Patent Application
20160258632
The present invention relates to a muffle oven equipped with a ventilated cooling system.
Before continuing this description, it is worth pointing out that in the following description and in the following claims reference will be made prevalently to ovens for household use: this should not however be considered to be a limiting factor, since the principles of the invention will also be applicable to, wherever compatible with, ovens intended for applications other than domestic ones.
Furthermore, the invention is applicable to ovens that are a part of a bigger household appliance, such as a gas cooker, as well as to separate ovens that can be embedded into kitchen cabinets or other kitchen structures.
As is known, in ovens reaching high temperatures (up to 500-550° C.), such as, for example, those executing pyrolysis cycles, a system is included for cooling those components, the integrity and reliability of which might otherwise be jeopardized by thermal stresses.
This is mostly the case, for example, of electric and/or electronic components, such as integrated circuits, semiconductors, photodiodes, displays, indicators, electric contacts, switches, etc.: in fact, these components deteriorate at high temperatures, and therefore require the use of special materials and technical solutions, resulting in higher costs.
Alternatively, in order to overcome this situation it is known to provide ovens with the above-mentioned cooling system.
For this purpose, since the electric and/or electronic components that are most sensitive to thermal stresses are generally located in the control panel, ventilation apertures are arranged near the latter, allowing entry and exit of cooling air, which is circulated by a fan.
This state of the art is well described and illustrated in U.S. Pat. No. 4,601,279 (to Guerin), which also explains the operation of an oven wherein a cooling system like the above-mentioned one is arranged in the part above the muffle.
This United States patent also provides a review of the prior art, which already taught how to prevent the electronic components from overheating because of high oven temperatures by using a cooling air flow.
Although from a general viewpoint it can be said that the ovens known in the art can provide the necessary cooling effect, their construction appears nevertheless to be inadequate.
In fact, cooling air is taken in and exhausted towards the outside through apertures arranged in the area between the oven door and the oven control panel.
For this reason, the oven structure comprises an air intake and/or exhaust channel mounted on top of the muffle.
The channel is usually made of sheet metal and is secured to the muffle by means of screws or the like.
It is therefore subject to differential thermal expansions with respect to the muffle, which cause mechanical stresses that, in the long run, may damage its structure and the stability of its connection with the muffle.
Moreover, in U.S. Pat. No. 4,601,279 this effect is further amplified by the fact that the air channel rests entirely on the muffle, resulting in maximal thermal exchange.
As a consequence, the cooling effect on the electronic components is poor or anyway at least partly compromised by this configuration: a need is felt, therefore, to improve this state of the art.
The technical problem at the basis of the present invention is thus to provide an oven wherein the cooling system can offer better performance in terms of thermodynamics and construction, so as to overcome the above-mentioned drawbacks suffered by the prior art.
The idea that solves this problem is to provide a cooling air channel that is associated with the oven structure, preferably through at least one shape coupling, so as to comply with differential thermal expansions with respect to the muffle.
Furthermore, according to one possible embodiment the contact surface between the channel and the muffle of the oven is reduced by said shape coupling.
The features of the oven according to the invention are specifically set out in the claims appended to this description; such features and the effects deriving therefrom, as well as the advantages attained by the invention, will become more apparent in the light of the following description of a preferred but non-limiting example of an oven as shown in the annexed drawings, wherein:
With reference to the above-listed drawings, reference numeral 1 designates as a whole the front panel of an oven according to the invention, which comprises a frame 2 that surrounds a window-like aperture 3, and an upper part 5 adapted to house a control panel.
A door is also associated with the front panel 1 for closing the window-like aperture 3, which door is not shown in the drawings for simplicity's sake.
In the intermediate region of the front panel comprised between the window-like aperture 3 and the upper part 5, there are ventilation apertures 8 for the cooling system.
In this example, the ventilation apertures 8 have a substantially rectangular shape and are aligned along two horizontal rows; advantageously, at least the apertures 8 of the upper row have a bent edge 8a protruding towards the inside of the oven.
The protruding edge 8a can be obtained by cupping the metal sheet of the front panel 1 of the oven, or by any other appropriate processing that will depend on the material of the front panel.
Furthermore, from the edge 8a of the apertures 8 in the upper row respective tangs 8b extend in a cantilever fashion, which are intended for supporting a cooling air channel 10.
The channel 10 has a configuration that, when viewed from the top, vaguely reminds of a fan, with a front portion essentially as wide as the front panel 1 of the oven, which then narrows towards the back, where a ventilation fan is accommodated (which is not shown in the drawings because per se known).
As shown in the drawings, the channel 10 has a hollow body that, in its upper portion, has an aperture 11 where the ventilation fan is installed, while in the lower portion there is a downward protruding base 12; optionally, holes 13 are provided in said base 12 for screws securing the channel to the oven muffle 20.
As shown in the drawings, the thickness of the channel 10 decreases towards the front, resulting in a profile that tapers towards an air outlet mouth 15.
From the latter, a first front appendix 16 resting on the door 1 of the oven extends in a cantilever fashion, as well as a second transversal appendix 17 that abuts on the same door; the function of said appendices 16, 17 will be further explained below.
In this respect, it must be pointed out that the appendices 16, 17 are also present in the variant embodiment of the channel 10 shown in
The inlet mouth 18 allows the channel 10 to take in air from the environment outside the oven, the temperature of which will thus be lower than that of the air coming from the muffle 20.
This variant, therefore, provides a better cooling effect because, in addition to evacuating air from the muffle 20, it also takes in air from the outside environment at a temperature that is lower than that in the oven.
In both of these implementation variants of the invention, the appendices 16 and 17 of the channel 10 engage frontally with the oven door 1, thus keeping the apertures 8 of the latter aligned with the outlet mouth 15 and with the air inlet mouth 18 (if present) of the channel 10.
To this end, it must be remarked that the tangs 8b protruding from the edge 8a of the apertures 8 engage with the inner wall of the channel 10 corresponding to the lower wall of the outlet mouth 15 (
In this frame, it should also be noted that the appendix 16 extending in a cantilever fashion relative to the outlet mouth 15 rests on the window-like aperture 3 of the front panel 1, thus preventing the channel 10 from moving downwards.
In accordance with a preferred embodiment, the body of the channel 10 is made out of two halves or half-shells, an upper one and a lower one, joined together along a junction edge 21; the junction along the edge 21 may advantageously be obtained by clinching the metal sheet out of which the channel 10 is preferably made.
In addition to contributing to lowering the production costs and ensuring good resistance to the high temperatures of a pyrolytic oven, to which the invention particularly applies, this characteristic permits spacer protrusions 23, 24 to be easily formed for stiffening and stabilizing the channel structure.
Such protrusions, obtained by cupping the metal sheet, have a loop-shaped profile and keep the distance between the assembled halves forming the channel body, and also act as elements compensating for the thermal expansions of the metal sheet, thus reducing the mechanical stresses undergone by the material, caused by the working temperatures of the oven.
Thermal expansion compensation is also provided by the base 12 through which the channel 10 rests on the oven muffle 20, since its shape causes the channel bottom to have a loop-shaped profile.
Advantageously, also the muffle 20 has a protruding relief 30, on which the base 12 of the channel 10 rests when installed.
In the light of the above description, one can understand how the oven structure illustrated herein can solve the technical problem tackled by the invention.
In fact, the electronic components in the upper part 5 of the oven door 1 or on the oven structure above the door are cooled by the air that flows in and/or out through the apertures 8 with respect to the front panel 1 of the oven.
In practice, it can be stated that the air taken in by the channel 10 and exhausted through its outlet mouth 15 and the apertures 8 removes heat from the muffle 20, preventing it from being transmitted by conduction and convection to the electronic components located in the control panel, in the upper part 5 of the front panel 1 of the oven.
The channel 10 also prevents direct irradiation between the muffle 20 and the upper part 5 of the front panel 1, thus preventing also this form of thermal exchange. Finally, in the oven variant wherein the flow of environmental air taken in from the outside enters the channel 10 through the inlet mouth 18, external air cools the system even further, so that also in this case the channel 10 is de facto an element that provides a thermal barrier against heat transmitted by conduction, convection and irradiation from the muffle 20.
In fact, as far as conducted heat is concerned, it can be stated that the heat component transmitted by conduction from the muffle 20 to the channel 10 is limited by the fact that the area of contact between them consists of the relief 30 and the base 12.
In other words, the bottom of the channel 10 does not entirely rest on the muffle 20, since only a part (i.e. the base 12) of the surface is in contact therewith; it follows that thermal conduction only affects a small portion of the channel bottom.
As regards convection, it must be pointed out that the oven in which the muffle 20 and the channel 10 are installed has an external housing structure (which is not shown in the drawings because per se known) where there is air that, as it heats up, tends to rise and exchange heat with the channel 10.
Such heat is dissipated by the flow of environmental air through the channel 10, just like the heat irradiated from the muffle 20, which during a pyrolysis cycle for oven cleaning can reach high values.
Furthermore, since the channel 10 rests on the muffle 20 and on the front panel 1, it can compensate for the different thermal expansions that occur during the working cycle.
The operation of the oven according to the invention is therefore reliable.
| Number | Date | Country | Kind |
|---|---|---|---|
| TO2013A000863 | Oct 2013 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2014/065561 | 10/23/2014 | WO | 00 |
