Gas burner with improved primary air duct

[0001] The invention relates to a gas burner, preferably of the type generally used in domestic gas kitchen appliances, in particular built-in gas hobs, equipped with an improved means for transferring primary air to the Venturi pipe.

[0002] Under this description, reference is made to a gas burner equipped with both a peripheral flame crown and a peripheral body with two flame crowns, inward and outward, but with the intention that what is explained can be used identically, thus it is also suitable for gas burners equipped only with a peripheral body that is without a central flame body.

[0003] It is known that for this type of gas kitchen appliance there are two main requirements:

- the design requirement and assembly, i.e. a gas kitchen appliance, especially when it is a gas hob, must have a minimum height, due to limitations that are well known to the person skilled in the art, and therefore will not be repeated, and

- a functional requirement that burners, especially burners with a limited diameter, must provide adequate heat output in each case and in each case the maximum possible power.

[0004] These two requirements, however, are clearly contradictory, as the need to limit the overall height of the gas appliance also forces the same height of the Venturi pipes to supply gas to the burners; however, such a restriction also functions as a restriction on the amount of gas / air mixture that can be produced, and thus sets a limit on the heat output of the burner.

[0005] To overcome such mutual conditioning, some kitchen appliances have been proposed and disclosed which are equipped with one or more Venturi pipes that are horizontally routed, as for example in patents WO 2005/078342 and WO 2007/012766.

[0006] It is obvious that due to the horizontal positioning of the Venturi pipes, the problem of their height, which determines the overall height of the kitchen appliance, is automatically eliminated.

[0007] In addition, the two cited patents present the right solutions in which Venturi pipes exit the central zone of the burner and branch radially; therefore their overall length is limited by the radius, i.e. the horizontal size of the burner itself.

[0008] To eliminate this condition, it is proposed, for example in Publication EP 1120603 and in EP Application 07119078.9, a type of burner in which a pipe

Venturi is positioned horizontally across the entire width, i.e. essentially across the diameter of the torch body itself.

[0009] However, the solutions shown have a fairly common disadvantage in this type of burners, i.e. the fact that the primary air is sucked in and sent to the Venturi pipe inlet by only one access route, i.e. either from the internal housing body of the kitchen appliance or from the external space, i.e. from the area above the cooking hob itself.

[0010] Of course, such circumstances limit the total amount of available primary air, and thus limit the available thermal power.

[0011] To increase the primary air inlet stream, it has been proposed to take and transfer the primary air stream through a coaxial and preferably tubular channel whose end batch ends with a gas injection nozzle. [0012] This solution is disclosed, for example, in patents:

a) US 2006/0199119,

b) US 6,951,454,

c) JP 3-244905

d) US 2005/0279862.

[0013] However, none of these patents suggest or disclose all the features of claim 1.

[0014] As an additional prior art document, FR1043707 discloses a gas burner according to the preamble of claim 1, comprising a gas transfer unit, extending horizontally, a flame crown positioned at the burner body and a Venturi tube. The nozzle injects a gas stream into this Venturi pipe. Means for providing primary air suction are included having a first end and a second inlet path, the first inlet path being defined by an annular space, the second inlet path having a through hole partly positioned downstream of the nozzle and upstream of the Venturi tube.

[0015] US-A-5 567 148 discloses a gaseous fuel burner that includes a supply pipe formed with a supply opening at one end surrounded by sucker blades. The burner has a Venturi member with a reduced diameter area entering the burner inlet. Suction blades frictionally engage with the venturi throat region.

[0016] It would therefore be desirable and actually the main purpose of the invention to implement a type of burner equipped with two different and separate inlet paths for primary air streams into a Venturi pipe, formed by a channel that is coaxial with the gas channel, and through an opening or inlet located behind a gas injection nozzle, where these access routes are independently filled with air taken from the inside of the kitchen appliance housing body, and from the external space above it, which burner will provide an improved gas and air mixture.

[0017] However, such an objective proves to be advantageous not only for gas channels and associated Venturi pipes in a horizontal arrangement, where the benefits are more obvious, but also for kitchen appliances equipped with gas channels and Venturi pipes that are arranged vertically, even if several disadvantages due to the height of the kitchen appliance can be experienced, however, the same benefits are achieved due to the double intake of primary air, i.e. from the inside of the kitchen appliance body and from the external space above it.

[0018] According to the invention, this and further objects are achieved by means of a type of burner equipped with a Venturi pipe that can run horizontally or vertically, which is provided by means of connecting and inlet channels for the primary air stream, including the features listed in the appended claims and including such measures as described below by way of example with reference to the attached drawings, of which:

- Fig. 1 is a perspective view from the outside of the burner body of a suitable gas cooking appliance, here represented by a gas hob, according to a first embodiment of the invention,

- Fig. 2 is an exploded view of the kitchen burner shown in Fig. 1,

- Fig. 3 shows a vertical and side section according to section A-A of the assembly of Fig. 1,

- Fig. 3A shows a cross-sectional view that is perpendicular to the X axis of the gas channel, a detail of the burner assembly of Fig. 3,

- Fig. 4 shows a vertical and side section according to section A-A of another embodiment of the assembly of Fig. 1,

- Fig. 4A is a cross-sectional view that is perpendicular to the X axis of the gas channel, a detail of the burner assembly of Fig. 4,

- Figures 5 and 6 show perspective views of the details shown in figures 3A and 4A, respectively,

- Fig. 7 is a view that is equivalent to Fig. 4, but refers to a kitchen appliance equipped with a gas channel and a Venturi pipe that are arranged vertically.

[0019] With reference to figures 1 to 4, a kitchen appliance according to the invention comprises:

- gas supply channel 1, horizontal,

- burner body 2, on which one or more flame crowns 3B, 3C ... are mounted,

- a Venturi pipe 4, which is also oriented in a horizontal direction, and is substantially aligned with the end part of this channel 1,

- a gas injection nozzle 5 at the end of this channel 1 towards the venturi tube 4.

[0020] The primary air is transferred towards the nozzle 5 and to the Venturi pipe by two different flow paths, i.e.

- the first tract consists of a stream of suction air, which begins inside the kitchen appliance body, and which in its end part takes the form of a channel 6 coaxial with the first gas channel 1, preferably having a tubular shape, and which surrounds it at least in the end part; therefore, between this gas channel 1 and the coaxial channel 6, an extended annular space 7 is formed in which part of the primary air sucked in by the Venturi pipe flows.

As not clearly shown in the figures, the coaxial channel 6 extends towards the venturi pipe 4 to which it is connected via the corresponding extension 9; in fact, it can be seen that the Venturi tube is merely a suitably shaped continuation of this extension 9, which extends forward to the other side of the injector 5;

- the second route consists of a duct 13, the suction opening of which opens from the upper plane 12, and in its end part there is a through hole 8, preferably located on the side of the extension 9, just behind the injector 5 and in front of the Venturi pipe 4.

[0021] The through hole 8 therefore allows the primary air stream to flow from the outer space towards the Venturi pipe 4, thus achieving the first object of the invention, i.e. inducing primary air intake by splitting the entire stream into two separate streams, one of which is positioned above the upper plane 12, and the other is transferred from the interior of the kitchen appliance, and which at its final section enters the channel, which is coaxial to the gas channel.

[0022] The solution just described allows for several advantageous improvements;

the first improvement is that - as shown in figures 3 and 4 - the coaxial duct 6 extracts the corresponding primary air stream directly from the internal volume delimited by the body 34 of the kitchen appliance housing, while the opening 8 is connected to the external space, and exactly from above upper surface.

[0023] This circumstance promotes better air flow in case the kitchen appliance is placed in the wrong place in such a way that the air circulation is blocked or released; in addition, the two primary air streams thus transmitted do not interfere with any operating conditions.

[0024] Furthermore, it is preferred that the opening 8 is located upwards in this extension 9 to shorten and straighten the tract of this part of the primary air stream coming from the kitchen appliance.

[0025] This solution is suitable to suit the temperature rise; as heating from the burner reduces the primary air density, it is important to improve the primary air flow to avoid weakening the burner functionality (combustion efficiency, yellow end formation and soot).

[0026] To improve the mixture of gas and primary air, it has proved useful to set some of the means that may cause turbulence in the gas flow when exiting from channel 1, such that the gas stream itself is interrupted and thus more easily mixed with the primary air stream.

[0027] It has then been found to be advantageous to arrange some appropriate means that can create turbulence in the air passing through the space 7 so that the air coming out of it, and actually from the coaxial channel 6, is soon mixed in both the gas coming out of channel 1 and in primary air stream coming out of the opening 8.

[0028] Such a complete and fast mixing effect with both the gas and the primary air stream obviously causes the mixture itself to be optimized, which increases the combustion efficiency.

[0029] To this end, several mixing blades 10 are arranged inside the space 7 and on the outer surface 11 of the gas channel; according to the turbulence effect that is desired, as well as the diameter of the coaxial channel itself, the following two embodiments have been proposed:

- in the first embodiment and with reference to figures 3 and 3A, the blades 10 are flat, preferably pass along the X axis of the gas channel 1, are radially directed on the outer surface of the gas channel 1, are regularly spaced at the same angular distance from each other, and preferably they are quite elongated to extend the entire length of the coaxial channel 6.

- in the second embodiment and with reference to figures 4 and 4A, the blades 10A are bent and specifically arranged in a helical arrangement as a screw thread, the inner edge of which is still attached to the outer surface of the gas channel 1; the blades 10A are also regularly spaced at the same angular distance, and are preferably sufficiently elongated to extend over the entire length of the coaxial channel 6.

[0030] These two improved embodiments just described are of course helpful in creating a kitchen appliance that is particularly effective not only in terms of providing thermal power, but also which is small in size and particularly cheap and simple to build; in addition, the invention also gains in value due to the advantage that the nozzle can be replaced without opening the device, as this operation can be carried out through the opening 8.

[0031] As just described, the shown embodiments can be implemented through a gas channel and a Venturi tube that are horizontally oriented as shown in figures 2, 3 and 4; however, as previously recalled, the invention can also be made by positioning the gas channel and the corresponding Venturi pipe in a vertical orientation as schematically shown in Fig. 7.

[0032] In this case, it was proved that the most suitable embodiment, both in terms of functionality and construction, was proposed by Fig. 7, in which the Venturi pipe is substantially separated from the coaxial channel 6 (unlike Fig. 4, in which the devices are connected with each other by means of an extension 9).

[0033] Therefore, the outlet opening of the channel 6 is completely open, and thus the air flow path coming from outside and sucked into the channel 13, intersects the opening 20 exhibiting a generally cylindrical or frustoconical shape, running horizontally through 360 ° and connecting the opening outlet 6A of the coaxial duct with the inlet opening 4B of the Venturi pipe 4.

[0034] In addition, and preferably, the same upper plane 12 also forms the bottom wall of the channel 13 through which primary air is sucked into the second route and passed to the opening 8.

[0035] Thus, the inlet 14 of the channel 13 is then opened just above the upper plane 12; furthermore, according to the opening 14, the surface 12 adopts a convex profile 15, so that accidental ingress of liquid and food residues into the channel 13 is prevented; preferably the convex profile 15 can easily be obtained by proper pressing / bending operation of the upper plane 12 itself.