EP2558779B1

EP2558779B1 - Cooking top burner, cooking top comprising such a burner and method for manufacturing it

Info

Publication number: EP2558779B1
Application number: EP11721363.7A
Authority: EP
Inventors: Dino Bucci; Pietro Bartoccetti
Original assignee: Whirlpool EMEA SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2010-04-13
Filing date: 2011-04-08
Publication date: 2019-05-22
Anticipated expiration: 2031-04-08
Also published as: ITTO20100288A1; EP2558779A1; WO2011128822A1

Description

The present invention relates to a gas burner for a cooking top according to the preamble of claim 1, as well as to a cooking top comprising such a burner.
The present invention also relates to a method for manufacturing such a burner.
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.
A burner according to the preamble of claim 1 is known from EP234039 .
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.
Particularly delicate areas of this type of burner are the interfaces between the various parts of the flame divider assembly and the connection between the latter and the cup: in these areas, in fact, there is a relatively high risk of gas leaks, and it is therefore necessary to ensure a tight seal.
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 low production costs.
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 for cooking tops which comprises a cup and a flame divider assembly, wherein the latter is fitted with at least one flame divider comprising a plurality of holes for the outflow of a gas from the cup, and wherein the flame divider assembly can be sealingly engaged onto said cup and further comprises an annular frame wholly made of metal plate.
The annular frame has a sealing edge obtained by bending a peripheral sheet-metal edge of said annular frame.
This feature offers the advantage that a burner thus designed only has a few parts, namely only the flame divider, the annular frame and the cup, resulting in significant savings in terms of parts, machining and manufacturing costs.
Such advantages are complemented by another one consisting of substantial savings in terms of production times and costs, deriving from the fact that the hermetic sealing is ensured by simply bending a peripheral sheet-metal edge of the annular frame itself.
Thus the whole annular frame can advantageously be manufactured from a simple and inexpensive metal sheet, appropriately sheared and bent.
Since the perforated flame divider can be manufactured in a similar manner, it follows that, advantageously, the whole flame divider assembly can be manufactured by suitably bending and machining a metal sheet, without therefore requiring any extruded or die-cast or billet parts which would involve significant additional costs.
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 a sectional view of a burner which is not part of the present invention;
Fig. 2 is a sectional view of a detail of the burner of Fig. 1;
Fig. 3 is a perspective top view of the flame divider assembly of the burner of Fig. 1 in the assembled condition;
Fig. 4 is a perspective bottom view of the flame divider assembly of the burner of Fig. 1 in the assembled condition;
Fig. 5 is an exploded perspective top view of the flame divider assembly of Fig. 3;
Fig. 6 is an exploded perspective bottom view of the flame divider assembly of Fig. 3;
Fig. 7 is an exploded view of a section of the flame divider of Fig. 3;
Fig. 8 shows a section of the flame divider of Fig. 3 in the assembled condition;
Fig. 9 is a perspective view of the cup of the burner of Fig. 1;
Fig. 10 is a sectional view of the cup of Fig. 9
Figure 11 describes a burner according to the invention.

Referring now to Figs. 1 and 2, there is shown a gas burner 1 for cooking tops according to the present invention.
The burner 1 comprises a cup 2 and a flame divider assembly 3.
The flame divider assembly 3 comprises, in turn, a flame divider 4 provided with a plurality of holes 5 for the outflow of a gas from the cup 2.
The flame divider assembly 3 also comprises an annular frame 6, more clearly visible in Figs. 3 to 6, wherein it is shown assembled together with the flame divider 4 (Figs. 3 and 4) and in an exploded view (Figs. 5 and 6).
Still with reference to Figs. 1 and 2, it can be seen that the flame divider assembly 3 can be engaged onto the cup 2; more in particular, the annular frame 6 secures the flame divider 4 to the cup 2 while ensuring a tight seal between the flame divider assembly 3 and the cup 2. For this purpose, the tight seal is preferably obtained by means of mechanical machining steps: The annular frame portion in contact with the cup is coined, whereas the cup portion in contact with the annular frame is ground, the cup being preferably made of aluminium. Furthermore, this sealed engagement is also ensured by a ring nut 62 of the frame 6, which will be described later on.
The flame divider 4 has a substantially circular plan shape, and the holes 5 are localised in an annular area adjacent to the outer circumference of the flame divider 4 itself.
To this end, the flame divider 4 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 applicable enamel, if required, will preferably have the following specifications:

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.

The thickness of the plate of the flame divider 4 varies between 0.5 mm and 1.5 mm, preferably between 0.9 mm and 1.1 mm.
The holes 5 allow the gas to flow from the inner region of the cup 2 of the burner 1 to the outer region where the flame is generated.
The diameter of the holes 5 is preferably comprised between 0.5 mm and 2.0 mm, more preferably between 1.2 mm and 1.3 mm.
In general, the value of the diameter of the holes 5 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 1.
In this example, the arrangement of the holes 5 is such that they preferably occupy an annular portion of the flame divider 4, 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.
As far as the annular frame 6 is concerned, in the present example it is wholly made of metal plate, as can also be seen in Figs. 7 and 8.
The metal plate of the annular frame is preferably also made of decarburised steel, in particular of the DC04ED type or equivalent, as defined by the EN 10209 standard, and its thickness is between 0.5 mm and 1.5 mm, more preferably between 0.9 mm and 1.1 mm. The annular frame 6 can be sealingly secured to the cup 2 and supports the flame divider 4: to this end, the frame 6 comprises a flange 61 and a ring nut 62 perpendicular to each other. The flame divider assembly can thus advantageously be removed for cleaning, e.g. for washing it in a dishwasher or the like.
Both the flange 61 and the ring nut 62 are obtained by appropriately bending the metal sheet that the annular frame 6 is made from: in substance, during the manufacturing process a metal sheet is first sheared into the desired shape and then bent to create the flange 61 and the ring nut 62.
As an alternative, both the flange 61 and the ring nut 62 may be welded or screwed, though this solution is less advantageous in terms of costs and process complexity, with possible repercussions on the quality of the sealing as well.
More specifically, the ring nut 62 is obtained by bending into a "U" shape a peripheral edge of the metal plate of the annular frame 6, as can also be seen in the enlarged detail shown in the annexed Figs. 7 and 8.
Preferably, the ring nut 62 comprises two vertical wall portions 63, 64, substantially parallel or slightly converging, joined together by a horizontal support portion 65, visible in Figs. 2, 7 and 8.
As shown in Figs. 1, 2, 9 and 10, the ring nut 62 is used for sealingly engage the frame 6 (and hence the flame divider assembly 3) with the cup 2, which for this purpose has an annular engagement edge 21 jutting out from the body of the cup 2.
The annular engagement edge 21 and the ring nut 62 cooperate together to simultaneously secure the flame divider and ensure a tight seal, so as to prevent the gas from leaking in that interface area.
To this end, the dimensions of the ring nut 62 and of the annular engagement edge 21 are such that they can be engaged by interference one into the other, until the horizontal support portion 65 abuts against the cup 2.
The inside diameter of the annular engagement edge 21 therefore substantially coincides with or is slightly smaller than the outside diameter of the vertical wall portion 64, thus allowing the two parts to be coupled by interference fit.
In addition, the height of the annular engagement edge 21 and that of the vertical wall portions 63, 64 of the ring nut 62 are approximately the same, so that the horizontal support portion 65 can properly abut against the cup 2.
In order to improve the sealing and avoid any gas leakage, the face of the bottom wall 65 that abuts against the cup 2 is preferably coined, whereas the portion of the cup 2 that abuts against the bottom wall 65 is advantageously ground.
As concerns the fixing of the flame divider 4 onto the annular frame 6, it can be seen in Figs. 7 and 8 that it is obtained simply by bending the outer perimetric edge 40 of the flame divider 4 around the outer perimetric edge 70 of the flange 62 of the annular frame 6, thus simply and effectively preventing any gas leakage from that area.
As to the cup 2, it is shown in detail in Figs. 9 and 10 and defines internally a hollow volume 22 having substantially a truncated-cone shape and being open towards the flame divider 4 at the major base of the truncated cone.
In the assembled condition, as shown in Fig. 1, between the flame divider 4 and the cup a toroidal chamber 23 is generated which is filled with gas coming from the hollow volume 22.
It should be noted in this regard that in the example shown the diameter of the open mouth of the hollow volume 22 is substantially equal to or slightly smaller than the central diameter 5 with no holes of the flame divider 4, whereas the toroidal chamber 23 abuts on the flame divider portion with holes 5.
This is useful mainly to ensure a uniform gas distribution through the holes 5: in fact, the gas comes from the hollow volume 22 and flows towards the flame divider 4; hence it meets the non-perforated central diameter of the flame divider 4 and is thus deviated into the toroidal chamber 23, from where it is finally let out through the holes 5 that face said toroidal chamber 23.
The flame divider has a raised central portion (obtained, for example, by drawing); the perforated portion is thus obtained from a descending portion, so as to promote the secondary air supply (i.e. the additional air flow necessary for burning the gas thoroughly) at the innermost holes.
As can be seen in Figs. 3 to 6, both in the annular frame 6 and in the flame divider 4 there are suitable seats, designated 68, 69 and 41, 42, respectively, for an ignition spark plug CA and for a flame sensor SF, shown by way of example in Figs. 1,2,9 and 10.
Both the ignition spark plug CA and the flame sensor SF are of per se known types and will not therefore by discussed any further.
Also these seats 68, 69 and 41, 42 are advantageously obtained simply by shearing the metal plate of the flame divider 4 and of the annular frame 6.
Furthermore, as can be seen, the cup 2 comprises seats for the ignition spark plug CA and for the flame sensor SF, which are therefore associated with the cup 2 itself.
This solution also offers the advantage of providing a burner 1 complete with all its accessories in the form of a low-cost, compact assembly which can be easily preassembled and then installed on a cooking top with only a few simple steps.
The assembled burner B can thus be fitted to a cooking top and can be connected to the various supplies, such as gas and power, and to the various controls.
A cooking top may comprise one or more burners, even of different size, shape or type.
A cooking top 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 top, provided that they are of the type comprising a flame divider in which a plurality of holes are obtained.
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.
A burner according to the invention is illustrated in Fig. 11, wherein the same reference numerals designate the same parts.
With respect to the solution described above, the invention differs in that the annular engagement edge 21' comprises two opposite shoulders 23',24' that define the walls of a recess 22' having a truncated-cone cross-section or, more in general, a "V" cross-section, which in the coupled condition housed the ring nut 62, which also has side walls with a truncated-cone profile, so as to increase the contact surface and hence improve the sealing.
In this respect, it should be noted that the contact between the two parts is accomplished at the corner between the vertical wall portions 63, 64 and the horizontal wall portion 65 that abut against the facing walls of the "V" recess, thus sealing the coupling.
The perimetric walls 63, 64 of the ring nut 6 are in this case inclined, thus forming a truncated-cone profile with its minor base facing the cup 2.
Advantageously, said perimetric walls 63, 64 are not parallel to the opposite shoulders 23',24' of the recess 22'; 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 6 and the cup 2.
Said two sealing lines offer the advantage that the tightness of the interface area between the cup and the flame divider assembly is improved.
This provides the advantage that, should one sealing line be defective and cause a gas leak due to shape imperfections, there will still be another sealing line.
Moreover, if the ring nut is made of a harder material than the cup (e.g. sheet-metal or, more in general, steel for the former and aluminium for the latter), it can be conjectured that during the assembly stage the cup will get slightly deformed with respect to the ring nut so as to conform to the latter, thus further improving the sealing between the two parts.
The method for manufacturing a gas burner 1 according to the present invention is described by claim 10.

Claims

A gas burner (1) for a cooking top, of the type comprising a cup (2) and a flame divider assembly (3) provided with at least one flame divider (4) comprising a plurality of holes (5) for the outflow of a gas from the cup (2),
wherein said flame divider assembly (3) further comprises an annular frame (6) which can be secured to said flame divider (4) wholly made of metal plate,
wherein said flame divider (4) is provided with a sealing ring nut (62) obtained by bending a peripheral edge of said annular frame (6), said sealing ring nut (62) being sealingly engageable onto said cup (2) and
wherein said cup (2) comprises an annular engagement edge (21) which, in the assembled condition, cooperates with said ring nut (62) to secure the flame divider and ensure a tight seal, characterised in that
- said ring nut (62) comprises two vertical wall portions (63,64) joined together by a horizontal support portion (65),

- said vertical wall portions (63,64) of said ring nut (62) are inclined in a manner such as to create a profile having a truncated-cone cross-section and

- said cup (2) comprises an annular engagement edge (21') comprising two opposite shoulders (23',24') that define the walls of a recess (22') having a truncated-cone cross-section, which in the assembled condition is adapted to house said inclined vertical wall portions (63,64) of said ring nut (62).
A burner according to claim 1, wherein said flame divider (4) comprises a metal plate with holes (5) having a diameter between 0.5 mm and 1.5 mm, more preferably between 1.2 mm and 1.3 mm.
A burner according to one or more of the preceding claims, wherein said annular frame (6) comprises a flange (61) which is perpendicular to said ring nut (62).
A burner according to claim 1, wherein said ring nut (62) can be engaged into said annular engagement edge (21) by interference, and wherein, in the assembled condition, said horizontal support portion (65) abuts against said cup (2).
A burner (B) according to claim 1, wherein the opening angle of said perimetric walls (63,64) of said ring nut relative to a vertical axis is more acute than said opposite shoulders (23',24') of said recess (22').
A burner according to claim 3, wherein said flame divider (4) and said annular frame (6) are secured to each other by bending a perimetric edge of said flame divider (4) around said flange (61) of the annular frame (6).
A burner according to one or more of the preceding claims, wherein said cup (2) defines internally a hollow volume (22) having substantially a truncated-cone shape and being open towards the flame divider at the major base of the truncated cone, and wherein between said flame divider (4) and said cup (2) a toroidal chamber (23) is generated, an open mouth of the hollow volume (22) abutting on a portion with no holes of said flame divider (4), and said toroidal chamber (23) abutting on a flame divider portion with holes (5).
A burner according to one or more of the preceding claims, wherein said annular frame (6) and said flame divider (4) comprise seats (68,69,41,42) for housing an ignition spark plug (CA) and a flame sensor (SF).
A gas cooking top characterised by comprising at least one burner (1) according to one or more of the preceding claims.
A method for manufacturing a gas burner (1) according to claim 1 for a cooking top, of the type comprising a cup (2) and a flame divider assembly (3) provided with at least one flame divider (4) comprising a plurality of holes (5) for the outflow of a gas from the cup (2), wherein said flame divider (4) is wholly made of metal plate, comprising the steps of:
a- preparing said flame divider comprising gas outlet means

b- preparing an annular frame (6)

c- connecting said flame divider to said frame by bending an outer edge (40) of the flame divider onto an outer peripheral edge (70) of the annular frame (6);
the method is characterized in that it comprises a step of manufacturing a sealing ring nut (62) by bending a portion of said annular frame so as to realize two vertical wall portions (63,64) joined together by a horizontal support portion (65) and a step of assembling said sealing ring nut (62) on said cup (2) so as to make it cooperate with an annular engagement edge (21), said vertical wall portions (63,64) of said ring nut (62) being inclined in a manner such as to create a profile having a truncated-cone cross-section and said cup (2) comprising an annular engagement edge (21') comprising two opposite shoulders (23',24') that define the walls of a recess (22') having a truncated-cone cross-section, which in the assembled condition is adapted to house said inclined vertical wall portions (63,64) of said ring nut (62).
A method according to claim 10, wherein the mating surfaces of the cup and/or of the annular frame having been subjected to grinding and/or coining.