GB2305237A

GB2305237A - Forced convection oven

Info

Publication number: GB2305237A
Application number: GB9616592A
Authority: GB
Inventors: Mangina Franco Tassan; Luca Codazzi
Original assignee: Electrolux Zanussi Grandi Impianti SpA
Current assignee: Electrolux Zanussi Grandi Impianti SpA
Priority date: 1995-09-14
Filing date: 1996-08-07
Publication date: 1997-04-02
Anticipated expiration: 2016-08-07
Also published as: DK9600269U3; ES1035041U; GB2305237A8; ES1035041Y; FR2738900B1; GB9616592D0; ITPN950036V0; FR2738900A1; IT238862Y1; GB2305237B; ITPN950036U1

Abstract

A forced convection oven comprising a cooking chamber (1), a fume conveyor (5), a heating chamber (2), and ventilation chamber 7 including a fan, which communicate with each other. The fume conveyor is directly passed over by the flow of gas circulating within the ventilation chamber, so that the hot combustion gases are cooled in the interior of the fume conveyor before reaching the cooking chamber. The oven may be provided with a conduit (6) for discharge of combustion gases which are exhausted along with vapours produced within the cooking chamber, and a flue duct (4) for discharge of hot combustion gases, the ducts 4 and 6 being two completely separate conduits without common paths.

Description

COOKING OVEN WITH FORCED VENTILATION The present invention relates to a ventilated oven for cooking foods which is capable of effecting cooking by means of a flow of combustion gases which, generated by a plurality of heating elements, are forced by one or more fans to circulate in a heating chamber in which the food to be cooked or heated is disposed.

More particularly the invention relates to a direct-heating convection oven, that is to say of the type which involves direct introduction of combustion gases into the heating chamber.

In the course of the description particular reference will be made to an oven for cooking foods for large groups of people, but it will be appreciated that what is described and claimed is applied to any type of oven for cooking foods, provided that it has means for agitating the internal atmosphere in the cooking chamber.

It is known that cooking foods in an oven involves very different procedures according to the results and effects which are to be achieved but which also have specific disadvantages such as overheating of the conduits for feeding the combustion gases and poor accessibility to the various component parts, particularly to the heating elements which may be designed with burners.

Indeed normally in those ovens the combustion gases attain very high temperatures of the order of 700 to 900"C so that in order to limit the heating effect it is necessary to use special and thus expensive materials which afford particular characteristics in terms of resistance to the thermal stresses, or have recourse to contrivances and artifices which make the construction and use of the oven even more complicated.

In some cases moreover the combustion chamber and the burners are disposed in the vicinity of the bottom of the oven so that other components of the oven (such as the motor for the fan and the control devices) are obviously exposed to the high and undesirable temperatures which reduce the functional reliability thereof.

In particular the present applicants patent GB 1507371 discloses an oven for cooking foods which is provided with a combustion chamber disposed exactly behind the oven itself, and a device for diluting fumes by means of mixing with the hot gases coming from combustion and the colder gases which are present in the cooking chamber. That construction suffers from the disadvantage that the depleted dilution gases, transporting impurities and fat particles, contaminate the intake conduit in which they are disposed, as well as the combustion chamber at a position corresponding to the flow reversal edges.

Contact between the above-mentioned substances and the high temperatures of the hot gases causes cracking thereof with the production of unwanted volatile components and soot which, upon being passed into the cooking chamber, impair the quality and the appearance of the food present therein.

Moreover the above-mentioned patent provides a single flue duct through which the following are discharged: - combustion gases (in the transitional stage or motor failure); and - combustion gases and vapour, which are generated by cooking of the food (in the normal operating condition).

The volume of the gases varies in dependence on the temperature of the oven and the amount of water which evaporates from the food, giving rise to variations in the volumetric discharge capacities, which are highly sensitive, and that has an adverse effect on the efficiency of the cooking process since they have the effect of altering the normal conditions of intake of the combustion gases, with losses in terms of heat output.

In addition the position of the combustion chamber, just on the back of the oven, makes use thereof greatly complicated both because the flame of the burner is not directly visible to an operator normally positioned in front of the oven (and it is well known how important it is, in terms of safety, to be able immediately and directly to check whether a regular flame is or is not present), and because the overall longitudinal size of the oven which is already penalised by the arrangement of the fan disposed on the vertical end portion of the cooking chamber increases further frequently being detrimental to the instability of the oven.

There is therefore a requirement to provide a ventilated oven, in particular for feeding large groups of people, which overcomes the above-described disadvantages and the construction of which is simple, reliable and uses available technologies.

The aim of the present invention is that of providing an oven of the indicated type with forced convection in which the component parts, in particular the heating elements, are easily accessible.

Another aim of the invention is to provide an oven which does not involve increases in its longitudinal dimension.

A further aim of the invention is that of providing an oven of the type referred to having an improved system for circulation of air between the combustion chamber, the heating chamber and the discharge, in such a manner as to ensure an optimum technical operating condition, avoiding the use of special materials.

According to the present invention there is provided a forced convection oven, comprising a cooking chamber, a fume conveyor and a heating chamber with suitable heating means, which are substantially in communication with each other, said heating chamber being traversed and heated by ambient air which is drawn in by blowing means disposed in a ventilation chamber, which blowing means are capable of causing circulation in a substantially closed circuit formed by said cooking chamber, said fume conveyor and said ventilation chamber, of a flow of gases in heat exchange relationship with said heating chamber which is provided with a duct for discharge of the combustion gases, and a possible plurality of pans disposed vertically in said cooking chamber, wherein said fume conveyor is substantially included within said ventilation chamber and is directly passed over at least on both the horizontal surfaces by the flow of gases circulating in said ventilation chamber.

The invention will be better appreciated from the following description given solely by way of non-limiting example and with reference to the accompanying drawing in which: Figures 1, 2 and 3 respectively show in front section, side section and plan view an oven according to the invention provided with a single combustion chamber and a single fan; Figures 4 and 5 respectively show a front section and a side section of an oven provided with a single combustion chamber but with two superposed fans, according to the invention; and Figure 6 shows a front view of an oven provided with two fans and two superimposed burners, according to the invention.

For the sake of greater convenience herein after in the description reference will be made to the heating means contained in the heating chamber as typical gas burners in ambient atmosphere, but it will be appreciated that other types of heating devices may be advantageously used.

Referring to Figures 1, 2 and 3, shown therein is an oven for cooking foods for groups of people, with forced circulation, comprising a cooking chamber 1, a heating chamber 2 provided with heating means 3, preferably gas burners, a flue duct 4 for discharge of the combustion gases, a fume conveyor 5 for the combustion gases and a discharge conduit 6 for the combustion gases exhausted and the vapours produced in the cooking chamber.

The oven further has a ventilation chamber 7 which accommodates a motor-driven fan of conventional type (not referenced) disposed towards the back of the oven.

As is better illustrated in Figure 2, the intake wall 10 is shaped in its front portion in such a way as to terminate with an annular gap 8 which is open to the edge 9 that is directed towards the central portion of the ventilation chamber and of dimensions and position such that the flow of gas issuing from the annular gap 8 is of a consequently annular configuration and issues towards the interior of the ventilation chamber.

In fact intake of the combustion gases takes place along the whole of the annular intake section of the fan, thus improving both the suction intake effect and subsequent blowing into suitable conduits which are not shown but which are known in the art and which are capable of distributing the gas to the interior of the cooking chamber.

The advantage of that configuration arises out of the fact that the fume conveyor 5 is completely involved with the flow produced by the fan and therefore acts as a heat exchanger between "cold" gases (up and around 300"C) circulating in the ventilation chamber and the hot combustion gases coming from the combustion chamber, which cool down again and arrive at the intake gap 8 at a temperature such as not to cause overheating of the metal sheets.

That mode of operation overcomes the disadvantages arising out of dilution of the hot combustion gases with "cold" exhausted gases experienced with an oven according to the above-mentioned patent; indeed, the present invention not involving mixing of "cold dirty" gases with "hot clean" gases, the above-mentioned disadvantages cannot arise, having regard to the fact that the hot gases produced in the heating chamber are significantly cooled in the fume conveyor which functions as a "heat exchanger" before they are mixed with the dirty gases present in the cooking chamber.

In addition with the structural configuration shown in the Figures it is possible and advantageous to arrange the heating chamber 2 not rearwardly but laterally of the oven, with obvious advantages both in terms of overall size of the oven and in terms of operational safety, bearing in mind that in that way it is possible directly to observe from a space in front of the oven whether the flame 3 of the burners is or is not present of whether in any case the heating means are activated.

The illustrated construction also has a suitable conduit 6 for discharge of combustion gases which are exhausted and vapours which are produced in the cooking chamber.

The advantage of that construction is achieved by making the operation of the two flue ducts independent, in such a way that in the face of transitional or irregular situations in terms of operation in one of said conduits, that has only a minimum influence on the conditions of operation in the other conduit.

The intake wall 10 which is preferably formed by a substantially vertical flat wall separates the ventilation chamber from the cooking chamber.

Preferably the flat wall 10 is disposed adjacent to the front edges of the ventilation chamber and the fume conveyor 8 is open at a position corresponding to the suction intake mouth opening of the ventilation chamber.

Advantageously the fume conveyor 8 may be shaped in a substantially tapered configuration from the intake opening 11 for the gases coming from the heating chamber, in the opposite direction to the intake opening; the benefit of that solution lies in the fact that the progressive reduction in the size of the heated flow of gases which is drawn in requires a corresponding reduction in the dimensions of the conduits, subject to a lack of balance in the pressures and an irregular gas intake effect; it also permits more effective circulation over the conveyor for the purposes of better cooling it.

Naturally, having regard to the basic teachings of the present invention it is possible to design ovens with a plurality of intake walls 13,14 and a single fume conveyor 15 with corresponding heating chamber, as shown in Figures 4 and 5, as also in association with a single cooking chamber it is possible to provide a plurality of heating chambers 16,17, respective fume conveyors 19,20 and respective ventilation chambers 21,22.

It should be noted that in accordance with the invention the advantages can be achieved in convection ovens involving the most widely varying internal vertical dimensions, according to requirements. That makes it possible to keep the levels of performance of the oven substantially unaltered, independently of its capacity and the number of pans provided therein.

In addition it is noted that the convection oven according to the invention may be of a depth which is advantageously reduced in comparison with the conventional constructions. That is by virtue of the fact that the motors which operate the fans can be accommodated, without the need for suitable transmission means, outside the upper wall of the housing which contains the fans, that is to say in a region which normally does not involve any problems in terms of overall size.

The oven is naturally provided with numerous other devices which are not described herein as they are not relevant to the purposes of this application.

Although the invention has been described with reference to the preferred embodiment and using generally known terminology, it is not considered to be limited thereby since the man skilled in the art may make numerous variations and modifications in terms of structure and form.

Claims

1. A forced convection oven, comprising a cooking chamber, a fume conveyor and a heating chamber with suitable heating means, which are substantially in communication with each other, said heating chamber being traversed and heated by ambient air which is drawn in by blowing means disposed in a ventilation chamber, which blowing means are capable of causing circulation in a substantially closed circuit formed by said cooking chamber, said fume conveyor and said ventilation chamber, of a flow of gases in heat exchange relationship with said heating chamber which is provided with a duct for discharge of the combustion gases, and a possible plurality of pans disposed vertically in said cooking chamber, wherein said fume conveyor is substantially included within said ventilation chamber and is directly passed over at least on both the horizontal surfaces by the flow of gases circulating in said ventilation chamber.

2. A ventilated furnace according to claim 1, and comprising a discharge conduit for combustion gases which are exhausted and vapours which are produced within said cooking chamber, and wherein said flue duct for discharge of hot gases and said conduit for discharge of combustion gases which are exhausted and vapours are two completely separate conduits without a flow path in common.

3. A ventilated oven according to claim 2, wherein said fume conveyor terminates in the direction of the flow of gas which passes there through with an annular gap, of which one side opposite to the position of said cooking chamber is at least partially open towards the interior of said ventilation chamber, in such a way that the gas which passes through said intake chamber is passed with at least partially annular geometry against the intake edges of said blowing means.

4. A ventilated oven according to claims 1, 2 or 3, wherein said ventilation chamber is disposed on the vertical end wall of said ventilated oven, said fume conveyor is disposed substantially over said ventilation chamber and there are provided deflector means which separate on the one hand said cooking chamber and on the other hand said fume conveyor and said ventilation chamber, said separation means being open at a position corresponding to the intake opening of said ventilation chamber.

5. A ventilated oven according to claim 4, wherein said deflector means comprise a substantially vertical flat wall and that said wall is disposed substantially adjacent to the front edges of said ventilation chamber and said fume conveyor.

6. A ventilated oven according to any one of the preceding claims, wherein said heating chamber is disposed laterally of said fume conveyor with respect to a front view of said intake chamber.

7. A ventilated oven according to any one of the preceding claims, wherein said fume conveyor is shaped with a substantially tapered configuration from the intake mouth opening for the gases from said heating chamber in the opposite direction to said mouth opening.

8. A ventilated oven according to any one of the preceding claims, wherein said heating means comprise at least one gas burner disposed in a lower position with respect to the mouth opening which communicates said heating chamber with said fume conveyor.

9. A ventilated oven according to any one of the preceding claims, wherein the ventilation chambers are two and in superposed relationship, the fume conveyor is disposed in the intermediate space between said two ventilation chambers, and said fume conveyor terminates in the direction of the flow of gas which passes through it with two separate annular gaps of which a respective side, opposite to the position of said cooking chamber, is at least partially open towards the interior of the corresponding ventilation chamber, whereby the gas which passes through said annular gaps is passed with at least partially annular geometry against the intake edges of said respective ventilation chambers.

10. A ventilated oven according to any one of claims to 8, wherein disposed in association with a single cooking chamber are a plurality of heating chambers respective fume conveyors and respective ventilation chambers as described and claimed.

11. A ventilated oven constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3, Figures and 5 or Figure 6 of the accompanying drawings.