[0001] This invention concerns an improved gas cooker burner with three concentric flames,
and precisely of the type with flame dividing member in a single piece.
[0002] It is known that in hobs or gas cookers at least one of the burners, intended to
be used with the cooking containers of greater diameter, is preferably provided with
multiple concentric flames, typically three, to improve the distribution of heat on
the bottom of the container itself and thereby have a greater cooking efficiency.
This can be achieved with burners and relative flame dividers dismountable into several
pieces, but presenting in such a case drawbacks caused by the poor maintenance practicality
and the difficulty in obtaining a satisfying level of cleanliness of the pieces themselves.
[0003] Owing to these reasons burners have been used with three concentric flames or crowns
obtained by two rings in a single piece, but with two separate gas deliveries on the
inner ring and the outer ring, separately controlled by two different gastaps or even
a single gastap which controls the gas feeding to the outer ring only from a certain
level of opening of the delivery onwards, while for reduced supplies the gas flows
only from one of the rings or crowns, usually from the innermost one. Actually it
proves to be particularly difficult to achieve an even distribution of the gas in
the different members which give rise to the concentric flames, so as to have both
an exact balancing of the pressures and an adequate flow of secondary air by the different
flame areas, while assuring the propagation and preservation of the flame itself,
without the presence of frequent flame separation phenomena.
[0004] In any case accomplishing a burner of the type indicated, manufactured according
to the prior art, would have required the adoption of at least two spark-plugs and
two safety thermocouples, even in case of single delivery, supposing that such a burner
would have been able to work.
[0005] Consequently the object of this invention is to provide a burner of the above-mentioned
type which is free from the aforesaid faults and drawbacks, since it may be fed by
a single gas delivery with a single control tap and therefore has a single spark-plug
and a single safety thermocouple. In this way the flames spread immediately from the
ignition point on the outer crown all the way to the innermost one and there remain,
with no flame separation, even for reduced gas delivery, controlled by a single gastap
quite similar to the conventional ones for single flame burners.
[0006] This is achieved through a burner comprising a basic distributing body, connected
to a gas delivery tube of known type and having three radial gas passage areas and
three intermediate secondary air inlet areas, with a flame dividing member, fit to
be placed on said distributing body, comprising two concentric rings connected by
three radial members fit to form the cover of the above-mentioned gas passages, with
intermediate apertures for the secondary air, the inner ring having on its periphery
two staggered rows of holes one on top of the other as well as are present on the
surface confronting the latter on the inner periphery of the outer ring, whose outer
periphery has other two series of holes one on top of the other and level with the
latter a single spark-plug and a thermocouple connected to a known-type gas safety
valve are provided.
[0007] These and other objects, advantages and characteristics of the improved burner according
to this invention will appear mixture clearly from the following detailed description
of its preferred embodiment, reported as non-limiting example, referring to the annexed
drawings wherein :
Fig. 1 shows an exploded view of the burner according to the invention; and
Fig. 2 shows a partial radial sectional view of the burner of fig.1 assembled for its operation.
[0008] With reference to the drawings the burner according to this invention, fed by the
outlet 10a of a gas delivery tube 10 of conventional type, is formed by a body 1 of
the real burner upon which a flame dividing member 2 is placed, as it generally occurs
in the known single flame burners. The body of the burner 1 serves the purpose, particularly
important in this case, of properly distributing the gas, or rather the mixture of
gas and primary air fed by the tube 10, to the different flames of the member 2. In
order to do this the body 1 has radial passages 3 communicating with a central hole
5 coaxial with 10a, and separated one from the other by the raised walls 7 defining
the vertical passages 9, therefore perpendicular to the plane of the body 1, for the
entry of the secondary air by the central flames. The passages 3, as shown in fig.1,
are preferably ,three, as well as the secondary air inlet areas 9.
[0009] The flame dividing member 2, in a single piece according to the invention, substantially
includes an outer ring 4 and an inner disc 6. The three flames rise from proper holes
on the outer and inner periphery of the ring 4, as well as on the outer periphery
of the disc 6. The outer ring 4 and the inner disc 6 are connected by radial connecting
members 8, coinciding in number and position with said passages 3 of which they define
the upper wall or closing cover. On the outer edge of the circular plate forming the
burner body 1 there are also two holes 11a and 13a for the positioning of a spark-plug
11 and a safety thermocouple 13 respectively, as well as for the passage of the relative
connections to the respective controls, in such a position that the active parts of
both elements 11 and 13 are near the outer periphery of said ring 4 of the flame divider
2.
[0010] With particular reference to fig.2, the holes on the flame divider 2, through which
the gas comes out and by which the flame is formed, are shown in greater detail. The
holes on the inner crown 6 are indicated by 12 and those on the outer ring 4 by 14
and 16, on the inner and outer side respectively. All the holes are preferably oriented
upwards and particularly those indicated by 12 and 14, on confronting surfaces, are
directed one against the other so as to produce converging gas flows, thus meeting
in an intermediate position, substantially along a circumference having its diameter
included between that of the central crown 6 and the inner diameter of the ring 4.
[0011] According to a preferred embodiment of this invention all the holes 12, 14 and 16
are arranged as two series of holes one on top of the other, which are staggered by
the two inner flames in order to make the reciprocal preservation of the flame easier,
in that the lower row of holes, alternating with the upper ones, gives rise to the
so called "pilot light" which ignites and supports the flame on the upper row of holes,
or vice versa.
[0012] It should be noted that the gas flow is directed radially outwards, as already said
before, while the flame spreads inwards starting from the external spark-plug 11.
It should also be noted that by the inner holes 12 the gas has a higher pressure,
consequently their diameter will be smaller than that of the holes 14 and even smaller
compared to the outer holes 16. Moreover to avoid the separation of the flame, which
could take place anyway due to this higher pressure, above said holes 12, along the
periphery of the inner disc 6, a projecting ledge 18 is provided, capable of reducing
this pressure and the occurrence of this phenomenon.
[0013] Always with reference to the figures, it clearly appears that the holes 14 are provided
on limited areas only of the inner periphery of the ring 4, and precisely they are
missing by the radial connections 8, that is by the gas passages 3. Therefore in the
case shown and above illustrated there are three hole areas 14 by the secondary air
inlets 9.
[0014] As far as the outer flame is concerned the relative holes 16, of greater diameter,
are only slightly inclined upwards, while there is a second series of holes 16a below,
of smaller diameter, wherein each hole 16a is preferably vertically aligned with an
upper hole 16 for which it acts as pilot light, as besides is known in prior art.
The secondary air for the outer flame reaches the holes 16 and 16a with no particular
problems, but this is made easier by a preferred shape of the worktop 20, which forms
a raised area 21 on which the burner body 1 is mounted, so that between the latter
and the surrounding top remains a space of some millimeters, suitable to make the
passage of the secondary air easier, especially in the inner part through the ducts
9.
[0015] From what comes before it clearly appears that with a single delivery 10, adjustable
through a single control tap (not shown), the gas flow is adjusted from a minimum
to a maximum always preserving the three concentric flames. The ignition is single
as well by means of a single spark-plug 11 which first of all causes the ignition
of the gas that comes out of the holes 16 of the outer ring 4 and then the gas which
is pushed outwards from the inner holes 12, which in turn spreads the flame to the
as flow, converging with it, coming from the central holes 14. Obviously the thermocouple
13 is single too and controlled by the existence of the outer flame, which presupposes
the presence of the two innermost flame crowns too.
1. An improved gas cooker burner with three concentric flames, comprising a basic distributing
body (1) connected to the outlet (10a) of a gas delivery tube (10), with a flame dividing
member (2) fit to be placed on said distributing body, characterized in that said
body (1) has three radial gas passage areas (3) and three intermediate secondary air
inlet areas (9), said flame divider (2) being formed by two concentric rings (4,6)
connected by three radial members (8) fit to form the cover of the above-mentioned
gas passages (3), with intermediate through apertures (9) for the secondary air, the
inner ring (6) having on its periphery two staggered rows of holes one on top of the
other, as well as staggered are the rows of holes (14) on the confronting surface
formed by the inner periphery of the outer ring (4), whose outer periphery has other
two series of holes (16) one on top of the other, and level with the latter there
is a single spark-plug (11) and a safety thermocouple (13).
2. A burner according to claim 1, characterized in that the diameter of the holes (12,14,16)
is increasing from the inner crown to the outer one, all said holes having an upwards
inclination in the direction of the gas flow, so that the two confronting series of
holes 12 and 14 give rise to converging gas flows which intersect in an intermediate
position, substantially along a circumference having its diameter included between
that of the central crown (6) and the inner diameter of the ring (4).
3. A burner according to claim 1 or 2, characterized in that it has, all around the central
crown (6), a projecting ledge (18) to reduce the pressure of the outcoming gas.
4. A burner according to any of the preceding claims, characterized in that said intermediate
holes (14) on the inner periphery of said ring (4) are present by said secondary air
passages (9) only, missing in the connection areas of said members (8) which cover
the gas passages (3).
5. A burner according to any of the preceding claims, characterized in that the gas delivery
tube (10) ends up in the burner body (1) through a central hole (5) of the latter
coaxial with its outlet (10a), communicating with said passages (3) and the flow it
feeds is controlled by a single control tap, whereby the presence of the flame is
assured on all three series of holes (12,14,16) even in case of reduced delivery.
6. A burner according to claim 5, characterized in that said coaxial connection between
the outlet (10a) of the delivery tube (10) and the central hole (5) of the distributing
body (1) is carried out in a raised area (21) of the worktop (20) surrounding said
burner, so that the latter remains raised some millimeters from said worktop (20)
making easier the adduction of the secondary air both to said outer holes (16) and,
through said internal passages (9), to the inner ones (12,14).