In this type of burner ignition means is normally provided to cause the ignition of the mixture at one of the burner elements, the flames generated by the ignition of said mixture then have to spread to the other burner elements to obtain complete and regular ignition of the burner.

In the prior art, burners of this type are known in which propagation of the flame is obtained by means of turbulence generators means that causes a turbulence of the mixture escaping from the slits of the different bladed elements. This turbulence causes a part of this mixture to expand laterally at the outlet of said slits, thus facilitating the propagation of the flame at ignition.

This turbulence generating means is, however, of limited effectiveness, in particular when the speed of escape of the mixture from the slits is high.

The object of the present invention is to eliminate the drawbacks indicated above and to provide a burner of the type mentioned at the start in which mutual ignition between the burner elements is made more reliable, i. e. propagation of the flame between the different elements, at the moment of the ignition of the burner.

According to the present invention, a burner of the so-called "bladed"type is provided consisting of a plurality of burner elements of the"bladed"type supplied by a mixture of air and gas fuel, each burner element being provided with a respective diffuser in which openings are made for the escape of said mixture, said openings being arranged in such a way that said mixture escapes from them in a direction that is substantially

perpendicular to the surface of the diffuser, characterised in that in the diffuser of each burner element further openings are made arranged in such a way that the flow of the mixture that escapes from said further openings is directed in a direction substantially parallel to the surface of the diffuser.

This flow of mixture directed in a direction substantially parallel to the surface of the diffuser makes sure that when the mixture is ignited, at one of the burner elements, the flame caused by the ignition of the mixture easily extends to the other elements, thus ensuring rapid and reliable ignition of the burner.

Other embodiments of the invention will be disclosed below by way of non-limiting example, with reference to the attached drawings, in which: Figure 1 is a perspective view of a bladed burner element according to the prior art; Figure 2 is a view of the burner element in Figure 1, without the diffuser; Figure 3 is a perspective view of a first embodiment of a bladed burner element according to the invention; Figure 4 is a view of the burner element in Figure 3, without the diffuser; Figure 5 is an enlarged detail of Figure 3 ; Figure 6 is a view like the one in Figure 4 relating to a version of the burner element according to the invention; Figure 7 is a perspective view of a version of the diffuser of a burner element according to the invention; Figure 8 is an enlarged detail of Figure 7 ; Figure 9 is a perspective view of a further version of the diffuser of a burner element according to the invention ; Figure 10 is an enlarged detail of Figure 9 ; Figure 11 is a perspective view of a pair of burner elements assembled together in a burner according to the invention.

Figure 1 shows a burner element 1 according to the prior art, provided with a body 2 consisting of two opposite half shells, substantially symmetrical to one another, between which a Venturi 3 pipe is arranged, provided with an inlet port 4 through which a mixture of fuel and air is delivered. In the top part of the body 1, between the two half shells, a distribution chamber (not visible in the Figure) of said mixture of air and fuel is defined. The distribution chamber communicates at the top with the head 5 of the burner. The head 5 of the burner is closed at the top by a diffuser 6 in which openings 7 are made, for example in the form of slits for the escape and subsequent combustion of said mixture of fuel and air.

The head 5 of the burner comprises a central passage 8, open to the diffuser 6, and two side passages 8a, 8b, located at the ends of the central passage 8 and which are also open towards the diffuser 6, through which the mixture coming from the distribution chamber reaches the slits 7 of the diffuser 6.

On the sides of said central passage 8, side holes 9 are made to distribute the flow of mixture coming from the distribution chamber to the slits 7 of the diffuser 6.

Figure 3 shows a bladed burner element 10 according to the invention in which, in the head 5 of the burner, between the central passage 8 and at least one of the side passages, for example the side passage 8a, a further opening 11 is made, communicating with said distribution chamber.

On the diffuser 6 of the bladed burner element 10, at said further opening 11, at least one elongated slit 12 is made, preferably two elongated slits 12, having a length greater than that of the other vents 7 of the diffuser 6 and also extending on the sides of the diffuser 6.

The mixture coming from the distribution chamber passing through said further opening 11 reaches the elongated slits 12

and escapes from them by moving not only upwards but also sideways, in such a way as to interfere with the flow of mixture escaping from the corresponding elongated slits 12 of the adjacent elements 10 of the bladed burner.

In this way, when the mixture is ignited at one of the elements 10 of the burner, for example one of the end elements 10, the interference of the mixture escaping from the elongated slits 12 of adjacent elements 10 causes easy propagation of the flame between the elements 10 of the burner and rapid and reliable ignition of all the elements 10.

Figure 6 shows a version lla of the bladed burner element, in which the flow of mixture intended for the elongated slits 12, comes from one of the pairs of holes 9 made in the respective opposite sides of the central passage 8. To encourage the flow of the mixture to the elongated slits 12 there is provided a closing element 13 of the passage 8, at said pair of holes 9, in such a way as to force. the mixture that reaches the zone of the central passage 8 affected by said pair of holes 9 to escape exclusively through said pair of holes 9.

Figures 7 and 8 show a version of a diffuser 6 of a bladed burner element according to the invention, in which, instead of the pair of elongated slits 12 two pairs 14,14a of slits are provided, one end of which extends on a respective side of the diffuser 6.

Figures 9 and 10 illustrate a further'version of a diffuser 6 of a bladed burner element according to the invention, in which, at a pair of elongated slits 7 located near an end of the diffuser, pairs of holes 15 are made on opposite side walls of the diffuser 6 through which a flow of mixture flows that is directed sideways to interfere with corresponding mixture flows escaping from the corresponding holes 15 of adjacent burner elements, thereby making the mutual ignition between the different burner elements fast and reliable.

Figure 11 shows, by way of example only, the assembly of a plurality of burner elements to make a bladed burner according to the invention.

In the practical embodiment, the materials, the dimensions and the constructional details may be different from those indicated but be technically equivalent to them without falling outside the legal scope of the present invention.