[0001] This invention concerns electric convection ovens for cooking food or semifinished
food products, and in particular such an oven provided with a substantially octagonal
deflector and preferably also with a steam generator device, especially a professional
oven. It is known that there are mainly three types of electric cooking ovens, namely
static ovens, convection ovens and convection ovens with steam generators, with progressively
increasing performance and costs.
[0002] In static ovens the temperature is regulated only by the operating time of an electric
resistor, placed on the rear wall of the cooking chamber behind a deflector, which
heats the air in the cooking chamber where the circulation takes place by natural
convection. The thermal action is simple and rudimentary, since the food does not
come into direct contact with the electric resistor but reaches the cooking temperature
through the action of the surrounding superheated air. The structural simplicity of
the static oven does not allow to act in the cooking chamber with other parameters,
such as ventilation and steam, to achieve more sophisticated heat treatments of food.
[0003] In convection ovens there is a fan, also placed behind the deflector and preferably
inside a circular electric resistor, which causes a forced convection motion of the
air inside the cooking chamber. The dynamically forced air distributes the thermal
energy better, causing greater penetration into the food, thus obtaining significant
advantages compared to static cooking:
- greater efficiency and uniformity of the cooking action, with lower cooking times
and temperatures, and consequently a lower weight loss of the food;
- the possibility of handling different foods at the same time, since forced air convection
prevents the mixing of smells and flavours in the cooking chamber;
- energy saving associated with a qualitatively superior result.
[0004] In convection ovens with steam generator, especially in professional ovens, the user
has the possibility to activate the steam function to create an even wider range of
cooking, and the steam can also be used for regeneration and maintenance cycles of
already cooked foods.
[0005] In this type of oven the steam can be generated directly or indirectly: in the first
case by nozzles that spray water particles directly on the electric resistor and thanks
to the fan that distributes the steam evenly in the cooking chamber, while in the
second case by means of an autonomous steam generator (boiler) located inside the
structure of the oven but outside the cooking chamber, in which the steam is injected
through pipes from the boiler.
[0006] In the first case, the generation of steam is linked to the functioning of the cooking
resistor, whereby these ovens cannot cook only with steam, and furthermore the result
is a superheated steam that reaches temperatures >100°C and is more aggressive than
saturated steam, so it can give rise to peripheral oxidation, especially of leafy
vegetables. In the second case, the oven can also cook only with steam and at a lower
temperature, since the functioning of the cooking resistor is not required to generate
steam, and the boiler allows to operate at steam saturation with a steam that remains
at a constant temperature of about 100°C and is less aggressive for the food, thus
avoiding oxidation phenomena.
[0007] In these prior art ovens the deflector has a square or rectangular shape with a height
almost equal to the height of the cooking chamber and is mounted on the rear wall
of the latter at its top and bottom sides through two solid walls that prevent the
passage of air, whereas the other two left and right sides have no walls to allow
the circulation of air so that the flow extends over the whole height of the cooking
chamber. With this simple type of deflector, however, it was found that the air flow
exiting through the free sides is poorly uniform in terms of both speed and temperature,
which results in an uneven distribution of heat within the cooking chamber and therefore
a scarce uniformity of the cooking action.
[0008] EP 3399237 discloses an oven according to the preamble of claim 1 having a structure capable
of easily removing oil mist generated when food is cooked, so as to minimize contamination
of an inner surface of a cavity of the oven thus making unnecessary to resort to a
pyro-cleaning method or a steam cleaning method to remove such internal contamination.
To this purpose, the oven has a convection assembly that includes a deflector with
an inlet port in a front surface and outlet ports in a side surface extending from
the front surface to the rear wall of the cavity, wherein the air discharged from
the deflector moves in an upward inclined direction with respect to the rear wall.
[0009] Such an oven is designed to minimize the contamination of the internal cavity but
does not take into account the problems caused by the specific shape of the deflector
as to the distribution of heat within the cavity.
[0010] US 2006/0011607 discloses an oven with a steam-generating device installed behind a conventional
deflector and under the cooking resistor for supplying steam to the cooking chamber.
In this oven, the steam is generated by a specific heater that is housed in a heating
container closed by a cover member with the interposition of a seal for maintaining
an airtight state. As a consequence, the water supply pipe and the steam-generating
heater must pass through properly sealed passages in said cover, and the steam generated
in the heating container is delivered to the cooking chamber through suitable exhaust
pipes that also must pass through cover. In practice, this arrangement corresponds
to having the above-mentioned boiler located within the cooking chamber.
[0011] The purpose of this invention is therefore to provide an oven that is free from the
above-described drawbacks. This purpose is achieved with an oven equipped with a deflector
of semi-regular octagonal shape deriving from a rectangle or a square with bevelled
corners that, in addition to the two solid walls along the top and bottom sides, also
includes two pairs of oblique peripheral walls that are respectively adjacent to said
top and bottom walls and are provided with openings extending over 30-90% of the area
of said oblique walls, as well as two lateral walls extending between the oblique
walls and also having openings, the oven further including a water supply duct extending
from the rear wall of the cooking chamber, a tray located inside the cooking chamber
in a position to receive the water supplied through said duct, and a second resistor
that extends into said tray so that most of said second resistor is immersed in water
when the tray is filled, the deflector protecting a user also from contact with the
second resistor. Further advantageous features are recited in the dependent claims.
[0012] A first important advantage of this oven is to improve the cooking performance thanks
to the greater uniformity of the air flow exiting the deflector in terms of both speed
and temperature, which results in a more even distribution of heat within the cooking
chamber and therefore a more uniform cooking.
[0013] A second significant advantage of this oven is that of improving the performance
of the steam generator in terms of speed and energy efficiency, because the saturated
steam is generated directly inside the cooking chamber instead of coming from a device
external to it as a traditional boiler, whereby the steam does not pass through the
supply pipes where it cools down and disperses heat outside the cooking chamber. In
this case, there is the further advantage of being able to use the steam generating
resistor also for cooking when the tray is empty, which is not possible with the arrangement
disclosed in
US 2006/0011607, given the position in which it is located, so as to obtain a reduction in energy
consumption thanks to the better efficiency of the system. For example, a 6 KW cooking
resistor can be used to immediately bring the oven to temperature and then a 2 KW
steam resistor can be used to maintain the temperature during cooking, thus obtaining
lower power jumps when the oven thermostat switches the resistor on and off.
[0014] Still another important advantage of the above-mentioned oven is the reduction in
the number and complexity of its components, since the steam generator inside the
cooking chamber is much simpler than the external boiler or the arrangement disclosed
in
US 2006/0011607, and does not require connections with the cooking chamber. In this way, with the
same performance, a considerable economic saving is obtained both in the production
phase and in the maintenance of the oven.
[0015] Further advantages and characteristics of the oven according to the present invention
will be evident to those skilled in the art from the following detailed description
of some embodiments thereof with reference to the annexed drawings, in which:
Fig.1 is a front view of a prior art oven with a square deflector;
Fig.2 is a frontal perspective view of a preferred embodiment of the oven, provided with
a steam generator, with some components removed for greater clarity;
Fig.3 is a partial enlarged view of the oven of Fig.2 with the addition of a couple of
components;
Fig.4 is a magnified perspective view of the water diffuser;
Fig.5 is a rear perspective view of the deflector; and
Fig.6 is a frontal perspective view of the oven with the deflector.
[0016] Referring to Fig.1, there is seen that a prior art oven with direct steam generator
traditionally includes a square deflector 1 mounted on the rear wall 2 of the cooking
chamber, deflector 1 being formed by a front wall and peripheral walls at its top
and bottom sides, that are close respectively to the ceiling and floor of the cooking
chamber. The square deflector 1 protects the user from contact with the elements (cooking
resistor and fan) mounted on the rear wall 2, and it is provided with holes for the
passage of a duct 3 to supply the water used to generate the steam. Duct 3 extends
from the rear wall 2 and passes in front of deflector 1, with a section parallel to
the rear wall 2, to end inside it with an end section preferably coaxial to a centrally
arranged circular intake grille 1a.
[0017] A preferred embodiment of an oven according to the present invention, shown in figures
2 to 4, conventionally includes a cooking resistor 4 mounted on the rear wall 2 and
having preferably a circular shape so as to receive inside it a fan 5, preferably
coaxial thereto, to realize the forced convection of the air heated by resistor 4.
[0018] A first aspect of this oven lies in the presence inside the cooking chamber of a
tray 6, arranged in such a position as to receive the water fed through duct 3, and
of a second resistor 7 that extends into said tray 6 so that most of resistor 7 is
immersed in water when tray 6 is filled. In this way, resistor 7 can be used to generate
saturated steam directly inside the cooking chamber, which steam is then distributed
by fan 5, as mentioned above.
[0019] Note that since the water fed through duct 3 is not used to generate superheated
steam by spraying it on the cooking resistor 4, duct 3 does not have a spray nozzle
on its outlet. However, it is preferable that the water is not simply delivered from
duct 3 directly into tray 6, whereby the present oven preferably includes a diffuser
8 which is mounted so as to surround the outlet of duct 3, being preferably mounted
in the centre of fan 5.
[0020] This diffuser 8, as better illustrated in Fig.4, has a cylindrical shape with a plurality
of circumferential grooves 8a formed internally, preferably with a constant pitch,
and a plurality of radial holes 8b made in correspondence of said grooves 8a preferably
along the entire perimeter of diffuser 8. Thanks to this structure, diffuser 8 performs
a controlled release of the water supplied by duct 3 distributing it in tray 6 even
while diffuser 8 rotates with fan 5.
[0021] In the embodiment shown in Fig.2, tray 6 is a separate component mounted on the rear
wall 2 same as the other components 4, 5 and 7, tray 6 being preferably in a centered
position with respect to fan 5. However, the tray could also be integrated into the
deflector as shown in the following.
[0022] A second aspect of the present oven resides in the octagonal shape of the deflector,
instead of a square shape like the prior art deflector 1 shown in Fig.1, with a number
of openings formed in the peripheral walls. In particular, as illustrated in figures
5 and 6, deflector 21 has the shape of a semi-regular octagon deriving from a rectangle
with bevelled corners, but it could obviously be also a square with bevelled corners,
in which the peripheral walls 9, 10 respectively arranged along the top and bottom
sides are solid walls, whereas the other peripheral walls are provided with elongated
openings (slots) extending over 30-90% of the area of said walls.
[0023] More specifically, the two pairs of oblique walls 11, 12 respectively adjacent to
said top and bottom walls 9, 10 are provided with four slots 11a, 12a with the former
extending over about 80% of the relevant walls 11 and the latter extending over about
40% of the relevant walls 12, while the lateral walls 13 have four slots 13a extending
over about 60% thereof. This different extension of the slots in the oblique walls
11, 12 is due to the fact that the lower portion of deflector 21 is taken up by tray
6 or performs the function of tray 6 itself, by means of the bottom wall 10 that has
a raised rear edge 14 so that the lower portion of the deflector can contain the water
to be turned into steam (resistor 7 being obviously housed in this lower portion).
[0024] As shown in Fig.6, deflector 21 is preferably of reduced height compared to the cooking
chamber because its top wall 9 and bottom wall 10 are not near respectively the ceiling
and the floor of the cooking chamber as in prior art deflector 1 illustrated in Fig.1.
Moreover, thanks to the presence of oblique walls 11, 12, all the peripheral walls
of the deflector are preferably located close to the cooking resistor, which is typically
circular, and the applicant has found that this arrangement allows the flow to be
uniformed in an optimal manner both in terms of speed profile and temperature profile.
Such a deflector geometry is also more compact, which facilitates both maintenance
and cleaning in the cooking chamber.
[0025] A third aspect of this invention, in a preferred embodiment thereof, is given by
the greater extension in the vertical direction of the front intake grille of the
deflector.
[0026] This allows to improve the air suction and distribution along the height of the deflector
and consequently to optimize the heat distribution on the different shelves arranged
at different heights in the cooking chamber. Note that this can also be achieved by
providing for additional intake grilles above and below the traditional circular intake
grille 1a.
[0027] It is clear that the embodiments of the oven according to the invention described
and illustrated above are only examples susceptible to numerous variations. In particular,
both the cooking resistor 4 and the steam resistor 7 can be composed of multiple units
(e.g. 3 × 2 KW for resistor 4, 2 x 1 KW for resistor 7), the peripheral slots of the
deflector can have other shapes and/or different positions in the respective walls
and the relative arrangement of the components can vary depending on specific construction
requirements (e.g. duct 3 could follow a different path to supply water to tray 6).
1. Electric convection cooking oven comprising a cooking chamber, a cooking resistor
(4) and a fan (5) both mounted on the rear wall (2) of said cooking chamber and a
deflector (21), formed by a front wall and peripheral walls, mounted on said rear
wall (2) so as to protect a user from contact with said cooking resistor (4) and said
fan (5), said deflector (21) being provided with solid peripheral walls (9, 10) at
its top and bottom sides and at least one central intake grille (1a) in said front
wall, the deflector (21; 22) having a substantially octagonal shape that also includes
two pairs of oblique peripheral walls (11, 12), which are respectively adjacent to
said top and bottom walls (9, 10) and have openings (11a, 12a) that extend over 30-90%
of the area of said oblique walls (11, 12), as well as two lateral peripheral walls
(13) that extend between the oblique walls (11, 12), characterized in that the deflector (21) has the shape of a semi-regular octagon deriving from a rectangle
or a square with bevelled corners, with also the side walls (13) having openings (13a),
and in that it further includes a water supply duct (3) extending from the rear wall (2) of the
cooking chamber, a tray (6), located inside the cooking chamber in a position to receive
the water supplied through said duct (3), and a second resistor (7) that extends into
said tray (6) so that most of said second resistor (7) is immersed in water when the
tray (6) is filled, the deflector (21) protecting a user also from contact with the
second resistor (7).
2. Oven according to claim 1, characterized in that in the two oblique walls (11) that are adjacent to the top wall (9) there are formed
openings (11a) that extend over about 80% of said oblique walls (11).
3. Oven according to claim 1 or 2, characterized in that in the two oblique walls (12) that are adjacent to the bottom wall (10) there are
formed openings (12a) that extend over about 40% of said oblique walls (12).
4. Oven according to any of claims 1 to 3, characterized in that in the two lateral walls (13) there are formed openings (13a) that extend over about
60% of said lateral walls (13).
5. Oven according to any of the preceding claims, characterized in that the deflector (21) is of reduced height compared to the cooking chamber so that its
top wall (9) and bottom wall (10) are not near respectively to the ceiling and the
floor of the cooking chamber, and the peripheral walls of the deflector (21) are arranged
close to the cooking resistor (4).
6. Oven according to any of the preceding claims, characterized in that the central intake grille (1a) extends more vertically than horizontally, preferably
with an elliptical shape, or additional intake grilles are formed above and below
said central intake grille (1a).
7. Oven according to any of the preceding claims, characterized in that it further includes a diffuser (8) mounted so as to surround the outlet of the water
supply duct (3), said diffuser (8) having a cylindrical shape with a plurality of
circumferential grooves (8a) formed internally, preferably with a constant pitch,
and a plurality of through radial holes (8b) made in correspondence of said circumferential
grooves (8a), preferably along the entire perimeter of the diffuser (8).
8. Oven according to any of the preceding claims, characterized in that the tray (6) is integrated in the deflector (21) which has a solid bottom wall (10)
and has a raised rear edge (14) such that the lower portion of the deflector (21)
can contain the water supplied by the duct (3) and accommodate the second resistor
(7).
9. Oven according to any of the preceding claims, characterized in that the cooking resistor (4) has a circular shape and the fan (5) is mounted within said
circular shape, preferably coaxial thereto.
10. Oven according to the preceding claim, characterized in that the water supply duct (3) passes in front of the cooking resistor (4) and ends inside
said circular shape, preferably with an end section coaxial thereto.
11. Method of operation of an oven according to any of the preceding claims, including
a step of heating the oven by activating the cooking resistor (4) up to a set cooking
temperature and then deactivating the cooking resistor (4), characterized in that the maintenance of said cooking temperature is obtained by activating and deactivating
the second resistor (7).
12. Method of operation of an oven according to any of claims 1 to 10, including a step
of washing of the cooking chamber with a washing/rinse fluid, characterized in that said washing step is performed using vapours of washing/rinse fluid obtained by loading
the tray (6) with a mixture of water and detergent and activating the second resistor
(7).