GB2270972A - Gas fire burner - Google Patents

Abstract

A burner assembly has a heat-resistant ceramic layer 10 superimposed on the top wall 2 of a metal burner box 1. The ceramic layer 10 includes an array of burner apertures 11, which are coincident with an array of apertures 12 in the metal wall 2. Each of the apertures 12 is surrounded by a raised wall 14, which either projects into the corresponding aperture 11 of the ceramic layer or projects into the ceramic layer surrounding the respective aperture 11. A further heat resistant layer 18, a stainless steel mesh, is secured to the underside of the wall 2 to cover the apertures 12. <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 Burners for use in decorative gas fires are often formed of sheet metal which is covered by a layer of heat-resistant material, usually ceramic, to increase the life of the burner. The ceramic layer protects the surface of the metal from the effects of heat which is radiated back from the flames and imitation fuel bed on top of the burner.

One major problem with this arrangement is that the ceramic layer must be very effectively sealed to the metal layer in order to prevent leakage of un-burnt gases between the two layers. Such leakage, if it occurs, can result in the following problems: (a) The combustion of gases in areas where the air content is not controlled can result in an increase in the carbon monoxide content of the combustion products.

This could cause the appliance to fail the European Safety Standard for combustion.

(b) The escape of un-burnt gases into the spaces beneath the imitation fuel bed can cause the gases to accumulate until they ignite momentarily, causing popping noises as the gases continually light and extinguish themselves.

(c) The combustion of escaping gases in unwanted areas can cause other parts of the appliance to over-heat and fail prematurely.

In an attempt to overcome these difficulties, the ceramic layer is often secured to the underlying metal by an arrangement of clamps and/or the use of sealants.

Generally, silicon or ceramic adhesive sealants are used, and although these can give good service they tend to be costly, and their application can be messy and time consuming. In the long term, this seal is likely to fail. When this occurs, the ceramic layer cannot be removed easily without replacing the whole burner.

An aim of the present invention may be viewed as being to provide a form of burner assembly which is quick and inexpensive to manufacture, is easy and inexpensive to service and repair, and removes the problem of maintaining the long term integrity of a seal.

SUMMARY OF THE INVENTION In the burner assembly which is proposed according to the present invention, a heat-resistant layer is superimposed on a metal layer. The heat-resistant layer includes an array of burner apertures, which are coincident with an array of apertures in the metal layer. Each of the apertures in the second layer is surrounded by a raised wall, which either projects into the corresponding aperture of the heat-resistant layer or projects into the material of the first layer surrounding the respective aperture.

Where the raised wall projects into the aperture of the upper heat-resistant layer, the raised wall tends to act as a nozzle directing the gas/air mixture through the apertures to the combustion area. Thus, even if there is a small gap between the raised wall and the heat-resistant layer (which is undesirable), the risk of leakage of gases between the two layers is eliminated.

On the other hand, if the raised wall is inserted into the material of the upper layer, this in itself eliminates the possibility of gases passing between the two layers.

BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a section through a burner of the invention for use in a decorative gas fire, including an inset detail, and Figure 2 is a similar section to Fig. 1 showing a slightly different form of the burner.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig. 1, the burner assembly includes a sheet metal burner box 1 having a generally flat top wall 2 surrounded by a downwardly extending side wall 3. The lower end of the side wall is outturned to form a mounting flange 4. The space 5 within the burner box 1 forms a combustion chamber for receiving a gas and air mixture in known manner.

A heat-resistant board 10 formed of ceramic fibres is mounted on the top wall 2 of the burner box 1. The board 10 contains an array of burner apertures 11, typically between 5mm and 20mm in diameter. These apertures 11 are formed to coincide with a similar array of burner apertures 12 formed in the top wall 2 of the burner box. Apertures 12 are punched out of the sheet metal so as to form a short upwardly projecting wall 14. By way of example, the ceramic board 10 will usually be at least lOmm thick, and the upstanding walls 14 will usually be between 2mm and 6mm high.

When the heat-resistant board 10 is placed onto the burner box 1 as shown, the walls 14 are pressed into the burner apertures 11 of the ceramic board, thereby providing positive engagement of the board 10 on the burner box 1. Normally, the board 10 will also be secured to the burner box, e.g by metal clamps 16 arranged around the periphery of the board 10 to press the board flat against the top wall 2 of the burner As shown in the inset detail of Fig. 1, the upper margins of the upstanding walls 14 are brought to a thin edge, e.g 0.2mm to 0.5mm, to assist with entry of the walls 14 into the apertures 11. The internal faces of the walls 14 are substantially parallel with a smooth finish.

A stainless steel mesh 18, e.g having holes between 0.5mm and 1.5mm across, is spot welded or otherwise secured to the lower face of the top wall 2 to cover the burner apertures 12. This prevents the effect known as "back lighting", in which the flames travel back into the burner apertures.

In use of the burner, ceramic bodies which simulate fuel are placed on the top board 10 to be heated by the gases which burn as they leave the apertures 11. The flow of gases into the burner apertures 12 from the combustion chamber 5 creates a negative pressure around the upper region of the walls 14, which confines the flow of gas to an upward path through and out of the apertures 11. Thus, the upstanding walls 14 do not necessarily have to be a tight fit in the apertures 11.

Where smaller burner ports are required, the ceramic board 10 can be formed with smaller diameter apertures 11, as shown in Fig. 2. In this case, the walls 14 penetrate into the material of the board 10 surrounding the apertures 11, assisted by the narrowed leading upper edges of walls 14. This in itself provides an effective sealing engagement between the walls 14 and the ceramic - board 10, preventing escape of gases between the board 10 and the burner box 1. Hence, the size of the burner ports can be changed simply by changing the board 10 and retaining the same burner box 1.

It will be appreciated that although the burner apertures 11, 12 may conveniently be of circular shape, they could equally be formed in any other convenient shape, e.g by suitable stamping or casting operations.

In addition, the mesh 18 could be of any suitable heatresistant material and need not necessarily be continuous between the burner ports, although the burner is easier to construct with a continuous mesh.

It will thus be appreciated that assembly of the present burner is quick and convenient without requiring use of sealants. Servicing of the burner and replacement of the ceramic board 10 are also easier and quicker to achieve.

Claims (7)

1. A burner assembly in which a heat-resistant layer is superimposed on a metal layer, the heatresistant layer including an array of burner apertures which are coincident with an array of apertures in the metal layer, each of the apertures in the metal layer being surrounded by a raised wall which either projects into the corresponding aperture of the heat-resistant layer or projects into the material of the first layer surrounding the respective aperture, and heat-resistant mesh is secured on the underside of the metal layer to cover the apertures therein.

2. A burner assembly according to Claim 1, in which the raised walls reduce in thickness to form a relatively thin top edge.

3. A burner assembly according to Claim 2, in which the inside faces of the raised walls are substantially parallel whereas the outside faces are inclined inwardly to meet the top edges of the raised walls.

4. A burner assembly according to any preceding claim, in which the raised walls are formed by punching the apertures in the metal layer.

5. A burner assembly according to any preceding claim, in which the metal layer is comprised in the top wall of a burner box which contains a combustion chamber.

6. A burner assembly according to any preceding claim, in which the heat-resistant layer comprises ceramic fibres.

7. A burner assembly substantially as described with reference to Figures 1 or 2 of the drawings.