COOKING STOVE

Abstract

This invention relates to cooking stoves, in particular, to lightweight, efficient, and portable outdoor cooking stoves for use primarily by those undertaking general camping or other outdoor leisure pursuits, or by larger groups of people for entertaining or humanitarian purposes. The cooking stoves are designed to make efficient use of solid fuel blocks and to minimise the soot deposited on the cooking vessel.

Description

FIELD OF THE INVENTION

This invention relates to cooking stoves, in particular, to lightweight, efficient, and portable outdoor cooking stoves for use primarily by those undertaking general camping or other outdoor leisure pursuits, or by larger groups of people for entertaining or humanitarian purposes. The cooking stoves are designed to make efficient use of solid fuel blocks and to minimise the soot deposited on the cooking vessel.

BACKGROUND TO THE INVENTION

Outdoor enthusiasts and military personnel that carry their own equipment, often for extended periods of time, need their equipment to be lightweight and suitable for compact storage. Environments that do not offer a source of fuel, such as dried wood, are frequently encountered, requiring the prudent person also to carry their own fuel. Stoves that can be used with solid fuel blocks have been developed. In addition to their use by outdoor enthusiasts and military personnel, solid fuel blocks are well suited to humanitarian applications.

Solid fuel blocks that are on the market include hexamine blocks, trioxane blocks, solidified methyl decanoate blocks and gelled alcohol packs. These blocks prevent the need for extra containers (as with gas or liquid fuels) or regulation equipment (pressure regulators or valves) and reduce the risk of fuel spillage or other accidental release.

Methyl, ethyl, propyl, or butyl esters of a C6-C14 carboxylic acid, of which methyl decanoate is the most popular, are particularly advantageous as the fuel of solid fuel blocks. The C8-C14 methyl esters have favourable flash points and boiling ranges for solid fuel blocks. The present invention concerns stoves designed to be used with these particular fuels.

Prior art stoves have generally not been designed specifically with burning solid fuel blocks in mind. Instead, most prior art stoves have been designed to utilise a number of fuels, including wood. The efficiency with which these stoves transfer heat from burning solid fuel blocks to a cooking vessel is not optimal.

When using a solid fuel block, the fuel block is placed in the combustion chamber of the stove and a cooking vessel is placed on top of the stove. The solid fuel is set alight and the flames heat the cooking vessel. A problem that is typically encountered with solid fuel blocks is that fuel blocks burn aggressively leading to tall flames. These tall flames often spill out of the top of the combustion chamber and spread out around the sides of the cooking vessel, resulting in lost heat energy. This lost heat energy must be accounted for by burning additional fuel blocks. In the long term this has environmental implications and in the short term means that a greater number of fuel blocks must be carried by the operator.

Further, if prior art stoves are used with solid fuel blocks, the fuel from the fuel blocks often does not completely combust, which leads to dangerous volatile organic compounds (white smoke) and/or soot (black smoke) being produced. The volatile organic compounds and/or soot are deposited on the cooking vessel, which makes it dirty to handle and store, and is unhygienic.

There is, therefore, a need to provide a stove that can burn solid fuel blocks more efficiently and reduce the soot deposited on the cooking vessel. The present invention aims to meet this need.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention relates to a cooking stove, the cooking stove comprising walls which define a base at one end and a top at the other end, wherein the walls of the cooking stove additionally define:

• • a fuel zone which is defined by the section of the walls which extends up from the base to about one third of the height of the stove;
  • an exhaust zone which is defined by the section of the walls which extends down from the top by about one third of the height of the stove; and
  • a combustion zone which is defined by the section of the walls which extends from the fuel zone to the exhaust zone; wherein the cooking stove is characterised in that
  • the fuel zone has at least one air inlet, wherein the total surface area of this air inlet or air inlets is 0.5% to 2.5% of the total surface area of the fuel zone;
  • the exhaust zone has at least two exhaust outlets, wherein the total surface area of these exhaust outlets is 20% to 35% of the total surface area of the exhaust zone; and
  • the combustion zone has at least three air inlets, wherein the total surface area of these air inlets is 2.5% to 4.0% of the total surface area of the combustion zone.

As noted above, methyl, ethyl, propyl, and butyl esters of C6-C14 carboxylic acids, which shall be referred to as fatty acid esters (FAE), are particularly advantageous as the fuel of solid fuel blocks. Of these methyl decanoate is currently the most popular. The present invention concerns stoves which are specifically designed to efficiently burn these FAE solid fuel blocks.

In the past, cooking stoves that burn wood, charcoal briquettes, dried peat, coal, etc., have relied on having air inlets at fuel height to directly feed the burning fuel with air. A new way of burning adapted to FAE solid fuel blocks has been discovered by the inventor. If air is restricted from accessing the burning fuel at fuel height but is supplied to a headspace above the burning fuel, the main combustion occurs in this headspace above fuel height. The inventor has found that this leads to more efficient combustion than burning only the fuel block itself. This has led to the stove of the present invention, which has been designed to control the air flow in order to most efficiently combust FAE solid fuel blocks, resulting in more efficient transfer of energy from the fuel to a cooking vessel placed on the stove, and a reduction in the soot and unburned volatile organic compounds that are present in the exhaust fumes that can be deposited on the cooking vessel.

Lightweight portable cooking stoves which are designed to improve the efficiency with which solid fuel blocks can be burned have been described in the presently unpublished patent application number PCT/GB2013/000176. This patent application describes a cooking stove comprising sheet-like members which are coupled together at their side edges, with at least one exhaust opening at or close to the top edge, and with a lattice of perforations which acts as air inlets and which covers at least 60% of the surface area of the faces of the sheet-like member. Using a lattice of perforations to let air into the stove was found to restrict airflow into the stove in a manner that reduces the intensity with which a solid fuel block burns, so that more efficient combustion can take place. However, further investigations have revealed that soot deposition is still a problem. Soot deposition reveals that partial combustion has taken place.

As mentioned above, the cooking stove of the present invention is designed specifically to tightly control the air flow into and exhaust gas flow out of the cooking stove to ensure that it is optimal for combustion of a FAE solid fuel block.

To this end, a fuel zone is provided at the lowest third of the stove, which advantageously is approximately the same height a fuel block itself, or can be taller than a fuel block. In the fuel zone relatively small and/or few air inlets (just 0.5% to 2.5% of the total surface area in this zone) are provided to allow air to be drawn in to sustain just a small flame which, alone, would burn the fuel at a slow rate. The main purpose of the flame in the fuel zone is to create enough heat to vaporise the FAE so that complete combustion can take place in the headspace above the fuel, in the combustion zone. This is in stark contrast to many prior art stoves, where the biggest, and often the only, air inlets are at the level of the fuel. With traditional fuels that are not subject to vaporisation (wood, coal etc.) complete combustion has to take place at the level of the fuel itself. As noted above, the stove of the present invention has been carefully designed to fully optimise and control burning of FAE solid fuel blocks.

The combustion zone has been designed to take up the middle third of the cooking stove, and is typically above a fuel block when positioned in the stove. In order to facilitate complete combustion of the solid fuel block, larger and/or a greater number of air inlets are provided in the combustion zone compared to the fuel zone. At least three air inlets are provided in the combustion zone. These make up 2.5% to 4.0% of the surface area of this zone, so the total surface area of the air inlets in the combustion zone is generally greater than the total surface area of the air inlet or air inlets in the fuel zone. This helps to ensure that the flame is hot enough in the combustion zone to completely combust the fuel, compared to in prior art stoves where incomplete combustion can mean that partially combusted fuel, i.e. soot or, worse still, vaporised but completely unburned fuel, is deposited on the cooking vessel.

Controlling the flow of gasses out of the stove is also important. To this end, an exhaust zone is provided in the top third of the stove that has at least two exhaust outlets, with a total surface area of 20% to 35% of the total surface area of the exhaust zone. In particular, the fact that the air inlets in both the fuel zone and the combustion zone are severely restricted, and surface area of the air inlets in the combustion zone are equal to or greater than that of the air inlets in the fuel zone, is key to the improved performance.

The specific arrangement of air inlets and exhaust outlets in the three zones of the stove of the present invention advantageously allows the flow of gasses into and out of the stove to be tightly controlled in order to promote complete combustion of a FAE fuel block in a non-aggressive manner which can advantageously result in a clean blue flame and a good balance between burn time and flame temperature for optimal heating of food or liquid in a cooking vessel on the stove. Prior art stoves generally have the largest or indeed the only air inlets in the fuel zone. The unpublished patent application number PCT/GB2013/000176 discloses a stove which is designed to burn solid fuel blocks. This has a lattice of perforations forming the air inlets and outlets. The surface area of the perforations in the fuel zone are larger than in combustion zone (8 to 9% compared to 7 to 8%) and are both considerably larger than in the present invention. The exhaust outlets are considerably smaller than in the present invention (around 10%). Restricting the air inlets, as in the present invention leads to better performance, and significantly, to much lower soot deposition.

According to a second aspect, the present invention relates to a kit comprising a cooking stove according to the first aspect of the invention, and one or more solid fuel blocks, wherein the one or more solid fuel blocks comprise methyl, ethyl, propyl, or butyl esters of a C6 to C14 carboxylic acid or mixtures thereof. As set out above, the solid fuel block preferably comprises methyl decanoate.

According to a third aspect, the present invention relates to a method of heating a cooking vessel, the method comprising the steps of:

• • providing a cooking stove according to the first aspect of the invention;
  • providing a solid fuel block, wherein the solid fuel block comprises methyl, ethyl, propyl, or butyl ester of a C6 to C14 carboxylic acid or mixtures thereof;
  • placing the solid fuel block in the fuel zone of the cooking stove and setting light to the solid fuel block; and
  • placing the cooking vessel on top of the cooking stove.

According to a fourth aspect, the present invention relates to a cooking stove substantially as described herein, and/or as shown in the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 relates to a four sided cooking stove according to a preferred embodiment of the present invention.

FIG. 2 relates to the four sided cooking stove as shown in FIG. 1, which has been disassembled.

FIG. 3 relates to a four sided cooking stove according to a further preferred embodiment of the present invention.

FIG. 4 relates to the four sided cooking stove as shown in FIG. 3, which has been disassembled.

DESCRIPTION

The present invention relates to a cooking stove. As set out above, the cooking stoves of the present invention are designed to make efficient use of solid fuel blocks and to minimise the soot deposited on the cooking vessel. The cooking stove has walls which define a base at one end and a top at the other end. By walls, we mean a continuous loop of material that is open at both ends. One open end, designated the “base”, is positioned lowermost, and placed on a solid surface during use. The opposing open end, designated the “top”, is positioned uppermost during use, and provides a cooking surface upon which cooking vessels can be placed.

By “height” of the stove, we mean the dimension from the top to the base. The “width” is at 90 degrees to this, taking the widest cross-section through the stove, for example at the top or the base.

In the stove of the present invention, the height is preferably greater than the width of the stove at the widest point. For example, the height of the stove can be at least 20% greater than the width of the stove at the widest point. This can help to ensure that there is enough headspace in the combustion zone to efficiently and completely combust all the volatized fuel. In other embodiments, the height and width of the stove are approximately equal, or the stove can be up to 20% wider than it is high.

The walls of the cooking stove can be cylindrical or conical, or can comprise 3, 4, 5 or 6 sides wherein each side defines a substantially square, rectangular or trapezium shape so that the cooking stove defines a substantially cuboid, prism or pyramidal frustum shape.

Where the cooking stove has walls which comprise 3, 4, 5 or 6 sides, the sides can be described as “sheet-like members”. By sheet-like member we mean a sheet of material that can be either planar or curved, and is of a shape that can be defined as having a top edge, a bottom edge, two side edges and two faces. Typically this would be achieved by the sheet-like member having a substantially square, rectangular or trapezium shape when viewed face-on. When a rectangular sheet-like member is used, either the long edge or the short edge would define the bottom edge. When a trapezium-shaped sheet-like member, either of the parallel edges would define the bottom edge. It is intended that, during use, the bottom edge will be lowermost, typically on the ground, or other support, and i.e. would form the base, and the top edge will be uppermost i.e. would form the top.

The sheet-like members can be coupled together at their side edges to form the walls of the cooking stove. By coupled at their side edges, we mean that the side edges must be aligned such that the length of the side edge of one sheet-like member is substantially positioned along the length of the side edge of the other sheet-like member. The side edges, therefore, include a coupling mechanism that holds the two side edges together.

The coupling mechanism can be the shape of the side edge, or the region close to the side edge, or can be a hinge. The coupling mechanism is preferably such that no gaps are created which could act as air inlets or exhaust outlets.

In a preferred embodiment of the present invention, the coupling mechanism is reversible, so that the sheet-like members can be readily disassembled. By this we mean that after use, at least one of the couplings between sheet-like members can be separated. The sheet-like members can then be stored in a flat-packed configuration. By flat-packed configuration, we mean that the sheet-like members can be arranged such that they are stacked with their faces aligned, thus taking up minimal space. This makes the cooking stove more easily portable, which is highly advantageous.

The sheet-like members may, for example, be coupled using a slit substantially parallel to and within 50 mm of the side edges. By this, we mean that a substantially rectangular section, with two long edges and two short edges, is missing from the sheet-like member, the long edges of the slit running substantially parallel to the side edge, and the short edges defining a width that is at least that of the thickness of the sheet-like member. The slit may also be cut into a protruding section of the side edge. The slit may extend from either the top or the bottom edge, or the top or the bottom edge of a protruding section of the side edge, such that three edges of the slit are defined by the sheet-like member and the final edge is a short edge that is open. The slit may also be positioned such that the slit is closed on all four edges. The slit of one sheet-like member can couple with a complementary slit of another sheet-like member. By complementary, we mean that where one slit has an open edge facing the bottom edge of the sheet-like member, the other slit has an open edge facing the top edge of the sheet-like member, and the slits are both positioned such that they can be used to couple the members. Where a first slit is closed on all four edges, the complementary second slit is a slit with an open narrow edge facing either the top or bottom edge of the sheet-like member, and having a closed narrow edge at substantially the same height as either the upper or lower closed narrow edge of the first slit. Two complementary edges can be coupled by inserting the complementary slits into each other.

A further option is that the sheet-like members can be coupled using hinges. By this we mean that the mechanism that holds the two side edges together is a pivoting hinge that pivots along the same axis as the side edge. Using this mechanism, the sheet-like members can be folded into the stove configuration for use, and after use can be folded into a flat-pack configuration for storage. The hinges are preferably half hinges, that extend from the bottom of the sheet like members to the top, so that no gap is left which could act as an air inlet or exhaust outlet. In a preferred embodiment, all apart from one of the hinges cannot be disassembled by the user. One can be disassembled/assembled by the user. When it is disassembled, the sheet-like members can be collapsed on top of one another in a concertinaed arrangement, so as to be flat-packed. To be assembled, they are arranged to stand in a circuit, and the one hinge is assembled by the user to complete the stove.

The stove comprises at least three sheet-like members, and preferably comprises four to six sheet-like members, more preferably four sheet-like members. Using three sheet-like members as an example, a first side-edge of a first sheet-like member is coupled to a first side-edge of a second sheet-like member. The second side-edge of the second sheet-like member is coupled to a first-side edge of a third sheet-like member. The second side-edge of the third sheet-like member is coupled to the second side-edge of the first sheet-like member, thus creating a closed loop of sheet-like members. To create a stove with more sheet-like members, the same principle is applied to create a loop of sheet-like members, coupled at their side-edges.

Where a sheet-like member has a square or rectangular shape, the assembled stove will resemble a prism. Where three sheet-like members are used, the assembled stove will resemble a triangular-based prism. Where four sheet-like members are used, the assembled stove will resemble a square-based prism, or a cuboid. Where five sheet-like members are used, the assembled stove will resemble a pentagon-based prism. Where six sheet-like members are used, the assembled stove will resemble a hexagonal-based prism, and so on.

Where a sheet like-member has a trapezium-shaped sheet-like member, and the long parallel edge defines the bottom edge, the assembled stove will resemble a pyramidal frustum. Where a sheet-like member has a trapezium-shaped sheet-like member, and the short parallel edge defines the bottom edge, the assembled stove will resemble an inverted pyramidal frustum. Where three sheet-like members are used, the assembled stove will resemble a triangular-based pyramidal frustum. Where four sheet-like members are used, the assembled stove will resemble a square-based pyramidal frustum. Where five sheet-like members are used, the assembled stove will resemble a pentagon-based pyramidal frustum. Where six sheet-like members are used, the assembled stove will resemble a hexagon-based pyramidal frustum, and so on.

In the cooking stove of the present invention, the walls of the cooking stove define a fuel zone, a combustion zone and an exhaust zone. By referring to the difference zones, we are imagining that the stove is divided into three sections of equal height, based on the way the stove is used. There is no physical barrier or transition between the different zones. The fuel zone is defined by the section of the walls which extends up from the base to about one third of the height of the stove. The exhaust zone is defined by the section of the walls which extends down from the top by about one third of the height of the stove. The combustion zone is defined by the section of the walls which extends from the fuel zone to the exhaust zone, so occupies the middle third of the stove.

As set out above, the height of the stove is the dimension from top to base. Accordingly, the fuel zone is provided at the lowest third of the stove, which advantageously is approximately the same height a fuel block itself, or can be taller than a fuel block. The fuel zone has at least one air inlet, wherein the total surface area of this air inlet or air inlets is 0.5% to 2.5% of the total surface area of the fuel zone. The inventor has discovered that the air inlets in the fuel zone have an important effect on the cleanness of the flame and efficiency with which the fuel is burnt. When the air inlets(s) in the fuel zone comprise less than 0.5% of the total surface area of the fuel zone, it is believed that not enough air can enter to sustain flame. Above 2.5% of the total surface area of the fuel zone, the blue clean burn flame can be change into a yellow flame, and sooty deposits may appear on the cooking vessel.

Air inlets and exhaust outlets are essentially holes in the walls of the cooking stove. When we refer to the surface area of air inlets or exhaust outlets as a percentage of the total surface area of a zone, we mean the total surface area of the walls that is missing in that zone as a percentage of the total surface area of the walls of the zone, if there was no material missing.

Compared to traditional stoves, the fuel zone in a stove of the present invention has a relatively small proportion of air inlet surface area and typically allows air to be drawn in to sustain just a small flame which, alone, would burn the fuel at a slow rate. The main purpose of the flame in the fuel zone is to create enough heat to vaporise the FAE so that complete combustion can take place in the headspace above the fuel, in the combustion zone.

The air inlet or at least one of the air inlets in the fuel zone preferably has a diameter of at least 8 mm, preferably about 10 mm. This is convenient because it allows a match or other igniter to be passed through the air inlet to light the fuel.

The combustion zone has been designed to take up the middle third of the cooking stove, and is typically above a fuel block when positioned in the stove. In order to facilitate complete combustion of the solid fuel block, larger and/or a greater number of air inlets are provided in the combustion zone compared to the fuel zone. At least three air inlets are provided in the combustion zone. The total surface area of these air inlets is 2.5% to 4.0% of the total surface area of the combustion zone. This is in stark contrast to many prior art stoves, where the biggest, and often the only, air inlets are at the level of the fuel.

With traditional fuels that are not subject to vaporisation (wood, coal etc.) complete combustion has to take place at the level of the fuel itself. As noted above, the stove of the present invention has been carefully designed to fully optimise and control burning of FAE solid fuel blocks. Having relatively large air inlets in the combustion zone helps to ensure that the flame is hot enough in the combustion zone to completely combust the fuel, compared to in prior art stoves where incomplete combustion can mean that partially combusted fuel, i.e. soot or, worse still, vaporised but completely unburned fuel is deposited on the cooking vessel.

The inventor has found that by altering the surface area of the air inlets in the combustion zone, the rate of burn of a solid fuel block can be tuned. At below 2.5%, the burn is too slow to be of optimal use. Between 2.5% and 4%, the burn is of an acceptable time and optimal intensity to result in complete combustion with a clean blue flame giving no or almost no sooty deposits, with 2.5% giving a slower and steadier burn than 4%. Above 4%, a solid fuel block can burn too aggressively to completely combust, resulting in sooty deposits on the bottom of the cooking vessel.

Controlling the flow of gasses out of the stove is also important. To this end, an exhaust zone is provided in the top third of the stove that has at least two exhaust outlets. The total surface area of these exhaust outlets is optimally 20% to 35% of the total surface area of the exhaust zone.

During use, a cooking vessel is placed over the top of the walls of the stove, preferably so that it completely covers the top of the stove. In this way, the exhaust outlets are the only gaps between the cooking stove and the cooking vessel through which hot exhaust gasses can escape.

The specific arrangement of air inlets and exhaust outlets in the three zones of the stove of the present invention advantageously allows the flow of gasses into and out of the stove to be tightly controlled in order to promote complete combustion of a FAE fuel block in a non-aggressive manner which can advantageously result in a clean blue flame and a good balance between burn time and flame temperature for optimal heating of food or liquid in a cooking vessel on the stove.

The inventor has, surprisingly, found that the total surface area of the inlets/outlets in the particular zones is more important to the performance than the specific arrangement of inlets/outlets. Accordingly, any reasonable number and arrangement of inlets/outlets can be used, providing the number of and total surface area of the inlets/outlets falls within the claimed ranges. Specific examples are described below, and shown in the accompanying figures. It is preferred that there are 1 to 12 air inlets in the fuel zone, and/or 4 to 20 air inlets in the combustion zone, and/or 2 to 6 exhaust outlets in the exhaust zone.

In one embodiment of the present invention, the cooking stove has walls which comprise four sides, with one air inlet in the fuel zone, twelve air inlets in the combustion zone, and two exhaust outlets in the exhaust zone. In this embodiment, it is preferably that the air inlet in the fuel zone comprises about 1% of the total surface area of the fuel zone, the air inlets in the combustion zone comprise about 3.5% of the total surface area of the combustion zone, and the exhaust outlets comprise about 23% of the total surface area of the exhaust zone.

In another preferred embodiment of the present invention, the walls of the stove comprise four sides, with eight air inlets in the fuel zone, sixteen air inlets in the combustion zone, and four exhaust outlets in the exhaust zone. In this embodiment, it is preferred that the air inlets in the fuel zone comprise about 2.1% of the total surface area of the fuel zone, the air inlets in the combustion zone comprise about 3.5% of the total surface area of the combustion zone, and the exhaust outlets comprise about 23% of the total surface area of the exhaust zone.

As set out above, the cooking stoves of the present invention can be used by those undertaking general camping, military or other outdoor leisure pursuits, or by larger groups of people for entertaining or humanitarian purposes.

For camping and military uses, the stove is usually designed to heat around 500 ml of water or food. Such a stove is typically 5 cm to 10 cm high, preferably about 8 cm high and 5 to 10 cm wide at the widest point, typically around 8 cm wide at the widest point.

For humanitarian or family use, the stove is usually designed to heat around 51 of water or food. Such a stove is typically 10 cm to 20 cm high, preferably about 12 cm high and 10 to 20 cm wide at the widest point, typically around 14 cm wide at the widest point. A stove for humanitarian use advantageously has slotted rather than hinged sides to provide a stable base for a relatively large cooking vessel.

As noted above, the stove of the present invention is designed specifically for use with a FAE solid fuel block. FAE solid fuel blocks typically comprise a methyl, ethyl, propyl or butyl ester of a C6 to C14 carboxylic acid or combination thereof encapsulated in a solid emulsion. A solid fuel block comprising an emulsion of methyl decanoate encapsulated in a urea-formaldehyde resin is available on the market under the name “Zip Military Fuel”® These fuel blocks comprise about 20% by weight urea-formaldehyde/water/emulsifier matrix and about 80% by weight methyl decanoate. Two sizes are available, a 26 g block that is 42 mm long, 32 mm wide and 20 mm tall, and a 100 g block that is 60 mm long, 60 mm wide and 40 mm tall. The smaller block is usually for individual use, for example by campers or the military, and the larger block can be for humanitarian use.

Accordingly, the present invention also relates to a kit comprising a cooking stove and one or more such solid fuel blocks. The present invention also relates to a method of heating a cooking vessel using one of the solid fuel blocks. The relative dimensions of the solid fuel block and the stove should be such that the solid fuel block is dimensioned to fit inside the lowest third of the cooking stove i.e. the fuel zone. Accordingly, in one embodiment of the invention, the height of the fuel zone is equal to or greater than the height of the fuel block.

The cooking stove of the present invention is constructed from a fire-proof material, preferably wherein the material is a metal or alloy such as aluminium, titanium, nickel, copper, mild steel, stainless steel or brass. This ensures that the stove is able to withstand the heat of the burning fuel without burning or substantially deforming while being strong enough to support a cooking vessel and robust enough for repeated use.

DETAILED DESCRIPTION OF THE DRAWINGS

In one preferred embodiment, as shown in FIGS. 1 and 2, a cooking stove 1 has four sides, 2, 3, 4, 5. Preferably the sides are hinged together 6, 7, 8, with one of the hinges, 9, being suitable for disassembly by the user, to allow the stove to be flat packed. In FIG. 2, it is shown disassembled. The sides can be concertinaed to flat pack, not shown.

There is one air inlet 10 in the fuel zone 14, twelve air inlets 11 in the combustion zone 15, three on each side, and two exhaust outlets 12 in the exhaust zone 16. The air inlet 10 in the fuel zone 14 is a single 10 mm diameter hole, which comprises around 1% of the total surface area of the fuel zone. The air inlets 11 in the combustion zone 15 are each about 5 mm in diameter, which together make up about 3.5% of the total surface area of the combustion zone. The exhaust outlets 12 are scalloped and are positioned on opposing sides from each other. The exhaust outlets are not on the same side as the air inlet in the fuel zone. The exhaust outlets 12 make up about 23% of the total surface area of the exhaust zone 16.

This stove is particularly well suited to use on a small scale, for an individual or a couple, to boil a small amount, about 250-500 ml of water or food. It can be used with a small fuel block i.e. a 26 g block that is 42 mm long, 32 mm wide and 20 mm tall. The base of the stove 12 is placed on a level surface. A fuel block (not shown) is placed on the surface inside the stove. The fuel block is set alight by passing a match or other igniter through air inlet 10 in the fuel zone 14.

As described above, a restricted volume of air is drawn in through the inlet 10, to give rise to a small flame, which burns the fuel block with a small flame in the fuel zone 14, and which vaporises fuel which rises to the combustion zone 15. A higher volume of air can be drawn through the air inlets 11 in the combustion zone 15 where the majority of combustion takes place.

A cooking vessel (not shown) is placed over the entirety of the top 17 of the stove which forces the exhaust gasses out of the exhaust outlets 12. The flame produced is blue, showing that complete combustion has occurred, and soot or FAE deposits on the cooking vessel are minimal.

In a further preferred embodiment, as shown in FIGS. 3 and 4, a cooking stove 20 has four sides, 21, 22, 23 and 24. The sides are slotted together using slots 25, 26, 27 and 28 as shown disassembled in FIG. 4. This allows the stove to be flat packed.

There are eight air inlets 29 in the fuel zone 30, sixteen air inlets 33 in the combustion zone 31, four on each side, and four exhaust outlets 34 in the exhaust zone 32. The exhaust outlets 34 are shaped to allowed efficient burning, and are positioned with one on each of the four sides. The air inlets in the fuel zone comprise about 2.1%, in the combustion zone about 2.9% and exhaust outlets in the exhaust zone about 30% of the total surface area of each zone respectively.

This stove is particularly well suited to use on a humanitarian scale, for a whole family or group of families, up to 50 people. It would usually be used to boil a large amount, about 51 of water or food. It can be used with one or more large fuel blocks i.e. a 100 g block that is 60 mm long, 60 mm wide and 40 mm tall.

The base of the stove 35 is placed on a level surface. A fuel block (not shown) is placed on the surface inside the stove. The fuel block is set alight by passing a match or other igniter through one of the air inlets 29 in the fuel zone 30.

As described above, a restricted volume of air is drawn in through the inlets 29, to give rise to a small flame, which burns the fuel block with a small flame in the fuel zone 30, and which vaporises fuel which rises to the combustion zone 31. A higher volume of air can be drawn through the air inlets 33 in the combustion zone 31 where the majority of combustion takes place. A cooking vessel (not shown) is placed over the entirety of the top 36 of the stove 20 which forces the exhaust gasses out of the exhaust outlets 34. The flame produced is blue, showing that complete combustion has occurred, and soot or FAE deposits on the cooking vessel are minimal.

Claims

1. A cooking stove, the cooking stove comprising walls which define a base at one end and a top at the other end, wherein the walls of the cooking stove additionally define:

a fuel zone which is defined by the section of the walls which extends up from the base to about one third of the height of the stove;

an exhaust zone which is defined by the section of the walls which extends down from the top by about one third of the height of the stove; and

a combustion zone which is defined by the section of the walls which extends from the fuel zone to the exhaust zone; wherein the cooking stove is characterised in that

the fuel zone has at least one air inlet, wherein the total surface area of this air inlet or air inlets is 0.5% to 2.5% of the total surface area of the fuel zone;

the exhaust zone has at least two exhaust outlets, wherein the total surface area of these exhaust outlets is 20% to 35% of the total surface area of the exhaust zone; and

the combustion zone has at least three air inlets, wherein the total surface area of these air inlets is 2.5% to 4.0% of the total surface area of the combustion zone.

2. The cooking stove according to claim 1, wherein the walls are cylindrical, conical, or wherein the walls comprise 3, 4, 5 or 6 sides wherein each side defines a substantially square, rectangular or trapezium shape so that the cooking stove defines a substantially cuboid, prism or pyramidal frustum shape.

3. The cooking stove according to claim 1, wherein the walls comprise 3, 4, 5 or 6 sides which are sheet-like members, wherein each sheet-like member has two faces, a top edge, a bottom edge and two side edges, and wherein the sheet-like members are coupled together at their side edges.

4. The cooking stove according to claim 3, wherein the walls comprise 4 sides which are sheet-like members.

5. The cooking stove according to claim 3, wherein the coupling between the side edges of sheet-like members is not fixed, so the cooking stove can be assembled and disassembled during normal use, preferably wherein when the cooking stove is disassembled, the sheet-like members can be arranged to lie flat on top of one another.

6. The cooking stove according to claim 5, wherein the sheet-like members are coupled by hinges.

7. The cooking stove according to claim 5, wherein the sheet-like members have a slit substantially parallel to and within 50 mm of the side edges, wherein the sheet-like members are coupled at their side edges through the interlocking of complementary slits.

8. The cooking stove according to claim 1, wherein the height of the stove is greater than the width of the stove at the widest point.

9. The cooking stove according to claim 8, wherein the height of the stove is at least 20% greater than the width of the stove at the widest point.

10. The cooking stove according to claim 1, wherein the walls comprise four sides, and wherein there is one air inlet in the fuel zone, twelve air inlets in the combustion zone, and two exhaust outlets in the exhaust zone.

11. The cooking stove according to claim 10, wherein the air inlet in the fuel zone comprises about 1% of the total surface area of the fuel zone, the air inlets in the combustion zone comprise about 3.5% of the total surface area of the combustion zone, and the exhaust outlets comprise about 23% of the total surface area of the exhaust zone.

12. The cooking stove according to claim 1, wherein the walls comprise four sides, and wherein there are eight air inlets in the fuel zone, sixteen air inlets in the combustion zone, and four exhaust outlets in the exhaust zone.

13. The cooking stove according to claim 12, wherein the air inlets in the fuel zone comprise about 2.1% of the total surface area of the fuel zone, the air inlets in the combustion zone comprise about 3.5% of the total surface area of the combustion zone, and the exhaust outlets comprise about 23% of the total surface area of the exhaust zone.

14. The cooking stove according to claim 1, wherein the air inlet or at least one of the air inlets in the fuel zone has a diameter of at least 8 mm, preferably about 10 mm.

15. A kit comprising a cooking stove according to claim 1, and one or more solid fuel blocks, wherein the one or more solid fuel blocks comprise methyl, ethyl, propyl, or butyl esters of a C6 to C14 carboxylic acid or mixtures thereof.

16. A kit according to claim 15, wherein the solid fuel block comprises methyl decanoate.

17. A kit according to claim 15, wherein the solid fuel block fits inside the fuel zone of the cooking stove.

18. A method of heating a cooking vessel, the method comprising the steps of:

providing a cooking stove according to claim 1;

providing a solid fuel block, wherein the solid fuel block comprises methyl, ethyl, propyl, or butyl esters of a C6 to C14 carboxylic acid or mixtures thereof;

placing the solid fuel block in the fuel zone of the cooking stove and setting light to the solid fuel block; and

placing the cooking vessel on top of the cooking stove.

19. A method according to claim 18, wherein the solid fuel block comprises methyl decanoate.

20. A method according to claim 18 or 19, wherein the height of the fuel zone is equal to or greater than the height of the fuel block.

21. (canceled)