Patent Publication Number: US-7223943-B2

Title: Method and cooking apparatus for improved fresh air supply

Description:
BACKGROUND 
   The method and apparatus concerns a method for improved fresh air supply in a cooking apparatus and a cooking apparatus with an inner housing defining a cooking chamber as well as a fan chamber (separated from the cooking chamber via at least one flow guide element) for a fan with a fan wheel impeller which comprises primary blades on its side facing the first flow guide element and auxiliary blades on its side facing the wall (in particular back wall) of the inner housing through which the axle of the fan wheel passes to connect with a motor arranged outside of the inner housing. The fan wheel is provided for the circulation of cooking atmosphere and/or suction (intake) of fresh air into the inner housing via a fresh air channel whose mouth runs into the inner housing through the aforesaid wall of the same separated from the axle of the fan wheel. 
   Such cooking apparatuses are known in the prior art, see for example European Application 0 386 862 B1. They represent what are known as circulation air cooking apparatuses that allow an at least temporary fresh air supply to adjust desired climate proportions in the cooking chamber. For this purpose, fresh air is typically conveyed from a kitchen atmosphere into a cooking chamber of the cooking apparatus in order to displace portions of a cooking atmosphere, whereby the fresh air fraction of the aforesaid cooking atmosphere is increased while the fraction of other components such as water vapor, carbon dioxide, aromatic compounds and food-specific outgases is reduced. In such circulation cooking apparatuses in which the cooking atmosphere is significantly rotated via primary blades of a fan, a negative pressure for the take-up of fresh air via a fresh air channel is forced using auxiliary blades rotating with the primary blades and lying opposite the same. However, due to the scarce space ratios in a cooking device, it is sometimes not possible to place the mouth of the fresh air channel in the inner chamber (comprising the cooking chamber) of the cooking apparatus in axial proximity to the fan wheel where (in principle) optimal pressure ratios prevail. This has the disadvantage that now no maximum negative pressure is available as a driving force for the intake of the fresh air. 
   Furthermore, specified in DE 103 39 099.5 (not previously published) by the applicant is a cooking apparatus that ensures an improved fresh air supply in that the, so to speak, blind, mutually rotating air and/or cooking atmosphere is or are directed over at least one constriction on the back side of a fan wheel, thus on the side opposite the primary blades (which side is equipped with auxiliary blades) during each rotation of the fan wheel, such that there a streamline compression occurs. This streamline compression is accompanied with a pressure reduction given nearly isochoric state changes. 
   SUMMARY 
   It is an object to further develop the method such that the disadvantages of the prior art are overcome, and thus an improved fresh air supply is present. A design simpler in terms of construction should be provided that also enables a retrofitting of flow circulation cooking apparatuses. 
   A method is provided for improved fresh air supply in a cooking apparatus. An inner housing circumscribes a cooking chamber as well as a fan chamber. The fan chamber is separated from the cooking chamber via at least a first flow guide element. The fan chamber has a fan with a fan wheel comprising primary blades on its side facing the first flow guide element and auxiliary blades on its side facing a wall of the inner housing through which an axle of the fan passes. The fan wheel provides at least one of circulation of cooking atmosphere and suction of fresh air to the inner housing via a fresh air channel, a mouth of which runs into the inner housing through the inner housing wall separated from the axle of the fan wheel. Fresh air is sucked in through the fresh air channel via at least a second flow guide element, which prevents a direct impingement of the fresh air on the auxiliary blades and/or prevents an angular momentum caused by the auxiliary blades from being impressed onto the fresh air. The fresh air is then guided from the axle of the fan wheel into the cooking chamber via a radial guide effect of the auxiliary blades. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view through a cooking apparatus with fresh air supply in a first embodiment; 
       FIG. 2  is a sectional view through a cooking apparatus with fresh air supply in a second embodiment; 
       FIG. 3  is a sectional view through a cooking apparatus with fresh air supply in a third embodiment; and 
       FIG. 4  is a perspective plan view of the back wall of a cooking apparatus showing second and third glow guide elements. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated devices, and/or methods, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates. 
   With the disclosed method of the preferred embodiment, fresh air sucked in through the fresh air channel is initially conducted via at least a second flow guide element preventing a direct impingement on the auxiliary blades while allowing a rotary guiding effect by the auxiliary blades near the axle of the fan wheel. The air is then guided or conducted from the axle of the fan wheel into the cooking chamber via the radial conduction effect of the auxiliary blades. 
   Thus a rotation of the fresh air in the region between the second current conductor element and the aforesaid wall is significantly prevented via the use of at least one third flow guide element. 
   It is also provided that the current resistance for the fresh air upon entrance of the fresh air from the fresh air channel into the inner housing in the region between the aforesaid wall and the second flow guide element is reduced in that the cross-section of the mouth of the fresh air channel is selected larger than the cross-section of the fresh air channel. 
   The cooking apparatuses of the preferred embodiments are characterized by at least a second flow guide conductor element that partitions the region between the wall and the auxiliary blades into two intervening spaces at least in the region of the mouth of the fresh air channel, and leaves open the region of the axle of the fan wheel, whereby fresh air can be guided or conducted from the fresh air channel via a first intervening space, significantly without eddies near the axle, and from the area of the axle into the cooking chamber via the second intervening space via auxiliary blades. 
   It can thereby be provided that the second flow guide element significantly extends over the running area of the auxiliary blades and exhibits an opening for the passage of the axle of the fan wheel. 
   It is also provided with the preferred embodiment that the second flow guide element is aligned towards the axle of the fan wheel, in particular runs essentially perpendicular to the same, are preferably rotationally symmetrical to the same. 
   Preferred embodiments of the cooking chamber can be characterized by at least a third flow guide element between the second flow guide element and the aforesaid wall to prevent a rotation of the fresh air in the first intervening space, whereby the third flow guide element preferably stands essentially perpendicular to the second flow guide element and/or the aforementioned wall. 
   A plurality of third flow guide elements can thereby be provided, whereby preferably each third flow guide element spreads outwards radially from the axle of the fan wheel. 
   It also may be provided that the cross-section of the mouth of the fresh air channel is larger than the cross-section of the fresh air channel, whereby the cross-section of the mouth is preferably adjustable via at least one adjustment element. 
   It can be provided that a sealing element is arranged in the fresh air channel, preferably in the form of an adjustable diaphragm or flap. 
   Embodiments are also provided that are characterized by at least one sensor to detect at least one climate parameter. 
   Furthermore, it can be provided that a first, second and/or third flow guide element is or are movable, in particular portable, deployable, guidable, rotatable, and/or pivotable. 
   Finally, with preferred embodiments, by a control and/or regulation device in effective connection with the fan (in particular the motor of the fan wheel), the first flow guide element, the second flow guide element, the third flow guide element, the adjustment element, the sealing element and/or the sensor may be provided. 
   The preferred embodiment is based on the surprising realization that a supply of non-rotating fresh air in the region between the wall of an inner housing of a cooking device, in particular the back wall of the inner housing, and a fan wheel in the inner housing in direct proximity to the axle of the fan wheel itself, is possible when the mouth of a fresh air channel in the inner housing is spaced away from the aforesaid axle in order to use the entire length of auxiliary blades (that are provided on the side of the fan wheel facing towards the back wall) to convey the fresh air into the cooking chamber. For this purpose, the region between the auxiliary blades and the back wall is divided (via a flow guide element that acts as a partition wall) into two intervening spaces that are only connected with one another via an opening in the aforesaid flow guide element near the axle of the fan wheel. Fresh air drawn in via the fresh air channel can thus arrive in the region between the back wall and the flow guide element (first intervening space) in order to then flow via the opening of the flow guide element into the region between the current conductor element and the auxiliary blades (second intervening space), the fresh air arriving into the cooking atmosphere and finally into the cooking chamber via the conveying effect of the auxiliary blades. Nearly the same pressure ratios that would be present in the case in which the mouth of a fresh air channel were to lie in immediate proximity of the axle of the fan wheel are thus realized in the fresh air supply with a separation from the axle of the fan wheel. 
   In the structural embodiment of the mouth of the fresh air channel, both corresponding to the fresh air channel and the back wall of the inner housing, substantially no eddies should form between the flow guide element and the back wall that, due to their rotation, would oppose an inhibitive pressure of the fresh air supply in the first intervening space. On the one hand, in the arrangement of the partition wall-like flow guide element, care must be taken that the supplied fresh air is not accelerated in the first intervening space. Thus a minimum distance between the back wall and the aforesaid flow guide element is maintained. On the other hand, the flow guide element is to be separated from the auxiliary blades such that the drawn-in fresh air in the second intervening space is set in rotation to a degree that sets a desired flow volume. 
   As is to be learned from  FIG. 1 , a cooking apparatus which acts as a circulation air cooking apparatus comprises an outer housing  2  in which is arranged upon interposition of an insulation  3  an inner housing  4  which, among other things, comprises a back wall  4   a . A cooking chamber  5  and a fan chamber  6  that are separated from one another via a first flow guide element  7  are in turn provided within the inner housing  4 . Cooking atmosphere  8  can be circulated in the inner housing  4  via a fan  9 , while fresh air  11  can be introduced into the inner housing  4  via a fresh air channel  10  given an open flap  12  in the region of a mouth  13 . For this purpose, the fan  9  comprises a fan wheel  91  with primary blades (see primary blade edges  92 ) on its side facing the first current conductor element  7 , and thus the cooking chamber  5 , and auxiliary blades (see auxiliary blade edges  93 ) on its side facing away from the cooking chamber  5  and thus facing the back wall  4   a . The fan wheel  91  can be driven by a motor  99  via an axle  98 . 
   If, given an open flap  12 , fresh air  11  is drawn in via the fresh air channel  10  through the mouth  13  into the region between the back wall  4   a  and the auxiliary blades  93  (separated by the axle  98 ), a second flow guide element  100  provides that the fresh air  11  does not directly impinge on the auxiliary blades  93 , but rather initially is guided or conveyed within a first intervening space  110   a  into the proximity of the axle  98  in order to there be conveyed into the cooking chamber  5  via the conveying force of the auxiliary blades  93  via passage of a second intervening space  110   b . Both intervening spaces  110   a ,  110   b  are thus provided via the inter-arrangement of the flow guide element  100  between the back wall  4   b  and the auxiliary blades  93 , whereby a connection of both intervening spaces  110   a  and  110   b  is ensured by an opening  101  in the second flow guide element  100  in the region of the axle  98 . 
   The path of the flow of the fresh air  11 ,  11 ′,  11 ″ via use of the second flow guide element  100  is shown in  FIG. 2 . According to that Figure, the fresh air  11  is guided or conveyed (substantially without eddies) through the fresh air channel  10  and into the first intervening space  110   a , while in the region of the opening  101  of the second flow guide element  100  there is a rotary effect caused by the auxiliary blades  93 , so that the fresh air then placed into rotation for transport into the cooking chamber flows through the second intervening space  110   b , into the cooking chamber as shown at  11 ″. 
   It can be learned from  FIG. 2  that the back wall  4   a  runs displaced outwardly in the region of the fan wheel  91  to enlarge the intervening spaces  110   a ,  110   b  between the auxiliary blades  93  and the back wall  4   a.    
   The cooking apparatus of  FIG. 3  differs from that of  FIG. 2  inasmuch as the mouth  13 ′ of the fresh air channel  10  in the inner housing  4  exhibits a cross-section that is larger than the cross-section of the fresh air channel  10  itself. This provides for a reduction of the current resistance of the fresh air  11  upon entrance of the same into the first intervening space  110   a.    
   In  FIG. 4 , a cooking apparatus is shown that, to further prevent a rotation of the fresh air  11  in the first intervening space  110   a , comprises third flow guide elements  120  in the form of a plurality of ribs radially extending away from the axle  98  of the fan wheel  91 . The flow of the fresh air  11 ′″ runs between the ribs towards the axle  98  substantially without eddies. 
   While preferred embodiments have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention both now or in the future are desired to be protected.