FR2823557A1 - Gas cooker hob has burner beneath heat resistant panel with holes for gas flames - Google Patents

Abstract

The cooker hob has at least one burner (2) with a gas feed (10, 11) and main outlets (22), covered by a panel (4) of a heat-resistant material with holes (8) in line with the burner outlets and a free space (28b) between the panel and burner that contains part of the burning flame. When the gas is at maximum pressure the flames extend through the holes in the panel, while at low pressure they are confined within the space (28b). The burner has a combustion head (16) enclosing a mixing chamber (20) and situated at a distance of at least 2 mm from the panel, which has a hat-shaped boss (6) with top (6a) and side (6b) surfaces covering the burner, the holes being located in the side surfaces and in the form of elongated slots.

Description

guide device (I) according to any one of claims 1 to

11.

  The invention relates to a device comprising at least one gas burner having main orifices and disposed under a plate made of a material resistant to high temperatures and comprising

openings.

  Such devices, the general principle of which is known, are

  commonly used as cooktops or cooktops.

  DE-A-40 33 503 describes a device having a burner comprising gas outlet orifices in a free space provided under a plate surrounding said orifices and comprising holes for the evacuation of combustion gases. However, this device does not make it possible to design industrial constructions satisfying the service expected by the customer and meeting the standards in force applicable to gas cooking appliances. Indeed, the combustion of the flames under the plate requires limiting the gas flow to a relatively low level in order to respect the

  levels of polluting gases imposed by standards.

  The invention aims to provide a simple, reliable, inexpensive solution having satisfactory combustion conditions for the air / combustible gas mixture for a wide range of power speeds, while

  retaining burners of usual dimensions.

  To do this, the invention proposes that: - the openings are arranged substantially in correspondence with said main orifices, and - at the maximum gas flow rate, most of the flames pass through

the openings.

  It should be understood that the openings are considered to be in correspondence with the main orifices of the burner when they are arranged in the direction of the flow of gas coming from the main orifices,

  so that the flames generated do not "strike" against the plate.

  Thus, the flames convectionally heat the free space and therefore the zone of the plate located opposite the burner, which makes it possible to gently and uniformly heat the center of a pan or equivalent placed on or at least opposite this zone. The presence of the plate between the kitchen utensil and the flame avoids localized overheating in this area. On the other hand, the maximum heating power can be considerably high compared to DE-A-40 33 503, insofar as o

  most of the flame is in the open air.

  The invention also proposes that the device also comprises regulation means for varying the flow of gas leaving the main orifices between a first position in which they allow the maximum gas flow to pass and a second position in which they allow passage a gas detent generating flames extending essentially in said free space. Thus, at high power (in the first position), the flames mainly burn in the open air, so that it is possible to obtain a high power while respecting the pollution standards, and at low

  power the flames moderately heat the cookware.

  zo In a complementary manner, the invention proposes that the free space communicates with the atmosphere by a peripheral passage extending between the plate and the burner. The amount of air available near the main burner orifices to burn with gas is thus increased, which makes it possible to increase the maximum power of the burner while reducing

the emission of polluting gases.

  In order to further improve the reliability of the device, the invention further proposes that: - the burner comprises a combustion head containing a mixing chamber communicating with the atmosphere via the main orifices, - the essentials at least from the combustion head either at a distance greater than or equal to 2 millimeters from the plate. This distance allows air circulation necessary to avoid excessive overheating of the part of the plate placed opposite the combustion head. In addition, this air circulation promotes the combustion of

  gas, when the regulating means are in the first position.

  0 According to another characteristic, the invention proposes that: - the plate has, near the burner, a boss-shaped boss surrounding the combustion head, said boss comprising a substantially planar upper surface and a lateral surface extending substantially perpendicular to the upper surface, and - the openings are arranged in the lateral surface of the cap. Thus, the openings being made in a wall intended to be arranged substantially vertically, the burner is protected from

  liquid overflows on the plate.

  In addition, in order to further improve the operation of the device, the invention proposes that said free space has the following characteristics: - it extends continuously between the upper surface of the boss and the combustion head, and between the lateral surface of the boss and the combustion head, - it has a substantially constant thickness, perpendicular to the boss, so that it has no necking zone. According to another advantageous characteristic, the invention proposes

  that the orifices have in section the form of elongated slots.

  Thus, for a given diameter, it is possible to increase the power of the burner compared to a burner with orifices of circular or square section. In addition, this allows given power to reduce the height

  openings in the plate.

  In order to further improve the efficiency of the device, the invention proposes that: - the device comprises several groups of main orifices, where said groups are distant from each other and each comprise a plurality of main orifices arranged side by side , - an elongated opening is arranged in correspondence with

  each of the main port groups.

  The distribution of the orifices in spaced groups allows the flames to pass through the openings, while ensuring the continuity and solidity of the plate, without substantially reducing the power of the burner. According to another advantageous characteristic, the invention proposes that the device also comprises secondary orifices between the groups of main orifices, said secondary orifices having a section substantially smaller than the section of the main orifices, in order to generate flames of inter-ignition between the flame groups

  main from the main port groups.

  Thus, it suffices to ignite the gas leaving one of the main orifices to ignite the gas leaving all of the main orifices. The invention will appear even more clearly in the

  description which follows, made with reference to the drawings attached in

  which: Figure 1 is a sectional view of a device according to the invention, - Figure 2 is an enlarged view of the detail marked II in Figure 1, the regulating means being in the first position, - Figure 3 is a view in accordance with FIG. 2, the regulation means being in the second position, - FIG. 4 is a sectional view along the plane marked IV-IV in FIG. 1, schematically representing the air circulation, - Figure 5 is a sectional view along the plane marked VV in o Figure 4, - Figure 6 is a sectional view along the plane marked IV-IV in the

figure 1.

  Figures 1 to 6 illustrate a device 1 comprising a plate

  cooking 4 and burners 2 (only one has been shown).

  Each burner 2 is connected to gas supply means comprising an adjustable valve 10 for regulating the gas flow and an inlet duct 12. Each burner comprises an injector 14 and a circular combustion head 16 comprising a vertical mixer 18 of combustible gas and combustion air, a mixing chamber 20, main orifices 22 and secondary orifices 24. The main orifices 22 are arranged in the form of 4 groups of orifices arranged consecutively, close to one another ( separated by a distance substantially equal to approximately

2.5 times their height).

  The hob, advantageously made of glass ceramic and essentially planar, has projections (only one has been shown) in the form of a cap 6 covering each burner and substantially matching the

shape of the combustion head 16.

  Each cap 6 has an upper wall 6a, substantially planar and intended to receive a container, and a peripheral wall 6b, substantially cylindrical and disposed substantially vertically. The cap is provided on its periphery, in its peripheral wall 6b, and in front of the main orifices of the burner, with openings 8 in the form of slots allowing the passage, through the plate, of main flames 32 generated by the combustion of the mixture gaseous from

main ports 22.

  Alternatively, areas of material 26 are kept to securely hold the upper wall 6a relative to the rest of the plate. A free space 28 is provided between the combustion head 16 and the cap. It comprises a central part 28a situated between the upper wall 6a and the combustion head 16, not communicating directly with the atmosphere, and a peripheral part 28b situated between the peripheral wall 6b and the combustion head 16 and open to the atmosphere at its lower part. This space 28, and in particular its dimensioning, is essential for the correct functioning of the burner. It also allows the cap 6 to be brought to a uniform temperature on, or at least close to, the

  upper wall 6a from which the container will be placed.

  Figures 2 and 3 show the deployment of the main flames 32 at different walking speeds. Of course, it is possible to obtain many gaits between these two extremes, by variation

  continuous flow of combustible gas by means of valve 10.

  At full power (Figure 2) and at intermediate speeds, the air / gas mixture partly burns outside of the cap 6, only a fraction burning under the cap 6. At the minimum gas flow (Figure 3), combustion s '' performs entirely under the hat, in the

  free space device 28b.

  To avoid overheating of the material constituting the cap, it is necessary that the flame does not fully return under it until the power is at a low level. The distance between the combustion head 16 and the peripheral wall 6b must therefore be relatively small. Preferably, it will be less than about 7 millimeters, at least near the orifices

main 22.

  However, the free space 28 is essential for the operation of the burner. The combustion head 16 must therefore not be entirely at

  hat contact, even if localized contact would not be unacceptable.

  o Indeed, in the illustrated embodiment, the burner operates with a partial premix of air, obtained in the vertical mixer 18. It is therefore necessary to provide additional secondary air downstream of the premix to ensure complete combustion. The peripheral part 28a of the free space 28 communicating with the atmosphere provides this supply of air to the flames. So that this air supply is sufficient for satisfactory operation over the entire power range, the peripheral part 28a of the free space 28 will have a thickness opposite the

  main orifices 22 greater than or equal to 2 millimeters.

  The slots 8 formed in the cap are also produced at least 5 millimeters above the rest of the plate 4 in order to promote the

  combustion of main flames 32.

  In addition, for air circulation also above the flames, the free space 28 will also have a substantially constant thickness and greater than or equal to 2 millimeters, essentially at least in the central part 28a, and for this which relates to the peripheral part 28b,

  between the main orifice groups, and above the main flames.

  Thus, this air rises between the groups of main flames 32, as illustrated by the arrows 36 and circulates in the central part 28a of the free space, as illustrated by the arrows 38 in FIG. 4. It thus avoids overheating of water chap 6, harmonize the temperature of this water chap and

  further improves the quality of combustion.

  On the other hand, the secondary orifices 24 arranged all around the combustion head 16 generate secondary flames 34 ensuring on the one hand piloting of the main flames 32 and on the other hand inter-ignition between the groups of the main flames 32 So there is continuity of

  flame over the entire combustion head 16.

  The device also includes a spark plug 30, disposed opposite the main orifices 22 and intended to create a spark 0 to ignite the gas mixture, as well as a safety thermocouple 40 detecting the presence of a flame. The spark plug and the safety thermocouple are placed between the plate and the combustion head, away from

shocks and dirt.

  Furthermore, the main orifices 22 have in section a flattened shape, generating flat and wide flames as illustrated in FIG. 6, which makes it possible to increase the power of the burner for a given diameter of combustion head. Advantageously, the width / height ratio of the main orifices is greater than or equal to 5 and preferably close to 10. o The secondary orifices 24 have a section which is substantially

  lower than those of the main orifices, about ten times smaller.

  Of course, provision could be made for alternative embodiments of the device according to the invention. One could for example arrange the gas outlet orifices on top of the combustion head. By tilting them, for example 45 or 60 degrees from the vertical and arranging the openings in correspondence, the orifices could be protected against liquid overflowing on the plate. In the first position of the valve, the flames would exit through the openings, while in the second position, due to the inclination relative to the vertical and at the slightest gas flow, these flames would essentially remain under the plate. This realization would however be less advantageous than that illustrated. The secondary orifices 24 arranged all around the combustion head, below the main orifices 22 could be replaced by inter-ignition orifices arranged only between the groups of main orifices, in the continuity thereof, but always more

low section.

  The combustion head 16 and the cap-shaped projection 60 could have other shapes. They could for example be

triangular or oval.

  Rev end ic ati o ns 1. Device (1) comprising: - at least one gas burner (2) having main orifices (22), - a plate (4) covering this burner and having openings (8), - a free space (28) extending between the plate and the burner, and in which at least part of the flame is intended to burn, - means for supplying gas (10,12) to the burner up to a 0 determined maximum flow rate, characterized in that: - the openings are arranged substantially in correspondence with said main orifices, and - at the maximum gas flow rate, most of the flames pass through the openings. 2. Device according to claim 1, characterized in that it further comprises regulation means (10) for varying the flow of gas leaving the main orifices between a first position in which they allow the maximum flow of gas to pass and a second position in which they let pass a flow of gas generating flames

  extending essentially in said free space.

  3. Device according to claim 1 or claim 2, characterized in that the free space communicates with the atmosphere by a

  peripheral passage (28b) extending between the plate and the burner.

  4. Device according to any one of the claims

  above, characterized in that: - the burner comprises a combustion head (16) enclosing a mixing chamber (20) communicating with the atmosphere via the main orifices, - the essentials at least of the combustion head is at a distance greater than or equal to 2 millimeters from the plate. 5. Device according to claim 4, characterized in that: - the plate has, near the burner, a cap-shaped boss (6) surrounding the combustion head, said boss comprising an upper surface (6a) substantially planar and a surface lateral (6b) o extending substantially perpendicular to the upper surface, - the openings are arranged in the lateral surface of the cap. 6. Device according to claim 5, characterized in that: - said free space (28) extends continuously between the upper surface of the boss and the combustion head, and enke the lateral surface of the boss and the combustion head, - said free space has a substantially constant thickness, perpendicular to the boss, so that it is devoid of

skiction area.

  7. Device according to any one of the claims

  previous, characterized in that the orifices have the cross-sectional shape

elongated slits.

  8. Device according to any one of claims

  previous, characterized in that: - the device comprises several groups of main orifices distant from each other and each comprising a plurality of main orifices arranged side by side, and - a large opening is arranged in correspondence with

  each of the main port groups.

  9. Device according to claim 8, characterized in that it further comprises secondary orifices (24) between the groups of main orifices, said secondary orifices having a section substantially smaller than the section of the main orifices, in order to generate ignition flames between the main flame groups from the groups

main ports.

  10. Device according to any of the claims

  above, characterized in that it further comprises means for igniting the flame (30) and / or means for detecting the presence