Description

Technical Field

[1] The invention relates to the field of premix gas burners, more particularly to surface stabilized premix gas burners comprising a woven wire mesh as burner deck.

Background Art

[2] Surface stabilized premix gas burner having a woven wire mesh burner deck are known.

[3] US5474443A discloses a premix gas burner with a hemispherical burner deck out of a woven wire mesh.

[4] US2005/172915 shows a premix gas burner having a woven wire mesh combustion surface comprising rigidizing ribs.

Disclosure of Invention

[5] The first aspect of the invention is a premix gas burner comprising a metal mounting plate and a burner deck. The metal mounting plate comprises a plain section for mounting the burner in a heating appliance. The burner deck comprises - and preferably consists out of - a woven wire mesh onto which the flames are stabilized when the burner is in use. The woven wire mesh comprises a flange at its circumference. Part of the metal wires of the woven wire mesh are welded onto the metal mounting plate within the region of the flange. With part of the metal wires is meant that not all metal wires of the woven wire mesh are welded onto the metal mounting plate. Metal wires that are welded onto the metal mounting plate have a first end provided in a first zone of the flange, and the second end is provided in a second zone of the flange. Ends of the metal wires that are welded onto the metal mounting plate are only welded to the metal mounting plate in the first zone or in the second zone of the flange, not in both zones. It is meant that no metal wire has its both ends welded to the metal mounting plate.

[6] The woven wire mesh burner deck of surface stabilized premix gas burners gets hot when the burner is in use. The woven wire mesh burner deck needs to be able to cope with the stresses induced by the thermal expansion associated with the high temperature when the burner is in use and by the shrinkage when the burner cools down. If this is not the case, early mechanical failure or irregular permanent deformation of the burner deck will occur. As metal wires of the woven wire mesh that are welded to the mounting plate are welded to the mounting plate at one of their ends only, the other end of the metal wire is not firmly fixed. Therefore, the other end has a certain degree of freedom to move, which allows the burner deck to cope with the thermal stresses. Not only does the other wire end has a certain degree of freedom to move, but as a large part of the edges of the woven wire mesh burner deck is not attached via welds; there is a certain degree of movement of the parts of the woven wire mesh edges that are not fixed via welds, enabling the woven wire mesh burner deck to cope in a better way with the thermal stresses. Preferably, the full surface of the burner deck onto which flames are stabilized when the burner is in use, is provided by the woven wire mesh.

Preferably, the woven wire mesh has a thickness between 0.6 and 1 .3 mm. As an example, a woven wire mesh of 0.9 mm thickness can be advantageously used in the invention.

Preferably, the woven wire mesh does not comprise ribs, nor embossments.

Preferably, the flange is provided out of woven wire mesh. More preferably, the flange is an integral part of the woven wire mesh forming the burner deck.

Preferably, less than 10% of the ends of the metal wires of the woven wire mesh are welded onto the metal mounting plate. As in such embodiments less than 10% of the ends of the wires of the woven wire mesh are welded onto the metal mounting plate, it means that less than 20% of the metal wires are welded onto the metal mounting plate. Preferably, the woven wire mesh is bent, such that the flange is provided onto the woven wire mesh. More preferably, the flange is parallel with the plain section of the metal mounting plate. More preferably, the bent angle in the woven wire mesh providing the flange of the woven wire mesh is at least 90°.

In a preferred embodiment, not all metal wires of the woven wire mesh are welded to the metal mounting plate.

Preferably, the burner deck is provided in a convex shape. More preferably the burner deck is provided in a convex shape over the full surface of the burner deck provided for stabilizing the flames.

Preferably, the burner deck has a double curved surface. Where a surface is at a point on it double curved, there is at that point no direction in which the radius of curvature is infinite. As an example, a cylindrical burner is a burner that has a single curved surface, not a double curved surface.

Preferably, the metal mounting plate comprises an opening. The woven wire mesh is inserted through the opening of the metal mounting plate. More preferably, the opening is central to the metal mounting plate.

In a preferred embodiment, the flange surrounds the complete woven wire mesh.

Preferably, the flange of the woven wire mesh is parallel with the plain section of the metal mounting plate.

In a preferred embodiment, the flange is along the circumference of the woven wire mesh split in a plurality of flange segments.

Preferably, the premix gas burner comprises a metal plate structure. At least part of the metal plate structure is perforated. The perforations in the metal plate structure are provided for the premix gas to flow through the perforations before the premix gas flows through the woven wire mesh. Preferably, the metal wires that are welded onto the metal mounting plate within the region of the flange are welded between and onto the metal mounting plate and the metal plate structure.

In a preferred embodiment, the metal mounting plate comprises a first segment; and the metal plate structure comprises a second segment. The first segment of the metal mounting plate is parallel with the second segment of the metal plate structure. Metal wires that are welded onto the metal mounting plate are welded between and onto the first segment of the metal mounting plate and the second segment of the metal plate structure.

In a preferred embodiment, the metal plate structure is attached to a first side of the metal mounting plate; preferably by means of welding. The woven wire mesh is welded onto the metal mounting plate at the other side of the metal mounting plate than the first side.

Preferably, the circumference of the woven wires mesh has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded. More preferably, no ends of metal wires are welded onto the metal mounting plate along the short sides of the rectangular circumference of the woven wire mesh - it is meant that ends of metal wires are only welded onto the metal mounting plate along the long sides of the rectangular circumference of the woven wire mesh. Burners according to such embodiments are preferred as they are better suited to cope with the thermal stresses on the woven wire mesh burner deck.

In a preferred embodiment, metal wires that are welded onto the metal mounting plate are welded at a first side of the metal mounting plate; and the metal plate structure is provided at the other side than the first side of the metal mounting plate.

In a preferred embodiment, the welds welding metal wires onto the metal mounting plate also weld the metal mounting plate to the metal plate structure. Even more preferred is when the metal end is welded onto the metal mounting plate with the metal plate structure in between the metal wire and the metal mounting plate.

Preferably in burners wherein the circumference of the woven wire mesh has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded, the smallest angle between a parallel metal wire set in the woven wire mesh and the length direction of the rectangular circumference of the woven wire mesh is at least 30°, preferably at least 40°; and more preferably equal to 45°. A woven wire mesh contains two orthogonal sets of parallel metal wires. Each of the two sets of parallel metal wires has an angle with length direction of the rectangular circumference of the woven wire mesh. These angles depend on how the woven wire mesh is positioned with respect to the length direction of the rectangular circumference of the woven wire mesh. When one of the metal wire sets is parallel with the length direction of the rectangular circumference of the woven wire mesh, it means that the smallest angle between that parallel metal wire set in the woven wire mesh and the length direction of the rectangular circumference of the woven wire mesh equals 0°. By positioning the metal wire sets under an angle different from 0° with respect to the length direction of the rectangular circumference of the woven wire mesh, the smallest angle between a parallel metal wire set in the woven wire mesh and the length direction of the rectangular circumference of the woven wire mesh differs from 0°. Such embodiments provide burners of which the woven wire mesh burner deck is better suited to cope with the thermal stresses. Most preferred is when both orthogonal sets of parallel metal wires of the woven wire mesh have a 45° degree angle with the length direction of the rectangular circumference of the woven wire mesh.

[28] Preferably in embodiments comprising a perforated metal plate structure, all zones of the metal plate structure provided with perforations are provided at a distance from the woven wire mesh. It is meant that no perforation makes contact with the woven wire mesh, but that all perforations are positioned at a distance from the woven wire mesh. Such embodiments provide longer lifetime of the gas premix burner.

[29] In preferred embodiments wherein the metal mounting plate comprises an opening - preferably a central opening - through which the woven wire mesh is inserted, the metal mounting plate comprises an upstanding ridge at the opening through which the woven wire mesh is inserted through the metal mounting plate. The upstanding ridge is oriented in the direction opposite to the flange of the woven wire mesh.

[30] The second aspect of the invention is a condensing boiler comprising a premix gas

burner as in any embodiment of the first aspect of the invention. Preferably, the condensing boiler comprises a cast aluminium heat exchanger.

Brief Description of Figures in the Drawings

[31] Figures 1 - 3 show views of a premix gas burner according to the invention.

Figure 4 shows a cross section of another premix gas burner according to the invention. Figure 5 shows a top view of an exemplary premix gas burner with another burner deck arrangement.

Mode(s) for Carrying Out the Invention

[32] Figure 1 shows a top view 100 (on the burner deck) of a premix gas burner according to the invention. Figure 2 shows a bottom view 200 of a premix gas burner of figure 1 . Figure 3 shows a cross section 300 along Ill-Ill of figure 1.

[33] The premix gas burner of figures 1 - 3 comprises a metal mounting plate 102 and a woven wire mesh burner deck 104. The woven wire mesh consists out of two orthogonal sets of parallel metal wires 105. The metal mounting plate comprises a plain section for mounting the burner in a heating appliance. The woven wire mesh comprises a continuous flange 106 at its circumference. The flange 106 is provided by bending the woven wire mesh at its circumference. The flange 106 is provided parallel with the plain section of the metal mounting plate.

The circumference of the woven wires mesh burner deck has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded. The burner deck is double curved towards the two short side of the rectangular circumference of the burner deck. One set of the parallel metal wires in the woven wire mesh is aligned with the length direction of the rectangular circumference of the burner deck.

The woven wire mesh burner deck 104 is inserted through a central opening 108 in the metal mounting plate 102. The central opening 108 is also provided for the supply of premix gas to the burner. The metal mounting plate comprises a ridge 1 10 at the opening through which the woven wire mesh is inserted through the metal mounting plate. The ridge runs around the full circumference of the burner deck.

The premix gas burner comprises a metal plate structure 1 12. Part of the metal plate structure is perforated. The perforations 1 14 in the metal plate structure are provided for the premix gas to flow through the perforations before the premix gas flows through the woven wire mesh. All zones of the metal plate structure provided with perforations are provided at a distance from the woven wire mesh.

The metal mounting plate 102 comprises a first segment 1 16, which is planar. The metal plate structure 1 12 comprises a flange 1 18, parallel with the first segment 1 16 of the metal mounting plate. The flange 106 of the burner deck is positioned in between and in contact with the first segment of the metal mounting plate and the flange 1 18 of the metal plate structure. Welds 120 are made attaching the first segment 1 16 of the metal mounting plate to the flange 1 18 of the metal plate structure, with the flange of the burner deck in between the metal mounting plate and the metal plate structure. Because of the arrangement of the welds 120, less than 20% of the metal wires of the woven wire mesh are welded onto the metal mounting plate within the region of the flange of the burner deck and onto the flange of the metal plate structure. Metal 122 wires that are welded onto the metal mounting plate 102 have a first end provided in a first zone 128 of the flange of the burner deck, and the second end is provided in a second zone 130 of the flange of the burner deck. Ends of the metal wires 122 that are welded onto the metal mounting plate are only welded to the metal mounting plate in the first zone or in the second zone of the flange, not in both zones. It is meant that no metal wire has its both ends welded to the metal mounting plate. No welds are made along the continuously rounded short sides of the rectangular circumference of the burner deck.

Figure 4 shows a cross section 400 of another premix gas burner according to the invention. The premix gas burner of figure 4 is to a large extent similar to the premix gas burner shown in figures 1-3. Same reference numbers have the same meaning as in figures 1-3. In the burner of figure 4, the metal plate structure 1 12 is attached to a first side of the metal mounting plate 102, e.g. by means of welds 132. The woven wire mesh 104 is welded (by means of welds 121 ) onto the metal mounting plate at the other side of the metal mounting plate than the first side.

Figure 5 shows a top view 500 of an exemplary premix gas burner with another burner deck arrangement than in the burner of figures 1 - 4. Reference numbers have the same meaning as in the burner of figures 1 - 3. In the burner of figure 5, the woven wire mesh 104 is provided in the burner such that the angle a between the metal wire sets of the woven wire mesh and the length direction of the rectangular circumference of the woven wire mesh is equal to 45°. Welds 120 are again arranged such that no metal wire has its both ends welded to the metal mounting plate.