This invention relates to a gas burner, and particularly but not exclusively to a gas burner for use in domestic heating appliances.

The burner may be of the "premix" type, meaning that all the air required for combustion is mixed with a fuel gas prior to burning.

This invention relates to burners of the type which include a cavity for receiving a gas and air mixture, a cylindrical distributor surrounding the cavity with relatively large through holes therein. A cylindrical flame strip surrounds the distributor, with a plurality of relatively small through holes therein defining flame ports through which the gas and air mixture may pass immediately prior to combustion.

In some instances it is required to provide a restrictor tube which is a tube of a smaller diameter which extends coaxially within the distributor for part of the length thereof. Restrictor tubes can help to alleviate noise in gas burners.

According to one aspect of the present invention there is provided a gas burner, the gas burner including an internal cavity for receiving a gas and air mixture, a distributor in the form of a cylindrical wall surrounding the cavity with a plurality of through holes in the wall, a flame strip in the form of a cylindrical wall coaxially surrounding the distributor, with a plurality of through holes in the wall of the flame strip, an external mounting flange being provided at one end of the cavity, the mounting flange being formed by walls of the distributor and flame strip being turned outwardly at said one end to form annular flanges, with the flanges of the distributor and flame strip being joined together to form the external mounting flange. In one embodiment the outer edge of the flame strip flange is turned inwardly so as to sandwich the outer edge of the distributor flange between the outer edge of the flame strip flange and the remainder of the flame strip flange.

In a further embodiment the outer edge of the distributor flange is turned inwardly so as to sandwich the outer edge of the flame strip flange between the outer edge of the distributor flange and the remainder of the distributor flange.

The burner may also include a restrictor tube in the form of a cylindrical wall coaxially located in the distributor and extending for part of the length thereof from said one end, the wall of the restrictor tube being turned outwardly at said one end to form an annular flange, with the restrictor tube flange being joined to the distributor and flame strip flanges to form the mounting flange.

The restrictor tube flange may be sandwiched with the distributor flange between the flame strip flange and the inwardly turned outer edge thereof.

The flanges may be joined together by mechanical pressing. The flanges may be joined together by welding.

Openings which may be in the form of slots and may be axial or circumferential, may be provided in the walls of any of the flame strip, distributor or restrictor tube at said one end to facilitate formation of the respective flanges.

Openings may be provided in the flame strip wall where it folds over the distributor flange. Openings may be provided in the distributor wall where it folds over the flame strip flange. The burner may also include an end cap at the other end thereof, which end cap closes the flame strip and distributor. The end cap may be mounted on the other end of the flame strip by folding part of the end cap over the end of the flame strip. The distributor and/or flame strip may be formed from shaped sheet metal, and a mechanical join may be provided between ends of the sheet material to form the cylindrical shape.

According to a further aspect of the present invention there is provided a method of forming a gas burner, the method comprising providing a distributor within a flame strip, with each of the distributor and flame strip in the form of a cylinder with an external flange at one end, and joining together the distributor and flame strip flanges to form an external flange for the burner. The burner external flange may be formed by folding an outer part of a one of the external flanges of the flame strip and distributor over the external flange of the other of the flame strip or distributor.

The flame strip and distributor flanges may be joined together by mechanical pressing.

The flame strip and distributor flanges may be joined together by welding. Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:- Fig. 1 is a diagrammatic perspective view of a conventional burner in place within an appliance;

Fig. 2 is a diagrammatic cross sectional side view of a first burner according to the invention;

Fig. 3 is a diagrammatic perspective cut away view of the burner of Fig.

2; Fig. 4 is a diagrammatic perspective more detailed view of part of the burner of Fig. 2; and

Figs. 5, 6 and 7 are similar views respectively to Figs. 2, 3 and 4, but of a second burner according to the invention.

Fig. 1 shows by way of illustration a gas burner 10 located within a heating appliance including a combustion zone 12 and heat exchanger 14. The gas burner 10 includes a cylindrical flame strip 16 with a concentric inner distributor 18, enclosing an internal cavity 20. An end cap 22 is attached to the flame strip 16 and closes one axial end of the gas burner 10. A mounting flange 24 is attached to the other axial end of the flame strip 16 and extends radially outwardly therefrom. The gas burner 10 is attached to a housing 26 via the mounting flange 24. The flame strip is provided with through holes in the form of flame ports

32, just a few of which are shown in Fig. 1 . The flame ports are about 1 mm in diameter, and their centres are about 2 - 3mm apart. The flame ports 32 are arranged evenly over the flame strip 16. The distributor 18 is provided with a regular pattern of larger through holes 28.

In use, a gas and air mixture is passed into the cavity 20 and passes through the holes 28 in the distributor 20, and out through the flame ports 32 and into the combustion zone 12 where burning takes place. The heat thereby produced is utilised via the heat exchanger 14, with the flue products passing out of the unit as indicated by the arrow A. Figs. 2 to 4 show a first gas burner 40 according to the invention. The burner 40 comprises a flame strip 42, with a distributor 44 located therein. A mounting flange 46 is provided at one end of the burner 40, with an end cap 48 at the opposite end. The flame strip 42 comprises a cylindrical wall 50 with a plurality of openings therethrough which are not shown in the drawings. The openings, flame ports, in the flame strip 42 may be in a uniform pattern, or could for instance vary along the length of the flame strip 42. The openings may be circular and/or in the form of slots.

At the one end the wall 50 is turned outwardly to define a flange 52. An outer end 54 of the flange 52 is turned away from the remainder of the flame strip 42 and inwardly, and a plurality of axial slots 56 are provided at the join between the flange 52 and the outer end thereof 54. The axial slots 56 facilitate bending of the flange 52 to provide the outer part 54 parallel thereto. The wall 50 at the other end of the flame strip 42 is turned outwardly and back upon itself to define a lip 58.

The flame strip 42 may be made from a strip of material, and a mechanical joint may be provided at each end of the strip to enable the strip to be formed into the cylinder shown. The mechanical formation may be in the form of a plurality of tabs axially spaced alternately on each end which overlap respectively inside and outside of the cylinder to hold the flame strip in its configuration.

The distributor 44 is again of cylindrical form with through holes 60 formed in a cylindrical wall 62. The end of the wall 62 at the mounting flange 16 end is turned outwardly to define a flange 64 which locates between the flange 52 of the flame strip 42, and outer end 54 thereof to be sandwiched therebetween. The flame strip flange 52 and outer edge 54 are pressed onto the distributor flange 64, to mount the flame strip 42 and distributor 44 together.

The distributor 44 may be formed in a similar fashion to the flame strip 42 from a sheet of metal, with a mechanical fastening to retain the distributor 44 in a cylindrical configuration.

The end cap 48 comprises a shaped piece with an inner portion 66 which locates within the distributor 44 to retain same in a required position. The outer edge of the end cap 48 provides a rim 68 which can be formed to overlap the lip 58 to retain the end cap 48 in place. The outer edge of the end cap 48 may be in the form of a plurality of discrete tabs which can be urged to engage with the lip 58, for instance by spinning.

This therefore provides a gas burner which can be formed purely by mechnical steps and does not require for instance any welding or other joining techniques. This burner also only requires three components, namely the flame strip 42, distributor 44 and end cap 48, with the mounting flange 46 being formed by the flame strip 42 and distributor 44. This can provide a cost saving in material and also during manufacture, in a reduced number of steps involved.

Figs. 5 to 7 show a second burner 70 which is similar to the first burner 40, and similar reference numerals shall be applied. In this instance the burner 70 also includes a restrictor tube 72. The restrictor tube 72 comprises a cylindrical wall 74 substantially without openings therein except at each end thereof. The restrictor tube 72 extends coaxially within the distributor 44 for a little over half the length of the burner 70 from the mounting flange 46. A restrictor tube flange 76 extends from the wall 74 and locates between the distributor flange 64 and the flame strip flange 52 and outer end 54, to be sandwiched together therein.

A line of circumferential slots 78 is provided in the flange 76 towards an inner part thereof to facilitate bending of the material of the restrictor tube 72, and also to permit gas to pass therethrough.

A range of modifications may be made without departing from the scope of the invention. For instance, and particularly where there is no restrictor tube, the distributor flange could sandwich the flame strip flange rather than vice versa. Whilst mechanical fixing together of the flanges has been described above, as an alternative or in addition, the flanges could be welded together.

Other openings or formations could be provided in the walls of any of the flame strip, distributor or restrictor tube to facilitate shaping thereof. Slots or other openings could be provided extending to ends of the material of the flame strip, distributor or restrictor tubes to facilitate forming thereof.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.