EP1802919B1 - Ventilation device - Google Patents

Description

Field of application and state of the art

The invention relates to a ventilation device, in particular an extractor hood, according to the preamble of claim 1.

From the DE 195 09 612 C1 Hoods are known which have a transmitter and a receiver, the transmitter emitting radiation that is registered by the receiver. In this case, the radiation received by the receiver is used to control a fan of the hood that the difference between the emitted radiation and the received radiation component is interpreted as a measure of the amount of exhaust gases in the exhaust air stream. Depending on this, the power supply to the fan is controlled.

The EP 0 443 141 B1 describes an extractor hood with a UItraschallsender and an ultrasonic sensor, in which the signal recorded by the ultrasonic sensors signal fluctuations for the control of a fan level are based. A disadvantage here is considered that the ultrasonic sensor is expensive and therefore the appli cation only in extractor hoods of the upper price segment comes into question.

The US 6170480 A1 describes an extractor hood with a light path, which is formed by a laser beam. This can be detected, for example, in the IR range, smoke and activated depending on the hood or be set more. Furthermore, temperature sensors or the like may be provided.

The US 3723746 A1 describes a device for detecting fire by means of a double light path. Here, a laser is advantageously used. It can be detected how a laser beam is diffracted by increasing the temperature in the air it traverses more or less. A corresponding deviation can then be used as an indication of too high a temperature.

Task and solution

The invention has for its object to provide a ventilation device of the type mentioned, with the disadvantages of the prior art can be avoided and in particular a low-cost and reliable way to detect a cooking process and the associated air pollution such as cooking hobs or Air movements over a cooktop is possible.

This object is achieved by a ventilation device having the features of claim 1. Advantageous and preferred embodiment of the invention are specified in the further claims and are explained in more detail below. The wording of the claims is incorporated herein by express reference. According to the invention, the transmitting device is designed to emit a laser beam. The use of a laser beam has proven to be advantageous both economically and technically. By emitting nearly parallel laser light through a laser light transmitter, a clearly defined intensity relative to the cross-sectional area of the laser beam can be achieved. This makes it possible to realize even longer measurement distances within the fan, without a reasonable evaluation is difficult due to a too wide expansion of the light cone. When the laser beam emitted by the transmitter encounters airborne contaminants such as cooking sparks or fluctuating airtightness gradients, it is refracted, diffracted, deflected and / or scattered. As a result, the power registered by the receiving device is opposite to the output power of the transmitting device changed. These changes in power and the frequency of power fluctuations are dependent on the amount of air contaminants and / or the amount of air movement along the measuring path, in the case of cooker hoods on the amount of cooking heat such as cooking fume and water vapor and so-called air streaks as a result of heat on the cooktop. Air streaks are characterized by air movement and air areas of different densities. The good recognizability of air streaks and air movements in the ventilation device according to the invention is particularly advantageous because it compared with a particle detection operation of the ventilation device can be initiated earlier or adjusted. If the occurrence of particles triggers the operation, there is a high risk that air pollution or cooking spills have already developed and escaped, so that they are no longer detected by the ventilation unit.

The use of a laser beam offers particular advantages, since the frequency of the laser beam is largely uniform, so that receiving devices can be used that are particularly adapted to the specific laser frequency or a narrow frequency range. It is thereby achieved that ambient light, which usually occurs in a wide frequency spectrum, does not lead to misinterpretations by a control device or a control circuit. In addition, the use of a laser beam also allows long and multiple redirected measuring sections, which allows a particularly fine-meshed detection of air pollution. From an economic point of view, the use of a laser beam is very advantageous. Laser modules today are mass products and therefore very reliable and are also available at low cost.

In a further development of the invention, the signal generated by the receiving device with respect to electrical characteristics such as its frequency, its voltage or its current depends on the power or intensity of the received radiation. Corresponding sensors and receiving modules which generate corresponding electrical signals as a function of light irradiation are known today. When using a control device with a microcontroller, for example, a receiving device can be used, whose output signal with respect to the voltage depends on the incident light. This signal is connected to an A / D converter input of the microcontroller and is thus processed by him. It may also be expedient to use a sensor whose frequency depends on the power of the received radiation, since no A / D converter is required for such a frequency measurement.

In one embodiment of the invention, the signal generated by the receiving device depends only on the incident radiation in a frequency range which largely corresponds to the frequency range of the laser beam. As a result, interference by ambient light or, for example, a built-in an extractor hood lighting are avoided. Technically feasible is the restriction to such a frequency range, for example by means of a filter which is arranged in front of a sensor in the receiving device or by means of special sensors, which are designed for an exclusive reception of light in the corresponding frequency range.

In a development of the invention, the receiving device has a photoelectric sensor, which preferably has a photosensor or a photodiode. Such sensors are state of the art and economically favorable.

In a development of the invention, the receiving device is equipped with filter means which limit the angular range in which incident light is registered by the receiving device. In addition to the use of corresponding planar filters, it is in particular also expedient to provide the receiving device with an angle narrowing device, which allows a light incidence only in a narrow angular range, for example, with a aligned in the direction of the laser beam hollow channel. The same is achieved by arranging the receiving device at the base of a bore provided for this purpose.

In a development of the invention, the drive can be activated and deactivated by the control circuit or the control unit and can be controlled with respect to its power, preferably continuously. Many combinations are conceivable and appropriate. For example, the control unit can be designed so that it fully automatically activates the drive for generating the air flow, if a corresponding need has been registered, and also adapts the required power accordingly. However, it is also possible that only the power of the drive is automatically controlled, but the activation and deactivation of the ventilation is done manually by an operator. A stepless control of the power allows a particularly needs-based operation. On the other hand, it is advantageous in controlling the power at various discrete stages that such control is simpler and less expensive.

In the invention, the control circuit or the control unit for evaluating the signal generated by the receiving device with respect to air streaks or air movements with different density gradients in the measuring section is formed. The control unit is designed in such a way that it interprets lower attenuation in such a way that air streaks are detected on the measuring section. To what extent the damping is due to streaks of air, can be concluded from other parameters such as the oscillation frequency. One for the evaluation of the signal with regard to air streaks or Luftbegung trained control unit activates a ventilation device in principle even at lower attenuation and thus allows in particular in a period of time at the beginning or even before the Luftverunrei ments a very convenient ventilation control. Preferably, the ventilation device is adjustable with regard to its behavior in order to be operated in the right situation and to the correct extent depending on varying environmental situations, for example use above hotplates or gas flames.

In one development of the invention, the control circuit or the control device for controlling the drive is designed as a function of the intensity or registered power registered by the receiving device. The power is compared for this purpose with the output by the transmitter power or intensity or egg ner set target power or target intensity, with a reduction as an indication of absorption, refraction and / or diffraction due to cooking turf or air streaks or Air movement is interpreted. The controller can be designed so that a reduced registered power is interpreted as an increased degree of contamination of the air, for example by cooking turf, and as a result the power of the drive is increased.

In an advantageous development of the invention, the control circuit or the control device for controlling the drive is formed as a function of the intensity or power registered by the receiving device over time. In particular, the use of the first derivative of power over time is superior to pure ventilation control based on registered power. Rapid changes in performance are due to turbulence in general or boiling in the area of the measuring section and are indicative of a high concentration of air contaminants such as cooking torrents or air movements. A control of the drive depending on the change the registered intensity or the registered power can also be combined with an evaluation of the intensity or the performance itself. Thus, both frequency and amplitude of the power curve over time are used to analyze the impurities on the measuring section. The inclusion of the change in power over time leads to a particularly well-demand-oriented control of the drive. Such a control based on the frequency of the power fluctuations can be realized, for example, by counting the number of intensity maxima or minima in a time segment of defined length and controlling the ventilation on the basis of the value determined thereby. In the context of cooker hoods for the kitchen sector, it has been found to be particularly expedient to interpret a high signal attenuation with slight oscillation of the signal as an indication of a large amount of vapors or strong air movement, which requires a high ventilation performance. A strong oscillation can be interpreted as a normal cooking operation or gradual termination of the cooking operation, depending on the degree of damping, so that the fan is expediently placed in a main use stage or in a residual suction stage.

In one embodiment of the invention, the transmitting device for emitting a laser beam is formed, the Leuchtpun kt in the receiving device has areas of very different intensity, preferably in the form of an interference pattern. Here maxima and minima can alternate, in particular generated by interference. Such a luminous spot can be registered by the receiving device not only with regard to whether the luminous spot strikes the receiving device or the sensor. In addition, a shift of the luminous spot on the photodiode leads to a characteristic of air streaks and particles in the measuring section result, without that the luminous point would have to be deflected so far that he leaves the photodiode. The particularly advantageous evaluation Interference patterns can be achieved by using a laser with a comparatively wide frequency spectrum. Although it may be desirable for other aspects of the invention to use a laser with a particularly narrow frequency spectrum, it may therefore also be advantageous, depending on the requirements, to use, for example, a multimode laser diode with a broad frequency spectrum.

In one development of the invention, the transmitting device and the receiving device are designed such that the receiving device always lies within the luminous point during operation. In such an embodiment, it is provided that not the luminous spot descending from the receiving device or the photodiode is intended to influence the output signal of the receiving device, but the movement of the luminous spot via the receiving device. In particular, in this case, the maxima and the minima of the interference image of the luminous point move across the sensor. The size of the sensor should be chosen so that it is smaller than the extension of the maxima and minima, which can also be influenced by optical aids such as lenses. The advantage lies in the fact that an accurate calibration of receiving device and transmitting device can be omitted and the susceptibility of such a ventilation device is very low. The registration of the movement of the luminous spot via the receiving device can take place, for example, by evaluating a moving interference pattern with maxima and minima. This can advantageously be used for control of the extractor hood with a corresponding control method which carries out an evaluation of the output values of the sensor in the event of an interference pattern moving over it.

In a development of the invention, the transmitting device and receiving device are designed such that the diameter of the luminous point a few mm wider than the receiving device, preferably at least 5 to 8 mm wider. As a result, a particularly low susceptibility is achieved. In the field of ventilation devices often find large manufacturing tolerances application. Due to the fact that the mode of operation of the transmitting and receiving device according to this development does not depend on the transmitting and receiving devices being at their desired position to the nearest millimeter, more favorable production methods can be used and no additional measures are required to obtain the correct one and to ensure highly accurate alignment of these facilities.

In a development of the invention, the control circuit or the control unit evaluate the output signal with regard to signal frequency and signal attenuation. This is particularly useful when using a laser beam that is so pronounced that it always rests on the receiving element in normal operation, and has a luminous point with areas of greatly varying intensity. In such a constellation, the registered intensity or the determined attenuation of the laser beam can be regarded as an indicator of the presence of steam and the frequency as an indicator of the presence of heat. Together, these parameters are well suited to assess the nature of the cooking process taking place under the ventilation device and to generate a correspondingly adapted airflow. A strong damping can be seen as a sign of intensive cooking operation and a high signal frequency as a sign of intensive frying operation.

In one embodiment of the invention, the transmitting device and the receiving device are arranged opposite each other on both sides of the air flow in the ventilation unit and the transmitting device radiates in the direction of the receiving device. This represents the simplest construction of transmitting device and receiving device. The transmitting device and the receiving device are preferably on opposite sides Arranged sides of the air flow, in particular centrally above the cooktop, so that the measuring section thwarts the air flow. Such an arrangement with direct alignment of transmitting and receiving device to each other is simple and less prone to interference.

In a development of the invention, the transmitting device and the receiving device are arranged so that a laser beam emitted by the transmitting device passes from the at least one reflecting device to the receiving device. The use of such a reflection device is expedient, since on the one hand it extends the measuring path and thereby permits a more accurate measurement. On the other hand, it allows a larger area of the fan to be included in the measurement. In addition, a reflection device allows the arrangement of transmitting and receiving device in the immediate vicinity of each other by sending and receiving device are arranged on one side of the fan. On the opposite side of the reflection device is arranged. In this way, it is also possible to form the transmitting and receiving device as a module, whereby the assembly and adjustment effort compared to the use of two separate modules is significantly reduced.

In a further development of the invention, at least two reflection devices are provided which are arranged and aligned such that a laser beam emanating from the transmission device passes at least twice reflected by at least one reflection device to the reception device. In this way, it is possible, with a small number of Reflektseinrichtun gene, preferably with two reflection devices to realize a long measurement path, which allows a reliable conclusion on impurities in the air such as cooking turf and movements of the air.

In a further development of the invention, the two reflection devices face each other and are arranged parallel to one another. It is thus possible to allow the laser beam to be reflected several times by both reflection devices. The reflection means may e.g. be arranged on the front and rear or on the left and right inside of the ventilation unit or the hood. By appropriately arranged and aligned transmitting and receiving devices, it is possible to allow the laser beam reflect so many times from one side to the other and thus to lay almost the entire cross-section of the ventilation device for subsequent evaluation by the control unit or the control circuit.

In a development of the invention, the transmitting device has a laser diode for emitting the laser beam, in particular a multi-mode laser diode. Multimode laser diodes emit light of different frequencies and, for technical reasons, are well suited for the proposed ventilation devices. The beam emitted by them has increased divergence and increased diffraction tendency due to increased wavelength dispersion compared to singlemode laser diodes. In addition, due to their frequency spectrum, they generate an interference pattern in the luminous spot, which, as described above, enables a particularly good evaluation with maxima and minima with low susceptibility to interference. The increased divergence and the interference pattern are particularly advantageous in the detection of air streaks. Particularly suitable for a good readability is a dot diameter of 5 mm to 15 mm, in particular 10 mm. Sharp focusing of the laser beam can be disadvantageous for air streak detection. To improve the air schlieren and air movement detection, it may be appropriate to provide means to further increase the divergence of the multimode laser diode.

In a development, the transmitting device has a collimator lens. This collimator lens allows the adaptation of the position of their focal point a convenient optimization of the transmitting device. The widening of the laser beam in the region of the receiving device can be varied by means of the position of the collimator lens and / or the focal point of the collimator lens. The laser beam can also be made slightly divergent. An increased expansion increases the sensitivity of the receiving device, in particular with regard to air movements, so that the control unit is supplied with a signal that can be interpreted more easily. The controller accordingly controls the fan very needs, especially even before steam. However, an expansion of the laser beam also leads to a lower light output received by the receiving device. By adapting the collimator lens with regard to position and type, it is possible to produce an optimum divergence of the laser beam with regard to light output as well as air streak and cooking wheel detection. When using a separate lens can be dispensed with a finished laser module and a cost-effective design of laser diode and lens can be provided.

In a further development of the invention, the divergence of the laser beam from the control unit or the control circuit is adjustable. Since the attenuation of laser beams of lesser divergence by air streaks is less than the attenuation of laser beams of high divergence, can be achieved by adjustability of the divergence that can be differentiated particularly reliably between attenuations due to vapors or particles on the one hand and air streaks or air movements. The control unit of such a ventilation device can therefore measure, for example, alternately the damping at high and low divergence and set in the case of a low attenuation, which is due only to air streaks, the fan in operation. The adjustability is preferably achieved via an adjustable lens.

In a further development, at least two transmitting devices are provided for emitting laser beams of different divergence. By two transmitting devices can be achieved with different divergence setting that the cause of attenuation on the measuring section is reliably detected. Compared to an embodiment with a laser beam which can be adjusted with respect to its divergence, the adjustability and the resulting increased complexity of the transmitting device can thereby be avoided. Preferably, both transmitting devices are directed to only one receiving device, which measures the incoming power of the laser beams either simultaneously or alternately. However, it may also be expedient to assign each transmitting device its own receiving device.

These and other features of preferred embodiments of the invention against its own accord from the claims and from the description and drawings, wherein the individual features are realized individually or in each case in the form of sub-combinations in one embodiment of the invention and in other fields and can represent advantageous and protectable versions for which protection is claimed here. The subdivision of the application into individual sections and intermediate headings does not limit the statements made thereunder in their generality.

Brief description of the drawings

Figur 1 und 2

teilweise geschnittene Ansichten einer ersten Ausführungsform der erfindungsgemäßen Dunstabzugshaube, bei welcher Sende- und Empfangseinrichtung an gegenüberliegenden Innenseiten der Dunstabzugshaube angeordnet sind und bei der ein Laserstrahl unmittelbar in Richtung der Empfangseinrichtung abgestrahlt wird,

Figur 3

eine Detailansicht der Empfangseinrichtung der in den Figuren 1 und 2 dargestellten Dunstabzugshaube,

Figur 4

eine teilweise geschnittene Ansicht einer zweiten Ausführungsform einer erfindungsgemäßen Dunstabzugshaube, bei der die Sende- und Empfangseinrichtungen als einheitliches Modul an einer Innenseite der Dunstabzugshaube angeordnet sind und bei der auf der gegenüberliegenden Seite der Dunstabzugshaube eine Reflektionseinrichtung vorgesehen ist,

Figur 5

eine teilweise geschnittene Ansicht einer dritten Ausführungsform einer erfindungsgemäßen Dunstabzugshaube, bei der die Sendeeinrichtung und die Empfangseinrichtung ebenfalls an der gleichen Innenseite der Dunstabzugshaube angeordnet sind, wobei es sich um getrennte und voneinander beabstandete Module handelt,

Figur 6

eine teilweise geschnittene Ansicht einer vierten Ausführungsform einer erfindungsgemäßen Dunstabzugshaube, bei der zwei parallele Reflektionseinrichtungen an gegenüberliegenden Innenseiten der Dunstabzugshaube vorgesehen sind,

Figur 7

eine schematische Darstellung eines Steuergeräts für ein erfindungsgemäßes Lüftungsgerät und mit diesem Steuergerät verbundener Komponenten,

Figur 8a und 8b

den Strahlengang eines Laserstrahls im Bereich einer Messstrecke,

Figur 9

eine Darstellung der Funktionseinheiten der Steuerung und Auswertung,

Figur 10

ein Diagramm von Messwerten des zeitlichen Verhaltens der Intensität des Empfangssignals,

Figur 11 und 12

schematische Darstellungen des Bewegens einzelner Lichtpunkte aus dem Interferenzbild des Lasers über die Empfangseinrichtung und

Figur 13

eine Aufteilung zwischen Dämpfung und Frequenz des Oszillierens des Signals an der Empfangseinrichtung entsprechend Figur 10.

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings shows:

FIGS. 1 and 2

partly sectional views of a first embodiment of the extractor hood according to the invention, in which transmitting and receiving device are arranged on opposite inner sides of the extractor hood and in which a laser beam is emitted directly in the direction of the receiving device,

FIG. 3

a detailed view of the receiving device in the Figures 1 and 2 illustrated extractor hood,

FIG. 4

a partially sectioned view of a second embodiment of an extractor hood according to the invention, in which the transmitting and receiving devices are arranged as a unitary module on an inner side of the hood and in which on the opposite side of the hood a reflection device is provided

FIG. 5

a partially sectioned view of a third embodiment of an extractor hood according to the invention, in which the transmitting device and the receiving device are also arranged on the same inside of the hood, which are separate and spaced-apart modules,

FIG. 6

a partially sectioned view of a fourth embodiment of an extractor hood according to the invention, in which two parallel reflection means are provided on opposite inner sides of the hood,

FIG. 7

a schematic representation of a control device for an inventive ventilation device and connected to this controller components,

FIGS. 8a and 8b

the beam path of a laser beam in the region of a measuring path,

FIG. 9

a representation of the functional units of the control and evaluation,

FIG. 10

a diagram of measured values of the temporal behavior of the intensity of the received signal,

FIGS. 11 and 12

schematic representations of moving individual points of light from the interference pattern of the laser via the receiving device and

FIG. 13

a division between attenuation and frequency of the oscillation of the signal at the receiving device accordingly FIG. 10 ,

Detailed description of the embodiments

The Figures 1 and 2 show in each case partially cut manner, a first embodiment of a ventilation device according to the invention in the form of an extractor hood 10. The hood 10 is arranged above a cooktop 12 with four cooking zones 14. The hood 10 extends almost over the full width of the hob 12 and covers about three quarters of its depth. The extractor hood 10 itself consists of a box-shaped, open at the bottom of the base 16 and an upper part 18, wherein the lower part 16 and the upper part 18 are connected to each other, the cooking hobs emanating from the hob 12 as steam and cooking fume in the lower part 16 of the hood 10 arrive and be forwarded from there to the upper part 18. In the transition region between the lower part 16 and the upper part 18, a filter mat 19 and a fan 20 are arranged, which sucks the kitchen vapors through the filter mat 19 in the upper part 18. In the lower part 16, a transmitting device 22 with laser and a receiving device 24 are arranged on the right and left inside. The transmitting device 22 is aligned in such a way that a laser beam 25 emanating from it is directed directly onto the receiving device 24.

If, in the cooking mode, cooking hobs rise from the cooking zones 14 of the cooking hob 12, they reach the lower part 16 of the extractor hood 10. The laser beam 25, which is permanently or periodically activated, is partially absorbed by these cooking hobs and partially diffracted and broken. This results in a reduced input power at the receiving device 24 compared to the output power.

However, even before cooking sparks are produced or have reached the area of the measuring section between the transmitting device 22 and the receiving device 24, due to the heat emanating from the cooking point 14, air movements occur in the region of the measuring section, which results in a diffraction of the laser beam. This also reduces the input power at the receiving device 24.

In one in the Figures 1 and 2 not shown, a signal generated by the receiving device 24 is fed to a control unit, which on the basis of the power difference between the output power of the transmitting device 22 and input power of the receiving device 24 and based on the time change of this power difference conclusions about the degree of air movement and the presence and the amount allows cooking hobs. Depending on the thus determined amount of air streaks and / or cooking turf controls this controller, the power supplied to the fan 20, wherein the power is increased when the air movement is intense or the amount of cooking turf is high. If the input power at the receiving device 24 has returned to the output power of the transmitting device 22 in the course of adjusting the air and is no longer subject to large fluctuations, the fan 20 can again be throttled or completely deactivated by the control unit. The FIG. 3 shows the receiving device in the Figures 1 and 2 shown extractor hood in an enlarged view. The receiving device has a tubular portion 29a whose major axis coincides with the axis of incidence of the laser beam 25. At the bottom of this tubular portion 29a is disposed a photoelectric sensor 26 which generates a corresponding signal depending on the incident power. At the opposite end of the tubular portion 29a, a filter 29b is arranged, which serves the filtering of the incident light and only in a certain, matched to the laser beam 25 frequency range incident light passes. When light of another frequency range is incident, it is absorbed by the filter 29b and therefore does not reach the photoelectric sensor. The same applies to light of any frequency which strikes the receiving device 24 from a direction 28 which deviates significantly from the direction of the laser propagation direction. By these two measures, the tubular portion 29a and the filter 29b, it is achieved that the signal emitted by the photoelectric sensor 26 is determined exclusively or almost exclusively by the incident power of the laser beam and not by the ambient light.

The FIG. 4 shows a second embodiment of an extractor hood according to the invention. In contrast to the first embodiment, in this the transmitting and receiving device are housed in a common functional module 29, which is arranged on an inner side of the lower part 16 of the extractor hood 10. On the opposite inner side of the lower part 16, a reflection device 30 is arranged. This reflection device can be, for example, a mirror or even a cat's eye. The laser beam 31, which is emitted by the functional module 29, is aligned in the direction of the reflection device 30. From this it is reflected in such a way that it deviates only slightly from its course before the reflection back to the Function module 29 passes. The integrated in this functional module 29 receiving device registers the returned power and are in the same manner as in the first embodiment, a dependent signal to an unillustrated control unit from. Advantage of this embodiment is that only one module must be connected to the controller. This saves wiring costs and bypasses design difficulties. Moreover, in the illustrated second embodiment, the measuring path is opposite to the embodiment shown in FIGS Figures 1 and 2 approximately twice as long, which leads to more reliable results.

The FIG. 5 shows a third embodiment of an extractor hood according to the invention. Compared to the second embodiment, which in FIG. 4 is illustrated, this embodiment differs in that the transmitting device 32 and the receiving device 34 are arranged as separate modules, but on the same inside of the lower part 16 of the hood 10. In turn, a reflection device 36 is provided on the opposite inner side, wherein it is arranged and aligned such that a laser beam 38 emanating from the transmitting device 32 strikes the receiving device 34 after the reflection. Although the illustrated embodiment has the disadvantage that transmitting and receiving device must be connected separately from each other with a control unit, not shown. However, the fact that the laser beam 38 does not run nearly parallel before and after the reflection by the reflection device 36 is advantageous. This enlarges the area through which the laser beam passes. As a result, it is more likely to reliably detect cooking turf from all hotplates and to make the control of the fan 20 well adjusted accordingly.

The FIG. 6 shows a fourth embodiment of an extractor hood according to the invention. This has a transmitting device 40 and a receiving device 42, which in turn are arranged on the same inner side of the upper part 16 of the extractor hood 10. Of the embodiments that are in the FIGS. 4 and 5 are illustrated, this embodiment differs in that both on the inside of the transmitting and receiving means 40, 42 and on the opposite side in each case a reflection means 44, 46 is arranged. The two reflection devices are aligned parallel to one another. The transmitting device 40 is oriented so that a laser beam 48 emanating from it is reflected several times by the reflecting devices 44, 46 before it reaches the receiving device 42. This leads to a relatively long measuring path, which allows particularly precise conclusions about the presence of cooking turf and the like. Moreover, it is possible with such or a similar structure to cover the area over the cooking plates 14 largely nationwide, so that even a local limited occurrence of cooking turfs can be registered quickly and reliably. Especially with such a structure, the use of a laser is ideal. Due to the small expansion of the laser beam 48 even long measuring distances can be realized without problems.

The FIG. 7 shows a control unit of an extractor hood according to the invention and components connected thereto. The control unit has a control circuit 50 which has various connections. A transmitting device 52 is connected to a PWM output 54 (pulse width modulation output) of the control circuit 50. In this way it is possible for the control circuit to specifically control the power of the transmitting device 52 and in particular of the laser integrated in the transmitting device 52. This allows a basic adjustment, in which the laser is adjusted so that a desired input power is registered at the receiving device, for example, the input power, the total irradiation of the entire surface of the sensor of the receiving device occurs. Connected to an A / D converter input 56 is a receiving device 58 which has at least one photoelectric sensor which varies the voltage supplied to the control circuit 50 as a function of the amount of incident light. On the basis of the measured values of the receiving device 58 received in this way, it is detected in the control circuit 50 by means of a circuit or program provided for this purpose whether cooking torrents are present on the measuring path between the transmitting device 52 and the receiving device 58 and what density or degree of turbulence they have. Depending on the result of this analysis, a fan motor 60 is actuated, the power of which can be influenced by the control circuit 50. When the amount of cooking torrents is high, the fan motor 60 is driven so that it sucks cooking power at high power.

The FIGS. 8a and 8b show the beam path of a laser beam 62 of a ventilation device according to the invention in the range of a measuring section between a transmitting device 64 and a receiving device 66. The transmitting device 64 has a laser module 68 and a collimator lens 70, which expands the laser beam 62 emanating from the laser module 68 somewhat. The laser beam 62 passes through the measuring path and hits the photoelectric sensor 72 in the receiving device. The photoelectric sensor 72 is formed with respect to its surface, and the laser beam 62 is adjusted so that the laser beam 62 is fully unbroken and undeflected from the photoelectric sensor 72 is detected and its surface is largely completely irradiated. The photoelectric sensor 72 generates an output signal for a control unit of the ventilation unit as a function of the registered power. This signal can in various ways pass on the information about the registered power, for example by a correspondingly adapted voltage, by an adapted frequency or by other electrical characteristics.

FIG. 8a shows the unbroken and undeflected state of the laser beam 62. In this state, the maximum power is registered by the photoelectric sensor 72 and passed a corresponding signal to the control unit, not shown. If such a signal is constantly transmitted to the control unit, this is interpreted by the control unit as meaning that there are no cooking sparks and water vapors on the measuring section and that no activation of a fan of the ventilation unit is required.

FIG. 8b shows a second state of the same measuring section. In this second state, water vapor 74 is on the measuring section. The laser beam 62 emanating from the transmitting device 64 is refracted by the various water vapor concentrations and therefore deflects, and thus only partially, onto the photoelectric sensor 72. A portion 62a does not strike the photoelectric sensor 72, so that the power registered by the photoelectric sensor 72 is only one of the photoelectric sensor 72 remaining portion is 62b. An electrical parameter which gives information about the size of this component is forwarded to the control unit in the form of a corresponding signal. This can then cause by means of an activation or a power control of the fan, the suction of water vapor. Likewise, the reference numeral 74 could also be used to designate air streaks, which are also partially visible to the naked eye.

From the FIGS. 8a and 8b is the pure deflection of the laser beam 62 and the consequent change in registered power apparent. The fan control can be such that this proportion is used directly as a criterion for the registration of air movements or air contaminants such as cooking turf and a direct relationship between registered power and air movements or air pollution is assumed. The control of the fan However, it can be done additionally or exclusively based on the dynamic change of the registered service. In such a controller, the control unit evaluates, for example, with which frequency and / or amplitude the registered power changes. The frequency of the power is particularly high with a large amount of cooking turf, so that a control of the fan as a function of the frequency leads to very good results.

One to the in the FIGS. 8a and 8b The evaluation system shown alternative methods show the Figures 9 with the schematic structure and the FIGS. 11 and 12 ,

Fig. 9 indicates by analogy FIG. 1 or 4 and FIG. 7 a transmitter 122 with a laser diode or a laser module. In front of it sits a collimator lens 123 from which the correspondingly expanded and parallel laser beam 125 exits. It is reflected at the reflector 130, which may also be a so-called cat's eye. Under certain circumstances, this can also be done several times, as previously stated. The reflected laser beam 15 passes through a Fresnel lens 127 to the receiver 124 and its sensor 92. The detected by the sensor 92 electrical signal is applied to the A / D converter input and thus to the control circuit 150. This control circuit 150 may be a microcontroller and, in addition to the control of the transmitter 122, control the motor or the power electronics 160 via the PWM output 154.

In this case, the intelligence sits in the control circuit in order to control the extractor hood on the basis of the above-described and above all described processes. This should be done automatically, in particular depending on the state of the cooktop 12 and both get along without intervention of an operator and perform the trigger function as efficiently and well.

In this method for determining ventilation requirements, the diameter of the laser light spots 90, the through the interference image and the Fresnel lens according to FIG. 9 are generated in front of the receiver, much larger than the photoelectric sensor 92. The FIGS. 11 and 12 show only a small portion of the luminous point 90. This is generated by a laser diode with a comparatively wide frequency spectrum, resulting in an interference pattern with maxima 94 and minima 96. This interference pattern is shown here as relatively irregular, which is usually the case in practice because of not optimal formation of the Fresnel lens and the other optical path. Irrespective of the actual size of the maxima 94, it is important to have the concrete distance from one another, ie the size of the minima 96.

If there is a deflection of the laser beam 125 by air movements or even particles such as steam on the measuring path, so very small shifts of the light spot 90 or thus the maxima 94 and minima 96 relative to the photoelectric sensor 92 sufficient to those by the sensor to significantly change the measured intensity. Since the maxima 94, so to speak, dance over the sensor 92, that is to say their movement path is much larger than their diameter and that of the sensor anyway, the sensor 92 detects less a time-averaged average intensity. Rather, the sensor 92 detects the multiple or frequent moving over of the various maxima as short peaks. Since the speed of the luminous point 90 and thus of the maxima 94 is relatively large and these cover the sensor essentially completely or not at all when moving, the peaks are easy to distinguish or to recognize. Since each maximum 94 has space around it or the minima 96 are in between, it is also ensured that after every passing of a maximum 94 via the sensor 92, no light is registered in the minimum. So a good distinction is achieved. It is therefore important in general that the maxima 94 are approximately as large in terms of their area like the sensor 92, advantageously two to four times as large. This ratio can be influenced by the maxima 94 or the sensor. The luminous point 90 in turn is many times larger. He should always cover the sensor 92.

This is based on the difference between the FIGS. 11 and 12 seen. While the sensor is in the state of FIG. 11 is in the range of a minimum 96, so that the output signal is 0, it is after a shift of the maximum 94 compared to the dotted earlier position by a very small distance 98, in practice less than 1 mm, already largely in the range of this maximum , This results in a high output and produces a peak. The frequency of this change results in the oscillation or its frequency. The difference between 0 and the maximum of the peak gives the intensity and, in turn, the attenuation can be derived.

In FIG. 10 is shown over time, as the individual peaks as individual rashes in the overall course represent a kind of noise. However, it is still easy to recognize or optically evaluate via the sensor 92 and electronically via the controller. It should be noted that in FIG. 10 the attenuation a is shown over the time t or over the time course of the cooking process. The actual intensity of the measured maxima 94 on the sensor 92 is, so to speak, the reciprocal of the attenuation. The change in the frequency of oscillating or moving the maxima is difficult to recognize, only in connection with FIG. 13 ,

In connection with FIG. 13 this will be explained below. In FIG. 13 the signal behavior is shown at different states, which correspond to the different processes during the cooking process. In field I and at the beginning of the cooking process at FIG. 10 Damping A and Oscillation f are low, because not much is happening in the range of the extractor hood or over a hotplate 14 according to FIG. 2 , In field II the damping is low but the oscillation still medium, so that there is still a lot of heat here with little steam. This indicates the end of a cooking process. In field III, the attenuation is moderate, but the oscillation is low. This suggests in the conclusion rather on the beginning of a cooking process. In box IV, damping and oscillation are medium in size, so that a normal cooking process can be concluded. In particular, only one hotplate is operated here.

In field V, the attenuation a is medium, while the oscillation f increases significantly. This points to medium-sized steam development at very high heat, so rather to a strong frying operation. In the field VI, in turn, the oscillation remains medium, while the attenuation increases significantly. This indicates a very strong cooking operation with a lot of steam and not excessive heat. Finally, in field VII, damping and oscillation are strong, indicating strong cooking and frying, for example when using several cooking zones, some for roasting and some for cooking. Accordingly one can from the course in FIG. 10 Recognizing the course of a cooking process with the beginning of heating or cooking, within the dashed area normal cooking and then right of the dashed area final conclusion of the cooking process with residual heat. This can also detect the control in the control method for the hood accordingly, so that their performance is adjusted automatically, so to speak.

In addition to an automatic and adapted operation of the extractor fan so the contamination of the filter can be detected and a replacement exchange between cleaning promptly displayed.

Claims (21)

1. Ventilation device, particularly exhaust hood (10), having a drive unit (20) for producing an air flow, a control device (50) or a control circuit for controlling the drive unit (20) and a measurement section in the ventilation device in the vicinity of the air flow with a transmitter device (22; 29; 32; 40; 52; 64) and a receiver device (24; 29; 34; 42; 58; 66), in which the control device (50) or control circuit is constructed for controlling the drive unit (20) as a function of a signal generated by the receiver device (24; 29; 34; 42; 58; 66), in which the transmitter device (22; 29; 32; 40; 52; 64) is constructed for emitting a laser beam (25; 31; 38; 48, 62), characterized in that the control circuit or the control device (50) is constructed for evaluating the signal generated by receiver device (24; 29; 34; 42; 58; 66) with respect to air streaks in the measurement section.
2. Ventilation device according to claim 1, characterized in that with regard to electric characteristic values such as its frequency, voltage or current strength, the signal generated by the receiver device (24; 29; 34; 42; 58; 66) is dependent on the intensity or power of the radiation received by said receiver device.
3. Ventilation device according to claim 2, characterized in that the signal generated by the receiver device (24; 29; 34; 42; 58; 66) is only dependent on the radiation in a frequency range largely corresponding to the frequency range of the laser beam (25; 31; 38; 48).
4. Ventilation device according to any of the preceding claims, characterized in that the receiver device (24; 29; 34; 42; 58; 66) has a photoelectric sensor (26; 72), which preferably has a photodiode or a photosensor.
5. Ventilation device according to any of the preceding claims, characterized in that the receiver device (24) is equipped with filter means (29a), preferably a hollow duct (29a), said filter means (29a) restricting the angular range in which incident light (25; 28) is recorded by the receiver device.
6. Ventilation device according to any of the preceding claims, characterized in that the drive unit (20) can be activated and deactivated by the control circuit or control device (50) on the basis of the signal received from the receiver device (24; 29; 34; 42; 58; 66) and can be controlled, preferably in stepless manner with respect to its power.
7. Ventilation device according to any of the preceding claims, characterized in that the control circuit or control device (50) is constructed for controlling the drive unit (20) as a function of the intensity or power recorded by the receiver device (24; 29; 34; 42; 58; 66).
8. Ventilation device according to any of the preceding claims, characterized in that the control circuit or control device (50) is constructed for controlling the drive unit (20) as a function of the intensity or power over time recorded by the receiver device (24; 29; 34; 42; 58; 66).
9. Ventilation device according to any of the preceding claims, characterized in that the transmitter device (122) is a laser diode, preferably a multi-mode laser diode.
10. Ventilation device according to any of the preceding claims, characterized in that the transmitter device (122) is constructed for emitting a laser beam (125), whose light spot (90) in the vicinity of receiver device (124) has areas of widely varying intensity, preferably in the form of an interference pattern (94, 96).
11. Ventilation device according to claim 10, characterized in that the transmitter device (122) and the receiver device (124) are constructed in such a way that in operation the receiver device is always within the light spot (90).
12. Ventilation device according to claim 10 or 11, characterized in that the transmitter device (122) and the receiver device (124) are constructed in such a way that the diameter of light spot (90) is at least 5 mm wider than the receiver device or its sensor (92), preferably at least 8 mm wider.
13. Ventilation device according to any of the preceding claims, characterized in that the control circuit (150) or control device evaluate the output signal with respect to signal frequency and signal attenuation.
14. Ventilation device according to any of the preceding claims, characterized in that the transmitter device (22; 64) and the receiver device (24; 66) are positioned facing one another on either side of the air flow in ventilation device (10) and the transmitter device (22; 64) emits in the direction of the receiver device (24; 66).
15. Ventilation device according to any of the claims 1 to 13, characterized in that the transmitter device (29; 32; 40; 122) and the receiver device (29; 34; 42; 124) are so positioned that a laser beam (31; 38; 48; 125) emitted by the transmitter device reaches the receiver device reflected by at least one reflection device (30; 36; 44; 46; 130).
16. Ventilation device according to claim 15, characterized in that there are at least two reflection devices (44; 46), which are so positioned and oriented that a laser beam (48) emanating from the transmitter device (40) is reflected at least twice by at least one reflection device (44; 46) on its way to the receiver device (42).
17. Ventilation device according to claim 16, characterized in that the two reflection devices (44; 46) are facing and are parallel to one another.
18. Ventilation device according to any of the preceding claims, characterized in that the transmitter device (122) has a laser diode for emitting the laser beam (25; 48; 125), particularly a multimode laser diode.
19. Ventilation device according to any of the preceding claims, characterized in that the transmitter device (64, 122) has an optical device, preferably a collimator lens (70; 123), in the propagation path of the laser beam (48; 125).
20. Ventilation device according to any of the preceding claims, characterized in that the divergence of the laser beam (25; 48) can be adjusted by the control device (50) or the control circuit.
21. Ventilation device according to any of the preceding claims, characterized by at least two transmitter devices for emitting laser beams (25; 48) with a different divergence.

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