Patent Application
20170082297
The present application is directed to a windowed door for a cooking appliance, in particular to a windowed door for a cooking oven. Moreover the present application is directed to a cooking appliance with such a windowed door.
To be able to observe food while being cooked in a cooking chamber of a cooking appliance—such as ovens, steamers, microwaves, grills or combinations thereof for example—the cooking chamber is usually closed with a windowed door. Thereby it is no longer necessary to open the cooking appliance to check the cooking process and a stable cooking temperature can be maintained.
A windowed door for a pyrolytic self-cleaning oven is for example known from U.S. Pat. No. 3,760,792 A. The door of the oven includes a cooling air channel between two adjacent glass panes with air inlet means along the bottom of the door and air outlet means along the top of the door. A manually operable hollow shutter is mounted for movement within the air channel between an open position hidden within the door to permit viewing through the window and a closed position for covering the glass pane for both restricting the radiation of heat through the window openings and forcing the cooling air to pass through the shutter. By changing of the position of the shutter from the open to the closed position the air inlet means are opened. Such a cooling with air during a self-cleaning operation of the oven is necessary to reduce the temperature at the outer side of the door for avoiding injuries of a user by contact with the outer side of the door. Although with such a shutter the temperature on the outer side of the door can be reduced, it has turned out that users sometimes forget to change the position of the shutter and thereby opening of the air inlet means before activating the self-cleaning operation of the oven and therefore the danger of injuries of a user cannot be reliably excluded.
From DE 103 49 313 A1 a cooking oven with a windowed door is known which provides a front plate and a rear plate which are connected with each other by lateral U-shaped carriers. To avoid injuries of a user caused by high temperatures on the outer side of the front plate the hollow space between the plates can be cooled by external air flowing from bottom to top of the door and by passing through openings in the carriers in the upper part of the door wherein these openings are surrounded by mechanical barriers integrated within the carriers to prevent air warmed up by the flange of the muffle of the oven from flowing into the hollow space. However, in operation it has turned out that moisture can be drawn within the hollow space due to permanently flow of external air through the hollow space which can cause fogging of the glass panes of the front plate and rear plate.
It is an object of the present invention to remove the problems and inconveniences observed with state of the art. In particular a windowed door for a cooking appliance with user friendly handling and/or effecting a lower energy consumption of the cooking appliance shall be provided. Further a cooking appliance with such a windowed door shall be provided.
This object is solved by claims 1 and 14. Embodiments in particular result from dependent claims.
According to claim 1, a windowed door for a cooking appliance is provided comprising a front plate and at least one inner plate facing a cooking chamber of the cooking appliance, wherein the front plate and the at least one inner plate each provide a glass pane and are connected with each other by at least lateral frame parts to establish an air channel from at least one air inlet opening arranged at the bottom or in at least one lateral side of the door through a hollow space between the glass pane of the front plate and the glass pane of the at least one inner plate to at least one air outlet opening arranged at the top of the door and wherein at least one automatically moveable closure device is provided which permits the regulation of air flow through the air channel by changing the cross-section of at least one air passage aperture within or at the end or at the beginning of the air channel.
Expediently the glass panes of the front plate and the inner plate are aligned to each other to be able to look into the cooking chamber of the cooking appliance. The front plate can provide a frame with a window opening in which the glass pane is inserted or can be built by the glass pane itself. The same applies for the at least one inner plate.
The front plate and the at least one inner plate can be connected with each other not only by lateral frame parts, but by a U-shaped or a peripheral frame, too, which include such lateral frame parts. Furthermore, the lateral frame parts or the U-shaped frame or the peripheral frame for connection of the plates can be provided in the region of the outer edges of the plates or offset inwards with respect to the outer edges. Further on, the plates can be connected with each other only or additionally by at least lateral frame parts or a U-shaped frame or a peripheral frame in the region of the glass panes of the plates. The general function of the lateral frame parts or the U-shaped frame or the peripheral frame is to keep the front plate and the at least one inner plate fixed to each other. The front plate, the at least one inner plate together with the lateral frame parts or the U-shaped frame or the peripheral frame is hereinafter referred to “door mechanical structure”. Especially in the case of use of a U-shaped frame the upper part of the windowed door can be closed by a door cap to build a kind of peripheral frame comprising the U-shaped frame and the door cap.
By connection of the outer plate and the at least one inner plate by lateral frame parts the glass panes of outer plate and at least one inner plate are spaced from one another which results in formation of a hollow space between the plates or rather the panes. To establish an air flow through the hollow space between the glass panes of the front plate and the at least one inner plate in case of a peripheral frame at least one air passage aperture for air inlet and at least one air passage aperture for air outlet have to be provided in the frame. In case of a U-shaped frame in combination with a door cap at least one air passage aperture for air inlet has to be provided in the base of the U-shaped frame and at least one air passage aperture for air outlet has to be provided in the door cap or has to be built between door mechanical structure and door cap. If only lateral frame parts are provided the side areas of the hollow space not limited by the lateral frame parts can serve as air passage apertures for air inlet and air outlet and can serve as air inlet opening and air outlet opening. To establish a continuous air channel and especially an air flow from at least one air inlet opening to at least one air outlet opening thereby passing the hollow space between the glass panes it is necessary that in case of horizontal or inclined frame parts or other horizontal or inclined supports or struts within the door mechanical structure and situated between at least one air inlet opening and at least one air outlet opening these are provided with at least one air passage aperture. This or these air passage apertures can serve as air inlet opening and/or air outlet opening, too, and can be situated at the beginning of the air channel, that means near or at the at least one air inlet opening, or somewhere within the air channel—for example if the glass panes are fixed to each other with additional lateral frame parts or an additional U-shaped or peripheral frame—at the end of the air channel, that means near or at the end of the at least one air outlet opening, dependent on the individual design of the door mechanical structure.
The at least one air inlet opening or the at least one air outlet opening or the at least one air passage aperture can be constituted by a slot-like opening. Expediently more than one air inlet opening and/or air outlet opening are provided to provide a homogeneous air flow through the door and in particular through the hollow space between the front plate and the at least one inner plate. Especially the at least one air inlet opening at the bottom of the door is situated in the lower third of the windowed door, or in at least one lateral side of the windowed door and the at least one air outlet opening at the top of the door is situated in the upper third of the windowed door to achieve a good cooling effect of the front plate of the door and in particular a vertical air flow through the hollow space.
For instance, as mentioned before the at least one air passage aperture can be constituted by the at least one air inlet opening, the at least one air outlet opening or by an opening of the hollow space not limited by the lateral frame parts.
The term “automatically moveable” shall mean that no direct manual interaction with a user is necessary, user need not to effect directly a movement.
The invention is based on the recognition that a cooking appliance with a windowed door which provides an air channel between at least two glass panes of the door for providing a permanent air flow through the hollow space between the glass panes has an increased energy consumption in comparison to a cooking appliance with a windowed door which does not comprise such an air channel.
Moreover, the invention is based on the consideration that cooling of a windowed door is usually only necessary when the cooking appliance is operated at high temperatures, for example during a self-cleaning operation or so-called pyrolytic cycle of the cooking appliance, whereas during normal operation often only less or no cooling and in particular during a preheating operation no cooling of the door is required because the door will not reach temperatures which could cause injuries to a user by contact with the outer side of the door.
The applicant has found that by providing an automatically moveable closure device which permits the regulation of air flow through an air channel within a windowed door by changing the cross-section of at least one air passage aperture within or at the end or at the beginning of the air channel the air flow can be purposefully adapted to the operation mode of a cooking appliance. For example during a self-cleaning operation of the cooking appliance which is accompanied with high temperatures the closure device can provide that the cross-section of the at least one air passage aperture is completely permeable for air, whereas during normal operation the closure device provides at least a partial reduction of the cross-section of the at least one air passage aperture. Hereby the energy consumption of the cooking appliance can be positively influenced, dependent on the operation mode of the cooking appliance the cross-section of the at least one air passage aperture is changeable whereby energy loss because of unnecessary cooling of the windowed door can be avoided. Further on, applicant has found that by such an automatically moving closure device no damages to the windowed door and/or a corresponding cooking appliance as well as injuries of the user by unintentional contact with the door during operation of the cooking appliance at high temperatures will occur in comparison to closure devices which require for example manual operation by a user for opening an air inlet opening—because in the latter case it cannot be excluded that the user forgets to change the position of closure device. Because a windowed door with an automatically moveable closure device requires no explicit action of the user to induce or stop cooling of the windowed door the handling of a cooking appliance with a windowed door according to the invention is much more convenient and easier for the user.
In embodiments of the windowed door, the at least one closure device is designed so that it can completely interrupt an air flow through the hollow space. This is advantageous because the energy consumption of a cooking appliance during a preheating mode can be reduced because in this mode no cooling of the windowed door and in particular of the front plate is required, in particular it is favourable that the glass panes stay warm in this mode. Further on, if in the surrounding of the cooking appliance exists high air moisture or if the cooking appliance is operated in a steam mode a complete interrupt of the air flow, in particular at the beginning of the air channel or rather at the at least one air inlet opening is favourable to avoid fogging of the glass panes due to air moisture.
In embodiments of the windowed door, the at least one closure device is arranged within a door cap which is arranged at the top of the windowed door. The term “arranged within” shall mean that the closure device is part of the door cap, however, the closure device does not have to be completely within a housing of the door cap, but can build a part of the door cap, especially a replaceable part. The door cap itself can be a removable, exchangeable part which at least partially covers the top of the windowed door. Such door caps are usually provided with at least one air outlet opening, in particular with one or several slot-like openings. By providing the at least one closure device within the door cap an easy exchange of the closure device in case of failure is possible, even a complete change of the door cap can be considered. By arrangement of the at least one closure device within the door cap the air flow through the air channel can be regulated by changing the cross-section of the at least one air outlet opening provided in the door cap. However, dependent on the design of the door cap and the at least one closure device the cross-section of the hollow space between front plate and at least one inner plate could be changed, too.
In embodiments of the windowed door, the at least one closure device is arranged between the front plate and the at least one inner plate. The term “between the plates” shall mean that the closure device can be arranged within the door mechanical structure of the windowed door, in particular in such cases in which the at least one inner plate is the rear plate of the windowed door. The arrangement of the at least one closure device can be in longitudinal direction or in cross direction with respect to the front plate and the at least one inner plate. Preferably the at least one closure device is arranged at least partially above or beyond the glass panes of the front plate and the at least one inner plate, whereby an upper or lower opening of the hollow space between the glass panes can be regarded as the at least one air passage aperture whose cross-section can be changed with help of the at least one closure device.
In embodiments of the windowed door, the at least one closure device is in direct contact with the front plate or the at least one inner plate when interrupting the air flow through the hollow space. The term “direct contact” shall include a contact with a sealing provided at the front plate or at the at least one inner plate, too. It is especially advantageous if the at least one closure device is in direct contact with the front plate as well as with the at least one inner plate and is arranged above or beyond an opening of the hollow space. Thereby it can be ensured that a reliable closure of the opening and thus an interruption of an air flow through the hollow space can be achieved.
In embodiments of the windowed door, between the front plate and the at least one inner plate at least one further plate comprising a glass pane is arranged. Advantageously, the at least one inner plate constitutes the rear plate of the windowed door. To achieve a better insulation effect of the cooking chamber of a cooking appliance which is closed with a windowed door it is advantageous to provide multiple-glazing. Loss of heat and thus energy consumption of the cooking appliance can be reduced. It is also possible that front plate or rear plate or any intermediate plates of a windowed door do not only comprise a single glass pane, but a—in particular integral—subunit of several glass panes.
In embodiments of the windowed door, the at least one closure device is designed to carry out a horizontal movement to regulate the air flow through the hollow space. In particular by an arrangement of the closure device between the front plate and the at least one inner plate and/or above or beyond an opening of the hollow space with a horizontal movement the cross-section of the opening can be easily progressively or gradually changed.
In embodiments of the windowed door, the at least one automatically moveable closure device comprises at least one shape memory alloy element designed to change the cross-section of the at least one air passage aperture by moving of a cover element.
The cover element is preferably adapted to fully cover the cross-section of the at least one air passage aperture. Expediently the cover element is movable in three mutually orthogonal directions.
The shape memory alloy element can be made from a copper-aluminum-nickel or a nickel-titanium alloy. Shape memory alloy elements have the ability to return to a previously defined shape or size when subjected to an appropriate thermal procedure. Generally these materials can be plastically deformed at relatively low temperature and upon exposure to higher temperature they return to their shape prior to the deformation. Shape memory alloys can have different shape memory effects, a so-called “one-way memory effect” and a so-called “two-way memory effect”. The one-way memory effect can be described as follows: When the shape memory alloy is in its cold state the metal can be bent or stretched and will hold those shapes until heated above a transition temperature. Upon heating the shape changes to its original. When the metal cools again, it will remain in the hot shape, until deformed again. The two-way memory effect is the effect that the material remembers two different shapes: one at low temperatures and one at high temperatures. In other words: A material that shows a shape memory effect during both heating and cooling is called two-way shape memory. To achieve this the material has to be “trained” to “remember” its shape in the deformed low-temperature condition.
The shape memory alloy element can be designed for example as strip, wire, spring, lamella, fin or vane. To be able to withstand more than 10.000 movement cycles and/or deformation cycles a thickness of at least 0.1 mm of the shape memory alloy element is favourable. In particular a thickness of the shape memory alloy element of 0.1 to 1.2 mm is advantageous.
Further on, it is favourable if the shape memory alloy element can carry out a stroke in a range of 1 to 25 mm. With a stroke in this range a change of a cross-section of the at least one air passage aperture with the cover element with an ascertainable change of cooling of the windowed door can be realized.
In one embodiment the shape memory alloy element is designed to cause a movement of the cover element at a predefined temperature, in particular at a temperature within a temperature range of 40° C. to 100° C. For example the shape memory alloy can be designed to return to its original shape at a temperature of 80° C. That means, when the shape memory alloy element reaches this temperature it will return to its original shape and provide a movement of the cover element whereby a cross-section of the at least one air passage aperture can be changed, in particular can be increased. To be able to change the size of the cross-section of the at least one air passage aperture step-by-step the at least one automatically moveable closure device can be provided with more than one shape memory alloy element which can cause different strokes or lengths of movement of the cover element at different predefined temperatures. For instance three shape memory alloy elements with different transition temperatures, for example 60° C., 80° C. and 100° C. could be provided which lead to different grades of movement of the cover element, for example 5 mm, 10 mm and 15 mm.
In another embodiment the shape memory alloy element is designed to cause a progressive movement of the cover element, in particular dependent on the temperature change of air within the air channel. Thereby a progressive change of the cross-section of the at least one air passage opening can be achieved, which allows a very good adjustment of the air cooling effect of the windowed door. For example with a shape memory element providing a “two-way memory effect” at 60° C. and 80° C. a progressive shape modification or rather a progressive movement within this temperature range is possible. At a temperature of 70° C. that shape memory element can be in an intermediate position for example, that means the shape memory element will have a shape between its shape at 60° C. and its shape at 80° C. In other words, a movement or shape modification of the shape memory element between a starting temperature (first shape) and a final temperature (second shape) will occur progressively. If final or target temperature is not completely reached shape memory element will have a shape between first and second shape. If temperature of shape memory element is further increased to final temperature shape memory element will reach its second shape, however if shape memory element cools down again to starting temperature shape memory element will return from its intermediate shape to its first shape.
In embodiments the at least one automatically moving closure device comprises at least one return member designed to bring back the shape memory alloy element into an initial shape after a warming up process followed by a cooling down process of the shape memory alloy element. To be able to repeatedly use a shape memory alloy element which comprises a one-way memory effect as an actuator a return member has to be provided with which the shape memory alloy element can be brought back from its original shape to its initial, deformed shape after being heated to a temperature above its transition temperature. The return member can be a spring, in particular a coil spring or flat spring.
In embodiments the shape modification of the shape memory alloy element is caused by heating of the shape memory alloy element via radiation heat emanating of the cooking chamber of the cooking appliance or via Joule heating or via induction heating. A shape modification of a shape memory alloy element which can be induced by radiation heat, in particular radiation heat emanating of the cooking chamber of the cooking appliance has the advantage that no further components with which a heating of the shape memory alloy element can be effected are required, whereby the closure device can be realized compact and light-weight. A shape modification of a shape memory alloy element which can be induced by Joule heating by providing an electric current flow through the shape memory alloy element as well as a shape modification of a shape memory alloy element which can be induced via induction heating allows a precise control of the shape memory alloy element and especially a precise control of the stroke that the shape memory alloy element will perform, whereby the amount of change of the cross-section of the at least one air passage aperture can be adjusted.
In particular, the cover element is essentially made from metal or plastic. A cover element made from metal, for example steel, has the advantage that it can withstand high temperatures and does not suffer material fatigue or deformation despite repeated large temperature changes. A cover element made from plastic has the advantage that it provides a lower weight in comparison to a cover element made from metal and therefore not so much force to move the cover element is required, that means with even a less powerful closure device a reliable movement of the cover element can be realized. The cover element can be made from a combination of metal or plastic, too, to make use of the advantages of both materials. Also a cover element made from a composite material is possible because such materials can for example withstand high temperatures and exhibit a certain flexibility which can ensure a reliable sealing of the cross-section of the at least one air passage aperture if required.
According to claim 14, a cooking appliance, in particular a cooking oven, is provided. The cooking appliance comprises a windowed door according to any embodiment and configuration as set out above. As to advantages, reference is made to the description above.
In embodiments of the cooking appliance, the cooking appliance provides a first and a second channel which are placed one above the other and wherein the first channel is arranged above the housing of a cooking chamber and the second channel is arranged beyond a control unit of the cooking appliance. Further on, a cooling fan is arranged at an area where the first and second channel are in operative connection with each other to provide an air flow of air entering into the at least one air inlet opening, passing through the hollow space and then escaping via the at least one air outlet opening, the first channel and the second channel. Hereby the air entering the windowed door through the at least one air inlet opening cannot only be used for cooling the door and in particular its front plate, but additionally for cooling the control unit. Thus malfunction or failure of electronic components of control unit or in particular electronic control mechanisms arranged above the housing of the cooking chamber due to strong heat loads—for example during a self-cleaning operation of the cooking appliance with high temperatures within the cooking chamber—can be avoided.
As to advantages and advantageous effects of the windowed door and the cooking appliance further reference is made to the description above and below.
Preferred embodiments of the invention will now be described in connection with the enclosed figures, in which:
Note, that the windowed door and the cooking appliance will be described only as far as is necessary for covering the invention.
In
As can be seen in
In
Air flow as indicated by arrows 50, 52 is lead along a first channel 54 above the housing 31 of the cooking chamber 30 from the front side of the cooking appliance 2 to its back side where a cooling fan 56 is arranged. By means of this cooling fan 54 the air passing through the first channel 54 can be redirected into a second channel 58. The air flow passing through the second channel 58 can escape through the recess 17 as indicated by arrow 16. As can be seen in
It has turned out that the energy consumption of a cooking appliance 2 provided with such a windowed door 4 with an automatically moveable closure device 40 can be reduced of about 10 to 20 Wh without risk of high temperatures at the front plate 6 during normal operation in comparison to cooking appliances without such a door, in particular because the time for preheating of the cooking appliance 2 can be reduced. Moreover, especially during a self-cleaning operation of the cooking appliance 2 high temperatures at the outer side of front plate 6 and thus injuries of an user are avoidable, whereas food leftovers at the inner side of inner plate 22 are still easily removable. Furthermore, during a steaming operation especially fogging of the inner side of the glass pane 8 is avoidable, too.
Instead of arranging the closure device 40 above the glass panes 8, 22, 36, 38 an arrangement beyond would be possible, too. Dependent on the design of the windowed door 4 and its glass panes 8, 24 an arrangement within air channel, for example at position 64, might be possible. Also an arrangement next to the air inlet openings 13 or air outlet opening 14 to change the cross-section of these openings could be considered. Furthermore, instead of providing only one closure device 40 several closure devices could be provided, too, and/or one or more shape memory alloy elements 44, 44′ and corresponding return members 46, 46′ could be used for moving the cover element 42. A use of a shape memory alloy element 44, 44′ with which step-by-step movements of the cover element 42 are possible could be also considered.
| Number | Date | Country | Kind |
|---|---|---|---|
| 14168591.7 | May 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/060657 | 5/13/2015 | WO | 00 |
