AU2014305221A1

AU2014305221A1 - Gas burner and burner cover

Info

Publication number: AU2014305221A1
Application number: AU2014305221A
Authority: AU
Inventors: Jeroen VAN EERTEN; Sjoerd Michiel VAN HAASTER; Antonius Cornelis Maria WOUTERS
Original assignee: Intell Properties BV
Current assignee: Intell Properties BV
Priority date: 2013-08-09
Filing date: 2014-08-07
Publication date: 2016-03-17
Anticipated expiration: 2034-08-07
Also published as: RU2016107822A; RU2016107822A3; EP3030839A2; RU2705533C2; WO2015020525A3; ES2919868T3; WO2015020525A2; NL2011286C2; AU2014305221B2; EP3030839B1; CN105612387A; CN105612387B

Abstract

A gas burner, for instance for a cooking device, comprises a burner housing (10) with a burner cover (20). The burner cover comprises separated groups of burner ports (21, 22) which are supplied individually: A first group (21) of burner ports thus forms a first burner part with a first gas inlet (41). A second group (22) of burner ports provides a second burner part (22) with a second gas inlet (42).

Description

WO 2015/020525 PCT/NL2014/050552 Gas burner and burner cover The present invention relates to a gas burner comprising a burner housing with a first mixing chamber and with a second mixing chamber separated from the first mixing chamber and provided with a second gas inlet, wherein the first mixing chamber is provided with a first gas inlet and the second mixing chamber is provided with a second gas inlet, and wherein a first group of burner ports is provided at the position of the first mixing chamber and a second group of burner ports is provided at the position of the second mixing chamber in order to open the first mixing chamber and the second mixing chamber toward a pan bottom. The invention also relates to a burner cover for application in such a gas burner. Although not exclusively, the invention nevertheless relates particularly here to a gas burner for a cooking device or cooker for domestic and/or professional use. Conventional burners for cooking devices have the drawback that the burner ports thereof are arranged radially on a periphery of the burner head. Heat is hereby lost because the burner ports are oriented outward and not directly at a bottom of a pan. This is therefore detrimental to the efficiency of the burner because a great deal of heat is relinquished unused to the surrounding area. These burners are usually embodied with high capacity in order to compensate for this. The burner is provided here with an auxiliary gas construction which ensures that the burner ignites and reignites uniformly and that the burner continues to burn in stable manner at both low setting and high setting. This construction makes a control range between a lowest and highest capacity of the burner which is greater than if such an auxiliary gas construction were not present. A conventional burner of this type thus has a control range which is typically in the order of 1:5, which translates to for instance typically in the order of 200 W at low capacity and 1000 W at full capacity. So-called flat burners also exist in addition to such radial burners. An example thereof is described in the international patent application WO 2007/036772. In contrast to a radial burner, the burner known herefrom has burner ports in an upper surface of the burner cover, so oriented upward and directly at the bottom of the pan. Significantly less heat is hereby lost to the surrounding area, which directly enhances efficiency. Furthermore, a flat burner can in some cases be operated with a relatively low flame bed, this helping to reduce WO 2015/020525 2 PCT/NL2014/050552 harmful nitrogen oxide emission. A conventional auxiliary gas construction, such as an auxiliary gas ring of a radial burner, is however not practically feasible in the case of such a flat burner, which makes ignition and reignition of the burner more difficult and adversely affects a stable flame pattern of the burner at high capacity. In order to preclude unacceptable incomplete combustion, such flat burners are therefore usually embodied with only a relatively limited maximum capacity, which adversely affects the control range, which usually extends no further than about 1:3, for instance typically from 250 W to 750 W. In order to increase the overall capacity available for cooking in the case of a flat burner it is known from American patent application US 2010/0101557 to embody such a flat burner with two burners. A first burner extends here around a central part in which a second burner is accommodated. Both burners have their own mixing chamber with gas feed and control means and can be employed independently of each other in order to together provide a greater cooking capacity. The first burner of this known device is formed by a first membrane in which burner ports are accommodated, while the second burner comprises a separate second membrane with burner ports, wherein the second membrane is wholly enclosed in the device by the first one. The second membrane follows a roughly convex path here so that the surface thereof slopes downward as seen from a centre, in which surface the burner ports are arranged. Although it is thus possible with the flat burner known from this American patent application to realize a broader control range in respect of the output capacity of the burner, this known construction requires considerably more components and complexity, which is disadvantageous. The present invention has for its object, among others, to provide a burner, in particular a burner for a cooking device, which is able to combine an adequate efficiency with an adequate control range with a relatively simple construction. In order to achieve the intended object a burner of the type described in the preamble has for this purpose the feature according to the invention that the burner housing is provided with a burner cover which covers both the first mixing chamber and the second mixing chamber and which at the position of the first mixing chamber comprises the first group of burner ports in open communication with the first mixing chamber and extending through WO 2015/020525 3 PCT/NL2014/050552 the burner cover in order to open the first mixing chamber toward the pan bottom, and which at the position of the second mixing chamber comprises the second group of burner ports in open communication with the second mixing chamber and extending through the burner cover in order to open the second mixing chamber toward the pan bottom. Thus dividing the total number of burner ports in a flat burner into two optionally equally dimensioned groups or zones creates as it were in the burner a first burner and a second burner, which are separated from each other and can each be ignited and controlled independently of each other. The gas feed means are configured for this purpose to switch a gas feed between at least two configurations, i.e. A. only to the first burner zone or simultaneously to the first and second burner zones, or B. only to the second burner zone or simultaneously to the first and second burner zones. If both burner zones have the same capacity, each with a control range of 1:3, the assembly can thus be controlled within a range of 1:6, which already exceeds an average control range of a conventional radial burner, while the advantageous efficiency of a flat burner is retained. Because use is made according to the invention of a shared burner cover in which these zones are provided for the two burners, the complexity and required number of components for the burner as a whole can be kept relatively limited. A preferred embodiment of the gas burner according to the invention has the feature however that the first group of burner ports and the second group of burner ports are dimensioned differently. Such a different dimension can for instance be manifest in the surface area taken up by the relevant group, the number of burner ports per group, the (average) cross-section of the burner ports, which may or may not be constant in a group, or a combination of one or more of suchlike or other factors. Both burner zones thus have different (peak) capacities. While the control range per burner zone is for instance in the order of 1:3 here, the combined control range can thus be made significantly broader. Assuming for instance a maximum capacity of 200-700 W for the first group of burner ports and a capacity of 1-3 kW for the second group, it is thus possible to realize a combined control range of 200 W to 3 kW, i.e. 1:15 for the burner overall. A flat burner is thus created WO 2015/020525 4 PCT/NL2014/050552 with a one-part burner head, without auxiliary gas construction but nevertheless having a control range far exceeding the control range of a conventional radial burner. In a further preferred embodiment the gas burner according to the invention has the feature that the second mixing chamber at least partially encircles the first mixing chamber and that the first group of burner ports is situated in an inner zone of the burner cover located inside an outer zone defined by the second group of burner ports. A radial burner with individual concentric burner parts is known per se. Such a conventional multi-ring burner can be applied to increase the control range of the burner. A drawback of the conventional multi ring burner is that the burner cover cannot consist of one part here, but the burner always has more than one head. This is a particular result of the necessary presence of an auxiliary gas construction, which serves for both the inner burner and outer burner and for the purpose of producibility. This preferred embodiment of the burner according to the invention does not requires an auxiliary gas construction and hereby allows a burner cover from one optionally assembled part. In a further particular embodiment the gas burner according to the invention is characterized here in that at the position of the inner zone the burner cover has a concave form on a main surface facing away from the first mixing chamber. Such a concave form is not only desirable from an aesthetic viewpoint, it moreover results in a mechanical durability at the greatly varying temperatures to which a burner is after all exposed. The burner ports of the inner zone can here either be arranged vertically therein parallel to each other or be arranged more or less transversely of the concave surface. In the latter case central axes of burner ports from the first group of burner ports will mutually converge. The converging central axes in the central part, whether or not resulting from the concave form, orient the burner ports toward an optionally common focal point and thereby concentrate the flame pattern onto a centre of a pan. This is particularly desirable when a wok is used. In order to help sufficient secondary air in being able to reach the inner zone, a further preferred embodiment of the gas burner according to the invention has the feature that the burner ports in the inner zone open at least substantially at a first level in the burner cover and that the burner ports in the second zone open at least substantially below the first level WO 2015/020525 5 PCT/NL2014/050552 in the burner cover, particularly in that at the position of the outer zone the burner cover slopes downward on a main surface facing away from the second mixing chamber, and more particularly has a convex downward form at that position. The position of the outer zone at least substantially below the level of the inner zone enhances a feed of secondary air over the flame bed from the outer zone toward the inner zone. This results in a better combustion and thereby a higher efficiency and lower harmful emission from the inner zone. A downward sloping, particularly convex form in this part of the burner moreover enhances a natural evacuation and outflow of (cooking) liquids in the unlikely event these were to fall onto the burner during or after operation thereof, so making it less easy for them to get inside the burner. From a viewpoint of cost-saving and structural simplicity it is recommended to provide the first burner zone and second burner zone with shared igniting means. A further particular embodiment of the gas burner according to the invention has for this purpose the feature that flame igniting means are provided with at least one spark electrode extending at the position of an area of the burner cover lying between the first group of burner ports and the second group of burner ports. In a more particular embodiment the gas burner according to the invention is further characterized here in that a shared spark electrode for the first group of burner ports and second group of burner ports extends at least substantially halfway along the area of the burner cover. The spark electrode is thus positioned such that the spark emitted thereby will be able to ignite both the first burner zone and the second burner zone. The same applies mutatis mutandis for a thermocouple which is normally applied with the spark electrode for safety purposes and will thus be heated by each of the two zones. From a viewpoint of simplicity and operating comfort a further particular embodiment of the gas burner according to the invention has the feature that the first gas inlet and the second gas inlet are at least connectable to shared gas feed control means, and that the gas feed control means are able and configured to selectively provide a controllable gas path to at least one of the two said gas inlets individually or to both gas inlets jointly. It is thus possible to control the two burner zones using the same control means and uniform operating means extending therefrom. All logic and control of the two burner zones can be provided therein without the user being aware of it.

WO 2015/020525 6 PCT/NL2014/050552 A particularly practical embodiment of the gas burner according to the invention has the feature that the first chamber with the first group of burner ports is able and configured to produce a burner capacity in a range between about 100 W and 1200 W. The first chamber thus provides a group of burner ports in a first burner zone with which warming, simmering or medium cooking can take place at moderate to average capacity, with a control range varying from a minimum of the order of 100-400 W to a maximum of the order of 700-1200 W. In a further practical embodiment the gas burner according to the invention is characterized in that the second chamber with the second group of burner ports is able and configured to produce a burner capacity in a range between about 400 W and 3800 W. The second chamber with burner ports thus provides a second burner zone which allows an average to high capacity so that slow cooking or frying or even stir-frying can be realized with the same burner. In the latter case both zones can optionally be operated simultaneously at full capacity. This thus produces a combined maximum capacity in the order of 5 kW. Because the burner ports in the burner cover in a flat burner are oriented substantially toward the pan bottom, a flat burner is in principle more vulnerable and susceptible to the ingress of moisture and other contamination, for instance in the event a pan being used for cooking were to boil over. In order to prevent this, a further preferred embodiment of the burner according to the invention has the feature that at least at the position of at least one of the first group of burner ports and the second group of burner ports the burner cover has a hydrophobic surface on a side thereof facing toward the pan bottom. Ingress of moisture into the mixing chamber via the burner ports is thus rendered more difficult by an action of the hydrophobic surface which increases the surface tension of the moisture at this location. Various surface treatments can be applied per se to make a less hydrophobic surface of the cover more hydrophobic. A further preferred embodiment of the burner according to the invention has in this respect the feature that the hydrophobic surface of the burner cover comprises a heat-resistant hydrophobic covering of the cover, in particular a heat-resistant coating on the basis of silicon dioxide. This covering or coating is preferably applied after the WO 2015/020525 7 PCT/NL2014/050552 burner ports have been provided in the cover so that the walls of the ports are hereby likewise covered and will have a hydrophobic character. The invention also relates to such a burner cover comprising a hydrophobic surface at the position of a group of burner ports located on the surface, these burner ports extending through the cover. The invention will now be further elucidated on the basis of an exemplary embodiment and an accompanying drawing. In the drawing: figure 1 shows a perspective view of an exemplary embodiment of a gas burner according to the invention; and figure 2 shows a cross-section of the gas burner of figure 1. The figures are otherwise purely schematic and not always drawn to scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are generally designated with the same reference numerals. The gas burner shown in the figures is particularly suitable for application in a gas cooking device, optionally in combination with other types of burner or heat source. The burner comprises a burner housing 10 which is fixedly mounted with a base part 11 in a hob (not further shown) of a cooking device (not further shown). A fireproof burner head 12 lies on base part 11 of the burner housing. Burner head 12 comprises on an upper side thereof a burner cover 20 which is riveted or welded thereto or otherwise firmly connected thereto. Instead of being assembled to form this part of the burner, the burner head and the burner cover can optionally also be formed integrally, for instance be an aluminium casting. For practical maintenance purposes the burner head with the burner cover lies in freely detachable manner on the base part of the burner housing during use so that it can be easily removed at any time, for instance in order to be cleaned. The base part is on the other hand fixed in a lower tray of a hob and coupled therein, usually together with one or more further burners, to gas feed means of the hob. A collecting tray with openings at the position of the burner(s) is arranged over the burner(s) and received here on a flanged edge 13 of the burner provided for the purpose. Such a collecting tray can be formed from enamelled, lacquered or otherwise coated or preserved steel (plate) and in that case be screwed or WO 2015/020525 8 PCT/NL2014/050552 riveted onto flanged edge 13. In the case of a glass collecting tray it is fixed on the flanged edge via an adapter ring in order to avoid point load(s) in the glass. Selected here as material for the parts of the burner is cast aluminium, although other heat resistant materials such as ceramics and other metals such as (stainless) steel and brass are also suitable for the purpose. Burner cover 20 provides on an exposed main surface thereof an extra-smooth top layer or coating, for instance of enamel, which prevents encrusting of cooking residues and moreover imparts an aesthetically attractive appearance to the burner. Instead of using a casting in respect of the burner cover it is optionally possible to make use of a flat plate part which is eventually shaped into the desired form. According to the invention the burner housing comprises a first mixing chamber 31 and at least one further, second mixing chamber 32. In both cases these are cavities located partially in base part 11 of the burner housing and partially in burner cover 12. Both chambers are bounded on an upper side by burner cover 20. The burner cover comprises here a first group 21 of burner ports at the position of first mixing chamber 31 and a second group 22 of burner ports at the position of the second mixing chamber. In both cases the burner ports lie on the substantially flat main surface of the burner cover. The burner ports can be arranged in diverse ways and openings are for instance formed during casting of the burner cover or arranged therein afterward by means of a mechanical material-removing operation such as drilling, milling, stamping or punching, or cut into the burner cover using a laser. Burner ports 21, 22 extend in the burner cover over a whole thickness thereof, so that mixing chambers 31, 32 open to outside via the burner ports. Burner ports 21, 22 typically have a diameter in the order of 0.4 to 2.5 mm, particularly between 1.2 and 1.6 mm, and are placed close together such that they will ignite each other. This provides for a stable flame pattern without a separate auxiliary gas construction (ring) or other provision being necessary for this purpose. In order to prevent water/moisture running into mixing chambers 31, 32 or other fouling of the burner ports, the cover takes a hydrophobic form over the whole surface area facing toward the pan bottom. This is achieved in this embodiment by applying thereto a thin, WO 2015/020525 9 PCT/NL2014/050552 heat-resistant hydrophobic coating not further shown in the figure. In this embodiment a coating is selected in this respect on the basis of silicon dioxide, which is commercially available under the brand name Poliant*. This coating is transparent, scratch-resistant and heat-resistant up to at least 500"C. In combination with the relatively narrow burner port dimensions, an effective barrier is raised against penetration of moisture. The coating can be arranged in relatively simple manner by being sprayed or brushed onto a clean and grease free metal surface, and then only further requires adequate drying. Mixing chambers 31, 32 are each individually provided with respectively a first and a second gas inlet 41, 42 which are in turn coupled, at least in assembled state, to gas feed means 51, 52. The gas feed means are controllable and provided in a gas feed to one of the two mixing chambers individually or both mixing chambers jointly. Use can optionally also be made of a configuration wherein only one of the two groups is individually controllable, in combination with a position in which both groups are controlled. Primary air which is necessary for the combustion of the gas is also drawn in here. Although the two groups of burner ports can also be arranged completely adjacently of each other or in other configuration relative to each other, a concentric arrangement is selected in the present embodiment. The first group of burner ports forms here a central burner part and the second group lies therearound in a ring as peripheral burner part. This can be seen particularly clearly in the perspective view of figure 1. In an area between the two burner parts 21, 22 igniting means 25 are provided in the form of an electronic spark ignition and flame safety (thermocouple). An electrical connection 45 therefor exits the burner on an underside and is connected to control means 75, which also control the gas feed to both burner parts 21, 22. Due to the at least roughly central position of igniting means 25 between the two burner parts 21, 22, the two burner parts 21, 22 can be ignited thereby. Manual operation of the gas feed means 70 and spark ignition 25 is possible with an operating means 75, such as for instance an intuitive rotary knob. The gas feed means guide a gas flow via first inlet 41 to the first mixing chamber 31 with a first group 21 of burner ports so that only the central part of the burner ignites. This central WO 2015/020525 10 PCT/NL2014/050552 part has a slightly convex (hollow) form, see figure 2, wherein or whereby burner ports 21 are oriented slightly inward. The hollow form enhances an elastic accommodation of mechanical stresses which can occur at greatly varying temperatures. The embodiment of the central part of the cover thus contributes toward the durability thereof. Burner ports 21 are provided more or less parallel to each other in the central part and are oriented vertically here. They can however optionally also be arranged more or less transversely of the convex surface, whereby a flame pattern of the central burner part will converge to some extent in order to thus heat in particularly efficient manner a central part of a bottom of a pan placed thereabove. Central burner part 21 is dimensioned such that it generates a peak capacity of about 800 W, which is controllable in continuously variable or stepwise manner from a minimum in the order of 200 W to this maximum in the order of 800 W. In a second situation the gas feed means guide a gas flow to inlet 42 and mixing chamber 32 for the second burner part 22, which has a downward sloping concave form on the main surface. Burner ports 22 in this part of the cover are arranged more or less transversely of the surface thereof, so that the flame pattern originating therefrom will diverge so as to spread over the pan bottom. Because this part of the cover slopes downward from central part 21, the burner ports of the second group all lie at least substantially below a level of burner ports 21 of the central part. This greatly enhances a sufficient secondary air transport to the burner ports in the central part, which will thereby produce a better combustion. The secondary air flows here over the second burner ports. The downward sloping form moreover ensures that possible cooking liquid or other liquid can flow away easily off this part and is less likely to enter the burner through ports 22. The second burner part is dimensioned such that it generates a maximum burner capacity of about 2200 W, which is controllable in continuously variable or stepwise manner from the order of 400 W to this maximum of 2200 W. If desired, this burner part can be given larger dimensions and can be scaled to a maximum capacity in the order of 4 kW. In a third situation both inlets 41, 42 are supplied simultaneously by the gas feed means and the burner can be operated at full capacity. A total burner capacity of 3 kW is thus provided in this case. All in all, the gas burner described in this embodiment, in contrast to a flat burner construction without auxiliary gas device, can be operated over an enormous WO 2015/020525 11 PCT/NL2014/050552 capacity range extending from a relatively light minimum capacity of 200 W to a maximum capacity of 3000 W. This corresponds to a control ratio of 1:15, which even exceeds that of at least many radial burners. If the second part is scaled to the order of 4 kW, a peak capacity in the order of 5 kW can thus even be realized for the burner as a whole. Although the invention has been further elucidated above on the basis of only a single embodiment, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art. The burner will thus be applied mainly in a gas cooker together with a number of optionally similar burners. The burners can have mutually differing dimensions here in order to provide different cooking levels within the cooker. The two burner parts can also be selected with a different mutual ratio in terms of capacity per burner in order to provide a broader or narrower range per burner. Instead of two separate zones, it is also possible within the scope of the invention to provide a plurality of zones with burner ports in the burner cover, each with their own mixing chamber extending thereunder. If desired, the zones can moreover have the same or differing dimensions in terms of capacity. In the shown exemplary embodiment the outer zone lies in a downward sloping, concave part of the burner cover, although this part can also be given a flat form more or less parallel to the central part. Besides lying at the same level, use can also be made here of a step wherein this outer part nevertheless lies at a lower level in order to impede to lesser extent a secondary air transport to the inner zone. In respect of the gas control the embodiment is based on the option of being able to operate the two burner parts with groups of burner ports individually as well as both parts together. It is also possible to opt instead for a control wherein only one of the two burner parts will be supplied individually in combination with one or more positions in which the two burner parts are in operation together. With the invention a wide control range is always obtained in combination with a structurally and energetically exceptionally efficient burner design.

Claims

1. Gas burner comprising a burner housing with a first mixing chamber and with a second mixing chamber separated from the first mixing chamber and provided with a second gas inlet, wherein the first mixing chamber is provided with a first gas inlet and the second mixing chamber is provided with a second gas inlet, and wherein a first group of burner ports is provided at the position of the first mixing chamber and a second group of burner ports is provided at the position of the second mixing chamber in order to open the mixing chamber toward a pan bottom, characterized in that the burner housing is provided with a burner cover which covers both the first mixing chamber and the second mixing chamber and which at the position of the first mixing chamber comprises the first group of burner ports in open communication with the first mixing chamber and extending through the burner cover in order to open the first mixing chamber toward the pan bottom, and which at the position of the second mixing chamber comprises the second group of burner ports in open communication with the second mixing chamber and extending through the burner cover in order to open the second mixing chamber toward the pan bottom.

2. Gas burner as claimed in claim 1, characterized in that the first group of burner ports and the second group of burner ports are dimensioned differently.

3. Gas burner as claimed in claim 1 or 2, characterized in that the second mixing chamber at least partially encircles the first mixing chamber and that the first group of burner ports is situated in an inner zone of the burner cover located inside an outer zone defined by the second group of burner ports.

4. Gas burner as claimed in claim 3, characterized in that at the position of the inner zone the burner cover has a concave form on a main surface facing away from the first mixing chamber.

5. Gas burner as claimed in claim 3 or 4, characterized in that the burner ports in the inner zone open at least substantially at a first level in the burner cover and that the burner ports in the second zone of burner ports open at least substantially below the first level in WO 2015/020525 13 PCT/NL2014/050552 the burner cover, particularly in that at the position of the outer zone the burner cover slopes downward on a main surface facing away from the second mixing chamber, and more particularly has a convex downward form at that position.

6. Gas burner as claimed in one or more of the foregoing claims, characterized in that flame igniting means are provided with at least one spark electrode extending at the position of an area of the burner cover lying between the first group of burner ports and the second group of burner ports.

7. Gas burner as claimed in claim 6, characterized in that a shared spark electrode for the first group of burner ports and second group of burner ports extends at least substantially halfway along the area of the burner cover.

8. Gas burner as claimed in one or more of the foregoing claims, characterized in that the first gas inlet and the second gas inlet are at least connectable to shared gas feed control means, and that the gas feed control means are able and configured to selectively provide a controllable gas path to at least one of the two said gas inlets individually or to both gas inlets jointly.

9. Gas burner as claimed in one or more of the foregoing claims, characterized in that the first chamber with the first group of burner ports is able and configured to produce a burner capacity in a range between about 100 W and 1200 W.

10. Gas burner as claimed in one or more of the foregoing claims, characterized in that the second chamber with the second group of burner ports is able and configured to produce a burner capacity in a range between about 400 W and about 3800 W.

11. Gas burner as claimed in one or more of the foregoing claims, characterized in that at least at the position of at least one of the first group of burner ports and the second group of burner ports the burner cover has a hydrophobic surface on a side thereof facing toward the pan bottom. WO 2015/020525 14 PCT/NL2014/050552

12. Gas burner as claimed in claim 11, characterized in that the hydrophobic surface of the burner cover comprises a heat-resistant hydrophobic covering of the cover, in particular a heat-resistant coating on the basis of silicon dioxide.

13. Burner cover for applying in the gas burner as claimed in one or more of the foregoing claims, comprising at least a first group of burner ports and at least a second group of burner ports separated spatially therefrom, which burner ports extend therethrough.

14. Burner cover for applying in a gas burner, comprising a hydrophobic surface at the position of a group of burner ports located on the surface, these burner ports extending through the cover.