US20090165775A1

US20090165775A1 - Cooking Appliance

Info

Publication number: US20090165775A1
Application number: US11/990,535
Authority: US
Inventors: Ingo Bally; Kerstin Feldmann; Wolfgang Fuchs; Martin Keller; Edmund Kuttalek; Maximilian Neuhauser; Klemens Roch; Wolfgang Schnell; Günter Zschau
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2005-08-17
Filing date: 2006-07-26
Publication date: 2009-07-02
Also published as: DE102005038882A1; WO2007020162A1; EP1917479A1

Abstract

A cooking appliance, in particular, a cooking appliance which is mounted at an elevated level, comprising at least one muffle which defines a cooking area, and the muffle opening thereof is surrounded by a muffle frame, a door which closes the muffle opening and a drive device which is used to drive the door and which is controlled by a control circuit. The drive device can be controlled by the control circuit in such a manner that a predetermined driving parameter of the door can be controlled by at least one defined ramp.

Description

The present invention relates to a cooking appliance, particularly a cooking appliance mounted at an elevated level, comprising at least one muffle which defines a cooking compartment, with a muffle opening, a door which closes the muffle opening and a drive device controlled by a control device for driving the door.
A cooking appliance mounted at an elevated level is known from U.S. Pat. No. 2,944,540, in which a base door is driven by means of an electric motor.
A cooking appliance mounted at an elevated level comprising a base door driven by electric motor, said appliance having an electric current sensor, is described for example in DE 101 64 235 A1 and DE 101 64 239 A1.
The travel of the base door is effected in the case of the known appliances by turning the drive motor on or off, in other words by applying a particular voltage to, or removing it from, the motor.
The disadvantage in this situation is the fact that as a result of suddenly turning the drive motor on and off the base door starts and stops moving unevenly, juddering for example. This juddering appears unpleasant to the operator and can also result in spillage of food.
The object of the present invention is therefore to provide a cooking appliance of the type described above with an improved, in particular more even, travel behavior.
The present object is achieved by the cooking appliance having the features described in claim 1 and also a method as claimed in claim 13.
To this end, the cooking appliance, particularly a cooking appliance mounted at an elevated level, is equipped such that the drive device can be controlled or regulated by the control circuit in such a manner that a predefined travel parameter for the door, for example a nominal motor voltage or nominal speed, can be controlled by means of at least one defined ramp, for example a voltage or speed ramp. An undefined, often juddering, travel behavior caused by simply turning on the drive motor is thereby avoided. The shape of the ramps is not restricted for example to a linear shape and can also be multistage.
In this situation it is advantageous, for improved user friendliness amongst other things, if the travel parameter is a travel speed of the door, in other words the door travel is speed dependent and not load dependent. In order that when the door starts to travel it moves gently and without juddering, a nominal speed to be achieved is passed by means of a first defined speed ramp. The travel movement of the door is then also dependent for example on a payload or on a change in the mechanical friction circumstances. It is possible to define for example the acceleration and/or the time to attain the nominal speed and so forth. If the travel path is too short to attain a nominal speed, the ramps can naturally also overlap one another at lower speed values.
It can be advantageous if it is also possible to pass a second defined speed ramp, this time with negative acceleration, when stopping the door to a further, lower nominal speed, for example also to a standstill. This is more user friendly than an abrupt stop, for example by short-circuiting the drive motor.
If a plurality of nominal speeds are to be passed in succession, then a corresponding plurality of ramps is to be passed. The ramps do not basically need to exhibit the same shape or (for example absolute) gradient.
In an automatic mode of operation in particular it is advantageous if after—usually momentarily—actuation of a travel switch panel the door can travel by means of the first speed ramp to a nominal speed and automatically come to a standstill from the nominal speed by means of the second speed ramp.
In a manual mode of operation in particular it is advantageous for improved operational safety if the door travels by means of the first speed ramp to a nominal speed while at least one travel switch panel is being actuated—advantageously both travel switch panels at the same time—and abruptly comes to a standstill after releasing at least one travel switch panel.
For the purposes of simple implementation and high accuracy of measurement it is advantageous if the travel speed can be sensed by means of a speed measuring device which comprises at least one sensor, particularly a Hall sensor, located on a motor shaft of a drive motor of the drive device. In this situation, the speed measuring device can measure the speed of the door either directly, for example by being located on the door, or through indirect determination, for example by measuring the rotational speed of a shaft, for example the motor shaft. The motor shaft can also be fitted before or after a gearbox.
For the purpose of increased user friendliness it is advantageous if the travel speed can be set by the user. The travel speed can thus be set by selecting from at least two speed levels, whereby the speed levels can also be predefined ex-works. For older users in particular it is advantageous if the travel speed can be switched over at least between a first, lower speed level in the range of 40 mm/s to 55 mm/s, 50 mm/s in particular, and a second speed level in the range of 60 mm/s to 80 mm/s, particularly in the range of 65 mm/s to 75 mm/s, 65 mm/s in particular. In order to increase the operational safety and customer satisfaction it is then advantageous if a preset travel speed corresponds to the lowest speed level. In order that a user should not then need to set the travel speed(s) anew each time the appliance is turned on, the user setting for the travel speed can be stored in a nonvolatile memory, an EEPROM for example.
In the case of speed dependent control it is additionally advantageous if any trapping at the door can be detected by monitoring the travel speed, whereby the anti-trap facility is advantageously activated only when the nominal speed of the door has been attained.
Particularly with regard to the closure of the cooking compartment by the base door it can be advantageous if the travel movement of the door can be switched between a speed dependent travel movement and a load or force dependent travel movement.
The invention is particularly suited for cooking appliances mounted at an elevated level in which the muffle opening is a base-side muffle opening and the door is a base door which preferably moves in a linear fashion.

The invention will be described in detail in the following with reference to the attached schematic figures. In the figures:

FIG. 1 shows a perspective view of a cooking appliance wall-mounted at an elevated level with the base door lowered;

FIG. 2 shows a perspective view of the cooking appliance mounted at an elevated level with the base door closed;

FIG. 3 shows a perspective view of a housing of the cooking appliance for mounting at an elevated level without the base door;

FIG. 4 shows a schematic side sectional view along the line I-I from FIG. 1 of the cooking appliance wall-mounted at an elevated level with the base door lowered;

FIG. 5 shows a front view of a further embodiment of a cooking appliance mounted at an elevated level;

FIGS. 6 to 11 show diagrams of travel movements of a base door under different basic conditions;

FIGS. 12 and 13 show force-time profile curves for a base door.

FIG. 1 shows a cooking appliance mounted at an elevated level with a housing 1. The rear panel of the housing 1 is mounted on a wall 2 in the manner of a wall cabinet. Defined in the housing 1 is a cooking compartment 3 which can be monitored by way of a viewing window 4 incorporated in the housing 1. It can be seen from FIG. 4 that the cooking compartment 3 is delimited by a muffle 5 which is provided with a heat insulating casing which is not shown, and that the muffle 5 has a muffle opening 6 in its base. The muffle opening 6 can be closed with a base door 7. FIG. 1 shows the base door 7 in its lowered position, whereby its underside is in contact with a worktop 8 of a kitchen unit. In order to close the cooking compartment 3, the base door 7 must be moved to the position shown in FIG. 2, the so-called “null position”. In order to move the base door 7, the cooking appliance mounted at an elevated level has a drive device 9, 10. The drive device 9, 10 has a drive motor 9 represented in FIGS. 1, 2 and 4 by dashed lines, which is located between the muffle 5 and an exterior wall of the housing 1. The drive motor 9 is located in the area of the rear panel of the housing 1 and, as shown in FIG. 1 or 4, is in active engagement with a pair of lifting elements 10 which are connected to the base door 7. In this situation, according to the schematic side view shown in FIG. 4, each lifting element 10 is formed as an L-shaped carrier whose vertical component extends out of the drive motor 9 at the side of the appliance. In order to move the base door 7, the drive motor 9 can be actuated with the aid of a control panel 12 and a control circuit 13, which according to FIGS. 1 and 2 is located on the front of the base door 7. As shown in FIG. 4, the control circuit 13 is situated behind the control panel 12 inside the base door 7. The control circuit 13, which here is made up of a plurality of spatially and functionally separate printed circuit boards communicating by way of a communication bus, constitutes a central control unit for operation of the appliance and controls and/or regulates for example the heating, the travel of the base door 3, the implementation of user inputs, the illumination, the anti-trap facility, the pulsing of the heating elements 16, 17, 18, 22 and much more.
It can be seen from FIG. 1 that the upper side of the base door 7 has a cook zone 15. Almost the entire surface of the cook zone 15 is taken up by heating elements 16, 17, 18 which are indicated in FIG. 1 by dot and dash lines. In FIG. 1, the heating elements 16, 17 are two hotplate heating elements of different sizes which are spaced apart from one another, while the heating element 18 is a surface heating element provided between the two hotplate heating elements 16, 17, which almost surrounds the hotplate heating elements 16, 17. The hotplate heating elements 16, 17 define associated cooking zones or cook tops for the user; the hotplate heating elements 16, 17 together with the surface heating element 18 define a bottom heating zone. The zones can be indicated by means of a suitable decor on the surface. The heating elements 16, 17, 18 can be controlled by way of the control circuit 13 in each case.
In the embodiment illustrated the heating elements 16, 17, 18 are configured as radiant heating elements which are covered by a glass ceramic plate 19. The glass ceramic plate 19 has approximately the dimensions of the upper side of the base door 7. The glass ceramic plate 19 is moreover equipped with assembly openings (not shown) through which project pedestals for mounting holders 20 for food shelves 21, as also shown in FIG. 4. Instead of a glass ceramic plate 19, it is also possible to use other covers—preferably having a fast response—a thin plate for example.
With the aid of a control toggle provided on the control panel 12 the cooking appliance mounted at an elevated level can be switched to a hotplate or a bottom heat operating mode, which are described in the following.
In the hotplate operating mode, the hotplate heating elements 16, 17 can be individually controlled by way of the control circuit 13 by means of control elements 11 which are provided on the control panel 12, while the surface heating element 18 remains out of operation. The hotplate operating mode can be used when the base door 7 is lowered, as is shown in FIG. 1. It can however also be used with the cooking compartment 3 closed by the raised base door 7 in an energy saving function.
In the bottom heat operating mode, not only the hotplate heating elements 16, 17 but also the surface heating element 18 are controlled by the control device 13.
In order to achieve the most even possible browning of the food during cooking with bottom heat operation, it is crucial that the cook zone 15 providing the bottom heat exhibits an even distribution of the heating power output over the area of the cook zone 15 even though the heating elements 16, 17, 18 have different rated power outputs. By preference, the heating elements 16, 17, 18 are therefore not switched to continuous operation by the control circuit 13 but the power supply to the heating elements 16, 17, 18 is pulsed. In this situation, the differently rated heating power outputs of the heating elements 16, 17, 18 are reduced individually in such a manner that the heating elements 16, 17, 18 provide an even distribution of the heating power output over the area of the cook zone 15.
FIG. 4 schematically illustrates the location of a fan 23, used for example to generate an air circulation in the case of hot air operation or to provide a fresh air feed. Furthermore, a top-heating heating element 22 is provided mounted on an upper side of the muffle 5, which can be implemented in a single-circuit or multi-circuit form, for example with an inner and an outer circuit. Further heating elements—not shown here so as improve clarity—such as a ring heating element can also be present between the rear wall of the housing 1 and the muffle. Through the control circuit 13, the different modes of operation including also top heat, hot air or rapid heating for example can be selected by appropriately turning on and setting the heating power of the heating elements 16, 17, 18, 22, and if necessary activating the fan 23. The setting of the heating power can take place by means of suitable pulsing. In addition, the cook zone 15 can also be implemented differently, for example with or without an extended cooking zone, as a pure—single- or multi-circuit—warming zone without cook tops and so forth. The housing 1 has a seal 24 with the base door 7.
The control panel 12 is principally located on the front side of the base door 7. Alternatively, other arrangements are also conceivable, for example on the front side of the housing 1, divided up over different subfields and/or partially on side surfaces of the cooking appliance. Further configurations are possible. The control elements 11 are not restricted in respect of their type of construction and can for example include control toggles, toggle switches, pushbuttons and membrane keys, the display elements 14 include for example LED, LCD and/or touchscreen displays.
FIG. 5 shows a schematic front view, not to scale, of a cooking appliance mounted at an elevated level in which the base door 7 is open in contact with the worktop 8. The closed state is drawn in dashed lines.
In this embodiment, two travel switch panels 25 are situated on the front side of the permanently mounted housing 1. Each travel switch panel 25 comprises two pushbuttons, namely an upper CLOSE pushbutton 25 a for a base door 7 traveling upward in the closing direction and a lower OPEN pushbutton 25 b for a base door 7 traveling downward in the opening direction. In the absence of automatic operation (see below), the base door 7 travels upward only as a result of continuous depression of the CLOSE pushbuttons 25a on both travel switch panels 25, if possible; the base door 7 also travels downward only as a result of continuous depression of the OPEN pushbuttons 25 b on both travel switch panels 25, if possible (manual operation). Since increased attentiveness on the part of the user is implicit in manual operation and, in addition, both hands are used here, an anti-trap facility is then only optional. With regard to an alternative embodiment, travel switch panels 26 are placed at opposite outer sides of the housing 1 with corresponding CLOSE pushbuttons 26 a and OPEN pushbuttons 26 b, as drawn in dashed lines.
The control circuit 13 drawn in dot and dash lines, which is situated in the interior of the base door 7 behind the control panel 12, switches the drive motor 9 in such a manner that the base door 7 travels gently, in other words not abruptly by simply turning on the drive motor 9 but by means of a defined ramp.
In this embodiment the control circuit 13 includes a memory unit 27 for storing at least one destination or travel position P0, P1, P2, PZ of the base door 7, preferably using volatile memory modules, for example DRAMs. If a destination position P0, P1, P2, PZ has been stored, after actuation of one of the pushbuttons 25 a, 25 b or 26 a, 26 b on the travel switch panels 25 or 26 respectively the base door can travel independently in the selected direction until the next destination position has been reached or one of the pushbuttons 25 a, 25 b or 26 a, 26 b is actuated again (automatic operation). In this embodiment the lowest destination position PZ corresponds to the maximum opening, the (null) position P0 corresponds to the closed state, and P1 and P2 are freely selectable intermediate positions. If the last destination position for a direction has been reached, it is moreover necessary to continue the travel in manual mode, if this is possible (in other words the most last end positions do not correspond to a maximum open state or to the closed end state). Similarly, if no destination position has been stored for one direction—which for example would be the case for an upward movement into the closed situation if only PZ is stored and not P0, P1, P2—it is then necessary for the travel in this direction to take place in manual mode. If no destination position is stored, for example in the case of a new installation or after a power disconnection, no automatic operation is possible. If the base door 7 travel takes place in automatic mode, then an anti-trap facility is preferably activated.
Automatic mode and manual mode are not mutually exclusive: as a result of continuous actuation of the travel switch panel(s) 25, 26 the base door 7 then also travels in manual mode if it were possible to travel in this direction to a destination position. In this situation, it is possible for example to define a maximum actuation time for the travel switch panels 25 and 26, or the associated pushbuttons 25 a, 25 b and 26 a, 26 b respectively, relating to activation of automatic mode, 0.4 seconds for example.
A destination position P0, P1, P2, PZ can be any position of the base door 7 between and including the null position P0 and the maximum opening position PZ. The maximum stored opening position PZ need not however be the position in contact with the worktop 8. Storing of the destination position P0, P1, P2, PZ can be performed with the base door 7 in the desired destination position P0, P1, P2, PZ, by means of, for example, actuating a confirmation pushbutton 28 on the control panel 12 for several seconds (duration two seconds for example). Existing optical and/or acoustic signal generators which output corresponding signals after storage of a destination position are not included in the drawing in order to improve clarity. Travel to the desired destination position P0, P1, P2, PZ to be selected occurs for example as a result—in this embodiment—of two-handed operation of the travel switch panels 25 and 26 and manual travel to this position.
The memory unit 27 can store only one or, as illustrated in this embodiment, also a plurality of destination positions P0, P1, P2, PZ. In the case of a plurality of destination positions P0, P1, P2, PZ, these can be reached in sequence by actuating the corresponding travel pushbuttons 25 a, 25 b and 26 a, 26 b. By having a plurality of destination positions P0, P1, P2, PZ, the cooking appliance mounted at an elevated level can be conveniently adapted to the desired operating height for a plurality of users. The destination position(s) can advantageously be deleted and/or overwritten. In one embodiment, for example, only one destination position can be stored in the open state, while the null position P0 is detected automatically and can be reached automatically. Alternatively, the null position P0 must also be stored in order for it to be automatically reachable.
It is particularly advantageous for ergonomic use if the or a destination position P1, P2, PZ opens the base door 7 at least approx. 400 mm to approx. 540 mm (in other words P1-P0, P2-P0, PZ-P0>40 cm to 54 cm). Given this dimension of opening, the food shelves 21 can be simply inserted into the holders 20. In this situation, it is advantageous if the viewing window 4 is mounted approximately at or slightly below the eye level of the user, for example by using a template which indicates the dimensions of the cooking appliance.
Not included in the drawing is a power outage bridging facility provided for bridging a power outage of approx. 1 to 3 s, preferably up to 1.5 s.
The drive motor 9 from FIG. 1 has at least one sensor unit 31, 32 located on a motor shaft 30, before or after a gearbox where applicable, in order to measure a travel path or a position and/or a speed of the base door 7. The sensor unit can for example comprise one or more induction sensors, Hall sensors, opto-sensors, SAW sensors and so forth. In this situation, in order to perform simple distance and speed measurement two Hall (part) elements 31 are fitted here displaced by 180° —opposite one another in other words—on the motor shaft 30, and a Hall measuring sensor 32 is fitted at a fixed distance in this area of the motor shaft. If a Hall element 31 then travels past the measuring sensor 32 when the motor shaft 30 is rotating, a measurement or sensor signal is produced which is digital to a good approximation. With (not necessarily) two Hall elements 31, two signals are thus output during a rotation of the motor shaft 30. By carrying out a timing assessment of these signals, their time difference for example, the speed vL of the base door 7 can be determined, for example by using comparison tables or a conversion into real time in the control circuit 13. By means of addition or subtraction of the measurement signals it is possible to determine a travel path or a position of the base door 7.
A speed regulation facility can implement the speed for example by way of a PWM-controlled power semiconductor.
For the purpose of null point determination, the travel path measurement is automatically newly adjusted through initialization in the null position P0 of the base door 7 each time it starts to travel, in order for example to prevent an incorrect sensor signal output or recording from being passed on.
The drive motor 9 can be operated by actuating both travel switch panels 25 and 26 even if the main switch 29 is turned off.
Instead of two separate switches per travel switch panel 25, 26, one individual switch per travel switch panel is also possible, for example a toggle switch with a neutral position which switches only under pressure. Other forms are also possible. There is also no restriction on the type and arrangement of the control elements 28, 29 on the control panel 12.
In this situation the arrangement and distribution of the control circuit 13 is flexible and not restricted, in other words it can also comprise a plurality of boards, for example a display board, a control board and a lift board which are spatially separated.
A 4 mm opening dimension can be detected by limit switches 33 which deactivate an anti-trap facility when actuated.
The cooking appliance mounted at an elevated level can also be implemented without a memory unit 27, whereby no automatic operation is then possible. This can be useful for increased operational safety, for example to protect against trapping.
FIG. 6 shows a diagram, not to scale, of the travel speed vL of the base door 7 in mm/s plotted against the position of the base door in mm from the null position P0 for the base door 7 traveling from the closed state at P0=0 mm to PZ=maximum opening here of 530 mm in manual travel mode (in other words without automatic travel mode), and also, indicated by the dotted arrow, a stop in the travel movement between P0 and PZ. The curve progresses in the direction of the arrow, in other words from right to left. The downward pointing arrows present above the curve indicate actuations of the control panel 12.
The downward travel movement of the base door 7 begins with two-handed actuation of the travel switch panels 25, 26 or of the OPEN switches 25 b or 26 b, as indicated by the upper lefthand vertical arrow. The control circuit 13 regulates the drive motor 9 such that the base door 7 travels gently, in other words with a defined ramp R1, to its nominal speed here of vL=50 mm/s. The ramp R1 is linear here. The drive motor 9 is thus not simply turned on.
The travel movement is also load independent as a result, in particular it is independent of the payload of the base door 7 or changed mechanical friction circumstances. One input variable for this can be the rotational speed of the drive motor 9, which can be measured for example by means of Hall sensors.
After attaining the nominal speed of vL=50 mm/s, the base door 7 travels downward at a constant speed until it approaches the maximum opening PZ which results from the designed predefined maximum travel of the base door 7 or from reaching the worktop 8. In this figure it is assumed that the designed maximum opening PZ is reached. In this case, the control circuit 13 detects this approach and gently brakes the base door 7 automatically, in other words with a defined ramp R2, to PZ. Both ramps R1 and R2 can exhibit other gradients or shapes. The approach to the worktop can be detected by means of limit switches 33 and/or by monitoring the travel path.
If one or both of the travel switches 25 b, 26 b is/are released, as indicated by the upper lefthand vertical arrow, the base door 7 stops abruptly without a ramp, as indicated by the dotted arrow. In this mode, although the approach travel is thus gentle, this comes to an abrupt halt however—except on reaching the end position.
The cooking compartment 3 is not opened, in other words the base door 7 does not travel out of the null position P0 if an opening safety device is active, if therefore for example a particular temperature in the cooking compartment, 425° C. or 600° F. for example, is exceeded or if a child safety device is activated.
FIG. 7 shows a diagram similar to FIG. 6, not to scale, for the travel of the base door 7 from the closed state to a stored position P1=476 mm in automatic travel mode.
In this case, as a result of briefly actuating one of the OPEN switches 25 b or 26 b, as indicated by the upper righthand vertical arrow, the base door 7 begins automatically to travel to the position P1. In this situation also the base door 7 travels gently (righthand ramp) and is braked automatically (lefthand ramp). In this embodiment, in automatic mode it is possible to choose between two fixed nominal speeds, namely 75 mm/s (dashed line) and 50 mm/s (solid line), whereby the slower speed is advantageous particularly for older users. The ex-works default, for example, is the slower speed level. It is also possible to provide more than two speed levels, or nominal speeds; a free choice of setting for the nominal speed(s) by the user is also conceivable. Advantageously, it is also possible to switch at least between two speed levels of 50 mm/s and 65 mm/s, for example during initialization of an appliance.
FIG. 8 shows a diagram, not to scale, of the travel of the base door 7 from the maximum opening position PZ to the null position P0, in other words into the closed state, in manual mode.
The upward travel movement of the base door 7 begins with two-handed actuation of the CLOSE switches 25 a and 26 a, as indicated by the upper lefthand vertical arrow. The control circuit 13 regulates the drive motor 9 such that the base door 7 travels gently from PZ to its nominal speed of vL=50 mm/s, and then travels constantly at this nominal speed (to the right).
The control circuit 13 detects an approach to the null position P0 and gently brakes the base door 7 in good time beforehand. However, instead of now decelerating directly to the null position P0 by means of the linear ramp, 4 mm before the null position P0, speed dependent control is switched over to control using a defined voltage, in other words by supplying the motor 9 with an appropriate voltage. As a result, a maximum force development can be set with regard to blocking the drive motor 9. This voltage differs according to the previous history of the travel (payload, friction circumstances etc.). The detection of the 4 mm opening dimension is carried out by means of path measurement or additionally or alternatively by way of the limit switches 33. In the area from P0 to P0+4 mm it is also possible to dispense with an anti-trap facility.
If, as in FIG. 6, one or both of the travel switches 25 b, 26 b is/are released, as indicated by the upper righthand vertical arrow, the base door 7 stops abruptly with a ramp, as indicated by the dotted arrow.
FIG. 9 shows a diagram, not to scale, of the travel of the base door 7 from a stored position P1=476 mm to the closed state P0 in automatic travel mode. In contrast to the manual travel mode shown in FIG. 8, only one of the CLOSE switches 25 a, 26 a now needs to be actuated briefly, as indicated by the upper vertical arrow. The travel of the base door 7 is then analogous to that of FIG. 7, but in the other direction. On approaching the null position P0, by analogy with the situation from FIG. 8 the braking ramp for the last 4 mm of opening changes over from a speed controlled state to a load or closing force controlled state.
FIG. 10 shows a diagram analogous to FIG. 8, in which trapping now occurs at a nominal speed of vL=50 mm/s, as indicated by the upper vertical arrow. If a hand or cooking vessel etc., for example, becomes trapped between the base door 7 and the housing 1 the speed of the base door 7 drops because the object impedes further travel. Monitoring of the lift speed takes place here for example through evaluation of the sensor signals from the motor shaft, whereby for example the time between the measurement signals or pulses is evaluated. Only in the second instance is the motor current monitored, which is a slower method. In particular, the force which can be generated by the motor 9 for traveling is limited in order to avoid accidents resulting from excessively strong trapping (see also FIGS. 12 and 13). The deviation from the nominal speed is detected by the control circuit 13, for example through a speed deviation or a temporal change in the speed. Thereupon the base door reverses in order to allow the object to be removed; where appropriate a warning signal, for example an audible warning, is also output. Thereafter the base door 7 starts traveling only in the event of renewed appropriate actuation of a travel switch panel 25, 26.
In order to prevent the trapping situation from being incorrectly triggered, for example by a changed payload or a change in the running characteristics of the mechanism, firstly the anti-trap facility may only be activated if the base door 7 has attained its nominal speed (if a travel pushbutton 25 a, 25 b, 26 a, 26 b is previously released, the base door 7 immediately stops), and secondly a plurality of sensor signals may be evaluated, averaged for example.
FIG. 11 shows the trapping situation (upper vertical arrow) during the opening travel of the base door 7 in automatic mode to a destination position P1, in which an object becomes trapped between the underside of the base door 7 and the worktop 8. In this case, the trapping detection can take place by way of two redundant limit switches which detect a—in particular uneven—removal of load from the base door 7, whereupon the drive motor 9 reverses. The maximum permitted force-time profile (see FIGS. 12 and 13) is not exceeded in this situation.
FIG. 12 shows a maximum force F in N which can be applied to the base door 7 in a trapping situation occurring during travel in a closing direction (upwards in other words) plotted against the elapsed time t in s as a first force-time profile FT1.
In the trapping situation where t=0 s the possible closing force is limited to 100 N, corresponding to approx. 10 kg, for 5 s. This is useful for example if the motor 9 is boosted by the control device 13 in order to maintain the nominal speed. In particular this ensures that parts of the body are not injured. If the base door is operated for 5 s with (a maximum of) 100 N, the maximum force that can be applied is further reduced to 25 N, for example for 5 seconds. Thereafter this force level can be maintained or for example further reduced to 0 N. It should be stressed that this force-time profile FT1 specifies only the maximum force that can be applied, and the force actually applied lies beneath this as a rule, for example if the trapping situation is detected by the control device 13 and the base door 7 is correspondingly reversed after t=0.5, whereupon the applied force of 100 N drops to 0 N for example.
The maximum force threshold value of 100 N can also apply to further travel situations.
FIG. 13 shows a maximum force F in N which can be applied to the base door 7 in a trapping situation occurring during travel in an opening direction (downwards in other words) plotted against the elapsed time t in s as a second force-time profile FT2. Here the drive motor 9 can apply up to 400 N to the base door 7 in a first block of t=[0 s; 0.5 s], thereafter at t=[0.5 s; 5 s] 150 N and thereafter 25 N.
The time intervals and force threshold values for the force-time profiles FT1, FT2 can naturally be adapted to the structure and further basic conditions.


List of reference characters

	1	Housing
	2	Wall
	3	Cooking compartment
	4	Viewing window
	5	Muffle
	6	Muffle opening
	7	Base door
	8	Worktop
	9	Drive motor
	10	Lifting element
	11	Control element
	12	Control panel
	13	Control circuit
	14	Display elements
	15	Cook zone
	16	Hotplate heating element
	17	Hotplate heating element
	18	Surface heating element
	19	Glass ceramic plate
	20	Holder
	21	Food shelf
	22	Top-heating heating element
	23	Fan
	24	Seal
	25	Travel switch panel
	25a	CLOSE switch
	25b	OPEN switch
	26	Travel switch panel
	26a	CLOSE switch
	26b	OPEN switch
	27	Memory unit
	28	Confirmation pushbutton
	29	Main switch
	30	Motor shaft
	31	Hall element
	32	Measuring sensor
	33	Limit switch
	FT1	First force-time profile
	FT2	Second force-time profile
	P0	Null position
	P1	Intermediate position
	P2	Intermediate position
	PZ	End position
	R1	Speed ramp
	R2	Speed ramp
	vL	Travel speed of base door

Claims

1-14. (canceled)

15. A cooking appliance comprising:

a muffle having a muffle body defining a cooking compartment with a cooking compartment access opening formed in the muffle body;

a door configured for traveling movement in and out of a covering relation with the muffle access opening;

a drive device in mechanical communication with the door for applying motive force thereto; and

a control circuit in operational communication with the drive device for controlling at least one travel parameter of the door wherein the at least one travel parameter is changed linearly for a predetermined time period.

16. The cooking appliance according to claim 15 wherein the control circuit is configured for controlling at least one travel parameter including door speed.

17. The cooking appliance according to claim 16 wherein the control circuit is configured for controlling door movement wherein a first predetermined linear acceleration can be exceeded as the door starts to travel to a nominal speed.

18. The cooking appliance according to claim 17 wherein the control circuit is configured for controlling door movement wherein a second predetermined linear acceleration can be exceeded as the door is being slowed to a further nominal speed.

19. The cooking appliance according to claim 15 wherein the control circuit is configured to control door movement wherein the door can travel according to a first predetermined linear acceleration to a nominal speed after actuation of a travel switch panel and can automatically come to a standstill from the nominal speed according to a second predetermined linear acceleration.

20. The cooking appliance according to claim 15 wherein the control circuit is configured to control door movement wherein the door can travel according to a first predetermined linear acceleration to a nominal speed while at least one travel switch is actuated and can come to a standstill after at least one travel switch is released.

21. The cooking appliance according to claim 15 and further comprising a speed measuring device for determining door travel speed including at least one sensor located on a motor shaft of a drive motor of the drive device.

22. The cooking appliance according to claim 15 and further comprising a speed measuring device for determining door travel speed including at least one Hall sensor located on a motor shaft of a drive motor of the drive device.

23. The cooking appliance according to claim 15 and further comprising user-operable door speed controls operatively associated with the control circuit.

24. The cooking appliance according to claim 15 and further comprising a door speed monitoring device in communication with the control circuit and means for detecting a trapping event at the door using the speed monitoring device.

25. The cooking appliance according to claim 21 and further comprising an anti-trap arrangement in communication with the control circuit that can be activated only when the nominal speed of the door has been reached as determined by the speed measuring device.

26. The cooking appliance according to claim one 15 wherein the control circuit is operable to control the speed of door movement in one of a speed-dependent travel mode and a load-dependent travel mode.

27. The cooking appliance according to claim 15 wherein said cooking appliance is configured for mounting above countertop level with a plurality of sides and a downwardly directed muffle opening and the door is configured for covering the downwardly directed muffle opening.

28. A method for operating a cooking appliance comprising the steps of:

providing a muffle having a muffle opening, a door configured for traveling movement toward and away from a covering relation with the muffle opening and a control circuit for controlling door movement; and

controlling door movement according to one of a first defined speed ramp when the door begins movement and a second defined speed ramp when the door is stopped.

29. A method for operating a cooking appliance comprising the steps of:

providing a muffle having a muffle body defining a cooking compartment with a cooking compartment access opening formed in the muffle body; a door configured for traveling movement in and out of a covering relation with the muffle access opening; a drive device in mechanical communication with the door for applying motive force thereto; and a control circuit in operational communication with the drive device; and

controlling at least one travel parameter of the door using the control circuit wherein the at least one travel parameter is changed linearly for a predetermined time period.