GB2162306A - Domestic fireplace - Google Patents

Abstract

An improved domestic fireplace having a high rate of transfer of heat from the burning fuel and combustion gases to the water incorporates a water boiler 5,10,12 which extends in a continuous manner behind the grate 19 to the sides of the grate and beneath the grate, so as thereby largely to define the grate 19. The part of the water boiler 12 which extends beneath the grate 19 is either completely continuous or so little interrupted (Fig. 1) that only a minor proportion of the air supply to the grate can pass through it. For example, 75% or 90% or more of the air supply to the grate may come from above the grate bottom. <IMAGE>

Description

SPECIFICATION Domestic fireplace The present invention is a novel form of domestic fireplace, which is an improvement over other forms of fireplace which have hitherto been described. It is particularly concerned with domestic fireplaces which incorporate a boilder for heating water.

In such prior fireplaces, the boiler has usually been disposed at the rear of the grate in which the fuel is burned, and/or at the sides of the grate. In this way, normal burning of the fuel heats the water to an elevated temperature which is dependent upon the rate at which the fuel is burned. In order to limit the water temperature when ambient conditions require a large heat output from the fire, or when the demand for hot water is low, a deflector may be provided to divert combustion gases away from contact with the boiler.

However, in conditions of warmer weather, when the need for hot water requires a fire larger than would be needed for heating the adjacent room, the temperature in the living area may become uncomfortably high.

In order to minimise the fire level while still providing satisfactory water heating, it is important to maximise the heat transfer from burning fuel and combustion products to the water. To this end, many attempts have been made to modify the form of domestic fireplaces. Enhanced heat transfer has to some extent been achieved but there is still a need for an improved fireplace in which the transfer is further enhanced.

It is therefore an object of my invention to provide a domestic fireplace having a high rate of heat transfer from the burning fuel and combustion gases to the water.

According to my invention, an improved domestic fireplace incorporates a water boiler which extends in a continuous manner behind the grate, to the sides of the grate and beneath the grate, so as thereby largely to define the grate, that part of said boiler which is beneath the grate being itself either completely continuous or so little interrupted that only a minor proportion of the air supply to the grate can pass therethrough.

Advantageously a chimney insert is disposed above the grate and is double-walled so as to define a water-cavity in communication with the boiler.

It has already been proposed to include in a domestic fireplace a grate having hollow firebars beneath the fire, water then being allowed to flow through the fire bars and into the boiler. Such bars have been spaced apart to enable a significant quantity of air to pass between them to feed the fire. In contrast to such prior proposals, in the present invention the boiler itself extends beneath the fire-grate and thus such under-fire air supply is either totally excluded or reduced to a small amount.

In one form of my invention, the boiler is essentially box-shaped adjacent to the grate, that is it has upright back and side portions and a flat under-grate portion, the front of the grate being either left open or defined by a separate fret or other front member, preferably apertured to allow air to flow into the grate. However, in a particularly preferred form of my fireplace, the boiler extends below the grate in two distinct parts, defining between them a downwardly-tapered grate. Preferably, an aperture is provided between the two said parts at the lowest point of the grate cross-section, to permit ash to fall through into an ash pan or trap. Such aperture should not be so large as to afford a steady input of air to the fire, nor wide enough to permit coals to fall therethrough. Removal of ash through the aperture may be assisted by the provision of a shaker bar.

Thus, in my invention, at least a major proportion of the air required to sustain the fire comes from above the grate bottom. Indeed, it is possible for 75% or 90% or more of the air supply to come in this direction.

This supply may advantageously be augmented by the provision of a pipe to feed air from outside the grate to within the grate.

Preferably this additional air is fed by means of a fan. The fan speed may advantageously be adjustable to accommodate different desired burning rates.

The boiler in the fireplace according to my invention is preferably surrounded by insulating material to minimise heat loss. One advantage of my novel fireplace is that combustion heat which in other fireplaces would be lost through the bottom of the firegrate is, according to my invention, taken up by the water in that part of the boiler which extends beneath the grate. This important saving is preferably assisted by locating insulating material beneath that part of the boiler.

My invention will now be further described with reference to the accompanying drawings, in which: Figure 1 is an elevation from the front of one preferred embodiment of the fireplace according to my invention; and Figure 2 is a cross-sectional view of the fireplace of Fig. 1.

Referring to the drawings, a firebox 3 is defined on three sides by a boiler 4 having a rear portion 5 and side-cheeks 6 and 7. The rear portion 5 is formed integral with a chimney insert 8 and together they define a flue 9 by means of which combustion gases are conveyed away from the grate in contact with the boiler surface. As shown in Fig. 1, the flue 9 is divided into two upwardly-diverging tapering sections 9a and 9b.

The lower section of the rear boiler portion 5 extends vertically downwardly to form a rear grate wall 1 0. The side-cheeks 6 and 7 are extended downwardly and inwardly to form grate side-walls 11 and 1 2 respectively. Thus the grate 1 3 defined by the rear wail 10 and side-walls 11 and 1 2 is seen from the front as a downwardly-tapering hopper-like cavity. This shape makes for greater economy of fuel than a parallel-sided box-like grate and also assists settling and ultimate removal of ash. Removal of the ash, through an elongated aperture 14 defined by the lower edges of the grate sidewalls 11 and 12, is further assisted by a shaker-bar 1 5. An ash-pan 1 6 is disposed below the aperture 14.

The front of the grate 1 3 is defined by an upright fixed fret 1 7 (omitted, for the sake of clarity, from Fig. 1). The fret 1 7 has apertures 1 8 which allow admission of air to the grate.

In addition a perforated cast iron pipe 19, located centrally in the grate 1 3 above the aperture 14, is fed with air via a supply pipe 20, which is mounted within the fret 1 7 and extends to a point below the hearth level and at the side of the fireplace overall. A fan (not shown) is disposed at the outer end of the supply pipe 20 to enable regulation of the air feed rate according to varying requirements.

Insulation, not shown, surrounds the boiler and minimises heat loss. In particular, additional insulation is provided adjacent the inclined side walls 11 and 1 2 of the grate 1 3.

No deliberate provision is made for air ingress below the grate and any such air flow from that direction (and thence in through the aperture 14) is minimal, and in any case much less than the air supplied from above the grate and/or via the pipe 1 9.

The fireplace according to the invention affords high levels of heat transfer from burning fuel and from combustion gases to the water in the boiler and thereby makes it possible to meet the hot water requirements of a house with the fire itself damped down to low burning level. Thus not only are temperatures in the associated living air kept down, if desired, to comfortably low levels but heat losses are reduced and fuel economy thereby improved.

Claims (11)

1. A domestic fireplace incorporating a water boiler which extends in a continuous manner behind the grate, to the sides of the grate and beneath the grate, so as thereby largely to define the grate, that part of said boiler which is beneath the grate being itself either completely continuous or so little interrupted that only a minor proportion of the air supply to the grate can pass therethrough.

2. A domestic fireplace as claimed in claim 1, having in addition a chimney insert disposed above the grate, which insert is double-walled so as to define a water cavity in communication with the boiler.

3. A domestic fireplace as claimed in claim 1 or claim 2, wherein the water boiler is essentially box-shaped adjacent to the grate, in that it has upright back and side portions and a flat under-grate portion but no front portion.

4. A domestic fireplace as claimed in claim 3, having a separate front member, apertured to allow in-flow of air to the grate.

5. A domestic fireplace as claimed in claim 1 or claim 2, wherein the water boiler extends below the grate in two distinct parts, defining between them a downwardly-tapering grate.

6. A domestic fireplace as claimed in claim 5, having an aperture between said two boiler parts at the lowest point of the grate cross-section.

7. A domestic fireplace as claimed in claim 6, having a shaker bar so disposed as to assist removal of ash through said aperture.

8. A domestic fireplace as claimed in any of the preceding claims, wherein at least 75% of the air supply to the grate comes from above the grate bottom.

9. A domestic fireplace as claimed in claim 8, wherein at least 90% of the air supply to the grate comes from above the grate bottom.

10. A domestic fireplace as claimed in any of the preceding claims, having in addition a pipe located to feed air from outside the grate to within the grate.

11. A domestic fireplace as claimed in claim 10, wherein said additional air is fed by means of a fan.

1 2. A domestic fireplace as claimed in claim 11, wherein the speed of said fan is adjustable.

1 3. A domestic fireplace substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.