Patent Abstract:
A cooking appliance including an interior, a fan mechanism having at least one fan wheel in the interior, at least one first flow directing member for subdividing the interior into a pressure chamber that houses the fan wheel and a cooking chamber, in which the first flow directing member includes at least one suction port for sucking atmosphere from the cooking chamber into the pressure chamber when the fan wheel is in operation and at least one blow-off port for blowing atmosphere from the pressure chamber into the cooking chamber when the fan wheel is in operation; and at least one second flow directing member that is included with the fan mechanism in the area of the suction port of the first flow directing member in order to improve the flow from the cooking chamber into the pressure chamber by forcing an axial main flow H in the suction zone of the fan mechanism, where the second flow directing member performs a nozzle function, extends from the fan mechanism into the cooking chamber, and overlaps the edge of the suction port of the first flow directing member, and where the first flow directing member extends into the second flow directing member.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application of International Application No. PCT/EP2009/064020, filed on Oct. 23, 2009, which claims the benefit of German Patent Application No. DE 10 2008 053 145.6, filed on Oct. 24, 2008, the entire contents of both applications are incorporated herein by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the present invention relate to a flow directing device for a cooking appliance with a fan mechanism, which comprises at least one fan wheel in an interior of the cooking appliance for circulating atmosphere, comprising at least one first flow directing member for subdividing the interior into a pressure chamber with the fan wheel and a cooking chamber, wherein the first flow directing member leaves free at least one suction port for sucking atmosphere from the cooking chamber into the pressure chamber in the area of the fan wheel and at least one blow-off port for blowing atmosphere from the pressure chamber into the cooking chamber when the fan wheel is in operation, at least one second flow directing member, which is mounted onto the fan mechanism or molded with the fan mechanism in the area of the suction port of the first flow directing member in order to improve the flow from the cooking chamber into the pressure chamber by forcing an axial main flow in the suction zone of the fan mechanism, and a cooking appliance with such a flow directing device. 
     Description of the Related Art 
     In the prior art, numerous measures for optimising a flow in the interior of a cooking appliance are known. Usually, a first flow directing member is used in the form of an air directing plate between a cooking chamber and a fan chamber or pressure chamber, which comprises a central suction port and leaves open blow-off ports facing the walls of the interior, so that a fan wheel arranged in the pressure chamber can suck atmosphere from the cooking chamber through the suction port and blow it out via the blow-off ports. 
     DE 203 14 818 U1, for example, deals with the targeted blowing of atmosphere from the pressure chamber into the cooking chamber via specially arranged blow-off ports in the first flow directing member. DE 10 2007 023 767, which is not pre-published, also deals with the blow-off ports of a first flow directing member, wherein movable elements should be arranged in blow-off ports, which move depending on the pressure progression in the cooking chamber. Another approach can be found, for example, in DE 203 09 268 U1 by using second flow directing members in the fan chamber in which a breaking up of the eddies should be forced while passing through a blow-off port between the pressure chamber and the cooking chamber, so that eddies spread out in the cooking chamber. Second flow directing members for forcing a homogeneous flow in the cooking chamber are also described in DE 203 12 031 U1. 
     A further flow directing device can be found, for example, in DE 10 2004 004 393 B4, in which a first flow directing member is in the form of a single piece with a second flow directing member. More precisely, the edge of the first flow directing member is turned in the form of an air directing plate in the area of its suction port to form a flow directing nozzle. This nozzle is a suction nozzle and is designed to improve the suction of atmosphere from a cooking chamber into a fan chamber of a cooking appliance. However, the disadvantage here is that a gap must be present at all times between a rotating fan wheel in the pressure chamber on the one hand, and the suction nozzle on the air directing plate on the other, in order to avoid damage. With cooking appliances in industrial kitchens in particular, this gap is large enough, due to tolerances, to enable atmosphere to flow from the pressure chamber directly into the suction area of the fan wheel, i.e., it is not directed via a blow-off port into the cooking chamber and via the suction port of the air directing plate into the suction area of the fan wheel, so that a short-circuit occurs with the atmosphere, which flows in from the cooking chamber through the suction port of the air directing plate. For this reason, this flow, which penetrates through the gap, is also known as a short-circuit flow, and occurs at a very sensitive point in the suction area of the fan wheel, i.e., in the deflection area of a main flow from the cooking chamber into the pressure chamber, more precisely, where a deflection occurs from a radial direction into an axial direction of the main flow. Thus, the short-circuit flow runs transverse to the main flow in the suction area of the fan wheel, so that it narrows the main flow and can itself cause a displacement and swirling of the main flow, which leads to an overall reduction in the effectiveness of the circulation of cooking chamber atmosphere by the fan wheel. 
     Generic flow directing devices for cooking appliances are described in EP 1 767 869 A2 and DT 25 19 604, wherein in both cases, a first flow directing member spreads out at least up to the suction port of a fan wheel, and in the case of DT 25 19 604, even extends into the suction port, while the second flow directing member is provided in the form of an outer contour of the fan wheel. 
     SUMMARY OF THE INVENTION 
     The object of the embodiments of the present invention is therefore to further develop the generic flow directing device in such a manner that it overcomes the disadvantages of the prior art. In particular, the effectiveness of a circulation within the interior of a cooking appliance should be improved. 
     This object is attained according to the embodiments of the present invention by means of the fact that each second flow directing member fulfils or performs a nozzle function, extends from the fan mechanism into the cooking chamber, and protrudes over or overlaps the edge of the suction port of the first flow directing member, while the first flow directing member spreads out into each second flow directing member. 
     Here, it is preferred that in cases when the fan mechanism comprises at least one radial fan, which includes a plurality of blades that are attached to a holding device, in particular, in the form of a support ring, and are arranged concentrically with a drive shaft, the second flow directing member is attached or molded with the shaft, the holding device, in particular, the support ring, and/or at least one blade. 
     According to embodiments of the present invention, it can here in turn be provided that the second flow directing member is in the form of a ring, in particular when attaching it to the holding device or molding it to the holding device. 
     Embodiments of the present invention are also directed to second flow directing members that extend into the pressure chamber up to the pressure area of the fan wheel. 
     Furthermore, it can be provided that each second flow directing member comprises a profile form of such a type that a flow from the cooking chamber into the pressure chamber only separates from the axial main flow as far as possible inside the pressure chamber, wherein preferably, an essentially hook-shaped profile or, in particular an asymmetric, U-shaped profile with an extended free end of the second flow directing member, is molded in the pressure chamber. 
     Additionally, embodiments of the present invention are directed to first flow directing members that are attached or are attachable to a wall of the interior. 
     Further embodiments of the present invention can also include by a third flow directing member in the pressure chamber, which, in particular, limits a blow-off area of the radial fan that extends conically outwards from the fan wheel of the radial fan. 
     Additionally, the third flow directing member can be attached to the first flow directing member, or can be moulded together with it. 
     Alternatively, the third flow directing member can be an extension of the second flow directing member, in particular at the free end of the second flow directing member in the pressure chamber. 
     According to the embodiments of the present invention, it is also recommended that the first flow directing member, the second flow directing member and/or the third flow directing member is or are in each case molded from at least one punched bending part and/or plate and/or is or are detachably affixed and/or is or are at least partially movable, or movable in sections. 
     Furthermore, the end of the second flow directing device can extend into the pressure chamber into a recess in the first and/or third flow directing device. 
     Particularly advantageous embodiments of the present invention are characterized by a plurality of fourth flow directing members, in particular, one fourth flow directing member for each blade, wherein, preferably, each fourth flow directing member is designed as a blade and/or as a blade extension, and most preferably extending through the support ring. 
     The embodiments of the present invention also provide a cooking appliance with a heating mechanism for heating atmosphere in a cooking chamber, a fan mechanism for circulating atmosphere at least in the cooking chamber and a flow directing device according to the embodiments of the present invention. 
     Additionally, the first flow directing member, the second flow directing member and/or the third flow directing member can be movable at least partially or in sections, preferably via a control or regulating mechanism, which interacts with the heating mechanism, the fan mechanism, a steam feed mechanism, a steam removal mechanism, a cooling mechanism, an energy saving mechanism, a microwave source, a gas feed mechanism, a gas removal mechanism, a sensing mechanism and/or a cleaning mechanism. 
     Finally, a shield, which can be of a grid or screen type, at least of the second flow directing member in the cooking chamber, can be affixed or is affixable in particular, to the first flow directing member, preferably in a detachable manner. 
     The embodiments of the present invention are thus based on the surprising finding that on the one hand, at least one first stationary flow directing member, for example, in the form of a standard air directing plate, is used in the interior of a cooking appliance, in order to separate the interior into a pressure chamber and a cooking chamber, wherein the first flow directing member leaves free a central suction port and at least one blow-off port on the edge side, and is affixed to the wall of the interior, while on the other hand, at least one second flow directing member is used, which fulfils or performs the function of a nozzle and which extends from a fan wheel in the pressure chamber, to which it is attached or molded together, through the suction port of the first flow directing member, so that the second flow directing member turns with the fan wheel. In a particularly advantageous manner, the nozzle, in particular, in the form of a ring is attached to a support ring for the blades of a radial fan, or is formed from a plurality of blade extensions. In any case, due to the nozzle, which rotates with the fan wheel, a radial flow is avoided in the suction area of the fan wheel, and thus, a short-circuit flow is also prevented. This increases the efficiency of the fan wheel and reduces the sensitivity of the entire cooking appliance to size tolerances. 
     Because radial fans are in principle relatively compact and are highly efficient, they are preferably used with a flow directing device according to the embodiments of the present invention. The high pressure area (the pressure side of the fan) and the suction area (the suction side of the fan) of a radial fan are relatively close to each other, so that due to the nozzle on the radial fan, a significant increase in fan capacity or reduction in the consumption capacity of the fan motor, is provided. 
     When the nozzle and the blades of the radial fan are affixed to a shared shaft, a separate fan housing is no longer required. The air directing plate and the nozzle, together with a wall of the interior, which is arranged opposite the air directing plate, form a type of fan housing. However, it is preferred that a shield is provided over the suction area of the radial fan in the cooking chamber in order to avoid injury, and is preferably attached to the first flow directing member. 
     Due to the size and geometry of the nozzle, further advantages can be attained, namely for the targeted directing of the flow. If the nozzle extends, on the one hand, in the pressure chamber into the area in which the blades of the radial fan create a pressure increase, the quantity of short-circuit flow is further reduced. If, on the other hand, the nozzle extends into the cooking chamber, an eddy formation in the suction area of the radial fan is reduced. 
     It is preferred according to the embodiments of the present invention that a third flow directing member is also used, which ensures that in the blow-off area of the radial fan, the pressure chamber comprises a chamber that extends radially outwards, so that the third flow directing member acts as a diffuser and further reduces the occurrence of short-circuit flows. The third flow directing member can be realised together with the first flow directing member. 
     Further features and advantages of the embodiments of the present invention are explained in the description of exemplary embodiments below with reference to the accompanying figures described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a partial profile view of a cooking appliance according to an embodiment of the present invention; 
         FIG. 2  shows an enlarged view of detail AA in  FIG. 1 ; and 
         FIG. 3  shows a perspective view of an alternative fan wheel for a cooking appliance according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A cooking appliance according to the embodiments of the present invention comprises, as is shown in  FIG. 1 , an interior  1 , which houses a fan wheel  2  in the form of a radial fan wheel. The fan wheel  2  is mounted on a drive shaft  3  of a motor (not shown), which is located outside the interior  1 . If, as an alternative, the motor were to be located inside the interior  1 , then cooling measures would be required. 
     Although in principle, an axial fan could also be used, a radial fan has the advantage that atmosphere, which is brought into rotation, in particular cooking chamber atmosphere, does not impact against a rear wall  4  of the interior  1 , but is instead deflected into the fan wheel  2 . As a result, the arrangement is compact and has a high degree of efficiency. 
     The fan wheel  2  sucks in atmosphere centrally, namely, from a suction area  5 , (see the suction flow E in  FIG. 1 ), and blows it off radially, namely, into a blow-off area  6 , (see the blow-off flow A in  FIG. 1 ). In principle, a variant would also be feasible in which the atmosphere flows in the reverse direction, wherein measures would then have to be provided in order to avoid a transverse flow in the blow-off area  6 . 
     The interior  1  is divided by a first flow directing member, for example, in the form of an air directing plate  7 , at least partially into a cooking chamber  8  and a pressure chamber  9 . The air directing plate  7  is, for example, affixed in a detachable and lockable manner via bridges or bars (not shown) to the walls of the interior  1 . The fan wheel  2  is mounted separately in the cooking appliance, namely, with the fan wheel  2  in the pressure chamber  9 , without a fixed connection to the air directing plate  7 . The air directing plate  7  leaves gaps  10   a  on its outer edges open for the blow-off flow A and comprises a central opening  10   b  for the suction flow E, which is regulated in accordance with the suction area  5 . 
     Due to the circulation of the atmosphere in the interior  1 , evened heating of the item of food to be cooked (not shown) in the cooking chamber  8  is possible after the atmosphere has been heated using a heating means (not shown), both in conventional ovens and baking and roasting ovens, which also have a steam function and/or microwave charge, for example. The heating means can be designed in the form of heating coils around the fan wheel  2 , for example. 
     In order to improve the deflection of atmosphere from the suction area  5  into the fan wheel  2 , and to avoid transverse and counterflows, which could lead to short-circuit flows that could negatively impact the capacity of the fan, a nozzle  11  is provided as a second flow directing member in the area of the opening  10   b  of the air directing member  7  on the fan wheel  2 . The nozzle  11  primarily directs atmosphere in the axial direction into the fan wheel  2 . As is shown in  FIG. 1 , atmosphere is predominantly sucked in in the radial edge area of the suction area  5  of the fan wheel  2  in the form of a main flow H, for which reason the nozzle  11  is not only matched in terms of its arrangement and size to the suction area  5 , but also to the opening  10   b  of the air directing plate  7 . 
     The fan wheel  2  comprises blades  12 . The end of each blade  12 , which, from the perspective of the axial direction, is located on the suction side of the fan wheel  2 , is here restricted by a ring-shaped wall  13  of a support ring, which is part of the fan wheel  2  and which is thus affixed on the shaft  3  in such a manner that it rotates. The nozzle  11  as depicted in the exemplary embodiment shown in  FIG. 1 , is firmly attached to this support ring or to this ring-shaped wall  13  and is itself in the form of a ring, so that a continuous sealing off of the pressure chamber  9  against the main flow H is provided. As a result, transverse and counterflows are to a large extent avoided in the area of the main flow H. 
     In an alternative embodiment, the nozzle can be affixed in another manner to the fan wheel for the purpose of avoiding the aforementioned transverse and counterflows. In principle, it would be possible, for example, to mount the nozzle onto an extension of the shaft in such a manner that it either rotates or does not rotate, which, however would require a precise maintenance of tolerance limits in terms of the distance between the fan wheel and the nozzle, which should be kept as small as possible. This, however, would not be advantageous. By contrast, it is advantageous to mold the nozzle in the form of additional blades that extend from the wall  13  in the direction of the air directing plate  7 , or that extend as extensions of the blades  12 , which extend through the wall  13  in the direction of the air directing plate  7 . This embodiment enlarges the suction area  5  of the fan wheel  2  while maintaining the same installation space. Furthermore, the conveyance capacity of the fan wheel  2  is also enlarged, so that the cooking speed is increased or the capacity of the fan drive can be reduced. At the same time, the ejection behaviour of the fan wheel  2  is improved due to the fact that the profile through which the flow moves is enlarged when the fan wheel  2  is left. Due to the larger profile through which the flow moves, circulation around the heating means is also more effective, which leads to an improved heating of the item of food to be cooked. 
     Whether the nozzle  11  is in the form of a ring or in the form of a plurality of blade extensions on the support ring wall  13 , has no influence over the fact that the opening  10   b  of the air directing plate  7  can be relatively freely selected, and the cooking appliance is no longer dependent to a high degree on tolerances with regard to the flow directing members  7 ,  11 . 
     With regard to  FIG. 2 , the progression of the various flows between the pressure chamber  9  and the cooking chamber  8  will now be described in detail. 
     In the area between the fan wheel  2 , which rotates when in operation, and the air directing plate  7 , there is a gap  14 . The gap  14  here is of such a size that it is guaranteed that the rotating fan wheel  2  together with the nozzle  11  under no circumstances brushes against the air directing plate  7 , which does not rotate. The dimensions of the gap  14  are in a way dependent on the production tolerances of both the air directing plate  7  or its opening  10   b,  of the fan wheel  2  or its blades  12 , of the wall  13 , and of the nozzle  11 . The gap  14  opens a connection between areas with large pressure differences that leads to a counterflow G, which separates from the blow-off flow A, and which flows from the pressure chamber  9  into the cooking chamber  8 , more precisely from the blow-off area  6  of the fan wheel  2  into its suction area  5 . In order for this counterflow G to run first radially in the pressure chamber  9  in the direction of the rotation axis of the fan wheel  2 , then essentially axially in the area of the air directing plate  7 , and finally radially outwards in the cooking chamber  8  in order to avoid to the greatest extent possible an interaction with the main flow H, i.e. to form no short-circuit flow, the nozzle  11  extends from the perspective of the axial direction until at least up to the opening  10   b  in the air directing plate  7 . In order to prevent the counterflow G from immediately flowing back into the suction area  5 , the nozzle  11  itself protrudes through the opening  10   b  into the cooking chamber  8 . Furthermore, the counterflow G is deflected away in the radial direction from the suction flow E by the nozzle  11  widening out towards the suction area  5 . The radius of the edge  15  of the nozzle  11 , which faces away from the cooking chamber  8 , is by contrast larger than the radius of the opening  10   b  in the air directing plate  7 . As a result, the flow resistance of the gap  14  is increased, on the one hand, and on the other hand the strength of an eddy formation and the volume of the counterflow G, is are reduced. 
     In order to prevent the rotating nozzle  11  from touching objects located in the cooking chamber  8 , such as an oven rack or similar structures, an air permeable shield  16  is provided. This shield  16 , which can be, for example, in the form of a grid or screen, is attached to the air directing plate  7  and also serves to protect against injury by preventing access to the fan wheel  2 . 
     An eddy formation can be further reduced in one embodiment according to embodiments of the present invention by the use of a third flow directing member in the form of an additional air directing plate  17  which functions as a diffuser. The additional air directing plate  17  can be mounted onto the first air directing plate  7  or be molded with the first air directing plate  7 . In any case, a distance B 1  between the additional air directing plate  17  and the rear wall  4  of the pressure chamber  9  is increased radially outwards relative to the longitudinal axis of the shaft  3  (rotation axis of the fan wheel), at least in the blow-off area  6 . The blow-off flow A, which flows out of the fan wheel  2  thus reaches the blow-off area  6  without significant changes to its profile, and flows onwards to the gaps  10   a  between the first air directing plate  7  and the interior wall, wherein due to the flow directing mechanisms, eddy formations are avoided and short-circuit flows are reduced. 
     The invention is not restricted to the embodiments described in detail herein, but can be varied within the scope of protection of the appended claims. For example, the edge  15  of the nozzle  11  can protrude into a recess formed by a branching of the first and/or second air directing plate  7 ,  9  for the purpose of further increasing the resistance experienced by the counterflow G. 
     An alternative fan wheel, or radial fan wheel  210  is shown in  FIG. 3  and comprises a disc-shaped bearing disc  212 , several main blades  214 , which are affixed on the bearing disc  212  with the same degree of separation, and a support or bearing ring  218 , which is equipped with directing blades  216  and which is affixed at a distance to the bearing disc  212  on the main blades  214 . 
     The bearing disc  212  is provided with a central recess  220 , wherein a central axis of the recess  220  corresponds with a central axis  222  of the bearing disc  212 . In an area located radially in the interior, the bearing disc  212 , which is produced from a plate board, is provided with a hub designed to guarantee a reliable attachment to a drive device (not shown) and a stable radial runout of the radial wheel  210 , even under high rotational speeds. The main blades  214  are with the present embodiment arranged in such a manner that they incline backwards on the bearing disc  212 . In other words, a rotational speed vector  224 , which is applied tangentially on the outer circumference of the bearing disc  212 , incorporates an acute angle with a largest surface  226  of the main blade  214 , as is shown symbolically in  FIG. 3 . 
     With the embodiment of the radial wheel  210  shown in  FIG. 3 , the directing blades  216  are designed as a single piece with the main blades  214  so that largest surfaces of the directing blades  216  incorporate the same acute angle with the rotational speed vector  224  as the largest surfaces  226  of the main blades  214 . The main blades  214  are in each case angled at right-angles on an end area, which is set opposite the directing blades  216 , so that they can be affixed by adhesive bonding, for example, by glueing or spot-welding, to the bearing disc  212  which is preferably made of metal. 
     The directing blades  216  protrude orthogonally from the surface of the bearing disc  212 . 
     The bearing ring  218  is provided with slits, not shown in greater detail, which are punctuated by the directing blades  216 , which are connected as a single piece with the main blades  214 . The directing blades  216  are affixed using a adhesively bonded connection, in particular a weld or solder connection, to the bearing ring  218 , and protrude orthogonally from said ring. Radially external front sides of the main blades  214  and of the directing blades  216  are with the present embodiment of the radial wheel, aligned orthogonally to a largest surface  230  of the bearing disc  212 . Radially internal front sides  232  of the main blades  214  are curved, and thus only essentially aligned orthogonally to the largest surface  230  of the bearing disc  212 . 
     As depicted in  FIG. 3 , the bearing ring  218  of the present embodiment, is designed as a single piece, made of a planar ring  234  and a suction mouth  236 , which connects radially internally, and is formed as a cone sheath section profile, and which provides a nozzle and thus also acts as a second flow directing member. The directing blades  216  are sized in such a manner that they extend from the radially external edge  238  of the planar ring  234  through to the radially internal edge  240  of the planar ring  234 . The inner edge  242  of the suction mouth  236  limits the suction profile of the radial wheel  210 . 
     Cooking chamber atmosphere that is sucked in by the radial wheel  210  and which flows through the suction port of a first flow directing member according to  FIGS. 1 and 2 , is either directed through the suction mouth  236 , i.e., the second flow directing member, and accelerated outwards by the main blades  214  in the radial direction, or enters a gap, which remains between the suction mouth  236  and the first flow directing member. In the gap, the directing blades  216  ensure that unwanted turbulences, which could reduce the effectiveness of a fan arrangement that is equipped with the radial wheel  210 , are avoided. The directing blades  216  thus act as further flow directing members (fourth flow directing members) in order to increase the efficiency of the radial wheel  210 . 
     The features of the embodiments of the present invention explained in the above description, in the drawings and in the claims, can be integral both individually as well as in any combination required in order to realise the invention in its different embodiments. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Interior 
           2  Fan wheel 
           3  Shaft 
           4  Rear wall 
           5  Suction area 
           6  Blow-off area 
           7  Air directing plate 
           8  Cooking chamber 
           9  Pressure chamber 
           10   a  Gap 
           10   b  Opening 
           11  Nozzle 
           12  Blade 
           13  Support ring wall 
           14  Gap 
           15  Edge 
           16  Shield 
           17  Air directing plate 
           210  Radial wheel 
           212  Bearing disc 
           214  Main blade 
           216  Directing blade 
           218  Bearing ring 
           220  Recess 
           222  Central axis 
           224  Rotational speed vector 
           226  Surface 
           230  Surface 
           232  Front side 
           234  Planar ring 
           236  Suction mouth/nozzle 
           238  Radially external edge 
           240  Radially internal edge 
           242  Inner edge 
         H Main flow 
         G Counterflow 
         E Suction flow 
         A Blow-off flow 
         B 1  Distance

Technology Classification (CPC): 5