GB2160642A - Gas fire - Google Patents

Abstract

A gas fire 10 comprising a stack of artificial coals 12 or logs to give the appearance of an open fire, and a gas/air supply means 37,41 which provides two areas of flames, one area comprising a clean hot flame, and the other area a yellow flame. <IMAGE>

Description

SPECIFICATION Gas fire The present invention relates to a gas fire. The invention relates to a gas fire of the type which is commonly referred to as a "feature gas fire" in which gas is fed to a set of artificial logs or coals (which may be simply referred to hereafter as "coals"), made of non-combustive material such as coloured ceramic material, the gas burning through the coals to give the appearance that the coals are themselves burning.

Such fires normally comprise a steel tray into which is fixed a steel gas pipe drilled along its length with a series of small holes and covered with a gas diffusion material such as silica sand or clay granules. The gas, controlled by a gas tap, is let into the pipe, exits through the holes in the steel tube, percolates through the diffusion material and when ignited burns over the surface. This so called "neat gas burner" then relies on secondary air penetrating the ceramic coals or logs placed on the sand diffusion material to a height of at least six inches to partially complete the combustion and heat up the coals to look like a glowing real coal or log fire. Such a burner looks realistic but the gas does not completely combust and burns with a cool, yellow and slightly sooty flame because there is insufficient air supplied to the gas.

Variations have been made on the above by bringing in primary air through the tray to give better combustion and a hotter flame but the problem with this is that gas when burnt properly in this way produces an almost colourless blue flame which of course does not provide a realistic fire.

For many years commercially made gas burners of all types have consisted of a gas/ air mixing tube leading to a burner surface that has been carefully designed to allow sufficient primary and secondary air to reach every gas port, whether the gas port be a hole or slot or any other shape orifice. Thus complete combustion takes place at the burner and the gas burns with a clear blue and very hot flame. Attempts have been made to place such a gas burner below artificial logs or coals and it heats them up so that they glow red hot but no flame is visible and the result is not very realistic.

The present invention provides a gas fire comprising a stack of artificial coals and gas/ air supply means below said stack to pass a gas/air mixture through said stack, said gas/ air supply means being arranged so as to provide a gas/air mixture in one region of the stack which burns with a clear hot flame and a gas air mixture in another region of the stack which burns with a yellow flame.

In a preferred arrangement the gas/air supply means provides a gas/air mixture which burns with a clean hot flame at the front of the stack of artificial coals, and a gas/air mixture which burns with a yellow flame at the rear of the stack of artificial coals.

In this case we may provide a gas fire in which the gas/air supply means comprises two burners, one burner being mounted at the front below a stack of artificial coals and the second burner being mounted at the rear below the stack of artificial coals, the front burner being arranged so as to have an adequate supply of primary and secondary air so that the gas/air mixture burns with a clear hot flame and the second burner being provided with insufficient primary or secondary air so as to burn with a yellow flame.

In another arrangement there may be provided a gas fire in which the gas/air supply means includes a plenum chamber in which gas and primary air is mixed, a generally horizontal plate above the plenum chamber to which the gas and primary air mixture in use is passed from the plenum chamber, and a secondary air supply means being arranged around the periphery of the plate so that above the periphery of the plate the gas/air mixture burns with a clean hot flame and towards the middle of the plate the gas/air mixture burns with a yellow flame. The plate may be solid or may have holes therethrough.

Two preferred arrangements of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic vertical section from front to rear of a first gas fire according to the invention, Figure 2 is a plan view of the gas fire of Fig. 1 with the artificial coals removed, Figure 3 is a view of some of the components of the fire of Fig. 1, Figure 4 is a part plan view of a second gas fire according to the invention, Figure 5 is a perspective view of part of the gas fire of Fig. 4, Figure 6 is a vertical cross section through the part of the fire shown in Fig. 4, Figure 7 is a perspective view of a part of the fire of Fig. 4.

Figure 8 is a vertical section generally corresponding to Fig. 1 of a third gas fire according to the invention, Figure 9 is a front perspective view of the gas fire of Fig. 7, and, Figure 10 is a perspective view of a typical burner for use with the gas fire of Fig. 8.

Referring to Fig. 1 there is illustrated a gas fire 10 mounted within a fireplace 11, artificial coals 1 2 of non-combustible material being mounted on top of the gas fire 10. The coals are supported by a coal support assembly 1 3 illustrated further in Fig. 3. The coal support assembly comprising two side plates 14, 15, front and rear plates 16, 1 7 extending between the side plates 14, 1 5 together with a centrally located bar 18. The front and rear plates 1 6,1 7 each includes a secondary air slot 19, 20 respectively and the end plates 14,15 also include secondary air slots 21, 22.Mounted by means of welding to the rear of the coal support assembly 1 3 (in practice by spot welds along rear plate 17) is a sloping coal support plate 23 (not illustrated in Fig. 3) which is shaped so as to fit neatly within the fireplace 11.

Mounted on legs 26, 27 below the coal support assembly 1 3 is a burner tray 28 comprising a rectangular box having bottom wall 31, side walls 32, 33 and front and rear walls 34, 35. Mounted to the top of the burner tray 28 is a perforated plate 36.

Mounted to the rear wall 35 and passing therethrough is a gas/air mixing tube 37 which supplies a mixture of gas and primary air to the interior of the burner tray 28. Above the inlet from the gas/air mixing tube 37 is mounted a baffle plate 38.

To the upper edge of the rear wall 35 is mounted a rearwardly extending rear area filler tray 39 which, like the sloping coal support plate 23 is shaped ta fit the fireplace 11.

To the rear of the gas/air mixing tube 37 there is mounted a conventional gas jet 41 surrounded by a tube to provide a primary air supply. The supply of gas to the gas jet 41 is controlled by means of a conventional gas valve (not shown).

The apparatus thus far described may be manufactured of sheet steel or other appropriate material which may be spot welded together as appropriate.

The apparatus thus far described is used as follows. Referring particularly to Fig. 1 gas is supplied to the gas jet 41 and this draws in primary air through the primary air supply 42.

Within the tube 37 the gas and primary air is mixed and is then fed to the burner tray 28.

The baffle plate 38 prevents direct passage of the gas/air mixture from the tube 37 out of the burner tray 28 and so gas/primary air is fed out of the burner tray 28 through the generally horizontal perforated plate 36, the supply of gas/air being evenly distributed across the horizontally disposed perforated plate 36. The space between the perforated plate 36 and the level at which the coal 1 2 is supported is important. The distance from the perforated plate to the coal is relatively small compared with its width and secondary air is only allowed to pass into this area through slots 1 9 to 22 around the outer periphery.

Thus there is only sufficient air to burn the gas properly around the periphery of this area and so yellow flames are produced in the middle of this area. The flames and gas and air mixture pass up through the coals 1 2 where combustion is, completed, the combustion being completed by means of the mixing effect of the gas passing through the coals 12.

Thus there is provided a very hot blue flame around the circumference of the gas fire but due to the lack of secondary air in the centre the gas is not fully burnt until it has passed through the centre of the coals 1 2 where it burns with a blue/yellow flame. This gives a realistic appearance to the fire and yet little or no sooting takes place and the coals glow very bright.

Varying the gas supply by means of a gas tap changes the appearance of the fire. When the gas tap is low it may be that there is sufficient secondary air to provide complete combustion of the gas and this simply heats up the coals so that they glow. When an increased amount of gas is passed to the gas jet 41 the amount of secondary air in proportion to the gas is reduced and so there is an increased amount of yellow flame.

The alternative arrangement gas fire illustrated in Figs. 4 to 7 incorporates many of the features of the gas fire of Figs. 1 to 3. There is provided (not illustrated) a coal support assembly 13, a filler try 39 and in general terms the burner tray 28 is similar. However the perforated plate 36 is replaced by a solid plate 51 which is slightly smaller than the burner tray 28 and as is clear from Fig. 4 the solid plate 51 is mounted within the burner tray 28 so as to provide a gap 52 around the solid plate 51. The solid plate 51 is mounted in the burner tray 28 by means of spacers 53 which maintain the width of the gap 52.

In addition, the other change is the shape and design of the baffle plate 38. The baffle plate 56 which replaces the baffle plate 38 extends virtually from side to side of the burner tray 28 and incorporates a lip 57 so that the gas/air mixture entering the burner tray is more evenly spread throughout the burner tray.

The gap 52 is arranged so as to be approximately 1-2 mm.

By using an oversize jet ie one which is capable of handling a larger volume of gas but in which the amount of gas passing is restricted by means of the gas cock, the gas/air mixture is spread evenly throughout the burner tray 28 by means of the baffle plate 56, the gas/air mixture passes up through the gap 52 and burns at that point where secondary air is able to reach it. The effect of this is to provide a flame around the periphery of the stacked coals with an area of low pressure in the centre and this tends to provide a yellowing flame which at the same time combusts substantially completely after passing through the artificial coals.

Although round holes are shown in the perforated plate 36 elongated slots may be provided. The air/gas mixing tube 37 may be welded into the rear wall 35 or may alternatively be removably fixed by means of a flange which in turn is bolted to the wall 35 through a gasket so as make it airtight but removable.

The sloping coal support 23 can be welded to the coal support assembly as described or may be fixed by screws or even used as a loose plate.

Referring now to Figs. 7 to 10, Fig. 7 shows a vertical section from front to rear of a third gas fire according to the invention. In this them is provided two longitudinal gas burners 101, 102 which extend below a stack of artificial coals 103 supported by means of a support 104, the gas burners 101, 102 being generally longitudinal (see Fig. 10) and extending generally from end to end of the stack of coals 1 03. The front gas burner 101 and rear gas burner 102 are mounted on a plate 106 which has perforations or slots 107, 108 therethrough to provide secondary air from below the plate 106. The plate is folded so as to provide a backing portion 109 and a support potion 111 to underlie the stack 103 of coals, an insulating pad 11 2 of non-flammable material being provided between the coals and the support 111.The rear edge of the plate 106 is folded down to form a rear support member 11 2. The front edge of the plate 106 is folded up to provide a front mounting plate 11 3 to the front of which is attached a fret 114 which may be of any suitable attractive material. The gas burners 101, 102 may be of a generally standard type and are provided with a gas supply to one end and an outlet slot 11 6 running along their upper surface. The arrangement is such that primary air is fed to the gas burners 101, 102 but the supply of primary air to the rear gas burner 102 is insufficient for complete combustion whereas the supply of primary air to the gas burner 101 is sufficient. Thus, in use, the front gas burner 101 burns with a bright clear flame generating considerable heat and the rear gas burner 11 6 burns with a bright yellow flame which provides the flickering flame effect required. The complete combustion of the gas from gas burner 102 will take place through the coals 103 or immediately above them. Thus the burner 101 is burning efficiently and providing a large amount of heat whereas the burner 102 is burning less efficiently and whilst producing some heat is also producing the flickering flame effect.

An arrangement may be provided to vary the quantity of primary air passed to the rear gas burner 102 so as to vary the extent of the yellow flame produced.

The principle of the invention may also be applied to a gas fire which incorporates a log or coal basket.

Claims (10)

1. A gas fire comprising a stack of artificial coals and gas/air supply means below said stack to pass a gas/air mixture through said stack, said gas/air supply means being arranged so as to provide a gas/air mixture in one region of the stack which burns with a clear hot flame and a gas air mixture in another region of the stack which burns with a yellow flame.

2. A gas fire as claimed in claim 1 in which the gas/air supply means provides a gas/air mixture which burns with a clean hot flame at the front of the stack of artificial coals, and a gas/air mixture which burns with a yellow flame at the rear of the stack of artificial coals.

3. A gas fire as claimed in claim 1 or claim 2 in which the gas/air supply means comprises two burners, one burner being mounted at the front below a stack of artificial coals and the second burner being mounted at the rear below the stack of artificial coals, the front burner being arranged so as to have an adequate supply of primary and secondary air so that the gas/air mixture burns with a clear hot flame and the second burner being provided with insufficient primary or secondary air so as to burn with a yellow flame.

4. A gas fire as claimed in claim 3 in which the first and second burners each comprise longitudinal burners each extending below and between opposite ends of the stack of artificial coals.

5. A gas fire as claimed in claim 1 in which the gas/air supply means includes a plenum chamber in which gas and primary air is mixed, a plate above the plenum chamber to which the gas and primary air mixture in use is passed from the plenum chamber, and a secondary air supply means being arranged around the periphery of the plate so that above the periphery of the plate the gas/air mixture burns with a clean hot flame and towards the middle of the plate the gas/air mixture burns with a yellow flame.

6. A gas fire as claimed in claim 5 in which the plate is solid.

7. A gas fire as claimed in claim 5 in which the plate includes holes therethrough.

8. A gas fire as claimed in claim 1 substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

9. A gas fire as claimed in claim 1 substantially as hereinbefore described with reference to Figs. 4 to 7 of the accompanying drawings.

10. A gas fire as claimed in claim 1 substantially as hereinbefore described with reference to Figs. 8 to 10 of the accompanying drawings.