A GAS HOTPLATE BURNER

Abstract: The power of a gas burner with a crown and cap may traditionally be related to its diameter, i.e. its circumference. The invention provides a burner which not only has peripheral flames but also flames burning nearer the centre. This is obtained by means of a special crown and cap structure and by providing secondary air for the inwards directed flames by means of a scoop plate (S) which takes part of the primary air stream (A) supplied to the burner. The result is a burner which has an appreciably larger power as compared to traditional burners of the same diameter.

Description: A gas hotplate burner The invention relates to a gas hotplate burner of the kind comprising a gas nozzle fitted into the bottom part of a burner body assembly, a supply passage for primary air, preferably taking the form of a circular slit, a mixing venturi, a crown structure defining a chamber, and a cap structure providing a lid for same. Burners based on the principle of a cap covering a crown being a circular array of openings for the gas mixture burning on the outside of the crown are known as is the use of a short venturi which has the advantage that the mixing takes place in a short vertical distance as opposed to the traditional long venturi. This enables a low profile of a cooker arrangement, which is particularly suitable for fitting into existing cupboards without wasted space. In order to increase the power of such a burner it is necessary supply a larger amount of gas per time unit, i.e. a larger diameter nozzle or injector for the same pressure, and this calls for more primary air in order to obtain the correct gas/air mixture. This is traditionally obtained by means of a larger supply passage for primary air. Simultaneously it is also desirable to provide more flame openings in order to create a larger sheet of flames for heating large-diameter pots placed on the hob, and this is traditionally obtained by making the diameter of the crown larger. It is the purpose of the invention to obtain a larger power from a gas burner with a reduced outer diameter in comparison with known burners, and in effect this means that it is desirable to utilize the area of the circle rather than the circumference as is known today. This is obtained by means of a crown and cap which define a ring-shaped chamber having flame openings on at least part of the inside perimeter as well as on the outside. In this manner there is obtained, not only the outwards directed ring of flames known from traditional burners of a particular diameter, but also that there is a - smaller - ring of flames directed towards the centre of the burner. This means that the total flame area may be increased by at least 30% within the same overall diameter. This is, however, crtitically dependent on efficient supply of secondary air, i.e. the air needed for burning the gas/air mixture exiting from the inside part of the crown. This may be obtained by special conduits for outside air leading to the centre area of the cap. In case these are fed from the space below the hotplate, the flow of this secondary air becomes very sensitive to the opening of cupboard doors, etc. It has turned out that an efficient construction of an improved burner providing avoiding the complication of special conduits is obtained by letting the primary air enter via the circular slit-like passage surrounding each burner and with a lower delimitation being the top surface of the hotplate and an upper delimitation constituted by a circular plate, and in that a scoop plate is provided for extracting secondary air from the stream of mainly primary air entering the slit-like passage. The term scoop plate is used for a thin structure which will divide the primary air flowing into two streams, one of which is the secondary air necessary for the combustion in the inside part of the burner. In this manner a kind of self-regulation in the supply of secondary air is obtained, because a greater pulling-in of primary air by the venturi will also provide a greater supply of secondary air. This construction has the further particular advantage that disassembly of the parts will enable complete cleaning of the top surface with the the burner body in it, without having to disassemble special conduits. A further advantageous embodiment is particular in that the crown and cap define a ring-shaped chamber as well as a central circular chamber, flame openings being available on the outside perimeter, on part of the inside perimeter, and on the outside of the central circular chamber. The cap will be in two parts, one predominantly ring-shaped, the other a central disc. This construction allows increasing the performance of a burner of a given diameter by about 80%. A further advantageous embodiment is particular in that an electric ignition device is fitted in a cut-out in the crown close to the outside perimeter, said cut-out having an outwards directed flame opening directed at an angle towards the ignition device which lights the outwards directed flames and an inwards directed flame opening which lights the inwards directed flames . The invention will be described in greater detail with reference to the drawings, in which Fig. 1 shows a cross section of a burner according to an embodiment of the invention fitted into a hotplate, Fig. 2 shows a cap for the burner shown in Fig. 1, Fig. 3 shows a crown for the burner shown in Fig. 1, Fig. 4 shows the cross section of a burner according to another embodiment of the invention fitted into a hotplate, Fig. 5 shows the crown structure for the burner shown in Fig. 5, and Fig. 6 shows the ignition system for a burner such as that shown in Figs . 4 and 5. In Fig. 1 it is seen how in this embodiment of the invention gas G is provided to an injector i which directs a jet of gas upwards and pulls in fresh air A from peripheral openings . The gas is mixed in the venturi structure constituted by the vertical part Vv and a horizontal part Vh which an expanding cross section as the gas/air mixture travels outwards between the cap Ca and the conical surface of the crown Cr. The gas/air mixture burns at the outside edge of the crown shown at FI and F2 as well as at the inside at F3. The flames FI, F2 (which in reality is a complete circle of flames surrounding the crown Cr) use the surrounding air as the source of secondary air, and the flames F3 (which in reality form parts of a circle of flame) use air "scooped" up from the indraught of primary air by means of a scoop S . The components of the gas burner according to this embodiment of the invention are specifically constructed to this purpose, and Fig. 2 shows the cap Ca having openings H in which the flames burn inwards towards the centre. Fig. 3 shows the corresponding crown Cr with e.g. milled bottoms of flame openings Fo for the outwards directed flames and Foi for the inwards directed flames . The flame openings are completely defined when the crown is closed by the cap. In Fig. 4 is shown how the basic idea of the invention is extended in a different embodiment having an inner ring of outwards directed flames . Gas G is provided to an injector i which directs a jet of gas upwards and pulls in fresh air A from peripheral openings . The gas is mixed in the venturi structure constituted by the vertical part Vv and a horizontal part V which an expanding cross section as the gas/air mixture travels outwards between the cap Ca and the conical surface of the crown Cr. The gas/air mixture burns at the outside edge of the crown shown at FI and F2 as well as at the inside at F3. Furthermore gas/air mixture enters the space beneath the central cap Cac and burns with the flames F4 directed outwards from the central part of the burner. The flames FI, F2 (which in reality is a complete circle of flames surrounding the crown Cr) use the surrounding air as the source of secondary air, and the flames F3 (which in reality form parts of a circle of flame) as well as the flames F4 directed into the same space use air "scooped" up from the indraught of primary air by means of a scoop S . In order to light the flames of the burner an electric ignition device is shown at E . In Fig. 5 is shown the central part of the crown structure, i.e. the openings causing the flames F3 and F4. In Fig. 6 is shown how the ignition device E functions in the burner according to the invention. When the gas is turned on it creates a combustible gas/air mixture in the space M, and it flows out through all the flame openings, both outwards and inwards. Furthermore two particular flame openings are provided, II being directed towards the active part Ea of the ignition device which ignites the exiting gas, creating the ring of flames FI, F2. The other particular flame opening 12 is directed towards the inside and the gas is ignited by the first flame at II, whereafter it ignites the inner ring F3 of flames which in their turn ignite the central ring F4.

Claims: P A T E N T C L A I M S 1. A gas hotplate burner of the kind comprising a gas nozzle (i) fitted into the bottom part of a burner body assembly, a supply passage for primary air (A) , preferably taking the form of a circular slit, a mixing venturi, a crown structure (Cr) defining a chamber, and a cap structure (Ca) providing a lid for same, c h a r a c t e r i z e d i n that the crown (Cr) and cap (Ca) define a ring-shaped chamber having flame openings on at least part of the inside perimeter as well as on the outside. 2. A gas hotplate burner according to claim 1, c h a r a c t e r i z e d i n that the primary air (A) enters via the circular slit-like passage surrounding each burner and with a lower delimitation being the top surface of the hotplate and an upper delimitation constituted by a circular plate, and in that a scoop plate (S) is provided for extracting secondary air from the stream of mainly primary air entering the slit-like passage. 3. A gas hotplate burner according to claim 1, c h a r a c t e r i z e d i n that the crown and cap define a ring-shaped chamber as well as a central circular chamber, flame openings being available on the outside perimeter, on part of the inside perimeter, and on the outside of the central circular chamber. 4. A gas hotplate burner according to claim 1, c h a r a c t e r i z e d i n that an electric ignition device (E) is fitted in a cut-out in the crown close to the outside perimeter, said cut-out having an outwards directed flame opening (II) directed at an angle towards the ignition device which lights the outwards directed flames and an inwards directed flame opening (12) which lights the inwards directed flames.

Inventors: ARMANNI PIERO, ESKILDSEN CHRISTIAN, ARMANNI, PIERO, ESKILDSEN, CHRISTIAN
Applicants: ARMANNI PIERO, ELECTROLUX AB, ESKILDSEN CHRISTIAN, AKTIEBOLAGET ELECTROLUX, ARMANNI, PIERO, ESKILDSEN, CHRISTIAN
Application year: 1997
Main classification: F23D14
IPC codes: F23D14, F24C3