Vent-free heating apparatus differ from vented heating apparatus in that they discharge combustion products into the room where the apparatus is situated rather than discharging them to the exterior via a chimney or flue. They are used in circumstances where it is difficult or undesirable to vent the combustion products via a chimney or flue and they also have the advantage that they tend to be less bulky, which is useful when space is limited.

Some vent-free heating devices are of the flame-effect type which comprise a flame-resistant bed (typically a cast ceramic block which is shaped to resemble a bed of coal or logs) beneath which is situated a burner. Flames from the burner pass through holes extending from the undersurface to the upper surface of the bed and are visible in use. As the bed heats up in the manner of a conventional coal or log fire the bed glows in the manner of a real fuel bed. In vent-free flame-effect heaters the bed is located behind a heat-resistant glass screen which is sealingly located over an aperture, in order to prevent"spillage"of combustion products. The combustion products then pass over or through a catalytic converter which is heated by the combustion products to its working temperature, in order to convert harmful components in the combustion gases (e. g. carbon monoxide and unburnt fuel) into less harmful products.

Some apparatuses of this type allow air to pass from the undersurface of the bed around its periphery to the upper surface. This can interfere with achieving the optimum fuel/air mixture and also has the disadvantage that if air is allowed to flow over the inner face of the glass cover sheet minute particles of dust will be deposited on the glass sheet which can detract from the visual appearance of the fire.

In accordance with a first aspect of the present invention, a heating apparatus comprises a housing, a flame-resistant bed having a plurality of apertures extending from an undersurface to an upper surface, a bed viewing aperture in the housing, a fuel burner located in the housing beneath the bed and air inlet means in the housing to allow the ingress of air to the burner, the bed being mounted within the housing to prevent the flow of gas around its periphery from its undersurface to its upper surface.

By preventing the flow of gas around the periphery of the flame-resistant bed, all of the gases (whether combustion gases or excess air) are forced to pass through the apertures in the flame-resistant bed. Not only does this assist in obtaining the optimum fuel/air ratio for more complete and therefore safer combustion but it also prevents any significant flow of gas over the inner face of a transparent cover sheet normally positioned in front of the flame-resistant bed and thus reduces the deposition of dust and the like.

In accordance with a second aspect of the present invention, a heating apparatus comprises a housing, a flame-resistant bed having a plurality of apertures extending from an undersurface to an upper surface, a bed viewing aperture in the housing, a combustion chamber beneath the bed and a burner in the combustion chamber, the combustion chamber communicating with the upper surface of the flame-resistant bed only via the apertures in the bed.

In one embodiment, the flame-resistant bed comprises a block, e. g. a cast ceramic block.

Preferably, the flame-resistant bed is shaped to simulate a bed of fuel.

The apertures extending from the undersurface to an upper surface of the flame-resistant bed are preferably for the passage of combustion products from the burner.

Preferably, the flame-resistant bed engages sealingly with the housing.

For example, the flame-resistant bed may engage sealingly with the housing around the whole of its periphery. More preferably, the flame resistant bed is supported by, and engages sealingly with, the housing. In one embodiment, the housing comprises a ledge which supports the flame-resistant bed. The ledge may support, and engage sealingly with, the periphery of the flame-resistant bed.

There may be a sealing means between the flame-resistant bed and the housing.

Preferably, the housing comprises an outlet for combustion gases emerging from the apertures in the flame-resistant bed. The housing may comprise a roof portion and the outlet for combustion gases may be located in the roof portion.

There may be catalyst means in communication with the outlet in the housing and also in communication with exhaust means for exhausting gases from the catalyst means out of the housing. The catalyst means is preferably located sealingly with respect to the outlet in the housing, whereby all the combustion gases passing through the outlet also pass through the catalyst means.

The housing may further comprise an exhaust aperture in communication with the outlet of the catalyst means. The outlet of the catalyst means may communication with the exhaust aperture in the housing via an exhaust chamber.

There may be a plurality of catalyst means, each in communication with a respective outlet in the housing for exhaust gases.

In one embodiment, the heating apparatus further comprises a transparent sheet which closes the bed viewing aperture. The bed viewing aperture may be sealingly closed by engagement of the transparent sheet with the housing.

The fuel burner may be elongate. Preferably, the fuel burner is located in a burner chamber defined by the housing and the undersurface of the flame-resistant bed.

The air inlet preferably allows the ingress of air to the undersurface of the flame-resistant bed.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:- Fig. 1 is a cross-sectional side elevation of an embodiment of heating apparatus in accordance with the present invention; and Fig. 2 is a longitudinal cross-section of the heating apparatus of Fig. 1, looking in the direction of arrows 11-11.

The heating apparatus illustrated in a vent-free, living flame effect fire and comprises a pressed metal housing 10 having a planar rear wall 12, two opposed side walls 14,16 inclined to the rear wall 12, a planar base wall 18 and a planar top wall 20. A front wall 22 has a rectangular viewing aperture 24 which is sealingly closed by means of a heat-resistant glass sheet 26 which engages sealingly with a silicone rubber gasket 27 extending around the periphery of the aperture 24.

An inwardly-directed ledge 28 extends from the rear wall 12, the front wall 22 and the side walls 14,16 and supports a conventional cast flame-resistant ceramic simulated coal block 30. The ledge 28 also supports a rear generally planar ceramic liner 32 which rests on its lowermost edge between the rear wall 12 and the block 30, and two lateral ceramic liners 34,36 each of which rests on the ledge 28 on a lowermost edge between a respective one end of the block 30 and the adjacent side wall 14,16. The front face of the liners 32,34, 36 may be profiled to simulate a traditional fire back and they each extend upwardly to an inclined roof 38 which, together with the liners 32,34, 36, the upper surface 40 of the simulated block and the glass sheet 26, define a flame chamber 42.

The simulated coal block is conventional and has a plurality of through apertures 44 extending from its planar undersurface 46 to the upper face 40 of the block which is shaped to resemble coals. A conventional elongate burner 48 is located beneath the undersurface 46 in a combustion chamber 50 defined by the base wall 18, the undersurface 46 of the block 30 and the ledge 28 and the portions of the rear wall 12, the side walls 14,16 and front wall 22 below the ledge 28. The chamber 50 is supplied with air via apertures 52 at the base of the front wall 22.

It is important to note that the periphery of the planar undersurface 34 of the ceramic simulated coal block 30 rests sealingly on the ledge 28. In the illustrated embodiment, this is achieved by means of a flat silicone rubber gasket 54 between the upper face of the ledge 28 and the periphery of the undersurface 34 of the block 30. However, if the engaging face of the ledge 28 and the block 30 engage sufficiently closely, the gasket may be omitted. Whichever method is chosen, it should not be possible for any significant amount of air to pass from the combustion chamber 50 to the upper face 40 of the simulated fuel block 30 except through the apertures 44 extending through the block. In particular, the seal between the ledge 28 and the block 30 should prevent a flow of air from passing from the combustion chamber 50 and around the side walls of the block 30 to its upper surface 40.

Located above the inclined roof 38 is a second inclined roof 56. The two roofs 38, 56 are provided with two large identical circular apertures 58, 60,62, 64, each aperture being aligned with a respective one of the two apertures in the other roof. Two conventional cylindrical catalysts 66, 68 are located between the two parallel inclined roofs, each catalyst being aligned with a respective aligned pair of apertures 58, 62; 60,64. The diameter of the catalysts 66,68 is slightly larger than the diameter of the apertures and the catalysts engage sealingly with the opposed faces of the two inclined roofs to ensure that all gases passing through one of the apertures 58, 60 in the lower roof 38 must pass through one of the catalysts 66,68 before passing through the corresponding aligned aperture 62,64 in the upper roof 56. The apertures 62,64 in the upper roof open into an exhaust chamber 70 defined by the top wall 20, the upper roof 56 and the rear wall 12.

The exhaust chamber 70 in turn opens into the atmosphere via an elongate exhaust aperture 72 in the top of the front wall 22.

In use, fuel (typically a gaseous fuel such as methane) is fed to the burner 48 and is ignited in the conventional manner, with air for combustion entering the combustion chamber 50 via the apertures 52 in the foot of the front wall 22.

Flames from the burner 48 pass through the apertures 44 in the simulated coal block 30 and emerge from the upper end at the upper surface 40 of the block.

After a while the heat from the combustion causes the ceramic simulated fuel block to glow, in a manner which is visually similar to a bed of real coal. The hot combustion products pass upwardly and since the glass screen is sealingly attached over the viewing aperture 24 in the front wall 22, all the combustion products are forced to pass through one of the two apertures 58,60 in the lower inclined roof 38. The catalysts 66,68 are heated by the hot combustion products and very quickly after combustion has started they reach their working temperature, at which they act to convert undesirable constituents in the combustion gases (e. g. carbon monoxide and unburnt hydrocarbons) into less harmful gases (e. g. carbon dioxide and water). Since all of the combustion gases must pas through one or other of the apertures 58, 60 in the lower inclined roof 38, all of the combustion gases pass through one of the catalysts 66,68, after which the altered combustion gases are discharged via the exhaust chamber 70 and the elongate exhaust aperture 72 into the area where the heating apparatus is situated.

As explained previously, as a result of the sealing action between the undersurface 46 of the simulated coal block and the ledge 28, all the combustion products emanating from the burner 48, together with air drawn by the combustion gases, pass through the apertures 44 in the simulated coal block. In particular, there is effectively no supply or flow of air from the combustion chamber 50 (or indeed from anywhere else) to the upper surface 40 of the simulated coal block 30 except through the apertures 44 passing through the block. In this way, it is possible to match more accurately the fuel/air ratio in order to achieve the desired combustion characteristics and to prevent the flow of air over the inner face of the glass sheet 26 which might otherwise result in deposition of minute dust particles.

The invention is not restricted to the details of the foregoing embodiment.