EP2217037B1

EP2217037B1 - Combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches

Info

Publication number: EP2217037B1
Application number: EP10152647.3A
Authority: EP
Inventors: Maurizio Mazzoni; Egidio D'Incà; Francesco Boriani; Cesare Croci; Alberto Maccagni
Original assignee: Sca Srl
Current assignee: Sca Srl
Priority date: 2009-02-09
Filing date: 2010-02-04
Publication date: 2016-04-13
Anticipated expiration: 2030-02-04
Also published as: IT1393086B1; ITMI20090167A1; EP2217037A1

Description

The present invention refers to a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches.
Currently, for warming sandwiches, flat bread or similar products, mobile heated plates, that are brought together like a clamp resting on the upper and lower outer faces of the sandwiches to be heated, are usually used.
Such plates thus provide for warming and "browning" the outer surfaces of sandwiches by direct contact.
However, disadvantageously, such plates do not always provide for sufficiently heating the inside of the sandwiches apart from after a very long time.
Moreover, with these plates, a suitable inner heating of the sandwiches can cause excessive heating of the outer surfaces of the sandwiches themselves to the point of burning them. Another drawback of the aforementioned plates is the fact that, in order to reduce the waiting time of the warming, it is necessary to always keep the plates supplied with power, i.e. hot, with a relatively high energy consumption. Alternatively, nowadays, so called "microwave ovens" are largely used to warm sandwiches in both working/commercial environments, such as canteens or snack bars or others, as well as at the home.
Microwave ovens are a particular type of oven in which the warming and cooking of the food products is mainly carried out by the warming effect of microwaves generated by the oven itself.
The operating mechanism of such ovens is fairly simple and it is related to a device, called magnetron, that generates a microwave radiation in the form of a variable electromagnetic field in a food cooking and housing chamber.
The oscillation of the electromagnetic field, with a frequency of about 2.45 GHz, is able to produce oscillations in the molecules of the food products having polarization, mainly water.
Such a molecular shaking, induced in the aforementioned water molecules, provides for increasing the temperature of the food products hit by the aforementioned wave oscillations. The cooking chamber is substantially a Faraday cage, that prevents microwaves from coming out, in which the oven door is generally made from glass so as to allow the dish inside it to be seen, but at the same time it includes a layer of thin metallic mesh as an electromagnetic shield.
Since the width of the links is less than the wavelength of the microwaves, 12 cm, the radiation cannot cross the mesh, whereas light, having a wavelength which is much shorter than the mesh, can.
For safety reasons, the closing mechanism of the door includes suitable switches that turn off the magnetron in the case in which it opens, thus preventing microwaves from coming out.
The magnetron must be supplied with energy with a direct current voltage of several thousands of volts, which is produced from the voltage of the electrical mains by means of a transformer followed by a rectifier and by a condenser. Suitable devices turn the system on and off by command of the microprocessor that manages the operation time based upon parameters set with the controls present on the front panel.
Even if the ovens foresee the adjustment of the cooking power, the magnetron is always operated at full power to keep the efficiency at its maximum. The modulation of the power is carried out by adjusting the ratio between the turning on period and the turning off period according to a technique called pulse-width modulation.
In order to obtain, for example, a power which is equal to half of the maximum power, the magnetron turns on for a few seconds, to then turn off for an identical amount of time and so on until the end of the set cooking time.
It should thus be clear that the warming of food products through microwave ovens is totally different with respect to the conventional warming of the heated plates.
Indeed, in the case of sandwiches, the inside of which generally has a lot more water with respect to the outer surfaces, in microwave ovens their inside is heated more with respect to the outer layer.
There is thus an opposite effect to that found in the analysis of the heated plates in which the heat passes through radiation and conduction only from the outermost layers of bread towards the inner ones.
The main advantage of microwave ovens with respect to conventional plate cooking systems lies in the very fast cooking and defrosting of the food products.
However, even microwave ovens have some drawbacks like, for example, the fact that the warming of sandwiches is not homogeneous, but rather concentrated in particular areas, usually exclusively on the inside, which absorbs more of the energy of the microwaves with respect to the outer faces.
If it is wished to continue the heating also for the outer faces of the bread with known microwave ovens, keeping the bread in the microwave itself for a long time, the inner portion is unfortunately damaged/hardened such that the sandwich does not meet the common expectations of the consumer.
A further limitation of microwave ovens lies in the fact that the temperature of the food products being cooked is relatively low and in any case not suitable at all for giving the outer surface of sandwiches their desired "browning".
Such a browning phenomenon is indeed closely related to a very precise combination of time/temperature and heating method which cannot be obtained with common microwave ovens.
In order to reach an optimal heating, it is thus currently necessary to first heat the sandwich in the microwave oven for a few seconds, which allows the inside to rapidly warm up, and subsequently take out the sandwich to brown the outer faces through the heated plates.
Alternatively, nowadays, there are combined microwave ovens, which combine microwaves, suitable for rapidly warming the inside of the sandwich, with an infrared beam system, which is able to brown the outer surface to give it a better flavour and fragrance.
However, also these ovens have drawbacks, like for example, a long time needed for the infrared beams to complete the aforementioned outer cooking of the bread, which greatly exceeds the time needed for the microwaves to heat the inside of the same sandwich.
The US 5204503 and US 5155318 patents describe microwave ovens in which the plane supporting the food products is of the heated-plate type suitable for heating the lower surface of the sandwich through direct contact.
However, also such devices described in US 5204503 and US 5155318 have drawbacks related to the fact that the browning of the bread only occurs on the lower surface of the sandwich, forcing the user to interrupt the cooking and to turn the sandwich over to obtain a browning also on the other surfaces.
Of course, such a procedure makes the waiting time for the cooking/browning of the sandwich longer, forcing the user to carry out the aforementioned turning over operation of the sandwich manually.
Therefore, also the combined solutions known today and briefly outlined above for warming sandwiches, i.e. the plates, the common microwave oven, microwaves having infrared or having the lower heated supporting plane, have some drawbacks. Finally, US 6018157 describes a combined oven of the microwave type equipped with a supporting plane of the heated type. US 6018157 also foresees the presence of a further mobile element of the heated type accommodated in the cooking chamber above the supporting plane.
Disadvantageously, in such an oven neither the supporting plane, nor the upper heated element can be activated independently with respect to the magnetron, since there is an inert gas provided inside them which can be activated by the microwaves present in the cooking chamber and generated by the magnetron.
It is not therefore possible, according to US 6018157 , to use the supporting plane and the upper element as means for heating the outer surfaces of a sandwich without necessarily having to simultaneously warm it with the microwaves as well.
Such an aspect is extremely disadvantageous in view of the fact that, in order to obtain an optimal outer browning of the sandwich, the latter necessarily absorbs an excessive amount of microwaves such as to damage the inner portions and the possible fillings, beyond repair.
All this due to the fact that, as it should be obvious, the outer browning requires more time than that necessary to correctly warm the inner portions and the possible filling of a sandwich through microwaves.
Moreover, another drawback of such a prior art lies in the fact that, due to the high humidity generated by cooking with microwaves, it is not possible to make the outer surfaces of the sandwich crispy, since they remain too wet.
The purpose of the present invention is that of making a device which is able to overcome the aforementioned drawbacks of the prior art in an extremely simple, cost-effective and particularly functional manner.
Another purpose of the invention is that of making a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, in which the warming of the food products is homogeneous and is not concentrated only in particular areas.
A further purpose is that of obtaining a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, in which both the internal warming and the outer browning of the sandwich occur rapidly and without any manual intervention.
Yet another purpose is that of having a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, in which it is possible to simultaneously brown the outer lower surface as well as the upper surface of a sandwich without ever having to interrupt the cooking of the inside of the sandwich itself.
A further purpose is that of having a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, in which the outer browning through plates and the cooking of the inside of the sandwich through microwaves can be activated totally independently from one another and with different activation times according to needs.
These purposes, according to the present invention, are achieved by making a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, as outlined in claim 1.
Further characteristics of the invention are highlighted in the subsequent claims.
The characteristics and the advantages of a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention, shall become clearer from the following description, given as an example and not for limiting purposes, with reference to the attached schematic drawings, in which:

figure 1 is a perspective view of a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention;
figure 2 is a partial section elevational view of the oven of figure 1.

With reference to the figures, a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention, is shown with reference numeral 10.
Such a combined oven 10 is of the microwave type comprising at least one magnetron for generating microwaves in a chamber 11 for cooking, warming and defrosting, said chamber 11 being selectively able to be accessed from outside through a moveable closure door 20 provided with a handle 21.
The combined oven 10 is able to operate like known microwave ovens, in which the magnetron, through a suitable electronic control circuit and a wave guide, generates a flow of microwaves such as to excite the molecules of water that make up the food products to be heated into movement.
In the case of sandwiches, the microwaves substantially act in the inner area of the sandwich, which contains a greater amount of water, introduced into the oven 10.
Such water molecules, indeed, absorb the energy of the microwaves in a dielectric heating process and start to vibrate generating heat.
Like in common microwave ovens, such a procedure, i.e. warming the inside of the sandwich, occurs very quickly. The cooking chamber 11 of the combined oven 10 is also provided with a, preferably fixed, plane 12 for supporting the food products to be heated.
In particular, such a plane 12 is of the heated-plate type, for example a grill provided with resistances, suitable for rapidly cooking, warming and defrosting the products supported in the chamber 11 by heat conduction from below.
Therefore, in the case in which a sandwich is being heated, such a plane 12 can operate both simultaneously, as well as in a completely independent manner from the microwaves, providing for quickly obtaining a perfect browning on the lower surface of the sandwich, with which it is in direct contact.
By shaping the plane 12 in an undulating manner it is also possible to brown the lower surface of the sandwich with the same result as that which can be obtained through common plates used for warming sandwiches found on the market today.
According to the invention, it is also foreseen-for there to be a further element 13 of the heated-plate type, completely similar to the plane 12, said element 13 being mobile and being accommodated in the chamber 11 spaced above the plane 12 itself.
Such a further heated-plate element 13, for example a grill provided with resistances, can be activated both simultaneously and in a completely independent manner from the microwaves to cook, warm and defrost the food products supported in the chamber 11 from above.
The nature of the type of heating offered by such a further heated-plate element 13 shall be explained in detail hereafter and it shall depend on the position that the element 13 itself takes, which is indeed defined as being mobile, with respect to the food products supported on the plane 12.
For such a purpose, it is foreseen for there to be suitable movement means of the further heated-plate element 13. towards/away from the plane 12 such as, for example, pulley elements supporting mobile belts connected above the element 13 itself.
Therefore, according to the above, the further heated-plate element 13 can remain spaced away from the product resting on the plane 12, and in such a case the thermal heating offered shall be of the natural convective or radiation type, or the further heated-plate element 13 can come into contact with the upper surface of the food products, in particular of a sandwich, offering a conductive type thermal heating.
In such a latter case, steps are taken to make a perfect browning also on the upper surface of the sandwich after the inside has been heated through microwaves and at the same time as the browning of the lower surface by means of the heated-plate plane 12.
In order for such a conductive type thermal heating of the upper plate 13 to occur in a correct manner without excessively pressing against the upper surface of bread of the sandwich, sensors are foreseen for detecting the contact of the further heated-plate element 13 with an upper portion of the sandwich resting in the chamber 11, in which such sensors are connected to the movement means to block the descent of the further heated-plate element 13 once a particular pressure exerted by contact with the sandwich itself has been exceeded.
In such a case, since the further heated-plate element 13 is in upper contact with the sandwich with a desired pressure, such an element 13 proceeds to cook, warm and defrost the sandwich itself browning the upper surface from above by heat conduction.
As mentioned previously, both the production of the microwaves and the activation of heating of the supporting plane 12 and of the further heated-plate element 13 can independently be actuated, for example by acting manually upon the controls 30 on the outside of the oven 10. Therefore, according to the invention, the oven 10 can carry out steps, according to the needs, in which it is provided for it to exclusively brown the outer surfaces of the sandwich thanks to the supporting plane 12 and to the further plate element 13, steps in which it is provided for it to exclusively warm/defrost the sandwich thanks to the microwaves and/or a step in which both the supporting plane 12 and the further plate element 13 are activated in sequence, followed by the magnetron.
An example of an automatic process that such an oven 10 makes it possible to carry out can foresee a succession of steps in which initially for a few tens of seconds it is provided for it to only warm/defrost the sandwich exclusively through microwaves, a subsequent step, of the order of a minute, of only toasting the surfaces of the sandwich when the magnetron is turned off, and a last step, of a few tens of seconds, of simultaneous action of both the supporting plane 12 and of the magnetron to finish off the outer lower browning while simultaneously warming the inside and the possible filling of the sandwich.
Moreover, according to the invention, also the supporting plane 12 and the further plate element 13 can be independently actuated to selectively brown only one and/or both the two outer surfaces of the sandwich.
In particular, the controls 30, connected to a control unit, make it possible to independently set the power of the microwaves, in watts, the temperature of the plates, in degrees, and the overall cooking time, in seconds, subdivided into independent actuation steps of the supporting plane 12, of the further plate element 13 and of the magnetron. Alternatively, it is foreseen for there to be the possibility of controlling such factors listed above in a coordinated manner based upon preset programs according to the kind and size of the sandwiches or of the other products to be treated.
In other embodiments it is possible to independently set the actuation time of the microwaves and of the plates as well as the different temperatures of the heated plates.
It should be very easy to understand how the combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, object of the invention, works.
In order to proceed to warm a sandwich in a homogeneous and extremely quick way, while heating the inner portion and while browning the upper and lower outer portions, it is only required for the user to rest the sandwich on the heated-plate plane 12.
At that point, by actuating the oven 10 through the controls 30, the microwaves provide for warming the inside of the sandwich in a very rapid manner, while the heated-plate plane 12 and the heated-plate element 13 subsequently proceed to brown the lower and upper outer surfaces of the sandwich.
Since the supporting plane and the plate element can be independently actuated with respect to the magnetron, it is possible to independently set the browning of the outer surfaces with respect to the cooking of the inside of the sandwich, according to needs.
In such a way, every plate and/or microwave heating step shall be activated independently for the desired time according to needs.
Finally, the combined oven according to the present invention can also comprise a humidity extractor device, like a centrifugal fan 50 schematically shown in figure 2 at the back wall of the oven 10, capable of extracting from the cooking chamber the humidity generated while microwave cooking the sandwich.
In such a way, thus avoiding that the outer surfaces of the sandwich withhold excessive humidity, it is possible to make these surfaces crispy in an optimal manner and substantially in the same way that can be obtained by conventional free plate cooking.
It has thus been seen that a combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention achieves the purposes previously highlighted. Indeed, the combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention achieves a homogeneous inner warming as well as an outer browning of both the upper and lower surfaces of the sandwich to be heated, in a rapid manner and without needing any manual intervention.
The combined oven for cooking, warming and defrosting frozen or fresh food products, in particular for warming sandwiches, according to the present invention thus conceived can undergo numerous modifications and variants, all covered by the same inventive concept; moreover, all the details can be replaced by technically equivalent elements. In practice, the materials used, as well as their sizes, can be of any type according to the technical requirements.

Claims

Combined oven (10) of the microwave type for cooking, warming and/or defrosting frozen or fresh food products, in particular for warming sandwiches, comprising at least one magnetron for generating microwaves in a chamber (11) selectively accessible from outside through a moveable closure door, said chamber (11) being provided with a plane (12) for supporting said food products, said plane (12) being of the heated-plate type, a further heated-plate element (13) being also foreseen accommodated in said chamber (11) in a moveable manner and spaced above said plane (12) to cook, warm and/or defrost said food products supported in said chamber (11) from above, characterized in that said supporting plane (12) and said plate element (13) can be actuated independently from each other and also independently or in combination with respect to said magnetron.
Combined oven (10) according to claim 1 characterised in that said supporting plane (12) and said plate element (13) can be actuated independently.
Combined oven (10) according to any one of the previous claims characterised in that it comprises means for moving said further heated-plate element (13) towards/away from said heated-plate plane (12).
Combined oven (10) according to claim 3 characterised in that said means for moving said further heated-plate element (13) towards/away from said heated-plate plane (12) comprise pulley elements.
Combined oven (10) according to claim 3 characterised in that it comprises sensors for detecting the contact of said further heated-plate element (13) with an upper portion of said food products supported in said chamber (11), said sensors being connected to said movement means to block said further heated-plate element (13) in upper contact position with said food products, said further heated-plate element (13) cooking, warming and defrosting, at least by heat conduction from above, said food products supported in said chamber (11).
Combined oven (10) according to claim 5 characterised in that said sensors for detecting contact of said heated-plate element (13) with an upper portion of said food products supported in said chamber (11) comprise pressure sensors.
Combined oven (10) according to any one of the previous claims characterised in that it comprises means for independent actuation of said microwaves, said heated-plate supporting plane (12) and said further heated-plate element (13).
Combined oven (10) according to any one of the previous claims characterised in that it comprises means for combined actuation, according to preset programmes, of said microwaves, said heated-plate supporting plane (12) and said further heated-plate element (13).
Combined oven (10) according to any one of the previous claims characterised in that both said heated-plate supporting plane (12) and said further heated-plate element (13) are crossed by electrical resistances.
Combined oven (10) according to any one of the previous claims characterised in that it comprises a device (50) for extracting the humidity generated in said cooking chamber when said food products are being microwaved.