GB2087535A

GB2087535A - Improvements in or relating to gas cookers

Info

Publication number: GB2087535A
Application number: GB8013973A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-04-27
Filing date: 1980-04-28
Publication date: 1982-05-26
Also published as: DE3014937C2; AT368268B; ATA320179A; GB2087535B; DE3014937A1

Abstract

A gas cooker includes a cooking area a formed by a heat transmitting plate 5 which is heated by a burner. The burner comprises a burner plate 1 of heat resistant porous or perforated ceramic which burns a gas air mixture at its surface 3 in a combustion space 4. An exhaust gas guide duct 8 is connected directly to the combustion space and is covered by the heat retaining plate to form a heat retaining zone b. Heat absorbing elements 11 of metal are disposed in the guide duct 8 and extend transversely to the flow of exhaust gases. The heat absorbing elements have guide faces 15 in the region of the heat retaining zone which guide the exhaust gases towards the heat transmitting plate. <IMAGE>

Description

SPECIFICATION Improvements in or relating to gas cookers The invention relates to gas cookers of the type including a cooking area formed by a heat transmitting plate, for example a glass ceramic plate, arranged to be heated by a radiation burner comprising a burner plate which consists of a heat resistant porous or perforated ceramic plate and which is arranged to burn a gas air mixture at the surface thereof in a combustion space or chamber, an exhaust gas guide duct being directly connected to the combustion chamber and being covered by the heat transmitting plate and forming a heat retaining zone. In known gas cookers of this type, the heat of the exhaust gases in the exhaust gas duct is utilized insufficiently for the heat retaining zone.

According to the invention, there is provided a gas cooker including a cooking area formed by a heat transmitting plate arranged to be heated by a radiation burner comprising a burner plate which consists of a heat resistant porous or perforated ceramic plate and which is arranged to burn a gas air mixture at the surface thereof in a combustion space, an exhaust gas guide duct being connected directly to the combustion space and being covered by the heat transmitting plate and forming a heat retaining zone, there being provided in the exhaust gas guide duct heat absorbing elements of metal which extend through the exhaust gas guide duct transversely to the flow direction of exhaust gases and which comprise guide faces in the region of the heat retaining zone arranged to guide the exhaust gases towards the heat transmitting plate.

Thus, in the region of the heat retaining zone the heat transmitting plate is intensively loaded by the gases flowing through the exhaust gas duct by means of the guide surfaces.

The output of radiation burners in which the gas air mixture is burned at the surface of the burner plate is controlled by switching the radiation burner periodically on and off. During the switched-on period, the heat absorbing elements receive heat from the hot exhaust gases, whereby the temperature of the exhaust gases which flow out of the exhaust gas duct is lowered. During the switched-off period, during which the gases flowing through the exhaust gas guide duct consist mainly of air, the heat absorbing elements deliver a portion of the stored heat to the gases flowing through the exhaust gas guide duct. Thus, the temperature of the gases in the exhaust gas guide duct is lowered during the switched-on period of the radiation burner and raised during the switched-off period, so that the temperature in the exhaust gas duct is rendered substantially constant to a large extent.In the usual known radiation burners, for example, the ratio between the switched-on periods and the switched-off periods may fluctuate, dependently upon the control position, between 5 min switched-on and 1 min switched-off and 1 min switched-on and 10 min switched off. In such burners, high temperatures result during the switched-on period and low temperatures during the switched-off period; this is unfavourable for heat retention.

Equalization of these temperatures is thus advantageous, since both the high temperature during the switched-on period and the low temperature during the switched-off period have an unfavourable effect in the heat retaining zone.

Consequently, in conjunction with the effect of the guide surfaces which guide the gases towards the heat transmitting plate, the heat content of the exhaust gases in the exhaust gas guide duct is utilized better and more uniformly for heating of the heat retaining zone.

Preferably the heat absorbing elements are connected together in a heat conducting manner by side bars to form a unit, possibly in one piece therewith, the unit which consists of the heat absorbing elements and the side bars being heat insulated from the walls of the exhaust gas guide duct. Due to the fact that the heat absorbing elements are connected together by the side bars in a heat conducting manner, a certain constancy of the temperature is also obtained in the flow direction in the exhaust gas guide duct and, due to the fact that the unit formed by heat absorbing elements and side bars is heat insulated from the walls of the exhaust gas guide duct, heat losses to the outside are reduced, so that improved utilization of the heat content of the gases in the heat retaining zone is obtained.

Preferably, the unit formed by the heat absorbing elements and the side bars has plane faces which are arranged in a common plane and by which it lies against the heat transmitting plate, and is pressed against the latter in a resilient manner. Additionally a direct heat transfer from the heat absorbing elements to the heat transmitting plate is obtained thereby by means of the plane faces, whereby again an improvement of the utilization of the heat content of the exhaust gases is obtained. Preferably, the unit formed by the heat absorbing elements and the size bars is supported against a wall of the exhaust gas guide duct, the exhaust gas guide duct being pressed resiliently against the heat transmitting plate in this case.This has the advantage that springs are omitted within the exhaust gas guide duct which would be disadvantageously affected by the hot exhaust gases and that the springs are arranged in a region which is largely unaffected by heat.

Preferably, the exhaust gas guide duct comprises a cross-section which increases in the flow direction, whereby the flow of the exhaust gases is further favourably affected.

The heat absorbing elements are arranged outside the cooking area, considered from above, so that they are heated only by the outflowing exhaust gases, and, when a plurality of cooking areas is provided, a separate exhaust gas guide duct is preferably provided for each cooking area.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates a section through a cooking area on line I-I of Figure 2, and Figure 2 illustrates a view from above of the cooking area, with heat transmitting plate removed.

A burner plate 1 is formed by a porous or perforated ceramic plate to which a gas-air mixure is supplied from below from a chamber 2. This gas-air mixture flows upwards through the pores or perforations of the burner plate 1 and burns in a surface zone 3 of the burner plate 1. A combustion space 4 above the burner plate 1 is covered by a heat transmitting plate 5, for example of glass ceramic material, and extends over a cooking area a as well as over a heat retaining zone b. A sheet metal casing 6 lies against the heat transmitting plate 5, for example with the intervention of a compressible seal 7 of asbestos or the like, and limits the cooking area a as well as an exhaust gas guide duct 8. A sleeve 9 of the sheet metal casing 6 surrounds the burner plate 1 in a sealing manner.The exhaust gases produced in the combustion space 4 are guided away through the exhaust gas guide duct 8 and issue therefrom at 10.

In the exhaust gas guide duct 8, heat absorbing elements 11 of metal are disposed transverse to the flow direction of the exhaust gases and partly comprise guide surfaces 1 5 which guide the cases towards the heat transmitting plate 5, whereby the heat transmitting plate is intensively loaded by the gases. The exhaust gas guide duct 8 is connected directly to the combustion space 4, so that the heat content of the gases can be utilized satisfactorily in the heat retaining zone b. Side bars 14 are arranged on both sides of the exhaust gas guide duct 8 and connect the heat absorbing elements 11 to each other. The heat absorbing elements 11 are in one piece with the side bars 14 and heat delivering elements 12 and are made from aluminium because of the good heat conductance thereof.The heat absorbing elements 11 and the side bars 14 form a unit which by plane abutment faces 13 and 17 lie against the heat transmitting plate 5, so that heat transfer to the heat transmitting plate takes place also by way of these plane faces. The abutment faces 13 are arranged on the elements 12 and are larger than the abutment faces 17, in order to favour heat transfer in the vicinity of the cooking area a. All abutment faces 13 and 1 7 are located in one plane and the unit formed by the heat absorbing elements 11 and the side bars 14 is pressed resiliently against the heat transmitting plate 5.At the same time the unit formed by the heat absorbing elements 11 and the side bars 14 is supported against the sheet metal casing 6 enclosing the exhaust gas guide duct 8 and the combustion space 4, and the sheet metal casing 6 is pressed against the heat transmitting plate 5 by means of springs 16 which are removed from the heat effect of the exhaust gases. The unit formed by the heat absorbing elements 11 and the side bars 14 is heat insulated from the sheet metal walls of the exhaust gas guide duct 8; as illustrated in the drawing, an air gap remains between the side bars 14 and the side walls of the exhaust gas guide duct. Since the side bars 14 are arranged at the sides of the exhaust gas guide duct 8 and only the heat absorbing elements 11 extend through the exhaust gas guide duct transversely to the flow direction of the exhaust gases, the flow in the exhaust gas guide duct is not disadvantageously affected by the side bars 14.

Claims

1. A gas cooker including a cooking area formed by a heat transmitting plate arranged to be heated by a radiation burner comprising a burner plate which consists of a heat resistant porous or perforated ceramic plate and which is arranged to burn a gas air mixture at the surface thereof in a combustion space, an exhaust gas guide duct being connected directly to the combustion space and being covered by the heat transmitting plate and forming a heat retaining zone, there being provided in the exhaust gas guide duct heat absorbing elements of metal which extend through the exhaust gas guide duct transversely to the flow direction of exhaust gases and which comprise guide faces in the region of the heat retaining zone arranged to guide the exhaust gases towards the heat transmitting plate.

2. A gas cooker as claimed in Claim 1, in which the heat transmitting plate is a glass ceramic plate.

3. A gas cooker as claimed in Claim 1 or 2, in which the heat absorbing elements are connected together by means of side bars in a heat conducting manner to form a unit, the unit comprising the heat absorbing elements and the side bars being heat insulated from the walls of the exhaust gas guide duct.

4. A gas cooker as claimed in Claim 3, in which the heat absorbing elements are integral with the side bars.

5. A gas cooker as claimed in Claim 3 or 4, in which the unit formed by the heat absorbing elements and the side bars lies against the heat transmitting plate and is pressed resiliently thereagainst at plate faces which are disposed in a common plane.

6. A gas cooker as claimed in any one of the Claims 3 to 5, in which the unit formed by the heat absorbing elements and the side bars is supported against a wall of the exhaust gas guide duct and the exhaust gas guide duct is pressed resiliently against the heat transmitting plate.

7. A gas cooker as claimed in any one of the preceding claims, in which the exhaust gas guide duct has a cross-section which increases in the flow direction.

8. A gas cooker as claimed in any one of the preceding claims, in which a plurality of cooking areas is provided and a separate exhaust gas guide duct is provided for each cooking area.

9. A gas cooker substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.