GB2142718A - An open hearth for a log fire - Google Patents

Abstract

An open-topped receptacle (11 and 12) has a front end (11) which extends out of a cavity (1) of a domestic fireplace and a rear end (12) arranged within the cavity (1). The receptacle (11 and 12) has a base portion (7 and 8) comprising a plate (7) supporting a slab (8) of refractory material and a side wall portion (9 and 10) extending around the entire periphery of the base portion (7 and 8) and comprising a plate (9) and tiles (10) of refractory material. The plates (7 and 9) provide an impervious outer layer for the receptacle (11 and 12). Legs (13 and 14) support the receptacle (11 and 12) above the floor (2) of the fireplace cavity (1) and the rear end (12) of the receptacle is spaced from the rear wall (3) of the fireplace cavity (1) so that combustion air can be pre- heated as it flows between the floor (2) of the fireplace cavity (1) and the base portion (7 and 8) of the receptacle (11 and 12), to complete combustion of gases rising from the receptacle (11 and 12), cooperating with combustion air preheated by passage over the wall portion (9 and 10) and the material burning in the receptacle (11 and 12) to complete combustion of gases rising from the receptacle (11 and 12) and thereby to enhance the flow of gases up the chimney (18) through a chimney opening (6) in the ceiling (5) of the fireplace cavity (1). Combustion air flows into the receptacle (11 and 12) at the front end (11) for the primary combustion. <IMAGE>

Description

SPECIFICATION An open hearth for a log fire Technical Field of the Invention The invention relates to an open-hearth, for accommodation in a fireplace cavity having a floor, a rear wall, opposed side walls, and a ceiling with a chimney opening, for supporting a log fire in a domestic fireplace and to a fireplace incorporating such an open-hearth.

Background Art Conventional log fire hearths comprise a base portion and a wall portion which extends around the base portion to form a receptacle.

To promote combustion of logs supported in the receptacle, the base and wall portions are constructed with openings so as to facilitate the flow of combustion air through the base and wall portions. For this reason, these receptacles are normally constructed in the form of metal grates in which elongate members are spaced apart to provide slots for the flow of combustion air into the grate.

However, it has been found that in spite of the provision of flow paths for combustion air, it is very difficult to carry out the combustion of logs in a stable, continuous manner. The rate of combustion normally varies throughout the combustion process and depends on unavoidable variations in temperature and on performance of the chimney extending from the fireplace.

Disclosure of the Invention The purpose of the present invention is to provide a log fire hearth which will permit more stable, steady-state combustion of logs in a domestic fireplace.

According to the invention, this is achieved by ensuring that the wall portion extends around the entire periphery of the base portion so that the receptacle is open-topped; by providing layers of refractory material which line the receptacle; and by making the base and wall portions impervious to air so that, in use, combustion air is prevented from flowing into the receptacle through the base portion and/or through the wall portion and is thereby caused to flow into the top of the receptacle.

The invention also provides a fireplace in which an open hearth, as hereinbefore described, is accommodated in a fireplace cavity having a floor, a rear wall, opposed side walls, and a ceiling with a chimney opening, characterised in that the receptacle is mounted above the floor and spaced from the rear wall of the fireplace cavity; the front end of the receptacle extends out of the fireplace cavity; and the rear end of the receptacle is disposed below the ceiling of the fireplace cavity.

Combustion air can therefore flow into the front end of the receptacle from above. It is also able to flow between the floor of the fireplace cavity and the base portion of the receptacle and then between the rear wall of the fireplace cavity and the rear end of the receptacle, being preheated by the heat emanating from the receptacle, to complete combustion of gases rising from the receptacle and to thereby enhance the flow of gases up the chimney through the chimney opening.

Prevention of the flow of combustion air through the base and wall portions of the receptacle results in a more satisfactory combustion of logs within the receptacle without smoke flowing into the room. This results, in part, from the intense temperature to which the refractory lining is heated and the fact that most of the combustion air, because of the configuration of the receptacle and also because of the disposition of the receptacle within the fireplace cavity, is drawn into the front part of the receptacle. The refractory material must therefore be capable of withstanding the intense temperatures generated within the receptacle.

In a preferred embodiment, the receptacle is provided with spacing means for preventing the rear end of the receptacle from being pressed against the rear wall of the fireplace cavity.

In a preferred embodiment of the fireplace, the receptacle is arranged so that there can be no flow of air between the opposed side walls of the fireplace cavity and the adjacent parts of the wall portion of the receptacle.

An embodiment of the present invention is hereinafter described, by way of example, with reference to and as illustrated in the accompanying drawings.

Brief Description of the Drawing Figure 1 is a sectional side elevation of a fireplace incorporating an open log fire hearth according to the invention; and Figure 2 is a plan view of the open log fire hearth shown in Fig. 1.

Mode for Carrying Out the Invention The open log fire hearth shown in Figs. 1 and 2 comprises a receptacle 11 and 1 2 in which a base portion 7 and 8 and a wall portion 9 and 10 respectively include stainless plates 7 and 9. The plate 7 is lined with a 63.5 mm (2+ inch) slab 8 of top quality furnace refractory and the plate 9 is lined with a 25.4 mm (1 inch) layer of top quality furnace refractory bricks 10 loosely inserted between the slab 8 lining the plate 7 and the plate 9. Firebrick could be used for the slab 8 and bricks 10.

As shown in Fig. 2, the front end 11 of the receptacle 11 and 1 2 is rectangular in plan view and projects from a trapezium-shaped fireplace cavity 1 into the room in which the fireplace is situated. The rear end 1 2 of the receptacle 11 and 1 2 is tapered in plan view so as to fit within the trapezium-shaped cavity 1, below the ceiling 5 of the cavity 1. Two front legs 1 3 and two rear legs 14 are attached to the plate 7 for respectively support ng the front and rear ends 11 and 1 2 of the receptacle 11 and 1 2 above a floor 2 which forms the floor of the cavity 1.Resiliently deformable end portions 15, in the form of plastic plugs, are inserted into the bottom ends of the front legs 1 3 so that even if the surface of floor 2 is of polished marble, or other delicate material, the surface will not be damaged.

Spacing stops 16 on the plate 9 forming a rear part of the wall portion 9 and 10 abut a rear wall 3 of the fireplace cavity 1 so as to prevent the rear end 1 2 of the receptacle 11 and 1 2 from being pressed against the rear wall 3 to thereby maintain an 20 mm (roughly i inch) ) air flow passage 1 7 between the rear end 1 2 of the receptacle 11 and 1 2 and the rear wall 3 of the fireplace cavity 1.

During combustion, combustion air flows into the top of the receptacle 11 and 1 2 at the front end 11. To complete combustion of gas rising from the receptacle 11 and 1 2 and thereby enhance the flow of gases up the chimney 18, further combustion air mixes with this gas after being preheated either by passage over the wall portion 9 and 10 and the burning logs, or by passage between the floor 2 and the base portion 7 and 8 and thereafter through the passage 1 7. The combustion air in this last flow path receives heat emanating from the receptacle 7 and 8 and its rear wall 9 and 10 and thus serves to cool the floor 2 of the cavity 1. This is important when the floor 2 is of decorative material such as marble.

As shown in Fig. 2, those parts of the wall portion 9 and 10 bounding the rear end 12 of the receptacle 11 and 12, adjacent the side walls 4 of the fireplace cavity 1, abut the side walls 4 so as to prevent the flow of combustion air between the side walls 4 and the receptacle 11 and 1 2. In this case, the rearwardly convergent parts of the wall portion 9 and 10 adjacent the side walls 4 serve as spacing means which prevent the rear end 1 2 of the receptacle 11 and 12 from being pressed against the rear wall 3 of the fireplace cavity 1 and the spacing stops 1 6 are not necessary.However, when a receptacle 11 and 1 2 as shown in Fig. 2 is installed in a fireplace cavity which is rectangular in plan, 4he spacing stops 1 6 ensure that an air flow passage 1 7 is provided. In any case, any gaps between the side walls 4 of the fireplace 1 and the adjacent part of the wall portion 9 and 10 must be blanked off to prevent the flow of combustion air between them, so that the only passage for combustion air between the rear end 12 of the receptacle and the walls 3 and 4 of the cavity is the passage 1 7.

Blanking off can be achieved by a tube laid horizontally along the top edges of the wall portion 9 adjacent the side walls 14 and loosely secured to the rear end 12 of the receptacle so that the tube can take up its position resting on the top of the wall portion 9 and against the side wall 14, thus blanking off the passage for air between these components. The tube, which is not illustrated is preferably formed of the same material as the plates 7 and 9.

A removable guard 1 9 has front and rear legs 20 and 21 respectively seated in holes 22 in the refractory bricks 10 lining the plate 9 and in bushes 23 embedded in the refractory bricks 10.

Claims (9)

1. An open hearth for a log fire, for accommodation in a fireplace cavity having a floor, a rear wall, opposed side walls, and a ceiling with a chimney opening, comprising a base portion; and a wall portion extending around the base portion to form a receptacle; characterised in that the wall portion extends around the entire periphery of the base portion so that the receptacle is open-topped; in that the base portion and the wall portion include layers of refractory material which line the receptacle; and in that the base portion and the wall portion are impervious to air so that, in use, combustion air is prevented from flowing into the receptacle through the base portion and/or through the wall portion and is thereby caused to flow into the top of the receptacle.

2. A hearth, according to Claim 1, in which the base portion and the wall portion include outer metal layers which support the layers of refractory material.

3. A hearth, according to Claim 1, in which the receptacle has front and rear ends and is provided with at least three legs; and each leg supporting the front end is provided with a resiliently deformable end portion which is engagable with the floor.

4. A hearth, according to Claim 1, in which the receptacle is provided with spacing means for preventing the rear end of the receptacle from being pressed against the rear wall of the fireplace cavity.

5. A fireplace in which an open hearth for a log fire, according to Claim 1, is accommodated in a fireplace cavity having a floor, a rear wall, opposed side walls, and a ceiling with a chimney opening, characterised in that the receptacle is mounted above the floor and spaced from the rear wall; the front end of the receptacle extends out of the fireplace cavity; and the rear end of the receptacle is disposed below the ceiling of the fireplace cavity.

6. A fireplace, according to any one of Claims 1 to 5, in which the receptacle is arranged so that there can be no flow of air between the opposed side walls of the fire place cavity and adjacent parts of the wall portion of the receptacle.

7. A fireplace as claimed in Claim 6 comprising ceiling means mounted on said adjacent parts of the wall portion to engage said opposed walls.

8. An open hearth, for a log fire, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

9. A fireplace substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.