GB2393510A

GB2393510A - Pyrolytic cooking oven

Info

Publication number: GB2393510A
Application number: GB0319400A
Authority: GB
Inventors: Giuseppe Milanesi; Walter Zanzani; Silvano Todoli; Giuiliano Zanetti
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2002-09-25
Filing date: 2003-08-18
Publication date: 2004-03-31
Anticipated expiration: 2023-08-18
Also published as: ITPN20020048U1; GB2393510B; DE20312790U1; FR2844869A1; FR2844869B3; SE0302496L; SE0302496D0; ES1055618U; SE525463C2; ES1055618Y; GB0319400D0

Abstract

Pyrolytic cooking oven, comprises a lining (10) communicating with a cavity (15) by means of two apertures (16) for generating a natural circulation of gases and vapours in a closed circuit when the oven is in operation. It is characterised in that it has a screen (17) placed in the gas and vapour circulation path passing between the lining (10) and the cavity (15). The solution makes it possible to eliminate the filter normally used to reduce the concentration of toxic gases produced during the pyrolysis. The screen (17) may be fixed outside the cavity (see Fig 3, not shown).

Description

23935 1 0

PYROLYTIC COOKING OVEN

The present invention relates to a pyrolytic cooking oven, particularly for domestic kitchens, having an innovative design to eliminate the problems arising from the 5 use of appropriate filters required for the self-cleaning cycles of such ovens.

Self-cleaning pyrolytic ovens have been known for some time; they are ovens in which the inside of the lining is cleaned by the complete combustion of cooking residues. The combustion is normally carried out by overheating the lining, which causes the carbonization of the food residues and therefore leads to the evolution of carbon 10 monoxide. This gas is highly toxic and cannot be released into the environment outside the oven. Pyrolytic ovens in use at the present time are therefore provided with appropriate filters which reduce the concentration of carbon monoxide to levels below those stipulated by the regulations.

Filters for pyrolytic ovens are made from various types of material and are 15 treated with precious metals which improve their technical characteristics, particularly the selectivity of elimination of the gas. These filters can be of various shapes and sizes, and can have special pyrolytic reaction characteristics for filtering both solid and gaseous components. They must also be capable of operating at different temperatures and pressures while still providing the necessary efficiency.

20 These filters present farther problems in respect of their constructional characteristics. For example, ceramic filters cannot be fitted with ordinary fixing elements such as screws and supports, owing to their fragility which exposes them to risks of breakage during the transport of the oven, and during its operation, due to the vibrations produced by the fans which circulate the hot air within the lining. For this reason, use is 25 made of metallic filters, which are more adaptable than ceramic ones, but are less effective, require more maintenance and have a shorter life.

Consequently, the principal object of the present invention is to provide a pyrolytic cooking oven, particularly for domestic kitchens, which dispenses with the use of a filter and components connected to it for eliminating combustion gases, particularly 30 carbon monoxide.

A further object of the present invention is to simplify the construction of a pyrolytic oven while providing greater efficiency in terms of cleaning and the elimination of the gases produced in the pyrolytic cleaning process.

Another object of the present invention is to reduce the problems of 35 maintaining a pyrolytic oven, thus increasing its life and economy of operation.

European patent application no. 02010716.5, in the name of the present applicant, describes a cooking oven whose lining is in communication with a cavity through which a natural circulation of hot air and vapour is generated in a closed circuit during the operation of the oven. This constructional solution is particularly effective for

solving the problem of the condensation of the vapour produced during the cooking of food. The solution described in the patent application cited above has also been tested in a pyrolytic oven, and has been surprisingly found to have a degree of effectiveness 5 in terms of the elimination of carbon monoxide during the pyrolytic cleaning of the oven.

This test was followed by a subsequent study which resulted in the present improvement, by means of which a much more significant effect is achieved without excessively complicating the construction of the oven.

According to the invention there is provided a pyrolytic cooking oven, 10 comprising a lining communicating with a cavity by means of two apertures for generating a natural circulation of gases and vapours in a closed circuit between the lining and the cavity when the oven is in operation, wherein at least one screen is placed in the gas and vapour circulation path passing between the lining and the cavity.

The invention will be further described by way of non-limitative example 1 S with reference to the accompanying drawings, in which: Figure 1 shows a partial schematic view of a pyrolytic oven according to the prior art;

Figure 2 shows a partial schematic view of a pyrolytic oven according to the invention, in a first embodiment; and 20 Figure 3 shows a partial schematic view of a pyrolytic oven according to the invention, in a second embodiment.

The conventional pyrolytic oven shown in Figure 1 essentially comprises a lining 10 which is closed frontally by a door 1 1 and which is connected to a chamber 12 located above the lining. The chamber 12 normally houses a tangential fan 13 for removing 25 the vapour and the gases produced in the lining during the processes of cooking food and pyrolytic cleaning respectively. A filter 14, for retaining the solid and gaseous particles extracted from the lining during the operation of the oven, is placed in the connecting duct between the lining 10 and the chamber 12. In particular, the filter 14 retains the carbon monoxide produced by the pyrolytic cleaning.

30 This known technical solution therefore requires the use of two special components, namely the fan 13 and the filter 14, which complicate the construction and operation of the oven. These components also require periodic maintenance and replacement when necessary.

According to the invention, the lining 10 (Figures 2 and 3) communicates 35 with an external cavity IS, preferably located above the said lining. The communication between the lining 10 and the cavity IS is provided simply by means of two apertures 16, which are advantageously formed in positions on opposite sides of the central plane of the lining.

As described in the previously cited European patent application no. 02010716.5, it has been found experimentally that, when the oven is in operation, a natural circulation of the gases and vapours is generated in a closed circuit between the lining 10 and the cavity 15. Gases and vapour leave the lining through one of the apertures 16 and re 5 enter through the other. This circulation is generated by the fact that the pressure is not uniform throughout the areas within the lining.

The aforesaid effect is also produced during the pyrolytic self-cleaning process, although to a limited degree. It may be hypothesized that, in this case, the pressure differences between one area and another within the lining are less significant because the 10 lining is essentially empty during this cleaning phase. However, it is important to note that the circulation of the vapours and gases through the cavity 15 causes a considerable elimination of the carbon monoxide produced by the pyrolysis. It is therefore no longer necessary to filter the gases and vapours and discharge them to the external environment.

To enhance the observed effect, in such a way as to obtain the virtually total 15 elimination of the percentage of carbon monoxide, or at least its reduction to levels well below those permitted by the safety regulations, the present invention proposes the fitting of at least one suitable screen 17 in the gas and vapour circulation path that passes through the lining 10 and the cavity 15 of an oven as described above.

The screen 17 is to be made from any material that can withstand the high 20 temperatures (450-600 C) which are reached in the lining during the pyrolysis process.

Preferably, the material used for the screen 17 is the same as that used for the walls of the lining. This screen can be fitted inside the lining 10 (Figure 3) or inside the cavity 15 (Figure 2); clearly, it is also possible to fit both screens.

The shape and dimensions of the screen 17 must be such as to provide an 25 adequate circulation of the gases and vapours and must be adapted to the specific location of the said screen. Where fixing is concerned, any ordinary means may be used, such as screws, rivets, bonding or welding. It should also be noted that the efficiency of the screen can be increased by forming its surface with particular characteristics, for example by dimpling, slotting or knurling.

30 In conclusion, the described solution provides numerous advantages, such

as: a saving of energy, since the superheated gases and vapours from the pyrolysis process do not leave the oven; the elimination of static and moving components which complicate the construction and operation of the oven; and the improvement of the self-cleaning cycle, since heat is not dissipated to the exterior of the oven.

Claims

-4 CLAIMS

1. A pyrolytic cooking oven, comprising a lining communicating with a cavity by means of two apertures for generating a natural circulation of gases and vapours in a 5 closed circuit between the lining and the cavity when the oven is in operation, wherein at least one screen is placed in the gas and vapour circulation path passing between the lining and the cavity.

2. A pyrolytic cooking oven according to Claim 1, wherein the screen is fixed

10 inside the lining.

3. A pyrolytic cooking oven according to Claim 1, wherein the screen is fixed inside the cavity.

15

4. A pyrolytic cooking oven according to any one of the preceding claims, wherein the screen has a surface which is dimpled, knurled or provided with slots.

5. A pyrolytic cooking oven constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying 20 drawings.