GB2258036A

GB2258036A - Burner for a decorative gas fire

Info

Publication number: GB2258036A
Application number: GB9115877A
Authority: GB
Inventors: Gregory Richard Taylor; Richard Paul Drake
Original assignee: Gazco Ltd
Current assignee: Gazco Ltd
Priority date: 1991-07-23
Filing date: 1991-07-23
Publication date: 1993-01-27
Anticipated expiration: 2011-07-23
Also published as: GB9115877D0; GB2258036B

Abstract

The burner comprises a plaque 17 formed of ceramic fibres and containing an array of burner apertures 18. The plaque is clamped on top of a stainless steel mesh 16 containing numerous relatively small apertures, which prevents back lighting. The burner has a minimum restriction to gas/air flow so that a good flame is produced, and in addition, the mesh has a lower operating temperature so that the life expectancy of the burner is increased. <IMAGE>

Description

GAS FIRE BURNER TECHNICAL FIELD OF THE INVENTION This invention relates to burners for use in gas fires, mainly decorative gas fires.

BACKGROUND Hitherto, decorative gas fires have been designed with aesthetic considerations as the main priority, efficiency and correct combustion being of secondary importance. In order to burn efficiently, the gas must be mixed with air, and the balance between good appearance and good combustion is largely determined by the ratio of gas to air.

Aeration is achieved by a combination of primary and secondary aeration. The secondary aeration takes place after the burner itself, but the primary aeration, which takes place prior to the burner, has the greatest effect upon combustion. Such primary aeration normally takes place in a venturi or mixer tube, and in order for a venturi to work effectively the burner must be free-flowing with as little restriction to flow as possible. The burner must therefore have a large open area for the gas/air mixture to pass through.

In the past, two forms of burner have been employed.

Firstly, metal burners containing numerous small holes have been used, but the surface temperature of the burner tends to be too hot for use in a decorative gas fire. In addition, tooling costs are high, and can be prohibitive where a number of different shapes are required, the range of design possibilities is limited, and the visual effect is poor.

A second form of burner comprises a ceramic plaque containing many small holes, but these are very fragile, and again, tooling costs are high, the range of shapes and sizes is limited, and the visual effect is poor.

An aim of the present invention may be viewed as being to provide a form of burner which gives an aesthetically acceptable flame appearance, has a robust temperature-resistant burner surface, provides a free gas/air flow, and can easily and inexpensively be produced for use in fires of different shapes and sizes.

SUMMARY OF THE INVENTION The present invention proposes a burner for a gas fire, which includes a heat-resistant body containing an array of burner apertures, and in which the burner apertures are covered by a mesh having numerous apertures which are relatively small in relation to the size of the burner apertures.

With such an arrangement the burner apertures can be large enough to provide a virtually unrestricted air flow and thus provide a good flame effect whilst the mesh prevents the effect known as "back lighting" where the flame travels back into a burner aperture. The mesh will usually have little effect on the flow rate.

The mesh is preferably closely applied to the undersurface of the heat-resistant body, upstream of the burner apertures. The heat-resistant body thus tends to shield the mesh from heat so that the temperature of the mesh is much lower than in an all metal burner (typically being reduced from 7000C to 5000C) greatly improving the life expectancy of the burner.

The heat-resistant body preferably comprises a ceramic material. The body may be of the kind known as hard ceramic, but since this is relatively expensive to form the body is preferably of the kind known as soft ceramic which comprises ceramic fibres. In order to shield the area of mesh which is exposed in the burner apertures the heat-resistant body is preferably at least 5mm thick, and is ideally at least lOmm thick.

The burner apertures preferably have a width of between 5 and 20 mm depending upon the type of gas being used.

The burner apertures are preferably spaced apart by at least their own width so that the strength of the heatresistant body is maintained.

The mesh may be of any metal which is capable of operating for prolonged periods at high temperatures.

Stainless steel provides long life combined with a relatively low cost. The apertures of the mesh are preferably between 0.5 and 1.5 mm in width. Below 0.5 mm they tend to restrict flow and above 1.5 mm the risk of back lighting increases. The optimum size will however depend upon the characteristics of the gas being used.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is exemplified in the accompanying drawings, in which: Figure 1 is a section through a decorative gas fire incorporating a burner of the invention, and Figure 2 is an exploded perspective view of part of the burner.

DETAILED DESCRIPTION OF THE DRAWINGS The gas fire comprises a metal casing 1 which defines an aeration chamber 2 disposed beneath a burner chamber 3. Gas from a regulated supply enters the aeration chamber 2 via an inlet pipe 4 and is metered into the chamber by an injector 5. The aeration chamber 2 contains a venturi 6 having an inlet 7 diposed opposite to the injector 5. Air is drawn into the chamber 2 via apertures 8 in its bottom wall, and after travelling over the outside of the venturi 6 enters its inlet 7 along with the gas. The gas and air are forcibly mixed as they travel along the length of the venturi 6.

The outlet end of the venturi passes through the wall of the aeration chamber 2 to feed the gas and air mixture into the burner chamber 3 via a passage 12. A baffle 15 is mounted in the burner chamber 3 opposite the opening of the passage 12, to distribute the gas and air mixture evenly along the length of the chamber.

The top wall of the burner chamber 3 is formed by a burner of the invention, which includes a stainless steel mesh 16. A heat-insulating board 17 formed of ceramic fibres and containing an array of burner apertures 18 is clamped by any suitable means (not shown) onto the top of the mesh 16. By way of example, for normal UK gas supplies the mesh may be formed of 0.7 mm diameter stainless steel wires which are interwoven perpendicularly to form square apertures having a width of 0.7 mm, although it will be appreciated that the size of the mesh can be varied for use with different gases. The board 17 will typically be about 15 mm thick, and the burner apertures can be about 12mm in diameter with a minimum spacing of about 20 mm. Again though, it will be appreciated that the size of the apertures can be varied for different gases and/or sizes of flame.Similarly, the configuration of the array of apertures and their minimum spacing can both be varied to produce different flame distributions. Although the apertures may conveniently be formed of circular shape, e.g. by drilling, they could equally well be of other shapes, for example by stamping or casting operations.

Combustion of the gas/air mixture takes place upon leaving the apertures 18, the mesh 16 serving primarily to prevent back lighting. Ceramic bodies will normally be placed on the burner to be heated by the flames and give off heat energy by radiation. As noted above, the heat-insulating board 17 shields the areas of the mesh between the apertures 18 from the heat energy radiated by the ceramic bodies so that heat is conducted away from the areas of the mesh which are exposed in the burner apertures. In addition, the relative thickness of the board 17 reduces the amount of radiated heat energy to which the areas of mesh disposed in the burner apertures are exposed. As a result, the mesh stays relatively cool.

It should be noted that the mesh 16 need not necessarily be continuous between the burner apertures 18, although the burner would be easier to construct with a continuous mesh.

Claims

1. A burner for a gas fire, which includes a heat-resistant body containing an array of burner apertures, and in which the burner apertures are covered by a mesh having numerous apertures which are relatively small in relation to the size of the burner apertures.

2. A burner according to Claim 1, in which the mesh is closely applied to the undersurface of the heat-resistant body, upstream of the burner apertures.

3. A burner according to Claim 1 or 2, in which the heat-resistant body comprises a ceramic material.

4. A burner according to Claim 3, in which the heat-resistant body comprises ceramic fibres.

5. A burner according to any preceding claim, in which the heat-resistant body is at least 5mm thick.

6. A burner according to Claim 5, in which the heat-resistant body is at least 10 mm thick.

7. A burner according to any preceding claim, in which the burner apertures have a width of between 5 and 20 mm.

8. A burner according to any preceding claim, in which the burner apertures are spaced apart by at least their own width.

9. A burner according to any preceding claim, in which the apertures of the mesh are between 0.5 and 1.5 mm in width.

10. A gas fire burner which is substantially as described with reference to the drawings.

10. A burner according to any preceding claim, in which the mesh is formed of stainless steel.

11. A gas fire burner which is substantially as described with reference to the drawings.

Amendments to the claims have been filed as follows 1. A burner for a gas fire, which includes a heat-resistant body containing an array of burner apertures having a width in the range of 5 mm to 20 mm, and in which each of the burner apertures is covered by a mesh having numerous apertures which are relatively small in relation to the size of the burner apertures.

7. A burner according to any preceding claim, in which the burner apertures are spaced apart by at least their own width.

8. A burner according to any preceding claim, in which the apertures of the mesh are between 0.5 and 1.5 mm in width.

9. A burner according to any preceding claim, in which the mesh is formed of stainless steel.