BARTOCCETTI, Pietro (Via Pascoli 14, Cerreto d'Esi, I-60043, IT)
CORRIAS, Silvio (Strada Madonnina Sorine Levante 17, Moncalvo, I-14036, IT)
BARTOCCETTI, Pietro (Via Pascoli 14, Cerreto d'Esi, I-60043, IT)
| CLAIMS 1. A gas burner (B) for a cooking top, of the type comprising a flame divider assembly (S) provided with at least one flame divider (1) comprising a plurality of gas outlet holes, characterised in that said flame divider assembly (S) further comprises an annular frame (5) and a fixing ring (11), said flame divider (1) being positioned between said annular frame (5) and said ring (11). 2. A burner according to claim 1, wherein said flame divider (1) is locked in position between said annular frame (5) and said ring (1 1) by securing said ring (11) onto said annular frame (5), said flame divider (1) comprising at least one peripheral edge which, in the assembled condition, is sealingly compressed between said annular frame (5) and said ring (11). 3. A burner (B) according to claim 1 or 2, wherein said annular frame (5) comprises a flange (6) and a ring nut (30), wherein at least said ring nut (30) comprises a plurality of radial projections (7) protruding towards the inside of said annular frame (5), and wherein said ring comprises a plurality of seats (12) adapted to be coupled with said radial projections (7) in the assembled condition. 4. A burner (B) according to claim 3, wherein said flame divider (1) comprises a plurality of notches (4) adapted to be coupled with said radial projections (7). 5. A burner (B) according to claim 4, wherein said ring is locked in position onto said frame by clinching said radial projections (7). 6. A burner (B) according to one or more of the preceding claims, wherein said flame divider (1) is made of a material which is harder than the material used for manufacturing at least one of said ring (11) and said annular frame (5). 7. A burner (B) according to one or more of the preceding claims, further comprising a cup (20) arranged underneath said metal plate (1) and a preferential passage for a portion of a gas coming from said cup (20), said preferential passage being adapted to put the inside of the cup (20) in direct communication with a seat for an ignition spark plug. 8. A burner (B) according to the preceding claim, wherein said preferential passage comprises an axial channel (15) obtained in said ring (11), which is in fluidic communication with at least one radial channel (14) obtained in said annular frame (5), wherein said radial channel (14) opens towards said cup (20) in a more internal position than the metal plate (1) when the burner (B) is in the assembled condition. 9. A burner (B) according to one or more of the preceding claims, wherein said annular frame (5) further comprises a radial channel directed towards a seat for a flame sensor. 10. A burner (B) according to one or more of the preceding claims, wherein said flame divider comprises a microperforated metal plate including at least holes having a diameter between 0.5 mm and 2.0 mm, more preferably between 1.2 mm and 1.3 mm., said metal plate having a thickness between 0.5 mm and 1.5 mm, more preferably between 0.9 mm and 1.1 mm. . 11. A burner (B) according to one or more of the preceding claims, comprising a cup (20), wherein said annular frame (5) can be sealingly engaged onto said cup (20). 12. A burner (B) according to the preceding claim, wherein said annular frame comprises a ring nut (30) which includes at least one end portion having a truncated-cone cross-section with the major base towards said flame divider 1 , and wherein said cup (20) comprises a circumferential engagement channel (35) to house said end portion of said ring nut (30), said engagement channel (35) having a truncated-cone cross-section with the major base towards said flame divider (1). 13. A cooking apparatus characterised by comprising at least one burner according to one or more of the preceding claims. 14. A method for manufacturing a gas burner (B) according to one or more of claims 1 to 12, characterised by comprising the following steps: - preparing a flame divider (1) comprising a plurality of gas outlet holes - preparing an annular frame (5) - preparing a fixing ring (11) - mounting said flame divider (1) onto said annular frame (5) - mounting said ring (11) onto said annular frame, in a manner such that edges of said flame divider (1) are positioned between said annular frame (5) and said fixing ring (11) - locking said flame divider (1) in position between said annular frame (5) and said ring (1 1) by securing said ring (11) onto said annular frame (5). 15. A method according to the preceding claim, further comprising the following steps: - securing said annular frame (5) onto said fixing ring (11) by clinching radial projections associated with said annular frame (5). |
DESCRIPTION
The present invention relates to a gas burner for a cooking top according to the preamble of claim 1.
In the cooking top industry, two distinct typologies of gas burners are known which differ mainly in the design of the flame divider.
The first typology includes traditional burners, which are fitted with a flame divider having a series of radial channels from which the gas comes out, thus generating a flame crown extending radially from the flame divider.
The second typology, which has been developed more recently, includes those burners in which the frame divider comprises a gas-permeable metallic element such as a microperforated metal plate, originating a flame that extends axially upwards (the so-called "carpet flame").
In general, in the present description and in the appended claims reference will generically be made to a "gas" flowing out of the flame divider; it is understood that this "gas" is normally a mixture of methane (or, more in general, a similar fuel gas) and air (the so-called primary air).
One example of such burners is discussed in international patent application WO2007/036772 by the present Applicant.
In this type of burners, the flame divider comprises a microperforated plate resting on the burner cup and made integral therewith by a central screw-type fixing device that is inserted into a housing hole of the flame divider and into a corresponding threaded hole of a retaining means; the latter is in turn made integral with the burner cup, e.g. by means of welding spots. This design implies a certain number of mechanical machining steps (milling, threading, welding) and a relatively complex construction (comprising parts such as the fixing device and the retaining means).
What is more, some of these machining steps are difficult on metal sheets which are only a few tenths of millimetre thick (the thickness of the microperforated plate is normally approx. one millimetre).
When the microperforated plate is enamelled (e.g. to facilitate cleaning or to improve the aesthetic appearance thereof), the above-mentioned machining steps are even more complex, since it is necessary to avoid damaging the enamel.
The present invention aims at providing a gas burner comprising a flame divider with at least one microperforated plate which overcomes the drawbacks of the prior art.
In particular, it is one object of the present invention to provide a gas burner of the aforementioned type which can be easily manufactured without requiring complex machining steps, while at the same time ensuring an optimal hermetic sealing of the burner and a reduced risk of damaging the enamel, if present.
This and other objects of the present invention are achieved through a gas burner incorporating the features set out in the appended claims, which are intended as an integral part of the present description.
The general idea at the basis of the present invention is to provide a gas burner comprising a flame divider assembly provided with at least one flame divider, an annular frame and a sealing ring, wherein the flame divider is secured between the annular frame and the sealing ring.
The flame divider comprises a microperforated plate with holes having a diameter between 0.5 mm and 2.0 mm, more preferably between 1.2 mm and 1.3 mm.
As an alternative, the flame divider may comprise a semi-permeable porous element or a fibrous material suitable for this purpose.
Preferably, the fixing takes place by locking the ring in position onto the annular frame, the flame divider being engaged along its edges between said two parts.
The ring is locked in position on the frame by means of radial projections associated with the frame, which are clinched against the ring itself.
Advantageously, this solution only requires a few simple mechanical assembly steps.
Moreover, such steps do not compress locally the flame divider's metal plate, which on the contrary is compressed evenly along its peripheral edge between the ring and the annular frame.
In the first place, this allows to obtain a perfectly hermetic sealing of the burner in the coupling areas of the various parts of the flame divider assembly and between the latter and the cup.
Furthermore, the hermetic seal is advantageously obtained without generating local stresses which might deform the plate or ruin the enamel thereof, if present.
Also, no welding is required, which implies a number of advantages: first of all, the materials of the flame divider, the frame and the ring may be different and may not be welding compatible (e.g. steel plate and aluminium frame and ring).
Secondly, the absence of welds simplifies the manufacturing process, especially taking into account the limited thickness of the plate, which requires the adoption of special measures during the welding process.
Moreover, as will be described in detail later on, additional radial or axial gas passages are preferably obtained in the ring to ensure a better ignition and operation of the gas burner. The present invention also relates to a cooking apparatus comprising such a burner and to a method for manufacturing such a burner.
Further objects and advantages of the present invention will become more apparent from the following detailed description and from the annexed drawings, which are supplied by way of non-limiting example, wherein:
Fig. 1 is an exploded perspective view of an embodiment of a flame divider assembly of a gas burner according to the present invention;
Fig. 2 is a perspective bottom view of the flame divider assembly of Fig. 1 in the assembled condition;
Fig. 3 is a top view of the flame divider assembly of Fig. 2;
Figs. 4a and 4b are two partial sectional views of the flame divider assembly of Fig. 3;
Fig. 5 is a perspective view of an embodiment of the gas burner according to the present invention;
Fig. 6 is a longitudinal sectional view of the burner of Fig. 5;
Fig. 7 is a sectional view of a portion of the flame divider assembly of Fig. 1 secured to a cup in an alternative manner.
The example of Fig. 1 shows an embodiment of a flame divider assembly S included in the gas burner B of Figs. 5 and 6 according to the present invention.
The flame divider S of the example shown has a cylindrical symmetry, and therefore reference will be made hereafter to such a design; it is nonetheless apparent that the symmetry may be different (elliptic, oval or the like) or that there may even be no symmetry at all, e.g. in the case of burners having a polygonal shape or the like, which however should be considered to be equivalent for the purposes of the present invention.
With reference to Figs. 1-3, the flame divider assembly S of the example described above comprises a perforated flame divider 1 having a substantially circular plan shape, wherein localised holes 2 are obtained in an annular region adjacent to the outer circumference 3 of the flame divider 1.
To this end, the flame divider 1 comprises, in fact, a perforated plate preferably made of decarburised steel specific for enamel coating, in particular of the DC04ED or equivalent type, as defined by the EN 10209 standard.
The thickness of the plate of the flame divider 1 varies between 0.5 mm and 1.5 mm, preferably between 0.9 mm and 1.1 mm.
The holes 2 allow the gas to pass from the inner region of the burner B to the outer region where the flame is generated; the holes 2 have preferably a diameter between 0.5 mm and 2.0 mm, more preferably between 1.2 mm and 1.3 mm.
The value of the diameter of the holes 2 is determined as a function of the power to be obtained from the burner; the larger the holes the greater the gas flow, and therefore the maximum power output of the burner B.
In this example, the arrangement of the holes 2 is such that they preferably occupy an annular portion of the flame divider 1, or anyway it is such as to ensure a homogeneous gas distribution in the outer region, for better combustion heating homogeneity.
As an alternative, the holes may be evenly distributed over the whole surface of the flame divider or they may be distributed unevenly, e.g. denser at the periphery and less dense towards the centre, depending on specific requirements and on the shape and dimensions of the flame divider.
Along the outer edge 3 of the flame divider 1 notches 4 are obtained, the coupling function of which will be described below.
Preferably, the plate of the flame divider 1 further comprises a portion enamelled on at least the side not shown in Fig. 1, i.e. the side facing outwards from the burner B, where the flame extends.
The applicable enamel, if used, preferably meets the following requirements:
Acid resistance (according to the UNI 5717 standard): AA
Heat resistance (according to the ISO 4530 standard): 600°C Thermal shock resistance (according to the UNI 7674 standard): 450°C
Adherence (according to the UNI 8883 standard): SUFF.
In accordance with the teachings of the present invention, the flame divider assembly S of Figs. 1-3 also comprises an annular frame 5.
The latter comprises, in turn, a support flange 6 and a ring nut 30: in the example discussed herein, these are made as one piece, the annular frame being one aluminium piece for the reasons that will be described later on.
The support flange 6 is used for firmly housing the gas burner B on the cooking top; to this end, the underside of the flange 6 rests upon the surface of the cooking top.
The annular frame 5 also comprises a ring nut 30 from which a plurality of radial projections 7 protrude radially towards the centre, said projections being obtained on the inner edge of the ring nut 30 itself.
The shape, number and layout of the radial projections 7 are such as to allow mounting the flame divider 1 into the annular frame 5 by inserting them into the above-described notches 4.
The annular frame 5 preferably comprises at least one radial alignment projection 9 obtained on the inner edge of the ring nut 30, the shape of which allows it to be coupled to a matching alignment notch 10 obtained on the plate 1; this ensures that the flame divider 1 is mounted correctly 1, i.e. properly aligned and arranged inside the annular frame 5.
This alignment is optional in this case due to the holes 2 being symmetrical, but it might be required in other embodiments.
As aforementioned, the annular frame 5 is preferably a monolithic aluminium piece, or anyway it is made of a softer material than the flame divider 1 : this allows to obtain, when coupling the two parts, a deformation of the frame 5 but not of the flame divider 1, which is necessary to ensure a perfect adherence between the two and prevent any gas leakage in the coupling area; it should be noted that the very same effect could be obtained in the opposite case (aluminium flame divider and steel frame), but this would cause a deformation of the flame divider 1.
The flame divider assembly S also comprises a ring 11 having an outside diameter approximately equal to the diameter of the flame divider 1.
The ring 11 is so shaped as to include seats 12 and at least one alignment seat 13. The seats 12 of the ring 11 substantially coincide with the housings 4 of the flame divider 1, so that also the ring 11 can be housed inside the ring nut 30 of the annular frame 5 in a similar manner.
For this purpose, the ring 11 includes a housing seat having dimensions and shape being complementary to those of the radial alignment projection 9, thus allowing a proper installation of the parts making up the flame divider assembly S, as shown in Fig. 2.
It should be noted that, in this example, the alignment of the ring 11 with the frame 5 is more important than the alignment of the flame divider 1 as previously described; the reason for this will become more apparent below.
Referring back to the ring 11, its thickness is less than the height of the radial projections 7 in order to allow the burner to be secured by plastic deformation of the radial projections 7, e.g. obtained by clinching them.
The inside diameter of the ring 11 is just a little smaller than the outside diameter, so as to promote the gas flow through the holes 2 from the burner chamber when the burner is in operation.
In the assembled condition, as shown in Fig. 2, the flame divider 1 is inserted in the annular frame 5 and is locked against it by the ring 11.
The radial projections 7, inserted in the matching notches obtained in the plate 1 and in the ring 11, are deformed plastically towards the ring, e.g. by clinching and by exerting local pressure onto the ring 11.
Said pressure is distributed evenly along the entire outer circular crown of the flame divider 1 , which is engaged between the frame 5 and the ring 1 1 , so as to ensure a tight and uniform contact with the annular frame 5, thereby improving the sealing of the flame divider.
The ring 11 is preferably made of aluminium or anyway of a softer material than that of the flame divider 1 : this, similarly to the above, allows the ring to deform so as to ensure a hermetic sealing of the interface area, while at the same time not deforming the flame divider 1.
This also reduces the risk that the flame divider 1 is subject to stresses which might damage the enamel; in fact, the latter is held in place through a force distributed (as opposed to localised) along its entire edge.
Advantageously, both the annular frame 5 and the ring 11 are made of aluminium, while the plate 1 is made of steel: thus, during the assembly process the former two parts are deformed plastically and adhere perfectly to the plate (without damaging it), thereby ensuring an optimal sealing of the flame divider assembly S and preventing any gas leakage from the interface areas of the various parts 1,5,11.
The surface of the plate 1 in the plan view of the assembly of Figs. 1 and 2 shown in Fig. 3 is enamelled to make the flame-exposed area stronger and easier to clean.
Advantageously, then, the whole flame divider assembly S can be removed from the cooking top in order to be cleaned, e.g. by washing it in a dishwasher.
Likewise, the surface of the annular frame 5 shown in the drawing, which remains exposed on the cooking top, may optionally be painted for cleaning or aesthetic reasons.
In Fig. 3 it is also possible to see the spark plug seat 12 that houses an ignition spark plug of a known type, which allows to ignite the flame as the gas comes out of the holes 2, thus firing up the burner.
Fig. 3 also shows the thermocouple seat 13 that houses a flame sensor, preferably consisting of a thermocouple detecting the temperature around the flame (or, more in general, the presence of a flame) and determines, for safety reasons, if the ignition has occurred correctly.
Through the flame sensor, in fact, it is possible to monitor the operation of the burner, mainly for safety reasons, e.g. in order to stop the gas flow in the event that a flame accidentally goes out.
Figs. 4a and 4b show two partial cross-sections of the flame divider assembly, respectively along the section planes A-A and B-B of Fig. 3.
In particular, Fig. 4a (section A-A) allows to see the spark plug seat 12 and the neighbouring passages.
As will be explained more in detail below, the burner B according to the present invention is advantageously characterised by comprising a preferential passage for the gas coming from the cup, so that a part of the gas coming from the cup does not flow through the flame divider 1, but avoids it and directly reaches the ignition spark plug.
To this end, the spark plug seat 12 is in fluidic communication, through the radial channel 14, with the axial passage 15 obtained in the body of the ring 11, as also shown in Fig. 1.
The radial channel 14 opens on the ring nut 30 in a more internal position (e.g. towards the cup 20) than the position taken by the flame divider 1 in the assembled condition.
With this design, a part of the gas coming from the cup 20 (shown in Figs. 5 and 6) arrives at the spark plug seat 12 by following the path exemplified by the arrow 16.
The preferential path thus obtained prevents at least a part of the gas from flowing through the flame divider 1.
Therefore, this gas flow directly reaches the region of the ignition spark plug, which ignites the flame in the immediate vicinity thereof; the flame then propagates naturally towards the gas that is exiting the holes 2, thus completing the ignition of the burner.
Thanks to this particular configuration of passages that create a preferential path for a part of the gas coming from the cup, which leads directly to the ignition spark plug, it is possible to obtain an effective flame ignition while still keeping the burner body construction very simple.
In this type of burner, in fact, ignition is sometimes difficult due to the slow speed of the gas flowing out of the holes 2 of the flame divider 1 , since there is a significant load loss when the gas meets the flame divider 1 so designed.
In order to overcome this drawback it would be necessary to bring the spark plug excessively close to the flame divider 1, but this would lead to problems in terms of average spark plug life, due to the fact that the spark plug would be too close to the flame.
This new design effectively overcomes this drawback, because the spark plug can be placed at a sufficient distance from the flame divider 1 while still ensuring optimum burner ignition. With reference to section B-B of Fig. 4b, there is shown the thermocouple seat 13 and the neighbouring passages.
The thermocouple seat 13 is in fluidic communication, through the radial channel 17, with the radial passage 18 obtained in the body of the ring 11 , as also shown in Fig. 1.
Through these passages, the burnt gas coming from the perforated region of the plate 1 hits the flame sensor fitted into the thermocouple seat 13, by following the path exemplified by the arrow 19.
In this way, the high-temperature burnt gas hits the thermocouple, which detects the difference in temperature with respect to a cold junction and verifies the proper operation of the cooker.
A an alternative, it is conceivable that the flame sensor recognises the presence of a flame based on irradiation, since said passages let the sensor "see" the flame without any obstacles in between.
With this particular configuration of passages leading to the sensor, it is possible to effectively monitor the operating state of the burner without having to employ a complex burner body.
The radial channels 14 and 17 are preferably multiple channels, i.e. comprising several channels having a reduced width, in this case three channels each.
This improves the fluidic communication without requiring large single channels, which might be obstructed by foreign bodies.
Fig. 5 shows the gas burner B with the flame divider assembly S and the cup 20; the annular frame 5 is assembled with the plate 1 through the interposition of the ring 11 (not visible in the drawing), and this assembly is then mounted on the cup 20.
Fig. 6 is a longitudinal sectional view of the burner B of Fig. 5.
The burner cup 20 comprises a gas supply duct portion 23 that reaches a truncated cone- shaped portion 24 centred underneath the plate 1.
The truncated cone-shaped portion 24 ends with a protrusion that defines the inner volume 25 of the burner.
The particular shape of the burner cup 20, which comprises the truncated cone-portion 24, provides an optimal gas supply to the external combustion region of the burner, in the area of the holes 2.
The flame divider assembly S can be fitted onto the cup simply by laying it onto the latter, and the contact surfaces therebetween are advantageously ground to ensure an effective sealing.
More in particular, said contact surfaces are the underside 31 of the ring nut 30, which in the assembled condition faces the cup 20, and the upward-facing surface 29 of the latter, which supports the ring nut 30 when engaged.
One variant of the flame divider assembly S is shown in Fig. 7.
In this case, the ring nut 30 has a truncated cone cross-section having the shape of a rectangular trapezium with the major base towards the flame divider 1 and the minor base towards the cup 20, the wall 82 adjacent to the ring being perpendicular to the bases of the trapezium and the other wall 81 being such as to determine a reduction in the thickness of the ring nut 30 as it gets farther from the flame divider.
The cup 20 has a circumferential engagement channel 35 that houses the end portion of the ring nut.
The engagement channel 35 has a truncated cone cross-section, with the major base towards the flame divider 1 and the minor base facing the opposite direction.
The perimetric walls 81,82 of the ring nut 30 are not parallel to the inclined walls 83,84 of the engagement channel 35; on the contrary, the opening angle of the former with respect to a vertical axis is more acute than that of the latter: thus, in the coupled condition two circular sealing lines are generated between the ring nut 30 and the cup 20.
Said two sealing lines offer the advantage that the tightness of the interface area between the cup 20 and the flame divider assembly S is improved.
The assembled burner B can be fitted to a cooking apparatus and can be connected to the various supplies, such as gas and power, and to the various controls.
A cooking apparatus may comprise one or more burners, even of different size, shape or type.
A cooking apparatus typically comprises four burners, one of which has a standard size, two are bigger "fast" burners, and another one is an "ultrafast" burner which is even bigger. The idea at the basis of the present invention is applicable to one, more than one or all of the burners of a cooking apparatus, provided that they are of the type comprising a flame divider in which a plurality of holes are obtained.
The present invention also relates to a cooking apparatus provided with at least one burner according to the present invention.
It is apparent that many changes may be made to the present invention by those skilled in the art without departing from the protection scope thereof as stated in the appended claims. For example, it is conceivable to provide a flame divider comprising a plate having holes obtained over the whole free surface, or anyway having configurations other than annular, e.g. double annular or star configurations.
Furthermore, the ring 11 may be constrained in a manner such that it exerts pressure between the plate 1 and the annular frame 5 through different mechanical retention systems, which may be either removable, like threaded junctions, or permanent, like welding, brazing or glueing by using heat-resistant glues. The method for manufacturing such a gas burner B according to the present invention, which is also an object of the present invention, comprises at least the following steps:
- preparing a flame divider 1 comprising a plurality of gas outlet holes
- preparing an annular frame 5
- preparing a fixing ring 11
- mounting said flame divider 1 onto said annular frame 5
- mounting said ring 11 onto said annular frame, in a manner such that edges of said flame divider 1 are positioned between said annular frame 5 and said fixing ring 11
- locking said flame divider 1 in position between said annular frame 5 and said ring 11 by securing said ring 11 onto said annular frame 5.
Preferably, the ring 11 is secured to the annular frame 5 by clinching radial projections associated with the annular frame against said ring.
In particular, before being used in the method according to the present invention, the flame divider 1 is subjected to a step of enamelling at least one of its surfaces.
Finally, the flame divider assembly S obtained by implementing the method according to the present invention is laid over the cup of a gas burner in a manner such as to attain a gasproof seal, the underside 31 of the annular frame 5 having also been subjected to a grinding step.