Patent Publication Number: US-6712605-B2

Title: Gas burner for a cooking hob

Description:
FIELD OF THE INVENTION 
     The present invention relates to a gas burner for a cooking hob, intended to be used advantageously in any type of gas cooker, in particular of the household type, for cooking food products. 
     BACKGROUND ART 
     As is known, burners are conventionally mounted on cooking hobs, opposite gas injection nozzles. 
     In greater detail, each burner is formed by a plurality of components which can be separated from each other and suitably assembled so as to form the burner as a single unit which allows in particular correct mixing between the air and gas and consequent optimum combustion of the mixture thus obtained. 
     In accordance with the art known hitherto, each burner is conventionally composed of a bowl (or cup) fixed to the cooking hob and provided on the bottom with a gas injection nozzle, a mushroom-shaped burner body which can be inserted inside the cup and a flame-dividing element which can be mounted on the burner body and associated at the top with a top piece. 
     The burner body, in turn, is conventionally composed of a hollow axial shank provided with a plurality of side openings for entry of the air and by an overlying disk-shaped portion having an annular seat for receiving the flame-dividing element. The latter is of a type known per se and is provided with a series of orifices for the outflow of the air/gas mixture. 
     During operation, the shank is inserted inside the cup until the bottom surface of the disk-shaped portion rests against the top of the said cup. 
     As is known, moreover, the shank generally has a frustoconical shape with a bottom opening having a smaller cross-section arranged in a position facing the gas-injection nozzle. In this way, the flow of gas inside the shank causes a Venturi effect with consequent drawing of primary air via the side openings. 
     Essentially all the burners of the known type perform air/gas mixing by means of the Venturi effect using a tubular element which is positioned vertically with respect to the burner and in line with the outflow of the gas from the nozzle. 
     Numerous configurations of burners with different arrangements of the openings for the flow of the primary air intended to be mixed with the gas supplied from the nozzle are known. In particular, a burner configuration is known whereby the shank is arranged facing the nozzle at a certain distance therefrom so as to allow air to be drawn directly through the bottom opening of the shank. 
     This latter burner embodiment is described and illustrated in European patent EP-B-0,485,645. 
     Burners in which the flame-dividing element forms a single body with the burner body are also known, being made as one piece by means of a die-casting process. In this case the disk-shaped portion of the burner body incorporates the flame-dividing element in a single unit. 
     In practice, the burners of the known type, described in brief above, have numerous drawbacks. 
     A major drawback of these burners of the known type consists in the fact that they have a large number of constructional components. This fact means that a not insignificant amount of time is required in order to assemble the individual components as a single unit. Moreover, often an excessive amount of time is required in order to assemble burners of the known type on the cooking hobs. 
     The presence of numerous constructional components also poses an intrinsic operational difficulty every time it is required to assemble or disassemble the burner, for example for maintenance or routine cleaning purposes. 
     A further drawback of burners of the known type consists in the fact that the production of the individual components is performed by means of die-casting processes which per se are complex and such that they increase the overall production costs of burners of the known type. 
     Generally, moreover, these components are made of pressure-cast aluminium which, as is known, has a limited duration over time, among other things being able to be easily corroded by the cleaning agents which are widely used. 
     All these disadvantages therefore constitute an obvious limitation of the burners of the known type which may have a significant negative effect on the entire burner manufacturing process. 
     It should be noted, finally, that, owing to the vertical insertion of a Venturi tube, the height of the burner may result in an excessive volume occupied by the burner on the cooking hob. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is therefore that of eliminating the drawbacks of the prior art mentioned above by providing a gas burner for a cooking hob, which is simple and inexpensive to manufacture and allows rapid assembly of its constructional components. 
     Another object of the present invention is to provide a gas burner which is easy to assemble and/or disassemble and which allows rapid maintenance and cleaning operations. 
     Another object of the present invention is to provide a gas burner which has small overall dimensions with, in particular, a low height. 
     Another object of the present invention is to provide a gas burner which has a small number of constructional components. 
     Another object of the present invention is to provide gas burner which is long-wearing over time and which is made of material able to resist the cleaning agents which are commonly used. 
     A further object of the present invention is to provide a burner which is simple from a constructional point of view and operationally entirely reliable. 
     These objects, together with others, are all achieved by the gas burner for a cooking hob which, in accordance with the present invention, comprises a burner body provided with at least one opening for entry of primary air, a flame-dividing element defining together with the burner body an air/gas mixing chamber, a gas injector intended to be mounted on the cooking hob in order to inject gas inside the mixing chamber, and a converging/diverging duct defining a Venturi tube located downstream of the gas injector for drawing air into the mixing chamber, characterized in that he burner body, the flame-dividing element and the converging/diverging duct consist of a monolithic structure in the form of a pressed sheet-metal casing. 
     As a result of this gas burner the number of constructional components is reduced, allowing more economical and faster and simpler assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention will more clearly understood in the light of a preferred embodiment of a burner for cooking hob given by way of non limiting example with reference to the accompanying drawings, in which: 
     FIG. 1 shows a cross-sectional side view of the gas burner according to the present invention, mounted on a cooking hob; 
     FIG. 2 shows an exploded perspective view of the burner-in question; 
     FIGS. 3 and 4 show, respectively, a side view and a plan view of a constructional detail of the burner in question associated with a burner body; 
     FIG. 5 shows a cross-sectional side view of an enlarged detail of FIG. 1, relating to the mounted arrangement of a burner body on a cooking hob. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the accompanying drawings,  1  denotes in its entirety a burner for a cooking hob according to the present invention. 
     This burner  1  is suitable for use advantageously on a cooking hob  2 , of the type partially illustrated in FIG.  1  and for example designed for use in gas cookers so as to allow in particular the heating, in a known manner, of any kind of food product. 
     With particular reference to the accompanying FIG. 1, the burner  1  comprises a burner body  3  resting on the cooking hob  2  in a position centred around a gas injector  4 , and a flame-dividing element  5  mounted on top of the burner body  3  so as to define therewith and with the cooking hob  2  an air/gas mixing chamber  6 . 
     In accordance with the example of embodiment illustrated in FIGS. 1 and 2, the gas injector  4  is mounted in a seat  7  formed directly on the cooking hob  2 . The gas burner  3  is, in turn, arranged centred around the gas injector  4  and rests on the cooking hob  2  by means of annular contact surface  30  (see FIG.  5 ). For the sake of greater clarity it is pointed out that, in FIG. 2,  8  denotes a portion of the cooking hob  2 . 
     In greater detail, in the non-limiting example of embodiment illustrated in FIG. 1, the gas injector  4  has a gas outlet nozzle  9  with an orifice  10  directed upwards inside the mixing chamber  6  and a supporting body  11  provided with a seat  12  able to contain the nozzle  9  and connected by means of a duct  13  to gas supply means, not shown in that they are of a type known per se. 
     A top piece  14  is mounted so as to rest on top of the flame-dividing element  5  and defines, by means of fins  15  formed above the flame-dividing element  5 , outlet ducts  16  for the air/gas mixture. 
     Openings  23  which are advantageously distributed at regular intervals around the burner body  3  are formed in the burner body  3 , as will emerge more clearly below when the form of the burner body  3  itself will be defined in detail. 
     The burner  1  moreover defines with its components a converging/diverging duct which can be assimilated to a Venturi tube located downstream of the gas injection nozzle  9  and can be operationally used to draw air into the mixing chamber  6  via the openings  23 . 
     The configuration of this converging/diverging duct will specified more clearly below. 
     According to the invention, the burner body  3 , the flame-dividing element  5  and the converging/diverging duct consist of a single monolithic structure in the form of a pressed sheet-metal casing. In particular, the metal sheet may be advantageously made of steel. 
     The flame-dividing element  5  has a central hole  17  which is centred around the central axis A of symmetry of the burner  1  and faces frontally the gas injection nozzle  9 . 
     In greater detail, in accordance with a preferred embodiment of the present invention, the burner body  3  is essentially composed of a frustoconically shaped upper portion  3 ′ which is tapered at the top and delimited by the flame-dividing element  5 , and by a lower portion  3 ″ which extends continuously from the upper portion  3 ′ by means of a first fold  18  in the sheet metal and extends substantially on the outside of the upper portion  3 ′, radially widening the form of burner body  3 . 
     In turn, the lower portion  3 ″ has, extending from the upper portion  3 ′, a first section  19  inclined outwardly of the burner  1  and a second section  20  extending from the first section  19  and inclined inwardly of the burner  1 . The two sections  19  and  20  are connected together in a continuous manner and are formed by means of a second fold  21  in the sheet metal. 
     The bottom edge of the second section  20  has, extending from it, in a substantially vertical manner as far as the cooking hob  2 , a plurality of teeth  22  between which the abovementioned openings  23  for the flow of air inside the mixing chamber  6  are defined (see FIG.  2 ). 
     Obviously, without departing from the scope of protection of the present patent, the shape of the burner body  3  may also be different from that illustrated above and in particular may also be simply cylindrical or frustoconical. 
     Advantageously, these openings  23  may be easily obtained during the pressing step of the production process. 
     The flame-dividing element  5  extends in a mainly horizontal direction and is peripherally joined to the burner body  3  by means of a third fold  24  in the sheet metal. The central part of the flame-dividing element  5  is occupied by a conveying portion  25  in the form of a dome with a central hole  17  and with its concavity directed towards the inside of the mixing chamber  5 . 
     Obviously, it is possible to devise a different shape for the conveying portion  25  of the flame-dividing element  5  (for example a frustoconical shape) without thereby departing from the scope of protection of the present invention. 
     The converging/diverging duct mentioned above is defined by the conveying portion  25  which forms the converging section of the duct, by the central hole  17  which forms the narrowest section of the duct and by the ducts  16  for the outflow of the air/gas mixture which form the diverging section of the duct. 
     Functionally speaking, the gas is emitted from the nozzle  4  into the mixing chamber  6  where it is mixed, in the correct proportions, with the air for producing a suitable mixture which is conveyed by the conveying portion  25  through the central hole  17 , from where it then spreads into the outlet ducts  16 . The constriction due to the presence of the central hole  17  and the subsequent widening of the gas flow cross-section due to the form of the outlet ducts  16  results in the creation of a Venturi effect with consequent drawing of air inside the mixing chamber  6  via the openings  23  formed radially on the burner body  3 . 
     It should be noted finally that, in accordance with the present invention, the configuration of the burner  1  described hitherto requires the manufacture of a limited number of constructional components since, in particular, the flame-dividing element  5  and the burner body  3  are formed as one piece by means of processes involving the pressing of a steel sheet. This possibility of forming the burner  1  with a limited number of constructional components obviously also results in major cost-related advantages. 
     Moreover, since there is no Venturi tube in the form of a vertical element, it is possible to produce burners with a lower height and, ultimately, smaller dimensions. 
     The invention thus conceived therefore achieves the predefined objects. Obviously it may also assume, in its practical embodiment, forms and configurations different from those illustrated above without thereby departing from the present scope of protection. 
     Moreover, all the details may be replaced by technically equivalent elements and the dimensions, the forms and the materials used may be any in accordance with requirements.