GB2146762A - Fire bottom grate - Google Patents

Abstract

The invention is a new design of bottom grate for solid fuel fires. Instead of the traditional flat surface the invention has a convex surface. The invention also includes a dome-shaped metal casting with slots or airways as in a bottom grate. It can be placed on a flat bottom grate to give a convex centre. The object of the invention is to reduce the amount of fuel in the interior or core of the fire without reducing the surface area of the fire. By this means, the heat radiated into the room is maintained or increased (due to increased air supply) but the heat generated in the interior of the fire, which is lost up the chimney by convection, is reduced by virtue of the fact that the amount of fuel in that part of the fire has been reduced. <IMAGE>

Description

SPECIFICATION Improved fire bottom grate SUMMARY The invention is a new design of fire bottom grate (also known as fire bars) which gives increased combustion efficiency of solid fuels.

It includes a device by means of which the conventional flat bottom grate can be adopted to give similar results.

INTRODUCTION Conventional fire bottom grates have a flat or nearly flat surface which contains slots to allow access of air and to allow ash to escape into the pan below. The surface is usually horizontal although in some cases it slopes slightly to increase fuel capacity or it may be slightly concave for the same reason.

The sole purpose of these bottom grates is to support the fuel and allow access of air and escape of ash. (Figure 1.) The invention differs from these in that its surface is not entiely plane, flat or concave but has a convex section in the centre. (Figure 2.) THEORETICAL The inventor has established the fact that the heat supplied to a room from a solid fuel open fire, is emitted as radiation from the surface of the fire only and that most of the heat produced in the interior or core of the fire is lost up the chimney by convection.

(Figure 3.) The object of the invention is to reduce the volume of the fire core and hence reduce the amount of wasted heat, thus increasing the efficiency of the fire by producing the same or better heat output to the room with less fuel.

The improved bottom grate is designed in such a way as to eliminate a major part of the fire core without reducing the radiating surface area of the fire. This is achieved by a dome-shaped centre which occupies about 25% of the available fuel space. (Figure 4.) A similar result can be achieved by placing a separate metal cone (with slots for air access and ash escape) on to a conventional bottom grate. This device is also claimed as part of the invention. (Figures 5 and 6.) PRACTICAL Trials have confirmed the theory and have demonstrated that the fuel consumption is reduced by about 25% without any loss of heat output to the room.

It has also been confirmed that the increased air supply resulting from the greater surface area of the improved bottom grate allows more efficient combustion of the fuel.

The combination of these two factors results in an increased output of radiant heat from a reduced amount of fuel.

1. Is for a convex fire bottom grate, the central area being higher than the rest. It is a metal casting with slots or airways. The grate may be convex in the centre area only, the outer, surrounding area being flat. This novel design reduces the amount of solid fuel needed without reducing the surface area of the fire.

2. Is for a dome-shaped metal casting with airways. This can be placed on a flat-fire bottom grate to provide the convex centre area as described in Claim 1.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improved fire bottom grate SUMMARY The invention is a new design of fire bottom grate (also known as fire bars) which gives increased combustion efficiency of solid fuels. It includes a device by means of which the conventional flat bottom grate can be adopted to give similar results. INTRODUCTION Conventional fire bottom grates have a flat or nearly flat surface which contains slots to allow access of air and to allow ash to escape into the pan below. The surface is usually horizontal although in some cases it slopes slightly to increase fuel capacity or it may be slightly concave for the same reason. The sole purpose of these bottom grates is to support the fuel and allow access of air and escape of ash. (Figure 1.) The invention differs from these in that its surface is not entiely plane, flat or concave but has a convex section in the centre. (Figure 2.) THEORETICAL The inventor has established the fact that the heat supplied to a room from a solid fuel open fire, is emitted as radiation from the surface of the fire only and that most of the heat produced in the interior or core of the fire is lost up the chimney by convection. (Figure 3.) The object of the invention is to reduce the volume of the fire core and hence reduce the amount of wasted heat, thus increasing the efficiency of the fire by producing the same or better heat output to the room with less fuel. The improved bottom grate is designed in such a way as to eliminate a major part of the fire core without reducing the radiating surface area of the fire. This is achieved by a dome-shaped centre which occupies about 25% of the available fuel space. (Figure 4.) A similar result can be achieved by placing a separate metal cone (with slots for air access and ash escape) on to a conventional bottom grate. This device is also claimed as part of the invention. (Figures 5 and 6.) PRACTICAL Trials have confirmed the theory and have demonstrated that the fuel consumption is reduced by about 25% without any loss of heat output to the room. It has also been confirmed that the increased air supply resulting from the greater surface area of the improved bottom grate allows more efficient combustion of the fuel. The combination of these two factors results in an increased output of radiant heat from a reduced amount of fuel. CLAIMS

1. Is for a convex fire bottom grate, the central area being higher than the rest. It is a metal casting with slots or airways. The grate may be convex in the centre area only, the outer, surrounding area being flat. This novel design reduces the amount of solid fuel needed without reducing the surface area of the fire.

2. Is for a dome-shaped metal casting with airways. This can be placed on a flat-fire bottom grate to provide the convex centre area as described in Claim 1.