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(11) | EP 3 546 832 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | KITCHEN OVEN WITH HYBRID POWER SUPPLY |
| (57) Kitchen oven with hybrid gas and electric power supply, comprising a main gas burner
(9) and an electrical resistor (12) alternatively operable to heat a cooking cavity
(2), as well as a ventilation system (7; 11) specifically adapted to allow a homogeneous
heat distribution by convection both during the gas operation and during the electric
operation.
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Field of application
[0001] The present invention relates to the field of kitchen ovens of the type intended for food cooking, and particularly it relates to a cooking oven for household applications arranged to allow dishes inserted into the cooking cavity thereof to be cooked.
Prior art
[0002] On the market of household appliances there are kitchen ovens with two different kinds of power supply: electric and gas.
[0003] If gas ovens historically represent the first of the two technologies which was developed, nowadays both power supplies allow satisfactory results in food cooking, and they are considered as substantially equivalent from the quality point of view.
[0004] Nevertheless, the different power supply affects - although not to a decisive extent - the cooking dynamics and modes of use of the oven, so that several users can have different tastes and consider the one or the other mode more suitable for cooking different foods.
[0005] An oven with hybrid power supply, wherein the cooking cavity can be alternatively heated in a gas or electric mode, would represent therefore a possibly interesting solution, allowing the cooking type to be varied according to the different needs and preferences of the users.
[0006] On the other hand, such an embodiment has several technical difficulties, particularly when a high-end product is to be made, which ensures an ideal cooking quality in all the operating modes of the household appliance.
[0007] One of those difficulties relates for example to ventilation. Ventilation systems, nowadays widely employed both in electric ovens and in gas ovens, perform a convective heat transmission which allows the internal temperature of the cooking chamber to be uniformed as much as possible. On the other hand, the shape thereof is necessarily linked to the type and position of the heat source, be it a gas burner or an electrical resistor. From this perspective, the use of two alternative power supplies would thus involve a duplication of the ventilation system, with the subsequent disadvantages due to the resulting structural complexity.
[0008] Other difficulties derive from the needs to control the temperature in the different power supply modes, from the integration of the different heating elements within a limited volume, from the general structural complexity of the hybrid device.
[0009] The technical problem underlying the present invention is thus to make a kitchen oven which solves the above-complained prior art limits, and which can, in particular, operate in the ventilated mode both with a gas power supply and with an electric power supply, with satisfactory cooking results in both cases.
Summary of the invention
[0010] The above-mentioned technical problem is solved by a kitchen oven comprising:
a cooking cavity bounded by a lower panel, a first side panel and a second side panel opposite to the first one, an upper panel, and a rear surface opposite to a front opening;
a main gas burner placed at said lower panel;
a ventilation cavity behind said cooking cavity;
a cover which separates the cooking cavity and the ventilation cavity, said cover having air inlet openings and outlet openings in the ventilation cavity;
a fan placed within said ventilation cavity;
an electrical resistor placed within said ventilation cavity peripherally to said fan;
a control unit operatively connected to the main gas burner, to the fan and to the electrical resistor, and configured to control a plurality of cooking modes wherein the main gas burner or the electrical resistor are alternatively operated to reach a temperature of the cooking cavity being enough to cook foods introduced therein;
said cooking modes comprising at least: an electric mode wherein the electrical resistor is operated, and the fan is driven into rotation in a predetermined rotational direction; and a ventilated gas mode wherein the main gas burner is operated and the fan is driven into rotation in the same predetermined rotational direction;
where said rear surface is defined by a peripheral rear panel and by the cover, projecting in a forward direction with respect to said rear panel;
where said cover develops in projection within the cooking cavity and it has a main face facing the front opening, a first side edge and a second side edge facing the first side panel and the second side panel respectively, an upper edge facing the upper panel and a lower edge facing the lower panel;
where said inlet openings are obtained on said main face at the fan, said outlet openings comprising first outlet openings obtained on the first side edge and second outlet openings obtained on the second side edge of the cover;
where, by splitting the first side edge horizontally in two halves with the same height, the overall area (AaL) of the first outlet openings which open into the lower half is larger than the overall area (Aau) of the first outlet openings which lie in the upper half; by splitting the second side edge horizontally in two halves with the same height, the overall area (AbL) of the second outlet openings which open into the lower half is smaller than the overall area (Abu) of the second outlet openings which lie in the upper half;
where the lower edge of the cover has no openings;
where, finally, when viewing through the front opening:
the first side edge whereon the first outlet openings are obtained is on the left with respect to the second side edge whereon the second outlet openings are obtained, and the predetermined rotational direction of the fan is clockwise; or
the first side edge whereon the first outlet openings are obtained is on the right with respect to the second side edge whereon the second outlet openings are obtained, and the predetermined rotational direction of the fan is counterclockwise.
[0011] The oven according to the invention, identified by the above-identified relevant features, is not only able to effectively operate both with a gas power supply and with an electric power supply, but it has also a ventilation system - defined by the fan and by the overhanging perforated cover - arranged to obtain an unusually homogeneous heat distribution in both power supply modes.
[0012] That surprising result is achieved due to the particular cover shape and to the modulation of air outlet openings, which define a fairly uniform convective flow both when the heat source is located around the fan - electric mode - and when it is instead located at the lower panel of the cooking cavity - gas mode.
[0013] Among the relevant aspects which contribute to define the result, the Applicant has pointed out the asymmetrical shape of the side outlet openings of the cover, which is believed to offset the flow asymmetry linked to the clockwise or counterclockwise movement of the fan.
[0014] Another decisive aspect turned out to be the complete absence of lower outlet openings on the cover. The tests of the Applicant established in fact how the lower outlet openings, although traditionally employed in the ventilation systems for electric ovens, can cause an overheating of the lower portion of the cooking cavity in case the ventilation is implemented with a gas power supply.
[0015] Other aspects, not fundamental but anyway advantageous, which can be implemented in an oven according to the present invention, are discussed hereafter.
[0016] The first outlet openings can have an asymmetrical development along the vertical axis with respect to the opposite second outlet openings, i.e. the morphologies of the outlet openings on the two side edges of the cover are identical but reversed.
[0017] The first and second outlet openings can have the shape of a rectangle trapezoid and be defined by C-shaped brakes, facing the rear panel, of the respective side edges. The inclination of the trapezoid oblique side advantageously allows the opening amplitude along the vertical axis to be varied, so as to progressively fit the transition to the flow asymmetry due to the fan movement.
[0018] The inclined sides of rectangle trapezoids which define the first outlet openings and the second outlet openings can be advantageously aligned with each other along a same line inclined with respect to the vertical, respectively departing from and approaching the rear panel when moving downwards. The above-mentioned transition progressiveness is so maintained from one opening to the next one.
[0019] Outlet openings have preferably a vertically-elongate shape, fitting to the elongate shape of the side edge whereon they are obtained.
[0020] Outlet openings have preferably a variable amplitude comprised between 30% and 90% of the thickness of the respective side edge.
[0021] In a preferred embodiment the first outlet openings are two and the second outlet openings are two, preferably positioned near lower and upper corners of the respective first or second side edge. In this case, given the asymmetrical shape on the two edges, the first upper opening will have an identical and overturned shape with respect to the second lower opening, and conversely the first lower opening will have an identical and overturned shape with respect to the second upper opening.
[0022] Preferably, the upper edge of the cover has no openings, the entirety of the outlet openings being obtained on side edges.
[0023] Always preferably, inlet openings are all made in a central area of the main face of the cover and they define an air intake grid directly facing the fan.
[0024] The main gas burner is preferably located below the lower panel, so that the flame is not open in the cooking cavity.
[0025] The oven can advantageously comprise a gas thermostat arranged to stop the gas power supply to the main gas burner upon reaching a temperature set by the user and an electric thermostat arranged to stop the electric power supply to the electrical resistor. This feature combines with the alternative nature of gas and electric power supplies in the oven according to the present invention, allowing in both cases an appropriate temperature feedback control.
[0026] The oven can further comprise a secondary gas burner at the upper panel, with a grill cooking function.
[0027] In this case, the cooking modes which can be controlled by the control unit can comprise a grill mode wherein said secondary gas burner is actuated, preferably without driving the fan into rotation.
[0028] The cooking modes which can be controlled by the control unit can also comprise a static gas mode wherein the main gas burner is operated without operating the fan.
[0029] Further features and advantages will become more apparent from the following detailed description of a preferred, but not exclusive, embodiment of the present invention, with reference to the attached figures, given by way of non-limiting examples.
Brief description of the drawings
[0030]
Figure 1 shows a schematic view of an oven according to the present invention, with separate identification of the control unit;
figure 2 shows a perspective view of a muffle of the oven of figure 1;
figure 3 shows a front view of the muffle of figure 2;
figure 4 shows a right side view, sectioned according to the plane A-A, of the muffle represented in figure 3;
figure 5 shows a front view, sectioned according to a median plane, of the muffle of figure 2;
figure 6 shows a left side view, sectioned according to a median plane, of the muffle represented in figure 3;
figure 7 shows a perspective view of a cover of the fan mounted in the oven according to the present invention;
figure 8 shows a front view of the cover of figure 7;
figure 9 shows a right side view, sectioned according to the plane B-B, of the cover of figure 8;
figure 10 shows a left side view, sectioned according to the plane A-A, of the cover of figure 8.
Detailed description
[0031] With reference to the attached figure 1, a kitchen oven according to the present invention is generally identified with 100.
[0032] Kitchen oven means in particular in the present patent an oven intended for cooking or anyway preparing foods and dishes, regardless of the industrial or household destination of use thereof. The latter is however to be considered as preferred and the below-described specific embodiment refers thereto.
[0033] The kitchen oven 100 has a muffle 1, individually illustrated in the attached figures 2-6, intended to be mounted within an external structure which coats it and whereon a control interface 21 for the user is provided.
[0034] The whole kitchen oven 100 and the muffle 1 are illustrated in the attached figures in the normal configuration of use thereof. The relative and absolute positions and orientations of the various elements composing the oven, defined by terms like upper and lower, above and below, horizontal and vertical or other equivalent terms, are always to be interpreted with reference to that configuration. Other terms like front and rear, right or left, clockwise or counterclockwise and equivalents are to be interpreted by considering as a point of view the one of a user facing the main opening of the kitchen oven 100 in an operating position, and which considers the parts which are closer thereto as front parts.
[0035] The muffle 1 defines therewithin a cooking cavity 2 intended for introducing the foods to be heated or cooked.
[0036] The substantially parallelepiped cooking cavity 2 is bounded at the bottom by a lower panel 3, from whose rectangular perimeter a first side panel 4a, a rear panel 60 and a second side panel 4b raise, which connect to an upper panel 5. The fourth side face of the cooking cavity 2 defines a front opening 8, reclosable by a suitable door 80.
[0037] A main gas burner 9 capable of heating the above cooking cavity 2 is present below the lower panel 3, which has peripheral passage slots.
[0038] On the other hand, a secondary gas burner 15 directly facing the cooking cavity 2 with a grill cooking function is provided below the upper panel 5.
[0039] A gas thermostat 13, arranged to stop the gas power supply upon reaching a temperature set by the user through the control interface 21, and an electric thermostat 14 arranged instead to stop the power supply to an electrical resistor 12 introduced thereafter, always upon reaching a set temperature, face the second side panel 4b.
[0040] The rear panel 60 has a central hollow surrounded by a peripheral portion which joins to the other panels. That central hollow is covered by a cover 7, slightly projecting with respect to the peripheral portion of the panel 60. The chamber defined between the central hollow and the cover 7, separated with respect to the cooking cavity, is called hereafter ventilation cavity 10 and it centrally houses a fan 11 surrounded by the electrical resistor 12.
[0041] The peripheral portion of the rear panel 60 has at the top the mouth of a fume exhaust channel 16 which extends at the top outside the cooking cavity 2.
[0042] It must be noticed that both the rear panel 60 and the cover 7 can be easily made from a single plate through traditional moulding techniques.
[0043] The rear bottom of the cooking cavity 2 closes therefore on a rear surface 6 peripherally defined by the flat portion of the rear panel 60 and centrally defined by the projecting cover 7, the latter defining the interface between cooking cavity 2 and ventilation cavity 10.
[0044] The cover 7 provides a substantially box-like geometry, i.e. a rectangular-parallelepiped-like one, where a front main face 70 is joined to the rear panel 60 by means of faces with a limited thickness, indicatively comprised between 8 mm and 20 mm, which are referred to in the present description with the term edges. In particular, the cover 7 comprises a first side edge 71a and a second side edge 71b, facing the respective side panels 4a, 4b; as well as an upper edge 72 and a lower edge 73.
[0045] The cover 7 defines, together with the fan 11, a ventilation system adapted to define a convective current within the oven. The cover 7 has therefore air inlet openings 74, obtained in front of the fan 11, and air outlet openings 75a, 75b obtained on the side edges 71a, 71b. The rotation of the fan 11 radially blows the air entering from the inlet opening 74 towards the outlet openings 75a, 75b.
[0046] When the electrical resistor 12 is actuated, the air flow is heated within the ventilation cavity 10; when instead the main gas burner 9 is actuated, the fan 11 sucks an already-hot air flow defining a convective current within the cooking cavity 2.
[0047] In the present embodiment, the inlet openings 74 are defined by a plurality of vertical slots, which define a round grid facing the body of the fan 11. The electrical resistor 12 is placed instead beyond the diameter of said round grid, i.e. it does not face the inlet openings 74.
[0048] The outlet openings 75a, 75b split in first outlet openings 75a and second outlet openings 75b, respectively obtained on the two opposite side edges 71a, 71b of the cover 7.
[0049] The first outlet openings 75a and the second outlet openings 75b have an asymmetrical shape, i.e. the profile of the openings on the first side edge 71a is overturned with respect to the profile of the openings on the second side edge 71b.
[0050] In particular, the first outlet openings 75a - which in the embodiment described here, are the openings on the left - are wider in the lower part and narrow at the top; on the contrary the second outlet openings 75b - in the present version, on the right - are narrow in the lower portion and widen at the top.
[0051] It must be noticed that the above-mentioned shape is linked to the fan rotational direction, clockwise in the embodiment described here. In the case of a fan with a counterclockwise rotational direction, the outlet openings 75a, 75b must be made in a specular way with respect to what is said above: the first outlet openings 75a, wide at the base and narrow at the top, will be in this case on the right; the second outlet openings 75b, narrow at the base and wide at the top, will be on the left.
[0052] The outlet openings 75a, 75b are two on both side edges 71a, 71b, respectively located near the upper and lower corner of the respective edge.
[0053] The outlet openings 75a, 75b are bounded by C-shaped recesses obtained by shearing on the edge of the cover 7 and by the surface of the rear panel 60 which the edge approaches. The perimeter, substantially in the shape of a rectangle trapezoid, is thus defined by a long side at the interface with the rear panel, and by the three profile sides of the C-shaped recess. The latter ones comprise two parallel short sides, which define the thickness of the outlet opening 75a, 75b, and an oblique long side with respect to the vertical corner of the cover 7.
[0054] Preferably, the skew long sides of the outlet openings 75a, 75b obtained on the same side edge 71a, 71b are aligned. A progressive widening/narrowing of the slots defining the outlet openings 75a, 75b on a same edge is thus defined.
[0055] In the attached figures 8-9, in order to highlight the above-mentioned widening/narrowing, four progressive dimensions l1-4 are pointed out, related to the distance of the outlet openings 75a, 75b from the front vertical corner of the respective side edge 71a, 71b, at the two opposite ends of the skew sides of each trapezoidal opening. Given the above-discussed asymmetrical shape, the dimensions are identical and reversed for the first side edge 71a and for the second side edge 71b.
[0056] By way of mere non-limiting example, the following numeral values for the above-mentioned dimensions are identified:
| l1 = 4.7 mm | l2 = 5.5 mm | l3 = 6.7 mm | l4= 7.5 mm |
[0057] Values within a tolerance margin of 20% with respect to the above-indicated ones appear to be particularly advantageous in the context of the invention, although they are absolutely not to be intended as a limitation of the present protection.
[0058] In the attached figures 8-9, the area surfaces of the various outlet openings are also pointed out: the first upper outlet opening 75a has a first upper area Aau; the first lower outlet opening 75a has a first lower area AaL; the second upper outlet opening 75b has a second lower area Abu; the second lower outlet opening 75a has a second lower area AbL. It is observed that the first upper area Aau is equal to the second lower area AbL, while the first lower area AaL is equal to the second upper area Abu.
[0059] The kitchen oven 1 has, as hinted above, a control interface 21 connected to a control unit 20. The control unit 20 is operatively connected in turn to the different functional units of the kitchen oven 1, among which at least: the main gas burner 9, the secondary gas burner 15, the electrical resistor 12 and the fan 11.
[0060] Through the control interface 21, the user can program different cooking modes, which the control unit 20 implements by operating the above-said different functional units.
[0061] In particular the following cooking modes are provided:
electric mode, wherein the electrical resistor 12 is operated and the fan 11 is driven into rotation;
static gas mode, wherein the main gas burner 9 is operated and the fan 11 is not driven into rotation;
ventilated gas mode, wherein the main gas burner 9 is operated and the fan 11 is driven into rotation;
grill mode, wherein the secondary gas burner 15 is operated in case in combination with the main gas burner 9, without rotation of the fan 11.
a cooking cavity (2) bounded by a lower panel (3), a first side panel (4a) and a second side panel (4b) opposite to the first, an upper panel (5), and a rear surface (6) opposite to a front opening (8);
a main gas burner (9) placed at said lower panel (3);
a ventilation cavity (10) behind said cooking cavity (2);
a cover (7) which separates the cooking cavity (2) and the ventilation cavity (10), said cover having air inlet openings (74) and air outlet openings (75a; 75b) in the ventilation cavity (10);
a fan (11) placed within said ventilation cavity (10);
an electrical resistor (12) placed within said ventilation cavity (10) peripherally to said fan (11);
a control unit (20) operatively connected to the main gas burner (9), to the fan (10) and to the electrical resistor (12), and configured to control a plurality of cooking modes wherein the main gas burner (9) or the electrical resistor (12) are alternatively operated to reach a temperature of the cooking cavity (2) being enough to cook foods introduced therein;
said cooking modes comprising at least: an electric mode wherein the electrical resistor (12) is operated and the fan (11) is driven into rotation in a predetermined rotational direction; and a ventilated gas mode wherein the main gas burner (9) is operated and the fan (11) is driven into rotation in said predetermined rotational direction;
where said rear surface (6) is defined by a peripheral rear panel (60) and by the cover (7), projecting in a forward direction with respect to said rear panel (6);
where said cover (7) develops in projection within the cooking cavity (2) and it has a main face (70) facing the front opening (8), a first side edge (71a) and a second side edge (71b) respectively facing the first side panel (4a) and the second side panel (4b), an upper edge (72) facing the upper panel (5) and a lower edge (73) facing the lower panel (3);
where said inlet openings (74) are obtained on said main face (70) at the fan (11), said outlet openings (75a; 75b) comprising first outlet openings (75a) obtained on the first side edge (71a) and second outlet opening (75b) obtained on the second side edge (71b) of the cover (7);
where, by splitting the first side edge (71a) horizontally in two halves with the same height, the overall area of the first outlet openings (75a) which open into the lower half (AaL) is larger than the overall area of the first outlet openings (75a) which lie in the upper half (Aau); by splitting the second side edge (71b) horizontally in two halves with the same height, the overall area of the second outlet openings (75b) which open into the lower half (AbL) is smaller than the overall area of the second outlet openings (75b) which lie in the upper half (Abu);
where the lower edge (73) of the cover (7) has no openings;
where, when viewing through the front opening (8):
the first side edge (71a) whereon the first outlet openings (75a) are obtained is on the left with respect to the second side edge (71b) whereon the second outlet openings (75b) are obtained and the predetermined rotational direction of the fan (12) is clockwise; or
the first side edge (71a) whereon the first outlet openings (75a) are obtained is on the right with respect to the second side edge (71b) whereon the second outlet openings (75b) are obtained and the predetermined rotational direction of the fan (12) is counterclockwise.