The invention relates to a burner, particularly a burner for industrial ovens of the non- regenerative type, such as ceramic ovens, ovens for firing tableware, ovens for firing sanitary fixtures, ovens for bricks.

In the prior art, burners for industrial ovens are known comprising a burner body inside which a combustion chamber is defined, in which a fuel and air are introduced and mixed and the combustion of the thus formed mixture occurs. The combustion chamber comprises a tubular element that is designed to protrude into the oven.

Burners known from the prior art exhibit an unsatisfactory efficiency since a not negligible part of the heat produced by the combustion of the air and fuel mixture is arranged to heat the air composing the mixture, which is introduced into the combustion chamber substantially at room temperature. This produces a flame temperature that is noticeably lower than the temperature theoretically obtainable, with a consequent decrease of the amount of heat that can be exchanged with the material to be heated within the oven, or a greater consumption of fuel to reach a preset flame temperature.

In order to improve the efficiency of the burner, burners are also known in the prior art in which the air is preheated before being introduced into the combustion chamber. For example, this can be obtained by arranging in the burner at least one passage interspace of the air adjacent to the combustion chamber in such a manner that the higher temperatures of the latter heat by conduction the air passing through the interspace. Consequently, the air has a higher temperature when it is introduced into the combustion chamber. By way of example, a burner of this type is disclosed in international patent application WO2007/113186, of the same applicant.

These burners has an efficiency certainly higher than the burners of known type disclosed above, for example they are about 16% higher, as disclosed in WO2007/113186.

Nevertheless, it is clear that it would be desirable to have even greater burner efficiency. One drawback of burners with the air preheating disclosed above is that they do not enable the efficiency of the burner to be increased by more than a certain value.

The amount of air preheating depends in this case on both the extent and thickness of the heat exchange wall, i.e. the wall interposed between the combustion chamber and the passage interspace of the air that is adjacent to the combustion chamber, and to the thermal gradient between the combustion chamber and the interspace. It is thus clear that there are structural and functional constraints that do not enable the dimensions and the thickness of the heat exchange wall and the temperatures of the combustion chamber and of the interspace travelled by the air to be altered at will in order to obtain the greatest possible efficiency. Thus in these burners, the obtainable efficiency increase is limited and cannot exceed a certain limit value.

Alternatively, the prior art further comprises so-called "regenerative" burners, because in such burners the air is preheated owing to the heat exchange with smoke or gas that are generated during operation of the oven with which the burner is associated. In this type of burner there is a conduit that is arranged for being travelled by the aforesaid hot smoke. The conduit typically surrounds the combustion chamber and is surrounded by the conduits through which the air travels that is directed to the combustion chamber.

Preheating of the air by the hot smoke causes the regenerative burners to have high efficiency.

Examples of this type of burner are disclosed by JP 2009168309, JPS 280309 and JP 201 1 185468.

One drawback of these burners is that they are associable only with ovens having a structure that is compatible and specifically designed to receive regenerative burners. For example, the structure has to provide smoke evacuating chimneys that are used for preheating the air, typically one chimney for each burner.

Consequently, these burners require an oven having a more complex and bulkier structure in terms of plant.

Another drawback is that regenerative burners, and the ovens arranged for receiving them, are much more costly than conventional prior-art burners (and ovens).

Further, regenerative burners cannot be used in an oven in place of other types of burner because, as said, they need a structure that is compatible and specifically designed to receive regenerative burners.

One object of the present invention is to further improve the efficiency of a burner for industrial ovens.

Another object of the present invention is to increase significantly the efficiency of a burner for industrial ovens.

A further object of the present invention is to increase the quantity of heat that can be exchanged with the material to be heated inside the oven.

According to the present invention, a burner is provided as defined in claim 1. The invention can be better understood and implemented with reference to the attached drawings, which show one embodiment by way of non-limiting example, in which:

Figure 1 is a perspective view of a burner according to the invention, a portion of which has been removed to make an internal part thereof visible.

Figure 2 is a front view of the burner of Figure 1 ;

Figure 3 is a longitudinal section of the burner of Figure 1 , taken along the section plane

III- III of Figure 2;

Figure 4 is a longitudinal section of the burner of Figure 1 , taken along the section plane

IV- IV of Figure 3;

Figure 5 is an enlarged detail of Figure 4;

Figure 6 is a section view in which the burner, sectioned as in Figure 3, is mounted inside a wall of an industrial oven.

With reference to Figures, with 1 a burner is indicated overall that is associable with an industrial oven (not shown). In particular, with 1 a burner of non-regenerative type is indicated.

The burner 1 comprises a burner body 2 provided with a flange F for fixing to the wall of an oven.

The burner 1 further comprises a combustion chamber 3 in which a fuel and air are introduced. In the combustion chamber 3 a plurality of openings 11 are made that enable air to enter inside the combustion chamber 3. The fuel is a suitable fuel that is typically used in this type of industrial oven. It can be either a liquid and a gaseous fuel, for example, liquefied petroleum gas, or methane or diesel.

In the combustion chamber 3 an end zone 3 a is defined, which is the zone where the mixture of air and fuel is formed and in which combustion actually occurs.

The burner 1 comprises first introducing means 13 arranged for introducing the fuel into the combustion chamber 3.

The burner 1 further comprises second introducing means 10 for introducing the air into the body 2 through an opening 9 of the body.

The burner 1 comprises protruding means 15 that extends from the body 2 and is intended for projecting towards the oven (in particular towards a firing chamber C thereof), when the burner 1 is inserted into a through hole 27 in the wall 28 of the oven. An outer wall 16 of the protruding means 15 is intended to be arranged adjacent to a hot wall 26 of the oven, which consists of the internal surface of the through hole 27 made in the wall 28 of the oven and arranged for receiving, in use, the burner 1. The wall of the oven 28 is configured for insulating the oven and thus avoiding heat dispersion to the exterior. For this purpose, the wall 28, which separates the firing chamber C from the external environment A, has a suitable thickness s. The latter is sized in such a manner as to ensure appropriate thermal insulation of the oven, without increasing the weight and manufacturing cost thereof excessively.

The burner 1 comprises passage interspace means 6, 7 that define a path for the air extending from the opening 9 to the combustion chamber 3. The passage interspace means 6, 7 is made in the protruding means 15 in such a manner that at least one portion 6 (first interspace) of the passage interspace means 6, 7 is adjacent to the outer wall 16. In particular, the outer wall 16 can also contact the hot wall 26.

When the burner is inserted into the through hole 27, the outer wall 16 can be extended near the hot wall 26 for a length that is equal to at least one third of the thickness s. In particular, the outer wall 16 can be extended near the hot wall 26 for a length that is equal to about half the thickness s.

It is clear that the temperature of the hot wall 26 decreases moving away from the firing chamber C. Typically, a first face 29 of the wall 28 of the oven that faces the firing chamber C reaches very high temperatures, for example also above 1200 °C, whereas a second face 30 of the wall 28 that faces the external environment A can have temperatures of a few dozen degrees Celsius.

Experimental measurements have established that the zone of the hot wall 26 at the end of the protruding means 15 (the innermost end of the through hole 27) has a high temperature that can even reach about 60-70 % of the temperature value of the first face 29. In other words, in this zone of the hot wall 26 temperatures above 750 °C are reached. The protruding means 15 comprises an external hollow tubular element 17 and an internal hollow tubular element 18, both fixed to the body 2 and positioned so as to surround the combustion chamber 3. The outer wall 16 is the wall of the external hollow tubular element 17 facing the hot wall 26, when the burner 1 is inserted into the through hole 27. The protruding means 15 comprises an internal wall 25 that can be substantially parallel to the outer wall 16. The internal wall 25 surrounds, at least partially, the combustion chamber 3 and is adjacent to the combustion chamber 3.

Between the internal wall 25 and the combustion chamber 3 a heat exchange chamber 31 is defined. It should be noted that a portion 7 (second interspace) of the passage interspace means 6, 7 is adjacent to the internal wall 25.

The heat exchange chamber 31 has an open end 32. In use, the open end 32 is intended to face the firing chamber C.

The heat exchange chamber 31 further has a closed end 33, on the opposite side to the open end 32, i.e. near a cover 19 that closes a rear side of the body 2.

In use, the heat exchange chamber 31 is intended for receiving high temperature heat transmitting means that can yield heat by conduction and/or radiation to the surrounding environment. In particular, the heat exchange chamber 31 can be filled with smoke produced by firing (for example ceramic tiles), steam, or in general high-temperature gas that may originate during operation of the oven. For example, the heat transmitting means may even reach temperatures of several hundred degrees.

The closed end 33 of the heat exchange chamber 31 prevents the flow connection between the heat exchange chamber 31 and at least the passage interspace means 6, 7. In other words, the closed end 33 prevents the heat transmitting means (smoke, steam, gas) from leaving the heat exchange chamber 31.

In use, the heat exchange chamber 31 is filled with the heat transmitting means (smoke, steam, gas) that, being of a high temperature, yield heat, in particular by conduction and/or radiation, to the internal wall 25 and thus to the passage interspace means 6, 7 (in particular to the second interspace 7 adjacent to the heat exchange chamber 31).

In the illustrated embodiment, sealing means 34 is provided at the closed end 33 of the heat exchange chamber 31 that acts as closing means of the heat exchange chamber 31. In other embodiments, which are not shown, it is understood that the closing means of the heat exchange chamber can comprise elements differing from the aforesaid sealing means, but equivalent thereto, such as, for example, a bush or a suitably shaped sheet- metal element.

The external hollow tubular element 17 is fixed to the body 2 at the flange F.

The internal hollow tubular element 18 is on the other hand fixed to the body 2 at the cover 19.

The internal hollow tubular element 18 has a plurality of fins 20 that define a spiral path that is arranged for guiding the air travelling from the opening 9 to the passage interspace means 6, 7. Further, in use, the walls of the fins 20 are heated by conduction and thus have the auxiliary function of preheating the air introduced into the body 2 by the second introducing means 10 before it reaches the passage interspace means 6, 7. Further, by travelling along the spiral path the air absorbs heat from the body 2 of the burner, cooling the burner.

The external hollow tubular element 17 and the internal hollow tubular element 18 are shaped in such a manner as to penetrate one another for at least part of the length thereof so as to define the passage interspace means 6, 7. In practice, for part of the length, the tubular elements 17 and 18 are shaped as concentric cylinders. In particular, the outer wall 16 and the internal wall 25 have the shape of concentric cylinders and define together an annular space into which the internal hollow tubular element 18 is intended to be inserted.

The passage interspace means 6, 7 comprises a first interspace 6 and a second interspace 7 that extend respectively annularly respectively outside and inside of the internal hollow tubular element 18. In other words, the interspaces 6 and 7 are annular interspaces defined between the tubular elements 17 and 18, the first interspace 6 being outside the second interspace 7.

The first interspace 6 and the second interspace 7 are connected by an annular passage 8. The burner 1 comprises a distributing element 12 that projects from the cover 19 inside the combustion chamber 3 to support the first introducing means 13 and ignition means 14. The latter is arranged for causing combustion of the mixture formed by air and fuel in the combustion chamber 3.

In the distributing element 12 a further plurality of openings 1 1a is made, arranged substantially at the openings 11, that enables the air to enter the distributing element 12. It should be noted that the closed end 33 of the heat exchange chamber 31 prevents the heat transmitting means from even entering the distributing element 12.

The distributing element 12 comprises a bottom wall 22, facing the end zone 3 a and supporting both the first introducing means 13 and the ignition means 14. The first introducing means can be shaped as a nozzle 13 that is substantially aligned on the longitudinal axis of the combustion chamber 3. The fuel is supplied to the nozzle 13 through a conduit 23 that extends outside the burner 1 to be connected to a fuel supply source. The conduit 23 then passes through the cover 19 and is supported by the cover 19 in cooperation with the bottom wall 22. The distributing element 12 is provided with an annular end slit 24, more visible in Figure 5, through which the air inside the distributing element 12 can be introduced into the combustion chamber 3.

In use, air is introduced inside the burner 1 by the second introducing means 10, for example shaped as a conduit.

The air introduced then traverses the opening 9, enters the first interspace 6, passes through the annular opening 8 so as to enter the second interspace 7, from which it then reaches the combustion chamber 3 through the plurality of openings 11. The path of the air from the introducing conduit 10 to the combustion chamber 3 is shown by arrows in Figures 3 and 4.

Once the air has reached the combustion chamber 3, the air flows to the end zone 3 a, partially outside and partially inside the distributing element 12. The air that flows to the end zone 3 a enters the distributing element 12 through the further plurality of openings 1 1a and exits the distributing element 12 through the annular end slit 24.

In the end zone 3 a the air mixes with the fuel so as to form the mixture to be burnt, which is ignited by the ignition means 14.

Whilst travelling along the interspaces 6, 7, the air introduced through the conduit 10 absorbs heat and heats up in such a manner that the temperature thereof at the moment of entry into the combustion chamber 3 is noticeably greater than ambient temperature. Owing to the fact that the first interspace 6 is adjacent to the hot wall 26 and the second interspace 7 is adjacent to the heat exchange chamber 31, the interspaces 6, 7 are heated both by the heat coming from the combustion chamber 3, and by the heat coming from the hot wall 26.

This enables less fuel to be consumed for the same temperature and volumes of smoke introduced into the oven, in addition to a higher flame temperature being obtained that makes the transmission of heat to the products that are present inside the oven more efficient, thus improving the efficiency of the burner.

It is clear that, with respect to the burner disclosed by WO2007/1 13186, the interspaces 6, 7 of the burner 1 according to the invention are heated by two distinct sources of heat (hot combustion smoke and oven), which are both at a high temperature.

On the other hand, in the aforesaid prior-art burner the interspaces were heated only by the heat coming from the combustion chamber through the walls of the chamber. One advantage of the invention is to make a burner available that is extremely efficient, which enables the air that is introduced into the burner to be preheated so as to bring the air to a temperature that is significantly higher than the temperature in prior-art burners, starting from the same temperature of the supplied air entering the burner.

This is obtainable owing to the fact that the air that travels along the interspaces 6 and 7 is both heated through the outer wall 16 (owing to the heat transmitted to the outer wall 16 by the hot wall 26 of the oven) and through the internal wall 25 (owing to the heat transmitted to the internal wall 25 by the heat transmitting means that fills the heat exchange chamber 31).

As disclosed previously, the hot wall 26 of the oven, at the width portion shared with the outer wall 16, reaches high temperatures, even above 750 °C. Further, also the heat transmitting means that fills the heat exchange chamber 31 reaches temperatures equal to several hundreds of degrees.

Thus the fact that the protruding means 15 in which the interspaces 6, 7 are made is arranged adjacent, on one side, to the hot wall 26 of the oven, and, on the other side, to the heat exchange chamber 31, enables the efficiency of the burner to be increased significantly. Consequently, this enables the quantity of heat to be increased that can be exchanged with the material to be heated inside the oven.

Another advantage of a burner according to the invention is thus that of a lower fuel consumption for the same temperature and volumes of smoke introduced into the oven, in addition to a better mixture between air and fuel. This is obtainable because the air enters the combustion chamber at a noticeably higher temperature than in prior-art burners. Variations on and/or additions to what has been disclosed above and/or shown in the attached drawings are further possible.