GB2193802A - Simulated solid fuel gas fire - Google Patents

Abstract

A burner tray (10) for a simulated solid fuel gas fire has a gas inlet (12), and a ceramic fibre blanket (18) lining its bottom surface (11), the blanket distributing gas over substantially the whole area of the tray while reducing heat loss to the tray and increasing the heat output of the fire. A bar 17 initially directs the gas towards the sides of the fire. <IMAGE>

Description

SPECIFICATION Domestic gas fires This invention relates to a domestic gas fire, particularly a decorative coal or log effect gas fire.

To provide a coal or log effect gas fire, the gas from a domestic supply is first distributed over the area of a fire burner tray which is fitted in the fire grate. The most common method at present used for distributing the gas is to fill the tray with silica sand which covers a gas inlet in the bottom of the tray.

In one alternative, the gas is introduced into a hollow perforated tube resting on the bottom of the tray, the tube then being covered with the silica sand.

Apart from silica sand, alternative distributing materials have included vermiculite granules, expanded clay and other refractory aggregates, as weli as slotted refractory boards.

Existing gas fires sometimes incorporate a flame failure valve responsive to a pilot light.

The pilot light generally requires its own piped supply of gas, the pilot assembly being provided as a "bolt-on" accessory to the basic fire. These accessories add to the cost of the fire and are often difficult to instal and adjust.

According to the present invention at least the bottom of a burner tray for a domestic gas fire is lined with an insulating refractory material. It has been found that the use of such a lining reduces heat loss to the tray by as much as 509/0 and thereby significantly increases the heat output from the fire. The increased heat output is accompanied by a brighter glow which therefore enhances the decorative effect of the fire.

The insulating material is preferably fibrous and in a preferred embodiment of the invention the lining serves the dual function of distributing gas and providing insulation.

The insulating fibrous refractory material is conveniently provided in the form of a blanket, and particularly good results have been achieved using a 128 kg/m3 ceramic fibre blanket 50 mm thick and having a thermal conductivity ranging from about 0. 1 W/mk at 500"C to about 0.22 W/mk at 1000 C.

The ceramic fibre may comprise, for example, a blown alumino-silicate fibre made from blends of high purity alumina and silica.

Suitable ceramic fibre blankets may comprise a flexible, insulating refractory material made solely from bulk fibre without the inclusion of binders. Such blankets are already available in a range of thicknesses from 6mm to 50mm and in a range of densities from 48 kg/m3 to 128 kg/m3, the blankets at present being used primarily as a lining material for low thermal mass furnaces, including ceramics kilns and petrochemical process plant.

In the present application, however, the blankets not only provide substantial insulation which reduces heat loss to the metal tray by up to 50%, but also provide improved distribution of gas over the area of the tray. The blankets are also easier to handie than sand or other loose particulate materials.

The improved gas distribution enables the use of an improved pilot light arrangement, the burner tray including a pilot hole located adjacent to an external flame sensing device, such as a thermocouple, the gas emerging from the pilot hole being automatically ignited to provide a pilot flame when the burner tray is ignited.

Some possible alternative insulating refractory materials are loose fill ceramic fibre, rock wool fibre, glass fibre, and ceramic paper with silica fibre.

The sides and back of the fire tray might also be lined with the insulating material, particularly if the height of the tray is increased to provide more of a fire box.

The invention also envisages lining the bottom of the burner tray with insulating material and having gas entering above the lining for distribution by conventional means.

It is also possible to make an aerated burner using a fibre blanket to distribute the gas/air mixture and insulate the bottom of the fire. Bearing in mind the relatively large area of the burner and the consequent low velocity of the gas/air mixture through the fibre, the resistance of the fibre in such a burner would be low enough to prevent blow backs as a result of back pressure at the gas injector.

In the accompanying drawings, by way of example only: Fig. 1 is a top plan view of a burner tray embodying the present invention, and Fig. 2 is a cross-sectional view on line A-A of Fig. 1.

The tapered metal burner tray 10 is designed to fit in a fire grate positioned in a conventional domestic fire back. It has a bottom surface 11 with a gas inlet 12, two upstanding side walls 13, 14 and front and back walls 15, 16. The tray 10 could have other shapes and might, for example fit in a rectangular fire basket. It could also be free standing.

The inlet 12 is located toward the front of the tray, and immediately behind the inlet 12 is a distribution bar 17 which is welded or otherwise secured to the bottom surface 11.

A ceramic fibre blanket 18 is then laid over the bar 17 and rests on the bottom surface 11. The resulting clearance around the bar 17 provides a passage 19 for the gas emerging from inlet 12, the passage 19 extending in both directions toward the opposite side walls 13, 14. When the burner is ignited, the draft from the chimney generally draws the gas backwards toward the rear wall 16 and the blanket 18 effectively distributes this gas over the entire area of the tray 10 while at the same time providing insulation between the gas flames and the bottom of the tray.

A small pilot hole 20 is located in the side wall 13 opposite one end of the distribution bar 17 and just below the top edge of the side wall. The tip of a thermocouple heat sensing device 21 is located outside the tray close to the hole 20, the device 21 being secured to the side wall 13. The fibre blanket 18 is such an efficient gas distributor that a proportion of the gas entering through the inlet 12 emerges from the pilot hole 20 where it automatically ignites when the gas distributed over the burner tray 10 is ignited. The presence of the pilot flame is detected by the thermocouple 21 which feeds a signal to a flame failure valve 22 in the gas supply line to maintain the valve open. Since the pilot is taken directly from the main burner, it no longer requires a separate gas supply nor does it require adjustment since it is self-adjusting with the main burner gas pressure. This has the added advantage of enabling the burner to be used on natural gas or bottled liquid propane gas without any pilot adjustment.

Claims (10)

1. A domestic gas fire comprising a metal burner tray the tray including a gas inlet for connection to a gas supply line, and means for distributing gas emerging from the inlet over substantially the whole area of the tray, at least the bottom of the tray being lined with an insulating refractory material.

2. A fire according to claim 1 in which the gas distributing means comprises the said lining of insulating refractory material.

3. A fire according to claim 2 in which the insulating refractory material comprises a fibrous blanket.

4. A fire according to any one of the preceding claims in which the refractory material includes ceramic fibres.

5. A fire according to claim 1 in which the tray comprises a bottom surface, two opposed side walls and front and back walls, the gas inlet being-in the bottom surface and located toward the front wall substantially mid-way between the opposed side walls.

6. A fire according to claim 5 in which a transverse elongate barrier is disposed behind the gas inlet for initially directing gas outwardly toward the opposed side walls.

7. A fire according to claim 6 in which the barrier supports the insulating material-clear of the bottom surface of the tray to provide a passageway alongside the barrier for the unimpeded flow of gas.

8. A fire according to claim 7 in which the barrier comprises an elongate bar welded or otherwise secured to the bottom of the tray.

9. A fire according to claim 6 in which one of the upstanding side walls includes a pilot hole disposed generally opposite one end of the barrier, the pilot hole providing a pilot flame when the burner is ignited, and in which a heat sensing device is arranged to sense the pilot flame to control a flame failure valve in the gas supply.

10. A domestic gas fire substantially as herein described with reference to the accompanying drawings.