given blow in which practical examples of a cooking appliance according to
the invention are explained in detail with the aid of schematic drawings. The following
are shown:
Figure 1 is a schematic cross-sectional representation of a cooking appliance
according to the invention;
Figure 2 is a schematic cross-section of an alternative embodiment of a cooking
appliance according to the invention; and
Figure 3 is a representation of a gas sensor array in combination with essential
components of a cooking appliance according to the invention.
16

Figure 1 is a cooking appliance according to the invention in the form of a hot air
convection steamer 100, comprising a cooking compartment 1 with a cooking
compartment door 8 and a drain 10, an aeration system 7 as well as an installation
compartment 9. In this embodiment, a gas sensor array 2 is located in the installation
compartment 9. A gas sample to be analyzed from the cooking compartment 1, aeration
system 7, installation compartment 9 or at the atmosphere 11 outside the cooking
appliance 100 can be introduced to the gas sensor array 2 through lines 20, 22, 24 and 26,
separately or simultaneously. The sampling can be completed easily with the aid of
controllable valves 4 as well as a pump 3, which is connected after the gas sensor array 2.
It has been found to be advantageous to equip the feeds 20, 22, 24, 26 with suitable filters
5 or 6. For example, for the measurement of the atmosphere in cooking compartment 1,
it can be provided that, except for the valve 4 in feed 20, all other valves 4 are closed, so
that only the desired cooking compartment atmosphere is introduced to the gas sensor
array 2.
Alternatively, as shown in Figure 2, each sampling system can be equipped with
its own gas sensor array 2. In this variation, the atmosphere can be introduced to the
particular gas sensor array 2 from the cooking compartment 1 through feed 20, from the
aeration system 7 through feed 22, from the installation compartment 9 through line 24
and atmosphere 11 from outside the cooking compartment 100 through line 26. As
already explained in connection with Figure 1, the variation shown in Figure 2 is also
operated with filters 5 and 6, in the area of the inlets to feeds 20, 22, 24 and 26. With the
aid of separately controllable pumps 3, the introduction of the sample can be controlled
for each gas sensor array 2.
As can be seen from the embodiments of Figures 1 and 2, gas samples can be
taken simply at different locations in or on the cooking appliance 100, and can be
introduced either to a central gas sensor array 2 or separately to several ones of these.
Since the samples can be introduced from the internal compartment as well as the outside
of the cooking equipment 100 to the gas sensor array(s) 2 and measured, perturbations by
environmental influences in the determination of the optimum cooking process can, for
example, be avoided.
As can be seen in Figure 3, a gas sensor array 2, as can be used in a cooking
appliance 100 according to Figure 1 or Figure 2, can have a number of fields each of
which serves to detect a gas whereby the sensitivity to a specific gas can be adjusted
17

through a temperature profile which is applied specially in each case. The temperature
profile can in this way be selected or adjusted depending on the type of cooking product,
such as beef, pork, fish or poultry, according to a degree of cooking, determined by the
core temperature and/or the browning, or similar, for example through a control panel
101 of the cooking appliance 100, and namely preferably with the connection of a control
or regulation device 102 of the cooking appliance 100 in between. An adjustment control
of the temperature profile 200 is then also possible depending on the output data of the
gas sensor array 2 itself. Thus, during a cooking process, one can optimize the sensitivity
and thus optimize the assignment of a cooking process to a standard cooking process and
finally arrive at a special cooking program, which in the end ensures that one obtains
reproducible, good cooking results.
The characteristics of the invention disclosed in the above specification, in the
drawings as well as in the claims can be essential both individually as well as in any
arbitrary combination for the realization of the invention in its various embodiments.
18

Reference list
1 Cooking compartment
2 Gas sensor array
3 Pump
4 Valve
5 Filter
6 Filter
7 Aeration system
8 Cooking compartment door
9 Installation compartment
10 Drain
11 Atmosphere
12 Discharge
20 Feed
22 Feed
24 Feed
26 Feed
100 Cooking appliance, hot air convection steamer
101 Control panel
102 Control or regulation device
200 Temperature profile
19

Patent Claims
1. Cooking appliance (100) comprising at least one cooking compartment (1), at
least one installation compartment (9), at least one gas sensor array (2) with at
least two separate, different individual sensors and/or with at least one coherent
sensor field with at least two different sensor segments for the detection of the
atmosphere of the cooking compartment (1), the atmosphere of the installation
compartment and/or of the atmosphere (11) surrounding the cooking appliance
(100), at least one memory unit for storing the signals detected by the gas sensor
array (2), at least one evaluation unit for processing the detected signals, at least
one control unit for controlling the cooking processes or cleaning processes
depending on the evaluated signals and at least one first feed (20) for the
atmosphere from the cooking compartment (1) to the gas sensor array (2) with
at least one valve (4) at the inlet and/or in the area of the first feed (20).
2. Cooking appliance (100) according to Claim 1, characterized by the fact that the
cooking appliance (100) comprises an aeration system (7) for the cooking
compartment (1) whereby preferably the atmosphere of the aeration system (7)
is detectable by the gas sensor array (2).
3. Cooking appliance (100) according to Claim 1 or 2, characterized by a first gas
sensor array (2) for the detection of the atmosphere of the cooking compartment
(1), a second gas sensor array (2) for the detection of the atmosphere of the
installation compartment (9), a third gas sensor array (2) for the detection of the
atmosphere of the aeration system (7) and/or a fourth gas sensor array (2) for
the detection of the atmosphere (11) surrounding the cooking appliance (100),
whereby preferably at least one gas sensor array (2) is arranged in the cooking
compartment (1), in the installation compartment (9), in the aeration system (7)
and/or outside the cooking compartment (100).
4. Cooking appliance (100) according to one of the previous claims, characterized
by at least one second feed (24) for the atmosphere from the installation
compartment (9) to the first, second, third and/or fourth gas sensor array (2), at
least one third feed (22) for the atmosphere from the aeration system (7) to the
first, second, third and/or fourth gas sensor array (2) and/or at least one fourth
20

feed (26) for the atmosphere (11) surrounding the cooking appliance (100) to
the first, second, third and/or fourth gas sensor array (2).
5. Cooking appliance (100) according to Claim 4, characterized by the fact that at
least two feeds (20, 22, 24, 26) are connected to a gas sensor array (2), directly
or indirectly.
6. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that
at least one gas sensor array (2) is integrated into the inner wall of the cooking
compartment (1), of the installation compartment (9) and/or in the outer wall of
the cooking appliance (100).
7. Cooking appliance (100) according to Claim 6, characterized by the fact that in
at least two inner walls of the cooking compartment (1) at least one gas sensor
array (2) is integrated.
8. Cooking appliance (100) according to one of the previous claims, characterized
by at least one pump unit (3) in working connection with the first, second, third
and/or fourth feed (20, 22, 24, 26) for transport of atmosphere to be analyzed to
at least one gas sensor array (2).
9. Cooking appliance (100) according to one of the previous claims, characterized
by at least one filter (5, 6) in front of at least one gas sensor array (2), especially
in front of its measuring surface, preferably in or at the inlet of the first, second,
third and/or fourth feed (20, 22, 24, 26).
10. Cooking appliance (100) according to one of Claims 3 to 9, characterized by at
least one first discharge (12) from the first, second, third and/or fourth gas
sensor array (2).
11. Cooking appliance (100) according to one of Claims 4 to 10, characterized by at
least one valve (4) at the inlet and/or in the area of the second, third and/or
fourth feed (22, 24, 26) and/or of the first discharge (12).
24

12. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that
each valve (4) can be controlled with the control unit.
13. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that
the memory unit, the evaluation unit and/or the control unit is/are arranged in
the installation compartment (9), preferably integrated into a control or
regulation unit (102).
14. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that
each gas sensor array (2) comprises several fields of a semiconducting metal
oxide film, to each of which two electrodes are connected, whereby the fields
form an essentially continuous surface, the electrodes have a band-like shape
and the continuous surface is divided into fields in such a way that each field in
the continuous surface is delineated by two electrodes.
15. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that
different sensors, sensor segments and/or fields of each gas sensor array (2)
exhibit different conductivity changes as a function of the temperature,
composition, doping and/or coating when they come into contact with reducing
or oxidizing gases.
16. Cooking appliance (100) according to Claim 15, characterized by the fact that
the temperature of each sensor, sensor segment and/or field is adjustable,
preferably manually through a control panel (101) of the cooking appliance
(100) and/or automatically through the evaluation unit and/or control unit (102).
17. Cooking appliance (100) according to Claim 15 or 16, characterized by the fact
that a certain temperature gradient selected from a multiple number of
temperature gradients or a certain temperature profile selected from a multiple
number of temperature profiles, that are preferably stored in the memory unit,
can be applied to each gas sensor array (2).
22

18. Cooking appliance (100) according to one of Claims 15 to 17, characterized by
the fact that
the temperature, the temperature gradient or the temperature profile can be
varied before or during a cooking process or cleaning process.
19. Cooking appliance (100) according to one Claims 15 to 18, characterized by the
fact that
that at least one thermocouple and/or at least one heating element is assigned to
one sensor, sensor segment and/or field of the gas sensor array (2) and/or can be
controlled by the control unit.
20. Cooking appliance (100) according to one of the previous claims, characterized
by the fact that this is a hot air convection steam cooking appliance.
21. Sampling system for a cooking appliance (100) comprising:
at least one first gas sensor array (2) for the detection of the atmosphere from a
cooking compartment (1) of the cooking appliance (100), a second gas sensor
array (2) for the detection of the atmosphere from an installation compartment
(9) of the cooking appliance (100), a third gas sensor array (2) for the detection
of the atmosphere from an aeration system (7) of the cooking appliance (100)
and/or a fourth gas sensor array (2) for the detection of the atmosphere (11)
surrounding the cooking appliance (100), and at least one first feed (20) for the
atmosphere from the cooking compartment (1) to the first, second, third and/or
fourth gas sensor array (2), at least one second feed (24) for the atmosphere
from the installation compartment (9) to the first, second, third and/or fourth gas
sensor array (2), at least one third feed (22) for the atmosphere from the aeration
system (7) to the first, second, third and/or fourth gas sensor array (2) and/or at
least one fourth feed (26) for the atmosphere (11) surrounding the cooking
appliance (100) to the first, second, third and/or fourth gas sensor array (2),
whereby
at least one valve (4) is arranged at the inlet and/or in the area of the first,
second, third and/or fourth feed (20, 22, 24, 26).
22. Sampling system according to Claim 21, characterized by at least one first
discharge (12) from the first, second, third and/or fourth gas sensor array (2),
23

whereby preferably at least one valve is arranged at the inlet and/or in the area
of the discharge.
23. Sampling system according to Claim 21 or 22, characterized by at least one
filter (5, 6) in front of at least one gas sensor array (2), especially in front of its
measuring surface, and/or at the inlet of the first, second, third and/or fourth
feed (20, 22, 24, 26).
24. Sampling system according to one of Claims 21 to 23, characterized by the fact
that
the at least one valve (4) is controllable.
25. Sampling system according to one of Claims 21 to 24, characterized by at least
one pump unit (3) in combination with the first, second, third and/or fourth feed
(20, 22, 24, 26) for transport of atmosphere to be analyzed to the gas sensor
array(s) (2).
26. Sampling system according to one of Claims 21 to 25, characterized by the fact
that
the gas sensor array (2) comprises several fields made of a semiconducting
metal oxide film, each of which is connected to two electrodes, whereby the
fields form an essentially continuous surface, the electrodes have a band-like
shape and the continuous surface is divided into fields in such a way that each
field in the continuous surface is delineated by two electrodes.
27. Sampling system according to one of Claims 21 to 26, characterized by the fact
that
different sensors, sensor segments and/or fields of each gas sensor array (2)
exhibit different conductivity changes as a function of temperature,
composition, doping and/or coating, upon contact with reducing or oxidizing
gases.
28. Sampling system according to Claim 27, characterized by the fact that the
temperature of each sensor, sensor segment and/or field of the gas sensor array
(2) is adjustable, preferably a specific temperature gradient or a specific
temperature profile can be applied to the gas sensor array (2).
24

29. Sampling system according to Claim 27 or 28, characterized by the fact that
each sensor, each sensor segment and/or each field is in working connection
with a preferably controllable thermocouple and/or heating element.
30. Method for the cooking of cooking product with a cooking appliance according
to one of Claims 1 to 20, characterized by the fact that
at least the cooking compartment atmosphere is introduced to a gas sensor array
(2) with at least two separate, different individual sensors and/or at least one
coherent sensor field with at least two different sensor segments and is detected
at intervals or continuously during cooking, the analysis result in the evaluation
unit is compared to a standard stored in the memory unit and the cooking
process is conducted depending on the analysis result.
31. Method according to Claim 30, characterized by the fact that the analysis results
do not deviate from a selected standard or deviate from it only within a
predetermined band width.
32. Method according to Claims 30 or 31, characterized by the fact that the
temperature of the sensor, sensor segment or field and/or of the standard used
for comparison is/are varied, especially before or during the cooking process.
33. Method according to one of Claims 30 to 32, characterized by the fact that the
standards are stored in a learning phase in the form of profiles or patterns of the
detected signals of each gas sensor array, especially as a function of the type of
cooking product, amount of cooking product, cooking product quality and/or
desired degree of cooking, preferably for different temperatures of each sensor,
sensor segment, and/or field.
34. Method according to one of Claims 30 to 33, characterized by the fact that, after
introduction of a cooking product into the internal compartment of the cooking
appliance, especially during a first heating phase, the type and/or the initial state
of the cooking product is/are determined with the gas sensor array(s).
25

35. Method according to Claim 34, characterized by the fact that the determined
nature and/or determined initial state is/are taken into consideration during the
control of the cooking process.
36. Method according to Claim 34 or 35, characterized by the fact that if the initial
state of a cooking product is qualified as spoiled, the cooking process is stopped
and/or a warning signal is given.
37. Method according to one of Claims 30 to 36, characterized by the fact that a
cooking program is assigned to each standard in a learning phase.
38. Method for the cleaning of a cooking appliance according to one of Claims 1 to
20, characterized by the fact that
after completion of a cooking process, the degree of contamination of the
cooking compartment is determined by the gas sensor array(s), a corresponding
cleaning program is determined by the evaluation unit corresponding to the
degree of contamination, and this cleaning program is carried out by the control
unit.
39. Method according to Claim 38, characterized by the fact that
the degree of contamination is detected by comparison with standards,
preferably in the form of profiles or patterns of the signals of each gas sensor
array, which are stored especially in a learning phase.

The invention relates to a cooking appliance which comprises at least one cooking compartment, at least one installation compartment, at least one gas sensor array having at least two separate, different individual sensors and/or at least one coherent sensor field including at least two different sensor segments for detecting the atmosphere within the cooking compartment, the atmosphere with the installation compartment and/or the atmosphere surrounding the cooking appliance, at least one storage unit for storing the signals detected by the gas sensor array, at least one evaluation unit for processing the detected signals, at least one control unit for controlling cooking processes or cleaning processes depending on the evaluated signals and at least one first feed line for the atomsphere from the cooking appliance to the gas sensor array including at least one valve at the inlet and/or in the area of the first feed line. The invention also relates to a sampling system for said cooking appliance, to a method for cooking using said cooking device and to a method for cleaning the same.