Convection cooking oven

Abstract

Convection cooking oven comprising: - a muffle (10) having muffle side walls (60), a muffle top wall, a muffle bottom wall and a muffle rear wall (50, 500, 600) forming a cavity (20); - at least one fan cover (700, 800, 900, 600, 300) being arranged inside of the cavity (20) and in front of the muffle rear wall (50, 500, 600), separating the cavity (20) into a cooking chamber and a fan chamber (7011, 8011, 9011, 6011, 311); - at least one fan impeller (80) being arranged inside of the cavity (20) and in the fan chamber (7011, 8011, 9011) for generating an air flow (FFan) in the fan chamber (7011, 8011, 9011); - wherein the fan chamber (7011, 8011, 9011, 6011, 311) is at least partially enclosed by the muffle rear wall (50, 500, 600) and the fan cover (700, 800, 900, 600, 300) and wherein the muffle rear wall (50, 500, 600) and / or the fan cover (700, 800, 900, 600, 300) comprise air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b); - wherein the air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b) are configured to guide a part (FCL, FCR) of the air flow (FFan) that is generated by the fan impeller (80) in the fan chamber (7011, 8011, 9011, 6011, 311) out of the fan chamber (7011, 8011, 9011, 6011, 311) and into the cooking chamber; and wherein the air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b) guide the part (FCL, FCR) of the air flow (FFan) such that at least one sub-part (FOutL, FOutR) of the part (FCL, FCR) of the air flow (FFan) is accelerated on its way from the fan impeller (80) to the cooking chamber.

Description

[0001] The present invention relates to a convection cooking oven and to a method for operating such a convection cooking oven.

[0002] EP 3 365 606 B1 discloses a convection oven with an oven chamber and a recirculating ducting for recirculating gas from the oven chamber back to the oven chamber, the recirculation ducting including a fan scroll housing. A centrifugal fan is provided in the fan scroll housing for moving gas, wherein the fan scroll housing comprises fan discharge ducts defining respective gas flow paths and multiple cutoffs for dividing gas flow from the fan to the fan discharge ducts. Each second discharge duct includes an eddy wall section extending downstream from a cutoff being configured to create an eddy in the gas flow path.

[0003] EP 2 060 854 A1 discloses a convection cooking oven with a heating assembly that is mounted in a cooking chamber of the cooking oven and that comprises an electrical heating element, a fan and a baffle. The baffle is provided with air inlets and air outlets in communication with the cooking chamber. The baffle is formed in a way such that a forced air flow is evenly distributed, wherein the heat exchange from the heating element is maximized.

[0004] EP 3 364 113 A1 discloses a cooking appliance with a convection heating assembly having a fan and a baffle. The baffle has air outlets that are dimensioned in a specific way to generate an even distribution of hot air in the cooking chamber.

[0005] An objective of the present invention is to improve convection cooking ovens known in the art by reducing the energy consumption and / or improving the cooking performance, particularly by improving the cooking performance quality in terms of achieving even heat distribution in the cooking chamber of the convection cooking oven and / or by acceleration of the cooking process.

[0006] These objectives are at least partially solved by the present invention, which is respectively defined by the features of the independent claim. Embodiments result from the dependent claims and the exemplary embodiments described below and in connection with the annexed figures.

[0007] According to the invention, a convection cooking oven comprises: a muffle having muffle side walls, a muffle top wall, a muffle bottom wall and a muffle rear wall forming a cavity; at least one fan cover being arranged inside of the cavity and in front of the muffle rear wall, separating the cavity into a cooking chamber and a fan chamber; at least one fan impeller being arranged inside of the cavity and in the fan chamber for generating an air flow in the fan chamber; wherein the fan chamber is at least partially enclosed by the muffle rear wall and the fan cover and wherein the muffle rear wall and / or the fan cover comprise air guiding structures; wherein the air guiding structures are configured to guide a part of the air flow that is generated by the fan impeller in the fan chamber out of the fan chamber and into the cooking chamber; and wherein the air guiding structures guide the part of the air flow such that at least one sub-part of the part of the air flow is accelerated on its way from the fan impeller to the cooking chamber.

[0008] Additionally, at least one heating element may be provided within the fan chamber for heating the air in the fan chamber, such as a ring-shaped heating element that may be arranged coaxially with the fan impeller. A convection oven according to the invention enables an air flow, particularly a heated air flow that is created in the fan chamber to be evenly distributed in the cooking chamber. Even distribution is achieved by accelerating the air flow to be ejected out of the fan chamber into the cooking chamber by means of air flow streams. An increased ejection speed enables the air flow entering the cooking chamber to reach faraway parts of the cooking chamber as well as parts being in closed distance. The heat that is transported by the air flow is therefore distributed more evenly over the entire volume of the cooking chamber. The air flow generated by the fan impeller has a specific flow velocity when leaving the fan chamber. After leaving the fan chamber, the air flow or a part of the air flow is guided by the air guiding structures which accelerate the air flow such that the velocity of the air flow is increased and a type of a jet air flow may be created. The accelerated air flow or part of air flow forces the air out of the outlets of the fan chamber which results in a relatively high velocity of the air flow in the cooking chamber. In this way, the problem in the prior art is addressed that convection ovens that are currently on the market do not achieve sufficiently even heating of food within the cooking chamber if more than one tray is placed in the cooking chamber at the same time. This problem has been recognized by the applicant and the above solution has been found.

[0009] According to an advantageous embodiment, that the sub-part is accelerated on its way from the fan impeller to the cooking chamber by curved surfaces of the air guiding structures.

[0010] The curved surfaces of the air guiding structures may form divergent and / or convergent passages through which the sub-part of the air flow streams, or in other words, is pressed through by the fan, and which result in an acceleration of the sub-part of the air flow which streams therethrough.

[0011] According to an advantageous embodiment, the part of the at least one part of the air flow or, in other words, the sub-part, forms at least one vortex air flow, in particular in a vortex zone formed by the air guiding structures, on its way from the fan impeller to the cooking chamber, in particular wherein the sub-part accelerated when it forms the vortex air flow.

[0012] Generating a vortex air flow advantageously accelerates the air flow exiting into the cooking chamber. The proposed embodiment is particularly advantageous in situations when several trays with food to be cooked are placed in the oven and have to be evenly flowed on and / or heated by hot air.

[0013] According to an advantageous embodiment, the fan impeller may be configured to selectively rotate in a counterclockwise direction or to rotate in a clockwise direction. The air guiding structures may be configured to form an at least one first vortex air flow when the fan impeller rotates in a counterclockwise direction and to form an at least one second vortex air flow when the fan impeller rotates in a clockwise direction.

[0014] Thus, acceleration of the air flow by means of generating vortices can be achieved in both possible rotation directions of the fan impeller. In particular, in this embodiment, the rotation direction of the fan impeller may be alternated periodically to achieve temporal and spatial uniform cooking chamber temperature distribution which leads, as a consequence, to homogeneous cooking with multilevel trays.

[0015] Furthermore, it might be advantageous that the first vortex air flow rotates in a direction of rotation opposite to the direction of rotation in which the fan impeller rotates when it generates the air flow that partially forms the first vortex air flow, and / or in that the second vortex air flow rotates in a direction of rotation opposite to the direction of rotation in which the fan impeller rotates when it generates the air flow that partially forms the second vortex air flow.

[0016] In other words, the respective vortex is generated simultaneously in a direction of rotation opposite to the direction of rotation of the fan impeller. In that way a particular advantageous acceleration of the air flow is achieved.

[0017] In a further advantageous embodiment, the air guiding structures include at least one duct for guiding the at least one part of the air flow out of the fan chamber and into the cooking chamber, in particular wherein the at least one duct comprises two duct walls that face each other and that have each a curved (or: curvilinear) shape, preferably wherein the curved shape of the first duct wall substantially corresponds to the curved shape of the second duct wall, further preferably wherein the shape of the first duct wall is mirrored about a horizontal axis X in the shape of the second duct wall.

[0018] In this way, vortex chambers are provided in one duct for both possible rotation directions of the fan impeller. Thus, homogeneous air and heat distribution can be achieved by operating the fan impeller alternatingly in both rotation directions, as similar air flows can be generated in both the left and the right duct.

[0019] Further advantageously, the air guiding structures include at least one duct for guiding the at least one part of the air flow out of the fan chamber and into the cooking chamber, wherein the at least one duct comprises two duct walls that face each other at a varying distance. A first distance between the two duct walls at a duct inlet connecting the fan chamber with the at least one duct may be smaller than a second distance in an intermediate section of the duct. Additionally, or alternatively, a second distance in the intermediate section of the duct may be greater than a third distance in the intermediate section of the duct or at a duct outlet of the duct, wherein the second distance is closer to the fan chamber than the third distance. Additionally, or alternatively, the / a third distance in the intermediate section of the duct may be smaller than a fourth distance at a duct outlet of the duct.

[0020] An embodiment with a first distance minor to a second distance and a second distance major to a third distance and a third distance minor to a fourth distance advantageously creates a Coanda effect when the air flow leaves the duct outlet. Further, contractions of the duct according to the embodiment provide for an increase in velocity of the air flow and additionally form a wall along which the air flows and supports the formation of vortices in the vortex chamber. All these effects contribute to an increase in the flow speed and to an optimized distribution of the air flow at the duct outlet.

[0021] An embodiment with a first distance minor to a second distance and a second distance major to a third distance, where the third distance is the distance at the duct outlet, provides for a convergent duct outlet. The convergent duct outlets are configured to accelerate the air flow to reach longer distances inside the cooking chamber.

[0022] According to a further advantageous embodiment, the first vortex air flow and the second vortex air flow are formed in the same duct.

[0023] Thus, different vortices can be generated in the same duct, in particular one vortex can be generated when the fan impeller rotates clockwise, and the second vortex can be generated when the fan impeller rotates counterclockwise.

[0024] It is also advantageous, when the air flow forms at least one vortex air flow in a region of the intermediate section of the duct, where the duct walls are arranged in the second distance, in particular wherein the center of the vortex air flow is formed closer or adjacent to a first one of the duct walls when the fan impeller rotates in a counterclockwise direction which results in the formation of the first vortex air flow, and wherein the center of the vortex air flow is formed closer or adjacent to a second one of the duct walls when the fan impeller rotates in a clockwise direction which results in the formation of the second vortex air flow.

[0025] Thus, the vortices are a result of the specific shape of the ducts and of an operation of the fan impeller in a specific rotation direction with a specific rotational speed.

[0026] Advantageously, the fan chamber and / or the at least one duct are formed by embossment sections provided on the fan cover, but not on the muffle rear wall, wherein a height of the fan chamber and / or a height of the at least one duct may be defined by a depth of the respective embossment section provided on the fan cover for forming said fan chamber and / or duct.

[0027] According to such an embodiment, the fan chamber and ducts may be created by providing a specifically manufactured fan cover which is attached to a substantially flat muffle rear wall. The same muffle wall can be used for convention cooking ovens having different fan covers and thus having different convection properties.

[0028] Alternatively, the fan chamber and / or the at least one duct may be formed by embossment sections provided on the fan cover and embossment sections provided on the muffle rear wall, wherein a height of the fan chamber and / or a height of the at least one duct is defined by a depth of the respective embossment section provided on the fan cover in addition to a depth of the respective corresponding embossment section provided on the muffle rear wall for forming said fan chamber and / or duct.

[0029] In such an embodiment, the necessary embossment depth in the fan cover can be reduced and therefore the fan cover is less prone to manufacturing defects, e.g. with respect to the deep drawing process or with respect to an enamel process or coating process to which the fan cover is subjected.

[0030] Further alternatively, the fan chamber and / or the at least one duct may be formed by embossment sections on the muffle rear wall, but not on the fan cover, wherein a height of the fan chamber and / or a height of the at least one duct is defined by a depth of the respective corresponding embossment section provided on the muffle rear wall for forming said fan chamber and / or duct.

[0031] According to such an embodiment, the fan chamber and duct are substantially formed by the muffle rear wall and only enclosed by a substantially flat fan cover. In that way, high quality optical appearance of the fan cover can be achieved, since only substantially flat and smooth surfaces are visible.

[0032] According to a further advantageous embodiment, at least one duct may extend from the fan chamber to an at least one duct outlet, in particular wherein a height of the duct may decrease at least in sections in its extension from the fan chamber to the at least one duct outlet, preferably wherein the height of the duct decreases linearly or stepwise or increasingly or decreasingly.

[0033] In this way, the air flow speed in the ducts can be increased in the direction towards the duct outlets. The air flow reaches its greatest speed at the outlet and therefore is enabled to reach the farthest regions of the cooking chamber. This leads to an even heat distribution within the cooking chamber.

[0034] Additionally or alternatively, the at least one duct may extend from the fan chamber towards a muffle side wall and the least one duct outlet may be arranged adjacent to the muffle side wall.

[0035] Thus, the air flow exiting the duct outlet flows towards the muffle side wall and is deflected by the muffle side wall into the cooking chamber.

[0036] Additionally or alternatively, the at least one duct outlet has an outlet opening with a width of not more than 1 / 2, preferably not more than 1 / 3, of a cooking chamber height.

[0037] These ratios have been found as advantageous for the speed of the air flow leaving the outlet ducts and as enabling an even and quick distribution of the hot air delivered via the outlet ducts into the cooking chamber.

[0038] Also advantageously, at least one duct outlet comprises, in particular sinusoidal serrations, preferably integrally formed to the fan cover.

[0039] Such serrations reduce the noise generated by the jet-like air flow on the duct outlet.

[0040] Furthermore, an advantageous embodiment defines that the fan impeller comprises a fan plate and a plurality of fan blades attached to the fan plate, wherein the fan plate may be arranged substantially parallel to the muffle rear wall and to the fan cover. The fan blades may have planar fan blade sections that may be formed integrally to the fan plate. The planar fan blade sections may be arranged at an angle between 45° and 95°, preferably of approximately 90°, relative to the fan plate. The planar fan blade sections may extend in an angle of approximately 90° relative to a tangent of a circular path on which a radially outermost tip of the fan blades moves when the fan impeller rotates.

[0041] Such a fan impeller is adapted to impulse an air flow with substantially the same properties in clockwise rotation direction as well as in counterclockwise rotation direction. Further, such a fan impeller generates sufficient impulse for the air flow to reach the front end of the cooking chamber and at the same time generates relatively low noise.

[0042] According to a further advantageous embodiment, the fan cover may comprise centrally arranged inlet openings for air to be sucked into the fan chamber by the fan impeller, wherein the inlet openings are arranged radially inwards from a radially innermost section of the planar fan blade sections.

[0043] Thus, the air inlet openings of the fan cover are out of reach of the parts of the fan blades that generate a sucking effect for drawing air through the inlet openings. Thus, backflow through the air inlet openings is avoided when the rotation direction of the fan impeller is changed.

[0044] Additionally or alternatively, it may be advantageous to provide a method for operating a convection oven according to the invention, wherein the fan impeller is operated periodically in alternating rotation directions.

[0045] In that way, even hot air distribution in the cooking chamber can be achieved.

[0046] Non-limiting embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings. Same or functionally corresponding elements are reference with same reference signs. In the drawings: Figure 1A is a frontal view of a fan cover for a cooking oven according to a first embodiment the present invention; Figure 1B is a top view of the fan cover of Figure 1A; Figure 1C is a side view of the fan cover of Figure 1A; Figure 1D is a frontal view as in Figure 1A with the embossment sections made transparent to enable a view into the fan chamber and the fan cover ducts; An air flow is shown that is generated by a clockwise rotation of the fan impeller; Figure 1E is the same view as in Figure 1D, wherein the air flow shown is generated by a counterclockwise rotation of the fan impeller; Figure 2A is a frontal view of a fan cover for a cooking oven according to a second embodiment the present invention; Figure 2B is a top view of the fan cover of Figure 2A; Figure 2C is a side view of the fan cover of Figure 2A; Figure 2D is a frontal view as in Figure 2A with the embossment sections made transparent to enable a view into the fan chamber and the fan cover ducts; An air flow is shown that is generated by a clockwise rotation of the fan impeller; Figure 2E is the same view as in Figure 2D, wherein the air flow shown is generated by a counterclockwise rotation of the fan impeller; Figure 3A is a frontal view of a fan cover for a cooking oven according to a third embodiment of the present invention; Figure 3B is a sectional top view of a fan cover for a cooking oven according to the third embodiment of the present invention; Figure 4A is a frontal view of a fan cover for a cooking oven according to a fourth embodiment of the present invention; Figure 4B is a sectional top view of a fan cover for a cooking oven according to the third embodiment of the present invention; Figure 5A is a frontal view of a fan cover assembly with a front surface of the fan cover made transparent for a cooking oven according to a fourth embodiment of the present invention; Figure 5B is a side view of a fan cover assembly for a cooking oven according to the fourth embodiment of the present invention;

[0047] Figs. 1A to 1E illustrates fan cover 700 for being attached or being attached to a muffle rear wall of 50 of a convection cooking oven. The fan cover 700 may comprise a base plate part from which a first embossment section 7010, a second embossment section 7020 and a third embossment section 7030 may be formed. The first embossment section 7010 may form an enclosure of circular shape for a fan chamber 7011 to be arranged between the fan cover 700 and the muffle rear wall of 50.,

[0048] The first embossment section 7010 may fit over and cover a heating element 90 that may have a single or double ring shape and a fan impeller 80. A plurality of slots which may be concentrically arranged on the first embossment section 7010 may be provided as inlet openings 7120 for allowing air to be sucked into the fan chamber 7011 by the fan impeller 80. The slots are preferably located out of the reach of the blades to avoid backflow when the fan rotates in clock- or counterclockwise direction. This means that inlet openings 7120 may be arranged in a region towards which an air flow generated in the fan chamber F Fan by the fan impeller 80, or more precise by fan blades of the fan impeller 80, is not pushed. The total area of fan cover air inlet openings to air outlet openings may have a strongly reduced ratio.

[0049] The first embossment section 7010 may form a passage cover section 7040 for covering terminals of the heating element 90 and / or a passage through which the heating element 90 passes from outside of the cavity into the inside of the cavity. On the top surface of the first embossment section 7010 a plurality of openings 7070 may be provided to allow an airflow to reach a temperature sensor that may be disposed in the vicinity of the openings (7070) (not shown) .

[0050] From the first embossment section 7010 two side extensions in the form of second and third embossment sections 7020, 7030 may form a left duct 7050 and a right duct 7060 that fluidically couple the fan chamber 7011 to the cooking chamber by forming a channel through which at least a part of an air flow F Fan generated in the fan chamber 7011 can be guided towards left and right duct outlets 7051, 7061.

[0051] The second and third embossment sections 7020, 7030 may be substantially symmetric relative to the longitudinal (X) and transversal (Z) axis. From Figs. 1B and 1C, it can be seen that the second and third embossment sections 7020, 7030 may have a convergent cross section starting from the first embossment section 7010 and ending at the duct outlets 7051, 7061 of the ducts 7050, 7060. Expressed differently, the height of the ducts 7050, 7060 may decrease linearly from the first embossment section 7010 to the duct outlets 7051, 7061 as shown in the illustrated embodiment, but the decrease might be stepwise or increasingly or decreasingly. The convergent cross section allows to accelerate the airflow when it travels from the periphery of the fan impeller 80 to the duct outlets 7051, 7061. The height of the ducts 7050, 7060 can be understood as the distance between a base plane A-A defined by a base plate of the fan cover may lie and an embossment plane C-C defined by a top surface of the second or third embossment 7020, 7030.

[0052] Further, the second and third embossment sections 7020, 7030 may have a curvilinear profile. More specifically, the second and third embossment sections 7020, 7030 may have ducts walls 7050a, 7050b, 7060a, 7060b that extend from the circular shape of the first embossment section 7010 and that may have a curvilinear form.

[0053] The left and right ducts 7050, 7060 are provided for guiding at least one part of the air flow that is generated by the fan impeller 80 in the fan chamber 7011, i.e. air flows F CL , F CR , F OutL , F OutR , out of the fan chamber (7011, 8011, 9011, 6011, 311) and into the cooking chamber, wherein the at least one duct (7050,...,361) may comprise two duct walls (7050a,..., 304b) that face each other at a varying distance.

[0054] More specifically a first distance d11, d21 between the two duct walls 7050a, 7050b or 7060a, 7060b at a duct inlet connecting the fan chamber 7011 with the at least left or right duct 7050, 7060 may be smaller than a second distance d12, d22 at an intermediate section of the respective duct 7050, 7060. The second distance d12, d22 in the intermediate section of the duct 7050, 7060 may be greater than a third distance d13, d23 in the intermediate section of the duct 7050, 7060 or at a duct outlet 7051, 7061 of the respective duct 7050, 7060, wherein the second distance d12, d22 may be closer to the fan chamber 7011 than the third distance d13, d23. The third distance d13, d23 in the intermediate section of the duct 7050, 7060 may be smaller than a fourth distance d14, d24 at a duct outlet 7051, 7061 of the duct 7050, 7060. In the embodiment according to Figs. 1A to 1E, the fourth distance d14, d24 defines the width of the duct outlets 7051, 7061.

[0055] The curvilinear form of the duct walls 7050a, 7050b or 7060a, 7060b in the region of the first distance d11, d21 constraints the flow once is released from the fan impeller 80. The second distance d12, d22 widens the duct 7050, 7060 in such a way that the duct walls 7050a, 7050b or 7060a, 7060b form a divergent cross section. In the region of the third distance d13, d23 the velocity of the air flow is increased prior to the release through the divergent outlets 7051, 7061 whose shape is intended to spread the flow along the outlets.

[0056] The regions of the third distance d13, d23 cause the Coanda effect when the air flow leaves the duct outlets 7051, 7061. In the left duct 7050, the curvilinear profiles may form a left vortex chamber in which a first and a second vortex air flow F VL can be formed, while the curvilinear profiles of the right duct 7060 may form a right vortex chamber in which corresponding first and a second vortex air flows F VR can be. Moreover, as shown in Figures 1D and 1E for the first embodiment and in Figures 2D and 2E for the second embodiment, one or each of the left and right vortex chambers may have two different vortex zones. The left vortex chamber may comprise an upper left vortex zone VZ UL and a lower left vortex zone VZ LL , wherein the right vortex chamber may comprise an upper right vortex zone VZ UR and a lower right vortex zone VZ LR .

[0057] The vortex chambers have the function to create a vortex in a specific vortex zone that will deviate the air flow F CL , F CR to the opposite direction compared to the direction in which the flow was released by the fan impeller 80. In other words, when the fan impeller 80 rotates clockwise, the resulting air flow vortices F VL and F VR rotate counterclockwise. When the fan impeller 80 rotates counterclockwise, the resulting air flow vortices F VL and F VR rotate clockwise.

[0058] The vortex chambers connect to the duct outlets 7051, 7061 where the air flow F OutL , F OutR is released to the cavity. The duct outlets 7051, 7061 can preferably have a nozzle type shape to spread the exiting flow over the entire height of the cavity. Since the fan cover 700 may be arranged substantially in an upright or vertical position adjacent to the vertical muffle rear wall 50, each of left and right duct 7050, 7060 may provide an upper vortex zone VZ UL or VZ UR and a lower vortex zone VZ LR or VZ LL inside the vortex chamber.

[0059] This can be derived from Fig. 1D in which the fan impeller 80 generates an air flow F Fan in the fan chamber 7011 by rotating clockwise that results in the generation of an air flow vortex F VL in the lower left vortex zone VZ LL inside the vortex chamber of the left duct 7050 and of an air flow vortex F VR in the upper right vortex zone VZ UR inside the vortex chamber of the right duct 7060. During clockwise rotation of the fan impeller 80 no air flow vortex is created in the upper left vortex zone VZ UL inside the vortex chamber of the left duct 7050 and not in the lower right vortex zone VZ LR inside the vortex chamber of the right duct 7060.

[0060] When the fan impeller 80 rotates counterclockwise as shown in Fig. 1E, air flow vortices are generated in the upper left vortex zone VZ UL inside the vortex chamber of the left duct 7050, namely F VL , and in the lower right vortex zone VZ LR inside the vortex chamber of the right duct 7060, namely F VR .

[0061] Referring to Fig. 1D and Fig. 1E, the flow mechanism is explained. It shall be understood that this flow mechanism is achieved in all described embodiments. The circular shape of the first embossment section 7010 and the fan impeller 80 have to be adapted to each other to confine the airflow between the impeller periphery and the circular wall. By looking only at the second embossment section 7050 in Fig. 1D, once that the air flow F CL exits from the circular shape, just below the curvilinear profile of the upper duct wall 7050a, the flow accelerates and creates a jet F VL that enters into the left divergent section representing a vortex chamber.

[0062] The jet air flow F VL in the vortex chamber travels to the surface of upper duct wall 7050a. Once the jet air flow F VL encounters the curvilinear profile of upper duct wall 7050a, it deviates the flow downwards in opposite direction to the jet, following the curvilinear profile. Finally, the flow travels to the left duct outlet 7051 and the shape of the duct outlet 7051 makes the air flow F OutL to be spread when it leaves the fan cover.

[0063] The shape of the vortex chamber and the jet air flow F VL induce a vortex just downwards where the jet air flow F VL travels in the direction of the left duct outlet 7051. The vortex rotates in counterclockwise direction and helps to create an aerodynamic obstruction to partially seal the left duct 7020. This allows to keep the jet acceleration up to the left duct outlet 7051 and finally impacting on the left muffle side wall 60.

[0064] The diameter and vorticity, i.e. the local rotational movement, of the vortex will be influenced mainly by the dimensions of the vortex chamber and the dimensions of the region in which the duct 7020 is connected to the fan chamber 7011, in particular by the distance d 11 between the duct walls 7050a, 7050b in the region where the duct 7020 connects with the fan chamber 7011.

[0065] These two parameters will be chosen and adjusted mainly to guarantee the jet air flow F VL and the size of the vortex to achieve the proper direction of the flow F OutL exiting the duct outlet 7051.

[0066] The height of the ducts 7050, 7060 tapers towards the muffle rear wall 50, as it is shown in Fig. 1B or 2B, to create a venturi effect that increasing the air flow speed.

[0067] By looking on the right duct 7060, the same flow mechanism occurs mirror wise. Described in general terms, air guiding structures that may comprises the left and right ducts 7050, 7060 and their respective walls 7050a, 7050b, 7060a, 7060b and outlet openings 7051, 7061 guide a part F CL , F CR of the air flow F Fan that is generated by the fan impeller 80 in the fan chamber 7011 out of the fan chamber 7011 and into the cooking chamber. The air guiding structures guide the part (F CL , F CR ) of the air flow (F Fan ) such that at least one sub-part F OutL , F OutR of the part F CL , F CR of the air flow F Fan is accelerated on its way from the fan impeller 80 to the cooking chamber.

[0068] Figs. 2A to 2E illustrate a fan cover 800 according to an alternative embodiment. It shall be understood that the embodiments of Figs. 1A to 1E and of Figs. 2A to 2E may have identical features, apart from the differences described in the following. One difference in comparison of both fan cover designs relates to the region in which the duct walls 8050a, 8050b or 8060a, 8060b are arranged in the second distance d12, d22 to each other. This region may be connected directly to the duct outlets 8051, 8061 with a straight section of the respective duct walls 8050a, 8050b or 8060a, 8060b creating convergent duct outlets 8051, 8061. The second and third embossments 8020, 8030 may form the vortex chambers identical to the second and third embossments 7020, 7030 of the first embodiment. Convergent outlets as of the embodiment of Figs. 2A to 2E may be created to accelerate the air flow F OutL , F OutR exiting the left or right ducts 8050, 8060 to reach longer distances inside the cavity. In the embodiment according to Figs. 2A to 2E, the third distance d13, d23 defines the width of the duct outlets 8051, 8061. Also in the second embodiment, air guiding structures that may comprises the left and right ducts 8050, 8060 and their respective walls 8050a, 8050b, 8060a, 8060b and outlet openings 8051, 8061 guide the part F CL , F CR of the air flow F Fan that is generated by the fan impeller 80 in the fan chamber 8011. The air guiding structures guide the part (F CL , F CR ) of the air flow (F Fan ) such that at least one sub-part F OutL , F OutR of the part F CL , F CR of the air flow F Fan is accelerated on its way from the fan impeller 80 to the cooking chamber.

[0069] Figs. 3A and 3B illustrate a fan cover 900 according to a third embodiment. It shall be understood that the embodiments shown in Figs. 2A to 2E and Figs. 3A and 3B may have identical features, apart from the differences described in the following.

[0070] The fan cover 900 comprises first, second and third embossment sections 9010, 9020, 9030 having the same shape as the corresponding embossment sections in Figs. 2A to 2E and, thus, provide correspondingly air guiding structures for forming a fan chamber 9011 between the first embossment section 9010 and the muffle rear wall 500 in which a, in this specific embodiment double-ring, heating element 90 and the fan impeller 80 are disposed. In comparison to the second embodiment, the depth of the embossment sections 9010, 9020, 9030 is reduced to the half compared to the depth of the embossment sections 8010, 8020, 8030 of the second embodiment. In order to compensate the lesser depth of the fan cover embossment section, the muffle rear wall 500 is provided with first, second and third embossment sections 9015, 9032, 9031 complementary to the first, second and third embossment sections 9010, 9020, 9030 of the fan cover 900. Also with respect to the third embodiment, air guiding structures are provided that may comprises the left and right ducts 9050, 9060 and their respective walls and outlet openings 9051, 9061 that guide a part F CL , F CR of the air flow F Fan that is generated by the fan impeller 80 in the fan chamber 9011 out of the fan chamber 011 and into the cooking chamber. Also in this embodiment, the air guiding structures guide the part F CL , F CR of the air flow F Fan such that at least one sub-part F OutL , F OutR of the part F CL , F CR of the air flow F Fan is accelerated on its way from the fan impeller 80 to the cooking chamber.

[0071] The depth can be any ratio between a full depth fan cover in combination with a flat muffle rear wall to a flat fan cover in combination with full-depth embossed muffle rear wall. The shape on the muffle rear wall corresponds to the same profile and shape of the fan cover to guarantee proper sealing and to guide the air flow properly to the duct outlets 9051, 9061. The heating element 90 can be positioned inside of first embossment section 9010 of the muffle rear wall 500.

[0072] Due to the manufacturing process, the enameling of components can be difficult to implement in the daily basis production for the fan cover. The third embodiment is optimized to address this problem and may provide a high-quality optical appearance for the consumer.

[0073] According to a fourth embodiment shown in Figs. 4A and 4B, the depth of the fan cover can be fully recessed into the muffle rear wall 5000. It shall be understood that the embodiments shown in Figs. 3A and 3B and Figs. 4A to 4B and may have identical features, apart from the differences described in the following. The entire fan cover 600 is substantially flat and has no first embossment section, but only second and third embossment sections 6020, 6030 for forming a part of the left and right ducts 6050, 6060 and the left and right duct outlets 6051, 6061.

[0074] The muffle rear wall 5000 comprises a first embossment section 6015 that provides space for accommodation of the heating element 90 and the fan impeller 80 in fan chamber 6011 and second and third embossment sections 6020, 6030 for forming the left and right ducts 6050, 6060. The vortex chambers are provided by the curvilinear shape of the ducts 6050, 6060 implemented by the second and third embossment sections 6020, 6030 of the muffle rear wall 5000. The curvilinear shape may be identical to the curvilinear shape of the second and third embossment sections 9020, 9030 of the third embodiment. Since the fan cover 600 is substantially flat, this embodiment provides a high-quality optical impression for the consumer. Also with respect to the fourth embodiment, air guiding structures are provided that may comprises the left and right ducts 6050, 6060 and their respective walls and outlet openings that guide a part F CL , F CR of the air flow F Fan that is generated by the fan impeller 80 in the fan chamber 6011 out of the fan chamber 6011 and into the cooking chamber. Also in this embodiment, the air guiding structures guide the part (F CL , F CR ) of the air flow (F Fan ) such that at least one sub-part F OutL , F OutR of the part F CL , F CR of the air flow F Fan is accelerated on its way from the fan impeller 80 to the cooking chamber.

[0075] According to a fifth embodiment shown in Figs. 5A and 5B, a fan cover 300 may be provided having an air guiding part 301 and separate cover part 302. The air guiding part 301 comprises duct walls 303a, 303b, 304a, 304b of a left and right duct 351, 361 forming left and right duct outlets 305, 306. Further, the air guiding part 301 forms a fan chamber 311. The muffle rear wall 50 may be substantially flat.

[0076] The separate cover part 302 closes the fan chamber 311 and the left and right ducts 351, 361 against the cooking chamber and provide a substantially flat surface for an advantageous optical appearance. The fan chamber 311 comprises substantially the same shape as the fan chamber according to the first embodiment. The duct walls 303a, 303b, 304a, 304b comprise the same curvilinear shape as the second and third embossment sections 7020, 7030. The cover part 302 can be fixed to the air guiding part 301 by appropriate means.

[0077] Such a multi-component concept by having the air guiding part 301 and the separate cover part 302 provides for an aesthetical cover to hide the air guiding part 301. The air guiding part 301 may be provided with small radii and "sharp" angles that are difficult to enamel and that might be subject to enameling defects. The aesthetical separate cover part 301 may be designed with smooth radii for enameling, and thus may have a better cleanability. In addition, it gives more flexibility to apply special coatings to the separate cover part 301 that is suitable to be provided with treatments like easy-to-clean coatings, e.g. solgel coatings. The smooth surface supports the coating process and could be a benefit to not overheat the surface as the coated surface could have bigger distances to the heating element. In addition, also here the cleanability is improved with a plane and smooth aesthetical cover. Also with respect to the fifth embodiment, air guiding structures are provided that may comprises the left and right ducts 351, 361 and their respective walls 303a, 303b, 304a, 304b and outlet openings 305, 306 that guide a part F CL , F CR of the air flow F Fan that is generated by the fan impeller 80 in the fan chamber 311 out of the fan chamber 311 and into the cooking chamber. Also in this embodiment, the air guiding structures guide the part F CL , F CR of the air flow F Fan such that at least one sub-part F OutL , F OutR of the part F CL , F CR of the air flow F Fan is accelerated on its way from the fan impeller 80 to the cooking chamber.List of Reference Signs

[0078] 10 muffle 20 cavity 30 side grid 50, 500, 5000 muffle rear wall 60 muffle side wall 700, 800, 900, 600, 300 fan cover 301 air guiding part 302 cover part 601 planar front area 80 fan impeller 90 heating element 7010, 8010, 9010 first embossment section 9015, 6015 first embossment section in rear wall 7011, 8011, 9011, 6011, 311 fan chamber 7020, 8020, 9020, 6020 second embossment section 7030, 8030, 9030, 6030 third embossment section 9032, 6032 second embossment section of rear wall 9031, 6031 third embossment section of rear wall 7040, 8040, 9040 passage cover section 7050, 7060, 8050, 8060, 9050, 9060, 6050, 6060, 351, 361 left duct, right duct 7051, 7061, 8051, 8061, 9051, 9061, 6051, 6061, 305, 306 left duct outlet, right duct outlet 7050a, 7050b, 8050a, 8050b, 303a, 303b duct walls of left duct 7060a, 7060b, 8060a, 8060b, 304a, 304b duct walls of right duct 7050, 7060, 8050, 8060, 9050, 9060, 6050, 6060, 351, 361; 7051, 7061, 8051, 8061, 9051, 9061, 6051, 6061, 305, 306; 7050a, 7050b, 8050a, 8050b, 303a, 303b; 7060a, 7060b, 8060a, 8060b, 304a,304b; 301; air guiding structures 7070 openings 7120, 8120, 9120 , 6120 inlet openings X, Z horizontal axis, vertical axis A-A base plane B-B second embossment plane C-C third embossment plane R CW clockwise rotation direction R CCW counterclockwise rotation direction F Fan Air flow in fan chamber F CL , F CR Air flow entering left / right duct F VL , F VR Air flow in left / right vortex F OutL , F OutR Air flow exiting left / right duct VZ UL Vortex zone upper left VZ LL Vortex zone lower left VZ UR Vortex zone upper right VZ LR Vortex zone lower right

Claims

1. Convection cooking oven comprising: - a muffle (10) having muffle side walls (60), a muffle top wall, a muffle bottom wall and a muffle rear wall (50, 500, 600) forming a cavity (20) ; - at least one fan cover (700, 800, 900, 600, 300) being arranged inside of the cavity (20) and in front of the muffle rear wall (50, 500, 600), separating the cavity (20) into a cooking chamber and a fan chamber (7011, 8011, 9011, 6011, 311); - at least one fan impeller (80) being arranged inside of the cavity (20) and in the fan chamber (7011, 8011, 9011) for generating an air flow (FFan) in the fan chamber (7011, 8011, 9011); - wherein the fan chamber (7011, 8011, 9011, 6011, 311) is at least partially enclosed by the muffle rear wall (50, 500, 600) and the fan cover (700, 800, 900, 600, 300) and wherein the muffle rear wall (50, 500, 600) and / or the fan cover (700, 800, 900, 600, 300) comprise air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b) ; - wherein the air guiding structures (7050,...,361;7051,...,306;7050a, .., 303b; 7060a, ..., 304b) are configured to guide a part (FCL, FCR) of the air flow (FFan) that is generated by the fan impeller (80) in the fan chamber (7011, 8011, 9011, 6011, 311) out of the fan chamber (7011, 8011, 9011, 6011, 311) and into the cooking chamber; and - wherein the air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b) guide the part (FCL, FCR) of the air flow (FFan) such that at least one sub-part (FOutL, FOutR) of the part (FCL, FCR) of the air flow (FFan) is accelerated on its way from the fan impeller (80) to the cooking chamber.

2. Convection cooking oven according to claim 1, characterized in that the sub-part (FOutL, FOutR) is accelerated on its way from the fan impeller (80) to the cooking chamber by curved surfaces of the air guiding structures (7050,...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b).

3. Convection cooking oven according to any of the preceding claims, characterized in that the sub-part (FOutL, FOutR) forms at least one vortex air flow (FVL, FVR), in particular in a vortex zone (VZUL, VZLL, VZVR, VZLR) formed by the air guiding structures (7050, ...,361; 7051,...,306; 7050a, .., 303b; 7060a, ..., 304b), on its way from the fan impeller (80) to the cooking chamber, in particular wherein the sub-part (FOutL, FOutR) is accelerated when it forms the vortex air flow (FVL, FVR).

4. Convection cooking oven according to any of the preceding claims, characterized in that the fan impeller is configured to selectively rotate in a counterclockwise direction (RCCW) or to rotate in a clockwise direction (RCW) and wherein the air guiding structures (7050,...,361;7051,...,306;7050a,..,303b;7060a, ...,304b) are configured to form an at least one first vortex air flow (FVL, FVR) when the fan impeller rotates in a counterclockwise direction (RCCW) and to form an at least one second vortex air flow (FVL, FVR) when the fan impeller rotates in a clockwise direction (Rcw) .

5. Convection cooking oven according to claim 4, characterized in that the first vortex air flow (FVL, FVR) rotates in a direction of rotation opposite to the direction of rotation in which the fan impeller (80) rotates when it generates the air flow (FFan) that partially forms the first vortex air flow (FVL, FVR), and / or in that the second vortex air flow (FVL, FVR) rotates in a direction of rotation opposite to the direction of rotation in which the fan impeller (80) rotates when it generates the air flow (FFan) that partially forms the second vortex air flow (FVL, FVR).

6. Convection cooking oven according to any of the preceding claims, characterized in that the air guiding structures (7050,...,361; 7051,...,306; 7050a,..,303b; 7060a, ...,304b) include at least one duct (7050,...,361) for guiding the at least one part (FCL, FCR) of the air flow (FFan)) out of the fan chamber (7011, 8011, 9011, 6011, 311) and into the cooking chamber, in particular wherein the at least one duct (7050,...,361) comprises two duct walls (7050a,..., 304b) that face each other and that have each a curved shape, preferably wherein the curved shape of the first duct wall (7050a,..., 304b) substantially corresponds to the curved shape of the second duct wall (7050a,..., 304b), further preferably wherein the shape of the first duct wall (7050a,..., 304b) is mirrored about a horizontal axis (X) in the shape of the second duct wall (7050a,..., 304b) .

7. Convection cooking oven according to any of the preceding claims, characterized in that the air guiding structures (7050,...,361; 7051,...,306; 7050a, 303b; 7060a, ...,304b) include at least one duct (7050,...,361) for guiding the at least one part (FCL, FCR) of the air flow (FFan)) out of the fan chamber (7011, 8011, 9011, 6011, 311) and into the cooking chamber, wherein the at least one duct (7050,...,361) comprises two duct walls (7050a,..., 304b) that face each other at a varying distance, in particular wherein a first distance (d11, d21) between the two duct walls duct walls (7050a,..., 304b) at a duct inlet connecting the fan chamber (7011, 8011, 9011, 6011, 311) with the at least one duct (7050,...,361) is smaller than a second distance (d12, d22) in an intermediate section of the duct (7050,...,361), and / or wherein the / a second distance (d12, d22) in the intermediate section of the duct (7050,...,361) is greater than a third distance (d13, d23) in the intermediate section of the duct (7050,...,361) or at a duct outlet (7051,306) of the duct (7050,...,361), wherein the second distance (d12, d22) is closer to the fan chamber (7011, 8011, 9011, 6011, 311) than the third distance (d13, d23), and / or wherein the / a third distance (d13, d23) in the intermediate section of the duct (7050,...,361) is smaller than a fourth distance ((d14, d24) at a duct outlet (7051,306) of the duct (7050,...,361).

8. Convection cooking oven according to any of the claims 6 to 7, characterized in that the first vortex air flow (FVL, FVR) and the second vortex air flow (FVL, FVR) are formed in the same duct (7050,...,361), in particular one vertically above the other.

9. Convection cooking oven according to any of the claims 6 to 8, characterized in that the air flow (FCL, FCR) forms at least one vortex air flow (FVL, FVR) in a region of the intermediate section of the duct (7050,...,361), where the duct walls are arranged in the second distance (d12, d22), in particular wherein the center of the vortex air flow (FVL, FVR) is formed closer or adjacent to a first one of the duct walls (7050a,..., 304b) when the fan impeller rotates in a counterclockwise direction (RCCW) which results in the formation of the first vortex air flow (FVL, FVR), and wherein the center of the vortex air flow (FVL, FVR) is formed closer or adjacent to a second one of the duct walls (7050a,..., 304b) when the fan impeller rotates in a clockwise direction (RCW) which results in the formation of the second vortex air flow (FVL, FVR).

10. Convection cooking oven according to any of the preceding claims, characterized in that the fan chamber (7011, 8011, 9011) and / or the at least one duct (7050,..., 361) are formed by embossment sections (7100,..., 6030) provided on the fan cover (700, 800, 900, 600, 300), but not on the muffle rear wall (50, 500, 600), wherein a height of the fan chamber (7011, 8011, 9011) and / or a height of the at least one duct (7050,..., 361) is defined by a depth of the respective embossment section (7100,..., 6030) provided on the fan cover (700, 800, 900, 600, 300) for forming said fan chamber (7011, 8011, 9011) and / or duct (7050,..., 361), or wherein the fan chamber (7011, 8011, 9011) and / or the at least one duct (7050,..., 361) are formed by embossment sections (7100,..., 6030) provided on the fan cover (700, 800, 900, 600, 300) and embossment sections (9015,...,6032) provided on the muffle rear wall (50, 500, 600), wherein a height of the fan chamber (7011, 8011, 9011) and / or a height of the at least one duct (7050,..., 361) is defined by a depth of the respective embossment section (7100,..., 6030) provided on the fan cover (700, 800, 900, 600, 300) in addition to a depth of the respective corresponding embossment section (9015,...,6032) provided on the muffle rear wall (50, 500, 600) for forming said fan chamber (7011, 8011, 9011) and / or duct (7050,..., 361), or wherein the fan chamber (7011, 8011, 9011) and / or the at least one duct (7050,..., 361) are formed by embossment sections (9015,...,6032) on the muffle rear wall (50, 500, 600), but not on the fan cover (700, 800, 900, 600, 300), wherein a height of the fan chamber (7011, 8011, 9011) and / or a height of the at least one duct (7050,..., 361) is defined by a depth of the respective corresponding embossment section (9015,...,6032) provided on the muffle rear wall (50, 500, 600) for forming said fan chamber (7011, 8011, 9011) and / or duct (7050,..., 361).

11. Convection cooking oven according to any of the claims 6 to 10, characterized in that the at least one duct (7050,...,361) extends from the fan chamber (7011, 8011, 9011) to an at least one duct outlet (7051,...,306), in particular wherein a height of the duct (7050,...,361) decreases at least in sections from the fan chamber (7011, 8011, 9011) to the at least one duct outlet (7051,...,306), preferably wherein the height of the duct (7050,...,361) decreases linearly or stepwise or increasingly or decreasingly, and / or in particular wherein the at least one duct (7050,...,361) extends from the fan chamber (7011, 8011, 9011) towards a muffle side wall (60) and wherein the least one duct outlet (7051,...,306) is arranged adjacent to the muffle side wall (60), and / or in particular wherein the at least one duct outlet has an outlet opening with a width (d14, d13, d24, d23) of not more than 1 / 2, preferably not more than 1 / 3, of a cooking chamber height.

12. Convection cooking oven according to claim 11, characterized in that at least one duct outlet (7051,...,306) comprises, in particular sinusoidal, serrations, preferably integrally formed to the fan cover (700, 800, 900, 600, 300).

13. Convection cooking oven according to any of the preceding claims, characterized in that the fan impeller (80) comprises a fan plate and a plurality of fan blades attached to the fan plate, wherein the fan plate is arranged substantially parallel to the muffle rear wall (50, 500, 600) and to the fan cover (700, 800, 900, 600, 300), in particular wherein the fan blades have planar fan blade sections that are, preferably formed integrally to the fan plate, arranged at an angle between 45° and 95°, preferably of approximately 90°, relative to the fan plate and / or wherein the planar fan blade sections extend in an angle of approximately 90° relative to a tangent of a circular path on which a radially outermost tip of the fan blades moves when the fan impeller (80) rotates.

14. Convection cooking oven according to claim 13, characterized in that the fan cover (700, 800, 900, 600, 300) comprises centrally arranged inlet openings (7120, 8120, 9120, 6120) for air to be sucked into the fan chamber by the fan impeller (80), wherein the inlet openings (7120, 8120, 9120, 6120) are arranged radially inwards from a radially innermost section of the planar fan blade sections.

15. Method for operating a convection oven according to any of the preceding claims, characterized in that the fan impeller (80) is operated periodically in alternating rotation directions (RCW, RCCW).

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